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Sample records for adherens junction formation

  1. The Drosophila genes crumbs and stardust are involved in the biogenesis of adherens junctions.

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    Grawe, F; Wodarz, A; Lee, B; Knust, E; Skaer, H

    1996-03-01

    Morphogenetic movements of epithelia during development underlie the normal elaboration of the final body plan. The tissue integrity critical for these movements is conferred by anchorage of the cytoskeleton by adherens junctions, initially spot and later belt-like, zonular structures, which encircle the apical side of the cell. Loss-of-function mutations in the Drosophila genes crumbs and stardust lead to the loss of cell polarity in most ectodermally derived epithelia, followed in some, such as the epidermis, by extensive apoptosis. Here we show that both mutants fail to establish proper zonulae adherentes in the epidermis. Our results suggest that the two genes are involved in different aspects of this process. Further, they are compatible with the hypothesis that crumbs delimits the apical border, where the zonula adherens usually forms and where Crumbs protein is normally most abundant. In contrast, stardust seems to be required at an earlier stage for the assembly of the spot adherence junctions. In both mutants, the defect observed at the ultrastructural level are preceded by a misdistribution of Armadillo and DE-cadherin, the homologues of beta-catenin and E-cadherin, respectively, which are two constituents of the vertebrate adherens junctions. Strikingly, expansion of the apical membrane domain in epidermal cells by overexpression of crumbs also abolishes the formation of adherens junctions and results in the disruption of tissue integrity, but without loss of membrane polarity. This result supports the view that membrane polarity is independent of the formation of adherens junctions in epidermal cells.

  2. The adherens junctions control susceptibility to Staphylococcus aureus α-toxin.

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    Popov, Lauren M; Marceau, Caleb D; Starkl, Philipp M; Lumb, Jennifer H; Shah, Jimit; Guerrera, Diego; Cooper, Rachel L; Merakou, Christina; Bouley, Donna M; Meng, Wenxiang; Kiyonari, Hiroshi; Takeichi, Masatoshi; Galli, Stephen J; Bagnoli, Fabio; Citi, Sandra; Carette, Jan E; Amieva, Manuel R

    2015-11-17

    Staphylococcus aureus is both a transient skin colonizer and a formidable human pathogen, ranking among the leading causes of skin and soft tissue infections as well as severe pneumonia. The secreted bacterial α-toxin is essential for S. aureus virulence in these epithelial diseases. To discover host cellular factors required for α-toxin cytotoxicity, we conducted a genetic screen using mutagenized haploid human cells. Our screen identified a cytoplasmic member of the adherens junctions, plekstrin-homology domain containing protein 7 (PLEKHA7), as the second most significantly enriched gene after the known α-toxin receptor, a disintegrin and metalloprotease 10 (ADAM10). Here we report a new, unexpected role for PLEKHA7 and several components of cellular adherens junctions in controlling susceptibility to S. aureus α-toxin. We find that despite being injured by α-toxin pore formation, PLEKHA7 knockout cells recover after intoxication. By infecting PLEKHA7(-/-) mice with methicillin-resistant S. aureus USA300 LAC strain, we demonstrate that this junctional protein controls disease severity in both skin infection and lethal S. aureus pneumonia. Our results suggest that adherens junctions actively control cellular responses to a potent pore-forming bacterial toxin and identify PLEKHA7 as a potential nonessential host target to reduce S. aureus virulence during epithelial infections.

  3. Rab11 helps maintain apical crumbs and adherens junctions in the Drosophila embryonic ectoderm.

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    Jeremiah F Roeth

    Full Text Available BACKGROUND: Tissue morphogenesis and organogenesis require that cells retain stable cell-cell adhesion while changing shape and moving. One mechanism to accommodate this plasticity in cell adhesion involves regulated trafficking of junctional proteins. METHODOLOGY/PRINCIPAL FINDINGS: Here we explored trafficking of junctional proteins in two well-characterized model epithelia, the Drosophila embryonic ectoderm and amnioserosa. We find that DE-cadherin, the transmembrane protein of adherens junctions, is actively trafficked through putative vesicles, and appears to travel through both Rab5-positive and Rab11-positive structures. We manipulated the functions of Rab11 and Rab5 to examine the effects on junctional stability and morphogenesis. Reducing Rab11 function, either using a dominant negative construct or loss of function alleles, disrupts integrity of the ectoderm and leads to loss of adherens junctions. Strikingly, the apical junctional regulator Crumbs is lost before AJs are destabilized, while the basolateral protein Dlg remains cortical. Altering Rab5 function had less dramatic effects, not disrupting adherens junction integrity but affecting dorsal closure. CONCLUSIONS/SIGNIFICANCE: We contrast our results with what others saw when disrupting other trafficking regulators, and when disrupting Rab function in other tissues; together these data suggest distinct mechanisms regulate junctional stability and plasticity in different tissues.

  4. DHT deficiency perturbs the integrity of the rat seminiferous epithelium by disrupting tight and adherens junctions.

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    Kolasa, Agnieszka; Marchlewicz, Mariola; Wenda-Różewicka, Lidia; Wiszniewska, Barbara

    2011-01-01

    In rats with a DHT deficiency induced by finasteride, morphological changes in the seminiferous epithelium were observed. The structural alterations were manifested by the premature germ cells sloughing into the lumen of seminiferous tubules. The etiology of this disorder could be connected with intercellular junctions disintegration. We showed in the immunohistochemical study the changes in expression of some proteins building tight and adherens junctions. The depression of N-cadherin, β-catenin and occludin immunoexpressions could be the reason for the release of immature germ cells from the seminiferous epithelium. However, the observed increase of the immunohistochemical reaction intensity of vinculin, one of the cadherin/catenin complex regulators, could be insufficient to maintain the proper function of adherens junctions. The hormonal imbalance appears to influence the pattern of expression of junctional proteins in the seminiferous epithelium. It could lead to untimely germ cells sloughing, and ultimately could impair fertility.

  5. Fibroblast growth factor signaling potentiates VE-cadherin stability at adherens junctions by regulating SHP2.

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    Kunihiko Hatanaka

    Full Text Available BACKGROUND: The fibroblast growth factor (FGF system plays a critical role in the maintenance of vascular integrity via enhancing the stability of VE-cadherin at adherens junctions. However, the precise molecular mechanism is not well understood. In the present study, we aimed to investigate the detailed mechanism of FGF regulation of VE-cadherin function that leads to endothelial junction stabilization. METHODS AND FINDINGS: In vitro studies demonstrated that the loss of FGF signaling disrupts the VE-cadherin-catenin complex at adherens junctions by increasing tyrosine phosphorylation levels of VE-cadherin. Among protein tyrosine phosphatases (PTPs known to be involved in the maintenance of the VE-cadherin complex, suppression of FGF signaling reduces SHP2 expression levels and SHP2/VE-cadherin interaction due to accelerated SHP2 protein degradation. Increased endothelial permeability caused by FGF signaling inhibition was rescued by SHP2 overexpression, indicating the critical role of SHP2 in the maintenance of endothelial junction integrity. CONCLUSIONS: These results identify FGF-dependent maintenance of SHP2 as an important new mechanism controlling the extent of VE-cadherin tyrosine phosphorylation, thereby regulating its presence in adherens junctions and endothelial permeability.

  6. Differential regulation of the Hippo pathway by adherens junctions and apical-basal cell polarity modules.

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    Yang, Chih-Chao; Graves, Hillary K; Moya, Ivan M; Tao, Chunyao; Hamaratoglu, Fisun; Gladden, Andrew B; Halder, Georg

    2015-02-10

    Adherens junctions (AJs) and cell polarity complexes are key players in the establishment and maintenance of apical-basal cell polarity. Loss of AJs or basolateral polarity components promotes tumor formation and metastasis. Recent studies in vertebrate models show that loss of AJs or loss of the basolateral component Scribble (Scrib) cause deregulation of the Hippo tumor suppressor pathway and hyperactivation of its downstream effectors Yes-associated protein (YAP) and Transcriptional coactivator with PDZ-binding motif (TAZ). However, whether AJs and Scrib act through the same or independent mechanisms to regulate Hippo pathway activity is not known. Here, we dissect how disruption of AJs or loss of basolateral components affect the activity of the Drosophila YAP homolog Yorkie (Yki) during imaginal disc development. Surprisingly, disruption of AJs and loss of basolateral proteins produced very different effects on Yki activity. Yki activity was cell-autonomously decreased but non-cell-autonomously elevated in tissues where the AJ components E-cadherin (E-cad) or α-catenin (α-cat) were knocked down. In contrast, scrib knockdown caused a predominantly cell-autonomous activation of Yki. Moreover, disruption of AJs or basolateral proteins had different effects on cell polarity and tissue size. Simultaneous knockdown of α-cat and scrib induced both cell-autonomous and non-cell-autonomous Yki activity. In mammalian cells, knockdown of E-cad or α-cat caused nuclear accumulation and activation of YAP without overt effects on Scrib localization and vice versa. Therefore, our results indicate the existence of multiple, genetically separable inputs from AJs and cell polarity complexes into Yki/YAP regulation.

  7. Carcinoembryonic antigen promotes colorectal cancer progression by targeting adherens junction complexes

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    Bajenova, Olga, E-mail: o.bazhenova@spbu.ru [Theodosius Dobzhansky Center for Genome Bioinformatics, St. Petersburg State University, St. Petersburg 199034 (Russian Federation); Department of Genetics and Biotechnology, St. Petersburg State University, St. Petersburg 199034 (Russian Federation); Department of Surgery and Biomedical Sciences, Creighton University, Omaha, NE 68178 (United States); Chaika, Nina [Department of Surgery and Biomedical Sciences, Creighton University, Omaha, NE 68178 (United States); Tolkunova, Elena; Davydov-Sinitsyn, Alexander [Institute of Cytology, Russian Academy of Sciences, St. Petersburg 194064 (Russian Federation); Gapon, Svetlana [Boston Children' s Hospital, Boston, MA 02115 (United States); Thomas, Peter [Department of Surgery and Biomedical Sciences, Creighton University, Omaha, NE 68178 (United States); O’Brien, Stephen [Theodosius Dobzhansky Center for Genome Bioinformatics, St. Petersburg State University, St. Petersburg 199034 (Russian Federation)

    2014-06-10

    Oncomarkers play important roles in the detection and management of human malignancies. Carcinoembryonic antigen (CEA, CEACAM5) and epithelial cadherin (E-cadherin) are considered as independent tumor markers in monitoring metastatic colorectal cancer. They are both expressed by cancer cells and can be detected in the blood serum. We investigated the effect of CEA production by MIP101 colorectal carcinoma cell lines on E-cadherin adherens junction (AJ) protein complexes. No direct interaction between E-cadherin and CEA was detected; however, the functional relationships between E-cadherin and its AJ partners: α-, β- and p120 catenins were impaired. We discovered a novel interaction between CEA and beta-catenin protein in the CEA producing cells. It is shown in the current study that CEA overexpression alters the splicing of p120 catenin and triggers the release of soluble E-cadherin. The influence of CEA production by colorectal cancer cells on the function of E-cadherin junction complexes may explain the link between the elevated levels of CEA and the increase in soluble E-cadherin during the progression of colorectal cancer. - Highlights: • Elevated level of CEA increases the release of soluble E-cadherin during the progression of colorectal cancer. • CEA over-expression alters the binding preferences between E-cadherin and its partners: α-, β- and p120 catenins in adherens junction complexes. • CEA produced by colorectal cancer cells interacts with beta-catenin protein. • CEA over-expression triggers the increase in nuclear beta-catenin. • CEA over-expression alters the splicing of p120 catenin protein.

  8. An introduction to adherens junctions: from molecular mechanisms to tissue development and disease.

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    Harris, Tony J C

    2012-01-01

    Adherens junctions (AJs) are fundamental for the development of animal tissues and organs. The core complex is formed from transmembrane cell-cell adhesion molecules, cadherins, and adaptor molecules, the catenins, that link to cytoskeletal and regulatory networks within the cell. This complex can be considered over a wide range of biological organization, from atoms to molecules, protein complexes, molecular networks, cells, tissues, and overall animal development. AJs have also been an integral part of animal evolution, and play central roles in cancer development and pathogen infection. This book addresses major questions encompassing these aspects of AJ biology. How did AJs evolve? How do the cadherins and catenins interact to assemble AJs and mediate adhesion? How do AJs interface with other cellular machinery to couple adhesion with the whole cell? How do AJs affect cell behaviour and multicellular development? How can abnormal AJ activity lead to disease?

  9. Endothelial Cell Permeability and Adherens Junction Disruption Induced by Junín Virus Infection

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    Lander, Heather M.; Grant, Ashley M.; Albrecht, Thomas; Hill, Terence; Peters, Clarence J.

    2014-01-01

    Junín virus (JUNV) is endemic to the fertile Pampas of Argentina, maintained in nature by the rodent host Calomys musculinus, and the causative agent of Argentine hemorrhagic fever (AHF), which is characterized by vascular dysfunction and fluid distribution abnormalities. Clinical as well as experimental studies implicate involvement of the endothelium in the pathogenesis of AHF, although little is known of its role. JUNV has been shown to result in productive infection of endothelial cells (ECs) in vitro with no visible cytopathic effects. In this study, we show that direct JUNV infection of primary human ECs results in increased vascular permeability as measured by electric cell substrate impedance sensing and transwell permeability assays. We also show that EC adherens junctions are disrupted during virus infection, which may provide insight into the role of the endothelium in the pathogenesis of AHF and possibly, other viral hemorrhagic fevers. PMID:24710609

  10. Photoperiod-Dependent Effects of 4-tert-Octylphenol on Adherens and Gap Junction Proteins in Bank Vole Seminiferous Tubules

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    Anna Hejmej

    2013-01-01

    Full Text Available In the present study we evaluated in vivo and in vitro effects of 4-tert-octylphenol (OP on the expression and distribution of adherens and gap junction proteins, N-cadherin, β-catenin, and connexin 43 (Cx43, in testes of seasonally breeding rodents, bank voles. We found that in bank vole testes expression and distribution of N-cadherin, β-catenin, and Cx43 were photoperiod dependent. Long-term treatment with OP (200 mg/kg b.w. resulted in the reduction of junction proteins expressions (P<0.05, P<0.01 and their delocalization in the testes of males kept in long photoperiod, whereas in short-day animals slight increase of Cx43 (P<0.05, N-cadherin, and β-catenin (statistically nonsignificant levels was observed. Effects of OP appeared to be independent of FSH and were maintained during in vitro organ culture, indicating that OP acts directly on adherens and gap junction proteins in the testes. An experiment performed using an antiestrogen ICI 182,780 demonstrated that the biological effects of OP on β-catenin and Cx43 involve an estrogen receptor-mediated response. Taken together, in bank vole organization of adherens and gap junctions and their susceptibility to OP are related to the length of photoperiod. Alterations in cadherin/catenin and Cx43-based junction may partially result from activation of estrogen receptor α and/or β signaling pathway.

  11. HIV-associated disruption of tight and adherens junctions of oral epithelial cells facilitates HSV-1 infection and spread.

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    Sufiawati, Irna; Tugizov, Sharof M

    2014-01-01

    Herpes simplex virus (HSV) types 1 and 2 are the most common opportunistic infections in HIV/AIDS. In these immunocompromised individuals, HSV-1 reactivates and replicates in oral epithelium, leading to oral disorders such as ulcers, gingivitis, and necrotic lesions. Although the increased risk of HSV infection may be mediated in part by HIV-induced immune dysfunction, direct or indirect interactions of HIV and HSV at the molecular level may also play a role. In this report we show that prolonged interaction of the HIV proteins tat and gp120 and cell-free HIV virions with polarized oral epithelial cells leads to disruption of tight and adherens junctions of epithelial cells through the mitogen-activated protein kinase signaling pathway. HIV-induced disruption of oral epithelial junctions facilitates HSV-1 paracellular spread between the epithelial cells. Furthermore, HIV-associated disruption of adherens junctions exposes sequestered nectin-1, an adhesion protein and critical receptor for HSV envelope glycoprotein D (gD). Exposure of nectin-1 facilitates binding of HSV-1 gD, which substantially increases HSV-1 infection of epithelial cells with disrupted junctions over that of cells with intact junctions. Exposed nectin-1 from disrupted adherens junctions also increases the cell-to-cell spread of HSV-1 from infected to uninfected oral epithelial cells. Antibodies to nectin-1 and HSV-1 gD substantially reduce HSV-1 infection and cell-to-cell spread, indicating that HIV-promoted HSV infection and spread are mediated by the interaction of HSV gD with HIV-exposed nectin-1. Our data suggest that HIV-associated disruption of oral epithelial junctions may potentiate HSV-1 infection and its paracellular and cell-to-cell spread within the oral mucosal epithelium. This could be one of the possible mechanisms of rapid development of HSV-associated oral lesions in HIV-infected individuals.

  12. HIV-associated disruption of tight and adherens junctions of oral epithelial cells facilitates HSV-1 infection and spread.

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    Irna Sufiawati

    Full Text Available Herpes simplex virus (HSV types 1 and 2 are the most common opportunistic infections in HIV/AIDS. In these immunocompromised individuals, HSV-1 reactivates and replicates in oral epithelium, leading to oral disorders such as ulcers, gingivitis, and necrotic lesions. Although the increased risk of HSV infection may be mediated in part by HIV-induced immune dysfunction, direct or indirect interactions of HIV and HSV at the molecular level may also play a role. In this report we show that prolonged interaction of the HIV proteins tat and gp120 and cell-free HIV virions with polarized oral epithelial cells leads to disruption of tight and adherens junctions of epithelial cells through the mitogen-activated protein kinase signaling pathway. HIV-induced disruption of oral epithelial junctions facilitates HSV-1 paracellular spread between the epithelial cells. Furthermore, HIV-associated disruption of adherens junctions exposes sequestered nectin-1, an adhesion protein and critical receptor for HSV envelope glycoprotein D (gD. Exposure of nectin-1 facilitates binding of HSV-1 gD, which substantially increases HSV-1 infection of epithelial cells with disrupted junctions over that of cells with intact junctions. Exposed nectin-1 from disrupted adherens junctions also increases the cell-to-cell spread of HSV-1 from infected to uninfected oral epithelial cells. Antibodies to nectin-1 and HSV-1 gD substantially reduce HSV-1 infection and cell-to-cell spread, indicating that HIV-promoted HSV infection and spread are mediated by the interaction of HSV gD with HIV-exposed nectin-1. Our data suggest that HIV-associated disruption of oral epithelial junctions may potentiate HSV-1 infection and its paracellular and cell-to-cell spread within the oral mucosal epithelium. This could be one of the possible mechanisms of rapid development of HSV-associated oral lesions in HIV-infected individuals.

  13. Adherens junction distribution mechanisms during cell-cell contact elongation in Drosophila.

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    Gabrielle Goldenberg

    Full Text Available During Drosophila gastrulation, amnioserosa (AS cells flatten and spread as an epithelial sheet. We used AS morphogenesis as a model to investigate how adherens junctions (AJs distribute along elongating cell-cell contacts in vivo. As the contacts elongated, total AJ protein levels increased along their length. However, genetically blocking this AJ addition indicated that it was not essential for maintaining AJ continuity. Implicating other remodeling mechanisms, AJ photobleaching revealed non-directional lateral mobility of AJs along the elongating contacts, as well as local AJ removal from the membranes. Actin stabilization with jasplakinolide reduced AJ redistribution, and live imaging of myosin II along elongating contacts revealed fragmented, expanding and contracting actomyosin networks, suggesting a mechanism for lateral AJ mobility. Actin stabilization also increased total AJ levels, suggesting an inhibition of AJ removal. Implicating AJ removal by endocytosis, clathrin endocytic machinery accumulated at AJs. However, dynamin disruption had no apparent effect on AJs, suggesting the involvement of redundant or dynamin-independent mechanisms. Overall, we propose that new synthesis, lateral diffusion, and endocytosis play overlapping roles to populate elongating cell-cell contacts with evenly distributed AJs in this in vivo system.

  14. Segmentation and tracking of adherens junctions in 3D for the analysis of epithelial tissue morphogenesis.

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    Cilla, Rodrigo; Mechery, Vinodh; Hernandez de Madrid, Beatriz; Del Signore, Steven; Dotu, Ivan; Hatini, Victor

    2015-04-01

    Epithelial morphogenesis generates the shape of tissues, organs and embryos and is fundamental for their proper function. It is a dynamic process that occurs at multiple spatial scales from macromolecular dynamics, to cell deformations, mitosis and apoptosis, to coordinated cell rearrangements that lead to global changes of tissue shape. Using time lapse imaging, it is possible to observe these events at a system level. However, to investigate morphogenetic events it is necessary to develop computational tools to extract quantitative information from the time lapse data. Toward this goal, we developed an image-based computational pipeline to preprocess, segment and track epithelial cells in 4D confocal microscopy data. The computational pipeline we developed, for the first time, detects the adherens junctions of epithelial cells in 3D, without the need to first detect cell nuclei. We accentuate and detect cell outlines in a series of steps, symbolically describe the cells and their connectivity, and employ this information to track the cells. We validated the performance of the pipeline for its ability to detect vertices and cell-cell contacts, track cells, and identify mitosis and apoptosis in surface epithelia of Drosophila imaginal discs. We demonstrate the utility of the pipeline to extract key quantitative features of cell behavior with which to elucidate the dynamics and biomechanical control of epithelial tissue morphogenesis. We have made our methods and data available as an open-source multiplatform software tool called TTT (http://github.com/morganrcu/TTT).

  15. Alteration of Tight and Adherens Junctions on 50-Hz Magnetic Field Exposure in Madin Darby Canine Kidney (MDCK Cells

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    Zoltán Somosy

    2004-01-01

    Full Text Available Adherens (AJ and tight junctions (TJ, as integrated parts of the junctional complex, are multifunctional specialized regions of the cell membrane in epithelial cells. They are responsible for cell-to-cell interactions and also have great importance in cellular signaling processes including Wnt protein-mediated signals. As electromagnetic field (EMF exposure is known to cause alterations in the function as well as supramolecular organization of different cell contacts, our goal was to investigate the effect of 50-Hz magnetic field (MF exposures on the subcellular distribution of some representative structural proteins (occludin, β-catenin, and cadherin found in AJ and TJ. Additionally, cellular β-catenin content was also quantified by Western blot analysis. 50-Hz MF exposures seemed to increase the staining intensity (amount of occludin, cadherins, and β-catenin in the junctional area of MDCK cells, while Western blot data indicated the quantity of b-catenin was found significantly decreased at both time points after EM exposures. Our results demonstrate that MF are able to modify the distribution of TJ and AJ structural proteins, tending to stabilize these cell contacts. The quantitative changes of β-catenin suggest a causative relationship between MF effects on the cell junctional complex and the Wnt signaling pathway.

  16. A vertebrate-specific Chp-PAK-PIX pathway maintains E-cadherin at adherens junctions during zebrafish epiboly.

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    Tay, Hwee Goon; Ng, Yuen Wai; Manser, Ed

    2010-04-12

    In early vertebrate development, embryonic tissues modulate cell adhesiveness and acto-myosin contractility to correctly orchestrate the complex processes of gastrulation. E-cadherin (E-cadh) is the earliest expressed cadherin and is needed in the mesendodermal progenitors for efficient migration. Regulatory mechanisms involving directed E-cadh trafficking have been invoked downstream of Wnt11/5 signaling. This non-canonical Wnt pathway regulates RhoA-ROK/DAAM1 to control the acto-myosin network. However, in this context nothing is known of the intracellular signals that participate in the correct localization of E-cadh, other than a need for Rab5c signaling. By studying loss of Chp induced by morpholino-oligonucleotide injection in zebrafish, we find that the vertebrate atypical Rho-GTPase Chp is essential for the proper disposition of cells in the early embryo. The underlying defect is not leading edge F-actin assembly (prominent in the cells of the envelope layer), but rather the failure to localize E-cadh and beta-catenin at the adherens junctions. Loss of Chp results in delayed epiboly that can be rescued by mRNA co-injection, and phenocopies zebrafish E-cadh mutants. This new signaling pathway involves activation of an effector kinase PAK, and involvement of the adaptor PAK-interacting exchange factor PIX. Loss of signaling by any of the three components results in similar underlying defects, which is most prominent in the epithelial-like envelope layer. Our current study uncovers a developmental pathway involving Chp/PAK/PIX signaling, which helps co-ordinate E-cadh disposition to promote proper cell adhesiveness, and coordinate movements of the three major cell layers in epiboly. Our data shows that without Chp signaling, E-cadh shifts to intracellular vesicles rather than the adhesive contacts needed for directed cell movement. These events may mirror the requirement for PAK2 signaling essential for the proper formation of the blood-brain barrier.

  17. Drosophila PATJ supports adherens junction stability by modulating Myosin light chain activity

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    Sen, Arnab; Nagy-Zsvér-Vadas, Zsanett; Krahn, Michael P

    2012-01-01

    ... (Pals1-associated tight junction protein) was not per se crucial for the maintenance of apical-basal polarity in Drosophila melanogaster epithelial cells but rather regulated Myosin localization and phosphorylation...

  18. PLEKHA7 is an adherens junction protein with a tissue distribution and subcellular localization distinct from ZO-1 and E-cadherin.

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    Pamela Pulimeno

    Full Text Available The pleckstrin-homology-domain-containing protein PLEKHA7 was recently identified as a protein linking the E-cadherin-p120 ctn complex to the microtubule cytoskeleton. Here we characterize the expression, tissue distribution and subcellular localization of PLEKHA7 by immunoblotting, immunofluorescence microscopy, immunoelectron microscopy, and northern blotting in mammalian tissues. Anti-PLEKHA7 antibodies label the junctional regions of cultured kidney epithelial cells by immunofluorescence microscopy, and major polypeptides of M(r approximately 135 kDa and approximately 145 kDa by immunoblotting of lysates of cells and tissues. Two PLEKHA7 transcripts ( approximately 5.5 kb and approximately 6.5 kb are detected in epithelial tissues. PLEKHA7 is detected at epithelial junctions in sections of kidney, liver, pancreas, intestine, retina, and cornea, and its tissue distribution and subcellular localization are distinct from ZO-1. For example, PLEKHA7 is not detected within kidney glomeruli. Similarly to E-cadherin, p120 ctn, beta-catenin and alpha-catenin, PLEKHA7 is concentrated in the apical junctional belt, but unlike these adherens junction markers, and similarly to afadin, PLEKHA7 is not localized along the lateral region of polarized epithelial cells. Immunoelectron microscopy definitively establishes that PLEKHA7 is localized at the adherens junctions in colonic epithelial cells, at a mean distance of 28 nm from the plasma membrane. In summary, we show that PLEKHA7 is a cytoplasmic component of the epithelial adherens junction belt, with a subcellular localization and tissue distribution that is distinct from that of ZO-1 and most AJ proteins, and we provide the first description of its distribution and localization in several tissues.

  19. Alpha-catenin-Dependent Recruitment of the Centrosomal Protein CAP350 to Adherens Junctions Allows Epithelial Cells to Acquire a Columnar Shape

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    Zurbano, Angel; Formstecher, Etienne; Martinez-Morales, Juan R.; Bornens, Michel; Rios, Rosa M.

    2015-01-01

    Epithelial morphogenesis involves a dramatic reorganisation of the microtubule cytoskeleton. How this complex process is controlled at the molecular level is still largely unknown. Here, we report that the centrosomal microtubule (MT)-binding protein CAP350 localises at adherens junctions in epithelial cells. By two-hybrid screening, we identified a direct interaction of CAP350 with the adhesion protein α-catenin that was further confirmed by co-immunoprecipitation experiments. Block of epithelial cadherin (E-cadherin)-mediated cell-cell adhesion or α-catenin depletion prevented CAP350 localisation at cell-cell junctions. Knocking down junction-located CAP350 inhibited the establishment of an apico-basal array of microtubules and impaired the acquisition of columnar shape in Madin-Darby canine kidney II (MDCKII) cells grown as polarised epithelia. Furthermore, MDCKII cystogenesis was also defective in junctional CAP350-depleted cells. CAP350-depleted MDCKII cysts were smaller and contained either multiple lumens or no lumen. Membrane polarity was not affected, but cortical microtubule bundles did not properly form. Our results indicate that CAP350 may act as an adaptor between adherens junctions and microtubules, thus regulating epithelial differentiation and contributing to the definition of cell architecture. We also uncover a central role of α-catenin in global cytoskeleton remodelling, in which it acts not only on actin but also on MT reorganisation during epithelial morphogenesis. PMID:25764135

  20. Mild hypothermia alleviates brain oedema and blood-brain barrier disruption by attenuating tight junction and adherens junction breakdown in a swine model of cardiopulmonary resuscitation

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    Li, Jiebin; Li, Chunsheng; Yuan, Wei; Wu, Junyuan; Li, Jie; Li, Zhenhua; Zhao, Yongzhen

    2017-01-01

    Mild hypothermia improves survival and neurological recovery after cardiac arrest (CA) and cardiopulmonary resuscitation (CPR). However, the mechanism underlying this phenomenon is not fully elucidated. The aim of this study was to determine whether mild hypothermia alleviates early blood–brain barrier (BBB) disruption. We investigated the effects of mild hypothermia on neurologic outcome, survival rate, brain water content, BBB permeability and changes in tight junctions (TJs) and adherens junctions (AJs) after CA and CPR. Pigs were subjected to 8 min of untreated ventricular fibrillation followed by CPR. Mild hypothermia (33°C) was intravascularly induced and maintained at this temperature for 12 h, followed by active rewarming. Mild hypothermia significantly reduced cortical water content, decreased BBB permeability and attenuated TJ ultrastructural and basement membrane breakdown in brain cortical microvessels. Mild hypothermia also attenuated the CPR-induced decreases in TJ (occludin, claudin-5, ZO-1) and AJ (VE-cadherin) protein and mRNA expression. Furthermore, mild hypothermia decreased the CA- and CPR-induced increases in matrix metalloproteinase-9 (MMP-9) and vascular endothelial growth factor (VEGF) expression and increased angiogenin-1 (Ang-1) expression. Our findings suggest that mild hypothermia attenuates the CA- and resuscitation-induced early brain oedema and BBB disruption, and this improvement might be at least partially associated with attenuation of the breakdown of TJ and AJ, suppression of MMP-9 and VEGF expression, and upregulation of Ang-1 expression. PMID:28355299

  1. Genetic deletion of afadin causes hydrocephalus by destruction of adherens junctions in radial glial and ependymal cells in the midbrain.

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    Hideaki Yamamoto

    Full Text Available Adherens junctions (AJs play a role in mechanically connecting adjacent cells to maintain tissue structure, particularly in epithelial cells. The major cell-cell adhesion molecules at AJs are cadherins and nectins. Afadin binds to both nectins and α-catenin and recruits the cadherin-β-catenin complex to the nectin-based cell-cell adhesion site to form AJs. To explore the role of afadin in radial glial and ependymal cells in the brain, we generated mice carrying a nestin-Cre-mediated conditional knockout (cKO of the afadin gene. Newborn afadin-cKO mice developed hydrocephalus and died neonatally. The afadin-cKO brain displayed enlarged lateral ventricles and cerebral aqueduct, resulting from stenosis of the caudal end of the cerebral aqueduct and obliteration of the ventral part of the third ventricle. Afadin deficiency further caused the loss of ependymal cells from the ventricular and aqueductal surfaces. During development, radial glial cells, which terminally differentiate into ependymal cells, scattered from the ventricular zone and were replaced by neurons that eventually covered the ventricular and aqueductal surfaces of the afadin-cKO midbrain. Moreover, the denuded ependymal cells were only occasionally observed in the third ventricle and the cerebral aqueduct of the afadin-cKO midbrain. Afadin was co-localized with nectin-1 and N-cadherin at AJs of radial glial and ependymal cells in the control midbrain, but these proteins were not concentrated at AJs in the afadin-cKO midbrain. Thus, the defects in the afadin-cKO midbrain most likely resulted from the destruction of AJs, because AJs in the midbrain were already established before afadin was genetically deleted. These results indicate that afadin is essential for the maintenance of AJs in radial glial and ependymal cells in the midbrain and is required for normal morphogenesis of the cerebral aqueduct and ventral third ventricle in the midbrain.

  2. CMTM3 (CKLF-Like Marvel Transmembrane Domain 3) Mediates Angiogenesis by Regulating Cell Surface Availability of VE-Cadherin in Endothelial Adherens Junctions.

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    Chrifi, Ihsan; Louzao-Martinez, Laura; Brandt, Maarten; van Dijk, Christian G M; Burgisser, Petra; Zhu, Changbin; Kros, Johan M; Duncker, Dirk J; Cheng, Caroline

    2017-06-01

    Decrease in VE-cadherin adherens junctions reduces vascular stability, whereas disruption of adherens junctions is a requirement for neovessel sprouting during angiogenesis. Endocytosis plays a key role in regulating junctional strength by altering bioavailability of cell surface proteins, including VE-cadherin. Identification of new mediators of endothelial endocytosis could enhance our understanding of angiogenesis. Here, we assessed the function of CMTM3 (CKLF-like MARVEL transmembrane domain 3), which we have previously identified as highly expressed in Flk1(+) endothelial progenitor cells during embryonic development. Using a 3-dimensional coculture of human umbilical vein endothelial cells-GFP (green fluorescent protein) and pericytes-RFP (red fluorescent protein), we demonstrated that siRNA-mediated CMTM3 silencing in human umbilical vein endothelial cells impairs angiogenesis. In vivo CMTM3 inhibition by morpholino injection in developing zebrafish larvae confirmed that CMTM3 expression is required for vascular sprouting. CMTM3 knockdown in human umbilical vein endothelial cells does not affect proliferation or migration. Intracellular staining demonstrated that CMTM3 colocalizes with early endosome markers EEA1 (early endosome marker 1) and Clathrin(+) vesicles and with cytosolic VE-cadherin in human umbilical vein endothelial cells. Adenovirus-mediated CMTM3 overexpression enhances endothelial endocytosis, shown by an increase in Clathrin(+), EEA1(+), Rab11(+), Rab5(+), and Rab7(+) vesicles. CMTM3 overexpression enhances, whereas CMTM3 knockdown decreases internalization of cell surface VE-cadherin in vitro. CMTM3 promotes loss of endothelial barrier function in thrombin-induced responses, shown by transendothelial electric resistance measurements in vitro. In this study, we have identified a new regulatory function for CMTM3 in angiogenesis. CMTM3 is involved in VE-cadherin turnover and is a regulator of the cell surface pool of VE-cadherin. Therefore

  3. Cigarette smoke disrupts the integrity of airway adherens junctions through the aberrant interaction of p120-catenin with the cytoplasmic tail of MUC1

    Science.gov (United States)

    Zhang, Lili; Gallup, Marianne; Zlock, Lorna; Basbaum, Carol; Finkbeiner, Walter E.; McNamara, Nancy A.

    2014-01-01

    Adherens junctions (AJs) containing epithelial cadherin (E-cad) bound to p120-catenin (p120ctn) and β-catenin (β-ctn) play a crucial role in regulating cell–cell adhesion. Cigarette smoke abrogates cell–cell adhesion between epithelial cells by disrupting E-cad, a hallmark of epithelial–mesenchymal transition (EMT), yet the underlying mechanism remains unknown. We used an organotypic culture of primary human bronchial epithelial (HBE) cells treated with smoke-concentrated medium (Smk) to establish an essential role for the interaction between p120ctn and the cytoplasmic tail of MUC1 (MUC1-CT) in regulating E-cad disruption. Within the first 4 h of smoke exposure, apical MUC1-CT repositioned to the basolateral membrane of pseudo-stratified HBE cells, where it interacted with p120ctn. A time-dependent increase in MUC1-CT/p120ctn complexes occurred in conjunction with a time-dependent dissociation of p120ctn/E-cad/β-ctn complexes, as well as the coordinated degradation of p120ctn and E-cad. Interestingly, Smk induced a similar interaction between MUC1-CT and β-ctn, but this occurred 44 h after MUC1-CT’s initial interaction with p120ctn, and well after the AJs were destroyed. Blocking MUC1-CT’s interaction with p120ctn using a MUC1-CT dominant-negative peptide, PMIP, successfully abolished Smk’s disruptive effects on AJs and recovered apical-basolateral polarity of HBE cells. The MUC1-CT/p120ctn interaction was highly dependent on EGFR/Src/Jnk-mediated tyrosine phosphorylation (TyrP) of MUC1-CT. Accordingly, EGFR, Src or Jnk inhibitors (AG1478, PP2, SP600125, respectively) abrogated Smk-induced MUC1-CT-TyrP, MUC1-CT/p120ctn interaction, AJ disruption, and loss of cellular polarity. Our work identified MUC1-CT and p120ctn as important regulators of epithelial polarity and cell-cell adhesion during a smoke-induced EMT-like process. Novel therapeutics designed to inhibit MUC1-CT/p120ctn complex formation may prevent EMT in the smoker’s airway. PMID

  4. 'Special K' and a Loss of Cell-To-Cell Adhesion in Proximal Tubule-Derived Epithelial Cells: Modulation of the Adherens Junction Complex by Ketamine

    Science.gov (United States)

    Hills, Claire E.; Jin, Tianrong; Siamantouras, Eleftherios; Liu, Issac K-K; Jefferson, Kieran P.; Squires, Paul E.

    2013-01-01

    Ketamine, a mild hallucinogenic class C drug, is the fastest growing ‘party drug’ used by 16–24 year olds in the UK. As the recreational use of Ketamine increases we are beginning to see the signs of major renal and bladder complications. To date however, we know nothing of a role for Ketamine in modulating both structure and function of the human renal proximal tubule. In the current study we have used an established model cell line for human epithelial cells of the proximal tubule (HK2) to demonstrate that Ketamine evokes early changes in expression of proteins central to the adherens junction complex. Furthermore we use AFM single-cell force spectroscopy to assess if these changes functionally uncouple cells of the proximal tubule ahead of any overt loss in epithelial cell function. Our data suggests that Ketamine (24–48 hrs) produces gross changes in cell morphology and cytoskeletal architecture towards a fibrotic phenotype. These physical changes matched the concentration-dependent (0.1–1 mg/mL) cytotoxic effect of Ketamine and reflect a loss in expression of the key adherens junction proteins epithelial (E)- and neural (N)-cadherin and β-catenin. Down-regulation of protein expression does not involve the pro-fibrotic cytokine TGFβ, nor is it regulated by the usual increase in expression of Slug or Snail, the transcriptional regulators for E-cadherin. However, the loss in E-cadherin can be partially rescued pharmacologically by blocking p38 MAPK using SB203580. These data provide compelling evidence that Ketamine alters epithelial cell-to-cell adhesion and cell-coupling in the proximal kidney via a non-classical pro-fibrotic mechanism and the data provides the first indication that this illicit substance can have major implications on renal function. Understanding Ketamine-induced renal pathology may identify targets for future therapeutic intervention. PMID:24009666

  5. Downregulation of blood-brain barrier phenotype by proinflammatory cytokines involves NADPH oxidase-dependent ROS generation: consequences for interendothelial adherens and tight junctions.

    Directory of Open Access Journals (Sweden)

    Keith D Rochfort

    Full Text Available Blood-brain barrier (BBB dysfunction is an integral feature of neurological disorders and involves the action of multiple proinflammatory cytokines on the microvascular endothelial cells lining cerebral capillaries. There is still however, considerable ambiguity throughout the scientific literature regarding the mechanistic role(s of cytokines in this context, thereby warranting a comprehensive in vitro investigation into how different cytokines may cause dysregulation of adherens and tight junctions leading to BBB permeabilization.The present study employs human brain microvascular endothelial cells (HBMvECs to compare/contrast the effects of TNF-α and IL-6 on BBB characteristics ranging from the expression of interendothelial junction proteins (VE-cadherin, occludin and claudin-5 to endothelial monolayer permeability. The contribution of cytokine-induced NADPH oxidase activation to altered barrier phenotype was also investigated.In response to treatment with either TNF-α or IL-6 (0-100 ng/ml, 0-24 hrs, our studies consistently demonstrated significant dose- and time-dependent decreases in the expression of all interendothelial junction proteins examined, in parallel with dose- and time-dependent increases in ROS generation and HBMvEC permeability. Increased expression and co-association of gp91 and p47, pivotal NADPH oxidase subunits, was also observed in response to either cytokine. Finally, cytokine-dependent effects on junctional protein expression, ROS generation and endothelial permeability could all be attenuated to a comparable extent using a range of antioxidant strategies, which included ROS depleting agents (superoxide dismutase, catalase, N-acetylcysteine, apocynin and targeted NADPH oxidase blockade (gp91 and p47 siRNA, NSC23766.A timely and wide-ranging investigation comparing the permeabilizing actions of TNF-α and IL-6 in HBMvECs is presented, in which we demonstrate how either cytokine can similarly downregulate the

  6. armadillo, bazooka, and stardust are critical for early stages in formation of the zonula adherens and maintenance of the polarized blastoderm epithelium in Drosophila.

    Science.gov (United States)

    Müller, H A; Wieschaus, E

    1996-07-01

    Cellularization of the Drosophila embryo results in the formation of a cell monolayer with many characteristics of a polarized epithelium. We have used antibodies specific to cellular junctions and nascent plasma membranes to study the formation of the zonula adherens (ZA) in relation to the establishment of basolateral membrane polarity. The same approach was then used as a test system to identify X-linked zygotically active genes required for ZA formation. We show that ZA formation begins during cellularization and that the basolateral membrane domain is established at mid-gastrulation. By creating deficiencies for defined regions of the X chromosome, we have identified genes that are required for the formation of the ZA and the generation of basolateral membrane polarity. We show that embryos mutant for both stardust (sdt) and bazooka (baz) fail to form a ZA. In addition to the failure to establish the ZA, the formation of the monolayered epithelium is disrupted after cellularization, resulting in formation of a multilayered cell sheet by mid-gastrulation. SEM analysis of mutant embryos revealed a conversion of cells exhibiting epithelial characteristics into cells exhibiting mesenchymal characteristics. To investigate how mutations that affect an integral component of the ZA itself influence ZA formation, we examined embryos with reduced maternal and zygotic supply of wild-type Arm protein. These embryos, like embryos mutant for both sdt and baz, exhibit an early disruption of ZA formation. These results suggest that early stages in the assembly of the ZA are critical for the stability of the polarized blastoderm epithelium.

  7. Nectin/PRR: an immunoglobulin-like cell adhesion molecule recruited to cadherin-based adherens junctions through interaction with Afadin, a PDZ domain-containing protein.

    Science.gov (United States)

    Takahashi, K; Nakanishi, H; Miyahara, M; Mandai, K; Satoh, K; Satoh, A; Nishioka, H; Aoki, J; Nomoto, A; Mizoguchi, A; Takai, Y

    1999-05-03

    We have isolated a novel actin filament-binding protein, named afadin, localized at cadherin-based cell-cell adherens junctions (AJs) in various tissues and cell lines. Afadin has one PDZ domain, three proline-rich regions, and one actin filament-binding domain. We found here that afadin directly interacted with a family of the immunoglobulin superfamily, which was isolated originally as the poliovirus receptor-related protein (PRR) family consisting of PRR1 and -2, and has been identified recently to be the alphaherpes virus receptor. PRR has a COOH-terminal consensus motif to which the PDZ domain of afadin binds. PRR and afadin were colocalized at cadherin-based cell-cell AJs in various tissues and cell lines. In E-cadherin-expressing EL cells, PRR was recruited to cadherin-based cell-cell AJs through interaction with afadin. PRR showed Ca2+-independent cell-cell adhesion activity. These results indicate that PRR is a cell-cell adhesion molecule of the immunoglobulin superfamily which is recruited to cadherin-based cell-cell AJs through interaction with afadin. We rename PRR as nectin (taken from the Latin word "necto" meaning "to connect").

  8. Structural alteration of tight and adherens junctions in villous and crypt epithelium of the small and large intestine of conventional nursing piglets infected with porcine epidemic diarrhea virus.

    Science.gov (United States)

    Jung, Kwonil; Eyerly, Bryan; Annamalai, Thavamathi; Lu, Zhongyan; Saif, Linda J

    2015-06-12

    Integrity of the intestinal epithelium is critical for proper functioning of the barrier that regulates absorption of water and restricts uptake of luminal bacteria. It is maintained mainly by tight junctions (TJs) and adherens junctions (AJs). We conducted immunofluorescence (IF) staining for in situ identification of zonula occludin (ZO)-1 proteins for TJ and E-Cadherin proteins for AJ in the small and large intestinal villous and crypt epithelium of nursing pigs infected with porcine epidemic diarrhea virus (PEDV). Twenty 9-day-old piglets [PEDV-infected (n=9) and Mock (n=11)] from PEDV seronegative sows, were orally inoculated [8.9 log₁₀ genomic equivalents/pig] with PEDV PC21A strain or mock. At post-inoculation days (PIDs) 1-5, infected pigs showed severe watery diarrhea and/or vomiting and severe atrophic enteritis. By immunohistochemistry, PEDV antigens were evident in enterocytes lining the villous epithelium. At PIDs 1-5, PEDV-infected pigs exhibited mildly to extensively disorganized, irregular distribution and reduced expression of ZO-1 or E-Cadherin in villous, but not crypt epithelial cells of the jejunum and ileum, but not in the large intestine, when compared to the negative controls. The structural destruction and disorganization of TJ and AJ were extensive in PEDV-infected pigs at PIDs 1-3, but then appeared to reversibly recover at PID 5, as evident by increased numbers of ZO-1-positive epithelial cells and markedly improved appearance of E-Cadherin-positive villous epithelium. Our results suggest a possible involvement of structurally impaired TJ and AJ in the pathogenesis of PEDV, potentially leading to secondary bacterial infections.

  9. Defect formation in long Josephson junctions

    DEFF Research Database (Denmark)

    Gordeeva, Anna; Pankratov, Andrey

    2010-01-01

    We study numerically a mechanism of vortex formation in a long Josephson junction within the framework of the one-dimensional sine-Gordon model. This mechanism is switched on below the critical temperature. It is shown that the number of fluxons versus velocity of cooling roughly scales according...

  10. Model Building to Facilitate Understanding of Holliday Junction and Heteroduplex Formation, and Holliday Junction Resolution

    Science.gov (United States)

    Selvarajah, Geeta; Selvarajah, Susila

    2016-01-01

    Students frequently expressed difficulty in understanding the molecular mechanisms involved in chromosomal recombination. Therefore, we explored alternative methods for presenting the two concepts of the double-strand break model: Holliday junction and heteroduplex formation, and Holliday junction resolution. In addition to a lecture and…

  11. ROCK activity regulates functional tight junction assembly during blastocyst formation in porcine parthenogenetic embryos

    Directory of Open Access Journals (Sweden)

    Jeongwoo Kwon

    2016-04-01

    Full Text Available The Rho-associated coiled-coil-containing protein serine/threonine kinases 1 and 2 (ROCK1 and ROCK2 are Rho subfamily GTPase downstream effectors that regulate cell migration, intercellular adhesion, cell polarity, and cell proliferation by stimulating actin cytoskeleton reorganization. Inhibition of ROCK proteins affects specification of the trophectoderm (TE and inner cell mass (ICM lineages, compaction, and blastocyst cavitation. However, the molecules involved in blastocyst formation are not known. Here, we examined developmental competence and levels of adherens/tight junction (AJ/TJ constituent proteins, such as CXADR, OCLN, TJP1, and CDH1, as well as expression of their respective mRNAs, after treating porcine parthenogenetic four-cell embryos with Y-27632, a specific inhibitor of ROCK, at concentrations of 0, 10, 20, 100 µM for 24 h. Following this treatment, the blastocyst development rates were 39.1, 20.7, 10.0, and 0% respectively. In embryos treated with 20 µM treatment, expression levels of CXADR, OCLN, TJP1, and CDH1 mRNA and protein molecules were significantly reduced (P < 0.05. FITC-dextran uptake assay revealed that the treatment caused an increase in TE TJ permeability. Interestingly, the majority of the four-cell and morula embryos treated with 20 µM Y-27643 for 24 h showed defective compaction and cavitation. Taken together, our results indicate that ROCK activity may differentially affect assembly of AJ/TJs as well as regulate expression of genes encoding junctional proteins.

  12. Formation of bubbles in a multisection flow-focusing junction.

    Science.gov (United States)

    Hashimoto, Michinao; Whitesides, George M

    2010-05-01

    The formation of bubbles in a flow-focusing (FF) junction comprising multiple rectangular sections is described. The simplest junctions comprise two sections (throat and orifice). Systematic investigation of the influence on the formation of bubbles of the flow of liquid and the geometry of the junction identifies regimes that generate monodisperse, bidisperse, and tridisperse trains of bubbles. The mechanisms by which these junctions form monodisperse and bidisperse bubbles are inferred from the shapes of the gas thread during breakup: these mechanisms differ primarily by the process in which the gas thread collapses in the throat and/or orifice. The dynamic self-assembly of bidisperse bubbles leads to unexpected groupings of bubbles during their flow along the outlet channel.

  13. Transcriptional mechanisms coordinating tight junction assembly during epithelial differentiation.

    Science.gov (United States)

    Boivin, Felix J; Schmidt-Ott, Kai M

    2017-06-01

    Epithelial tissues form a selective barrier via direct cell-cell interactions to separate and establish concentration gradients between the different compartments of the body. Proper function and formation of this barrier rely on the establishment of distinct intercellular junction complexes. These complexes include tight junctions, adherens junctions, desmosomes, and gap junctions. The tight junction is by far the most diverse junctional complex in the epithelial barrier. Its composition varies greatly across different epithelial tissues to confer various barrier properties. Thus, epithelial cells rely on tightly regulated transcriptional mechanisms to ensure proper formation of the epithelial barrier and to achieve tight junction diversity. Here, we review different transcriptional mechanisms utilized during embryogenesis and disease development to promote tight junction assembly and maintenance of intercellular barrier integrity. We focus particularly on the Grainyhead-like transcription factors and ligand-activated nuclear hormone receptors, two central families of proteins in epithelialization. © 2017 New York Academy of Sciences.

  14. Involvement of YAP, TAZ and HSP90 in contact guidance and intercellular junction formation in corneal epithelial cells.

    Directory of Open Access Journals (Sweden)

    Vijay Krishna Raghunathan

    Full Text Available The extracellular environment possesses a rich milieu of biophysical and biochemical signaling cues that are simultaneously integrated by cells and influence cellular phenotype. Yes-associated protein (YAP and transcriptional co-activator with PDZ-binding motif (WWTR1; TAZ, two important signaling molecules of the Hippo pathway, have been recently implicated as nuclear relays of cytoskeletal changes mediated by substratum rigidity and topography. These proteins intersect with other important intracellular signaling pathways (e.g. Wnt and TGFβ. In the cornea, epithelial cells adhere to the stroma through a 3-dimensional topography-rich basement membrane, with features in the nano-submicron size-scale that are capable of profoundly modulating a wide range of fundamental cell behaviors. The influences of substratum-topography, YAP/TAZ knockdown, and HSP90 inhibition on cell morphology, YAP/TAZ localization, and the expression of TGFβ2 and CTGF, were investigated. The results demonstrate (a that knockdown of TAZ enhances contact guidance in a YAP dependent manner, (b that CTGF is predominantly regulated by YAP and not TAZ, and (c that TGFβ2 is regulated by both YAP and TAZ in these cells. Additionally, inhibition of HSP90 resulted in nuclear localization and subsequent transcriptional-activation of YAP, formation of cell-cell junctions and co-localization of E-cadherin and β-catenin at adherens junctions. Results presented in this study reflect the complexities underlying the molecular relationships between the cytoskeleton, growth factors, heat shock proteins, and co-activators of transcription that impact mechanotransduction. The data reveal the importance of YAP/TAZ on the cell behaviors, and gene and protein expression.

  15. Systematic study of shallow junction formation on germanium substrates

    DEFF Research Database (Denmark)

    Hellings, Geert; Rosseel, Erik; Clarysse, Trudo

    2011-01-01

    Published results on Ge junctions are benchmarked systematically using RS–XJ plots. The electrical activation level required to meet the ITRS targets is calculated. Additionally, new results are presented on shallow furnace-annealed B junctions and shallow laser-annealed As junctions. Co-implanti...

  16. Multicellular rosette formation links planar cell polarity to tissue morphogenesis.

    Science.gov (United States)

    Blankenship, J Todd; Backovic, Stephanie T; Sanny, Justina S P; Weitz, Ori; Zallen, Jennifer A

    2006-10-01

    Elongation of the body axis is accompanied by the assembly of a polarized cytoarchitecture that provides the basis for directional cell behavior. We find that planar polarity in the Drosophila embryo is established through a sequential enrichment of actin-myosin cables and adherens junction proteins in complementary surface domains. F-actin accumulation at AP interfaces represents the first break in planar symmetry and occurs independently of proper junctional protein distribution at DV interfaces. Polarized cells engage in a novel program of locally coordinated behavior to generate multicellular rosette structures that form and resolve in a directional fashion. Actin-myosin structures align across multiple cells during rosette formation, and adherens junction proteins assemble in a stepwise fashion during rosette resolution. Patterning genes essential for axis elongation selectively affect the frequency and directionality of rosette formation. We propose that the generation of higher-order rosette structures links local cell interactions to global tissue reorganization during morphogenesis.

  17. Evaluation of the formation of a junctional DNA nanostructure through annealing curve analysis.

    Science.gov (United States)

    Shin, Seung Won; Park, Kyung Soo; Um, Soong Ho

    2015-02-20

    During the self-assembly of different numbers of oligonucleotides comprising junctional DNA nanostructures, a change in environmental variables (e.g., temperature or salt concentration) has a substantial influence on the final products. Further, distinctive annealing temperatures of oligonucleotides are observed depending on the state of hybridization. Here, we present an evaluation of the annealing characteristics of oligonucleotides for the formation of a simple junctional DNA nanostructure using an annealing curve analysis. This method may be useful for analyzing the formation of complex junctional DNA nanostructures.

  18. Excimer laser annealing: A gold process for CZ silicon junction formation

    Science.gov (United States)

    Wong, David C.; Bottenberg, William R.; Byron, Stanley; Alexander, Paul

    A cold process using an excimer laser for junction formation in silicon has been evaluated as a way to avoid problems associated with thermal diffusion. Conventional thermal diffusion can cause bulk precipitation of SiOx and SiC or fail to completely activate the dopant, leaving a degenerate layer at the surface. Experiments were conducted to determine the feasibility of fabricating high quality p-n junctions using a pulsed excimer laser for junction formation at remelt temperature with ion-implanted surfaces. Solar-cell efficiency exceeding 16 percent was obtained using Czochralski single-crystal silicon without benefit of back surface field or surface passivation. Characterization shows that the formation of uniform, shallow junctions (approximately 0.25 micron) by excimer laser scanning preserves the minority carrier lifetime that leads to high current collection. However, the process is sensitive to initial surface conditions and handling parameters that drive the cost up.

  19. The Rho target PRK2 regulates apical junction formation in human bronchial epithelial cells.

    Science.gov (United States)

    Wallace, Sean W; Magalhaes, Ana; Hall, Alan

    2011-01-01

    Rho GTPases regulate multiple signaling pathways to control a number of cellular processes during epithelial morphogenesis. To investigate the downstream pathways through which Rho regulates epithelial apical junction formation, we screened a small interfering RNA (siRNA) library targeting 28 known Rho target proteins in 16HBE human bronchial epithelial cells. This led to the identification of the serine-threonine kinase PRK2 (protein kinase C-related kinase 2, also called PKN2). Depletion of PRK2 does not block the initial formation of primordial junctions at nascent cell-cell contacts but does prevent their maturation into apical junctions. PRK2 is recruited to primordial junctions, and this localization depends on its C2-like domain. Rho binding is essential for PRK2 function and also facilitates PRK2 recruitment to junctions. Kinase-dead PRK2 acts as a dominant-negative mutant and prevents apical junction formation. We conclude that PRK2 is recruited to nascent cell-cell contacts through its C2-like and Rho-binding domains and promotes junctional maturation through a kinase-dependent pathway.

  20. Formation and stability of ridge-ridge-ridge triple junctions in rheologically realistic lithosphere model

    Science.gov (United States)

    Gerya, Taras; Burov, Evgueni

    2015-04-01

    Triple junctions are probably the most remarkable features of plate boundaries since their presence constitutes one of the major demonstrations of plate tectonics theory. Divergent (R-R-R) triple junctions (at 120° and T junctions) are particular ones since their stability depends on the exact values of the relative velocities of plate divergence and hence is strongly affected by plate rheology and processes of crustal accretion. The mechanisms of their formation and long-term steadiness are not well understood even though it is commonly accepted, generally based on common sense, that the geometry and stability of triple junctions should be related to the intuitively acceptable geometric considerations that 3-branch configurations should be "stable" over the time on a 3D Earth surface. That said, most plate boundaries are in fact 2D in terms that they involve only two plates, while junctions with 3 and more branches, if even mechanically not excluded, are generally short-lived and hence rarely observed at tectonic scale. Indeed, it has been long-time suggested that triple junctions result from evolution of short-lived quadruple junctions, yet, without providing a consistent mechanical explanation or experimental demonstration of this process, due to the rheological complexity of the lithosphere and that of strain localization and crustal accretion processes. For example, it is supposed that R-R-R junctions form as result of axisymmetric mantle upwellings. However, impingement of buoyant fluid on a non-pre-stressed lithosphere should result in multiple radial cracks, as is well known from previous analog and numerical experiments. In case of uni-directionally pre-stressed lithosphere, it has also shown that linear 2D rift structures should be formed. Therefore, a complete 3D thermos-mechanically consistent approach is needed to understand the processes of formation of multi-branch junctions. With this goal we here reproduce and study the processes of multi

  1. Droplet formation in microfluidic T-junction generators operating in the transitional regime. II. Modeling.

    Science.gov (United States)

    Glawdel, Tomasz; Elbuken, Caglar; Ren, Carolyn L

    2012-01-01

    This is the second part of a two-part study on the generation of droplets at a microfluidic T-junction operating in the transition regime. In the preceding paper [Phys. Rev. E 85, 016322 (2012)], we presented our experimental observations of droplet formation and decomposed the process into three sequential stages defined as the lag, filling, and necking stages. Here we develop a model that describes the performance of microfluidic T-junction generators working in the squeezing to transition regimes where confinement of the droplet dominates the formation process. The model incorporates a detailed geometric description of the drop shape during the formation process combined with a force balance and necking criteria to define the droplet size, production rate, and spacing. The model inherently captures the influence of the intersection geometry, including the channel width ratio and height-to-width ratio, capillary number, and flow ratio, on the performance of the generator. The model is validated by comparing it to speed videos of the formation process for several T-junction geometries across a range of capillary numbers and viscosity ratios.

  2. The Rho Target PRK2 Regulates Apical Junction Formation in Human Bronchial Epithelial Cells ▿

    OpenAIRE

    Wallace, Sean W.; Magalhaes, Ana; Hall, Alan

    2010-01-01

    Rho GTPases regulate multiple signaling pathways to control a number of cellular processes during epithelial morphogenesis. To investigate the downstream pathways through which Rho regulates epithelial apical junction formation, we screened a small interfering RNA (siRNA) library targeting 28 known Rho target proteins in 16HBE human bronchial epithelial cells. This led to the identification of the serine-threonine kinase PRK2 (protein kinase C-related kinase 2, also called PKN2). Depletion of...

  3. Dynamic formation of microenvironments at the myotendinous junction correlates with muscle fiber morphogenesis in zebrafish

    OpenAIRE

    Snow, Chelsi J.; Henry, Clarissa A.

    2008-01-01

    Muscle development involves the specification and morphogenesis of muscle fibers that attach to tendons. After attachment, muscles and tendons then function as an integrated unit to transduce force to the skeletal system and stabilize joints. The attachment site is the myotendinous junction, or MTJ, and is the primary site of force transmission. We find that attachment of fast-twitch myofibers to the MTJ correlates with the formation of novel microenvironments within the MTJ. The expression o...

  4. Interfering amino terminal peptides and functional implications for heteromeric gap junction formation

    Directory of Open Access Journals (Sweden)

    Richard David Veenstra

    2013-05-01

    Full Text Available Connexin43 (Cx43 is widely expressed in many different tissues of the human body. In cells of some organs, Cx43 is co-expressed with other connexins (Cx, including Cx46 and Cx50 in lens, Cx40 in atrium, Purkinje fibers, and the blood vessel wall, Cx45 in heart, and Cx37 in the ovary. Interactions with the co-expressed connexins may have profound functional implications. The abilities of Cx37, Cx45, Cx46, and Cx50 to function in heteromeric gap junction combinations with Cx43 are well documented. Different studies disagree regarding the ability of Cx43 and Cx40 to produce functional heteromeric gap junctions with each other. We review previous studies regarding the heteromeric interactions of Cx43. The possibility of negative functional interactions between the cytoplasmic pore-forming amino terminal (NT domains of these connexins was assessed using pentameric connexin sequence-specific NT domain (iNT peptides applied to cells expressing homomeric Cx40, Cx37, Cx45, Cx46, and Cx50 gap junctions. A Cx43 iNT peptide corresponding to amino acids 9 to 13 (Ac-KLLDK-NH2 specifically inhibited the electrical coupling of Cx40 gap junctions in a transjunctional (Vj voltage-dependent manner without affecting the function of homologous Cx37, Cx46, Cx50, and Cx45 gap junctions. A Cx40 iNT (Ac-EFLEE-OH peptide counteracted the Vj-dependent block of Cx40 gap junctions, whereas a similarly charged Cx50 iNT (Ac-EEVNE-OH peptide did not, suggesting that these NT domain interactions are not solely based on electrostatics. These data are consistent with functional Cx43 heteromeric gap junction formation with Cx37, Cx45, Cx46, and Cx50 and suggest that Cx40 uniquely experiences functional suppressive interactions with a Cx43 NT domain sequence. These findings present unique functional implications about the heteromeric interactions between Cx43 and Cx40 that may influence cardiac conduction in atrial myocardium and the specialized conduction system.

  5. Fluid displacement during droplet formation at microfluidic flow-focusing junctions.

    Science.gov (United States)

    Huang, Haishui; He, Xiaoming

    2015-11-07

    Microdroplets and microcapsules have been widely produced using microfluidic flow-focusing junctions for biomedical and chemical applications. However, the multiphase microfluidic flow at the flow-focusing junction has not been well investigated. In this study, the displacement of two (core and shell) aqueous fluids that disperse into droplets altogether in a carrier oil emulsion was investigated both numerically and experimentally. It was found that extensive displacement of the two aqueous fluids within the droplet during its formation could occur as a result of the shear effect of the carrier fluid and the capillary effect of interfacial tension. We further identified that the two mechanisms of fluid displacement can be evaluated by two dimensionless parameters. The quantitative relationship between the degree of fluid displacement and these two dimensionless parameters was determined experimentally. Finally, we demonstrated that the degree of fluid displacement could be controlled to generate hydrogel microparticles of different morphologies using planar or nonplanar flow-focusing junctions. These findings should provide useful guidance to the microfluidic production of microscale droplets or capsules for various biomedical and chemical applications.

  6. APP-dependent glial cell line-derived neurotrophic factor gene expression drives neuromuscular junction formation.

    Science.gov (United States)

    Stanga, Serena; Zanou, Nadège; Audouard, Emilie; Tasiaux, Bernadette; Contino, Sabrina; Vandermeulen, Gaëlle; René, Frédérique; Loeffler, Jean-Philippe; Clotman, Frédéric; Gailly, Philippe; Dewachter, Ilse; Octave, Jean-Noël; Kienlen-Campard, Pascal

    2016-05-01

    Besides its crucial role in the pathogenesis of Alzheimer's disease, the knowledge of amyloid precursor protein (APP) physiologic functions remains surprisingly scarce. Here, we show that APP regulates the transcription of the glial cell line-derived neurotrophic factor (GDNF). APP-dependent regulation of GDNF expression affects muscle strength, muscular trophy, and both neuronal and muscular differentiation fundamental for neuromuscular junction (NMJ) maturation in vivo In a nerve-muscle coculture model set up to modelize NMJ formation in vitro, silencing of muscular APP induces a 30% decrease in secreted GDNF levels and a 40% decrease in the total number of NMJs together with a significant reduction in the density of acetylcholine vesicles at the presynaptic site and in neuronal maturation. These defects are rescued by GDNF expression in muscle cells in the conditions where muscular APP has been previously silenced. Expression of GDNF in muscles of amyloid precursor protein null mice corrected the aberrant synaptic morphology of NMJs. Our findings highlight for the first time that APP-dependent GDNF expression drives the process of NMJ formation, providing new insights into the link between APP gene regulatory network and physiologic functions.-Stanga, S., Zanou, N., Audouard, E., Tasiaux, B., Contino, S., Vandermeulen, G., René, F., Loeffler, J.-P., Clotman, F., Gailly, P., Dewachter, I., Octave, J.-N., Kienlen-Campard, P. APP-dependent glial cell line-derived neurotrophic factor gene expression drives neuromuscular junction formation.

  7. A membrane fusion protein αSNAP is a novel regulator of epithelial apical junctions.

    Directory of Open Access Journals (Sweden)

    Nayden G Naydenov

    Full Text Available Tight junctions (TJs and adherens junctions (AJs are key determinants of the structure and permeability of epithelial barriers. Although exocytic delivery to the cell surface is crucial for junctional assembly, little is known about the mechanisms controlling TJ and AJ exocytosis. This study was aimed at investigating whether a key mediator of exocytosis, soluble N-ethylmaleimide sensitive factor (NSF attachment protein alpha (αSNAP, regulates epithelial junctions. αSNAP was enriched at apical junctions in SK-CO15 and T84 colonic epithelial cells and in normal human intestinal mucosa. siRNA-mediated knockdown of αSNAP inhibited AJ/TJ assembly and establishment of the paracellular barrier in SK-CO15 cells, which was accompanied by a significant down-regulation of p120-catenin and E-cadherin expression. A selective depletion of p120 catenin effectively disrupted AJ and TJ structure and compromised the epithelial barrier. However, overexpression of p120 catenin did not rescue the defects of junctional structure and permeability caused by αSNAP knockdown thereby suggesting the involvement of additional mechanisms. Such mechanisms did not depend on NSF functions or induction of cell death, but were associated with disruption of the Golgi complex and down-regulation of a Golgi-associated guanidine nucleotide exchange factor, GBF1. These findings suggest novel roles for αSNAP in promoting the formation of epithelial AJs and TJs by controlling Golgi-dependent expression and trafficking of junctional proteins.

  8. Lattice Boltzmann simulation of droplet formation in T-junction geometries

    Science.gov (United States)

    Busuioc, Sergiu; Ambruş, Victor E.; Sofonea, Victor

    2017-01-01

    The formation of droplets in T-junction configurations is investigated using a two-dimensional Lattice Boltzmann model for liquid-vapor systems. We use an expansion of the equilibrium distribution function with respect to Hermite polynomials and an off-lattice velocity set. To evolve the distribution functions we use the second order corner transport upwind numerical scheme and a third order scheme is used to compute the gradient operators in the force term. The droplet formation successfully recovers the squeezing, dripping and jetting regimes. We find that the droplet length decreases proportionally with the flow rate of the continuous phase and increases with the flow rate of the dispersed phase in all simulation configurations and has a linear dependency on the surface tension parameter κ.

  9. Insular dentin formation pattern in human odontogenesis in relation to the scalloped dentino-enamel junction.

    Science.gov (United States)

    Radlanski, Ralf J; Renz, Herbert

    2007-01-01

    This study is a first report on the modality of early dentin formation in respect to the scalloped pattern of the dentino-enamel junction (DEJ). We applied scanning electron microscopy (SEM), transmission electron microscopy (TEM), histological serial sections, and three-dimensional (3D) reconstructions. TEM and SEM showed scallops and secondary scallops on the DEJ of deciduous dental primordia and on deciduous teeth with the enamel cap removed. This peculiar outline of the DEJ requires a specific dentin formation pattern; histological sections showed that dentin formation began at the brims of the scallops, seen as triangular spikes in serial sections. The dentin formation front was not uniform; instead, it was characterized by multiple, insular forming centers, as revealed by our 3D reconstructions. As thicker dentin layers formed, the islands became confluent. Factors are discussed, which may lead to crimpling of the inner enamel epithelium, and maintained as the scalloped pattern of the DEJ develops. Signaling patterns in accordance with the insular dentin formation are unknown so far.

  10. Afadin regulates puncta adherentia junction formation and presynaptic differentiation in hippocampal neurons.

    Directory of Open Access Journals (Sweden)

    Daisaku Toyoshima

    Full Text Available The formation and remodeling of mossy fiber-CA3 pyramidal cell synapses in the stratum lucidum of the hippocampus are implicated in the cellular basis of learning and memory. Afadin and its binding cell adhesion molecules, nectin-1 and nectin-3, together with N-cadherin, are concentrated at puncta adherentia junctions (PAJs in these synapses. Here, we investigated the roles of afadin in PAJ formation and presynaptic differentiation in mossy fiber-CA3 pyramidal cell synapses. At these synapses in the mice in which the afadin gene was conditionally inactivated before synaptogenesis by using nestin-Cre mice, the immunofluorescence signals for the PAJ components, nectin-1, nectin-3 and N-cadherin, disappeared almost completely, while those for the presynaptic components, VGLUT1 and bassoon, were markedly decreased. In addition, these signals were significantly decreased in cultured afadin-deficient hippocampal neurons. Furthermore, the interevent interval of miniature excitatory postsynaptic currents was prolonged in the cultured afadin-deficient hippocampal neurons compared with control neurons, indicating that presynaptic functions were suppressed or a number of synapse was reduced in the afadin-deficient neurons. Analyses of presynaptic vesicle recycling and paired recordings revealed that the cultured afadin-deficient neurons showed impaired presynaptic functions. These results indicate that afadin regulates both PAJ formation and presynaptic differentiation in most mossy fiber-CA3 pyramidal cell synapses, while in a considerable population of these neurons, afadin regulates only PAJ formation but not presynaptic differentiation.

  11. Kartogenin induces cartilage-like tissue formation in tendon-bone junction

    Institute of Scientific and Technical Information of China (English)

    Jianying Zhang; James H-C Wang

    2014-01-01

    Tendon-bone junctions (TBJs) are frequently injured, especially in athletic settings. Healing of TBJ injuries is slow and is often repaired with scar tissue formation that compromises normal function. This study explored the feasibility of using kartogenin (KGN), a biocompound, to enhance the healing of injured TBJs. We first determined the effects of KGN on the proliferation and chondrogenic differentiation of rabbit bone marrow stromal cells (BMSCs) and patellar tendon stem/progenitor cells (PTSCs) in vitro. KGN enhanced cell proliferation in both cell types in a concentration-dependent manner and induced chondrogenic differentiation of stem cells, as demonstrated by high expression levels of chondrogenic markers aggrecan, collagen II and Sox-9. Besides, KGN induced the formation of cartilage-like tissues in cell cultures, as observed through the staining of abundant proteoglycans, collagen II and osteocalcin. When injected into intact rat patellar tendons in vivo, KGN induced cartilage-like tissue formation in the injected area. Similarly, when KGN was injected into experimentally injured rat Achilles TBJs, wound healing in the TBJs was enhanced, as evidenced by the formation of extensive cartilage-like tissues. These results suggest that KGN may be used as an effective cell-free clinical therapy to enhance the healing of injured TBJs.

  12. Afadin Regulates Puncta Adherentia Junction Formation and Presynaptic Differentiation in Hippocampal Neurons

    Science.gov (United States)

    Toyoshima, Daisaku; Mandai, Kenji; Maruo, Tomohiko; Supriyanto, Irwan; Togashi, Hideru; Inoue, Takahito; Mori, Masahiro; Takai, Yoshimi

    2014-01-01

    The formation and remodeling of mossy fiber-CA3 pyramidal cell synapses in the stratum lucidum of the hippocampus are implicated in the cellular basis of learning and memory. Afadin and its binding cell adhesion molecules, nectin-1 and nectin-3, together with N-cadherin, are concentrated at puncta adherentia junctions (PAJs) in these synapses. Here, we investigated the roles of afadin in PAJ formation and presynaptic differentiation in mossy fiber-CA3 pyramidal cell synapses. At these synapses in the mice in which the afadin gene was conditionally inactivated before synaptogenesis by using nestin-Cre mice, the immunofluorescence signals for the PAJ components, nectin-1, nectin-3 and N-cadherin, disappeared almost completely, while those for the presynaptic components, VGLUT1 and bassoon, were markedly decreased. In addition, these signals were significantly decreased in cultured afadin-deficient hippocampal neurons. Furthermore, the interevent interval of miniature excitatory postsynaptic currents was prolonged in the cultured afadin-deficient hippocampal neurons compared with control neurons, indicating that presynaptic functions were suppressed or a number of synapse was reduced in the afadin-deficient neurons. Analyses of presynaptic vesicle recycling and paired recordings revealed that the cultured afadin-deficient neurons showed impaired presynaptic functions. These results indicate that afadin regulates both PAJ formation and presynaptic differentiation in most mossy fiber-CA3 pyramidal cell synapses, while in a considerable population of these neurons, afadin regulates only PAJ formation but not presynaptic differentiation. PMID:24587018

  13. Treatment with AICAR inhibits blastocyst development, trophectoderm differentiation and tight junction formation and function in mice.

    Science.gov (United States)

    Calder, Michele D; Edwards, Nicole A; Betts, Dean H; Watson, Andrew J

    2017-09-13

    What is the impact of adenosine monophosphate-activated protein kinase (AMPK) activation on blastocyst formation, gene expression, and tight junction formation and function? AMPK activity must be tightly controlled for normal preimplantation development and blastocyst formation to occur. AMPK isoforms are detectable in oocytes, cumulus cells and preimplantation embryos. Cultured embryos are subject to many stresses that can activate AMPK. Two primary experiments were carried out to determine the effect of AICAR treatment on embryo development and maintenance of the blastocoel cavity. Embryos were recovered from superovulated mice. First, 2-cell embryos were treated with a concentration series (0-2000 μM) of AICAR for 48 h until blastocyst formation would normally occur. In the second experiment, expanded mouse blastocysts were treated for 9 h with 1000 μM AICAR. Outcomes measured included development to the blastocyst stage, cell number, blastocyst volume, AMPK phosphorylation, Cdx2 and blastocyst formation gene family expression (mRNAs and protein measured using quantitative RT-PCR, immunoblotting, immunofluorescence), tight junction function (FITC dextran dye uptake assay), and blastocyst ATP levels. The reversibility of AICAR treatment was assessed using Compound C (CC), a well-known inhibitor of AMPK, alone or in combination with AICAR. Prolonged treatment with AICAR from the 2-cell stage onward decreases blastocyst formation, reduces total cell number, embryo diameter, leads to loss of trophectoderm cell contacts and membrane zona occludens-1 staining, and increased nuclear condensation. Treatment with CC alone inhibited blastocyst development only at concentrations that are higher than normally used. AICAR treated embryos displayed altered mRNA and protein levels of blastocyst formation genes. Treatment of blastocysts with AICAR for 9 h induced blastocyst collapse, altered blastocyst formation gene expression, increased tight junction permeability and

  14. The role of Rap1 in cell-cell junction formation

    NARCIS (Netherlands)

    Kooistra, M.R.H.

    2008-01-01

    Both epithelial and endothelial cells form cell-cell junctions at the cell-cell contacts to maintain tissue integrity. Proper regulation of cell-cell junctions is required for the organisation of the tissue and to prevent leakage of blood vessels. In endothelial cells, the cell-cell junctions are

  15. A Lattice Boltzmann study of the effects of viscoelasticity on droplet formation in microfluidic cross-junctions

    CERN Document Server

    Gupta, Anupam

    2015-01-01

    Based on mesoscale lattice Boltzmann (LB) numerical simulations, we investigate the effects of viscoelasticity on the break-up of liquid threads in microfluidic cross-junctions, where droplets are formed by focusing a liquid thread of a dispersed (d) phase into another co-flowing continuous (c) immiscible phase. Working at small Capillary numbers, we investigate the effects of non-Newtonian phases in the transition from droplet formation at the cross-junction (DCJ) to droplet formation downstream of the cross-junction (DC) (Liu $\\&$ Zhang, ${\\it Phys. ~Fluids.}$ ${\\bf 23}$, 082101 (2011)). We will analyze cases with ${\\it Droplet ~Viscoelasticity}$ (DV), where viscoelastic properties are confined in the dispersed phase, as well as cases with ${\\it Matrix ~Viscoelasticity}$ (MV), where viscoelastic properties are confined in the continuous phase. Moderate flow-rate ratios $Q \\approx {\\cal O}(1)$ of the two phases are considered in the present study. Overall, we find that the effects are more pronounced in ...

  16. Actin-interacting protein 1 controls assembly and permeability of intestinal epithelial apical junctions.

    Science.gov (United States)

    Lechuga, Susana; Baranwal, Somesh; Ivanov, Andrei I

    2015-05-01

    Adherens junctions (AJs) and tight junctions (TJs) are crucial regulators of the integrity and restitution of the intestinal epithelial barrier. The structure and function of epithelial junctions depend on their association with the cortical actin cytoskeleton that, in polarized epithelial cells, is represented by a prominent perijunctional actomyosin belt. The assembly and stability of the perijunctional cytoskeleton is controlled by constant turnover (disassembly and reassembly) of actin filaments. Actin-interacting protein (Aip) 1 is an emerging regulator of the actin cytoskeleton, playing a critical role in filament disassembly. In this study, we examined the roles of Aip1 in regulating the structure and remodeling of AJs and TJs in human intestinal epithelium. Aip1 was enriched at apical junctions in polarized human intestinal epithelial cells and normal mouse colonic mucosa. Knockdown of Aip1 by RNA interference increased the paracellular permeability of epithelial cell monolayers, decreased recruitment of AJ/TJ proteins to steady-state intercellular contacts, and attenuated junctional reassembly in a calcium-switch model. The observed defects of AJ/TJ structure and functions were accompanied by abnormal organization and dynamics of the perijunctional F-actin cytoskeleton. Moreover, loss of Aip1 impaired the apico-basal polarity of intestinal epithelial cell monolayers and inhibited formation of polarized epithelial cysts in 3-D Matrigel. Our findings demonstrate a previously unanticipated role of Aip1 in regulating the structure and remodeling of intestinal epithelial junctions and early steps of epithelial morphogenesis.

  17. Gap Junction in the Teleost Fish Lineage: Duplicated Connexins May Contribute to Skin Pattern Formation and Body Shape Determination.

    Science.gov (United States)

    Watanabe, Masakatsu

    2017-01-01

    Gap junctions are intercellular channels that allow passage of ions and small molecules between adjacent cells. Gap junctions in vertebrates are composed of connexons, which are an assembly of six proteins, connexins. Docking of two connexons on the opposite cell surfaces forms a gap junction between the cytoplasm of two neighboring cells. Connexins compose a family of structurally related four-pass transmembrane proteins. In mammals, there are ~20 connexins, each of which contributes to unique permeability of gap junctions, and mutations of some connexin-encoding genes are associated with human diseases. Zebrafish has been predicted to contain 39 connexin-encoding genes; the high number can be attributed to gene duplication during fish evolution, which resulted in diversified functions of gap junctions in teleosts. The determination of body shapes and skin patterns in animal species is an intriguing question. Mathematical models suggest principle mechanisms explaining the diversification of animal morphology. Recent studies have revealed the involvement of gap junctions in fish morphological diversity, including skin pattern formation and body shape determination. This review focuses on connexins in teleosts, which are integrated in the mathematical models explaining morphological diversity of animal skin patterns and body shapes.

  18. Soft versus hard junction formation for α-terthiophene molecular wires and their charge transfer complexes

    Science.gov (United States)

    Vezzoli, Andrea; Grace, Iain M.; Brooke, Carly; Nichols, Richard J.; Lambert, Colin J.; Higgins, Simon J.

    2017-03-01

    We used a range of scanning tunnelling microscopy (STM)-based methods to conduct a detailed study of single molecule junction conductance enhancement upon charge transfer complex formation, using bis(thiaalkyl)arene molecular wires as electron donors and tetracyanoethylene (TCNE) as an electron acceptor. Using the "hard" STM break junction (STM-BJ) method, in which a Au STM tip is pushed into a Au substrate and then withdrawn in the presence of molecules, we see a single, very broad, peak in the resulting conductance histogram when all data are used; the conductance enhancement is 25-fold for a terthiophene donor and 15-fold for a phenyl group. After rational data selection, in which only current-distance curves that contain a current plateau >0.2 nm long are used in the conductance histogram, three sharper peaks are resolved in the histograms for the charge transfer complexes; two substantially lower-conductance peaks are resolved for the uncomplexed molecules. Using the "soft" STM I(s) technique, in which initial contact between tip and substrate is avoided and the current limit is about an order of magnitude lower, we were able to resolve two peaks for the uncomplexed molecules depending upon the initial set point current (i.e., tip height), one at the same value as the lower of the two data-selected STM-BJ histogram peaks and an additional peak beyond the low-current limit for the STM-BJ experiment. For the terthiophene, the low, medium, and high conductance peaks for the TCNE complex are, respectively, ca. 70, 70, and 46 times higher in conductance than the corresponding peaks for the free molecule.

  19. Formation and branch migration of Holliday junctions mediated by eukaryotic recombinases.

    Science.gov (United States)

    Murayama, Yasuto; Kurokawa, Yumiko; Mayanagi, Kouta; Iwasaki, Hiroshi

    2008-02-21

    Holliday junctions (HJs) are key intermediates in homologous recombination and are especially important for the production of crossover recombinants. Bacterial RecA family proteins promote the formation and branch migration of HJs in vitro by catalysing a reciprocal DNA-strand exchange reaction between two duplex DNA molecules, one of which contains a single-stranded DNA region that is essential for initial nucleoprotein filament formation. This activity has been reported only for prokaryotic RecA family recombinases, although eukaryotic homologues are also essential for HJ production in vivo. Here we show that fission yeast (Rhp51) and human (hRad51) RecA homologues promote duplex-duplex DNA-strand exchange in vitro. As with RecA, a HJ is formed between the two duplex DNA molecules, and reciprocal strand exchange proceeds through branch migration of the HJ. In contrast to RecA, however, strand exchange mediated by eukaryotic recombinases proceeds in the 3'-->5' direction relative to the single-stranded DNA region of the substrate DNA. The opposite polarity of Rhp51 makes it especially suitable for the repair of DNA double-strand breaks, whose repair is initiated at the processed ends of breaks that have protruding 3' termini.

  20. Extracellular domains play different roles in gap junction formation and docking compatibility.

    Science.gov (United States)

    Bai, Donglin; Wang, Ao Hong

    2014-02-15

    GJ (gap junction) channels mediate direct intercellular communication and play an important role in many physiological processes. Six connexins oligomerize to form a hemichannel and two hemichannels dock together end-to-end to form a GJ channel. Connexin extracellular domains (E1 and E2) have been shown to be important for the docking, but the molecular mechanisms behind the docking and formation of GJ channels are not clear. Recent developments in atomic GJ structure and functional studies on a series of connexin mutants revealed that E1 and E2 are likely to play different roles in the docking. Non-covalent interactions at the docking interface, including hydrogen bonds, are predicted to form between interdocked extracellular domains. Protein sequence alignment analysis on the docking compatible/incompatible connexins indicate that the E1 domain is important for the formation of the GJ channel and the E2 domain is important in the docking compatibility in heterotypic channels. Interestingly, the hydrogen-bond forming or equivalent residues in both E1 and E2 domains are mutational hot spots for connexin-linked human diseases. Understanding the molecular mechanisms of GJ docking can assist us to develop novel strategies in rescuing the disease-linked connexin mutants.

  1. Claudin-16 Deficiency Impairs Tight Junction Function in Ameloblasts, Leading to Abnormal Enamel Formation.

    Science.gov (United States)

    Bardet, Claire; Courson, Frédéric; Wu, Yong; Khaddam, Mayssam; Salmon, Benjamin; Ribes, Sandy; Thumfart, Julia; Yamaguti, Paulo M; Rochefort, Gael Y; Figueres, Marie-Lucile; Breiderhoff, Tilman; Garcia-Castaño, Alejandro; Vallée, Benoit; Le Denmat, Dominique; Baroukh, Brigitte; Guilbert, Thomas; Schmitt, Alain; Massé, Jean-Marc; Bazin, Dominique; Lorenz, Georg; Morawietz, Maria; Hou, Jianghui; Carvalho-Lobato, Patricia; Manzanares, Maria Cristina; Fricain, Jean-Christophe; Talmud, Deborah; Demontis, Renato; Neves, Francisco; Zenaty, Delphine; Berdal, Ariane; Kiesow, Andreas; Petzold, Matthias; Menashi, Suzanne; Linglart, Agnes; Acevedo, Ana Carolina; Vargas-Poussou, Rosa; Müller, Dominik; Houillier, Pascal; Chaussain, Catherine

    2016-03-01

    Claudin-16 protein (CLDN16) is a component of tight junctions (TJ) with a restrictive distribution so far demonstrated mainly in the kidney. Here, we demonstrate the expression of CLDN16 also in the tooth germ and show that claudin-16 gene (CLDN16) mutations result in amelogenesis imperfecta (AI) in the 5 studied patients with familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC). To investigate the role of CLDN16 in tooth formation, we studied a murine model of FHHNC and showed that CLDN16 deficiency led to altered secretory ameloblast TJ structure, lowering of extracellular pH in the forming enamel matrix, and abnormal enamel matrix protein processing, resulting in an enamel phenotype closely resembling human AI. This study unravels an association of FHHNC owing to CLDN16 mutations with AI, which is directly related to the loss of function of CLDN16 during amelogenesis. Overall, this study indicates for the first time the importance of a TJ protein in tooth formation and underlines the need to establish a specific dental follow-up for these patients. © 2015 American Society for Bone and Mineral Research.

  2. Cluster-formation in the Rosette molecular cloud at the junctions of filaments

    CERN Document Server

    Schneider, N; Hennemann, M; Motte, F; Didelon, P; Federrath, C; Bontemps, S; Di Francesco, J; Arzoumanian, D; Minier, V; André, Ph; Hill, T; Zavagno, A; Nguyen-Luong, Q; Attard, M; Bernard, J -Ph; Elia, D; Fallscheer, C; Griffin, M; Kirk, J; Klessen, R; Könyves, V; Martin, P; Men'shchikov, A; Palmeirim, P; Peretto, N; Pestalozzi, M; Russeil, D; Sadavoy, S; Sousbie, T; Testi, L; Tremblin, P; Ward-Thompson, D; White, G

    2012-01-01

    For many years feedback processes generated by OB-stars in molecular clouds, including expanding ionization fronts, stellar winds, or UV-radiation, have been proposed to trigger subsequent star formation. However, hydrodynamic models including radiation and gravity show that UV-illumination has little or no impact on the global dynamical evolution of the cloud. The Rosette molecular cloud, irradiated by the NGC2244 cluster, is a template region for triggered star-formation, and we investigated its spatial and density structure by applying a curvelet analysis, a filament-tracing algorithm (DisPerSE), and probability density functions (PDFs) on Herschel column density maps, obtained within the HOBYS key program. The analysis reveals not only the filamentary structure of the cloud but also that all known infrared clusters except one lie at junctions of filaments, as predicted by turbulence simulations. The PDFs of sub-regions in the cloud show systematic differences. The two UV-exposed regions have a double-peak...

  3. Vitamin D3 regulates the formation and degradation of gap junctions in androgen-responsive human prostate cancer cells.

    Directory of Open Access Journals (Sweden)

    Linda Kelsey

    Full Text Available 1α-25(OH2 vitamin D3 (1-25D, an active hormonal form of Vitamin D3, is a well-known chemopreventive and pro-differentiating agent. It has been shown to inhibit the growth of several prostate cancer cell lines. Gap junctions, formed of proteins called connexins (Cx, are ensembles of cell-cell channels, which permit the exchange of small growth regulatory molecules between adjoining cells. Cell-cell communication mediated by gap junctional channels is an important homeostatic control mechanism for regulating cell growth and differentiation. We have investigated the effect of 1-25D on the formation and degradation of gap junctions in an androgen-responsive prostate cancer cell line, LNCaP, which expresses retrovirally-introduced Cx32. Connexin32 is expressed by the luminal and well-differentiated cells of normal prostate and prostate tumors. Our results document that 1-25D enhances the expression of Cx32 and its subsequent assembly into gap junctions. Our results further show that 1-25D prevents androgen-regulated degradation of Cx32, post-translationally, independent of androgen receptor (AR-mediated signaling. Finally, our findings document that formation of gap junctions sensitizes Cx32-expressing LNCaP cells to the growth inhibitory effects of 1-25D and alters their morphology. These findings suggest that the growth-inhibitory effects of 1-25D in LNCaP cells may be related to its ability to modulate the assembly of Cx32 into gap junctions.

  4. Eya1 protein phosphatase regulates tight junction formation in lung distal epithelium.

    Science.gov (United States)

    El-Hashash, Ahmed H K; Turcatel, Gianluca; Varma, Saaket; Berika, Mohamed; Al Alam, Denise; Warburton, David

    2012-09-01

    Little is known about the regulatory mechanisms underlying lung epithelial tight junction (TJ) assembly, which is inextricably linked to the preservation of epithelial polarity, and is highly coordinated by proteins that regulate epithelial cell polarity, such as aPKCζ. We recently reported that Eya1 phosphatase functions through aPKCζ-Notch1 signaling to control cell polarity in the lung epithelium. Here, we have extended these observations to TJ formation to demonstrate that Eya1 is crucial for the maintenance of TJ protein assembly in the lung epithelium, probably by controlling aPKCζ phosphorylation levels, aPKCζ-mediated TJ protein phosphorylation and Notch1-Cdc42 activity. Thus, TJs are disassembled after interfering with Eya1 function in vivo or during calcium-induced TJ assembly in vitro. These effects are reversed by reintroduction of wild-type Eya1 or partially inhibiting aPKCζ in Eya1siRNA cells. Moreover, genetic activation of Notch1 rescues Eya1(-/-) lung epithelial TJ defects. These findings uncover novel functions for the Eya1-aPKCζ-Notch1-Cdc42 pathway as a crucial regulatory mechanism of TJ assembly and polarity of the lung epithelium, providing a conceptual framework for future mechanistic and translational studies in this area.

  5. Dynamic formation of microenvironments at the myotendinous junction correlates with muscle fiber morphogenesis in zebrafish.

    Science.gov (United States)

    Snow, Chelsi J; Henry, Clarissa A

    2009-01-01

    Muscle development involves the specification and morphogenesis of muscle fibers that attach to tendons. After attachment, muscles and tendons then function as an integrated unit to transduce force to the skeletal system and stabilize joints. The attachment site is the myotendinous junction, or MTJ, and is the primary site of force transmission. We find that attachment of fast-twitch myofibers to the MTJ correlates with the formation of novel microenvironments within the MTJ. The expression or activation of two proteins involved in anchoring the intracellular cytoskeleton to the extracellular matrix, Focal adhesion kinase (Fak) and beta-dystroglycan is up-regulated. Conversely, the extracellular matrix protein Fibronectin (Fn) is down-regulated. This degradation of Fn as fast-twitch fibers attach to the MTJ results in Fn protein defining a novel microenvironment within the MTJ adjacent to slow-twitch, but not fast-twitch, muscle. Interestingly, however, Fak, laminin, Fn and beta-dystroglycan concentrate at the MTJ in mutants that do not have slow-twitch fibers. Taken together, these data elucidate novel and dynamic microenvironments within the MTJ and indicate that MTJ morphogenesis is spatially and temporally complex.

  6. Functional consequences of heterogeneous gap junction channel formation and its influence in health and disease.

    Science.gov (United States)

    Cottrell, G Trevor; Burt, Janis M

    2005-06-10

    The capacity of multiple connexins to hetero-oligomerize into functional heterogeneous gap junction channels has been demonstrated in vivo, in vitro, and in nonmammalian expression systems. These heterogeneous channels display gating activity, channel conductances, selectivity and regulatory behaviors that are sometimes not predicted by the behaviors of the corresponding homogeneous channels. Such observations suggest that heteromerization of gap junction proteins offers an efficient cellular strategy for finely regulating cell-to-cell communication. The available evidence strongly indicates that heterogeneous gap junction assembly is important to normal growth and differentiation, and may influence the appearance of several disease states. Definitive evidence that heterogeneous gap junction channels differentially regulate electrical conduction in excitable cells is absent. This review examines the prevalence, regulation, and implications of gap junction channel hetero-oligomerization.

  7. aPKC phosphorylates JAM-A at Ser285 to promote cell contact maturation and tight junction formation.

    Science.gov (United States)

    Iden, Sandra; Misselwitz, Steve; Peddibhotla, Swetha S D; Tuncay, Hüseyin; Rehder, Daniela; Gerke, Volker; Robenek, Horst; Suzuki, Atsushi; Ebnet, Klaus

    2012-03-05

    The PAR-3-atypical protein kinase C (aPKC)-PAR-6 complex has been implicated in the development of apicobasal polarity and the formation of tight junctions (TJs) in vertebrate epithelial cells. It is recruited by junctional adhesion molecule A (JAM-A) to primordial junctions where aPKC is activated by Rho family small guanosine triphosphatases. In this paper, we show that aPKC can interact directly with JAM-A in a PAR-3-independent manner. Upon recruitment to primordial junctions, aPKC phosphorylates JAM-A at S285 to promote the maturation of immature cell-cell contacts. In fully polarized cells, S285-phosphorylated JAM-A is localized exclusively at the TJs, and S285 phosphorylation of JAM-A is required for the development of a functional epithelial barrier. Protein phosphatase 2A dephosphorylates JAM-A at S285, suggesting that it antagonizes the activity of aPKC. Expression of nonphosphorylatable JAM-A/S285A interferes with single lumen specification during cyst development in three-dimensional culture. Our data suggest that aPKC phosphorylates JAM-A at S285 to regulate cell-cell contact maturation, TJ formation, and single lumen specification.

  8. Arc/Forearc Lengthening at Plate Triple Junctions and the Formation of Ophiolitic Soles

    Science.gov (United States)

    Casey, John; Dewey, John

    2013-04-01

    The principal enigma of large obducted ophiolite slabs is that they clearly must have been generated by some form of organized sea-floor spreading/plate-accretion, such as may be envisioned for the oceanic ridges, yet the volcanics commonly have arc affinity (Miyashiro) with boninites (high-temperature/low-pressure, high Mg and Si andesites), which are suggestive of a forearc origin. PT conditions under which boninites and metamorphic soles form and observations of modern forearc systems lead us to the conclusion that ophiolite formation is associated with overidding plate spreading centers that intersect the trench to form ridge-trench-trench of ridge-trench-tranform triple junctions. The spreading centers extend and lengthen the forearc parallel to the trench and by definition are in supra-subduction zone (SSZ) settings. Many ophiolites likewise have complexly-deformed associated mafic-ultramafic assemblages that suggest fracture zone/transform t along their frontal edges, which in turn has led to models involving the nucleation of subduction zones on fracture zones or transpressional transforms. Hitherto, arc-related sea-floor-spreading has been considered to be either pre-arc (fore-arc boninites) or post-arc (classic Karig-style back arc basins that trench-parallell split arcs). Syn-arc boninites and forearc oceanic spreading centers that involve a stable ridge/trench/trench triple or a ridge-trench-transform triple junction, the ridge being between the two upper plates, are consistent with large slab ophiolite formation in a readied obduction settting. The direction of subduction must be oblique with a different sense in the two subduction zones and the oblique subduction cannot be partitioned into trench orthogonal and parallel strike-slip components. As the ridge spreads, new oceanic lithosphere is created within the forearc, the arc and fore-arc lengthen significantly, and a syn-arc ophiolite forearc complex is generated by this mechanism. The ophiolite

  9. Formation of Schottky-type metal/SrTiO{sub 3} junctions and their resistive properties

    Energy Technology Data Exchange (ETDEWEB)

    Stoecker, Hartmut; Zschornak, Matthias [Technische Universitaet Dresden, Institut fuer Strukturphysik, Dresden (Germany); TU Bergakademie Freiberg, Institut fuer Experimentelle Physik, Freiberg (Germany); Seibt, Juliane; Hanzig, Florian; Wintz, Susi; Abendroth, Barbara; Meyer, Dirk C. [TU Bergakademie Freiberg, Institut fuer Experimentelle Physik, Freiberg (Germany); Kortus, Jens [TU Bergakademie Freiberg, Institut fuer Theoretische Physik, Freiberg (Germany)

    2010-08-15

    Motivated by the successful use of strontium titanate with different doping metals for memory cells on the basis of resistive switching and the recent findings on the major importance of oxygen vacancy redistribution in this compound, the present work shows the possibility of a non-volatile resistance change memory based on vacancy-doped SrTiO{sub 3}. The formation of corresponding metal/SrTiO{sub 3-{delta}} junctions ({delta}>0) in an electric field will be discussed as well as the switching between ohmic and Schottky-type contact behavior. A notable hysteresis in the current-voltage characteristics is used to carry out Write, Read, and Erase operations exemplifying the memory cell properties of such junctions. But whereas the electric field-induced formation of Schottky-type junctions is explainable by oxygen vacancy redistribution, the resistive switching needs to be discussed in terms of vacancies serving as electron trap states at the metal/oxide interface. (orig.)

  10. Connexins, E-cadherin, Claudin-7 and β-catenin transiently form junctional nexuses during the post-natal mammary gland development.

    Science.gov (United States)

    Dianati, Elham; Poiraud, Jérémy; Weber-Ouellette, Anne; Plante, Isabelle

    2016-08-01

    Gap junctions are intercellular channels made of connexins (Cxs) that allow direct communication between adjacent cells. Modulation of Cxs has been associated with abnormal development and function of the mammary gland and breast cancer. However, the mechanisms underlying their expression during normal mammary gland are not yet known. Cxs interact with components of tight and adherens junctions. Thus, we hypothesized that the expression levels of Cxs vary during mammary gland development and are regulated through stage-dependent interactions with members of the tight and adherens junctions. Our specific objectives were to: 1) determine the expression of Cxs and tight and adherens junction proteins throughout development and 2) characterize Cxs interactions with components of tight and adherens junctions. Murine mammary glands were sampled at various developmental stages (pre-pubescent to post-weaning). RT-qPCR and western-blot analyses demonstrated differential expression patterns for all gap (Cx43, Cx32, Cx26, Cx30), tight (Claudin-1, -3, -4, -7) and adherens (β-catenin, E- and P-cadherins) junctions throughout development. Interestingly, co-immunoprecipitation demonstrated interactions between these different types of junctions. Cx30 interacted with Cx26 just at the late pregnancy stage. While Cx43 showed a persistent interaction with β-catenin from virginity to post-weaning, its interactions with E-cadherin and Claudin-7 were transient. Cx32 interacted with Cx26, E-cadherin and β-catenin during lactation. Immunofluorescence results confirmed the existence of a junctional nexus that remodeled during mammary gland development. Together, our results confirm that the expression levels of Cxs vary concomitantly and that Cxs form junctional nexuses with tight and adherens junctions, suggesting the existence of common regulatory pathways.

  11. Laser Annealing of Self-Aligned As+ Implants in Contact Windows for Ultrashallow Junction Formation

    NARCIS (Netherlands)

    Biasotto, C.; Gonda, V.; Nanver, L.K.; Van der Cingel, J.; Jovanovic, V.

    2009-01-01

    In the past it has been shown that ultrashallow junctions with minimum lateral dimensions can be made by implanting self-aligned to the contact window and using one-shot excimer laser annealing (ELA) to activate the dopants. Besides the recrystallization of the implanted Si, the final structuring at

  12. Zurek-Kibble domain structures: The dynamics of spontaneous vortex formation in annular Josephson tunnel junctions

    DEFF Research Database (Denmark)

    Monaco, R.; Mygind, Jesper; Rivers, R.J.

    2002-01-01

    Phase transitions create a domain structure with defects, which has been argued by Zurek and Kibble (ZK) to depend in a characteristic way on the quench rate. We present an experiment to measure the ZK scaling exponent sigma. Using long symmetric Josephson tunnel junctions, for which the predicted...

  13. Droplet formation in microfluidic T-junction generators operating in the transitional regime. III. Dynamic surfactant effects.

    Science.gov (United States)

    Glawdel, Tomasz; Ren, Carolyn L

    2012-08-01

    This study extends our previous work on droplet generation in microfluidic T-junction generators to include dynamic interfacial tension effects created by the presence of surfactants. In Paper I [T. Glawdel, C. Elbuken, and C. L. Ren, Phys. Rev. E 85, 016322 (2012)], we presented experimental findings regarding the formation process in the squeezing-to-transition regime, and in Paper II [T. Glawdel, C. Elbuken, and C. L. Ren, Phys. Rev. E 85, 016323 (2012)] we developed a theoretical model that describes the performance of T-junction generators without surfactants. Here we study dynamic interfacial tension effects for two surfactants, one with a small molecular weight that adsorbs quickly, and the other with a large molecular weight that adsorbs slowly. Using the force balance developed in Paper II we extract the dynamic interfacial tension from high speed videos obtained during experiments. We then develop a theoretical model to predict the dynamic interfacial tension in microfluidic T-junction generators as a function of the surfactant properties, flow conditions, and generator design. This model is then incorporated into the overall model for generator performance to effectively predict the size of droplets produced when surfactants are present.

  14. Unique cell type-specific junctional complexes in vascular endothelium of human and rat liver sinusoids.

    Directory of Open Access Journals (Sweden)

    Cyrill Géraud

    Full Text Available Liver sinusoidal endothelium is strategically positioned to control access of fluids, macromolecules and cells to the liver parenchyma and to serve clearance functions upstream of the hepatocytes. While clearance of macromolecular debris from the peripheral blood is performed by liver sinusoidal endothelial cells (LSECs using a delicate endocytic receptor system featuring stabilin-1 and -2, the mannose receptor and CD32b, vascular permeability and cell trafficking are controlled by transcellular pores, i.e. the fenestrae, and by intercellular junctional complexes. In contrast to blood vascular and lymphatic endothelial cells in other organs, the junctional complexes of LSECs have not yet been consistently characterized in molecular terms. In a comprehensive analysis, we here show that LSECs express the typical proteins found in endothelial adherens junctions (AJ, i.e. VE-cadherin as well as α-, β-, p120-catenin and plakoglobin. Tight junction (TJ transmembrane proteins typical of endothelial cells, i.e. claudin-5 and occludin, were not expressed by rat LSECs while heterogenous immunreactivity for claudin-5 was detected in human LSECs. In contrast, junctional molecules preferentially associating with TJ such as JAM-A, B and C and zonula occludens proteins ZO-1 and ZO-2 were readily detected in LSECs. Remarkably, among the JAMs JAM-C was considerably over-expressed in LSECs as compared to lung microvascular endothelial cells. In conclusion, we show here that LSECs form a special kind of mixed-type intercellular junctions characterized by co-occurrence of endothelial AJ proteins, and of ZO-1 and -2, and JAMs. The distinct molecular architecture of the intercellular junctional complexes of LSECs corroborates previous ultrastructural findings and provides the molecular basis for further analyses of the endothelial barrier function of liver sinusoids under pathologic conditions ranging from hepatic inflammation to formation of liver metastasis.

  15. Time-resolved mixing and flow-field measurements during droplet formation in a flow-focusing junction

    Science.gov (United States)

    Carrier, Odile; Gökhan Ergin, F.; Li, Huai-Zhi; Watz, Bo B.; Funfschilling, Denis

    2015-08-01

    Highly monodispersed emulsions can be produced in microfluidic flow-focusing junctions (Anna et al 2003 Appl. Phys. Lett. 82 364-6, Baroud et al 2010 Lab Chip 10 2032-45). This is the reason why many industrial processes in the medical industry among others are based on droplet manipulation and involve at some point a step of dripping within a junction. However, only a few studies have focused on the flow field inside and outside the droplet, even though it is a necessary step for understanding the physical mechanism involved and for modeling the droplet formation process. Water-in-oil emulsions are produced in flow-focusing junctions of square cross sections. The fluids constituting the emulsion are (i) a 5.0 mPa·s silicon oil for the oil phase and (ii) distilled water containing 2.0 wt% of sodium dodecyl sulfate surfactant for the aqueous phase. Time-resolved shadow particle images are acquired using a microscale particle image velocimetry (µPIV) system and flow fields are calculated using an adaptive PIV algorithm in combination with dynamic masking. Inside the microchannel and in the permanent regime, the droplet has an internal circulation that has been well established by Sarrazin et al (AICHE J. 52 4061-70). But during the formation of a droplet in a flow-focusing junction, the flow field is not so well known, and the circulation in the finger flows forward along the sides and returns along the center. The mechanism can be described in terms of four distinct steps: droplet growth, necking, rupture, and recoil. The liquid expelled from the neck just before rupture is also well observed. The flow field and mixing are measured in detail during a complete cycle of formation of a main droplet and satellite droplets using high-speed imaging. This allows us to develop a better understanding of the different forces that are present and of the physical mechanism of droplet formation.

  16. ROCK2 primes the endothelium for vascular hyperpermeability responses by raising baseline junctional tension.

    Science.gov (United States)

    Beckers, Cora M L; Knezevic, Nebojsa; Valent, Erik T; Tauseef, Mohammad; Krishnan, Ramaswamy; Rajendran, Kavitha; Hardin, C Corey; Aman, Jurjan; van Bezu, Jan; Sweetnam, Paul; van Hinsbergh, Victor W M; Mehta, Dolly; van Nieuw Amerongen, Geerten P

    2015-07-01

    Rho kinase mediates the effects of inflammatory permeability factors by increasing actomyosin-generated traction forces on endothelial adherens junctions, resulting in disassembly of intercellular junctions and increased vascular leakage. In vitro, this is accompanied by the Rho kinase-driven formation of prominent radial F-actin fibers, but the in vivo relevance of those F-actin fibers has been debated, suggesting other Rho kinase-mediated events to occur in vascular leak. Here, we delineated the contributions of the highly homologous isoforms of Rho kinase (ROCK1 and ROCK2) to vascular hyperpermeability responses. We show that ROCK2, rather than ROCK1 is the critical Rho kinase for regulation of thrombin receptor-mediated vascular permeability. Novel traction force mapping in endothelial monolayers, however, shows that ROCK2 is not required for the thrombin-induced force enhancements. Rather, ROCK2 is pivotal to baseline junctional tension as a novel mechanism by which Rho kinase primes the endothelium for hyperpermeability responses, independent from subsequent ROCK1-mediated contractile stress-fiber formation during the late phase of the permeability response.

  17. Junction formation of Cu3BiS3 investigated by Kelvin probe force microscopy and surface photovoltage measurements

    Science.gov (United States)

    Mesa, Fredy; Chamorro, William; Vallejo, William; Baier, Robert; Dittrich, Thomas; Grimm, Alexander; Lux-Steiner, Martha C

    2012-01-01

    Summary Recently, the compound semiconductor Cu3BiS3 has been demonstrated to have a band gap of ~1.4 eV, well suited for photovoltaic energy harvesting. The preparation of polycrystalline thin films was successfully realized and now the junction formation to the n-type window needs to be developed. We present an investigation of the Cu3BiS3 absorber layer and the junction formation with CdS, ZnS and In2S3 buffer layers. Kelvin probe force microscopy shows the granular structure of the buffer layers with small grains of 20–100 nm, and a considerably smaller work-function distribution for In2S3 compared to that of CdS and ZnS. For In2S3 and CdS buffer layers the KPFM experiments indicate negatively charged Cu3BiS3 grain boundaries resulting from the deposition of the buffer layer. Macroscopic measurements of the surface photovoltage at variable excitation wavelength indicate the influence of defect states below the band gap on charge separation and a surface-defect passivation by the In2S3 buffer layer. Our findings indicate that Cu3BiS3 may become an interesting absorber material for thin-film solar cells; however, for photovoltaic application the band bending at the charge-selective contact has to be increased. PMID:22497001

  18. Junction formation of Cu3BiS3 investigated by Kelvin probe force microscopy and surface photovoltage measurements

    Directory of Open Access Journals (Sweden)

    Fredy Mesa

    2012-03-01

    Full Text Available Recently, the compound semiconductor Cu3BiS3 has been demonstrated to have a band gap of ~1.4 eV, well suited for photovoltaic energy harvesting. The preparation of polycrystalline thin films was successfully realized and now the junction formation to the n-type window needs to be developed. We present an investigation of the Cu3BiS3 absorber layer and the junction formation with CdS, ZnS and In2S3 buffer layers. Kelvin probe force microscopy shows the granular structure of the buffer layers with small grains of 20–100 nm, and a considerably smaller work-function distribution for In2S3 compared to that of CdS and ZnS. For In2S3 and CdS buffer layers the KPFM experiments indicate negatively charged Cu3BiS3 grain boundaries resulting from the deposition of the buffer layer. Macroscopic measurements of the surface photovoltage at variable excitation wavelength indicate the influence of defect states below the band gap on charge separation and a surface-defect passivation by the In2S3 buffer layer. Our findings indicate that Cu3BiS3 may become an interesting absorber material for thin-film solar cells; however, for photovoltaic application the band bending at the charge-selective contact has to be increased.

  19. Junction formation in CuInSe{sub 2}-based thin-film devices

    Energy Technology Data Exchange (ETDEWEB)

    Ramanathan, K.; Wiesner, H.; Asher, S.; Bhattacharya, R.N.; Keane, J.; Contreras, M.A.; Noufi, R. [National Center for Photovoltaics, National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado 80401 (United States)

    1999-03-01

    The nature of the interface between CuInSe{sub 2} (CIS) and the chemical bath deposited CdS layer has been investigated. We show that heat-treating the absorbers in Cd- or Zn-containing solutions in the presence of ammonium hydroxide sets up a chemical reaction which facilitates an extraction of Cu from the lattice and an in-diffusion of Cd. The characteristics of devices made in this manner suggest that the reaction generates a thin, n-doped region in the absorber. It is quite possible that the CdS/CuInSe{sub 2} device is a buried, shallow junction with a CdS window layer, rather than a heterojunction. We have used these ideas to develop methods for fabricating devices without CdS or Cd. A 14.2{percent} efficiency ZnO/CIGS device was obtained through aqueous treatment in Zn solutions. {copyright} {ital 1999 American Institute of Physics.}

  20. Junction Formation in CuInSe{sub 2} Based Thin Film Devices

    Energy Technology Data Exchange (ETDEWEB)

    Ramanathan, K.; Wiesner, H.; Asher, S.; Bhattacharya, R. N.; Keane, J.; Contreras, M.; Noufi, R.

    1998-11-18

    The nature of the interface between CuInSe{sub 2} (CIS) and the chemical bath deposited CdS layer has been investigated. We show that heat-treating the absorbers in Cd- or Zn-containing solutions in the presence of ammonium hydroxide sets up a chemical reaction which facilitates an extraction of Cu from the lattice and an in-diffusion of Cd. The characteristics of devices made in this manner suggest that the reaction generates a thin, n-doped region in the absorber. It is quite possible that the CdS/CuInSe{sub 2} device is a buried, shallow junction with a CdS window layer, rather than a heterojunction. We have used these ideas to develop methods for fabricating devices without CdS or Cd. A 14.2% efficiency ZnO/CIGS device was obtained through aqueous treatment in Zn solutions.

  1. Alteration of cadherin isoform expression and inhibition of gap junctions in stomach carcinoma cells

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    To explore cell malignant phenotype correlated changes of cell surface adhesion molecules and cell-cell communication in carcinogenesis, human stomach transformed and cancer cell lines were investigated. Expressions of E-cadherin, N-cadherin, ?-catenin, ?-catenin as well as gap junction (GJ) protein Cx32 were studied by utilization of immunoblotting, immunocytochemical and fluorescent dye transfer methods. Mammalian normal stomach mucosal cells expressed E-cadherin but not N-cadherin. E-cadherin immunofluorescence was detected at cell membranous adherens junctions (AJ) where colocalization with immunofluorescent staining of inner surface adhesion plaque proteins ?- and ?-catenins was observed. The existence of E-cadherin/ catenin (?-, ?-) protein complexes as AJ was suggested. In transformed and stomach cancer cells E-cadherin was inhibited, instead, N-cadherin was expressed and localized at membranous AJ where co-staining with ?- and ?-catenin fluorescence was observed. Formation of N-cadherin/catenin (?-, ?-) protein complex at AJs of transformed and cancer cells was suggested. The above observations were further supported by immunoblotting results. Normal stomach muscosal and transformed cells expressed Cx32 at membranous GJ and were competent of gap junction communication (GJIC). In stomach cancer cells, Cx32 was inhibited and GJIC was defective. The results suggested that changes of signal pathways mediated by both cell adhesion and cell communication systems are associated intracellular events of stomach carcinogenesis. The alteration of cadherin isoform from E- to N-cadherin in transformed and stomach cancer cells is the first report.

  2. THE CELULAR JUNCTIONS AND THE EMERGENCE OF ANIMALS

    Directory of Open Access Journals (Sweden)

    Urquiza-Bardone, Sergio

    2013-07-01

    Full Text Available The emergence of multicellularity and epithelia in relation to the appearance of cellular junctions, in order to illustrate the first steps of animal evolution, is discussed. We analyzed the structure and roles of adherens and occludins, considered to be the oldest. Also treated are some aspects of the main proteins that constitute them, the cadherins and claudins, as well as the related structures observed in sponges and choanoflagellates, the most ancient animals and the ancestors of these, respectively. It was concluded that the animal ancestor probably possessed some kind of adherens and possibly occludins, appearing as the first of major importance. These junctions increased in complexity through until the complexity observed in modern times.

  3. JNK signaling regulates E-cadherin junctions in germline cysts and determines primordial follicle formation in mice.

    Science.gov (United States)

    Niu, Wanbao; Wang, Ye; Wang, Zhengpin; Xin, Qiliang; Wang, Yijing; Feng, Lizhao; Zhao, Lihua; Wen, Jia; Zhang, Hua; Wang, Chao; Xia, Guoliang

    2016-05-15

    Physiologically, the size of the primordial follicle pool determines the reproductive lifespan of female mammals, while its establishment largely depends on a process of germline cyst breakdown during the perinatal period. The mechanisms regulating this process are poorly understood. Here we demonstrate that c-Jun amino-terminal kinase (JNK) signaling is crucial for germline cyst breakdown and primordial follicle formation. JNK was specifically localized in oocytes and its activity increased as germline cyst breakdown progressed. Importantly, disruption of JNK signaling with a specific inhibitor (SP600125) or knockdown technology (Lenti-JNK-shRNAs) resulted in significantly suppressed cyst breakdown and primordial follicle formation in cultured mouse ovaries. Our results show that E-cadherin is intensely expressed in germline cysts, and that its decline is necessary for oocyte release from the cyst. However, inhibition of JNK signaling leads to aberrantly enhanced localization of E-cadherin at oocyte-oocyte contact sites. WNT4 expression is upregulated after SP600125 treatment. Additionally, similar to the effect of SP600125 treatment, WNT4 overexpression delays cyst breakdown and is accompanied by abnormal E-cadherin expression patterns. In conclusion, our results suggest that JNK signaling, which is inversely correlated with WNT4, plays an important role in perinatal germline cyst breakdown and primordial follicle formation by regulating E-cadherin junctions between oocytes in mouse ovaries. © 2016. Published by The Company of Biologists Ltd.

  4. Formation of antiwaves in gap-junction-coupled chains of neurons

    Science.gov (United States)

    Urban, Alexander; Ermentrout, Bard

    2012-07-01

    Using network models consisting of gap-junction-coupled Wang-Buszaki neurons, we demonstrate that it is possible to obtain not only synchronous activity between neurons but also a variety of constant phase shifts between 0 and π. We call these phase shifts intermediate stable phase-locked states. These phase shifts can produce a large variety of wavelike activity patterns in one-dimensional chains and two-dimensional arrays of neurons, which can be studied by reducing the system of equations to a phase model. The 2π periodic coupling functions of these models are characterized by prominent higher order terms in their Fourier expansion, which can be varied by changing model parameters. We study how the relative contribution of the odd and even terms affects what solutions are possible, the basin of attraction of those solutions, and their stability. These models may be applicable to the spinal central pattern generators of the dogfish and also to the developing neocortex of the neonatal rat.

  5. Doping Evolution and Junction Formation in Stacked Cyanine Dye Light-Emitting Electrochemical Cells.

    Science.gov (United States)

    Jenatsch, Sandra; Wang, Lei; Bulloni, Matia; Véron, Anna C; Ruhstaller, Beat; Altazin, Stéphane; Nüesch, Frank; Hany, Roland

    2016-03-01

    Cyanine dyes are fluorescent organic salts with intrinsic conductivity for ionic and electronic charges. Recently ( J. Am. Chem. Soc. 2013 , 135 , 18008 - 18011 ), these features have been exploited in cyanine light-emitting electrochemical cells (LECs). Here, we demonstrate that stacked, constant-voltage driven trimethine cyanine LECs with various counteranions develop a p-i-n junction that is composed of p- and n-doped zones and an intrinsic region where light-emission occurs. We introduce a method that combines spectral photocurrent response measurements with optical modeling and find that at maximum current the intrinsic region is centered at ∼37% away from the anode. Transient capacitance, photoluminescence and attenuance experiments indicate a device situation with a narrow p-doped region, an undoped region that occupies ∼72% of the dye layer thickness and an n-doped region with a maximum doping concentration of 0.08 dopant/cyanine molecule. Finally, we observe that during device relaxation the parent cyanines are not reformed. We ascribe this to irreversible reactions between doped cyanine radicals. For sterically conservative cyanine dyes, this suggests that undesired radical decomposition pathways limit the LEC long-term stability in general.

  6. ATP Is Required and Advances Cytokine-Induced Gap Junction Formation in Microglia In Vitro

    Directory of Open Access Journals (Sweden)

    Pablo J. Sáez

    2013-01-01

    Full Text Available Microglia are the immune cells in the central nervous system. After injury microglia release bioactive molecules, including cytokines and ATP, which modify the functional state of hemichannels (HCs and gap junction channels (GJCs, affecting the intercellular communication via extracellular and intracellular compartments, respectively. Here, we studied the role of extracellular ATP and several cytokines as modulators of the functional state of microglial HCs and GJCs using dye uptake and dye coupling techniques, respectively. In microglia and the microglia cell line EOC20, ATP advanced the TNF-α/IFN-γ-induced dye coupling, probably through the induction of IL-1β release. Moreover, TNF-α/IFN-γ, but not TNF-α plus ATP, increased dye uptake in EOC20 cells. Blockade of Cx43 and Panx1 HCs prevented dye coupling induced by TNF-α/IFN-γ, but not TNF-α plus ATP. In addition, IL-6 prevented the induction of dye coupling and HC activity induced by TNF-α/IFN-γ in EOC20 cells. Our data support the notion that extracellular ATP affects the cellular communication between microglia through autocrine and paracrine mechanisms, which might affect the timing of immune response under neuroinflammatory conditions.

  7. JAM-A and aPKC: A close pair during cell-cell contact maturation and tight junction formation in epithelial cells.

    Science.gov (United States)

    Ebnet, Klaus

    2013-01-01

    Cell-cell adhesion plays a critical role in the formation of barrier-forming epithelia. The molecules which mediate cell-cell adhesion frequently act as signaling molecules by recruiting and/or assembling cytoplasmic protein complexes. Junctional Adhesion Molecule (JAM)-A interacts with the cell polarity protein PAR-3, a member of the PAR-3-aPKC-PAR-6 complex, which regulates the formation of cell-cell contacts and the development of tight junctions (TJs). In our recent study we found that JAM-A is localized at primordial, spot-like cell-cell junctions (pAJs) in a non-phosphorylated form. After the recruitment of the PAR-aPKC complex and its activation at pAJs, aPKC phosphorylates JAM-A at Ser285 to promote the maturation of immature junctions. In polarized epithelial cells, aPKC phosphorylates JAM-A selectively at the TJs to maintain the barrier function of TJs. Thus, through mutual regulation, JAM-A and aPKC form a functional unit that regulates the establishment of barrier-forming junctions in vertebrate epithelial cells.

  8. Role of Two Cell Wall Amidases in Septal Junction and Nanopore Formation in the Multicellular Cyanobacterium Anabaena sp. PCC 7120

    Directory of Open Access Journals (Sweden)

    Jan Bornikoel

    2017-09-01

    Full Text Available Filamentous cyanobacteria have developed a strategy to perform incompatible processes in one filament by differentiating specialized cell types, N2-fixing heterocysts and CO2-fixing, photosynthetic, vegetative cells. These bacteria can be considered true multicellular organisms with cells exchanging metabolites and signaling molecules via septal junctions, involving the SepJ and FraCD proteins. Previously, it was shown that the cell wall lytic N-acetylmuramyl-L-alanine amidase, AmiC2, is essential for cell–cell communication in Nostoc punctiforme. This enzyme perforates the septal peptidoglycan creating an array of nanopores, which may be the framework for septal junction complexes. In Anabaena sp. PCC 7120, two homologs of AmiC2, encoded by amiC1 and amiC2, were identified and investigated in two different studies. Here, we compare the function of both AmiC proteins by characterizing different Anabaena amiC mutants, which was not possible in N. punctiforme, because there the amiC1 gene could not be inactivated. This study shows the different impact of each protein on nanopore array formation, the process of cell–cell communication, septal protein localization, and heterocyst differentiation. Inactivation of either amidase resulted in significant reduction in nanopore count and in the rate of fluorescent tracer exchange between neighboring cells measured by FRAP analysis. In an amiC1 amiC2 double mutant, filament morphology was affected and heterocyst differentiation was abolished. Furthermore, the inactivation of amiC1 influenced SepJ localization and prevented the filament-fragmentation phenotype that is characteristic of sepJ or fraC fraD mutants. Our findings suggest that both amidases are to some extent redundant in their function, and describe a functional relationship of AmiC1 and septal proteins SepJ and FraCD.

  9. Droplet formation in a T-shaped microchannel junction: A model system for membrane emulsification

    NARCIS (Netherlands)

    Graaf, van der S.; Steegmans, M.L.J.; Sman, van der R.G.M.; Schroën, C.G.P.H.; Boom, R.M.

    2005-01-01

    Droplet formation was studied in a glass microchip with a small channel containing to-be-dispersed phase perpendicular to a large channel with a cross-flowing continuous phase. This resembles the situation during cross-flow membrane emulsification. In this model system, droplets are formed at a

  10. Effect of gating and pressure on the electronic transport properties of crossed nanotube junctions: formation of a Schottky barrier

    Energy Technology Data Exchange (ETDEWEB)

    Havu, P; Hashemi, M J; Kaukonen, M; Nieminen, R M [Department of Applied Physics, Aalto University, PO Box 11100, FI-00076 Aalto (Finland); Seppaelae, E T [Nokia Research Center, Itaemerenkatu 11-13, FI-00180 Helsinki (Finland)

    2011-03-23

    The electronic transport properties of crossed carbon nanotube junctions are investigated using ab initio methods. The optimal atomic structures and the intertube distances of the junctions are obtained using van der Waals corrected density functional theory. The effect of gating on the intertube conductance of the junctions is explored, showing the charge accumulation to the nanotube contact and the charge depletion region at the metal-semiconductor Schottky contact. Finally, it is shown how the conductance of the junctions under the gate voltage is affected by pressure applied to the nanotube film. (fast track communication)

  11. Expression pattern of odontogenic ameloblast-associated and amelotin during formation and regeneration of the junctional epithelium

    Directory of Open Access Journals (Sweden)

    S Kuroda

    2010-12-01

    Full Text Available The junctional epithelium (JE adheres to the tooth surface, and seals off periodontal tissues from the oral environment. This incompletely differentiated epithelium is formed initially by the fusion of the reduced enamel organ with the oral epithelium (OE. Two proteins, odontogenic ameloblast-associated (ODAM and amelotin (AMTN, have been identified in the JE. The objective of this study was to evaluate their expression pattern during formation and regeneration of the JE. Cytokeratin 14 was used as a differentiation marker for oral epithelial cells, and Ki67 for cell proliferation. Immunohistochemistry was carried out on erupting rat molars, and in regenerating JE following gingivectomy. In the reducing enamel organ and in established JE, ODAM and AMTN were present at the cell-tooth interface while only ODAM and CK14 were found throughout the JE. Both were also conspicuously present in cell clusters situated between the erupting tooth and OE. During JE regeneration, ODAM was detected first at the leading wound edge and then in the regenerating JE. Some cell clusters in the subjacent connective tissue were also positive for ODAM. AMTN appeared later and both AMTN and ODAM accumulated at the interface with the tooth. Cytokeratin 14 gradually appeared in the regenerating JE but the cell clusters showed variable labeling. Cells associated with JE formation and regeneration exhibited higher division activity than adjacent epithelial cells. These findings suggest that ODAM and AMTN have a role at the cell-tooth interface, and that ODAM is likely also implicated in cellular events during formation and regeneration of the JE.

  12. Syringomyelia associated with arachnoid septum at the craniovertebral junction, contradicting the currently prevailing theory of syringomyelia formation.

    Science.gov (United States)

    Chang, Han Soo; Tsuchiya, Tsukasa; Fujisawa, Naoaki; Oya, Soichi; Matsui, Toru

    2012-01-01

    Despite a number of various hypotheses in the literature, the pathophysiology of syringomyelia is still not well understood. In this article, we report two cases of cervical syringomyelia not associated with Chiari I malformation. Both cases had a septum-like structure in the subarachnoid space on the dorsal side of the cord at the craniovertebral junction. Cardiac-gated phase-contrast cine-mode magnetic resonance imaging (MRI) demonstrated decreased cerebrospinal fluid (CSF) flow on the dorsal side of the spinal cord. Surgical excision of this septum, restoring the CSF flow, resulted in a prompt reduction of the syrinx size in both cases. Findings in these cases contradict the currently prevailing hypothesis of syrinx formation that postulate that the piston-like movement of the cerebellar tonsils enhance the pulsatile CSF flow in the spinal subarachnoid space, driving the CSF into the syrinx through the perivascular space of Virchow and Robin. The authors propose that a mechanism based on the decreased pulsatile CSF flow in the spinal subarachnoid space will be more suitable as a hypothesis in studying the pathophyisiology of syringomyelia. These cases also provide an important lesson in managing the patients with syringomyelia not associated with Chiari I malformation.

  13. Evolution and cell physiology. 4. Why invent yet another protein complex to build junctions in epithelial cells?

    Science.gov (United States)

    Le Bivic, André

    2013-12-15

    The formation of the first epithelium was an essential step for animal evolution, since it has allowed coordination of the behavior of a cell layer and creation of a selective barrier between the internal medium and the outside world. The possibility of coupling the cells in a single layer has allowed morphogenetic events, such as tube formation, or gastrulation, to form more complex animal morphologies. The invention of sealed junctions between cells has allowed, on the other hand, creation of an asymmetry of nutrients or salts between the apical and the basal side of the epithelial layer. Creation of an internal medium has led to homeostasis, allowing the evolution of more complex physiological functions and the emergence of sophisticated animal shapes. During evolution, the origins of the first animals coincided with the invention of several protein complexes, including true cadherins and the polarity protein complexes. How these complexes regulate formation of the apicolateral border and the adherens junctions is still not fully understood. This review focuses on the role of these apical polarity complexes and, in particular, the Crumbs complex, which is essential for proper organization of epithelial layers from Drosophila to humans.

  14. Traction force dynamics predict gap formation in activated endothelium.

    Science.gov (United States)

    Valent, Erik T; van Nieuw Amerongen, Geerten P; van Hinsbergh, Victor W M; Hordijk, Peter L

    2016-09-10

    In many pathological conditions the endothelium becomes activated and dysfunctional, resulting in hyperpermeability and plasma leakage. No specific therapies are available yet to control endothelial barrier function, which is regulated by inter-endothelial junctions and the generation of acto-myosin-based contractile forces in the context of cell-cell and cell-matrix interactions. However, the spatiotemporal distribution and stimulus-induced reorganization of these integral forces remain largely unknown. Traction force microscopy of human endothelial monolayers was used to visualize contractile forces in resting cells and during thrombin-induced hyperpermeability. Simultaneously, information about endothelial monolayer integrity, adherens junctions and cytoskeletal proteins (F-actin) were captured. This revealed a heterogeneous distribution of traction forces, with nuclear areas showing lower and cell-cell junctions higher traction forces than the whole-monolayer average. Moreover, junctional forces were asymmetrically distributed among neighboring cells. Force vector orientation analysis showed a good correlation with the alignment of F-actin and revealed contractile forces in newly formed filopodia and lamellipodia-like protrusions within the monolayer. Finally, unstable areas, showing high force fluctuations within the monolayer were prone to form inter-endothelial gaps upon stimulation with thrombin. To conclude, contractile traction forces are heterogeneously distributed within endothelial monolayers and force instability, rather than force magnitude, predicts the stimulus-induced formation of intercellular gaps. Copyright © 2016 Elsevier Inc. All rights reserved.

  15. Characterization of cytoskeletal and junctional proteins expressed by cells cultured from human arachnoid granulation tissue

    Directory of Open Access Journals (Sweden)

    Mehta Bhavya C

    2005-10-01

    the in vitro culture of arachnoidal cells grown from human AG tissue. We demonstrated that these cells in vitro continue to express some of the cytoskeletal and junctional proteins characterized previously in human AG tissue, such as proteins involved in the formation of gap junctions, desmosomes, epithelial specific adherens junctions, as well as tight junctions. These junctional proteins in particular may be important in allowing these arachnoidal cells to regulate CSF outflow.

  16. High-T(sub c) Superconductor-Normal-Superconductor Junctions with Polyimide-Passivated Ambient Temperature Edge Formation

    Science.gov (United States)

    Barner, J. B.; Kleinsasser, A. W.; Hunt, B. D.

    1996-01-01

    The ability to controllably fabricate High-Temperature Superconductor (HTS) S-Normal-S (SNS) Josephson Juntions (JJ's) enhances the possibilities fro many applications, including digital circuits, SQUID's, and mixers. A wide variety of approaches to fabricating SNS-like junctions has been tried and analyzed in terms of proximity effect behavior.

  17. Formation of a Stable p-n Junction in a Liquid-Gated MoS2 Ambipolar Transistor

    NARCIS (Netherlands)

    Zhang, Y. J.; Ye, J. T.; Yornogida, Y.; Takenobu, T.; Iwasa, Y.

    2013-01-01

    Molybdenum disulfide (MoS2) has gained attention because of its high mobility and circular dichroism. As a crucial step to merge these advantages into a single device, we present a method that electronically controls and locates p-n junctions in liquid-gated ambipolar MoS2 transistors. A bias-indepe

  18. Effect of Gas- and Liquid-injection Methods on Formation of Bubble and Liquid Slug at Merging Micro T-junction

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jun Kyoung [Kyungnam Univ., Changwon (Korea, Republic of); Lee, Chi Young [Pukyong Nat’l Univ., Busan (Korea, Republic of)

    2016-04-15

    In the present experimental study, the effect of gas- and liquid-injected methods on the formation of bubble and liquid slug at the merging micro T-junction of a square microchannel with dimensions 600 μm × 600 μm was investigated. Nitrogen and water were used as test fluids. The superficial velocities of the liquid and gas were in the range of 0.05 - 1 m/s, and 0.1 - 1 m/s, respectively, where the Taylor flow was observed. The bubble length, liquid slug length, bubble velocity, and bubble generation frequency were measured by analyzing the images captured using a high-speed camera. Under similar inlet superficial velocity conditions, in the case of gas injection to the main channel at the merging T-junction (T{sub g}as-liquid), the lengths of the bubble and liquid slug were longer, and the bubble generation frequency was lower than in the case of liquid injection to the main channel at the merging T-junction (T{sub l}iquid-gas). On the other hand, in both cases, the bubble velocity was almost the same. The previous correlation proposed using experimental data for T{sub l}iquid-gas had predicted the present experimental data of bubble length, bubble velocity, liquid slug length, and bubble generation frequency for T{sub g}as-liquid to be ~24%, ~9%, ~39%, ~55%, respectively.

  19. Endocytosis and Recycling of Tight Junction Proteins in Inflammation

    Directory of Open Access Journals (Sweden)

    Markus Utech

    2010-01-01

    Full Text Available A critical function of the epithelial lining is to form a barrier that separates luminal contents from the underlying interstitium. This barrier function is primarily regulated by the apical junctional complex (AJC consisting of tight junctions (TJs and adherens junctions (AJs and is compromised under inflammatory conditions. In intestinal epithelial cells, proinflammatory cytokines, for example, interferon-gamma (IFN-γ, induce internalization of TJ proteins by endocytosis. Endocytosed TJ proteins are passed into early and recycling endosomes, suggesting the involvement of recycling of internalized TJ proteins. This review summarizes mechanisms by which TJ proteins under inflammatory conditions are internalized in intestinal epithelial cells and point out comparable mechanism in nonintestinal epithelial cells.

  20. Formation of a pn junction on an anisotropically etched GaAs surface using metalorganic chemical vapor deposition

    Science.gov (United States)

    Leon, R. P.; Bailey, S. G.; Mazaris, G. A.; Williams, W. D.

    1986-01-01

    A continuous p-type GaAs epilayer has been deposited on an n-type sawtooth GaAs surface using MOCVD. A wet chemical etching process was used to expose the intersecting (111)Ga and (-1 -1 1)Ga planes with 6-micron periodicity. Charge-collection microscopy was used to verify the presence of the pn junction thus formed and to measure its depth. The ultimate goal of this work is to fabricate a V-groove GaAs cell with improved absorptivity, high short-circuit current, and tolerance to particle radiation.

  1. Transforming growth factor-alpha abrogates glucocorticoid-stimulated tight junction formation and growth suppression in rat mammary epithelial tumor cells.

    Science.gov (United States)

    Buse, P; Woo, P L; Alexander, D B; Cha, H H; Reza, A; Sirota, N D; Firestone, G L

    1995-03-24

    The glucocorticoid and transforming growth factor-alpha (TGF-alpha) regulation of growth and cell-cell contact was investigated in the Con8 mammary epithelial tumor cell line derived from a 7,12-dimethylbenz(alpha)anthracene-induced rat mammary adenocarcinoma. In Con8 cell monolayers cultured on permeable filter supports, the synthetic glucocorticoid, dexamethasone, coordinately suppressed [3H]thymidine incorporation, stimulated monolayer transepithelial electrical resistance (TER), and decreased the paracellular leakage of [3H]inulin or [14C]mannitol across the monolayer. These processes dose dependently correlated with glucocorticoid receptor occupancy and function. Constitutive production of TGF-alpha in transfected cells or exogenous treatment with TGF-alpha prevented the glucocorticoid growth suppression response and disrupted tight junction formation without affecting glucocorticoid responsiveness. Treatment with hydroxyurea or araC demonstrated that de novo DNA synthesis is not a requirement for the growth factor disruption of tight junctions. Immunofluorescence analysis revealed that the ZO-1 tight junction protein is localized exclusively at the cell periphery in dexamethasone-treated cells and that TGF-alpha caused-ZO-1 to relocalize from the cell periphery back to a cytoplasmic compartment. Taken together, our results demonstrate that glucocorticoids can coordinately regulate growth inhibition and cell-cell contact of mammary tumor cells and that TGF-alpha, can override both effects of glucocorticoids. These results have uncovered a novel functional "cross-talk" between glucocorticoids and TGF-alpha which potentially regulates the proliferation and differentiation of mammary epithelial cells.

  2. Electro-Optical Characteristics of P+n In0.53Ga0.47As Hetero-Junction Photodiodes in Large Format Dense Focal Plane Arrays

    Science.gov (United States)

    DeWames, R.; Littleton, R.; Witte, K.; Wichman, A.; Bellotti, E.; Pellegrino, J.

    2015-08-01

    This paper is concerned with focal plane array (FPA) data and use of analytical and three-dimensional numerical simulation methods to determine the physical effects and processes limiting performance. For shallow homojunction P+n designs the temperature dependence of dark current for T InGaAs interface. In this description the fitting property is the effective conductivity, σ eff( T), in mho cm-1. Variation in the data suggests σ eff (300 K) values of 1.2 × 10-11-4.6 × 10-11 mho cm-1). Substrate removal extends the quantum efficiency (QE) spectral band into the visible region. However, dead-layer effects limit the QE to 10% at a wavelength of 0.5 μm. For starlight-no moon illumination conditions, the signal-to-noise ratio is estimated to be 50 at an operating temperature of 300 K. A major result of the 3D numerical simulation of the device is the prediction of a perimeter G-R current not associated with the properties of the metallurgical interface. Another is the prediction that for a junction positioned in the larger band gap InP cap layer the QE is bias-dependent and that a relatively large reverse bias ≥0.9 V is needed for the QE to saturate to the shallow homojunction value. At this higher bias the dark current is larger than the shallow homojunction value. The 3D numerical model and the analytical model agree in predicting and explaining the measured radiatively limited diffusion current originating at the n-side of the junction. The calculations of the area-dependent G-R current for the condition studied are also in agreement. Unique advantages of the 3D numerical simulation are the ability to mimic real device structures, achieve deeper understanding of the real physical effects associated with the various methods of junction formation, and predict how device designs will function.

  3. ADAM10 Is Involved in Cell Junction Assembly in Early Porcine Embryo Development.

    Directory of Open Access Journals (Sweden)

    Jeongwoo Kwon

    Full Text Available ADAM10 (A Disintegrin and Metalloprotease domain-containing protein 10 is a cell surface protein with a unique structure possessing both potential adhesion and protease domains. However, the role of ADAM10 in preimplantation stage embryos is not clear. In this study, we examined the expression patterns and functional roles of ADAM10 in porcine parthenotes during preimplantation development. The transcription level of ADAM10 dramatically increased from the morula stage onward. Immunostaining revealed that ADAM10 was present in both the nucleus and cytoplasm in early cleavage stage embryos, and localized to the apical region of the outer cells in morula and blastocyst embryos. Knockdown (KD of ADAM10 using double strand RNA did not alter preimplantation embryo development until morula stage, but resulted in significantly reduced development to blastocyst stage. Moreover, the KD blastocyst showed a decrease in gene expression of adherens and tight junction (AJ/TJ, and an increase in trophectoderm TJ permeability by disrupting TJ assembly. Treatment with an ADAM10 specific chemical inhibitor, GI254023X, at the morula stage also inhibited blastocyst development and led to disruption of TJ assembly. An in situ proximity ligation assay demonstrated direct interaction of ADAM10 with coxsackie virus and adenovirus receptor (CXADR, supporting the involvement of ADAM10 in TJ assembly. In conclusion, our findings strongly suggest that ADADM10 is important for blastocyst formation rather than compaction, particularly for TJ assembly and stabilization in preimplantation porcine parthenogenetic development.

  4. Gap Junctions

    Science.gov (United States)

    Nielsen, Morten Schak; Axelsen, Lene Nygaard; Sorgen, Paul L.; Verma, Vandana; Delmar, Mario; Holstein-Rathlou, Niels-Henrik

    2013-01-01

    Gap junctions are essential to the function of multicellular animals, which require a high degree of coordination between cells. In vertebrates, gap junctions comprise connexins and currently 21 connexins are known in humans. The functions of gap junctions are highly diverse and include exchange of metabolites and electrical signals between cells, as well as functions, which are apparently unrelated to intercellular communication. Given the diversity of gap junction physiology, regulation of gap junction activity is complex. The structure of the various connexins is known to some extent; and structural rearrangements and intramolecular interactions are important for regulation of channel function. Intercellular coupling is further regulated by the number and activity of channels present in gap junctional plaques. The number of connexins in cell-cell channels is regulated by controlling transcription, translation, trafficking, and degradation; and all of these processes are under strict control. Once in the membrane, channel activity is determined by the conductive properties of the connexin involved, which can be regulated by voltage and chemical gating, as well as a large number of posttranslational modifications. The aim of the present article is to review our current knowledge on the structure, regulation, function, and pharmacology of gap junctions. This will be supported by examples of how different connexins and their regulation act in concert to achieve appropriate physiological control, and how disturbances of connexin function can lead to disease. © 2012 American Physiological Society. Compr Physiol 2:1981-2035, 2012. PMID:23723031

  5. Gap junctions.

    Science.gov (United States)

    Nielsen, Morten Schak; Axelsen, Lene Nygaard; Sorgen, Paul L; Verma, Vandana; Delmar, Mario; Holstein-Rathlou, Niels-Henrik

    2012-07-01

    Gap junctions are essential to the function of multicellular animals, which require a high degree of coordination between cells. In vertebrates, gap junctions comprise connexins and currently 21 connexins are known in humans. The functions of gap junctions are highly diverse and include exchange of metabolites and electrical signals between cells, as well as functions, which are apparently unrelated to intercellular communication. Given the diversity of gap junction physiology, regulation of gap junction activity is complex. The structure of the various connexins is known to some extent; and structural rearrangements and intramolecular interactions are important for regulation of channel function. Intercellular coupling is further regulated by the number and activity of channels present in gap junctional plaques. The number of connexins in cell-cell channels is regulated by controlling transcription, translation, trafficking, and degradation; and all of these processes are under strict control. Once in the membrane, channel activity is determined by the conductive properties of the connexin involved, which can be regulated by voltage and chemical gating, as well as a large number of posttranslational modifications. The aim of the present article is to review our current knowledge on the structure, regulation, function, and pharmacology of gap junctions. This will be supported by examples of how different connexins and their regulation act in concert to achieve appropriate physiological control, and how disturbances of connexin function can lead to disease. © 2012 American Physiological Society. Compr Physiol 2:1853-1872, 2012.

  6. Graphene-SnO2 nanocomposites decorated with quantum tunneling junctions: preparation strategies, microstructures and formation mechanism.

    Science.gov (United States)

    Wang, Qingxiu; Wu, Xianzheng; Wang, Lijun; Chen, Zhiwen; Wang, Shilong

    2014-09-28

    Tin dioxide (SnO2) and graphene are versatile materials that are vitally important for creating new functional and smart materials. A facile, simple and efficient ultrasonic-assisted hydrothermal synthesis approach has been developed to prepare graphene-SnO2 nanocomposites (GSNCs), including three samples with graphene/Sn weight ratios = 1 : 2 (GSNC-2), 1 : 1 (GSNC-1), and graphene oxide/Sn weight ratio = 1 : 1 (GOSNC-1). Low-magnification electron microscopy analysis indicated that graphene was exfoliated and adorned with SnO2 nanoparticles, which were dispersed uniformly on both the sides of the graphene nanosheets. High-magnification electron microscopy analysis confirmed that the graphene-SnO2 nanocomposites presented network tunneling frameworks, which were decorated with the SnO2 quantum tunneling junctions. The size distribution of SnO2 nanoparticles was estimated to range from 3 to 5.5 nm. Comparing GSNC-2, GSNC-1, and GOSNC-1, GOSNC-1 was found to exhibit a significantly better the homogeneous distribution and a considerably smaller size distribution of SnO2 nanoparticles, which indicated that it was better to use graphene oxide as a supporting material and SnCl4·5H2O as a precursor to synthesize hybrid graphene-SnO2 nanocomposites. Experimental results suggest that the graphene-SnO2 nanocomposites with interesting SnO2 quantum tunneling junctions may be a promising material to facilitate the improvement of the future design of micro/nanodevices.

  7. An outdoor investigation of the absorption degradation of single-junction amorphous silicon photovoltaic module due to localized heat/hot spot formation

    Indian Academy of Sciences (India)

    Osayemwenre Gilbert O; Meyer Edson L; Mamphweli Sampson

    2016-04-01

    This paper investigates the absorbance degradation of single-junction amorphous silicon (a-Si:H) photovoltaic (PV) module, due to the presence of localized heat. The decrease in optical density is a huge challenge due to the long-term degradation of PV modules. The reduction in solar cell optical density causes a decline in its conversion efficiency. This decreases the photogenerating current, hence reduces the effective efficiency of the PV device. An infrared thermography was used for mapping the module temperature profile. Fourier transform infrared spectroscopy (FTIR) was used for the absorption characterization. The rationale behind the outdoor deployment was to deduce a practical effect of hot spot formation on the module’s absorption ability.The results show a direct correlation between localized heat and the absorption degradation.

  8. Loss of αT-catenin alters the hybrid adhering junctions in the heart and leads to dilated cardiomyopathy and ventricular arrhythmia following acute ischemia.

    Science.gov (United States)

    Li, Jifen; Goossens, Steven; van Hengel, Jolanda; Gao, Erhe; Cheng, Lan; Tyberghein, Koen; Shang, Xiying; De Rycke, Riet; van Roy, Frans; Radice, Glenn L

    2012-02-15

    It is generally accepted that the intercalated disc (ICD) required for mechano-electrical coupling in the heart consists of three distinct junctional complexes: adherens junctions, desmosomes and gap junctions. However, recent morphological and molecular data indicate a mixing of adherens junctional and desmosomal components, resulting in a 'hybrid adhering junction' or 'area composita'. The α-catenin family member αT-catenin, part of the N-cadherin-catenin adhesion complex in the heart, is the only α-catenin that interacts with the desmosomal protein plakophilin-2 (PKP2). Thus, it has been postulated that αT-catenin might serve as a molecular integrator of the two adhesion complexes in the area composita. To investigate the role of αT-catenin in the heart, gene targeting technology was used to delete the Ctnna3 gene, encoding αT-catenin, in the mouse. The αT-catenin-null mice are viable and fertile; however, the animals exhibit progressive cardiomyopathy. Adherens junctional and desmosomal proteins were unaffected by loss of αT-catenin, with the exception of the desmosomal protein PKP2. Immunogold labeling at the ICD demonstrated in the αT-catenin-null heart a preferential reduction of PKP2 at the area composita compared with the desmosome. Furthermore, gap junction protein Cx43 was reduced at the ICD, including its colocalization with N-cadherin. Gap junction remodeling in αT-catenin-knockout hearts was associated with an increased incidence of ventricular arrhythmias after acute ischemia. This novel animal model demonstrates for the first time how perturbation in αT-catenin can affect both PKP2 and Cx43 and thereby highlights the importance of understanding the crosstalk between the junctional proteins of the ICD and its implications for arrhythmogenic cardiomyopathy.

  9. Reggies/flotillins regulate E-cadherin-mediated cell contact formation by affecting EGFR trafficking.

    Science.gov (United States)

    Solis, Gonzalo P; Schrock, Yvonne; Hülsbusch, Nikola; Wiechers, Marianne; Plattner, Helmut; Stuermer, Claudia A O

    2012-05-01

    The reggie/flotillin proteins are implicated in membrane trafficking and, together with the cellular prion protein (PrP), in the recruitment of E-cadherin to cell contact sites. Here, we demonstrate that reggies, as well as PrP down-regulation, in epithelial A431 cells cause overlapping processes and abnormal formation of adherens junctions (AJs). This defect in cell adhesion results from reggie effects on Src tyrosine kinases and epidermal growth factor receptor (EGFR): loss of reggies reduces Src activation and EGFR phosphorylation at residues targeted by Src and c-cbl and leads to increased surface exposure of EGFR by blocking its internalization. The prolonged EGFR signaling at the plasma membrane enhances cell motility and macropinocytosis, by which junction-associated E-cadherin is internalized and recycled back to AJs. Accordingly, blockage of EGFR signaling or macropinocytosis in reggie-deficient cells restores normal AJ formation. Thus, by promoting EGFR internalization, reggies restrict the EGFR signaling involved in E-cadherin macropinocytosis and recycling and regulate AJ formation and dynamics and thereby cell adhesion.

  10. The role of gap junctions and mechanical loading on mineral formation in a collagen-I scaffold seeded with osteoprogenitor cells.

    Science.gov (United States)

    Damaraju, Swathi; Matyas, John R; Rancourt, Derrick E; Duncan, Neil A

    2015-05-01

    Fracture nonunions represent one of many large bone defects where current treatment strategies fall short in restoring both form and function of the injured tissue. In this case, the use of a tissue-engineered scaffold for promoting bone healing offers an accessible and easy-to-manipulate environment for studying bone formation processes in vitro. We have previously shown that mechanical prestimulation using confined compression of differentiating osteoblasts results in an increase in mineralization formed in a 3D collagen-I scaffold. This study builds on this knowledge by evaluating the short and long-term effects of blocking gap junction-mediated intercellular communication among osteogenic cells on their effectiveness to mineralize collagen-I scaffolds in vitro, and in the presence and absence of mechanical stimulation. In this study, confined compression was applied in conjunction with octanol (a general communication blocker) or 18-α-glycerrhetinic acid (AGA, a specific gap junction blocker) using a modified FlexCell plate to collagen-I scaffolds seeded with murine embryonic stem cells stimulated toward osteoblast differentiation using beta-glycerol phosphate. The activity, presence, and expression of osteoblast cadherin, connexin-43, as well as various pluripotent and osteogenic markers were examined at 5-30 days of differentiation. Fluorescence recovery after photobleaching, immunofluorescence, viability, histology assessments, and reverse-transcriptase polymerase chain reaction assessments revealed that inhibiting communication in this scaffold altered the lineage and function of differentiating osteoblasts. In particular, treatment with communication inhibitors caused reduced mineralization in the matrix, and dissociation between connexin-43 and integrin α5β1. This dissociation was not restored even after long-term recovery. Thus, in order for this scaffold to be considered as an alternative strategy for the repair of large bone defects, cell

  11. Glutamine supplementation attenuates ethanol-induced disruption of apical junctional complexes in colonic epithelium and ameliorates gut barrier dysfunction and fatty liver in mice.

    Science.gov (United States)

    Chaudhry, Kamaljit K; Shukla, Pradeep K; Mir, Hina; Manda, Bhargavi; Gangwar, Ruchika; Yadav, Nikki; McMullen, Megan; Nagy, Laura E; Rao, RadhaKrishna

    2016-01-01

    Previous in vitro studies showed that glutamine (Gln) prevents acetaldehyde-induced disruption of tight junctions and adherens junctions in Caco-2 cell monolayers and human colonic mucosa. In the present study, we evaluated the effect of Gln supplementation on ethanol-induced gut barrier dysfunction and liver injury in mice in vivo. Ethanol feeding caused a significant increase in inulin permeability in distal colon. Elevated permeability was associated with a redistribution of tight junction and adherens junction proteins and depletion of detergent-insoluble fractions of these proteins, suggesting that ethanol disrupts apical junctional complexes in colonic epithelium and increases paracellular permeability. Ethanol-induced increase in colonic mucosal permeability and disruption of junctional complexes were most severe in mice fed Gln-free diet. Gln supplementation attenuated ethanol-induced mucosal permeability and disruption of tight junctions and adherens junctions in a dose-dependent manner, indicating the potential role of Gln in nutritional intervention to alcoholic tissue injury. Gln supplementation dose-dependently elevated reduced-protein thiols in colon without affecting the level of oxidized-protein thiols. Ethanol feeding depleted reduced protein thiols and elevated oxidized protein thiols. Ethanol-induced protein thiol oxidation was most severe in mice fed with Gln-free diet and absent in mice fed with Gln-supplemented diet, suggesting that antioxidant effect is one of the likely mechanisms involved in Gln-mediated amelioration of ethanol-induced gut barrier dysfunction. Ethanol feeding elevated plasma transaminase and liver triglyceride, which was accompanied by histopathologic lesions in the liver; ethanol-induced liver damage was attenuated by Gln supplementation. These results indicate that Gln supplementation ameliorates alcohol-induced gut and liver injury.

  12. Testicular cell junction: a novel target for male contraception.

    Science.gov (United States)

    Lee, Nikki P Y; Wong, Elissa W P; Mruk, Dolores D; Cheng, C Yan

    2009-01-01

    Even though various contraceptive methods are widely available, the number of unwanted pregnancies is still on the rise in developing countries, pressurizing the already resource limited nations. One of the major underlying reasons is the lack of effective, low cost, and safe contraceptives for couples. During the past decade, some studies were performed using animal models to decipher if the Sertoli-germ cell junction in the testis is a target for male fertility regulation. Some of these study models were based on the use of hormones and/or chemicals to disrupt the hypothalamic-pituitary-testicular axis (e.g., androgen-based implants or pills) and others utilized a panel of chemical entities or synthetic peptides to perturb spermatogenesis either reversibly or non-reversibly. Among them, adjudin, a potential male contraceptive, is one of the compounds exerting its action on the unique adherens junctions, known as ectoplasmic specializations, in the testis. Since the testis is equipped with inter-connected cell junctions, an initial targeting of one junction type may affect the others and these accumulative effects could lead to spermatogenic arrest. This review attempts to cover an innovative theme on how male infertility can be achieved by inducing junction instability and defects in the testis, opening a new window of research for male contraceptive development. While it will still take much time and effort of intensive investigation before a product can reach the consumable market, these findings have provided hope for better family planning involving men.

  13. The cell adhesion molecule nectin-1 is critical for normal enamel formation in mice.

    Science.gov (United States)

    Barron, Martin J; Brookes, Steven J; Draper, Clare E; Garrod, David; Kirkham, Jennifer; Shore, Roger C; Dixon, Michael J

    2008-11-15

    Nectin-1 is a member of a sub-family of immunoglobulin-like adhesion molecules and a component of adherens junctions. In the current study, we have shown that mice lacking nectin-1 exhibit defective enamel formation in their incisor teeth. Although the incisors of nectin-1-null mice were hypomineralized, the protein composition of the enamel matrix was unaltered. While strong immunostaining for nectin-1 was observed at the interface between the maturation-stage ameloblasts and the underlying cells of the stratum intermedium (SI), its absence in nectin-1-null mice correlated with separation of the cell layers at this interface. Numerous, large desmosomes were present at this interface in wild-type mice; however, where adhesion persisted in the mutant mice, the desmosomes were smaller and less numerous. Nectins have been shown to regulate tight junction formation; however, this is the first report showing that they may also participate in the regulation of desmosome assembly. Importantly, our results show that integrity of the SI-ameloblast interface is essential for normal enamel mineralization.

  14. Virus interaction with the apical junctional complex.

    Science.gov (United States)

    Gonzalez-Mariscal, Lorenza; Garay, Erika; Lechuga, Susana

    2009-01-01

    In order to infect pathogens must breach the epithelial barriers that separate the organism from the external environment or that cover the internal cavities and ducts of the body. Epithelia seal the passage through the paracellular pathway with the apical junctional complex integrated by tight and adherens junctions. In this review we describe how viruses like coxsackie, swine vesicular disease virus, adenovirus, reovirus, feline calcivirus, herpes viruses 1 and 2, pseudorabies, bovine herpes virus 1, poliovirus and hepatitis C use as cellular receptors integral proteins present at the AJC of epithelial cells. Interaction with these proteins contributes in a significant manner in defining the particular tropism of each virus. Besides these proteins, viruses exhibit a wide range of cellular co-receptors among which proteins present in the basolateral cell surface like integrins are often found. Therefore targeting proteins of the AJC constitutes a strategy that might allow viruses to bypass the physical barrier that blocks their access to receptors expressed on the basolateral surface of epithelial cells.

  15. Specific detection of DNA and RNA targets using a novel isothermal nucleic acid amplification assay based on the formation of a three-way junction structure.

    Science.gov (United States)

    Wharam, S D; Marsh, P; Lloyd, J S; Ray, T D; Mock, G A; Assenberg, R; McPhee, J E; Brown, P; Weston, A; Cardy, D L

    2001-06-01

    The formation of DNA three-way junction (3WJ) structures has been utilised to develop a novel isothermal nucleic acid amplification assay (SMART) for the detection of specific DNA or RNA targets. The assay consists of two oligonucleotide probes that hybridise to a specific target sequence and, only then, to each other forming a 3WJ structure. One probe (template for the RNA signal) contains a non-functional single-stranded T7 RNA polymerase promoter sequence. This promoter sequence is made double-stranded (hence functional) by DNA polymerase, allowing T7 RNA polymerase to generate a target-dependent RNA signal which is measured by an enzyme-linked oligosorbent assay (ELOSA). The sequence of the RNA signal is always the same, regardless of the original target sequence. The SMART assay was successfully tested in model systems with several single-stranded synthetic targets, both DNA and RNA. The assay could also detect specific target sequences in both genomic DNA and total RNA from Escherichia coli. It was also possible to generate signal from E.coli samples without prior extraction of nucleic acid, showing that for some targets, sample purification may not be required. The assay is simple to perform and easily adaptable to different targets.

  16. Doped semiconductor nanocrystal junctions

    Energy Technology Data Exchange (ETDEWEB)

    Borowik, Ł.; Mélin, T., E-mail: thierry.melin@isen.iemn.univ-lille1.fr [Institut d’Electronique, de Microélectronique et de Nanotechnologie, CNRS-UMR8520, Avenue Poincaré, F-59652 Villeneuve d’Ascq (France); Nguyen-Tran, T.; Roca i Cabarrocas, P. [Laboratoire de Physique des Interfaces et des Couches Minces, CNRS-UMR7647, Ecole Polytechnique, F-91128 Palaiseau (France)

    2013-11-28

    Semiconductor junctions are the basis of electronic and photovoltaic devices. Here, we investigate junctions formed from highly doped (N{sub D}≈10{sup 20}−10{sup 21}cm{sup −3}) silicon nanocrystals (NCs) in the 2–50 nm size range, using Kelvin probe force microscopy experiments with single charge sensitivity. We show that the charge transfer from doped NCs towards a two-dimensional layer experimentally follows a simple phenomenological law, corresponding to formation of an interface dipole linearly increasing with the NC diameter. This feature leads to analytically predictable junction properties down to quantum size regimes: NC depletion width independent of the NC size and varying as N{sub D}{sup −1/3}, and depleted charge linearly increasing with the NC diameter and varying as N{sub D}{sup 1/3}. We thus establish a “nanocrystal counterpart” of conventional semiconductor planar junctions, here however valid in regimes of strong electrostatic and quantum confinements.

  17. Direct Exposure to Ethanol Disrupts Junctional Cell-Cell Contact and Hippo-YAP Signaling in HL-1 Murine Atrial Cardiomyocytes.

    Directory of Open Access Journals (Sweden)

    Kanako Noritake

    Full Text Available Direct exposure of cardiomyocytes to ethanol causes cardiac damage such as cardiac arrythmias and apoptotic cell death. Cardiomyocytes are connected to each other through intercalated disks (ID, which are composed of a gap junction (GJ, adherens junction, and desmosome. Changes in the content as well as the subcellular localization of connexin43 (Cx43, the main component of the cardiac GJ, are reportedly involved in cardiac arrythmias and subsequent damage. Recently, the hippo-YAP signaling pathway, which links cellular physical status to cell proliferation, differentiation, and apoptosis, has been implicated in cardiac homeostasis under physiological as well as pathological conditions. This study was conducted to explore the possible involvement of junctional intercellular communication, mechanotransduction through cytoskeletal organization, and the hippo-YAP pathway in cardiac damage caused by direct exposure to ethanol. HL-1 murine atrial cardiac cells were used since these cells retain cardiac phenotypes through ID formation and subsequent synchronous contraction. Cells were exposed to 0.5-2% ethanol; significant apoptotic cell death was observed after exposure to 2% ethanol for 48 hours. A decrease in Cx43 levels was already observed after 3 hours exposure to 2% ethanol, suggesting a rapid degradation of this protein. Upon exposure to ethanol, Cx43 translocated into lysosomes. Cellular cytoskeletal organization was also dysregulated by ethanol, as demonstrated by the disruption of myofibrils and intermediate filaments. Coinciding with the loss of cell-cell adherence, decreased phosphorylation of YAP, a hippo pathway effector, was also observed in ethanol-treated cells. Taken together, the results provide evidence that cells exposed directly to ethanol show 1 impaired cell-cell adherence/communication, 2 decreased cellular mechanotransduction by the cytoskeleton, and 3 a suppressed hippo-YAP pathway. Suppression of hippo-YAP pathway

  18. Expression of TM4SF10, a Claudin/EMP/PMP22 family cell junction protein, during mouse kidney development and podocyte differentiation.

    Science.gov (United States)

    Bruggeman, Leslie A; Martinka, Scott; Simske, Jeffrey S

    2007-02-01

    Cell junctions in the nephron are highly specialized to perform specific and distinct filtration and reabsorption functions. The mature kidney forms complex cell junctions including slit diaphragms that prevent the passage of serum proteins into the filtrate, and tubule cell junctions that regulate specific paracellular ion reuptake. We have investigated the expression of TM4SF10 (Trans-Membrane tetra(4)-Span Family 10) in mouse kidneys. TM4SF10 is the vertebrate orthologue of Caenorhabditis elegans VAB-9, a tetraspan adherens junction protein in the PMP22/EMP/Claudin family of proteins. We found that TM4SF10 localizes at the basal-most region of podocyte precursors before the capillary loop stage, at some tubule precursors, and at the ureteric bud junction with S-shaped bodies. Overall expression of TM4SF10 peaked at postnatal day 4 and was virtually absent in adult kidneys. The very limited expression of TM4SF10 protein that persisted into adulthood was restricted to a few tubule segments but remained localized to the basal region of lateral membranes. In undifferentiated cultured podocytes, TM4SF10 localized to the perinuclear region and translocated to the cell membrane after Cadherin appearance at cell-cell contacts. TM4SF10 colocalized with ZO1 and p120ctn in undifferentiated confluent podocytes and also colocalized with the tips of actin filaments at cell contacts. Upon differentiation of cultured podocytes, TM4SF10 protein disappeared from cell contacts and expression ceased. These results suggest that TM4SF10 functions during differentiation of podocytes and may participate in the maturation of cell junctions from simple adherens junctions to elaborate slit diaphragms. TM4SF10 may define a new class of Claudin-like proteins that function during junctional development.

  19. Disturbances in the positioning, proliferation and apoptosis of neural progenitors contribute to subcortical band heterotopia formation.

    Science.gov (United States)

    Fitzgerald, M P; Covio, M; Lee, K S

    2011-03-10

    Cortical malformations are commonly associated with intractable epilepsy and other developmental disorders. Our studies utilize the tish rat, a spontaneously occurring genetic model of subcortical band heterotopia (SBH) associated with epilepsy, to evaluate the developmental events underlying SBH formation in the neocortex. Our results demonstrate that Pax6(+) and Tbr2(+) progenitors are mislocalized in tish(+/-) and tish(-/-)- neocortex throughout neurogenesis. In addition, mislocalized tish(-/-) progenitors possess a longer cell cycle than wild type or normally-positioned tish(-/-) progenitors, owing to a lengthened G(2)+M+G(1) time. This mislocalization is not associated with adherens junction breakdown or loss of radial glial polarity in the ventricular zone (VZ), as assessed by immunohistochemistry against phalloidin (to identify F-actin), aPKC-λ and Par3. However, vimentin immunohistochemistry indicates that the radial glial scaffold is disrupted in the region of the tish(-/-) heterotopia. Moreover, lineage tracing experiments using in utero electroporation in tish(-/-) neocortex demonstrate that mislocalized progenitors do not retain contact with the ventricular surface and that ventricular/subventricular zone (SVZ) progenitors produce neurons that migrate into both the heterotopia and cortical plate (CP). Taken together, these findings define a series of developmental errors contributing to SBH formation that differs fundamentally from a primary error in neuronal migration.

  20. Desmosomal Molecules In and Out of Adhering Junctions: Normal and Diseased States of Epidermal, Cardiac and Mesenchymally Derived Cells

    Directory of Open Access Journals (Sweden)

    Sebastian Pieperhoff

    2010-01-01

    Full Text Available Current cell biology textbooks mention only two kinds of cell-to-cell adhering junctions coated with the cytoplasmic plaques: the desmosomes (maculae adhaerentes, anchoring intermediate-sized filaments (IFs, and the actin microfilament-anchoring adherens junctions (AJs, including both punctate (puncta adhaerentia and elongate (fasciae adhaerentes structures. In addition, however, a series of other junction types has been identified and characterized which contain desmosomal molecules but do not fit the definition of desmosomes. Of these special cell-cell junctions containing desmosomal glycoproteins or proteins we review the composite junctions (areae compositae connecting the cardiomyocytes of mature mammalian hearts and their importance in relation to human arrhythmogenic cardiomyopathies. We also emphasize the various plakophilin-2-positive plaques in AJs (coniunctiones adhaerentes connecting proliferatively active mesenchymally-derived cells, including interstitial cells of the heart and several soft tissue tumor cell types. Moreover, desmoplakin has also been recognized as a constituent of the plaques of the complexus adhaerentes connecting certain lymphatic endothelial cells. Finally, we emphasize the occurrence of the desmosomal transmembrane glycoprotein, desmoglein Dsg2, out of the context of any junction as dispersed cell surface molecules in certain types of melanoma cells and melanocytes. This broadening of our knowledge on the diversity of AJ structures indicates that it may still be too premature to close the textbook chapters on cell-cell junctions.

  1. Molecular electronic junction transport

    DEFF Research Database (Denmark)

    Solomon, Gemma C.; Herrmann, Carmen; Ratner, Mark

    2012-01-01

    Whenasinglemolecule,oracollectionofmolecules,isplacedbetween two electrodes and voltage is applied, one has a molecular transport junction. We discuss such junctions, their properties, their description, and some of their applications. The discussion is qualitative rather than quantitative, and f...

  2. Comparison of boron diffusion in silicon during shallow p{sup +}/n junction formation by non-melt excimer and green laser annealing

    Energy Technology Data Exchange (ETDEWEB)

    Aid, Siti Rahmah; Matsumoto, Satoru [Department of Electronics and Electrical Engineering, Keio University, 3-14-1 Hiyoshi, Kouhoku-ku, Yokohama, Kanagawa 223-8522 (Japan); Fuse, Genshu [SEN Corporation, SBS Tower 9F, 4-10-1 Yoga, Setagaya-ku, Tokyo 158-0097 (Japan); Sakuragi, Susumu [Sumitomo Heavy Industries Ltd., 19 Natsushima-cho, Yokosuka, Kanagawa 237-8555 (Japan)

    2011-12-15

    The combination of Ge pre-amorphization implantation, low-energy boron implantation, and non-melt laser annealing is a promising method for forming ultrashallow p{sup +}/n junctions in silicon. In this study, shallow p{sup +}/n junctions were formed by non-melt annealing implanted samples using a green laser (visible laser). The dopant diffusion, activation, and recrystallization of an amorphous silicon layer were compared with those obtained in our previous study in which non-melt annealing was performed using a KrF excimer laser (UV laser). The experimental results reveal that only slight diffusion of boron in the tail region occurred in green-laser-annealed samples. In contrast, remarkable boron diffusion occurred in KrF-laser-annealed samples for very short annealing times. Recrystallization of the amorphous silicon layer was slower in green-laser-annealed samples than in KrF-laser-annealed samples. We consider the penetration depth and the pulse duration are important factors that may affect boron diffusion. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  3. Reduced expression of adherens and gap junction proteins can have a fundamental role in the development of heart failure following cardiac hypertrophy in rats.

    Science.gov (United States)

    dos Santos, Daniele O; Blefari, Valdecir; Prado, Fernanda P; Silva, Carlos A; Fazan, Rubens; Salgado, Helio C; Ramos, Simone G; Prado, Cibele M

    2016-02-01

    Hypertension causes cardiac hypertrophy, cardiac dysfunction and heart failure (HF). The mechanisms implicated in the transition from compensated to decompensated cardiac hypertrophy are not fully understood. This study was aimed to investigate whether alterations in the expression of intercalated disk proteins could contribute to the transition of compensated cardiac hypertrophy to dilated heart development that culminates in HF. Male rats were submitted to abdominal aortic constriction and at 90 days post surgery (dps), three groups were observed: sham-operated animals (controls), animals with hypertrophic hearts (HH) and animals with hypertrophic + dilated hearts (HD). Blood pressure was evaluated. The hearts were collected and Western blot and immunofluorescence were performed to desmoglein-2, desmocollin-2, N-cadherin, plakoglobin, Bcatenin, and connexin-43. Cardiac systolic function was evaluated using the Vevo 2100 ultrasound system. Data were considered significant when p b 0.05. Seventy percent of the animals presented with HH and 30% were HD at 90 dps. The blood pressure increased in both groups. The amount of desmoglein-2 and desmocollin-2 expression was increased in both groups and no difference was observed in either group. The expression of N-cadherin, plakoglobin and B-catenin increased in the HHgroup and decreased in the HDgroup; and connexin-43 decreased only in theHDgroup. Therewas no difference between the ejection fraction and fractional shortening at 30 and 60 dps; however, they were decreased in the HD group at 90 dps. We found that while some proteins have increased expression accompanied by the increase in the cell volume associated with preserved systolic cardiac function in theHHgroup, these same proteins had decreased expression evenwithout significant reduction in the cell volume associated with decreased systolic cardiac function in HD group. The increased expression of desmoglein-2 and desmocollin-2 in both the HH and HD groups could work as a protective compensatory mechanism, helping tomaintain the dilated heart.We can hypothesize that inappropriate intercellular mechanical and electrical coupling associated with necrosis and/or apoptosis are important factors contributing to the transition to HF.

  4. Modulation of intercellular junctions by cyclic-ADT peptides as a method to reversibly increase blood-brain barrier permeability.

    Science.gov (United States)

    Laksitorini, Marlyn D; Kiptoo, Paul K; On, Ngoc H; Thliveris, James A; Miller, Donald W; Siahaan, Teruna J

    2015-03-01

    It is challenging to deliver molecules to the brain for diagnosis and treatment of brain diseases. This is primarily because of the presence of the blood-brain barrier (BBB), which restricts the entry of many molecules into the brain. In this study, cyclic-ADT peptides (ADTC1, ADTC5, and ADTC6) have been shown to modify the BBB to enhance the delivery of marker molecules [e.g., (14) C-mannitol, gadolinium-diethylenetriaminepentacetate (Gd-DTPA)] to the brain via the paracellular pathways of the BBB. The hypothesis is that these peptides modulate cadherin interactions in the adherens junctions of the vascular endothelial cells forming the BBB to increase paracellular drug permeation. In vitro studies indicated that ADTC5 had the best profile to inhibit adherens junction resealing in Madin-Darby canine kidney cell monolayers in a concentration-dependent manner (IC50 = 0.3 mM) with a maximal response at 0.4 mM. Under the current experimental conditions, ADTC5 improved the delivery of (14) C-mannitol to the brain about twofold compared with the negative control in the in situ rat brain perfusion model. Furthermore, ADTC5 peptide increased in vivo delivery of Gd-DTPA to the brain of Balb/c mice when administered intravenously. In conclusion, ADTC5 has the potential to improve delivery of diagnostic and therapeutic agents to the brain.

  5. Overexpression of galectin-7 in mouse epidermis leads to loss of cell junctions and defective skin repair.

    Directory of Open Access Journals (Sweden)

    Gaëlle Gendronneau

    Full Text Available The proteins of the galectin family are implicated in many cellular processes, including cell interactions, polarity, intracellular trafficking, and signal transduction. In human and mouse, galectin-7 is almost exclusively expressed in stratified epithelia, notably in the epidermis. Galectin-7 expression is also altered in several human tumors of epithelial origin. This study aimed at dissecting the consequences of galectin-7 overexpression on epidermis structure and functions in vivo.We established transgenic mice specifically overexpressing galectin-7 in the basal epidermal keratinocytes and analyzed the consequences on untreated skin and after UVB irradiation or mechanical injury.The intercellular cohesion of the epidermis is impaired in transgenic animals, with gaps developing between adjacent keratinocytes, associated with loss of adherens junctions. The epidermal architecture is aberrant with perturbations in the multilayered cellular organisation of the tissue, and structural defects in the basement membrane. These transgenic animals displayed a reduced re-epithelialisation potential following superficial wound, due to a defective collective migration of keratinocytes. Finally, a single mild dose of UVB induced an abnormal apoptotic response in the transgenic epidermis.These results indicate that an excess of galectin-7 leads to a destabilisation of adherens junctions associated with defects in epidermal repair. As this phenotype shares similarities with that of galectin-7 null mutant mice, we conclude that a critical level of this protein is required for maintaining proper epidermal homeostasis. This study brings new insight into the mode of action of galectins in normal and pathological situations.

  6. Sputter deposition of Cu{sub 2}O thin films, nitrogen-doping and formation of Cu{sub 2}O-ZnO p/n junctions

    Energy Technology Data Exchange (ETDEWEB)

    Graubner, Swen; Kronenberger, Achim; Benz, Julian; Reppin, Daniel; Fischer, Martin; Polity, Angelika; Hofmann, Detlef; Henning, Torsten; Klar, Peter; Meyer, Bruno K. [I. Physikalisches Institut, JLU Giessen (Germany)

    2010-07-01

    Cu{sub 2}O is one of the rare intrinsically p-type conducting semiconductors, in addition the energy of its band gap is in the visible spectral range. Thus it is considered to be a promising material for thin-film-solar cell applications. Metallic and ceramic sputtering processes can be used for the thin-film deposition. Depending on the oxygen partial-pressure, the stoichiometric properties of Cu{sub x}O are adjustable from x=2 to x=1. The electrical properties change considerably depending on the copper-to-oxygen-ratio. It is commonly assumed that copper-vacancies are the dominant intrinsic acceptors in Cu{sub 2}O, thus high carrier concentrations come along with a reduced crystalline quality. Using nitrogen-gas for doping allows carrier concentrations of p=10{sup 15}-10{sup 17} cm{sup -3} without significantly reducing the structural properties of the Cu{sub 2}O-thin-films. By using ZnO as n-type semiconductor, first p/n hetero-junctions were realized. The mesa etched structures show rectifying behaviour and its electrical properties are discussed on the conference.

  7. Identification of neuronal and angiogenic growth factors in an in vitro blood-brain barrier model system: Relevance in barrier integrity and tight junction formation and complexity.

    Science.gov (United States)

    Freese, Christian; Hanada, Sanshiro; Fallier-Becker, Petra; Kirkpatrick, C James; Unger, Ronald E

    2017-05-01

    We previously demonstrated that the co-cultivation of endothelial cells with neural cells resulted in an improved integrity of the in vitro blood-brain barrier (BBB), and that this model could be useful to evaluate the transport properties of potential central nervous system disease drugs through the microvascular brain endothelial. In this study we have used real-time PCR, fluorescent microscopy, protein arrays and enzyme-linked immunosorbent assays to determine which neural- and endothelial cell-derived factors are produced in the co-culture and improve the integrity of the BBB. In addition, a further improvement of the BBB integrity was achieved by adjusting serum concentrations and growth factors or by the addition of brain pericytes. Under specific conditions expression of angiogenic, angiostatic and neurotrophic factors such as endostatin, pigment epithelium derived factor (PEDF/serpins-F1), tissue inhibitor of metalloproteinases (TIMP-1), and vascular endothelial cell growth factor (VEGF) closely mimicked the in vivo situation. Freeze-fracture analysis of these cultures demonstrated the quality and organization of the endothelial tight junction structures and their association to the two different lipidic leaflets of the membrane. Finally, a multi-cell culture model of the BBB with a transendothelial electrical resistance up to 371 (±15) Ω×cm(2) was developed, which may be useful for preliminary screening of drug transport across the BBB and to evaluate cellular crosstalk of cells involved in the neurovascular unit.

  8. Gap junction communication in myelinating glia.

    Science.gov (United States)

    Nualart-Marti, Anna; Solsona, Carles; Fields, R Douglas

    2013-01-01

    Gap junction communication is crucial for myelination and axonal survival in both the peripheral nervous system (PNS) and central nervous system (CNS). This review examines the different types of gap junctions in myelinating glia of the PNS and CNS (Schwann cells and oligodendrocytes respectively), including their functions and involvement in neurological disorders. Gap junctions mediate intercellular communication among Schwann cells in the PNS, and among oligodendrocytes and between oligodendrocytes and astrocytes in the CNS. Reflexive gap junctions mediating transfer between different regions of the same cell promote communication between cellular compartments of myelinating glia that are separated by layers of compact myelin. Gap junctions in myelinating glia regulate physiological processes such as cell growth, proliferation, calcium signaling, and participate in extracellular signaling via release of neurotransmitters from hemijunctions. In the CNS, gap junctions form a glial network between oligodendrocytes and astrocytes. This transcellular communication is hypothesized to maintain homeostasis by facilitating restoration of membrane potential after axonal activity via electrical coupling and the re-distribution of potassium ions released from axons. The generation of transgenic mice for different subsets of connexins has revealed the contribution of different connexins in gap junction formation and illuminated new subcellular mechanisms underlying demyelination and cognitive defects. Alterations in metabolic coupling have been reported in animal models of X-linked Charcot-Marie-Tooth disease (CMTX) and Pelizaeus-Merzbarcher-like disease (PMLD), which are caused by mutations in the genes encoding for connexin 32 and connexin 47 respectively. Future research identifying the expression and regulation of gap junctions in myelinating glia is likely to provide a better understanding of myelinating glia in nervous system function, plasticity, and disease. This

  9. Shh and Gli3 regulate formation of the telencephalic-diencephalic junction and suppress an isthmus-like signaling source in the forebrain.

    Science.gov (United States)

    Rash, Brian G; Grove, Elizabeth A

    2011-11-15

    In human holoprosencephaly (HPE), the forebrain does not separate fully into two hemispheres. Further, the border between the telencephalon and diencephalon, the telencephalic/diencephalic junction (TDJ), is often indistinct, and the ventricular system can be blocked at the third ventricle, creating a forebrain 'holosphere'. Mice deficient in Sonic Hedgehog (Shh) have previously been described to show HPE and associated cyclopia. Here we report that the third ventricle is blocked in Shh null mutants, similar to human HPE, and that characteristic telencephalic and diencephalic signaling centers, the cortical hem and zona limitans intrathalamica (ZLI), are merged, obliterating the TDJ. The resulting forebrain holosphere comprises Foxg1-positive telencephalic- and Foxg1-negative diencephalic territories. Loss of one functional copy of Gli3 in Shh nulls rescues ventricular collapse and substantially restores the TDJ. Characteristic regional gene expression patterns are rescued on the telencephalic side of the TDJ but not in the diencephalon. Further analysis of compound Shh;Gli3 mutants revealed an unexpected type of signaling center deregulation. In Shh;Gli3 mutants, adjacent rings of Fgf8 and Wnt3a expression are induced in the diencephalon at the ZLI, reminiscent of the Fgf8/Wnt1-expressing isthmic organizer. Neither Shh nor Gli3 single mutants show this forebrain double ring of Fgf/Wnt expression; thus both Shh and Gli3 are independently required to suppress it. Adjacent tissue is not respecified to a midbrain/hindbrain fate, but shows overgrowth, consistent with ectopic mitogen expression. Our observations indicate that the separation of the telencephalon and diencephalon depends on interactions between Shh and Gli3, and, moreover, demonstrate that both Shh and Gli3 suppress a potential Fgf/Wnt signaling source in the forebrain. That optional signaling centers are actively repressed in normal development is a striking new insight into the processes of vertebrate

  10. On the formation and evolution of the Pannonian Basin: Constraints derived from the structure of the junction area between the Carpathians and Dinarides

    NARCIS (Netherlands)

    Matenco, L.; Radivojević, D.

    2012-01-01

    The large number and distribution of rollback systems in Mediterranean orogens infer the possibility of interacting extensional back-arc deformation driven by different slabs. The formation of the Pannonian back-arc basin is generally related to the rapid Miocene rollback of a slab attached to the E

  11. The fission yeast meiosis-specific Dmc1 recombinase mediates formation and branch migration of Holliday junctions by preferentially promoting strand exchange in a direction opposite to that of Rad51.

    Science.gov (United States)

    Murayama, Yasuto; Tsutsui, Yasuhiro; Iwasaki, Hiroshi

    2011-03-01

    Homologous recombination proceeds via the formation of several intermediates including Holliday junctions (HJs), which are important for creating crossover products. DNA strand exchange is a core reaction that produces these intermediates that is directly catalyzed by RecA family recombinases, of which there are two types in eukaryotes: universal Rad51 and meiosis-specific Dmc1. We demonstrated previously that Rad51 promotes four-strand exchange, mimicking the formation and branch migration of HJs. Here we show that Dmc1 from fission yeast has a similar activity, which requires ATP hydrolysis and is independent of an absolute requirement for the Swi5-Sfr1 complex. These features are critically different from three-strand exchange mediated by Dmc1, but similar to those of four-strand exchange mediated by Rad51, suggesting that strand exchange reactions between duplex-duplex and single-duplex DNAs are mechanistically different. Interestingly, despite similarities in protein structure and in reaction features, the preferential polarities of Dmc1 and Rad51 strand exchange are different (Dmc1 promotes exchange in the 5'-to-3' direction and Rad51 promotes exchange in the 3'-to-5' direction relative to the ssDNA region of the DNA substrate). The significance of the Dmc1 polarity is discussed within the context of the necessity for crossover production.

  12. Magnetic tunnel junctions (MTJs)

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    We review the giant tunnel magnetoresistance (TMR) in ferromagnetic-insulator-ferromagnetic junctions discovered in recent years, which is the magnetoresistance (MR) associated with the spin-dependent tunneling between two ferromagnetic metal films separated by an insulating thin tunnel barrier. The theoretical and experimental results including junction conductance, magnetoresistance and their temperature and bias dependences are described.

  13. Stacked Josephson Junctions

    DEFF Research Database (Denmark)

    Madsen, Søren Find; Pedersen, Niels Falsig; Christiansen, Peter Leth

    2010-01-01

    Long Josephson junctions have for some time been considered as a source of THz radiation. Solitons moving coherently in the junctions is a possible source for this radiation. Analytical computations of the bunched state and bunching-inducing methods are reviewed. Experiments showing THz radiation...

  14. The effect of an East Pacific Rise offset on the formation of secondary cracks ahead of the Cocos-Nazca Rift at the Galapagos Triple Junction

    Science.gov (United States)

    Smith, D. K.; Montesi, L. G.; Schouten, H.; Zhu, W.

    2011-12-01

    A succession of short-lived, E-W trending cracks at the Galapagos Triple Junction north and south of the Cocos-Nazca (C-N) Rift, has been explained by a simple crack interaction model. The locations of where the cracks initiate are controlled by tensile stresses generated at the East Pacific Rise (EPR) by two interacting cracks: One representing the north-south trending EPR, and the other the large, westward propagating C-N Rift, whose tip is separated from the EPR by a distance D. The model predicts symmetric cracking at the EPR north and south of the C-N Rift tip. Symmetry in the distribution of cracks north and south of the C-N Rift is observed and especially remarkable between 2.5 and 1.5 Ma when the rapid jumping of cracks toward the C-N Rift appears synchronous. The rapid jumping can be explained by decreasing D, which means that the tip of the C-N Rift was moving closer to the EPR. Symmetry of cracking breaks down at 1.5 Ma, however, with the establishment of the Dietz Deep Rift, the southern boundary of the Galapagos microplate. Symmetry of cracking also breaks down on older crust to the east between about 100 35'W and 100 45'W (about 2.6 Ma) where a rapid jumping of cracks toward the C-N Rift is observed in the south cracking region. There is no evidence of similar rapid jumping in the north cracking region. It could be simply that the response to changing the value of D is not always as predicted. It could also be that the shape of the EPR has not always been symmetric about the C-N Rift, as assumed in the model. Currently, an overlapping spreading center with a 15 km east-west offset between the limbs of the EPR has formed at 1 50'N. We assess the importance of the geometry of the EPR on the crack interaction model. The model has been modified to include a ridge offset similar to what is observed today. We find that the region of stress enhancement at the EPR (where cracks initiate) is subdued south of the C-N Rift tip because of the EPR offset. It is

  15. A role for the retinoblastoma protein as a regulator of mouse osteoblast cell adhesion: implications for osteogenesis and osteosarcoma formation.

    Directory of Open Access Journals (Sweden)

    Bernadette Sosa-García

    Full Text Available The retinoblastoma protein (pRb is a cell cycle regulator inactivated in most human cancers. Loss of pRb function results from mutations in the gene coding for pRb or for any of its upstream regulators. Although pRb is predominantly known as a cell cycle repressor, our data point to additional pRb functions in cell adhesion. Our data show that pRb regulates the expression of a wide repertoire of cell adhesion genes and regulates the assembly of the adherens junctions required for cell adhesion. We conducted our studies in osteoblasts, which depend on both pRb and on cell-to-cell contacts for their differentiation and function. We generated knockout mice in which the RB gene was excised specifically in osteoblasts using the cre-lox P system and found that osteoblasts from pRb knockout mice did not assemble adherens junction at their membranes. pRb depletion in wild type osteoblasts using RNAi also disrupted adherens junctions. Microarrays comparing pRb-expressing and pRb-deficient osteoblasts showed that pRb controls the expression of a number of cell adhesion genes, including cadherins. Furthermore, pRb knockout mice showed bone abnormalities consistent with osteoblast adhesion defects. We also found that pRb controls the function of merlin, a well-known regulator of adherens junction assembly, by repressing Rac1 and its effector Pak1. Using qRT-PCR, immunoblots, co-immunoprecipitation assays, and immunofluorescent labeling, we observed that pRb loss resulted in Rac1 and Pak1 overexpression concomitant with merlin inactivation by Pak1, merlin detachment from the membrane, and adherens junction loss. Our data support a pRb function in cell adhesion while elucidating the mechanism for this function. Our work suggests that in some tumor types pRb inactivation results in both a loss of cell cycle control that promotes initial tumor growth as well as in a loss of cell-to-cell contacts, which contributes to later stages of metastasis.

  16. Septal Junctions in Filamentous Heterocyst-Forming Cyanobacteria.

    Science.gov (United States)

    Flores, Enrique; Herrero, Antonia; Forchhammer, Karl; Maldener, Iris

    2016-02-01

    In the filaments of heterocyst-forming cyanobacteria, septal junctions that traverse the septal peptidoglycan join adjacent cells, allowing intercellular communication. Perforations in the septal peptidoglycan have been observed, and proteins involved in the formation of such perforations and putative protein components of the septal junctions have been identified, but their relationships are debated.

  17. Characterization and significance of adhesion and junction-related proteins in mouse ovarian follicles.

    Science.gov (United States)

    Mora, Jocelyn M; Fenwick, Mark A; Castle, Laura; Baithun, Marianne; Ryder, Timothy A; Mobberley, Margaret; Carzaniga, Raffaella; Franks, Stephen; Hardy, Kate

    2012-05-01

    In the ovary, initiation of follicle growth is marked by cuboidalization of flattened granulosa cells (GCs). The regulation and cell biology of this shape change remains poorly understood. We propose that characterization of intercellular junctions and associated proteins is key to identifying as yet unknown regulators of this important transition. As GCs are conventionally described as epithelial cells, this study used mouse ovaries and isolated follicles to investigate epithelial junctional complexes (tight junctions [TJ], adherens junctions [AJ], and desmosomes) and associated molecules, as well as classic epithelial markers, by quantitative PCR and immunofluorescence. These junctions were further characterized using ultrastructural, calcium depletion and biotin tracer studies. Junctions observed by transmission electron microscopy between GCs and between GCs and oocyte were identified as AJs by expression of N-cadherin and nectin 2 and by the lack of TJ and desmosome-associated proteins. Follicles were also permeable to biotin, confirming a lack of functional TJs. Surprisingly, GCs lacked all epithelial markers analyzed, including E-cadherin, cytokeratin 8, and zonula occludens (ZO)-1alpha+. Furthermore, vimentin was expressed by GCs, suggesting a more mesenchymal phenotype. Under calcium-free conditions, small follicles maintained oocyte-GC contact, confirming the importance of calcium-independent nectin at this stage. However, in primary and multilayered follicles, lack of calcium resulted in loss of contact between GCs and oocyte, showing that nectin alone cannot maintain attachment between these two cell types. Lack of classic markers suggests that GCs are not epithelial. Identification of AJs during GC cuboidalization highlights the importance of AJs in regulating initiation of follicle growth.

  18. Assemble four-arm DNA junctions into nanoweb

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    DNA is of structural polymorphism, which is useful in nanoarchitecture; especially, four-arm DNA junc tions can be used to assemble nanowebs. The static four-arm DNA junctions were designed and synthesized. One-arm DNA and two-arm DNA came out simultaneously with the four-arm DNA junction's formation. A new method, termed the two-step method, was proposed and the productivity of four-arm DNA junctions was increased. A nanoweb was assembled successfully, but it showed irregularity itself. It was not the same as we expected. We consider that it is aresult from the flexibility of four-arm DNA junction.

  19. Basolateral junction proteins regulate competition for the follicle stem cell niche in the Drosophila ovary.

    Science.gov (United States)

    Kronen, Maria R; Schoenfelder, Kevin P; Klein, Allon M; Nystul, Todd G

    2014-01-01

    Epithelial stem cells are routinely lost or damaged during adult life and must therefore be replaced to maintain homeostasis. Recent studies indicate that stem cell replacement occurs through neutral competition in many types of epithelial tissues, but little is known about the factors that determine competitive outcome. The epithelial follicle stem cells (FSCs) in the Drosophila ovary are regularly lost and replaced during normal homeostasis, and we show that FSC replacement conforms to a model of neutral competition. In addition, we found that FSCs mutant for the basolateral junction genes, lethal giant larvae (lgl) or discs large (dlg), undergo a biased competition for niche occupancy characterized by increased invasion of neighboring FSCs and reduced loss. Interestingly, FSCs mutant for a third basolateral junction gene, scribble (scrib), do not exhibit biased competition, suggesting that Lgl and Dlg regulate niche competition through a Scrib-independent process. Lastly, we found that FSCs have a unique cell polarity characterized by broadly distributed adherens junctions and the lack of a mature apical domain. Collectively, these observations indicate that Lgl and Dlg promote the differentiation of FSC progeny to a state in which they are less prone to invade the neighboring niche. In addition, we demonstrate that the neutral drift model can be adapted to quantify non-neutral behavior of mutant clones.

  20. Basolateral junction proteins regulate competition for the follicle stem cell niche in the Drosophila ovary.

    Directory of Open Access Journals (Sweden)

    Maria R Kronen

    Full Text Available Epithelial stem cells are routinely lost or damaged during adult life and must therefore be replaced to maintain homeostasis. Recent studies indicate that stem cell replacement occurs through neutral competition in many types of epithelial tissues, but little is known about the factors that determine competitive outcome. The epithelial follicle stem cells (FSCs in the Drosophila ovary are regularly lost and replaced during normal homeostasis, and we show that FSC replacement conforms to a model of neutral competition. In addition, we found that FSCs mutant for the basolateral junction genes, lethal giant larvae (lgl or discs large (dlg, undergo a biased competition for niche occupancy characterized by increased invasion of neighboring FSCs and reduced loss. Interestingly, FSCs mutant for a third basolateral junction gene, scribble (scrib, do not exhibit biased competition, suggesting that Lgl and Dlg regulate niche competition through a Scrib-independent process. Lastly, we found that FSCs have a unique cell polarity characterized by broadly distributed adherens junctions and the lack of a mature apical domain. Collectively, these observations indicate that Lgl and Dlg promote the differentiation of FSC progeny to a state in which they are less prone to invade the neighboring niche. In addition, we demonstrate that the neutral drift model can be adapted to quantify non-neutral behavior of mutant clones.

  1. Slowdown promotes muscle integrity by modulating integrin-mediated adhesion at the myotendinous junction.

    Science.gov (United States)

    Gilsohn, Eliezer; Volk, Talila

    2010-03-01

    The correct assembly of the myotendinous junction (MTJ) is crucial for proper muscle function. In Drosophila, this junction comprises hemi-adherens junctions that are formed upon arrival of muscles at their corresponding tendon cells. The MTJ mainly comprises muscle-specific alphaPS2betaPS integrin receptors and their tendon-derived extracellular matrix ligand Thrombospondin (Tsp). We report the identification and functional analysis of a novel tendon-derived secreted protein named Slowdown (Slow). Homozygous slow mutant larvae exhibit muscle or tendon rupture, sluggish larval movement, partial lethality, and the surviving adult flies are unable to fly. These defects result from improper assembly of the embryonic MTJ. In slow mutants, Tsp prematurely accumulates at muscle ends, the morphology of the muscle leading edge changes and the MTJ architecture is aberrant. Slow was found to form a protein complex with Tsp. This complex is biologically active and capable of altering the morphology and directionality of muscle ends. Our analysis implicates Slow as an essential component of the MTJ, crucial for ensuring muscle and tendon integrity during larval locomotion.

  2. Equivalent Josephson junctions

    Science.gov (United States)

    Boyadjiev, T. L.; Semerdjieva, E. G.; Shukrinov, Yu. M.

    2008-01-01

    The magnetic field dependences of critical current are numerically constructed for a long Josephson junction with a shunt-or resistor-type microscopic inhomogeneities and compared to the critical curve of a junction with exponentially varying width. The numerical results show that it is adequate to replace the distributed inhomogeneity of a long Josephson junction by an inhomogeneity localized at one of its ends, which has certain technological advantages. It is also shown that the critical curves of junctions with exponentially varying width and inhomogeneities localized at the ends are unaffected by the mixed fluxon-antifluxon distributions of the magnetic flow. This fact may explain the improvement of the spectra of microwave radiation noted in the literature.

  3. Formats

    Directory of Open Access Journals (Sweden)

    Gehmann, Ulrich

    2012-03-01

    Full Text Available In the following, a new conceptual framework for investigating nowadays’ “technical” phenomena shall be introduced, that of formats. The thesis is that processes of formatting account for our recent conditions of life, and will do so in the very next future. It are processes whose foundations have been laid in modernity and which will further unfold for the time being. These processes are embedded in the format of the value chain, a circumstance making them resilient to change. In addition, they are resilient in themselves since forming interconnected systems of reciprocal causal circuits.Which leads to an overall situation that our entire “Lebenswelt” became formatted to an extent we don’t fully realize, even influencing our very percep-tion of it.

  4. Quantum Junction Solar Cells

    KAUST Repository

    Tang, Jiang

    2012-09-12

    Colloidal quantum dot solids combine convenient solution-processing with quantum size effect tuning, offering avenues to high-efficiency multijunction cells based on a single materials synthesis and processing platform. The highest-performing colloidal quantum dot rectifying devices reported to date have relied on a junction between a quantum-tuned absorber and a bulk material (e.g., TiO 2); however, quantum tuning of the absorber then requires complete redesign of the bulk acceptor, compromising the benefits of facile quantum tuning. Here we report rectifying junctions constructed entirely using inherently band-aligned quantum-tuned materials. Realizing these quantum junction diodes relied upon the creation of an n-type quantum dot solid having a clean bandgap. We combine stable, chemically compatible, high-performance n-type and p-type materials to create the first quantum junction solar cells. We present a family of photovoltaic devices having widely tuned bandgaps of 0.6-1.6 eV that excel where conventional quantum-to-bulk devices fail to perform. Devices having optimal single-junction bandgaps exhibit certified AM1.5 solar power conversion efficiencies of 5.4%. Control over doping in quantum solids, and the successful integration of these materials to form stable quantum junctions, offers a powerful new degree of freedom to colloidal quantum dot optoelectronics. © 2012 American Chemical Society.

  5. A vertex model of Drosophila ventral furrow formation.

    Directory of Open Access Journals (Sweden)

    Philipp Spahn

    Full Text Available Ventral furrow formation in Drosophila is an outstanding model system to study the mechanisms involved in large-scale tissue rearrangements. Ventral cells accumulate myosin at their apical sides and, while being tightly coupled to each other via apical adherens junctions, execute actomyosin contractions that lead to reduction of their apical cell surface. Thereby, a band of constricted cells along the ventral epithelium emerges which will form a tissue indentation along the ventral midline (the ventral furrow. Here we adopt a 2D vertex model to simulate ventral furrow formation in a surface view allowing easy comparison with confocal live-recordings. We show that in order to reproduce furrow morphology seen in vivo, a gradient of contractility must be assumed in the ventral epithelium which renders cells more contractile the closer they lie to the ventral midline. The model predicts previous experimental findings, such as the gain of eccentric morphology of constricting cells and an incremental fashion of apical cell area reduction. Analysis of the model suggests that this incremental area reduction is caused by the dynamical interplay of cell elasticity and stochastic contractility as well as by the opposing forces from contracting neighbour cells. We underpin results from the model through in vivo analysis of ventral furrow formation in wildtype and twi mutant embryos. Our results show that ventral furrow formation can be accomplished as a "tug-of-war" between stochastically contracting, mechanically coupled cells and may require less rigorous regulation than previously thought.For the developmental biologist it is a fascinating question how cells can coordinate major tissue movements during embryonic development. The so-called ventral furrow of the Drosophila embryo is a well-studied example of such a process when cells from a ventral band, spanning nearly the entire length of the embryo, undergo dramatic shape change by contracting their

  6. Instigation of endothelial Nlrp3 inflammasome by adipokine visfatin promotes inter-endothelial junction disruption: role of HMGB1.

    Science.gov (United States)

    Chen, Yang; Pitzer, Ashley L; Li, Xiang; Li, Pin-Lan; Wang, Lei; Zhang, Yang

    2015-12-01

    Recent studies have indicated that the inflammasome plays a critical role in the pathogenesis of vascular diseases. However, the pathological relevance of this inflammasome activation, particularly in vascular cells, remains largely unknown. Here, we investigated the role of endothelial (Nucleotide-binding Oligomerization Domain) NOD-like receptor family pyrin domain containing three (Nlrp3) inflammasomes in modulating inter-endothelial junction proteins, which are associated with endothelial barrier dysfunction, an early onset of obesity-associated endothelial injury. Our findings demonstrate that the activation of Nlrp3 inflammasome by visfatin markedly decreased the expression of inter-endothelial junction proteins including tight junction proteins ZO-1, ZO-2 and occludin, and adherens junction protein VE-cadherin in cultured mouse vascular endothelial (VE) cell monolayers. Such visfatin-induced down-regulation of junction proteins in endothelial cells was attributed to high mobility group box protein 1 (HMGB1) release derived from endothelial inflammasome-dependent caspase-1 activity. Similarly, in the coronary arteries of wild-type mice, high-fat diet (HFD) treatment caused a down-regulation of inter-endothelial junction proteins ZO-1, ZO-2, occludin and VE-cadherin, which was accompanied with enhanced inflammasome activation and HMGB1 expression in the endothelium as well as transmigration of CD43(+) T cells into the coronary arterial wall. In contrast, all these HFD-induced alterations in coronary arteries were prevented in mice with Nlrp3 gene deletion. Taken together, these data strongly suggest that the activation of endothelial Nlrp3 inflammasomes as a result of the increased actions of injurious adipokines such as visfatin produces HMGB1, which act in paracrine or autocrine fashion to disrupt inter-endothelial junctions and increase paracellular permeability of the endothelium contributing to the early onset of endothelial injury during metabolic

  7. Dislocation Multi-junctions and Strain Hardening

    Energy Technology Data Exchange (ETDEWEB)

    Bulatov, V; Hsiung, L; Tang, M; Arsenlis, A; Bartelt, M; Cai, W; Florando, J; Hiratani, M; Rhee, M; Hommes, G; Pierce, T; Diaz de la Rubia, T

    2006-06-20

    At the microscopic scale, the strength of a crystal derives from the motion, multiplication and interaction of distinctive line defects--dislocations. First theorized in 1934 to explain low magnitudes of crystal strength observed experimentally, the existence of dislocations was confirmed only two decades later. Much of the research in dislocation physics has since focused on dislocation interactions and their role in strain hardening: a common phenomenon in which continued deformation increases a crystal's strength. The existing theory relates strain hardening to pair-wise dislocation reactions in which two intersecting dislocations form junctions tying dislocations together. Here we report that interactions among three dislocations result in the formation of unusual elements of dislocation network topology, termed hereafter multi-junctions. The existence of multi-junctions is first predicted by Dislocation Dynamics (DD) and atomistic simulations and then confirmed by the transmission electron microscopy (TEM) experiments in single crystal molybdenum. In large-scale Dislocation Dynamics simulations, multi-junctions present very strong, nearly indestructible, obstacles to dislocation motion and furnish new sources for dislocation multiplication thereby playing an essential role in the evolution of dislocation microstructure and strength of deforming crystals. Simulation analyses conclude that multi-junctions are responsible for the strong orientation dependence of strain hardening in BCC crystals.

  8. Endoplasmic reticulum-plasma membrane junctions: structure, function and dynamics.

    Science.gov (United States)

    Okeke, Emmanuel; Dingsdale, Hayley; Parker, Tony; Voronina, Svetlana; Tepikin, Alexei V

    2016-06-01

    Endoplasmic reticulum (ER)-plasma membrane (PM) junctions are contact sites between the ER and the PM; the distance between the two organelles in the junctions is below 40 nm and the membranes are connected by protein tethers. A number of molecular tools and technical approaches have been recently developed to visualise, modify and characterise properties of ER-PM junctions. The junctions serve as the platforms for lipid exchange between the organelles and for cell signalling, notably Ca(2+) and cAMP signalling. Vice versa, signalling events regulate the development and properties of the junctions. Two Ca(2+) -dependent mechanisms of de novo formation of ER-PM junctions have been recently described and characterised. The junction-forming proteins and lipids are currently the focus of vigorous investigation. Junctions can be relatively short-lived and simple structures, forming and dissolving on the time scale of a few minutes. However, complex, sophisticated and multifunctional ER-PM junctions, capable of attracting numerous protein residents and other cellular organelles, have been described in some cell types. The road from simplicity to complexity, i.e. the transformation from simple 'nascent' ER-PM junctions to advanced stable multiorganellar complexes, is likely to become an attractive research avenue for current and future junctologists. Another area of considerable research interest is the downstream cellular processes that can be activated by specific local signalling events in the ER-PM junctions. Studies of the cell physiology and indeed pathophysiology of ER-PM junctions have already produced some surprising discoveries, likely to expand with advances in our understanding of these remarkable organellar contact sites. © 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.

  9. Ephrin-Bs Drive Junctional Downregulation and Actin Stress Fiber Disassembly to Enable Wound Re-epithelialization.

    Science.gov (United States)

    Nunan, Robert; Campbell, Jessica; Mori, Ryoichi; Pitulescu, Mara E; Jiang, Wen G; Harding, Keith G; Adams, Ralf H; Nobes, Catherine D; Martin, Paul

    2015-11-17

    For a skin wound to successfully heal, the cut epidermal-edge cells have to migrate forward at the interface between scab and healthy granulation tissue. Much is known about how lead-edge cells migrate, but very little is known about the mechanisms that enable active participation by cells further back. Here we show that ephrin-B1 and its receptor EphB2 are both upregulated in vivo, just for the duration of repair, in the first 70 or so rows of epidermal cells, and this signal leads to downregulation of the molecular components of adherens and tight (but not desmosomal) junctions, leading to loosening between neighbors and enabling shuffle room among epidermal cells. Additionally, this signaling leads to the shutdown of actomyosin stress fibers in these same epidermal cells, which may act to release tension within the wound monolayer. If this signaling axis is perturbed, then disrupted healing is a consequence in mouse and man.

  10. The human myotendinous junction

    DEFF Research Database (Denmark)

    Knudsen, A B; Larsen, M; Mackey, Abigail

    2015-01-01

    The myotendinous junction (MTJ) is a specialized structure in the musculotendinous system, where force is transmitted from muscle to tendon. Animal models have shown that the MTJ takes form of tendon finger-like processes merging with muscle tissue. The human MTJ is largely unknown and has never ...

  11. Junction trees of general graphs

    Institute of Scientific and Technical Information of China (English)

    Xiaofei WANG; Jianhua GUO

    2008-01-01

    In this paper,we study the maximal prime subgraphs and their corresponding structure for any undirected graph.We introduce the notion of junction trees and investigate their structural characteristics,including junction properties,induced-subtree properties,running-intersection properties and maximum-weight spanning tree properties.Furthermore,the characters of leaves and edges on junction trees are discussed.

  12. Mechanical tugging force regulates the size of cell–cell junctions

    Science.gov (United States)

    Liu, Zhijun; Tan, John L.; Cohen, Daniel M.; Yang, Michael T.; Sniadecki, Nathan J.; Ruiz, Sami Alom; Nelson, Celeste M.; Chen, Christopher S.

    2010-01-01

    Actomyosin contractility affects cellular organization within tissues in part through the generation of mechanical forces at sites of cell–matrix and cell–cell contact. While increased mechanical loading at cell–matrix adhesions results in focal adhesion growth, whether forces drive changes in the size of cell–cell adhesions remains an open question. To investigate the responsiveness of adherens junctions (AJ) to force, we adapted a system of microfabricated force sensors to quantitatively report cell–cell tugging force and AJ size. We observed that AJ size was modulated by endothelial cell–cell tugging forces: AJs and tugging force grew or decayed with myosin activation or inhibition, respectively. Myosin-dependent regulation of AJs operated in concert with a Rac1, and this coordinated regulation was illustrated by showing that the effects of vascular permeability agents (S1P, thrombin) on junctional stability were reversed by changing the extent to which these agents coupled to the Rac and myosin-dependent pathways. Furthermore, direct application of mechanical tugging force, rather than myosin activity per se, was sufficient to trigger AJ growth. These findings demonstrate that the dynamic coordination of mechanical forces and cell–cell adhesive interactions likely is critical to the maintenance of multicellular integrity and highlight the need for new approaches to study tugging forces. PMID:20463286

  13. Tight junction modulation of the blood brain barrier: CNS delivery of small molecules.

    Science.gov (United States)

    Greene, Chris; Campbell, Matthew

    2016-01-01

    The blood brain barrier (BBB) represents a major obstacle for targeted drug delivery to the brain for the treatment of central nervous system (CNS) disorders. Significant advances in barrier research over the past decade has led to the discovery of an increasing number of structural and regulatory proteins in tight junctions (TJ) and adherens junctions (AJ). These discoveries are providing the framework for the development of novel TJ modulators which can act specifically and temporarily to alter BBB function and regulate paracellular uptake of molecules. TJ modulators that have shown therapeutic potential in preclinical models include claudin-5 and occludin siRNAs, peptides derived from zonula occludens toxin as well as synthetic peptides targeting the extracellular loops of TJs. Adding to the array of modulating agents are novel mechanisms of BBB regulation such as focused ultrasound (FUS). This review will give a succinct overview of BBB biology and TJ modulation in general. Novel insights into BBB regulation in health and disease will also be summarized.

  14. The stardust family protein MPP7 forms a tripartite complex with LIN7 and DLG1 that regulates the stability and localization of DLG1 to cell junctions.

    Science.gov (United States)

    Bohl, Joanna; Brimer, Nicole; Lyons, Charles; Vande Pol, Scott B

    2007-03-30

    MPP7, a previously uncharacterized member of the p55 Stardust family of membrane-associated guanylate kinase (MAGUK) proteins, was found in a tripartite complex with DLG1 and LIN7A or LIN7C. MPP7 dimerizes with all three LIN7 family members (LIN7A, -B, and -C) through interaction of the single L27 domain of LIN7 with the carboxyl-terminal L27 domain of MPP7, thereby stabilizing both proteins. The dimer of MPP7 with LIN7A or LIN7C associates with DLG1 through an interaction requiring the amino-terminal L27 domain of MPP7. The amino-terminal L27 domain of MPP7 is not sufficient for interaction with DLG1 but interacts efficiently only if MPP7 is in a complex with LIN7A or -C. Thus the specificity of interaction of DLG1 with the LIN7-MPP7 complex is determined by L27 interactions with both MPP7 and LIN7. The tripartite complex forms in a ratio of 1:1:1 and localizes to epithelial adherens junctions in a manner dependent upon MPP7. Expression of MPP7 stabilizes DLG1 in an insoluble compartment. Expression of MPP7 deleted of the PDZ or Src homology 3 domain redistributes MPP7, DLG1, and LIN7 out of adherens junctions and into the soluble cytoplasmic fraction without changing the localization of E-cadherin. Thus, the stability and localization of DLG1 to cell-cell junctions are complex functions determined by the expression and association of particular Stardust family members together with particular LIN7 family members.

  15. Holliday junction resolvases.

    Science.gov (United States)

    Wyatt, Haley D M; West, Stephen C

    2014-09-02

    Four-way DNA intermediates, called Holliday junctions (HJs), can form during meiotic and mitotic recombination, and their removal is crucial for chromosome segregation. A group of ubiquitous and highly specialized structure-selective endonucleases catalyze the cleavage of HJs into two disconnected DNA duplexes in a reaction called HJ resolution. These enzymes, called HJ resolvases, have been identified in bacteria and their bacteriophages, archaea, and eukaryotes. In this review, we discuss fundamental aspects of the HJ structure and their interaction with junction-resolving enzymes. This is followed by a brief discussion of the eubacterial RuvABC enzymes, which provide the paradigm for HJ resolvases in other organisms. Finally, we review the biochemical and structural properties of some well-characterized resolvases from archaea, bacteriophage, and eukaryotes. Copyright © 2014 Cold Spring Harbor Laboratory Press; all rights reserved.

  16. Wireless Josephson Junction Arrays

    Science.gov (United States)

    Adams, Laura

    2015-03-01

    We report low temperature, microwave transmission measurements on a wireless two- dimensional network of Josephson junction arrays composed of superconductor-insulator -superconductor tunnel junctions. Unlike their biased counterparts, by removing all electrical contacts to the arrays and superfluous microwave components and interconnects in the transmission line, we observe new collective behavior in the transmission spectra. In particular we will show emergent behavior that systematically responds to changes in microwave power at fixed temperature. Likewise we will show the dynamic and collective response of the arrays while tuning the temperature at fixed microwave power. We discuss these spectra in terms of the Berezinskii-Kosterlitz-Thouless phase transition and Shapiro steps. We gratefully acknowledge the support Prof. Steven Anlage at the University of Maryland and Prof. Allen Goldman at the University of Minnesota. Physics and School of Engineering and Applied Sciences.

  17. String networks with junctions in competition models

    Science.gov (United States)

    Avelino, P. P.; Bazeia, D.; Losano, L.; Menezes, J.; de Oliveira, B. F.

    2017-03-01

    In this work we give specific examples of competition models, with six and eight species, whose three-dimensional dynamics naturally leads to the formation of string networks with junctions, associated with regions that have a high concentration of enemy species. We study the two- and three-dimensional evolution of such networks, both using stochastic network and mean field theory simulations. If the predation, reproduction and mobility probabilities do not vary in space and time, we find that the networks attain scaling regimes with a characteristic length roughly proportional to t 1 / 2, where t is the physical time, thus showing that the presence of junctions, on its own, does not have a significant impact on their scaling properties.

  18. String networks with junctions in competition models

    CERN Document Server

    Avelino, P P; Losano, L; Menezes, J; de Oliveira, B F

    2016-01-01

    In this work we give specific examples of competition models, with six and eight species, whose three-dimensional dynamics naturally leads to the formation of string networks with junctions, associated with regions that have a high concentration of enemy species. We study the two- and three-dimensional evolution of such networks, both using stochastic network and mean field theory simulations. If the predation, reproduction and mobility probabilities do not vary in space and time, we find that the networks attain scaling regimes with a characteristic length roughly proportional to $t^{1/2}$, where $t$ is the physical time, thus showing that the presence of junctions, on its own, does not have a significant impact on their scaling properties.

  19. An induced junction photovoltaic cell

    Science.gov (United States)

    Call, R. L.

    1974-01-01

    Silicon solar cells operating with induced junctions rather than diffused junctions have been fabricated and tested. Induced junctions were created by forming an inversion layer near the surface of the silicon by supplying a sheet of positive charge above the surface. Measurements of the response of the inversion layer cell to light of different wavelengths indicated it to be more sensitive to the shorter wavelengths of the sun's spectrum than conventional cells. The greater sensitivity occurs because of the shallow junction and the strong electric field at the surface.

  20. Mixing in T-junctions

    NARCIS (Netherlands)

    Kok, Jacobus B.W.; van der Wal, S.

    1996-01-01

    The transport processes that are involved in the mixing of two gases in a T-junction mixer are investigated. The turbulent flow field is calculated for the T-junction with the k- turbulence model by FLOW3D. In the mathematical model the transport of species is described with a mixture fraction

  1. Low-Frequency Noise Characterization of Ultra-shallow Gate N-channel Junction Field Effect Transistors

    NARCIS (Netherlands)

    Piccolo, G.; Sarubbi, F.; Vandamme, L.J.K.; Macucci, M.; Scholtes, T.L.M.; Nanver, L.K.

    2007-01-01

    A recently developed technique for ultra shallow pn junction formation has been applied for the fabrication of ring-gate n-channel junction field effect devices (JFET) devices. Several different geometries, gate formation parameters and channel doping profiles have been realized and characterized wi

  2. Metallic Junction Thermoelectric Device Simulations

    Science.gov (United States)

    Duzik, Adam J.; Choi, Sang H.

    2017-01-01

    Thermoelectric junctions made of semiconductors have existed in radioisotope thermoelectric generators (RTG) for deep space missions, but are currently being adapted for terrestrial energy harvesting. Unfortunately, these devices are inefficient, operating at only 7% efficiency. This low efficiency has driven efforts to make high-figure-of-merit thermoelectric devices, which require a high electrical conductivity but a low thermal conductivity, a combination that is difficult to achieve. Lowered thermal conductivity has increased efficiency, but at the cost of power output. An alternative setup is to use metallic junctions rather than semiconductors as thermoelectric devices. Metals have orders of magnitude more electrons and electronic conductivities higher than semiconductors, but thermal conductivity is higher as well. To evaluate the viability of metallic junction thermoelectrics, a two dimensional heat transfer MATLAB simulation was constructed to calculate efficiency and power output. High Seebeck coefficient alloys, Chromel (90%Ni-10%Cr) and Constantan (55%Cu-45%Ni), produced efficiencies of around 20-30%. Parameters such as the number of layers of junctions, lateral junction density, and junction sizes for both series- and parallel-connected junctions were explored.

  3. High-speed carrier-depletion silicon Mach-Zehnder optical modulators with lateral PN junctions

    Directory of Open Access Journals (Sweden)

    Graham Trevor Reed

    2014-12-01

    Full Text Available This paper presents new experimental data from a lateral PN junction silicon Mach-Zehnder optical modulator. Efficiencies in the 1.4V.cm to 1.9V.cm range are demonstrated for drive voltages between 0V and 6V. High speed operation up to 52Gbit/s is also presented. The performance of the device which has its PN junction positioned in the centre of the waveguide is then compared to previously reported data from a lateral PN junction device with the junction self-aligned to the edge of the waveguide rib. An improvement in modulation efficiency is demonstrated when the junction is positioned in the centre of the waveguide. Finally we propose schemes for achieving high modulation efficiency whilst retaining self-aligned formation of the PN junction.

  4. Breakdown of interlocking domains may contribute to formation of membranous globules and lens opacity in ephrin-A5(-/-) mice.

    Science.gov (United States)

    Biswas, Sondip; Son, Alexander; Yu, Qili; Zhou, Renping; Lo, Woo-Kuen

    2016-04-01

    further suggest that dissociations of N-cadherin and adherens junctions in the associated interlocking domains may result in the formation of isolated globules and nuclear opacities in the ephrin-A5(-/-) mice.

  5. Dissecting contact mechanics from quantum interference in single-molecule junctions of stilbene derivatives.

    Science.gov (United States)

    Aradhya, Sriharsha V; Meisner, Jeffrey S; Krikorian, Markrete; Ahn, Seokhoon; Parameswaran, Radha; Steigerwald, Michael L; Nuckolls, Colin; Venkataraman, Latha

    2012-03-14

    Electronic factors in molecules such as quantum interference and cross-conjugation can lead to dramatic modulation and suppression of conductance in single-molecule junctions. Probing such effects at the single-molecule level requires simultaneous measurements of independent junction properties, as conductance alone cannot provide conclusive evidence of junction formation for molecules with low conductivity. Here, we compare the mechanics of the conducting para-terminated 4,4'-di(methylthio)stilbene and moderately conducting 1,2-bis(4-(methylthio)phenyl)ethane to that of insulating meta-terminated 3,3'-di(methylthio)stilbene single-molecule junctions. We simultaneously measure force and conductance across single-molecule junctions and use force signatures to obtain independent evidence of junction formation and rupture in the meta-linked cross-conjugated molecule even when no clear low-bias conductance is measured. By separately quantifying conductance and mechanics, we identify the formation of atypical 3,3'-di(methylthio)stilbene molecular junctions that are mechanically stable but electronically decoupled. While theoretical studies have envisaged many plausible systems where quantum interference might be observed, our experiments provide the first direct quantitative study of the interplay between contact mechanics and the distinctively quantum mechanical nature of electronic transport in single-molecule junctions.

  6. Imaging of cervicothoracic junction trauma

    Directory of Open Access Journals (Sweden)

    Wongwaisayawan S

    2013-01-01

    Full Text Available Sirote Wongwaisayawan,1 Ruedeekorn Suwannanon,2 Rathachai Kaewlai11Department of Radiology, Ramathibodi Hospital and Mahidol University, Bangkok, Thailand; 2Department of Radiology, Faculty of Medicine, Prince of Songkla University, Hat Yai, ThailandAbstract: Cervicothoracic junction trauma is an important cause of morbidity and mortality in trauma patients. Imaging has played an important role in identifying injuries and guiding appropriate, timely therapy. Computed tomography is currently a method of choice for diagnosing cervicothoracic junction trauma, in which the pattern of injuries often suggests possible mechanisms and potential injuries. In this article, the authors describe and illustrate common and uncommon injuries that can occur in the cervicothoracic junction.Keywords: cervicothoracic junction, cervical spine, trauma, imaging, radiology

  7. Demonstrated Anomalous Pancreaticobiliary Ductal Junction

    OpenAIRE

    Koçkar, Cem; ?ENOL, Altu?; BA?TÜRK, Abdulkadir; AYDIN, Bünyamin; Cüre, Erkan

    2015-01-01

    Anomalies of the pancreaticobiliary junction are rare. Clinically anomalies of the pancreaticobiliary junction are uncommonly symptomatic but may present themselves with associated conditions ranging from benign acute abdominal pain to carcinomas. A 52 years old man was admitted to gastroenterology service with complaints of fever, nausea, vomiting and recurrent epigastric pain. He was diagnosed with biliary pancreatitis. Endoscopic retrograde cholangiopancreato-graphy was performed. Papilla ...

  8. Josephson junctions with ferromagnetic interlayer

    Energy Technology Data Exchange (ETDEWEB)

    Wild, Georg Hermann

    2012-03-04

    We report on the fabrication of superconductor/insulator/ferromagnetic metal/superconductor (Nb/AlO{sub x}/Pd{sub 0.82}Ni{sub 0.18}/Nb) Josephson junctions (SIFS JJs) with high critical current densities, large normal resistance times area products, and high quality factors. For these junctions, a transition from 0- to {pi}-coupling is observed for a thickness d{sub F}=6 nm of the ferromagnetic Pd{sub 0.82}Ni{sub 0.18} interlayer. The magnetic field dependence of the critical current of the junctions demonstrates good spatial homogeneity of the tunneling barrier and ferromagnetic interlayer. Magnetic characterization shows that the Pd{sub 0.82}Ni{sub 0.18} has an out-of-plane anisotropy and large saturation magnetization indicating negligible dead layers at the interfaces. A careful analysis of Fiske modes up to about 400 GHz provides valuable information on the junction quality factor and the relevant damping mechanisms. Whereas losses due to quasiparticle tunneling dominate at low frequencies, at high frequencies the damping is explained by the finite surface resistance of the junction electrodes. High quality factors of up to 30 around 200 GHz have been achieved. They allow to study the junction dynamics, in particular the switching probability from the zero-voltage into the voltage state with and without microwave irradiation. The experiments with microwave irradiation are well explained within semi-classical models and numerical simulations. In contrast, at mK temperature the switching dynamics without applied microwaves clearly shows secondary quantum effects. Here, we could observe for the first time macroscopic quantum tunneling in Josephson junctions with a ferromagnetic interlayer. This observation excludes fluctuations of the critical current as a consequence of an unstable magnetic domain structure of the ferromagnetic interlayer and affirms the suitability of SIFS Josephson junctions for quantum information processing.

  9. Electronic thermometry in tunable tunnel junction

    Energy Technology Data Exchange (ETDEWEB)

    Maksymovych, Petro

    2016-03-15

    A tunable tunnel junction thermometry circuit includes a variable width tunnel junction between a test object and a probe. The junction width is varied and a change in thermovoltage across the junction with respect to the change in distance across the junction is determined. Also, a change in biased current with respect to a change in distance across the junction is determined. A temperature gradient across the junction is determined based on a mathematical relationship between the temperature gradient, the change in thermovoltage with respect to distance and the change in biased current with respect to distance. Thermovoltage may be measured by nullifying a thermoelectric tunneling current with an applied voltage supply level. A piezoelectric actuator may modulate the probe, and thus the junction width, to vary thermovoltage and biased current across the junction. Lock-in amplifiers measure the derivatives of the thermovoltage and biased current modulated by varying junction width.

  10. Confocal Annular Josephson Tunnel Junctions

    Science.gov (United States)

    Monaco, Roberto

    2016-09-01

    The physics of Josephson tunnel junctions drastically depends on their geometrical configurations and here we show that also tiny geometrical details play a determinant role. More specifically, we develop the theory of short and long annular Josephson tunnel junctions delimited by two confocal ellipses. The behavior of a circular annular Josephson tunnel junction is then seen to be simply a special case of the above result. For junctions having a normalized perimeter less than one, the threshold curves in the presence of an in-plane magnetic field of arbitrary orientations are derived and computed even in the case with trapped Josephson vortices. For longer junctions, a numerical analysis is carried out after the derivation of the appropriate motion equation for the Josephson phase. We found that the system is modeled by a modified and perturbed sine-Gordon equation with a space-dependent effective Josephson penetration length inversely proportional to the local junction width. Both the fluxon statics and dynamics are deeply affected by the non-uniform annulus width. Static zero-field multiple-fluxon solutions exist even in the presence of a large bias current. The tangential velocity of a traveling fluxon is not determined by the balance between the driving and drag forces due to the dissipative losses. Furthermore, the fluxon motion is characterized by a strong radial inward acceleration which causes electromagnetic radiation concentrated at the ellipse equatorial points.

  11. Octagonal Defects at Carbon Nanotube Junctions

    Science.gov (United States)

    Jaskólski, W.; Pelc, M.; Chico, Leonor; Ayuela, A.

    2013-01-01

    We investigate knee-shaped junctions of semiconductor zigzag carbon nanotubes. Two dissimilar octagons appear at such junctions; one of them can reconstruct into a pair of pentagons. The junction with two octagons presents two degenerate localized states at Fermi energy (EF). The reconstructed junction has only one state near EF, indicating that these localized states are related to the octagonal defects. The inclusion of Coulomb interaction splits the localized states in the junction with two octagons, yielding an antiferromagnetic system. PMID:24089604

  12. N-glycosylation controls the function of junctional adhesion molecule-A.

    Science.gov (United States)

    Scott, David W; Tolbert, Caitlin E; Graham, David M; Wittchen, Erika; Bear, James E; Burridge, Keith

    2015-09-15

    Junctional adhesion molecule-A (JAM-A) is an adherens and tight junction protein expressed by endothelial and epithelial cells. JAM-A serves many roles and contributes to barrier function and cell migration and motility, and it also acts as a ligand for the leukocyte receptor LFA-1. JAM-A is reported to contain N-glycans, but the extent of this modification and its contribution to the protein's functions are unknown. We show that human JAM-A contains a single N-glycan at N185 and that this residue is conserved across multiple mammalian species. A glycomutant lacking all N-glycans, N185Q, is able to reach the cell surface but exhibits decreased protein half-life compared with the wild- type protein. N-glycosylation of JAM-A is required for the protein's ability to reinforce barrier function and contributes to Rap1 activity. We further show that glycosylation of N185 is required for JAM-A-mediated reduction of cell migration. Finally, we show that N-glycosylation of JAM-A regulates leukocyte adhesion and LFA-1 binding. These findings identify N-glycosylation as critical for JAM-A's many functions. © 2015 Scott et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

  13. Single Molecule Junctions: Probing Contact Chemistry and Fundamental Circuit Laws

    Energy Technology Data Exchange (ETDEWEB)

    Hybertsen M. S.

    2013-04-11

    By exploiting selective link chemistry, formation of single molecule junctions with reproducible conductance has become established. Systematic studies reveal the structure-conductance relationships for diverse molecules. I will draw on experiments from my collaborators at Columbia University, atomic-scale calculations and theory to describe progress in two areas. First, I will describe a novel route to form single molecule junctions, based on SnMe3 terminated molecules, in which gold directly bonds to carbon in the molecule backbone resulting in near ideal contact resistance [1]. Second, comparison of the conductance of junctions formed with molecular species containing either one backbone or two backbones in parallel allows demonstration of the role of quantum interference in the conductance superposition law at the molecular scale [2].

  14. Oxygen adsorption at noble metal/TiO2 junctions

    Science.gov (United States)

    Hossein-Babaei, F.; Alaei-Sheini, Navid; Lajvardi, Mehdi M.

    2016-03-01

    Electric conduction in titanium dioxide is known to be oxygen sensitive and the conductivity of a TiO2 ceramic body is determined mainly by the concentration of its naturally occurring oxygen vacancy. Recently, fabrications and electronic features of a number of noble metal/TiO2-based electronic devices, such as solar cells, UV detectors, gas sensors and memristive devices have been demonstrated. Here, we investigate the effect of oxygen adsorption at the noble metal/TiO2 junction in such devices, and show the potentials of these junctions in chemical sensor fabrication. The polycrystalline, poly-phase TiO2 layers are grown by the selective and controlled oxidation of titanium thin films vacuum deposited on silica substrates. Noble metal thin films are deposited on the oxide layers by physical vapor deposition. Current-voltage (I-V) diagrams of the fabricated devices are studied for Ag/, Au/, and Pt/TiO2 samples. The raw samples show no junction energy barrier. After a thermal annealing in air at 250° C, I-V diagrams change drastically. The annealed samples demonstrate highly non-linear I-V indicating the formation of high Schottky energy barriers at the noble metal/TiO2 junctions. The phenomenon is described based on the effect of the oxygen atoms adsorbed at the junction.

  15. Modelling of Dual-Junction Solar Cells including Tunnel Junction

    Directory of Open Access Journals (Sweden)

    Abdelaziz Amine

    2013-01-01

    Full Text Available Monolithically stacked multijunction solar cells based on III–V semiconductors materials are the state-of-art of approach for high efficiency photovoltaic energy conversion, in particular for space applications. The individual subcells of the multi-junction structure are interconnected via tunnel diodes which must be optically transparent and connect the component cells with a minimum electrical resistance. The quality of these diodes determines the output performance of the solar cell. The purpose of this work is to contribute to the investigation of the tunnel electrical resistance of such a multi-junction cell through the analysis of the current-voltage (J-V characteristics under illumination. Our approach is based on an equivalent circuit model of a diode for each subcell. We examine the effect of tunnel resistance on the performance of a multi-junction cell using minimization of the least squares technique.

  16. Investigation of Junction Properties of CdS/CdTe Solar Cells and their Correlation to Device Properties (Presentation)

    Energy Technology Data Exchange (ETDEWEB)

    Dhere, R. G.; Zhang, Y.; Romero, M. J.; Asher, S. E.; Young, M.; To, B.; Noufi, R.; Gessert, T. A.

    2008-05-01

    The objective of the Junction Studies are: (1) understand the nature of the junction in the CdTe/CdS device; (2) correlate the device fabrication parameters to the junction formation; and (3) develop a self consistent device model to explain the device properties. Detailed analysis of CdS/CdTe and SnO{sub 2}/CdTe devices prepared using CSS CdTe is discussed.

  17. Tight junction disruption induced by type 3 secretion system effectors injected by Enteropathogenic and Enterohemorrhagic Escherichia coli

    Directory of Open Access Journals (Sweden)

    Paul Ugalde-Silva

    2016-08-01

    Full Text Available The intestinal epithelium consists of a single cell layer, which is a critical selectively permeable barrier to both absorb nutrients and avoid the entry of potentially harmful entities, including microorganisms. Epithelial cells are held together by the apical junctional complexes, consisting of adherens junctions and tight junctions (TJs, and by underlying desmosomes. TJs lay in the apical domain of epithelial cells and are mainly composed by transmembrane proteins such as occludin, claudins, JAMs, and tricellulin, that are associated with the cytoplasmic plaque formed by proteins from the MAGUK family, such as ZO-1/2/3, connecting TJ to the actin cytoskeleton, and cingulin and paracingulin connecting TJ to the microtubule network. Extracellular bacteria such as EPEC and EHEC living in the intestinal lumen inject effectors proteins directly from the bacterial cytoplasm to the host cell cytoplasm, where they play a relevant role in the manipulation of the eukaryotic cell functions by modifying or blocking cell signaling pathways. TJ integrity depends on various cell functions such as actin cytoskeleton, microtubule network for vesicular trafficking, membrane integrity, inflammation, and cell survival. EPEC and EHEC effectors target most of these functions. Effectors encoded inside or outside of locus of enterocyte effacement (LEE disrupt the TJ strands. EPEC and EHEC exploit the TJ dynamics to open this structure, for causing diarrhea. EPEC and EHEC secrete effectors that mimic host proteins to manipulate the signaling pathways, including those related to TJ dynamics. In this review, we focus on the known mechanisms exploited by EPEC and EHEC effectors for causing TJ disruption.

  18. Electron Transport through Porphyrin Molecular Junctions

    Science.gov (United States)

    Zhou, Qi

    The goal of this work is to study the properties that would affect the electron transport through a porphyrin molecular junction. This work contributes to the field of electron transport in molecular junctions in the following 3 aspects. First of all, by carrying out experiments comparing the conductance of the iron (III) porphyrin (protected) and the free base porphyrin (protected), it is confirmed that the molecular energy level broadening and shifting occurs for porphyrin molecules when coupled with the metal electrodes, and this level broadening and shifting plays an important role in the electron transport through molecular junctions. Secondly, by carrying out an in-situ deprotection of the acetyl-protected free base porphyrin molecules, it is found out that the presence of acetyl groups reduces the conductance. Thirdly, by incorporating the Matrix-assisted laser desorption/ionization (MALDI) spectrum and the in-situ deprotection prior to formation of molecular junctions, it allows a more precise understanding of the molecules involved in the formation of molecular junctions, and therefore allows an accurate analysis of the conductance histogram. The molecules are prepared by self-assembly and the junctions are formed using a Scanning Tunneling Microscopy (STM) molecular break junction technique. The porphyrin molecules are characterized by MALDI in solution before self-assembly to a gold/mica substrate. The self-assembled monolayers (SAMs) of porphyrins on gold are characterized by Ultraviolet-visible (UV-Vis) reflection spectroscopy to confirm that the molecules are attached to the substrate. The SAMs are then characterized by Angle-Resolved X-ray photoelectron spectroscopy (ARXPS) to determine the thickness and the average molecular orientation of the molecular layer. The electron transport is measured by conductance-displacement (G-S) experiments under a given bias (-0.4V). The conductance value of a single molecule is identified by a statistical analysis

  19. Gap junctions - guards of excitability.

    Science.gov (United States)

    Stroemlund, Line Waring; Jensen, Christa Funch; Qvortrup, Klaus; Delmar, Mario; Nielsen, Morten Schak

    2015-06-01

    Cardiomyocytes are connected by mechanical and electrical junctions located at the intercalated discs (IDs). Although these structures have long been known, it is becoming increasingly clear that their components interact. This review describes the involvement of the ID in electrical disturbances of the heart and focuses on the role of the gap junctional protein connexin 43 (Cx43). Current evidence shows that Cx43 plays a crucial role in organizing microtubules at the intercalated disc and thereby regulating the trafficking of the cardiac sodium channel NaV1.5 to the membrane.

  20. The role of gap junctions in the brain in health and disease.

    Science.gov (United States)

    Dere, Ekrem; Zlomuzica, Armin

    2012-01-01

    Gap junctions connect the cytosolic compartments of adjacent cells for direct electrotonic and metabolic cell-to-cell communication. Gap junctions between glial cells or neurons are ubiquitously expressed in the brain and play a role in brain development including cell differentiation, cell migration and survival, tissue homeostasis, as well as in human diseases including hearing loss, skin disease, neuropathies, epilepsy, brain trauma, and cardiovascular disease. Furthermore, gap junctions are involved in the synchronization and rhythmic oscillation of hippocampal and neocotical neuronal ensembles which might be important for memory formation and consolidation. In this review the accumulated evidence from mouse mutant and pharmacological studies using gap junction blockers is summarized and the progress made in dissecting the physiological, pathophysiological and behavioral roles of gap junction mediated intercellular communication in the brain is discussed. Copyright © 2011 Elsevier Ltd. All rights reserved.

  1. Regulating cell-cell junctions from A to Z.

    Science.gov (United States)

    Hardin, Jeff

    2016-04-25

    Epithelial sheets often present a "cobblestone" appearance, but the mechanisms underlying the dynamics of this arrangement are unclear. In this issue, Choi et al. (2016. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201506115) show that afadin and ZO-1 regulate tension and maintain zonula adherens architecture in response to changes in contractility.

  2. Control over Rectification in Supramolecular Tunneling Junctions

    NARCIS (Netherlands)

    Wimbush, K.S.; Wimbush, Kim S.; Reus, William F.; van der Wiel, Wilfred Gerard; Reinhoudt, David; Whitesides, George M.; Nijhuis, C.A.; Velders, Aldrik

    2010-01-01

    In complete control: The magnitude of current rectification in well-defined supramolecular tunneling junctions can be controlled by changing the terminal functionality (red spheres) of dendrimers (gray spheres) immobilized on a supramolecular platform (see picture). Junctions containing biferrocene

  3. Nano-Molecular Junctions on STM Tips

    Institute of Scientific and Technical Information of China (English)

    Chun Huang∗; Jianshu Yang

    2011-01-01

    We present a technique for building metal-organic-metal junctions, which contain ten or fewer conjugated molecules between each of such junction, and the investigations of the I-V response of these junctions. The junctions are made by self assembling thiolated molecules onto gold coated tips for use in scanning tunneling microscopy. We show that this easy technique probes the qualitative properties of the molecules. Current-voltage characteristics of a Tour wire and a new molecular rectifier are presented.

  4. Nano-Molecular Junctions on STM Tips

    Institute of Scientific and Technical Information of China (English)

    Chun Huang; Jianshu Yang

    2011-01-01

    We present a technique for building metal-organic-metal junctions, which contain ten or fewer conjugated molecules between each of such junction, and the investigations of the I-V response of these junctions.The junctions are made by self assembling thiolated molecules onto gold coated tips for use in scanning tunneling microscopy. We show that this easy technique probes the qualitative properties of the molecules. Currentvoltage characteristics of a Tour wire and a new molecular rectifier are presented.

  5. Current noise in tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Frey, Moritz; Grabert, Hermann [Physikalisches Institut, Universitaet Freiburg, Hermann-Herder-Strasse 3, 79104, Freiburg (Germany)

    2017-06-15

    We study current fluctuations in tunnel junctions driven by a voltage source. The voltage is applied to the tunneling element via an impedance providing an electromagnetic environment of the junction. We use circuit theory to relate the fluctuations of the current flowing in the leads of the junction with the voltage fluctuations generated by the environmental impedance and the fluctuations of the tunneling current. The spectrum of current fluctuations is found to consist of three parts: a term arising from the environmental Johnson-Nyquist noise, a term due to the shot noise of the tunneling current and a third term describing the cross-correlation between these two noise sources. Our phenomenological theory reproduces previous results based on the Hamiltonian model for the dynamical Coulomb blockade and provides a simple understanding of the current fluctuation spectrum in terms of circuit theory and properties of the average current. Specific results are given for a tunnel junction driven through a resonator. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. Josephson tunnel junction microwave attenuator

    DEFF Research Database (Denmark)

    Koshelets, V. P.; Shitov, S. V.; Shchukin, A. V.

    1993-01-01

    A new element for superconducting electronic circuitry-a variable attenuator-has been proposed, designed, and successfully tested. The principle of operation is based on the change in the microwave impedance of a superconductor-insulator-superconductor (SIS) Josephson tunnel junction when dc bias...

  7. Stability of large-area molecular junctions

    NARCIS (Netherlands)

    Akkerman, Hylke B.; Kronemeijer, Auke J.; Harkema, Jan; van Hal, Paul A.; Smits, Edsger C. P.; de Leeuw, Dago M.; Blom, Paul W. M.

    The stability of molecular junctions is crucial for any application of molecular electronics. Degradation of molecular junctions when exposed to ambient conditions is regularly observed. In this report the stability of large-area molecular junctions under ambient conditions for more than two years

  8. Soliton bunching in annular Josephson junctions

    DEFF Research Database (Denmark)

    Vernik, I.V; Lazarides, Nickos; Sørensen, Mads Peter

    1996-01-01

    By studying soliton (fluxon) motion in long annular Josephson junctions it is possible to avoid the influence of the boundaries and soliton-soliton collisions present in linear junctions. A new experimental design consisting of a niobium coil placed on top of an annular junction has been used...

  9. Long Range Magnetic Interaction between Josephson Junctions

    DEFF Research Database (Denmark)

    Grønbech-Jensen, Niels; Samuelsen, Mogens Rugholm

    1995-01-01

    A new model for magnetic coupling between long Josephson junctions is proposed. The coupling mechanism is a result of the magnetic fields outside the junctions and is consequently effective over long distances between junctions. We give specific expressions for the form and magnitude of the inter...

  10. Dynamics of pi-junction interferometer circuits

    DEFF Research Database (Denmark)

    Kornkev, V.K.; Mozhaev, P.B.; Borisenko, I.V.;

    2002-01-01

    The pi-junction superconducting circuit dynamics was studied by means of numerical simulation technique. Parallel arrays consisting of Josephson junctions of both 0- and pi-type were studied as a model of high-T-c grain-boundary Josephson junction. The array dynamics and the critical current...

  11. Dynamics of pi-junction interferometer circuits

    DEFF Research Database (Denmark)

    Kornkev, V.K.; Mozhaev, P.B.; Borisenko, I.V.

    2002-01-01

    The pi-junction superconducting circuit dynamics was studied by means of numerical simulation technique. Parallel arrays consisting of Josephson junctions of both 0- and pi-type were studied as a model of high-T-c grain-boundary Josephson junction. The array dynamics and the critical current...

  12. Direct Preparation of Carbon Nanotube Intramolecular Junctions on Structured Substrates

    Science.gov (United States)

    An, Jianing; Zhan, Zhaoyao; Sun, Gengzhi; Mohan, Hari Krishna Salila Vijayalal; Zhou, Jinyuan; Kim, Young-Jin; Zheng, Lianxi

    2016-12-01

    Leveraging the unique properties of single-walled carbon nanotube (SWNT) intramolecular junctions (IMJs) in innovative nanodevices and next-generation nanoelectronics requires controllable, repeatable, and large-scale preparation, together with rapid identification and comprehensive characterization of such structures. Here we demonstrate SWNT IMJs through directly growing ultralong SWNTs on trenched substrates. It is found that the trench configurations introduce axial strain in partially suspended nanotubes, and promote bending deformation in the vicinity of the trench edges. As a result, the lattice and electronic structure of the nanotubes can be locally modified, to form IMJs in the deformation regions. The trench patterns also enable pre-defining the formation locations of SWNT IMJs, facilitating the rapid identification. Elaborate Raman characterization has verified the formation of SWNT IMJs and identified their types. Rectifying behavior has been observed by electrical measurements on the as-prepared semiconducting-semiconducting (S-S) junction.

  13. The development of the myotendinous junction. A review.

    Science.gov (United States)

    Charvet, Benjamin; Ruggiero, Florence; Le Guellec, Dominique

    2012-04-01

    The myotendinous junction (MTJ) is a complex specialized region located at the muscle-tendon interface that represents the primary site of force transmission. Despite their different embryologic origins, muscle and tendon morphogenesis occurs in close spatial and temporal association. After muscle attachment, muscle and tendon constitute a dynamic and functional integrated unit that transduces muscle contraction force to the skeletal system. We review here the current understanding of MTJ formation describing changes during morphogenesis and focusing on the crosstalk between muscle and tendon cells that leads to the development of a functional MTJ. Molecules involved in the formation of the linkage, both at the tendon side and at the muscle side of the junction are described. Much of this knowledge comes from studies using different animal models such as mice, zebrafish and Drosophila where powerful methods for in vivo imaging and genetic manipulations can be used to enlighten this developmental process.

  14. Assessing individual radial junction solar cells over millions on VLS-grown silicon nanowires.

    Science.gov (United States)

    Yu, Linwei; Rigutti, Lorenzo; Tchernycheva, Maria; Misra, Soumyadeep; Foldyna, Martin; Picardi, Gennaro; Roca i Cabarrocas, Pere

    2013-07-12

    Silicon nanowires (SiNWs) grown on low-cost substrates provide an ideal framework for the monolithic fabrication of radial junction photovoltaics. However, the quality of junction formation over a random matrix of SiNWs, fabricated via a vapor-liquid-solid (VLS) mechanism, has never been assessed in a realistic context. To address this, we probe the current response of individual radial junction solar cells under electron-beam and optical-beam excitations. Excellent current generation from the radial junction units, compared to their planar counterparts, has been recorded, indicating a high junction quality and effective doping in the ultra-thin SiNWs with diameters thinner than 20 nm. Interestingly, we found that the formation of radial junctions by plasma deposition can be quite robust against geometrical disorder and even the crossings of neighboring cell units. These results provide a strong support to the feasibility of building high-quality radial junction solar cells over high-throughput VLS-grown SiNWs on low-cost substrates.

  15. Synthesis of Y-junction carbon nanofibres by ethanol catalytic combustion technique

    Institute of Scientific and Technical Information of China (English)

    LI Fei; ZOU Xiao-ping; CHENG Jin; ZHANG Hong-dan; REN Peng-fei

    2006-01-01

    Y-shaped structure was synthesized by ethanol catalytic combustion(ECC) technique on the copper plate substrate,without directly seeding catalyst into the flame. The as-grown Y-junction carbon nanofibres were investigated by transmission electron microscopy (TEM). The very common laboratory ethanol burner was used for synthesizing carbon nanofibres. Two kinds of the catalyst precursor,which are iron nitrate (Fe(NO3)3) and nickel nitrate (Ni(NO3)2),were respectively employed to assist the formation of Y-junction carbon nanofibres. TEM analysis confirm the formation of Y-junction in the coiled and noncoiled carbon nanofibres. The type of the catalyst is found to be crucial to grow different Y-junction carbon nanofibres. Different Y-shaped structure may possess different mechanical and electronic properties. These three-terminal nanofibres provide the nanoelectronics community with a novel material for the development of molecular-scale electronic devices.

  16. Si/Ge Junctions Formed by Nanomembrane Bonding

    Science.gov (United States)

    2011-01-01

    Electromagnetics Technology Division Source Code: 437890 Sensors Directorate 10. SPONSOR/MONITOR’S ACRONYM(S) AFRL/RYHC Air Force Research...of Wisconsin-Madison, Madison, Wisconsin 53706, United States, and ‡ Sensors Directorate, Air Force Research Laboratory, Hanscom AFB, Massachusetts...devices1-3 and micro- and nanoelectromechanical systems (MEMS and NEMS ).4 The formation of high-quality inter- faces and electronic junctions directly be

  17. Effect of interjunction coupling on superconducting current and charge correlations in intrinsic Josephson junctions

    Science.gov (United States)

    Shukrinov, Yu. M.; Hamdipour, M.; Kolahchi, M. R.

    2009-07-01

    Charge formations on superconducting layers and creation of the longitudinal plasma wave in the stack of intrinsic Josephson junctions change crucially the superconducting current through the stack. Investigation of the correlations of superconducting currents in neighboring Josephson junctions and the charge correlations in neighboring superconducting layers allows us to predict the additional features in the current-voltage characteristics. The charge autocorrelation functions clearly demonstrate the difference between harmonic and chaotic behavior in the breakpoint region. Use of the correlation functions gives us a powerful method for the analysis of the current-voltage characteristics of coupled Josephson junctions.

  18. Octagonal Defects at Carbon Nanotube Junctions

    Directory of Open Access Journals (Sweden)

    W. Jaskólski

    2013-01-01

    Full Text Available We investigate knee-shaped junctions of semiconductor zigzag carbon nanotubes. Two dissimilar octagons appear at such junctions; one of them can reconstruct into a pair of pentagons. The junction with two octagons presents two degenerate localized states at Fermi energy (EF. The reconstructed junction has only one state near EF, indicating that these localized states are related to the octagonal defects. The inclusion of Coulomb interaction splits the localized states in the junction with two octagons, yielding an antiferromagnetic system.

  19. Fabrication of high quality ferromagnetic Josephson junctions

    Energy Technology Data Exchange (ETDEWEB)

    Weides, M. [Institute for Solid State Research, Research Centre Juelich, D-52425 Juelich (Germany) and CNI-Center of Nanoelectronic Systems for Information Technology, Research Centre Juelich, D-52425 Juelich (Germany)]. E-mail: m.weides@fz-juelich.de; Tillmann, K. [Institute for Solid State Research, Research Centre Juelich, D-52425 Juelich (Germany); Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Research Centre Juelich, D-52425 Juelich (Germany); Kohlstedt, H. [Institute for Solid State Research, Research Centre Juelich, D-52425 Juelich (Germany); CNI-Center of Nanoelectronic Systems for Information Technology, Research Centre Juelich, D-52425 Juelich (Germany); Department of Material Science and Engineering and Department of Physics, University of Berkeley, CA 94720 (United States)

    2006-05-15

    We present ferromagnetic Nb/Al{sub 2}O{sub 3}/Ni{sub 60}Cu{sub 40}/Nb Josephson junctions (SIFS) with an ultrathin Al{sub 2}O{sub 3} tunnel barrier. The junction fabrication was optimized regarding junction insulation and homogeneity of current transport. Using ion-beam-etching and anodic oxidation we defined and insulated the junction mesas. The additional 2 nm thin Cu-layer below the ferromagnetic NiCu (SINFS) lowered interface roughness and ensured very homogeneous current transport. A high yield of junctional devices with j {sub c} spreads less than 2% was obtained.

  20. Ephrin-Bs Drive Junctional Downregulation and Actin Stress Fiber Disassembly to Enable Wound Re-epithelialization

    Directory of Open Access Journals (Sweden)

    Robert Nunan

    2015-11-01

    Full Text Available For a skin wound to successfully heal, the cut epidermal-edge cells have to migrate forward at the interface between scab and healthy granulation tissue. Much is known about how lead-edge cells migrate, but very little is known about the mechanisms that enable active participation by cells further back. Here we show that ephrin-B1 and its receptor EphB2 are both upregulated in vivo, just for the duration of repair, in the first 70 or so rows of epidermal cells, and this signal leads to downregulation of the molecular components of adherens and tight (but not desmosomal junctions, leading to loosening between neighbors and enabling shuffle room among epidermal cells. Additionally, this signaling leads to the shutdown of actomyosin stress fibers in these same epidermal cells, which may act to release tension within the wound monolayer. If this signaling axis is perturbed, then disrupted healing is a consequence in mouse and man.

  1. Selective permeability of gap junction channels.

    Science.gov (United States)

    Goldberg, Gary S; Valiunas, Virginijus; Brink, Peter R

    2004-03-23

    Gap junctions mediate the transfer of small cytoplasmic molecules between adjacent cells. A family of gap junction proteins exist that form channels with unique properties, and differ in their ability to mediate the transfer of specific molecules. Mutations in a number of individual gap junction proteins, called connexins, cause specific human diseases. Therefore, it is important to understand how gap junctions selectively move molecules between cells. Rules that dictate the ability of a molecule to travel through gap junction channels are complex. In addition to molecular weight and size, the ability of a solute to transverse these channels depends on its net charge, shape, and interactions with specific connexins that constitute gap junctions in particular cells. This review presents some data and interpretations pertaining to mechanisms that govern the differential transfer of signals through gap junction channels.

  2. Abl tyrosine kinases modulate cadherin-dependent adhesion upstream and downstream of Rho family GTPases.

    Science.gov (United States)

    Zandy, Nicole L; Pendergast, Ann Marie

    2008-02-15

    Formation and dissolution of intercellular adhesions are processes of paramount importance during tissue morphogenesis and for pathological conditions such as tumor metastasis. Cadherin-mediated intercellular adhesion requires dynamic regulation of the actin cytoskeleton. The pathways that link cadherin signaling to cytoskeletal regulation remain poorly defined. We have recently uncovered a novel role for the Abl family of tyrosine kinases linking cadherin-mediated adhesion to actin dynamics via the regulation of Rho family GTPases. Abl kinases are activated by cadherin engagement, localize to cell-cell junctions and are required for the formation of adherens junctions. Notably, we showed that Abl kinases are required for Rac activation during formation of adherens junctions, and also regulate a Rho-ROCK-myosin signaling pathway that is required for the maintenance of intercellular adhesion. Here we show that Abl kinases regulate the formation and strengthening of adherens junctions downstream of active Rac, and that Abl tyrosine kinases are components of a positive feed-back loop that employs the Crk/CrkL adaptor proteins to promote the formation and maturation of adherens junctions.

  3. Chaos begets order: asynchronous cell contractions drive epithelial morphogenesis.

    Science.gov (United States)

    Paluch, Ewa; Heisenberg, Carl-Philipp

    2009-01-01

    Apical cell contraction triggers tissue folding and invagination in epithelia. During Drosophila gastrulation, ventral furrow formation was thought to be driven by smooth, purse-string-like constriction of an acto-myosin belt underlying adherens junctions. Now Martin et al. report in Nature that ventral furrow formation is triggered by asynchronous pulsed contractions of the apical acto-myosin cortex in individual cells.

  4. Seebeck effect in molecular junctions

    Science.gov (United States)

    Zimbovskaya, Natalya A.

    2016-05-01

    Advances in the fabrication and characterization of nanoscale systems presently allow for a better understanding of their thermoelectric properties. As is known, the building blocks of thermoelectricity are the Peltier and Seebeck effects. In the present work we review results of theoretical studies of the Seebeck effect in single-molecule junctions and similar systems. The behavior of thermovoltage and thermopower in these systems is controlled by several factors including the geometry of molecular bridges, the characteristics of contacts between the bridge and the electrodes, the strength of the Coulomb interactions between electrons on the bridge, and of electron-phonon interactions. We describe the impact of these factors on the thermopower. Also, we discuss a nonlinear Seebeck effect in molecular junctions.

  5. Electron transport in molecular junctions

    DEFF Research Database (Denmark)

    Jin, Chengjun

    This thesis addresses the electron transport in molecular junctions, focusing on the energy level alignment and correlation effects. Various levels of theory have been applied to study the structural and electronic effects in different molecular junctions, starting from the single particle density...... charge position are in quantitative agreement with the experiments, while pure DFT is not. This is the consequence of the accurate energy level alignment, where the DFT+∑ method corrects the self-interaction error in the standard DFT functional and uses a static image charge model to include the image...... charge effect on the energy level renormalization. Additionally, the gating of the 4,4’-bipyridine (44BP) molecule contacted to either Ni or Au electrodes has been investigated. Here it is found that the gating mechanism is conceptually different between two cases. In the case of Ni contacts where...

  6. How coherent are Josephson junctions?

    CERN Document Server

    Paik, Hanhee; Bishop, Lev S; Kirchmair, G; Catelani, G; Sears, A P; Johnson, B R; Reagor, M J; Frunzio, L; Glazman, L; Schoelkopf, R J

    2011-01-01

    Attaining sufficient coherence is a requirement for realizing a large-scale quantum computer. We present a new implementation of a superconducting transmon qubit that is strongly coupled to a three-dimensional superconducting cavity. We observe a reproducible increase in the coherence times of qubit (both $T_1$ and $T_2$ > 10 microseconds) and cavity ($T_{cav}$ ~ 50 microseconds) by more than an order of magnitude compared to the current state-of-art superconducting qubits. This enables the study of the stability and quality of Josephson junctions at precisions exceeding one part per million. Surprisingly, we see no evidence for $1/f$ critical current noise. At elevated temperatures, we observe the dissipation due to a small density (< 1 - 10 ppm) of thermally-excited quasiparticles. The results suggest that the overall quality of Josephson junctions will allow error rates of a few $10^{-4}$, approaching the error correction threshold.

  7. Morphogenesis of rat myotendinous junction.

    Science.gov (United States)

    Curzi, Davide; Ambrogini, Patrizia; Falcieri, Elisabetta; Burattini, Sabrina

    2013-10-01

    Myotendinous junction (MTJ) is the highly specialized complex which connects the skeletal muscle to the tendon for transmitting the contractile force between the two tissues. The purpose of this study was to investigate the MTJ development and rat EDL was chosen as a model. 1, 15, 30 day animals were considered and the junctions were analyzed by light and electron microscopy. The MTJ interface architecture increased during the development, extending the interaction between muscle and tendon. 1-day-old rats showed disorganized myofibril bundles, spread cytosol and incomplete rough endoplasmic reticulum, features partially improved in 15-day-old rats, and completely developed in 30-day-old animals. These findings indicate that muscle-tendon interface displays, during rat lifetime, numerically increased and longer tendon interdigitations, correlated with an improved organization of both tissues and with a progressive acquirement of full functionality.

  8. Ligation of pork skin gelatin with glucose moieties affects the junction zones in gelled networks

    NARCIS (Netherlands)

    Baigts Allende, Diana; Jongh, de H.H.J.

    2015-01-01

    This study aims to investigate the role of the ligation of steric moieties on the formation of junction zones during network formation of gelatin gels. The molecular conformational propensities, heat stability and mechanical properties of gradually chemically modified pork skin gelatin have been

  9. Ligation of pork skin gelatin with glucose moieties affects the junction zones in gelled networks

    NARCIS (Netherlands)

    Baigts Allende, Diana; Jongh, de H.H.J.

    2015-01-01

    This study aims to investigate the role of the ligation of steric moieties on the formation of junction zones during network formation of gelatin gels. The molecular conformational propensities, heat stability and mechanical properties of gradually chemically modified pork skin gelatin have been

  10. Conductance of Alkanedithiol Single-Molecule Junctions: A Molecular Dynamics Study

    DEFF Research Database (Denmark)

    Paulsson, Magnus; Krag, Casper; Frederiksen, Thomas;

    2009-01-01

    We study formation and conductance of alkanedithiol junctions using density functional based molecular dynamics. The formation involves straightening of the molecule, migration of thiol end-groups, and pulling out Au atoms. Plateaus are found in the low-bias conductance traces which decrease by 1...

  11. Thermoelectric efficiency of molecular junctions

    Science.gov (United States)

    Perroni, C. A.; Ninno, D.; Cataudella, V.

    2016-09-01

    Focus of the review is on experimental set-ups and theoretical proposals aimed to enhance thermoelectric performances of molecular junctions. In addition to charge conductance, the thermoelectric parameter commonly measured in these systems is the thermopower, which is typically rather low. We review recent experimental outcomes relative to several junction configurations used to optimize the thermopower. On the other hand, theoretical calculations provide estimations of all the thermoelectric parameters in the linear and non-linear regime, in particular of the thermoelectric figure of merit and efficiency, completing our knowledge of molecular thermoelectricity. For this reason, the review will mainly focus on theoretical studies analyzing the role of not only electronic, but also of the vibrational degrees of freedom. Theoretical results about thermoelectric phenomena in the coherent regime are reviewed focusing on interference effects which play a significant role in enhancing the figure of merit. Moreover, we review theoretical studies including the effects of molecular many-body interactions, such as electron-vibration couplings, which typically tend to reduce the efficiency. Since a fine tuning of many parameters and coupling strengths is required to optimize the thermoelectric conversion in molecular junctions, new theoretically proposed set-ups are discussed in the conclusions.

  12. Elucidating drivers of oral epithelial dysplasia formation and malignant transformation to cancer using RNAseq.

    Science.gov (United States)

    Conway, Caroline; Graham, Jennifer L; Chengot, Preetha; Daly, Catherine; Chalkley, Rebecca; Ross, Lisa; Droop, Alastair; Rabbitts, Pamela; Stead, Lucy F

    2015-11-24

    Oral squamous cell carcinoma (OSCC) is a prevalent cancer with poor prognosis. Most OSCC progresses via a non-malignant stage called dysplasia. Effective treatment of dysplasia prior to potential malignant transformation is an unmet clinical need. To identify markers of early disease, we performed RNA sequencing of 19 matched HPV negative patient trios: normal oral mucosa, dysplasia and associated OSCC. We performed differential gene expression, principal component and correlated gene network analysis using these data. We found differences in the immune cell signatures present at different disease stages and were able to distinguish early events in pathogenesis, such as upregulation of many HOX genes, from later events, such as down-regulation of adherens junctions. We herein highlight novel coding and non-coding candidates for involvement in oral dysplasia development and malignant transformation, and speculate on how our findings may guide further translational research into the treatment of oral dysplasia.

  13. Trimethylsilyl-terminated oligo(phenylene ethynylene)s: an approach to single-molecule junctions with covalent Au-C σ-bonds.

    Science.gov (United States)

    Hong, Wenjing; Li, Hui; Liu, Shi-Xia; Fu, Yongchun; Li, Jianfeng; Kaliginedi, Veerabhadrarao; Decurtins, Silvio; Wandlowski, Thomas

    2012-11-28

    A new and efficient approach using cleaving of trimethylsilyl groups to create covalent Au-C anchoring sites has been developed for single-molecule junction conductance measurements. Employing the mechanically controllable break junction (MCBJ) technique in liquid, we demonstrate the formation of highly conducting single molecular junctions of several OPE derivatives. The created junctions are mechanically stable and exhibit conductances around one order of magnitude higher than those of their dithiol analogues. Extended assembly and reaction times lead to oligomerization. Combined STM imaging and gap-mode Raman experiments provide structure evidence to support the formation of covalent Au-C contacts and further oligomerization.

  14. Chaos induced by coupling between Josephson junctions

    Science.gov (United States)

    Shukrinov, Yu. M.; Azemtsa-Donfack, H.; Botha, A. E.

    2015-02-01

    It is found that, in a stack of intrinsic Josephson junctions in layered high temperature superconductors under external electromagnetic radiation, the chaotic features are triggered by interjunction coupling, i.e., the coupling between different junctions in the stack. While the radiation is well known to produce chaotic effects in the single junction, the effect of interjunction coupling is fundamentally different and it can lead to the onset of chaos via a different route to that of the single junction. A precise numerical study of the phase dynamics of intrinsic Josephson junctions, as described by the CCJJ+DC model, is performed. We demonstrate the charging of superconducting layers, in a bias current interval corresponding to a Shapiro step subharmonic, due to the creation of a longitudinal plasma wave along the stack of junctions. With increase in radiation amplitude chaotic behavior sets in. The chaotic features of the coupled Josephson junctions are analyzed by calculations of the Lyapunov exponents. We compare results for a stack of junctions to the case of a single junction and prove that the observed chaos is induced by the coupling between the junctions. The use of Shapiro step subharmonics may allow longitudinal plasma waves to be excited at low radiation power.

  15. Marker of cemento-periodontal ligament junction associated with periodontal regeneration.

    Science.gov (United States)

    Hara, Ryohko; Wato, Masahiro; Tanaka, Akio

    2005-06-01

    The purpose of this study was to identify factors promoting formation of the cemento-periodontal ligament junction. Regeneration of the cemento-periodontal ligament junction is an important factor in recovery of the connective tissue attachment to the cementum and it is important to identify all specific substances that promote its formation. To clarify the substances involved in cemento-periodontal ligament junction formation, we produced a monoclonal antibody (mAb) to human cemento-periodontal ligament junction (designated as the anti-TAP mAb) and examined its immunostaining properties and reactive antigen. Hybridomas producing monoclonal antibody against human cemento-periodontal ligament junction antigens were established by fusing P3U1 mouse myeloma cells with spleen cells from BALB/c mice immunized with homogenized human cemento-periodontal ligament junction. The mAb, the anti-TAP mAb for cemento-periodontal ligament junction, was then isolated. The immunoglobulin class and light chain of the mAb were examined using an isotyping kit. Before immunostaining, antigen determination using an enzymatic method or heating was conducted. Human teeth, hard tissue-forming lesions, and animal tissues were immunostained by the anti-TAP mAb. The anti-TAP mAb was positive in human cemento-periodontal ligament junction and predentin but negative in all other human and animal tissues examined. In the cemento-osseous lesions, the anti-TAP mAb was positive in the peripheral area of the cementum and cementum-like hard tissues and not in the bone and bone-like tissues. The anti-TAP mAb showed IgM (kappa) and recognized phosphoprotein. The anti-TAP mAb is potentially useful for developing new agents promoting cementogenesis and periodontal regeneration.

  16. [Remodeling of cardiac gap junctions and arrhythmias].

    Science.gov (United States)

    Yu, Zhi-Bin; Sheng, Juan-Juan

    2011-12-25

    In the heart, gap junctions mediate electrical and chemical coupling between adjacent cardiomyocytes, forming the cell-to-cell pathways for orderly spread of the wave of electrical excitation responsible for a functional syncytium. Three principal connexins are expressed in cardiomyocytes, connexin 43 (CX43), CX40, and CX45. CX43 predominates in ventricular muscle cells. Most of the gap junctions, assembled from CX43, are located at the intercalated discs, often with larger junctional plaques at the disc periphery. The gap junctions are rarely distributed to the sides of the cardiomyocyte. The ischemia-reperfusion, cardiac hypertrophy, heart failure, hypercholesterolemia, and diabetes mellitus induce gap junction remodeling. The gap junction remodeling induced by above-mentioned diseases shows similar characteristics, including down-regulation of CX43, reduction in gap junction plaque size, increased heterogeneity and lateralization of gap junction distribution, and dephosphorylation of CX43. The elevated angiotensin II concentration in local myocardium may play an important role in the gap junction remodeling. The down-regulation of CX43 and lateralization of gap junction distribution alter anisotropic spread of the impulse of ventricular myocardium. The dephosphorylation of CX43 not only reduces electrical conductance, but also decreases permeability of chemicals between cardiomyocytes. The lateralization of gap junctions may increase the number of hemichannels formed by CX43. The opening of hemichannels induces ATP efflux and Na(+) influx, which forms a delayed after-depolarization. The gap junction remodeling in pathological condition produces arrhythmia substrate in the ventricles. In this review, the current knowledge on the relationship between the remodeling of cardiac gap junctions and arrhythmias were summarized.

  17. Physics and Applications of NIS Junctions

    Energy Technology Data Exchange (ETDEWEB)

    Ullom, J N

    2001-08-24

    This paper reviews the physics and applications of Normal-Insulator-Superconductor (NIS) tunnel junctions. The current-voltage properties of NIS junctions are diode-like with a strong temperature dependence. Hence, these structures can be used as sensitive thermometers at temperatures well below the energy gap, {Delta}, of the superconducting electrode. For junction voltages comparable to {Delta}/q, current flow removes energy from the normal electrode. This property has been exploited to build refrigerators capable of cooling thin-film circuits from 0.3 K to 0.1 K. Calorimeters and bolometers for the detection of X-rays and millimeter-wave radiation, respectively, have successfully been built from NIS junctions. NIS junctions have also been used to probe the superconducting state. Finally, recent ideas for the use of NIS junctions as simple circuit elements are described.

  18. Algorithms for Junctions in Directed Acyclic Graphs

    CERN Document Server

    Ferreira, Carlos Eduardo

    2012-01-01

    Given a pair of distinct vertices u, v in a graph G, we say that s is a junction of u, v if there are in G internally vertex disjoint directed paths from s to u and from s to v. We show how to characterize junctions in directed acyclic graphs. We also consider the two problems in the following and derive efficient algorithms to solve them. Given a directed acyclic graph G and a vertex s in G, how can we find all pairs of vertices of G such that s is a junction of them? And given a directed acyclic graph G and k pairs of vertices of G, how can we preprocess G such that all junctions of k given pairs of vertices could be listed quickly? All junctions of k pairs problem arises in an application in Anthropology and we apply our algorithm to find such junctions on kinship networks of some brazilian indian ethnic groups.

  19. Phase dynamics of two parallel stacks of coupled Josephson junctions

    Science.gov (United States)

    Shukrinov, Yu M.; Rahmonov, I. R.; Plecenik, A.; Seidel, P.; Ilʼichev, E.; Nawrocki, W.

    2014-12-01

    Two parallel stacks of coupled Josephson junctions (JJs) are investigated to clarify the physics of transitions between the rotating and oscillating states and their effect on the IV-characteristics of the system. The detailed study of phase dynamics and bias dependence of the superconducting and diffusion currents allows one to explain all features of simulated IV-characteristics and demonstrate the correspondence in their behavior. The coupling between JJ in the stacks leads to the branching of IV-characteristics and a decrease in the hysteretic region. The crucial role of the diffusion current in the formation of the IV-characteristic of the parallel stacks of coupled JJs is demonstrated. We discuss the effect of symmetry in a number of junctions in the stacks and show a decrease of the branching in the symmetrical stacks. The observed effects might be useful for development of superconducting electronic devices based on intrinsic JJs.

  20. Low-high junction theory applied to solar cells

    Science.gov (United States)

    Godlewski, M. P.; Baraona, C. R.; Brandhorst, H. W., Jr.

    1974-01-01

    Recent use of alloying techniques for rear contact formation has yielded a new kind of silicon solar cell, the back surface field (BSF) cell, with abnormally high open-circuit voltage and improved radiation resistance. Several analytical models for open-circuit voltage based on the reverse saturation current are formulated to explain these observations. The zero surface recombination velocity (SRV) case of the conventional cell model, the drift field model, and the low-high junction (LHJ) model can predict the experimental trends. The LHJ model applies the theory of the low-high junction and is considered to reflect a more realistic view of cell fabrication. This model can predict the experimental trends observed for BSF cells.

  1. Molecular junctions: can pulling influence optical controllability?

    Science.gov (United States)

    Parker, Shane M; Smeu, Manuel; Franco, Ignacio; Ratner, Mark A; Seideman, Tamar

    2014-08-13

    We suggest the combination of single molecule pulling and optical control as a way to enhance control over the electron transport characteristics of a molecular junction. We demonstrate using a model junction consisting of biphenyl-dithiol coupled to gold contacts. The junction is pulled while optically manipulating the dihedral angle between the two rings. Quantum dynamics simulations show that molecular pulling enhances the degree of control over the dihedral angle and hence over the transport properties.

  2. Loss models for long Josephson junctions

    DEFF Research Database (Denmark)

    Olsen, O. H.; Samuelsen, Mogens Rugholm

    1984-01-01

    A general model for loss mechanisms in long Josephson junctions is presented. An expression for the zero-field step is found for a junction of overlap type by means of a perturbation method. Comparison between analytic solution and perturbation result shows good agreement.......A general model for loss mechanisms in long Josephson junctions is presented. An expression for the zero-field step is found for a junction of overlap type by means of a perturbation method. Comparison between analytic solution and perturbation result shows good agreement....

  3. Organization of cellular receptors into a nanoscale junction during HIV-1 adhesion.

    Directory of Open Access Journals (Sweden)

    Terrence M Dobrowsky

    Full Text Available The fusion of the human immunodeficiency virus type 1 (HIV-1 with its host cell is the target for new antiretroviral therapies. Viral particles interact with the flexible plasma membrane via viral surface protein gp120 which binds its primary cellular receptor CD4 and subsequently the coreceptor CCR5. However, whether and how these receptors become organized at the adhesive junction between cell and virion are unknown. Here, stochastic modeling predicts that, regarding binding to gp120, cellular receptors CD4 and CCR5 form an organized, ring-like, nanoscale structure beneath the virion, which locally deforms the plasma membrane. This organized adhesive junction between cell and virion, which we name the viral junction, is reminiscent of the well-characterized immunological synapse, albeit at much smaller length scales. The formation of an organized viral junction under multiple physiopathologically relevant conditions may represent a novel intermediate step in productive infection.

  4. Annealing Behavior at Triple Junctions in High-Purity Aluminum After Slight Cold Rolling

    Science.gov (United States)

    Yin, Wenhong; Wang, Weiguo; Fang, Xiaoying; Qin, Congxiang

    2017-04-01

    High-purity polycrystalline aluminum samples with a typical grain size of approximately 30 μm were slightly cold-rolled with a thickness reduction of 15%, and then, off-line in situ electron backscatter diffraction was used to identify the annealing behavior at triple junctions during annealing at 400 °C. The results show that recrystallization nuclei are developed at some triple junctions during annealing. High-angle grain boundaries migrate from harder grains to softer grains at the triple junctions leading to the formation of nuclei. All such nuclei show Σ3 orientation relationships with the parent grains, and the bounded Σ3 boundaries are found to be incoherent. During further annealing, these nuclei are consumed by other growing grains, indicating that their presence is just a release of the strain concentration at the triple junctions.

  5. Carbon nanobamboo: Junctions between left and right handed single walled carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Rusznyak, A.; Koltai, J.; Kuerti, J. [Department of Biological Physics, Eoetvoes University, Pazmany Peter setany 1/A, 1117 Budapest (Hungary); Zolyomi, V. [Department of Physics, Lancaster University, Lancaster LA1 4YB (United Kingdom); Institute for Solid State Physics and Optics, Wigner Research Center for Physics, Hungarian Academy of Sciences, P.O. Box 49, 1525 Budapest (Hungary)

    2012-12-15

    Heating of organic molecules, for example, fullerenes encapsulated in single walled carbon nanotubes can result in the coalescence of the molecules forming an inner tube. The growth of tubes with different diameters and/or chiralities can start at different places at the same time. The formation of a junction between the two different tubes depends on many parameters. A special case is when the two tubes have the same chiralities, but opposite handedness. We have shown using topological and combinatorial arguments that at least two non-equivalent junctions can be formed in these cases, with different arrangements of the pentagons and heptagons in the junction. We optimized the geometry using first principles method and investigated the effect of the junction on the electronic density of states of the bamboo-type nanotube. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. Organization of cellular receptors into a nanoscale junction during HIV-1 adhesion.

    Science.gov (United States)

    Dobrowsky, Terrence M; Daniels, Brian R; Siliciano, Robert F; Sun, Sean X; Wirtz, Denis

    2010-07-15

    The fusion of the human immunodeficiency virus type 1 (HIV-1) with its host cell is the target for new antiretroviral therapies. Viral particles interact with the flexible plasma membrane via viral surface protein gp120 which binds its primary cellular receptor CD4 and subsequently the coreceptor CCR5. However, whether and how these receptors become organized at the adhesive junction between cell and virion are unknown. Here, stochastic modeling predicts that, regarding binding to gp120, cellular receptors CD4 and CCR5 form an organized, ring-like, nanoscale structure beneath the virion, which locally deforms the plasma membrane. This organized adhesive junction between cell and virion, which we name the viral junction, is reminiscent of the well-characterized immunological synapse, albeit at much smaller length scales. The formation of an organized viral junction under multiple physiopathologically relevant conditions may represent a novel intermediate step in productive infection.

  7. Annealing Behavior at Triple Junctions in High-Purity Aluminum After Slight Cold Rolling

    Science.gov (United States)

    Yin, Wenhong; Wang, Weiguo; Fang, Xiaoying; Qin, Congxiang

    2017-02-01

    High-purity polycrystalline aluminum samples with a typical grain size of approximately 30 μm were slightly cold-rolled with a thickness reduction of 15%, and then, off-line in situ electron backscatter diffraction was used to identify the annealing behavior at triple junctions during annealing at 400 °C. The results show that recrystallization nuclei are developed at some triple junctions during annealing. High-angle grain boundaries migrate from harder grains to softer grains at the triple junctions leading to the formation of nuclei. All such nuclei show Σ3 orientation relationships with the parent grains, and the bounded Σ3 boundaries are found to be incoherent. During further annealing, these nuclei are consumed by other growing grains, indicating that their presence is just a release of the strain concentration at the triple junctions.

  8. Nonequilibrium electron-vibration coupling and conductance fluctuations in a C-60 junction

    DEFF Research Database (Denmark)

    Ulstrup, Soren; Frederiksen, Thomas; Brandbyge, Mads

    2012-01-01

    We investigate chemical bond formation and conductance in a molecular C-60 junction under finite bias voltage using first-principles calculations based on density functional theory and nonequilibrium Green's functions (DFT-NEGF). At the point of contact formation we identify a remarkably strong...... the significance of nonequilibrium effects in chemical bond formation/breaking and in electron-vibration coupling in molecular electronics....

  9. Nonequilibrium electron-vibration coupling and conductance fluctuations in a C60 junction

    DEFF Research Database (Denmark)

    Ulstrup, Søren; Frederiksen, Thomas; Brandbyge, Mads

    2012-01-01

    We investigate chemical bond formation and conductance in a molecular C60 junction under finite bias voltage using first-principles calculations based on density functional theory and nonequilibrium Green's functions (DFT-NEGF). At the point of contact formation we identify a remarkably strong...... the significance of nonequilibrium effects in chemical bond formation/breaking and in electron-vibration coupling in molecular electronics....

  10. Gap junctions and connexin-interacting proteins

    NARCIS (Netherlands)

    Giepmans, Ben N G

    2004-01-01

    Gap junctions form channels between adjacent cells. The core proteins of these channels are the connexins. Regulation of gap junction communication (GJC) can be modulated by connexin-associating proteins, such as regulatory protein phosphatases and protein kinases, of which c-Src is the best-studied

  11. Gap junctions and connexin-interacting proteins

    NARCIS (Netherlands)

    Giepmans, Ben N G

    2004-01-01

    Gap junctions form channels between adjacent cells. The core proteins of these channels are the connexins. Regulation of gap junction communication (GJC) can be modulated by connexin-associating proteins, such as regulatory protein phosphatases and protein kinases, of which c-Src is the

  12. Gap junctions and connexin-interacting proteins

    NARCIS (Netherlands)

    Giepmans, Ben N G

    2004-01-01

    Gap junctions form channels between adjacent cells. The core proteins of these channels are the connexins. Regulation of gap junction communication (GJC) can be modulated by connexin-associating proteins, such as regulatory protein phosphatases and protein kinases, of which c-Src is the best-studied

  13. Shot noise in YBCO bicrystal Josephson junctions

    DEFF Research Database (Denmark)

    Constantinian, K.Y.; Ovsyannikov, G.A.; Borisenko, I.V.;

    2003-01-01

    We measured spectral noise density in YBCO symmetric bicrystal Josephson junctions on sapphire substrates at bias voltages up to 100 mV and T 4.2 K. Normal state resistance of the Josephson junctions, R-N = 20-90 Omega and ICRN up to 2.2 mV have been observed in the experimental samples. Noise...

  14. The small GTPase RhoA is required to maintain spinal cord neuroepithelium organization and the neural stem cell pool

    DEFF Research Database (Denmark)

    Herzog, Dominik; Loetscher, Pirmin; van Hengel, Jolanda

    2011-01-01

    The regulation of adherens junctions (AJs) is critical for multiple events during CNS development, including the formation and maintenance of the neuroepithelium. We have addressed the role of the small GTPase RhoA in the developing mouse nervous system using tissue-specific conditional gene abla...

  15. Identification of MarvelD3 as a tight junction-associated transmembrane protein of the occludin family

    Directory of Open Access Journals (Sweden)

    Balda Maria S

    2009-12-01

    Full Text Available Abstract Background Tight junctions are an intercellular adhesion complex of epithelial and endothelial cells, and form a paracellular barrier that restricts the diffusion of solutes on the basis of size and charge. Tight junctions are formed by multiprotein complexes containing cytosolic and transmembrane proteins. How these components work together to form functional tight junctions is still not well understood and will require a complete understanding of the molecular composition of the junction. Results Here we identify a new transmembrane component of tight junctions: MarvelD3, a four-span transmembrane protein. Its predicted transmembrane helices form a Marvel (MAL and related proteins for vesicle traffic and membrane link domain, a structural motif originally discovered in proteins involved in membrane apposition and fusion events, such as the tight junction proteins occludin and tricellulin. In mammals, MarvelD3 is expressed as two alternatively spliced isoforms. Both isoforms exhibit a broad tissue distribution and are expressed by different types of epithelial as well as endothelial cells. MarvelD3 co-localises with occludin at tight junctions in intestinal and corneal epithelial cells. RNA interference experiments in Caco-2 cells indicate that normal MarvelD3 expression is not required for the formation of functional tight junctions but depletion results in monolayers with increased transepithelial electrical resistance. Conclusions Our data indicate that MarvelD3 is a third member of the tight junction-associated occludin family of transmembrane proteins. Similar to occludin, normal expression of MarvelD3 is not essential for the formation of functional tight junctions. However, MarvelD3 functions as a determinant of epithelial paracellular permeability properties.

  16. Shear zone junctions: Of zippers and freeways

    Science.gov (United States)

    Passchier, Cees W.; Platt, John P.

    2017-02-01

    Ductile shear zones are commonly treated as straight high-strain domains with uniform shear sense and characteristic curved foliation trails, bounded by non-deforming wall rock. Many shear zones, however, are branched, and if movement on such branches is contemporaneous, the resulting shape can be complicated and lead to unusual shear sense arrangement and foliation geometries in the wall rock. For Y-shaped shear zone triple junctions with three joining branches and transport direction at a high angle to the branchline, only eight basic types of junction are thought to be stable and to produce significant displacement. The simplest type, called freeway junctions, have similar shear sense in all three branches. The other types show joining or separating behaviour of shear zone branches similar to the action of a zipper. Such junctions may have shear zone branches that join to form a single branch (closing zipper junction), or a single shear zone that splits to form two branches, (opening zipper junction). All categories of shear zone junctions show characteristic foliation patterns and deflection of markers in the wall rock. Closing zipper junctions are unusual, since they form a non-active zone with opposite deflection of foliations in the wall rock known as an extraction fault or wake. Shear zipper junctions can form domains of overprinting shear sense along their flanks. A small and large field example are given from NE Spain and Eastern Anatolia. The geometry of more complex, 3D shear zone junctions with slip parallel and oblique to the branchline is briefly discussed.

  17. Forming a stone in pelviureteric junction obstruction: cause or effect?

    Science.gov (United States)

    Stasinou, Theodora; Bourdoumis, Andreas; Masood, Junaid

    2017-01-01

    ABSTRACT Objectives To investigate a possible causal relationship for stone formation in pelviureteric junction obstruction and to outline management options. Materials and Methods A literature search and evidence synthesis was conducted via electronic databases in the English language using the key words pelviureteric junction obstruction; urolithiasis; hyperoxaluria; laparoscopic pyeloplasty; flexible nephroscopy; percutaneous nephrolithotomy, alone or in combination. Relevant articles were analysed to extract conclusions. Results Concomitant pelviureteric junction obstruction (PUJO) and renal lithiasis has been reported only scarcely in the literature. Although PUJO has been extensively studied throughout the years, the presence of calculi in such a patient has not received equal attention and there is still doubt surrounding the pathophysiology and global management. Conclusions Metabolic risk factors appear to play an important role, enough to justify metabolic evaluation in these patients. Urinary stasis and infection are well known factors predisposing to lithiasis and contribute to some extent. The choice for treatment is not always straightforward. Management should be tailored according to degree of obstruction, renal function, patient symptoms and stone size. Simultaneous treatment is feasible with the aid of minimally invasive operative techniques and laparoscopy in particular.

  18. Gold-gold junction electrodes:the disconnection method.

    Science.gov (United States)

    Dale, Sara E C; Vuorema, Anne; Ashmore, Ellen M Y; Kasprzyk-Horden, Barbara; Sillanpää, Mika; Denuault, Guy; Marken, Frank

    2012-02-01

    The formation of gold-gold junction electrodes for application in electroanalysis is described here based on electro-deposition from a non-cyanide gold plating bath. Converging growth of two hemispherical gold deposits on two adjacent platinum microelectrodes (both 100 µm diameter in glass, ca. 45 µm gap) followed by careful etching in aqueous chloride solution was employed. During growth both gold hemispheres "connect" and during etching "disconnection" is evident in a drop in current. Gold-gold junctions with sub-micron gaps are formed and applied for the electroanalytical detection of sub-micromolar concentrations of hydroquinone in 0.1 M phosphate buffer pH 7 (E(rev) = 0.04 V vs. SCE) and sub-micromolar concentration of dopamine in 0.1 M phosphate buffer pH 7 (E(rev) = 0.14 V vs. SCE). The potential future uses in analysis and limitations of gold-gold junction electrodes are discussed.

  19. Junction conditions of cosmological perturbations

    CERN Document Server

    Tomita, K

    2004-01-01

    The behavior of perturbations is studied in cosmological models which consist of two different homogeneous regions connected in a spherical shell boundary. The junction conditions for the metric perturbations and the displacements of the shell boundary are analyzed and the surface densities of the perturbed energy and momentum in the shell are derived, using Mukohyama's gauge-invariant formalism and the Israel discontinuity condition. In both homogeneous regions the perturbations of scalar, vector and tensor types are expanded using the 3-dimensional harmonic functions, but the model coupling among them is caused in the shell by the inhomogeneity. By treating the perturbations with odd and even parities separately, it is found, however, that we can have consistent displacements and surface densities for given metric parturbations

  20. Spontaneous fluxon formation in annular Josephson tunnel junctions

    DEFF Research Database (Denmark)

    Monaco, R.; Mygind, Jesper; Rivers, R.

    2003-01-01

    It has been argued by Zurek and Kibble that the likelihood of producing defects in a continuous phase transition depends in a characteristic way on the quench rate. In this paper we discuss our experiment for measuring the Zurek-Kibble (ZK) scaling exponent sigma for the production of fluxons...

  1. Experiments on spontaneous vortex formation in Josephson tunnel junctions

    DEFF Research Database (Denmark)

    Monaco, R.; Aarøe, Morten; Mygind, Jesper

    2006-01-01

    It has been argued by Zurek and Kibble that the likelihood of producing defects in a continuous phase transition depends in a characteristic way on the quench rate. In this paper we discuss an improved experiment for measuring the scaling exponent sigma for the production of single fluxons...

  2. The Ly6 protein coiled is required for septate junction and blood brain barrier organisation in Drosophila.

    Directory of Open Access Journals (Sweden)

    Assia Hijazi

    Full Text Available BACKGROUND: Genetic analysis of the Drosophila septate junctions has greatly contributed to our understanding of the mechanisms controlling the assembly of these adhesion structures, which bear strong similarities with the vertebrate tight junctions and the paranodal septate junctions. These adhesion complexes share conserved molecular components and have a common function: the formation of paracellular barriers restraining the diffusion of solutes through epithelial and glial envelopes. METHODOLOGY/PRINCIPAL FINDINGS: In this work we characterise the function of the Drosophila cold gene, that codes for a protein belonging to the Ly6 superfamily of extracellular ligands. Analysis of cold mutants shows that this gene is specifically required for the organisation of the septate junctions in epithelial tissues and in the nervous system, where its contribution is essential for the maintenance of the blood-brain barrier. We show that cold acts in a cell autonomous way, and we present evidence indicating that this protein could act as a septate junction component. CONCLUSION/SIGNIFICANCE: We discuss the specific roles of cold and three other Drosophila members of the Ly6 superfamily that have been shown to participate in a non-redundant way in the process of septate junction assembly. We propose that vertebrate Ly6 proteins could fulfill analogous roles in tight junctions and/or paranodal septate junctions.

  3. Effect of Front-Side Silver Metallization on Underlying n+-p Junction in Multicrystalline Silicon Solar Cells: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, C. S.; Li, Z. G.; Moutinho, H. R.; Liang, L.; Ionkin, A.; Al-Jassim, M. M.

    2012-06-01

    We report on the effect of front-side Ag metallization on the underlying n+-p junction of multicrystalline Si solar cells. The junction quality beneath the contacts was investigated by characterizing the uniformities of the electrostatic potential and doping concentration across the junction, using scanning Kelvin probe force microscopy and scanning capacitance microscopy. We investigated cells with a commercial Ag paste (DuPont PV159) and fired at furnace setting temperatures of 800 degrees, 840 degrees, and 930 degrees C, which results in actual cell temperatures ~100 degrees C lower than the setting temperature and the three cells being under-, optimal-, and over-fired. We found that the uniformity of the junction beneath the Ag contact was significantly degraded by the over-firing, whereas the junction retained good uniformity with the optimal- and under-fire temperatures. Further, Ag crystallites with widely distributed sizes from <100 nm to several μm were found at the Ag/Si interface of the over-fired cell. Large crystallites were imaged as protrusions into Si deeper than the junction depth. However, the junction was not broken down; instead, it was reformed on the entire front of the crystallite/Si interface. We propose a mechanism of the junction-quality degradation, based on emitter Si melting at the temperature around the Ag-Si eutectic point during firing, and subsequent recrystallization with incorporation of impurities in the Ag paste and with formation of crystallographic defects during quenching.

  4. Comparative Study on Single-Molecule Junctions of Alkane- and Benzene-Based Molecules with Carboxylic Acid/Aldehyde as the Anchoring Groups

    Science.gov (United States)

    Chen, Fang; Peng, Lin-Lu; Hong, Ze-Wen; Mao, Jin-Chuan; Zheng, Ju-Fang; Shao, Yong; Niu, Zhen-Jiang; Zhou, Xiao-Shun

    2016-08-01

    We have measured the alkane and benzene-based molecules with aldehyde and carboxylic acid as anchoring groups by using the electrochemical jump-to-contact scanning tunneling microscopy break junction (ECSTM-BJ) approach. The results show that molecule with benzene backbone has better peak shape and intensity than those with alkane backbone. Typically, high junction formation probability for same anchoring group (aldehyde and carboxylic acid) with benzene backbone is found, which contributes to the stronger attractive interaction between Cu and molecules with benzene backbone. The present work shows the import role of backbone in junction, which can guide the design molecule to form effective junction for studying molecular electronics.

  5. Coordinate transformation in the model of long Josephson junctions: geometrically equivalent Josephson junctions

    Science.gov (United States)

    Semerdzhieva, E. G.; Boyadzhiev, T. L.; Shukrinov, Yu. M.

    2005-10-01

    The transition from the model of a long Josephson junction of variable width to the model of a junction with a coordinate-dependent Josephson current amplitude is effected through a coordinate transformation. This establishes the correspondence between the classes of Josephson junctions of variable width and quasi-one-dimensional junctions with a variable thickness of the barrier layer. It is shown that for a junction of exponentially varying width the barrier layer of the equivalent quasi-one-dimensional junction has a distributed resistive inhomogeneity that acts as an attractor for magnetic flux vortices. The curve of the critical current versus magnetic field for a Josephson junction with a resistive microinhomogeneity is constructed with the aid of a numerical simulation, and a comparison is made with the critical curve of a junction of exponentially varying width. The possibility of replacing a distributed inhomogeneity in a Josephson junction by a local inhomogeneity at the end of the junction is thereby demonstrated; this can have certain advantages from a technological point of view.

  6. Atomically Abrupt Topological p-n Junction.

    Science.gov (United States)

    Kim, Sung Hwan; Jin, Kyung-Hwan; Kho, Byung Woo; Park, Byeong-Gyu; Liu, Feng; Kim, Jun Sung; Yeom, Han Woong

    2017-08-24

    Topological insulators (TI's) are a new class of quantum matter with extraordinary surface electronic states, which bear great potential for spintronics and error-tolerant quantum computing. In order to put a TI into any practical use, these materials need to be fabricated into devices whose basic units are often p-n junctions. Interesting electronic properties of a 'topological' p-n junction were proposed theoretically such as the junction electronic state and the spin rectification. However, the fabrication of a lateral topological p-n junction has been challenging because of materials, process, and fundamental reasons. Here, we demonstrate an innovative approach to realize a p-n junction of topological surface states (TSS's) of a three-dimensional (3D) topological insulator (TI) with an atomically abrupt interface. When a ultrathin Sb film is grown on a 3D TI of Bi2Se3 with a typical n-type TSS, the surface develops a strongly p-type TSS through the substantial hybridization between the 2D Sb film and the Bi2Se3 surface. Thus, the Bi2Se3 surface covered partially with Sb films bifurcates into areas of n- and p-type TSS's as separated by atomic step edges with a lateral electronic junction of as short as 2 nm. This approach opens a different avenue toward various electronic and spintronic devices based on well-defined topological p-n junctions with the scalability down to atomic dimensions.

  7. Fluxon dynamics in three stacked Josephson junctions

    DEFF Research Database (Denmark)

    Gorria, Carlos; Christiansen, Peter Leth; Gaididei, Yuri Borisovich

    2002-01-01

    /sub -/, the coupling between junctions leads to a repulsion of the fluxons with the same polarity. Above this critical velocity a fluxon will induce radiation in the neighboring junctions, leading to a bunching of the fluxons in the stacked junctions. Using the Sakai-Bodin-Pedersen model, three coupled perturbed sine......-Gordon equations are numerically studied for different values of coupling, damping, and bias parameters. In a narrow range of velocities bunching occurs. Outside this interval the fluxons split and new fluxons may be created. I-V characteristics are presented...

  8. Temperature dependence of thermopower in molecular junctions

    Science.gov (United States)

    Kim, Youngsang; Lenert, Andrej; Meyhofer, Edgar; Reddy, Pramod

    2016-07-01

    The thermoelectric properties of molecular junctions are of considerable interest due to their promise for efficient energy conversion. While the dependence of thermoelectric properties of junctions on molecular structure has been recently studied, their temperature dependence remains unexplored. Using a custom built variable temperature scanning tunneling microscope, we measured the thermopower and electrical conductance of individual benzenedithiol junctions over a range of temperatures (100 K-300 K). We find that while the electrical conductance is independent of temperature, the thermopower increases linearly with temperature, confirming the predictions of the Landauer theory.

  9. Phase qubits fabricated with trilayer junctions

    Energy Technology Data Exchange (ETDEWEB)

    Weides, M; Bialczak, R C; Lenander, M; Lucero, E; Mariantoni, Matteo; Neeley, M; O' Connell, A D; Sank, D; Wang, H; Wenner, J; Yamamoto, T; Yin, Y; Cleland, A N; Martinis, J, E-mail: martin.weides@nist.gov, E-mail: martinis@physics.ucsb.edu [Department of Physics, University of California, Santa Barbara, CA 93106 (United States)

    2011-05-15

    We have developed a novel Josephson junction geometry with minimal volume of lossy isolation dielectric, suitable for higher quality trilayer junctions implemented in qubits. The junctions are based on in situ deposited trilayers with thermal tunnel oxide, have micron-sized areas and a low subgap current. In qubit spectroscopy only a few avoided level crossings are observed, and the measured relaxation time of T{sub 1{approx}}400 ns is in good agreement with the usual phase qubit decay time, indicating low loss due to the additional isolation dielectric.

  10. Characterization of pure boron depositions integrated in silicon diodes for nanometer-deep junction applications

    NARCIS (Netherlands)

    Sarubbi, F.

    2010-01-01

    Doping technologies for formation of ultrashallow and highly-doped p+ junctions are continuously demanded to face the challenges in front-end processing that have emerged due to the aggressive downscaling of vertical dimensions for future semiconductor devices. As an alternative to implantations, cu

  11. Characterization of pure boron depositions integrated in silicon diodes for nanometer-deep junction applications

    NARCIS (Netherlands)

    Sarubbi, F.

    2010-01-01

    Doping technologies for formation of ultrashallow and highly-doped p+ junctions are continuously demanded to face the challenges in front-end processing that have emerged due to the aggressive downscaling of vertical dimensions for future semiconductor devices. As an alternative to implantations, cu

  12. Modeling single molecule junction mechanics as a probe of interface bonding

    Science.gov (United States)

    Hybertsen, Mark S.

    2017-03-01

    -acceptor bond formation at the junction interfaces. The force extension characteristic of longer molecules such as diaminooctane, where the dipole interaction effects drop to a negligible level, accurately fit to the renormalized single-bond potential form. The results suggest that measured force extension characteristics for single molecule junctions could be analyzed with a modified potential form that accounts for the energy stored in deformable mechanical components in series.

  13. Increasing gap junctional coupling: a tool for dissecting the role of gap junctions.

    Science.gov (United States)

    Axelsen, Lene Nygaard; Haugan, Ketil; Stahlhut, Martin; Kjølbye, Anne-Louise; Hennan, James K; Holstein-Rathlou, Niels-Henrik; Petersen, Jørgen Søberg; Nielsen, Morten Schak

    2007-03-01

    Much of our current knowledge about the physiological and pathophysiological role of gap junctions is based on experiments where coupling has been reduced by either chemical agents or genetic modification. This has brought evidence that gap junctions are important in many physiological processes. In a number of cases, gap junctions have been implicated in the initiation and progress of disease, and experimental uncoupling has been used to investigate the exact role of coupling. The inverse approach, i.e., to increase coupling, has become possible in recent years and represents a new way of testing the role of gap junctions. The aim of this review is to summarize the current knowledge obtained with agents that selectively increase gap junctional intercellular coupling. Two approaches will be reviewed: increasing coupling by the use of antiarrhythmic peptide and its synthetic analogs and by interfering with the gating of gap junctional channels.

  14. Presynaptic spike broadening reduces junctional potential amplitude.

    Science.gov (United States)

    Spencer, A N; Przysiezniak, J; Acosta-Urquidi, J; Basarsky, T A

    1989-08-24

    Presynaptic modulation of action potential duration may regulate synaptic transmission in both vertebrates and invertebrates. Such synaptic plasticity is brought about by modifications to membrane currents at presynaptic release sites, which, in turn, lead to changes in the concentration of cytosolic calcium available for mediating transmitter release. The 'primitive' neuromuscular junction of the jellyfish Polyorchis penicillatus is a useful model of presynaptic modulation. In this study, we show that the durations of action potentials in the motor neurons of this jellyfish are negatively correlated with the amplitude of excitatory junctional potentials. We present data from in vitro voltage-clamp experiments showing that short duration voltage spikes, which elicit large excitatory junctional potentials in vivo, produce larger and briefer calcium currents than do long duration action potentials, which elicit small excitatory junctional potentials.

  15. Laparoscopically assisted pyeloplasty for ureteropelvic junction ...

    African Journals Online (AJOL)

    junction obstruction: a transperitoneal versus a retroperitoneal approach ... laparoscopic-assisted dismembered pyeloplasty (TLADP) ... to an open technique for two patients of the TLADP group; ... Annals of Pediatric Surgery 2012, 8:29–31.

  16. Tight Junctions in Salivary Epithelium

    Directory of Open Access Journals (Sweden)

    Olga J. Baker

    2010-01-01

    Full Text Available Epithelial cell tight junctions (TJs consist of a narrow belt-like structure in the apical region of the lateral plasma membrane that circumferentially binds each cell to its neighbor. TJs are found in tissues that are involved in polarized secretions, absorption functions, and maintaining barriers between blood and interstitial fluids. The morphology, permeability, and ion selectivity of TJ vary among different types of tissues and species. TJs are very dynamic structures that assemble, grow, reorganize, and disassemble during physiological or pathological events. Several studies have indicated the active role of TJ in intestinal, renal, and airway epithelial function; however, the functional significance of TJ in salivary gland epithelium is poorly understood. Interactions between different combinations of the TJ family (each with their own unique regulatory proteins define tissue specificity and functions during physiopathological processes; however, these interaction patterns have not been studied in salivary glands. The purpose of this review is to analyze some of the current data regarding the regulatory components of the TJ that could potentially affect cellular functions of the salivary epithelium.

  17. Androgen-Dependent Sertoli Cell Tight Junction Remodeling Is Mediated by Multiple Tight Junction Components

    National Research Council Canada - National Science Library

    Chakraborty, Papia; William Buaas, F; Sharma, Manju; Smith, Benjamin E; Greenlee, Anne R; Eacker, Stephen M; Braun, Robert E

    2014-01-01

    Sertoli cell tight junctions (SCTJs) of the seminiferous epithelium create a specialized microenvironment in the testis to aid differentiation of spermatocytes and spermatids from spermatogonial stem cells...

  18. Junction Plasmon-Induced Molecular Reorientation

    Energy Technology Data Exchange (ETDEWEB)

    El-Khoury, Patrick Z.; Hu, Dehong; Hess, Wayne P.

    2013-10-17

    Time and frequency dependent intensity variations in sequences of Raman spectra recorded at plasmonic junctions can be assigned to molecular reorientation. This is revealed through Raman trajectories recorded at a nanojunction formed between a silver AFM tip and a corrugated silver surface coated with biphenyl-4,4’-dithiol. Molecular motion is not observed when the tip is retracted and only surface enhancement is operative. In effect, junction plasmon induced molecular reorientation is tracked.

  19. [Clinical anatomy of the esophagogastric junction].

    Science.gov (United States)

    Tănase, M; Aldea, A S

    2012-01-01

    The esophagogastric junction is a controversial anatomical area, due to its sphincteric mechanism which does not show an obvious anatomical basis. The aim of this study is to investigate the anatomical components that endoscopically indicate the mucosal esophagogastric junction in hiatal hernia patients. The esophagogastric junction was investigated in 27 hiatal hernia patients undergoing surgery. Hiatal hernia is an extension of the stomach situated between the esophagogastric junction and the diaphragmatic indentation. The following types of hiatal hernia were found: sliding hiatal hernia (type I) in 4 patients (14.81%), rolling hiatal hernia (type II) in 2 (7.4%), mixed hiatal hernia (type III) in 12 (44.44%), type IV hiatal hernia in 4 (14.81%) and recurrent hiatal hernia in 5 (18.51%). Of the 27 hiatal hernia patients, 8 (29.6%) were operated using classical procedures: laparotomy--6 (75%) and laparoscopic surgery--2 (25%). The angle of His cannot be used for marking the mucosal esophagogastric junction due to the severe damage of the lower esophageal sphincter in hiatal hernia patients. The squamocolumnar junction is displaced in hiatal hernia patients and was not an option for the study group. The distal end of the esophageal longitudinal palisading vessels needs medication (proton pump inhibitors that reduce the gastric acid production), in order to enhance the visibility of these vessels. The proximal end of gastric longitudinal mucosal folds proved to be the most reliable site to identify endoscopically the mucosal esophagogastric junction. The anatomical structure of the esophagogastric junction differs in hiatal hernia patients and these peculiarities are very important in surgery.

  20. The Dissolution of Double Holliday Junctions

    DEFF Research Database (Denmark)

    Bizard, Anna H; Hickson, Ian D

    2014-01-01

    as "double Holliday junction dissolution." This reaction requires the cooperative action of a so-called "dissolvasome" comprising a Holliday junction branch migration enzyme (Sgs1/BLM RecQ helicase) and a type IA topoisomerase (Top3/TopoIIIα) in complex with its OB (oligonucleotide/oligosaccharide binding......) fold containing accessory factor (Rmi1). This review details our current knowledge of the dissolution process and the players involved in catalyzing this mechanistically complex means of completing homologous recombination reactions....

  1. Gap junction intercellular communication and benzene toxicity.

    Science.gov (United States)

    Rivedal, Edgar; Witz, Gisela; Leithe, Edward

    2010-03-19

    Aberrant regulation of gap junction intercellular communication (GJIC) has been linked to several human diseases, including cancer and abnormal hematopoietic development. Benzene exposure has been shown to cause hematotoxicity and leukemia, but the underlying mechanisms involved remain unclear. We have observed that several metabolites of benzene have the ability to block gap junction intercellular communication. The ring-opened trans,trans-muconaldehyde (MUC) was found to be the most potent inhibitor of gap junction channels. MUC was found to induce cross-linking of the gap junction protein connexin43, which seemed to be responsible for the induced inhibition of GJIC. Glutaraldehyde, which has a similar molecular structure as MUC, was found to possess similar effects on gap junctions as MUC, while the mono-aldehyde formaldehyde shows lower potency, both as a connexin cross-linker, and as an inhibitor of GJIC. Both glutaraldehyde and formaldehyde have previously been associated with induction of leukemia and disturbance of hematopoiesis. Taken together, the data support a possible link between the effect of MUC on gap junctions, and the toxic effects of benzene. Copyright (c) 2009 Elsevier Ireland Ltd. All rights reserved.

  2. Gap junctions: structure and function (Review).

    Science.gov (United States)

    Evans, W Howard; Martin, Patricia E M

    2002-01-01

    Gap junctions are plasma membrane spatial microdomains constructed of assemblies of channel proteins called connexins in vertebrates and innexins in invertebrates. The channels provide direct intercellular communication pathways allowing rapid exchange of ions and metabolites up to approximately 1 kD in size. Approximately 20 connexins are identified in the human or mouse genome, and orthologues are increasingly characterized in other vertebrates. Most cell types express multiple connexin isoforms, making likely the construction of a spectrum of heteromeric hemichannels and heterotypic gap junctions that could provide a structural basis for the charge and size selectivity of these intercellular channels. The precise nature of the potential signalling information traversing junctions in physiologically defined situations remains elusive, but extensive progress has been made in elucidating how connexins are assembled into gap junctions. Also, participation of gap junction hemichannels in the propagation of calcium waves via an extracellular purinergic pathway is emerging. Connexin mutations have been identified in a number of genetically inherited channel communication-opathies. These are detected in connexin 32 in Charcot Marie Tooth-X linked disease, in connexins 26 and 30 in deafness and skin diseases, and in connexins 46 and 50 in hereditary cataracts. Biochemical approaches indicate that many of the mutated connexins are mistargeted to gap junctions and/or fail to oligomerize correctly into hemichannels. Genetic ablation approaches are helping to map out a connexin code and point to specific connexins being required for cell growth and differentiation as well as underwriting basic intercellular communication.

  3. Predictive modelling of ferroelectric tunnel junctions

    Science.gov (United States)

    Velev, Julian P.; Burton, John D.; Zhuravlev, Mikhail Ye; Tsymbal, Evgeny Y.

    2016-05-01

    Ferroelectric tunnel junctions combine the phenomena of quantum-mechanical tunnelling and switchable spontaneous polarisation of a nanometre-thick ferroelectric film into novel device functionality. Switching the ferroelectric barrier polarisation direction produces a sizable change in resistance of the junction—a phenomenon known as the tunnelling electroresistance effect. From a fundamental perspective, ferroelectric tunnel junctions and their version with ferromagnetic electrodes, i.e., multiferroic tunnel junctions, are testbeds for studying the underlying mechanisms of tunnelling electroresistance as well as the interplay between electric and magnetic degrees of freedom and their effect on transport. From a practical perspective, ferroelectric tunnel junctions hold promise for disruptive device applications. In a very short time, they have traversed the path from basic model predictions to prototypes for novel non-volatile ferroelectric random access memories with non-destructive readout. This remarkable progress is to a large extent driven by a productive cycle of predictive modelling and innovative experimental effort. In this review article, we outline the development of the ferroelectric tunnel junction concept and the role of theoretical modelling in guiding experimental work. We discuss a wide range of physical phenomena that control the functional properties of ferroelectric tunnel junctions and summarise the state-of-the-art achievements in the field.

  4. Search for the in-phase Flux Flow mode in stacked Josephson junctions

    DEFF Research Database (Denmark)

    Pedersen, Niels Falsig; Madsen, Søren Peder

    2006-01-01

    Josephson vortex flux flow states in stacked Josephson junctions are investigated numerically. The aim of the work is to understand the mechanisms behind the formation of triangular (anti-phase) and square (in-phase) vortex lattices, and is motivated by recent experiments on layered BSCCO type hi......-T-c superconductors in a magnetic field. In order to keep the problem as simple as possible we consider in detail only the case with two junctions in the stack. (c) 2006 Elsevier B.V. All rights reserved....

  5. Cell culture model predicts human disease: Altered expression of junction proteins and matrix metalloproteinases in cervical dysplasia

    Directory of Open Access Journals (Sweden)

    Kivi Niina

    2012-08-01

    Full Text Available Abstract Background Cervical cancer is necessarily caused by human papillomaviruses, which encode three oncogenes manifesting their functions by interfering with a number of cellular proteins and pathways: the E5, E6, and E7 proteins. We have earlier found in our microarray studies that the E5 oncogene crucially affects the expression of cellular genes involved in adhesion and motility of epithelial cells. Methods In order to biologically validate our previous experimental findings we performed immunohistochemical staining of a representative set of tissue samples from different grades of high-risk human papillomavirus associated cervical disease as well as normal squamous and columnar cervical epithelium. Three-dimensional collagen raft cultures established from E5-expressing and control epithelial cells were also examined. The expression of p16, matrix metalloproteinase (MMP -7, MMP-16, cytokeratin (CK 8/18, laminin, E-cadherin and beta-catenin was studied. Results In agreement with our previous microarray studies, we found intense staining for E-cadherin and beta-catenin in adherens junctions even in high-grade cervical lesions. Staining for MMP-16 was increased in severe disease as well. No significant change in staining for MMP-7 and cytokeratin 8/18 along with the grade of cervical squamous epithelial disease was observed. Conclusions Here we have confirmed, using tissue material from human papillomavirus associated lesions, some of the cellular gene expression modifications that we earlier reported in an experimental system studying specifically the E5 oncogene of papillomaviruses. These findings were partially surprising in the context of cervical carcinogenesis and emphasize that the complexity of carcinogenesis is not yet fully understood. Microarray approaches provide a wide overwiev of gene expression in experimental settings, which may yield biologically valid biomarkers for disease diagnostics, prognosis, and follow-up.

  6. Macrophages and dendritic cells express tight junction proteins and exchange particles in an in vitro model of the human airway wall.

    Science.gov (United States)

    Blank, Fabian; Wehrli, Marc; Lehmann, Andrea; Baum, Oliver; Gehr, Peter; von Garnier, Christophe; Rothen-Rutishauser, Barbara M

    2011-01-01

    The human airway epithelium serves as structural and functional barrier against inhaled particulate antigen. Previously, we demonstrated in an in vitro epithelial barrier model that monocyte derived dendritic cells (MDDC) and monocyte derived macrophages (MDM) take up particulate antigen by building a trans-epithelial interacting network. Although the epithelial tight junction (TJ) belt was penetrated by processes of MDDC and MDM, the integrity of the epithelium was not affected. These results brought up two main questions: (1) Do MDM and MDDC exchange particles? (2) Are those cells expressing TJ proteins, which are believed to interact with the TJ belt of the epithelium to preserve the epithelial integrity? The expression of TJ and adherens junction (AJ) mRNA and proteins in MDM and MDDC monocultures was determined by RT-PCR, and immunofluorescence, respectively. Particle uptake and exchange was quantified by flow cytometry and laser scanning microscopy in co-cultures of MDM and MDDC exposed to polystyrene particles (1 μm in diameter). MDM and MDDC constantly expressed TJ and AJ mRNA and proteins. Flow cytometry analysis of MDM and MDDC co-cultures showed increased particle uptake in MDDC while MDM lost particles over time. Quantitative analysis revealed significantly higher particle uptake by MDDC in co-cultures of epithelial cells with MDM and MDDC present, compared to co-cultures containing only epithelial cells and MDDC. We conclude from these findings that MDM and MDDC express TJ and AJ proteins which could help to preserve the epithelial integrity during particle uptake and exchange across the lung epithelium.

  7. Expression of Tight Junction Proteins and Cadherin 17 in the Small Intestine of Young Goats Offered a Reduced N and/or Ca Diet

    Science.gov (United States)

    Wilkens, Mirja R.; Breves, Gerhard; Langeheine, Marion; Brehm, Ralph; Muscher-Banse, Alexandra S.

    2016-01-01

    Diets fed to ruminants should contain nitrogen (N) as low as possible to reduce feed costs and environmental pollution. Though possessing effective N-recycling mechanisms to maintain the N supply for rumen microbial protein synthesis and hence protein supply for the host, an N reduction caused substantial changes in calcium (Ca) and phosphate homeostasis in young goats including decreased intestinal transepithelial Ca absorption as reported for monogastric species. In contrast to the transcellular component of transepithelial Ca transport, the paracellular route has not been investigated in young goats. Therefore, the aim of the present study was to characterise the effects of dietary N and/or Ca reduction on paracellular transport mechanisms in young goats. Electrophysiological properties of intestinal epithelia were investigated by Ussing chamber experiments. The expression of tight junction (TJ) and adherens junction (AJ) proteins in intestinal epithelia were examined on mRNA level by qPCR and on protein level by western blot analysis. Dietary N reduction led to a segment specific increase in tissue conductances in the proximal jejunum which might be linked to concomitantly decreased expression of cadherin 17 mRNA. Expression of occludin (OCLN) and zonula occludens protein 1 was increased in mid jejunal epithelia of N reduced fed goats on mRNA and partly on protein level. Reduced dietary Ca supply resulted in a segment specific increase in claudin 2 and claudin 12 expression and decreased the expression of OCLN which might have been mediated at least in part by calcitriol. These data show that dietary N as well as Ca reduction affected expression of TJ and AJ proteins in a segment specific manner in young goats and may thus be involved in modulation of paracellular Ca permeability. PMID:27120348

  8. Expression of Tight Junction Proteins and Cadherin 17 in the Small Intestine of Young Goats Offered a Reduced N and/or Ca Diet.

    Directory of Open Access Journals (Sweden)

    Kristin Elfers

    Full Text Available Diets fed to ruminants should contain nitrogen (N as low as possible to reduce feed costs and environmental pollution. Though possessing effective N-recycling mechanisms to maintain the N supply for rumen microbial protein synthesis and hence protein supply for the host, an N reduction caused substantial changes in calcium (Ca and phosphate homeostasis in young goats including decreased intestinal transepithelial Ca absorption as reported for monogastric species. In contrast to the transcellular component of transepithelial Ca transport, the paracellular route has not been investigated in young goats. Therefore, the aim of the present study was to characterise the effects of dietary N and/or Ca reduction on paracellular transport mechanisms in young goats. Electrophysiological properties of intestinal epithelia were investigated by Ussing chamber experiments. The expression of tight junction (TJ and adherens junction (AJ proteins in intestinal epithelia were examined on mRNA level by qPCR and on protein level by western blot analysis. Dietary N reduction led to a segment specific increase in tissue conductances in the proximal jejunum which might be linked to concomitantly decreased expression of cadherin 17 mRNA. Expression of occludin (OCLN and zonula occludens protein 1 was increased in mid jejunal epithelia of N reduced fed goats on mRNA and partly on protein level. Reduced dietary Ca supply resulted in a segment specific increase in claudin 2 and claudin 12 expression and decreased the expression of OCLN which might have been mediated at least in part by calcitriol. These data show that dietary N as well as Ca reduction affected expression of TJ and AJ proteins in a segment specific manner in young goats and may thus be involved in modulation of paracellular Ca permeability.

  9. Structure-Property Relationships in Atomic-Scale Junctions: Histograms and Beyond.

    Science.gov (United States)

    Hybertsen, Mark S; Venkataraman, Latha

    2016-03-15

    Over the past 10 years, there has been tremendous progress in the measurement, modeling and understanding of structure-function relationships in single molecule junctions. Numerous research groups have addressed significant scientific questions, directed both to conductance phenomena at the single molecule level and to the fundamental chemistry that controls junction functionality. Many different functionalities have been demonstrated, including single-molecule diodes, optically and mechanically activated switches, and, significantly, physical phenomena with no classical analogues, such as those based on quantum interference effects. Experimental techniques for reliable and reproducible single molecule junction formation and characterization have led to this progress. In particular, the scanning tunneling microscope based break-junction (STM-BJ) technique has enabled rapid, sequential measurement of large numbers of nanoscale junctions allowing a statistical analysis to readily distinguish reproducible characteristics. Harnessing fundamental link chemistry has provided the necessary chemical control over junction formation, enabling measurements that revealed clear relationships between molecular structure and conductance characteristics. Such link groups (amines, methylsuflides, pyridines, etc.) maintain a stable lone pair configuration that selectively bonds to specific, undercoordinated transition metal atoms available following rupture of a metal point contact in the STM-BJ experiments. This basic chemical principle rationalizes the observation of highly reproducible conductance signatures. Subsequently, the method has been extended to probe a variety of physical phenomena ranging from basic I-V characteristics to more complex properties such as thermopower and electrochemical response. By adapting the technique to a conducting cantilever atomic force microscope (AFM-BJ), simultaneous measurement of the mechanical characteristics of nanoscale junctions as they

  10. Charge transport in nanoscale junctions.

    Science.gov (United States)

    Albrecht, Tim; Kornyshev, Alexei; Bjørnholm, Thomas

    2008-09-03

    many particle excitations, new surface states in semiconductor electrodes, various mechanisms for single molecule rectification of the current, inelastic electron spectra and SERS spectroscopy. Three terminal architectures allowing (electrochemical) gating and transistor effects. Electrochemical nanojunctions and gating: intermolecular electron transfer in multi-redox metalloproteins, contact force modulation, characteristic current-noise patterns due to conformational fluctuations, resonance effects and electrocatalysis. Novel architectures: linear coupled quantum-dot-bridged junctions, electrochemical redox mediated transfer in two center systems leading to double maxima current-voltage plots and negative differential resistance, molecular-nanoparticle hybrid junctions and unexpected mesoscopic effects in polymeric wires. Device integration: techniques for creating stable metal/molecule/metal junctions using 'nano-alligator clips' and integration with 'traditional' silicon-based technology. The Guest Editors would like to thank all of the authors and referees of this special issue for their meticulous work in making each paper a valuable contribution to this research area, the early-bird authors for their patience, and Journal of Physics: Condensed Matter editorial staff in Bristol for their continuous support.

  11. Fabrication of high-quality submicron Nb/Al-AlOx/Nb tunnel junctions

    Institute of Scientific and Technical Information of China (English)

    Yu Hai-Feng; Cao Wen-Hui; Zhu Xiao-Bo; Yang Hai-Fang; Yu Hong-Wei; Ren Yu-Feng; Gu Chang-Zhi; Chen Geng-Hua; Zhao Shi-Ping

    2008-01-01

    Nb/Al-AlOx/Nb tunnel junctions are often used in the studies of macroscopic quantum phenomena and supercon-ducting qubit applications of the Josepheon devices. In this work, we describe a convenient and reliable process using electron beam lithography for the fabrication of high-quality, submicron-sized Nb/Al-AlOx/Nb Josephson junctions.The technique follows the well-known selective Nb etching process and produces high-quality junctions with Vm=100 mV at 2.3 K for the typical critical current density of 2.2 kA/cm2, which can be adjusted by controlling the oxygen pressure and oxidation time during the formation of the tunnelling barrier. We present the results of the temperature depen-dence of the sub-gap current and in-plane magnetic-field dependence of the critical current, and compare them with the theoretical predictions.

  12. Predictive model for the size of bubbles and droplets created in microfluidic T-junctions.

    Science.gov (United States)

    van Steijn, Volkert; Kleijn, Chris R; Kreutzer, Michiel T

    2010-10-07

    We present a closed-form expression that allows the reader to predict the size of bubbles and droplets created in T-junctions without fitting. Despite the wide use of microfluidic devices to create bubbles and droplets, a physically sound expression for the size of bubbles and droplets, key in many applications, did not yet exist. The theoretical foundation of our expression comprises three main ingredients: continuity, geometrics and recently gained understanding of the mechanism which leads to pinch-off. Our simple theoretical model explains why the size of bubbles and droplets strongly depends on the shape of a T-junction, and teaches how the shape can be tuned to obtain the desired size. We successfully validated our model experimentally by analyzing the formation of gas bubbles, as well as liquid droplets, in T-junctions with a wide variety of shapes under conditions typical to multiphase microfluidics.

  13. Fullerene as alligator clips for electrical conduction through anthracene molecular junctions

    Indian Academy of Sciences (India)

    RUPAN PREET KAUR; RAVINDER SINGH SAWHNEY; DERICK ENGLES

    2017-05-01

    The conductance of a single molecule transport junction comprising anthracene molecular junction (AMJ) with fullerene as alligator clips was investigated using $\\it{ab-initio}$ density functional theory (DFT) in the Landauer–Imry regime of coherent tunnelling transport. In our previous research, we have already calculatedthe electrical transport properties of aromatic molecules with thiol, amine, hydroxyl and selenol end groups concluding the exceptional assistance in the formation of robust molecular junctions. In this article, we have presented the suitability of fullerene anchoring in coupling anthracene molecule with gold electrodes. AMJ with boron-20 (B-20) and C-20 alligator clips exhibited strongest conduction in contrast to nitrogen, oxygen, fluorine and neon alligator clips.

  14. Intrinsic inhomogeneity in barrier height at monolayer graphene/SiC Schottky junction

    Science.gov (United States)

    Tomer, D.; Rajput, S.; Hudy, L. J.; Li, C. H.; Li, L.

    2014-07-01

    Graphene interfaced with a semiconductor forms a Schottky junction with rectifying properties. The inherent spatial inhomogeneity due to the formation of ripples and ridges in graphene can lead to fluctuations in the Schottky barrier height (SBH). The non-ideal behavior of the temperature dependent barrier height and ideality factor greater than 4 can be attributed to these spatial inhomogeneities. Assuming a Gaussian distribution of the barrier, mean SBHs of 1.30 ± 0.18 eV and 1.16 ± 0.16 eV are found for graphene/SiC junctions on the C- and Si-face, respectively. These findings reveal intrinsic spatial inhomogeneities in the SBHs in graphene based Schottky junctions.

  15. Josephson tunnel junctions with ferromagnetic interlayer

    Energy Technology Data Exchange (ETDEWEB)

    Weides, M.P.

    2006-07-01

    Superconductivity and ferromagnetism are well-known physical properties of solid states that have been widely studied and long thought about as antagonistic phenomena due to difference in spin ordering. It turns out that the combination of both superconductor and ferromagnet leads to a very rich and interesting physics. One particular example, the phase oscillations of the superconducting order parameter inside the ferromagnet, will play a major role for the devices discussed in this work. In this thesis, I present Josephson junctions with a thin Al{sub 2}O{sub 3} tunnel barrier and a ferromagnetic interlayer, i.e. superconductor-insulator-ferromagnet-superconductor (SIFS) stacks. The fabrication of junctions was optimized regarding the insulation of electrodes and the homogeneity of the current transport. The junctions were either in the 0 or {pi} coupled ground state, depending on the thickness of the ferromagnetic layer and on temperature. The influence of ferromagnetic layer thickness on the transport properties and the coupling (0, {pi}) of SIFS tunnel junctions was studied. Furthermore, using a stepped ferromagnetic layer with well-chosen thicknesses, I obtained the so-called 0-{pi} Josephson junction. At a certain temperature this 0-{pi} junction can be made perfectly symmetric. In this case the ground state corresponds to a vortex of supercurrent creating a magnetic flux which is a fraction of the magnetic flux quantum {phi}{sub 0}. Such structures allow to study the physics of fractional vortices and to build various electronic circuits based on them. The SIFS junctions presented here have an exponentially vanishing damping at T {yields} 0. The SIFS technology developed within the framework of this work may be used to construct classical and quantum devices such as oscillators, memory cells and qubits. (orig.)

  16. Fabrication of BiOBr nanosheets@TiO{sub 2} nanobelts p–n junction photocatalysts for enhanced visible-light activity

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Yang [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Huang, Xiang [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); School of Science, Tibet University, Lhasa 850000 (China); Tan, Xin [School of Science, Tibet University, Lhasa 850000 (China); Yu, Tao, E-mail: yutao@tju.edu.cn [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072 (China); Li, Xiangli [School of Environmental Science and Engineering, Tianjin University, Tianjin 300072 (China); Yang, Libin [College of Chemical Engineering and Materials Science, Tianjin University of Science & Technology, Tianjin Key Laboratory of Marine Resources and Chemistry, Tianjin 300457 (China); Wang, Shucong [School of Environmental Science and Engineering, Tianjin University, Tianjin 300072 (China)

    2016-03-01

    Graphical abstract: - Highlights: • BiOBr nanosheets@TiO{sub 2} nanobelts p–n junction photocatalysts have been synthesized. • The p–n junction photocatalysts improved water splitting and dye degradation activity. • BiOBr amount in the BiOBr@TiO{sub 2} photocatalysts was investigated. - Abstract: The construction of p–n junction structure is a smart strategy for improving the photocatalytic activity, since p–n junctions can inhibit the recombination of photo-induced charges. Herein, BiOBr nanosheets@TiO{sub 2} nanobelts p–n junction photocatalysts were prepared by assembling BiOBr nanosheets on the surface of TiO{sub 2} nanobelts via a hydrothermal route followed by a co-precipitation process. BiOBr@TiO{sub 2} p–n junction photocatalysts exhibited enhanced photocatalytic activity in photocatalytic H{sub 2} production over water splitting and photodegradation of Rhodamine B (RhB) under visible light irradiation. Mott–Schottky plots confirmed the formation of p–n junctions in the interface of BiOBr and TiO{sub 2}. The enhanced photocatalytic performance can be ascribed to the 1D nanostructure and the formation of p–n junctions. This work shows a potential application of low cost BiOBr as a substitute for noble metals in photocatalytic H{sub 2} production under visible light irradiation.

  17. Increasing gap junctional coupling: a tool for dissecting the role of gap junctions

    DEFF Research Database (Denmark)

    Axelsen, Lene Nygaard; Haugan, Ketil; Stahlhut, Martin;

    2007-01-01

    . In a number of cases, gap junctions have been implicated in the initiation and progress of disease, and experimental uncoupling has been used to investigate the exact role of coupling. The inverse approach, i.e., to increase coupling, has become possible in recent years and represents a new way of testing......Much of our current knowledge about the physiological and pathophysiological role of gap junctions is based on experiments where coupling has been reduced by either chemical agents or genetic modification. This has brought evidence that gap junctions are important in many physiological processes...... the role of gap junctions. The aim of this review is to summarize the current knowledge obtained with agents that selectively increase gap junctional intercellular coupling. Two approaches will be reviewed: increasing coupling by the use of antiarrhythmic peptide and its synthetic analogs...

  18. A study on NiGe-contacted Ge n+/p Ge shallow junction prepared by dopant segregation technique

    Science.gov (United States)

    Tsui, Bing-Yue; Shih, Jhe-Ju; Lin, Han-Chi; Lin, Chiung-Yuan

    2015-05-01

    In this work, the effect of dopant segregation on the NiGe/n-Ge contact is studied by experiments and first-principles calculations. Both Al-contacted and NiGe-contacted n+/p junctions were fabricated. Phosphorus and arsenic ions were Implanted Before Germanide (IBG) formation or Implanted After Germanide (IAG) formation. The NiGe-contacted junction always exhibit higher forward current than the Al-contacted junction due to dopant segregation. First principles calculations predict that phosphorus atoms tend to segregate on both NiGe side and Ge side while arsenic atoms tend to segregate at Ge side. Since phosphorus has higher activation level and lower diffusion coefficient than arsenic, we propose a phosphorus IBG + arsenic IAG process. Shallow n+/p junction with junction depth 90 nm below the NiGe/Ge interface is achieved. The lowest and average contact resistivity is 2 × 10-6 Ω cm2 and 6.7 × 10-6 Ω cm2, respectively. Methods which can further reduce the junction depth and contact resistivity are suggested.

  19. Comparative analysis of gas–liquid flow in T-junction microchannels with different inlet orientations

    Directory of Open Access Journals (Sweden)

    Dongren Liu

    2016-03-01

    Full Text Available In this study, a comparative analysis of two-phase flow in T-junction microchannels with different inlet orientations was carried out. Based on computational fluid dynamics and the volume-of-fluid model, bubble size, bubble velocities, and pressure distributions were analyzed. The numerical algorithm was validated with the experimental observations from former literatures; the results show that when the capillary number, Ca, is low, the length of gas and liquid slug in the symmetric T-junction is higher than that in the cross-flow T-junction. The effect of different forces acting on the slugs during the process of bubble formation was studied by investigating the velocity gradient and pressure distribution in the mixing zone. The result shows that the shear stress in cross-flow T-junction is over two times of that in T-junction with two symmetric inlets under the same operating conditions, which indicates that the size of bubble and liquid slug depends on the shear stress at low Ca number.

  20. Musical molecules: the molecular junction as an active component in audio distortion circuits.

    Science.gov (United States)

    Bergren, Adam Johan; Zeer-Wanklyn, Lucas; Semple, Mitchell; Pekas, Nikola; Szeto, Bryan; McCreery, Richard L

    2016-03-09

    Molecular junctions that have a non-linear current-voltage characteristic consistent with quantum mechanical tunneling are demonstrated as analog audio clipping elements in overdrive circuits widely used in electronic music, particularly with electric guitars. The performance of large-area molecular junctions fabricated at the wafer level is compared to currently standard semiconductor diode clippers, showing a difference in the sound character. The harmonic distributions resulting from the use of traditional and molecular clipping elements are reported and discussed, and differences in performance are noted that result from the underlying physics that controls the electronic properties of each clipping component. In addition, the ability to tune the sound using the molecular junction is demonstrated. Finally, the hybrid circuit is compared to an overdriven tube amplifier, which has been the standard reference electric guitar clipped tone for over 60 years. In order to investigate the feasibility of manufacturing molecular junctions for use in commercial applications, devices are fabricated using a low-density format at the wafer level, where 38 dies per wafer, each containing two molecular junctions, are made with exceptional non-shorted yield (99.4%, representing 718 out of 722 tested devices) without requiring clean room facilities.

  1. Musical molecules: the molecular junction as an active component in audio distortion circuits

    Science.gov (United States)

    Bergren, Adam Johan; Zeer-Wanklyn, Lucas; Semple, Mitchell; Pekas, Nikola; Szeto, Bryan; McCreery, Richard L.

    2016-03-01

    Molecular junctions that have a non-linear current-voltage characteristic consistent with quantum mechanical tunneling are demonstrated as analog audio clipping elements in overdrive circuits widely used in electronic music, particularly with electric guitars. The performance of large-area molecular junctions fabricated at the wafer level is compared to currently standard semiconductor diode clippers, showing a difference in the sound character. The harmonic distributions resulting from the use of traditional and molecular clipping elements are reported and discussed, and differences in performance are noted that result from the underlying physics that controls the electronic properties of each clipping component. In addition, the ability to tune the sound using the molecular junction is demonstrated. Finally, the hybrid circuit is compared to an overdriven tube amplifier, which has been the standard reference electric guitar clipped tone for over 60 years. In order to investigate the feasibility of manufacturing molecular junctions for use in commercial applications, devices are fabricated using a low-density format at the wafer level, where 38 dies per wafer, each containing two molecular junctions, are made with exceptional non-shorted yield (99.4%, representing 718 out of 722 tested devices) without requiring clean room facilities.

  2. Photocurrent generation in lateral graphene p-n junction created by electron-beam irradiation

    KAUST Repository

    Yu, Xuechao

    2015-07-08

    Graphene has been considered as an attractive material for optoelectronic applications such as photodetectors owing to its extraordinary properties, e.g. broadband absorption and ultrahigh mobility. However, challenges still remain in fundamental and practical aspects of the conventional graphene photodetectors which normally rely on the photoconductive mode of operation which has the drawback of e.g. high dark current. Here, we demonstrated the photovoltaic mode operation in graphene p-n junctions fabricated by a simple but effective electron irradiation method that induces n-type doping in intrinsic p-type graphene. The physical mechanism of the junction formation is owing to the substrate gating effect caused by electron irradiation. Photoresponse was obtained for this type of photodetector because the photoexcited electron-hole pairs can be separated in the graphene p-n junction by the built-in potential. The fabricated graphene p-n junction photodetectors exhibit a high detectivity up to ~3 × 1010 Jones (cm Hz1/2 W−1) at room temperature, which is on a par with that of the traditional III–V photodetectors. The demonstrated novel and simple scheme for obtaining graphene p-n junctions can be used for other optoelectronic devices such as solar cells and be applied to other two dimensional materials based devices.

  3. ABI2-deficient mice exhibit defective cell migration, aberrant dendritic spine morphogenesis, and deficits in learning and memory.

    Science.gov (United States)

    Grove, Matthew; Demyanenko, Galina; Echarri, Asier; Zipfel, Patricia A; Quiroz, Marisol E; Rodriguiz, Ramona M; Playford, Martin; Martensen, Shelby A; Robinson, Matthew R; Wetsel, William C; Maness, Patricia F; Pendergast, Ann Marie

    2004-12-01

    The Abl-interactor (Abi) family of adaptor proteins has been linked to signaling pathways involving the Abl tyrosine kinases and the Rac GTPase. Abi proteins localize to sites of actin polymerization in protrusive membrane structures and regulate actin dynamics in vitro. Here we demonstrate that Abi2 modulates cell morphogenesis and migration in vivo. Homozygous deletion of murine abi2 produced abnormal phenotypes in the eye and brain, the tissues with the highest Abi2 expression. In the absence of Abi2, secondary lens fiber orientation and migration were defective in the eye, without detectable defects in proliferation, differentiation, or apoptosis. These phenotypes were consistent with the localization of Abi2 at adherens junctions in the developing lens and at nascent epithelial cell adherens junctions in vitro. Downregulation of Abi expression by RNA interference impaired adherens junction formation and correlated with downregulation of the Wave actin-nucleation promoting factor. Loss of Abi2 also resulted in cell migration defects in the neocortex and hippocampus, abnormal dendritic spine morphology and density, and severe deficits in short- and long-term memory. These findings support a role for Abi2 in the regulation of cytoskeletal dynamics at adherens junctions and dendritic spines, which is critical for intercellular connectivity, cell morphogenesis, and cognitive functions.

  4. Created-by-current states in long Josephson junctions

    Science.gov (United States)

    Boyadjiev, T. L.; Andreeva, O. Yu.; Semerdjieva, E. G.; Shukrinov, Yu. M.

    2008-08-01

    Critical curves "critical current-external magnetic field" of long Josephson junctions with inhomogeneity and variable width are studied. We demonstrate the existence of regions of magnetic field where some fluxon states are stable only if the external current through the junction is different from zero. Position and size of such regions depend on the length of the junction, its geometry, parameters of inhomogeneity and form of the junction. The noncentral (left and right) pure fluxon states appear in the inhomogeneous Josephson junction with the increase in the junction length. We demonstrate new bifurcation points with change in width of the inhomogeneity and amplitude of the Josephson current through the inhomogeneity.

  5. Thermionic refrigeration at CNT-CNT junctions

    Science.gov (United States)

    Li, C.; Pipe, K. P.

    2016-10-01

    Monte Carlo (MC) simulation is used to study carrier energy relaxation following thermionic emission at the junction of two van der Waals bonded single-walled carbon nanotubes (SWCNTs). An energy-dependent transmission probability gives rise to energy filtering at the junction, which is predicted to increase the average electron transport energy by as much as 0.115 eV, leading to an effective Seebeck coefficient of 386 μV/K. MC results predict a long energy relaxation length (˜8 μm) for hot electrons crossing the junction into the barrier SWCNT. For SWCNTs of optimal length, an analytical transport model is used to show that thermionic cooling can outweigh parasitic heat conduction due to high SWCNT thermal conductivity, leading to a significant cooling capacity (2.4 × 106 W/cm2).

  6. Silicon fiber with p-n junction

    Energy Technology Data Exchange (ETDEWEB)

    Homa, D.; Cito, A.; Pickrell, G.; Hill, C.; Scott, B. [Department of Materials Science and Engineering, Virginia Polytechnic Institute and State University, 312 Holden Hall, Blacksburg, Virginia 24060 (United States)

    2014-09-22

    In this study, we fabricated a p-n junction in a fiber with a phosphorous doped silicon core and fused silica cladding. The fibers were fabricated via a hybrid process of the core-suction and melt-draw techniques and maintained overall diameters ranging from 200 to 900 μm and core diameters of 20–800 μm. The p-n junction was formed by doping the fiber with boron and confirmed via the current-voltage characteristic. The demonstration of a p-n junction in a melt-drawn silicon core fiber paves the way for the seamless integration of optical and electronic devices in fibers.

  7. Vortex structures in exponentially shaped Josephson junctions

    Science.gov (United States)

    Shukrinov, Yu. M.; Semerdjieva, E. G.; Boyadjiev, T. L.

    2005-04-01

    We report the numerical calculations of the static vortex structure and critical curves in exponentially shaped long Josephson junctions for in-line and overlap geometries. Stability of the static solutions is investigated by checking the sign of the smallest eigenvalue of the associated Sturm-Liouville problem. The change in the junction width leads to the renormalization of the magnetic flux in comparison with the case of a linear one-dimensional model. We study the influence of the model's parameters, and particularly, the shape parameter on the stability of the states of the magnetic flux. We compare the vortex structure and critical curves for the in-line and overlap geometries. Our numerically constructed critical curve of the Josephson junction matches well with the experimental one.

  8. Holographic Josephson Junction from Massive Gravity

    CERN Document Server

    Hu, Ya-Peng; Zeng, Hua-Bi; Zhang, Hai-Qing

    2015-01-01

    We study the holographic superconductor-normal metal-superconductor (SNS) Josephon junction in the massive gravity. In the homogeneous case of the chemical potential, we find that the graviton mass will make the normal metal-superconductor phase transition harder to take place. In the holographic model of Josephson junction, it is found that the maximal tunneling current will decrease according to the graviton mass. Besides, the coherence length of the junction decreases as well with respect to the graviton mass. If one interprets the graviton mass as the effect of momentum dissipation in the boundary field theory, it indicates that the stronger the momentum dissipation is, the smaller the coherence length is.

  9. Characterization of magnetic tunnel junction test pads

    DEFF Research Database (Denmark)

    Østerberg, Frederik Westergaard; Kjær, Daniel; Nielsen, Peter Folmer

    2015-01-01

    We show experimentally as well as theoretically that patterned magnetic tunnel junctions can be characterized using the current-in-plane tunneling (CIPT) method, and the key parameters, the resistance-area product (RA) and the tunnel magnetoresistance (TMR), can be determined. The CIPT method...... on square tunnel junction pads with varying sizes and analyze the measured data using both the original and the modified CIPT model. Thus, we determine in which sample size range the modified CIPT model is needed to ensure validity of the extracted sample parameters, RA and TMR. In addition, measurements...... as a function of position on a square tunnel junction pad are used to investigate the sensitivity of the measurement results to probe misalignment....

  10. Gap junction diseases of the skin.

    Science.gov (United States)

    van Steensel, M A M

    2004-11-15

    Gap junctions are intercellular channels that allow the passage of water, ions, and small molecules. They are involved in quick, short-range messaging between cells and are found in skin, nervous tissue, heart, and muscle. An increasing number of hereditary skin disorders appear to be caused by mutations in one of the genes coding for the constituent proteins of gap junctions, known as connexins. In this review, the currently known connexin disorders that feature skin abnormalities are described: keratitis-ichthyosis deafness syndrome, erythrokeratoderma variabilis, Vohwinkel's syndrome, and a novel disorder called hypotrichosis-deafness syndrome. What is known about the pathogenesis of these disorders is discussed and related to gap junction physiology. (c) 2004 Wiley-Liss, Inc.

  11. Overdamped Josephson junctions for digital applications

    Energy Technology Data Exchange (ETDEWEB)

    Febvre, P., E-mail: Pascal.Febvre@univ-savoie.fr [University of Savoie, IMEP-LAHC – CNRS UMR5130, 73376 Le Bourget du Lac (France); De Leo, N.; Fretto, M.; Sosso, A. [I.N.Ri.M., Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135 Torino (Italy); Belogolovskii, M. [Donetsk Institute for Physics and Engineering, 72 R. Luxemburg str., 83114 Donetsk (Ukraine); Collot, R. [University of Savoie, IMEP-LAHC – CNRS UMR5130, 73376 Le Bourget du Lac (France); Lacquaniti, V. [I.N.Ri.M., Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135 Torino (Italy)

    2013-01-15

    Highlights: ► Properties of self-shunted sub-micron Nb/Al–AlO{sub x}/Nb SNIS junctions are studied. ► 1–100 kA/cm{sup 2} current densities and 0.1–0.7 mV critical voltages are obtained. ► The critical voltage-vs-temperature behavior of SNIS junctions is discussed. ► Numerical results showing an effect of the aluminum film thickness are presented. ► A Josephson balanced comparator is studied for different temperatures of operation. -- Abstract: An interesting feature of Superconductor–Normal metal–Superconductor Josephson junctions for digital applications is due to their non-hysteretic current–voltage characteristics in a broad temperature range below T{sub c}. This allows to design Single-Flux-Quantum (SFQ) cells without the need of external shunts. Two advantages can be drawn from this property: first the SFQ cells can be more compact which leads to a more integrated solution towards nano-devices and more complex circuits; second the absence of electrical parasitic elements associated with the wiring of resistors external to the Josephson junctions increases the performance of SFQ circuits, in particular regarding the ultimate speed of operation. For this purpose Superconductor–Normal metal–Insulator–Superconductor Nb/Al–AlO{sub x}/Nb Josephson junctions have been recently developed at INRiM with aluminum layer thicknesses between 30 and 100 nm. They exhibit non-hysteretic current–voltage characteristics with I{sub c}R{sub n} values higher than 0.5 mV in a broad temperature range and optimal Stewart McCumber parameters at 4.2 K for RSFQ applications. The main features of obtained SNIS junctions regarding digital applications are presented.

  12. Superconducting tunnel junctions as direct detectors for submillimeter astronomy

    Science.gov (United States)

    Teufel, John Daniel

    This thesis presents measurements on the of performance of superconducting tunnel junctions (STJ) as direct detectors for submillimeter radiation. Over the past several decades, STJ's have been successfully implemented as energy-resolving detectors of X-ray and optical photons. This work extends their application to ultra-sensitive direct detection of photons near 100 GHz. The focus of this research is to integrate the detector with a readout that is sensitive, fast, and able to be scaled for use in large format arrays. We demonstrate the performance of a radio frequency single electron transistor (RF-SET) configured as a transimpedance current amplifier as one such readout. Unlike traditional semiconductor amplifiers, the RF-SET is compatible with cryogenic operation and naturally lends itself to frequency domain multiplexing. This research progressed to the invention of RF-STJ, whereby the same RF reflectometry as used in the RF-SET is applied directly to the detector junction. This results in a greatly simplified design that preserves many of the advantages of the RF-SET while achieving comparable sensitivity. These experiments culminate in calibration of the detector with an on-chip, mesoscopic noise source. Millimeter wave Johnson noise from a gold microbridge illuminates the detector in situ. This allows for direct measurement of the "optical" properties of the detector and its RF readout, including the response time, responsivity and sensitivity.

  13. Canonical Wnt Signaling Regulates Atrioventricular Junction Programming and Electrophysiological Properties

    Science.gov (United States)

    Gillers, Benjamin S; Chiplunkar, Aditi; Aly, Haytham; Valenta, Tomas; Basler, Konrad; Christoffels, Vincent M.; Efimov, Igor R; Boukens, Bastiaan J; Rentschler, Stacey

    2014-01-01

    Rationale Proper patterning of the atrioventricular canal (AVC) is essential for delay of electrical impulses between atria and ventricles, and defects in AVC maturation can result in congenital heart disease. Objective To determine the role of canonical Wnt signaling in the myocardium during AVC development. Methods and Results We utilized a novel allele of β-catenin that preserves β-catenin’s cell adhesive functions but disrupts canonical Wnt signaling, allowing us to probe the effects of Wnt loss of function independently. We show that loss of canonical Wnt signaling in the myocardium results in tricuspid atresia with hypoplastic right ventricle associated with loss of AVC myocardium. In contrast, ectopic activation of Wnt signaling was sufficient to induce formation of ectopic AV junction-like tissue as assessed by morphology, gene expression, and electrophysiologic criteria. Aberrant AVC development can lead to ventricular preexcitation, a characteristic feature of Wolff-Parkinson-White syndrome. We demonstrate that postnatal activation of Notch signaling downregulates canonical Wnt targets within the AV junction. Stabilization of β-catenin protein levels can rescue Notch-mediated ventricular preexcitation and dysregulated ion channel gene expression. Conclusions Our data demonstrate that myocardial canonical Wnt signaling is an important regulator of AVC maturation and electrical programming upstream of Tbx3. Our data further suggests that ventricular preexcitation may require both morphologic patterning defects, as well as myocardial lineage reprogramming, to allow robust conduction across accessory pathway tissue. PMID:25599332

  14. Multiplication in Silicon p-n Junctions

    DEFF Research Database (Denmark)

    Moll, John L.

    1965-01-01

    Multiplication values were measured in the collector junctions of silicon p-n-p and n-p-n transistors before and after bombardment by 1016 neutrons/cm2. Within experimental error there was no change either in junction fields, as deduced from capacitance measurements, or in multiplication values...... in any of the transistors. The implication is that the electron and hole ionization rates did not change as a result of the addition of extra scattering centers. This result is in direct contradiction to observations of Lee et al. The most likely explanation for the discrepancy is erroneous determination...

  15. Fast transient response of novel Peltier junctions

    Energy Technology Data Exchange (ETDEWEB)

    Hoyos, G.E.; Rao, K.R.; Jerger, D.

    1977-01-01

    The fast transient response of a thermoelectric (TE) cooler with novel geometry is discussed. This geometry involves conical semiconductor legs whose hot to cold junction cross-sectional area ratios can be varied. The novel TE junctions are fabricated such that the thermal capacitance and electrical conductance are decreased while simultaneously increasing the thermal resistance. The experimental apparatus which includes the vacuum system, power supplies, pulse and control circuitry, sensing and measuring instrumentation etc. is described. With narrow pulse width and large amplitudes, additional cooling of the order of 45/sup 0/C below the steady-state maximum with recovery times in the range of 1 to 3 sec is obtained.

  16. The Geometric Field at a Josephson Junction

    CERN Document Server

    Atanasov, Victor

    2016-01-01

    A geometric potential from the kinetic term of a constrained to a curved hyper-plane of space-time quantum superconducting condensate is derived. An energy conservation relation involving the geometric field at every material point in the superconductor is demonstrated. At a Josephson junction the energy conservation relation implies the possibility to transform electric energy into geometric field energy, that is curvature of space-time. Experimental procedures to verify that the Josephson junction can act as a voltage-to-curvature converter are discussed.

  17. Microscopic tunneling theory of long Josephson junctions

    DEFF Research Database (Denmark)

    Grønbech-Jensen, N.; Hattel, Søren A.; Samuelsen, Mogens Rugholm

    1992-01-01

    We present a numerical scheme for solving a nonlinear partial integro-differential equation with nonlocal time dependence. The equation describes the dynamics in a long Josephson junction modeled by use of the microscopic theory for tunneling between superconductors. We demonstrate that the detai......We present a numerical scheme for solving a nonlinear partial integro-differential equation with nonlocal time dependence. The equation describes the dynamics in a long Josephson junction modeled by use of the microscopic theory for tunneling between superconductors. We demonstrate...

  18. Rectangular-to-circular groove waveguide junction

    Institute of Scientific and Technical Information of China (English)

    CUI; Licheng; (崔立成); YANG; Hongsheng; (杨鸿生)

    2003-01-01

    Mode matching method is used to analyze the scattering characteristics of the rectangular-to-circular groove waveguide junction. Firstly, the scattering matrix equation is obtained by matching the electromagnetic fields at the boundary of the junction. The scattering coefficients can be obtained from the equation. Secondly the scattering characteristics of the iris with rectangular window positioned in circular groove waveguide are briefly analyzed. Thirdly, the convergent problem is discussed and the numerical results are given. At last experiment is made and good agreement is found between the calculated results and the measured results.

  19. Electroplated Ni on the PN Junction Semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jin Joo; Uhm, Young Rang; Son, Kwang Jae; Kim, Jong Bum; Choi, Sang Moo; Park, Jong Han; Hong, Jintae [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-05-15

    Nickel (Ni) electroplating was implemented by using a metal Ni powder in order to establish a Ni-63 plating condition on the PN junction semiconductor needed for production of betavoltaic battery. PN junction semiconductors with a Ni seed layer of 500 and 1000 A were coated with Ni at current density from 10 to 50 mA cm{sup 2}. The surface roughness and average grain size of Ni deposits were investigated by XRD and SEM techniques. The roughness of Ni deposit was increased as the current density was increased, and decreased as the thickness of Ni seed layer was increased.

  20. Common features of a vortex structure in long exponentially shaped Josephson junctions and Josephson junctions with inhomogeneities

    Science.gov (United States)

    Boyadjiev, T. L.; Semerdjieva, E. G.; Shukrinov, Yu. M.

    2007-09-01

    We study the vortex structure in three different models of the long Josephson junction: the exponentially shaped Josephson junction and the Josephson junctions with the resistor and the shunt inhomogeneities in the barrier layer. For these three models the critical curves “critical current-magnetic field” are numerically constructed. We develop the idea of the equivalence of the exponentially shaped Josephson junction and the rectangular junction with the distributed inhomogeneity and demonstrate that at some parameters of the shunt and the resistor inhomogeneities in the ends of the junction the corresponding critical curves are very close to the exponentially shaped one.

  1. Common features of a vortex structure in long exponentially shaped Josephson junctions and Josephson junctions with inhomogeneities

    Energy Technology Data Exchange (ETDEWEB)

    Boyadjiev, T.L. [Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Semerdjieva, E.G. [Plovdiv University, 24 Tzar Asen Str., Plovdiv 4000 (Bulgaria); Shukrinov, Yu.M. [Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation)], E-mail: shukrinv@theor.jinr.ru

    2007-09-01

    We study the vortex structure in three different models of the long Josephson junction: the exponentially shaped Josephson junction and the Josephson junctions with the resistor and the shunt inhomogeneities in the barrier layer. For these three models the critical curves 'critical current-magnetic field' are numerically constructed. We develop the idea of the equivalence of the exponentially shaped Josephson junction and the rectangular junction with the distributed inhomogeneity and demonstrate that at some parameters of the shunt and the resistor inhomogeneities in the ends of the junction the corresponding critical curves are very close to the exponentially shaped one.

  2. Ballistic transport in InSb Josephson junctions

    Science.gov (United States)

    Damasco, John Jeffrey; Gill, Stephen; Car, Diana; Bakkers, Erik; Mason, Nadya

    We present transport measurements on Josephson junctions consisting of InSb nanowires contacted by Al at various junction lengths. Junction behavior as a function of gate voltage, electric field, and magnetic field is discussed. We show that short junctions behave as 1D quantum wires, exhibiting quantized conductance steps. In addition, we show how Josephson behavior changes as transport evolves from ballistic to diffusive as a function of contact spacing.

  3. Dynamics near Resonance Junctions in Hamiltonian Systems

    CERN Document Server

    Goto, S; Goto, Shin-itiro; Nozaki, Kazuhiro

    1999-01-01

    An approximate Poincare map near equally strong multiple resonances is reduced by means the method of averaging. Near the resonance junction of three degrees of freedom, we find that some homoclinic orbits ``whiskers'' in single resonance lines survive and form nearly periodic orbits, each of which looks like a pair of homoclinic orbits.

  4. Cooling of suspended nanostructures with tunnel junctions

    OpenAIRE

    Koppinen, P. J.; Maasilta, I. J.

    2009-01-01

    We have investigated electronic cooling of suspended nanowires with SINIS tunnel junction coolers. The suspended samples consist of a free standing nanowire suspended by four narrow ($\\sim$ 200 nm) bridges. We have compared two different cooler designs for cooling the suspended nanowire. We demonstrate that cooling of the nanowire is possible with a proper SINIS cooler design.

  5. Polyphosphonium-based ion bipolar junction transistors.

    Science.gov (United States)

    Gabrielsson, Erik O; Tybrandt, Klas; Berggren, Magnus

    2014-11-01

    Advancements in the field of electronics during the past few decades have inspired the use of transistors in a diversity of research fields, including biology and medicine. However, signals in living organisms are not only carried by electrons but also through fluxes of ions and biomolecules. Thus, in order to implement the transistor functionality to control biological signals, devices that can modulate currents of ions and biomolecules, i.e., ionic transistors and diodes, are needed. One successful approach for modulation of ionic currents is to use oppositely charged ion-selective membranes to form so called ion bipolar junction transistors (IBJTs). Unfortunately, overall IBJT device performance has been hindered due to the typical low mobility of ions, large geometries of the ion bipolar junction materials, and the possibility of electric field enhanced (EFE) water dissociation in the junction. Here, we introduce a novel polyphosphonium-based anion-selective material into npn-type IBJTs. The new material does not show EFE water dissociation and therefore allows for a reduction of junction length down to 2 μm, which significantly improves the switching performance of the ion transistor to 2 s. The presented improvement in speed as well the simplified design will be useful for future development of advanced iontronic circuits employing IBJTs, for example, addressable drug-delivery devices.

  6. Flux interactions on stacked Josephson junctions

    DEFF Research Database (Denmark)

    Scott, Alwyn C.; A., Petraglia

    1996-01-01

    Perturbation methods are used to study the dynamics of locked fluxon modes on stacked Josephson junctions and single crystals of certain high-T-c, superconductors. Two limiting cases are considered: (i) The nonlinear diffusion regime in which fluxon dynamics are dominated by energy exchange betwe...

  7. Gap junction diseases of the skin.

    NARCIS (Netherlands)

    Steensel, M.A.M. van

    2004-01-01

    Gap junctions are intercellular channels that allow the passage of water, ions, and small molecules. They are involved in quick, short-range messaging between cells and are found in skin, nervous tissue, heart, and muscle. An increasing number of hereditary skin disorders appear to be caused by muta

  8. Gap junctions-guards of excitability

    DEFF Research Database (Denmark)

    Stroemlund, Line Waring; Jensen, Christa Funch; Qvortrup, Klaus;

    2015-01-01

    Cardiomyocytes are connected by mechanical and electrical junctions located at the intercalated discs (IDs). Although these structures have long been known, it is becoming increasingly clear that their components interact. This review describes the involvement of the ID in electrical disturbances...

  9. Fluxon density waves in long Josephson junctions

    DEFF Research Database (Denmark)

    Olsen, O. H.; Ustinov, A. V.; Pedersen, Niels Falsig

    1993-01-01

    Numerical simulations of the multiple fluxon dynamics stimulated by an external oscillating force applied at a boundary of a long Josephson junction are presented. The calculated IV characteristics agree well with a recent experimental observation of rf-induced satellite flux-flow steps. The volt...... density waves....

  10. Transmembrane potentials of canine AV junctional tissues.

    Science.gov (United States)

    Tse, W W

    1986-06-01

    The atrioventricular (AV) junction comprises the AV node, His bundle (HB), and specialized tissues proximal to the node called paranodal fibers (PNF). In the present study, an in vitro, dissection-exposed canine right atrial (RA), transitional fiber (TF), AV junctional preparation was used. The TF and PNF formed a pathway running along the base of the septal cusp of the tricuspid valve (SCTV). In the first experiment, impulses elicited at the RA were monitored to propagate sequentially through the TF, PNF, AV node, and then the HB. This functional evidence supports the concept that a conduction pathway connecting the RA and the AV node exists along the base of the SCTV. This internodal pathway is referred to as the septal cusp pathway. In another experiment, transmembrane potentials and Vmax were determined on each of the AV junctional tissues. Results showed that PNF had the lowest Vmax (2.5 V/sec), followed by AV node (7.0 V/sec) and HB (33 V/sec). This finding showed that PNF, and not the AV node, has the lowest Vmax, suggesting that the PNF has the lowest conductivity among the AV junctional tissues, and this study advances our understanding on the mechanism of AV conduction delay in dog hearts.

  11. Lateral junction dynamics lead the way out.

    Science.gov (United States)

    Behrndt, Martin; Heisenberg, Carl-Philipp

    2014-02-01

    Epithelial cell layers need to be tightly regulated to maintain their integrity and correct function. Cell integration into epithelial sheets is now shown to depend on the N-WASP-regulated stabilization of cortical F-actin, which generates distinct patterns of apical-lateral contractility at E-cadherin-based cell-cell junctions.

  12. Soliton excitations in Josephson tunnel junctions

    DEFF Research Database (Denmark)

    Lomdahl, P. S.; Sørensen, O. H.; Christiansen, Peter Leth

    1982-01-01

    on the Nth ZFS yields the frequency Nf1 Coexistence of two adjacent frequencies is found on the third ZFS of the longer junction (L / λJ=6) in a narrow range of bias current as also found in the experiments. Small asymmetries in the experimental environment, a weak magnetic field, e.g., is introduced via...

  13. Gap junction diseases of the skin.

    NARCIS (Netherlands)

    Steensel, M.A.M. van

    2004-01-01

    Gap junctions are intercellular channels that allow the passage of water, ions, and small molecules. They are involved in quick, short-range messaging between cells and are found in skin, nervous tissue, heart, and muscle. An increasing number of hereditary skin disorders appear to be caused by muta

  14. Fluxon Dynamics in Elliptic Annular Josephson Junctions

    DEFF Research Database (Denmark)

    Monaco, Roberto; Mygind, Jesper

    2016-01-01

    We analyze the dynamics of a magnetic flux quantum (current vortex) trapped in a current-biased long planar elliptic annular Josephson tunnel junction. The system is modeled by a perturbed sine-Gordon equation that determines the spatial and temporal behavior of the phase difference across the tu...

  15. Intercellular junctions in nerve-free hydra

    DEFF Research Database (Denmark)

    McDowall, A W; Grimmelikhuijzen, C J

    1980-01-01

    with particles in an "enplaque conformation appearing as a raised plateau on the E-face or as a depression on the P-face; (ii) structures morphologically similar to gap junctions in rat liver, containing particles on the P-face and corresponding pits on the E-face, both having hexagonal packing with a lattice...

  16. All-carbon molecular tunnel junctions.

    Science.gov (United States)

    Yan, Haijun; Bergren, Adam Johan; McCreery, Richard L

    2011-11-30

    This Article explores the idea of using nonmetallic contacts for molecular electronics. Metal-free, all-carbon molecular electronic junctions were fabricated by orienting a layer of organic molecules between two carbon conductors with high yield (>90%) and good reproducibility (rsd of current density at 0.5 V carbon devices exhibit current density-voltage (J-V) behavior similar to those with metallic Cu top contacts. However, the all-carbon devices display enhanced stability to bias extremes and greatly improved thermal stability. Completed carbon/nitroazobenzene(NAB)/carbon junctions can sustain temperatures up to 300 °C in vacuum for 30 min and can be scanned at ±1 V for at least 1.2 × 10(9) cycles in air at 100 °C without a significant change in J-V characteristics. Furthermore, these all-carbon devices can withstand much higher voltages and current densities than can Cu-containing junctions, which fail upon oxidation and/or electromigration of the copper. The advantages of carbon contacts stem mainly from the strong covalent bonding in the disordered carbon materials, which resists electromigration or penetration into the molecular layer, and provides enhanced stability. These results highlight the significance of nonmetallic contacts for molecular electronics and the potential for integration of all-carbon molecular junctions with conventional microelectronics.

  17. Mesh Currents and Josephson Junction Arrays

    OpenAIRE

    1995-01-01

    A simple but accurate mesh current analysis is performed on a XY model and on a SIMF model to derive the equations for a Josephson junction array. The equations obtained here turn out to be different from other equations already existing in the literature. Moreover, it is shown that the two models come from an unique hidden structure

  18. Superconducting tunnel junction detectors for soft x-ray astrophysics

    Science.gov (United States)

    Verhoeve, P.; Hijmering, R. A.; Martin, D. D. E.; Jerjen, I.; Peacock, A.; Venn, R.

    2006-06-01

    The requirement on energy resolution for detectors in future X-ray satelite missions such as XEUS (X-ray Evolving Universe Spectroscopy mission) is 80%. In addition, the requirements for field of view and angular resolution demand a detector array of typically 150x150 micron sized pixels in a 30x30 pixel format. DROIDs (Distributed Read Out Imaging Devices), consisting of a superconducting absorber strip with superconducting tunnel junctions (STJs) as read-out devices on either end, can fulfill these requirements. The amplitudes of the two signals from the STJs provide information on the absorption position and the energy of the incoming photon in the absorber. In this paper we present the development status of Ta/Al 1-D DROIDs, as well as the the short term development program that should result in a full size XEUS array.

  19. Alternative types of molecule-decorated atomic chains in Au–CO–Au single-molecule junctions

    Directory of Open Access Journals (Sweden)

    Zoltán Balogh

    2015-06-01

    Full Text Available We investigate the formation and evolution of Au–CO single-molecule break junctions. The conductance histogram exhibits two distinct molecular configurations, which are further investigated by a combined statistical analysis. According to conditional histogram and correlation analysis these molecular configurations show strong anticorrelations with each other and with pure Au monoatomic junctions and atomic chains. We identify molecular precursor configurations with somewhat higher conductance, which are formed prior to single-molecule junctions. According to detailed length analysis two distinct types of molecule-affected chain-formation processes are observed, and we compare these results to former theoretical calculations considering bridge- and atop-type molecular configurations where the latter has reduced conductance due to destructive Fano interference.

  20. Irsogladine maleate regulates gap junctional intercellular communication-dependent epithelial barrier in human nasal epithelial cells.

    Science.gov (United States)

    Miyata, Ryo; Nomura, Kazuaki; Kakuki, Takuya; Takano, Ken-Ichi; Kohno, Takayuki; Konno, Takumi; Sawada, Norimasa; Himi, Tetsuo; Kojima, Takashi

    2015-04-01

    The airway epithelium of the human nasal mucosa acts as the first physical barrier that protects against inhaled substances and pathogens. Irsogladine maleate (IM) is an enhancer of gastric mucosal protective factors via upregulation of gap junctional intercellular communication (GJIC). GJIC is thought to participate in the formation of functional tight junctions. However, the effects of IM on GJIC and the epithelial barrier in human nasal epithelial cells (HNECs) remain unknown. To investigate the effects of IM on GJIC and the tight junctional barrier in HNECs, primary cultures of HNECs transfected with human telomerase reverse transcriptase (hTERT-HNECs) were treated with IM and the GJIC inhibitors oleamide and 18β-GA. Some cells were pretreated with IM before treatment with TLR3 ligand poly(I:C) to examine whether IM prevented the changes via TLR3-mediated signal pathways. In hTERT-HNECs, GJIC blockers reduced the expression of tight junction molecules claudin-1, -4, -7, occludin, tricellulin, and JAM-A. IM induced GJIC activity and enhanced the expression of claudin-1, -4, and JAM-A at the protein and mRNA levels with an increase of barrier function. GJIC blockers prevented the increase of the tight junction proteins induced by IM. Furthermore, IM prevented the reduction of JAM-A but not induction of IL-8 and TNF-α induced by poly(I:C). In conclusion, IM can maintain the GJIC-dependent tight junctional barrier via regulation of GJIC in upper airway nasal epithelium. Therefore, it is possible that IM may be useful as a nasal spray to prevent the disruption of the epithelial barrier by viral infections and exposure to allergens in human nasal mucosa.

  1. Connexin43 mutation causes heterogeneous gap junction loss and sudden infant death.

    Science.gov (United States)

    Van Norstrand, David W; Asimaki, Angeliki; Rubinos, Clio; Dolmatova, Elena; Srinivas, Miduturu; Tester, David J; Saffitz, Jeffrey E; Duffy, Heather S; Ackerman, Michael J

    2012-01-24

    An estimated 10% to 15% of sudden infant death syndrome (SIDS) cases may stem from channelopathy-mediated lethal arrhythmias. Loss of the GJA1-encoded gap junction channel protein connexin43 is known to underlie formation of lethal arrhythmias. GJA1 mutations have been associated with cardiac diseases, including atrial fibrillation. Therefore, GJA1 is a plausible candidate gene for premature sudden death. GJA1 open reading frame mutational analysis was performed with polymerase chain reaction, denaturing high-performance liquid chromatography, and direct DNA sequencing on DNA from 292 SIDS cases. Immunofluorescence and dual whole-cell patch-clamp studies were performed to determine the functionality of mutant gap junctions. Immunostaining for gap junction proteins was performed on SIDS-associated paraffin-embedded cardiac tissue. Two rare, novel missense mutations, E42K and S272P, were detected in 2 of 292 SIDS cases, a 2-month-old white boy and a 3-month-old white girl, respectively. Analysis of the E42K victim's parental DNA demonstrated a de novo mutation. Both mutations involved highly conserved residues and were absent in >1000 ethnically matched reference alleles. Immunofluorescence demonstrated no trafficking abnormalities for either mutation, and S272P demonstrated wild-type junctional conductance. However, junctional conductance measurements for the E42K mutation demonstrated a loss of function not rescued by wild type. Moreover, the E42K victim's cardiac tissue demonstrated a mosaic immunostaining pattern for connexin43 protein. This study provides the first molecular and functional evidence implicating a GJA1 mutation as a novel pathogenic substrate for SIDS. E42K-connexin43 demonstrated a trafficking-independent reduction in junctional coupling in vitro and a mosaic pattern of mutational DNA distribution in deceased cardiac tissue, suggesting a novel mechanism of connexin43-associated sudden death.

  2. Connexin26 regulates assembly and maintenance of cochlear gap junction macromolecular complex for normal hearing

    Science.gov (United States)

    Kamiya, Kazusaku; Fukunaga, Ichiro; Hatakeyama, Kaori; Ikeda, Katsuhisa

    2015-12-01

    Hereditary deafness affects about 1 in 2000 children and GJB2 gene mutation is most frequent cause for this disease in the world. GJB2 encodes connexin26 (Cx26), a component in cochlear gap junction. Recently, we found macromolecular change of gap junction plaques with two different types of Cx26 mutation as major classification of clinical case, one is a model of dominant negative type, Cx26R75W+ and the other is conditional gene deficient mouse, Cx26f/fP0Cre as a model for insufficiency of gap junction protein [6]. Gap junction composed mainly of Cx26 and Cx30 in wild type mice formed large planar gap junction plaques (GJP). In contrast, Cx26R75W+ and Cx26f/fP0Cre showed fragmented small round GJPs around the cell border. In Cx26f/fP0Cre, some of the cells with Cx26 expression due to their cellular mosaicism showed normal large GJP with Cx26 and Cx30 only at the cell junction site between two Cx26 positive cells. These indicate that bilateral Cx26 expressions from both adjacent cells are essential for the formation of the cochlear linear GJP, and it is not compensated by other cochlear Connexins such as Connexin30. In the present study, we demonstrated a new molecular pathology in most common hereditary deafness with different types of Connexin26 mutations, and this machinery can be a new target for drag design of hereditary deafness.

  3. Zero-voltage nondegenerate parametric mode in Josephson tunnel junctions

    DEFF Research Database (Denmark)

    Pedersen, Niels Falsig

    1976-01-01

    A new parametric mode in a Josephson tunnel junction biased in the zero-voltage mode is suggested. It is a nondegenerate parametric excitation where the junction plasma resonance represents the input circuit, and a junction geometrical resonance represents the idler circuit. This nondegenerate mo...... for such a coupling. Journal of Applied Physics is copyrighted by The American Institute of Physics....

  4. Long Josephson Junction Stack Coupled to a Cavity

    DEFF Research Database (Denmark)

    Madsen, Søren Peder; Pedersen, Niels Falsig; Groenbech-Jensen, N.

    2007-01-01

    A stack of inductively coupled long Josephson junctions are modeled as a system of coupled sine-Gordon equations. One boundary of the stack is coupled electrically to a resonant cavity. With one fluxon in each Josephson junction, the inter-junction fluxon forces are repulsive. We look at a possible...

  5. Structure Stability of Ⅰ-Type Carbon Nanotube Junctions

    Institute of Scientific and Technical Information of China (English)

    夏丹; 袁喆; 李家明

    2002-01-01

    Carbon nanotubes with junctions may play an important role in future ‘nanoelectronics' and future ‘nano devices'.In particular, junctions constructed with metal and semiconducting nanotubes have potential applications. Basedon the orthogonal tight-binding molecular dynamics method, we present our study of the structure stability ofI-type carbon nanotube junctions.

  6. Vacuum Tight Threaded Junctions (VTTJ): A new solution for reliable heterogeneous junctions in ITER

    Energy Technology Data Exchange (ETDEWEB)

    Agostinetti, P., E-mail: piero.agostinetti@igi.cnr.it; Palma, M. Dalla; Agostini, F. Degli; Marcuzzi, D.; Rizzolo, A.; Rossetto, F.; Sonato, P.; Zaccaria, P.

    2015-10-15

    Highlights: • Heterogeneous junctions represent a critical issue in Nuclear Fusion experiments. • We have developed a new technique for heterogeneous junctions, called VTTJ, whose main advantages are low cost, high reliability and easiness of construction. • The VTTJ junctions have passed all the tests required by ITER for the heterogeneous junctions of the divertor. • Further tests have demonstrated wide margins for operation (up to 700 °C and 500 bar). - Abstract: A new technique, called Vacuum Tight Threaded Junction (VTTJ), has been developed and patented by Consorzio RFX, permitting to obtain low-cost and reliable non-welded junctions, able to maintain vacuum tightness also in heavy loading conditions (high temperature and high mechanical loads). The technique can be applied also if the materials to be joint are not weldable and for heterogeneous junctions (for example, between steel and copper) and has been tested up to 500 bar internal pressure and up to 700 °C, showing excellent leak tightness in vacuum conditions and high mechanical resistance. The main advantages with respect to existing technologies (for example, friction welding and electron beam welding) are an easy construction, a low cost, a precise positioning of the junction and a high repeatability of the process. Due to these advantages, the new technique has been adopted for several components of the SPIDER experiment and it is proposed for ITER, in particular for the ITER Heat and Current Drive Neutral Beam Injector and for its prototype, the MITICA experiment, to be tested at Consorzio RFX. This paper gives a detailed description of the VTTJ technique, of the samples manufactured and of the qualification tests that have been carried out so far.

  7. Hybrid pn-junction solar cells based on layers of inorganic nanocrystals and organic semiconductors: optimization of layer thickness by considering the width of the depletion region.

    Science.gov (United States)

    Saha, Sudip K; Guchhait, Asim; Pal, Amlan J

    2014-03-07

    We report the formation and characterization of hybrid pn-junction solar cells based on a layer of copper diffused silver indium disulfide (AgInS2@Cu) nanoparticles and another layer of copper phthalocyanine (CuPc) molecules. With copper diffusion in the nanocrystals, their optical absorption and hence the activity of the hybrid pn-junction solar cells was extended towards the near-IR region. To decrease the particle-to-particle separation for improved carrier transport through the inorganic layer, we replaced the long-chain ligands of copper-diffused nanocrystals in each monolayer with short-ones. Under illumination, the hybrid pn-junctions yielded a higher short-circuit current as compared to the combined contribution of the Schottky junctions based on the components. A wider depletion region at the interface between the two active layers in the pn-junction device as compared to that of the Schottky junctions has been considered to analyze the results. Capacitance-voltage characteristics under a dark condition supported such a hypothesis. We also determined the width of the depletion region in the two layers separately so that a pn-junction could be formed with a tailored thickness of the two materials. Such a "fully-depleted" device resulted in an improved photovoltaic performance, primarily due to lessening of the internal resistance of the hybrid pn-junction solar cells.

  8. Graphene junction field-effect transistor

    Science.gov (United States)

    Ou, Tzu-Min; Borsa, Tomoko; van Zeghbroeck, Bart

    2014-03-01

    We have demonstrated for the first time a novel graphene transistor gated by a graphene/semiconductor junction rather than an insulating gate. The transistor operates much like a semiconductor junction Field Effect Transistor (jFET) where the depletion layer charge in the semiconductor modulates the mobile charge in the channel. The channel in our case is the graphene rather than another semiconductor layer. An increased reverse bias of the graphene/n-silicon junction increases the positive charge in the depletion region and thereby reduces the total charge in the graphene. We fabricated individual graphene/silicon junctions as well as graphene jFETs (GjFETs) on n-type (4.5x1015 cm-3) silicon with Cr/Au electrodes and 3 μm gate length. As a control device, we also fabricated back-gated graphene MOSFETs using a 90nm SiO2 on a p-type silicon substrate (1019 cm-3) . The graphene was grown by APCVD on copper foil and transferred with PMMA onto the silicon substrate. The GjFET exhibited an on-off ratio of 3.75, an intrinsic graphene doping of 1.75x1012 cm-2, compared to 1.17x1013 cm-2 in the MOSFET, and reached the Dirac point at 13.5V. Characteristics of the junctions and transistors were measured as a function of temperature and in response to light. Experimental data and a comparison with simulations will be presented.

  9. Heteroepitaxial Junction in Au-ZnSe Nanostructure: Experiment versus First-Principle Simulation.

    Science.gov (United States)

    Bose, Riya; Wasey, A H M Abdul; Das, Gour P; Pradhan, Narayan

    2014-06-05

    Composing together the experimental as well as the simulated results, we demonstrate here the atomic placements and the electronic structure at the epitaxial junction of a solution-processed heteronanostructure Au-ZnSe. Despite the large lattice mismatch (∼32%) between fcc Au and zinc-blende structured ZnSe, the heterostructures are formed via coincidence site epitaxy, which appears periodically because of the arrangements of their proper unit cell placements at the junction. This reduces the interface energy and drives the formation of such heteronanostructures. Details of the physical processes involved in the formation of these nanostructures have been discussed in this letter, and epitaxy at the heterojunction is strongly supported by HRTEM measurement and DFT calculation. This material has the possibility of plasmon-exciton coupling and therefore might be a futuristic material for utilizations in catalysis, nanoelectronics, and other related applications.

  10. Mapping of single-base differences between two DNA strands in a single molecule using holliday junction nanomechanics.

    Directory of Open Access Journals (Sweden)

    Camille Brème

    Full Text Available OBJECTIVE: The aim of this work is to demonstrate a novel single-molecule DNA sequence comparison assay that is purely based on DNA mechanics. METHODS: A molecular construct that contained the two homologous but non-identical DNA sequences that were to be compared was prepared such that a four-way (Holliday junction could be formed by the formation of heteroduplexes through the inter-recombination of the strands. Magnetic tweezers were used to manipulate the force and the winding applied to this construct for inducing both the formation and the migration of a Holliday junction. The end-to-end distance of the construct was measured as a function of the winding and was used to monitor the behavior of the Holliday junction in different regions of the intra-molecular recombination. MAIN RESULTS: In the appropriate buffer, the magnet rotation induces the migration of the Holliday junction in the regions where there is no sequence difference between the recombining sequences. In contrast, even a single-base difference between the recombining sequences leads to a long-lasting blockage of the migration in the same buffer; this effect was obtained when the junction was positioned near this locus (the site of the single-base difference and forced toward the formation of heteroduplexes that comprise the locus. The migration blockages were detected through the identification of the formation of plectonemes. The detection of the presence of sequence differences and their respective mappings were obtained from the series of blockages that were detected. SIGNIFICANCE: This work presents a novel single-molecule sequence comparison assay that is based on the use of a Holliday junction as an ultra-sensitive nanomechanism; the mismatches act as blocking grains of sand in the Holliday "DNA gearbox". This approach will potentially have future applications in biotechnology.

  11. YBa2Cu3O7-δ long Josephson junctions on bicrystal Zr1-xYxO2 substrates fabricated by preliminary topology masks

    Science.gov (United States)

    Masterov, D. V.; Parafin, A. E.; Revin, L. S.; Chiginev, A. V.; Skorokhodov, E. V.; Yunin, P. A.; Pankratov, A. L.

    2017-02-01

    YBa2Cu3O{}7-δ (YBCO) films were fabricated by magnetron sputtering with modification of the substrate surface by preliminary topology masks. Formation features of Josephson junctions on bicrystal Zr1-xYxO2 (YSZ) substrates have been considered. The structural and electrical properties of such junctions were investigated. As a result, the presented technology allows us to fabricate YBCO structures on YSZ substrates with a buffer cerium dioxide (CeO2) layer where YBCO film sputtering is the final stage of structure formation. In particular, long Josephson junctions with good characteristics have been fabricated by this technology and measured, allowing us to achieve critical currents of 80 mA for 150 um junctions.

  12. A mechanism of gap junction docking revealed by functional rescue of a human-disease-linked connexin mutant.

    Science.gov (United States)

    Gong, Xiang-Qun; Nakagawa, So; Tsukihara, Tomitake; Bai, Donglin

    2013-07-15

    Gap junctions are unique intercellular channels formed by the proper docking of two hemichannels from adjacent cells. Each hemichannel is a hexamer of connexins (Cxs) - the gap junction subunits, which are encoded by 21 homologous genes in the human genome. The docking of two hemichannels to form a functional gap junction channel is only possible between compatible Cxs, but the underlying molecular mechanism is unclear. On the basis of the crystal structure of the Cx26 gap junction, we developed homology models for homotypic and heterotypic channels from Cx32 and/or Cx26; these models predict six hydrogen bonds at the docking interface of each pair of the second extracellular domain (E2). A Cx32 mutation N175H and a human-disease-linked mutant N175D were predicted to lose the majority of the hydrogen bonds at the E2 docking-interface; experimentally both mutations failed to form morphological and functional gap junctions. To restore the lost hydrogen bonds, two complementary Cx26 mutants - K168V and K168A were designed to pair with the Cx32 mutants. When docked with Cx26K168V or K168A, the Cx32N175H mutant was successfully rescued morphologically and functionally in forming gap junction channels, but not Cx32 mutant N175Y. By testing more homotypic and heterotypic Cx32 and/or Cx26 mutant combinations, it is revealed that a minimum of four hydrogen bonds at each E2-docking interface are required for proper docking and functional channel formation between Cx26 and Cx32 hemichannels. Interestingly, the disease-linked Cx32N175D could be rescued by Cx26D179N, which restored five hydrogen bonds at the E2-docking interface. Our findings not only provide a mechanism for gap junction docking for Cx26 and Cx32 hemichannels, but also a potential therapeutic strategy for gap junction channelopathies.

  13. Rho/Rho-associated Kinase-II Signaling Mediates Disassembly of Epithelial Apical Junctions

    OpenAIRE

    2007-01-01

    Apical junctional complex (AJC) plays a vital role in regulation of epithelial barrier function. Disassembly of the AJC is observed in diverse physiological and pathological states; however, mechanisms governing this process are not well understood. We previously reported that the AJC disassembly is driven by the formation of apical contractile acto-myosin rings. In the present study, we analyzed the signaling pathways regulating acto-myosin–dependent disruption of AJC by using a model of ext...

  14. The mysterious droplet birth in a microfluidic cross junction

    Science.gov (United States)

    van Loo, Stephanie; Gilet, Tristan

    2015-11-01

    In microfluidics flow focusing is widely used to produce water-in-oil droplets in microchannels at high frequency. Nevertheless, the scaling laws associated to droplet length, speed and frequency could not be identified yet, owing to the large number of parameters involved (incl. complex geometry). We here present an experimental study of droplet formation in a microfluidic cross-junction with a minimum number of geometrical parameters. We mostly focus on the dripping regime. The formation sequence is decomposed in two steps, inflation and squeezing, that vary differently according to both water and oil flow rates. These variations reveal several insights about the fluid flows in both phases. From there we infer the scaling law that relates droplet volume and frequency to the Capillary number associated to each inlet flow rate. This law involves a minimum of fitting parameters. We finally discuss the influence of inlet control (flow rate vs. pressure) and surfactants on the formation dynamics. Supported by the FRIA/FNRS and the Interuniversity Attraction Poles Programme (IAP7/38 MicroMAST) initiated by the Belgian Science Policy Office.

  15. Planar Josephson tunnel junctions in a transverse magnetic field

    DEFF Research Database (Denmark)

    Monacoa, R.; Aarøe, Morten; Mygind, Jesper

    2007-01-01

    Traditionally, since the discovery of the Josephson effect in 1962, the magnetic diffraction pattern of planar Josephson tunnel junctions has been recorded with the field applied in the plane of the junction. Here we discuss the static junction properties in a transverse magnetic field where...... demagnetization effects imposed by the tunnel barrier and electrodes geometry are important. Measurements of the junction critical current versus magnetic field in planar Nb-based high-quality junctions with different geometry, size, and critical current density show that it is advantageous to use a transverse...

  16. The computation of first order moments on junction trees

    CERN Document Server

    Djuric, Milos B; Stankovic, Miomir S

    2012-01-01

    We review some existing methods for the computation of first order moments on junction trees using Shafer-Shenoy algorithm. First, we consider the problem of first order moments computation as vertices problem in junction trees. In this way, the problem is solved using the memory space of an order of the junction tree edge-set cardinality. After that, we consider two algorithms, Lauritzen-Nilsson algorithm, and Mau\\'a et al. algorithm, which computes the first order moments as the normalization problem in junction tree, using the memory space of an order of the junction tree leaf-set cardinality.

  17. Photodetection in p–n junctions formed by electrolyte-gated transistors of two-dimensional crystals

    KAUST Repository

    Kozawa, Daichi

    2016-11-16

    Transition metal dichalcogenide monolayers have attracted much attention due to their strong light absorption and excellent electronic properties. These advantages make this type of two-dimensional crystal a promising one for optoelectronic device applications. In the case of photoelectric conversion devices such as photodetectors and photovoltaic cells, p–n junctions are one of the most important devices. Here, we demonstrate photodetection with WSe2 monolayer films. We prepare the electrolyte-gated ambipolar transistors and electrostatic p–n junctions are formed by the electrolyte-gating technique at 270 K. These p-n junctions are cooled down to fix the ion motion (and p-n junctions) and we observed the reasonable photocurrent spectra without the external bias, indicating the formation of p-n junctions. Very interestingly, two-terminal devices exhibit higher photoresponsivity than that of three-terminal ones, suggesting the formation of highly balanced anion and cation layers. The maximum photoresponsivity reaches 5 mA/W in resonance with the first excitonic peak. Our technique provides important evidence for optoelectronics in atomically thin crystals.

  18. Magnetic Tunnel Junctions Incorporating a Near-Zero-Moment Ferromagnetic Semiconductor

    Science.gov (United States)

    Warring, H.; Trodahl, H. J.; Plank, N. O. V.; Natali, F.; Granville, S.; Ruck, B. J.

    2016-10-01

    We present a fully semiconductor-based magnetic tunnel junction that uses spin-orbit coupled materials made of intrinsic ferromagnetic semiconductors. Unlike more common approaches, one of the electrodes consists of a near-zero magnetic-moment ferromagnetic semiconductor, samarium nitride, with the other electrode composed of the more conventional ferromagnetic semiconductor gadolinium nitride. Fabricated tunnel junctions show a magnetoresistance as high as 200%, implying strong spin polarization in both electrodes. In contrast to conventional tunnel junctions, the resistance is largest at high fields, a direct result of the orbital-dominant magnetization in samarium nitride that requires that the spin in this electrode must align opposite to that in the gadolinium nitride when the magnetization is saturated. The magnetoresistance at intermediate fields is controlled by the formation of a twisted magnetization phase in the samarium nitride, a direct result of the orbital-dominant ferromagnetism. Thus, an alternative type of functionality can be brought to magnetic tunnel junctions by the use of different electrode materials, in contrast to the usual focus on tuning the barrier properties.

  19. The energy barrier at noble metal/TiO{sub 2} junctions

    Energy Technology Data Exchange (ETDEWEB)

    Hossein-Babaei, F., E-mail: fhbabaei@kntu.ac.ir, E-mail: fhbabaei@yahoo.com; Lajvardi, Mehdi M., E-mail: mm.lajvardi@gmail.com; Alaei-Sheini, Navid, E-mail: navid-alaei@yahoo.com [Electronic Materials Laboratory, Industrial Control Center of Excellence, Electrical Engineering Department, K. N. Toosi University of Technology, Tehran 16317-14191 (Iran, Islamic Republic of)

    2015-02-23

    Nobel metal/TiO{sub 2} structures are used as catalysts in chemical reactors, active components in TiO{sub 2}-based electronic devices, and connections between such devices and the outside circuitry. Here, we investigate the energy barrier at the junctions between vacuum-deposited Ag, Au, and Pt thin films and TiO{sub 2} layers by recording their electrical current vs. voltage diagrams and spectra of optical responses. Deposited Au/, Pt/, and Ag/TiO{sub 2} behave like contacts with zero junction energy barriers, but the thermal annealing of the reverse-biased devices for an hour at 523 K in air converts them to Schottky diodes with high junction energy barriers, decreasing their reverse electric currents up to 10{sup 6} times. Similar thermal processing in vacuum or pure argon proved ineffective. The highest energy barrier and the lowest reverse current among the devices examined belong to the annealed Ag/TiO{sub 2} contacts. The observed electronic features are described based on the physicochemical parameters of the constituting materials. The formation of higher junction barriers with rutile than with anatase is demonstrated.

  20. Gate-controlled energy barrier at a graphene/molecular semiconductor junction

    Science.gov (United States)

    Parui, S.; Pietrobon, L.; Ciudad, D.; Velez, S.; Sun, X.; Stoliar, P.; Casanova, F.; Hueso, L. E.

    The formation of an energy barrier at a metal/molecular semiconductor junction is both a ubiquitous phenomenon as well as the subject of intense research in order to improve the performance of molecular semiconductor-based electronic and optoelectronic devices. For these devices, a junction with a large energy barrier provides rectification, leading to a diode behavior, whereas a relatively small energy barrier provides nearly-ohmic behavior, resulting in efficient carrier injection (extraction) into the molecular semiconductor. Typically, a specific metal/molecular semiconductor combination leads to a fixed energy barrier; therefore, the possibility of a gate-controlled energy barrier is very appealing for advanced applications. Here, we present a graphene/C60 junction-based vertical field-effect transistor in which we demonstrate control of the interfacial energy-barrier such that the junction switches from a highly rectifying diode at negative gate voltages to a nearly-ohmic behavior at positive gate voltages and at room temperature. We extract an energy-barrier modulation of up to 660 meV, a transconductance of up to five orders of magnitude and a gate-modulated photocurrent.

  1. Oligodendrocyte gap junction loss and disconnection from reactive astrocytes in multiple sclerosis gray matter.

    Science.gov (United States)

    Markoullis, Kyriaki; Sargiannidou, Irene; Schiza, Natasa; Roncaroli, Federico; Reynolds, Richard; Kleopa, Kleopas A

    2014-09-01

    Gap junctions are essential for glial cell function and have been increasingly implicated in multiple sclerosis (MS). Because increasing cortical abnormalities correlate with disease progression and cognitive dysfunction, we examined the expression of oligodendrocytic connexin32 (Cx32) and Cx47 and their astrocytic partners Cx30 and Cx43 in cortical lesions and normal-appearing gray matter (NAGM) in MS patients. Postmortem brain tissue samples from 9 MS cases were compared with 10 controls using real-time polymerase chain reaction, immunoblot, and immunohistochemical analyses. Connexin32 and Cx47 gap junction formation in oligodendrocytes was reduced within lesions, whereas Cx32 loss also extended to NAGM. In contrast, astrocytic Cx30 expression was increased within cortical lesions, whereas Cx43 was elevated in both lesions and NAGM. Diffuse microglial activation and marked astrogliotic changes accompanied these connexin abnormalities. Increased expression of Cx43 correlated with inflammatory load (r = 0.828, p = 0.042), whereas Cx32 expression correlated with longer disease duration and, therefore, milder course (r = 0.825, p = 0.043). Thus, there is a loss of intramyelin and intercellular oligodendrocyte gap junctions in MS gray matter lesions and NAGM, whereas interastrocytic gap junctions are increased, reflecting astrogliosis. These changes correlate with inflammation and disease duration and suggest that disconnection of oligodendrocytes from reactive astrocytes may play a role in failed remyelination and disease progression.

  2. Vibrational Heat Transport in Molecular Junctions

    Science.gov (United States)

    Segal, Dvira; Agarwalla, Bijay Kumar

    2016-05-01

    We review studies of vibrational energy transfer in a molecular junction geometry, consisting of a molecule bridging two heat reservoirs, solids or large chemical compounds. This setup is of interest for applications in molecular electronics, thermoelectrics, and nanophononics, and for addressing basic questions in the theory of classical and quantum transport. Calculations show that system size, disorder, structure, dimensionality, internal anharmonicities, contact interaction, and quantum coherent effects are factors that combine to determine the predominant mechanism (ballistic/diffusive), effectiveness (poor/good), and functionality (linear/nonlinear) of thermal conduction at the nanoscale. We review recent experiments and relevant calculations of quantum heat transfer in molecular junctions. We recount the Landauer approach, appropriate for the study of elastic (harmonic) phononic transport, and outline techniques that incorporate molecular anharmonicities. Theoretical methods are described along with examples illustrating the challenge of reaching control over vibrational heat conduction in molecules.

  3. Junction between surfaces of two topological insulators

    Science.gov (United States)

    Sen, Diptiman; Deb, Oindrila

    2012-02-01

    We study scattering from a line junction which separates the surfaces of two three-dimensional topological insulators; some aspects of this problem were recently studied in Takahashi and Murakami, Phys. Rev. Lett. 107, 166805 (2011). The velocities of the Dirac electrons on the two surfaces may be unequal and may even have opposite signs; in the latter case, we find that the electrons must, in general, go into the two-dimensional interface separating the two topological insulators. We also study what happens if the two surfaces are at an angle φ with respect to each other. We find in this case that there are bound states which propagate along the line junction with a velocity and direction of spin which depend on the bending angle φ.

  4. Current distributions in stripe Majorana junctions

    Science.gov (United States)

    Osca, Javier; Llorenç, Serra

    2017-02-01

    We calculate current and density distributions in stripe (2D planar) junctions between normal and Majorana nanowires having a finite ( y) transverse length. In presence of a magnetic field with vertical and in-plane components, the y-symmetry of the charge current distribution in the normal lead changes strongly across the Majorana phase transition: from center-symmetric if a Majorana mode is present to laterally-shifted (as expected by the Hall effect) if the field is tilted such as to destroy the Majorana mode due to the projection rule. We compare quasi-particle and charge distributions of current and density, as well as spin magnetizations. The Majorana mode causes opposite spin accumulations on the transverse sides of the junction and the emergence of a spin current.

  5. Boson Josephson Junction with Trapped Atoms

    Science.gov (United States)

    Raghavan, S.; Smerzi, A.; Fantoni, S.; Shenoy, S. R.

    We consider coherent atomic tunneling between two weakly coupled Bose-Einstein condensates at T=0 in a double-well trap. The condensate dynamics of the macroscopic amplitudes in the two wells is modeled by two Gross-Pitaevskii equations (GPE) coupled by a tunneling matrix element. Analytic elliptic function solutions are obtained for the time evolution of the inter-well fractional population imbalance z(t) (related to the condensate phase difference) of the Boson Josephson junction (BJJ). Surprisingly, the neutral-atom BJJ shows (non-sinusoidal generalizations of) effects seen in charged-electron superconductor Josephson junctions (SJJ). The BJJ elliptic-function behavior has a singular dependence on a GPE parameter ratio Λ at a critical ratio Λ=Λc, beyond which a novel 'macroscopic quantum self-trapping' effect sets in with a non-zero time-averaged imbalance ≠0.

  6. Non-Lagrangian theories from brane junctions

    Energy Technology Data Exchange (ETDEWEB)

    Bao, Ling [Chalmers Univ. of Technology, Goeteborg (Sweden); Mitev, Vladimir [Humboldt Univ., Berlin (Germany). Inst. fuer Mathematik und Inst. fuer Physik; Pomoni, Elli [Deutsches Elektronen-Synchrotron DESY, Hamburg (Germany). Theory Group; Taki, Masato [RIKEN Nishina Center, Saitama (Japan). Mathematical Physics Lab.; Yagi, Futoshi [International School of Advanced Studies (SISSA), Trieste (Italy); INFN, Trieste (Italy); Korea Institute for Advanced Study (KIAS), Seoul (Korea, Republic of)

    2013-10-15

    In this article we use 5-brane junctions to study the 5D T{sub N} SCFTs corresponding to the 5D N=1 uplift of the 4D N=2 strongly coupled gauge theories, which are obtained by compactifying N M5 branes on a sphere with three full punctures. Even though these theories have no Lagrangian description, by using the 5-brane junctions proposed by Benini, Benvenuti and Tachikawa, we are able to derive their Seiberg-Witten curves and Nekrasov partition functions. We cross-check our results with the 5D superconformal index proposed by Kim, Kim and Lee. Through the AGTW correspondence, we discuss the relations between 5D superconformal indices and n-point functions of the q-deformed W{sub N} Toda theories.

  7. An Important Member of Tight Junctions: Claudins

    Directory of Open Access Journals (Sweden)

    Ozlem Demirpence

    2016-01-01

    Full Text Available The tight junction (TJs, the most apically located of the intercellular junctional complexes, inhibits solute and water flow through the paracellular space, termed the %u201Cbarrier%u201D function. TJs participate in signal transduction mechanisms that regulate epithelial cell proliferation, gene expression, differentiation and morphogenesis. The claudin family of transmembrane proteins localized to the TJ. Loss of expression of Claudin causes of suppression TJs function. Recent studies have shown that altered levels of the different claudins may be related to invasion and progression of carcinoma cells in several primary neoplasms. A better knowledge of the mechanisms underlying carcinogenesis will likely result in the development of novel approaches for the diagnosis and therapy.

  8. Electron transport in doped fullerene molecular junctions

    Science.gov (United States)

    Kaur, Milanpreet; Sawhney, Ravinder Singh; Engles, Derick

    The effect of doping on the electron transport of molecular junctions is analyzed in this paper. The doped fullerene molecules are stringed to two semi-infinite gold electrodes and analyzed at equilibrium and nonequilibrium conditions of these device configurations. The contemplation is done using nonequilibrium Green’s function (NEGF)-density functional theory (DFT) to evaluate its density of states (DOS), transmission coefficient, molecular orbitals, electron density, charge transfer, current, and conductance. We conclude from the elucidated results that Au-C16Li4-Au and Au-C16Ne4-Au devices behave as an ordinary p-n junction diode and a Zener diode, respectively. Moreover, these doped fullerene molecules do not lose their metallic nature when sandwiched between the pair of gold electrodes.

  9. Charge Transport Phenomena in Peptide Molecular Junctions

    Directory of Open Access Journals (Sweden)

    Alessandra Luchini

    2008-01-01

    Full Text Available Inelastic electron tunneling spectroscopy (IETS is a valuable in situ spectroscopic analysis technique that provides a direct portrait of the electron transport properties of a molecular species. In the past, IETS has been applied to small molecules. Using self-assembled nanoelectronic junctions, IETS was performed for the first time on a large polypeptide protein peptide in the phosphorylated and native form, yielding interpretable spectra. A reproducible 10-fold shift of the I/V characteristics of the peptide was observed upon phosphorylation. Phosphorylation can be utilized as a site-specific modification to alter peptide structure and thereby influence electron transport in peptide molecular junctions. It is envisioned that kinases and phosphatases may be used to create tunable systems for molecular electronics applications, such as biosensors and memory devices.

  10. Peltier Junction heats and cools car seat

    Energy Technology Data Exchange (ETDEWEB)

    Gottschalk, M.A.

    1994-10-10

    Electrically heated seats may soon become heated and cooled seats. The design called the CCS module exploits the heat-pump capability of a class of semiconductor thermoelectric devices (TEDs) known as Peltier Junction. Every CCS module contain two TEDs. Heating and cooling occurs through convection and conduction. The heart of the system is the thermoelectric heat pump. This is originally conceived as the sole heating/cooling options for a prototype electric vehicle.

  11. Josephson junction microwave modulators for qubit control

    Science.gov (United States)

    Naaman, O.; Strong, J. A.; Ferguson, D. G.; Egan, J.; Bailey, N.; Hinkey, R. T.

    2017-02-01

    We demonstrate Josephson junction based double-balanced mixer and phase shifter circuits operating at 6-10 GHz and integrate these components to implement both a monolithic amplitude/phase vector modulator and an I/Q quadrature mixer. The devices are actuated by flux signals, dissipate no power on chip, exhibit input saturation powers in excess of 1 nW, and provide cryogenic microwave modulation solutions for integrated control of superconducting qubits.

  12. Internal dynamics of long Josephson junction oscillators

    DEFF Research Database (Denmark)

    Christiansen, Peter Leth; Lomdahl, P. S.; Scott, Alwyn C.;

    1981-01-01

    Numerical computations on a sine-Gordon model of the Josephson junction fluxon oscillator are compared with experimental measurements. Good agreement is found for the voltage current characteristic, oscillator power output, and range of current bias over which oscillation is observed. Our numeric...... results imply a ''bunched-fluxon'' mode of oscillation at larger values of bias current. Applied Physics Letters is copyrighted by The American Institute of Physics....

  13. Decreased Vision and Junctional Scotoma from Pituicytoma

    Directory of Open Access Journals (Sweden)

    Nancy Huynh

    2012-05-01

    Full Text Available Pituicytomas are rare neoplasms of the sellar region. We report a case of vision loss and a junctional scotoma in a 43-year-old woman caused by compression of the optic chiasm by a pituitary tumor. The morphological and immunohistochemical characteristics of the tumor were consistent with the diagnosis of pituicytoma. The tumor was debulked surgically, and the patient’s vision improved.

  14. Brownian refrigeration by hybrid tunnel junctions

    OpenAIRE

    Peltonen, J. T.; Helle, M.; Timofeev, A. V.; Solinas, P.; Hekking, F. W. J.; Pekola, Jukka P.

    2011-01-01

    Voltage fluctuations generated in a hot resistor can cause extraction of heat from a colder normal metal electrode of a hybrid tunnel junction between a normal metal and a superconductor. We extend the analysis presented in Phys. Rev. Lett. 98, 210604 (2007) of this heat rectifying system, bearing resemblance to a Maxwell’s demon. Explicit analytic calculations show that the entropy of the total system is always increasing. We then consider a single-electron transistor configuration with two ...

  15. RADIOLOGICAL EVALUATION OF CRANIOVERTEBRAL JUNCTION ANOMALIES

    Directory of Open Access Journals (Sweden)

    Joji Reddy

    2015-08-01

    Full Text Available INTRODUCTION: Detailed discussions of the CVJ are conspicuously absent in many standard textbooks and chapters addressing the skull or cervical spine, since it lies in between these regions . CVJ anomalies are common in India subcontinent. OBJECTIVES : To outline the normal anatomy and various abnormalities of craniovertebral junction. To evaluate the most common developmental and acquired craniovertebral junction abnormalities . CRANIOMETRY AND DIAGNOSIS: Radiological evaluation of CVJ requir es identification of only a few anatomic structures. Over the years multiple lines , planes and angles have been described for assessment of CVJ relationship , initially with radiography and later with polytomography. Two lines have remained particularly use ful for evaluation of CVJ relationship with virtually any imaging modality: the chamberlain`s line and weckenheim ’ s clivus base line . Two angles also continue to be useful: the welcher basal angle and atlanto occipital joint axis angle. PATIENTS AND METHOD S: The prospective study of craniovertebral junction anomalies was carried out at Kurnool medical college , Governament general hospital Kurnool from NOV 2012 to AUG 2014. The patients are subjected to clinical evaluation and radiological evaluation. OBSERV ATIONS AND RESULTS : In our study there is male predominance with male to female ratio of 2:1 . Majority of patients are in the age group of 11 - 40 (73.26%. The commonest symptom seen is weakness of extremities ( 70% with associated numbness (50%. On clinica l examination pyramidal tract involvement noticed in 70% of cases. Basilar invagination is the most common followed by Atlantoocoipital assimilation (40% and AAD (30% . CONCLUSION : Computed tomography and magnetic resonance imaging are invalvable adjuncts to the plain radiographs in the evaluation of the craniovertebral junction anomalies. Chamberlain’s line and McGregor line are the most commonly applied craniometric measurements

  16. Interfacial capacitance effects in magnetic tunneling junctions

    CERN Document Server

    Landry, G; Du, J; Xiao, J Q

    2001-01-01

    We have investigated the AC transport properties of magnetic tunnel junctions (MTJ) in order to characterize interfacial properties. One such property is interfacial charge accumulation, which leads to a voltage drop in the electrodes of the MTJ and the measured capacitance differing from the geometrical capacitance. Through measurement of capacitance spectra, we have extracted an interfacial capacitance of 16 mu F/cm sup 2 per interface and a screening length of 0.55 A for FeNi electrodes.

  17. Gap junction channels and cardiac impulse propagation.

    Science.gov (United States)

    Desplantez, Thomas; Dupont, Emmanuel; Severs, Nicholas J; Weingart, Robert

    2007-08-01

    The role of gap junction channels on cardiac impulse propagation is complex. This review focuses on the differential expression of connexins in the heart and the biophysical properties of gap junction channels under normal and disease conditions. Structural determinants of impulse propagation have been gained from biochemical and immunocytochemical studies performed on tissue extracts and intact cardiac tissue. These have defined the distinctive connexin coexpression patterns and relative levels in different cardiac tissues. Functional determinants of impulse propagation have emerged from electrophysiological experiments carried out on cell pairs. The static properties (channel number and conductance) limit the current flow between adjacent cardiomyocytes and thus set the basic conduction velocity. The dynamic properties (voltage-sensitive gating and kinetics of channels) are responsible for a modulation of the conduction velocity during propagated action potentials. The effect is moderate and depends on the type of Cx and channel. For homomeric-homotypic channels, the influence is small to medium; for homomeric-heterotypic channels, it is medium to strong. Since no data are currently available on heteromeric channels, their influence on impulse propagation is speculative. The modulation by gap junction channels is most prominent in tissues at the boundaries between cardiac tissues such as sinoatrial node-atrial muscle, atrioventricular node-His bundle, His bundle-bundle branch and Purkinje fibers-ventricular muscle. The data predict facilitation of orthodromic propagation.

  18. Gap Junctions: The Claymore for Cancerous Cells

    Directory of Open Access Journals (Sweden)

    Ailar Nakhlband

    2011-07-01

    Full Text Available Introduction: Gap junctions play an important role in the cell proliferation in mammalian cells as well as carcinogenesis. However, there are controversial issues about their role in cancer pathogenesis. This study was designed to evaluate genotoxicity and cytotoxicity of Carbenoxolone (CBX as a prototype of inter-cellular gap junction blocker in MCF7 and BT20 human breast cancer cells. Methods: The MCF7and BT20 human breast cancer cell lines were cultivated, and treated at designated confluency with different doses of CBX. Cellular cytotoxicity was examined using standard colorimetric assay associated with cell viability tests. Gene expression evaluation was carried out using real time polymerase chain reaction (PCR. Results: MCF7 and BT20 cells were significantly affected by CBX in a dose dependent manner in cell viability assays. Despite varying expression of genes, down regulation of pro- and anti-apoptotic genes was observed in these cells. Conclusion: Based upon this investigation, it can be concluded that CBX could affect both low and high proliferative types of breast cancer cell lines and disproportionate down regulation of both pre- and anti-apoptotic genes may be related to interacting biomolecules, perhaps via gap junctions.

  19. Volatile Anesthetics Influence Blood-Brain Barrier Integrity by Modulation of Tight Junction Protein Expression in Traumatic Brain Injury

    OpenAIRE

    Thal, Serge C.; Clara Luh; Eva-Verena Schaible; Ralph Timaru-Kast; Jana Hedrich; Luhmann, Heiko J.; Kristin Engelhard; Zehendner, Christoph M.

    2012-01-01

    Disruption of the blood-brain barrier (BBB) results in cerebral edema formation, which is a major cause for high mortalityrnafter traumatic brain injury (TBI). As anesthetic care is mandatory in patients suffering from severe TBI it may be importantrnto elucidate the effect of different anesthetics on cerebral edema formation. Tight junction proteins (TJ) such as zonularnoccludens-1 (ZO-1) and claudin-5 (cl5) play a central role for BBB stability. First, the influence of the volatile anesthet...

  20. Molecular beam epitaxy growth of germanium junctions for multi-junction solar cell applications

    Science.gov (United States)

    Masuda, T.; Faucher, J.; Lee, M. L.

    2016-11-01

    We report on the molecular beam epitaxy (MBE) growth and device characteristics of Ge solar cells. Integrating a Ge bottom cell beneath a lattice-matched triple junction stack grown by MBE could enable ultra-high efficiencies without metamorphic growth or wafer bonding. However, a diffused junction cannot be readily formed in Ge by MBE due to the low sticking coefficient of group-V molecules on Ge surfaces. We therefore realized Ge junctions by growth of homo-epitaxial n-Ge on p-Ge wafers within a standard III-V MBE system. We then fabricated Ge solar cells, finding growth temperature and post-growth annealing to be key factors for achieving high efficiency. Open-circuit voltage and fill factor values of ~0.175 V and ~0.59 without a window layer were obtained, both of which are comparable to diffused Ge junctions formed by metal-organic vapor phase epitaxy. We also demonstrate growth of high-quality, single-domain GaAs on the Ge junction, as needed for subsequent growth of III-V subcells, and that the surface passivation afforded by the GaAs layer slightly improves the Ge cell performance.

  1. S and Te inter-diffusion in CdTe/CdS hetero junction

    Energy Technology Data Exchange (ETDEWEB)

    Enriquez, J. Pantoja [Cuerpo Academico-Energia y Sustentabilidad, Universidad Politecnica de Chiapas, Eduardo J. Selvas S/N, Col. Magisterial, Tuxtla Gutierrez 29010, Chiapas (Mexico); Gomez Barojas, E. [CIDS-ICUAP, Apdo. Postal 1651, 72000 Puebla (Mexico); Silva Gonzalez, R.; Pal, U. [Instituto de Fisica, Benemerita Universidad Autonoma de Puebla, Puebla (Mexico)

    2007-09-22

    Effects of post formation thermal annealing of the CdTe-CdS device on the inter-diffusion of S and Te at the junction in a substrate configuration device have been studied by Auger electron spectroscopy. While the migration of S and Te atoms increases with annealing temperature, the extent of S diffusion is always higher than the diffusion of Te atoms. Inter-diffusion of S and Te causes the formation of CdTe{sub 1-x}S{sub x} ternary compound at the CdTe-CdS interface. (author)

  2. Current fluctuations in unconventional superconductor junctions with impurity scattering

    Science.gov (United States)

    Burset, Pablo; Lu, Bo; Tamura, Shun; Tanaka, Yukio

    2017-06-01

    The order parameter of bulk two-dimensional superconductors is classified as nodal if it vanishes for a direction in momentum space, or gapful if it does not. Each class can be topologically nontrivial if Andreev bound states are formed at the edges of the superconductor. Nonmagnetic impurities in the superconductor affect the formation of Andreev bound states and can drastically change the tunneling spectra for small voltages. Here, we investigate the mean current and its fluctuations for two-dimensional tunnel junctions between normal-metal and unconventional superconductors by solving the quasiclassical Eilenberger equation self-consistently, including the presence of nonmagnetic impurities in the superconductor. As the impurity strength increases, we find that superconductivity is suppressed for almost all order parameters since (i) at zero applied bias, the effective transferred charge calculated from the noise-current ratio tends to the electron charge e , and (ii) for finite bias, the current-voltage characteristics follows that of a normal-state junction. There are notable exceptions to this trend. First, gapful nontrivial (chiral) superconductors are very robust against impurity scattering due to the linear dispersion relation of their surface Andreev bound states. Second, for nodal nontrivial superconductors, only px-wave pairing is almost immune to the presence of impurities due to the emergence of odd-frequency s -wave Cooper pairs near the interface. Due to their anisotropic dependence on the wave vector, impurity scattering is an effective pair-breaking mechanism for the remaining nodal superconductors. All these behaviors are neatly captured by the noise-current ratio, providing a useful guide to find experimental signatures for unconventional superconductivity.

  3. Local dynamics of gap-junction-coupled interneuron networks

    Science.gov (United States)

    Lau, Troy; Gage, Gregory J.; Berke, Joshua D.; Zochowski, Michal

    2010-03-01

    Interneurons coupled by both electrical gap-junctions (GJs) and chemical GABAergic synapses are major components of forebrain networks. However, their contributions to the generation of specific activity patterns, and their overall contributions to network function, remain poorly understood. Here we demonstrate, using computational methods, that the topological properties of interneuron networks can elicit a wide range of activity dynamics, and either prevent or permit local pattern formation. We systematically varied the topology of GJ and inhibitory chemical synapses within simulated networks, by changing connection types from local to random, and changing the total number of connections. As previously observed we found that randomly coupled GJs lead to globally synchronous activity. In contrast, we found that local GJ connectivity may govern the formation of highly spatially heterogeneous activity states. These states are inherently temporally unstable when the input is uniformly random, but can rapidly stabilize when the network detects correlations or asymmetries in the inputs. We show a correspondence between this feature of network activity and experimental observations of transient stabilization of striatal fast-spiking interneurons (FSIs), in electrophysiological recordings from rats performing a simple decision-making task. We suggest that local GJ coupling enables an active search-and-select function of striatal FSIs, which contributes to the overall role of cortical-basal ganglia circuits in decision-making.

  4. Drosophila RSK negatively regulates bouton number at the neuromuscular junction.

    Science.gov (United States)

    Fischer, Matthias; Raabe, Thomas; Heisenberg, Martin; Sendtner, Michael

    2009-03-01

    Ribosomal S6 kinases (RSKs) are growth factor-regulated serine-threonine kinases participating in the RAS-ERK signaling pathway. RSKs have been implicated in memory formation in mammals and flies. To characterize the function of RSK at the synapse level, we investigated the effect of mutations in the rsk gene on the neuromuscular junction (NMJ) in Drosophila larvae. Immunostaining revealed transgenic expressed RSK in presynaptic regions. In mutants with a full deletion or an N-terminal partial deletion of rsk, an increased bouton number was found. Restoring the wild-type rsk function in the null mutant with a genomic rescue construct reverted the synaptic phenotype, and overexpression of the rsk-cDNA in motoneurons reduced bouton numbers. Based on previous observations that RSK interacts with the Drosophila ERK homologue Rolled, genetic epistasis experiments were performed with loss- and gain-of-function mutations in Rolled. These experiments provided evidence that RSK mediates its negative effect on bouton formation at the Drosophila NMJ by inhibition of ERK signaling.

  5. Targeting Holliday junctions by origin DNA-binding protein of herpes simplex virus type 1.

    Science.gov (United States)

    Moiseeva, E D; Bazhulina, N P; Gursky, Y G; Grokhovsky, S L; Surovaya, A N; Gursky, G V

    2017-03-01

    In the present paper, the interactions of the origin binding protein (OBP) of herpes simplex virus type 1 (HSV1) with synthetic four-way Holliday junctions (HJs) were studied using electrophoresis mobility shift assay and the FRET method and compared with the interactions of the protein with duplex and single-stranded DNAs. It has been found that OBP exhibits a strong preference for binding to four-way and three-way DNA junctions and possesses much lower affinities to duplex and single-stranded DNAs. The protein forms three types of complexes with HJs. It forms complexes I and II which are reminiscent of the tetramer and octamer complexes with four-way junction of HJ-specific protein RuvA of Escherichia coli. The binding approaches saturation level when two OBP dimers are bound per junction. In the presence of Mg(2+) ions (≥2 mM) OBP also interacts with HJ in the stacked arm form (complex III). In the presence of 5 mM ATP and 10 mM Mg(2+) ions OBP catalyzes processing of the HJ in which one of the annealed oligonucleotides has a 3'-terminal tail containing 20 unpaired thymine residues. The observed preference of OBP for binding to the four-way DNA junctions provides a basis for suggestion that OBP induces large DNA structural changes upon binding to Box I and Box II sites in OriS. These changes involve the bending and partial melting of the DNA at A+T-rich spacer and also include the formation of HJ containing Box I and Box II inverted repeats and flanking DNA sequences.

  6. A synaptic nidogen: Developmental regulation and role of nidogen-2 at the neuromuscular junction

    Directory of Open Access Journals (Sweden)

    Smyth Neil

    2008-09-01

    Full Text Available Abstract Background The skeletal neuromuscular junction is a useful model for elucidating mechanisms that regulate synaptogenesis. Developmentally important intercellular interactions at the neuromuscular junction are mediated by the synaptic portion of a basal lamina that completely ensheaths each muscle fiber. Basal laminas in general are composed of four main types of glycosylated proteins: laminins, collagens IV, heparan sulfate proteoglycans and nidogens (entactins. The portion of the muscle fiber basal lamina that passes between the motor nerve terminal and postsynaptic membrane has been shown to bear distinct isoforms of the first three of these. For laminins and collagens IV, the proteins are deposited by the muscle; a synaptic proteoglycan, z-agrin, is deposited by the nerve. In each case, the synaptic isoform plays key roles in organizing the neuromuscular junction. Here, we analyze the fourth family, composed of nidogen-1 and -2. Results In adult muscle, nidogen-1 is present throughout muscle fiber basal lamina, while nidogen-2 is concentrated at synapses. Nidogen-2 is initially present throughout muscle basal lamina, but is lost from extrasynaptic regions during the first three postnatal weeks. Neuromuscular junctions in mutant mice lacking nidogen-2 appear normal at birth, but become topologically abnormal as they mature. Synaptic laminins, collagens IV and heparan sulfate proteoglycans persist in the absence of nidogen-2, suggesting the phenotype is not secondary to a general defect in the integrity of synaptic basal lamina. Further genetic studies suggest that synaptic localization of each of the four families of synaptic basal lamina components is independent of the other three. Conclusion All four core components of the basal lamina have synaptically enriched isoforms. Together, they form a highly specialized synaptic cleft material. Individually, they play distinct roles in the formation, maturation and maintenance of the

  7. General anesthetics have differential inhibitory effects on gap junction channels and hemichannels in astrocytes and neurons.

    Science.gov (United States)

    Liu, Xinhe; Gangoso, Ester; Yi, Chenju; Jeanson, Tiffany; Kandelman, Stanislas; Mantz, Jean; Giaume, Christian

    2016-04-01

    Astrocytes represent a major non-neuronal cell population actively involved in brain functions and pathologies. They express a large amount of gap junction proteins that allow communication between adjacent glial cells and the formation of glial networks. In addition, these membrane proteins can also operate as hemichannels, through which "gliotransmitters" are released, and thus contribute to neuroglial interaction. There are now reports demonstrating that alterations of astroglial gap junction communication and/or hemichannel activity impact neuronal and synaptic activity. Two decades ago we reported that several general anesthetics inhibited gap junctions in primary cultures of astrocytes (Mantz et al., (1993) Anesthesiology 78(5):892-901). As there are increasing studies investigating neuroglial interactions in anesthetized mice, we here updated this previous study by employing acute cortical slices and by characterizing the effects of general anesthetics on both astroglial gap junctions and hemichannels. As hemichannel activity is not detected in cortical astrocytes under basal conditions, we treated acute slices with the endotoxin LPS or proinflammatory cytokines to induce hemichannel activity in astrocytes, which in turn activated neuronal hemichannels. We studied two extensively used anesthetics, propofol and ketamine, and the more recently developed dexmedetomidine. We report that these drugs have differential inhibitory effects on gap junctional communication and hemichannel activity in astrocytes when used in their respective, clinically relevant concentrations, and that dexmedetomidine appears to be the least effective on both channel functions. In addition, the three anesthetics have similar effects on neuronal hemichannels. Altogether, our observations may contribute to optimizing the selection of anesthetics for in vivo animal studies.

  8. Holliday junction trap shows how cells use recombination and a junction-guardian role of RecQ helicase.

    Science.gov (United States)

    Xia, Jun; Chen, Li-Tzu; Mei, Qian; Ma, Chien-Hui; Halliday, Jennifer A; Lin, Hsin-Yu; Magnan, David; Pribis, John P; Fitzgerald, Devon M; Hamilton, Holly M; Richters, Megan; Nehring, Ralf B; Shen, Xi; Li, Lei; Bates, David; Hastings, P J; Herman, Christophe; Jayaram, Makkuni; Rosenberg, Susan M

    2016-11-01

    DNA repair by homologous recombination (HR) underpins cell survival and fuels genome instability, cancer, and evolution. However, the main kinds and sources of DNA damage repaired by HR in somatic cells and the roles of important HR proteins remain elusive. We present engineered proteins that trap, map, and quantify Holliday junctions (HJs), a central DNA intermediate in HR, based on catalytically deficient mutant RuvC protein of Escherichia coli. We use RuvCDefGFP (RDG) to map genomic footprints of HR at defined DNA breaks in E. coli and demonstrate genome-scale directionality of double-strand break (DSB) repair along the chromosome. Unexpectedly, most spontaneous HR-HJ foci are instigated, not by DSBs, but rather by single-stranded DNA damage generated by replication. We show that RecQ, the E. coli ortholog of five human cancer proteins, nonredundantly promotes HR-HJ formation in single cells and, in a novel junction-guardian role, also prevents apparent non-HR-HJs promoted by RecA overproduction. We propose that one or more human RecQ orthologs may act similarly in human cancers overexpressing the RecA ortholog RAD51 and find that cancer genome expression data implicate the orthologs BLM and RECQL4 in conjunction with EME1 and GEN1 as probable HJ reducers in such cancers. Our results support RecA-overproducing E. coli as a model of the many human tumors with up-regulated RAD51 and provide the first glimpses of important, previously elusive reaction intermediates in DNA replication and repair in single living cells.

  9. Claudin-5 is restricted to the tight junction region of uterine epithelial cells in the uterus of pregnant/gravid squamate reptiles.

    Science.gov (United States)

    Biazik, Joanna M; Thompson, Michael B; Murphy, Christopher R

    2008-05-01

    Claudin-5, a tight junctional protein associated with ion and size selectivity, has been found in the uterus of skinks. This study has generated critical information about the molecular assembly of the tight junction at various stages of the reproductive cycle in the skink uterus. Recent studies looking at tight junctional proteins found occludin expression in the tight junction region of uterine epithelial cells in the skink uterus; however, occludin did not disclose any further information about the ions and size of ions permeating across the paracellular pathway. A approximately 22-kDa claudin-5 band was detected in the uterus of the skinks present in this study and immunohistochemistry revealed that claudin-5 redistributes to the tight junction region of the lateral plasma membrane of uterine epithelial cells in late stage pregnancy/gravidity. This finding indicates that the tight junction becomes more assembled to precisely regulate ion and solute permeation in late stage pregnancy/gravidity. Claudin-5 with its functional role as a molecular sieve due to the formation of ion and size selective pores suggests that permeation of ions smaller than 0.8 kDa are restricted when claudin-5 is redistributed to the tight junction region of the later plasma membrane. This report is the first description of the molecular mechanisms that may be involved in regulating nutrient provision in the reptilian uterus.

  10. High-performance germanium n+/p junction by nickel-induced dopant activation of implanted phosphorus at low temperature

    Science.gov (United States)

    Wei, Huang; Chao, Lu; Jue, Yu; Jiang-Bin, Wei; Chao-Wen, Chen; Jian-Yuan, Wang; Jian-Fang, Xu; Chen, Wang; Cheng, Li; Song-Yan, Chen; Chun-Li, Liu; Hong-Kai, Lai

    2016-05-01

    High-performance Ge n+/p junctions were fabricated at a low formation temperature from 325 °C to 400 °C with a metal(nickel)-induced dopant activation technique. The obtained NiGe electroded Ge n+/p junction has a rectification ratio of 5.6× 104 and a forward current of 387 A/cm2 at -1 V bias. The Ni-based metal-induced dopant activation technique is expected to meet the requirement of the shallow junction of Ge MOSFET. Project supported by the National Natural Science Foundation of China (Grant Nos. 61176092 and 61474094), the National Basic Research Program of China (Grant Nos. 2012CB933503 and 2013CB632103), and the National Natural Science Foundation of China-National Research Foundation of Korea Joint Research Project (Grant No. 11311140251).

  11. Electron optics with p-n junctions in ballistic graphene

    Science.gov (United States)

    Chen, Shaowen; Han, Zheng; Elahi, Mirza M.; Habib, K. M. Masum; Wang, Lei; Wen, Bo; Gao, Yuanda; Taniguchi, Takashi; Watanabe, Kenji; Hone, James; Ghosh, Avik W.; Dean, Cory R.

    2016-09-01

    Electrons transmitted across a ballistic semiconductor junction are expected to undergo refraction, analogous to light rays across an optical boundary. In graphene, the linear dispersion and zero-gap band structure admit highly transparent p-n junctions by simple electrostatic gating. Here, we employ transverse magnetic focusing to probe the propagation of carriers across an electrostatically defined graphene junction. We find agreement with the predicted Snell’s law for electrons, including the observation of both positive and negative refraction. Resonant transmission across the p-n junction provides a direct measurement of the angle-dependent transmission coefficient. Comparing experimental data with simulations reveals the crucial role played by the effective junction width, providing guidance for future device design. Our results pave the way for realizing electron optics based on graphene p-n junctions.

  12. Single P-N junction tandem photovoltaic device

    Science.gov (United States)

    Walukiewicz, Wladyslaw; Ager, III, Joel W.; Yu, Kin Man

    2011-10-18

    A single P-N junction solar cell is provided having two depletion regions for charge separation while allowing the electrons and holes to recombine such that the voltages associated with both depletion regions of the solar cell will add together. The single p-n junction solar cell includes an alloy of either InGaN or InAlN formed on one side of the P-N junction with Si formed on the other side in order to produce characteristics of a two junction (2J) tandem solar cell through only a single P-N junction. A single P-N junction solar cell having tandem solar cell characteristics will achieve power conversion efficiencies exceeding 30%.

  13. The critical power to maintain thermally stable molecular junctions

    Science.gov (United States)

    Wang, Yanlei; Xu, Zhiping

    2014-07-01

    With the rise of atomic-scale devices such as molecular electronics and scanning probe microscopies, energy transport processes through molecular junctions have attracted notable research interest recently. In this work, heat dissipation and transport across diamond/benzene/diamond molecular junctions are explored by performing atomistic simulations. We identify the critical power Pcr to maintain thermal stability of the junction through efficient dissipation of local heat. We also find that the molecule-probe contact features a power-dependent interfacial thermal resistance RK in the order of 109 kW-1. Moreover, both Pcr and RK display explicit dependence on atomic structures of the junction, force and temperature. For instance, Pcr can be elevated in multiple-molecule junctions, and streching the junction enhances RK by a factor of 2. The applications of these findings in molecular electronics and scanning probing measurements are discussed, providing practical guidelines in their rational design.

  14. Single P-N junction tandem photovoltaic device

    Science.gov (United States)

    Walukiewicz, Wladyslaw [Kensington, CA; Ager, III, Joel W.; Yu, Kin Man [Lafayette, CA

    2012-03-06

    A single P-N junction solar cell is provided having two depletion regions for charge separation while allowing the electrons and holes to recombine such that the voltages associated with both depletion regions of the solar cell will add together. The single p-n junction solar cell includes an alloy of either InGaN or InAlN formed on one side of the P-N junction with Si formed on the other side in order to produce characteristics of a two junction (2J) tandem solar cell through only a single P-N junction. A single P-N junction solar cell having tandem solar cell characteristics will achieve power conversion efficiencies exceeding 30%.

  15. Structure, regulation and function of gap junctions in liver

    Science.gov (United States)

    Maes, Michaël; Decrock, Elke; Wang, Nan; Leybaert, Luc; da Silva, Tereza Cristina; Veloso Alves Pereira, Isabel; Jaeschke, Hartmut; Cogliati, Bruno; Vinken, Mathieu

    2016-01-01

    Gap junctions are a specialized group of cell-to-cell junctions that mediate direct intercellular communication between cells. They arise from the interaction of 2 hemichannels of adjacent cells, which in turn are composed of 6 connexin proteins. In liver, gap junctions are predominantly found in hepatocytes and play critical roles in virtually all phases of the hepatic life cycle, including cell growth, differentiation, liver-specific functionality and cell death. Liver gap junctions are directed through a broad variety of mechanisms ranging from epigenetic control of connexin expression to posttranslational regulation of gap junction activity. This paper reviews established and novel aspects regarding the architecture, control and functional relevance of liver gap junctions. PMID:27001459

  16. Advanced transmission electron microscopy studies in low-energy ion implanted Si Semiconductors; Junctions; Silicon

    CERN Document Server

    Wang, T S

    2002-01-01

    As the dimensions of semiconductor devices shrink down to 0.1 mu m and beyond, low energy ion implantation is required to introduce shallower junctions to match such small devices. In this work, transmission electron microscopy (TEM) is employed to analyse low energy implanted junctions with both structural and chemical analyses. High resolution transmission electron microscopy (HRTEM) has been employed to observe Si crystal damage and amorphization due to low energy B sup + /As sup + ion implantations, and also, defect formation/annihilation during rapid thermal annealing (RTA). The damage effects due to different implant temperatures between 300 deg C and -150 deg C are also discussed. Since knowledge of the distribution of low energy ion implanted dopants in Si is extremely important for semiconductor device processing, energy filtered transmission electron microscopy (EFTEM) has been employed to determine implanted B distributions in Si while Z-contrast imaging and X-ray analytical mapping techniques are ...

  17. Effect of temperature and magnetic field on the photocurrent response of biomolecular bulk-hetero junction

    Science.gov (United States)

    Tajima, Hiroyuki; Sekiguchi, Yusuke; Matsuda, Masaki

    2012-02-01

    The photocurrent responses were investigated for the biomolecular bulk-hetero junction of chlorophyll α (Chl-α) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-1-phenyl-(6,6)C61 (PCBM) in the temperature range between 300 K and 1.5 K under the magnetic field up to 8 T. The chopped-light photocurrent decreases on lowering the temperature. Below 10 K, photocurrent decrease was observed under the applied magnetic field. Decay of the photocurrent observed at 10 K was ascribed to the formation of the charged trap under light irradiation. The magnetic field effect (MFE) observed in this device was found to be very similar to that observed in P3HT:PCBM bulk-hetero junction at low temperatures.

  18. Enhanced photocatalytic performance of porous TiO2 nanobelts with phase junctions

    Science.gov (United States)

    Pang, Lai-xue; Wang, Xiao-ying; Tang, Xin-de

    2015-01-01

    Porous TiO2 nanobelts with rutile/anatase phase junctions are successfully prepared through a hydrothermal route and ion exchange process. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were conducted to characterize the products. The photocatalytic performance of the porous nanobelts was evaluated by measuring the degradation of methyl blue under UV light irradiation. The photocatalytic activity of the porous nanobelts is much superior to that of P-25 and pristine non-porous nanobelts. The excellent photocatalytic of porous nanobelts can be attributed to pores which enhanced ability in UV-light harvesting. What's more, the existence of rutile/anatase phase junction is favorable for the formation and separation of the hole-electron pair, resulting in a reduced electron-hole recombination.

  19. Numerical Simulation and Analysis of Gas-Liquid Flow in a T-Junction Microchannel

    Directory of Open Access Journals (Sweden)

    Hongtruong Pham

    2012-01-01

    Full Text Available Gas-liquid flow in microchannels is widely used in biomedicine, nanotech, sewage treatment, and so forth. Particularly, owing to the high qualities of the microbubbles and spheres produced in microchannels, it has a great potential to be used in ultrasound imaging and controlled drug release areas; therefore, gas-liquid flow in microchannels has been the focus in recent years. In this paper, numerical simulation of gas-liquid flows in a T-junction microchannel was carried out with computational fluid dynamics (CFD software FLUENT and the Volume-of-Fluid (VOF model. The distribution of velocity, pressure, and phase of fluid in the microchannel was obtained, the pressure distribution along the channel walls was analyzed in order to give a better understanding on the formation of microbubbles in the T-junction microchannel.

  20. Large lateral photovoltaic effect with ultrafast relaxation time in SnSe/Si junction

    Science.gov (United States)

    Wang, Xianjie; Zhao, Xiaofeng; Hu, Chang; Zhang, Yang; Song, Bingqian; Zhang, Lingli; Liu, Weilong; Lv, Zhe; Zhang, Yu; Tang, Jinke; Sui, Yu; Song, Bo

    2016-07-01

    In this paper, we report a large lateral photovoltaic effect (LPE) with ultrafast relaxation time in SnSe/p-Si junctions. The LPE shows a linear dependence on the position of the laser spot, and the position sensitivity is as high as 250 mV mm-1. The optical response time and the relaxation time of the LPE are about 100 ns and 2 μs, respectively. The current-voltage curve on the surface of the SnSe film indicates the formation of an inversion layer at the SnSe/p-Si interface. Our results clearly suggest that most of the excited-electrons diffuse laterally in the inversion layer at the SnSe/p-Si interface, which results in a large LPE with ultrafast relaxation time. The high positional sensitivity and ultrafast relaxation time of the LPE make the SnSe/p-Si junction a promising candidate for a wide range of optoelectronic applications.

  1. Planar intrinsic Josephson junctions with in-plane aligned YBCO films

    CERN Document Server

    Zhang, L; Kobayashi, T; Goto, T; Mukaida, M

    2002-01-01

    Planar type devices were fabricated by patterning in-plane aligned YBa sub 2 Cu sub 3 O sub 7 sub - subdelta (YBCO) films. The current-voltage characteristics along the c-axis at various temperatures and oxygen contents were measured. The current voltage curves showing supercurrent and hysteresis were obtained for the samples annealed at an oxygen pressure of 1.3 x 10 sup 4 Pa, while the supercurrent and hysteresis became smaller and even disappeared as the oxygen pressure decreased. The relationships between the critical currents and temperatures are similar to those of d-wave superconducting tunnel junctions. These results indicate the formation of stacks of intrinsic Josephson junctions, which are useful for developing high-frequency electron devices.

  2. Geometrical theory of triple junctions of CSL boundaries.

    Science.gov (United States)

    Gertsman, V Y

    2001-07-01

    When three grain boundaries having misorientations generating coincidence site lattices (CSLs) meet at a triple junction, a common (triple-junction) CSL is formed. A theory is developed as a set of theorems establishing the relationships between the geometrical parameters of the grain-boundary and triple-junction CSLs. Application of the theory is demonstrated in detail for the case of the cubic crystal system. It is also shown how the theory can be extended to an arbitrary crystal lattice.

  3. Turbulence-induced magnetic flux asymmetry at nanoscale junctions

    OpenAIRE

    2007-01-01

    It was recently predicted [J. Phys.: Condens. Matter 18, 11059 (2006)] that turbulence of the electron flow may develop at nonadiabatic nanoscale junctions under appropriate conditions. Here we show that such an effect leads to an asymmetric current-induced magnetic field on the two sides of an otherwise symmetric junction. We propose that by measuring the fluxes ensuing from these fields across two surfaces placed at the two sides of the junction would provide direct and noninvasive evidence...

  4. Magnetic interaction between spatially extended superconducting tunnel junctions

    DEFF Research Database (Denmark)

    Grønbech-Jensen, Niels; Samuelsen, Mogens Rugholm

    2002-01-01

    A general description of magnetic interactions between superconducting tunnel junctions is given. The description covers a wide range of possible experimental systems, and we explicitly explore two experimentally relevant limits of coupled junctions. One is the limit of junctions with tunneling...... been considered through arrays of superconducting weak links based on semiconductor quantum wells with superconducting electrodes. We use the model to make direct interpretations of the published experiments and thereby propose that long-range magnetic interactions are responsible for the reported...

  5. Engineering of Droplet Manipulation in Tertiary Junction Microfluidic Channels

    Science.gov (United States)

    2017-06-30

    in silico investigation of path selection by a single droplet inside a tertiary junction microchannel using oil-in-water as a model system. The...droplet was generated at a T-junction inside a microfluidic chip and its flow behaviour as a function of droplet size, streamline position, viscosity...investigation of path selection by a single droplet inside a tertiary- junction microchannel using oil-in-water as a model system. The droplet was generated at

  6. ACCIDENT PREDICTION MODELS FOR UNSIGNALISED URBAN JUNCTIONS IN GHANA

    OpenAIRE

    Mohammed SALIFU, MSc., PhD, MIHT, MGhIE

    2004-01-01

    The main objective of this study was to provide an improved method for safety appraisal in Ghana through the development and application of suitable accident prediction models for unsignalised urban junctions. A case study was designed comprising 91 junctions selected from the two most cosmopolitan cities in Ghana. A wide range of traffic and road data together with the corresponding accident data for each junction for the three-year period 1996-1998 was utilized in the model development p...

  7. Mouse Hepatitis Virus Infection Remodels Connexin43-Mediated Gap Junction Intercellular Communication In Vitro and In Vivo.

    Science.gov (United States)

    Basu, Rahul; Banerjee, Kaveri; Bose, Abhishek; Das Sarma, Jayasri

    2015-12-16

    Gap junctions (GJs) form intercellular channels which directly connect the cytoplasm between neighboring cells to facilitate the transfer of ions and small molecules. GJs play a major role in the pathogenesis of infection-associated inflammation. Mutations of gap junction proteins, connexins (Cxs), cause dysmyelination and leukoencephalopathy. In multiple sclerosis (MS) patients and its animal model experimental autoimmune encephalitis (EAE), Cx43 was shown to be modulated in the central nervous system (CNS). The mechanism behind Cx43 alteration and its role in MS remains unexplored. Mouse hepatitis virus (MHV) infection-induced demyelination is one of the best-studied experimental animal models for MS. Our studies demonstrated that MHV infection downregulated Cx43 expression at protein and mRNA levels in vitro in primary astrocytes obtained from neonatal mouse brains. After infection, a significant amount of Cx43 was retained in endoplasmic reticulum/endoplasmic reticulum Golgi intermediate complex (ER/ERGIC) and GJ plaque formation was impaired at the cell surface, as evidenced by a reduction of the Triton X-100 insoluble fraction of Cx43. Altered trafficking and impairment of GJ plaque formation may cause the loss of functional channel formation in MHV-infected primary astrocytes, as demonstrated by a reduced number of dye-coupled cells after a scrape-loading Lucifer yellow dye transfer assay. Upon MHV infection, a significant downregulation of Cx43 was observed in the virus-infected mouse brain. This study demonstrates that astrocytic Cx43 expression and function can be modulated due to virus stress and can be an appropriate model to understand the basis of cellular mechanisms involved in the alteration of gap junction intercellular communication (GJIC) in CNS neuroinflammation. We found that MHV infection leads to the downregulation of Cx43 in vivo in the CNS. In addition, results show that MHV infection impairs Cx43 expression in addition to gap junction

  8. Junctional neurulation: a unique developmental program shaping a discrete region of the spinal cord highly susceptible to neural tube defects.

    Science.gov (United States)

    Dady, Alwyn; Havis, Emmanuelle; Escriou, Virginie; Catala, Martin; Duband, Jean-Loup

    2014-09-24

    In higher vertebrates, the primordium of the nervous system, the neural tube, is shaped along the rostrocaudal axis through two consecutive, radically different processes referred to as primary and secondary neurulation. Failures in neurulation lead to severe anomalies of the nervous system, called neural tube defects (NTDs), which are among the most common congenital malformations in humans. Mechanisms causing NTDs in humans remain ill-defined. Of particular interest, the thoracolumbar region, which encompasses many NTD cases in the spine, corresponds to the junction between primary and secondary neurulations. Elucidating which developmental processes operate during neurulation in this region is therefore pivotal to unraveling the etiology of NTDs. Here, using the chick embryo as a model, we show that, at the junction, the neural tube is elaborated by a unique developmental program involving concerted movements of elevation and folding combined with local cell ingression and accretion. This process ensures the topological continuity between the primary and secondary neural tubes while supplying all neural progenitors of both the junctional and secondary neural tubes. Because it is distinct from the other neurulation events, we term this phenomenon junctional neurulation. Moreover, the planar-cell-polarity member, Prickle-1, is recruited specifically during junctional neurulation and its misexpression within a limited time period suffices to cause anomalies that phenocopy lower spine NTDs in human. Our study thus provides a molecular and cellular basis for understanding the causality of NTD prevalence in humans and ascribes to Prickle-1 a critical role in lower spinal cord formation.

  9. Innexin7a forms junctions that stabilize the basal membrane during cellularization of the blastoderm in Tribolium castaneum.

    Science.gov (United States)

    van der Zee, Maurijn; Benton, Matthew A; Vazquez-Faci, Tania; Lamers, Gerda E M; Jacobs, Chris G C; Rabouille, Catherine

    2015-06-15

    In insects, the fertilized egg undergoes a series of rapid nuclear divisions before the syncytial blastoderm starts to cellularize. Cellularization has been extensively studied in Drosophila melanogaster, but its thick columnar blastoderm is unusual among insects. We therefore set out to describe cellularization in the beetle Tribolium castaneum, the embryos of which exhibit a thin blastoderm of cuboidal cells, like most insects. Using immunohistochemistry, live imaging and transmission electron microscopy, we describe several striking differences to cellularization in Drosophila, including the formation of junctions between the forming basal membrane and the yolk plasmalemma. To identify the nature of this novel junction, we used the parental RNAi technique for a small-scale screen of junction proteins. We find that maternal knockdown of Tribolium innexin7a (Tc-inx7a), an ortholog of the Drosophila gap junction gene Innexin 7, leads to failure of cellularization. In Inx7a-depleted eggs, the invaginated plasma membrane retracts when basal cell closure normally begins. Furthermore, transiently expressed tagged Inx7a localizes to the nascent basal membrane of the forming cells in wild-type eggs. We propose that Inx7a forms the newly identified junctions that stabilize the forming basal membrane and enable basal cell closure. We put forward Tribolium as a model for studying a more ancestral mode of cellularization in insects.

  10. Some chaotic features of intrinsically coupled Josephson junctions

    Energy Technology Data Exchange (ETDEWEB)

    Kolahchi, M.R., E-mail: kolahchi@iasbs.ac.ir [Institute for Advanced Studies in Basic Sciences, Zanjan 45195-1159 (Iran, Islamic Republic of); Shukrinov, Yu.M. [BLTP, JINR, Dubna, Moscow Region 141980 (Russian Federation); Max-Planck-Institute for the Physics of Complex Systems, 01187 Dresden (Germany); Hamdipour, M. [Institute for Advanced Studies in Basic Sciences, Zanjan 45195-1159 (Iran, Islamic Republic of); BLTP, JINR, Dubna, Moscow Region 141980 (Russian Federation); Botha, A.E. [Department of Physics, University of South Africa, P.O. Box 392, Pretoria 0003 (South Africa); Suzuki, M. [Photonics and Electronics Science and Engineering Center and Department of Electronic Science and Engineering, Kyoto University, Kyoto 615-8510 (Japan)

    2013-08-15

    Highlights: ► Intrinsically coupled Josephson junctions model a high-T{sub c} superconductor. ► Intrinsically coupled Josephson junctions can act as a chaotic nonlinear system. ► Chaos could be due to resonance overlap. ► Avoiding parameters that lead to chaos is important for the design of resonators. -- Abstract: We look for chaos in an intrinsically coupled system of Josephson junctions. This study has direct applications for the high-T{sub c} resonators which require coherence amongst the junctions.

  11. Imaging snake orbits at graphene n -p junctions

    Science.gov (United States)

    Kolasiński, K.; Mreńca-Kolasińska, A.; Szafran, B.

    2017-01-01

    We consider conductance mapping of the snake orbits confined along the n -p junction defined in graphene by the electrostatic doping in the quantum Hall regime. We explain the periodicity of conductance oscillations at the magnetic field and the Fermi energy scales by the properties of the n -p junction as a conducting channel. We evaluate the conductance maps for a floating gate scanning the surface of the device. In the quantum Hall conditions the currents flow near the edges of the sample and along the n -p junction. The conductance mapping resolves only the n -p junction and not the edges. The conductance oscillations along the junction are found in the maps with periodicity related to the cyclotron orbits of the scattering current. Stronger probe potentials provide support to localized resonances at one of the sides of the junction with current loops that interfere with the n -p junction currents. The interference results in a series of narrow lines parallel to the junction with positions that strongly depend on the magnetic field through the Aharonov-Bohm effect. The consequences of a limited transparency of finite-width n -p junctions are also discussed.

  12. Terahertz Detection with Twin Superconductor-Insulator-Superconductor Tunnel Junctions

    Institute of Scientific and Technical Information of China (English)

    LI Jing; WANG Ming-Jye; SHI Sheng-Cai; Hiroshi Mat-suo

    2007-01-01

    Terahertz detection with twin superconductor-insulator-superconductor (SIS) tunnel junctions, which are connected in parallel via an inductive thin-film superconducting microstrip line, is mainly studied. Firstly, we investigate the direct-detection response of a superconducting twin-junction device by means of a Fourier transform spectrometer. Secondly, we construct a direct-detection model of twin SIS tunnel junctions. The superconducting twin-junction device is then simulated in terms of the constructed model. The simulation result is found to be in good agreement with the measured one. In addition, we observe that the direct-detection response of the device is consistent with the noise temperature behaviour.

  13. F-Theory Description of 3-String Junction

    Institute of Scientific and Technical Information of China (English)

    YANGFu-Zhong

    2003-01-01

    The geometrical description of BPS 3-string junction in the F-theory background is given by lifting a string junction in lib into F-theory and constructing a holomorphic curve in K3 with respect to a special complex structure of K3. The holomorphic curve is fibration of 1-cycles of the elliptic fiber over the geodesic string junction. The F-theory picture in this paper provides a unifying description of both string and string junction, and is advantageous over their M-theory picture.

  14. F-Theory Description of 3-String Junction

    Institute of Scientific and Technical Information of China (English)

    YANG Fu-Zhong

    2003-01-01

    The geometrical description of BPS 3-string junction in the F-theory background is given by lifting a string junction in IIB into F-theory and constructing a holomorphic curve in K3 with respect to a special complex structure of K3. The holomorphic curve is fibration of 1-cycles of the elliptic fiber over the geodesic string junction. The F-theory picture in this paper provides a unifying description of both string and string junction, and is advantageous over their M-theory picture.

  15. ‘Gap Junctions and Cancer: Communicating for 50 Years’

    Science.gov (United States)

    Aasen, Trond; Mesnil, Marc; Naus, Christian C.; Lampe, Paul D.; Laird, Dale W.

    2017-01-01

    Fifty years ago, tumour cells were found to lack electrical coupling, leading to the hypothesis that loss of direct intercellular communication is commonly associated with cancer onset and progression. Subsequent studies linked this phenomenon to gap junctions composed of connexin proteins. While many studies support the notion that connexins are tumour suppressors, recent evidence suggests that, in some tumour types, they may facilitate specific stages of tumour progression through both junctional and non-junctional signalling pathways. This Timeline article highlights the milestones connecting gap junctions to cancer, and underscores important unanswered questions, controversies and therapeutic opportunities in the field. PMID:27782134

  16. Superconducting Tunnel Junction Arrays for UV Photon Detection Project

    Data.gov (United States)

    National Aeronautics and Space Administration — An innovative method is described for the fabrication of superconducting tunnel junction (STJ) detector arrays offering true "three dimensional" imaging throughout...

  17. Improving transition voltage spectroscopy of molecular junctions

    DEFF Research Database (Denmark)

    Markussen, Troels; Chen, Jingzhe; Thygesen, Kristian Sommer

    2011-01-01

    Transition voltage spectroscopy (TVS) is a promising spectroscopic tool for molecular junctions. The principles in TVS is to find the minimum on a Fowler-Nordheim plot where ln(I/V2) is plotted against 1/V and relate the voltage at the minimum Vmin to the closest molecular level. Importantly, Vmin...... is approximately half the voltage required to see a peak in the dI/dV curve. Information about the molecular level position can thus be obtained at relatively low voltages. In this work we show that the molecular level position can be determined at even lower voltages, Vmin(α), by finding the minimum of ln...

  18. Anatomy and biomechanics of the craniovertebral junction.

    Science.gov (United States)

    Lopez, Alejandro J; Scheer, Justin K; Leibl, Kayla E; Smith, Zachary A; Dlouhy, Brian J; Dahdaleh, Nader S

    2015-04-01

    The craniovertebral junction (CVJ) has unique anatomical structures that separate it from the subaxial cervical spine. In addition to housing vital neural and vascular structures, the majority of cranial flexion, extension, and axial rotation is accomplished at the CVJ. A complex combination of osseous and ligamentous supports allow for stability despite a large degree of motion. An understanding of anatomy and biomechanics is essential to effectively evaluate and address the various pathological processes that may affect this region. Therefore, the authors present an up-to-date narrative review of CVJ anatomy, normal and pathological biomechanics, and fixation techniques.

  19. Magnetic resonance imaging in craniovertebral junction anomaly

    Energy Technology Data Exchange (ETDEWEB)

    Tada, Shimpei; Hata, Yuichi; Miyamoto, Yukio

    1985-03-01

    Materials consisted of 6 cases with occipitalization of the atlas, (4 of them complicated by basilar impression), 7 with basilar impression, one with hypoplasia of the atlas and C2-3 fusion, and one with os odontoideum. Basal angles after Welcker were all more than 130 in contrast to 118-138 (127 an average) in control group. Basal angle more than 140 denoted platybasia. Syringomyelia was seen in 7 of all 15 cases and 4 of 5 cases with platybasia. Chiari malformation was seen in 9 of all 15 cases and 4 of 5 with platybasia. Basal angles were closely related to craniovertebral junction bone anomaly, syringomyelia, and Chiari malformation. (author).

  20. Magic-T Junction using Microstrip/Slotline Transitions

    Science.gov (United States)

    U-yen, Kongpop; Wollack, Edward J.; Doiron, Terence

    2008-01-01

    An improved broadband planar magic-T junction that incorporates microstrip/slotline transitions has been developed. In comparison with a prior broadband magic-T junction incorporating microstrip/slotline transitions, this junction offers superior broadband performance. In addition, because this junction is geometrically simpler and its performance is less affected by fabrication tolerances, the benefits of the improved design can be realized at lower fabrication cost. There are potential uses for junctions like this one in commercial microwave communication receivers, radar and polarimeter systems, and industrial microwave instrumentation. A magic-T junction is a four-port waveguide junction consisting of a combination of an H-type and an E-type junction. An E-type junction is so named because it includes a junction arm that extends from a main waveguide in the same direction as that of the electric (E) field in the waveguide. An H-type junction is so named because it includes a junction arm parallel to the magnetic (H) field in a main waveguide. A magic-T junction includes two input ports (here labeled 1 and 2, respectively) and two output ports (here labeled E and H, respectively). In an ideal case, (1) a magic-T junction is lossless, (2) the input signals add (that is, they combine in phase with each other) at port H, and (3) the input signals subtract (that is, they combine in opposite phase) at port E. The prior junction over which the present junction is an improvement affords in-phase-combining characterized by a broadband frequency response, and features a small slotline area to minimize in-band loss. However, with respect to isolation between ports 1 and 2 and return loss at port E, it exhibits narrowband frequency responses. In addition, its performance is sensitive to misalignment of microstrip and slotline components: this sensitivity is attributable to a limited number of quarter-wavelength (lambda/4) transmission-line sections for matching impedances

  1. Grades 1-8, Apache Junction Unified School District 43, Apache Junction, Arizona. PLATO Evaluation Series.

    Science.gov (United States)

    Quinn, David W.; Quinn, Nancy W.

    Apache Junction Unified School District, Arizona, has embarked on a 5-year program of instructional improvement using technology. PLATO Elementary reading and mathematics products were installed in the district's elementary and middle schools at the beginning of the 1999-2000 school year. This evaluation studied the use and preliminary student…

  2. Fabrication of magnetic tunnel junctions with epitaxial and textured ferromagnetic layers

    Science.gov (United States)

    Chang, Y. Austin; Yang, Jianhua Joshua

    2008-11-11

    This invention relates to magnetic tunnel junctions and methods for making the magnetic tunnel junctions. The magnetic tunnel junctions include a tunnel barrier oxide layer sandwiched between two ferromagnetic layers both of which are epitaxial or textured with respect to the underlying substrate upon which the magnetic tunnel junctions are grown. The magnetic tunnel junctions provide improved magnetic properties, sharper interfaces and few defects.

  3. Gap junctions in the nervous system.

    Science.gov (United States)

    Rozental, R; Giaume, C; Spray, D C

    2000-04-01

    Synapses are classically defined as close connections between two nerve cells or between a neuronal cell and a muscle or gland cell across which a chemical signal (i.e., a neurotransmitter) and/or an electrical signal (i.e., current-carrying ions) can pass. The definition of synapse was developed by Charles Sherrington and by Ramon y Cajal at the beginning of this century and refined by John Eccles and Bernard Katz 50 years later; in this collection of papers, the definition of synapses is discussed further in the chapter by Mike Bennett. who provided the first functional demonstration of electrical transmission via gap junction channels between vertebrate neurons. As is evidenced by the range of topics covered in this issue, research dealing with gap junctions in the nervous system has expanded enormously in the past decade, major findings being that specific cell types in the brain expresses specific types of connexins and that expression patterns coincide with tissue compartmentalization and function and that these compartments change during development.

  4. Electrophysiological study in neuromuscular junction disorders

    Directory of Open Access Journals (Sweden)

    Ajith Cherian

    2013-01-01

    Full Text Available This review is on ultrastructure and subcellular physiology at normal and abnormal neuromuscular junctions. The clinical and electrophysiological findings in myasthenia gravis, Lambert-Eaton myasthenic syndrome (LEMS, congenital myasthenic syndromes, and botulinum intoxication are discussed. Single fiber electromyography (SFEMG helps to explain the basis of testing neuromuscular junction function by repetitive nerve stimulation (RNS. SFEMG requires skill and patience and its availability is limited to a few centers. For RNS supramaximal stimulation is essential and so is display of the whole waveform of each muscle response at maximum amplitude. The amplitudes of the negative phase of the first and fourth responses are measured from baseline to negative peak, and the percent change of the fourth response compared with the first represents the decrement or increment. A decrement greater than 10% is accepted as abnormal and smooth progression of response amplitude train and reproducibility form the crux. In suspected LEMS the effect of fast rates of stimulation should be determined after RNS response to slow rates of stimulation. Caution is required to avoid misinterpretation of potentiation and pseudofacilitation.

  5. Improving transition voltage spectroscopy of molecular junctions

    Science.gov (United States)

    Markussen, Troels; Chen, Jingzhe; Thygesen, Kristian S.

    2011-04-01

    Transition voltage spectroscopy (TVS) is a promising spectroscopic tool for molecular junctions. The principles in TVS is to find the minimum on a Fowler-Nordheim plot where ln(I/V2) is plotted against 1/V and relate the voltage at the minimum Vmin to the closest molecular level. Importantly, Vmin is approximately half the voltage required to see a peak in the dI/dV curve. Information about the molecular level position can thus be obtained at relatively low voltages. In this work we show that the molecular level position can be determined at even lower voltages, Vmin(α), by finding the minimum of ln(I/Vα) with α<2. On the basis of a simple Lorentzian transmission model we analyze theoretical ab initio as well as experimental I-V curves and show that the voltage required to determine the molecular levels can be reduced by ~30% as compared to conventional TVS. As for conventional TVS, the symmetry/asymmetry of the molecular junction needs to be taken into account in order to gain quantitative information. We show that the degree of asymmetry may be estimated from a plot of Vmin(α) vs α.

  6. Development of superconducting tunnel junction radiation detectors

    Energy Technology Data Exchange (ETDEWEB)

    Katagiri, Masaki; Kishimoto, Maki; Ukibe, Masahiro; Nakamura, Tatsuya; Nakazawa, Masaharu [Japan Atomic Energy Research Inst., Tokyo (Japan); Kurakado, Masahiko; Ishibashi, Kenji; Maehata, Keisuke

    1998-07-01

    Study on development of high energy resolution X-ray detector using superconducting tunnel junction (STJ) for radiation detection was conducted for 5 years under cooperation of University of Tokyo group and Kyushu University group by Quantum measurement research group of Advanced fundamental research center of JAERI. As the energy resolution of STJ could be obtained better results than that of Si semiconductor detector told to be actually best at present, this study aimed to actualize an X-ray detector usable for the experimental field and to elucidate radiation detection mechanism due to STJ. The STJ element used for this study was the one developed by Kurakado group of Nippon Steel Corp. As a results, some technical problems were almost resolved, which made some trouble when using the STJ element to detection element of X-ray spectrometer. In order to make the X-ray detector better, it is essential to manufacture a STJ element and develop serial junction type STJ element on the base of optimization of the element structure and selection and single crystallization of new superconducting materials such as Ta and others, activating the research results. (G.K.)

  7. Junction like behavior in polycrystalline diamond films

    Energy Technology Data Exchange (ETDEWEB)

    Bhaskaran, Shivakumar, E-mail: sbhaskar@mail.uh.edu [Department of Electrical and Computer Engineering, Cullen College of Engineering, University of Houston, TX 77004 (United States); Charlson, Earl Joe; Litvinov, Dmitri [Department of Electrical and Computer Engineering, Cullen College of Engineering, University of Houston, TX 77004 (United States); Makarenko, Boris [Department of Chemistry, University of Houston, TX 77004 (United States)

    2012-01-25

    Highlights: Black-Right-Pointing-Pointer The result that we obtained are compared with single crystalline diamond devices. Black-Right-Pointing-Pointer The barrier height of 4.4 eV matches the ideal pn-junction barrier height of diamond thin film. - Abstract: We have successfully fabricated polycrystalline diamond rectifying junction devices on n-type (1 0 0) silicon substrates by Hot Filament Chemical Vapor Deposition (HFCVD) using methane/hydrogen process gas and trimethyl borate and trimethyl phosphite dissolved in acetone as p- and n-type dopants, respectively. Impedance spectroscopy and current-voltage analysis indicates that the conduction is vertical down the grains and facets and not due to surface effects. Electrical characteristics were analyzed with In and Ti/Au top metal contacts with Al as the substrate contact. Current-voltage characteristics as a function of temperature showed barrier potentials of 1.1 eV and 0.77 eV for the In and Ti/Au contacts, respectively. Barrier heights of 4.8 eV (In) and 4.4 eV (Ti/Au) were obtained from capacitance-voltage measurements.

  8. GAP junctional communication in brain secondary organizers.

    Science.gov (United States)

    Bosone, Camilla; Andreu, Abraham; Echevarria, Diego

    2016-06-01

    Gap junctions (GJs) are integral membrane proteins that enable the direct cytoplasmic exchange of ions and low molecular weight metabolites between adjacent cells. They are formed by the apposition of two connexons belonging to adjacent cells. Each connexon is formed by six proteins, named connexins (Cxs). Current evidence suggests that gap junctions play an important part in ensuring normal embryo development. Mutations in connexin genes have been linked to a variety of human diseases, although the precise role and the cell biological mechanisms of their action remain almost unknown. Among the big family of Cxs, several are expressed in nervous tissue but just a few are expressed in the anterior neural tube of vertebrates. Many efforts have been made to elucidate the molecular bases of Cxs cell biology and how they influence the morphogenetic signal activity produced by brain signaling centers. These centers, orchestrated by transcription factors and morphogenes determine the axial patterning of the mammalian brain during its specification and regionalization. The present review revisits the findings of GJ composed by Cx43 and Cx36 in neural tube patterning and discuss Cx43 putative enrollment in the control of Fgf8 signal activity coming from the well known secondary organizer, the isthmic organizer. © 2016 The Authors. Development, Growth & Differentiation published by John Wiley & Sons Australia, Ltd on behalf of Japanese Society of Developmental Biologists.

  9. Annealing free magnetic tunnel junction sensors

    Science.gov (United States)

    Knudde, S.; Leitao, D. C.; Cardoso, S.; Freitas, P. P.

    2017-04-01

    Annealing is a major step in the fabrication of magnetic tunnel junctions (MTJs). It sets the exchange bias between the pinned and antiferromagnetic layers, and helps to increase the tunnel magnetoresistance (TMR) in both amorphous and crystalline junctions. Recent research on MTJs has focused on MgO-based structures due to their high TMR. However, the strict process control and mandatory annealing step can limit the scope of the application of these structures as sensors. In this paper, we present AlOx-based MTJs that are produced by ion beam sputtering and remote plasma oxidation and show optimum transport properties with no annealing. The microfabricated devices show TMR values of up to 35% and using NiFe/CoFeB free layers provides tunable linear ranges, leading to coercivity-free linear responses with sensitivities of up to 5.5%/mT. The top-pinned synthetic antiferromagnetic reference shows a stability of about 30 mT in the microfabricated devices. Sensors with linear ranges of up to 60 mT are demonstrated. This paves the way for the integration of MTJ sensors in heat-sensitive applications such as flexible substrates, or for the design of low-footprint on-chip multiaxial sensing devices.

  10. Switching and Rectification in Carbon-Nanotube Junctions

    Science.gov (United States)

    Srivastava, Deepak; Andriotis, Antonis N.; Menon, Madhu; Chernozatonskii, Leonid

    2003-01-01

    Multi-terminal carbon-nanotube junctions are under investigation as candidate components of nanoscale electronic devices and circuits. Three-terminal "Y" junctions of carbon nanotubes (see Figure 1) have proven to be especially interesting because (1) it is now possible to synthesize them in high yield in a controlled manner and (2) results of preliminary experimental and theoretical studies suggest that such junctions could exhibit switching and rectification properties. Following the preliminary studies, current-versus-voltage characteristics of a number of different "Y" junctions of single-wall carbon nanotubes connected to metal wires were computed. Both semiconducting and metallic nanotubes of various chiralities were considered. Most of the junctions considered were symmetric. These computations involved modeling of the quantum electrical conductivity of the carbon nanotubes and junctions, taking account of such complicating factors as the topological defects (pentagons, heptagons, and octagons) present in the hexagonal molecular structures at the junctions, and the effects of the nanotube/wire interfaces. A major component of the computational approach was the use of an efficient Green s function embedding scheme. The results of these computations showed that symmetric junctions could be expected to support both rectification and switching. The results also showed that rectification and switching properties of a junction could be expected to depend strongly on its symmetry and, to a lesser degree, on the chirality of the nanotubes. In particular, it was found that a zigzag nanotube branching at a symmetric "Y" junction could exhibit either perfect rectification or partial rectification (asymmetric current-versus-voltage characteristic, as in the example of Figure 2). It was also found that an asymmetric "Y" junction would not exhibit rectification.

  11. MgB2 tunnel junctions and SQUIDs

    NARCIS (Netherlands)

    Brinkman, A.; Rowell, J.M.

    2007-01-01

    Recent advances in the realization and understanding of MgB2 tunnel junctions and SQUIDs are surveyed. High quality MgB2 junctions with suitable tunnel barriers have been realized based on both oriented and epitaxial thin MgB2 films. Multiband transport properties, such as the existence of two energ

  12. Craniovertebral Junction Instability in the Setting of Chiari I Malformation.

    Science.gov (United States)

    Goldstein, Hannah E; Anderson, Richard C E

    2015-10-01

    This article addresses the key features, clinical presentation, and radiographic findings associated with craniovertebral junction instability in the setting of Chiari I malformation. It further discusses surgical technique for treating patients with Chiari I malformation with concomitant craniovertebral junction instability, focusing on modern posterior rigid instrumentation and fusion techniques.

  13. Parametric excitation of plasma oscillations in a Josephson tunnel junction

    DEFF Research Database (Denmark)

    Bak, Christen Kjeldahl; Kofoed, Bent; Pedersen, Niels Falsig

    1975-01-01

    Experimental evidence for subharmonic parametric excitation of plasma oscillations in Josephson tunnel junctions is presented. The experiments described are performed by measuring the microwave power necessary to switch a Josephson−tunnel junction biased in the zero−voltage state to a finite−volt......−voltage state. Journal of Applied Physics is copyrighted by The American Institute of Physics....

  14. Shapiro and parametric resonances in coupled Josephson junctions

    Science.gov (United States)

    Gaafar, Ma A.; Shukrinov, Yu M.; Foda, A.

    2012-11-01

    The effect of microwave irradiation on the phase dynamics of intrinsic Josephson junctions in high temperature superconductors is investigated. We compare the current-voltage characteristics for a stack of coupled Josephson junctions under external irradiation calculated in the framework of CCJJ and CCJJ+DC models.

  15. Microwave phase locking of Josephson-junction fluxon oscillators

    DEFF Research Database (Denmark)

    Salerno, M.; Samuelsen, Mogens Rugholm; Filatrella, G.;

    1990-01-01

    -dimensional functional map. Phase-locked states correspond to fixed points of the map. For junctions of in-line geometry, the existence and stability of such fixed points can be studied analytically. Study of overlap-geometry junctions requires the numerical inversion of a functional equation, but the results...

  16. Josephson junctions in high-T/sub c/ superconductors

    Science.gov (United States)

    Falco, C.M.; Lee, T.W.

    1981-01-14

    The invention includes a high T/sub c/ Josephson sperconducting junction as well as the method and apparatus which provides the junction by application of a closely controlled and monitored electrical discharge to a microbridge region connecting two portions of a superconducting film.

  17. Junction leakage measurements with micro four-point probes

    DEFF Research Database (Denmark)

    Lin, Rong; Petersen, Dirch Hjorth; Wang, Fei

    2012-01-01

    We present a new, preparation-free method for measuring the leakage current density on ultra-shallow junctions. The junction leakage is found by making a series of four-point sheet resistance measurements on blanket wafers with variable electrode spacings. The leakage current density is calculate...

  18. How good are one-dimensional Josephson junction models?

    DEFF Research Database (Denmark)

    Lomdahl, P. S.; Olsen, O.H.; Eilbeck, J. C.

    1985-01-01

    A two-dimensional model of Josephson junctions of overlap type is presented and shown to reduce to the usual one-dimensional (1D) model in the limit of a very narrow junction. Comparisons between the stability limits for fluxon reflection obtained from the two models suggest that the many results...

  19. Relaxation towards phase-locked dynamics in long Josephson junctions

    DEFF Research Database (Denmark)

    Salerno, M.; Grønbech-Jensen, Niels; Samuelsen, Mogens Rugholm

    1995-01-01

    We study the relaxation phenomenon towards phase-locked dynamics in long Josephson junctions. In particular the dependence of the relaxation frequency for the equal time of flight solution on the junction parameters is derived. The analysis is based on a phase-locked map and is compared with dire...

  20. Processing of Superconductor-Normal-Superconductor Josephson Edge Junctions

    Science.gov (United States)

    Kleinsasser, A. W.; Barner, J. B.

    1997-01-01

    The electrical behavior of epitaxial superconductor-normal-superconductor (SNS) Josephson edge junctions is strongly affected by processing conditions. Ex-situ processes, utilizing photoresist and polyimide/photoresist mask layers, are employed for ion milling edges for junctions with Yttrium-Barium-Copper-Oxide (YBCO) electrodes and primarily Co-doped YBCO interlayers.

  1. 75 FR 76294 - Radio Broadcasting Services: Pacific Junction, IA

    Science.gov (United States)

    2010-12-08

    ... From the Federal Register Online via the Government Publishing Office FEDERAL COMMUNICATIONS COMMISSION 47 CFR Part 73 Radio Broadcasting Services: Pacific Junction, IA AGENCY: Federal Communications Commission. ACTION: Final rule. SUMMARY: The staff deletes FM Channel 299C2 at Pacific Junction,...

  2. Shunted-Josephson-junction model. I. The autonomous case

    DEFF Research Database (Denmark)

    Belykh, V. N.; Pedersen, Niels Falsig; Sørensen, O. H.

    1977-01-01

    of the junction behavior in different regions of the parameter space. Approximate formulas are given for the parameter-space decomposition into regions of qualitatively different junction behavior corroborated by the associated-phase plane portraits and also approximate expressions for the corresponding dc...

  3. Gap junction protein connexin-43 interacts directly with microtubules

    NARCIS (Netherlands)

    Giepmans, B N; Verlaan, I; Hengeveld, T; Janssen, H; Calafat, J; Falk, M M; Moolenaar, W H

    2001-01-01

    Gap junctions are specialized cell-cell junctions that mediate intercellular communication. They are composed of connexin proteins, which form transmembrane channels for small molecules [1, 2]. The C-terminal tail of connexin-43 (Cx43), the most widely expressed connexin member, has been implicated

  4. Vortex dynamics in Josephson ladders with II-junctions

    DEFF Research Database (Denmark)

    Kornev, Victor K.; Klenov, N. V.; Oboznov, V.A.;

    2004-01-01

    Both experimental and numerical studies of a self-frustrated triangular array of pi-junctions are reported. The array of SFS Josephson junctions shows a transition to the pi-state and self-frustration with a decrease in temperature. This manifests itself in a half-period shift of the bias critica...

  5. Determination of Relaxation Time of a Josephson Tunnel Junction

    Institute of Scientific and Technical Information of China (English)

    WEN Xue-Da; YU Yang

    2008-01-01

    We propose a non-stationary method to measure the energy relaxation time of Josephson tunnel junctions from microwave enhanced escape phenomena.Compared with the previous methods,our method possesses simple and accurate features.Moreover,having determined the energy relaxation time,we can further obtain the coupling strength between the microwave source and the junction by changing the microwave power.

  6. Shunted-Josephson-junction model. II. The nonautonomous case

    DEFF Research Database (Denmark)

    Belykh, V. N.; Pedersen, Niels Falsig; Sørensen, O. H.

    1977-01-01

    The shunted-Josephson-junction model with a monochromatic ac current drive is discussed employing the qualitative methods of the theory of nonlinear oscillations. As in the preceding paper dealing with the autonomous junction, the model includes a phase-dependent conductance and a shunt capacitance...

  7. Conditions for synchronization in Josephson-junction arrays

    Energy Technology Data Exchange (ETDEWEB)

    Chernikov, A.A.; Schmidt, G. [Stevens Institute of Technology, Hoboken, NJ (United States)

    1995-12-31

    An effective perturbation theoretical method has been developed to study the dynamics of Josephson Junction series arrays. It is shown that the inclusion of Junction capacitances, often ignored, has a significant impact on synchronization. Comparison of analytic with computational results over a wide range of parameters shows excellent agreement.

  8. Structured chaos in a devil's staircase of the Josephson junction

    Science.gov (United States)

    Shukrinov, Yu. M.; Botha, A. E.; Medvedeva, S. Yu.; Kolahchi, M. R.; Irie, A.

    2014-09-01

    The phase dynamics of Josephson junctions (JJs) under external electromagnetic radiation is studied through numerical simulations. Current-voltage characteristics, Lyapunov exponents, and Poincaré sections are analyzed in detail. It is found that the subharmonic Shapiro steps at certain parameters are separated by structured chaotic windows. By performing a linear regression on the linear part of the data, a fractal dimension of D = 0.868 is obtained, with an uncertainty of ±0.012. The chaotic regions exhibit scaling similarity, and it is shown that the devil's staircase of the system can form a backbone that unifies and explains the highly correlated and structured chaotic behavior. These features suggest a system possessing multiple complete devil's staircases. The onset of chaos for subharmonic steps occurs through the Feigenbaum period doubling scenario. Universality in the sequence of periodic windows is also demonstrated. Finally, the influence of the radiation and JJ parameters on the structured chaos is investigated, and it is concluded that the structured chaos is a stable formation over a wide range of parameter values.

  9. The role of tight junctions in mammary gland function.

    Science.gov (United States)

    Stelwagen, Kerst; Singh, Kuljeet

    2014-03-01

    Tight junctions (TJ) are cellular structures that facilitate cell-cell communication and are important in maintaining the three-dimensional structure of epithelia. It is only during the last two decades that the molecular make-up of TJ is becoming unravelled, with two major transmembrane-spanning structural protein families, called occludin and claudins, being the true constituents of the TJ. These TJ proteins are linked via specific scaffolding proteins to the cell's cytoskeleton. In the mammary gland TJ between adjacent secretory epithelial cells are formed during lactogenesis and are instrumental in establishing and maintaining milk synthesis and secretion, whereas TJ integrity is compromised during mammary involution and also as result of mastitis and periods of mammary inflamation (including mastitis). They prevent the paracellular transport of ions and small molecules between the blood and milk compartments. Formation of intact TJ at the start of lactation is important for the establishment of the lactation. Conversely, loss of TJ integrity has been linked to reduced milk secretion and mammary function and increased paracellular transport of blood components into the milk and vice versa. In addition to acting as a paracellular barrier, the TJ is increasingly linked to playing an active role in intracellular signalling. This review focusses on the role of TJ in mammary function of the normal, non-malignant mammary gland, predominantly in ruminants, the major dairy producing species.

  10. Hydrologic controls on junction angle of river networks

    Science.gov (United States)

    Hooshyar, Milad; Singh, Arvind; Wang, Dingbao

    2017-05-01

    The formation and growth of river channels and their network evolution are governed by the erosional and depositional processes operating on the landscape due to the movement of water. The branching angles, i.e., the angle between two adjoining channels, in drainage networks are important features related to the network topology and contain valuable information about the forming mechanisms of the landscape. Based on the channel networks extracted from 1 m Digital Elevation Models of 120 catchments with minimal human impacts across the United States, we show that the junction angles have two distinct modes with α1¯≈49.5° and α2¯≈75.0°. The observed angles are physically explained as the optimal angles that result in minimum energy dissipation and are linked to the exponent characterizing the slope-area curve. Our findings suggest that the flow regimes, debris-flow dominated or fluvial, have distinct characteristic angles which are functions of the scaling exponent of the slope-area curve. These findings enable us to understand the geomorphic signature of hydrologic processes on drainage networks and develop more refined landscape evolution models.

  11. Internal resonances in periodically modulated long Josephson junctions

    DEFF Research Database (Denmark)

    Larsen, Britt Hvolbæk; Mygind, Jesper; Ustinov, Alexey V.

    1995-01-01

    Current-voltage (I-V) characteristics of long Josephson junctions with a periodic lattice of localized inhomogeneities are studied. The interaction between the moving fluxons and the inhomogeneities causes resonant steps in the IV-curve. Some of these steps are due to a synchronization to resonan...... into account the interaction between the resonance in the sub-junction and the magnetic flux density waves excited in the whole junction is given....... Fiske modes in the sub-junctions formed between the inhomogeneities. The voltage positions of the resonant steps oscillate as function of the applied magnetic field with a period corresponding to the inclusion of one magnetic flux quantum, Φ0=h/2e, per sub-junction. A qualitative explanation that takes...

  12. Parametric resonance in the system of long Josephson junctions

    Science.gov (United States)

    Rahmonov, I. R.; Shukrinov, Yu. M.; Irie, A.

    2014-08-01

    The phase dynamics of the system of long Josephson junctions whose length exceeds the Josephson penetration depth has been studied. The possibility of the appearance of a longitudinal plasma wave and parametric resonance has been demonstrated. Both inductive and capacitive couplings between Josephson junctions have been taken into account in the calculations. The current-voltage characteristics, as well as time evolution of the spatial distribution of the electric charge in superconducting layers and the magnetic field, have been calculated in all Josephson junctions of the system. The coexistence of the longitudinal plasma wave and fluxon states has been observed in the region of parametric resonance beginning with a certain length of the Josephson junction. This indicates the appearance of a new unique collective excitation in the system of coupled Josephson junctions, namely, a composite state of the Josephson current, electric field, and vortex magnetic field.

  13. Design of Steerable Wavelets to Detect Multifold Junctions.

    Science.gov (United States)

    Püspöki, Zsuzsanna; Uhlmann, Virginie; Vonesch, Cédric; Unser, Michael

    2016-02-01

    We propose a framework for the detection of junctions in images. Although the detection of edges and key points is a well examined and described area, the multiscale detection of junction centers, especially for odd orders, poses a challenge in pattern analysis. The goal of this paper is to build optimal junction detectors based on 2D steerable wavelets that are polar-separable in the Fourier domain. The approaches we develop are general and can be used for the detection of arbitrary symmetric and asymmetric junctions. The backbone of our construction is a multiscale pyramid with a radial wavelet function where the directional components are represented by circular harmonics and encoded in a shaping matrix. We are able to detect M -fold junctions in different scales and orientations. We provide experimental results on both simulated and real data to demonstrate the effectiveness of the algorithm.

  14. Observation of supercurrent in graphene-based Josephson junction

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Libin; Li, Sen; Kang, Ning [Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871 (China); Xu, Chuan; Ren, Wencai [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China)

    2015-07-01

    Josephson junctions with a normal metal region sandwiched between two superconductors (S) are known as superconductor- normal-superconductor (SNS) structures. It has attracted significant attention especially when changing the normal metal with graphene, which allow for high tunability with the gate voltage and to study the proximity effect of the massless Dirac fermions. Here we report our work on graphene-based Josephson junction with a new two dimensional superconductor crystal, which grown directly on graphene, as superconducting electrodes. At low temperature, we observer proximity effect induced supercurrent flowing through the junction. The temperature and the magnetic field dependences of the critical current characteristics of the junction are also studied. The critical current exhibits a Fraunhofer-type diffraction pattern against magnetic field. Our experiments provided a new route of fabrication of graphene-based Josephson junction.

  15. Low conductance of nickel atomic junctions in hydrogen atmosphere

    Science.gov (United States)

    Li, Shuaishuai; Xie, Yi-Qun; Hu, Yibin

    2017-08-01

    The low conductance of nickel atomic junctions in the hydrogen environment is studied using the nonequilibrium Green's function theory combined with first-principles calculations. The Ni junction bridged by a H2 molecule has a conductance of approximately 0.7 G 0. This conductance is contributed by the anti-bonding state of the H2 molecule, which forms a bonding state with the 3 d orbitals of the nearby Ni atoms. In contrast, the Ni junction bridged by the two single H atoms has a conductance of approximately 1 G 0, which is weakly spin-polarized. The spin-up channels were found to contribute mostly to the conductance at a small junction gap, while the spin-down channels play a dominant role at a larger junction gap.

  16. Visualizing supercurrents in 0-{pi} ferromagnetic Josephson tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Goldobin, Edward; Guerlich, Christian; Gaber, Tobias; Koelle, Dieter; Kleiner, Reinhold [Physikalisches Institut and Center for Collective Quantum Phenomena, Universitaet Tuebingen (Germany); Weides, Martin; Kohlstedt, Hermann [Institute of Solid State Physics, Reserch Center Juelich (Germany)

    2009-07-01

    So-called 0 and {pi} Josephson junctions can be treated as having positive and negative critical currents. This implies that the same phase shift applied to a Josephson junction causes counterflow of supercurrents in 0 and in {pi} junctions connected in parallel provided they are short in comparison with Josephson penetration depth {lambda}{sub J}. We have fabricated several 0, {pi}, 0-{pi}, 0-{pi}-0 and 20 x (0-{pi}-) planar superconductor-insulator-ferromagnet-superconductor Josephson junctions and studied the spatial supercurrent density distribution j{sub s}(x,y) across the junction area using low temperature scanning electron microscopy. At zero magnetic field we clearly see counterflow of the supercurrents in 0 and {pi} regions. The picture also changes consistently in the applied magnetic field.

  17. The current-phase relation in HTS Josephson junctions

    Science.gov (United States)

    Il'ichev, E.; Zakosarenko, V.; Ijsselsteijn, R. P. J.; Schultze, V.; Meyer, H.-G.; Hoenig, H. E.

    The current-phase relation of YBa2Cu3O7-x step-edge as well as 24° and 45° grain boundary Josephson junctions has been investigated experimentally. The junctions were incorporated into a washer-shaped superconducting ring with inductance L≈80-300 pH. The ring was inductively coupled to a tank circuit with a resonance frequency 9…40 MHz. The current-phase relation was obtained from the measurement of the impedance of the phase-biased junction. It is shown, that experimentally observed deviations from harmonic behavior of the apparent current-phase relation for step-edge and 24° grain boundary junctions can be explained by the influence of thermal noise. The current-phase relation of 45° grain boundary junctions was found to be extremely non-harmonic. The reasons of this unusual behavior are discussed.

  18. Glial connexins and gap junctions in CNS inflammation and disease.

    Science.gov (United States)

    Kielian, Tammy

    2008-08-01

    Gap junctions facilitate direct cytoplasmic communication between neighboring cells, facilitating the transfer of small molecular weight molecules involved in cell signaling and metabolism. Gap junction channels are formed by the joining of two hemichannels from adjacent cells, each composed of six oligomeric protein subunits called connexins. Of paramount importance to CNS homeostasis are astrocyte networks formed by gap junctions, which play a critical role in maintaining the homeostatic regulation of extracellular pH, K+, and glutamate levels. Inflammation is a hallmark of several diseases afflicting the CNS. Within the past several years, the number of publications reporting effects of cytokines and pathogenic stimuli on glial gap junction communication has increased dramatically. The purpose of this review is to discuss recent observations characterizing the consequences of inflammatory stimuli on homocellular gap junction coupling in astrocytes and microglia as well as changes in connexin expression during various CNS inflammatory conditions.

  19. Fixed-gap tunnel junction for reading DNA nucleotides.

    Science.gov (United States)

    Pang, Pei; Ashcroft, Brian Alan; Song, Weisi; Zhang, Peiming; Biswas, Sovan; Qing, Quan; Yang, Jialing; Nemanich, Robert J; Bai, Jingwei; Smith, Joshua T; Reuter, Kathleen; Balagurusamy, Venkat S K; Astier, Yann; Stolovitzky, Gustavo; Lindsay, Stuart

    2014-12-23

    Previous measurements of the electronic conductance of DNA nucleotides or amino acids have used tunnel junctions in which the gap is mechanically adjusted, such as scanning tunneling microscopes or mechanically controllable break junctions. Fixed-junction devices have, at best, detected the passage of whole DNA molecules without yielding chemical information. Here, we report on a layered tunnel junction in which the tunnel gap is defined by a dielectric layer, deposited by atomic layer deposition. Reactive ion etching is used to drill a hole through the layers so that the tunnel junction can be exposed to molecules in solution. When the metal electrodes are functionalized with recognition molecules that capture DNA nucleotides via hydrogen bonds, the identities of the individual nucleotides are revealed by characteristic features of the fluctuating tunnel current associated with single-molecule binding events.

  20. Scattering form factors for self-assembled network junctions

    Science.gov (United States)

    Foster, T.; Safran, S. A.; Sottmann, T.; Strey, R.

    2007-11-01

    The equilibrium microstructures in microemulsions and other self-assembled systems show complex, connected shapes such as symmetric bicontinuous spongelike structures and asymmetric bicontinuous networks formed by cylinders interconnected at junctions. In microemulsions, these cylinder network microstructures may mediate the structural transition from a spherical or globular phase to the bicontinuous microstructure. To understand the structural and statistical properties of such cylinder network microstructures as measured by scattering experiments, models are needed to extract the real-space structure from the scattering data. In this paper, we calculate the scattering functions appropriate for cylinder network microstructures. We focus on such networks that contain a high density of network junctions that connect the cylindrical elements. In this limit, the network microstructure can be regarded as an assembly of randomly oriented, closed packed network junctions (i.e., the cylinder scattering contributions are neglected). Accordingly, the scattering spectrum of the network microstructure can be calculated as the product of the junction number density, the junction form factor, which describes the scattering from the surface of a single junction, and a structure factor, which describes the local correlations of different junctions due to junction interactions (including their excluded volume). This approach is applied to analyze the scattering data from a bicontinuous microemulsion with equal volumes of water and oil. In a second approach, we included the cylinder scattering contribution in the junction form factor by calculating the scattering intensity of Y junctions to which three rods with spherical cross section are attached. The respective theoretical predictions are compared with results of neutron scattering measurements on a water-in-oil microemulsion with a connected microstructure.

  1. Effect of phase noise on quantum correlations in Bose-Josephson junctions

    Energy Technology Data Exchange (ETDEWEB)

    Ferrini, G.; Minguzzi, A.; Hekking, F. W. J. [Universite Grenoble 1 and CNRS, Laboratoire de Physique et Modelisation des Milieux Condenses UMR5493, B.P. 166, F-38042 Grenoble (France); Spehner, D. [Universite Grenoble 1 and CNRS, Laboratoire de Physique et Modelisation des Milieux Condenses UMR5493, B.P. 166, F-38042 Grenoble (France); Universite Grenoble 1 and CNRS, Institut Fourier UMR5582, B.P. 74, F-38402 Saint Martin d' Heres (France)

    2011-10-15

    In a two-mode Bose-Josephson junction the dynamics induced by a sudden quench of the tunnel amplitude leads to the periodic formation of entangled states. For instance, squeezed states are formed at short times and macroscopic superpositions of phase states at later times. In atom interferometry, the two modes of the junction play the role of the two arms of a Mach-Zehnder interferometer; use of multiparticle entangled states allows the enhancement of phase sensitivity with respect to that obtained from uncorrelated atoms. Decoherence due to the presence of noise degrades quantum correlations between atoms, thus reducing phase sensitivity. We consider decoherence due to stochastic fluctuations of the energies of the two modes of the junction. We analyze its effect on squeezed states and macroscopic superpositions and calculate the squeezing parameter and the quantum Fisher information during the quenched dynamics. The latter quantity measures the amount of quantum correlations useful in interferometry. For moderate noise intensities, we show that it increases on time scales beyond the squeezing regime. This suggests multicomponent superpositions of phase states as interesting candidates for high-precision atom interferometry.

  2. Transient Tissue-Scale Deformation Coordinates Alignment of Planar Cell Polarity Junctions in the Mammalian Skin.

    Science.gov (United States)

    Aw, Wen Yih; Heck, Bryan W; Joyce, Bradley; Devenport, Danelle

    2016-08-22

    Planar cell polarity (PCP) refers to the collective alignment of polarity along the tissue plane. In skin, the largest mammalian organ, PCP aligns over extremely long distances, but the global cues that orient tissue polarity are unknown. Here, we show that Celsr1 asymmetry arises concomitant with a gradient of tissue deformation oriented along the medial-lateral axis. This uniaxial tissue tension, whose origin remains unknown, transiently transforms basal epithelial cells from initially isotropic and disordered states into highly elongated and aligned morphologies. Reorienting tissue deformation is sufficient to shift the global axis of polarity, suggesting that uniaxial tissue strain can act as a long-range polarizing cue. Observations both in vivo and in vitro suggest that the effect of tissue anisotropy on Celsr1 polarity is not a direct consequence of cell shape but rather reflects the restructuring of cell-cell interfaces during oriented cell divisions and cell rearrangements that serve to relax tissue strain. We demonstrate that cell intercalations remodel intercellular junctions predominantly between the mediolateral interfaces of neighboring cells. This restructuring of the cell surface polarizes Celsr1, which is slow to accumulate at nascent junctions yet stably associates with persistent junctions. We propose that tissue anisotropy globally aligns Celsr1 polarity by creating a directional bias in the formation of new cell interfaces while simultaneously aligning the persistent interfaces at which Celsr1 prefers to accumulate.

  3. Atomistic simulations of highly conductive molecular transport junctions under realistic conditions

    KAUST Repository

    French, William R.

    2013-01-01

    We report state-of-the-art atomistic simulations combined with high-fidelity conductance calculations to probe structure-conductance relationships in Au-benzenedithiolate (BDT)-Au junctions under elongation. Our results demonstrate that large increases in conductance are associated with the formation of monatomic chains (MACs) of Au atoms directly connected to BDT. An analysis of the electronic structure of the simulated junctions reveals that enhancement in the s-like states in Au MACs causes the increases in conductance. Other structures also result in increased conductance but are too short-lived to be detected in experiment, while MACs remain stable for long simulation times. Examinations of thermally evolved junctions with and without MACs show negligible overlap between conductance histograms, indicating that the increase in conductance is related to this unique structural change and not thermal fluctuation. These results, which provide an excellent explanation for a recently observed anomalous experimental result [Bruot et al., Nat. Nanotechnol., 2012, 7, 35-40], should aid in the development of mechanically responsive molecular electronic devices. © 2013 The Royal Society of Chemistry.

  4. Andreev reflection and bound states in topological insulator based planar and step Josephson junctions

    Science.gov (United States)

    Choudhari, Tarun; Deo, Nivedita

    2017-01-01

    A superconductor-topological insulator-superconductor (S/TI/S) junction having normal region at angle θ is studied theoretically to investigate the junction angle dependency of the Andreev reflection and the formation of the Andreev bound states in the step and planar S/TI/S structures. It is found that the Andreev reflection becomes θ dependent only in the presence of the potential barrier at the TI/S interface. In particular, the step and planar TI/S junction have totally different conductive behavior with bias voltage and potential barrier in the regime of retro and specular Andreev reflection. Interestingly, we find that the elliptical cross section of Dirac cone, an important feature of topological insulator with step surface defect, affects the Fabry-Perot resonance of the Andreev reflection induced Andreev bound states (which become Majorana zero energy states at low chemical potential) in the step S/TI/S structure. Unlike the usual planar S/TI/S structures, we find these ellipticity affected Andreev bound states lead to non-monotonic Josephson super-current in the step S/TI/S structure whose non-monotonicity can be controlled with the use of the potential barrier, which may find applications in nanoelectronics.

  5. ADAMTS-10 and -6 differentially regulate cell-cell junctions and focal adhesions

    Science.gov (United States)

    Cain, Stuart A.; Mularczyk, Ewa J.; Singh, Mukti; Massam-Wu, Teresa; Kielty, Cay M.

    2016-01-01

    ADAMTS10 and ADAMTS6 are homologous metalloproteinases with ill-defined roles. ADAMTS10 mutations cause Weill-Marchesani syndrome (WMS), implicating it in fibrillin microfibril biology since some fibrillin-1 mutations also cause WMS. However little is known about ADAMTS6 function. ADAMTS10 is resistant to furin cleavage, however we show that ADAMTS6 is effectively processed and active. Using siRNA, over-expression and mutagenesis, it was found ADAMTS6 inhibits and ADAMTS10 is required for focal adhesions, epithelial cell-cell junction formation, and microfibril deposition. Either knockdown of ADAMTS6, or disruption of its furin processing or catalytic sites restores focal adhesions, implicating its enzyme activity acts on targets in the focal adhesion complex. In ADAMTS10-depleted cultures, expression of syndecan-4 rescues focal adhesions and cell-cell junctions. Recombinant C-termini of ADAMTS10 and ADAMTS6, both of which induce focal adhesions, bind heparin and syndecan-4. However, cells overexpressing full-length ADAMTS6 lack heparan sulphate and focal adhesions, whilst depletion of ADAMTS6 induces a prominent glycocalyx. Thus ADAMTS10 and ADAMTS6 oppositely affect heparan sulphate-rich interfaces including focal adhesions. We previously showed that microfibril deposition requires fibronectin-induced focal adhesions, and cell-cell junctions in epithelial cultures. Here we reveal that ADAMTS6 causes a reduction in heparan sulphate-rich interfaces, and its expression is regulated by ADAMTS10. PMID:27779234

  6. Constructing higher order DNA origami arrays using DNA junctions of anti-parallel/parallel double crossovers

    Science.gov (United States)

    Ma, Zhipeng; Park, Seongsu; Yamashita, Naoki; Kawai, Kentaro; Hirai, Yoshikazu; Tsuchiya, Toshiyuki; Tabata, Osamu

    2016-06-01

    DNA origami provides a versatile method for the construction of nanostructures with defined shape, size and other properties; such nanostructures may enable a hierarchical assembly of large scale architecture for the placement of other nanomaterials with atomic precision. However, the effective use of these higher order structures as functional components depends on knowledge of their assembly behavior and mechanical properties. This paper demonstrates construction of higher order DNA origami arrays with controlled orientations based on the formation of two types of DNA junctions: anti-parallel and parallel double crossovers. A two-step assembly process, in which preformed rectangular DNA origami monomer structures themselves undergo further self-assembly to form numerically unlimited arrays, was investigated to reveal the influences of assembly parameters. AFM observations showed that when parallel double crossover DNA junctions are used, the assembly of DNA origami arrays occurs with fewer monomers than for structures formed using anti-parallel double crossovers, given the same assembly parameters, indicating that the configuration of parallel double crossovers is not energetically preferred. However, the direct measurement by AFM force-controlled mapping shows that both DNA junctions of anti-parallel and parallel double crossovers have homogeneous mechanical stability with any part of DNA origami.

  7. GEN1 promotes Holliday junction resolution by a coordinated nick and counter-nick mechanism.

    Science.gov (United States)

    Chan, Ying Wai; West, Stephen

    2015-12-15

    Holliday junctions (HJs) that physically link sister chromatids or homologous chromosomes are formed as intermediates during DNA repair by homologous recombination. Persistent recombination intermediates are acted upon by structure-selective endonucleases that are required for proper chromosome segregation at mitosis. Here, we have purified full-length human GEN1 protein and show that it promotes Holliday junction resolution by a mechanism that is analogous to that exhibited by the prototypic HJ resolvase E. coli RuvC. We find that GEN1 cleaves HJs by a nick and counter-nick mechanism involving dual co-ordinated incisions that lead to the formation of ligatable nicked duplex products. As observed with RuvC, cleavage of the first strand is rate limiting, while second strand cleavage is rapid. In contrast to RuvC, however, GEN1 is largely monomeric in solution, but dimerizes on the HJ. Using HJs containing non-cleavable phosphorothioate-containing linkages in one strand, we show that the two incisions can be uncoupled and that the first nick occurs upon GEN1 dimerization at the junction. These results indicate that the mechanism of HJ resolution is largely conserved from bacteria to man, despite a lack of sequence homology between the resolvases. © The Author(s) 2015. Published by Oxford University Press on behalf of Nucleic Acids Research.

  8. Resolution of Holliday junction recombination intermediates by wild-type and mutant IntDOT proteins.

    Science.gov (United States)

    Kim, Seyeun; Gardner, Jeffrey F

    2011-03-01

    CTnDOT encodes an integrase that is a member of the tyrosine recombinase family. The recombination reaction proceeds by sequential sets of genetic exchanges between the attDOT site in CTnDOT and an attB site in the chromosome. The exchanges are separated by 7 base pairs in each site. Unlike most tyrosine recombinases, IntDOT exchanges sites that contain different DNA sequences between the exchange sites to generate Holliday junctions (HJs) that contain mismatched bases. We demonstrate that IntDOT resolves synthetic HJs in vitro. Holliday junctions that contain identical sequences between the exchange sites are resolved into both substrates and products, while HJs that contain mismatches are resolved only to substrates. This result implies that resolution of HJs to products requires the formation of a higher-order nucleoprotein complex with natural sites containing IntDOT. We also found that proteins with substitutions of residues (V95, K94, and K96) in a putative alpha helix at the junction of the N and CB domains (coupler region) were defective in resolving HJs. Mutational analysis of charged residues in the coupler and the N terminus of the protein did not provide evidence for a charge interaction between the regions of the protein. V95 may participate in a hydrophobic interaction with another region of IntDOT.

  9. Large tunable image-charge effects in single-molecule junctions.

    Science.gov (United States)

    Perrin, Mickael L; Verzijl, Christopher J O; Martin, Christian A; Shaikh, Ahson J; Eelkema, Rienk; van Esch, Jan H; van Ruitenbeek, Jan M; Thijssen, Joseph M; van der Zant, Herre S J; Dulić, Diana

    2013-04-01

    Metal/organic interfaces critically determine the characteristics of molecular electronic devices, because they influence the arrangement of the orbital levels that participate in charge transport. Studies on self-assembled monolayers show molecule-dependent energy-level shifts as well as transport-gap renormalization, two effects that suggest that electric-field polarization in the metal substrate induced by the formation of image charges plays a key role in the alignment of the molecular energy levels with respect to the metal's Fermi energy. Here, we provide direct experimental evidence for an electrode-induced gap renormalization in single-molecule junctions. We study charge transport through single porphyrin-type molecules using electrically gateable break junctions. In this set-up, the position of the occupied and unoccupied molecular energy levels can be followed in situ under simultaneous mechanical control. When increasing the electrode separation by just a few ångströms, we observe a substantial increase in the transport gap and level shifts as high as several hundreds of meV. Analysis of this large and tunable gap renormalization based on atomic charges obtained from density functional theory confirms and clarifies the dominant role of image-charge effects in single-molecule junctions.

  10. Influence of Coupling between Junctions on Breakpoint Current in Intrinsic Josephson Junctions

    Science.gov (United States)

    Shukrinov, Yu. M.; Mahfouzi, F.

    2007-04-01

    We study theoretically the current-voltage characteristics of intrinsic Josephson junctions in high-Tc superconductors. An oscillation of the breakpoint current on the outermost branch as a function of coupling α and dissipation β parameters is found. We explain this oscillation as a result of the creation of longitudinal plasma waves at the breakpoint with different wave numbers. We demonstrate the commensurability effect and predict a group behavior of the current-voltage characteristics for the stacks with a different number of junctions. A method to determine the wave number of longitudinal plasma waves from α and β dependence of the breakpoint current is suggested. We model the α and β dependence of the breakpoint current and obtain good agreement with the results of the simulation.

  11. Ruptured venous aneurysm of cervicomedullary junction

    Directory of Open Access Journals (Sweden)

    Ashish Aggarwal

    2014-01-01

    Full Text Available Background: Ruptured venous aneurysm is often seen with arterio-venous malformation (AVM or developmental venous anomaly (DVA. However, isolated venous aneurysm is unusual. Case Description: We present a case of ruptured venous aneurysm that presented with subarachnoid hemorrhage (SAH and intraventricular hemorrhage (IVH. Digital substraction angiography (DSA revealed a saccular contrast filling pouch in the left lateral aspect of cervicomedullary junction (CMJ. Endovascular intervention was not a viable option. During surgery, a saccular pliable structure approx. 1.5 Χ 1 cm was found in the subarachnoid space that was clipped and excised. There were no arterial feeders, no evidence of surrounding AVM, and no dilated perimedullary vein. Conclusion: This is perhaps the first reported case of ruptured venous aneurysm (without associated AVM of CMJ, which was successfully managed surgically. The possible etiologies remain an unnoticed head trauma or a congenital vessel wall abnormality. Surgically clipping and excision remains the treatment of choice for such lesion.

  12. Nonlinear nonequilibrium quasiparticle relaxation in Josephson junctions.

    Science.gov (United States)

    Krasnov, V M

    2009-11-27

    I solve numerically a full set of nonlinear kinetic balance equations for stacked Josephson junctions, which allows analysis of strongly nonequilibrium phenomena. It is shown that nonlinearity becomes significant already at very small disequilibrium. The following new, nonlinear effects are obtained: (i) At even-gap voltages V = 2nDelta/e (n = 2, 3, ...) nonequilibrium bosonic bands overlap. This leads to enhanced emission of Omega = 2Delta bosons and to the appearance of dips in tunnel conductance. (ii) A new type of radiative solution is found at strong disequilibrium. It is characterized by the fast stimulated relaxation of quasiparticles. A stack in this state behaves as a light emitting diode and directly converts electric power to boson emission, without utilization of the ac-Josephson effect. The phenomenon can be used for realization of a new type of superconducting cascade laser in the THz frequency range.

  13. Fully magnetic manganite spin filter tunnel junctions

    Science.gov (United States)

    Prasad, Bhagwati; Blamire, Mark G.

    2016-09-01

    In this paper we demonstrate spintronic devices which combine magnetic tunnel junctions with a spin-filtering tunnel barrier. These consist of an ultrathin ferromagnetic insulating barrier, Sm0.75Sr0.25MnO3, sandwiched between two ferromagnetic half-metallic manganite electrodes, La0.7Sr0.3MnO3 and La0.7Ca0.3MnO3, in a nanopillar structure. Depending on the relative magnetic configurations of barrier and electrode layers, three resistance states are well defined, which therefore represent a potential three-state memory concept. These results open the way for the development of spintronic devices by exploiting the many degrees of freedom of perovskite manganite heterostructure systems.

  14. Electron and Phonon Transport in Molecular Junctions

    DEFF Research Database (Denmark)

    Li, Qian

    transmission at the Fermi energy. We propose and analyze a way of using π   stacking to design molecular junctions to control heat transport. We develop a simple model system to identify optimal parameter regimes and then use density functional theory (DFT) to extract model parameters for a number of specific....... The system we are interested in here are π-stacked molecules connected with two semi-infinite leads. π-stacked aromatic rings, connected via π-π electronic coupling, provides a rather soft mechanical bridge while maintaining high electronic conductivity. We investigate electron transport...... and the thermoelectric response of five representative π-stacked systems. We find that the transmission and power factor are both enhanced by increasing the conjugation length or adding substituent groups. The local transmission shows that several extra paths are added by cyano groups, which increases the total...

  15. Electronic transport properties of phenylacetylene molecular junctions

    Institute of Scientific and Technical Information of China (English)

    Liu Wen; Cheng Jie; Yah Cui-Xia; Li Hai-Hong; Wang Yong-Juan; Liu De-Sheng

    2011-01-01

    Electronic transport properties of a kind of phenylacetylene compound- (4-mercaptophenyl)-phenylacetylene are calculated by the first-principles method in the framework of density functional theory and the nonequilibrium Green's function formalism.The molecular junction shows an obvious rectifying behaviour at a bias voltage larger than 1.0 V.The rectification effect is attributed to the asymmetry of the interface contacts.Moreover,at a bias voltage larger than 2.0 V,which is not referred to in a relevant experiment [Fang L,Park J Y,Ma H,Jan A K Y and Salmeron M 2007 Langmuir 23 11522],we find a negative differential resistance phenomenon.The negative differential resistance effect may originate from the change of the delocalization degree of the molecular orbitais induced by the bias.

  16. Functional oesophago-gastric junction imaging

    Institute of Scientific and Technical Information of China (English)

    Barry P McMahon; Asbj(φ)rn M Drewes; Hans Gregersen

    2006-01-01

    Despite its role in disease there is still no definitive method to assess oesophago-gastric junction competence (OGJ). Traditionally the OGJ has been assessed using manometry with lower oesophageal sphincter pressure as the indicator. More recently this has been shown not to be a very reliable marker of sphincter function and competence against reflux.Disorders such as gastro-oesophageal reflux disease and to a lesser extend achalasia still effects a significant number of patients. This review looks at using a new technique known as impedance planimetry to profile the geometry and pressure in the OGJ during distension of a bag. The data gathered can be reconstructed into a dynamic representation of OGJ action. This has been shown to provide a useful representation of the OGJ and to show changes to the competence of the OGJ in terms of compliance and distensibility as a result of endoluminal therapy.

  17. Shot Noise in Ferromagnetic Superconductor Tunnel Junctions

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    In this paper, the superconducting order parameter and the energy spectrum of the Bogoliubov excitations are obtained from the Bogoliubov-de Gennes (BdG) equation for a ferromagnetic superconductor (FS). Taking into account the rough interface scattering effect, we calculate the shot noise and the differential conductance of the normal- metal insulator ferromagnetic superconductor junction. It is shown that the exchange energy Eh in FS can lead to splitting of the differential shot noise peaks and the conductance peaks. The energy difference between the two splitting peaks is equal to 2Eh. The rough interface scattering strength results in descent of conductance peaks and the shot noise-to-current ratio but increases the shot noise.

  18. Permanent junctional reciprocating tachycardia in a dog.

    Science.gov (United States)

    Santilli, Roberto A; Santos, Luis F N; Perego, Manuela

    2013-09-01

    A 5-year-old male English Bulldog was presented with a 1-year history of paroxysmal supraventricular tachycardia (SVT) partially responsive to amiodarone. At admission the surface ECG showed sustained runs of a narrow QRS complex tachycardia, with a ventricular cycle length (R-R interval) of 260 ms, alternating with periods of sinus rhythm. Endocardial mapping identified the electrogenic mechanism of the SVT as a circus movement tachycardia with retrograde and decremental conduction along a concealed postero-septal atrioventricular pathway (AP) and anterograde conduction along the atrioventricular node. These characteristics were indicative of a permanent junctional reciprocating tachycardia (PJRT). Radiofrequency catheter ablation of the AP successfully terminated the PJRT, with no recurrence of tachycardia on Holter monitoring at 12 months follow-up.

  19. Exotic Brane Junctions from F-theory

    CERN Document Server

    Kimura, Tetsuji

    2016-01-01

    Applying string dualities to F-theory, we obtain various $[p,q]$-branes whose constituents are standard branes of codimension two and exotic branes. We construct junctions of the exotic five-branes and their Hanany-Witten transitions associated with those in F-theory. In this procedure, we understand the monodromy of the single $5^2_2$-brane. We also find the objects which are sensitive to the branch cut of the $5^2_2$-brane. Considering the web of branes in the presence of multiple exotic five-branes analogous to the web of five-branes with multiple seven-branes, we obtain novel brane constructions for $SU(2)$ gauge theories with $n$ flavors and their superconformal limit with enhanced $E_{n+1}$ symmetry in five, four, and three dimensions. Hence, adapting the techniques of the seven-branes to the exotic branes, we will be able to construct F-theories in diverse dimensions.

  20. Operating modes of superconducting tunnel junction device

    Energy Technology Data Exchange (ETDEWEB)

    Maehata, Keisuke [Kyushu Univ., Fukuoka (Japan). Faculty of Engineering

    1998-07-01

    In the Electrotechnical Laboratory, an Nb type superconducting tunnel junction (STJ) device with 200 x 200 sq. micron in area and super high quality was manufactured. By using 55-fe source, response of this large area STJ to X-ray was measured. In this measurement, two action modes with different output wave height from front amplifier were observed. Then, in this study, current-voltage feature of the element in each action mode was analyzed to elucidate a mechanism to form such two action modes. The feature was analyzed by using first order approximate solution on cavity resonance mode of Sine-Gordon equation. From the analytical results, it could be supposed that direction and magnitude of effective magnetic field penetrating into jointed area changed by an induction current effect owing to impressing speed of the magnetic field, which brings two different current-voltage features to make possible to observe two action modes with different pulse wave height. (G.K.)

  1. Studies of silicon pn junction solar cells

    Science.gov (United States)

    Lindholm, F. A.; Neugroschel, A.

    1977-01-01

    Modifications of the basic Shockley equations that result from the random and nonrandom spatial variations of the chemical composition of a semiconductor were developed. These modifications underlie the existence of the extensive emitter recombination current that limits the voltage over the open circuit of solar cells. The measurement of parameters, series resistance and the base diffusion length is discussed. Two methods are presented for establishing the energy bandgap narrowing in the heavily-doped emitter region. Corrections that can be important in the application of one of these methods to small test cells are examined. Oxide-charge-induced high-low-junction emitter (OCI-HLE) test cells which exhibit considerably higher voltage over the open circuit than was previously seen in n-on-p solar cells are described.

  2. Tantalum oxide barrier in magnetic tunnel junctions

    Institute of Scientific and Technical Information of China (English)

    Guanghua Yu; Tingting Ren; Wei Ji; Jiao Teng; Fengwu Zhu

    2004-01-01

    Tantalum as an insulating barrier can take the place of Al in magnetic tunnel junctions (MTJs). Ta barriers in MTJs were fabricated by natural oxidation. X-ray photoelectron spectroscopy (XPS) was used to characterize the oxidation states of Ta barrier.The experimental results show that the chemical state of tantalum is pure Ta5+ and the thickness of the oxide is 1.3 nm. The unoxidized Ta in the barrier may chemically reacted with NiFe layer which is usually used in MTJs to form an intermetallic compound,NiTa2. A magnetic "dead layer" could be produced in the NiFe/Ta interface. The "dead layer" is likely to influence the spinning electron transport and the magnetoresistance effect.

  3. Controlling local currents in molecular junctions

    CERN Document Server

    Yadalam, Hari Kumar

    2016-01-01

    The effect of non-equilibrium constraints and dephasing on the circulating currents in molecular junctions are analyzed. Circulating currents are manifestations of quantum effects and can be induced either by externally applied bias or an external magnetic field through the molecular system. In symmetric Aharonov-Bohm ring, bond currents have two contributions, bias driven and magnetic field driven. We analyze the competition between these two contributions and show that, as a consequence, current through one of the branches can be completely suppressed. We then study the effect of asymmetry (as a result of chemical substitution) on the current pathways inside the molecule and study asymmetry induced circulating currents (without magnetic field) by tuning the coupling strength of the substituent (at finite bias).

  4. Tunable Magnetic Proximity Effects in Graphene Junctions

    Science.gov (United States)

    Lazic, Predrag; Belashchenko, Kirill; Zutic, Igor

    2015-03-01

    The characteristic length of the magnetic proximity effects exceed the thickness of a graphene layer leading to an important, but typically overlooked, modifications of equilibrium and transport properties, as well as the implications for graphene spintronics. Using the first-principles studies that integrate a real space density functional theory (GPAW) with the state-of-the art boundary elements electrostatic code based on the Robin Hood method, we explore tunable electronic structure and magnetic proximity effects in the ferromagnet/insulator/graphene junctions. We show that the inclusion of a finite-size gate electrodes and van der Walls interaction lead to nontrivial effects that could also be important in other two-dimensional materials beyond graphene. Work supported by US ONR, NSF-DMR and Nebraska NSF MRSEC.

  5. Enamelin Directs Crystallite Organization at the Enamel-Dentine Junction.

    Science.gov (United States)

    Siddiqui, S; Al-Jawad, M

    2016-05-01

    Enamel is an acellular material formed by the intricate process of amelogenesis. Disruption caused at the initial stages of development, by means of mutations in the ENAM gene encoding the enamelin protein, results in enamel hypoplasia. Little is known about the consequence of ENAM mutation on the enamel structure at a crystallographic level. The aim of this study was to characterize the structure of ENAM-mutated enamel to develop a deeper understanding of the role of enamelin protein during formation with regard to crystal organization. Synchrotron X-ray microdiffraction (SXRD) and scanning electron microscopy (SEM) have been used to measure and correlate enamel crystallography and microstructure in hypoplastic and healthy enamel. Rietveld refinement carried out on 2-dimensional diffraction patterns, collected from the Advanced Photon Source, were used to quantify changes in the preferred orientation (crystallographic texture) within the labial regions of each tooth slice and then correlated with the local microstructure. In general, healthy deciduous incisors displayed a higher degree of crystal organization across the labial surface in comparison with the hypoplastic enamel. ENAM plays the greatest functional role at the enamel-dentine junction (EDJ), as it was the region that exhibited lowest texture relative to unaffected controls. Other areas within the tooth, however, such as the cusp tip, displayed greater organization in line with healthy enamel, suggesting its effects are restricted to the early stages of enamel secretion. Observed clinically, the surface of ENAM-mutated hypoplastic enamel can appear to be normal, yet severe sub-nano and microstructural defects appear beneath the subsurface layer. Quantitative characterization of the crystallographic properties from enamel with known genotype expands the understanding of enamel formation processes and can aid better clinical diagnosis and tailor-made treatment.

  6. Computation of flow through the oesophagogastric junction

    Institute of Scientific and Technical Information of China (English)

    Barry P McMahon; Karl D Odie; Kenneth W Moloney; Hans Gregersen

    2007-01-01

    Whilst methods exist to indirectly measure the effects of increased flow or gastro-oesophageal refluxing,they cannot quantitatively measure the amount of acid travelling back up into the oesophagus during reflux, nor can they indicate the flow rate through the oesophagogastric junction (OGJ). Since OGJ dysfunction affects flow it seems most appropriate to describe the geometry of the OGJ and its effect on the flow.A device known as the functional lumen imaging probe (FLIP) has been shown to reliably measure the geometry of and pressure changes in the OGJ. FLIP cannot directly measure flow but the data gathered from the probe can be used to model flow through the junction by using computational flow dynamics (CFD).CFD uses a set of equations known as the Navier-Stokes equations to predict flow patterns and is a technique widely used in engineering. These equations are complex and require appropriate assumptions to provide simplifications before useful data can be obtained. With the assumption that the cross-sectional areas obtained via FLIP are circular, the radii of these circles can be obtained. A cubic interpolation scheme can then be applied to give a high-resolution geometry for the OGJ.In the case of modelling a reflux scenario, it can be seen that at the narrowest section a jet of fluid squirts into the oesophagus at a higher velocity than the fluid surrounding it. This jet has a maximum velocity of almost 2 ms-1 that occurs where the OGJ is at its narrowest. This simple prediction of acid 'squirting' into the oesophagus illustrates how the use of numerical methods can be used to develop a better understanding of the OGJ. This initial work using CFD shows some considerable promise for the future.

  7. Influence of coupling between junctions on breakpoint current in intrinsic Josephson junctions

    OpenAIRE

    Shukrinov, Yu M.; Mahfouzi, F.

    2006-01-01

    We study theoretically the current-voltage characteristics of intrinsic Josephson junctions in high-$T_c$ superconductors. An oscillation of the breakpoint current on the outermost branch as a function of coupling $\\alpha$ and dissipation $\\beta$ parameters is found. We explain this oscillation as a result of the creation of longitudinal plasma waves at the breakpoint with different wave numbers. We demonstrate the commensurability effect and predict a group behavior of the current-voltage ch...

  8. Incompressible Turbulent Wing-Body Junction Flow

    Science.gov (United States)

    Krishnamurthy, R.; Cagle, Corey D.; Chandra, S.

    1998-01-01

    The overall objective of this study is to contribute to the optimized design of fan bypass systems in advanced turbofan engines. Increasing the engine bypass ratios have provided a major boost in engine performance improvement over the last fifty years. An engine with high bypass ratio (11-16:1) such as the Advanced Ducted Propulsion (ADP) is being developed and is expected to provide an additional 25% improvement in overall efficiency over the early turbofans. Such significant improvements in overall efficiency would reduce the cost per seat mile, which is a major government and Industry challenge for the 21th century. The research is part of the Advanced Subsonic Technology (AST) program that involves a NASA, U.S. Industry and FAA partnership with the goal of a safe and highly productive global air transportation system. The immediate objective of the study is to perform numerical simulation of duct-strut interactions to elucidate the loss mechanisms associated with this configuration that is typical of advanced turbofan engines such as ADP. However, at present experimental data for a duct-strut configuration are not available. Thus, as a first step a wing-body junction flow would be studied and is the specific objective of the present study. At the outset it is to be recognized that while duct-strut interaction flow is similar to that of wing-body junction flows, there are some differences owing to the presence of a wall at both ends of the strut. Likewise, some differences are due to the sheared inflow (as opposed to a uniform inflow) velocity profile. It is however expected that some features of a wing-body junction flow would persist. Next, some of the salient aspects of the complex flow near a wing-body junction, as revealed by various studies reported in the literature will be reviewed. One of the principle characteristics of the juncture flow, is the presence of the mean flow components in a plane perpendicular to the direction of the oncoming free

  9. Interaction of Branch Migration Translocases with the Holliday Junction-resolving Enzyme and Their Implications in Holliday Junction Resolution*

    Science.gov (United States)

    Cañas, Cristina; Suzuki, Yuki; Marchisone, Chiara; Carrasco, Begoña; Freire-Benéitez, Verónica; Takeyasu, Kunio; Alonso, Juan C.; Ayora, Silvia

    2014-01-01

    Double-strand break repair involves the formation of Holliday junction (HJ) structures that need to be resolved to promote correct replication and chromosomal segregation. The molecular mechanisms of HJ branch migration and/or resolution are poorly characterized in Firmicutes. Genetic evidence suggested that the absence of the RuvAB branch migration translocase and the RecU HJ resolvase is synthetically lethal in Bacillus subtilis, whereas a recU recG mutant was viable. In vitro RecU, which is restricted to bacteria of the Firmicutes phylum, binds HJs with high affinity. In this work we found that RecU does not bind simultaneously with RecG to a HJ. RuvB by interacting with RecU bound to the central region of HJ DNA, loses its nonspecific association with DNA, and re-localizes with RecU to form a ternary complex. RecU cannot stimulate the ATPase or branch migration activity of RuvB. The presence of RuvB·ATPγS greatly stimulates RecU-mediated HJ resolution, but the addition of ATP or RuvA abolishes this stimulatory effect. A RecU·HJ·RuvAB complex might be formed. RecU does not increase the RuvAB activities but slightly inhibits them. PMID:24770420

  10. Interaction of branch migration translocases with the Holliday junction-resolving enzyme and their implications in Holliday junction resolution.

    Science.gov (United States)

    Cañas, Cristina; Suzuki, Yuki; Marchisone, Chiara; Carrasco, Begoña; Freire-Benéitez, Verónica; Takeyasu, Kunio; Alonso, Juan C; Ayora, Silvia

    2014-06-20

    Double-strand break repair involves the formation of Holliday junction (HJ) structures that need to be resolved to promote correct replication and chromosomal segregation. The molecular mechanisms of HJ branch migration and/or resolution are poorly characterized in Firmicutes. Genetic evidence suggested that the absence of the RuvAB branch migration translocase and the RecU HJ resolvase is synthetically lethal in Bacillus subtilis, whereas a recU recG mutant was viable. In vitro RecU, which is restricted to bacteria of the Firmicutes phylum, binds HJs with high affinity. In this work we found that RecU does not bind simultaneously with RecG to a HJ. RuvB by interacting with RecU bound to the central region of HJ DNA, loses its nonspecific association with DNA, and re-localizes with RecU to form a ternary complex. RecU cannot stimulate the ATPase or branch migration activity of RuvB. The presence of RuvB·ATPγS greatly stimulates RecU-mediated HJ resolution, but the addition of ATP or RuvA abolishes this stimulatory effect. A RecU·HJ·RuvAB complex might be formed. RecU does not increase the RuvAB activities but slightly inhibits them. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

  11. Optical trapping of microparticles using silicon nitride waveguide junctions and tapered-waveguide junctions on an optofluidic chip.

    Science.gov (United States)

    Cai, Hong; Poon, Andrew W

    2012-10-01

    We study optical trapping of microparticles on an optofluidic chip using silicon nitride waveguide junctions and tapered-waveguide junctions. We demonstrate the trapping of single 1 μm-sized polystyrene particles using the evanescent field of waveguide junctions connecting a submicrometer-sized input-waveguide and a micrometer-sized output-waveguide. Particle trapping is localized in the vicinity of the junction. We also demonstrate trapping of one and two 1μm-sized polystyrene particles using tapered-waveguide junctions connecting a submicrometer-sized singlemode input-waveguide and a micrometer-sized multimode output-waveguide. Particle trapping occurs near the taper output end, the taper center and the taper input end, depending on the taper aspect ratio.

  12. Molecular signatures in the transport properties of molecular wire junctions: what makes a junction "molecular"?

    Science.gov (United States)

    Troisi, Alessandro; Ratner, Mark A

    2006-02-01

    The simplest component of molecular electronics consists of a single-molecule transport junction: a molecule sandwiched between source and drain electrodes, with or without a third gate electrode. In this Concept article, we focus on how molecules control transport in metal-electrode molecular junctions, and where the molecular signatures are to be found. In the situation where the molecule is relatively short and the gap between injection energy and molecular eigenstates is large, transport occurs largely by elastic tunneling, stochastic switching is common, and the vibronic signature can be found using inelastic electron tunneling spectroscopy (IETS). As the energy gaps for injection become smaller, one begins to see stronger molecular signatures - these include Franck-Condon-like structures in the current/voltage characteristic and strong vibronic interactions, which can lead to hopping behavior at the polaron limit. Conformational changes induced by the strong electric field lead to another strong manifestation of the molecular nature of the junction. We overview some of this mechanistic landscape, focusing on significant effects of switching (both stochastic and controlled by the electric field) and of molecular vibronic coupling.

  13. Generation of Oil Droplets in a Non-Newtonian Liquid Using a Microfluidic T-Junction

    Directory of Open Access Journals (Sweden)

    Enrico Chiarello

    2015-11-01

    Full Text Available We have compared the formation of oil drops in Newtonian and non-Newtonian fluids in a T-junction microfluidic device. As Newtonian fluids, we used aqueous solutions of glycerol, while as non-Newtonian fluids we prepared aqueous solutions of xanthan, a stiff rod-like polysaccharide, which exhibit strong shear-thinning effects. In the squeezing regime, the formation of oil droplets in glycerol solutions is found to scale with the ratio of the dispersed flow rate to the continuous one and with the capillary number associated to the continuous phase. Switching to xanthan solutions does not seem to significantly alter the droplet formation process. Any quantitative difference with respect to the Newtonian liquid can be accounted for by a suitable choice of the capillary number, corresponding to an effective xanthan viscosity that depends on the flow rates. We have deduced ample variations in the viscosity, on the order of 10 and more, during normal operation conditions of the T-junction. This allowed estimating the actual shear rates experienced by the xanthan solutions, which go from tens to hundreds of s−1.

  14. 3D Architecture of the Trypanosoma brucei Flagella Connector, a Mobile Transmembrane Junction.

    Directory of Open Access Journals (Sweden)

    Johanna L Höög

    2016-01-01

    Full Text Available Cellular junctions are crucial for the formation of multicellular organisms, where they anchor cells to each other and/or supportive tissue and enable cell-to-cell communication. Some unicellular organisms, such as the parasitic protist Trypanosoma brucei, also have complex cellular junctions. The flagella connector (FC is a three-layered transmembrane junction that moves with the growing tip of a new flagellum and attaches it to the side of the old flagellum. The FC moves via an unknown molecular mechanism, independent of new flagellum growth. Here we describe the detailed 3D architecture of the FC suggesting explanations for how it functions and its mechanism of motility.We have used a combination of electron tomography and cryo-electron tomography to reveal the 3D architecture of the FC. Cryo-electron tomography revealed layers of repetitive filamentous electron densities between the two flagella in the interstitial zone. Though the FC does not change in length and width during the growth of the new flagellum, the interstitial zone thickness decreases as the FC matures. This investigation also shows interactions between the FC layers and the axonemes of the new and old flagellum, sufficiently strong to displace the axoneme in the old flagellum. We describe a novel filament, the flagella connector fibre, found between the FC and the axoneme in the old flagellum.The FC is similar to other cellular junctions in that filamentous proteins bridge the extracellular space and are anchored to underlying cytoskeletal structures; however, it is built between different portions of the same cell and is unique because of its intrinsic motility. The detailed description of its structure will be an important tool to use in attributing structure / function relationships as its molecular components are discovered in the future. The FC is involved in the inheritance of cell shape, which is important for the life cycle of this human parasite.

  15. Influence of the diffusion current on the hysteretic behavior in the system of coupled Josephson junctions

    Science.gov (United States)

    Shukrinov, Yu. M.; Rahmonov, I. R.

    2010-09-01

    The detailed investigation of the phase dynamics and the I-V curves in the system of coupled Josephson junctions have been carried out. The superconducting, quasiparticle, diffusion, and displacement currents have been calculated as functions of the total current through the system. The role of the diffusion current in the formation of the I-V curves has been studied and the influence of this quantity on the I-V curve branching and the magnitude of the return current has been revealed. The calculation results agree qualitatively with the experimental data.

  16. Spontaneous fluxon production in annular Josephson tunnel junctions in the presence of a magnetic field

    DEFF Research Database (Denmark)

    Monaco, Roberto; Aarøe, Morten; Mygind, Jesper;

    2008-01-01

    We report on the spontaneous production of fluxons in annular Josephson tunnel junctions during a thermal quench in the presence of a symmetry-breaking magnetic field. The dependence on field intensity B of the probability (f) over bar (1) to trap a single defect during the N-S phase transition...... depends drastically on the sample circumferences. We show that this can be understood in the framework of the same picture of spontaneous defect formation that leads to the experimentally well attested scaling behavior of (f) over bar (1) with quench rate in the absence of an external field....

  17. Biomimetic tendon extracellular matrix composite gradient scaffold enhances ligament-to-bone junction reconstruction.

    Science.gov (United States)

    Liu, Huanhuan; Yang, Long; Zhang, Erchen; Zhang, Rui; Cai, Dandan; Zhu, Shouan; Ran, Jisheng; Bunpetch, Varitsara; Cai, Youzhi; Heng, Boon Chin; Hu, Yejun; Dai, Xuesong; Chen, Xiao; Ouyang, Hongwei

    2017-07-01

    Management of ligament/tendon-to-bone-junction healing remains a formidable challenge in the field of orthopedic medicine to date, due to deficient vascularity and multi-tissue transitional structure of the junction. Numerous strategies have been employed to improve ligament-bone junction healing, including delivery of stem cells, bioactive factors, and synthetic materials, but these methods are often inadequate at recapitulating the complex structure-function relationships at native tissue interfaces. Here, we developed an easily-fabricated and effective biomimetic composite to promote the regeneration of ligament-bone junction by physically modifying the tendon extracellular matrix (ECM) into a Random-Aligned-Random composite using ultrasound treatment. The differentiation potential of rabbit bone marrow stromal cells on the modified ECM were examined in vitro. The results demonstrated that the modified ECM enhanced expression of chondrogenesis and osteogenesis-associated epigenetic genes (Jmjd1c, Kdm6b), transcription factor genes (Sox9, Runx2) and extracellular matrix genes (Col2a1, Ocn), resulting in higher osteoinductivity than the untreated tendon ECM in vitro. In the rabbit anterior cruciate ligament (ACL) reconstruction model in vivo, micro-computed tomography (Micro-CT) and histological analysis showed that the modified Random-Aligned-Random composite scaffold enhanced bone and fibrocartilage formation at the interface, more efficaciously than the unmodified tendon ECM. Therefore, these results demonstrated that the biomimetic Random-Aligned-Random composite could be a promising scaffold for ligament/tendon-bone junction repair. The native transitional region consists of several distinct yet contiguous tissue regions, composed of soft tissue, non-calcified fibrocartilage, calcified fibrocartilage, and bone. A stratified graft whose phases are interconnected with each other is essential for supporting the formation of functionally continuous multi

  18. The Wnt/planar cell polarity signaling pathway contributes to the integrity of tight junctions in brain endothelial cells

    OpenAIRE

    2013-01-01

    Wnt morphogens released by neural precursor cells were recently reported to control blood–brain barrier (BBB) formation during development. Indeed, in mouse brain endothelial cells, activation of the Wnt/β-catenin signaling pathway, also known as the canonical Wnt pathway, was shown to stabilize endothelial tight junctions (TJs) through transcriptional regulation of the expression of TJ proteins. Because Wnt proteins activate several distinct β-catenin-dependent and independent signaling path...

  19. Spin transport and dynamics in the F/N junction

    Science.gov (United States)

    Li, Hua; Bedell, Kevin

    2015-03-01

    We study the spin transport in the low temperature regime (often referred to as the precession-dominated regime) between a ferromagnetic Fermi liquid (FFL) and a normal metal metallic Fermi liquid (NFL), the F/N junction, which is considered one of the basic spintronic devices. In particular, we explore the propagation of spin waves and transport of magnetization through the interface of the F/N junction where non-equilibrium spin polarization is created on the normal metal side of the junction by spin injection. We calculate the probable spin wave modes in the precession-dominated regime on both sides of the junction especially on the NFL side where the system is out of equilibrium. Proper boundary conditions at the interface are introduced to establish the transport of the spin properties through the F/N junction. In the end, a possible transmission conduction electron spin resonance experiment is suggested on the F/N junction to see if the predicted spin wave modes could propagate through the junction.

  20. Solar cell junction temperature measurement of PV module

    KAUST Repository

    Huang, B.J.

    2011-02-01

    The present study develops a simple non-destructive method to measure the solar cell junction temperature of PV module. The PV module was put in the environmental chamber with precise temperature control to keep the solar PV module as well as the cell junction in thermal equilibrium with the chamber. The open-circuit voltage of PV module Voc is then measured using a short pulse of solar irradiation provided by a solar simulator. Repeating the measurements at different environment temperature (40-80°C) and solar irradiation S (200-1000W/m2), the correlation between the open-circuit voltage Voc, the junction temperature Tj, and solar irradiation S is derived.The fundamental correlation of the PV module is utilized for on-site monitoring of solar cell junction temperature using the measured Voc and S at a short time instant with open circuit. The junction temperature Tj is then determined using the measured S and Voc through the fundamental correlation. The outdoor test results show that the junction temperature measured using the present method, Tjo, is more accurate. The maximum error using the average surface temperature Tave as the junction temperature is 4.8 °C underestimation; while the maximum error using the present method is 1.3 °C underestimation. © 2010 Elsevier Ltd.

  1. High electronic couplings of single mesitylene molecular junctions

    Directory of Open Access Journals (Sweden)

    Yuki Komoto

    2015-12-01

    Full Text Available We report on an experimental analysis of the charge transport properties of single mesitylene (1,3,5-trimethylbenzene molecular junctions. The electronic conductance and the current–voltage characteristics of mesitylene molecules wired into Au electrodes were measured by a scanning tunnelling microscopy-based break-junction method at room temperature in a liquid environment. We found the molecular junctions exhibited two distinct conductance states with high conductance values of ca. 10−1G0 and of more than 10−3G0 (G0 = 2e2/h in the electronic conductance measurements. We further performed a statistical analysis of the current–voltage characteristics of the molecular junctions in the two states. Within a single channel resonant tunnelling model, we obtained electronic couplings in the molecular junctions by fitting the current–voltage characteristics to the single channel model. The origin of the high conductance was attributed to experimentally obtained large electronic couplings of the direct π-bonded molecular junctions (ca. 0.15 eV. Based on analysis of the stretch length of the molecular junctions and the large electronic couplings obtained from the I–V analysis, we proposed two structural models, in which (i mesitylene binds to the Au electrode perpendicular to the charge transport direction and (ii mesitylene has tilted from the perpendicular orientation.

  2. Gap-junction-mediated cell-to-cell communication.

    Science.gov (United States)

    Hervé, Jean-Claude; Derangeon, Mickaël

    2013-04-01

    Cells of multicellular organisms need to communicate with each other and have evolved various mechanisms for this purpose, the most direct and quickest of which is through channels that directly connect the cytoplasms of adjacent cells. Such intercellular channels span the two plasma membranes and the intercellular space and result from the docking of two hemichannels. These channels are densely packed into plasma-membrane spatial microdomains termed "gap junctions" and allow cells to exchange ions and small molecules directly. A hemichannel is a hexameric torus of junctional proteins around an aqueous pore. Vertebrates express two families of gap-junction proteins: the well-characterized connexins and the more recently discovered pannexins, the latter being related to invertebrate innexins ("invertebrate connexins"). Some gap-junctional hemichannels also appear to mediate cell-extracellular communication. Communicating junctions play crucial roles in the maintenance of homeostasis, morphogenesis, cell differentiation and growth control in metazoans. Gap-junctional channels are not passive conduits, as previously long regarded, but use "gating" mechanisms to open and close the central pore in response to biological stimuli (e.g. a change in the transjunctional voltage). Their permeability is finely tuned by complex mechanisms that have just begun to be identified. Given their ubiquity and diversity, gap junctions play crucial roles in a plethora of functions and their dysfunctions are involved in a wide range of diseases. However, the exact mechanisms involved remain poorly understood.

  3. High electronic couplings of single mesitylene molecular junctions.

    Science.gov (United States)

    Komoto, Yuki; Fujii, Shintaro; Nishino, Tomoaki; Kiguchi, Manabu

    2015-01-01

    We report on an experimental analysis of the charge transport properties of single mesitylene (1,3,5-trimethylbenzene) molecular junctions. The electronic conductance and the current-voltage characteristics of mesitylene molecules wired into Au electrodes were measured by a scanning tunnelling microscopy-based break-junction method at room temperature in a liquid environment. We found the molecular junctions exhibited two distinct conductance states with high conductance values of ca. 10(-1) G 0 and of more than 10(-3) G 0 (G 0 = 2e (2)/h) in the electronic conductance measurements. We further performed a statistical analysis of the current-voltage characteristics of the molecular junctions in the two states. Within a single channel resonant tunnelling model, we obtained electronic couplings in the molecular junctions by fitting the current-voltage characteristics to the single channel model. The origin of the high conductance was attributed to experimentally obtained large electronic couplings of the direct π-bonded molecular junctions (ca. 0.15 eV). Based on analysis of the stretch length of the molecular junctions and the large electronic couplings obtained from the I-V analysis, we proposed two structural models, in which (i) mesitylene binds to the Au electrode perpendicular to the charge transport direction and (ii) mesitylene has tilted from the perpendicular orientation.

  4. Flicker (1/f) noise in tunnel junction DC SQUIDS

    Energy Technology Data Exchange (ETDEWEB)

    Koch, R.H.; Clarke, J.; Goubau, W.M.; Martinis, J.M.; Pegrum, C.M.; Van Harlingen, D.J.

    1983-04-01

    We have measured the spectral density of the 1/f voltage noise in current-biased resistively shunted Josephson tunnel junctions and dc SQUIDs. A theory in which fluctuations in the temperature give rise to fluctuations in the critical current and hence in the voltage predicts the magnitude of the noise quite accurately for junctions with areas of about 2 x 10/sup 4/ ..mu..m/sup 2/, but significantly overestimates the noise for junctions with areas of about 6 ..mu..m/sup 2/. DC SQUIDs fabricated from these two types of junctions exhibit substantially more 1/f voltage noise than would be predicted from a model in which the noise arises from critical current fluctuations in the junctions. This result was confirmed by an experiment involving two different bias current and flux modulation schemes, which demonstrated that the predominant 1/f voltage noise arises not from critical current fluctuations, but from some unknown source that can be regarded as an apparent 1/f flux noise. Measurements on five different configurations of dc SQUIDs fabricated with thin-film tunnel junctions and with widely varying areas, inductances, and junction capacitances show that the spectral density of the 1/f equivalent flux noise is roughtly constant, within a factor of three of (10/sup -10//f)phi/sup 2//sub 0/Hz/sup -1/. It is emphasized that 1/f flux noise may not be the predominant source of 1/f noise in SQUIDS fabricated with other technologies.

  5. Mechanical deformations of boron nitride nanotubes in crossed junctions

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Yadong; Chen, Xiaoming; Ke, Changhong, E-mail: cke@binghamton.edu [Department of Mechanical Engineering, State University of New York at Binghamton, Binghamton, New York 13902 (United States); Park, Cheol [NASA Langley Research Center, Hampton, Virginia 23681 (United States); Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States); Fay, Catharine C. [NASA Langley Research Center, Hampton, Virginia 23681 (United States); Stupkiewicz, Stanislaw [Institute of Fundamental Technological Research, Warsaw (Poland)

    2014-04-28

    We present a study of the mechanical deformations of boron nitride nanotubes (BNNTs) in crossed junctions. The structure and deformation of the crossed tubes in the junction are characterized by using atomic force microscopy. Our results show that the total tube heights are reduced by 20%–33% at the crossed junctions formed by double-walled BNNTs with outer diameters in the range of 2.21–4.67 nm. The measured tube height reduction is found to be in a nearly linear relationship with the summation of the outer diameters of the two tubes forming the junction. The contact force between the two tubes in the junction is estimated based on contact mechanics theories and found to be within the range of 4.2–7.6 nN. The Young's modulus of BNNTs and their binding strengths with the substrate are quantified, based on the deformation profile of the upper tube in the junction, and are found to be 1.07 ± 0.11 TPa and 0.18–0.29 nJ/m, respectively. Finally, we perform finite element simulations on the mechanical deformations of the crossed BNNT junctions. The numerical simulation results are consistent with both the experimental measurements and the analytical analysis. The results reported in this paper contribute to a better understanding of the structural and mechanical properties of BNNTs and to the pursuit of their applications.

  6. Association of visceral adiposity with oesophageal and junctional adenocarcinomas.

    LENUS (Irish Health Repository)

    Beddy, P

    2012-02-01

    BACKGROUND: Obesity is associated with an increased incidence of oesophageal and oesophagogastric junction adenocarcinoma, in particular Siewert types I and II. This study compared abdominal fat composition in patients with oesophageal\\/junctional adenocarcinoma with that in patients with oesophageal squamous cell carcinoma and gastric adenocarcinoma, and in controls. METHOD: In total, 194 patients (110 with oesophageal\\/junctional adenocarcinoma, 38 with gastric adenocarcinoma and 46 with oesophageal squamous cell carcinoma) and 90 matched control subjects were recruited. The abdominal fat area was assessed using computed tomography (CT), and the total fat area (TFA), visceral fat area (VFA) and subcutaneous fat area (SFA) were calculated. RESULTS: Patients with oesophageal\\/junctional adenocarcinoma had significantly higher TFA and VFA values compared with controls (both P < 0.001), patients with gastric adenocarcinoma (P = 0.013 and P = 0.006 respectively) and patients with oesophageal squamous cell carcinoma (both P < 0.001). For junctional tumours, the highest TFA and VFA values were seen in patients with Siewert type I tumours (respectively P = 0.041 and P = 0.033 versus type III; P = 0.332 and P = 0.152 versus type II). CONCLUSION: Patients with oesophageal\\/junctional adenocarcinoma, in particular oesophageal and Siewert type I junctional tumours, have greater CT-defined visceral adiposity than patients with gastric adenocarcinoma or oesophageal squamous cell carcinoma, or controls.

  7. Josephson radiation from InSb-nanowire junction

    Science.gov (United States)

    van Woerkom, David; Proutski, Alexander; Krivachy, Tamas; Bouman, Daniel; van Gulik, Ruben; Gul, Onder; Cassidy, Maja; Car, Diana; Bakkers, Erik; Kouwenhoven, Leo; Geresdi, Attila

    Semiconducting nanowire Josephson junctions has recently gained interest as building blocks for Majorana circuits and gate-tuneable superconducting qubits . Here we investigate the rich physics of the Andreev bound state spectrum of InSb nanowire junctions utilizing the AC Josephson relation 2eV_bias =hf . We designed and characterized an on-chip microwave circuit coupling the nanowire junction to an Al/AlOx/Al tunnel junction. The DC response of the tunnel junction is affected by photon-assisted quasiparticle current, which gives us the possibility to measure the radiation spectrum of the nanowire junction up to several tens of GHz in frequency. Our circuit design allows for voltage or phase biasing of the Josephson junction enabling direct mapping of Andreev bound states. We discuss our fabrication methods and choice of materials to achieve radiation detection up to a magnetic field of few hundred milliTesla, compatible with Majorana states in spin-orbit coupled nanowires. This work has been supported by the Netherlands Foundations FOM, Abstract NWO and Microsoft Corporation Station Q.

  8. Negative differential resistance in Josephson junctions coupled to a cavity

    DEFF Research Database (Denmark)

    Pedersen, Niels Falsig; Filatrella, G.; Pierro, V.

    2014-01-01

    or external – is often used. A cavity may also induce a negative differential resistance region at the lower side of the resonance frequency. We investigate the dynamics of Josephson junctions with a negative differential resistance in the quasi particle tunnel current, i.e. in the McCumber curve. We find......Regions with negative differential resistance can arise in the IV curve of Josephson junctions and this phenomenon plays an essential role for applications, in particular for THz radiation emission. For the measurement of high frequency radiation from Josephson junctions, a cavity – either internal...

  9. Temporal correlations and structural memory effects in break junction measurements

    DEFF Research Database (Denmark)

    Magyarkuti, A.; Lauritzen, Kasper Primdal; Balogh, Zoltan Imre

    2017-01-01

    that correlations between the opening and subsequent closing traces may indicate structural memory effects in atomic-sized metallic and molecular junctions. Applying these methods on measured and simulated gold metallic contacts as a test system, we show that the surface diffusion induced flattening of the broken......-molecule junctions, we demonstrate pronounced contact memory effects and recovery of the molecule for junctions breaking before atomic chains are formed. However, if chains are pulled the random relaxation of the chain and molecule after rupture prevents opening-closing correlations....

  10. Vortex structure in a long Josephson junction with two inhomogeneities

    Energy Technology Data Exchange (ETDEWEB)

    Andreeva, O.Yu. [Tumen Thermal Networks OAO ' TRGK' , Tobolsk 626150 (Russian Federation); Boyadjiev, T.L. [Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Shukrinov, Yu.M. [Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation)], E-mail: shukrinv@theor.jinr.ru

    2007-09-01

    We study the vortex structure in the long Josephson junctions with one and two rectangular inhomogeneities in the barrier layer. In case of one inhomogeneity we demonstrate the existence of the asymmetric fluxon states. The disappearance of the mixed fluxon-antifluxon states is shown when the position of the inhomogeneity shifted to the end of the junction. In case of two inhomogeneities the change of the amplitude of Josephson current through the inhomogeneity in the end of the junction makes strong effect on the stability of the fluxon states and smoothes the maximums on the dependence 'critical current-magnetic field'.

  11. Vortex structure in a long Josephson junction with two inhomogeneities

    Science.gov (United States)

    Andreeva, O. Yu.; Boyadjiev, T. L.; Shukrinov, Yu. M.

    2007-09-01

    We study the vortex structure in the long Josephson junctions with one and two rectangular inhomogeneities in the barrier layer. In case of one inhomogeneity we demonstrate the existence of the asymmetric fluxon states. The disappearance of the mixed fluxon-antifluxon states is shown when the position of the inhomogeneity shifted to the end of the junction. In case of two inhomogeneities the change of the amplitude of Josephson current through the inhomogeneity in the end of the junction makes strong effect on the stability of the fluxon states and smoothes the maximums on the dependence “critical current-magnetic field”.

  12. Bloch inductance in small-capacitance Josephson junctions.

    Science.gov (United States)

    Zorin, A B

    2006-04-28

    We show that the electrical impedance of a small-capacitance Josephson junction also includes, in addition to the capacitive term -i/(omega)CB, an inductive term i(omega)LB. Similar to the known Bloch capacitance CB(q), the Bloch inductance LB(q) also depends periodically on the quasicharge, q, and its maximum value achieved at q=e(mod 2e) always exceeds the value of the Josephson inductance of this junction LJ(phi) at fixed phi=0. The effect of the Bloch inductance on the dynamics of a single junction and a one-dimensional array is described.

  13. Two new septate junctions in the phylum Coelenterata.

    Science.gov (United States)

    Green, C R; Flower, N E

    1980-04-01

    Freeze-fracture of fixed and unfixed tissue, lanthanum tracer and conventional thin-section studies have revealed 2 new types of septate junction in the class Anthozoa, phylum Coelenterata. These new junctions have the 15-18-nm intercellular spacing of all other described septate junctions and are found around the apical circumference of cells lining a lumen or outside edge. However, in freeze-fracture replicas and tangential views of lanthanum-impregnated tissue, they are seen to be quite different from other known septate junction types. One of the new junctions is found in endothelial tissue such as that lining the gut or the inside of the tentacles. In tangential view it is seen to consist of relatively short, straight, double septa, again with lateral projections. In feeeze-fracture of unfixed tissue, the junction consists of double rows of particles on the P face, the particles of one row being rounded, those of the other being elongated at right angles to the line of the septum. This dichotomy in particle size is unexpected, as the 2 halves of the septa as seen in tangential view are symmetrical. In freeze-fracture of fixed material the particle arrays remain on the P face and appear similar to those of unfixed material, but never as clear. In fixed tissue, some distortion had occurred and in extreme cases septa appear as a single broad jumbled row of particles. In this double septa junction, the rows of particles seen in freeze-fracture are occasionally seen to anastomose with a septum dividing into 2 and a third row of particles aligning with the 2 new septa to form their double particle rows. In both fixed and unfixed tissues, the E face of the junction consists of wide, shallow grooves. The second of the new junctions occurs in epithelial tissue, such as around the outer edge of sea-anemone tentacles, and consists of long wavy septa with lateral projections. In views where these projections appear longest, they arise predominantly from one side of the

  14. Externally pumped millimeter-wave Josephson-junction parametric amplifier

    DEFF Research Database (Denmark)

    Levinsen, M.T; Pedersen, Niels Falsig; Sørensen, Ole;

    1980-01-01

    A unified theory of the singly and doubly degenerate Josephson-junction parametric amplifier is presented. Experiments with single junctions on both amplifier modes at frequencies 10, 35, and 70 GHz are discussed. Low-noise temperature (∼100 K, single sideband (SSB)) and reasonable gain (∼8 d......B) were obtained at 35 GHz in the singly degenerate mode. On the basis of the theory and experiments, a general procedure for optimizing junction parameters is discussed and illustrated by the specific design of a 100-GHz amplifier....

  15. Junction temperature estimation for an advanced active power cycling test

    DEFF Research Database (Denmark)

    Choi, Uimin; Blaabjerg, Frede; Jørgensen, S.

    2015-01-01

    estimation method using on-state VCE for an advanced active power cycling test is proposed. The concept of the advanced power cycling test is explained first. Afterwards the junction temperature estimation method using on-state VCE and current is presented. Further, the method to improve the accuracy......On-state collector-emitter voltage (VCE) is a good indicator to determine the wear-out condition of power device modules. Further, it is a one of the Temperature Sensitive Electrical Parameters (TSEPs) and thus can be used for junction temperature estimation. In this paper, the junction temperature...

  16. Turbulence-induced magnetic flux asymmetry at nanoscale junctions.

    Science.gov (United States)

    Bushong, Neil; Pershin, Yuriy; Di Ventra, Massimiliano

    2007-11-30

    It was recently predicted [J. Phys. Condens. Matter 18, 11059 (2006)] that turbulence of electron flow may develop at nonadiabatic nanoscale junctions under appropriate conditions. Here we show that such an effect leads to an asymmetric current-induced magnetic field on the two sides of an otherwise symmetric junction. We propose that measuring the fluxes ensuing from these fields across two surfaces placed at the two sides of the junction would provide direct and noninvasive evidence of the transition from laminar to turbulent electron flow. The flux asymmetry is predicted to first increase, reach a maximum, and then decrease with increasing current, i.e., with increasing amount of turbulence.

  17. Nonequilibrium and proximity effects in superconductor-normal metal junctions

    Science.gov (United States)

    Kauppila, V. J.; Nguyen, H. Q.; Heikkilä, T. T.

    2013-08-01

    We study the consequences of nonequilibrium heating and inverse proximity effect in normal metal-insulator-superconductor-insulator-normal metal (NISIN) junctions with a simple quasi-one-dimensional model. We especially focus on observables and parameter regions that are of interest in the design of SINIS coolers with quasiparticle traps. We present numerical results calculated by solving the Usadel equation and also present analytical approximations in two limiting cases: a short junction with a non-negligible resistance in both ends and a long junction with a transparent contact at one end.

  18. Gap junction modulation and its implications for heart function.

    Science.gov (United States)

    Kurtenbach, Stefan; Kurtenbach, Sarah; Zoidl, Georg

    2014-01-01

    Gap junction communication (GJC) mediated by connexins is critical for heart function. To gain insight into the causal relationship of molecular mechanisms of disease pathology, it is important to understand which mechanisms contribute to impairment of gap junctional communication. Here, we present an update on the known modulators of connexins, including various interaction partners, kinases, and signaling cascades. This gap junction network (GJN) can serve as a blueprint for data mining approaches exploring the growing number of publicly available data sets from experimental and clinical studies.

  19. Gap junction modulation and its implications for heart function

    Directory of Open Access Journals (Sweden)

    Stefan eKurtenbach

    2014-02-01

    Full Text Available Gap junction communication mediated by connexins is critical for heart function. To gain insight into the causal relationship of molecular mechanisms of disease pathology, it is important to understand which mechanisms contribute to impairment of gap junctional communication. Here, we present an update on the known modulators of connexins, including various interaction partners, kinases and signaling cascades. This gap junction network can serve as a blueprint for data mining approaches exploring the growing number of publicly available data sets from experimental and clinical studies.

  20. No junctional communication between epithelial cells in hydra

    DEFF Research Database (Denmark)

    de Laat, S W; Tertoolen, L G; Grimmelikhuijzen, C J

    1980-01-01

    junctions between epithelial cells of hydra. However, until now, there has been no report published on whether these junctions enable the epithelial cells to exchange molecules of small molecular weight, as has been described in other organisms. Therefore we decided to investigate the communicative...... properties of the junctional membranes by electrophysiological methods and by intracellular-dye iontophoresis. We report here that no electrotonic coupling is detectable between epithelial cells of Hydra attenuata in: (1) intact animals, (2) head-regenerating animals, (3) cell re-aggregates, and (4) hydra...