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Sample records for adherens junctions connect

  1. Adherens junction function and regulation during zebrafish gastrulation

    Schepis, Antonino; Nelson, W. James

    2012-01-01

    The adherens junction (AJ) comprises multi-protein complexes required for cell-cell adhesion in embryonic development and adult tissue homeostasis. Mutations in key proteins and mis-regulation of AJ adhesive properties can lead to pathologies such as cancer. In recent years, the zebrafish has become an excellent model organism to integrate cell biology in the context of a multicellular organization. The combination of classical genetic approaches with new tools for live imaging and biophysica...

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

    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.

  3. PLEKHA7 Recruits PDZD11 to Adherens Junctions to Stabilize Nectins.

    Guerrera, Diego; Shah, Jimit; Vasileva, Ekaterina; Sluysmans, Sophie; Méan, Isabelle; Jond, Lionel; Poser, Ina; Mann, Matthias; Hyman, Anthony A; Citi, Sandra

    2016-05-20

    PLEKHA7 is a junctional protein implicated in stabilization of the cadherin protein complex, hypertension, cardiac contractility, glaucoma, microRNA processing, and susceptibility to bacterial toxins. To gain insight into the molecular basis for the functions of PLEKHA7, we looked for new PLEKHA7 interactors. Here, we report the identification of PDZ domain-containing protein 11 (PDZD11) as a new interactor of PLEKHA7 by yeast two-hybrid screening and by mass spectrometry analysis of PLEKHA7 immunoprecipitates. We show that PDZD11 (17 kDa) is expressed in epithelial and endothelial cells, where it forms a complex with PLEKHA7, as determined by co-immunoprecipitation analysis. The N-terminal Trp-Trp (WW) domain of PLEKHA7 interacts directly with the N-terminal 44 amino acids of PDZD11, as shown by GST-pulldown assays. Immunofluorescence analysis shows that PDZD11 is localized at adherens junctions in a PLEKHA7-dependent manner, because its junctional localization is abolished by knock-out of PLEKHA7, and is rescued by re-expression of exogenous PLEKHA7. The junctional recruitment of nectin-1 and nectin-3 and their protein levels are decreased via proteasome-mediated degradation in epithelial cells where either PDZD11 or PLEKHA7 have been knocked-out. PDZD11 forms a complex with nectin-1 and nectin-3, and its PDZ domain interacts directly with the PDZ-binding motif of nectin-1. PDZD11 is required for the efficient assembly of apical junctions of epithelial cells at early time points in the calcium-switch model. These results show that the PLEKHA7-PDZD11 complex stabilizes nectins to promote efficient early junction assembly and uncover a new molecular mechanism through which PLEKHA7 recruits PDZ-binding membrane proteins to epithelial adherens junctions. PMID:27044745

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

    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.

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

    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

  6. Mammary epithelial cell phagocytosis downstream of TGF-β3 is characterized by adherens junction reorganization.

    Fornetti, J; Flanders, K C; Henson, P M; Tan, A-C; Borges, V F; Schedin, P

    2016-02-01

    After weaning, during mammary gland involution, milk-producing mammary epithelial cells undergo apoptosis. Effective clearance of these dying cells is essential, as persistent apoptotic cells have a negative impact on gland homeostasis, future lactation and cancer susceptibility. In mice, apoptotic cells are cleared by the neighboring epithelium, yet little is known about how mammary epithelial cells become phagocytic or whether this function is conserved between species. Here we use a rat model of weaning-induced involution and involuting breast tissue from women, to demonstrate apoptotic cells within luminal epithelial cells and epithelial expression of the scavenger mannose receptor, suggesting conservation of phagocytosis by epithelial cells. In the rat, epithelial transforming growth factor-β (TGF-β) signaling is increased during involution, a pathway known to promote phagocytic capability. To test whether TGF-β enhances the phagocytic ability of mammary epithelial cells, non-transformed murine mammary epithelial EpH4 cells were cultured to achieve tight junction impermeability, such as occurs during lactation. TGF-β3 treatment promoted loss of tight junction impermeability, reorganization and cleavage of the adherens junction protein E-cadherin (E-cad), and phagocytosis. Phagocytosis correlated with junction disruption, suggesting junction reorganization is necessary for phagocytosis by epithelial cells. Supporting this hypothesis, epithelial cell E-cad reorganization and cleavage were observed in rat and human involuting mammary glands. Further, in the rat, E-cad cleavage correlated with increased γ-secretase activity and β-catenin nuclear localization. In vitro, pharmacologic inhibitors of γ-secretase or β-catenin reduced the effect of TGF-β3 on phagocytosis to near baseline levels. However, β-catenin signaling through LiCl treatment did not enhance phagocytic capacity, suggesting a model in which both reorganization of cell junctions and

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

    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.

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

    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.

  9. The asymmetric self-assembly mechanism of adherens junctions: a cellular push–pull unit

    To form adherens junctions (AJ), cells first establish contact by sending out lamellipodia onto neighboring cells. We investigated the role of contacting cells in AJ assembly by studying an asymmetric AJ motif: finger-like AJ extending across the cell–cell interface. Using a cytoskeleton replica and immunofluorescence, we observed that actin bundles embedded in the lamellipodia are co-localized with stress fibers in the neighboring cell at the AJ. This suggests that donor lamellipodia present actin fingers, which are stabilized by acceptor lamellae via acto-myosin contractility. Indeed, we show that changes in actin network geometry promoted by Rac overexpression lead to corresponding changes in AJ morphology. Moreover, contractility inhibition and enhancement (via drugs or local traction) lead respectively to the disappearance and further growth of AJ fingers. Thus, we propose that receiving lamellae exert a local pull on AJ, promoting further polymerization of the donor actin bundles. In spite of different compositions, AJ and focal contacts both act as cellular mechanosensors

  10. Curcumin prevents cisplatin-induced decrease in the tight and adherens junctions: relation to oxidative stress.

    Trujillo, Joyce; Molina-Jijón, Eduardo; Medina-Campos, Omar Noel; Rodríguez-Muñoz, Rafael; Reyes, José Luis; Loredo, María L; Barrera-Oviedo, Diana; Pinzón, Enrique; Rodríguez-Rangel, Daniela Saraí; Pedraza-Chaverri, José

    2016-01-20

    Curcumin is a polyphenol and cisplatin is an antineoplastic agent that induces nephrotoxicity associated with oxidative stress, apoptosis, fibrosis and decrease in renal tight junction (TJ) proteins. The potential effect of curcumin against alterations in TJ structure and function has not been evaluated in cisplatin-induced nephrotoxicity. The present study explored whether curcumin is able to prevent the cisplatin-induced fibrosis and decreased expression of the TJ and adherens junction (AJ) proteins occludin, claudin-2 and E-cadherin in cisplatin-induced nephrotoxicity. Curcumin (200 mg kg(-1)) was administered in three doses, and rats were sacrificed 72 h after cisplatin administration. Curcumin was able to scavenge, in a concentration-dependent way, superoxide anion, hydroxyl radical, peroxyl radical, singlet oxygen, peroxynitrite anion, hypochlorous acid and hydrogen peroxide. Cisplatin-induced renal damage was associated with alterations in plasma creatinine, expression of neutrophil gelatinase-associated lipocalin and of kidney injury molecule-1, histological damage, increase in apoptosis, fibrosis (evaluated by transforming growth factor β1, collagen I and IV and α-smooth muscle actin expressions), increase in oxidative/nitrosative stress (evaluated by Hsp70/72 expression, protein tyrosine nitration, superoxide anion production in isolated glomeruli and proximal tubules, and protein levels of NADPH oxidase subunits p47(phox) and gp91(phox), protein kinase C β2, and Nrf2) as well as by decreased expression of occludin, claudin-2, β-catenin and E-cadherin. Curcumin treatment prevented all the above-described alterations. The protective effect of curcumin against cisplatin-induced fibrosis and decreased proteins of the TJ and AJ was associated with the prevention of glomerular and proximal tubular superoxide anion production induced by NADPH oxidase activity. PMID:26467482

  11. Negative pressure induces p120-catenin-dependent adherens junction disassembly in keratinocytes during wound healing.

    Huang, Ching-Hui; Hsu, Chih-Chin; Chen, Carl Pai-Chu; Chow, Shu-Er; Wang, Jong-Shyan; Shyu, Yu-Chiau; Lu, Mu-Jie

    2016-09-01

    A negative-pressure of 125mmHg (NP) has been widely used to treat chronic wounds in modern medicine. Keratinocytes under NP treatment have shown accelerated cell movement and decreased E-cadherin expression. However, the molecular mechanism of E-cadherin regulation under NP remains incompletely understood. Therefore, we investigated the E-cadherin regulation in keratinocytes (HaCaT cells) under NP. HaCaT cells were treated at ambient pressure (AP) and NP for 12h. Cell movement was measured by traditional and electric wound healing assays at the 2 different pressures. Mutants with overexpression of p120-catenin (p120(ctn)) were used to observe the effect of NP on p120(ctn) and E-cadherin expression during wound healing. Cell fractionation and immunoblotting data showed that NP increased Y228-phosphorylated p120(ctn) level and resulted in the translocation of p120(ctn) from the plasma membrane to cytoplasm. Immunofluorescence images revealed that NP decreased the co-localization of p120(ctn) and E-cadherin on the plasma membrane. Knockdown of p120(ctn) reduced E-cadherin expression and accelerated cell movement under AP. Overexpression of the Y228-phosphorylation-mimic p120(ctn) decreased E-cadherin membrane expression under both AP and NP. Phosphorylation-deficient mutants conferred restored adherens junctions (AJs) under NP. The Src inhibitor blocked the phosphorylation of p120(ctn) and impeded cell migration under NP. In conclusion, Src-dependent phosphorylation of p120(ctn) can respond rapidly to NP and contribute to E-cadherin downregulation. The NP-induced disassembly of the AJ further accelerates wound healing. PMID:27220534

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

    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.

  13. The F-BAR protein pacsin2 inhibits asymmetric VE-cadherin internalization from tensile adherens junctions.

    Dorland, Yvonne L; Malinova, Tsveta S; van Stalborch, Anne-Marieke D; Grieve, Adam G; van Geemen, Daphne; Jansen, Nicolette S; de Kreuk, Bart-Jan; Nawaz, Kalim; Kole, Jeroen; Geerts, Dirk; Musters, René J P; de Rooij, Johan; Hordijk, Peter L; Huveneers, Stephan

    2016-01-01

    Vascular homoeostasis, development and disease critically depend on the regulation of endothelial cell-cell junctions. Here we uncover a new role for the F-BAR protein pacsin2 in the control of VE-cadherin-based endothelial adhesion. Pacsin2 concentrates at focal adherens junctions (FAJs) that are experiencing unbalanced actomyosin-based pulling. FAJs move in response to differences in local cytoskeletal geometry and pacsin2 is recruited consistently to the trailing end of fast-moving FAJs via a mechanism that requires an intact F-BAR domain. Photoconversion, photobleaching, immunofluorescence and super-resolution microscopy reveal polarized dynamics, and organization of junctional proteins between the front of FAJs and their trailing ends. Interestingly, pacsin2 recruitment inhibits internalization of the VE-cadherin complex from FAJ trailing ends and is important for endothelial monolayer integrity. Together, these findings reveal a novel junction protective mechanism during polarized trafficking of VE-cadherin, which supports barrier maintenance within dynamic endothelial tissue. PMID:27417273

  14. Striatins as plaque molecules of zonulae adhaerentes in simple epithelia, of tessellate junctions in stratified epithelia, of cardiac composite junctions and of various size classes of lateral adherens junctions in cultures of epithelia- and carcinoma-derived cells.

    Franke, Werner W; Rickelt, Steffen; Zimbelmann, Ralf; Dörflinger, Yvette; Kuhn, Caecilia; Frey, Norbert; Heid, Hans; Rosin-Arbesfeld, Rina

    2015-03-01

    Proteins of the striatin family (striatins 1-4; sizes ranging from 90 to 110 kDa on SDS-polyacrylamide gel electrophoresis) are highly homologous in their amino acid sequences but can differ in their cell-type-specific gene expression patterns and biological functions. In various cell types, we have found one, two or three polypeptides of this evolutionarily old and nearly ubiquitous family of proteins known to serve as scaffold proteins for diverse protein complexes. Light and electron microscopic immunolocalization methods have revealed striatins in mammalian cell-cell adherens junctions (AJs). In simple epithelia, we have localized striatins as constitutive components of the plaques of the subapical zonulae adhaerentes of cells, including intestinal, glandular, ductal and urothelial cells and hepatocytes. Striatins colocalize with E-cadherin or E-N-cadherin heterodimers and with the plaque proteins α- and β-catenin, p120 and p0071. In some epithelia and carcinomas and in cultured cells derived therefrom, striatins are also seen in lateral AJs. In stratified epithelia and in corresponding squamous cell carcinomas, striatins can be found in plaques of some forms of tessellate junctions. Moreover, striatins are major plaque proteins of composite junctions (CJs; areae compositae) in the intercalated disks connecting cardiomyocytes, colocalizing with other CJ molecules, including plectin and ankyrin-G. We discuss the "multimodulator" scaffold roles of striatins in the initiation and regulation of the formation of various complex particles and structures. We propose that striatins are included in the diagnostic candidate list of proteins that, in the CJs of human hearts, can occur in mutated forms in the pathogeneses of hereditary cardiomyopathies, as seen in some types of genetically determined heart damage in boxer dogs. PMID:25501894

  15. Microtubule plus-end and minus-end capture at adherens junctions is involved in the assembly of apico-basal arrays in polarised epithelial cells.

    Bellett, Gemma; Carter, Jane M; Keynton, Jennifer; Goldspink, Deborah; James, Colin; Moss, David K; Mogensen, Mette M

    2009-10-01

    Apico-basal polarisation of epithelial cells involves a dramatic reorganisation of the microtubule cytoskeleton. The classic radial array of microtubules focused on a centrally located centrosome typical of many animal cells is lost or greatly reduced and a non-centrosomal apico-basal array develops. The molecules and mechanisms responsible for the assembly and positioning of these non-centrosomal microtubules have not been fully elucidated. Using a Nocodazole induced regrowth assay in invitro culture (MDCK) and in situ epithelial (cochlear Kolliker's) cell models we establish that the apico-basal array originates from the centrosome and that the non-centrosomal microtubule minus-end anchoring sites do not contribute significantly to their nucleation. Confocal and electron microscopy revealed that an extended radial array assembles with microtubule plus-ends targeting cadheren sites at adherens junctions and EB1 and CLIP-170 co-localising with beta-catenin and dynein clusters at the junction sites. The extended radial array is likely to be a vital intermediate step in the assembly process with cortical anchored dynein providing the mechanical force required for microtubule release, translocation and capture. Ultrastructural analyses of the apico-basal arrays in fully polarised MDCK and Kolliker's cells revealed microtubule minus-end association with the most apical adherens junction (Zonula adherens). We propose that a release and capture model involving both microtubule plus- and minus-end capture at adherens junctions is responsible for the generation of non-centrosomal apico-basal arrays in most centrosome containing polarised epithelial cells. PMID:19479825

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

    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

  17. Protective role of p120-catenin in maintaining the integrity of adherens and tight junctions in ventilator-induced lung injury

    Gu, Changping; LIU, MENGJIE; Zhao, Tao; Wang, Dong; Wang, Yuelan

    2015-01-01

    Background Ventilator-induced lung injury (VILI) is one of the most common complications for patients with acute lung injury (ALI) or acute respiratory distress syndrome (ARDS). Although p120 is an important protein in the regulation of cell junctions, further mechanisms should be explored for prevention and treatment of VILI. Methods Mouse lung epithelial cells (MLE-12), which were transfected with p120 small interfering (si)RNA, p120 cDNA, wild-type E-cadherin juxtamembrane domain or a K83R...

  18. Long Josephson tunnel junctions with doubly connected electrodes

    Monaco, R.; Mygind, J.; Koshelets, V. P.

    2012-03-01

    In order to mimic the phase changes in the primordial Big Bang, several cosmological solid-state experiments have been conceived, during the last decade, to investigate the spontaneous symmetry breaking in superconductors and superfluids cooled through their transition temperature. In one of such experiments, the number of magnetic flux quanta spontaneously trapped in a superconducting loop was measured by means of a long Josephson tunnel junction built on top of the loop itself. We have analyzed this system and found a number of interesting features not occurring in the conventional case with simply connected electrodes. In particular, the fluxoid quantization results in a frustration of the Josephson phase, which, in turn, reduces the junction critical current. Further, the possible stable states of the system are obtained by a self-consistent application of the principle of minimum energy. The theoretical findings are supported by measurements on a number of samples having different geometrical configuration. The experiments demonstrate that a very large signal-to-noise ratio can be achieved in the flux quanta detection.

  19. Ultrastructural studies of the junctional complex in the musculature of the arrow-worm (Sagitta setosa) (Chaetognatha).

    Duvert, M; Gros, D; Salat, C

    1980-01-01

    In the A fibres of the primary musculature of Sagitta, the junctional complex is made up of three kinds of junctions. From the apex to the base they occur in the following order: an apical zonula adherens, a columnar zonula then columnar maculae intermingled with gap junction. Each columnar junction joins two intracellular filament networks in adjacent cells; this cytoskeleton is largely developed around the nucleus of the A fibres and in close relation with the contractile apparatus, especially at the I band level. The B fibres, which never reach the general cavity, lack zonula adherens and columnar zonula. The columnar junction constitutes a new type of junction which seems to belong to the adherens kind. At their level fibrous columns cross the extracellular space, joining the membranes. Each column faces two cytoplasmic densities localized against the cytoplasmic leaflets of the membranes. A cytoskeleton composed of bunldes of cytoplasmic filaments is in close contact with these cytoplasmic densities. The great number of columnar junctions and associated cytoskeleton assure the cohesion of the tissue and the distribution of contractile forces in the absence of connective tissue. The abundance of gap junctions can account for the metabolic and ionic coupling of the fibres. PMID:7189067

  20. Radiation effects on adherens contacts in cultured Madin-Darby canine kidney (MDCK) cells

    The cell contacts (junctions) are considered to be sensitive and important targets of ionizing radiation. In this work, the effect of X-irradiation was studied on the localization and relative quantity of two structural proteins of adherent junction, i.e. cadherins and b-catenin, in cultured Madin-Darby canine kidney (MDCK) cells by immunohistochemical and Western blotting procedures. Irradiation was found to induce the rapid redistribution and quantitative loss in these proteins resulting in their separation from the adherens junction sites. As a consequence, the structure and functionality of adherent junctions are also suggested to be affected by ionizing radiation in MDCK cells. Since morphological alteration of cell contact sites is also leading to temporary or permanent disturbances in adherens junction related functions (i.e. paracellular permeability), cell junctions might really be regarded as primary biomembrane target areas for radiation effects. The radiation-induced loss of b-catenin is probably related to the altered Wnt-signaling, too. (author)

  1. Long Josephson tunnel junctions with doubly connected electrodes

    Monaco, R.; Mygind, J.; Koshelets, V. P.

    2012-01-01

    In order to mimic the phase changes in the primordial Big Bang, several cosmological solid-state experiments have been conceived, during the last decade, to investigate the spontaneous symmetry breaking in superconductors and superfluids cooled through their transition temperature. In one...... of such experiments, the number of magnetic flux quanta spontaneously trapped in a superconducting loop was measured by means of a long Josephson tunnel junction built on top of the loop itself. We have analyzed this system and found a number of interesting features not occurring in the conventional case with simply....... The theoretical findings are supported by measurements on a number of samples having different geometrical configuration. The experiments demonstrate that a very large signal-to-noise ratio can be achieved in the flux quanta detection....

  2. Imbalance in subregional connectivity of the right temporoparietal junction in major depression.

    Poeppl, Timm B; Müller, Veronika I; Hoffstaedter, Felix; Bzdok, Danilo; Laird, Angela R; Fox, Peter T; Langguth, Berthold; Rupprecht, Rainer; Sorg, Christian; Riedl, Valentin; Goya-Maldonado, Roberto; Gruber, Oliver; Eickhoff, Simon B

    2016-08-01

    Major depressive disorder (MDD) involves impairment in cognitive and interpersonal functioning. The right temporoparietal junction (RTPJ) is a key brain region subserving cognitive-attentional and social processes. Yet, findings on the involvement of the RTPJ in the pathophysiology of MDD have so far been controversial. Recent connectivity-based parcellation data revealed a topofunctional dualism within the RTPJ, linking its anterior and posterior part (aRTPJ/pRTPJ) to antagonistic brain networks for attentional and social processing, respectively. Comparing functional resting-state connectivity of the aRTPJ and pRTPJ in 72 MDD patients and 76 well-matched healthy controls, we found a seed (aRTPJ/pRTPJ) × diagnosis (MDD/controls) interaction in functional connectivity for eight regions. Employing meta-data from a large-scale neuroimaging database, functional characterization of these regions exhibiting differentially altered connectivity with the aRTPJ/pRTPJ revealed associations with cognitive (dorsolateral prefrontal cortex, parahippocampus) and behavioral (posterior medial frontal cortex) control, visuospatial processing (dorsal visual cortex), reward (subgenual anterior cingulate cortex, medial orbitofrontal cortex, posterior cingulate cortex), as well as memory retrieval and social cognition (precuneus). These findings suggest that an imbalance in connectivity of subregions, rather than disturbed connectivity of the RTPJ as a whole, characterizes the connectional disruption of the RTPJ in MDD. This imbalance may account for key symptoms of MDD in cognitive, emotional, and social domains. Hum Brain Mapp 37:2931-2942, 2016. © 2016 Wiley Periodicals, Inc. PMID:27090056

  3. Shear-induced reorganization of renal proximal tubule cell actin cytoskeleton and apical junctional complexes.

    Duan, Yi; Gotoh, Nanami; Yan, Qingshang; Du, Zhaopeng; Weinstein, Alan M; Wang, Tong; Weinbaum, Sheldon

    2008-08-12

    In this study, we demonstrate that fluid shear stress (FSS)-induced actin cytoskeletal reorganization and junctional formation in renal epithelial cells are nearly completely opposite the corresponding changes in vascular endothelial cells (ECs) [Thi MM et al. (2004) Proc Natl Acad Sci USA 101:16483-16488]. Mouse proximal tubule cells (PTCs) were subjected to 5 h of FSS (1 dyn/cm(2)) to investigate the dynamic responses of the cytoskeletal distribution of filamentous actin (F-actin), ZO-1, E-cadherin, vinculin, and paxillin to FSS. Immunofluorescence analysis revealed that FSS caused basal stress fiber disruption, more densely distributed peripheral actin bands (DPABs), and the formation of both tight junctions (TJs) and adherens junctions (AJs). A dramatic reinforcement of vinculin staining was found at the cell borders as well as the cell interior. These responses were abrogated by the actin-disrupting drug, cytochalasin D. To interpret these results, we propose a "junctional buttressing" model for PTCs in which FSS enables the DPABs, TJs, and AJs to become more tightly connected. In contrast, in the "bumper-car" model for ECs, all junctional connections were severely disrupted by FSS. This "junctional buttressing" model explains why a FSS of only 1/10 of that used in the EC study can cause a similarly dramatic, cytoskeletal response in these tall, cuboidal epithelial cells; and why junctional buttressing between adjacent cells may benefit renal epithelium in maximizing flow-activated, brush border-dependent, transcellular salt and water reabsorption. PMID:18685100

  4. Functional connectivity profile of the human inferior frontal junction: involvement in a cognitive control network

    Sundermann Benedikt

    2012-10-01

    Full Text Available Abstract Background The human inferior frontal junction area (IFJ is critically involved in three main component processes of cognitive control (working memory, task switching and inhibitory control. As it overlaps with several areas in established anatomical labeling schemes, it is considered to be underreported as a functionally distinct location in the neuroimaging literature. While recent studies explicitly focused on the IFJ's anatomical organization and functional role as a single brain area, it is usually not explicitly denominated in studies on cognitive networks. However based on few analyses in small datasets constrained by specific a priori assumptions on its functional specialization, the IFJ has been postulated to be part of a cognitive control network. Goal of this meta-analysis was to establish the IFJ’s connectivity profile on a high formal level of evidence by aggregating published implicit knowledge about its co-activations. We applied meta-analytical connectivity modeling (MACM based on the activation likelihood estimation (ALE method without specific assumptions regarding functional specialization on 180 (reporting left IFJ activity and 131 (right IFJ published functional neuroimaging experiments derived from the BrainMap database. This method is based on coordinates in stereotaxic space, not on anatomical descriptors. Results The IFJ is significantly co-activated with areas in the dorsolateral and ventrolateral prefrontal cortex, anterior insula, medial frontal gyrus / pre-SMA, posterior parietal cortex, occipitotemporal junction / cerebellum, thalamus and putamen as well as language and motor areas. Results are corroborated by an independent resting-state fMRI analysis. Conclusions These results support the assumption that the IFJ is part of a previously described cognitive control network. They also highlight the involvement of subcortical structures in this system. A direct line is drawn from works on the functional

  5. Mechanics of lipid bilayer junctions affecting the size of a connecting lipid nanotube

    Karlsson, Roger; Kurczy, Michael; Grzhibovskis, Richards; Adams, Kelly L.; Ewing, Andrew G.; Cans, Ann-Sofie; Voinova, Marina V.

    2011-06-01

    In this study we report a physical analysis of the membrane mechanics affecting the size of the highly curved region of a lipid nanotube (LNT) that is either connected between a lipid bilayer vesicle and the tip of a glass microinjection pipette (tube-only) or between a lipid bilayer vesicle and a vesicle that is attached to the tip of a glass microinjection pipette (two-vesicle). For the tube-only configuration (TOC), a micropipette is used to pull a LNT into the interior of a surface-immobilized vesicle, where the length of the tube L is determined by the distance of the micropipette to the vesicle wall. For the two-vesicle configuration (TVC), a small vesicle is inflated at the tip of the micropipette tip and the length of the tube L is in this case determined by the distance between the two interconnected vesicles. An electrochemical method monitoring diffusion of electroactive molecules through the nanotube has been used to determine the radius of the nanotube R as a function of nanotube length L for the two configurations. The data show that the LNT connected in the TVC constricts to a smaller radius in comparison to the tube-only mode and that tube radius shrinks at shorter tube lengths. To explain these electrochemical data, we developed a theoretical model taking into account the free energy of the membrane regions of the vesicles, the LNT and the high curvature junctions. In particular, this model allows us to estimate the surface tension coefficients from R( L) measurements.

  6. Mechanics of lipid bilayer junctions affecting the size of a connecting lipid nanotube

    Voinova Marina

    2011-01-01

    Full Text Available Abstract In this study we report a physical analysis of the membrane mechanics affecting the size of the highly curved region of a lipid nanotube (LNT that is either connected between a lipid bilayer vesicle and the tip of a glass microinjection pipette (tube-only or between a lipid bilayer vesicle and a vesicle that is attached to the tip of a glass microinjection pipette (two-vesicle. For the tube-only configuration (TOC, a micropipette is used to pull a LNT into the interior of a surface-immobilized vesicle, where the length of the tube L is determined by the distance of the micropipette to the vesicle wall. For the two-vesicle configuration (TVC, a small vesicle is inflated at the tip of the micropipette tip and the length of the tube L is in this case determined by the distance between the two interconnected vesicles. An electrochemical method monitoring diffusion of electroactive molecules through the nanotube has been used to determine the radius of the nanotube R as a function of nanotube length L for the two configurations. The data show that the LNT connected in the TVC constricts to a smaller radius in comparison to the tube-only mode and that tube radius shrinks at shorter tube lengths. To explain these electrochemical data, we developed a theoretical model taking into account the free energy of the membrane regions of the vesicles, the LNT and the high curvature junctions. In particular, this model allows us to estimate the surface tension coefficients from R(L measurements.

  7. Three-Year Performance Evaluation of Single Junction Amorphous Solar Cells Grid-Connected Power Station in Libya

    2013-01-01

    Photovoltaic (PV) conservation of solar energy is one of the most promising sources of future energy. Grid-connected PV systems are widely used in many countries, but in Libya it is just started. A PV grid-connected of 24 KWP PV system has been installed as a pilot project to deliver AC energy to the Tripoli University electric grid; the system is of single junction amorphous solar cells which were erected in Sep. 2009; it consists of 240 Mitsubishi thin film amorphous PV Modules of MA100T2 t...

  8. Focal junctions retard lateral movement and disrupt fluid phase connectivity in the plasma membrane

    Vind-Kezunovic, D.; Wojewodzka, U.; Gniadecki, R.

    2008-01-01

    containing liquid-ordered (L-o) lipids. Indeed, values of maximal fluorescence recovery after photobleaching revealed that the long-range mobility of cholera toxin B subunit (CTB, marker of L-o) was similar to 1.5-fold retarded within the focal junctions compared to the surrounding membrane. However, 1...

  9. Molecular anatomy of interendothelial junctions in human blood-brain barrier microvessels.

    Andrzej W Vorbrodt

    2004-07-01

    Full Text Available Immunogold cytochemical procedure was used to study the localization at the ultrastructural level of interendothelial junction-associated protein molecules in the human brain blood microvessels, representing the anatomic site of the blood-brain barrier (BBB. Ultrathin sections of Lowicryl K4M-embedded biopsy specimens of human cerebral cortex obtained during surgical procedures were exposed to specific antibodies, followed by colloidal gold-labeled secondary antibodies. All tight junction-specific integral membrane (transmembrane proteins--occludin, junctional adhesion molecule (JAM-1, and claudin-5--as well as peripheral zonula occludens protein (ZO-1 were highly expressed. Immunoreactivity of the adherens junction-specific transmembrane protein VE-cadherin was of almost similar intensity. Immunolabeling of the adherens junction-associated peripheral proteins--alpha-catenin, beta-catenin, and p120 catenin--although positive, was evidently less intense. The expression of gamma-catenin (plakoglobin was considered questionable because solitary immunosignals (gold particles appeared in only a few microvascular profiles. Double labeling of some sections made possible to observe strict colocalization of the junctional molecules, such as occludin and ZO-1 or JAM-1 and VE-cadherin, in the interendothelial junctions. We found that in human brain microvessels, the interendothelial junctional complexes contain molecular components specific for both tight and adherens junctions. It is assumed that the data obtained can help us find the immunodetectable junctional molecules that can serve as sensitive markers of normal or abnormal function of the BBB.

  10. Mechanics of lipid bilayer junctions affecting the size of a connecting lipid nanotube

    Voinova Marina; Kurczy Michael; Cans Ann-Sofie; Adams Kelly; Grzhibovskis Richards; Karlsson Roger; Ewing Andrew

    2011-01-01

    Abstract In this study we report a physical analysis of the membrane mechanics affecting the size of the highly curved region of a lipid nanotube (LNT) that is either connected between a lipid bilayer vesicle and the tip of a glass microinjection pipette (tube-only) or between a lipid bilayer vesicle and a vesicle that is attached to the tip of a glass microinjection pipette (two-vesicle). For the tube-only configuration (TOC), a micropipette is used to pull a LNT into the interior of a surfa...

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

    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 (...

  12. THE CELULAR JUNCTIONS AND THE EMERGENCE OF ANIMALS

    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.

  13. A microfluidic liquid-junction electrospray interface for on line connection of capillary electrophoresis with mass spectrometry

    Klepárník, Karel; Luksch, Jaroslav; Křenková, Jana; Foret, František

    2013. s. 67. [International Symposium on High Performance Liquid Phase Separations and Related Techniques /40./. 18.11.2013-21.11.2013, Hobart] Institutional support: RVO:68081715 Keywords : CE-ESI-MS * liquid-junction electrospray Subject RIV: CB - Analytical Chemistry, Separation

  14. A microfluidic liquid-junction electrospray interface for on line connection of capillary electrophoresis with mass spectrometry

    Klepárník, Karel; Luksch, Jaroslav; Křenková, Jana; Foret, František

    2013. s. 67. [International Symposium on High Performance Liquid Phase Separations and Related Techniques /40./. 18.11.2013-21.11.2013, Hobart] R&D Projects: GA ČR GAP206/11/2377 Institutional support: RVO:68081715 Keywords : CE-ESI-MS * liquid-junction electrospray Subject RIV: CB - Analytical Chemistry, Separation

  15. Tight Junction Disruption Induced by Type 3 Secretion System Effectors Injected by Enteropathogenic and Enterohemorrhagic Escherichia coli.

    Ugalde-Silva, Paul; Gonzalez-Lugo, Octavio; Navarro-Garcia, Fernando

    2016-01-01

    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. PMID:27606286

  16. Regulation of cytoskeletal organization and junctional remodeling by the atypical cadherin Fat

    Marcinkevicius, Emily; Zallen, Jennifer A.

    2013-01-01

    The atypical cadherin Fat is a conserved regulator of planar cell polarity, but the mechanisms by which Fat controls cell shape and tissue structure are not well understood. Here, we show that Fat is required for the planar polarized organization of actin denticle precursors, adherens junction proteins and microtubules in the epidermis of the late Drosophila embryo. In wild-type embryos, spatially regulated cell-shape changes and rearrangements organize cells into highly aligned columns. Junc...

  17. Morphological analysis of the hagfish heart. I. The ventricle, the arterial connection and the ventral aorta.

    Icardo, José M; Colvee, Elvira; Schorno, Sarah; Lauriano, Eugenia R; Fudge, Douglas S; Glover, Chris N; Zaccone, Giacomo

    2016-03-01

    We have studied the heart in three species of hagfish: Myxine glutinosa, Eptatretus stoutii, and Eptatretus cirrhatus and report about the morphology of the ventricle, the arterial connection and the ventral aorta. On the whole, the hagfish heart lacks outflow tract components, the ventricle and atrium adopt a dorso-caudal rather than a ventro-dorsal relationship, and the sinus venosus opens into the left side of the atrium. This may indicate a "defective" cardiac looping during embryogenesis. The ventral aorta is elongated in M. glutinosa and E. stoutii but sac-like in E. cirrhatus. The ventricles are entirely trabeculated. The myocytes show a low myofibrillar content and junctional complexes formed by fascia adherens and desmosomes. Gap junctions could not be demonstrated. Myocardial cells in M. glutinosa contain numerous lipid droplets. These droplets are less numerous in E. stoutii and practically absent in E. cirrhatus, suggesting different metabolic requirements. Other cell types present in the ventricle are chromaffin cells and granular leukocytes that contain rod-shaped granules. The ventricle-aorta connection is guarded by a bicuspid valve with left and right, pocket-like leaflets. The leaflets extend from the cranial end of the ventricle into the aorta but the junction is asymmetrical. This junction contains a ganglion-like structure in E. cirrhatus. The ventral aorta shows endothelial, media, and adventitial layers. The media contains smooth muscle cells surrounded by dense bands formed by tightly-packed extracellular filaments. In addition, a short number of elastic fibers are observed in M. glutinosa and E. stoutii. Cellular and extracellular elements are more loosely organized in the aorta of E. cirrhatus. The collagenous adventitia contains ganglion-like cells in the three species. In the absence of nerves, chromaffin and ganglion-like cells may control the activity of the myocardium and that of the aortic smooth muscle cells, respectively. PMID

  18. Applications of the Junction Conditions Connecting the Robertson-Walker Metric and the Metric of a Local System on Our Universe

    QIN Yi-Ping

    2006-01-01

    @@ We investigate how the local and global metrics are connected in an ideal model of spacetime where the local system is assumed to be highly symmetric and the cosmological matter is kept away from the local system and does not disturbed by the local system. A boundary condition arising from the junction conditions is obtained and its implication in our universe is studied. We know that the total mass of a sufficiently large system must be that of the cosmological matter within the region of that size. This requirement is satisfied since it is just a consequence of the boundary condition. The analysis shows that at the very late epoch of the universe, there exists a particular time when the largest symmetric local systems stop growing and the observation of this time can be used to check the cosmological parameters. Adopting the popular values (ΩM, ΩΛ) = (0.28, 0.72), we find that particular time would be associated with z = 0.726, the effect of dark matter on the clustering of objects would be insignificant, and the Virgo cluster would be gravitationally bound even if dark matter is ignored.

  19. Gap Junctions

    Goodenough, Daniel A.; Paul, David L.

    2009-01-01

    Gap junctions are aggregates of intercellular channels that permit direct cell–cell transfer of ions and small molecules. Initially described as low-resistance ion pathways joining excitable cells (nerve and muscle), gap junctions are found joining virtually all cells in solid tissues. Their long evolutionary history has permitted adaptation of gap-junctional intercellular communication to a variety of functions, with multiple regulatory mechanisms. Gap-junctional channels are composed of hex...

  20. Gap Junctions

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

    2012-01-01

    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 ...

  1. Congenital ureteropelvic junction obstruction: physiopathology, decoupling of tout court pelvic dilatation-obstruction semantic connection, biomarkers to predict renal damage evolution.

    Alberti, C

    2012-02-01

    The widespread use of fetal ultrasonography results in a frequent antenatally observation of hydronephrosis, ureteropelvic junction obstruction (UPJO) accounting for the greatest fraction of congenital obstructive nephropathy. UPJO may be considered, in most cases, as a functional obstructive condition, depending on defective fetal smooth muscle/nerve development at this level, with lack of peristaltic wave propagation--aperistaltic segment--and, therefore, poor urine ejection from the renal pelvis into the ureter. The UPJO-related physiopathologic events are, at first, the compliant dilatation of renal pelvis that, acting as hydraulic buffer, protects the renal parenchyma from the rising intrapelvic pressure-related potential damages, and, subsequently, beyond such phase of dynamic balance, the tubular cell stretch-stress induced by increased intratubular pressure and following parenchymal inflammatory lesions: inflammatory infiltrates, fibroblast proliferation, activation of myofibroblasts, tubulo-interstitial fibrosis. Reactive oxygen species (ROS), nitric oxide (NO), several chemo- and cytokines, growth factors, prostaglandins and eicosanoids, angiotensin-II are the main pathogenetic mediators of the obstructive nephropathy. Apoptosis of tubular cells is the major cause of the tubular atrophy, together with epithelial-mesenchymal transdifferentiation. Some criticisms on tout court semantic renal pelvis dilatation-obstruction connection have been raised considering that the renal pelvis expansion isn't, in any case, linked to an ostructive condition, as it may be verified by diuretic (furosemide) renogram together with scintiscan-based evaluation of differential renal function. In this regard, rather than repetitive invasive nuclear procedures that expose the children to ionizing radiations, an intriguing noninvasive strategy, based on the evaluation of urinary biomarkers and urinary proteome, can define the UPJO-related possible progress of parenchymal lesions

  2. Adipocytes in both brown and white adipose tissue of adult mice are functionally connected via gap junctions: implications for Chagas disease.

    Burke, Shoshana; Nagajyothi, Fnu; Thi, Mia M; Hanani, Menachem; Scherer, Philipp E; Tanowitz, Herbert B; Spray, David C

    2014-11-01

    Adipose tissue serves as a host reservoir for the protozoan Trypanosoma cruzi, the causative organism in Chagas disease. Gap junctions interconnect cells of most tissues, serving to synchronize cell activities including secretion in glandular tissue, and we have previously demonstrated that gap junctions are altered in various tissues and cells infected with T. cruzi. Herein, we examined the gap junction protein connexin 43 (Cx43) expression in infected adipose tissues. Adipose tissue is the largest endocrine organ of the body and is also involved in other physiological functions. In mammals, it is primarily composed of white adipocytes. Although gap junctions are a prominent feature of brown adipocytes, they have not been explored extensively in white adipocytes, especially in the setting of infection. Thus, we examined functional coupling in both white and brown adipocytes in mice. Injection of electrical current or the dye Lucifer Yellow into adipocytes within fat tissue spread to adjacent cells, which was reduced by treatment with agents known to block gap junctions. Moreover, Cx43 was detected in both brown and white fat tissue. At thirty and ninety days post-infection, Cx43 was downregulated in brown adipocytes and upregulated in white adipocytes. Gap junction-mediated intercellular communication likely contributes to hormone secretion and other functions in white adipose tissue and to nonshivering thermogenesis in brown fat, and modulation of the coupling by T. cruzi infection is expected to impact these functions. PMID:25150689

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

    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. PMID:26365579

  4. Calcium-Ask1-MKK7-JNK2-c-Src Signaling Cascade Mediates Disruption of Intestinal Epithelial Tight Junctions by Dextran Sulfate Sodium

    Samak, Geetha; Chaudhry, Kamaljit K.; Gangwar, Ruchika; Narayanan, Damodaran; Jaggar, Jonathan H.; Rao, RadhaKrishna

    2015-01-01

    Disruption of intestinal epithelial tight junctions is an important event in the pathogenesis of ulcerative colitis. Dextran sodium sulfate (DSS) induces colitis in mice with the symptoms similar to ulcerative colitis. However, the mechanism of DSS-induced colitis is unknown. We investigated the mechanism of DSS-induced disruption of intestinal epithelial tight junctions and barrier dysfunction in Caco-2 cell monolayers in vitro and mouse colon in vivo. DSS treatment resulted in disruption of tight junctions, adherens junctions and actin cytoskeleton leading to barrier dysfunction in Caco-2 cell monolayers. DSS induced a rapid activation of c-jun N-terminal kinase (JNK), and the inhibition or knockdown of JNK2 attenuated DSS-induced tight junction disruption and barrier dysfunction. In mice, DSS administration for 4 days caused redistribution of tight junction and adherens junction proteins from the epithelial junctions, which was blocked by JNK inhibitor. In Caco-2 cell monolayers, DSS increased intracellular Ca2+ concentration, and depletion of intracellular Ca2+ by BAPTA or thapsigargin attenuated DSS-induced JNK activation, tight junction disruption and barrier dysfunction. Knockdown of Ask1 or MKK7 blocked DSS-induced tight junction disruption and barrier dysfunction. DSS activated c-Src by a Ca2+ and JNK-dependent mechanism. Inhibition of Src kinase activity or knockdown of c-Src blocked DSS-induced tight junction disruption and barrier dysfunction. DSS increased Tyr-phosphorylation of occludin, ZO-1, E-cadherin and β-catenin. SP600125 abrogated DSS-induced Tyr-phosphorylation of junctional proteins. Recombinant JNK2 induced threonine phosphorylation and auto phosphorylation of c-Src. This study demonstrates that Ca2+-Ask1-MKK7-JNK2-cSrc signaling cascade mediates DSS-induced tight junction disruption and barrier dysfunction. PMID:25377781

  5. Electronic properties of nanotube junctions

    Lambin, Ph.; Meunier, V.

    1998-08-01

    The possibility of realizing junctions between two different nanotubes has recently attracted a great interest, even though much remains to be done for putting this idea in concrete form. Pentagon-heptagon pair defects in the otherwise perfect graphitic network make such connections possible, with virtually infinite varieties. In this paper, the literature devoted to nanotube junctions is briefly reviewed. A special emphasize is put on the electronic properties of C nanotube junctions, together with an indication on how their current-voltage characteristics may look like.

  6. SIS junction reactance complete compensation

    SIS junction geometrical capacitance together with out of phase current Ikk impedance component forms sufficient junction reactance XSIS = (ωC + BQ)-1. This paper suggests the way to resonate out both ωC and BQ by using additional identical SIS junction connected to the first through a long line impedance inverter and RF + DC biased symmetrically to the first. Pumped IV curves without quantum reactance and frequency impedance patterns of the system were calculated. Calculations demonstrated the presence of high and even negative induced dynamic resistance regions at high order quasiparticle steps for the case of SIS junction reactance complete compensation. The suggested method may be used in SIS mixers and detectors for a better RF matching

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

    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. Neisseria gonorrhoeae induced disruption of cell junction complexes in epithelial cells of the human genital tract.

    Rodríguez-Tirado, Carolina; Maisey, Kevin; Rodríguez, Felipe E; Reyes-Cerpa, Sebastián; Reyes-López, Felipe E; Imarai, Mónica

    2012-03-01

    Pathogenic microorganisms, such as Neisseria gonorrhoeae, have developed mechanisms to alter epithelial barriers in order to reach subepithelial tissues for host colonization. The aim of this study was to examine the effects of gonococci on cell junction complexes of genital epithelial cells of women. Polarized Ishikawa cells, a cell line derived from endometrial epithelium, were used for experimental infection. Infected cells displayed a spindle-like shape with an irregular distribution, indicating potential alteration of cell-cell contacts. Accordingly, analysis by confocal microscopy and cellular fractionation revealed that gonococci induced redistribution of the adherens junction proteins E-cadherin and its adapter protein β-catenin from the membrane to a cytoplasmic pool, with no significant differences in protein levels. In contrast, gonococcal infection did not induce modification of either expression or distribution of the tight junction proteins Occludin and ZO-1. Similar results were observed for Fallopian tube epithelia. Interestingly, infected Ishikawa cells also showed an altered pattern of actin cytoskeleton, observed in the form of stress fibers across the cytoplasm, which in turn matched a strong alteration on the expression of fibronectin, an adhesive glycoprotein component of extracellular matrix. Interestingly, using western blotting, activation of the ERK pathway was detected after gonococcal infection while p38 pathway was not activated. All effects were pili and Opa independent. Altogether, results indicated that gonococcus, as a mechanism of pathogenesis, induced disruption of junction complexes with early detaching of E-cadherin and β-catenin from the adherens junction complex, followed by a redistribution and reorganization of actin cytoskeleton and fibronectin within the extracellular matrix. PMID:22146107

  9. Motorway junction design with emphasis on traffic performance and safety assesment - case study junction Ljubljana Rudnik

    Mlaker, Pavel

    2013-01-01

    Thesis encompasses reconstruction predesign of the motorway junction Ljubljana Rudnik into motorway interchange. In this area is intended to be the junction of main arterial road with highway network, while today serves only as a minor junction of Rudnik and Ig area on the motorway. The purpose of reconstruction is to enable free traffic flow on most congested directions of the interchange, but also preserve the present function, in which Ig and Rudnik area are connected with the motorway. Bu...

  10. Drosophila Homolog of Human KIF22 at the Autism-Linked 16p11.2 Loci Influences Synaptic Connectivity at Larval Neuromuscular Junctions.

    Park, Sang Mee; Littleton, J Troy; Park, Hae Ryoun; Lee, Ji Hye

    2016-02-01

    Copy number variations at multiple chromosomal loci, including 16p11.2, have recently been implicated in the pathogenesis of autism spectrum disorder (ASD), a neurodevelopmental disease that affects 1~3% of children worldwide. The aim of this study was to investigate the roles of human genes at the 16p11.2 loci in synaptic development using Drosophila larval neuromuscular junctions (NMJ), a well-established model synapse with stereotypic innervation patterns. We conducted a preliminary genetic screen based on RNA interference in combination with the GAL4-UAS system, followed by mutational analyses. Our result indicated that disruption of klp68D, a gene closely related to human KIF22, caused ectopic innervations of axon branches forming type III boutons in muscle 13, along with less frequent re-routing of other axon branches. In addition, mutations in klp64D, of which gene product forms Kinesin-2 complex with KLP68D, led to similar targeting errors of type III axons. Mutant phenotypes were at least partially reproduced by knockdown of each gene via RNA interference. Taken together, our data suggest the roles of Kinesin-2 proteins, including KLP68D and KLP64D, in ensuring proper synaptic wiring. PMID:26924931

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

    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.

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

    Abdelaziz Amine; Yamina Mir; Mimoun Zazoui

    2013-01-01

    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 p...

  13. Tight junctions in Hailey-Hailey and Darier’s diseases

    Laura Raiko

    2009-11-01

    Full Text Available Hailey-Hailey disease (HHD and Darier’s disease (DD are caused by mutations in Ca2+-ATPases with the end result of desmosomal disruption and suprabasal acantholysis. Tight junctions (TJ are located in the granular cell layer in normal skin and contribute to the epidermal barrier. Aberrations in the epidermal differentiation, such as in psoriasis, have been shown to lead to changes in the expression of TJ components. Our aim was to elucidate the expression and dynamics of the TJ proteins during the disruption of desmosomes in HHD and DD lesions. Indirect immunofluorescence and avidin-biotin labeling for TJ, desmosomal and adherens junction proteins, and subsequent analyses with the confocal laser scanning microscope were carried out on 14 HHD and 14 DD skin samples. Transepidermal water loss (TEWL was measured in normal and lesional epidermis of nine HHD and eight DD patients to evaluate the function of the epidermal barrier in HHD and DD skin. The localization of TJ proteins claudin-1, claudin-4, ZO-1, and occludin in perilesional HHD and DD epidermis was similar to that previously described in normal skin. In HHD lesions the tissue distribution of ZO-1 expanded to the acantholytic spinous cells. In agreement with previous findings, desmoplakin was localized intracellularly. In contrast claudin-1 and ZO-1 persisted in the cell-cell contact sites of acantholytic cells. TEWL was increased in the lesional skin. The current results suggest that TJ components follow different dynamics in acantholysis of HHD and DD compared to desmosomal and adherens junction proteins.

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

    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.

  15. αT-catenin in restricted brain cell types and its potential connection to autism

    Folmsbee, Stephen Sai; Wilcox, Douglas R.; Tyberghein, Koen; De Bleser, Pieter; Tourtellotte, Warren G.; van Hengel, Jolanda; van Roy, Frans; Gottardi, Cara J.

    2016-01-01

    Background Recent genetic association studies have linked the cadherin-based adherens junction protein alpha-T-catenin (αT-cat, CTNNA3) with the development of autism. Where αT-cat is expressed in the brain, and how its loss could contribute to this disorder, are entirely unknown. Methods We used the αT-cat knockout mouse to examine the localization of αT-cat in the brain, and we used histology and immunofluorescence analysis to examine the neurobiological consequences of its loss. Results We...

  16. Solitons in Josephson junctions

    Ustinov, A. V.

    1998-11-01

    Magnetic flux quanta in Josephson junctions, often called fluxons, in many cases behave as solitons. A review of recent experiments and modelling of fluxon dynamics in Josephson circuits is presented. Classic quasi-one-dimensional junctions, stacked junctions (Josephson superlattices), and discrete Josephson transmission lines (JTLs) are discussed. Applications of fluxon devices as high-frequency oscillators and digital circuits are also addressed.

  17. Japanese encephalitis virus disrupts cell-cell junctions and affects the epithelial permeability barrier functions.

    Tanvi Agrawal

    Full Text Available Japanese encephalitis virus (JEV is a neurotropic flavivirus, which causes viral encephalitis leading to death in about 20-30% of severely-infected people. Although JEV is known to be a neurotropic virus its replication in non-neuronal cells in peripheral tissues is likely to play a key role in viral dissemination and pathogenesis. We have investigated the effect of JEV infection on cellular junctions in a number of non-neuronal cells. We show that JEV affects the permeability barrier functions in polarized epithelial cells at later stages of infection. The levels of some of the tight and adherens junction proteins were reduced in epithelial and endothelial cells and also in hepatocytes. Despite the induction of antiviral response, barrier disruption was not mediated by secreted factors from the infected cells. Localization of tight junction protein claudin-1 was severely perturbed in JEV-infected cells and claudin-1 partially colocalized with JEV in intracellular compartments and targeted for lysosomal degradation. Expression of JEV-capsid alone significantly affected the permeability barrier functions in these cells. Our results suggest that JEV infection modulates cellular junctions in non-neuronal cells and compromises the permeability barrier of epithelial and endothelial cells which may play a role in viral dissemination in peripheral tissues.

  18. Endothelial cell senescence is associated with disrupted cell-cell junctions and increased monolayer permeability

    Krouwer Vincent J D

    2012-08-01

    Full Text Available Abstract Background Cellular senescence is associated with cellular dysfunction and has been shown to occur in vivo in age-related cardiovascular diseases such as atherosclerosis. Atherogenesis is accompanied by intimal accumulation of LDL and increased extravasation of monocytes towards accumulated and oxidized LDL, suggesting an affected barrier function of vascular endothelial cells. Our objective was to study the effect of cellular senescence on the barrier function of non-senescent endothelial cells. Methods Human umbilical vein endothelial cells were cultured until senescence. Senescent cells were compared with non-senescent cells and with co-cultures of non-senescent and senescent cells. Adherens junctions and tight junctions were studied. To assess the barrier function of various monolayers, assays to measure permeability for Lucifer Yellow (LY and horseradish peroxidase (PO were performed. Results The barrier function of monolayers comprising of senescent cells was compromised and coincided with a change in the distribution of junction proteins and a down-regulation of occludin and claudin-5 expression. Furthermore, a decreased expression of occludin and claudin-5 was observed in co-cultures of non-senescent and senescent cells, not only between senescent cells but also along the entire periphery of non-senescent cells lining a senescent cell. Conclusions Our findings show that the presence of senescent endothelial cells in a non-senescent monolayer disrupts tight junction morphology of surrounding young cells and increases the permeability of the monolayer for LY and PO.

  19. Reinforcing endothelial junctions prevents microvessel permeability increase and tumor cell adhesion in microvessels in vivo

    Fu, Bingmei M.; Yang, Jinlin; Cai, Bin; Fan, Jie; Zhang, Lin; Zeng, Min

    2015-10-01

    Tumor cell adhesion to the microvessel wall is a critical step during tumor metastasis. Vascular endothelial growth factor (VEGF), a secretion of tumor cells, can increase microvessel permeability and tumor cell adhesion in the microvessel. To test the hypothesis that inhibiting permeability increase can reduce tumor cell adhesion, we used in vivo fluorescence microscopy to measure both microvessel permeability and adhesion rates of human mammary carcinoma MDA-MB-231 cells in post-capillary venules of rat mesentery under the treatment of VEGF and a cAMP analog, 8-bromo-cAMP, which can decrease microvessel permeability. By immunostaining adherens junction proteins between endothelial cells forming the microvessel wall, we further investigated the structural mechanism by which cAMP abolishes VEGF-induced increase in microvessel permeability and tumor cell adhesion. Our results demonstrate that 1) Pretreatment of microvessels with cAMP can abolish VEGF-enhanced microvessel permeability and tumor cell adhesion; 2) Tumor cells prefer to adhere to the endothelial cell junctions instead of cell bodies; 3) VEGF increases microvessel permeability and tumor cell adhesion by compromising endothelial junctions while cAMP abolishes these effects of VEGF by reinforcing the junctions. These results suggest that strengthening the microvessel wall integrity can be a potential approach to inhibiting hematogenous tumor metastasis.

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

    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.

  1. Molecular electronic junction transport

    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 focuses on mechanism, structure/function relations, regimes and mechanisms of transport, some molecular regularities, and some substantial challenges facing the field. Because there are many regimes and mechanisms in transport junctions, we will discuss time scales, geometries, and inelastic scattering...

  2. Gap junctions-guards of excitability

    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...... 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....

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

    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.

  4. Self-organizing actomyosin patterns on the cell cortex at epithelial cell-cell junctions.

    Moore, Thomas; Wu, Selwin K; Michael, Magdalene; Yap, Alpha S; Gomez, Guillermo A; Neufeld, Zoltan

    2014-12-01

    The behavior of actomyosin critically determines morphologically distinct patterns of contractility found at the interface between adherent cells. One such pattern is found at the apical region (zonula adherens) of cell-cell junctions in epithelia, where clusters of the adhesion molecule E-cadherin concentrate in a static pattern. Meanwhile, E-cadherin clusters throughout lateral cell-cell contacts display dynamic movements in the plane of the junctions. To gain insight into the principles that determine the nature and organization of these dynamic structures, we analyze this behavior by modeling the 2D actomyosin cell cortex as an active fluid medium. The numerical simulations show that the stability of the actin filaments influences the spatial structure and dynamics of the system. We find that in addition to static Turing-type patterns, persistent dynamic behavior occurs in a wide range of parameters. In the 2D model, mechanical stress-dependent actin breakdown is shown to produce a continuously changing network of actin bridges, whereas with a constant breakdown rate, more isolated clusters of actomyosin tend to form. The model qualitatively reproduces the dynamic and stable patterns experimentally observed at the junctions between epithelial cells. PMID:25468344

  5. Stacked Josephson Junctions

    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...

  6. Magnetic tunnel junctions (MTJs)

    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.

  7. Gap junctions in developing thalamic and neocortical neuronal networks.

    Niculescu, Dragos; Lohmann, Christian

    2014-12-01

    The presence of direct, cytoplasmatic, communication between neurons in the brain of vertebrates has been demonstrated a long time ago. These gap junctions have been characterized in many brain areas in terms of subunit composition, biophysical properties, neuronal connectivity patterns, and developmental regulation. Although interesting findings emerged, showing that different subunits are specifically regulated during development, or that excitatory and inhibitory neuronal networks exhibit various electrical connectivity patterns, gap junctions did not receive much further interest. Originally, it was believed that gap junctions represent simple passageways for electrical and biochemical coordination early in development. Today, we know that gap junction connectivity is tightly regulated, following independent developmental patterns for excitatory and inhibitory networks. Electrical connections are important for many specific functions of neurons, and are, for example, required for the development of neuronal stimulus tuning in the visual system. Here, we integrate the available data on neuronal connectivity and gap junction properties, as well as the most recent findings concerning the functional implications of electrical connections in the developing thalamus and neocortex. PMID:23843439

  8. Magnesium gating of cardiac gap junction channels.

    Matsuda, Hiroyuki; Kurata, Yasutaka; Oka, Chiaki; Matsuoka, Satoshi; Noma, Akinori

    2010-09-01

    We aimed to study kinetics of modulation by intracellular Mg(2+) of cardiac gap junction (Mg(2+) gate). Paired myocytes of guinea-pig ventricle were superfused with solutions containing various concentrations of Mg(2+). In order to rapidly apply Mg(2+) to one aspect of the gap junction, the non-junctional membrane of one of the pair was perforated at nearly the connecting site by pulses of nitrogen laser beam. The gap junction conductance (G(j)) was measured by clamping the membrane potential of the other cell using two-electrode voltage clamp method. The laser perforation immediately increased G(j), followed by slow G(j) change with time constant of 3.5 s at 10 mM Mg(2+). Mg(2+) more than 1.0 mM attenuated dose-dependently the gap junction conductance and lower Mg(2+) (0.6 mM) increased G(j) with a Hill coefficient of 3.4 and a half-maximum effective concentration of 0.6 mM. The time course of G(j) changes was fitted by single exponential function, and the relationship between the reciprocal of time constant and Mg(2+) concentration was almost linear. Based on the experimental data, a mathematical model of Mg(2+) gate with one open state and three closed states well reproduced experimental results. One-dimensional cable model of thirty ventricular myocytes connected to the Mg(2+) gate model suggested a pivotal role of the Mg(2+) gate of gap junction under pathological conditions. PMID:20553744

  9. Tight junction protein ZO-2 expression and relative function of ZO-1 and ZO-2 during mouse blastocyst formation

    Apicolateral tight junctions (TJs) between epithelial cells are multiprotein complexes regulating membrane polarity and paracellular transport and also contribute to signalling pathways affecting cell proliferation and gene expression. ZO-2 and other ZO family members form a sub-membranous scaffold for binding TJ constituents. We investigated ZO-2 contribution to TJ biogenesis and function during trophectoderm epithelium differentiation in mouse preimplantation embryos. Our data indicate that ZO-2 is expressed from maternal and embryonic genomes with maternal ZO-2 protein associated with nuclei in zygotes and particularly early cleavage stages. Embryonic ZO-2 assembled at outer blastomere apicolateral junctional sites from the late 16-cell stage. Junctional ZO-2 first co-localised with E-cadherin in a transient complex comprising adherens junction and TJ constituents before segregating to TJs after their separation from the blastocyst stage (32-cell onwards). ZO-2 siRNA microinjection into zygotes or 2-cell embryos resulted in specific knockdown of ZO-2 mRNA and protein within blastocysts. Embryos lacking ZO-2 protein at trophectoderm TJs exhibited delayed blastocoel cavity formation but underwent normal cell proliferation and outgrowth morphogenesis. Quantitative analysis of trophectoderm TJs in ZO-2-deficient embryos revealed increased assembly of ZO-1 but not occludin, indicating ZO protein redundancy as a compensatory mechanism contributing to the mild phenotype observed. In contrast, ZO-1 knockdown, or combined ZO-1 and ZO-2 knockdown, generated a more severe inhibition of blastocoel formation indicating distinct roles for ZO proteins in blastocyst morphogenesis

  10. Josephson φ_0-junction in nanowire quantum dots

    Szombati, D. B.; Nadj-Perge, S.; Car, D.; Plissard, S.R.; Bakkers, E. P. A. M.; Kouwenhoven, L. P.

    2015-01-01

    The Josephson effect describes supercurrent flowing through a junction connecting two superconducting leads by a thin barrier. This current is driven by a superconducting phase difference ϕ between the leads. Due to the chiral and time reversal symmetry of the Cooper pair tunneling process the current is strictly zero when ϕ vanishes. Only if these underlying symmetries are broken the supercurrent for ϕ = 0 may be finite. This corresponds to a ground state of the junction being offset by a ph...

  11. Quantum Junction Solar Cells

    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.

  12. Symmetry properties of the heat current in non-ballistic asymmetric junctions: A case study

    We consider quantum heat flow in two-terminal junctions and inquire on the connection between the transport mechanism and the junction functionality. Using simple models, we demonstrate that the violation of the Landauer behavior in asymmetric junctions does not necessarily imply the onset of thermal rectification. We also demonstrate through a simple example that a spatial inhomogeneity of the energy spectra is not a necessary condition for thermal rectification.

  13. Oncostatin M induces upregulation of claudin-2 in rodent hepatocytes coinciding with changes in morphology and function of tight junctions

    In rodent livers, integral tight junction (TJ) proteins claudin-1, -2, -3, -5 and -14 are detected and play crucial roles in the barrier to keep bile in bile canaculi away from the blood circulation. Claudin-2 shows a lobular gradient increasing from periportal to pericentral hepatocytes, whereas claudin-1 and -3 are expressed in the whole liver lobule. Although claudin-2 expression induces cation-selective channels in tight junctions of epithelial cells, the physiological functions and regulation of claudin-2 in hepatocytes remain unclear. Oncostatin M (OSM) is a multifunctional cytokine implicated in the differentiation of hepatocytes that induces formation of E-cadherin-based adherens junctions in fetal hepatocytes. In this study, we examined whether OSM could induce expression and function of claudin-2 in rodent hepatocytes, immortalized mouse and primary cultured proliferative rat hepatocytes. In the immortalized mouse and primary cultured proliferative rat hepatocytes, treatment with OSM markedly increased mRNA and protein of claudin-2 together with formation of developed networks of TJ strands. The increase of claudin-2 enhanced the paracellular barrier function which depended on molecular size. The increase of claudin-2 expression induced by OSM in rodent hepatocytes was regulated through distinct signaling pathways including PKC. These results suggest that expression of claudin-2 in rodent hepatocytes may play a specific role as controlling the size of paracellular permeability in the barrier to keep bile in bile canaculi

  14. Junction-FET dosimeter

    The performance of a new junction-FET dosimeter and its application to the beam profile measurement are presented. One of the two junction FET's making up an astable multivibrator is used as a small-size (approx.0.4x0.4 mm) high-level dose detector. The irradiated dose can be estimated by the amount of the decrease of the oscillator period of the multivibrator. The distinct advantages in its small size and superior resistive property to radiation effect enable us to measure the cross-sectional profile of the electron beam from a linac with high spatial resolution of about 0.4 mm

  15. An Evaluation of Test and Physical Uncertainty of Measuring Vibration in Wooden Junctions

    Dickow, Kristoffer Ahrens; Kirkegaard, Poul Henning; Andersen, Lars Vabbersgaard

    2012-01-01

    In the present paper a study of test and material uncertainty in modal analysis of certain wooden junctions is presented. The main structure considered here is a T-junction made from a particleboard plate connected to a spruce beam of rectangular cross section. The size of the plate is 1.2 m by 0...... plate is significant....

  16. Particulate matter air pollution disrupts endothelial cell barrier via calpain-mediated tight junction protein degradation

    Wang Ting

    2012-08-01

    Full Text Available Abstract Background Exposure to particulate matter (PM is a significant risk factor for increased cardiopulmonary morbidity and mortality. The mechanism of PM-mediated pathophysiology remains unknown. However, PM is proinflammatory to the endothelium and increases vascular permeability in vitro and in vivo via ROS generation. Objectives We explored the role of tight junction proteins as targets for PM-induced loss of lung endothelial cell (EC barrier integrity and enhanced cardiopulmonary dysfunction. Methods Changes in human lung EC monolayer permeability were assessed by Transendothelial Electrical Resistance (TER in response to PM challenge (collected from Ft. McHenry Tunnel, Baltimore, MD, particle size >0.1 μm. Biochemical assessment of ROS generation and Ca2+ mobilization were also measured. Results PM exposure induced tight junction protein Zona occludens-1 (ZO-1 relocation from the cell periphery, which was accompanied by significant reductions in ZO-1 protein levels but not in adherens junction proteins (VE-cadherin and β-catenin. N-acetyl-cysteine (NAC, 5 mM reduced PM-induced ROS generation in ECs, which further prevented TER decreases and atteneuated ZO-1 degradation. PM also mediated intracellular calcium mobilization via the transient receptor potential cation channel M2 (TRPM2, in a ROS-dependent manner with subsequent activation of the Ca2+-dependent protease calpain. PM-activated calpain is responsible for ZO-1 degradation and EC barrier disruption. Overexpression of ZO-1 attenuated PM-induced endothelial barrier disruption and vascular hyperpermeability in vivo and in vitro. Conclusions These results demonstrate that PM induces marked increases in vascular permeability via ROS-mediated calcium leakage via activated TRPM2, and via ZO-1 degradation by activated calpain. These findings support a novel mechanism for PM-induced lung damage and adverse cardiovascular outcomes.

  17. Disordered graphene Josephson junctions

    Munoz, W. A.; Covaci, L.; Peeters, F. M.

    2014-01-01

    A tight-binding approach based on the Chebyshev-Bogoliubov-de Gennes method is used to describe disordered single-layer graphene Josephson junctions. Scattering by vacancies, ripples or charged impurities is included. We compute the Josephson current and investigate the nature of multiple Andreev reflections, which induce bound states appearing as peaks in the density of states for energies below the superconducting gap. In the presence of single atom vacancies, we observe a strong suppressio...

  18. Phonon interference effects in molecular junctions

    We study coherent phonon transport through organic, π-conjugated molecules. Using first principles calculations and Green's function methods, we find that the phonon transmission function in cross-conjugated molecules, like meta-connected benzene, exhibits destructive quantum interference features very analogous to those observed theoretically and experimentally for electron transport in similar molecules. The destructive interference features observed in four different cross-conjugated molecules significantly reduce the thermal conductance with respect to linear conjugated analogues. Such control of the thermal conductance by chemical modifications could be important for thermoelectric applications of molecular junctions

  19. Phonon interference effects in molecular junctions

    Markussen, Troels, E-mail: troels.markussen@gmail.com [Center for Atomic-scale Materials Design (CAMD), Department of Physics, Technical University of Denmark, DK-2800 Kgs. Lyngby (Denmark)

    2013-12-28

    We study coherent phonon transport through organic, π-conjugated molecules. Using first principles calculations and Green's function methods, we find that the phonon transmission function in cross-conjugated molecules, like meta-connected benzene, exhibits destructive quantum interference features very analogous to those observed theoretically and experimentally for electron transport in similar molecules. The destructive interference features observed in four different cross-conjugated molecules significantly reduce the thermal conductance with respect to linear conjugated analogues. Such control of the thermal conductance by chemical modifications could be important for thermoelectric applications of molecular junctions.

  20. Gap junctions in the cardiovascular and immune systems

    R. Rozental

    2000-04-01

    Full Text Available Gap junctions are clusters of intercellular channels directly connecting the cytoplasm of adjacent cells. These channels are formed by proteins named connexins and are present in all metazoan organisms where they serve diverse functions ranging from control of cell growth and differentiation to electric conduction in excitable tissues. In this overview we describe the presence of connexins in the cardiovascular and lympho-hematopoietic systems giving the reader a summary of the topics to be covered throughout this edition and a historical perspective of the discovery of gap junctions in the immune system.

  1. Age-dependant expression of alpha-macula adherens protein in rat heart%α-黏着斑蛋白在大鼠心脏表达分布随增龄变化的特征

    张光谋; 吴俊琢; 张艳芬; 郭志坤

    2005-01-01

    BACKGROUND: Macula adherens protein is found closely associated with congenital cardiac malformation and myocardial differentiation. OBJECTIVE: To investigate the expression characteristics of α-macula adherens protein in rat heart, as well as the property of age-dependant expression during myocardial growth. DESIGN: Randomized controlled, observational comparative study. SETTING: Department of Cell Biology of Xinxiang Medical College; Department of Bioengineering and Agricultural Economics of Puyang Vocational Technical School. MATERIALS: This study was conducted at the Morphological Laboratory of Xinxiang Medical College between January and June 2003. Totally 28 Wistar rats of clean grade were divided into infant group, youth group,middle-age group, and old-age group with 7 rats in each group. METHODS: All rats were anaesthetized and then cardiac tissues were cut into consecutive coronal slices of 5 μm thick. The expression of α-macula adherens protein in rat myocardium of infant, youth, middle-age and oldage groups was detected using IHC method. The positive cells displayed brownish yellow granules on the surface, cytoplasm and intercalated disc. Routine HE staining was performed on all specimens for structural comparison. MAIN OUTCOME MEASURES: The expression of α-macula adherens protein in rat myocardium of different groups. RESULTS: All the 28 rats entered the final results analysis. ① α-macula adherens protein was found to be expressed in myocardium in atrium, ventricle, papilla muscles and interventricular septum. ② In infant rats, the expression of α-macula adherens protein was mainly observed in intercalated disc at the end of myocardium, with less expression on cell surface and in cytoplasm; in contrast, α-macula adherens protein in young, middleaged and old rats was found to be typically expressed in intercalated disc at the end of myocardium. CONCLUSION: The expression of α-macula adherens protein displays age-dependant manner during rat

  2. Molecular dynamics study of Ar flow and He flow inside carbon nanotube junction as a molecular nozzle and diffuser

    Itsuo Hanasaki, Akihiro Nakatani and Hiroshi Kitagawa

    2004-01-01

    A carbon nanotube junction consists of two connected nanotubes with different diameters. It has been extensively investigated as a molecular electronic device since carbon nanotubes can be metallic and semiconductive, depending on their structure. However, a carbon nanotube junction can also be viewed as a nanoscale nozzle andv diffuser. Here, we focus on the nanotube junction from the perspective of an intersection between machine, material and device. We have conducted a molecular dynamics ...

  3. Josephson junction simulation of neurons

    Crotty, Patrick; Schult, Daniel; Segall, Ken

    2010-01-01

    With the goal of understanding the intricate behavior and dynamics of collections of neurons, we present superconducting circuits containing Josephson junctions that model biologically realistic neurons. These "Josephson junction neurons" reproduce many characteristic behaviors of biological neurons such as action potentials, refractory periods, and firing thresholds. They can be coupled together in ways that mimic electrical and chemical synapses. Using existing fabrication technologies, lar...

  4. Fluid Flow at Branching Junctions

    Sochi, Taha

    2013-01-01

    The flow of fluids at branching junctions plays important kinematic and dynamic roles in most biological and industrial flow systems. The present paper highlights some key issues related to the flow of fluids at these junctions with special emphasis on the biological flow networks particularly blood transportation vasculature.

  5. Josephson ϕ0-junction in nanowire quantum dots

    Szombati, D. B.; Nadj-Perge, S.; Car, D.; Plissard, S. R.; Bakkers, E. P. A. M.; Kouwenhoven, L. P.

    2016-06-01

    The Josephson effect describes supercurrent flowing through a junction connecting two superconducting leads by a thin barrier. This current is driven by a superconducting phase difference ϕ between the leads. In the presence of chiral and time-reversal symmetry of the Cooper pair tunnelling process, the current is strictly zero when ϕ vanishes. Only if these underlying symmetries are broken can the supercurrent for ϕ = 0 be finite. This corresponds to a ground state of the junction being offset by a phase ϕ0, different from 0 or π. Here, we report such a Josephson ϕ0-junction based on a nanowire quantum dot. We use a quantum interferometer device to investigate phase offsets and demonstrate that ϕ0 can be controlled by electrostatic gating. Our results may have far-reaching implications for superconducting flux- and phase-defined quantum bits as well as for exploring topological superconductivity in quantum dot systems.

  6. Gap junction modulation by extracellular signaling molecules: the thymus model

    Alves L.A.

    2000-01-01

    Full Text Available Gap junctions are intercellular channels which connect adjacent cells and allow direct exchange of molecules of low molecular weight between them. Such a communication has been described as fundamental in many systems due to its importance in coordination, proliferation and differentiation. Recently, it has been shown that gap junctional intercellular communication (GJIC can be modulated by several extracellular soluble factors such as classical hormones, neurotransmitters, interleukins, growth factors and some paracrine substances. Herein, we discuss some aspects of the general modulation of GJIC by extracellular messenger molecules and more particularly the regulation of such communication in the thymus gland. Additionally, we discuss recent data concerning the study of different neuropeptides and hormones in the modulation of GJIC in thymic epithelial cells. We also suggest that the thymus may be viewed as a model to study the modulation of gap junction communication by different extracellular messengers involved in non-classical circuits, since this organ is under bidirectional neuroimmunoendocrine control.

  7. Connected Traveler

    Schroeder, Alex

    2015-11-01

    The Connected Traveler project is a multi-disciplinary undertaking that seeks to validate potential for transformative transportation system energy savings by incentivizing efficient traveler behavior. This poster outlines various aspects of the Connected Traveler project, including market opportunity, understanding traveler behavior and decision-making, automation and connectivity, and a projected timeline for Connected Traveler's key milestones.

  8. Herlitz junctional epidermolysis bullosa.

    Laimer, Martin; Lanschuetzer, Christoph M; Diem, Anja; Bauer, Johann W

    2010-01-01

    Junctional epidermolysis bullosa type Herlitz (JEB-H) is the autosomal recessively inherited, more severe variant of "lucidolytic" JEB. Characterized by generalized, extensive mucocutaneous blistering at birth and early lethality, this devastating condition is most often caused by homozygous null mutations in the genes LAMA3, LAMB3, or LAMC2, each encoding for 1 of the 3 chains of the heterotrimer laminin-332. The JEB-H subtype usually presents as a severe and clinically diverse variant of the EB group of mechanobullous genodermatoses. This article outlines the epidemiology, presentation, and diagnosis of JEB-H. Morbidity and mortality are high, necessitating optimized protocols for early (including prenatal) diagnosis and palliative care. Gene therapy remains the most promising perspective. PMID:19945616

  9. The human myotendinous junction

    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...... from all 14 patients. TEM images displayed similarities to observations in animals: Sarcolemmal evaginations observed as finger-like processes from the tendon and endomysium surrounding the muscle fibers, with myofilaments extending from the final Z-line of the muscle fiber merging with the tendon...... been described in three dimensions (3D). The aim of this study was to describe the ultrastructure of the human MTJ and render 3D reconstructions. Fourteen subjects (age 25 ± 3 years) with isolated injury of the anterior cruciate ligament (ACL), scheduled for reconstruction with a semitendinosus...

  10. Disordered graphene Josephson junctions

    Muñoz, W. A.; Covaci, L.; Peeters, F. M.

    2015-02-01

    A tight-binding approach based on the Chebyshev-Bogoliubov-de Gennes method is used to describe disordered single-layer graphene Josephson junctions. Scattering by vacancies, ripples, or charged impurities is included. We compute the Josephson current and investigate the nature of multiple Andreev reflections, which induce bound states appearing as peaks in the density of states for energies below the superconducting gap. In the presence of single-atom vacancies, we observe a strong suppression of the supercurrent, which is a consequence of strong intervalley scattering. Although lattice deformations should not induce intervalley scattering, we find that the supercurrent is still suppressed, which is due to the presence of pseudomagnetic barriers. For charged impurities, we consider two cases depending on whether the average doping is zero, i.e., existence of electron-hole puddles, or finite. In both cases, short-range impurities strongly affect the supercurrent, similar to the vacancies scenario.

  11. Preparation and properties of two types of submicron high-Tc Josephson junctions

    There is a variety of different types of high-Tc Josephson junctions corresponding to the short coherence length, high anisotropy and some interface problems of the oxide superconductors. Using submicron technologies nanobridges and bridges modified by ion beams in a hundred nanometer region can be fabricated. Depending on preparation parameters the ion beam influence causes implantation, sputtering or a modification of the lattice changing the superconducting properties. The case of modification is discussed in details. It is shown how parameters of the preparation process influence the physical properties of these junctions. The application of such junctions is shown for DC-SQUIDs and gradiometers including a comparison to other junction types like bicrystal or step-edge junctions. Submicron technology is useful for preparation of intrinsic stacked junctions out of thin films. In this case the single junction dimension is determined by the coupling of two copper oxide planes in an atomic scale. A mesa structure acts as a series connection of a number of single junctions corresponding to the stack height. Preparation and physical properties of these types of junction arrays are given in detail. The possible application of such new kind of devices as radiation sources or voltage standard will be discussed

  12. Electrical transport through a metal-molecule-metal junction

    We investigate the electrical transport through a very few molecules connected to metallic electrodes at room temperature. First, the state of the art in molecular electronics is outlined. We present the most convincing molecular devices reported so far in the literature and the theoretical tools available to analyze the electron transport mechanism through a molecular junction. Second, we describe the use of mechanically controllable break junctions to investigate the electron transport properties through a metal-molecule-metal junction. Two kinds of molecules were adsorbed on the two facing gold electrodes, dodecane-thiol (DT) and bis-thiol-ter-thiophene (α,ω T3), that are basically expected to behave as an insulator and as a molecular wire, respectively. In the latter case, we study the chemical reactivity of the molecule and show that α,ω T3 is chemically adsorbed on gold electrodes. Current-voltage characteristics of the junction were observed at room temperature. The Gold-DT-Gold junction behaves as a simple metal-insulator-metal junction. On the other hand, the electron transport through a Gold-α,ω T3-Gold junction explicitly involves the electronic structure of the molecule which gives rise to step-like features in the current-voltage characteristics. The measured zero bias conductance is interpreted using the scattering theory. At high bias, we discuss two different models: a coherent model where the electron has no time to be completely re-localized in the molecule and a sequential model where the electron is localized in the molecule during the transfer. Finally, we show that the mechanical action of decreasing the inter-electrodes spacing can be used to induce a strong modification of the current-voltage characteristics. (author)

  13. TRANSITIONAL FLOW IN CHANNEL JUNCTIONS

    NI Han-gen; LIU Ya-kun

    2004-01-01

    On the basis of energy and continuity equations a simple one-dimensional formulation was proposed to predict the transitional flow at an open-channel junction. An empilical relation between the junction losses, the junction angle, and the discharge ratio was suggested which agrees well with the experimental results. The results calculated by the present formulation for the depth ratio were compared with the results of earlier one-dimensional formulations and experiments. It is found that the present results coincide better with experiments than those of others.

  14. Current-Voltage Characteristics of MIM(S) Light Emission Tunnel Junctions

    WANG Maoxiang; YU Jianhua; SUN Chengxiu; WU Zonghan

    2001-01-01

    Double-barrier Au/Al2O3/Al/Al2O3/Al and Si-based Au/SiO2/Si light emission tunnel junctions were constructed. Light emission from these junctions was observed successfully. In this paper,we introduced simply the fabrication process of the double-barrier MIMJ and MIS J, and analyzed especially the I- V property and the negative resistance phenomenon (NRP) of these junctions. We concluded that the NRP resulted from obstructive effect of SPP to the electron's tunneling in the insulator layer, which will widen the barrier's width. The NRP was closely connected with the light emission. The SPP was a bridge of light emission and NRP of the junction. Discussion on the NRP was helpful to understand the electron tunneling characteristic and the light emission physical picture of these junctions.

  15. Josephson $\\varphi_{0}$-junction in nanowire quantum dots

    Szombati, D. B.; Nadj-Perge, S.; Car, D.; Plissard, S.R.; Bakkers, E. P. A. M.; Kouwenhoven, L. P.

    2015-01-01

    The Josephson effect describes supercurrent flowing through a junction connecting two superconducting leads by a thin barrier [1]. This current is driven by a superconducting phase difference $\\phi$ between the leads. In the presence of chiral and time reversal symmetry of the Cooper pair tunneling process [2] the current is strictly zero when $\\phi$ vanishes. Only if these underlying symmetries are broken the supercurrent for $\\phi=0$ may be finite [3-5]. This corresponds to a ground state o...

  16. Gap-Junction Channels Dysfunction in Deafness and Hearing Loss

    MARTÍNEZ, Agustín D.; Acuña, Rodrigo; Figueroa, Vania; Maripillan, Jaime; Nicholson, Bruce

    2009-01-01

    Gap-junction channels connect the cytoplasm of adjacent cells, allowing the diffusion of ions and small metabolites. They are formed at the appositional plasma membranes by a family of related proteins named connexins. Mutations in connexins 26, 31, 30, 32, and 43 have been associated with nonsyndromic or syndromic deafness. The majority of these mutations are inherited in an autosomal recessive manner, but a few of them have been associated with dominantly inherited hearing loss. Mutations i...

  17. Monitoring drilling mud composition using flowing liquid junction electrodes

    Jasinski, R.; Fletcher, P.; Vercaemer, C.

    1990-06-27

    The concentration of a chosen ionic component of a drilling mud is determined from the potential difference between an ion selective electrode, selective to the component and a reference electrode, the reference electrode being connected to the mud by a liquid junction through which reference electrolyte flows from the electrode to the mud. The system avoids errors due to undesirable interactions between the mud and the reference electrode materials. (author).

  18. Gap junctions in the cardiovascular and immune systems

    2000-01-01

    Gap junctions are clusters of intercellular channels directly connecting the cytoplasm of adjacent cells. These channels are formed by proteins named connexins and are present in all metazoan organisms where they serve diverse functions ranging from control of cell growth and differentiation to electric conduction in excitable tissues. In this overview we describe the presence of connexins in the cardiovascular and lympho-hematopoietic systems giving the reader a summary of the topics to be c...

  19. Radiation dosimetry using junction field-effect transistor detectors

    The use of junction field effect transistors (JFET) has been studied by connecting them in a bridge circuit. With a suitable back-up circuit, it was possible to measure doses as well as dose-rates. It was possible to alter the sensitivity of the JFET bridge by varying the biasing components of the JFET. Easy temperature compensation was also possible. However, response of the JFET to radiation showed energy dependency similar to that of semiconductor diodes. (author)

  20. Thermal conductance of superlattice junctions

    Lu, Simon; McGaughey, Alan J. H., E-mail: mcgaughey@cmu.edu [Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States)

    2015-05-15

    We use molecular dynamics simulations and the lattice-based scattering boundary method to compute the thermal conductance of finite-length Lennard-Jones superlattice junctions confined by bulk crystalline leads. The superlattice junction thermal conductance depends on the properties of the leads. For junctions with a superlattice period of four atomic monolayers at temperatures between 5 and 20 K, those with mass-mismatched leads have a greater thermal conductance than those with mass-matched leads. We attribute this lead effect to interference between and the ballistic transport of emergent junction vibrational modes. The lead effect diminishes when the temperature is increased, when the superlattice period is increased, and when interfacial disorder is introduced, but is reversed in the harmonic limit.

  1. Thermal conductance of superlattice junctions

    Simon Lu

    2015-05-01

    Full Text Available We use molecular dynamics simulations and the lattice-based scattering boundary method to compute the thermal conductance of finite-length Lennard-Jones superlattice junctions confined by bulk crystalline leads. The superlattice junction thermal conductance depends on the properties of the leads. For junctions with a superlattice period of four atomic monolayers at temperatures between 5 and 20 K, those with mass-mismatched leads have a greater thermal conductance than those with mass-matched leads. We attribute this lead effect to interference between and the ballistic transport of emergent junction vibrational modes. The lead effect diminishes when the temperature is increased, when the superlattice period is increased, and when interfacial disorder is introduced, but is reversed in the harmonic limit.

  2. Experimental demonstration of Aharonov-Casher interference in a Josephson junction circuit

    Pop, I. M.; Douçot, B.; Ioffe, L.; Protopopov, I.; Lecocq, F.; Matei, I.; Buisson, O.; Guichard, W.

    2011-01-01

    A neutral quantum particle with magnetic moment encircling a static electric charge acquires a quantum mechanical phase (Aharonov-Casher effect). In superconducting electronics the neutral particle becomes a fluxon that moves around superconducting islands connected by Josephson junctions. The full understanding of this effect in systems of many junctions is crucial for the design of novel quantum circuits. Here we present measurements and quantitative analysis of fluxon interference patterns...

  3. ESD test for triple-junction solar cells with monolithic diode

    Nozaki, Yukishige; Masui, Hirokazu; Toyoda, Kazuhiro; 野崎 幸重; 増井 博一; 豊田 和弘; Cho, Mengu

    2008-01-01

    Recently many spacecraft use Triple-Junction (TJ) solar cells as their primary electrical power source because of their excellent efficiency. However it is also known that triple-junction solar cells are easy to be broken by a low reverse bias voltage. Therefore a discrete by-pass diode should be connected to every solar cell in parallel for the shadow protection. Under these circumstances, TJ solar cells with integrate Monolithic Diode (MD) have been introduced to market recently. In the CIC...

  4. Electronic thermometry in tunable tunnel junction

    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.

  5. Josephson junctions with ferromagnetic interlayer

    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.

  6. Josephson junctions with ferromagnetic interlayer

    We report on the fabrication of superconductor/insulator/ferromagnetic metal/superconductor (Nb/AlOx/Pd0.82Ni0.18/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 π-coupling is observed for a thickness dF=6 nm of the ferromagnetic Pd0.82Ni0.18 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 Pd0.82Ni0.18 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.

  7. Josephson current in parallel SFS junctions

    Ioselevich, Pavel; Ostrovsky, Pavel; Fominov, Yakov; Feigelman, Mikhail

    We study a Josephson junction between superconductors connected by two parallel ferromagnetic arms. If the ferromagnets are fully polarised, supercurrent can only flow via Cooper pair splitting between the differently polarised arms. The disorder-average current is suppressed, but mesoscopic fluctuations lead to a significant typical current. We extract the typical current from a current-current correlator. The current is proportional to sin2 α / 2 , where α is the angle between the polarisations of the two arms, revealing the spin dependence of crossed Andreev reflection. Compared to an SNS device of the same geometry, the typical SFS current is small by a factor determined by the properties of the superconducting leads alone. The current is insensitive to the flux threading the area between the ferromagnetic arms of the junction. However, if the ferromagnetic arms are replaced by metal with magnetic impurities, or partially polarised ferromagnets, the Josephson current starts depending on the flux with a period of h / e , i.e. twice the superconducting flux quantum.

  8. Neuromuscular junctional disorders.

    Girija, A S; Ashraf, V V

    2008-07-01

    Neuromuscular junctional disorders (NMJ) in children are distinct entity. They may be acquired or hereditary. They pose problem in diagnosis because of the higher occurrence of sero negative Myasthenia Gravis (MG) cases in children. The identity of MusK antibody positivity in a good percentage of sero negative cases further adds to problems in diagnosis. The Congenital Myasthenic Syndrome (CMS) which are rare disorders of hereditary neuromuscular transmission (NMT) has to be differentiated because immunotherapy has no benefit in this group. Molecular genetic studies of these diseases helps to identify specific type of CMS which is important as other drugs like Fluoxetine, Quinidine are found to be effective in some. In infancy, all can manifest as floppy infant syndrome. The important key to diagnosis is by detailed electrophysiological studies including repetitive nerve stimulation at slow and high rates and its response to anticholinesterases and estimation of Acetyl choline receptor antibodies. Other causes of neuromuscular transmission defects viz. snake venom poisoning and that due to drugs are discussed. PMID:18716738

  9. Photoresponse of a Single Y-Junction Carbon Nanotube.

    Samanta, Sudeshna; Saini, Deepika; Singha, Achintya; Das, Kaustuv; Bandaru, Prabhakar R; Rao, Apparao M; Raychaudhuri, Arup Kumar

    2016-07-27

    We report investigation of optical response in a single strand of a branched carbon nanotube (CNT), a Y-junction CNT composed of multiwalled CNTs. The experiment was performed by connecting a pair of branches while grounding the remaining one. Of the three branch combinations, only one combination is optically active which also shows a nonlinear semiconductor-like I-V curve, while the other two branch combinations are optically inactive and show linear ohmic I-V curves. The photoresponse includes a zero-bias photocurrent from the active branch combination. Responsivity of ≈1.6 mA/W has been observed from a single Y-CNT at a moderate bias of 150 mV with an illumination of wavelength 488 nm. The photoresponse experiment allows us to understand the nature of internal connections in the Y-CNT. Analysis of data locates the region of photoactivity at the junction of only two branches and only the combination of these two branches (and not individual branches) exhibits photoresponse upon illumination. A model calculation based on back-to-back Schottky-type junctions at the branch connection explains the I-V data in the dark and shows that under illumination the barriers at the contacts become lowered due to the presence of photogenerated carriers. PMID:27379988

  10. Confocal Annular Josephson Tunnel Junctions

    Monaco, Roberto

    2016-04-01

    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. Confocal Annular Josephson Tunnel Junctions

    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.

  12. Development of Superconducting Tunnel Junction as an Imaging Radiation Detector

    Yamasaki, N. Y.; Rokutanda, E.; Kikuchi, K.; Kushino, A.; Ohashi, T.; Kurakado, M.

    Superconducting tunnel junctions (STJs) as X-ray detectors have been developed mainly aiming at high resolution spectrometers. We archived an energy resolution of 106 eV at 5.9 keV (FWHM) using an STJ developed at Nippon Steel Corporation with a cooled (~ 100K) FET. Furthermore, series-connected STJs as an imaging radiation detector are developed. Both the pulse hight and the rise time of signals from 241Am α-particles irradiated on a series-connected STJ give a good position sensitivity, indicating the intrinsic position resolution less than 0.5 mm

  13. Giant tunnel magneto-resistance in graphene based molecular tunneling junction

    Wang, Bin; Li, Jianwei; Yu, Yunjin; Wei, Yadong; Wang, Jian; Guo, Hong

    2016-02-01

    We propose and theoretically investigate a class of stable zigzag graphene nanoribbon (ZGNR) based molecular magnetic tunneling junctions (MTJs). For those junctions having pentagon-connecting formations, huge tunnel magneto-resistance (TMR) is found. Different from most of the other proposed molecular junctions, the huge TMR in our structures is generic, and is not significantly affected by external parameters such as bias voltage, gate voltage, length of the molecule and width of the ZGNRs. The double pentagon-connecting formation between the molecule and ZGNRs is critical for the remarkable TMR ratio, which is as large as ~2 × 105. These molecular MTJs behave as almost perfect spin filters and spin valve devices. Other connecting formations of the ZGNR based MTJs lead to much smaller TMR. By first principles analysis, we reveal the microscopic physics responsible for this phenomenon.

  14. Gap junctions between CA3 pyramidal cells contribute to network synchronization in neonatal hippocampus.

    Molchanova, Svetlana M; Huupponen, Johanna; Lauri, Sari E; Taira, Tomi

    2016-08-01

    Direct electrical coupling between neurons through gap junctions is prominent during development, when synaptic connectivity is scarce, providing the additional intercellular connectivity. However, functional studies of gap junctions are hampered by the unspecificity of pharmacological tools available. Here we have investigated gap-junctional coupling between CA3 pyramidal cells in neonatal hippocampus and its contribution to early network activity. Four different gap junction inhibitors, including the general blocker carbenoxolone, decreased the frequency of network activity bursts in CA3 area of hippocampus of P3-6 rats, suggesting the involvement of electrical connections in the generation of spontaneous network activity. In CA3 pyramidal cells, spikelets evoked by local stimulation of stratum oriens, were inhibited by carbenoxolone, but not by inhibitors of glutamatergic and GABAergic synaptic transmission, signifying the presence of electrical connectivity through axo-axonic gap junctions. Carbenoxolone also decreased the success rate of firing antidromic action potentials in response to stimulation, and changed the pattern of spontaneous action potential firing of CA3 pyramidal cells. Altogether, these data suggest that electrical coupling of CA3 pyramidal cells contribute to the generation of the early network events in neonatal hippocampus by modulating their firing pattern and synchronization. PMID:26926429

  15. Experimental testing and modeling analysis of solute mixing at water distribution pipe junctions.

    Shao, Yu; Jeffrey Yang, Y; Jiang, Lijie; Yu, Tingchao; Shen, Cheng

    2014-06-01

    Flow dynamics at a pipe junction controls particle trajectories, solute mixing and concentrations in downstream pipes. The effect can lead to different outcomes of water quality modeling and, hence, drinking water management in a distribution network. Here we have investigated solute mixing behavior in pipe junctions of five hydraulic types, for which flow distribution factors and analytical equations for network modeling are proposed. First, based on experiments, the degree of mixing at a cross is found to be a function of flow momentum ratio that defines a junction flow distribution pattern and the degree of departure from complete mixing. Corresponding analytical solutions are also validated using computational-fluid-dynamics (CFD) simulations. Second, the analytical mixing model is further extended to double-Tee junctions. Correspondingly the flow distribution factor is modified to account for hydraulic departure from a cross configuration. For a double-Tee(A) junction, CFD simulations show that the solute mixing depends on flow momentum ratio and connection pipe length, whereas the mixing at double-Tee(B) is well represented by two independent single-Tee junctions with a potential water stagnation zone in between. Notably, double-Tee junctions differ significantly from a cross in solute mixing and transport. However, it is noted that these pipe connections are widely, but incorrectly, simplified as cross junctions of assumed complete solute mixing in network skeletonization and water quality modeling. For the studied pipe junction types, analytical solutions are proposed to characterize the incomplete mixing and hence may allow better water quality simulation in a distribution network. PMID:24675269

  16. The lateral S-(S/F)-S Josephson junctions

    Up to now the proximity effect at the superconductor-ferromagnet (S-F) interface was mainly demonstrated by the transport properties across the S-F interface. We present the results on lateral transport along the S-F interface and its utilization as a Josephson junction. We have prepared Nb based Josephson junctions which consist of Nb micro bridges with a Pd0.95Fe0.05 or Fe strip deposited perpendicular to the bridge. The width of the ferromagnetic strip was varied between 50 and 800 nm. The critical current (IC) of the Nb-Pd0.95Fe0.05 and Nb-Fe bi-layer, respectively, is found to be significantly reduced by the proximity effect with the ferromagnet. We have studied the temperature and magnetic field (B) dependencies of the critical current. In magnetic field an interference pattern IC(B) is observed. In perpendicular magnetic field the junction exhibits IC(B) dependence similar to a Fraunhofer pattern which proves the dc Josephson effect. We also investigate the dependence of IC(B) oscillations on the orientation of the magnetic field. The control of the Josephson junction parameters is provided by third electrode connected to the F strip.

  17. Perfect spin filtering by symmetry in molecular junctions

    Li, Dongzhe; Dappe, Yannick J.; Smogunov, Alexander

    2016-05-01

    Obtaining highly spin-polarized currents in molecular junctions is crucial and important for nanoscale spintronics devices. Motivated by our recent symmetry-based theoretical argument for complete blocking of one spin conductance channel in model molecular junctions [A. Smogunov and Y. J. Dappe, Nano Lett. 15, 3552 (2015), 10.1021/acs.nanolett.5b01004], we explore the generality of the proposed mechanism and the degree of achieved spin-polarized current for realistic molecular junctions made of various ferromagnetic electrodes (Ni, Co, Fe) connected by different molecules (quaterthiophene or p -quaterphenyl). A simple analysis of the spin-resolved local density of states of a free electrode allowed us to identify the Fe(110) as the most optimal electrode, providing perfect spin filtering and high conductance at the same time. These results are confirmed by ab initio quantum transport calculations and are similar to those reported previously for model junctions. It is found, moreover, that the distortion of the p -quaterphenyl molecule plays an important role, reducing significantly the overall conductance.

  18. Host-Bacteria Crosstalk at the Dentogingival Junction

    M. T. Pöllänen

    2012-01-01

    Full Text Available The dentogingival junction is of crucial importance in periodontal host defense both structurally and functionally. Oral bacteria exert a constant challenge to the host cells and tissues at the dentogingival junction. The host response is set up to eliminate the pathogens by the innate and adaptive defense mechanisms. In health, the commensal bacteria and the host defense mechanisms are in a dynamic steady state. During periodontal disease progression, the dental bacterial plaque, junctional epithelium (JE, inflammatory cells, connective tissue, and bone all go through a series of changes. The tissue homeostasis is turned into tissue destruction and progression of periodontitis. The classical study of Slots showed that in the bacterial plaque, the most remarkable change is the shift from gram-positive aerobic and facultatively anaerobic flora to a predominantly gram-negative and anaerobic flora. This has been later confirmed by several other studies. Furthermore, not only the shift of the bacterial flora to a more pathogenic one, but also bacterial growth as a biofilm on the tooth surface, allows the bacteria to communicate with each other and exert their virulence aimed at favoring their growth. This paper focuses on host-bacteria crosstalk at the dentogingival junction and the models studying it in vitro.

  19. Transport properties of molecular junctions

    Zimbovskaya, Natalya A

    2013-01-01

    A comprehensive overview of the physical mechanisms that control electron transport and the characteristics of metal-molecule-metal (MMM) junctions is presented. As far as possible, methods and formalisms presented elsewhere to analyze electron transport through molecules are avoided. This title introduces basic concepts—a description of the electron transport through molecular junctions—and briefly describes relevant experimental methods. Theoretical methods commonly used to analyze the electron transport through molecules are presented. Various effects that manifest in the electron transport through MMMs, as well as the basics of density-functional theory and its applications to electronic structure calculations in molecules are presented. Nanoelectronic applications of molecular junctions and similar systems are discussed as well. Molecular electronics is a diverse and rapidly growing field. Transport Properties of Molecular Junctions presents an up-to-date survey of the field suitable for researchers ...

  20. NbN tunnel junctions

    All-niobium nitride Josephon junctions have been prepared successfully using a new processing called SNOP: Selective Niobium (nitride) Overlap Process. Such a process involves the ''trilayer'' deposition on the whole wafer before selective patterning of the electrodes by optically controlled dry reactive ion etching. Only two photomask levels are need to define an ''overlap'' or a ''cross-type'' junction with a good accuracy. The properties of the niobium nitride films deposited by DC-magnetron sputtering and the surface oxide growth are analysed. The most critical point to obtain high quality and high gap value junctions resides in the early stage of the NbN counterelectrode growth. Some possibilities to overcome such a handicap exist even if the fabrication needs substrate temperatures below 2500C

  1. Gap Junctions in C. elegans

    ChristianC.Naus

    2014-02-01

    Full Text Available As in other multicellular organisms, the nematode Caenorhabditis elegans uses gap junctions to provide direct cell-to-cell contact. The nematode gap junctions are formed by innexins (invertebrate analogs of the connexins; a family of proteins that surprisingly share no primary sequence homology, but do share structural and functional similarity with connexins. The model organism C. elegans contains 25 innexin genes and innexins are found in virtually all cell types and tissues. Additionally, many innexins have dynamic expression patterns during development, and several innexins are essential genes in the nematode. C. elegans is a popular invertebrate model due to several features including a simple anatomy, a complete cell lineage, sequenced genome and an array of genetic resources. Thus the worm has potential to offer valuable insights into the various functions of gap junction mediated intercellular communication.

  2. Ochratoxim A alters cell adhesion and gap junction intercellular communication in MDCK cells

    Ochratoxin A (OTA) is one of the most potent renal carcinogens studied to date, but the mechanism of tumor formation by ochratoxin A remains largely unknown. Cell adhesion and cell-cell communication participate in the regulation of signaling pathways involved in cell proliferation and growth control and it is therefore not surprising that modulation of cell-cell signaling has been implicated in cancer development. Several nephrotoxicants and renal carcinogens have been shown to alter cell-cell signaling by interference with gap junction intercell communication (GJIC) and/or cell adhesion, and the aim of this study was to determine if disruption of cell-cell interactions occurs in kidney epithelial cells in response to OTA treatment. MDCK cells were treated with OTA (0-50 μM) for up to 24 h and gap junction function was analyzed using the scrape-load/dye transfer assay. In addition, expression and intracellular localization of Cx43, E-cadherin and β-catenin were determined by immunoblot and immunofluorescence analysis. A clear decrease in the distance of dye transfer was evident following treatment with OTA at concentrations/incubation times which did not affect cell viability. Consistent with the functional inhibition of GJIC, treatment with OTA resulted in a dose-dependent decrease in Cx43 expression. In contrast to Cx43, OTA did not alter total amount of the adherens junction proteins E-cadherin and β-catenin. Moreover, Western blot analysis of Triton X-100 soluble and insoluble protein fractions did not indicate translocation of cell adhesion molecules from the membrane to the cytoplasm. However, a ∼78 kDa fragment of β-catenin was detected in the detergent soluble fraction, indicating proteolytic cleavage of β-catenin. Immunofluorescence analysis also revealed changes in the pattern of both β-catenin and E-cadherin labeling, suggesting that OTA may alter cell-adhesion. Taken together, these data support the hypothesis that disruption of cell

  3. Capacitively Coupled Hot-Electron Nanobolometer with SIN Tunnel Junctions

    Kuzmin, Leonid S.; Fominsky, M.; Kalabukhov, A.; Golubev, D.; Tarasov, M.

    2003-02-01

    A capacitively coupled hot-electron nanobolometer (CC-HEB) is the simplest and most effective antenna-coupled bolometer. The bolometer consists of a small absorber connected to the superconducting antenna by tunnel junctions. The tunnel junctions used for high-frequency coupling also give perfect thermal isolation of hot electrons in the small volume of the absorber. The same tunnel junctions are used for temperature measurements and electron cooling. This bolometer does not suffer from the frequency limitations in the submillimeter range due to the high potential barrier of the tunnel junctions as does the microbolometer with Andreev mirrors (A-HEB), which is limited by the superconducting gap. Theoretical analyses show that the two-junction configuration more than doubles the sensitivity of the bolometer in current-biased mode compared to the single-junction configuration used for A-HEB. Another important advantage of CC-HEB is its simple two-layer technology for sample fabrication. Samples were fabricated with an absorber made of a bilayer of Cr and Al to match the impedance of the antenna. Electrodes were made of Al and tunnel junctions were formed over the Al oxide layer. The coupling capacitances of the tunnel junctions, C ≍ 20 fF, in combination with the inductance of the 10 μm absorber create a bandpass filter with a central frequency around 300 GHz. Bolometers are integrated with log-periodic and double-dipole planar antennas made of Au. The temperature response of bolometer structures was measured at temperatures down to 256 mK. In our experiment we observed dV/dT=1.3 mV/K, corresponding to responsivity S=0.2.109 V/W. For amplifier noise Vna=3nV/Hz1/2 at 1 kHz the estimated total noise equivalent power is NEP=1.5.10-17 W/Hz1/2. The intrinsic bolometer self noise Vnbol=0.5 nV/Hz1/2 corresponds to NEP=3.10-18 W/Hz1/2. For microwave evaluation of bolometer sensitivity we used a black body radiation source comprising a thin NiCr stimulator placed on the

  4. Learning theories reveal loss of pancreatic electrical connectivity in diabetes as an adaptive response

    Goel, Pranay

    2013-01-01

    Cells of almost all solid tissues are connected with gap junctions which permit the direct transfer of ions and small molecules, integral to regulating coordinated function in the tissue. The pancreatic islets of Langerhans are responsible for secreting the hormone insulin in response to glucose stimulation. Gap junctions are the only electrical contacts between the beta-cells in the tissue of these excitable islets. It is generally believed that they are responsible for synchrony of the membrane voltage oscillations among beta-cells, and thereby pulsatility of insulin secretion. Most attempts to understand connectivity in islets are often interpreted, bottom-up, in terms of measurements of gap junctional conductance. This does not, however explain systematic changes, such as a diminished junctional conductance in type 2 diabetes. We attempt to address this deficit via the model presented here, which is a learning theory of gap junctional adaptation derived with analogy to neural systems. Here, gap junctions ...

  5. Gap junction networks in mushroom bodies participate in visual learning and memory in Drosophila

    Liu, Qingqing; Yang, Xing; Tian, Jingsong; Gao, Zhongbao; Wang, Meng; Li, Yan; Guo, Aike

    2016-01-01

    Gap junctions are widely distributed in the brains across species and play essential roles in neural information processing. However, the role of gap junctions in insect cognition remains poorly understood. Using a flight simulator paradigm and genetic tools, we found that gap junctions are present in Drosophila Kenyon cells (KCs), the major neurons of the mushroom bodies (MBs), and showed that they play an important role in visual learning and memory. Using a dye coupling approach, we determined the distribution of gap junctions in KCs. Furthermore, we identified a single pair of MB output neurons (MBONs) that possess a gap junction connection to KCs, and provide strong evidence that this connection is also required for visual learning and memory. Together, our results reveal gap junction networks in KCs and the KC-MBON circuit, and bring new insight into the synaptic network underlying fly’s visual learning and memory. DOI: http://dx.doi.org/10.7554/eLife.13238.001 PMID:27218450

  6. Josephson junctions based on pnictide superconductors

    Josephson junctions are a powerful tool for understanding more about the physical behaviour of pnictide superconductors. We built different kinds of Josephson junctions based on pnictide thin films. Planar junctions, edge type junctions, and junctions on bicrystalline substrates were prepared. We present manufacturing techniques and also the electronical properties of the different junctions and compare them. The measurement of I-V-characteristics show a strong excess current. We have to mind this when calculating the IcRN product. The effective IcRN values are 6.5 μV for the grain boundary junction, 7.9 μV for the planar structure, and 7.5 μV for the edge junction.

  7. Dynamics of pi-junction interferometer circuits

    Kornkev, V.K.; Mozhaev, P.B.; Borisenko, I.V.; Ovsyannikov, G.A.; Pedersen, Niels Falsig

    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...... dependence on magnetic field are discussed. Experimental results for dc interferometers with 0 and pi high-T-c bi-crystal Josephson junctions are reported and discussed in comparison with numerical simulation....

  8. Nano-Molecular Junctions on STM Tips

    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.

  9. Interfacial thermal transport in atomic junctions

    Zhang, Lifa; Keblinski, Pawel; Wang, Jian-Sheng; Li, Baowen

    2011-01-01

    We study ballistic interfacial thermal transport across atomic junctions. Exact expressions for phonon transmission coefficients are derived for thermal transport in one-junction and two-junction chains, and verified by numerical calculation based on a nonequilibrium Green's function method. For a single-junction case, we find that the phonon transmission coefficient typically decreases monotonically with increasing freqency. However, in the range between equal frequency spectrum and equal ac...

  10. Resistance of Single Ag Nanowire Junctions and Their Role in the Conductivity of Nanowire Networks.

    Bellew, Allen T; Manning, Hugh G; Gomes da Rocha, Claudia; Ferreira, Mauro S; Boland, John J

    2015-11-24

    Networks of silver nanowires appear set to replace expensive indium tin oxide as the transparent conducting electrode material in next generation devices. The success of this approach depends on optimizing the material conductivity, which until now has largely focused on minimizing the junction resistance between wires. However, there have been no detailed reports on what the junction resistance is, nor is there a known benchmark for the minimum attainable sheet resistance of an optimized network. In this paper, we present junction resistance measurements of individual silver nanowire junctions, producing for the first time a distribution of junction resistance values and conclusively demonstrating that the junction contribution to the overall resistance can be reduced beyond that of the wires through standard processing techniques. We find that this distribution shows the presence of a small percentage (6%) of high-resistance junctions, and we show how these may impact the performance of network-based materials. Finally, through combining experiment with a rigorous model, we demonstrate the important role played by the network skeleton and the specific connectivity of the network in determining network performance. PMID:26448205

  11. Josephson tunnel junction microwave attenuator

    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 biased...

  12. Dynamics of pi-junction interferometer circuits

    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...

  13. delta-biased Josephson tunnel junctions

    Monaco, R.; Mygind, Jesper; Koshelet, V.;

    2010-01-01

    Abstract: The behavior of a long Josephson tunnel junction drastically depends on the distribution of the dc bias current. We investigate the case in which the bias current is fed in the central point of a one-dimensional junction. Such junction configuration has been recently used to detect the...

  14. Soliton excitations in Josephson tunnel junctions

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

    1982-01-01

    A detailed numerical study of a sine-Gordon model of the Josephson tunnel junction is compared with experimental measurements on junctions with different L / λJ ratios. The soliton picture is found to apply well on both relatively long (L / λJ=6) and intermediate (L / λJ=2) junctions. We find good...

  15. Soliton bunching in annular Josephson junctions

    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 to...

  16. Innexin gap junctions in nerve cells coordinate spontaneous contractile behavior in Hydra polyps

    Takaku, Yasuharu

    2014-01-07

    Nerve cells and spontaneous coordinated behavior first appeared near the base of animal evolution in the common ancestor of cnidarians and bilaterians. Experiments on the cnidarian Hydra have demonstrated that nerve cells are essential for this behavior, although nerve cells in Hydra are organized in a diffuse network and do not form ganglia. Here we show that the gap junction protein innexin-2 is expressed in a small group of nerve cells in the lower body column of Hydra and that an anti-innexin-2 antibody binds to gap junctions in the same region. Treatment of live animals with innexin-2 antibody eliminates gap junction staining and reduces spontaneous body column contractions. We conclude that a small subset of nerve cells, connected by gap junctions and capable of synchronous firing, act as a pacemaker to coordinate the contraction of the body column in the absence of ganglia.

  17. Transient magnetic tunneling mediated by a molecular bridge in the junction region

    Kalvová, A.; Špička, V.; Velický, B.

    2014-07-01

    This paper extends our recent theoretical study of transient currents in molecular bridge junctions [1] to magnetic tunneling. Presently, we calculate the excess magnetic tunneling through the molecular bridge shunting the junction. The system is represented by two ferromagnetic electrodes bridged by a molecular size island with one electronic level and a local Hubbard type correlation. The island is linked with the electrodes by tunneling junctions whose coupling strength is assumed to undergo rapid changes affecting the connectivity of the system. We employ the non-equilibrium Green's functions. The numerical solution is obtained solving the real-time Dyson equation in the integro-differential form self-consistently. The switching events controlling the junctions give rise to transient changes of magnetisation of the island. They strongly depend on the static galvanic bias between the electrodes, mutual alignment of their magnetisation and on the time scale of the switching.

  18. Osmotic forces and gap junctions in spreading depression: a computational model

    Shapiro, B. E.

    2001-01-01

    In a computational model of spreading depression (SD), ionic movement through a neuronal syncytium of cells connected by gap junctions is described electrodiffusively. Simulations predict that SD will not occur unless cells are allowed to expand in response to osmotic pressure gradients and K+ is allowed to move through gap junctions. SD waves of [K+]out approximately 25 to approximately 60 mM moving at approximately 2 to approximately 18 mm/min are predicted over the range of parametric values reported in gray matter, with extracellular space decreasing up to approximately 50%. Predicted waveform shape is qualitatively similar to laboratory reports. The delayed-rectifier, NMDA, BK, and Na+ currents are predicted to facilitate SD, while SK and A-type K+ currents and glial activity impede SD. These predictions are consonant with recent findings that gap junction poisons block SD and support the theories that cytosolic diffusion via gap junctions and osmotic forces are important mechanisms underlying SD.

  19. Innexin gap junctions in nerve cells coordinate spontaneous contractile behavior in Hydra polyps.

    Takaku, Yasuharu; Hwang, Jung Shan; Wolf, Alexander; Böttger, Angelika; Shimizu, Hiroshi; David, Charles N; Gojobori, Takashi

    2014-01-01

    Nerve cells and spontaneous coordinated behavior first appeared near the base of animal evolution in the common ancestor of cnidarians and bilaterians. Experiments on the cnidarian Hydra have demonstrated that nerve cells are essential for this behavior, although nerve cells in Hydra are organized in a diffuse network and do not form ganglia. Here we show that the gap junction protein innexin-2 is expressed in a small group of nerve cells in the lower body column of Hydra and that an anti-innexin-2 antibody binds to gap junctions in the same region. Treatment of live animals with innexin-2 antibody eliminates gap junction staining and reduces spontaneous body column contractions. We conclude that a small subset of nerve cells, connected by gap junctions and capable of synchronous firing, act as a pacemaker to coordinate the contraction of the body column in the absence of ganglia. PMID:24394722

  20. About Connections

    Kathleen S Rockland

    2015-05-01

    Full Text Available Despite the attention attracted by connectomics, one can lose sight of the very real questions concerning What are connections? In the neuroimaging community, structural connectivity is ground truth and underlying constraint on functional or effective connectivity. It is referenced to underlying anatomy; but, as increasingly remarked, there is a large gap between the wealth of human brain mapping and the relatively scant data on actual anatomical connectivity. Moreover, connections have typically been discussed as pairwise, point x projecting to point y (or: to points y and z, or more recently, in graph theoretical terms, as nodes or regions and the interconnecting edges. This is a convenient shorthand, but tends not to capture the richness and nuance of basic anatomical properties as identified in the classic tradition of tracer studies. The present short review accordingly revisits connectional weights, heterogeneity, reciprocity, topography, and hierarchical organization, drawing on concrete examples. The emphasis is on presynaptic long-distance connections, motivated by the intention to probe current assumptions and promote discussions about further progress and synthesis.

  1. Molecular transport junctions: vibrational effects

    Transport of electrons in a single molecule junction is the simplest problem in the general subject area of molecular electronics. In the past few years, this area has been extended to probe beyond the simple tunnelling associated with large energy gaps between electrode Fermi level and molecular levels, to deal with smaller gaps, with near-resonance tunnelling and, particularly, with effects due to interaction of electronic and vibrational degrees of freedom. This overview is devoted to the theoretical and computational approaches that have been taken to understanding transport in molecular junctions when these vibronic interactions are involved. After a short experimental overview, and discussion of different test beds and measurements, we define a particular microscopic model Hamiltonian. That overall Hamiltonian can be used to discuss all of the phenomena dealt with subsequently. These include transition from coherent to incoherent transport as electron/vibration interaction increases in strength, inelastic electron tunnelling spectroscopy and its interpretation and measurement, affects of interelectronic repulsion treated at the Hubbard level, noise in molecular transport junctions, non-linear conductance phenomena, heating and heat conduction in molecular transport junctions and current-induced chemical reactions. In each of these areas, we use the same simple model Hamiltonian to analyse energetics and dynamics. While this overview does not attempt survey the literature exhaustively, it does provide appropriate references to the current literature (both experimental and theoretical). We also attempt to point out directions in which further research is required to answer cardinal questions concerning the behaviour and understanding of vibrational effects in molecular transport junctions. (topical review)

  2. Fabrication of high quality ferromagnetic Josephson junctions

    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.

  3. Fabrication of high quality ferromagnetic Josephson junctions

    We present ferromagnetic Nb/Al2O3/Ni60Cu40/Nb Josephson junctions (SIFS) with an ultrathin Al2O3 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 c spreads less than 2% was obtained

  4. HR Connect

    US Agency for International Development — HR Connect is the USAID HR personnel system which allows HR professionals to process HR actions related to employee's personal and position information. This system...

  5. RWGSCAT - RECTANGULAR WAVEGUIDE JUNCTION SCATTERING PROGRAM

    Hoppe, D. J.

    1994-01-01

    In order to optimize frequency response and determine the tolerances required to meet RF specifications, accurate computer modeling of passive rectangular waveguide components is often required. Many rectangular waveguide components may be represented either exactly or approximately as a number of different size rectangular waveguides which are connected in series. RWGSCAT, Rectangular WaveGuide junction SCATtering program, solves for the scattering properties of a waveguide device. This device must consist of a number of rectangular waveguide sections of different cross sectional area which are connected in series. Devices which fall into this category include step transformers, filters, and smooth or corrugated rectangular horns. RWGSCAT will model such devices and accurately predict the reflection and transmission characteristics, taking into account higher order (other than dominant TE 10) mode excitation if it occurs, as well as multiple reflections and stored energy at each discontinuity. For devices which are large with respect to the wavelength of operation, the characteristics of the device may be required for computing a higher order mode or a number of higher order modes exciting the device. Such interactions can be represented by defining a scattering matrix for each discontinuity in the device, and then cascading the individual scattering matrices in order to determine the scattering matrix for the overall device. The individual matrices are obtained using the mode matching method. RWGSCAT is written in FORTRAN 77 for IBM PC series and compatible computers running MS-DOS. It has been successfully compiled and implemented using Lahey FORTRAN 77 under MS-DOS. A sample MS-DOS executable is provided on the distribution medium. It requires 377K of RAM for execution. Sample input data is also provided on the distribution medium. The standard distribution medium for this program is one 5.25 inch 360K MS-DOS format diskette. The contents of the diskette are

  6. Fabrication-process-induced variations of Nb/Al/AlOx/Nb Josephson junctions in superconductor integrated circuits

    Currently, superconductor digital integrated circuits fabricated at HYPRES, Inc. can operate at clock frequencies approaching 40 GHz. The circuits present multilayered structures containing tens of thousands of Nb/Al/AlOx/Nb Josephson junctions (JJs) of various sizes interconnected by four Nb wiring layers, resistors, and other circuit elements. In order to be fully operational, the integrated circuits should be fabricated such that the critical currents of the JJs are within the tight design margins and the proper relationships between the critical currents of JJs of different sizes are preserved. We present experimental data and discuss mechanisms of process-induced variations of the critical current and energy gap of Nb/Al/AlOx/Nb JJs in integrated circuits. We demonstrate that the Josephson critical current may depend on the type and area of circuit elements connected to the junction, on the circuit pattern, and on the step in the fabrication process at which the connection is made. In particular, we discuss the influence of (a) the junction base electrode connection to the ground plane, (b) the junction counter electrode connection to the ground plane, and (c) the counter electrode connection to the Ti/Au or Ti/Pd/Au contact pads by Nb wiring. We show that the process-induced changes of the properties of Nb/Al/AlOx/Nb junctions are caused by migration of impurity atoms (hydrogen) between the different layers comprising the integrated circuits.

  7. Electrochemical Growth of Ag Junctions and Diffusion Limited Aggregate (DLA) Fractal Simulation

    Olson, Zak; Tuppan, Sam; Kim, Woo-Joong; Seattle University Team

    2015-03-01

    We attempt construction of a single atom connection between two copper wires. By applying a DC voltage across the wires when immersed in a silver nitrate solution, we deposit silver until a junction is formed. The deposited silver forms a fractal structure that can be simulated with a diffusion limited aggregation model.

  8. Metamorphic Ga0.76In0.24As/GaAs0.75Sb0.25 tunnel junctions grown on GaAs substrates

    García, I.; Geisz, J. F.; France, R. M.; Kang, J.; Wei, S.-H.; Ochoa, M.; Friedman, D. J.

    2014-08-01

    Lattice-matched and pseudomorphic tunnel junctions have been developed in the past for application in a variety of semiconductor devices, including heterojunction bipolar transistors, vertical cavity surface-emitting lasers, and multijunction solar cells. However, metamorphic tunnel junctions have received little attention. In 4-junction Ga0.51In0.49P/GaAs/Ga0.76In0.24As/Ga0.47In0.53As inverted-metamorphic solar cells (4J-IMM), a metamorphic tunnel junction is required to series connect the 3rd and 4th junctions. We present a tunnel junction based on a metamorphic Ga0.76In0.24As/GaAs0.75Sb0.25 structure for this purpose. This tunnel junction is grown on a metamorphic Ga0.76In0.24As template on a GaAs substrate. The band offsets in the resulting type-II heterojunction are calculated using the first-principles density functional method to estimate the tunneling barrier height and assess the performance of this tunnel junction against other material systems and compositions. The effect of the metamorphic growth on the performance of the tunnel junctions is analyzed using a set of metamorphic templates with varied surface roughness and threading dislocation density. Although the metamorphic template does influence the tunnel junction performance, all tunnel junctions measured have a peak current density over 200 A/cm2. The tunnel junction on the best template has a peak current density over 1500 A/cm2 and a voltage drop at 15 A/cm2 (corresponding to operation at 1000 suns) lower than 10 mV, which results in a nearly lossless series connection of the 4th junction in the 4J-IMM structure.

  9. Rapid disruption of intestinal epithelial tight junction and barrier dysfunction by ionizing radiation in mouse colon in vivo: protection by N-acetyl-l-cysteine.

    Shukla, Pradeep K; Gangwar, Ruchika; Manda, Bhargavi; Meena, Avtar S; Yadav, Nikki; Szabo, Erzsebet; Balogh, Andrea; Lee, Sue Chin; Tigyi, Gabor; Rao, RadhaKrishna

    2016-05-01

    The goals of this study were to evaluate the effects of ionizing radiation on apical junctions in colonic epithelium and mucosal barrier function in mice in vivo. Adult mice were subjected to total body irradiation (4 Gy) with or without N-acetyl-l-cysteine (NAC) feeding for 5 days before irradiation. At 2-24 h postirradiation, the integrity of colonic epithelial tight junctions (TJ), adherens junctions (AJ), and the actin cytoskeleton was assessed by immunofluorescence microscopy and immunoblot analysis of detergent-insoluble fractions for TJ and AJ proteins. The barrier function was evaluated by measuring vascular-to-luminal flux of fluorescein isothiocyanate (FITC)-inulin in vivo and luminal-to-mucosal flux in vitro. Oxidative stress was evaluated by measuring protein thiol oxidation. Confocal microscopy showed that radiation caused redistribution of occludin, zona occludens-1, claudin-3, E-cadherin, and β-catenin, as well as the actin cytoskeleton as early as 2 h postirradiation, and this effect was sustained for at least 24 h. Feeding NAC before irradiation blocked radiation-induced disruption of TJ, AJ, and the actin cytoskeleton. Radiation increased mucosal permeability to inulin in colon, which was blocked by NAC feeding. The level of reduced-protein thiols in colon was depleted by radiation with a concomitant increase in the level of oxidized-protein thiol. NAC feeding blocked the radiation-induced protein thiol oxidation. These data demonstrate that radiation rapidly disrupts TJ, AJ, and the actin cytoskeleton by an oxidative stress-dependent mechanism that can be prevented by NAC feeding. PMID:26822914

  10. Seebeck effect in molecular junctions

    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. (topical review)

  11. How coherent are Josephson junctions?

    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.

  12. Electron transport in molecular junctions

    Jin, Chengjun

    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......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...... the lowest unoccupied molecular level (LUMO) of the 44BP molecule hybridizes strongly with Ni 3d orbitals, the gating is auxiliary by the so-called spinterface. Finally, the correlation effect of the image charge beyond the energy level renormalization has been studied. It is shown that the finite response...

  13. Seebeck effect in molecular junctions

    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.

  14. Mechanical behavior of carbon nanotube and graphene junction as a building block for 3D carbon nanostructures

    Mina Moradi; Jamshid Aghazadeh Mohandesi

    2015-01-01

    The incorporation of defects in junction area of 1D and 2D carbon nanostructures has a major impact on properties of their 3D structures. In the present study, molecular dynamics simulation is utilized to examine the mechanical behavior of graphene sheet (GS) in carbon nanotube (CNT)-GS junctions. The tensile load was applied along the GS in connection with CNTs of different chiralities. The adaptive intermolecular reactive empirical bond order potential was chosen to model C-C interactions. ...

  15. Counting Statistics in Nanoscale Junctions

    Liu, Yu-Shen; Chen, Yu-Chang

    2010-01-01

    We present first-principles calculations for moments of the current up to the third order in atomic-scale junctions. The quantum correlations of the current are calculated using the current operator in terms of the wave functions obtained self-consistently within the static density-functional theory. We investigate the relationships of the conductance, the second, and the third moment of the current for carbon atom chains of various lengths bridging two metal electrodes in the linear and nonl...

  16. Imaging of cervicothoracic junction trauma

    Kaewlai, Rathachai

    2013-01-01

    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...

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

    Gerya, Taras; Burov, Evgueni

    2015-04-01

    -branch junction formation and evolution by using high-resolution 3D numerical mechanical experiments that take into account realistic thermo-rheological structure and rheology of the lithosphere. We find that two major types of quadruple and triple junctions are formed under bi-directional or multidirectional far-field stress field: (i) plate rifting junctions are formed by the initial plate fragmentation and can be subsequently re-arranged into (ii) oceanic spreading junctions controlled by the new oceanic crust accretion. In particular, we document initial formation and destabilization of quadruple R-R-R-R junctions as initial plate rifting structures under bi-directional extension. In most cases, quadruple plate rifting junctions rapidly (typically within 1-2 Myr) evolve towards formation of two diverging triple oceanic spreading junctions connected by a linear spreading center lengthening with time. This configuration remains stable over long time scales. However, under certain conditions, quadruple junctions may also remain relatively stable. Asymmetric stretching results in various configurations, for example formation of "T-junctions" with trans-extensional components and combination of fast and slow spreading ridges. Combined with plume impingement, this scenario evolves in realistic patterns closely resembling observed plate dynamics. In particular, opening of the Red Sea and of the Afar rift system find a logical explanation within a single model. Numerical experiments also suggest that several existing oceanic spreading junctions form as the result of plate motions rearrangements after which only one of two plates spreading along the ridge become subjected to bi-directional spreading.

  18. Multi-terminal Josephson junctions with ferromagnetic elements

    The interplay between magnetism and superconductivity in heterostructures has attracted considerable interest since the discovery of the 0-π transition in superconductor-ferromagnet (SF) contacts. Here we investigate the supercurrent in systems of multiple tunnel junctions in the framework of the quantum circuit theory. The considered network consists of two superconducting and two ferromagnetic reservoirs with non-collinear magnetization direction connected by tunnel contacts to a normal metal. We find and interesting interplay between the superconducting phase difference and the relative magnetization angle, which manifests itself in the current phase relation and the critical current

  19. Thermoelectric efficiency of molecular junctions.

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

    2016-09-21

    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. PMID:27420149

  20. Gendered Connections

    Jensen, Steffen Bo

    2009-01-01

    This article explores the gendered nature of urban politics in Cape Town by focusing on a group of female, township politicians. Employing the Deleuzian concept of `wild connectivity', it argues that these politically entrepreneurial women were able to negotiate a highly volatile urban landscape by...... space also drew on quite traditional notions of female respectability. Furthermore, the article argues, the form of wild connectivity to an extent was a function of the political transition, which destabilized formal structures of gendered authority. It remains a question whether this form of...

  1. Connected Traveler

    2016-06-01

    The Connected Traveler framework seeks to boost the energy efficiency of personal travel and the overall transportation system by maximizing the accuracy of predicted traveler behavior in response to real-time feedback and incentives. It is anticipated that this approach will establish a feedback loop that 'learns' traveler preferences and customizes incentives to meet or exceed energy efficiency targets by empowering individual travelers with information needed to make energy-efficient choices and reducing the complexity required to validate transportation system energy savings. This handout provides an overview of NREL's Connected Traveler project, including graphics, milestones, and contact information.

  2. Multi-Junction Switching in Bi2Sr1.6La0.4CuO6+δ Intrinsic Josephson Junctions

    Kashiwaya, Hiromi; Matsumoto, Tetsuro; Shibata, Hajime; Eisaki, Hiroshi; Yoshida, Yoshiyuki; Kambara, Hiroshi; Kawabata, Shiro; Kashiwaya, Satoshi

    2010-04-01

    We study the dynamics of multi-junction switching (MJS): several intrinsic Josephson junctions (IJJs) in an array switch to the finite voltage state simultaneously. The number of multi-switching junctions (N) was successfully tuned by changing the load resistance serially connected to an Bi2Sr1.6La0.4CuO6+δ IJJ array. The independence of the escape rates of N in the macroscopic quantum tunneling regime indicates that MJS is a successive switching process rather than a collective process. The origin of MJS is explained by the gradient of a load curve and the relative magnitudes of the switching currents of quasiparticle branches in the current-voltage plane.

  3. Nonmechanical Conductance Switching in a Molecular Tunnel Junction.

    Baratz, Adva; Baer, Roi

    2012-02-16

    We present a molecular junction composed of a donor (polyacetylene strands) and an acceptor (malononitrile) connected together via a benzene ring and coupled weakly to source and drain electrodes on each side, for which a gate electrode induces intramolecular charge transfer, switching reversibly the character of conductance. Using a new brand of density functional theory, for which orbital energies are similar to the quasiparticle energies, we show that the junction displays a single, gate-tunable differential conductance channel in a wide energy range. The gate field must align parallel to the displacement vector between donors and acceptor to affect their potential difference; for strong enough fields, spontaneous intramolecular electron transfer occurs. This event radically affects conductance, reversing the charge of carriers, enabling a spin-polarized current channel. We discuss the physical principles controlling the operation of the junction and find interplay of quantum interference, charging, Coulomb blockade, and electron-hole binding energy effects. We expect that this switching behavior is a generic property for similar donor-acceptor systems of sufficient stability. PMID:26286054

  4. AlGaAs/GaAs tunnel junctions in a 4-J tandem solar cell

    Lü Siyu; Qu Xiaosheng

    2011-01-01

    The Ⅲ-Ⅴ compound tandem solar cell is a third-generation new style solar cell with ultra-high efficiency.The energy band gaps of the sub-cells in a GaInP/GaAs/InGaAs/Ge 4-J tandem solar cell are 1.8,1.4,1.0and 0.7 eV,respectively.In order to match the currents between sub-cells,tunnel junctions are used to connect the sub-cells.The characteristics of the tunnel junction,the material used in the tunnel junction,the compensation of the tunnel junction to the overall cell's characteristics,the tunnel junction's influence on the current density of sub-cells and the efficiency increase are discussed in the paper.An A1GaAs/GaAs tunnel junction is selected to simulate the cell's overall characteristics by PC 1 D,current densities of 16.02,17.12,17.75 and 17.45 mA/cm2 are observed,with a Voc of 3.246 V,the energy conversion efficiency under AM0 is 33.9%.

  5. Algorithms for Junctions in Directed Acyclic Graphs

    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.

  6. 78 FR 55684 - ConnectED Workshop

    2013-09-11

    ... National Telecommunications and Information Administration ConnectED Workshop AGENCY: National... in the United States to next- generation broadband. This Notice announces that the ConnectED Workshop... ConnectED Workshop will discuss the growing bandwidth needs of K-12 schools as more schools use...

  7. Hysteresis development in superconducting Josephson junctions

    The resistively and capacitive shunted junction model is used to investigate hysteresis development in superconducting Josephson junctions. Two empirical formulas that relate the hysteresis width and the quasi-particle diffusion length in terms of the junctions electrical parameters, temperature and frequency are obtained. The obtained formulas provide a simple tool to investigate the full potentials of the hysteresis phenomena. (author). 9 refs, 3 figs

  8. The Fluxion in a Curved Josephson Junction

    Dobrowolski, Tomasz

    2014-01-01

    The curved Josephson junction is described. In the framework of the Maxwell equations the equation that describes the influence of the curvature on the fluxion motion was obtained. The method of geometrical reduction of the sine-Gordon model from three to lower dimensional manifold was applied to the long Josephson junction. It was argued that the geometrical reduction describes the junctions with slowly varying curvatures.

  9. Palladium Electrodes for Molecular Tunnel Junctions

    Chang, Shuai; Sen, Suman; Zhang, Peiming; Gyarfas, Brett; Ashcroft, Brian; Lefkowitz, Steven; Peng, Hongbo; Lindsay, Stuart

    2012-01-01

    Gold has been the metal of choice for research on molecular tunneling junctions, but it is incompatible with CMOS fabrication because it forms deep level traps in silicon. Palladium electrodes do not contaminate silicon, and also give higher tunnel current signals in the molecular tunnel junctions we have studied. The result is cleaner signals in a recognition-tunneling junction that recognizes the four natural DNA bases as well as 5-methyl cytosine, with no spurious background signals. More ...

  10. Electron optics with ballistic graphene junctions

    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.

    2016-01-01

    Electrons transmitted across a ballistic semiconductor junction undergo refraction, analogous to light rays across an optical boundary. A pn junction theoretically provides the equivalent of a negative index medium, enabling novel electron optics such as negative refraction and perfect (Veselago) lensing. In graphene, the linear dispersion and zero-gap bandstructure admit highly transparent pn junctions by simple electrostatic gating, which cannot be achieved in conventional semiconductors. M...

  11. Gap Junctions Couple Astrocytes and Oligodendrocytes

    Orthmann-Murphy, Jennifer L.; ABRAMS, CHARLES K.; Scherer, Steven S.

    2008-01-01

    In vertebrates, a family of related proteins called connexins form gap junctions (GJs), which are intercellular channels. In the central nervous system (CNS), GJs couple oligodendrocytes and astrocytes (O/A junctions) and adjacent astrocytes (A/A junctions), but not adjacent oligodendrocytes, forming a “glial syncytium.” Oligodendrocytes and astrocytes each express different connexins. Mutations of these connexin genes demonstrate that the proper functioning of myelin and oligodendrocytes req...

  12. String junction as a baryonic constituent

    Kalashnikova, Yu S

    1995-01-01

    We extend the model for QCD string with quarks to consider the Mercedes Benz string configuration describing the three-quark baryon. Under the assumption of adiabatic separation of quark and string junction motion we formulate and solve the classical equation of motion for the junction.We dare to quantize the motion of the junction, and discuss the impact of these modes on the baryon spectra.

  13. Structure and signaling at hydroid polyp-stolon junctions, revisited

    Katherine L. Harmata

    2015-09-01

    Full Text Available The gastrovascular system of colonial hydroids is central to homeostasis, yet its functional biology remains poorly understood. A probe (2′,7′-dichlorodihydrofluorescein diacetate for reactive oxygen species (ROS identified fluorescent objects at polyp-stolon junctions that emit high levels of ROS. A nuclear probe (Hoechst 33342 does not co-localize with these objects, while a mitochondrial probe (rhodamine 123 does. We interpret these objects as mitochondrion-rich cells. Confocal microscopy showed that this fluorescence is situated in large columnar cells. Treatment with an uncoupler (2,4-dinitrophenol diminished the ROS levels of these cells relative to background fluorescence, as did removing the stolons connecting to a polyp-stolon junction. These observations support the hypothesis that the ROS emanate from mitochondrion-rich cells, which function by pulling open a valve at the base of the polyp. The open valve allows gastrovascular fluid from the polyp to enter the stolons and vice versa. The uncoupler shifts the mitochondrial redox state in the direction of oxidation, lowering ROS levels. By removing the stolons, the valve is not pulled open, metabolic demand is lowered, and the mitochondrion-rich cells slowly regress. Transmission electron microscopy identified mitochondrion-rich cells adjacent to a thick layer of mesoglea at polyp-stolon junctions. The myonemes of these myoepithelial cells extend from the thickened mesoglea to the rigid perisarc on the outside of the colony. The perisarc thus anchors the myoepithelial cells and allows them to pull against the mesoglea and open the lumen of the polyp-stolon junction, while relaxation of these cells closes the lumen.

  14. Microwave photonics with Josephson junction arrays

    Zueco, David; Solano, Enrique; García-Ripoll, Juan José

    2011-01-01

    We introduce an architecture for a photonic crystal in the microwave regime based on superconducting transmission lines interrupted by Josephson junctions. A study of the scattering properties of a single junction in the line shows that the junction behaves as a perfect mirror when the photon frequency matches the Josephson plasma frequency. We generalize our calculations to periodic arrangements of junctions, demonstrating that they can be used for tunable band engineering, forming what we call a quantum circuit crystal. As a relevant application, we discuss the creation of stationary entanglement between two superconducting qubits interacting through a disordered media.

  15. Thermodynamics of two-dimensional Josephson junctions

    We derive the effective free energy of a two-dimensional Josephson junction in the presence of an external current and predict that the junction has a phase transition at a temperature TJ below the bulk transition temperature Tc. In the range TJ c is reduced by thermal fluctuations; for a junction of size L, Ic ∝ Lb(T) where b(T) J c vanishes at L → ∞) while 0 J. Our results may account for the absence of an observable supercurrent at temperatures below Tc in YBa2Cu3Ox-and Bi2Sr2CaCu2O8-based junctions. (orig.)

  16. Analysis of vertebrate gap junction protein.

    Finbow, M E; Shuttleworth, J.; Hamilton, A.E.; Pitts, J D

    1983-01-01

    A new method for the purification of gap junctions is described which depends on the extraction of cell monolayers or tissue homogenates with Triton X-100. The major band on SDS-polyacrylamide gel electrophoresis (PAGE) of junctional preparations from a variety of vertebrate sources has an apparent mol. wt. of 16,000 (16 K). Further evidence for the junctional origin of the 16 K protein is provided by the results of four different experimental approaches. (i) The junctions form a sharp band i...

  17. Effects of spin-orbit coupling and spatial symmetries on the Josephson current in SNS junctions

    Rasmussen, Asbjørn; Danon, Jeroen; Suominen, Henri; Nichele, Fabrizio; Kjaergaard, Morten; Flensberg, Karsten

    2016-04-01

    We present an analysis of the symmetries of the interference pattern of critical currents through a two-dimensional superconductor-semiconductor-superconductor junction, taking into account Rashba and Dresselhaus spin-orbit interaction, an arbitrarily oriented magnetic field, disorder, and structural asymmetries. We relate the symmetries of the pattern to the absence or presence of symmetries in the Hamiltonian, which provides a qualitative connection between easily measurable quantities and the spin-orbit coupling and other symmetries of the junction. We support our analysis with numerical calculations of the Josephson current based on a perturbative expansion up to eighth order in tunnel coupling between the normal region and the superconductors.

  18. Gap Junction Contributions to the Goldfish Electroretinogram at the Photopic Illumination Level

    Kim, Doh-Yeon; Jung, Chang-Sub

    2012-01-01

    Understanding how the b-wave of the electroretinogram (ERG) is generated by full-field light stimulation is still a challenge in visual neuroscience. To understand more about the origin of the b-wave, we studied the contributions of gap junctions to the ERG b-wave. Many types of retinal neurons are connected to similar and different neighboring neurons through gap junctions. The photopic (cone-dominated) ERG, stimulated by a small light beam, was recorded from goldfish (Carassius auratus) usi...

  19. Black Diamonds at Brane Junctions

    Chamblin, Andrew; Csaki, Csaba; Erlich, Joshua; Timothy J. Hollowood

    2000-01-01

    We discuss the properties of black holes in brane-world scenarios where our universe is viewed as a four-dimensional sub-manifold of some higher-dimensional spacetime. We consider in detail such a model where four-dimensional spacetime lies at the junction of several domain walls in a higher dimensional anti-de Sitter spacetime. In this model there may be any number p of infinitely large extra dimensions transverse to the brane-world. We present an exact solution describing a black p-brane wh...

  20. Effects of junction geometry in crossover temperature to macroscopic quantum tunneling regime of intrinsic Josephson junctions

    We investigated the phase dynamics of Bi-2212 intrinsic Josephson junctions with two types of junction geometry. We found that a crossover temperature to the macroscopic quantum tunneling regime was quite different between the two types of junction geometry. The observed behavior is discussed in terms of an edge effect in long Josephson junctions dependent on the junction geometry. We investigated the phase dynamics of long intrinsic Josephson junctions, which were fabricated on a narrow bridge structure of Bi2Sr2CaCu2Oy (Bi-2212) single crystals by using a focused ion-beam etching. We measured the probability distribution of the switching events from the zero-voltage state for two types of junction geometry. One is a junction where the bridge width (L1) is larger than the Josephson penetration depth, λJ, and the distance between two slits (L2) is comparable to λJ, while the other is a junction where L1 is comparable to λJ and L2 is larger than λJ. We found that a crossover temperature from the thermally activated regime to the macroscopic quantum tunneling regime was quite different between the two types of junction geometry. We discuss the observed behavior in terms of an edge effect in long Josephson junctions dependent on the junction geometry.

  1. Electron transport through molecular junctions

    At present, metal–molecular tunnel junctions are recognized as important active elements in molecular electronics. This gives a strong motivation to explore physical mechanisms controlling electron transport through molecules. In the last two decades, an unceasing progress in both experimental and theoretical studies of molecular conductance has been demonstrated. In the present work we give an overview of theoretical methods used to analyze the transport properties of metal–molecular junctions as well as some relevant experiments and applications. After a brief general description of the electron transport through molecules we introduce a Hamiltonian which can be used to analyze electron–electron, electron–phonon and spin–orbit interactions. Then we turn to description of the commonly used transport theory formalisms including the nonequilibrium Green’s functions based approach and the approach based on the “master” equations. We discuss the most important effects which could be manifested through molecules in electron transport phenomena such as Coulomb, spin and Frank–Condon blockades, Kondo peak in the molecular conductance, negative differential resistance and some others. Bearing in mind that first principles electronic structure calculations are recognized as the indispensable basis of the theory of electron transport through molecules, we briefly discuss the main equations and some relevant applications of the density functional theory which presently is often used to analyze important characteristics of molecules and molecular clusters. Finally, we discuss some kinds of nanoelectronic devices built using molecules and similar systems such as carbon nanotubes, various nanowires and quantum dots.

  2. Grand Junction Remedial Action Program

    The Grand Junction Remedial Action Program (hereinafter referred to as the Program) originated in 1972 due to a recognized need to reduce the levels of radiation found in some of the structures identified in Grand Junction, Colorado that were constructed in part with uranium mill tailings. Out of over 640 locations eventually identified as qualifying for corrective action, the Program performed remedial construction on 594 of them. The owners of over 45 unremediated structures either did not wish to participate in the voluntary Program, or the structures were torn down, burned down, or were abandoned before the Program could take action on them. Because this was the first remedial action program of its type, and because its task was to reduce the radiation levels as soon as practical, there was no time for lengthly research and development of remedial methods or techniques. Trial and error combined with basic engineering and health physics produced a Program that learned as it progressed. At a cost of $22.7 million over a 15-year period, a substantial portion of the community had radiation exposure reduced because many public buildings such as schools, churches, and businesses, as well as private residences were remediated. 21 refs., 10 figs., 6 tabs

  3. Linker-dependent Junction Formation Probability in Single-Molecule Junctions

    Yoo, Pil Sun; Kim, Taekyeong [HankukUniversity of Foreign Studies, Yongin (Korea, Republic of)

    2015-01-15

    We compare the junction formation probabilities of single-molecule junctions with different linker molecules by using a scanning tunneling microscope-based break-junction technique. We found that the junction formation probability varies as SH > SMe > NH2 for the benzene backbone molecule with different types of anchoring groups, through quantitative statistical analysis. These results are attributed to different bonding forces according to the linker groups formed with Au atoms in the electrodes, which is consistent with previous works. Our work allows a better understanding of the contact chemistry in the metal.molecule junction for future molecular electronic devices.

  4. Genetics Home Reference: junctional epidermolysis bullosa

    ... Junctional epidermolysis bullosa results from mutations in the LAMA3 , LAMB3 , LAMC2 , and COL17A1 genes. Mutations in each ... of all cases of junctional epidermolysis bullosa . The LAMA3 , LAMB3 , and LAMC2 genes each provide instructions for ...

  5. Gap junctions and connexin-interacting proteins

    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

  6. Electrophysiological study in neuromuscular junction disorders

    Cherian, Ajith; Baheti, Neeraj N.; Iype, Thomas

    2013-01-01

    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 i...

  7. Shot noise in YBCO bicrystal Josephson junctions

    Constantinian, K.Y.; Ovsyannikov, G.A.; Borisenko, I.V.; Mygind, Jesper; Pedersen, Niels Falsig

    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 me...

  8. Hall effect in NS and SNS junctions

    Zhou, F.; Spivak, B.

    1997-01-01

    Hall effect in SN and SNS junctions is considered. It is shown that at small temperature the Hall voltage is significantly suppressed as compared to its normal metal value. The time dependence of the Hall voltage in SNS junctions has a form of narrow pulses with the Josephson frequency.

  9. Zipper and freeway shear zone junctions

    Passchier, Cees; Platt, John

    2016-04-01

    Ductile shear zones are usually presented as isolated planar high-strain domains in a less deformed wall rock, characterised by shear sense indicators such as characteristic deflected foliation traces. Many shear zones, however, form branched systems and if movement on such branches is contemporaneous, the resulting geometry can be complicated and lead to unusual fabric geometries in the wall rock. For Y-shaped shear zone junctions with three simultaneously operating branches, and with slip directions at a high angle to the branch line, eight basic types of shear zone triple junctions are possible, divided into three groups. The simplest type, called freeway junctions, have similar shear sense on all three branches. If shear sense is different on the three branches, this can lead to space problems. Some of these junctions have shear zone branches that join to form a single branch, named zipper junctions, or a single shear zone which splits to form two, known as wedge junctions. Closing zipper junctions are most unusual, since they form a non-active high-strain zone with opposite deflection of foliations. Shear zipper and shear wedge junctions have two shear zones with similar shear sense, and one with the opposite sense. All categories of shear zone junctions show characteristic flow patterns in the shear zone and its wall rock. Shear zone junctions with slip directions normal to the branch line can easily be studied, since ideal sections of shear sense indicators lie in the plane normal to the shear zone branches and the branch line. Expanding the model to allow slip oblique and parallel to the branch line in a full 3D setting gives rise to a large number of geometries in three main groups. Slip directions can be parallel on all branches but oblique to the branch line: two slip directions can be parallel and a third oblique, or all three branches can have slip in different directions. Such more complex shear zone junctions cannot be studied to advantage in a

  10. Discordant connections

    Arora-Jonsson, Seema

    2009-01-01

    The importance of gender-equality and of women’s work in relation to the environment are considered to be crucial questions for development in ‘third world’ rural societies. ‘Development’ and a certain standard of welfare make these issues appear to be less urgent in a wealthier country like Sweden. In this paper I trace some of the contradictions and connections in the ways in which gender equality is conceptualised in women’s struggles vis á vis environmental issues in rural areas in Swede...

  11. Measuring quantum systems with tunnel junctions

    Full text: We present a formalism that allows to describe a quantum system modulating the transmission of a tunnel junction. The tunnel junction acts as an environment for the quantum system. Contrary to the conventional approach to open quantum systems we retain a degree of freedom of the environment, the charge passed through the junction, after averaging over the bath degrees of freedom, employing a projection operator technique. The resulting object characterizing the joint dynamics of the system and the charge is the charge specific density matrix. We derive a master equation describing the time evolution of the charge specific density matrix. We consider two examples of quantum systems coupled to the junction: a spin and a harmonic oscillator. In the spin case we are able to analyze a quantum measurement process in detail. For the oscillator we investigate the noise in the tunnel junction induced by the coupling. (author)

  12. Spin accumulation in triplet Josephson junction

    We employ a Hamiltonian method to study the equal-spin pairing triplet Josephson junction with different orbital symmetries of pair potentials. Both the spin/charge supercurrent and possible spin accumulation at the interface of the junction are analyzed by means of the Keldysh Green's function. It is found that a spontaneous angle-resolved spin accumulation can form at the junction's interface when the orbital symmetries of Cooper pairs in two triplet superconductors are different, the physical origin is the combined effect of the different orbital symmetries and different spin states of Cooper pairs due to the misalignment of two d vectors in triplet leads. An abrupt current reversal effect induced by misalignment of d vectors is observed and can survive in a strong interface barrier scattering because the zero-energy state appears at the interface of the junction. These properties of the p-wave Josephson junction may be helpful for identifying the order parameter symmetry.

  13. Regulation of gap junction channels by infectious agents and inflammation in the CNS

    Paul eCastellano

    2014-05-01

    Full Text Available Gap junctions are conglomerates of intercellular channels that connect the cytoplasm of two or more cells, and facilitate the transfer of second messengers, small peptides and RNA resulting in metabolic and electrical coordination. In general, loss of gap junctional communication (GJC has been associated with cellular damage and inflammation resulting in compromise of physiological functions. Recently, it has become evident that gap junction channels also play a critical role in the pathogenesis of infectious diseases and associated inflammation. Several pathogens use the transfer of intracellular signals through GJ channels to spread infection and toxic signals that amplify inflammation to neighboring cells. Thus, identification of the mechanisms by which several infectious agents alter GJC could result in new potential therapeutic approaches to reduce inflammation and their pathogenesis.

  14. Experimental study of noise and Josephson oscillation linewidths in bicrystal YBCO junctions

    Constatinian, K.Y.; Ovsyannikov, G.A.; Borisenko, I.V.; Pogosyan, N.G.; Hakuhoumian, A.A.; Yagoubov, P.; Mygind, J.; Pedersen, Niels Falsig

    range up to voltages V = 2 mV in connection with low-voltage noise rise. Both the features observed, the linewidth broadening and the excess noise over the noise level of thermal fluctuations, are discussed in terms of multiple Andreev reflection, giving rise to a nonequilibrium shot noise-the case...... which may take place in the d-wave superconducting junctions. Experimental results on noise performance are also compared with the qualitatively similar dependences of the current noise, known for the s-superconducting ballistic point-like or diffusive-type SNS junctions, where the excess low......-voltage noise is manifested due to multiple Andreev reflections. Increasing the operating temperature, the thermal (equilibrium) fluctuations were found to predominate, resulting in a decrease of ratio Deltaf(J)/Deltaf(RSJ). The characteristics of the ac Josephson effect in FITS junctions measured at submm...

  15. Synchronization dynamics on the picosecond timescale in coupled Josephson junction neurons

    Segall, Ken; Kaplan, Steven; Svitelskiy, Oleksiy; Khadka, Shreeya; Crotty, Patrick; Schult, Daniel

    2016-01-01

    Conventional digital computation is rapidly approaching physical limits for speed and energy dissipation. Here we fabricate and test a simple neuromorphic circuit that models neuronal somas, axons and synapses with superconducting Josephson junctions. Similar to biological neurons, two mutually-coupled Josephson junction neurons synchronize in one of two states, symmetric (in-phase) or anti-symmetric (anti-phase). The experimental alteration of the delay and strength of the connecting synapses can toggle the system back and forth in a collective behavior known as a phase-flip bifurcation. Firing synchronization states are calculated >70,000 times faster than conventional digital approaches. With their speed and very low energy dissipation (10-17 Joules/spike), Josephson junction neurons are now established as a viable approach for vast improvements in neuronal computation as well as applications in neuromorphic computing.

  16. Phonon effects on the current noise spectra and the ac conductance of a single molecular junction

    By using nonequilibrium Green’s functions and the equation of motion method, we formulate a self-consistent field theory for the electron transport through a single-molecule junction (SMJ) coupled with a vibrational mode. We show that the nonequilibrium dynamics of the phonons in a strong electron–phonon coupling regime can be taken into account appropriately in this self-consistent perturbation theory, and the self-energy of the phonons is connected with the current fluctuations in the molecular junction. We calculate the finite-frequency nonsymmetrized noise spectra and the ac conductance, which reveal a wealth of inelastic electron tunneling characteristics on the absorption and emission properties of this SMJ. In the presence of a finite bias voltage and the electron tunneling current, the vibration mode of the molecular junction is heated and driven to an unequilibrated state. The influences of unequilibrated phonons on the current and the noise spectra are investigated. (paper)

  17. Macroscopic quantum tunneling in Josephson tunnel junctions and Coulomb blockade in single small tunnel junctions

    Experiments investigating the process of macroscopic quantum tunneling in a moderately-damped, resistively shunted, Josephson junction are described, followed by a discussion of experiments performed on very small capacitance normal-metal tunnel junctions. The experiments on the resistively-shunted Josephson junction were designed to investigate a quantum process, that of the tunneling of the Josephson phase variable under a potential barrier, in a system in which dissipation plays a major role in the dynamics of motion. All the parameters of the junction were measured using the classical phenomena of thermal activation and resonant activation. Theoretical predictions are compared with the experimental results, showing good agreement with no adjustable parameters; the tunneling rate in the moderately damped (Q ∼ 1) junction is seen to be reduced by a factor of 300 from that predicted for an undamped junction. The phase is seen to be a good quantum-mechanical variable. The experiments on small capacitance tunnel junctions extend the measurements on the larger-area Josephson junctions from the region in which the phase variable has a fairly well-defined value, i.e. its wavefunction has a narrow width, to the region where its value is almost completely unknown. The charge on the junction becomes well-defined and is predicted to quantize the current through the junction, giving rise to the Coulomb blockade at low bias. I present the first clear observation of the Coulomb blockade in single junctions. The electrical environment of the tunnel junction, however, strongly affects the behavior of the junction: higher resistance leads are observed to greatly sharpen the Coulomb blockade over that seen with lower resistance leads. I present theoretical descriptions of how the environment influences the junctions; comparisons with the experimental results are in reasonable agreement

  18. Chaos in junctions and devices

    The plan of the paper is as follows. Section 2 is an introduction into chaos in dissipative systems with an emphasis on period doubling and intermittency. The logistic map and the circle map are discussed and their significance as describing systems of continuous dynamics is emphasized. Section 3 is subdivided into two parts after the introduction of the RSJ equations. The first is on the ac driven Josephson junction without a dc bias and the second on the same with a dc current. Each of these subdivisions includes a discussion of experiments as well. There is also a section on investigations that do not fit into either of the above categories. Section 4 is devoted to the dc-SQUID, in the first part as a magnetic flux gauge and in the second as a four dimensional dynamical system, which can be simulated with great accuracy and compared with one dimensional models. (orig./BUD)

  19. Cylindrical Josephson junctions in magnetic fields

    The radial Josephson current I/sub J/ between co-axial cylinders was measured as a function of axial and azimuthal magnetic fields. The junctions were of two types: 0.25 mm diameter Nb-oxide-Sn single junctions and 0.25 mm film diameter Nb-oxide-Sn film double junctions. The Sn film of the single junctions was 160 nm or 200 nm. The Sn films of the double junctions were both either 155 nm or 230 nm. For a pair of cylinders I/sub J/ is zero except when both members are in the same fluxoid quantum state. When I/sub J/not equal to O, the relative phase is independent of aximuthal angle theta. In all measurements the cylinders were in fluxoid state zero. There was a critical value of axial field B/sub s/ which destroyed the Josephson coupling for each junction. This critical field is smallest for the outer tin junction of the double junction. It depends upon geometry and film thickness but is independent of the value of I/sub J/. The calculated value of the Gibbs function per unit volume of the tin films is, however, nearly the same for all junctions at their respective critical fields. Th Josephson current for the 160 nm Sn film single cylindrical junction was measured as a function of axial field B/sub z/ and azimuthal field B/sub theta/. When the axial field was zero the Josephson current as a function of azimuthal field showed the Fraunhofer like pattern of a flat junction in a magnetic field. As the axial field was increased, the central lobe of the Fraunhofer pattern decreased and disappeared at the critical field leaving the side lobes broadened. It is well known that a Josephson junction may switch to the voltage state at any current less than the maximum Josephson current. For some cylindrical junctions the switching currents are not continuously distributed but discrete with certain values occurring repeatedly. This observation is not understood

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

    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

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

    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.

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

    Elfers, Kristin; Marr, Isabell; 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

  3. From four- to two-channel Kondo effect in junctions of XY spin chains

    Giuliano, Domenico; Sodano, Pasquale; Tagliacozzo, Arturo; Trombettoni, Andrea

    2016-08-01

    We consider the Kondo effect in Y-junctions of anisotropic XY models in an applied magnetic field along the critical lines characterized by a gapless excitation spectrum. We find that, while the boundary interaction Hamiltonian describing the junction can be recasted in the form of a four-channel, spin-1/2 antiferromagnetic Kondo Hamiltonian, the number of channels effectively participating in the Kondo effect depends on the chain parameters, as well as on the boundary couplings at the junction. The system evolves from an effective four-channel topological Kondo effect for a junction of XX-chains with symmetric boundary couplings into a two-channel one at a junction of three quantum critical Ising chains. The effective number of Kondo channels depends on the properties of the boundary and of the bulk. The XX-line is a "critical" line, where a four-channel topological Kondo effect can be recovered by fine-tuning the boundary parameter, while along the line in parameter space connecting the XX-line and the critical Ising point the junction is effectively equivalent to a two-channel topological Kondo Hamiltonian. Using a renormalization group approach, we determine the flow of the boundary couplings, which allows us to define and estimate the critical couplings and Kondo temperatures of the different Kondo (pair) channels. Finally, we study the local transverse magnetization in the center of the Y-junction, eventually arguing that it provides an effective tool to monitor the onset of the two-channel Kondo effect.

  4. Contact geometry and electronic transport properties of Ag–benzene–Ag molecular junctions

    Highlights: ► We simulate Ag–benzene–Ag junctions with different contact geometries. ► Moderate benzene–Ag interactions can be realized for adsorptions through Ag adatoms. ► Molecular orbitals dominating the low-bias conductance match the contact symmetry. ► Three contact geometries deliver similar conductance consistent with the experiments. - Abstract: Contact geometry and the electronic transport properties of Ag–benzene–Ag molecular junctions have been investigated by using first-principles quantum transport simulations. Our calculations show that a moderate benzene–silver interaction can be achieved when benzene is adsorbed on the Ag(1 1 1) surface through adatoms. In this case three symmetric Ag–benzene–Ag junction models can be constructed, in which the molecule is connected to the electrodes through one or two Ag adatoms on each side. Although the contribution to the transmission around the Fermi level made by the benzene molecular orbitals depends on the number of Ag adatoms and the detailed binding configuration, the transmission coefficients at the Fermi level of the three junctions are calculated to be respectively 0.20, 0.18 and 0.16. These values are well consistent with the experimental ones of 0.24 ± 0.08. Our results thus demonstrate that the conductance of Ag–benzene–Ag junctions is rather stable regardless of the molecule/electrode contact geometry.

  5. Symmetry-derived half-metallicity in atomic and molecular junctions.

    Smogunov, Alexander; Dappe, Yannick J

    2015-05-13

    Achieving highly spin-polarized electric currents in atomic-scale junctions is of great importance in the field of nanoelectronics and spintronics. Based on robust symmetry considerations, we propose a mechanism to block completely one of spin conduction channels for a broad class of atomic and molecular junctions bridging two ferromagnetic electrodes. This particular behavior is due to the wave function orthogonality between spin up s-like states in ferromagnetic electrode and available π channels in the junction. As a consequence, the system would ideally yield 100% spin-polarized current, with a junction acting thus as a "half-metallic" conductor. Using ab initio electron transport calculations, we demonstrate this principle on two examples: (i) a short carbon chain and (ii) a π-conjugated molecule (polythiophene) connected either to model semi-infinite Ni wires or to realistic Ni(111) electrodes. It is also predicted that such atomic-scale junctions should lead to very high (ideally, infinite) magneto-resistance ratios since the electric current gets fully blocked if two electrodes have antiparallel magnetic alignment. PMID:25871804

  6. Lateral V/VOx/V Tunnel Junctions Formed by Anodic Oxidation

    Kirkwood, David; West, Kevin; Lu, Jiwei; Wolf, Stuart

    2008-03-01

    Anodization has been found to be a simple and cost effective technique to produce oxide films of many transition metals. In this work, we have used anodic oxidation as a means of fabricating lateral V/VOx/V junctions. Vanadium wires grown by ion beam deposition were patterned by lithography and an active working window was defined on the wire. VOx was then grown under galvanostatic control in a two electrode electrochemical micro-cell. A droplet of oxygen rich saturated Boric acid was used as the electrolyte to electrically connect the Vandium working electrode to a Platinum wire counter electrode. A constant current of approximately 100 μA/cm^2 was maintained through the cell for various amounts of time. Electrical measurements of the resulting V/VOx/V junctions indicate a metal to insulator transition (MIT) near 340 ^oK that is similar to the structural phase transition and accompanied MIT of VO2 which occurs at this temperature. A 4-fold change in resistance is observed in the junctions. Below this transition temperature a typical junction behavior is observed with a dramatic change in resistance state from high to low with increasing applied current. This non-linear IV characteristic on the junction with a size of 5 μm by 15 μm suggests that the anodized VOx film behaves like a tunneling barrier.

  7. Electric field breakdown in single molecule junctions.

    Li, Haixing; Su, Timothy A; Zhang, Vivian; Steigerwald, Michael L; Nuckolls, Colin; Venkataraman, Latha

    2015-04-22

    Here we study the stability and rupture of molecular junctions under high voltage bias at the single molecule/single bond level using the scanning tunneling microscope-based break-junction technique. We synthesize carbon-, silicon-, and germanium-based molecular wires terminated by aurophilic linker groups and study how the molecular backbone and linker group affect the probability of voltage-induced junction rupture. First, we find that junctions formed with covalent S-Au bonds are robust under high voltage and their rupture does not demonstrate bias dependence within our bias range. In contrast, junctions formed through donor-acceptor bonds rupture more frequently, and their rupture probability demonstrates a strong bias dependence. Moreover, we find that the junction rupture probability increases significantly above ∼1 V in junctions formed from methylthiol-terminated disilanes and digermanes, indicating a voltage-induced rupture of individual Si-Si and Ge-Ge bonds. Finally, we compare the rupture probabilities of the thiol-terminated silane derivatives containing Si-Si, Si-C, and Si-O bonds and find that Si-C backbones have higher probabilities of sustaining the highest voltage. These results establish a new method for studying electric field breakdown phenomena at the single molecule level. PMID:25675085

  8. Supercurrent decay in extremely underdamped Josephson junctions

    We present an experimental study of the effective dissipation relevant in the thermally activated supercurrent decay of extremely underdamped Josephson junctions. Data referring to the supercurrent decay of Nb/AlOx/Nb Josephson junctions are compared with the Kramers theory. Our measurements allow us to obtain the open-quotes effectiveclose quotes resistance to be used in the resistively shunted junction model that results to be the subgap resistance due to the presence of thermally activated quasiparticles. The extremely low dissipation level obtained at low temperatures renders our result quite interesting in view of experiments in the quantum limit. copyright 1998 The American Physical Society

  9. δ-biased Josephson tunnel junctions

    The behavior of a long Josephson tunnel junction drastically depends on the distribution of the dc bias current. We investigate the case in which the bias current is fed in the central point of a one-dimensional junction. Such junction configuration has been recently used to detect the persistent currents circulating in a superconducting loop. Analytical and numerical results indicate that the presence of fractional vortices leads to remarkable differences from the conventional case of uniformly distributed dc bias current. The theoretical findings are supported by detailed measurements on a number of δ-biased samples having different electrical and geometrical parameters.

  10. Plasticity of single-atom Pb junctions

    Müller, M.; Salgado, C.; Néel, N.; Palacios, J. J.; Kröger, J.

    2016-06-01

    A low-temperature scanning tunneling microscope was used to fabricate atomic contacts on Pb(111). Conductance characteristics of the junctions were simultaneously recorded with forming and subsequent breaking of the contacts. A pronounced hysteresis effect in conductance traces was observed from junctions comprising the clean Pb(111) surface. The hysteretic behavior was less profound in contacts to single Pb atoms adsorbed to Pb(111). Density-functional calculations reproduced the experimental results by performing a full ab initio modeling of plastic junction deformations. A comprehensive description of the experimental findings was achieved by considering different atomic tip apex geometries.

  11. Graded junction termination extensions for electronic devices

    Merrett, J. Neil (Inventor); Isaacs-Smith, Tamara (Inventor); Sheridan, David C. (Inventor); Williams, John R. (Inventor)

    2007-01-01

    A graded junction termination extension in a silicon carbide (SiC) semiconductor device and method of its fabrication using ion implementation techniques is provided for high power devices. The properties of silicon carbide (SiC) make this wide band gap semiconductor a promising material for high power devices. This potential is demonstrated in various devices such as p-n diodes, Schottky diodes, bipolar junction transistors, thyristors, etc. These devices require adequate and affordable termination techniques to reduce leakage current and increase breakdown voltage in order to maximize power handling capabilities. The graded junction termination extension disclosed is effective, self-aligned, and simplifies the implementation process.

  12. Palladium electrodes for molecular tunnel junctions.

    Chang, Shuai; Sen, Suman; Zhang, Peiming; Gyarfas, Brett; Ashcroft, Brian; Lefkowitz, Steven; Peng, Hongbo; Lindsay, Stuart

    2012-10-26

    Gold has been the metal of choice for research on molecular tunneling junctions, but it is incompatible with complementary metal-oxide-semiconductor fabrication because it forms deep level traps in silicon. Palladium electrodes do not contaminate silicon, and also give higher tunnel current signals in the molecular tunnel junctions that we have studied. The result is cleaner signals in a recognition-tunneling junction that recognizes the four natural DNA bases as well as 5-methyl cytosine, with no spurious background signals. More than 75% of all the recorded signal peaks indicate the base correctly. PMID:23037952

  13. Palladium electrodes for molecular tunnel junctions

    Gold has been the metal of choice for research on molecular tunneling junctions, but it is incompatible with complementary metal–oxide–semiconductor fabrication because it forms deep level traps in silicon. Palladium electrodes do not contaminate silicon, and also give higher tunnel current signals in the molecular tunnel junctions that we have studied. The result is cleaner signals in a recognition-tunneling junction that recognizes the four natural DNA bases as well as 5-methyl cytosine, with no spurious background signals. More than 75% of all the recorded signal peaks indicate the base correctly. (paper)

  14. An Efficient Solution-Processed Intermediate Layer for Facilitating Fabrication of Organic Multi-Junction Solar Cells

    Ning Li; Baran, Derya; Forberich, Karen;

    2013-01-01

    ):poly(styrenesulfonate) (PEDOT:PSS) is demonstrated for series-connected multi-junction organic solar cells (OSCs). Drying at 80 °C in air is sufficient for this solution-processed IML to obtain excellent functionality and reliability, which allow the use of most of high performance donor materials in the tandem structure. An...

  15. Simultaneous description of conductance and thermopower in single-molecule junctions from many-body ab initio calculations

    Jin, Chengjun; Markussen, Troels; Thygesen, Kristian Sommer

    2014-01-01

    We investigate the electronic conductance and thermopower of a single-molecule junction consisting of bis-(4-aminophenyl) acetylene (B4APA) connected to gold electrodes. We use nonequilibrium Green's function methods in combination with density-functional theory (DFT) and the many-body GW...

  16. Influence of drugs on gap junctions in glioma cell lines and primary astrocytes in vitro

    Zahra eMoinfar; Hannes eDambach; Pedro Michael Faustmann

    2014-01-01

    Gap junctions (GJs) are hemichannels on cell membrane. Once they are intercellulary connected to the neighboring cells, they build a functional syncytium which allows rapid transfer of ions and molecules between cells. This characteristic makes GJs a potential modulator in proliferation, migration, and development of the cells. So far, several types of GJs are recognized on different brain cells as well as in glioma. Astrocytes, as one of the major cells that maintain neuronal homeostasis, ex...

  17. Estimation of the junctional resistance between electrically coupled receptor cells in Necturus taste buds

    1995-01-01

    Junctional resistance between coupled receptor cells in Necturus taste buds was estimated by modeling the results from single patch pipette voltage clamp studies on lingual slices. The membrane capacitance and input resistance of coupled taste receptor cells were measured to monitor electrical coupling and the results compared with those calculated by a simple model of electrically coupled taste cells. Coupled receptor cells were modeled by two identical receptor cells connected via a junctio...

  18. Full range of proximity effect probed with Superconductor/Graphene/Superconductor junctions

    Li, Chuan; Guéron, S.; Chepelianskii, A.; Bouchiat, H.

    2016-01-01

    The high tunability of the density of states of graphene makes it an ideal probe of quantum transport in different regimes. In particular, the supercurrent that can flow through a non-superconducting (N) material connected to two superconducting electrodes, crucially depends on the lenghth of the N relative to the superconducting coherence length. Using graphene as the N material we have investigated the full range of the superconducting proximity effect, from short to long diffusive junction...

  19. Current trends in salivary gland tight junctions.

    Baker, Olga J

    2016-01-01

    Tight junctions form a continuous intercellular barrier between epithelial cells that is required to separate tissue spaces and regulate selective movement of solutes across the epithelium. They are composed of strands containing integral membrane proteins (e.g., claudins, occludin and tricellulin, junctional adhesion molecules and the coxsackie adenovirus receptor). These proteins are anchored to the cytoskeleton via scaffolding proteins such as ZO-1 and ZO-2. In salivary glands, tight junctions are involved in polarized saliva secretion and barrier maintenance between the extracellular environment and the glandular lumen. This review seeks to provide an overview of what is currently known, as well as the major questions and future research directions, regarding tight junction expression, organization and function within salivary glands. PMID:27583188

  20. Josephson tunnel junctions in niobium films

    A method of fabricating stable Josephson tunnel junctions with reproducible characteristics is described. The junctions have a sandwich structure consisting of a vacuum evaporated niobium film, a niobium oxide layer produced by the glow discharge method and a lead film deposited by vacuum evaporation. Difficulties in producing thin-film Josephson junctions are discussed. Experimental results suggest that the lower critical field of the niobium film is the most essential parameter when evaluating the quality of these junctions. The dependence of the lower critical field on the film thickness and on the Ginzburg-Landau parameter of the film is studied analytically. Comparison with the properties of the evaporated films and with the previous calculations for bulk specimens shows that the presented model is applicable for most of the prepared samples. (author)

  1. Molecular junctions: Single-molecule contacts exposed

    Nichols, Richard J.; Higgins, Simon J.

    2015-05-01

    Using a scanning tunnelling microscopy-based method it is now possible to get an atomistic-level description of the most probable binding and contact configuration for single-molecule electrical junctions.

  2. Chirality effect in disordered graphene ribbon junctions

    We investigate the influence of edge chirality on the electronic transport in clean or disordered graphene ribbon junctions. By using the tight-binding model and the Landauer-Büttiker formalism, the junction conductance is obtained. In the clean sample, the zero-magnetic-field junction conductance is strongly chirality-dependent in both unipolar and bipolar ribbons, whereas the high-magnetic-field conductance is either chirality-independent in the unipolar or chirality-dependent in the bipolar ribbon. Furthermore, we study the disordered sample in the presence of magnetic field and find that the junction conductance is always chirality-insensitive for both unipolar and bipolar ribbons with adequate disorders. In addition, the disorder-induced conductance plateaus can exist in all chiral bipolar ribbons provided the disorder strength is moderate. These results suggest that we can neglect the effect of edge chirality in fabricating electronic devices based on the magnetotransport in a disordered graphene ribbon. (paper)

  3. Superconducting switch made of graphene nanoribbon junctions

    Liang, Qifeng; Dong, Jinming

    2008-09-01

    The transmission of superconductor-graphene nanoribbon-superconductor junctions (SGS) has been studied by the non-equilibrium Green's function method. It is found that the on-site potential U in the center zigzag graphene nanoribbon (ZGNR) of the SGS junction plays an important role in the magnitude of the supercurrent Ic. As the effective Fermi energy μeff (μeff = μF-U) goes from negative to positive, the SGS junction would suddenly transform from an 'OFF' state to an 'ON' state. And, as μeff increases further, the Ic will continue to increase. This switching behavior of the SGS junction shares the same origin with the zigzag GNR valley-isospin valve (Rycerz et al 2007 Nat. Phys. 3 172). Besides the valley-isospin, the density of states will also have an effect on the suppression of Ic.

  4. Bosons on the lattice: a new approach for connected Tomonaga-Luttinger liquid systems

    With the motivation of overcoming difficulties in studying systems of several one dimensional Tomonaga Luttinger liquid wires connected locally at a junction, we construct quadratic lattice field theories for the single non-chiral/chiral wire, the three wire fork and the chiral box junction. For a fork consisting of three identical non-chiral wires, we find that the permutation symmetries of the system, together with the requirement of charge and current continuity, determine the terms in the action governing the dynamics of the fields adjacent to the junction. These results are generalised to the case of N ≥ 3 identical (as well as different) TLL wires. A study of the chiral box junction circuit model reveals that junctions of several chiral wires can be formed by relating the TLL interaction parameters of their constituents. (author)

  5. Controllable spin transport in ferromagnetic graphene junctions

    Yokoyama, Takehito

    2008-01-01

    We study spin transport in normal/ferromagnetic/normal graphene junctions where a gate electrode is attached to the ferromagnetic graphene. We find that due to the exchange field of the ferromagnetic graphene, spin current through the junctions has an oscillatory behavior with respect to the chemical potential in the ferromagnetic graphene, which can be tuned by the gate voltage. Especially, we obtain a controllable spin current reversal by the gate voltage. Our prediction of high controllabi...

  6. Heat dissipation in atomic-scale junctions

    Lee, Woochul; Kim, Kyeongtae; Jeong, Wonho; Zotti, Linda Angela; Pauly, Fabian; Cuevas, Juan Carlos; Reddy, Pramod

    2013-01-01

    Atomic and single-molecule junctions represent the ultimate limit to the miniaturization of electrical circuits. They are also ideal platforms for testing quantum transport theories that are required to describe charge and energy transfer in novel functional nanometre-scale devices. Recent work has successfully probed electric and thermoelectric phenomena in atomic-scale junctions. However, heat dissipation and transport in atomic-scale devices remain poorly characterized owing to experimenta...

  7. Spinal Gap Junction Channels in Neuropathic Pain

    Jeon, Young Hoon; Youn, Dong Ho

    2015-01-01

    Damage to peripheral nerves or the spinal cord is often accompanied by neuropathic pain, which is a complex, chronic pain state. Increasing evidence indicates that alterations in the expression and activity of gap junction channels in the spinal cord are involved in the development of neuropathic pain. Thus, this review briefly summarizes evidence that regulation of the expression, coupling, and activity of spinal gap junction channels modulates pain signals in neuropathic pain states induced...

  8. Exotic hadron and string junction model

    Hadron structure is investigated adopting string junction model as a realization of confinement. Besides exotic hadrons (M4, B5 etc.), unconventional hadrons appear. A mass formula for these hadrons is proposed. New selection rule is introduced which requires the covalence of constituent line at hadron vertex. New duality appears due to the freedom of junction, especially in anti BB→anti BB reaction. A possible assignment of exotic and unconventional hadrons to recently observed narrow meson states is presented. (auth.)

  9. Degradation of connexins and gap junctions

    Falk, Matthias M.; Kells, Rachael M.; Berthoud, Viviana M.

    2014-01-01

    Connexin proteins are short-lived within the cell, whether present in the secretory pathway or in gap junction plaques. Their levels can be modulated by their rate of degradation. Connexins, at different stages of assembly, are degraded through the proteasomal, endo-/lysosomal, and phago-/lysosomal pathways. In this review, we summarize the current knowledge about connexin and gap junction degradation including the signals and protein-protein interactions that participate in their targeting f...

  10. Supercurrent Switch in Graphene π Junctions

    Linder, Jacob; Yokoyama, Takehito; Huertas-Hernando, Daniel; Sudbø, Asle

    2008-05-01

    We study the supercurrent in a superconductor/ferromagnet/superconductor graphene junction. In contrast to its metallic counterpart, the oscillating critical current in our setup decays only weakly upon increasing the exchange field and junction width. We find an unusually large residual value of the supercurrent at the oscillatory cusps due to a strong deviation from a sinusoidal current-phase relationship. Our findings suggest a very efficient device for dissipationless supercurrent switching.

  11. Supercurrent switch in graphene pi junctions.

    Linder, Jacob; Yokoyama, Takehito; Huertas-Hernando, Daniel; Sudbø, Asle

    2008-05-01

    We study the supercurrent in a superconductor/ferromagnet/superconductor graphene junction. In contrast to its metallic counterpart, the oscillating critical current in our setup decays only weakly upon increasing the exchange field and junction width. We find an unusually large residual value of the supercurrent at the oscillatory cusps due to a strong deviation from a sinusoidal current-phase relationship. Our findings suggest a very efficient device for dissipationless supercurrent switching. PMID:18518411

  12. Dynamical Coulomb blockade of tunnel junctions driven by alternating voltages

    Grabert, Hermann

    2015-12-01

    The theory of the dynamical Coulomb blockade is extended to tunneling elements driven by a time-dependent voltage. It is shown that, for standard setups where an external voltage is applied to a tunnel junction via an impedance, time-dependent driving entails an excitation of the modes of the electromagnetic environment by the applied voltage. Previous approaches for ac driven circuits need to be extended to account for the driven bath modes. A unitary transformation involving also the variables of the electromagnetic environment is introduced which allows us to split off the time dependence from the Hamiltonian in the absence of tunneling. This greatly simplifies perturbation-theoretical calculations based on treating the tunneling Hamiltonian as a perturbation. In particular, the average current flowing in the leads of the tunnel junction is studied. Explicit results are given for the case of an applied voltage with a constant dc part and a sinusoidal ac part. The connection with standard dynamical Coulomb blockade theory for constant applied voltage is established. It is shown that an alternating voltage source reveals significant additional effects caused by the electromagnetic environment. The hallmark of the dynamical Coulomb blockade in ac driven devices is a suppression of higher harmonics of the current by the electromagnetic environment. The theory presented basically applies to all tunneling devices driven by alternating voltages.

  13. Tunable Anomalous Supercurrent in a topological tri-junction SQUID

    Kurter, C.; Finck, A. D. K.; Ghaemi, P.; Hor, Y. S.; van Harlingen, D. J.

    2014-03-01

    There has been intense interest in realizing Majorana fermions (MFs) in solid-state systems. Circuits of Josephson junctions (JJs) made of closely spaced s-wave superconductors on 3D topological insulators have been proposed to host zero energy Andreev bound states (ABSs) that act like MFs. Here, we present signatures of an anomalous supercurrent carried by topologically non-trivial low energy ABSs in a Nb/Bi2Se3/Nb tri-junction SQUID where two of the three superconducting leads are connected by a loop. An electrostatic top gate allows strong modulation of the supercurrent despite a high bulk contribution to the normal state conductance. In response to a magnetic field threading flux within the superconducting loop, we find unconventional SQUID oscillations enclosed by an envelope associated with a clear diffraction pattern, indicating spatially uniform and symmetric JJs. At a critical gate voltage, when the trivial 2DEG at the surface is nearly depleted, we observe a sharp drop in the critical current, signaling a topological phase transition in which the nature of the supercurrent-carrying states is transformed. This transition is accompanied by qualitative changes in the SQUID oscillations, magnetic diffraction pattern, and temperature dependence of the critical current. We acknowledge funding from Microsoft Station-Q.

  14. Black diamonds at brane junctions

    Chamblin, Andrew; Csáki, Csaba; Erlich, Joshua; Hollowood, Timothy J.

    2000-08-01

    We discuss the properties of black holes in brane-world scenarios where our Universe is viewed as a four-dimensional sub-manifold of some higher-dimensional spacetime. We consider in detail such a model where four-dimensional spacetime lies at the junction of several domain walls in a higher dimensional anti-de Sitter spacetime. In this model there may be any number p of infinitely large extra dimensions transverse to the brane-world. We present an exact solution describing a black p-brane which will induce on the brane-world the Schwarzschild solution. This exact solution is unstable to the Gregory-Laflamme instability, whereby long-wavelength perturbations cause the extended horizon to fragment. We therefore argue that at late times a non-rotating uncharged black hole in the brane-world is described by a deformed event horizon in p+4 dimensions which will induce, to good approximation, the Schwarzschild solution in the four-dimensional brane world. When p=2, this deformed horizon resembles a black diamond and more generally for p>2, a polyhedron.

  15. Black Diamonds at Brane Junctions

    Chamblin, A; Erlich, J; Hollowood, Timothy J; Chamblin, Andrew; Csaki, Csaba; Erlich, Joshua; Hollowood, Timothy J.

    2000-01-01

    We discuss the properties of black holes in brane-world scenarios where ouruniverse is viewed as a four-dimensional sub-manifold of somehigher-dimensional spacetime. We consider in detail such a model wherefour-dimensional spacetime lies at the junction of several domain walls in ahigher dimensional anti-de Sitter spacetime. In this model there may be anynumber p of infinitely large extra dimensions transverse to the brane-world. Wepresent an exact solution describing a black p-brane which will induce on thebrane-world the Schwarzschild solution. This exact solution is unstable to theGregory-Laflamme instability, whereby long-wavelength perturbations cause theextended horizon to fragment. We therefore argue that at late times anon-rotating uncharged black hole in the brane-world is described by a deformedevent horizon in p+4 dimensions which will induce, to good approximation, theSchwarzschild solution in the four-dimensional brane world. When p=2, thisdeformed horizon resembles a black diamond and more gener...

  16. Black diamonds at brane junctions

    We discuss the properties of black holes in brane-world scenarios where our Universe is viewed as a four-dimensional sub-manifold of some higher-dimensional spacetime. We consider in detail such a model where four-dimensional spacetime lies at the junction of several domain walls in a higher dimensional anti-de Sitter spacetime. In this model there may be any number p of infinitely large extra dimensions transverse to the brane-world. We present an exact solution describing a black p-brane which will induce on the brane-world the Schwarzschild solution. This exact solution is unstable to the Gregory-Laflamme instability, whereby long-wavelength perturbations cause the extended horizon to fragment. We therefore argue that at late times a non-rotating uncharged black hole in the brane-world is described by a deformed event horizon in p+4 dimensions which will induce, to good approximation, the Schwarzschild solution in the four-dimensional brane world. When p=2, this deformed horizon resembles a black diamond and more generally for p>2, a polyhedron. (c) 2000 The American Physical Society

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

    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

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

    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.

  19. Gap junction- and hemichannel-independent actions of connexins

    Jiang, Jean X.; Gu, Sumin

    2004-01-01

    Connexins have been known to be the protein building blocks of gap junctions and mediate cell–cell communication. In contrast to the conventional dogma, recent evidence suggests that in addition to forming gap junction channels, connexins possess gap junction-independent functions. One important gap junction-independent function for connexins is to serve as the major functional component for hemichannels, the un-apposed halves of gap junctions. Hemichannels, as independent functional units, p...

  20. A SQUID gradiometer module with large junction shunt resistors

    A dual-washer superconducting quantum interference device (SQUID) with a loop inductance of 350 pH and two on-washer integrated input coils is designed according to conventional niobium technology. In order to obtain a large SQUID flux-to-voltage transfer coefficient, the junction shunt resistance is selected to be 33 Ω. A vertical SQUID gradiometer module with a baseline of 100 mm is constructed by utilizing such a SQUID and a first-order niobium wire-wound antenna. The sensitivity of this module reaches about 0.2 fT/(cm·Hz1/2) in the white noise range using a direct readout scheme, i.e., the SQUID is directly connected to an operational amplifier, in a magnetically shielded room. Some magnetocardiography (MCG) measurements with a sufficiently high signal-to-noise ratio (SNR) are demonstrated. (interdisciplinary physics and related areas of science and technology)

  1. The current concept of development of specialized intercellular connections between cardiomyocytes

    Petruk N.S.; Tverdokhleb I.V.

    2009-01-01

    The understanding of development of interrelation between electric and mechanical contacts in ontogenetic aspect can throw light on the mechanisms underlying heart pathologies related with local disturbance of gap junctions distribution. Despite of significant progress in understanding of structural biology of desmosome, fascia adherents and gap junctions which are a part of an intercalated disk, the detailed characteristic of interrelation between electric and mechanical connections it is no...

  2. The junctional complex in the intestine of Sagitta setosa (Chaetognatha): the paired septate junction.

    Duvert, M; Gros, D; Salat, C

    1980-04-01

    The junctional complex of the intestine of Sagitta setosa has been studied in tissues stained with uranyl acetate or after lanthanum impregnation, and by freeze-cleavage. All types of junctions have been characterized in both perpendicular and tangential planes. From the apex to the base of the cell the following junctions occur in this order: a zonula adhaerens; a septate junction where the septa occur in pairs; a pleated sheet septate junction; and numerous gap junctions of the A-type. From the upper part of the cells inwards to the septate junction, the membranes follow a relatively straight path. In the lower part of the cells the membranes are deeply interdigitating. At the intersection between 3 cells a very different junction is to be observed where small units, periodically disposed, bind the membranes of the 3 adjoining cells. Each unit is composed of 3 short segments which bind the cell membranes to a central ring 16.6 +/- 2.3 nm in outer diameter. The paired septate junction constitutes a new type. Its main features are that the septa are paired and occur in 2 formations, one the 'loose formation', with elements between the septa of each pair, and the other, a 'tight formation'. After lanthanum impregnation, the thickness of each septum is seen to be about 3 nm and the undulation period 12.6 +/- 1.6 nm. On freeze-fractures 10-nm particles are found on crests on the PF face and in furrows on the EF face. The possible significance of this type of junction is discussed. The junctional complex described is analogous to those found in various invertebrate epithelia. PMID:6105159

  3. Fluxons in a triangular set of coupled long Josephson junctions

    We report results of an analysis of the dynamics of magnetic flux solitons in the system of three long Josephson junctions between three bulk superconductors that form a prism. The system is modeled by coupled sine-Gordon equations for the phases of the junctions. The Aharonov-Bohm constraint takes into account the axial magnetic flux enclosed by the prism and reduces the system from three independent phases to two. The equations of motion for the phases include dissipative terms, and a control parameter δ which accounts for the deviation of the enclosed flux from half a quantum. Analyzing the effective potential of the coupled equations, we identify different species of topological and non-topological phase solitons (fluxons) in this system. In particular, subkinks with fractional topological charges ±1/3 and ±2/3, confined inside integer-charge fluxons, may be mapped onto the root diagrams for mesons and baryons in the original quark model of hadrons. Solutions for straight-line kinks and for two types of non-topological solitons are obtained in an explicit analytical form. Numerical tests demonstrate that the former species is unstable against breakup into pairs of separating single-fluxon kinks. The non-topological kinks feature metastability, eventually breaking up into fluxon-antifluxon pairs. Free fractional-fluxon kinks, that connect different potential minima and are, accordingly, pulled by the potential difference, are also considered. Using the momentum-balance method, we predict the velocity at which these kinks should move in the presence of the dissipation. Numerical tests demonstrate that the analysis predicts the velocity quite closely. Higher-energy static solutions for all of the stable kink types mentioned above, as well as kinks connecting false vacua, are found by means of the shooting method. Inelastic collisions among the stable fractional and single-fluxon kinks are investigated numerically

  4. Fluxons in a triangular set of coupled long Josephson junctions

    Yukon, Stanford P., E-mail: yukon@alum.mit.edu [Air Force Research Laboratory (United States); Malomed, Boris A. [Department of Physical Electronics, School of Electrical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978 (Israel)

    2015-09-15

    We report results of an analysis of the dynamics of magnetic flux solitons in the system of three long Josephson junctions between three bulk superconductors that form a prism. The system is modeled by coupled sine-Gordon equations for the phases of the junctions. The Aharonov-Bohm constraint takes into account the axial magnetic flux enclosed by the prism and reduces the system from three independent phases to two. The equations of motion for the phases include dissipative terms, and a control parameter δ which accounts for the deviation of the enclosed flux from half a quantum. Analyzing the effective potential of the coupled equations, we identify different species of topological and non-topological phase solitons (fluxons) in this system. In particular, subkinks with fractional topological charges ±1/3 and ±2/3, confined inside integer-charge fluxons, may be mapped onto the root diagrams for mesons and baryons in the original quark model of hadrons. Solutions for straight-line kinks and for two types of non-topological solitons are obtained in an explicit analytical form. Numerical tests demonstrate that the former species is unstable against breakup into pairs of separating single-fluxon kinks. The non-topological kinks feature metastability, eventually breaking up into fluxon-antifluxon pairs. Free fractional-fluxon kinks, that connect different potential minima and are, accordingly, pulled by the potential difference, are also considered. Using the momentum-balance method, we predict the velocity at which these kinks should move in the presence of the dissipation. Numerical tests demonstrate that the analysis predicts the velocity quite closely. Higher-energy static solutions for all of the stable kink types mentioned above, as well as kinks connecting false vacua, are found by means of the shooting method. Inelastic collisions among the stable fractional and single-fluxon kinks are investigated numerically.

  5. Fluxons in a triangular set of coupled long Josephson junctions

    Yukon, Stanford P.; Malomed, Boris A.

    2015-09-01

    We report results of an analysis of the dynamics of magnetic flux solitons in the system of three long Josephson junctions between three bulk superconductors that form a prism. The system is modeled by coupled sine-Gordon equations for the phases of the junctions. The Aharonov-Bohm constraint takes into account the axial magnetic flux enclosed by the prism and reduces the system from three independent phases to two. The equations of motion for the phases include dissipative terms, and a control parameter δ which accounts for the deviation of the enclosed flux from half a quantum. Analyzing the effective potential of the coupled equations, we identify different species of topological and non-topological phase solitons (fluxons) in this system. In particular, subkinks with fractional topological charges ±1/3 and ±2/3, confined inside integer-charge fluxons, may be mapped onto the root diagrams for mesons and baryons in the original quark model of hadrons. Solutions for straight-line kinks and for two types of non-topological solitons are obtained in an explicit analytical form. Numerical tests demonstrate that the former species is unstable against breakup into pairs of separating single-fluxon kinks. The non-topological kinks feature metastability, eventually breaking up into fluxon-antifluxon pairs. Free fractional-fluxon kinks, that connect different potential minima and are, accordingly, pulled by the potential difference, are also considered. Using the momentum-balance method, we predict the velocity at which these kinks should move in the presence of the dissipation. Numerical tests demonstrate that the analysis predicts the velocity quite closely. Higher-energy static solutions for all of the stable kink types mentioned above, as well as kinks connecting false vacua, are found by means of the shooting method. Inelastic collisions among the stable fractional and single-fluxon kinks are investigated numerically.

  6. Clarifying the atrioventricular junctional anatomy in the setting of double outlet right atrium

    Saurabh Kumar Gupta

    2015-01-01

    Full Text Available Double outlet atrium is a rare cardiac anomaly wherein one of the atriums, most frequently the right atrium, opens into both the ventricles. Although seen more commonly in the setting of atrioventricular septal defect, this arrangement can also be found when one of the atrioventricular connections is atretic due to absence of the atrioventricular connection and the other atrioventricular valve straddles the muscular ventricular septum. It is the specific anatomy and connections of the atrioventricular junction that clarifies the situation and distinguishes between these two types of double outlet atrium. In this report, we present a case of double outlet right atrium co-existing with the absence of left atrioventricular connection. We then discuss the morphologic aspects of this interesting anomaly.

  7. Charge transport in nanoscale junctions.

    Albrecht, Tim; Kornyshev, Alexei; Bjørnholm, Thomas

    2008-09-01

    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. PMID:21694407

  8. Josephson tunnel junctions with ferromagnetic interlayer

    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.)

  9. Josephson tunnel junctions with ferromagnetic interlayer

    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 Al2O3 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 π 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, π) of SIFS tunnel junctions was studied. Furthermore, using a stepped ferromagnetic layer with well-chosen thicknesses, I obtained the so-called 0-π Josephson junction. At a certain temperature this 0-π 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 Φ0. 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 → 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.)

  10. Role of mitochondria and network connectivity in intercellular calcium oscillations

    Dokukina, I V; Grachev, E A; Gunton, J D; Dokukina, Irina V.; Gracheva, Maria E.; Grachev, Eugene A.; Gunton, James D.

    2005-01-01

    Mitochondria are large-scale regulators of cytosolic calcium under normal cellular conditions. In this paper we model the complex behavior of mitochondrial calcium during the action of inositol 1,4,5-trisphosphate on a single cell and find results that are in good agreement with recent experimental studies. We also study the influence of the cellular network connectivity on intercellular signalling via gap junction diffusion. We include in our model the dependence of the junctional conductivity on the cytosolic calcium concentrations in adjacent cells. We consider three different mechanisms of calcium wave propagation through gap junctions: via calcium diffusion, inositol 1,4,5-trisphosphate diffusion, and both calcium and inositol 1,4,5-trisphosphate diffusion. We show that inositol 1,4,5-trisphosphate diffusion is the mechanism of calcium wave propagation and that calcium diffusion is the mechanism of synchronization of cytosolic calcium oscillations in adjacent cells. We also study the role of different to...