The time profit of using GPU processing over using the main processor (CPU) measured for two systems: modern, with Intel Core i7-7700K and actually installed in our tomograph, with Intel Core i7-960.
\r\n\tThe major pathogenetic mechanisms resulting from RAAS overactivity include activation of the sympathetic nervous system, endothelial dysfunction, proinflammatory, and procoagulant states.
\r\n\tEmerging from basic science evidence, major clinical trials established the beneficial effects of inhibitors of the different components of RAAS such as angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), aldosterone antagonists. These effects range from treatment of hypertension, diabetic nephropathy, CHF, as well as improvement of outcomes after myocardial infarction and improvement in glucose homeostasis and prevention of type 2 diabetes with some agents.
\r\n\tIn this book, written by a world-renowned scholar, we will address the major concepts and topics related to RAAS activation including the pathogenetic mechanisms underlying the deleterious effects of activated RAAS and the role of local tissue RAAS in various organ systems such as the heart and vasculature, the skeletal muscle, adipose tissues, pancreas and the angiotensinergic pathways in the brain. Cutting-edge information is provided that will address the need for a wide range of readers including a medical student, clinical practitioner, and basic science investigators alike. This book will be bridging the gap between basic science and clinical practice regarding the RAAS system, which is imminently critical and highly relevant to the practice of medicine.
\r\n\r\n\tFinally, with data emerging from the COVID-19 pandemic indicating overrepresentation of people with diseases associated with RAAS activation such as hypertension, chronic kidney disease, and diabetes, the role of RAAS activation and RAAS inhibition in the pathogenesis and clinical outcomes in COVID-19 has garnered a great deal of interest. In this book, we will dedicate a chapter addressing this topical and highly critical subject.
\r\n\t
Optical coherence tomography is a quite natural choice for examination of objects of art. This is because it is possible to make it portable and it is contactless and noninvasive. As for the former, it is significant that the distance to an examined object is usually relatively high—in a range of centimeters rather than millimeters. It is especially important for the fragile pieces of art examined in situ, with the portable instrument mounted on a tripod or similar provisional stand. As for the latter, the intensity of the probing radiation and low energy of infrared protons ensure lack of physicochemical damage to any material: let us consider an instrument with the power of the probing beam at the object of 1 mW. If the Fourier domain fast OCT system is considered, it is reasonable to assume that the 15-mm wide B-scan is acquired in less than 0.1 s and composed of, let us say, 3000 A-scans. It leads to the scanning speed over 150 mm/s and 33 μs/A-scan. If the spot diameter will be about 12 μm, what is a reasonable measure of the lateral resolution, the fluence of the OCT beam can be estimated at 30 mJ/cm2. This quantity is far below any damage thresholds for long pulses of infrared radiation, but a certain care in the case of work with photosensitive objects must be adopted [1].
The noninvasiveness of OCT encouraged heritage science researches to seek its applications to examination of objects of art. This subject is present in the literature since 2003 when first reports appeared [2, 3, 4, 5]. The major fields of application have been, from the very beginning, examination of subsurface, semitransparent layers of easel paintings, glazes at faience and ceramics, historic glass, jade, and occasionally some other materials. The main restriction is in limited transparency to the probing light of materials constituting those objects. This issue has been a subject of detailed examination by Liang et al. [6] in search for the optimum wavelength window for examination. As expected the mid-IR band, about 2 μm, was found as more suitable from the point of view of transparency of pigments and dyes usually present in easel paintings. However, OCT instruments (at least commonly available) working in this range exhibit lower axial resolution due to the known trade-off between resolution and the central wavelength of operation. Nevertheless, the bibliography [7] of the subject counts now over 130 positions which is a negligible amount in comparison to those dedicated to medical applications, but constituting a little community of researchers permanently devoted to this subject. The subject has been reviewed twice already [8, 9], so for the rest of this chapter, only some of the last reports (published after 2014) will be commented on. For the complete bibliography, the reader is directed to the aforementioned website.
As for the further development of the technique, a paper by Cheung et al. [10] may serve as a mature example of the system working in 800 nm band and taking a full advantage of the axial resolution available in the near-infrared range. Due to the careful design and very broad light source (with FWHM of ∼200 nm after shaping to Gaussian-like function), the axial resolution of 1.8 μm (1.2 μm in varnish-like medium of nR = 1.5) is reported. The system permits resolving varnish layers as thick as 2–6 μm what is sufficient for most of examinations of easel paintings. Unfortunately, this was not a case with the second system [11] reported by the same group: the use of the supercontinuum source with the bandwidth of 220 nm working in the 2 μm range resulted in very good transparency of many layers, not permeable in 900 nm band, but the measured axial resolution was 13 μm in air which may not be sufficient for some applications.
Numerical post-processing of the results is one of the most decisive factors of the advance applications, going beyond simple feasibility studies. Usually, the solutions are adopted from the medical applications, and some concepts developed in our laboratory will be mentioned in the next sections. Here we would like to refer the reader to the paper by Callewaert et al. [12] devoted to the important subject of segmentation of thin layers, leading to, e.g., at least semiautomatic determination of thickness of superficial structures like varnish layers. This may pave the way to more efficient, or even fully automatic, monitoring of some restoration processes, even with the use of laser ablation of unwanted layers.
The area of applications of OCT to heritage objects is still expanding. Over the last few years, reports on the novel use of OCT for rock vulnerability assessment [13] and protective coatings on metal [14] have emerged. Moreover, recently the combined use of OCT with some other techniques, to take advantage of the synergy effect, has been reported. It is a known deficiency of the OCT that it does not provide information on chemical composition of structures visualized. To overcome this problem, it may be combined with other techniques, sensitive to the composition of the object, but lacking an in-depth resolution. The most promising solution seems to be linking OCT with X-ray fluorescence (XRF), especially with its macro-imaging modality MA-XRF. This combination has been presented in application for examination of the seventeenth-century Dutch still life painting [15, 16]—namely, to localize within the structure of paint layers the presence of zinc white and to clearly associate it with overpaintings present due to former restoration attempt and not with the original structures. It was important for dating of the painting since zinc white had been in common use since the second quarter of the nineteenth century only [17] and therefore, if present in the original paint layer, would shift the attribution and dating of the painting toward modern times. As for the application of MA-XRF and OCT to other kinds of artworks, in case of the late sixteenth-century illuminated manuscript (the gradual) [18], the initials made with cobalt glass pigment (smalt) and text written with iron-gall ink were in focus of the research and were well visualized by means of both OCT and MA-XRF. Another imaging technique used in combination with OCT is multispectral infrared reflectography. It permits inspection of the object in different wavelength ranges, beyond the OCT probing light [19, 20, 21]. The concept of expanding the examination window even further lies at the foundations of the complementary use of OCT and terahertz time domain imaging presented by Koch Dandolo et al. [22]. This preliminary test has shown that, as expected, the THz imaging overcomes the major limitation of OCT caused by the limited permeability of paint layer and allows imaging down to the canvas support. However, there are two other factors, which restrict the use of the THz imaging alone: the limited contrast sometimes impairs the ability to differentiate various structures (e.g., varnish versus paint) and the axial resolution, about tenfold lower than in the case of OCT. All this especially predesignate these techniques for complementary use.
The capabilities of the common use of OCT and nonlinear microscopy (NLM) were investigated by Liang et al. [1]. It was shown that NLM may in some cases provide a better contrast to differentiate between varnishes. On the other hand, this technique must be applied with care, to avoid light-induced damage of especially light-sensitive objects.
The holistic approach, including VIS-NIR multispectral imaging, high-spectral resolution VIS-NIR spectroscopy with fiber-optic reflectance spectroscopy (FORS), micro-Raman spectroscopy, XRF spectroscopy, and OCT imaging, was used by Kogou et al. [23] for examination of Chinese watercolors. In this case OCT could have been utilized as a complementary tool only, since watercolors do not exhibit permeable layers possible to examine with OCT. Therefore, it was applied in order to investigate a structure of supporting papers. Even though these materials are also essentially not permeable, some conclusions were possible to be drawn.
Properties of coatings on wood were intensively investigated lately with optical coherence microscopy exclusively [24], with OCT and hyperspectral imaging [25], as well as with OCT and synchrotron radiation micro-computed tomography (Sr-micro-CT) [26]. In this last case, the subject of examination was five large fragments removed during past restorations from historic string instruments produced by famous Italian historical violin makers: Jacobus Stainer, Gasparo da Salò, Giovanni Paolo Maggini, and Lorenzo Guadagnini. This research may be considered as feasibility study for planned examination of historic violins and showed a significant complementarity of both tomographic approaches. SR-micro-CT has better axial resolution enabling imaging some thin varnish layers, but in some cases, OCT provides better contrast permitting identification of a thin preparation layer spread over the wood, not seen with micro-CT.
The development of the OCT technique as a whole over the last 15 years as well as its applications to the examination of cultural heritage objects has permitted resolving of specific conservation issues, posted by art restorers and objects’ curators.
Preceding the restoration campaign, performed in Opificio delle Pietre Dure in Florence, the unfinished masterpiece by Leonardo da Vinci “Adoration of the Magi” was extensively examined with various techniques. Among others, OCT was used [27] to determine the condition and structure of secondary varnish layers covering the painting.
OCT examination is especially effective when it is used in combination with other techniques. One of the first holistic attempts was examination of the “Bessarion Reliquary” at Opificio delle Pietre Dure in 2012 [28]. The research was directed toward the understanding of the character of specific damages of the varnish covering the painted parts of the object and tracing of remains of the historical restoration commissioned by cardinal Bessarion in the fifteenth century. Apart from OCT also point-wise XRF examination was used. Additionally, on samples collected from the object, gas chromatography with mass spectroscopy detection (GC-MS), pyrolysis gas chromatography with mass spectroscopy detection (PGC-MS), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), and Fourier transform infrared (FTIR) spectroscopy techniques were used. Consequently, the results had been used for planning of the restoration campaign (already completed).
The combination of SEM and SEM-EDS with OCT was used by Yang et al. [29] to investigate optical properties and structure of Chinese Song Jun glaze on porcelain, especially the presence of copper and quartz additives.
During the same examination campaign as for the “Adoration of the Magi,” another painting by Leonardo and studio was examined: “The Lansdowne Virgin of the Yarnwinder” (“Madonna dei Fusi”). The results of its investigation with OCT, multispectral scanning, and more common techniques, X-radiography and UV-excited fluorescence, were published recently [21]. Data post-processing with the innovative generation of scattering maps from a given depth under the surface clearly revealed the shape and in-depth location of vast overpaintings, not seen clearly with other, conventional techniques. Probably, these interventions were performed to hide damage created during two transfers of paint layer: from wood panel to canvas and from canvas to composite rigid support. The evidence of the first transfer canvas, not existing presently, was found with OCT examination as well in a form of an imprint in the paint layer. Another multi-instrumental examination campaign, the comprehensive study of Amsterdam version of “Sunflowers” by Vincent van Gogh at Van Gogh Museum in Amsterdam, was performed in 2016 as a transnational access MOLAB activity [30] of H2020 IPERION CH project. The research was aimed at documentation of a state of preservation, possible threats related to exposition, and resolving the history of restorations of this masterpiece. The goal of the OCT research was to determine the number and thickness of varnish layers and the stratigraphy within the restored areas. OCT was also used for examination of deterioration phenomena typical for this painting: local darkening of varnish in the recesses of the brush strokes, migration of the paint layer into the varnish, as well as presence and potential development of lead soap formations [31].
Apart from these reports, devoted to examination of the structure and state of preservation of artworks, OCT has been also used to monitor or assess some restoration treatments. One of the early reports, from 2011, was about application of OCT to real-time monitoring of consolidation of paint layer in reverse painting on glass (Hinterglasmalerei) objects [32].
Due to transparency of varnish layer, OCT is especially well suited to monitor its removal. The most common restoration technique used for this purpose is with the use of solvents. OCT, especially if used together with FTIR spectroscopy examination, is capable of accurate assessment of the cleaning process [33, 34]. Some tests of this kind were also performed during the aforementioned examination campaign of van Gogh’s “Sunflowers” [35]. Selected aspects of OCT data processing for this purpose will be addressed in Section 5.
The use of lasers for ablation of unwanted layers (such as varnishes or mineral deposits) from paintings and other objects is a particularly delicate operation which needs precise control. Feasibility studies presented at LACONA (Lasers in the Conservation of Artworks) conferences in 2007, 2013, and 2015 [36, 37, 38] proved that it is possible to efficiently monitor such a process in real time. A specific case of removal of unwanted layers from the substrates of mural paintings was addressed by Striova et al. firstly in the case of removal of shellac varnish [39] and then of calcium oxalate layers [40], in both cases by means of laser and chemical treatment.
The instrument, constructed especially for examination of cultural heritage objects and being developed permanently in our laboratory, belongs to Fourier domain category with a broadband source and a spectrograph as detector. The instrument is designed as a portable one. To achieve this, a modular design composed of easy detachable parts connected with cables and optical fibers was chosen. All elements are of weight allowing easy handling by one person. Only a computer, comprising also all high power suppliers, weighs about 30 kg. This is important because objects of arts are often localized in old buildings with a limited access.
As for the operating parameters, the highest available axial resolution was chosen as the key parameter. This is because the ability to distinguish and visualize thin layers is a decisive factor for using in this area of applications. Therefore, short-infrared radiation was chosen even though the transparency of typical pigments is limited in this area and the optimum wavelength range lays around 2 μm [41]. By using portable commercial sources composed of coupled superluminescent diodes (Broadlighters: Q-870-HP or M-T-850-HP-I both from Superlum, Ireland) emitting in the range 770–970 nm (the former) and 750–960 (the latter), it was possible to achieve 3.3 μm of (measured) axial resolution in air, and 2.2 μm in medium of nR = 1.5. The resolution was measured as a width of the point spread function with sidelobes suppression better than 25 dB. This last condition is very important in the case of examination of CH objects since they are often composed of thin and clearly transparent layers. In this case sidelobes may be easy misinterpreted as an evidence of a thin, additional layer just under the surface.
After the source, light passes a fiber-optic polarization controller and an optical isolator and is transmitted to the second module—a head by the optical fiber. The head comprises a fiber coupler of the interferometer and its reference and object arms. The former is built of the collimator, light attenuator, dispersion compensator (LSM02DC from Thorlabs), and a mirror mounted on a small translation stage. The latter comprises a fiber-optic polarization controller, the identical collimator and attenuator as in the reference arm, galvanometric scanners (6220H galvanometer scanners with MicroMax HP servo driver amplifier from Cambridge Technology, USA), and the telecentric lens (LCM04 from Thorlabs, F = 54 mm).
This optical setup provides lateral resolution of 12 μm with the distance to the object from the most protruding element of the lens equal to 43 mm and maximum scanning area of 17 × 17 mm2. Alternatively the head can work with the LCM02 lens (F = 18 mm) that improves the lateral resolution to 6.5 × 6.5 mm2 but for the price of significantly smaller distance to the object, 7 mm, and scanning area, 5 × 5 mm2. A significant distance to the object is important for CH applications because it increases the safety of operation—objects sometimes have an irregular shape, and manipulating the head very close to the surface may pose a danger of direct contact with the artwork.
The head is equipped with two HR CCD cameras with USB-2 interface for precise documentation of the location of the OCT scanning and precise step motor-driven translators to position the head in plane and to control the distance to the object.
Finally, the light reflected in the reference arm and returning from the object undergoes the interference in the abovementioned fiber coupler and is transferred by the optical fiber to the third module—a spectrograph. Initially, the laboratory-built device with volume-phase holographic transmission grating optimized for 850 nm and with 1200 grooves/mm from Wasatch Photonics was used. Lately, it has been replaced by the complete Cobra CS800-840/180 spectrometer from Wasatch Photonics in order to improve mechanical stability and roll-off performance. Both spectrographs use 2048 pixel linear CCD cameras with fast 4-tap CameraLink interface.
In the case of Fourier domain OCT instruments utilizing spectrometers with linear cameras to collect interference spectra, the result is the vector of numbers of a length equal to the number of pixels of the camera (usually 2048). This data vector requires a set of numerical procedures to be converted into one axial line of the tomogram (A-scan). Over the time, by accumulating the common experience, a standard set of numerical procedures required to obtain a high-quality A-scan has been established. It comprises a sequence of six steps: background (BG) subtraction (labelled as 1 in Figure 1), λ-k remapping (2), numerical dispersion compensation (3), spectral shaping (4), fast Fourier transformation (FFT - 5), and finally displaying in logarithmic scale (6). No one of these steps may be omitted if the best available quality of results is expected. The influence of each of the abovementioned procedures on the cross-sectional image (B-scan) is presented in Figure 1: a completely illegible tomogram obtained only by executing the Fourier transform on recorded spectra and displayed in logarithmic scale is presented in Figure 1a. The next panels show the effect of the background (BG) subtraction procedure (Figure 1b) and remapping of the interference spectrum from the wavelength λ (or just a camera) domain to the wavenumber k domain (Figure 1c). Numerical dispersion compensation (Figure 1d) is sharpening the image by compensating the residual dispersion mismatch between both arms of the interferometer. It is especially useful when data is collected from the structures located deep in the object of high dispersion. For example, it is a case when measurement is performed though thick glass sheet covering the investigated structures of the artwork (see Figure 3 in the next chapter). Spectral shaping completes the set of procedures (Figure 1e), improving the sharpness of the boundaries of imaged structures by minimizing the sidelobes generated in the optical A-scan as a result of the Fourier transformation of the signal of the non-Gaussian envelope. This operation, being essentially the windowing of the data, may—however—slightly reduce the resolution of the system.
The impact of individual numerical procedures on the quality of the OCT tomogram applied to a single A-scan. The procedures are labelled with numbers 1..6 and described in the text. False color scale is applied.
In order to obtain the resultant tomogram (B-scan) of the best quality, the whole set of numerical procedures presented above must be performed for every spectrum. Assuming earlier preparation of the necessary data common for all spectra (in particular vectors used in procedures of numerical dispersion compensation and λ-k remapping [42]), this analysis does not require complicated calculations: BG subtraction needs calculation of the difference of two vectors (2048 elements each); dispersion compensation and shaping are just multiplications by vectors—element by element. FFT calculations are very well implemented and optimized in public domain libraries and do not take much time. λ-k remapping needs interpolation of the data (fourfold in our system, performed in Fourier domain, two FFT required) and mapping onto 2048 elements vector by a linear interpolation. The complexity of this problem arises with the number of A-scans, which must be processed—in the case of 3D volume analysis, this number typically exceeds 300,000.
Graphic processor units (GPU) are systems initially designed for fast rendering of graphic data by parallel calculations, but at present the area of applications is much broader. Often the visualization is not the major task but the massively parallel processing of any data. Obviously not all algorithms are appropriate for implementation and run fast on the GPU. However, if there is a possibility of parallelization of certain numerical tasks, the efficiency of calculations increases with the amount of data processed. In this context, the analysis of spectral optical tomography data is well suited for parallelization using the GPUs—calculations performed on successive spectra are independent of each other, and the complexity is primarily related to the amount of data being processed.
To benefit from this advantage of GPU, we have developed and successfully implemented our own software for parallel processing of the OCT data [43, 44]. It is worthwhile to note that in the case of this implementation, more time is needed to transfer the raw data to the GPU memory, and, after processing, the results back to the RAM memory of the workstation through the PCIe bus (Table 1). Nevertheless the profit of fast calculations is so high that the implementation of GPU is fully justified.
Task | Time [ms] Intel Core i7-7700K GTX 1080 | Time [ms] Intel Core i7-960 GTX 580 | |||
---|---|---|---|---|---|
GPU | Transfer data to the GPU | 5.77 | 15.27 | 7.45 | 24.36 |
Processing | 6.86 | 13.20 | |||
Transfer of the results to the host | 2.64 | 3.71 | |||
CPU | Processing | 940 | 1200 | ||
CPU/GPU time | 62 | 49 |
The time profit of using GPU processing over using the main processor (CPU) measured for two systems: modern, with Intel Core i7-7700K and actually installed in our tomograph, with Intel Core i7-960.
The efficiency of this data processing depends on the utilized hardware. On a modern workstation equipped with an Intel Core i7-7700K 4.2 GHz processor, 32 GB RAM memory, and NVIDIA GTX 1080 graphics processor, the computation acceleration is over 60 times when the process includes data transferring and almost 140 times for data processing only. The workstation actually used with our OCT configuration is equipped with Intel Core i7-960 3.2 GHz processors, 12 GB RAM, and NVIDIA GTX 580 GPU. The acceleration obtained with our software on this machine is slightly lower and amounts to 49 and 90 times (with and without data transfer). The details are presented in Table 1.
As a first example of application, OCT scans from examination of the early nineteenth-century painting on canvas “Portrait of Sir John Wylie” by F. Franck are presented (Figure 2). They are shown (as all tomograms in this chapter) with false color scale: structures strongly reflecting/scattering of the probing light are displayed in warm colors (red to yellow), whereas structures scattering/reflecting moderately or weekly in cold colors, from green to blue. Areas fully transparent or not accessible to the probing light are shown as black. The tomograms are corrected for refraction in the materials penetrated by the probing beam. Since most varnishes and binders have refractive indices from the range of 1.48 to 1.53 [45, 46], it is reasonable to assume an average value of 1.5 for recalculation of axial distances from optical to geometrical ones: for thin layers of varnishes possible systematic error will be below the axial resolution. The correction can be done either by the appropriate redrawing of the tomogram by application of a ray-tracing procedure taking into account ray refraction at the air-varnish boundary or by a simplified method. This approach, used in the examples presented herein, is acceptable for flat structures and is performed just by shortening of all vertical distances below the surface by a factor of 1.5. Alternatively, for uncorrected tomograms all axial optical distances below the surface and measured with scale appropriate for air above the object’s surface (and thus for the surface topography) must be divided by 1.5. Another typical feature of tomograms used for this application is that they are vertically stretched for better readability. It is acceptable since the axial resolution is usually significantly higher.
OCT cross section over subsurface structures of an early nineteenth-century oil painting on canvas “Portrait of Sir John Wylie” by F. Franck. Tomograms (A, original structure of paint layers; B, restored structure at right) are corrected for refraction; thus, scale bars show geometrical distances, and false color intensity scale is used. Upper panels, from the left: a photo of the paintings with two spots (12 × 12 mm2) of examination marked as A and B, images from the OCT annotation camera with areas of OCT scanning clearly marked. Below: exemplary tomograms and surface profiles rendered for OCT data with exact locations of OCT scans marked green. Tomograms and surface profiles are vertically stretched for better readability. Structures resolved: 1, three layers of varnish; 2, glaze layer; 3, loss in the varnish layer; 4, semitransparent paint layer; 5, opaque paint layer; 6, retouching covered by thin varnish layer; 7, putty.
In Figure 2, two examples are shown: (A) with original structure of paint layer and some secondary varnish layers and (B) area with original structure (left) and after considerable restoration (right) which included filing a paint loss with putty and reconstruction of the paint layer. Under surface of the painting, three varnish layers are seen and below, locally, a glaze layer. The last visible structure is always an opaque paint layer. If its absorption of OCT probing light is not extremely high, some multiscattering events within this layer occur, and fading tails of the signal are visible below the surface of paint (marked 5 and 7 in Figure 2).
Since OCT utilizes light to probe the object, it is possible to examine structures normally not accessible for inspection. As for the application to objects of art, it is often the case of reverse paintings on glass (la peinture sur verre inversé, Hinterglasmalerei) technique popular in Europe, especially favored since the middle of the eighteenth century. Later, in the nineteenth century, it has become popular in folk art, especially in Central Europe. The picture is painted on glass and intended to be viewed through it. Glass serves both as the support and the protection of the paint, which makes this technique suitable for items designed for continuous use, such as decorations of craftwork, miniatures, devotional items, etc. The major disadvantage inherent for this painting technique is an overtime decrease of adhesion of the paint layer to glass, causing delamination. Ironically, the protecting glass complicates significantly the conservation treatments since the paint layer is not accessible from the front and very often also from the back.
OCT provides in this case a convenient method for examination of the state of preservation of the object. The application to folk art was reported already [47]; here it is demonstrated for the miniature from the collection of the National Museum in Krakow, Poland (Figure 3). The tomogram was collected through the covering glass, and thus, its upper surface is not visible since it lies beyond the imaging range of the tomograph. Therefore, the first visible line from the top is a bottom surface of glass. Below, partially attached to the support, the paint layer is evident. The gap between glass and paint may be directly measured at the tomogram and in this case varies 0.19–0.26 mm for one flake and reaches even 0.5 mm for the other one. Additionally, some traces of further delamination (marked by white arrow) are discernible. It may be interpreted as an evidence of a progressing process of destruction.
Through glass OCT examination of the miniature from the collection of the National Museum in Krakow (MNK III-min 933), 5.2 × 6.3 cm2, reverse paintings on glass. Tomogram is not corrected for refraction; scale bars represent 200 μm in both directions. White arrow points to the early delamination of paint. Photos: Karol Kowalik, Photographic Laboratory of National Museum in Krakow, PL. Bottom right. An IR reflectogram generated from OCT data by integration over A-scans with exact localization of the tomogram.
Varnish removal is one of the most often performed restoration treatments. Despite the fact that according to the contemporary approach to conservation/restoration of artworks, interventions should be as minimal as possible, and removal of past varnishes is a commonly accepted practice. Most common reasons for this include yellowing of varnish changing the esthetic perception of the colors of the underlying paint as well as loss of varnish transparency due to its blanching, cracking, or delaminations. The action must be taken with caution so as not to damage the paint layer underneath. In particular, if most common chemical removal is planned, a proper solvent and means of use (through controlled swabbing or gel application) must be determined.
The ability of OCT to visualize varnish layers makes it a convenient tool to monitor a varnish removal with chemical treatment and/or laser ablation qualitatively [36, 37] and quantitatively [33, 39, 40]. An application of OCT for quantitative assessment of varnish removal by swabbing is experimentally challenging because it is difficult to avoid micro-displacements of the object between sequential measurements caused by the contact with a cotton swab. The amount of material removed in one step of swabbing (or other cleaning process, e.g., laser ablation) is measured by subtraction of two surface profiles, obtained before and after treatment. However, the result will be reliable only if the position of the object in 3D space before and after is the same with a micrometer precision. As it was mentioned earlier, it is usually not possible to mechanically maintain the position of the object with the required accuracy (especially in case of paintings on canvas). Therefore, one of OCT data set must be numerically shifted in all three dimensions to achieve desired correlation of surface profiles. If the cleaning spot is significantly smaller than the area covered by OCT 3D scan, the solution is quite simple: the requested shifts may be obtained by correlating the non-treated edges of the scanned area which—in this case—will be exactly the same [33]. If, however, for any reason, the surface of the whole scanned area was altered, another procedure must be applied. In order to determine the amount of the removed material, only surface profiles obtained from OCT data are needed. However, for the proper correlation of data cubes, the inner structure—obviously not altered by the treatment—must be used. In this case it is the surface of the opaque paint layer, well visible at the tomograms. To use it as a reference, however, the tomograms must be corrected for refraction: a thickness of varnish above is by definition different, and thus, the refraction deformation is different as well, and thus, correlation of images would be systematically wrong without such a correction.
In Figure 4 the entire procedure is illustrated on the example of a multistep test of secondary varnish removal from a panel painting. In this case, the solvent treatment by means of swabbing was chosen. In every step a cotton swab with solvent was rolled over the surface of the painting once. The aim of the test was to determine a safe amount of rolls which will not affect a paint layer and assay the homogeneity of the treatment. Before the test and after each of 13 cleaning steps, a 3D OCT scan was performed over an area of 10 × 10 mm2 by collection of 100 tomograms composed of 3000 A-scans each. Exemplary tomograms, chosen only for presentation in this account, are shown for all steps in Video 1 available from
Varnish removal monitoring by OCT; (a) superimposed OCT tomograms collected before (red) and after (blue) the 13th step of cleaning process, white dots represent pixels common in both tomograms, data not correlated, both tomograms corrected for refraction; (b) same but after correlation of the paint layer (ΔX = −30, ΔZ = −13 pixels); (c) surface profile before cleaning; (d) surface profile after cleaning; (e) photo from the OCT annotation camera taken after cleaning; (f) map of the varnish deficit after cleaning, red, area for averaging of varnish deficit; (g) average varnish thickness removed in consecutive steps.
Inspection of results obtained with OCT from this test permits to draw certain conclusions important for planning of the prospective restoration. Firstly, the varnish removal is not homogenous: after 13 steps it is almost completely removed from most protruding areas at the raised edges of paint layer along craquelure (fully covered by varnish before treatment), whereas it remains in about ½ of it its original thickness in recesses. Surprisingly, as it can be clearly seen from Figure 4, the mechanical action (during swabbing) has less impact in the raised areas along the craquelure than in the recesses. Apparently, the varnish is less soluble over the craquelure than in between. What is more, the analysis of Figure 4g leads to the conclusion that there is a critical range in the process around the eighth step, when it develops very quickly and the thickness of the varnish decreases rapidly. This is due to the phenomenon of swelling of varnish. Knowing at which point in the cleaning process this rapid leap in the varnish removal rate occurs aids the conservator-restorer to control the process with caution. In the case of the painting presented here, the varnish removal rate decreased in the last four steps of the OCT-monitored cleaning test. The reason for this is uncertain, one may hypothesize that the bottom varnish layers were less soluble since they were the oldest ones.
Such monitoring of the dynamic of varnish removal with OCT, even if performer locally, can then be utilized by the restorer to safely clean the whole painting, now without OCT assistance.
OCT has been used to study works of art for the last 15 years. During this time, a set of applications was developed, related to the study of the structure of the artwork, especially as a supporting tool for preventive conservation and restoration. The ability of OCT to inspect superficial layers like varnishes, glazes, and overpaintings—just to use examination of easel paining as an example—makes it especially efficient in tracing former restorations and detecting surface-related damages such as cracks, delaminations, lead soap formations, etc. In many cases, especially for most valuable artworks as well as the ones in a good state of preservation without visible losses, traditional method of investigation of the structure of an object of art by taking samples of the material is not permitted. Due to its noninvasiveness, OCT is in this case the only technique capable of visualization of the subsurface structures of works of art with desirable resolution and contrast. The OCT examination is also fast and possible to be carried out in a place where the objects are stored or displayed. This last remark is, as it is clear from the experience of the authors, very important, because in the focus of all the curators of collections is the safety of objects and their preservation for future generations. There is no doubt that optical coherence tomography contributes to this goal.
This research has been cofinanced by H2020 IPERION CH project (contract number: 654028) and conducted with the partial use of the research infrastructure of the Interdisciplinary Centre for Modern Technology of Nicolaus Copernicus University in Toruń, Poland, and financed by the Regional Operational Programme for Kujawsko-Pomorskie Voivodeship (Project No. RPKP.05.04.00-04-001/10). Results shown in Figure 3 are obtained in cooperation with the National Museum in Krakow in the framework of the offer of the Polish Research Consortium for Heritage Science E-RIHS.PL (project leader: Zofia Maniakowska-Jazownik). A valuable contribution of Ms. Hélène Dubois from KIK-IRPA, Brussels, to conducting a cleaning test is gratefully acknowledged.
The authors declare no conflict of interest.
The endothelial cells (ECs) have mesenchymal origin, length of 25–50 μm and form a flat epithelium called endothelium. The endothelium in a human adult is composed of approximately 1–6 × 1013 cells, constituting an organ that weighs approximately 1 kg and covers a surface area of approximately 1–7 m2 [1]. For decades, the endothelium was considered as a simple barrier between blood and the rest of the body’s tissues. However, since the early 1980s, this vision changed radically [2] and, today, the endothelium is considered a true organ that fulfills multiple functions in the physiology and pathophysiology of vascular system, including autocrine, paracrine, and endocrine actions and the regulation of coagulation and fibrinolysis processes [3].
\nOne of the most important functions of endothelial cells is their participation in the regulation of vascular tone. In the classic article of Furchgott and Zawadzki in 1980, it was demonstrated that the presence of the endothelium is essential for the vasodilator effect induced by acetylcholine in isolated blood vessels pre-constricted with norepinephrine. In those years, it was proposed that the vasodilation was produced through a factor that was released by the endothelium in response to agonists [4]. This factor was called the endothelial-derived relaxing factor (EDRF) [5]. Between 1986 and 1990, it was concluded that this factor corresponded to nitric oxide (NO) [6, 7]. The endothelium responds to mechanical stimuli such as pressure and flow stress (“shear stress”), hormonal stimuli, and vasoactive substances that regulate the vascular tone. The endothelial cells release molecules that regulate vasomotor function, inflammation, and hemostasis. Vasodilators agents include NO, prostacyclin, and endothelium-derived hyperpolarizing factor (EDHF). Vasoconstrictors agents include endothelin 1, angiotensin II, thromboxane A2, and reactive oxygen-derived species (ROS). Inflammatory mediators include NO, intercellular adhesion molecule 1 (ICAM-1), vascular adhesion molecule 1 (VCAM-1), E-selectin, and NFκB (Figure 1 [8]).
\nVascular tone regulation. The vascular tone is partially regulated by the local factors secreted by endothelial cells (ECs) in response to physical factors like shear stress and humoral and chemical factors like hormones and oxygen levels. The changes in blood flow are detected by membrane proteins, mainly receptors (Rs), transporters (Ts), and ion channels (ICs). There is a network connecting the activities of these proteins through signaling pathways that induce the release of different mediators like thromboxane A2 (TxA2), endothelin 1, reactive oxygen species (ROS), nitric oxide (NO), endothelium-derived hyperpolarizing factor (EDHF), or prostacyclin (PGI2), among others. The equilibrium between the vasoconstrictors and vasodilators factors maintains the endothelial function and vascular health.
Since the discovery of NO, the mechanisms of endothelial cell activation and endothelial dysfunction have been studied. In this way, the quiescent endothelial cells express a vasodilator, anticoagulant, and anti-adhesive phenotype, while the activated endothelial cell expresses procoagulant, pro-adhesive, and vasoconstrictive properties [9]. It has been considered that the decrease in the capacity of the vascular endothelium to stimulate vasodilation generates endothelial dysfunction, a phenomenon that is observed in several pathological conditions such as hypertension, hypercholesterolemia, diabetes mellitus, hyperhomocysteinemia, chronic kidney failure, chronic heart failure, etc. Although the molecular basis for endothelial dysfunction is not fully understood, numerous studies point to decreased biosynthesis and/or NO activity as a central mechanism [10, 11, 12, 13].
\nNO is synthesized from the semi-essential cationic amino acid L-arginine, which must be transported from the extracellular space into the endothelial cell by a family of cationic amino acid transporters (CATs) [14]. This amino acid is the substrate in a reaction where the metabolic product corresponds to L-citrulline in an equimolar proportion with the coproduct NO [15, 16]. This reaction is catalyzed by the enzyme NO synthase (NOS), which can be classified into their constitutive forms (cNOS) and their inducible form (iNOS) [17]. The cNOS includes the endothelial isoform (eNOS) and the neuronal isoform (nNOS), both producing NO in short bursts at low concentrations (nM) and in a calcium-dependent manner to fulfill the physiological functions of NO. The physiological activity of eNOS is dependent on several cofactors and is regulated by signaling pathways that induce phosphorylation in different sites for activation (serine 1177) or inhibition (threonine 495) [17]. NO diffuses from endothelial cells to smooth muscle cells (SMCs) and activates the soluble guanylate cyclase (sGC) pathway, to reduce the intracellular calcium and induce vasodilation (Figure 2). iNOS is mainly expressed in cells that participate in the inflammatory response after induction by cytokines and other inflammatory mediators, producing NO in high concentrations (μM) and independently of calcium [18, 19, 20].
\nL-arginine transport and nitric oxide synthesis in endothelial cells. hCAT-1 is a protein expressed in plasma membrane of endothelial cells, mainly in plasma membrane invagination called caveolae. The L-arginine enters to the cell from blood and is used by eNOS to synthesize L-citrulline and nitric oxide (NO). The eNOS needs different cofactors to maintain its function, which include tetrahydrobiopterin (BH4), nicotidamine adenine dinuclotide phosphate (NADPH), and heat shock protein 90 (Hsp90). Nitric oxide diffuses through the cell membranes and enters the smooth muscle cells to activate the soluble guanlylate cyclase (sGC). The sGC synthesizes cyclic GMP (cGMP), which activates protein kinase G and, after subsequent steps, the intracellular calcium decreases to induce the vasodilation.
The availability of NO in vivo is regulated by a combination of NO synthesis and inactivation. The decrease in the availability of NO may be due to a lower expression or activity of eNOS, as a result of the action of endogenous and exogenous inhibitors or due to the lower availability of the substrate L-arginine [8, 14]. The availability of NO can also be diminished by the rapid reaction between NO and reactive oxygen-derived species (ROS) [13].
\nEndothelial cells generate ROS, including the superoxide radical (O2\n.−), hydrogen peroxide (H2O2), peroxynitrite (ONOO−), hydroxyl radical (.OH), among others [15, 16]. In endothelial cells, the main sources of ROS are the enzymatic complex xanthine oxidoreductase (XOR) [17], the complex of membrane nicotinamide adenine dinucleotide phosphate oxidase (NADPH oxidase) [18], eNOS itself when it is “uncoupled” due to lack of tetrahydrobiopterin (BH4) or L-arginine [19], mitochondrial cytochromes [20], and hemoglobin [21].
\nAmong all endothelial ROS sources, NADPH oxidases are enzymes whose primary function is the generation of ROS and they play an important role in redox signaling [22]. On the other hand, the activity of NADPH oxidase can cause the uncoupling of eNOS by the oxidative degradation of BH4, leading to the eNOS-dependent synthesis of O2\n·− and detriment of the synthesis of NO [18, 23]. Once O2\n·− is synthesized, it can act as a precursor to other ROS due to its use by superoxide dismutase (SOD) to generate H2O2 that has greater stability and capacity to cross biological membranes, and it therefore can act as a modulator of signal transduction pathways [24]. Furthermore, O2\n·− reacts quickly with NO to generate ONOO−, a powerful oxidizing agent that causes DNA fragmentation and lipid oxidation [25].
\nIt is currently postulated that the mechanism by which O2\n·− “kidnaps” NO would play a central role in the development of endothelial dysfunction that is seen in pathologies such as diabetes mellitus [26, 27, 28], preeclampsia [29, 30], and hypertension [31].
\nThe amino acid L-arginine is taken up by endothelial cells through the transporter systems y+, y+L, b0,+, and y B0,+ [32, 33, 34, 35]. Of these systems, there are two that have been described in HUVEC, that is, y+ system [36, 37, 38] and y+L system [39]. The y+ system family is currently known to include at least five cationic amino acid transporters (CATs) called CAT-1, CAT-2A, CAT-2B, CAT-3, and CAT-4. CAT-1 is expressed ubiquitously, CAT-2A and CAT-3 are constitutively expressed in liver and brain, respectively, while CAT-2B is induced in a variety of cell types in response to bacterial endotoxins and pro-inflammatory cytokines [40, 41]. CAT-4 corresponds to a cDNA sequence with 41–42% identity with the other members of the CATs family, but its transport activity has not yet been determined [32, 34, 35]. CAT-1, CAT-2B, and CAT-3 are characterized by high affinity to the substrate (K\nm = 100–400 μM) and independency of Na+, while CAT-2A has low affinity for cationic amino acids (K\nm = 2–5 mM). Two members of CATs have been reported to be expressed in HUVEC, that is, hCAT-1 and hCAT-2B, while hCAT-2A and hCAT-3 transporters have not been detected in this cell type [34, 36, 37, 38, 39] (Table 1). Although the hCAT-1 and hCAT-2B transporters have similar kinetic characteristics, it is possible to differentiate them by their different sensitivities to L-lysine trans-stimulation. In Xenopus laevis oocytes injected with hCAT-1 and hCAT-2B mRNA, L-lysine increases L-arginine transport by 9.8-fold and 1.8-fold, respectively [42]. Thus, for L-lysine trans-stimulation assays in HUVEC, it has been possible to determine that the hCAT-1 transporter accounts for 60–80% of the total uptake of L-arginine in physiological conditions [36, 37, 38]. The importance of the hCAT-1 transporter in NO synthesis has been confirmed through a transgenic mouse model that overexpresses the protein exclusively in the endothelium. Aortic rings obtained from these transgenic mice have a higher sensitivity to relaxation in response to acetylcholine compared to native mice, while endothelial cell cultures obtained from these animals, that overexpress hCAT-1, exhibit a greater NO synthesis [43].
\n\nGene | \nProtein | \n\nK\nm (μM) | \nDistribution | \n
---|---|---|---|
\nSLC7A1\n | \nCAT-1 | \n70–250 | \nAll tissues except liver and lacrimal gland | \n
\nSLC7A2\n | \nCAT-2A | \n2.2–5.2 | \nLiver, skeletal muscle, and pancreas | \n
\nSLC7A2\n | \nCAT-2B | \n38–380 | \nEndothelium, and inducible in several tissues | \n
\nSLC7A3\n | \nCAT-3 | \n40–120 | \nThymus, ovary, testes, and brain | \n
\nSLC7A4\n | \nCAT-4 | \n— | \nBrain, testes, and placenta | \n
CATs’ family members.
Proteins CATs are coded in different genes (except CAT2A and 2B, same gene), have different kinetic constants for the transport of L-arginine (K\nm) and distribution in tissues.
Regarding the gene organization of CAT transporters, it is known that the SLC7 family is phylogenetically composed of two subfamilies formed by cationic amino acid transporters (CATs) and glycoprotein-associated amino acid transporters (HATs). The cationic amino acid transporter family is encoded by the SLC7A (1–4) genes and corresponds to proteins with 14 transmembrane domains [44]. Specifically, the gene that encodes the hCAT-1 protein corresponds to SLC7A1 whose open reading frame is formed by 11 exons and 10 introns. The gene is located on chromosome 13q12-13q14 [45].
\nAmong the genes encoding CAT-1 in rat, mouse and human have common characteristics: the promoter region lacks TATA box, and they have multiple binding sites for the transcription factor specific protein 1 (Sp1) and they have an extensive 3′ non-translatable region (3′UTR) that could perform functions in the regulation of mRNA stability or in translation [46, 47, 48, 49]. In rats, stress by amino acids deprivation induces an increase in the rCAT-1 mRNA expression by a mechanism related to increased mRNA stability [46]. This increased mRNA stability would be related to the presence of a regulatory region within the 3′UTR sequence of the gene [47]. Subsequent experiments have shown that the effect of amino acids deprivation on rCAT-1 expression would depend on both transcriptional [48] and posttranscriptional mechanisms [50].
\nIn humans, it is known that insulin increases leg blood flow in healthy subjects via stimulation of endothelial NO synthase (eNOS) [51]. Insulin also increases the synthesis and release of NO and release in primary cultures of HUVEC [38, 52]. Biological effects of insulin involve activation of several transcription factors, including Sp1 in several cell types [53, 54]. Insulin increases Sp1 nuclear protein abundance and its binding to a proximal region (−177 and −105 bp from ATG) of the SLC7A1 promoter containing four consensus sequences for Sp1 [55]. Interestingly, in patients with essential hypertension, a reduction of SLC7A1 transcriptional activity due to reduced Sp1 activity in the promoter region has been reported [12]. So, the transcriptional regulation of SLC7A1 is relevant for cardiovascular physiology, and the reduction of the promoter activity of this gene could be associated with cardiovascular disease (CVD).
\nOn the other hand, the first intron of SLC7A1 may play a bifunctional role in regulating the SLC7A1 transcriptional activity by the binding of the purine-rich element binding protein A (Pur alpha) in physiological conditions and by activating the transcription factor 4 (ATF4) in endoplasmic reticulum stress or by decreasing the SLC7A1 transcriptional activity by the C/EBP homologous protein 10 (CHOP) binding in C6 rat glioma cells [56].
\nFor the physiological regulation of hCAT-1 activity, both transcriptional regulation of SLC7A1 and/or posttranscriptional regulation of SLC7A1 transcript are relevant for the protein expression and L-arginine transport [55]. Insulin increases the expression of SLC7A1 gene due to an increased transcriptional activity, most likely due to higher Sp1 activity. So, hCAT-1 expression and activity are regulated by insulin in endothelium, suggesting that in insulin resistance there is a reduction of L-arginine transport and NO synthesis that contributes to endothelial dysfunction and cardiovascular diseases.
\nHyperglycemia and diabetes mellitus are pathological conditions associated with fetal endothelial dysfunction [55] and type 2 diabetes mellitus (T2DM) [57] or cardiovascular disease (CVD) [58]. CVD in patients with diabetes mellitus is associated with the generation of ROS.
\nHigh concentration of D-glucose (25 mM) increases L-arginine transport and cGMP accumulation in endothelium in a similar manner to that observed in HUVEC from pregnancies with gestational diabetes [33, 59]. Increased L-arginine transport in response to incubation with high D-glucose has been related to increased mRNA levels for the hCAT-1 and eNOS activity in HUVEC [60]. In human aortic endothelial cells, prolonged incubation (7 days) with 25 mM D-glucose induces a decrease in eNOS activity (determined by nitrite content), protein abundance, and mRNA level. This effect is associated with a decrease in eNOS promoter activity [61]. In bovine aortic endothelial cells (BAECs), there is a lower production of insulin-induced NO when the cells were incubated with high extracellular concentration of D-glucose, an effect that seems to depend on a signaling pathway that involves to the type 1 insulin receptor (IR-1), phosphatidyl inositol 3 kinase, and the inhibitor of nuclear factor kappa-B kinase [62]. On the other hand, the increase of cGMP production induced by high D-glucose in HUVEC is blocked by incubating the cells with 1 nM insulin [63]. Incubation with 1 nM insulin (8 h) has been shown in this same cell type to be sufficient to block the effect that D-glucose has on the decreased transport of adenosine [64], an important vasoactive nucleoside [65].
\nIn HUVEC, high extracellular D-glucose increases L-arginine transport, NO synthesis, and O2\n.− generation through eNOS and NADPH oxidase activation. Additionally, high D-glucose increased the contractile response in the human umbilical vein. Insulin reversed these effects of high D-glucose, leading to normal hCAT-1 expression, NO synthesis, ROS generation, and vascular tone. Insulin acts like antioxidant molecules (like tempol, ascorbic acid) to restore high D-glucose-increased oxidative stress in the fetoplacental vascular bed [66]. High D-glucose increases L-arginine transport, likely resulting from higher hCAT-1 expression and protein abundance in the plasma membrane. This mechanism could be an adaptive response of HUVEC to higher ROS generation from high D-glucose-activated NADPH oxidase. In parallel, high D-glucose increased NO synthesis. Insulin reversed the high D-glucose-mediated alterations in L-arginine transport involving the modulation of SLC7A1 gene expression, leading to altered umbilical vein reactivity. Modulation of hCAT-1 expression and activity by insulin is the key to maintaining umbilical vein tone and endothelial function in physiologic and pathophysiological conditions (Figure 3) [66].
\nEndothelial dysfunction induced by high D-glucose and protection by insulin in HUVEC. Exposure of HUVEC to high D-glucose leads to an increase (↑) in the plasma membrane abundance of the human cationic amino acid transporter 1 (hCAT-1) and higher L-arginine uptake. High D-glucose activates NADPH oxidase, leading to higher generation of ROS, including O2\n.−. Insulin restores ROS and O2\n.− generation to values in cells exposed to 5 mM D-glucose (normal), resulting in the restoration of hCAT-1-mediated L-arginine transport and nitric oxide (NO) synthesis. High D-glucose and insulin also activate the SLC7A1 promoter region (coding for hCAT-1) up to −650 bp from the ATG via a mechanism involving ROS and O2\n.− generation. In addition, insulin restores hCAT-1 protein abundance and its distribution in the cells via an NADPH oxidase-independent mechanism (data from González et al. [66]).
Another important mechanism that regulates the endothelial function is the activity of ion channels that modulate the cell membrane potential. The calcium-activated potassium channels (KCa) have been shown to be relevant to induce the necessary hyperpolarization to stimulate the relaxation of vascular smooth muscle cells (related with EDHF). In systemic circulation, large conductance KCa (BKCa) channels have been shown preferentially expressed in VSMC, meanwhile small (SKCa) and intermediate (IKCa) conductance KCa are preferentially expressed in endothelium [67, 68]. However, potassium currents inhibited by iberiotoxin (BKCa inhibitor) have been described in HUVEC stimulated by sildenafil or insulin [69]. In fact, insulin (10 nM) can directly activate native and recombinant BKCa currents in cell-attached patch-clamping experiments with a rapid effect that is MAPK-dependent when the hormone was added in the pipette [70]. There is evidence that insulin may induce endothelial cell hyperpolarization by modulating K channels activity [38, 71]. The insulin-induced relaxation in human placental veins (~368 μm diameter), pre-constricted with U46619, is a mechanism dependent on the BKCa channel activity. The co-incubation of vessels with genistein (tyrosine kinases inhibitor) and wortmannin (PI3K inhibitor) did not block the insulin’s relaxation, and by contrast potentiated the insulin-induced vasodilation. Also, insulin decreased perfusion pressure (34 ± 3%) in the isolated cotyledon of normal placenta with a basal perfusion pressure of 64 ± 5 mmHg (or pre-constricted with U46619) [72]. The effects of insulin on BKCa activity are associated with evidences that show that the constriction induced by U46619 and H2O2 in placental vasculature is partially decreased with 10 nM insulin preincubation (10 min) in a mechanism totally dependent of BKCa activity [72]. Recently, it has been determined that insulin-mediated NO synthesis requires the participation of both IKCa/ BKCa channels and eNOS activity in HUVECs [71]. In the same cell type, insulin increased the open probability (NPo) of BKCa, associated with hyperpolarization in single cell analysis [69]. In human placental arteries, the relaxation induced by the NO donor, SNAP, is partially blocked by charybdotoxin (BKCa inhibitor) and almost totally blocked by charybdotoxin and ODQ (sGC inhibitor) [73]. Therefore, an extracellular stimulus that increases the NO availability activates a mechanism that involves sGC and BKCa activities [71]. These findings constitute evidence for postulating a new mechanism induced by insulin in human vasculature related with the physiological regulation of KCa activity for NO synthesis (Figure 4).
\nProposal of mechanism for KCa activation by insulin. Evidence obtained in endothelial cells (ECs) shows that insulin activates KCa (mainly BKCa) in a mechanism still not fully understood. The activation of KCa by insulin induces hyperpolarization (↑ΔV), leading to activation of eNOS for NO synthesis from L-arginine uptake by hCAT-1 (modified from Rojas et al. [71]).
The relevance of the endothelium for cardiovascular physiology is well established, mainly by findings related to the capacity of endothelial cells to synthesize NO and regulate the plasma membrane potential of smooth muscle cells. Figure 5 shows a graphical summary of the L-arginine/NO pathway in the human blood vessels that highlight the capacity of endothelial cells to respond to extracellular stimuli and translate the mechanical forces and endocrine signals to intracellular mechanisms leading to NO synthesis and activation of potassium channels. It is important to note that the subcellular distribution of hCAT-1 and eNOS is also relevant for endothelial cells function. In physiological state, hCAT-1 colocalizes with caveolin-1 in the plasma membrane caveolae in proximity to eNOS.
\nRole of endothelium in the regulation of vascular tone. Endothelial cells, as a part of blood vessels walls, respond to mechanical stress induced by flow (shear stress) by activation of L-arginine/NO pathway to induce the NO release and relaxation of smooth muscle cells (SMCs). Subcellular localization of hCAT-1 in caveolae is relevant for its function, and the role of potassium channels (BKCa, mainly) has been recently described as important for endothelial cells function. The activity of the endothelium is regulated by different agonists like acetylcholine (Ach) through plasma membrane receptor (AchR) and others like insulin or serotonin, etc.
The authors would like to acknowledge the staff at Laboratorio de Investigación Materno-Fetal (LIMaF) and Department of Obstetrics and Gynecology from the Universidad de Concepción. The authors express special thanks to Alexandra Elbakyan for support the open science.
\nAs a company committed to the wider dissemination of knowledge, IntechOpen supports the OAI Metadata Harvesting Protocol (OAI-PMH Version 2.0).
',metaTitle:"OAI-PMH",metaDescription:"As a firm believer in the wider dissemination of knowledge, IntechOpen supports the OAI Metadata Harvesting Protocol (OAI-PMH Version 2.0).",metaKeywords:null,canonicalURL:"/page/oai-pmh",contentRaw:'[{"type":"htmlEditorComponent","content":"The OAI-PMH (Open Archives Initiative Protocol for Metadata Harvesting) is used to govern the collection of metadata descriptions and enables other archives to access our database. The Protocol has been developed by the Open Archives Initiative, based on ensuring interoperability standards in order to ease and promote broader and more efficient dissemination of information within the scientific community.
\\n\\nWe have adopted the Protocol to increase the number of readers of our publications. All our Works are more widely accessible, with resulting benefits for scholars, researchers, students, libraries, universities and other academic institutions. Through this method of exposing metadata, IntechOpen enables citation indexes, scientific search engines, scholarly databases, and scientific literature collections to gather metadata from our repository and make our publications available to a broader academic audience.
\\n\\nAs a Data Provider, metadata for published Chapters and Journal Articles are available via our interface at the base URL:http://www.intechopen.com/oai/?.
\\n\\nREQUESTS
\\n\\nYou can find out more about the Protocol by visiting the Open Archives website. For additional questions please contact us at info@intechopen.com.
\\n\\nDATABASES
\\n\\nDatabases, repositories and search engines that provide services based on metadata harvested using the OAI metadata harvesting protocol include:
\\n\\nBASE - Bielefeld Academic Search Engine
\\n\\nOne of the world's most powerful search engines, used primarily for academic Open Access web resources.
\\n\\n\\n\\nA search engine for online catalogues of publications from all over the world.
\\n"}]'},components:[{type:"htmlEditorComponent",content:'The OAI-PMH (Open Archives Initiative Protocol for Metadata Harvesting) is used to govern the collection of metadata descriptions and enables other archives to access our database. The Protocol has been developed by the Open Archives Initiative, based on ensuring interoperability standards in order to ease and promote broader and more efficient dissemination of information within the scientific community.
\n\nWe have adopted the Protocol to increase the number of readers of our publications. All our Works are more widely accessible, with resulting benefits for scholars, researchers, students, libraries, universities and other academic institutions. Through this method of exposing metadata, IntechOpen enables citation indexes, scientific search engines, scholarly databases, and scientific literature collections to gather metadata from our repository and make our publications available to a broader academic audience.
\n\nAs a Data Provider, metadata for published Chapters and Journal Articles are available via our interface at the base URL:http://www.intechopen.com/oai/?.
\n\nREQUESTS
\n\nYou can find out more about the Protocol by visiting the Open Archives website. For additional questions please contact us at info@intechopen.com.
\n\nDATABASES
\n\nDatabases, repositories and search engines that provide services based on metadata harvested using the OAI metadata harvesting protocol include:
\n\nBASE - Bielefeld Academic Search Engine
\n\nOne of the world's most powerful search engines, used primarily for academic Open Access web resources.
\n\n\n\nA search engine for online catalogues of publications from all over the world.
\n'}]},successStories:{items:[]},authorsAndEditors:{filterParams:{sort:"featured,name"},profiles:[{id:"54719",title:"Prof.",name:"Hany",middleName:null,surname:"El-Shemy",slug:"hany-el-shemy",fullName:"Hany El-Shemy",position:null,profilePictureURL:"https://mts.intechopen.com/storage/users/54719/images/system/54719.jpg",biography:"Prof. Hany A. El-Shemy received his two PhD degrees in Biochemistry and Genetic Engineering from the University of Cairo, Egypt and University of Hiroshima, Japan. He became an assistant professor in the Biochemistry Department of Cairo University, Egypt, from Sept. 1996 and advanced to associate professor in Sept. 2002 as well as a full professor in March 2007. His research interests are in the fields of plant biotechnology and medicinal plants (Molecular Biology). He registered 2 patents, wrote 12 international books, published more than 90 SCI journal papers and 45 conference presentations, and served as the technique committee member as well as chair in many international conferences and the editor in BMC Genomics as well as in Current Issues in Molecular Biology, and also a reviewer for more than 25 SCI cited journals. He received several awards, including State Prize awarded from the Academy of Science, Egypt (2004); Young Arab Researcher Prize awarded from Schuman Foundation, Jordan (2005); State Excellence Prize from the Academy of Science, Egypt (2011 and 2018); and Cairo University Prizes (2007, 2010, and 2014). He served as an expert for African Regional Center for Technology, Dakar, Senegal, plus a visiting professor at Pan African University, African Union, Nairobi, Kenya. He was appointed acting vice president of the Academy of Science and Technology from November 2013 to November 2014, Egypt. He was also a dean of the Faculty of Agriculture, Cairo University from 2014 to 2017.",institutionString:"Cairo University",institution:{name:"Cairo University",country:{name:"Egypt"}}},{id:"93369",title:"Dr.",name:"Yves",middleName:null,surname:"Gibon",slug:"yves-gibon",fullName:"Yves Gibon",position:null,profilePictureURL:"//cdnintech.com/web/frontend/www/assets/author.svg",biography:null,institutionString:null,institution:{name:"Institut National de la Recherche Agronomique",country:{name:"Morocco"}}},{id:"105746",title:"Dr.",name:"A.W.M.M.",middleName:null,surname:"Koopman-van Gemert",slug:"a.w.m.m.-koopman-van-gemert",fullName:"A.W.M.M. Koopman-van Gemert",position:null,profilePictureURL:"https://mts.intechopen.com/storage/users/105746/images/5803_n.jpg",biography:"Dr. Anna Wilhelmina Margaretha Maria Koopman-van Gemert MD, PhD, became anaesthesiologist-intensivist from the Radboud University Nijmegen (the Netherlands) in 1987. She worked for a couple of years also as a blood bank director in Nijmegen and introduced in the Netherlands the Cell Saver and blood transfusion alternatives. She performed research in perioperative autotransfusion and obtained the degree of PhD in 1993 publishing Peri-operative autotransfusion by means of a blood cell separator.\nBlood transfusion had her special interest being the president of the Haemovigilance Chamber TRIP and performing several tasks in local and national blood bank and anticoagulant-blood transfusion guidelines committees. Currently, she is working as an associate professor and up till recently was the dean at the Albert Schweitzer Hospital Dordrecht. She performed (inter)national tasks as vice-president of the Concilium Anaesthesia and related committees. \nShe performed research in several fields, with over 100 publications in (inter)national journals and numerous papers on scientific conferences. \nShe received several awards and is a member of Honour of the Dutch Society of Anaesthesia.",institutionString:null,institution:{name:"Albert Schweitzer Hospital",country:{name:"Gabon"}}},{id:"83089",title:"Prof.",name:"Aaron",middleName:null,surname:"Ojule",slug:"aaron-ojule",fullName:"Aaron Ojule",position:null,profilePictureURL:"//cdnintech.com/web/frontend/www/assets/author.svg",biography:null,institutionString:null,institution:{name:"University of Port Harcourt",country:{name:"Nigeria"}}},{id:"295748",title:"Mr.",name:"Abayomi",middleName:null,surname:"Modupe",slug:"abayomi-modupe",fullName:"Abayomi Modupe",position:null,profilePictureURL:"https://mts.intechopen.com/storage/users/no_image.jpg",biography:null,institutionString:null,institution:{name:"Landmark University",country:{name:"Nigeria"}}},{id:"94191",title:"Prof.",name:"Abbas",middleName:null,surname:"Moustafa",slug:"abbas-moustafa",fullName:"Abbas Moustafa",position:null,profilePictureURL:"https://mts.intechopen.com/storage/users/94191/images/96_n.jpg",biography:"Prof. Moustafa got his doctoral degree in earthquake engineering and structural safety from Indian Institute of Science in 2002. He is currently an associate professor at Department of Civil Engineering, Minia University, Egypt and the chairman of Department of Civil Engineering, High Institute of Engineering and Technology, Giza, Egypt. He is also a consultant engineer and head of structural group at Hamza Associates, Giza, Egypt. Dr. Moustafa was a senior research associate at Vanderbilt University and a JSPS fellow at Kyoto and Nagasaki Universities. He has more than 40 research papers published in international journals and conferences. He acts as an editorial board member and a reviewer for several regional and international journals. His research interest includes earthquake engineering, seismic design, nonlinear dynamics, random vibration, structural reliability, structural health monitoring and uncertainty modeling.",institutionString:null,institution:{name:"Minia University",country:{name:"Egypt"}}},{id:"84562",title:"Dr.",name:"Abbyssinia",middleName:null,surname:"Mushunje",slug:"abbyssinia-mushunje",fullName:"Abbyssinia Mushunje",position:null,profilePictureURL:"//cdnintech.com/web/frontend/www/assets/author.svg",biography:null,institutionString:null,institution:{name:"University of Fort Hare",country:{name:"South Africa"}}},{id:"202206",title:"Associate Prof.",name:"Abd Elmoniem",middleName:"Ahmed",surname:"Elzain",slug:"abd-elmoniem-elzain",fullName:"Abd Elmoniem Elzain",position:null,profilePictureURL:"//cdnintech.com/web/frontend/www/assets/author.svg",biography:null,institutionString:null,institution:{name:"Kassala University",country:{name:"Sudan"}}},{id:"98127",title:"Dr.",name:"Abdallah",middleName:null,surname:"Handoura",slug:"abdallah-handoura",fullName:"Abdallah Handoura",position:null,profilePictureURL:"//cdnintech.com/web/frontend/www/assets/author.svg",biography:null,institutionString:null,institution:{name:"École Supérieure des Télécommunications",country:{name:"Morocco"}}},{id:"91404",title:"Prof.",name:"Abdecharif",middleName:null,surname:"Boumaza",slug:"abdecharif-boumaza",fullName:"Abdecharif Boumaza",position:null,profilePictureURL:"//cdnintech.com/web/frontend/www/assets/author.svg",biography:null,institutionString:null,institution:{name:"Abbès Laghrour University of Khenchela",country:{name:"Algeria"}}},{id:"105795",title:"Prof.",name:"Abdel Ghani",middleName:null,surname:"Aissaoui",slug:"abdel-ghani-aissaoui",fullName:"Abdel Ghani Aissaoui",position:null,profilePictureURL:"https://mts.intechopen.com/storage/users/105795/images/system/105795.jpeg",biography:"Abdel Ghani AISSAOUI is a Full Professor of electrical engineering at University of Bechar (ALGERIA). He was born in 1969 in Naama, Algeria. He received his BS degree in 1993, the MS degree in 1997, the PhD degree in 2007 from the Electrical Engineering Institute of Djilali Liabes University of Sidi Bel Abbes (ALGERIA). He is an active member of IRECOM (Interaction Réseaux Electriques - COnvertisseurs Machines) Laboratory and IEEE senior member. He is an editor member for many international journals (IJET, RSE, MER, IJECE, etc.), he serves as a reviewer in international journals (IJAC, ECPS, COMPEL, etc.). He serves as member in technical committee (TPC) and reviewer in international conferences (CHUSER 2011, SHUSER 2012, PECON 2012, SAI 2013, SCSE2013, SDM2014, SEB2014, PEMC2014, PEAM2014, SEB (2014, 2015), ICRERA (2015, 2016, 2017, 2018,-2019), etc.). His current research interest includes power electronics, control of electrical machines, artificial intelligence and Renewable energies.",institutionString:"University of Béchar",institution:{name:"University of Béchar",country:{name:"Algeria"}}},{id:"99749",title:"Dr.",name:"Abdel Hafid",middleName:null,surname:"Essadki",slug:"abdel-hafid-essadki",fullName:"Abdel Hafid Essadki",position:null,profilePictureURL:"//cdnintech.com/web/frontend/www/assets/author.svg",biography:null,institutionString:null,institution:{name:"École Nationale Supérieure de Technologie",country:{name:"Algeria"}}}],filtersByRegion:[{group:"region",caption:"North America",value:1,count:5706},{group:"region",caption:"Middle and South America",value:2,count:5174},{group:"region",caption:"Africa",value:3,count:1690},{group:"region",caption:"Asia",value:4,count:10249},{group:"region",caption:"Australia and Oceania",value:5,count:889},{group:"region",caption:"Europe",value:6,count:15658}],offset:12,limit:12,total:1696},chapterEmbeded:{data:{}},editorApplication:{success:null,errors:{}},ofsBooks:{filterParams:{hasNoEditors:"0",sort:"dateEndThirdStepPublish"},books:[{type:"book",id:"10547",title:"Physiology and Disorders of Adipose Tissue",subtitle:null,isOpenForSubmission:!0,hash:"b423df09d9aaf08881b015f129af27d0",slug:null,bookSignature:"Dr. Hassan M. Heshmati",coverURL:"https://cdn.intechopen.com/books/images_new/10547.jpg",editedByType:null,editors:[{id:"313921",title:"Dr.",name:"Hassan M.",surname:"Heshmati",slug:"hassan-m.-heshmati",fullName:"Hassan M. Heshmati"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"10581",title:"Alkaline Chemistry and Applications",subtitle:null,isOpenForSubmission:!0,hash:"4ed90bdab4a7211c13cd432aa079cd20",slug:null,bookSignature:"Dr. Riadh Marzouki",coverURL:"https://cdn.intechopen.com/books/images_new/10581.jpg",editedByType:null,editors:[{id:"300527",title:"Dr.",name:"Riadh",surname:"Marzouki",slug:"riadh-marzouki",fullName:"Riadh Marzouki"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"10238",title:"Food Packaging",subtitle:null,isOpenForSubmission:!0,hash:"891ee7ffd87b72cf155fcdf9c8ae5d1a",slug:null,bookSignature:"Dr. Norizah Mhd Sarbon",coverURL:"https://cdn.intechopen.com/books/images_new/10238.jpg",editedByType:null,editors:[{id:"246000",title:"Dr.",name:"Norizah",surname:"Mhd Sarbon",slug:"norizah-mhd-sarbon",fullName:"Norizah Mhd Sarbon"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"10374",title:"Advances in Micro- and Nanofluidics",subtitle:null,isOpenForSubmission:!0,hash:"b7ba9cab862a9bca2fc9f9ee72ba5eec",slug:null,bookSignature:"Prof. S. M. Sohel Murshed",coverURL:"https://cdn.intechopen.com/books/images_new/10374.jpg",editedByType:null,editors:[{id:"24904",title:"Prof.",name:"S. M. Sohel",surname:"Murshed",slug:"s.-m.-sohel-murshed",fullName:"S. M. Sohel Murshed"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"7724",title:"Climate Issues in Asia and Africa - Examining Climate, Its Flux, the Consequences, and Society's Responses",subtitle:null,isOpenForSubmission:!0,hash:"c1bd1a5a4dba07b95a5ae5ef0ecf9f74",slug:null,bookSignature:" John P. Tiefenbacher",coverURL:"https://cdn.intechopen.com/books/images_new/7724.jpg",editedByType:null,editors:[{id:"73876",title:"Dr.",name:"John P.",surname:"Tiefenbacher",slug:"john-p.-tiefenbacher",fullName:"John P. Tiefenbacher"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"10358",title:"Silage - Recent Advances and New Perspectives",subtitle:null,isOpenForSubmission:!0,hash:"1e33f63e9311af352daf51d49f0a3aef",slug:null,bookSignature:"Dr. Juliana Oliveira and Dr. Edson Mauro Santos",coverURL:"https://cdn.intechopen.com/books/images_new/10358.jpg",editedByType:null,editors:[{id:"180036",title:"Dr.",name:"Juliana",surname:"Oliveira",slug:"juliana-oliveira",fullName:"Juliana Oliveira"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"9723",title:"Ciliates",subtitle:null,isOpenForSubmission:!0,hash:"7f7a6dc8b1229c1fd5839577497c6a79",slug:null,bookSignature:"Dr. Rosaura Mayén Estrada and Dr. Roberto Junio Pedroso Dias",coverURL:"https://cdn.intechopen.com/books/images_new/9723.jpg",editedByType:null,editors:[{id:"331546",title:"Dr.",name:"Rosaura",surname:"Mayén Estrada",slug:"rosaura-mayen-estrada",fullName:"Rosaura Mayén Estrada"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"10471",title:"Advances in Dynamical Systems Theory, Models, Algorithms and Applications",subtitle:null,isOpenForSubmission:!0,hash:"689fdf3cdc78ade03f0c43a245dcf818",slug:null,bookSignature:"Dr. Bruno Carpentieri",coverURL:"https://cdn.intechopen.com/books/images_new/10471.jpg",editedByType:null,editors:[{id:"92921",title:"Dr.",name:"Bruno",surname:"Carpentieri",slug:"bruno-carpentieri",fullName:"Bruno Carpentieri"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"10342",title:"Ovarian Cancer - Updates in Tumour Biology and Therapeutics",subtitle:null,isOpenForSubmission:!0,hash:"25a0adac7f6afa7bcd0b6daa3ef6b538",slug:null,bookSignature:"Dr. Gwo Yaw Ho and Dr. Kate Webber",coverURL:"https://cdn.intechopen.com/books/images_new/10342.jpg",editedByType:null,editors:[{id:"297757",title:"Dr.",name:"Gwo Yaw",surname:"Ho",slug:"gwo-yaw-ho",fullName:"Gwo Yaw Ho"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"10494",title:"Erythrocyte - a Peripheral Biomarker for Viral and Bacterial Infections",subtitle:null,isOpenForSubmission:!0,hash:"fa5f4b6ef59e28b6e7c1a739c57c5d2f",slug:null,bookSignature:"Prof. Kaneez Fatima Shad",coverURL:"https://cdn.intechopen.com/books/images_new/10494.jpg",editedByType:null,editors:[{id:"31988",title:"Prof.",name:"Kaneez",surname:"Fatima Shad",slug:"kaneez-fatima-shad",fullName:"Kaneez Fatima Shad"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"10352",title:"Abdominal Surgery",subtitle:null,isOpenForSubmission:!0,hash:"0d1d92b2286b03cf2fd8d88368d9d9cb",slug:null,bookSignature:"Dr. Ahmad Zaghal and Dr. arwa El Rifai",coverURL:"https://cdn.intechopen.com/books/images_new/10352.jpg",editedByType:null,editors:[{id:"240621",title:"Dr.",name:"Ahmad",surname:"Zaghal",slug:"ahmad-zaghal",fullName:"Ahmad Zaghal"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"10597",title:"Electric Grid Modernization",subtitle:null,isOpenForSubmission:!0,hash:"62f0e391662f7e8ae35a6bea2e77accf",slug:null,bookSignature:"Dr. Mahmoud Ghofrani",coverURL:"https://cdn.intechopen.com/books/images_new/10597.jpg",editedByType:null,editors:[{id:"183482",title:"Dr.",name:"Mahmoud",surname:"Ghofrani",slug:"mahmoud-ghofrani",fullName:"Mahmoud Ghofrani"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}}],filtersByTopic:[{group:"topic",caption:"Agricultural and Biological Sciences",value:5,count:11},{group:"topic",caption:"Biochemistry, Genetics and Molecular Biology",value:6,count:14},{group:"topic",caption:"Business, Management and Economics",value:7,count:2},{group:"topic",caption:"Chemistry",value:8,count:7},{group:"topic",caption:"Computer and Information Science",value:9,count:10},{group:"topic",caption:"Earth and Planetary Sciences",value:10,count:4},{group:"topic",caption:"Engineering",value:11,count:16},{group:"topic",caption:"Environmental Sciences",value:12,count:2},{group:"topic",caption:"Immunology and Microbiology",value:13,count:4},{group:"topic",caption:"Materials Science",value:14,count:5},{group:"topic",caption:"Mathematics",value:15,count:1},{group:"topic",caption:"Medicine",value:16,count:51},{group:"topic",caption:"Neuroscience",value:18,count:1},{group:"topic",caption:"Pharmacology, Toxicology and Pharmaceutical Science",value:19,count:5},{group:"topic",caption:"Physics",value:20,count:3},{group:"topic",caption:"Psychology",value:21,count:3},{group:"topic",caption:"Robotics",value:22,count:1},{group:"topic",caption:"Social Sciences",value:23,count:3},{group:"topic",caption:"Technology",value:24,count:1},{group:"topic",caption:"Veterinary Medicine and Science",value:25,count:2}],offset:12,limit:12,total:148},popularBooks:{featuredBooks:[{type:"book",id:"7802",title:"Modern Slavery and Human Trafficking",subtitle:null,isOpenForSubmission:!1,hash:"587a0b7fb765f31cc98de33c6c07c2e0",slug:"modern-slavery-and-human-trafficking",bookSignature:"Jane Reeves",coverURL:"https://cdn.intechopen.com/books/images_new/7802.jpg",editors:[{id:"211328",title:"Prof.",name:"Jane",middleName:null,surname:"Reeves",slug:"jane-reeves",fullName:"Jane Reeves"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter"}},{type:"book",id:"9961",title:"Data Mining",subtitle:"Methods, Applications and Systems",isOpenForSubmission:!1,hash:"ed79fb6364f2caf464079f94a0387146",slug:"data-mining-methods-applications-and-systems",bookSignature:"Derya Birant",coverURL:"https://cdn.intechopen.com/books/images_new/9961.jpg",editors:[{id:"15609",title:"Dr.",name:"Derya",middleName:null,surname:"Birant",slug:"derya-birant",fullName:"Derya Birant"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter"}},{type:"book",id:"8545",title:"Animal Reproduction in Veterinary Medicine",subtitle:null,isOpenForSubmission:!1,hash:"13aaddf5fdbbc78387e77a7da2388bf6",slug:"animal-reproduction-in-veterinary-medicine",bookSignature:"Faruk Aral, Rita Payan-Carreira and Miguel Quaresma",coverURL:"https://cdn.intechopen.com/books/images_new/8545.jpg",editors:[{id:"25600",title:"Prof.",name:"Faruk",middleName:null,surname:"Aral",slug:"faruk-aral",fullName:"Faruk Aral"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter"}},{type:"book",id:"9157",title:"Neurodegenerative Diseases",subtitle:"Molecular Mechanisms and Current Therapeutic Approaches",isOpenForSubmission:!1,hash:"bc8be577966ef88735677d7e1e92ed28",slug:"neurodegenerative-diseases-molecular-mechanisms-and-current-therapeutic-approaches",bookSignature:"Nagehan Ersoy Tunalı",coverURL:"https://cdn.intechopen.com/books/images_new/9157.jpg",editors:[{id:"82778",title:"Ph.D.",name:"Nagehan",middleName:null,surname:"Ersoy Tunalı",slug:"nagehan-ersoy-tunali",fullName:"Nagehan Ersoy Tunalı"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter"}},{type:"book",id:"8686",title:"Direct Torque Control Strategies of Electrical Machines",subtitle:null,isOpenForSubmission:!1,hash:"b6ad22b14db2b8450228545d3d4f6b1a",slug:"direct-torque-control-strategies-of-electrical-machines",bookSignature:"Fatma Ben Salem",coverURL:"https://cdn.intechopen.com/books/images_new/8686.jpg",editors:[{id:"295623",title:"Associate Prof.",name:"Fatma",middleName:null,surname:"Ben Salem",slug:"fatma-ben-salem",fullName:"Fatma Ben Salem"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter"}},{type:"book",id:"7434",title:"Molecular Biotechnology",subtitle:null,isOpenForSubmission:!1,hash:"eceede809920e1ec7ecadd4691ede2ec",slug:"molecular-biotechnology",bookSignature:"Sergey Sedykh",coverURL:"https://cdn.intechopen.com/books/images_new/7434.jpg",editors:[{id:"178316",title:"Ph.D.",name:"Sergey",middleName:null,surname:"Sedykh",slug:"sergey-sedykh",fullName:"Sergey Sedykh"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter"}},{type:"book",id:"9208",title:"Welding",subtitle:"Modern Topics",isOpenForSubmission:!1,hash:"7d6be076ccf3a3f8bd2ca52d86d4506b",slug:"welding-modern-topics",bookSignature:"Sadek Crisóstomo Absi Alfaro, Wojciech Borek and Błażej Tomiczek",coverURL:"https://cdn.intechopen.com/books/images_new/9208.jpg",editors:[{id:"65292",title:"Prof.",name:"Sadek Crisostomo Absi",middleName:"C. Absi",surname:"Alfaro",slug:"sadek-crisostomo-absi-alfaro",fullName:"Sadek Crisostomo Absi Alfaro"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter"}},{type:"book",id:"7831",title:"Sustainability in Urban Planning and Design",subtitle:null,isOpenForSubmission:!1,hash:"c924420492c8c2c9751e178d025f4066",slug:"sustainability-in-urban-planning-and-design",bookSignature:"Amjad Almusaed, Asaad Almssad and Linh Truong - Hong",coverURL:"https://cdn.intechopen.com/books/images_new/7831.jpg",editors:[{id:"110471",title:"Dr.",name:"Amjad",middleName:"Zaki",surname:"Almusaed",slug:"amjad-almusaed",fullName:"Amjad Almusaed"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter"}},{type:"book",id:"9343",title:"Trace Metals in the Environment",subtitle:"New Approaches and Recent Advances",isOpenForSubmission:!1,hash:"ae07e345bc2ce1ebbda9f70c5cd12141",slug:"trace-metals-in-the-environment-new-approaches-and-recent-advances",bookSignature:"Mario Alfonso Murillo-Tovar, Hugo Saldarriaga-Noreña and Agnieszka Saeid",coverURL:"https://cdn.intechopen.com/books/images_new/9343.jpg",editors:[{id:"255959",title:"Dr.",name:"Mario Alfonso",middleName:null,surname:"Murillo-Tovar",slug:"mario-alfonso-murillo-tovar",fullName:"Mario Alfonso Murillo-Tovar"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter"}},{type:"book",id:"9139",title:"Topics in Primary Care Medicine",subtitle:null,isOpenForSubmission:!1,hash:"ea774a4d4c1179da92a782e0ae9cde92",slug:"topics-in-primary-care-medicine",bookSignature:"Thomas F. Heston",coverURL:"https://cdn.intechopen.com/books/images_new/9139.jpg",editors:[{id:"217926",title:"Dr.",name:"Thomas F.",middleName:null,surname:"Heston",slug:"thomas-f.-heston",fullName:"Thomas F. Heston"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter"}},{type:"book",id:"9839",title:"Outdoor Recreation",subtitle:"Physiological and Psychological Effects on Health",isOpenForSubmission:!1,hash:"5f5a0d64267e32567daffa5b0c6a6972",slug:"outdoor-recreation-physiological-and-psychological-effects-on-health",bookSignature:"Hilde G. Nielsen",coverURL:"https://cdn.intechopen.com/books/images_new/9839.jpg",editors:[{id:"158692",title:"Ph.D.",name:"Hilde G.",middleName:null,surname:"Nielsen",slug:"hilde-g.-nielsen",fullName:"Hilde G. Nielsen"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter"}},{type:"book",id:"8697",title:"Virtual Reality and Its Application in Education",subtitle:null,isOpenForSubmission:!1,hash:"ee01b5e387ba0062c6b0d1e9227bda05",slug:"virtual-reality-and-its-application-in-education",bookSignature:"Dragan Cvetković",coverURL:"https://cdn.intechopen.com/books/images_new/8697.jpg",editors:[{id:"101330",title:"Dr.",name:"Dragan",middleName:"Mladen",surname:"Cvetković",slug:"dragan-cvetkovic",fullName:"Dragan Cvetković"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter"}}],offset:12,limit:12,total:5156},hotBookTopics:{hotBooks:[],offset:0,limit:12,total:null},publish:{},publishingProposal:{success:null,errors:{}},books:{featuredBooks:[{type:"book",id:"7802",title:"Modern Slavery and Human Trafficking",subtitle:null,isOpenForSubmission:!1,hash:"587a0b7fb765f31cc98de33c6c07c2e0",slug:"modern-slavery-and-human-trafficking",bookSignature:"Jane Reeves",coverURL:"https://cdn.intechopen.com/books/images_new/7802.jpg",editors:[{id:"211328",title:"Prof.",name:"Jane",middleName:null,surname:"Reeves",slug:"jane-reeves",fullName:"Jane Reeves"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter"}},{type:"book",id:"9961",title:"Data Mining",subtitle:"Methods, Applications and Systems",isOpenForSubmission:!1,hash:"ed79fb6364f2caf464079f94a0387146",slug:"data-mining-methods-applications-and-systems",bookSignature:"Derya Birant",coverURL:"https://cdn.intechopen.com/books/images_new/9961.jpg",editors:[{id:"15609",title:"Dr.",name:"Derya",middleName:null,surname:"Birant",slug:"derya-birant",fullName:"Derya Birant"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter"}},{type:"book",id:"8545",title:"Animal Reproduction in Veterinary Medicine",subtitle:null,isOpenForSubmission:!1,hash:"13aaddf5fdbbc78387e77a7da2388bf6",slug:"animal-reproduction-in-veterinary-medicine",bookSignature:"Faruk Aral, Rita Payan-Carreira and Miguel Quaresma",coverURL:"https://cdn.intechopen.com/books/images_new/8545.jpg",editors:[{id:"25600",title:"Prof.",name:"Faruk",middleName:null,surname:"Aral",slug:"faruk-aral",fullName:"Faruk Aral"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter"}},{type:"book",id:"9157",title:"Neurodegenerative Diseases",subtitle:"Molecular Mechanisms and Current Therapeutic Approaches",isOpenForSubmission:!1,hash:"bc8be577966ef88735677d7e1e92ed28",slug:"neurodegenerative-diseases-molecular-mechanisms-and-current-therapeutic-approaches",bookSignature:"Nagehan Ersoy Tunalı",coverURL:"https://cdn.intechopen.com/books/images_new/9157.jpg",editors:[{id:"82778",title:"Ph.D.",name:"Nagehan",middleName:null,surname:"Ersoy Tunalı",slug:"nagehan-ersoy-tunali",fullName:"Nagehan Ersoy Tunalı"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter"}},{type:"book",id:"8686",title:"Direct Torque Control Strategies of Electrical Machines",subtitle:null,isOpenForSubmission:!1,hash:"b6ad22b14db2b8450228545d3d4f6b1a",slug:"direct-torque-control-strategies-of-electrical-machines",bookSignature:"Fatma Ben Salem",coverURL:"https://cdn.intechopen.com/books/images_new/8686.jpg",editors:[{id:"295623",title:"Associate Prof.",name:"Fatma",middleName:null,surname:"Ben Salem",slug:"fatma-ben-salem",fullName:"Fatma Ben Salem"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter"}},{type:"book",id:"7434",title:"Molecular Biotechnology",subtitle:null,isOpenForSubmission:!1,hash:"eceede809920e1ec7ecadd4691ede2ec",slug:"molecular-biotechnology",bookSignature:"Sergey Sedykh",coverURL:"https://cdn.intechopen.com/books/images_new/7434.jpg",editors:[{id:"178316",title:"Ph.D.",name:"Sergey",middleName:null,surname:"Sedykh",slug:"sergey-sedykh",fullName:"Sergey Sedykh"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter"}},{type:"book",id:"9208",title:"Welding",subtitle:"Modern Topics",isOpenForSubmission:!1,hash:"7d6be076ccf3a3f8bd2ca52d86d4506b",slug:"welding-modern-topics",bookSignature:"Sadek Crisóstomo Absi Alfaro, Wojciech Borek and Błażej Tomiczek",coverURL:"https://cdn.intechopen.com/books/images_new/9208.jpg",editors:[{id:"65292",title:"Prof.",name:"Sadek Crisostomo Absi",middleName:"C. Absi",surname:"Alfaro",slug:"sadek-crisostomo-absi-alfaro",fullName:"Sadek Crisostomo Absi Alfaro"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter"}},{type:"book",id:"7831",title:"Sustainability in Urban Planning and Design",subtitle:null,isOpenForSubmission:!1,hash:"c924420492c8c2c9751e178d025f4066",slug:"sustainability-in-urban-planning-and-design",bookSignature:"Amjad Almusaed, Asaad Almssad and Linh Truong - Hong",coverURL:"https://cdn.intechopen.com/books/images_new/7831.jpg",editors:[{id:"110471",title:"Dr.",name:"Amjad",middleName:"Zaki",surname:"Almusaed",slug:"amjad-almusaed",fullName:"Amjad Almusaed"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter"}},{type:"book",id:"9343",title:"Trace Metals in the Environment",subtitle:"New Approaches and Recent Advances",isOpenForSubmission:!1,hash:"ae07e345bc2ce1ebbda9f70c5cd12141",slug:"trace-metals-in-the-environment-new-approaches-and-recent-advances",bookSignature:"Mario Alfonso Murillo-Tovar, Hugo Saldarriaga-Noreña and Agnieszka Saeid",coverURL:"https://cdn.intechopen.com/books/images_new/9343.jpg",editors:[{id:"255959",title:"Dr.",name:"Mario Alfonso",middleName:null,surname:"Murillo-Tovar",slug:"mario-alfonso-murillo-tovar",fullName:"Mario Alfonso Murillo-Tovar"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter"}},{type:"book",id:"9139",title:"Topics in Primary Care Medicine",subtitle:null,isOpenForSubmission:!1,hash:"ea774a4d4c1179da92a782e0ae9cde92",slug:"topics-in-primary-care-medicine",bookSignature:"Thomas F. Heston",coverURL:"https://cdn.intechopen.com/books/images_new/9139.jpg",editors:[{id:"217926",title:"Dr.",name:"Thomas F.",middleName:null,surname:"Heston",slug:"thomas-f.-heston",fullName:"Thomas F. Heston"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter"}}],latestBooks:[{type:"book",id:"6934",title:"Psycho-Social Aspects of Human Sexuality and Ethics",subtitle:null,isOpenForSubmission:!1,hash:"44731b106aa0d1ab5c64a7394483c7d5",slug:"psycho-social-aspects-of-human-sexuality-and-ethics",bookSignature:"Dhastagir Sultan Sheriff",coverURL:"https://cdn.intechopen.com/books/images_new/6934.jpg",editedByType:"Edited by",editors:[{id:"167875",title:"Dr.",name:"Dhastagir Sultan",middleName:null,surname:"Sheriff",slug:"dhastagir-sultan-sheriff",fullName:"Dhastagir Sultan Sheriff"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"10062",title:"Forecasting in Mathematics",subtitle:"Recent Advances, New Perspectives and Applications",isOpenForSubmission:!1,hash:"9a3ad05fef0502040d2a238ad22487c0",slug:"forecasting-in-mathematics-recent-advances-new-perspectives-and-applications",bookSignature:"Abdo Abou Jaoude",coverURL:"https://cdn.intechopen.com/books/images_new/10062.jpg",editedByType:"Edited by",editors:[{id:"248271",title:"Dr.",name:"Abdo",middleName:null,surname:"Abou Jaoude",slug:"abdo-abou-jaoude",fullName:"Abdo Abou Jaoude"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"9043",title:"Parenting",subtitle:"Studies by an Ecocultural and Transactional Perspective",isOpenForSubmission:!1,hash:"6d21066c7438e459e4c6fb13217a5c8c",slug:"parenting-studies-by-an-ecocultural-and-transactional-perspective",bookSignature:"Loredana Benedetto and Massimo Ingrassia",coverURL:"https://cdn.intechopen.com/books/images_new/9043.jpg",editedByType:"Edited by",editors:[{id:"193200",title:"Prof.",name:"Loredana",middleName:null,surname:"Benedetto",slug:"loredana-benedetto",fullName:"Loredana Benedetto"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"10075",title:"Nonlinear Optics",subtitle:"From Solitons to Similaritons",isOpenForSubmission:!1,hash:"b034b2a060292c8511359aec0db1002c",slug:"nonlinear-optics-from-solitons-to-similaritons",bookSignature:"İlkay Bakırtaş and Nalan Antar",coverURL:"https://cdn.intechopen.com/books/images_new/10075.jpg",editedByType:"Edited by",editors:[{id:"186388",title:"Prof.",name:"İlkay",middleName:null,surname:"Bakırtaş",slug:"ilkay-bakirtas",fullName:"İlkay Bakırtaş"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"10116",title:"Nano- and Microencapsulation",subtitle:"Techniques and Applications",isOpenForSubmission:!1,hash:"8d92c5999718734b36a0cc3a6af7c7f6",slug:"nano-and-microencapsulation-techniques-and-applications",bookSignature:"Nedal Abu-Thabit",coverURL:"https://cdn.intechopen.com/books/images_new/10116.jpg",editedByType:"Edited by",editors:[{id:"308436",title:"Associate Prof.",name:"Nedal",middleName:null,surname:"Abu-Thabit",slug:"nedal-abu-thabit",fullName:"Nedal Abu-Thabit"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"9881",title:"Perovskite and Piezoelectric Materials",subtitle:null,isOpenForSubmission:!1,hash:"8fa0e0f48567bbc50fbb3bfdde6f9a0b",slug:"perovskite-and-piezoelectric-materials",bookSignature:"Someshwar Pola, Neeraj Panwar and Indrani Coondoo",coverURL:"https://cdn.intechopen.com/books/images_new/9881.jpg",editedByType:"Edited by",editors:[{id:"177037",title:"Dr.",name:"Someshwar",middleName:null,surname:"Pola",slug:"someshwar-pola",fullName:"Someshwar Pola"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"9394",title:"Genotoxicity and Mutagenicity",subtitle:"Mechanisms and Test Methods",isOpenForSubmission:!1,hash:"9ee7e597358dbbfb5e33d0beb76e6fff",slug:"genotoxicity-and-mutagenicity-mechanisms-and-test-methods",bookSignature:"Sonia Soloneski and Marcelo L. Larramendy",coverURL:"https://cdn.intechopen.com/books/images_new/9394.jpg",editedByType:"Edited by",editors:[{id:"14863",title:"Dr.",name:"Sonia",middleName:null,surname:"Soloneski",slug:"sonia-soloneski",fullName:"Sonia Soloneski"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"7434",title:"Molecular Biotechnology",subtitle:null,isOpenForSubmission:!1,hash:"eceede809920e1ec7ecadd4691ede2ec",slug:"molecular-biotechnology",bookSignature:"Sergey Sedykh",coverURL:"https://cdn.intechopen.com/books/images_new/7434.jpg",editedByType:"Edited by",editors:[{id:"178316",title:"Ph.D.",name:"Sergey",middleName:null,surname:"Sedykh",slug:"sergey-sedykh",fullName:"Sergey Sedykh"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"8545",title:"Animal Reproduction in Veterinary Medicine",subtitle:null,isOpenForSubmission:!1,hash:"13aaddf5fdbbc78387e77a7da2388bf6",slug:"animal-reproduction-in-veterinary-medicine",bookSignature:"Faruk Aral, Rita Payan-Carreira and Miguel Quaresma",coverURL:"https://cdn.intechopen.com/books/images_new/8545.jpg",editedByType:"Edited by",editors:[{id:"25600",title:"Prof.",name:"Faruk",middleName:null,surname:"Aral",slug:"faruk-aral",fullName:"Faruk Aral"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"9569",title:"Methods in Molecular Medicine",subtitle:null,isOpenForSubmission:!1,hash:"691d3f3c4ac25a8093414e9b270d2843",slug:"methods-in-molecular-medicine",bookSignature:"Yusuf Tutar",coverURL:"https://cdn.intechopen.com/books/images_new/9569.jpg",editedByType:"Edited by",editors:[{id:"158492",title:"Prof.",name:"Yusuf",middleName:null,surname:"Tutar",slug:"yusuf-tutar",fullName:"Yusuf Tutar"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}}]},subject:{topic:{id:"770",title:"Renewable Energy",slug:"engineering-energy-engineering-renewable-energy",parent:{title:"Energy Engineering",slug:"engineering-energy-engineering"},numberOfBooks:43,numberOfAuthorsAndEditors:1315,numberOfWosCitations:1143,numberOfCrossrefCitations:816,numberOfDimensionsCitations:1827,videoUrl:null,fallbackUrl:null,description:null},booksByTopicFilter:{topicSlug:"engineering-energy-engineering-renewable-energy",sort:"-publishedDate",limit:12,offset:0},booksByTopicCollection:[{type:"book",id:"8871",title:"Renewable Energy",subtitle:"Resources, Challenges and Applications",isOpenForSubmission:!1,hash:"e00c59554fb355c16623c62064ecc3bb",slug:"renewable-energy-resources-challenges-and-applications",bookSignature:"Mansour Al Qubeissi, Ahmad El-kharouf and Hakan Serhad Soyhan",coverURL:"https://cdn.intechopen.com/books/images_new/8871.jpg",editedByType:"Edited by",editors:[{id:"241686",title:"Dr.",name:"Mansour",middleName:null,surname:"Al Qubeissi",slug:"mansour-al-qubeissi",fullName:"Mansour Al Qubeissi"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"7200",title:"Green Energy and Environment",subtitle:null,isOpenForSubmission:!1,hash:"72ad3cb35d7eb84855d6cb05c6e73897",slug:"green-energy-and-environment",bookSignature:"Eng Hwa Yap and Andrew Huey Ping Tan",coverURL:"https://cdn.intechopen.com/books/images_new/7200.jpg",editedByType:"Edited by",editors:[{id:"185577",title:"Associate Prof.",name:"Eng Hwa",middleName:null,surname:"Yap",slug:"eng-hwa-yap",fullName:"Eng Hwa Yap"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"9441",title:"Ocean Thermal Energy Conversion (OTEC)",subtitle:"Past, Present, and Progress",isOpenForSubmission:!1,hash:"b0f6032c45ead7f1cb11bb488bfcd48d",slug:"ocean-thermal-energy-conversion-otec-past-present-and-progress",bookSignature:"Albert S. Kim and Hyeon-Ju Kim",coverURL:"https://cdn.intechopen.com/books/images_new/9441.jpg",editedByType:"Edited by",editors:[{id:"21045",title:"Prof.",name:"Albert S.",middleName:null,surname:"Kim",slug:"albert-s.-kim",fullName:"Albert S. Kim"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"8896",title:"Sustainable Mobility",subtitle:null,isOpenForSubmission:!1,hash:"c5b28b438521dcd383df9b6e797ec462",slug:"sustainable-mobility",bookSignature:"Bernardo Llamas, Marcelo F. Ortega Romero and Eugenia Sillero",coverURL:"https://cdn.intechopen.com/books/images_new/8896.jpg",editedByType:"Edited by",editors:[{id:"169368",title:"Dr.",name:"Bernardo",middleName:null,surname:"Llamas",slug:"bernardo-llamas",fullName:"Bernardo Llamas"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"9425",title:"Advanced Statistical Modeling, Forecasting, and Fault Detection in Renewable Energy Systems",subtitle:null,isOpenForSubmission:!1,hash:"f9dfa41155499eb62f21917c77db5f7c",slug:"advanced-statistical-modeling-forecasting-and-fault-detection-in-renewable-energy-systems",bookSignature:"Fouzi Harrou and Ying Sun",coverURL:"https://cdn.intechopen.com/books/images_new/9425.jpg",editedByType:"Edited by",editors:[{id:"197090",title:"Dr.",name:"Fouzi",middleName:null,surname:"Harrou",slug:"fouzi-harrou",fullName:"Fouzi Harrou"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"10425",title:"Modeling, Simulation and Optimization of Wind Farms and Hybrid Systems",subtitle:null,isOpenForSubmission:!1,hash:"659adb2f2e862e51eab5b274c6673c30",slug:"modeling-simulation-and-optimization-of-wind-farms-and-hybrid-systems",bookSignature:"Karam Y. Maalawi",coverURL:"https://cdn.intechopen.com/books/images_new/10425.jpg",editedByType:"Edited by",editors:[{id:"18593",title:"Prof.",name:"Karam",middleName:"Youssef",surname:"Maalawi",slug:"karam-maalawi",fullName:"Karam Maalawi"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"7636",title:"Wind Solar Hybrid Renewable Energy System",subtitle:null,isOpenForSubmission:!1,hash:"49b63353c3d80ef6f449e55b1f6cee29",slug:"wind-solar-hybrid-renewable-energy-system",bookSignature:"Kenneth Eloghene Okedu, Ahmed Tahour and Abdel Ghani Aissaou",coverURL:"https://cdn.intechopen.com/books/images_new/7636.jpg",editedByType:"Edited by",editors:[{id:"172580",title:"Dr.",name:"Kenneth Eloghene",middleName:null,surname:"Okedu",slug:"kenneth-eloghene-okedu",fullName:"Kenneth Eloghene Okedu"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"7613",title:"Research Trends and Challenges in Smart Grids",subtitle:null,isOpenForSubmission:!1,hash:"ca836c407ba574b88af44b497d45d42b",slug:"research-trends-and-challenges-in-smart-grids",bookSignature:"Alfredo Vaccaro, Ahmed Faheem Zobaa, Prabhakar Karthikeyan Shanmugam and Kannaiah Sathish Kumar",coverURL:"https://cdn.intechopen.com/books/images_new/7613.jpg",editedByType:"Edited by",editors:[{id:"24725",title:"Dr.",name:"Alfredo",middleName:null,surname:"Vaccaro",slug:"alfredo-vaccaro",fullName:"Alfredo Vaccaro"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"8842",title:"Innovation in Energy Systems",subtitle:"New Technologies for Changing Paradigms",isOpenForSubmission:!1,hash:"75fdfb0206f7d487c3ac8dbe21dcef16",slug:"innovation-in-energy-systems-new-technologies-for-changing-paradigms",bookSignature:"Taha Selim Ustun",coverURL:"https://cdn.intechopen.com/books/images_new/8842.jpg",editedByType:"Edited by",editors:[{id:"272760",title:"Dr.",name:"Taha Selim",middleName:null,surname:"Ustun",slug:"taha-selim-ustun",fullName:"Taha Selim Ustun"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"6866",title:"Energy Conversion",subtitle:"Current Technologies and Future Trends",isOpenForSubmission:!1,hash:"62eaa46123434eb277ced91a69a3d525",slug:"energy-conversion-current-technologies-and-future-trends",bookSignature:"Ibrahim H. Al-Bahadly",coverURL:"https://cdn.intechopen.com/books/images_new/6866.jpg",editedByType:"Edited by",editors:[{id:"19588",title:"Dr.",name:"Ibrahim H.",middleName:null,surname:"Al-Bahadly",slug:"ibrahim-h.-al-bahadly",fullName:"Ibrahim H. Al-Bahadly"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"6708",title:"Stability Control and Reliable Performance of Wind Turbines",subtitle:null,isOpenForSubmission:!1,hash:"f33b0adf7c69362059657a16f10145df",slug:"stability-control-and-reliable-performance-of-wind-turbines",bookSignature:"Kenneth Eloghene Okedu",coverURL:"https://cdn.intechopen.com/books/images_new/6708.jpg",editedByType:"Edited by",editors:[{id:"172580",title:"Dr.",name:"Kenneth Eloghene",middleName:null,surname:"Okedu",slug:"kenneth-eloghene-okedu",fullName:"Kenneth Eloghene Okedu"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"6959",title:"Special Topics in Renewable Energy Systems",subtitle:null,isOpenForSubmission:!1,hash:"a1143b97846be593bd4a2a9917f84977",slug:"special-topics-in-renewable-energy-systems",bookSignature:"Ebubekir Yüksel, Abdülkerim Gök and Murat Eyvaz",coverURL:"https://cdn.intechopen.com/books/images_new/6959.jpg",editedByType:"Edited by",editors:[{id:"176701",title:"Prof.",name:"Ebubekir",middleName:null,surname:"Yüksel",slug:"ebubekir-yuksel",fullName:"Ebubekir Yüksel"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}}],booksByTopicTotal:43,mostCitedChapters:[{id:"48267",doi:"10.5772/59284",title:"Crystal Structures of CH3NH3PbI3 and Related Perovskite Compounds Used for Solar Cells",slug:"crystal-structures-of-ch3nh3pbi3-and-related-perovskite-compounds-used-for-solar-cells",totalDownloads:6510,totalCrossrefCites:31,totalDimensionsCites:70,book:{slug:"solar-cells-new-approaches-and-reviews",title:"Solar Cells",fullTitle:"Solar Cells - New Approaches and Reviews"},signatures:"Takeo Oku",authors:[{id:"31132",title:"Prof.",name:"Takeo",middleName:null,surname:"Oku",slug:"takeo-oku",fullName:"Takeo Oku"}]},{id:"8561",doi:"10.5772/8073",title:"Numerical Simulation of Solar Cells and Solar Cell Characterization Methods: the Open-Source on Demand Program AFORS-HET",slug:"numerical-simulation-of-solar-cells-and-solar-cell-characterization-methods-the-open-source-on-deman",totalDownloads:9169,totalCrossrefCites:30,totalDimensionsCites:54,book:{slug:"solar-energy",title:"Solar Energy",fullTitle:"Solar Energy"},signatures:"Rolf Stangl, Caspar Leendertz and Jan Haschke",authors:null},{id:"37686",doi:"10.5772/50702",title:"Cu2ZnSnS4 Thin Film Solar Cells: Present Status and Future Prospects",slug:"cu2znsns4-thin-film-solar-cells-present-status-and-future-prospects",totalDownloads:10240,totalCrossrefCites:21,totalDimensionsCites:41,book:{slug:"solar-cells-research-and-application-perspectives",title:"Solar Cells",fullTitle:"Solar Cells - Research and Application Perspectives"},signatures:"Minlin Jiang and Xingzhong Yan",authors:[{id:"42857",title:"Dr.",name:"Xingzhong",middleName:null,surname:"Yan",slug:"xingzhong-yan",fullName:"Xingzhong Yan"},{id:"153957",title:"MSc.",name:"Minlin",middleName:null,surname:"Jiang",slug:"minlin-jiang",fullName:"Minlin Jiang"}]}],mostDownloadedChaptersLast30Days:[{id:"70874",title:"Social, Economic, and Environmental Impacts of Renewable Energy Resources",slug:"social-economic-and-environmental-impacts-of-renewable-energy-resources",totalDownloads:1691,totalCrossrefCites:4,totalDimensionsCites:6,book:{slug:"wind-solar-hybrid-renewable-energy-system",title:"Wind Solar Hybrid Renewable Energy System",fullTitle:"Wind Solar Hybrid Renewable Energy System"},signatures:"Mahesh Kumar",authors:[{id:"309842",title:"Mr.",name:"Kamlesh",middleName:null,surname:"Kumar",slug:"kamlesh-kumar",fullName:"Kamlesh Kumar"}]},{id:"49438",title:"Perovskite Nanomaterials – Synthesis, Characterization, and Applications",slug:"perovskite-nanomaterials-synthesis-characterization-and-applications",totalDownloads:7469,totalCrossrefCites:13,totalDimensionsCites:25,book:{slug:"perovskite-materials-synthesis-characterisation-properties-and-applications",title:"Perovskite Materials",fullTitle:"Perovskite Materials - Synthesis, Characterisation, Properties, and Applications"},signatures:"Nada F. Atta, Ahmed Galal and Ekram H. El-Ads",authors:[{id:"30072",title:"Prof.",name:"Nada",middleName:null,surname:"F. Atta",slug:"nada-f.-atta",fullName:"Nada F. Atta"},{id:"174033",title:"Prof.",name:"Ahmed",middleName:null,surname:"Galal",slug:"ahmed-galal",fullName:"Ahmed Galal"},{id:"174034",title:"MSc.",name:"Ekram",middleName:null,surname:"El-Ads",slug:"ekram-el-ads",fullName:"Ekram El-Ads"},{id:"176164",title:"MSc.",name:"Ekram",middleName:null,surname:"Ekram H. El-Ads",slug:"ekram-ekram-h.-el-ads",fullName:"Ekram Ekram H. El-Ads"}]},{id:"48267",title:"Crystal Structures of CH3NH3PbI3 and Related Perovskite Compounds Used for Solar Cells",slug:"crystal-structures-of-ch3nh3pbi3-and-related-perovskite-compounds-used-for-solar-cells",totalDownloads:6510,totalCrossrefCites:31,totalDimensionsCites:70,book:{slug:"solar-cells-new-approaches-and-reviews",title:"Solar Cells",fullTitle:"Solar Cells - New Approaches and Reviews"},signatures:"Takeo Oku",authors:[{id:"31132",title:"Prof.",name:"Takeo",middleName:null,surname:"Oku",slug:"takeo-oku",fullName:"Takeo Oku"}]},{id:"70583",title:"Recycling of Waste Plastics into Pyrolytic Fuels and Their Use in IC Engines",slug:"recycling-of-waste-plastics-into-pyrolytic-fuels-and-their-use-in-ic-engines",totalDownloads:621,totalCrossrefCites:2,totalDimensionsCites:2,book:{slug:"sustainable-mobility",title:"Sustainable Mobility",fullTitle:"Sustainable Mobility"},signatures:"Sinan Erdogan",authors:[{id:"298608",title:"Dr.",name:"Sinan",middleName:null,surname:"Erdogan",slug:"sinan-erdogan",fullName:"Sinan Erdogan"}]},{id:"59381",title:"A Review of Recycling Processes for Photovoltaic Modules",slug:"a-review-of-recycling-processes-for-photovoltaic-modules",totalDownloads:1944,totalCrossrefCites:12,totalDimensionsCites:18,book:{slug:"solar-panels-and-photovoltaic-materials",title:"Solar Panels and Photovoltaic Materials",fullTitle:"Solar Panels and Photovoltaic Materials"},signatures:"Marina Monteiro Lunardi, Juan Pablo Alvarez-Gaitan, José I. Bilbao\nand Richard Corkish",authors:[{id:"233229",title:"Dr.",name:"Richard",middleName:null,surname:"Corkish",slug:"richard-corkish",fullName:"Richard Corkish"},{id:"233231",title:"Ms.",name:"Marina",middleName:null,surname:"Monteiro Lunardi",slug:"marina-monteiro-lunardi",fullName:"Marina Monteiro Lunardi"},{id:"242337",title:"Dr.",name:"Juan Pablo",middleName:null,surname:"Alvarez-Gaitan",slug:"juan-pablo-alvarez-gaitan",fullName:"Juan Pablo Alvarez-Gaitan"},{id:"242338",title:"Dr.",name:"Jose I.",middleName:null,surname:"Bilbao",slug:"jose-i.-bilbao",fullName:"Jose I. Bilbao"}]},{id:"67556",title:"A Review of Hybrid Renewable Energy Systems Based on Wind and Solar Energy: Modeling, Design and Optimization",slug:"a-review-of-hybrid-renewable-energy-systems-based-on-wind-and-solar-energy-modeling-design-and-optim",totalDownloads:881,totalCrossrefCites:0,totalDimensionsCites:1,book:{slug:"wind-solar-hybrid-renewable-energy-system",title:"Wind Solar Hybrid Renewable Energy System",fullTitle:"Wind Solar Hybrid Renewable Energy System"},signatures:"Salisu Muhammad Lawan and Wan Azlan Wan Zainal Abidin",authors:[{id:"286205",title:"Dr.",name:"Salisu",middleName:null,surname:"Muhammad Lawan",slug:"salisu-muhammad-lawan",fullName:"Salisu Muhammad Lawan"},{id:"286210",title:"Prof.",name:"Wan Azlan",middleName:null,surname:"Wan Zainal Abidin",slug:"wan-azlan-wan-zainal-abidin",fullName:"Wan Azlan Wan Zainal Abidin"}]},{id:"62541",title:"Free-Piston Stirling Engine Generators",slug:"free-piston-stirling-engine-generators",totalDownloads:2091,totalCrossrefCites:0,totalDimensionsCites:2,book:{slug:"energy-conversion-current-technologies-and-future-trends",title:"Energy Conversion",fullTitle:"Energy Conversion - Current Technologies and Future Trends"},signatures:"Songgang Qiu and Laura Solomon",authors:[{id:"248993",title:"Prof.",name:"Songgang",middleName:null,surname:"Qiu",slug:"songgang-qiu",fullName:"Songgang Qiu"},{id:"249207",title:"Dr.",name:"Laura",middleName:null,surname:"Solomon",slug:"laura-solomon",fullName:"Laura Solomon"}]},{id:"59993",title:"Adsorption Refrigeration Technologies",slug:"adsorption-refrigeration-technologies",totalDownloads:1979,totalCrossrefCites:0,totalDimensionsCites:8,book:{slug:"sustainable-air-conditioning-systems",title:"Sustainable Air Conditioning Systems",fullTitle:"Sustainable Air Conditioning Systems"},signatures:"Mahmoud B. Elsheniti, Osama A. Elsamni, Raya K. Al-dadah, Saad\nMahmoud, Eman Elsayed and Khaled Saleh",authors:[{id:"210207",title:"Dr.",name:"Khaled",middleName:null,surname:"Saleh",slug:"khaled-saleh",fullName:"Khaled Saleh"},{id:"210212",title:"Dr.",name:"Mahmoud",middleName:null,surname:"Badawy Elsheniti",slug:"mahmoud-badawy-elsheniti",fullName:"Mahmoud Badawy Elsheniti"},{id:"221896",title:"Dr.",name:"Osama",middleName:null,surname:"Elsamni",slug:"osama-elsamni",fullName:"Osama Elsamni"},{id:"221898",title:"Dr.",name:"Raya K.",middleName:null,surname:"Al-dadah",slug:"raya-k.-al-dadah",fullName:"Raya K. Al-dadah"},{id:"221900",title:"Dr.",name:"Sa’ad",middleName:null,surname:"Mahmoud",slug:"sa'ad-mahmoud",fullName:"Sa’ad Mahmoud"},{id:"221901",title:"MSc.",name:"Eman",middleName:null,surname:"Elsayed",slug:"eman-elsayed",fullName:"Eman Elsayed"}]},{id:"41233",title:"Modeling of Photovoltaic Cell Using Free Software Application for Training and Design Circuit in Photovoltaic Solar Energy",slug:"modeling-of-photovoltaic-cell-using-free-software-application-for-training-and-design-circuit-in-pho",totalDownloads:6422,totalCrossrefCites:1,totalDimensionsCites:9,book:{slug:"new-developments-in-renewable-energy",title:"New Developments in Renewable Energy",fullTitle:"New Developments in Renewable Energy"},signatures:"Miguel Pareja Aparicio, José Pelegrí-Sebastiá, Tomás Sogorb and Vicente Llario",authors:[{id:"2119",title:"Dr.",name:"Jose",middleName:null,surname:"Pelegri-Sebastia",slug:"jose-pelegri-sebastia",fullName:"Jose Pelegri-Sebastia"},{id:"156248",title:"Mr.",name:"Miguel",middleName:null,surname:"Pareja Aparicio",slug:"miguel-pareja-aparicio",fullName:"Miguel Pareja Aparicio"},{id:"164804",title:"Dr.",name:"Tomás",middleName:null,surname:"Sogorb",slug:"tomas-sogorb",fullName:"Tomás Sogorb"},{id:"164807",title:"MSc.",name:"Vicente",middleName:null,surname:"Llario",slug:"vicente-llario",fullName:"Vicente Llario"}]},{id:"68372",title:"Technical Requirements for Connecting Solar Power Plants to Electricity Networks",slug:"technical-requirements-for-connecting-solar-power-plants-to-electricity-networks",totalDownloads:1293,totalCrossrefCites:0,totalDimensionsCites:1,book:{slug:"innovation-in-energy-systems-new-technologies-for-changing-paradigms",title:"Innovation in Energy Systems",fullTitle:"Innovation in Energy Systems - New Technologies for Changing Paradigms"},signatures:"Omar H. Abdalla and Azza A.A. Mostafa",authors:[{id:"297249",title:"Prof.",name:"Omar H.",middleName:null,surname:"Abdalla",slug:"omar-h.-abdalla",fullName:"Omar H. Abdalla"},{id:"307567",title:"Ms.",name:"Azza",middleName:null,surname:"Aly",slug:"azza-aly",fullName:"Azza Aly"}]}],onlineFirstChaptersFilter:{topicSlug:"engineering-energy-engineering-renewable-energy",limit:3,offset:0},onlineFirstChaptersCollection:[{id:"74786",title:"Distributed Sources Optimal Sites and Sizes Search in Large Power Systems",slug:"distributed-sources-optimal-sites-and-sizes-search-in-large-power-systems",totalDownloads:11,totalDimensionsCites:0,doi:"10.5772/intechopen.95266",book:{title:"Renewable Energy - Technologies and Applications"},signatures:"Mustafa Mosbah, Redha Djamel Mohammedi and Salem Arif"},{id:"71520",title:"Formation and Transformation of Typical Pollutant from MSW by Hydrothermal Carbonization towards Biofuel Hydrochar Production",slug:"formation-and-transformation-of-typical-pollutant-from-msw-by-hydrothermal-carbonization-towards-bio",totalDownloads:58,totalDimensionsCites:0,doi:"10.5772/intechopen.91659",book:{title:"Renewable Energy - Technologies and Applications"},signatures:"Wentao Jiao, Nana Peng and Zhengang Liu"},{id:"73513",title:"New Generation Aero Combustor",slug:"new-generation-aero-combustor",totalDownloads:37,totalDimensionsCites:0,doi:"10.5772/intechopen.93916",book:{title:"Renewable Energy - Technologies and Applications"},signatures:"Jushan Chin and Jin Dang"}],onlineFirstChaptersTotal:22},preDownload:{success:null,errors:{}},aboutIntechopen:{},privacyPolicy:{},peerReviewing:{},howOpenAccessPublishingWithIntechopenWorks:{},sponsorshipBooks:{sponsorshipBooks:[{type:"book",id:"10176",title:"Microgrids and Local Energy Systems",subtitle:null,isOpenForSubmission:!0,hash:"c32b4a5351a88f263074b0d0ca813a9c",slug:null,bookSignature:"Prof. Nick Jenkins",coverURL:"https://cdn.intechopen.com/books/images_new/10176.jpg",editedByType:null,editors:[{id:"55219",title:"Prof.",name:"Nick",middleName:null,surname:"Jenkins",slug:"nick-jenkins",fullName:"Nick Jenkins"}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,productType:{id:"1",chapterContentType:"chapter"}}],offset:8,limit:8,total:1},route:{name:"profile.detail",path:"/profiles/153284/b.-m-veeregowda",hash:"",query:{},params:{id:"153284",slug:"b.-m-veeregowda"},fullPath:"/profiles/153284/b.-m-veeregowda",meta:{},from:{name:null,path:"/",hash:"",query:{},params:{},fullPath:"/",meta:{}}}},function(){var e;(e=document.currentScript||document.scripts[document.scripts.length-1]).parentNode.removeChild(e)}()