List of sleeve core samples analyzed.
\\n\\n
Released this past November, the list is based on data collected from the Web of Science and highlights some of the world’s most influential scientific minds by naming the researchers whose publications over the previous decade have included a high number of Highly Cited Papers placing them among the top 1% most-cited.
\\n\\nWe wish to congratulate all of the researchers named and especially our authors on this amazing accomplishment! We are happy and proud to share in their success!
Note: Edited in March 2021
\\n"}]',published:!0,mainMedia:{caption:"Highly Cited",originalUrl:"/media/original/117"}},components:[{type:"htmlEditorComponent",content:'IntechOpen is proud to announce that 191 of our authors have made the Clarivate™ Highly Cited Researchers List for 2020, ranking them among the top 1% most-cited.
\n\nThroughout the years, the list has named a total of 261 IntechOpen authors as Highly Cited. Of those researchers, 69 have been featured on the list multiple times.
\n\n\n\nReleased this past November, the list is based on data collected from the Web of Science and highlights some of the world’s most influential scientific minds by naming the researchers whose publications over the previous decade have included a high number of Highly Cited Papers placing them among the top 1% most-cited.
\n\nWe wish to congratulate all of the researchers named and especially our authors on this amazing accomplishment! We are happy and proud to share in their success!
Note: Edited in March 2021
\n'}],latestNews:[{slug:"intechopen-supports-asapbio-s-new-initiative-publish-your-reviews-20220729",title:"IntechOpen Supports ASAPbio’s New Initiative Publish Your Reviews"},{slug:"webinar-introduction-to-open-science-wednesday-18-may-1-pm-cest-20220518",title:"Webinar: Introduction to Open Science | Wednesday 18 May, 1 PM CEST"},{slug:"step-in-the-right-direction-intechopen-launches-a-portfolio-of-open-science-journals-20220414",title:"Step in the Right Direction: IntechOpen Launches a Portfolio of Open Science Journals"},{slug:"let-s-meet-at-london-book-fair-5-7-april-2022-olympia-london-20220321",title:"Let’s meet at London Book Fair, 5-7 April 2022, Olympia London"},{slug:"50-books-published-as-part-of-intechopen-and-knowledge-unlatched-ku-collaboration-20220316",title:"50 Books published as part of IntechOpen and Knowledge Unlatched (KU) Collaboration"},{slug:"intechopen-joins-the-united-nations-sustainable-development-goals-publishers-compact-20221702",title:"IntechOpen joins the United Nations Sustainable Development Goals Publishers Compact"},{slug:"intechopen-signs-exclusive-representation-agreement-with-lsr-libros-servicios-y-representaciones-s-a-de-c-v-20211123",title:"IntechOpen Signs Exclusive Representation Agreement with LSR Libros Servicios y Representaciones S.A. de C.V"},{slug:"intechopen-expands-partnership-with-research4life-20211110",title:"IntechOpen Expands Partnership with Research4Life"}]},book:{item:{type:"book",id:"7000",leadTitle:null,fullTitle:"Legume Crops - Characterization and Breeding for Improved Food Security",title:"Legume Crops",subtitle:"Characterization and Breeding for Improved Food Security",reviewType:"peer-reviewed",abstract:"Legumes are flowering plants found in most of the archeological records of plants. Legumes are efficiently used as food crops for humans and animals, pulps for paper and timber manufacturing, sources for fuel and oil production, ornamental plants, and cover crops such as cereals and other staple foods. Additionally, they can be utilized for other purposes, including the production of massive amounts of organic nitrogen. This book reviews the fundamental advances related to the characterization and breeding of legume crops for improved food security. Moreover, it sheds new light on the current research trends and future research directions related to legume crop studies. This book will provoke interest for various readers, researchers, and scientists, who may find this information useful for the advancement of legume productivity.",isbn:"978-1-83968-087-8",printIsbn:"978-1-83968-086-1",pdfIsbn:"978-1-83968-088-5",doi:"10.5772/intechopen.73753",price:119,priceEur:129,priceUsd:155,slug:"legume-crops-characterization-and-breeding-for-improved-food-security",numberOfPages:122,isOpenForSubmission:!1,isInWos:null,isInBkci:!1,hash:"4d0f73bf883bbb984cc2feef1259a9a7",bookSignature:"Mohamed Ahmed El-Esawi",publishedDate:"December 11th 2019",coverURL:"https://cdn.intechopen.com/books/images_new/7000.jpg",numberOfDownloads:7563,numberOfWosCitations:5,numberOfCrossrefCitations:8,numberOfCrossrefCitationsByBook:0,numberOfDimensionsCitations:16,numberOfDimensionsCitationsByBook:0,hasAltmetrics:1,numberOfTotalCitations:29,isAvailableForWebshopOrdering:!0,dateEndFirstStepPublish:"August 30th 2018",dateEndSecondStepPublish:"September 20th 2018",dateEndThirdStepPublish:"November 19th 2018",dateEndFourthStepPublish:"February 7th 2019",dateEndFifthStepPublish:"April 8th 2019",currentStepOfPublishingProcess:5,indexedIn:"1,2,3,4,5,6",editedByType:"Edited by",kuFlag:!1,featuredMarkup:null,editors:[{id:"191770",title:"Dr.",name:"Mohamed A.",middleName:null,surname:"El-Esawi",slug:"mohamed-a.-el-esawi",fullName:"Mohamed A. El-Esawi",profilePictureURL:"https://mts.intechopen.com/storage/users/191770/images/system/191770.jpeg",biography:"Dr. Mohamed A. El-Esawi is a visiting research fellow at the University of Cambridge, United Kingdom, and Associate Professor of Molecular Genetics, Botany Department, Faculty of Science, Tanta University, Egypt. Dr. El-Esawi received his BSc and MSc from Tanta University, and his Ph.D. degree in Plant Genetics and Molecular Biology from Dublin Institute of Technology, Technological University Dublin, Ireland. After obtaining his Ph.D., Dr. El-Esawi joined the University of Warwick, United Kingdom; University of Sorbonne, France; and University of Leuven (KU Leuven), Belgium as a visiting research fellow. His research focuses on plant genetics, genomics, molecular biology, molecular physiology, developmental biology, plant-microbe interaction, and bioinformatics. He has authored several international peer-reviewed articles, book chapters, and books, and has participated in more than sixty conferences and workshops worldwide. Dr. El-Esawi is currently involved in several biological science research projects.",institutionString:null,position:null,outsideEditionCount:0,totalCites:0,totalAuthoredChapters:"8",totalChapterViews:"0",totalEditedBooks:"9",institution:{name:"Tanta University",institutionURL:null,country:{name:"Egypt"}}}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,coeditorOne:null,coeditorTwo:null,coeditorThree:null,coeditorFour:null,coeditorFive:null,topics:[{id:"350",title:"Agrology",slug:"agrology"}],chapters:[{id:"69148",title:"Introductory Chapter: Characterization and Improvement of Legume Crops",doi:"10.5772/intechopen.89369",slug:"introductory-chapter-characterization-and-improvement-of-legume-crops",totalDownloads:598,totalCrossrefCites:1,totalDimensionsCites:1,hasAltmetrics:0,abstract:null,signatures:"Mohamed A. El-Esawi",downloadPdfUrl:"/chapter/pdf-download/69148",previewPdfUrl:"/chapter/pdf-preview/69148",authors:[{id:"191770",title:"Dr.",name:"Mohamed A.",surname:"El-Esawi",slug:"mohamed-a.-el-esawi",fullName:"Mohamed A. El-Esawi"}],corrections:null},{id:"68094",title:"Novel Therapeutic Uses of Legume Crops in Southern South America",doi:"10.5772/intechopen.85659",slug:"novel-therapeutic-uses-of-legume-crops-in-southern-south-america",totalDownloads:1138,totalCrossrefCites:1,totalDimensionsCites:1,hasAltmetrics:0,abstract:"The Argentine flora comprises more than 10,000 species, and many of them have been recorded as having medicinal, antimicrobial, and nutraceutical uses in humans as well as veterinary uses. In this chapter, native species/populations from the north of Argentina have been identified, selected, and characterized using morphological, chemical, and molecular techniques. Bauhinia forficata subsp. pruinosa was found to have anti-inflammatory, antidiabetic, diuretic, and analgesic activity and Senna spectabilis var. spectabilis has been found to have antibacterial, antibiofilm, antifungal, and antioxidant properties. The characterization and conservation of the native germplasm will allow us to propose future protocols of adaptation and technological processes to improve the quality of life in the rural areas and sustainable growth. This process will be achieved through a future integral and rational use that contemplates the conservation of the wild populations and their habitat. Thus, new resources will be generated, and the native flora of the country will gain value, strengthening the regional and territorial development of the agricultural and agroindustrial system. In addition, the domestication practices oriented to an integral management of the crop without extraction of the biological resource from the natural habitat minimize the impact of ecosystem degradation by overexploitation associated with landscape fragmentation.",signatures:"Renée Hersilia Fortunato, Virginia Fuentes Baluzzi, Fernando De Diego, Rodrigo T. Biagioni and Alejandro Daniel Esquivel",downloadPdfUrl:"/chapter/pdf-download/68094",previewPdfUrl:"/chapter/pdf-preview/68094",authors:[{id:"272187",title:"Dr.",name:"Renée",surname:"Fortunato",slug:"renee-fortunato",fullName:"Renée Fortunato"},{id:"288386",title:"BSc.",name:"Virginia",surname:"Fuentes Baluzzi",slug:"virginia-fuentes-baluzzi",fullName:"Virginia Fuentes Baluzzi"},{id:"288387",title:"MSc.",name:"Fernando",surname:"De Diego",slug:"fernando-de-diego",fullName:"Fernando De Diego"},{id:"288388",title:"Mr.",name:"Rodrigo",surname:"Biagioni",slug:"rodrigo-biagioni",fullName:"Rodrigo Biagioni"},{id:"288390",title:"Mr.",name:"Alejandro",surname:"Esquivel",slug:"alejandro-esquivel",fullName:"Alejandro Esquivel"}],corrections:null},{id:"64900",title:"Ethnomedicinal Values of Legume Plants in Pakistan",doi:"10.5772/intechopen.82762",slug:"ethnomedicinal-values-of-legume-plants-in-pakistan",totalDownloads:692,totalCrossrefCites:0,totalDimensionsCites:0,hasAltmetrics:0,abstract:"The data on medicinal plants in the vegetation of Pakistan was studied and surveyed from September to November, 2018. Different ethnomedicinal species were recorded which are used by local inhabitants as a medicine, fodder, fuel, and for agricultural purpose. Many of the medicinal plants recorded are used for the treatment of two or more diseases by the local people. The family Fabaceae was dominant with respect to medicinal plants. The precious knowledge of medicinal flora is rapidly vanishing due to the illiteracy among the local people and also due to destruction of the medicinal plants. The present study was designed to convey the knowledge and importance of medicinal flora as well as traditional uses of such plants in daily life.",signatures:"Faisal Hussain and Farzana Usman",downloadPdfUrl:"/chapter/pdf-download/64900",previewPdfUrl:"/chapter/pdf-preview/64900",authors:[{id:"199137",title:"Dr.",name:"Faisal",surname:"Hussain",slug:"faisal-hussain",fullName:"Faisal Hussain"},{id:"272448",title:"Dr.",name:"Farzana",surname:"Usman",slug:"farzana-usman",fullName:"Farzana Usman"}],corrections:null},{id:"66497",title:"Starch Granules from Cowpea, Black, and Carioca Beans in Raw and Cooked Forms",doi:"10.5772/intechopen.85656",slug:"starch-granules-from-cowpea-black-and-carioca-beans-in-raw-and-cooked-forms",totalDownloads:1121,totalCrossrefCites:0,totalDimensionsCites:0,hasAltmetrics:1,abstract:"Starch applications in food systems are mainly influenced by solubility, gelatinization, paste viscosity, digestibility, and retrogradation. These characteristics result from properties such as the size and shape of granules, amylose and amylopectin contents, distribution of polymer chains, degree of crystallinity, and extraction of waste. In beans, the percentage of starch contents on dry basis is between 45 and 60%, being 24–65% amylose. This chapter evaluated the structure of common beans starch granules (Phaseolus vulgaris) and cowpea (Vigna unguiculata) in raw and cooked forms, by optical microscopy (OM) and scanning electron microscopy (SEM). Thus it was possible to observe the gelatinization of the starch granules especially in cowpea and carioca beans, as well as the “hard-to-cook” phenomenon in the black beans.",signatures:"Joyce Aparecida Tavares de Miranda, Lucia Maria Jaeger de Carvalho, Izabela Miranda de Castro, José Luiz Viana de Carvalho, André Luiz de Alcântara Guimarães and Ana Cláudia de Macêdo Vieira",downloadPdfUrl:"/chapter/pdf-download/66497",previewPdfUrl:"/chapter/pdf-preview/66497",authors:[{id:"97047",title:"Prof.",name:"Lucia Maria Jaeger",surname:"De Carvalho",slug:"lucia-maria-jaeger-de-carvalho",fullName:"Lucia Maria Jaeger De Carvalho"},{id:"200652",title:"Dr.",name:"André",surname:"Guimarães",slug:"andre-guimaraes",fullName:"André Guimarães"},{id:"209351",title:"Dr.",name:"Joyce",surname:"Miranda",slug:"joyce-miranda",fullName:"Joyce Miranda"},{id:"209473",title:"Dr.",name:"Izabela Miranda De",surname:"Castro",slug:"izabela-miranda-de-castro",fullName:"Izabela Miranda De Castro"},{id:"276507",title:"Dr.",name:"Ana",surname:"Vieira",slug:"ana-vieira",fullName:"Ana Vieira"},{id:"295486",title:"MSc.",name:"Jose",surname:"Carvalho",slug:"jose-carvalho",fullName:"Jose Carvalho"}],corrections:null},{id:"66478",title:"Mungbean (Vigna radiata L. Wilczek): Retrospect and Prospects",doi:"10.5772/intechopen.85657",slug:"mungbean-em-vigna-radiata-em-l-wilczek-retrospect-and-prospects",totalDownloads:1273,totalCrossrefCites:2,totalDimensionsCites:3,hasAltmetrics:0,abstract:"Mungbean (Vigna radiata L. Wilczek) is economically most important crop of Vigna group. It is also known as green gram, golden gram, moong, Chickasaw, Oregon pea, and chop suey bean and this legumes have a strategic position in Southeast Asian countries for nutritional security and sustainable crop production. Being rich in quality protein, minerals and vitamins, they are inseparable ingredients in the diets of a vast majority of Indian population. When supplemented with cereals, they provide a perfect mix of essential amino acids with high biological value. These crops have the ability to fix atmospheric nitrogen (58–109 kg per ha in kg per ha mungbean) in symbiotic association with Rhizobium bacteria, which enables them to meet their own nitrogen requirement and also benefit the succeeding crops. This crop has also been reported to smother weed flora appreciably (20–45%) when intercropped with tall cereals or pigeonpea and consequently, minimize the cost incurred on weed control. On account of short duration and photo-thermo insensitivity, they are considered excellent crops for crop intensification and diversification. A seed of mungbean is highly nutritious containing 24–28% protein, 1.0–1.5% fat, 3.5–4.5% fibre, 4.5–5.5% ash and 59–65% carbohydrates on dry weight basis and provide 334–344 kcal energy. Mungbean protein is considered to be easily digestible. Mungbean are tropical grain legumes widely grown in the sub-tropical countries of South and Southeast Asia. Nevertheless, these crops are cultivated over a wide range of latitudes in the regions where average diurnal temperatures during the growing season are warmer than about 20°C.",signatures:"Suhel Mehandi, Syed Mohd. Quatadah, Sudhakar Prasad Mishra, Indra Prakash Singh, Nagmi Praveen and Namrata Dwivedi",downloadPdfUrl:"/chapter/pdf-download/66478",previewPdfUrl:"/chapter/pdf-preview/66478",authors:[{id:"275243",title:"Dr.",name:"Suhel",surname:"Mehandi",slug:"suhel-mehandi",fullName:"Suhel Mehandi"},{id:"275245",title:"Dr.",name:"Indra Prakash",surname:"Singh",slug:"indra-prakash-singh",fullName:"Indra Prakash Singh"},{id:"275246",title:"Prof.",name:"Sudhakar",surname:"Prasad Mishra",slug:"sudhakar-prasad-mishra",fullName:"Sudhakar Prasad Mishra"},{id:"290295",title:"Dr.",name:"Syed",surname:"Mohd. Quatadah",slug:"syed-mohd.-quatadah",fullName:"Syed Mohd. Quatadah"},{id:"290728",title:"MSc.",name:"Nagmi",surname:"Praveen",slug:"nagmi-praveen",fullName:"Nagmi Praveen"},{id:"290731",title:"Dr.",name:"Namrata",surname:"Dwivedi",slug:"namrata-dwivedi",fullName:"Namrata Dwivedi"}],corrections:null},{id:"64941",title:"The Productivity of Selected Species and Cultivars of Legumes Grown for Seeds in Organic Production System",doi:"10.5772/intechopen.82686",slug:"the-productivity-of-selected-species-and-cultivars-of-legumes-grown-for-seeds-in-organic-production-",totalDownloads:551,totalCrossrefCites:0,totalDimensionsCites:0,hasAltmetrics:0,abstract:"The aim of the study was to assess the yielding of selected legume species with diversified morphological structure cultivated for seeds in ecological system. The field experiment was carried out in 2016–2018. The first factor was legume species: faba bean, field pea, yellow lupine, and blue lupine, and the second factor was varieties of legumes: faba bean (Granit and Amulet), field pea (Hubal and Batuta), blue lupine (Kurant and Regent), and yellow lupine (Bursztyn and Perkoz). After the harvest, the grain yield of legume plants and the weight of a thousand seeds were determined. The plant structure was determined (length of the part of fruiting stem, number of pods and seeds per plant, number of seeds in the pod, number of fruiting nodes, number of pods and seeds from the node). In addition, the content of selected nutrients (protein, fiber, fat, macroelements) was determined in seeds. Studies showed that in ecological conditions, the pea cultivation, especially Hubal variety (with bipinnate leaves), enabled obtaining the largest seed yield, while the smallest seed yields yellow lupine independent of the morphological type. The self-completing varieties of faba bean, yellow lupine, and blue lupines were yielded at a higher level than varieties with a traditional growth type. Among the pea varieties assessed, the variety Hubal yielded better (with bipinnate leaves). Significantly, higher yield of protein is provided by faba bean cultivation, while the smaller level of pea and yellow lupine.",signatures:"Księżak Jerzy and Bojarszczuk Jolanta",downloadPdfUrl:"/chapter/pdf-download/64941",previewPdfUrl:"/chapter/pdf-preview/64941",authors:[{id:"170281",title:"Prof.",name:"Jerzy",surname:"Księżak",slug:"jerzy-ksiezak",fullName:"Jerzy Księżak"},{id:"170282",title:"Dr.",name:"Jolanta",surname:"Bojarszczuk",slug:"jolanta-bojarszczuk",fullName:"Jolanta Bojarszczuk"}],corrections:null},{id:"64927",title:"Influence of Adjuvants on Efficacy of Postemergence Herbicides Commonly Used in Peanut (Arachis hypogaea L.)",doi:"10.5772/intechopen.82708",slug:"influence-of-adjuvants-on-efficacy-of-postemergence-herbicides-commonly-used-in-peanut-em-arachis-hy",totalDownloads:922,totalCrossrefCites:0,totalDimensionsCites:0,hasAltmetrics:0,abstract:"Field studies were conducted for 2 years in the High Plains of Texas (34.1826o N, 101.9505o W) and in South Texas (29.1634o N, 97.0725o W) to evaluate weed control when using different adjuvants with commonly used peanut herbicides. In the High Plains, Amaranthus palmeri L. control with acifluorfen, imazapic, lactofen, and 2,4-DB at the 1X dose improved with the use of an adjuvant over no adjuvant. A. palmeri control with imazethapyr was similar to that seen with imazapic and lactofen with the exception of the 1/2X rate of imazethapyr, which showed improved control with Agridex over the use of no adjuvant or Induce in 1 year, while Induce was better than no adjuvant or Agridex in the other year. In 1 year in South Texas, A. palmeri control with imazapic at the 1X dose was ≥73% with/without an adjuvant. In another year, the 1X dose of imazapic controlled A. palmeri 64% without an adjuvant, while the addition of Cide Kick II resulted in 83% control. An adjuvant did not improve A. palmeri control with lactofen or Cucumis melo L. control with either imazapic or lactofen. Urochloa texana (Buckl.) control with clethodim at the 1X dose was not improved by the addition of an adjuvant in either year. U. texana control was not improved when using the 1X dose of fluazifop-P with any adjuvant.",signatures:"William James Grichar, Peter A. Dotray and Mark A. Matocha",downloadPdfUrl:"/chapter/pdf-download/64927",previewPdfUrl:"/chapter/pdf-preview/64927",authors:[{id:"13502",title:"Prof.",name:"W. James",surname:"Grichar",slug:"w.-james-grichar",fullName:"W. James Grichar"},{id:"14656",title:"Dr.",name:"Peter A.",surname:"Dotray",slug:"peter-a.-dotray",fullName:"Peter A. Dotray"},{id:"283163",title:"Prof.",name:"Mark",surname:"Matocha",slug:"mark-matocha",fullName:"Mark Matocha"}],corrections:null},{id:"65957",title:"Breeding Elite Cowpea [Vigna unguiculata (L.) Walp] Varieties for Improved Food Security and Income in Africa: Opportunities and Challenges",doi:"10.5772/intechopen.84985",slug:"breeding-elite-cowpea-em-vigna-unguiculata-em-l-walp-varieties-for-improved-food-security-and-income",totalDownloads:1270,totalCrossrefCites:4,totalDimensionsCites:11,hasAltmetrics:0,abstract:"Cowpea, Vigna unguiculata (L.) Walp, is among the most important grain legumes in Africa. Its nutritional value and biological nitrogen fixation (BNF) potential coupled with a high plasticity to environmental conditions places this legume in a unique position in Sub-Saharan Africa (SSA) in the context of food and nutritional security. However, cowpea yield and BNF contribution to agricultural systems in this sub-continent is far behind the average global values. The inability to run effective breeding programs to timely generate and deliver high yielding, nutritious and climate smart cowpea varieties, coupled with poor crop husbandry practices has been in the forefront of the current situation. In this chapter, the main constrains and opportunities to establish and run successful and effective cowpea production and breading programs in SSA are discussed. The discussion is built around the argument that SSA can benefit from its rich collection of landraces, as well as from high-throughput methodologies to assist the screening and the development of adapted, high yielding and nutritious varieties.",signatures:"Ana Maria Figueira Gomes, Nascimento Nhantumbo, Manuela Ferreira-Pinto, Rafael Massinga, José C. Ramalho and Ana Ribeiro-Barros",downloadPdfUrl:"/chapter/pdf-download/65957",previewPdfUrl:"/chapter/pdf-preview/65957",authors:[{id:"171036",title:"Dr.",name:"Ana I.",surname:"Ribeiro-Barros",slug:"ana-i.-ribeiro-barros",fullName:"Ana I. Ribeiro-Barros"},{id:"275914",title:"MSc.",name:"Ana",surname:"Gomes",slug:"ana-gomes",fullName:"Ana Gomes"},{id:"275915",title:"Prof.",name:"Nascimento",surname:"Nhantumbo",slug:"nascimento-nhantumbo",fullName:"Nascimento Nhantumbo"},{id:"275916",title:"Prof.",name:"Rafael",surname:"Massinga",slug:"rafael-massinga",fullName:"Rafael Massinga"},{id:"275917",title:"Dr.",name:"José",surname:"Ramalho",slug:"jose-ramalho",fullName:"José Ramalho"}],corrections:null}],productType:{id:"1",title:"Edited Volume",chapterContentType:"chapter",authoredCaption:"Edited by"},subseries:null,tags:null},relatedBooks:[{type:"book",id:"5781",title:"Phytohormones",subtitle:"Signaling Mechanisms and Crosstalk in Plant Development and Stress Responses",isOpenForSubmission:!1,hash:"054eaa85c13ebe3d04fb8852005d2bad",slug:"phytohormones-signaling-mechanisms-and-crosstalk-in-plant-development-and-stress-responses",bookSignature:"Mohamed El-Esawi",coverURL:"https://cdn.intechopen.com/books/images_new/5781.jpg",editedByType:"Edited by",editors:[{id:"191770",title:"Dr.",name:"Mohamed A.",surname:"El-Esawi",slug:"mohamed-a.-el-esawi",fullName:"Mohamed A. 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Electromagnetic interference (EMI) can be defined as electromagnetic signals that unintentionally disturb an electrical or electronic system’s normal operation. These perturbances can affect the electrical or magnetic magnitudes (voltage, current or electromagnetic field) of its circuits.
The problem of interferences is an issue that design engineers continually face [1]. Electromagnetic interferences can cause different kinds of problems in digital and analog systems, leading to malfunctions, system reboots, or even permanent damage to the system if the system is not adequately designed or protected [2]. The security of an electronic system in which coexist devices that produce electromagnetic interference and small signal circuits that can sensitive to these disturbances, depends on the compatibility of the signal levels used. Thereby, it is convenient to comply with specific design and installation rules that allow making the disturbance levels generated by the interferences source elements compatible with the signal levels used by the possible victim elements or elements sensitive to such interferences [3].
Some standards establish the maximum limits of interferences to ensure that the equipment is compatible and does not interfere. Thus, electromagnetic compatibility (EMC) is the ability of a system to operate satisfactorily in its electromagnetic environment without introducing disturbances above the normalized limits in that environment and withstanding those produced by other equipment. Electromagnetic compatibility is regulated by standards that require compliance with the limits of electromagnetic interferences in electronic systems by studying all the phenomena of generation, propagation, and susceptibility to EMI. Thereby, it is necessary to carry out measurements to certify that this equipment complies with regulations to meet these electronic equipment requirements.
When analyzing an EMI problem, the following elements should be identified (Figure 1): the source of interferences, the path of propagation, and receivers affected by the interferences. Based on this concept, when a designer faces an EMI problem, he/she must analyze the system, identify these three elements, and deal with interferences applying these strategies: eliminate EMI sources, increase the EMI immunity of the victim element and/or decrease the energy transmitted through the propagation path.
Main elements in electromagnetic interference phenomena.
EMI can spread through different means or paths, as shown in Figure 2, so they can be grouped into:
Conducted interference: when the propagation path is an electrical conductor that joins the sources with the affected receiver such as power cables, signal cables, metal chassis.
Radiated interferences: they can be classified as far- or near-field depending on the propagation’s wavelength and the distance between the source and victim elements. Radiated far-field interferences are identified when carried out through electromagnetic fields, fulfilling the following condition: propagation distance > wavelength/2π. Radiated near-field interferences are called coupling and can be identified as inductive coupling or capacitive coupling between neighboring conductors, depending on whether the interference is propagated by a magnetic or electric field, respectively.
Kind of propagation and coupling of electromagnetic interference.
The most appropriate strategy is to consider electromagnetic compatibility during the system design stage. If EMC is ignored until the problem arises during the first functional tests or product certification, the solutions usually result in a higher cost [4]. The possibility of applying specific techniques for the elimination of interferences is reduced as a system is developed. At the same time, the cost of EMI reduction increases [5]. However, it is not always possible to predict EMI problems during the design stage because it is complicated to emulate the real environment in which the system will work. Another possibility is that the designed system complies with the standards, but the problems appear when interconnected with other equipment or facilities. When this situation occurs, the right approach is to suppress EMI at its source whenever possible, rather than increasing immunity through victim circuit protections. This technique works best since a single EMI source can find multiple spread paths and affect different victims. If it is not possible to act directly on the source, it is recommended to focus on the EMI propagation path or, finally, on the affected receiver.
Detection and correct characterization of the EMI is an essential factor in designing a suitable solution. Thus, it is essential to perform EMI measurements using different instrumentation, measuring probes, and antennas to detect the electromagnetic fields that can provide information to the designer from undesired signals. These measurements make it possible to detect the disturbances’ magnitude and localize their frequency range in order to select the most optimal solution.
When the cables represent the EMI source, it could not pass the conducted or radiated emissions test. A widely used technique to reduce these problems is applying an EMI suppressor such as a sleeve core [5].
This contribution focuses on analyzing different nanocrystalline (NC) EMI suppressors’ performance intended for attenuating interferences in cables. Firstly, some applications of this kind of EMC components are described in section 2, while the description of the manufacturing process and main features of NC material are explained in section 3. The characterization methods employed to determine the NC samples’ effectiveness from the standpoint of the impedance and insertion loss they can provide are shown in section 4. Subsequently, in section 5, NC sleeve cores’ performance is discussed and compared to conventional ceramic samples. Finally, the main conclusions are summarized in section 6.
The Magnetic Field (H) is associated with electrodynamic phenomena and appears whenever there are electric currents. The H field can produce effects capable of seriously disturbing the operation of an electronic circuit. Whenever current flows in a circuit, this current creates a magnetic field in that circuit, which will vary as the current varies. Consequently, in any circuit that carries an alternating current, variations of magnetic flux occur. According to Lenz’s law, an electromotive force will be induced by the field variation. Therefore, if the current is constant, there will be no induced electromotive force.
Considering that the flux density (B) is proportional to the product of the permeability of the medium and the incident H field, B is the result of the action of H in a magnetic circuit, and its intensity will be higher or lower depending on the permeability of the matter (μr). For the shielding of conductors against EMI, the most common is to use ferromagnetic materials since they present a permeability much higher than that of vacuum (μ0).
When introducing the sample, the external field deforms considerably, being, at each point, the resultant of the initial magnetic field and the field created by the orientation of the magnetic domains. As shown in Figure 3, the material concentrates the field lines and regions outside and close to the material, reducing the emitted field.
Management of H field through introducing a sleeve core.
As explained above, unexpected EMI sources in cables can appear in our system when connected to another device. One of the most used techniques for reducing cables’ interferences is applying an EMI suppressor such as sleeve cores to them. This EMI suppressor provides selective attenuation of undesired interference components that the designer may wish to suppress and it does not affect the intended signal. Thereby, this component is widely used to filter EMI in power cables to reduce high-frequency oscillations generated by switching transients or parasitic resonances within a circuit, and EMI in peripheral cables of electronic devices such as multiconductor USB or video cables.
From the standpoint of the magnetic properties, a sleeve core is defined by the relative permeability since it is the main parameter that describes the performance of a specific magnetic material to concentrate the magnetic flux in the core. This parameter is generally expressed through its complex form represented by the real component (μr’) that quantifies the real or inductive part and the imaginary or resistive component (μr”) that is related to the material ability to absorb the electromagnetic interferences [6, 7].
The presence of noise current in a conductor generates an undesired magnetic field around it, resulting in EMI problems. The effectiveness of a sleeve core to reduce EMI in cables is defined by its capability to increase the flux density of a certain field strength created around a conductor. Thereby, noise current generates a magnetic field which is concentrated into magnetic flux inside the ferrite by the core’s magnetic permeability (μr’). This magnetic field inside the ferrite is reduced by the ferrite’s magnetic loss (μr”), converting it into heat energy. As a result of these two filtering mechanisms the flowing noise current in the conductors is reduced.
Currents that flow in cables (with two or more conductors) can be divided into differential mode (DM) and common mode (CM) depending on the directions of propagation. Although DM currents are usually significantly higher than CM currents, one of the most common EMI radiated problems is originated by CM currents flowing through the cables of the system [8]. CM currents have a much greater interfering potential, despite not having a high value. This fact is due to only a few microamps are required to flow through a cable to fail radiated emission requirements [5, 9]. The use of sleeve cores is an efficient solution to filter the CM currents in cables because, if a pair of adjacent conductors is considered, when the cable ferrite is placed over both signal and ground wires, the CM noise is reduced. As shown in Figure 4, the CM currents in both wires flow in the same direction, so the two magnetic fluxes in the cable ferrite are added together, and the filtering action occurs in the sleeve core. The intended (DM) current is not affected by the presence of the cable ferrite because the DM current travels in opposite directions and is transmitted through the signal and returns. Thus, the current of the two conductors is opposing, meaning they cancel out and the cable ferrite has no effect [10, 11]. In the case of wanting to filter the DM currents, it would be necessary to use a sleeve core in each of the cable’s conductors.
Diagram of CM and DM currents passing through a cable ferrite with two adjacent conductors (signal and return paths).
An external power supply (Figure 5) can be considered a specific example of the application of sleeve cores to reduce EMI in terms of both radiated and conducted emissions. Within the conducted emission range (150 kHz – 30 MHz), the conductors of the system are generally too short to be considered an EMI antenna source since the impedance of possible parasitic inductors is low, and the impedance of parasitic capacitors is typically high. Nevertheless, in the radiated emissions range (from 30 MHz), the parasitic associated with conductors and power line EMI filters can be significant if conductors are long enough to be considered an unintended antenna [12, 13]. External power supplies typically incorporate discrete inductors, capacitors in the AC input circuitry to implement common mode, and differential mode filters before the input bridge and the switching stage. This filtering stage’s main objective is to attenuate the interferences that can be conducted out from the power supply to the AC input power lines. Accordingly, the internal PCB is designed to hold these filtering components in order to pass regulatory safety and EMC testing. When these techniques are considered, a power supply design may meet conducted and radiated emission requirements when tested in isolation. Nevertheless, when the power supply is added to a complete system, the system may fail emissions testing due to the interferences emitted from the system load to the designed power supply through the DC output cable back. One of the most common solutions to solve this EMI problem is integrating a sleeve core that reduces the undesired interferences without affecting the DC intended signal.
Diagram of an external power supply elements.
The advantage of using this EMI solution is that it does not involve redesign the electronics and, generally, the mechanical redesign. This is an important advantage because determining in the testing stage, which is the EMI source, may not be straightforward. However, the use of a sleeve core involves adding an extra component whose drawbacks result in increasing the product’s size and weight besides the cost of the filtering component and its installation. Therefore, this is an effective solution to attenuate EMI emissions in cables when it is not possible to solve the problem through a system redesign, but it is essential to strike a balance between performance and other factors such as weight, dimensions, and cost [14].
Sleeve cores are manufactured with magnetic material that allows them to control interferences in a certain frequency range with a specific ratio. The values of these two parameters mainly depend on the EMI suppressor intrinsic composition and internal structure. The most used sleeve ferrite cores are based on ceramics or polycrystalline materials because they contain metal oxides, such as manganese or zinc oxide [15]. Thereby, MnZn and NiZn are the most popular EMI suppressor solution due to their heat resistant, hardness, and high resistance to pressure. One of the ceramics’ main advantages is the possibility of manufacturing samples with many different shapes able to provide a significant performance [16, 17]. The starting material of ceramics is iron oxide Fe2O3 mixed with one or more divalent transition metals, such as manganese, zinc, nickel, cobalt, or magnesium [18]. Nanocrystalline sleeve core represents an innovative and increasingly used solution for EMI suppression in cables. This solution has demonstrated excellent suitability to reduce interferences from the low-frequency region to the mid-frequency range [19, 20]. In this sense, some researchers have investigated the use of NC structure compositions to make EMC components because this kind of core can reduce its volume by 50–80% and yield greater magnetic properties and insertion losses than conventional ceramic components [21, 22, 23, 24].
Consequently, some NC novel samples are characterized and compare to MnZn and NiZn cores to determine this novel material’s effectiveness compared to the conventional ceramic solutions by analyzing samples with different dimensions.
The manufacturing procedure of ceramic materials (Figure 6) is based on, firstly, mixing raw materials into the desired proportions. Next, it is then pre-calcined to form the ferrite. The pre-sintered material is then milled to obtain a specific particle size. Subsequently, the granulated material is shaped by a pressing technique to obtain the final form. Finally, the resultant core is sintered, promoting any unreacted oxides to be formed into ferrite and protected with epoxy [25, 26]. The manufacturing procedure and the material mix are essential to define a ceramic core’s magnetic properties. Thereby, MnZn materials can provide a significant performance for EMI suppression applications, covering the range of frequency from hundreds of kHz to some MHz. In contrast, NiZn materials are intended for a higher frequency operation than MnZn, covering from tens of MHz to several hundreds of MHz [16, 19, 20, 27].
Diagram of the manufacturing procedure of ceramic cores.
Figure 7 shows two micrographs of the samples obtained using scanning electron microscopy (SEM). In these photographs, it is possible to observe the internal structure and the grain size of MnZn (a) and NiZn (b) ceramic materials.
SEM photographs of ceramics core materials: (a) MnZn material composition; (b) NiZn material composition.
The results presented in [19, 20] highlighted the great suitability of NC EMI suppressors to filter electromagnetic interference throughout the frequency band from 100 kHz to 100 MHz. Furthermore, data obtained from its magnetic properties indicate that this EMC solution could also provide good performance in terms of EMI suppression at higher frequencies. The advantages of iron-based nanocrystalline materials lie in the high values of relative permeability, the reduction of the magnetic components’ volume, and the stable operation up to high-temperatures. These properties are mainly defined by the manufacturing procedure. The manufacturing procedure of NC samples (Figure 8) is quite different from the used for ceramic production since it is formed by a continuous laminar structure that is wound to form the final core. The material is a two-phase structure consisting of an ultra-fine grain phase of FeSi embedded in an amorphous ribbon of 7–25 micrometers in thickness. Firstly, the base material is molten by heating it at 1300 °C and depositing it on a water-cooled wheel that reduces the temperature of the material to 20 °C. Next, the resulting amorphous metal ribbon is exposed to an annealing process under the presence of transversal and/or longitudinal magnetic fields. This treatment modifies the magnetic properties and the amorphous structure forms ultrafine crystals with a typical size of 7–20 nm, obtaining the nanocrystalline material. The last stage of this procedure corresponds to applying a protective coating or a plastic housing that protects the obtained cores due to the brittle nature of the tape [11, 18, 28].
Diagram of the manufacturing procedure of nanocrystalline cores.
Figure 9 shows a SEM photograph of a NC sample where it is possible to observe the difference in terms of the grain size if it is compared with the ceramic materials since it is in the order of nanometers.
SEM photograph of a nanocrystalline core material.
The evaluation of NC sleeve cores is carried out by analyzing the performance regarding two MnZn and NiZn ceramic cores. Therefore, the evaluation of the three different solutions in terms of EMI suppression from the standpoint of the magnetic properties, the impedance, and the insertion loss provided by different samples. One of the cores selected is based on MnZn, a material widely used to reduce EMI in the low-frequency region and the other selected core is made of NiZn that is generally employed to filter EMI from some tens of megahertz. Thus, it is important that the analyzed sleeve cores have a similar volume in order to conclude which solutions is more effective depending on the frequency range selected. Accordingly, different ceramic MnZn and NiZn sleeve core samples with similar dimensions to the NC samples have been selected to be characterized and evaluated, as shown in Table 1. Note that two sets of three different materials are analyzed. In the case of the small samples set (S1, S2, and S3), the ceramic samples are longer than the NC one, whereas in the large samples set (S4, S5, and S6), the three cores have similar dimensions.
Sample reference | Magnetic material | Outer diameter (OD) (mm) | Inner diameter (ID) (mm) | Height (H) (mm) |
---|---|---|---|---|
S1 | NC | 15.3 | 5.5 | 20.0 |
S2 | MnZn | 16.0 | 8.0 | 28.5 |
S3 | NiZn | 17.5 | 9.5 | 28.5 |
S4 | NC | 28.3 | 15.5 | 30.0 |
S5 | MnZn | 26.0 | 13.0 | 28.5 |
S6 | NiZn | 26.0 | 13.0 | 28.5 |
List of sleeve core samples analyzed.
The relative permeability (μr) is one of the most important parameters that define the material’s ability to absorb electromagnetic interferences. The permeability relates the magnetic flux density of a specific magnetic field in a defined medium. When a sleeve core is placed around a certain cable, it concentrates the magnetic flux. The material’s internal properties describe its ability to focus the magnetic flux is represented through the permeability complex parameter. The effectiveness to attenuate EM interferences of a material can be quantified by separating μr into its complex form. The real component is related to the stored energy or inductive part (μ’) and the imaginary component that provides the losses or resistive part (μ”). Thereby, the complex relative permeability is expressed by:
The magnitude of the NC material’s relative permeability is represented together with MnZn and NiZn permeability traces in Figure 10 to study the frequency region covered by each material. This graph shows the NC core provides higher permeability than the ceramic materials throughout almost the entire frequency range studied, despite being the material with higher initial permeability. MnZn has an initial permeability (μi) of 5000 and it is able to provide a permeability around 3000 up to the 2 MHz, providing a similar value to NC at this frequency point. NC demonstrates the best performance in the mid-frequency region, whereas the NiZn material (μi = 620) is more effective in the high-frequency region. The NC material has an initial permeability (μi) of 30000 and it provides a significant permeability up to 200 MHz.
Relative permeability of NC core compared to MnZn and NiZn compositions.
The permeability parameter is used to describe the core material’s behavior; however, manufacturers of EMI Suppressors generally provide their customers the impedance that it introduces in the cable in which it is applied. Typically, the datasheets only specify the impedance at several frequency points or the graph of the magnitude of the impedance in the frequency range where it is more effective. The impedance of a certain sleeve core considers, besides the material permeability, other variables such as the self-inductance defined by the dimensions and the shape. Thereby, sleeve cores are usually defined and classified by specifying the magnitude of the impedance (ZF), which is obtained from the equivalent component parameters such as resistance (R) and the impedance of the inductive part (XL). The magnitude of the impedance is given by:
The measurement of the impedance carried out in this contribution has been performed by using the E5061B Vector Network Analyzer (Keysight) connected to the Terminal Adapter 16201A (Keysight) and the Spring Clip Fixture 16092A (Keysight), as shown in Figure 11. These fixtures are internally compensated by an impedance standard calibration method to consider the electrical length path and the impedance variations caused by parasitic elements.
Setup for measuring impedance of sleeve core samples.
Another kind of EMC component datasheets, such as common-mode-chokes, show the attenuation ratio or insertion loss in terms of decibels (dB) that are able to provide. In the case of sleeve cores, it is also possible to determine the insertion loss that it introduces when applied in a cable. The insertion loss that a sleeve ferrite core is able to yield is strongly dependent on the impedance of the system in which it is placed, besides its impedance response depending on the frequency. Subsequently, these components are more effective against EMI when the source and load systems’ impedance is low. The equivalent circuit approach to determine the insertion loss parameter of a specific sleeve core requires considering the source impedance (ZA) and the load impedance (ZB) of the system with electromagnetic interference problems. The impedance introduced by the sleeve core (ZF) in that system is introduced in the path that connects both systems. The equivalent circuit diagram employed to determine this impedance relation and analyze the effect of introducing a sleeve core into a certain system is shown in Figure 12 [29].
Schematic of source and load equivalents circuits used to determine the insertion loss parameter of a sleeve core when introduced into a system.
According to this diagram, when the system impedance is known, the insertion loss (A) in terms of decibels can be calculated through the Eq. (3) considering the impedance of the sleeve core (ZF):
The results presented in this section correspond to the analysis of the performance provided by NC samples compared to ceramic solutions. This comparison is carried out by evaluating both the impedance and insertion loss parameters described in the previous section. Two sets of three sleeve cores are analyzing to study the performance provided by samples intended for thin cables (samples S1, S2, and S3) and those with larger diameters (samples S4, S5, and S6). These results make it possible to observe the performance of each EMI suppression solution. It allows the system designer to select the best component to solve EMI problems depending on the frequency range where it is located.
Firstly, the impedance measured of the two sets of samples is shown in Figures 13 and 14. Figure 13 shows the response of the three small samples and it can be observed that the MnZn sleeve core is able to provide the best performance in the low-frequency, achieving its maximum value at 1.5 MHz (132.08 Ω). NiZn sleeve core reaches the maximum impedance value at 50.1 MHz (145.63 Ω). This material represents an interesting solution to reduce EMI in the mid and high-frequency regions, whereas it does not provide a valuable impedance in the low-region. NC sample offers the highest impedance values in the mid-frequency region (from 4.1 MHz to 95.6 MHz), reaching the maximum impedance value at 34.9 MHz (162.04 Ω). Nevertheless, in contrast to ceramic materials, NC sample is able to provide a significant response in both the low and high-frequency region. NC sleeve core shows a better performance than ceramics to reduce EMI emissions in a wideband frequency range.
Magnitude impedance of the NC (S1), MnZn (S2), and NiZn (S3) samples.
Magnitude impedance of the NC (S4), MnZn (S5), and NiZn (S6) samples.
Figure 14 shows the performance of the large sleeve core samples in terms of the impedance response. It is possible to observe that the MnZn sample is the most effective solution to reduce interferences up to 1.2 MHz. From this frequency value, the NC sample is able to introduce a higher impedance value than the other two solutions, covering the range from 1.2 MHz to 77.7 MHz. NiZn sample provides larger impedance than NC in the high-frequency region. The maximum impedance value offered for the MnZn sample is located at 0.6 MHz (89.55 Ω). In the case of the NC sample, this value is achieved at 33.1 MHz (186.77 Ω), whereas the NiZn sample reaches the highest impedance value at 48.2 MHz (157.49 Ω). It is possible to observe that the frequency ranges where the large sleeve core is most effective are similar to the provided by the small samples. In Figure 14, the MnZn sample (S5) shows a less significant performance than the smaller sample response based on the same material (S2). The dimensional effect causes this shift in the resonance frequency (maximum impedance value). Thereby, MnZn material reduces its performance when it is used to manufacture large cores due to its internal structure and electrical features. Nevertheless, it is possible to observe that the dimensional effect does not affect the NC and NiZn material when used to manufacture large EMI suppressor cores. However, despite these aspects, the effectiveness in the different frequency regions is similar to the described for the last set of samples.
The insertion loss results have been obtained by considering a system with an input and output impedance of 50 Ω (ZA = ZB = 50 Ω). Thereby, the experimental results that are shown in Figures 15 and 16 can be compared by considering Eq. (3) and the impedance provided by each sleeve core (ZF). The results obtained in terms of insertion loss correlate with the impedance responses shown previously since MnZn samples provide a higher attenuation ratio in the low-frequency region. Specifically, the S2 sample provides up to −7.25 dB at 1.7 MHz and − 5.43 dB at 0.6 MHz in the case of S4. Thereby, MnZn material represents the best solution when the interferences are located below 4.2 MHz, considering the small sample set (see Figure 15). This frequency range is reduced when larger samples are analyzed since the MnZn S4 sample predominant frequency range is shorter up to 1.3 MHz if compared to the NC S3 sample (see Figure 16). As a result of this, the effectiveness of MnZn material is reduced compared to NC material when the dimensions of the sample are increased, since the S4 sample’s frequency range is shorted 3.9 MHz and the maximum attenuation has been reduced 1.82 dB. Considering this behavior of MnZn material when a large core is employed, NC represents an alternative solution to suppress EMI in the low-frequency region when a large sleeve core is needed due to it provides higher attenuation than NiZn in this range. Regarding the mid-frequency region, NC samples (S1 and S4) have a similar response, reaching the maximum values of insertion loss at 33.5 MHz (−8.33 dB) in the case of S1 and 28.2 MHz (−9.11 dB) for S4. NC S1 sample has the predominant response from 4.2 MHz to 60.4 MHz, considering the small sample set (see Figure 15) and from 1.3 MHz to 57.2 MHz in the case of the large samples (see Figure 16). NiZn S3 and S6 samples are able to offer the best performance in the high-frequency region since NC samples have a resonance frequency lower than the value shown by NiZn cores. This insertion loss difference between NC and NiZn in the high-frequency region is more significant when the large sample cores.
Insertion loss of the NC (S1), MnZn (S2), and NiZn (S3) samples.
Insertion loss of the NC (S4), MnZn (S5), and NiZn (S6) samples.
Consequently, MnZn samples are significantly effective in the low-frequency region, but their performance is strongly reduced in the high-frequency region. Contrary to this behavior, NiZn samples show great insertion loss in the high-frequency region, whereas it provides a poor performance in the low-region. However, NC samples show the best performance in the mid-frequency region at the same time that it provides a significant insertion loss in the low-frequency region and a comparable response than the offered by the NiZn samples in the high-frequency region.
Note that these results are related to the impedance of both systems where the cable in which the sleeve core is applied. Therefore, the insertion loss values obtained can be considered when the EMI suppression solution is applied to data or video cables. According to Eq. (3), if these samples were installed in power cables, it could be possible to obtain higher attenuation ratios. For instance, if the sleeve core is installed in a system where ZA = ZB = 5 Ω, the ZF provided by the sample is more significant than the system impedance. Thereby, if the maximum impedance provided by S1 is considered (ZF = 145.63 Ω) it can be able to introduce an insertion loss of −23.84 dB instead of the −8.33 dB obtained for ZA = ZB = 50 Ω.
The performance of NC samples has been compared with the effectiveness provided by ceramic cores. Thereby, it has been analyzed the performance of each EMI suppression solution from the standpoint of the magnetic properties, impedance, and insertion loss.
Considering the results presented, it is possible to identify the frequency regions where each material solution is effective to reduce EMI when applied in a certain cable. According to the relative permeability data, the MnZn material analyzed is suitable when the interferences are located in the low-frequency region (from hundreds of kilohertz up to some megahertz). In contrast, NiZn solution is not effective in this frequency region. NiZn samples show an interesting solution to reduce EMI in the mid and high-frequency region since it shows a better response than MnZn up to about 5 MHz. The relative permeability data shows that NC material is able to provide a wideband solution due to it is able to offer a comparable response to MnZn material in the low-frequency region and NiZn material in the high-frequency region. Furthermore, NC shows the highest permeability in the mid-frequency region. The excellent magnetic properties shown by the NC material have been verified from the standpoint of the impedance and the insertion loss that the NC samples can introduce in a certain cable with electromagnetic disturbances. Therefore, MnZn samples show a significant performance to reduce EMI in the low-frequency region in terms of impedance and insertion loss, whereas NiZn is effective against high-frequency interferences.
Consequently, if the EMI disturbances are specifically located in the low or high-frequency region, a ceramic core is able to provide significant effectiveness to reduce them. If the interferences are detected in the mid-region (from 5 MHz to 100 MHz), NiZn material is able to provide better performance than MnZn if only ceramic cores are considered. NC structures usually represent a higher cost than ceramic, so that this solution may not always be considered to solve an EMI problem located in a specific frequency region. This is the reason why a designer could select a ceramic core instead of a NC core to reduce an EMI problem despite the ceramic core could not be the most effective solution. Nevertheless, when the EMI disturbances are distributed in different frequency regions, NC sleeve core shows a better performance than ceramics to reduce EMI emissions in a wideband frequency range.
Atrioventricular septal defects are a group of malformations involving the atrioventricular (AV) septum and common atrioventricular junction (Figure 1). Previously, referred to as atrioventricular canal or endocardial cushion defects, is now called AV septal defect (AVSD). For the purpose of this chapter, we will use the term AV septal defects. They are divided into complete, partial and variations of both of them based on the orifices and septal communications which will be discussed in detail in this chapter.
Atrioventricular septum in the normal heart. The atrioventricular septum (AVS) lies between the right atrium (RA) and the left ventricle (LV). LA, left atrium; RV, right ventricle; MV, mitral valve; TV, tricuspid valve. “From: Cetta F, Truong D, Minich LL, Maleszewski JJ, O’Leary PW, Dearani JA & Burkhart HM. Chapter 29: Atrioventricular Septal Defects. In: Allen HD, editor. Moss & Adams’ Heart Disease in Infants, Children, and Adolescents, Including the Fetus and Young Adult, 9th Edition. Philadelphia: Lippincott Williams & Wilkins, 2016; used with permission of Mayo Foundation for Medical Education and Research, all rights reserved.”
Congenital heart disease (CHD) accounts for around 1–1.2% of live births both in the United States and globally [1, 2]. AVSDs account for around 4–5% of all CHDs, with 5.38 cases per 10,000 live births, an increase from prior reports [1, 3]. It is the most common fetal cardiac anomaly detected on prenatal screening (Figure 2). Around half of the patients with AVSD have Down syndrome. However, approximately 45% of CHD patients with Down syndrome have AVSD [4, 5]. Most of these cases are isolated, although some may have pulmonary stenosis or atresia. There is an association with other anomalies like heterotaxy and Ellis-Van Creveld syndrome [6].
Fetal echocardiogram four-chamber view: Complete AVSD. RA, right atrium; LA, left atrium; RV, right ventricle; LV, left ventricle. *Primum atrial septal defect and inlet ventricular septal defect.
In a normal heart, tricuspid and mitral valve annuli are positioned at different levels because of the atrioventricular septum. In AV septal defects, tricuspid valve annulus is located more apically in relation to mitral valve. The portion of the offset between tricuspid and mitral valve is the location of atrioventricular septum. It has overlapping atrial and ventricular walls [7]. Aortic valve is located anterior and superior between tricuspid and mitral valve, what is referred to as wedged between these valves. This makes the subaortic outflow region placed in between tricuspid and mitral valves. The papillary muscles in the left ventricle are located antero-superior and postero-inferior region. Another feature of importance to this topic, the distance from mitral valve to apex of left ventricle is same as the distance from left ventricular apex to aortic valve (Figure 3).
2D echocardiogram parasternal long axis view: A. In normal cardiac anatomy, distance from the mitral valve to left ventricular (LV) apex and from LV apex to aortic valve is same. B. In AVSD, LVOT is elongated and distance from LV apex to left AV valve annulus is shorter. LA, left atrium; RV, right ventricle; Ao, aorta.
In patients with AV septal defect, the fundamental abnormality is absence of the atrioventricular septum or having a common atrioventricular junction. This results in a cascade of features that are different from normal hearts. The common features shared by all forms of atrioventricular septal defects are:
Presence of common atrioventricular valve
Elongation of the left ventricular outflow tract
Clockwise rotation of papillary muscles
Cleft in the left AV valve
There are two major types of AV septal defects: complete and partial AVSDs. Two sub-types are described: intermediate and transitional, which are variations of complete and partial AV septal defects, respectively (Figure 4). It is preferable to describe the features of these subtypes rather than identifying them as an entity. Different combinations of shunting across atria and ventricles could happen based on the attachments and relationship of the bridging leaflets to septal structures. In general, we would see ostium primum defect and ventricular septal defect (VSD). If the bridging leaflets are attached to the atrial septum, there could be only a ventricular level shunt (Figure 5). When the bridging leaflets are attached to the crest of ventricular septum, it results in an atrial level shunt with an ostium primum defect. In rare instances, where the bridging leaflets close the septal defect(s), we will still see features of the common atrioventricular valve [8, 9, 10]. Complete AVSDs are classified further into three types based on the morphology of anterior bridging leaflet and is named after Giancarlo Rastelli who made significant contributions in his short career and life span:
Type A: In this type, anterior bridging leaflet (ABL) is divided and attached to the crest of the interventricular septum. It is the most common defect and is associated with Down syndrome.
Type B: ABL is partly divided and is not attached to the crest of the septum. Chordae attach usually to papillary muscle in the right ventricle (RV), on the septal surface. It is the least common of all types.
Type C: ABL is not attached or divided and is termed “free-floating”. There are chordal attachments to RV free wall. This type is seen in Down syndrome patients with Tetralogy of Fallot; double outlet right ventricle, complete transposition of the great arteries, and heterotaxy syndromes.
Summary of AVSD. Anatomic and physiologic similarities between the different forms of atrioventricular septal defect (AVSD) are illustrated. Complete AVSDs have one orifice with large interatrial and interventricular communications. Intermediate defects (two orifices) are a subtype of complete AVSD. Complete AVSDs have physiology of VSDs and atrial septal defects (ASDs). In contrast, partial AVSDs have physiology of ASDs. Transitional defects are a form of partial AVSD in which a small inlet VSD is present or the ventricular level shunt has been obliterated by chordal tissue. Partial AVSDs and the intermediate form of complete AVSD share a similar anatomic feature: A tongue of tissue divides the common atrioventricular valve into distinct right and left orifices. LA, left atrium; LPV, left pulmonary vein; LV, left ventricle; RA, right atrium; RPV, right pulmonary vein; RV, right ventricle. “From: Cetta F, Truong D, Minich LL, Maleszewski JJ, O’Leary PW, Dearani JA & Burkhart HM. Chapter 29: Atrioventricular Septal Defects. In: Allen HD, editor. Moss & Adams’ Heart Disease in Infants, Children, and Adolescents, Including the Fetus and Young Adult, 9th Edition. Philadelphia: Lippincott Williams & Wilkins, 2016; used with permission of Mayo Foundation for Medical Education and Research, all rights reserved.”
2D echocardiogram apical four-chamber view: A rare form of AVSD with large inlet ventricular septal defect (*) without a primum atrial septal defect. Note that AV valves are at same level. RA, right atrium; RV, right ventricle; LA, left atrium; LV, left ventricle.
In normal hearts, mitral valve has two leaflets, anterior and posterior with a zone of opposition in one plane. In hearts with AV septal defects, the left AV valve closes in tri-foliate fashion with zones of opposition between posterior, superior and inferior bridging leaflets. This characteristic feature of the left AV valve in AV septal defects will never achieve a mitral valve as in normal hearts. Usually, jet of LAVV cleft is directed to the ventricular septum when compared to isolated mitral valve clefts which are directed anteriorly towards the aortic valve [11]. Rarely, a fusion of the leaflets within the left AV valve (bridging and posterior leaflet) would lead to a double orifice valve. The combined area of the double orifice valve is always less than the single left AV valve area.
As described earlier, LVOT is wedged anteriorly and is narrow when compared to the aortic valve, irrespective of the type of AV septal defect. In partial form, where the superior bridging leaflet is attached to the crest of the septum, it is markedly narrow (Figure 6). This abnormality has been described as goose-neck deformity.
A. Diagram in a normal heart showing aortic valve (AoV) wedged between tricuspid valve (TV) and mitral valve (MV). B. In AVSD, aorta is not wedged between these valves, termed “sprung aortic valve”. PV, pulmonary valve; RAVV/LAVV, right and left atrioventricular valve. A. by Dr. Johannes Sobotta - Sobotta's atlas and text-book of human anatomy 1906, public domain,
Depending on the overall flow from the atrioventricular orifices to respective ventricles, the chambers are usually the same size which is termed as ‘balanced AVSD’. When a common AV valve opens more into the right ventricle or to the left ventricle, it would cause decreased growth of the contralateral ventricle and its great artery, leading to the term ‘unbalanced AVSD’. In right ventricle dominant atrioventricular septal defect, left ventricle and aorta are hypoplastic depending on the amount of blood flow, but usually, the atrial and ventricular septal alignment is maintained. In left ventricular dominance, there will be hypoplasia of the right ventricle and pulmonary artery, typically with septal malalignment. This chamber dominance when it involves the atrium would give rise to double outlet atrium (Figure 7).
2D echocardiogram showing right ventricle (RV) dominant AVSD with severely hypoplastic left AV valve and ventricle (LV). Moderately dilated right atrium (RA) and RV with large primum ASD. LA, left atrium.
In partial atrioventricular septal defects, the most common associated malformation includes secundum ASD, patent ductus arteriosus and persistent left superior vena cava to coronary sinus [12].
Tetralogy of Fallot with pulmonary stenosis is found in one-tenth of the patients with common atrioventricular septal defect and in these patients, Rastelli type C is common. Among others, common atrium, double outlet right atrium, double inlet ventricle with discordant ventriculoarterial connections can be seen.
In normal hearts, AV node is located in the triangle of Koch which is formed by Tendon of Todaro, coronary sinus ostium and septal leaflet of the tricuspid valve [13, 14, 15]. In patients with AVSDs, because of deficient AV septum, the atria will meet the ventricle at the crux of the heart, shifting the AV node more posteriorly and inferiorly.
In the past, failure of the fusion of endocardial cushions was thought to be the only reason for AV septal defects [16]. It could be the first step in the formation of these hearts, but not in entirety. Delamination of valve leaflets occurs late in development, with its formation occurring by undermining of the ventricular myocardium [17]. When the endocardial cushions fail to meet, subaortic outflow tract will not be normally wedged and there will be abnormal development of ventricular mass. Additionally, mesenchymal tissues surrounding the primum ostial foramen play a role in these defects [18, 19].
In patients with complete AVSD, there is one common AV valve with large atrial and inlet VSD (Figure 8). In intermediate form, there are two AV valve orifices, which are formed by a tongue of tissue between superior and inferior bridging leaflets. It has similar physiology as the complete form with large ASD and VSD. In partial AV septal defects, where there are two AV valve orifices with the bridging leaflet attached to ventricular septal crest, giving rise to only interatrial communication (Figure 9A). In some instances, there could be communication at the ventricular level from the chordal attachments which is described as a transitional type (Figure 9B). In all forms of AV septal defects, the left AV valve invariably has a cleft. Rarely there will be no septal communications seen with other common features of AVSD [8].
2D echocardiogram apical 4-chamber view: Complete balanced AVSD. A. When AV valve is closed, there is large primum atrial septal defect (ASD, *) and large inlet ventricular septal defect (VSD, +). Common AV valve and single orifice. B. with valve open. RA, right atrium; LA, left atrium; RV, right ventricle; LV, left ventricle.
Transesophageal echocardiogram, four-chamber view. A. Partial AVSD with large primum atrial septal defect (ASD) (*). Note the valvar attachments to crest of the septum. B. Transitional AVSD with small primum ASD and inlet ventricular septal defect (+) covered by right AVV chordal attachments to the crest of ventricular septum. RA, right atrium; LA, left atrium; RV, right ventricle; LV, left ventricle.
Usually, patients with partial AV septal defect (also called primum ASD) remain asymptomatic until early childhood. They rarely present early with failure to thrive depending on the size of the defect and severity of AV valve regurgitation. Patients with primum ASDs usually present earlier and with symptoms when compared with secundum ASDs. Auscultatory findings include widely split and fixed second heart sound, crescendo- decrescendo systolic ejection murmur at the left upper sternal border from the increased flow across pulmonary valve, and holosystolic murmur at the apex from LAVV regurgitation. A mid-diastolic murmur may be heard at the apex if there is significant mitral regurgitation or at the left lower sternal border if there is a large atrial shunt.
Patients with complete AV septal defects present in the neonatal period after first few days/weeks of life when pulmonary vascular resistance falls. This is attributed to the large atrial and ventricular level shunts leading to pulmonary over circulation. There will be tachypnea, increased work of breathing, failure to gain weight. More often, they would require high-calorie nutrition, diuretics to decrease the preload. On exam, there will be accentuated first heart sound, with S1- coincident holosystolic murmur from LAVV regurgitation, widely split and fixed S2, crescendo- decrescendo systolic ejection murmur at the left upper sternal border from the increased flow across pulmonary valve and sometimes mid-diastolic murmur at apex.
As previously described, AV node is displaced posteriorly and inferiorly in these defects; this may result in prolongation of the PR interval. There will be a left superior deviation of the mean frontal plane vector. Biventricular hypertrophy is seen in complete and intermediate forms. Right ventricular hypertrophy is seen in the partial form. If there is moderate to severe mitral insufficiency, left ventricular hypertrophy may be seen. Other abnormalities which might be seen are prolongation of PR interval (Figure 10) [20].
12-lead EKG in patient with CAVSD showing left superior axis deviation and right ventricular hypertrophy.
Chest roentgenogram shows cardiomegaly with increased pulmonary vascular markings. Features of pulmonary edema may be seen in subjects with congestive heart failure.
Echocardiography is the primary diagnostic modality for the evaluation of atrioventricular septal AV defects [21]. Assessment of the ASD can be best done from a subcostal coronal and sagittal view. VSD could be best evaluated in the parasternal short axis. En-face view of the common AV valves is best achieved with a modified subcostal left anterior oblique view (Figure 11). This view also demonstrates the bridging leaflets, their attachments and helps with the Rastelli classification in patients with complete AVSDs. Subcostal short axis view would assess atrial or ventricular level unbalance. An Apical four-chamber view would augment the information on previously mentioned variables along with AV valve inflow and regurgitation. Overall, all the views complement each other to get comprehensive information, as in any other heart. Associated malformations like tetralogy of Fallot, coarctation, patent ductus arteriosus, arch sidedness should be evaluated using modified subcostal right anterior oblique/parasternal long axis and high parasternal/suprasternal views [22]. 3D echocardiography demonstrates a comprehensive and accurate assessment of the size and extent of the septal defects, size, number, and abnormalities of AV valve leaflets and their attachment sites, as well as the relation of the valvular structures to the great vessels [23]. Other findings such as double orifice left AV-valve, single papillary muscle should be evaluated.
Echocardiogam left anterior oblique (LAO) view. 1. Rastelli type a with attachments of the anterior/superior bridging leaflet (SBL) to crest of venticular septum; B. when valve is closed, notice the cleft in LAVV valve; C. Rastelli type C with “free floating” anterior bridging leaflet (<−>) and chordal attachments to right ventricular (RV) free wall (−>); D. 3D image showing tri-foliate cleft LAVV. IBL, inferior bridging leaflet; ML, mural leaflet; RAL, right anterior leaflet; RPL, right posterior leaflet; ML, left mural leaflet; LV, left ventricle.
In determining the balance of ventricles, a quantitative approach was proposed by Cohen et al. [24] using a subcostal sagittal view. In this view, they measured the area of AV valve over each ventricle and calculated a left/right ventricular ratio, also known as AV valve index (AVVI). Based on the index, patients were stratified either to single-ventricle or bi-ventricular repair pathways. Patients with an AVVI <0.67 and a large VSD would be considered for the single-ventricle pathway. This was modified to the left AV valve area/total area. An AVVI >0.6 is considered left ventricular dominant whereas AVVI <0.4 was considered right ventricular dominant. It is important after surgical repair to assess for residual defects, progressive LVOT obstruction, AVV stenosis and regurgitation, systolic function.
Cardiac catheterization is not frequently performed in AVSDs. However, it is helpful in assessing the hemodynamic information like the degree of shunting, pulmonary vascular resistance. One would see the characteristic “gooseneck appearance” from elongated LVOT on angiography. Patients with severely elevated PVR are poor candidates for full repair and may eventually be candidates for lung transplantation [25].
Cardiac computed tomography (CT) is particularly helpful to assess for any extracardiac defects or associated anomalies in these patients. Retrospective gated approach is useful for the evaluation of ventricular function and ventricular sizes, allows volumetric measurements, and also allows evaluation of ventricular function and wall motion. This may be of particular relevance in patients with hypoplastic ventricles and unbalanced AVSDs [26]. Cardiac magnetic resonance imaging (MRI) is an important tool to assess the degree of unbalance and guide for future surgical planning. These modalities have proven to decrease the amount of radiation exposure during cardiac catheterization [27].
Patients with complete defects present early with signs and symptoms of pulmonary over circulation such as tachypnea, increased work of breathing. In the neonatal period, when the pulmonary vascular resistance decreases, they require diuretics to help with pulmonary congestion and control heart failure along with optimizing nutrition. Occasionally they require afterload reducing agents if there is significant AV valve regurgitation and rarely inotropes. If heart failure or failure to thrive persists despite maximizing medical management, they would be referred for surgery. Based on the corrected gestational age, weight, type of atrioventricular septal defect and associated anomalies, surgical options vary which will be discussed below. As mentioned earlier, patients with partial atrioventricular septal defects usually show symptoms in childhood.
The goals of the surgery are to close the septal defect(s), repair the AV valve, construct two separate and competent AV valves, and avoid injury to conduction tissue.
Balanced atrioventricular septal defects
Surgical Palliation
Palliation with main pulmonary artery band (PAB) is performed in babies less than 5 Kg who failed medical management. In the recent era, complete repair is done even in this weight range. Palliation is considered in patients who are premature, those deemed ineligible for definitive repair or with other co-morbidities. A recent study showed that PAB in complete AVSDs as a bridge to biventricular repair has similar survival as those for primary biventricular repair [28].
Surgical Correction
Patients with complete AVSDs frequently require surgical repair in early infancy with a median age of 3.6 months at the time of repair [29]. Surgical repair is achieved by singe-patch, modified single-patch (Australian/Nunn) or two-patch techniques. A meta-analysis, which compared modified single-patch and two patch techniques showed no significant difference between two groups, but modified single-patch performed when there is small VSD had shorter cardiopulmonary bypass and aortic cross-clamp time [30]. Several other studies showed similar findings [31, 32, 33, 34, 35]. The main advantages of the two-patch technique are maintaining planar alignment of AV valves, lower chances of narrowing of LVOT, not compromising ventricular volumes and preserving the integrity of bridging leaflets [36]. In the Pediatric Heart Network (PHN) study, earlier complete repair showed increased resource utilization with longer intensive care unit stay but no association with incidence of residual VSD or significant left AV valve regurgitation at six months of age (Figure 12). Moderate or greater left AV valve regurgitation was found in 22% at six months with the strongest predictor being moderate or greater left AV valve regurgitation at one month [32]. In the majority of the cases, cleft was closed, 93% in this study [37], it was partially closed, or left open in remaining cases.
A, B: Intra-operative transesophageal echocardiogram, color compare deep transgastric view of left AV valve. A. Pre-operative image showing moderate regurgitation. B. Postoperative after left AVV repair. Note cleft is completely closed without any regurgitation. C. Transthoracic apical 4-chamber view of another patient with severe left AVV regurgitation in multiple jets.
Associated anomalies like patent ductus arteriosus, double orifice left AV valve parachute left AV valve should be addressed. Patients with complete AVSDs and tetralogy of Fallot associated with Down syndrome may need initial palliation with systemic to pulmonary artery shunt or right ventricular outflow tract (RVOT) stent placement and full repair at a later age. In a retrospective study [38], RVOT stenting showed a significant increase in median Z-score for both branch pulmonary arteries at a median follow-up of 255 days. Four patients out of 26 patients died during follow- up period, but none after the initial intervention. Another meta-analysis found no significant difference in the 6-year survival between staged palliation and primary repair, with higher rate of reintervention for RVOT who underwent staged repair [39].
In patients with partial and transitional AVSDs, there has been controversy regarding the age of surgical correction. A PHN study in 2010, showed good results at a median age of 1.8 years, with left AV valve regurgitation being most common and more frequently in children repaired after 4 years of age [12, 40, 41]. One patient out of 87 died in the hospital. Another review showed excellent results at median age of 1.5 years with LV outflow tract obstruction being most common reason for reoperation at their center [42]. Several other studies showed good long-term outcomes with 30-day and 5-, 10-, 20-, and 40-year survivals at 98%, 94%, 93%, 87%, and 76%, respectively. Approximately 3% of the patients in the Mayo group required permanent pacemaker [40, 41]. A minimally invasive right axillary approach has also been performed with good results in partial AVSD patients [43].
Unbalanced atrioventricular septal defects
Surgical techniques in patients with unbalanced AVSDs include single ventricle palliation, biventricular repair and 1.5 ventricular repair.
Single Ventricle Palliation
Patients with severely hypoplastic right/left ventricle would be managed using staged single ventricle palliation. Initially, they are palliated with PAB and later undergo bidirectional Glenn around four to six months of age, if the pulmonary artery pressures are favorable. Around 2 to 3 years of age, extracardiac Fontan completion with or without fenestration is performed [44].
One and half or bi-ventricular repair (BVR)
There are no clear selection criteria to stratify patients into either single or bi-ventricular pathways. Several factors are taken into consideration such as hypoplastic ventricle end-diastolic volume (EDV) of >30 mL/m2, normal ventricular function, adequate AV valve size and function, and low end-diastolic pressures on cardiac catheterization [45].
In select patients with right ventricular dominant AVSD, a staged left ventricular recruitment approach is considered, especially in patients with trisomy 21. It includes ASD closure or restriction, without VSD closure, septation of the common AV valve and banding of the main pulmonary artery [45, 46]. This strategy allows rehabilitation of the left ventricle. With this approach, patient would not be committed at an early age to either a single or bi-ventricular approach and it would give an opportunity to monitor for LV growth [45].
On the other hand, in patients with LV dominant AVSD with inadequate RV size, one and a half ventricular repair has been proposed with primary AVSD repair along with a bidirectional Glenn procedure [47]. This would allow growth of the hypoplastic right ventricle for future biventricular conversion. In some institutions, routine 3-D printing is done for all complex AVSD for pre-surgical planning which permitted biventricular repair in some patients who were previously deemed to be candidates for single ventricle palliation [48, 49].
Even though the outcomes for partial AVSDs are excellent, approximately 10–15% of patients require additional operations. It is well known that pre-operative left AV valve regurgitation predicts the post-operative severity of regurgitation. Other factors are severely dysplastic valve, failure to close the cleft, age of initial surgery, left AV valve stenosis and LVOT obstruction [41]. A technical performance score (TPS) was proposed to grade residual lesions after partial and transitional AVSD repair. In that study, left AV valve regurgitation was the strongest predictor of in-hospital outcomes and unplanned reinterventions after discharge [50]. When compared to complete AVSD, LVOT obstruction occurs more frequently after repair of partial AVSD. Several technical strategies were proposed to decrease the likelihood of subaortic stenosis [51, 52, 53].
In complete AVSDs, late reoperation occurs in around 11–20% of patients with most common reason being left AV valve regurgitation [54, 55]. In these studies, freedom from further reoperation after the first reoperation was 63%, 48%, and 42% at 5, 10, and 15 years, respectively. On later follow-up (median 10.7 years, maximum 30 years), actuarial overall survival was 91%, 91%, and 86% at 5, 10, and 15 years, respectively [55]. A recent study showed improved outcomes with overall survival at 10, 15 and 20 years was 91.7%, 90.7% and 88.7%, respectively and freedom from reoperation was 82.7%, 81.1% and 77%, respectively [56].
Around 36.5–66% of Down patients have pulmonary hypertension with congenital heart disease less than six months of age [5, 57]. There has been controversy about the extent of pulmonary vascular changes with Down and non-Down syndrome patients. There are studies which showed earlier development of pulmonary parenchymal hypoplasia and pulmonary vascular obstructive disease (PVOD) in this patient population [58, 59, 60]. In children with Down syndrome, Rastelli type A is most common. But when associated with tetralogy of Fallot, Rastelli type C is common. In unbalanced AVSDs, left ventricular dominance is more common [6]. It’s known that this patient population tolerates single ventricle physiology poorly [61]. Nevertheless, surgical outcomes are not different for biventricular repair when compared with non-Down syndrome patients. Survival at 30 years was 85.6% for complete AVSD, in patients with trisomy 21 [62].
AVSDs are a group of disorders with deficient AV septum and abnormal AV valve morphology. It is the most common defect in Down syndrome. The definitive surgical repair has excellent outcomes in balanced AVSDs. For unbalanced AVSDs, it is a complex decision-making process and their repairs are usually categorized to single, one and half or bi- ventricular repair. For a select subset of patients, ventricular recruitment procedures improve the candidacy for future bi-ventricular circulation. Patients with Down syndrome should have similar surgical strategies as that of non-Down syndrome patients. The most common reason for reoperation is left AV valve regurgitation.
The authors declare no conflict of interest.
IntechOpen - where academia and industry create content with global impact
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The literature source was Web of Science and SSCI, SCI-EXPANDED, A&HCI, CPCI-S, CPCI-SSH, and ESCI indexes. Fifty-two articles were reviewed; however, 14 of them were not been included in the study. As a result, 38 articles were examined. Level of education, field of education, and material types of AR used in education and reported educational advantages of AR have been investigated. All articles are categorized according to target groups, which are early childhood education, primary education, secondary education, high school education, graduate education, and others. AR technology has been mostly carried out in primary and graduate education. “Science education” is the most explored field of education. Mobile applications and marker-based materials on paper have been mostly preferred. 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The more active a lesson, the more students tend to engage intellectually and emotionally in the learning activities. Cooperative learning is the foundation on which many of the active learning procedures are based. Cooperative learning is the instructional use of small groups so that students work together to maximize their own and each other’s learning. Most of the active learning procedures, such as problem-based learning, team-learning, collaborative learning, and PALS, require that students work cooperatively in small groups to achieve joint learning goals. Cooperative learning is based on two theories: Structure-Process-Outcome theory and Social Interdependence theory. Four types of cooperative learning have been derived: formal cooperative learning, informal cooperative learning, cooperative base groups, and constructive controversy. There is considerable research confirming the effectiveness of cooperative learning. 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Johnson",authors:[{id:"259976",title:"Dr.",name:"David",middleName:null,surname:"Johnson",slug:"david-johnson",fullName:"David Johnson"},{id:"263004",title:"Dr.",name:"Roger",middleName:null,surname:"Johnson",slug:"roger-johnson",fullName:"Roger Johnson"}]},{id:"58060",doi:"10.5772/intechopen.72341",title:"Pedagogy of the Twenty-First Century: Innovative Teaching Methods",slug:"pedagogy-of-the-twenty-first-century-innovative-teaching-methods",totalDownloads:8833,totalCrossrefCites:17,totalDimensionsCites:23,abstract:"In the twenty-first century, significant changes are occurring related to new scientific discoveries, informatization, globalization, the development of astronautics, robotics, and artificial intelligence. This century is called the age of digital technologies and knowledge. How is the school changing in the new century? How does learning theory change? Currently, you can hear a lot of criticism that the classroom has not changed significantly compared to the last century or even like two centuries ago. Do the teachers succeed in modern changes? The purpose of the chapter is to summarize the current changes in didactics for the use of innovative teaching methods and study the understanding of changes by teachers. In this chapter, we consider four areas: the expansion of the subject of pedagogy, environmental approach to teaching, the digital generation and the changes taking place, and innovation in teaching. The theory of education, figuratively speaking, has two levels. At the macro-level, in the “education-society” relationship, decentralization and diversification, internationalization of education, and the introduction of digital technologies occur. At the micro-level in the “teacher-learner” relationship, there is an active mix of traditional and innovative methods, combination of an activity approach with an energy-informational environment approach, cognition with constructivism and connectivism.",book:{id:"5980",slug:"new-pedagogical-challenges-in-the-21st-century-contributions-of-research-in-education",title:"New Pedagogical Challenges in the 21st Century",fullTitle:"New Pedagogical Challenges in the 21st Century - Contributions of Research in Education"},signatures:"Aigerim Mynbayeva, Zukhra Sadvakassova and Bakhytkul\nAkshalova",authors:[{id:"201997",title:"Dr.",name:"Aigerim",middleName:null,surname:"Mynbayeva",slug:"aigerim-mynbayeva",fullName:"Aigerim Mynbayeva"},{id:"209208",title:"Dr.",name:"Zukhra",middleName:null,surname:"Sadvakassova",slug:"zukhra-sadvakassova",fullName:"Zukhra Sadvakassova"},{id:"209210",title:"Dr.",name:"Bakhytkul",middleName:null,surname:"Akshalova",slug:"bakhytkul-akshalova",fullName:"Bakhytkul Akshalova"}]},{id:"59468",doi:"10.5772/intechopen.74344",title:"Virtual and Augmented Reality: New Frontiers for Clinical Psychology",slug:"virtual-and-augmented-reality-new-frontiers-for-clinical-psychology",totalDownloads:2364,totalCrossrefCites:13,totalDimensionsCites:21,abstract:"In the last decades, the applied approach for the use of virtual reality (VR) and augmented reality (AR) on clinical and health psychology has grown exponentially. These technologies have been used to treat several mental disorders, for example, phobias, stress-related disorders, depression, eating disorders, and chronic pain. The importance of VR/AR for the mental health field comes from three main concepts: (1) VR/AR as an imaginal technology, people can feel “as if they are” in a reality that does not exist in external world; (2) VR/AR as an embodied technology, the experience to feel user’s body inside the virtual environment; and (3) VR/AR as connectivity technology, the “end of geography’. In this chapter, we explore the opportunities provided by VR/AR as technologies to improve people’s quality of life and to discuss new frontiers for their application in mental health and psychological well-being promotion.",book:{id:"6543",slug:"state-of-the-art-virtual-reality-and-augmented-reality-knowhow",title:"State of the Art Virtual Reality and Augmented Reality Knowhow",fullTitle:"State of the Art Virtual Reality and Augmented Reality Knowhow"},signatures:"Sara Ventura, Rosa M. Baños and Cristina Botella",authors:[{id:"106036",title:"Dr.",name:"Rosa Maria",middleName:null,surname:"Baños",slug:"rosa-maria-banos",fullName:"Rosa Maria Baños"},{id:"227763",title:"Ph.D.",name:"Sara",middleName:null,surname:"Ventura",slug:"sara-ventura",fullName:"Sara Ventura"},{id:"229056",title:"Dr.",name:"Cristina",middleName:null,surname:"Botella",slug:"cristina-botella",fullName:"Cristina Botella"}]},{id:"64583",doi:"10.5772/intechopen.81714",title:"Evaluating a Course for Teaching Advanced Programming Concepts with Scratch to Preservice Kindergarten Teachers: A Case Study in Greece",slug:"evaluating-a-course-for-teaching-advanced-programming-concepts-with-scratch-to-preservice-kindergart",totalDownloads:1422,totalCrossrefCites:13,totalDimensionsCites:18,abstract:"Coding is a new literacy for the twenty-first century, and as a literacy, coding enables new ways of thinking and new ways of communicating and expressing ideas, as well as new ways of civic participation. A growing number of countries, in Europe and beyond, have established clear policies and frameworks for introducing computational thinking (CT) and computer programming to young children. In this chapter, we discuss a game-based approach to coding education for preservice kindergarten teachers using Scratch. The aim of using Scratch was to excite students’ interest and familiarize them with the basics of programming in an open-ended, project-based, and personally meaningful environment for a semester course in the Department of Preschool Education in the University of Crete. For 13 weeks, students were introduced to the main Scratch concepts and, afterward, were asked to prepare their projects. For the projects, they were required to design their own interactive stories to teach certain concepts about mathematics or physical science to preschool-age students. The results we obtained were more satisfactory than expected and, in some regards, encouraging if one considers the fact that the research participants had no prior experiences with computational thinking.",book:{id:"6936",slug:"early-childhood-education",title:"Early Childhood Education",fullTitle:"Early Childhood Education"},signatures:"Stamatios Papadakis and Michail Kalogiannakis",authors:null}],mostDownloadedChaptersLast30Days:[{id:"58060",title:"Pedagogy of the Twenty-First Century: Innovative Teaching Methods",slug:"pedagogy-of-the-twenty-first-century-innovative-teaching-methods",totalDownloads:8832,totalCrossrefCites:17,totalDimensionsCites:23,abstract:"In the twenty-first century, significant changes are occurring related to new scientific discoveries, informatization, globalization, the development of astronautics, robotics, and artificial intelligence. This century is called the age of digital technologies and knowledge. How is the school changing in the new century? How does learning theory change? Currently, you can hear a lot of criticism that the classroom has not changed significantly compared to the last century or even like two centuries ago. Do the teachers succeed in modern changes? The purpose of the chapter is to summarize the current changes in didactics for the use of innovative teaching methods and study the understanding of changes by teachers. In this chapter, we consider four areas: the expansion of the subject of pedagogy, environmental approach to teaching, the digital generation and the changes taking place, and innovation in teaching. The theory of education, figuratively speaking, has two levels. At the macro-level, in the “education-society” relationship, decentralization and diversification, internationalization of education, and the introduction of digital technologies occur. At the micro-level in the “teacher-learner” relationship, there is an active mix of traditional and innovative methods, combination of an activity approach with an energy-informational environment approach, cognition with constructivism and connectivism.",book:{id:"5980",slug:"new-pedagogical-challenges-in-the-21st-century-contributions-of-research-in-education",title:"New Pedagogical Challenges in the 21st Century",fullTitle:"New Pedagogical Challenges in the 21st Century - Contributions of Research in Education"},signatures:"Aigerim Mynbayeva, Zukhra Sadvakassova and Bakhytkul\nAkshalova",authors:[{id:"201997",title:"Dr.",name:"Aigerim",middleName:null,surname:"Mynbayeva",slug:"aigerim-mynbayeva",fullName:"Aigerim Mynbayeva"},{id:"209208",title:"Dr.",name:"Zukhra",middleName:null,surname:"Sadvakassova",slug:"zukhra-sadvakassova",fullName:"Zukhra Sadvakassova"},{id:"209210",title:"Dr.",name:"Bakhytkul",middleName:null,surname:"Akshalova",slug:"bakhytkul-akshalova",fullName:"Bakhytkul Akshalova"}]},{id:"61746",title:"Facilitation of Teachers’ Professional Development through Principals’ Instructional Supervision and Teachers’ Knowledge- Management Behaviors",slug:"facilitation-of-teachers-professional-development-through-principals-instructional-supervision-and-t",totalDownloads:3384,totalCrossrefCites:2,totalDimensionsCites:2,abstract:"With the rise of global competition and the focus on teacher quality, teacher professional development is becoming increasingly crucial, and the stress and challenges for principals are more severe than ever. Teachers can improve their professional abilities through principals’ instructional supervision and their own knowledge-management (KM) behaviors to benefit students. Thus, this chapter analyzes the relationship among principals’ instructional supervision, teachers’ KM, and teachers’ professional development. The author believes that principals’ instructional supervision and effective KM can facilitate the professional development of teachers. The author also believes the readers can know the relationships among them, and teachers’ professional development can be improved through principal’s instructional supervision and teachers’ KM behaviors.",book:{id:"6674",slug:"contemporary-pedagogies-in-teacher-education-and-development",title:"Contemporary Pedagogies in Teacher Education and Development",fullTitle:"Contemporary Pedagogies in Teacher Education and Development"},signatures:"Chien-Chin Chen",authors:[{id:"232569",title:"Ph.D.",name:"Chien Chih",middleName:null,surname:"Chen",slug:"chien-chih-chen",fullName:"Chien Chih Chen"}]},{id:"75908",title:"From the Classroom into Virtual Learning Environments: Essential Knowledge, Competences, Skills and Pedagogical Strategies for the 21st Century Teacher Education in Kenya",slug:"from-the-classroom-into-virtual-learning-environments-essential-knowledge-competences-skills-and-ped",totalDownloads:519,totalCrossrefCites:0,totalDimensionsCites:0,abstract:"As teachers in Kenya begin to migrate from the classroom to virtual learning spaces following COVID 19 pandemic, there is pressing need to realign Teacher Education to requisite Knowledge, competences, skills, and attitudes that will support online teaching. This chapter explores these needs using a combination of lived experiences and literature review that captured a meta-analysis of research trends on e-learning. While trends in Teacher Education indicate progression towards adoption of technology, there are disparities between the theory and practice. Evidence from recent research and reports; and the recollected experiences confirmed knowledge, competence, skills and pedagogical gaps in the implementation of online learning, that have been exacerbated by COVID-19. The researcher recommends that teacher education should sensitize and train teacher trainees on how to access, analyze and use new knowledge emerging with technology; they also should be coached on how learners learn with technology and on fundamentals of the communication process. Particularly the course on educational technology, should focus on how to create and manage online courses. The 5-stage E-Moderator Model and Universal Design for Learning (UDL) are recommended as effective pedagogical scaffold for online teaching.",book:{id:"10229",slug:"teacher-education-in-the-21st-century-emerging-skills-for-a-changing-world",title:"Teacher Education in the 21st Century",fullTitle:"Teacher Education in the 21st Century - Emerging Skills for a Changing World"},signatures:"Catherine Adhiambo Amimo",authors:[{id:"333482",title:"Dr.",name:"Catherine Adhiambo",middleName:null,surname:"Amimo",slug:"catherine-adhiambo-amimo",fullName:"Catherine Adhiambo Amimo"}]},{id:"75224",title:"Decoding the Digital Gap in Teacher Education: Three Perspectives across the Globe",slug:"decoding-the-digital-gap-in-teacher-education-three-perspectives-across-the-globe",totalDownloads:589,totalCrossrefCites:0,totalDimensionsCites:4,abstract:"Educational use of technology is regularly assessed, and results often show a gap between educational policies and what is actually practiced. This chapter will help clarify how teacher educators experience the changing educational contexts due to the digital revolution, how their meaning-making shifts, and how outside forces influence those processes. The results are based on comparative international studies. Central for this study is practitioners’ professional digital competence, their attitudes towards digital technology and the use of digital technology in education. We found that the influence and contribution of digital practice is carried out quite differently across the globe. Our research questions were: How do practitioners experience teaching in a rapidly changing context? How do attitudes change due to top-down governing of education? and What motivates teacher educators to implement digital technology?",book:{id:"10229",slug:"teacher-education-in-the-21st-century-emerging-skills-for-a-changing-world",title:"Teacher Education in the 21st Century",fullTitle:"Teacher Education in the 21st Century - Emerging Skills for a Changing World"},signatures:"Steinar Thorvaldsen and Siri Sollied Madsen",authors:[{id:"332624",title:"Associate Prof.",name:"Siri Sollied",middleName:null,surname:"Madsen",slug:"siri-sollied-madsen",fullName:"Siri Sollied Madsen"},{id:"332626",title:"Prof.",name:"Steinar",middleName:null,surname:"Thorvaldsen",slug:"steinar-thorvaldsen",fullName:"Steinar Thorvaldsen"}]},{id:"75416",title:"Self-Study Research: Challenges and Opportunities in Teacher Education",slug:"self-study-research-challenges-and-opportunities-in-teacher-education",totalDownloads:777,totalCrossrefCites:0,totalDimensionsCites:0,abstract:"This article aims to describe what self-study research is, why self-study can be a good approach to teacher educators’ professional development and improvements in practice and highlight some challenges and opportunities in this research approach. In addition, the article will shed light on some methodological aspects related to self-study. Self-study refers to teacher educators who in an intentionally and systematically way examine their practice to improve it, based on a deeper understanding of practice, as well as the context practice takes place. In the article, I argue that engaging in self-study is a learning and development process and an approach to developing personal professionalism, collective professionalism and improvements in practice.",book:{id:"10229",slug:"teacher-education-in-the-21st-century-emerging-skills-for-a-changing-world",title:"Teacher Education in the 21st Century",fullTitle:"Teacher Education in the 21st Century - Emerging Skills for a Changing World"},signatures:"Kåre Hauge",authors:[{id:"332053",title:"Associate Prof.",name:"Kåre",middleName:null,surname:"Hauge",slug:"kare-hauge",fullName:"Kåre Hauge"}]}],onlineFirstChaptersFilter:{topicId:"265",limit:6,offset:0},onlineFirstChaptersCollection:[],onlineFirstChaptersTotal:0},preDownload:{success:null,errors:{}},subscriptionForm:{success:null,errors:{}},aboutIntechopen:{},privacyPolicy:{},peerReviewing:{},howOpenAccessPublishingWithIntechopenWorks:{},sponsorshipBooks:{sponsorshipBooks:[],offset:8,limit:8,total:0},allSeries:{pteSeriesList:[{id:"14",title:"Artificial Intelligence",numberOfPublishedBooks:9,numberOfPublishedChapters:90,numberOfOpenTopics:6,numberOfUpcomingTopics:0,issn:"2633-1403",doi:"10.5772/intechopen.79920",isOpenForSubmission:!0},{id:"7",title:"Biomedical Engineering",numberOfPublishedBooks:12,numberOfPublishedChapters:107,numberOfOpenTopics:3,numberOfUpcomingTopics:0,issn:"2631-5343",doi:"10.5772/intechopen.71985",isOpenForSubmission:!0}],lsSeriesList:[{id:"11",title:"Biochemistry",numberOfPublishedBooks:33,numberOfPublishedChapters:330,numberOfOpenTopics:4,numberOfUpcomingTopics:0,issn:"2632-0983",doi:"10.5772/intechopen.72877",isOpenForSubmission:!0},{id:"25",title:"Environmental Sciences",numberOfPublishedBooks:1,numberOfPublishedChapters:19,numberOfOpenTopics:4,numberOfUpcomingTopics:0,issn:"2754-6713",doi:"10.5772/intechopen.100362",isOpenForSubmission:!0},{id:"10",title:"Physiology",numberOfPublishedBooks:14,numberOfPublishedChapters:145,numberOfOpenTopics:4,numberOfUpcomingTopics:0,issn:"2631-8261",doi:"10.5772/intechopen.72796",isOpenForSubmission:!0}],hsSeriesList:[{id:"3",title:"Dentistry",numberOfPublishedBooks:9,numberOfPublishedChapters:139,numberOfOpenTopics:2,numberOfUpcomingTopics:0,issn:"2631-6218",doi:"10.5772/intechopen.71199",isOpenForSubmission:!0},{id:"6",title:"Infectious Diseases",numberOfPublishedBooks:13,numberOfPublishedChapters:122,numberOfOpenTopics:4,numberOfUpcomingTopics:0,issn:"2631-6188",doi:"10.5772/intechopen.71852",isOpenForSubmission:!0},{id:"13",title:"Veterinary Medicine and Science",numberOfPublishedBooks:11,numberOfPublishedChapters:112,numberOfOpenTopics:3,numberOfUpcomingTopics:0,issn:"2632-0517",doi:"10.5772/intechopen.73681",isOpenForSubmission:!0}],sshSeriesList:[{id:"22",title:"Business, Management and Economics",numberOfPublishedBooks:1,numberOfPublishedChapters:21,numberOfOpenTopics:3,numberOfUpcomingTopics:0,issn:"2753-894X",doi:"10.5772/intechopen.100359",isOpenForSubmission:!0},{id:"23",title:"Education and Human Development",numberOfPublishedBooks:0,numberOfPublishedChapters:10,numberOfOpenTopics:1,numberOfUpcomingTopics:1,issn:null,doi:"10.5772/intechopen.100360",isOpenForSubmission:!0},{id:"24",title:"Sustainable Development",numberOfPublishedBooks:1,numberOfPublishedChapters:19,numberOfOpenTopics:5,numberOfUpcomingTopics:0,issn:"2753-6580",doi:"10.5772/intechopen.100361",isOpenForSubmission:!0}],testimonialsList:[{id:"13",text:"The collaboration with and support of the technical staff of IntechOpen is fantastic. The whole process of submitting an article and editing of the submitted article goes extremely smooth and fast, the number of reads and downloads of chapters is high, and the contributions are also frequently cited.",author:{id:"55578",name:"Antonio",surname:"Jurado-Navas",institutionString:null,profilePictureURL:"https://s3.us-east-1.amazonaws.com/intech-files/0030O00002bRisIQAS/Profile_Picture_1626166543950",slug:"antonio-jurado-navas",institution:{id:"720",name:"University of Malaga",country:{id:null,name:"Spain"}}}},{id:"6",text:"It is great to work with the IntechOpen to produce a worthwhile collection of research that also becomes a great educational resource and guide for future research endeavors.",author:{id:"259298",name:"Edward",surname:"Narayan",institutionString:null,profilePictureURL:"https://mts.intechopen.com/storage/users/259298/images/system/259298.jpeg",slug:"edward-narayan",institution:{id:"3",name:"University of Queensland",country:{id:null,name:"Australia"}}}}]},series:{item:{id:"24",title:"Sustainable Development",doi:"10.5772/intechopen.100361",issn:"2753-6580",scope:"