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Opp, Daniel. "Transendothelial Migration of Metastatic Cancer Under the Influence of Cigarette Smoke Condensate." Scholar Commons, 2007. http://scholarcommons.usf.edu/etd/3808.
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Cigarette smoke's influence on cancer has primarily been a subject of epidemilogic and tumorigenic studies. There have been no proper investigations with interests focused on how cigarette smoke affects the cellular mechanics of metastasis. Gathering an understanding of how smoke influences metastatic invasion could be vital in regulating or possibly eliminatings cancer's ability to initiate new tumor growth sites. This project focuses on cigarette smoke's influence on cellular mechanics of endothelial cells, and the invasive potential of cancer against a fully active endothelium. It is already known that cigarette smoke has a carcinogenic effect, but it is hypothesized that the cigarette smoke causes the endothelium to exhibit pro-invasive characteristics. Cancer cells are often ignorant to extra-cellular stimuli. It is suspected that there will be a less pronounced degradation of cellular mechanics of cancerous cells than endothelial cells when exposed to similar concentrations of cigarette smoke.
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Wu, Hawellek ZhenMing. "Formation mechanism and resistance fluctuations of atomic sized junctions /." [S.l.] : [s.n.], 2009. http://edoc.unibas.ch/diss/DissB_8758.
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Gokce, Aisha. "Low frequency current and resistance fluctuations in magnetic tunnel junctions." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 203 p, 2009. http://proquest.umi.com/pqdweb?did=1896928791&sid=9&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Jiang, Xiuguang. "Experimental study of discrete resistance fluctuations in normal metal tunnel junctions /." The Ohio State University, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487758680161861.
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Young, Elisa, and elisayoung@iprimus com au. "Endothelial dysfunction in insulin resistance: The role of EDHF and gap junction communication." RMIT University. Medical Sciences, 2007. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080110.162249.
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Background: Endothelial dysfunction is a key factor in the development of vascular complications in insulin resistance and diabetes and recent studies have established that endothelium-derived hyperpolarising factor (EDHF) plays an important physiological role in endothelium-derived relaxation responses, especially in small arteries and arterioles. Objective: This project aimed to identify the role of, and characterise, EDHF in animal models of insulin resistance, including the obese Zucker rat (OZR) as well as the fructose-fed (FF) Sprague-Dawley rat. Methods: Vascular function was studied in third-order mesenteric arteries from male and female Zucker rats using pressure myography, and in lobar arteries from male FF rats using wire myography. Endothelial function was determined by studying responses to the endothelium-dependent dilator acetylcholine (ACh) and the endothelium-independent dilator levcromakalim in the presence of a variety of inhibitors to study the roles of NO, EDHF and gap junctions. The effect of insulin resistance on gap junctions was further assessed by measuring the protein and mRNA expression of vascular connexins. Protein levels were determined by western blotting followed by semi-quantitative analysis of band intensity, whilst mRNA levels were quantified using real-time PCR, in which beta-actin was used as the housekeeping gene. Results: Metabolic parameter comparisons confirmed that male OZRs were type 2 diabetic, whilst female OZRs were insulin resistant. Responses to ACh were reduced in both the male and female OZRs compared with their gender controls, with the male OZR showing a greater degree of endothelial dysfunction. In all Zucker third-order mesenteric arteries, inhibition of NO had no effect; however inhibitors of EDHF abolished relaxation responses to ACh. Inhibitors of gap junctions associated with connexin 40 significantly (p less than 0.05, Student's t-test) attenuated the maximal response to ACh in the LZR, but had no effect in the OZR. Comparison of Western blot band intensity indicated that connexin 40 protein levels in mesenteric vascular homogenates in the OZR were significantly smaller (p less than 0.05, Student's t-test) than in the LZR, with no difference in connexin 43 protein levels. mRNA levels showed a significant (p less than 0.05, Student's t-test) decrease in connexin 40 expression in the OZR compar ed with the LZR, with no change in connexin 43 mRNA expression. Although FF rats did develop insulin resistance, responses to ACh were not altered in the FF rats as compared with their controls, and ACh responses were abolished by NO inhibitors. Conclusion: The findings presented in this thesis demonstrate that endothelial dysfunction is present in third-order mesenteric arteries from insulin-resistant female and type 2 diabetic male OZRs, and is associated with a defect in EDHF. However, endothelial function was not compromised in the insulin-resistant FF rats. Furthermore, the reduction in EDHF-mediated vasodilatation in the mesenteric arteries from female OZRs was associated with the functional absence of connexin 40-related gap junctions as well as a reduction in connexin 40 protein and mRNA levels. This novel finding suggests that gap junctions associated with connexin 40 may be a potential therapeutic target for diabetic vascular disease.
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Salvage, Samantha. "Modulation of gap junctions and the intracellular resistance pathway in guinea-pig myocardium." Thesis, University of Surrey, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604348.
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Myocardial intracellular communication via gap junctions (GJ) is fundamental to action potential (AP) propagation facilitating ordered atrial and ventricular contraction. Cardiac arrhythmias can be initiated by increased intracellular (Ca2+), and are associated with abnormal AP conduction due to increased intracellular resistivity (RI) and, specifically, gap junction resistivity (Rj), Recent evidence suggested the Ca2+/calmodulin (CaM)-dependent protein phosphatase calcineurin (Cn) slowed conduction, possibly through increasing RI. This work aimed to demonstrate the role of Cn-dependent pathways in modulating RJ when intracellular [(a2+] was raised, any role of CaMkinase-1I (CaMKII) was also assessed. Rj was measured by longitudinal impedance measurements using atrial and ventricular guinea-pig preparations in control and low-Na Tyrode's solutions, with or without the Cn inhibitors cyclosporin-A (5 IlM) and calcineurin auto-inhibitory peptide (50IlM). CaMKl1 was also assessed by using its inhibitor KN-93. Western blot and immunohistochemical confocal analyses, with Cx40, total Cx43 and phospho-specific Cx43 antibodies, were performed to quantify alterations in GJ abundance, localisation and phosphorylation state. The study established that a raised intracellular {Ca 2+J increased RJ by a CnA-dependent pathway, but CaMKII had no role. In atrial tissue RJ increase was associated with a Cn-dependent increase of Cx43-S368 phosphorylation in addition to a Cn-independent increase of Cx40 abundance. By contrast, ventricular myocardium showed an overall increase of de phosphorylated Cx43 typical of increased Ri and GJ uncoupling. These novel findings identify a potential pathway for investigation and clinical manipulation in cardiac pathologies consequent on an elevated intracellular [Ca 2+].
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Buono, Benedetto. "Simulation and Characterization of Silicon Carbide Power Bipolar Junction Transistors." Doctoral thesis, KTH, Integrerade komponenter och kretsar, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-95320.
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The superior characteristics of silicon carbide, compared with silicon, have suggested considering this material for the next generation of power semiconductor devices. Among the different power switches, the bipolar junction transistor (BJT) can provide a very low forward voltage drop, a high current capability and a fast switching speed. However, in order to compete on the market, it is crucial to a have high current gain and a breakdown voltage close to ideal. Moreover, the absence of conductivity modulation and long-term stability has to be solved. In this thesis, these topics are investigated comparing simulations and measurements. Initially, an efficient etched JTE has been simulated and fabricated. In agreement with the simulations, the fabricated diodes exhibit the highest BV of around 4.3 kV when a two-zone JTE is implemented. Furthermore, the simulations and measurements demonstrate a good agreement between the electric field distribution inside the device and the optical luminescence measured at breakdown. Additionally, an accurate model to simulate the forward characteristics of 4H-SiC BJTs is presented. In order to validate the model, the simulated current gains are compared with measurements at different temperatures and different base-emitter geometries. Moreover, the simulations and measurements of the on-resistance are compared at different base currents and different temperatures. This comparison, coupled with a detailed analysis of the carrier concentration inside the BJT, indicates that internal forward biasing of the base-collector junction limits the BJT to operate at high current density and low forward voltage drop simultaneously. In agreement with the measurements, a design with a highly-doped extrinsic base is proposed to alleviate this problem. In addition to the static characteristics, the comparison of measured and simulated switching waveforms demonstrates that the SiC BJT can provide fast switching speed when it acts as a unipolar device. This is crucial to have low power losses during transient. Finally, the long-term stability is investigated. It is observed that the electrical stress of the base-emitter diode produces current gain degradation; however, the degradation mechanisms are still unclear. In fact, the analysis of the measured Gummel plot suggests that the reduction of the carrier lifetime in the base-emitter region might be only one of the causes of this degradation. In addition, the current gain degradation due to ionizing radiation is investigated comparing the simulations and measurements. The simulations suggest that the creation of positive charge in the passivation layer can increase the base current; this increase is also observed in the electrical measurements.QC 20120522
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Lee, Hyung-Seok. "Fabrication and Characterization of Silicon Carbide Power Bipolar Junction Transistors." Doctoral thesis, Stockholm : Kungliga Tekniska högskolan, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4623.
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Giovannini, Federica. "Voltage-dependent calcium channel subtypes at the mouse neuromuscular junction : evidence for the role of a resistant component." Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365445.
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El, khatib Mariam. "Implication des porines dans la genèse et le développement des biofilms de Providencia stuartii." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAV012/document.
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Les biofilms, communautés multicellulaires bactériennes, sont omniprésents. Malgré leur importance pour l’écosystème, ils présentent une menace pour l'industrie autant que pour la santé humaine. La virulence des biofilms procède surtout de leur résistance élevée aux antibiotiques, qui rend leur éradication quasiment impossible. Ainsi, les biofilms sont impliqués dans la plupart des infections bactériennes chroniques, causant chaque année plus de 4000 décès en France. P. stuartii est une bactérie connue pour sa capacité à former des biofilms dans le tractus urinaire humain. Elle est responsable de 10% des INU chroniques et est décrite comme étant la plus résistante de son genre. Malgré ces faits, les études menées sur cette bactérie sont rares, freinant la compréhension du mécanisme de développement et de résistance de ses biofilms et compliquant ainsi l’avancement de nouvelles thérapies pour lutter, prévenir ou éradiquer ces infections. P. stuartii exprime au niveau de sa membrane externe deux porines, Omp-Pst1 et Omp-Pst2, qui constituent 70% du contenu protéique membranaire. Ces porines sont le conduit principal permettant à la bactérie de communiquer et d’échanger avec son milieu environnant. Ainsi, les porines sont vitales pour la bactérie.A ce jour, trois publications sont disponibles qui traitent de ces deux porines, mais aucune n’a exploré leur influence sur la formation des biofilms bactériens. Les travaux effectués au cours de ma thèse ont ainsi visé à réduire le manque de connaissance sur les biofilms de P. stuartii et à dévoiler le rôle des porines dans l’établissement et la résistance de ces biofilms. Pour cela, nous avons segmenté notre travail en quatre parties ayant pour objectifs (1) de comprendre la formation des biofilms de P. stuartii et leur réponse aux stress du milieu environnant ; (2) de décrire l’effet de la suppression ou la surexpression des porines ; (3) d’étudier à l’échelle moléculaire et atomique le comportement des porines isolées ; et (4) de développer des outils pour étudier les porines à l’échelle moléculaire au sein d’un biofilm de P. stuartiiBiofilms, bacterial multicellular communities, are ubiquitous. Despite their importance to the ecosystem, they pose a threat to both industry and human health. The virulence of biofilms is mainly due to their high resistance to antibiotics, which makes their eradication virtually impossible. Thus, biofilms are involved in most chronic bacterial infections, causing each year more than 4,000 deaths in France. P. stuartii is a bacterium known for its ability to form biofilms in the human urinary tract. It is responsible for 10% of chronic nosocomial urinary infections and is described as the most resistant of its kind. Despite these facts, studies on this bacterium are rare, hampering the understanding of the mechanism of development and resistance of its biofilms and thus complicating the advancement of new therapies to fight, prevent or eradicate these infections. P. stuartii expresses at its outer membrane two porins, Omp-Pst1 and Omp-Pst2, which constitute 70% of the membrane protein content. These porins are the main conduit allowing the bacterium to communicate and exchange with its surrounding environment. Thus, porins are vital for the bacteria.To date, three publications are available that deal with these two porins, but none have explored their influence on the formation of bacterial biofilms. The work carried out during my thesis thus aimed to reduce the lack of knowledge about P. stuartii's biofilm and to unveil the role of porins in the establishment and resistance of these biofilms. For this, we have divided our work into four parts aiming at (1) understanding of P. stuartii's biofilms formation and their response to the stresses of the surrounding environment; (2) describing the effect of suppression or overexpression of porins; (3) studying the behavior of isolated porins on a molecular and atomic scale; and (4) developing tools for studying porins on a molecular scale within a biofilm of P. stuartii
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Asada, Satoshi. "Improvement of ON-Characteristics in SiC Bipolar Junction Transistors by Structure Designing Based on Analyses of Material Properties and Carrier Recombination." Kyoto University, 2019. http://hdl.handle.net/2433/242510.
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Milatz, Susanne. "Funktionelle Charakterisierung des Tight Junction-Proteins Claudin-3 in Epithel- und Endothelzellen." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2011. http://dx.doi.org/10.18452/16293.
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Die Tight Junction (TJ) reguliert den parazellulären Transport von Ionen, Wasser und Soluten an Epithelien und Endothelien und ist von entscheidender Bedeutung für die Aufrechterhaltung der Funktion von Organen und Geweben. Obwohl Claudin-3 zu den zuerst identifizierten und ubiquitär exprimierten Komponenten der TJ gehört, konnte seine spezifische Funktion bislang nicht geklärt werden. Für die funktionelle Charakterisierung des humanen Claudin-3-Proteins wurden stabile Überexpressionsklone der lecken Nierenepithel-Zelllinie MDCK II generiert. Die Überexpression von Claudin-3 führte zu einer deutlichen Änderung des TJ-Strangmusters sowie zu einer starken Zunahme des transepithelialen Widerstandes und einer verminderten Permeabilität für Ionen und Moleküle der Größe 332 Da und 4000 Da. Der parazelluläre Durchtritt von Wasser war unverändert. Claudin-3 konnte eindeutig als abdichtende Komponente der TJ identifiziert werden. Anhand des endothelialen Zellkulturmodells HUVEC wurden Expression und Regulation von Claudin-3 und anderen TJ-Proteinen unter dem Einfluss mechanischer Strömungsverhältnisse und des Sauerstoffpartialdrucks analysiert. Die Behandlung mit fehlender Wandschubspannung führte zur Hochregulation der abdichtenden TJ-Proteine Occludin, Claudin-3, Claudin-5 und Claudin-11, nicht aber Claudin-23. Die Regulation der einzelnen TJ-Komponenten wurde durch unterschiedliche Signalwege vermittelt, wobei der verstärkten Proteinexpression jeweils eine Hochregulation auf mRNA-Ebene zugrunde lag. Die kombinierte Behandlung mit fehlender Wandschubspannung und Hypoxie resultierte in einer sehr stark erhöhten Expression von Claudin-3. Durch die Hochregulation abdichtender TJ-Komponenten unter Bedingungen fehlender Wandschubspannung und Hypoxie, wie sie in verschiedenen physiologischen und pathologischen Situationen auftreten, könnte einem unerwünschten Durchtritt von Substanzen aus dem Blut in das umliegende Gewebe vorgebeugt werden.The tight junction (TJ) regulates the paracellular transport of ions, water and solutes in epithelia and endothelia and is of particular importance for a correct function of organs and tissues. Although claudin-3 is one of the first identified and ubiquitously expressed TJ components, its specific function was unsolved as yet. For functional characterization, human claudin-3 was stably overexpressed in the leaky epithelial cell line MDCK II. Overexpression of claudin-3 led to a marked alteration of TJ meshwork pattern, a strong increase in transepithelial resistance and a decrease in permeability for ions and paracellular tracers (332 or 4000 Da). Paracellular water transport was not affected. It was proved that claudin-3 acts as a „tightening“ TJ component. The endothelial cell culture model HUVEC was used for analysis of expression and regulation of claudin-3 and several other TJ proteins under different conditions of wall shear stress and oxygen saturation. Treatment with lacking wall shear stress led to an upregulation of the “tightening” TJ proteins occludin, claudin-3, claudin-5, and claudin-11, but not claudin-23. Upregulation of all proteins was due to increased mRNA levels. Apparently, different signaling pathways were involved in regulation of particular TJ components. Combined treatment with lacking shear stress and hypoxia resulted in drastically increased claudin-3 expression. Upregulation of tightening TJ components under lacking shear stress and hypoxic conditions as occuring in different physiological or pathological situations would limit the passage of solutes from the blood into the surrounding tissue.
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Chung, Charlotte Yuk-Yan. "Tight Junctions - The Link Between HIV-Associated Intestinal Barrier Dysfunction and Loss of Immune Homeostasis." Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1417822947.
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Tyagi, Pawan. "FABRICATION AND CHARACTERIZATION OF MOLECULAR SPINTRONICS DEVICES." UKnowledge, 2008. http://uknowledge.uky.edu/gradschool_diss/614.
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Fabrication of molecular spin devices with ferromagnetic electrodes coupled with a high spin molecule is an important challenge. This doctoral study concentrated on realizing a novel molecular spin device by the bridging of magnetic molecules between two ferromagnetic metal layers of a ferromagnetic-insulator-ferromagnetic tunnel junction on its exposed pattern edges. At the exposed sides, distance between the two metal electrodes is equal to the insulator film thickness; insulator film thickness can be precisely controlled to match the length of a target molecule. Photolithography and thin-film deposition were utilized to produce a series of tunnel junctions based on molecular electrodes of multilayer edge molecular electrodes (MEME) for the first time. In order to make a microscopic tunnel junction with low leakage current to observe the effect of ~10,000 molecules bridged on the exposed edge of a MEME tunnel barrier, growth conditions were optimized; stability of a ~2nm alumina insulator depended on its ability to withstand process-induced mechanical stresses. The conduction mechanism was primarily 1) tunneling from metal electrode to oranometalic core by tunneling through alkane tether that acts as a tunnel barrier 2) rapid electron transfer within the oranometalic Ni-CN-Fe cube and 3) tunneling through alkane tether to the other electrode. Well defined spin-states in the oranometalic Ni-CN-Fe cube would determine electron spin-conduction and possibly provide a mechanism for coupling.
MEME with Co/NiFe/AlOx/NiFe configurations exhibited dramatic changes in the transport and magnetic properties after the bridging of oranometalic molecular clusters with S=6 spin state. The molecular cluster produced a strong antiferromagnetic coupling between two ferromagnetic electrodes to the extent, with a lower bound of 20 erg/cm,2 that properties of individual magnetic layers changed significantly at RT. Magnetization, ferromagnetic resonance and magnetic force microscopy studies were performed. Transport studies of this configuration of MEME exhibited molecule-induced current suppression by ~6 orders by blocking both molecular channels and tunneling between metal leads in the planar 25μm2 tunnel junction area. A variety of control experiments were performed to validate the current suppression observation, especially critical due to observed corrosion in electrochemical functionalization step. The spin devices were found to be sensitive to light radiation, temperature and magnetic fields.
Along with the study of molecular spin devices, several interesting ideas such as ~9% energy efficient ultrathin TaOx based photocell, simplified version of MEME fabrication, and chemical switching were realized. This doctoral study heralds a novel molecular spin device fabrication scheme; these molecular electrodes allow the reliable study of molecular components in molecular transport.
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Piehl, Christian. "Untersuchungen zu parazellulären Barriereeigenschaften von Claudinen." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2009. http://dx.doi.org/10.18452/15922.
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In multizellulären Organismen bilden Epithel- und Endothelzellen die äußere Begrenzung innerer und äußerer Körperoberflächen bzw. kleiden die Blutgefäße aus. So schaffen sie abgegrenzte Organkompartimente mit individuellen, der jeweiligen Funktion angepassten Bedingungen. Dazu muss die parazelluläre Diffusion von Stoffen eingeschränkt werden. Die Abdichtung des parazellulären Spalts erfolgt durch tight junctions (TJ). Claudine (Cld) bilden das strukturelle Rückgrat der TJ. Im Rahmen dieser Arbeit wurde erstmalig gezeigt, dass einzelne Aminosäuren der zweiten extrazellulären Schleife (2. EZS) eines Claudins für die parazelluläre Dichtigkeit essentiell sind. Da endogene TJ-Stränge fast ausschließlich aus mindestens zwei verschiedenen Claudinen aufgebaut sind, wurde die Wirkung von Aminosäuresubstitutionen in der 2. EZS von Cld5 auf die parazelluläre Dichtigkeit in einer claudinheterogenen Umgebung analysiert. Dafür wurden verschiedene Cld5-Mutanten stabil in MDCK-II-Zellen exprimiert. Die Aminosäuresubstitutionen in der 2. EZS von Cld5 führten nicht nur zum Verlust der durch Cld5wt bedingten parazellulären Abdichtung, sondern darüber hinaus zu einer geringeren parazellulären Dichtigkeit im Vergleich zur Vektorkontrolle. In einem weiteren Teil dieser Arbeit wurde mit einem Peptid, dessen Sequenz der C-terminalen Hälfte der 1. EZS von Cld1 entsprach (Cld153-81), eine reversible Öffnung der TJ von epithelialen Zelllinien erzielt. Mit dem N-terminal verkürzten Clostridium perfringens Enterotoxin-Fragment CPE194-319 wurde ebenfalls eine Reduktion der parazellulären Dichtigkeit von Epithelzellen erzielt. Insgesamt tragen die Untersuchungen dieser Arbeit zu einem besseren Verständnis der durch Claudine vermittelten Abdichtung des parazellulären Spalts bei. Darüber hinaus bieten Cld153-81 und CPE194-319 neue Perspektiven für eine gezielte therapeutische Öffnung der TJ, um beispielsweise die Wirkstoffzufuhr ins Gehirn zu verbessern.Epithelial and endothelial cells form the external lining of outer and inner body surfaces and blood vessels of multicellular organisms. Thus, they create separate compartments each exhibiting an environment optimally adjusted to their respective function. To build up such compartments epithelial and endothelial cells have to restrict the paracellular diffusion of substances. The paracellular cleft is sealed by tight junctions (TJ). In electron microscopical images TJs appear as a network of intermembranous strands in the apical region of the lateral cell membrane of epithelial and endothelial cells. Claudins (Cld) form the structural backbone of TJs. The present study provided evidence for the first time that single amino acids of the second extracellular loop (ECL) of a claudin are essential for the paracellular tightness of epithelial cells. The effect of single amino acid substitutions of the second ECL of Cld5 were studied in cells expressing various other endogenous claudins except Cld5. Point mutants of Cld5 were stably expressed in MDCK-II cells. While the expression of Cld5wt caused increased paracellular tightness, this effect was completely abolished by the Cld5 point mutants. Furthermore, the mutants even decreased the paracellular permeation of certain substances compared with the vector control. Further findings of the present study demonstrated that a peptide corresponding to the C-terminal half of the first ECL of Cld1 is capable of opening the TJ in a reversible manner. Using an N-terminal fragment of clostridium perfringens enterotoxin (CPE194-319) a reduction of the paracellular tightness of epithelial cells was demonstrated. Taken together, the findings of the present study contribute to a better understanding of the sealing of the paracellular cleft by claudins. Furthermore, Cld153-81 und CPE194-319 open new perspectives for a targeted therapeutic opening of the TJs suited for enhancing the transport of active substances into diseased tissue.
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Aygun, Seymen Murat. "Gas Sensors Based on Ceramic p-n Heterocontacts." Ames, Iowa : Oak Ridge, Tenn. : Ames Laboratory ; distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2004. http://www.osti.gov/servlets/purl/837264-2ckydm/webviewable/.
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Thesis (M.S.); Submitted to Iowa State Univ., Ames, IA (US); 19 Dec 2004.Published through the Information Bridge: DOE Scientific and Technical Information. "IS-T 2498" Seymen Murat Aygun. US Department of Energy 12/19/2004. Report is also available in paper and microfiche from NTIS.
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Oruganti, Prasad. "Drug Transport in Cell Preparations with Diffusional Dosing and Temporal Ratiometry." Case Western Reserve University School of Graduate Studies / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1269536608.
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Alcami, Ayerbe José. "Interactions synaptiques entre les interneurones de la couche moléculaire du cervelet." Thesis, Paris 5, 2013. http://www.theses.fr/2013PA05T021.
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Les interneurones de la couche moléculaire du cervelet (ICM: cellules en panier et cellules étoilées) sont connectés par des synapses électriques fréquentes et puissantes chez les jeunes rats et souris autour de la fin de la deuxième semaine postnatale. Les courants capacitifs des ICM montrent une composante lente qui reflète la charge des interneurones couplés électriquement. Leur analyse permet de quantifier le nombre de cellules directement couplées à une cellule et le nombre équivalent de cellules couplées (Alcami et Marty, soumis), et d'établir une difference de couplage entre les cellules en panier et les cellules étoilées pendant le développement postnatal. Elle a mené à proposer une topologie de réseau des cellules en panier. La force du couplage peut être modulée par les courants intrinsèques, dont Ih dans le domaine hyperpolarisant. Les synapses électriques modifient la propagation et les patrons d'activité dans le réseau des ICM en réponse à une excitation du réseau.L'étude de la connectivité des ICM par des synapses chimiques GABAergiques nous a mené à réexaminer les sources d'erreur des mesures d'activité électrique en configuration cellule attachée (Alcami et coll., 2012). Les mesures en cellule attachée peuvent modifier l'activité électrique des ICM en introduisant un couplage conductif entre la pipette d'enregistrement et l'intérieur cellulaire, résultant d'une combinaison de mécanismes de couplage passifs et actifsMolecular layer interneurons of the cerebellum (MLIs: basket cells and stellate cells) are connected by frequent and strong electrical synapses in young rats and mice around the end of the second postnatal week. Capacitive currents of MLIs show a slow component that reflects the charge of electrically-coupled MLIs. The analysis of capacitive currents makes it possible to quantify the number of directly connected cells and the equivalent number of coupled cells (Alcami and Marty, submitted). They were used to show a difference in coupling between basket and stellate cells and propose a model of the basket cell coupled network. Electrical coupling strength can be modulated by intrinsic currents, like the h current in the hyperpolarizing range. Electrical synapses modify the propagation and the patterns of activity in the MLI network, when the network is excited.The study of connectivity of MLIs by chemical GABAergic synapses led us to reevaluate the sources of error of cell-attached recordings (Alcami et al., 2012). Cell-attached measurements can modify cellular electrical activity of MLIs, by introducing a conductif coupling between the recording pipette and the cell interior, resulting from a combination of passive and active coupling
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Stein, Félix. "SPICE Modeling of TeraHertz Heterojunction bipolar transistors." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0281/document.
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Les études qui seront présentées dans le cadre de cette thèse portent sur le développement et l’optimisation des techniques pour la modélisation compacte des transistors bipolaires à hétérojonction (TBH). Ce type de modélisation est à la base du développement des bibliothèques de composants qu’utilisent les concepteurs lors de la phase de simulation des circuits intégrés. Le but d’une technologie BiCMOS est de pouvoir combiner deux procédés technologiques différents sur une seule et même puce. En plus de limiter le nombre de composants externes, cela permet également une meilleure gestion de la consommation dans les différents blocs digitaux, analogiques et RF. Les applications dites rapides peuvent ainsi profiter du meilleur des composants bipolaires et des transistors CMOS. Le défi est d’autant plus critique dans le cas des applications analogiques/RF puisqu’il est nécessaire de diminuer la puissance consommée tout en maintenant des fréquences de fonctionnement des transistors très élevées. Disposer de modèles compacts précis des transistors utilisés est donc primordial lors de la conception des circuits utilisés pour les applications analogiques et mixtes. Cette précision implique une étude sur un large domaine de tensions d’utilisation et de températures de fonctionnement. De plus, en allant vers des nœuds technologiques de plus en plus avancés, des nouveaux effets physiques se manifestent et doivent être pris en compte dans les équations du modèle. Les règles d’échelle des technologies plus matures doivent ainsi être réexaminées en se basant sur la physique du dispositif. Cette thèse a pour but d’évaluer la faisabilité d’une offre de modèle compact dédiée à la technologie avancée SiGe TBH de chez ST Microelectronics. Le modèle du transistor bipolaire SiGe TBH est présenté en se basant sur le modèle compact récent HICUMversion L2.3x. Grâce aux lois d’échelle introduites et basées sur le dessin même des dimensions du transistor, une simulation précise du comportement électrique et thermique a pu être démontrée.Ceci a été rendu possible grâce à l’utilisation et à l’amélioration des routines et méthodes d’extraction des paramètres du modèle. C’est particulièrement le cas pour la détermination des éléments parasites extrinsèques (résistances et capacités) ainsi que celle du transistor intrinsèque. Finalement, les différentes étapes d’extraction et les méthodes sont présentées, et ont été vérifiées par l’extraction de bibliothèques SPICE sur le TBH NPN Haute-Vitesse de la technologie BiCMOS avancée du noeud 55nm, avec des fréquences de fonctionnement atteignant 320/370GHz de fT = fmaxThe aim of BiCMOS technology is to combine two different process technologies intoa single chip, reducing the number of external components and optimizing power consumptionfor RF, analog and digital parts in one single package. Given the respectivestrengths of HBT and CMOS devices, especially high speed applications benefit fromadvanced BiCMOS processes, that integrate two different technologies.For analog mixed-signal RF and microwave circuitry, the push towards lower powerand higher speed imposes requirements and presents challenges not faced by digitalcircuit designs. Accurate compact device models, predicting device behaviour undera variety of bias as well as ambient temperatures, are crucial for the development oflarge scale circuits and create advanced designs with first-pass success.As technology advances, these models have to cover an increasing number of physicaleffects and model equations have to be continuously re-evaluated and adapted. Likewiseprocess scaling has to be verified and reflected by scaling laws, which are closelyrelated to device physics.This thesis examines the suitability of the model formulation for applicability to production-ready SiGe HBT processes. A derivation of the most recent model formulationimplemented in HICUM version L2.3x, is followed by simulation studies, whichconfirm their agreement with electrical characteristics of high-speed devices. Thefundamental geometry scaling laws, as implemented in the custom-developed modellibrary, are described in detail with a strong link to the specific device architecture.In order to correctly determine the respective model parameters, newly developed andexisting extraction routines have been exercised with recent HBT technology generationsand benchmarked by means of numerical device simulation, where applicable.Especially the extraction of extrinsic elements such as series resistances and parasiticcapacitances were improved along with the substrate network.The extraction steps and methods required to obtain a fully scalable model library wereexercised and presented using measured data from a recent industry-leading 55nmSiGe BiCMOS process, reaching switching speeds in excess of 300GHz. Finally theextracted model card was verified for the respective technology
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Najjari, Hamza. "Power Amplifier Design Based on Electro-Thermal Considerations." Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0422.
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L’objectif de ce travail de recherche est de concevoir un amplificateur de puissance sur la base de considérations électrothermiques. Il décrit la question du dynamique EVM et du « paquet long » lors de la conception de l’amplificateur avec des transistors bipolaires à hétérojonctions. Basé sur le comportement électrothermique du circuit, une méthode d’optimisation de l’EVM statique et dynamique est proposée. Un frontend RF complet (amplificateur de puissance + coupleur + interrupteur + amplificateur faible bruit) est conçu pour le dernier standard WLAN : le Wi-Fi 6. La distribution de temperature dynamique dans le circuit est analysée. Son effet sur les performances de la puce est quantifié. Enfin, une polarisation adaptative programmable a été conçue pour garder des performances optimales sur toute la plage de température. Les mesures du circuit montre tout l’effet bénéfique de cette compensation, permettant de garder le dynamique EVM en dessous de -47 dB sur la plage de température ambiante de -40 à 85°CThe aim of this work is to design a power amplifier based on electrothermal considerations. It describes the Dynamic Error Vector Magnitude challenge and long packet issue when designing a power amplifier with hetero-junction bipolar transistors. Based on the circuit electrothermal behavior, an optimization method of both the static and dynamic linearity is proposed. A complete RF front-end (PA + coupler + switch + LNA) is designed for the latest WLAN standard: the Wi-Fi 6. The dynamic temperature distribution in the circuit is analyzed. It’s impact on the performances is quantified. Finally, a programmable temperature dependent bias is designed to compensate for performance degradation. The measurements show a significant linearity improvement with this compensation, allowing the PA to maintain the DEVM lower than -47dB at 14.5 dBm output power, over a large ambient temperature range from -40°C to 85°C
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Sahoo, Amit Kumar. "Electro-thermal Characterizations, Compact Modeling and TCAD based Device Simulations of advanced SiGe : C BiCMOS HBTs and of nanometric CMOS FET." Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14557/document.
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Ce travail de thèse présente une évaluation approfondie des différentes techniques de mesure transitoire et dynamique pour l’évaluation du comportement électro-thermique des transistors bipolaires à hétérojonctions HBT SiGe:C de la technologie BiCMOS et des transistors Métal-Oxyde-Semiconducteur à effet de champ (MOSFET) de la technologie CMOS 45nm. En particulier, je propose une nouvelle approche pour caractériser avec précision le régime transitoire d'auto-échauffement, basée sur des mesures impulsionelles. La méthodologie a été vérifiée par des mesures statiques à différentes températures ambiantes, des mesures de paramètres S à basses fréquences et des simulations thermiques transitoires. Des simulations thermiques par éléments finis (TCAD) en trois dimensions ont été réalisées sur les transistors HBTs de la technologie submicroniques SiGe: C BiCMOS. Cette technologie est caractérisée par une fréquence de transition fT de 230 GHz et une fréquence maximum d’oscillation fMAX de 290 GHz. Par ailleurs, cette étude a été réalisée sur les différentes géométries de transistor. Une évaluation complète des mécanismes d'auto-échauffement dans les domaines temporels et fréquentiels a été réalisée. Une expression généralisée de l'impédance thermique dans le domaine fréquentiel a été formulée et a été utilisé pour extraire cette impédance en deçà de la fréquence de coupure thermique. Les paramètres thermiques ont été extraits par des simulations compactes grâce au modèle compact de transistors auquel un modèle électro-thermique a été ajouté via le nœud de température. Les travaux théoriques développés à ce jour pour la modélisation d'impédance thermique ont été vérifiés avec nos résultats expérimentaux. Il a été montré que, le réseau thermique classique utilisant un pôle unique n'est pas suffisant pour modéliser avec précision le comportement thermique transitoire et donc qu’un réseau plus complexe doit être utilisé. Ainsi, nous validons expérimentalement pour la première fois, le modèle distribué électrothermique de l'impédance thermique utilisant un réseau nodal récursif. Le réseau récursif a été vérifié par des simulations TCAD, ainsi que par des mesures et celles ci se sont révélées en excellent accord. Par conséquent, un modèle électro-thermique multi-géométries basé sur le réseau récursif a été développé. Le modèle a été vérifié par des simulations numériques ainsi que par des mesures de paramètre S à basse fréquence et finalement la conformité est excellente quelque soit la géométrie des dispositifsAn extensive evaluation of different techniques for transient and dynamic electro-thermal behavior of microwave SiGe:C BiCMOS hetero-junction bipolar transistors (HBT) and nano-scale metal-oxide-semiconductor field-effect transistors (MOSFETs) have been presented. In particular, new and simple approach to accurately characterize the transient self-heating effect, based on pulse measurements, is demonstrated. The methodology is verified by static measurements at different ambient temperatures, s-parameter measurements at low frequency region and transient thermal simulations. Three dimensional thermal TCAD simulations are performed on different geometries of the submicron SiGe:C BiCMOS HBTs with fT and fmax of 230 GHz and 290 GHz, respectively. A comprehensive evaluation of device self-heating in time and frequency domain has been investigated. A generalized expression for the frequency-domain thermal impedance has been formulated and that is used to extract device thermal impedance below thermal cut-off frequency. The thermal parameters are extracted through transistor compact model simulations connecting electro-thermal network at temperature node. Theoretical works for thermal impedance modeling using different networks, developed until date, have been verified with our experimental results. We report for the first time the experimental verification of the distributed electrothermal model for thermal impedance using a nodal and recursive network. It has been shown that, the conventional single pole thermal network is not sufficient to accurately model the transient thermal spreading behavior and therefore a recursive network needs to be used. Recursive network is verified with device simulations as well as measurements and found to be in excellent agreement. Therefore, finally a scalable electro-thermal model using this recursive network is developed. The scalability has been verified through numerical simulations as well as by low frequency measurements and excellent conformity has been found in for various device geometries
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Weisz, Mario. "Electrothermal device-to-circuit interactions for half THz SiGe∶C HBT technologies." Thesis, Bordeaux 1, 2013. http://www.theses.fr/2013BOR14909/document.
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Ce travail concerne les transistors bipolaires à hétérogène TBH SiGe. En particulier, l'auto-échauffement des transistors unitaires et le couplage thermique avec leurs plus proches voisins périphériques sont caractérisés et modélisés. La rétroaction électrothermique intra- et inter-transistor est largement étudiée. En outre, l’impact des effets thermiques sur la performance de deux circuits analogiques est évalué. L'effet d'autoéchauffement est évalué par des mesures à basse fréquence et des mesures impulsionnelles DC et AC. L'auto-échauffement est diminué de manière significative en utilisant des petites largeurs d'impulsion. Ainsi la dépendance fréquentielle de l’autoéchauffementa été étudiée en utilisant les paramètres H et Y. De nouvelles structures de test ont été fabriqués pour mesurer l'effet de couplage. Les facteurs de couplage thermique ont été extraits à partir de mesures ainsi que par simulations thermiques 3D. Les résultats montrent que le couplage des dispositifs intra est très prononcé. Un nouvel élément du modèle de résistance thermique récursive ainsi que le modèle de couplage thermique a été inclus dans un simulateur de circuit commercial. Une simulation transitoire entièrement couplée d'un oscillateur en anneau de 218 transistors a été effectuée. Ainsi, un retard de porte record de 1.65ps est démontré. À la connaissance des auteurs, c'est le résultat le plus rapide pour une technologie bipolaire. Le rendement thermique d'un amplificateur de puissance à 60GHz réalisé avec un réseau multi-transistor ou avec un transistor à plusieurs doigts est évalué. La performance électrique du transistor multidoigt est dégradée en raison de l'effet de couplage thermique important entre les doigts de l'émetteur. Un bon accord est constaté entre les mesures et les simulations des circuits en utilisant des modèles de transistors avec le réseau de couplage thermique. Enfin, les perspectives sur l'utilisation des résultats sont donnéesThe power generate by modern silicon germanium (SiGe) heterojunction bipolar transistors (HBTs) can produce large thermal gradients across the silicon substrate. The device opering temperature modifies model parameters and can significantly affect circuit operation. This work characterizes and models self-heating and thermal coupling in SiGe HBTs. The self-heating effect is evaluated with low frequency and pulsed measurements. A novel pulse measurement system is presented that allows isothermal DC and RF measurements with 100ns pulses. Electrothermal intra- and inter-device feedback is extensively studied and the impact on the performance of two analog circuits is evaluated. Novel test structures are designed and fabricated to measure thermal coupling between single transistors (inter-device) as well as between the emitter stripes of a multi-finger transistor (intra-device). Thermal coupling factors are extracted from measurements and from 3D thermal simulations. Thermally coupled simulations of a ring oscillator (RO) with 218 transistors and of a 60GHz power amplifier (PA) are carried out. Current mode logic (CML) ROs are designed and measured. Layout optimizations lead to record gate delay of 1.65ps. The thermal performance of a 60GHz power amplifier is compared when realized with a multi-transistor array (MTA) and with a multi-finger trasistor (MFT). Finally, perspectives of this work within a CAD based circuit design environment are discussed
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D'Esposito, Rosario. "Electro-thermal characterization, TCAD simulations and compact modeling of advanced SiGe HBTs at device and circuit level." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0147/document.
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Ce travail de thèse présente une étude concernant la caractérisation des effets électrothermiques dans les transistors bipolaires à hétérojonction (HBT) en SiGe. Lors de ces travaux, deux procédés technologiques BiCMOS à l’état de l’art ont été analysés: le B11HFC de Infineon Technologies (130nm) et le B55 de STMicroelectronics (55nm).Des structures de test dédiées ont étés conçues, pour évaluer l’impact électrothermique du back end of line (BEOL) de composants ayant une architecture à un ou plusieurs doigts d’émetteur. Une caractérisation complète a été effectuée en régime continu et en mode alternatif en petit et en grand signal. De plus, une extraction des paramètres thermiques statiques et dynamiques a été réalisée et présentée pour les structures de test proposées. Il est démontré que les figures de mérite DC et RF s’améliorent sensiblement en positionnant des couches de métal sur le transistor, dessinées de manière innovante et ayant pour fonction de guider le flux thermique vers l’extérieur. L’impact thermique du BEOL a été modélisé et vérifié expérimentalement dans le domaine temporel et fréquentiel et aussi grâce à des simulations 3D par éléments finis. Il est à noter que l’effet du profil de dopage sur la conductivité thermique est analysé et pris en compte.Des topologies de transistor innovantes ont étés conçues, permettant une amélioration des spécifications de l’aire de sécurité de fonctionnement, grâce à un dessin innovant de la surface d’émetteur et du deep trench (DTI).Un modèle compact est proposé pour simuler les effets de couplage thermique en dynamique entre les émetteurs des HBT multi-doigts; ensuite le modèle est validé avec de mesures dédiées et des simulations TCAD.Des circuits de test ont étés conçus et mesurés, pour vérifier la précision des modèles compacts utilisés dans les simulateurs de circuits; de plus, l’impact du couplage thermique entre les transistors sur les performances des circuits a été évalué et modélisé. Finalement, l’impact du dissipateur thermique positionné sur le transistor a été étudié au niveau circuit, montrant un réel intérêt de cette approcheThis work is focused on the characterization of electro-thermal effects in advanced SiGe hetero-junction bipolar transistors (HBTs); two state of the art BiCMOS processes have been analyzed: the B11HFC from Infineon Technologies (130nm) and the B55 from STMicroelectronics (55nm).Special test structures have been designed, in order to evaluate the overall electro-thermal impact of the back end of line (BEOL) in single finger and multi-finger components. A complete DC and RF electrical characterization at small and large signal, as well as the extraction of the device static and dynamic thermal parameters are performed on the proposed test structures, showing a sensible improvement of the DC and RF figures of merit when metal dummies are added upon the transistor. The thermal impact of the BEOL has been modeled and experimentally verified in the time and frequency domain and by means of 3D TCAD simulations, in which the effect of the doping profile on the thermal conductivity is analyzed and taken into account.Innovative multi-finger transistor topologies are designed, which allow an improvement of the SOA specifications, thanks to a careful design of the drawn emitter area and of the deep trench isolation (DTI) enclosed area.A compact thermal model is proposed for taking into account the mutual thermal coupling between the emitter stripes of multi-finger HBTs in dynamic operation and is validated upon dedicated pulsed measurements and TCAD simulations.Specially designed circuit blocks have been realized and measured, in order to verify the accuracy of device compact models in electrical circuit simulators; moreover the impact on the circuit performances of mutual thermal coupling among neighboring transistors and the presence of BEOL metal dummies is evaluated and modeled
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Chen, Kuan-chieh, and 程冠傑. "The investigation of AC LED junction temperature and thermal resistance measurement." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/46967063270239645476.
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碩士國立中央大學
能源工程研究所
97
The AC LED, which can be operated under alternating current without converter, is fabricated by several microchips in series and parallel. The conventional DC LED junction temperature and thermal resistance measurement system cannot be applied to AC LED, because of the different operation mode. In this study, the author built a system which can measure the highest junction temperature of AC LED. Besides, we also proposed a method for determining the average junction temperature and thermal resistance of AC LED. Furthermore, the junction temperature oscillation of AC LED can also be found using this method, and we found that the AC LED junction temperature oscillation of this experiment is about 7 ℃ under alternating current VRMS 23V with frequency of 60 HZ at room temperature 30℃.
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Tan, Qiao-Meng, and 陳俏蒙. "Resistance Switching in ZnO-Based Memristors with a p-n Junction." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/d3gz7g.
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碩士國立東華大學
物理學系
105
Resistance switching in ZnO-based memristive devices with a p-n junction has been investigated. Sputtering was performed to prepare devices with layered structures as Ti/ZnO/p+-Si. Programming strategies were developed in terms of using different operation modes, including voltage sweep mode, current sweep mode, and single-pulse mode. The single-pulse mode was found to suppress the multiplicity of the readout resistance levels as compared with the voltage/voltage sweep modes. Furthermore, current compliance was found to significantly affect the device stability during repeated switching operations. Conduction processes leading to the resistive switching were examined for the low-resistance and high-resistance states, conforming the mechanisms dominated by space charge limited current (SCLC) and Poole-Frenkel (PL) trap-associated processes respectively. Instability and device failures were attributed to structural imperfections resulting from preparations.
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Chou, Hung-Ju, and 周鴻儒. "A Study on N+-P Ge Shallow Junction and Contact Resistance." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/17604965803753477808.
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碩士國立交通大學
電子工程學系 電子研究所
104
Scaling down geometry to enhance transistor’s performance will encounter difficulty due to physical limitation. Therefore, high mobility materials and novel device structures become the emerging research topic. Germanium (Ge) has higher electron and hole bulk mobility than Silicon (Si) so that it is considered as the material for the next generation. However, because there are a lot of interface states distributing near the valence band of germanium, Fermi level would be pinned near valence band. It causes a high Schottky barrier height value nearly about a bandgap of germanium and a large contact resistance for a metal/n-Ge Schottky contact. Moreover, due to the high diffusivity of n-type dopants in Ge, it is hard to form a shallow junction to suppress short channel effect. In this thesis, we fabricate conventional Al-contacted N+-P junction at first. Low ion implantation energy or dose cause a very shallow junction but the leakage current increases. The junction characteristics is not good. Then, the Al-contact is replaced by NiGe-contact and dopant segregation is used to improve junction characteristics. There are two types of dopant segregation process. One is implantation before germanidation (IBG), the other one is implantation after germanidation (IAG). For the IBG process, due to high diffusivity of Ni in Ge, it would make nickel diffuse to the depletion region and cause a high leakage current if junction depth is too shallow. The NiGe-contacted junction can tolerate at 450℃ for 30 sec or 500℃ for 10sec at most as the junction depth becomes shallower than 100 nm (82.06nm). If increasing the temperature or extending the annealing time, the junction would exhibit voltage dependence generation leakage current due to Ni diffusion. Finally, we use the IBG+IAG process to enhance the doping concentration at the NiGe/Ge interface and lower the specific contact resistance to 3×10^(-6)Ω-cm^2 for the mean value. The specific contact resistance of the pure IBG process is 2×10^(-5) Ω-cm^2 for the mean value. Besides, the additional IAG process would not induce more leakage current. The leakage current for the IBG+IAG process keeps as low as that of the IBG junction. This thesis also demonstrates the effect of high dose implantation of Aluminum (Al), Selenium (Se), and Stannum (Sn) on the Schottky barrier height. It is predicted by first-principles calculations that the Se atom can lower the Schottky barrier height of NiGe/Ge the most, the Al atom is hardly to modify the SBH, and the Sn atom can raise the SBH. For the implementation of the Schottky junctions, the Se ion implantation can lower the SBH about 0.15 eV. In brief, this thesis focus on the IBG+IAG process to form a low leakage current and low contact resistance junction. Compared with other studies about contact resistance issue, our process is easier and our test structure of the contact resistance is more accurate. Employing Se ion implantation is expected to further reduce the contact resistance.
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Chiu, Chun Wei, and 邱俊維. "Junction Temperature and Thermal Resistance study in Light Emitting Diode Lamps." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/18694100740061163360.
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碩士長庚大學
光電工程研究所
98
This study used a generally and accurately method that was called diode forward-voltage method to measure junction temperature, and to obtain the entire thermal resistance. Then, a part of temperature from the radiator module was measured by the J-type thermocouples, and to obtain a part of thermal resistance. According to this measurement, a part of efficiency from the radiator could be analyzed. Compared the junction temperature from chip and lamp of AlGaInP LED under different operating conditions, and discuss the reason why worse radiator of AlGaInP LED lamp; Besides, measuring the power chip LED lamp whose type was Cree XLamp XR-E, and installed the power chip LED lamp on different radiators to compared the junction temperature. In the same manner, discussing the reason that efficiency of radiator from the power chip LED lamp on different radiators by parts of thermal resistance.
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Chen, Wei. "The dynamics of sustained reentry in a loop model with discrete gap junction resistance." Thèse, 2007. http://hdl.handle.net/1866/8085.
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Chen, C. H., and 陳健煌. "A Study of Sheet Resistance Uniformity in Ion-Implanted 12 inch Si Shallow Junction." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/01779653890634569628.
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碩士國立中興大學
材料科學與工程學系所
100
With the progress of semiconductor fabrication processes, the device size is getting smaller and circuit layout becomes more complicated. Nevertheless, the current channel of MOSFET is shortened with the shrinking of device size, which will lead to the problem of so-called short channel effect (SCE). In order to suppress the SCE, the ultra-shallow junction (USJ) structure of semiconductor device is introduced and the low energy ion implantation is an important factor in this technique. In this study, the ion implanter was applied to fabricate USJ using Boron ion in n-type (100) Si substrate. The implantation doseage and annealing temperature are 6×1015 ions/cm2 and 950 C, respectively. The drift, process chamber decel and double decel modes of ion implanter controlled conditions were optimized for USJ fabrication. The different decel ratios (1.5 %, 2 % and 3 %) and implant energies (2.5 keV, 3 keV and 3.5 keV) were used to investigate the implant concentration, thermal wave and sheet resistance. The uniformity of sheet resistance is 0.87 % with the decel ration of 1.57 %. The thermal wave unit is 1350 TWU with 3.5 keV implant energy. Finally, the measurement of secondary ion mass spectroscopy was adopted to confirm the implant depth.
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Shih, Che-Ju, and 施哲儒. "A Study on the Nickel Germanide Contacted N+-P Germanium Shallow Junction and Contact Resistance." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/75953686017457551375.
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碩士國立交通大學
電子工程學系 電子研究所
102
In the past several decades, the research on Si-based devices progresses very fast. Furthermore, the Si-based MOSFETs have been successfully scaled down to 20 nm regime. However, scaling down the devices becomes more and more difficult and reaches the physics limits soon. Therefore, developing another ways to promote the device performance is necessary. Using new semiconducting materials is a way to improve performance. Because germanium has higher mobility and process compatibility for MOSFET fabrication process, germanium is considered to replace Si as the channel material in the future. Nevertheless, the n-type dopant diffusion in germanium is fast so that it is not easy to form shallow n+/p junction, and the high Schottky barrier height at the metal/n-Ge interface causes a high contact resistance due to the Fermi level pinning near the Ge valance band at the interface between metal and germanium. Therefore, the thesis would focus on the forming of shallow n+/p-Ge junction and low resistance metal/n-Ge contact. Because NiGe has the lowest resistivity and low temperature formation, NiGe is selected as the contact metal. The implantation before germanide (IBG) process means ion implantation is performed before germanide formation, and the implantation after germanide (IAG) process means ion implantation is performed after germanide formation. For the IBG junctions fabricated on heavily-doped substrate, very poor junction characteristic is observed by high dose phosphorous ion implantation due to the fast diffusion of Ni by virtue of defects which are generated by ion implantation. Fluorine ion implantation before NiGe formation could effectively suppress Ni diffusion and reduce the leakage current. Moreover, better junction characteristic can be obtained by low dose ion implantation due to the less defects resulting in less Ni diffusion. However, fluorine implantation before NiGe formation would enhance the Ni diffusion to degrade junction characteristic because the fluorine ion implantation induces extra defects. Next, on the lightly-doped substrate, good junction characteristic is more easily to be obtained than on heavily-doped substrate because the deeper junction depth on lightly-doped substrate so that the Ni diffusion would not destroy the junctions. In particular, after NiGe formation, the forward current obviously increases owing to the dopant segregation at the NiGe/Ge interface. Furthermore, either phosphorous or arsenic n+/p junction would have the dopant segregation effect. The arsenic n+/p junctions have relatively low activation concentration inferred by the I-V characteristic. Finally, because the IAG junctions have poor junction characteristic due to the segregated n+ layer is too thin to maintain good n-p junction and the Ni fast diffusion induces large leakage current, the IBG+IAG process is proposed. The IBG+IAG junction could achieve shallow junction depth and raise the forward current at the same time. Furthermore, the measured contact resistance of the IBG junction is about 2x10-5 -cm2 and the lowest contact resistance of IBG+IAG junction is 2x10-6 -cm2.Therefore, this thesis has formed a junction with shallower junction depth, lower leakage current, and lower contact resistance in comparison with previous studies. This achievement is expected to improve the performance of Ge nMOSFETs.
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Liao, Hsiu-Hsien, and 廖修賢. "Studies of N+-P Junctions on Ultrathin GeSn/Ge Structure and Self-Aligned Contact Resistance Test Structure." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/2urh6a.
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碩士國立交通大學
電子研究所
107
In this thesis, we thoroughly studied N+-P junctions on ultrathin GeSn/Ge structure and successfully developed a novel contact resistance test structure, aimed for source/drain application in modern Si/Ge-based FETs. First, well-behaved N+-P junctions possessing high forward bias current density of 250 A/cm2 at −1 V and high On/Off ratio over 3×104 were realized on ultrathin GeSn/Ge Structure using P ion implantation and low-temperature thermal annealing. Also, various electrical characteristic analyses were carried out to investigate the leakage characteristic of these junctions. Moreover, by performing thermal annealing at different temperatures, we gain an overall insight into the effect of activation temperatures on junction leakage. It is found that the leakage current remains low when samples were annealed at a temperature range of 400oC to 500oC. But, the leakage current of junctions increases drastically when annealing temperatures exceed 550oC. A model is then proposed on the basis of the results of advanced electrical and material characterization to explain ascending junction leakage: A large numbers of defects induced by high-dose ion implantation intermix with Sn atoms escaping from original lattice site. As a result of enhanced Sn diffusion via vacancy-mediated mechanism, Sn atoms come closer to the metallurgical junction of N+-P diode after a high-temperature annealing. These Sn atoms then serve as effective generation-recombination centers in the space-charge region of junction devices. Besides, the effects of activation temperatures and contact interfaces on contact resistance and sheet resistance of Ni/GeSn is preliminarily explored. We observed that all the samples exhibit similar contact characteristics. On the other hand, a novel test structure called self-aligned TLM (SATLM) was designed and fabricated. By realizing self-aligned contact window definition, the robustness of TLM structure towards lateral current spreading effect and nanoscale contact patterning issues can be greatly improved. Using proposed test structure, we demonstrate significant ρ_c extraction of 4.7×10−8 Ω-cm2 for Ti/Si:P contact. In addition, the influence of post-metal annealing temperatures and contact width on extraction results was discussed. Finally, the extraction results of SATLM were verified and compared with that of CBKR structure fabricated under the identical fabrication processes. The proposed structure is thus confirmed to be less vulnerable to the parasitic elements which limit the measurement accuracy.
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Liu, Chihi, and 劉知易. "A Study Of Low Resistance Ultra Shallow Junction And Applied To MOSFETs By Low Temperature Microwave Annealing." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/93432138027102352473.
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碩士義守大學
電子工程學系
100
When the depth of the channel length is scaled down, will lead to cut-in current add at junction depletion region. As a result, the gate threshold voltage is reduced. The best approach to avoid this phenomenon is ultra-shallow junction. Therefore, ultra-shallow junction becomes an important process. We try to use the National Nano Device Laboratories (NDL) microwave annealing system (Microwave anneal) and with conventional rapid thermal annealing (RTA) for comparison. First, activation by ion implantation and compare MWA and RTA doping material spread. Found by the MWA activation can reduce the dopant diffusion. Second, form different thickness nickel-germanium by the different parameters of MWA and RTA, and the film structure were analyzed. Found that in the same process temperature, MWA can get batter film quality. Finally, reduce the dielectric thickness and use different parameters of MWA and RTA annealing, compared to the RTA, the stronger effect of the MWA patches dielectric layer defects. By MWA replaced RTA produced the CMOS and I-V measurement system for measuring and analyzing. We have successfully produced CMOS transistor gold of the whole microwave process.
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Wei, Houng-Chi, and 魏鴻基. "Study of Negative Differential Resistance Characteristics and Application of Delta-Doped Emitter Structure in GaAs-Based Bipolar Junction Transistor." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/50422876995945014468.
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博士國立成功大學
電機工程研究所
82
First, voltage-controllable negative differential resistance characteristics in a N-alGaAs/p-GaAs/n-GaAs transistor structure which the third terminal is placed in the collector are investi- gated. At the applied voltage smaller than the gate voltage, the base-emitter unction is modulated by the gate voltage to con- duct a peak current. When the large applied voltage is applied to the device, the gate voltage is suppressed due to the exist- ence of the gate resistive so that the device is looked like a base-open situation. Therefore, a low valley current is then obtained which in turns achieve a high peak-to-valley current ratio larger than 26000. Next, a new kind of GaAs homojunction bipolar transistor with a delta- doped emitter structure is proposed. The delta-doped emitter structure inducing a triangular barrier is employed to block the minority carriers injection from the base into the emitter. Like a heterojunction transistor, the heavily doped base and lightly doped emitter can be realized. Due to the base- emitter homojunction, the offset voltage is low. The experimental results of these two kinds of the devices in the thesis are in agreement with the theoretical results.
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Chen, Bo-Ruei, and 陳柏睿. "The Response Test and Thermal Resistance Analysis of the Junction Temperature for the LED under Different Thermal Interfacial Material." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/77860411862644448863.
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Adams, Emily. "Physiology and morphology of epithelia in the freshwater demosponge, Spongilla lacustris." Master's thesis, 2010. http://hdl.handle.net/10048/1411.
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Epithelia form protective barriers and regulate molecule transport between the mesenchyme and environment. Amongst all metazoans, only sponges are said to lack 'true' epithelia however the physiology of sponge cell layers are rarely studied empirically. Aggregates and gemmules of a freshwater demosponge, Spongilla lacustris, were used to grow confluent tissue over permeable culture wells which are required for transepithelial recordings. The transepithelial potential (TEP) of S. lacustris was slightly negative (-3mV), indicating possible control of ion transport. Transepithelial resistance (TER) was recorded between 1-2 k cm2, the same order of magnitude as many vertebrate epithelia. Cultures with high resistance blocked the passage of the small tracer molecules 14C-PEG, 3H-Inulin and ruthenium red. Pinacocytes were spatially stable over time and epithelial layers were morphologically similar in freshwater and marine species. These results suggest that sponge cell layers are able to control solute and ion transport, the physiological attributes of functional epithelia.Physiology, Cell and Development Biology
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Ngendahayo, Mukiza Clément. "L’entérotoxine STb d’Escherichia coli affecte les jonctions serrées des cellules intestinales épithéliales." Thèse, 2012. http://hdl.handle.net/1866/8937.
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La toxine thermostable d’E.coli (STb) est une cause de diarrhée chez l’homme et l’animal. STb se lie au sulfatide, son récepteur, puis s’internalise. Dans le cytoplasme, par une cascade d’événements, STb déclenche l’ouverture des canaux ioniques permettant la sécrétion des ions et la perte d’eau menant à la diarrhée. Les jonctions serrées forment une barrière physique intercellulaire dans les cellules épithéliales intestinales, contrôlant ainsi le flux paracellulaire des ions et de l’eau. Les jonctions serrées sont affectées par divers pathogènes et par leurs toxines. À ce jour, l’effet de STb sur les jonctions serrées n’a pas été étudié. L’étude entreprise visait à explorer l’effet de STb sur les jonctions serrées et la barrière épithéliale des cellules intestinales. Des cellules épithéliales intestinales du colon humain (T84) ont été traitées pendant 24h soit avec la toxine STb purifiée soit avec une souche d’E.coli exprimant STb. La résistance transépithéliale (TER), le flux de marqueurs paracellulaires et la microscopie confocale ont été utilisés pour analyser les effets de STb sur les jonctions serrées. Les monocouches traitées par la souche E.coli exprimant STb et la toxine STb purifiée ont manifesté une forte réduction de TER (p<0.0001) parallèlement à une augmentation significative de la perméabilité paracellulaire à l’Albumine de Sérum Bovin marqué avec l’IsoThioCyanate Fluoroscéine, BSA-FITC (p<0.0001) comparativement aux cellules non traitées et aux cellules traitées par une souche d’E.coli commensale non-toxinogène. L’augmentation de la perméabilité paracellulaire induite par STb a été associée à une dissolution générale et une condensation des fibres de stress centrales des filaments d’actine. Le réarrangement des filaments d’actine a été accompagné par une redistribution et une fragmentation des protéines des jonctions serrées dont l’occludine, la claudine-1 et la Zonula Occludens-1. Les mêmes modifications on été observées après l’intoxication des cellules T84 avec un octapeptide synthétique retrouvé dans la séquence de STb correspondant à une séquence consensus de la toxine ZOT de Vibrio cholerae, impliquée dans la réorganisation des jonctions serrées. Cet effet n’a pas été observé lorsque les cellules ont été traitées avec un octapeptide synthétique comportant les mêmes acides aminés mais distribués de façon aléatoire ou avec la toxine mutée (D30V). Nos résultats montrent pour la première fois que STb induit le dysfonctionnement de la barrière épithéliale intestinale en modifiant la distribution des protéines des jonctions serrées. Ces résultats ouvrent une nouvelle voie pour la compréhension de la pathogenèse de diarrhée causée par la toxine STb.Escherichia coli heat-stable toxin (STb) causes diarrhea in Man and animals. STb binds to sulfatide, its receptor, followed by its internalization. Inside the cytoplasm, through a cascade of events, STb triggers the opening of ion channels allowing ion secretion and water loss leading to diarrhea. Tight junctions (TJs) are well known for controlling paracellular traffic of ions and water by forming a physical intercellular barrier in epithelial cells. Some bacterial toxinz are known to affect adversibly TJs. To date, the impact of STb on TJs has not been investigated. The present study aimed to explore the effect of STb on TJs and the barrier function in intestinal epithelial cells. Human colon intestinal epithelial cells (T84) were treated for 24h with either purified STb toxin or an E. coli strains expressing STb. TransEpithelial Resistance (TER), paracellular flux marker and confocal microscopy were used to analyze the effect of STb toxin on TJs. An E. coli strains expressing STb as well as purified STb caused a significant reduction of TER (p<0.0001) parallely to an increase in paracellular permeability to BSA-FITC (p<0.0001) compared to untreated cells or a commensal non toxinogenic E.coli strain. The increased paracellular permeability induced by STb was associated with a marked general dissolution and condensation of central F-actin stress fibers. F-actin disorganisation was accompanied by redistribution and fragmentation of occludin, claudin-1 and ZO-1 (Zonula Occludens-1) proteins. These changes were also observed following intoxication of T84 cells with an 8 amino acids peptide found in the STb sequence corresponding to a consensus sequence of Vibrio cholerae Zot toxin, shown to be involved in TJs disassembly. This effect was not observed with the scramble peptide and D30V mutant. Our findings suggest that STb induces epithelial barrier dysfunction by changes in tight junction proteins that could contribute to the observed diarrhea. These results provide new insight into the diarrhea pathogenesis caused by STb.
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Schuhmann, Henning. "Hochauflösende mikroskopische und spektroskopische Untersuchungen zur strukturellen Ordnung an MgO-CoFeB-Grenzflächen." Doctoral thesis, 2014. http://hdl.handle.net/11858/00-1735-0000-0023-9929-2.
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Tunnelmagnetowiderstandselemente (MTJ) mit einer kristallinen MgO Tunnelbarriere zwischen amorphen CoFeB-Elektroden haben Aufgrund ihres hohen Tunnelmagnetowiderstandes (TMR) und der guten Integrationsmöglichkeit in bestehende Prozesse viel Aufmerksamkeit bekommen. Dabei zeigten vorherige Berechnungen, dass die strukturellen und chemischen Eigenschaften der Grenzfläche einen signifikanten Einfluss auf den TMR aufweisen, weshalb diese Grenzfläche im Rahmen dieser Arbeit mittels quantitativer, hochauflösender und analytischer Transmissionselektronenmikroskopie analysiert wurde.
Um einen hohen TMR in die diesen Systemen zu erzielen ist ein kristalliner Übergang zwischen der Tunnelbarriere und den Elektroden notwendig. Berechnungen zeigten, dass bereits wenige Monolagen kristallinen Materials an der Grenzfläche ausreichen, um einen hohen TMR in diesen Systemen zu erzielen. Ausgehend von diesen Berechnungen wurde die Mikrostruktur auf der Subnanometer-Skala an der kristallin/amorphen Grenzfläche von MgO-CoFeB in dieser Arbeit untersucht. Die experimentellen Daten wurden hierfür mittels aberrationskorrigierter, hochauflösender Transmissionselektronenmikroskopie (HRTEM) an Modellsystemproben erstellt und die vom MgO induzierte kristalline Ordnung an der Grenzfläche zum CoFeB mittels iterativen Bildserienvergleichs mit simulierten Daten quantifiziert. Zur Simulation der HRTEM-Grenzflächenabbildungen wurde die „Averaged-Projected-Potential“-Näherung genutzt, welche im Rahmen dieser Arbeit um die Berücksichtigung von monoatomaren Stufen entlang der Strahlrichtung des Mikroskops erweitert wurde. Es zeigte sich, dass mit dieser Methode die Ordnung an der MgO-CoFeB-Grenzfläche von nicht ausgelagerten Systemen gut beschrieben werden kann.
In ausgelagerten Systemen kommt es dagegen zu einer Bor-diffusion aus dem a-CoFeB heraus um damit eine Kristallisation am MgO zu ermöglichen. Im zweiten Teil dieser Arbeit werden die Bordiffusion und die Kristallisation in Abhängigkeit von der Deckschicht als auch der MgO-Depositionsmethode sowohl an Modellsystemproben als auch an funktionsfähigen MTJs untersucht. Elektronen-Energie-Verlustspektroskopie (EELS) an diesen Proben konnten zeigen, dass sowohl die Deckschicht also auch die MgO-Depositionsmethode einen entscheidenden Einfluss auf die Bor-Diffusion in diesen Systemen ausüben.