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Sample records for paranodal axoglial junctions

  1. GLIAL ANKYRINS FACILITATE PARANODAL AXOGLIAL JUNCTION ASSEMBLY

    PubMed Central

    Chang, Kae-Jiun; Zollinger, Daniel R.; Susuki, Keiichiro; Sherman, Diane L.; Makara, Michael A.; Brophy, Peter J.; Cooper, Edward C.; Bennett, Vann; Mohler, Peter J.; Rasband, Matthew N.

    2014-01-01

    Neuron-glia interactions establish functional membrane domains along myelinated axons. These include nodes of Ranvier, paranodal axoglial junctions, and juxtaparanodes. Paranodal junctions are the largest vertebrate junctional adhesion complex, are essential for rapid saltatory conduction, and contribute to assembly and maintenance of nodes. However, the molecular mechanisms underlying paranodal junction assembly are poorly understood. Ankyrins are cytoskeletal scaffolds traditionally associated with Na+ channel clustering in neurons and important for membrane domain establishment and maintenance in many cell types. Here, we show that ankyrinB, expressed by Schwann cells, and ankyrinG, expressed by oligodendrocytes, are highly enriched at the glial side of paranodal junctions where they interact with the essential glial junctional component neurofascin 155. Conditional knockout of ankyrins in oligodendrocytes disrupts paranodal junction assembly and delays nerve conduction during early development in mice. Thus, glial ankyrins function as major scaffolds that facilitate early and efficient paranodal junction assembly in the developing central nervous system. PMID:25362471

  2. The cytoskeletal adaptor protein band 4.1B is required for the maintenance of paranodal axoglial septate junctions in myelinated axons.

    PubMed

    Buttermore, Elizabeth D; Dupree, Jeffrey L; Cheng, JrGang; An, Xiuli; Tessarollo, Lino; Bhat, Manzoor A

    2011-06-01

    Precise targeting and maintenance of axonal domains in myelinated axons is essential for saltatory conduction. Caspr and Caspr2, which localize at paranodal and juxtaparanodal domains, contain binding sites for the cytoskeletal adaptor protein 4.1B. The exact role of 4.1B in the organization and maintenance of axonal domains is still not clear. Here, we report the generation and characterization of 4.1B-null mice. We show that loss of 4.1B in the PNS results in mislocalization of Caspr at paranodes and destabilization of paranodal axoglial septate junctions (AGSJs) as early as postnatal day 30. In the CNS, Caspr localization is progressively disrupted and ultrastructural analysis showed paranodal regions that were completely devoid of AGSJs, with axolemma separated from the myelin loops, and loops coming off the axolemma. Most importantly, our phenotypic analysis of previously generated 4.1B mutants, used in the study by Horresh et al. (2010), showed that Caspr localization was not affected in the PNS, even after 1 year; and 4.1R was neither expressed, nor enriched at the paranodes. Furthermore, ultrastructural analysis of these 4.1B mutants showed destabilization of CNS AGSJs at ∼ 1 year. We also discovered that the 4.1B locus is differentially expressed in the PNS and CNS, and generates multiple splice isoforms in the PNS, suggesting 4.1B may function differently in the PNS versus CNS. Together, our studies provide direct evidence that 4.1B plays a pivotal role in interactions between the paranodal AGSJs and axonal cytoskeleton, and that 4.1B is critically required for long-term maintenance of axonal domains in myelinated axons. PMID:21632923

  3. The Cytoskeletal Adaptor Protein Band 4.1B is Required for the Maintenance of Paranodal Axo-Glial Septate Junctions in Myelinated Axons

    PubMed Central

    Buttermore, Elizabeth D.; Dupree, Jeffrey L.; Cheng, JrGang; An, Xiuli; Tessarollo, Lino; Bhat, Manzoor A.

    2011-01-01

    Precise targeting and maintenance of axonal domains in myelinated axons is essential for saltatory conduction. Caspr and Caspr2, which localize at paranodal and juxtaparanodal domains, contain binding sites for the cytoskeletal adaptor protein 4.1B. The exact role of 4.1B in the organization and maintenance of axonal domains is still not clear. Here we report the generation and characterization of 4.1B null mice. We show that loss of 4.1B in the PNS results in mislocalization of Caspr at paranodes and destabilization of paranodal axo-glial septate junctions (AGSJs) as early as postnatal day 30. In the CNS, Caspr localization is progressively disrupted and ultrastructural analysis showed paranodal regions that were completely devoid of AGSJs, with axolemma separated from the myelin loops, and loops coming off the axolemma. Most importantly, our phenotypic analysis of previously generated 4.1B mutants, used in Horresh et al. (2010), showed that Caspr localization was not affected in the PNS, even after one year; and 4.1R was neither expressed, nor enriched at the paranodes. Furthermore, ultrastructural analysis of these 4.1B mutants showed destabilization of CNS AGSJs at about one year. We also discovered that the 4.1B locus is differentially expressed in the PNS and CNS, and generates multiple splice isoforms in the PNS, suggesting 4.1B may function differently in the PNS versus CNS. Together, our studies provide direct evidence that 4.1B plays a pivotal role in interactions between the paranodal AGSJs and axonal cytoskeleton, and that 4.1B is critically required for long-term maintenance of axonal domains in myelinated axons. PMID:21632923

  4. Dependence of nodal sodium channel clustering on paranodal axoglial contact in the developing CNS.

    PubMed

    Rasband, M N; Peles, E; Trimmer, J S; Levinson, S R; Lux, S E; Shrager, P

    1999-09-01

    Na(+) channel clustering at nodes of Ranvier in the developing rat optic nerve was analyzed to determine mechanisms of localization, including the possible requirement for glial contact in vivo. Immunofluorescence labeling for myelin-associated glycoprotein and for the protein Caspr, a component of axoglial junctions, indicated that oligodendrocytes were present, and paranodal structures formed, as early as postnatal day 7 (P7). However, the first Na(+) channel clusters were not seen until P9. Most of these were broad, and all were excluded from paranodal regions of axoglial contact. The number of detected Na(+) channel clusters increased rapidly from P12 to P22. During this same period, conduction velocity increased sharply, and Na(+) channel clusters became much more focal. To test further whether oligodendrocyte contact directly influences Na(+) channel distributions, nodes of Ranvier in the hypomyelinating mouse Shiverer were examined. This mutant has oligodendrocyte-ensheathed axons but lacks compact myelin and normal axoglial junctions. During development Na(+) channel clusters in Shiverer mice were reduced in numbers and were in aberrant locations. The subcellular location of Caspr was disrupted, and nerve conduction properties remained immature. These results indicate that in vivo, Na(+) channel clustering at nodes depends not only on the presence of oligodendrocytes but also on specific axoglial contact at paranodal junctions. In rats, ankyrin-3/G, a cytoskeletal protein implicated in Na(+) channel clustering, was detected before Na(+) channel immunoreactivity but extended into paranodes in non-nodal distributions. In Shiverer, ankyrin-3/G labeling was abnormal, suggesting that its localization also depends on axoglial contact. PMID:10460258

  5. Maintenance of axo-oligodendroglial paranodal junctions requires DCC and netrin-1.

    PubMed

    Jarjour, Andrew A; Bull, Sarah-Jane; Almasieh, Mohammadali; Rajasekharan, Sathyanath; Baker, K Adam; Mui, Jeannie; Antel, Jack P; Di Polo, Adriana; Kennedy, Timothy E

    2008-10-22

    Paranodal axoglial junctions are essential for the segregation of myelinated axons into distinct domains and efficient conduction of action potentials. Here, we show that netrin-1 and deleted in colorectal cancer (DCC) are enriched at the paranode in CNS myelin. We then address whether netrin-1 signaling influences paranodal adhesion between oligodendrocytes and axons. In the absence of netrin-1 or DCC function, oligodendroglial paranodes initially develop and mature normally but later become disorganized. Lack of DCC or netrin-1 resulted in detachment of paranodal loops from the axonal surface and the disappearance of transverse bands. Furthermore, the domain organization of myelin is compromised in the absence of netrin-1 signaling: K+ channels inappropriately invade the paranodal region, and the normally restricted paranodal distribution of Caspr expands longitudinally along the axon. Our findings identify an essential role for netrin-1 and DCC regulating the maintenance of axoglial junctions. PMID:18945908

  6. Contactin orchestrates assembly of the septate-like junctions at the paranode in myelinated peripheral nerve.

    PubMed

    Boyle, M E; Berglund, E O; Murai, K K; Weber, L; Peles, E; Ranscht, B

    2001-05-01

    Rapid nerve impulse conduction depends on specialized membrane domains in myelinated nerve, the node of Ranvier, the paranode, and the myelinated internodal region. We report that GPI-linked contactin enables the formation of the paranodal septate-like axo-glial junctions in myelinated peripheral nerve. Contactin clusters at the paranodal axolemma during Schwann cell myelination. Ablation of contactin in mutant mice disrupts junctional attachment at the paranode and reduces nerve conduction velocity 3-fold. The mutation impedes intracellular transport and surface expression of Caspr and leaves NF155 on apposing paranodal myelin disengaged. The contactin mutation does not affect sodium channel clustering at the nodes of Ranvier but alters the location of the Shaker-type Kv1.1 and Kv1.2 potassium channels. Thus, contactin is a crucial part in the machinery that controls junctional attachment at the paranode and ultimately the physiology of myelinated nerve. PMID:11395001

  7. Neurofascin is a glial receptor for the paranodin/Caspr-contactin axonal complex at the axoglial junction.

    PubMed

    Charles, Perrine; Tait, Steven; Faivre-Sarrailh, Catherine; Barbin, Gilles; Gunn-Moore, Frank; Denisenko-Nehrbass, Natalia; Guennoc, Anne-Marie; Girault, Jean-Antoine; Brophy, Peter J; Lubetzki, Catherine

    2002-02-01

    In myelinated fibers of the vertebrate nervous system, glial-ensheathing cells interact with axons at specialized adhesive junctions, the paranodal septate-like junctions. The axonal proteins paranodin/Caspr and contactin form a cis complex in the axolemma at the axoglial adhesion zone, and both are required to stabilize the junction. There has been intense speculation that an oligodendroglial isoform of the cell adhesion molecule neurofascin, NF155, expressed at the paranodal loop might be the glial receptor for the paranodin/Caspr-contactin complex, particularly since paranodin/Caspr and NF155 colocalize to ectopic sites in the CNS of the dysmyelinated mouse Shiverer mutant. We report that the extracellular domain of NF155 binds specifically to transfected cells expressing the paranodin/Caspr-contactin complex at the cell surface. This region of NF155 also binds the paranodin/Caspr-contactin complex from brain lysates in vitro. In support of the functional significance of this interaction, NF155 antibodies and the extracellular domain of NF155 inhibit myelination in myelinating cocultures, presumably by blocking the adhesive relationship between the axon and glial cell. These results demonstrate that the paranodin/Caspr-contactin complex interacts biochemically with NF155 and that this interaction is likely to be biologically relevant at the axoglial junction. PMID:11839274

  8. Progressive disorganization of paranodal junctions and compact myelin due to loss of DCC expression by oligodendrocytes.

    PubMed

    Bull, Sarah-Jane; Bin, Jenea M; Beaumont, Eric; Boutet, Alexandre; Krimpenfort, Paul; Sadikot, Abbas F; Kennedy, Timothy E

    2014-07-16

    Paranodal axoglial junctions are critical for maintaining the segregation of axonal domains along myelinated axons; however, the proteins required to organize and maintain this structure are not fully understood. Netrin-1 and its receptor Deleted in Colorectal Cancer (DCC) are proteins enriched at paranodes that are expressed by neurons and oligodendrocytes. To identify the specific function of DCC expressed by oligodendrocytes in vivo, we selectively eliminated DCC from mature myelinating oligodendrocytes using an inducible cre regulated by the proteolipid protein promoter. We demonstrate that DCC deletion results in progressive disruption of the organization of axonal domains, myelin ultrastructure, and myelin protein composition. Conditional DCC knock-out mice develop balance and coordination deficits and exhibit decreased conduction velocity. We conclude that DCC expression by oligodendrocytes is required for the maintenance and stability of myelin in vivo, which is essential for proper signal conduction in the CNS.

  9. Retention of a cell adhesion complex at the paranodal junction requires the cytoplasmic region of Caspr.

    PubMed

    Gollan, Leora; Sabanay, Helena; Poliak, Sebastian; Berglund, Erik O; Ranscht, Barbara; Peles, Elior

    2002-06-24

    An axonal complex of cell adhesion molecules consisting of Caspr and contactin has been found to be essential for the generation of the paranodal axo-glial junctions flanking the nodes of Ranvier. Here we report that although the extracellular region of Caspr was sufficient for directing it to the paranodes in transgenic mice, retention of the Caspr-contactin complex at the junction depended on the presence of an intact cytoplasmic domain of Caspr. Using immunoelectron microscopy, we found that a Caspr mutant lacking its intracellular domain was often found within the axon instead of the junctional axolemma. We further show that a short sequence in the cytoplasmic domain of Caspr mediated its binding to the cytoskeleton-associated protein 4.1B. Clustering of contactin on the cell surface induced coclustering of Caspr and immobilized protein 4.1B at the plasma membrane. Furthermore, deletion of the protein 4.1B binding site accelerated the internalization of a Caspr-contactin chimera from the cell surface. These results suggest that Caspr serves as a "transmembrane scaffold" that stabilizes the Caspr/contactin adhesion complex at the paranodal junction by connecting it to cytoskeletal components within the axon. PMID:12082082

  10. Dependence of paranodal junctional gap width on transverse bands.

    PubMed

    Rosenbluth, Jack; Petzold, Chris; Peles, Elior

    2012-08-15

    Mouse mutants with paranodal junctional (PNJ) defects display variable degrees of neurological impairment. In this study we compare control paranodes with those from three mouse mutants that differ with respect to a conspicuous PNJ component, the transverse bands (TBs). We hypothesize that TBs link the apposed junctional membranes together at a fixed distance and thereby determine the width of the junctional gap, which may in turn determine the extent to which nodal action currents can be short-circuited underneath the myelin sheath. Electron micrographs of aldehyde-fixed control PNJs, in which TBs are abundant, show a consistent junctional gap of ∼3.5 nm. In Caspr-null PNJs, which lack TBs entirely, the gap is wider (∼6-7 nm) and more variable. In CST-null PNJs, which have only occasional TBs, the mean PNJ gap width is comparable to that in Caspr-null mice. In the shaking mutant, in contrast, which has approximately 60% of the normal complement of TBs, mean PNJ gap width is not significantly different from that in controls. Correspondingly, shaking mice are much less impaired neurologically than either Caspr-null or CST-null mice. We conclude that in the absence or gross diminution of TBs, mean PNJ gap width increases significantly and suggest that this difference could underlie some of the neurological impairment seen in those mutants. Surprisingly, even in the absence of TBs, paranodes are to some extent maintained in their usual form, implying that in addition to TBs, other factors govern the formation and maintenance of overall paranodal structure. PMID:22434587

  11. Reduced raft-association of NF155 in active MS-lesions is accompanied by the disruption of the paranodal junction.

    PubMed

    Maier, Olaf; Baron, Wia; Hoekstra, Dick

    2007-06-01

    Neurofascin155 (NF155) is required for the establishment of the paranodal axo-glial junction, the predominant interaction site between myelin and axon. It has been shown that the distribution of NF155 is altered in demyelinating diseases such as multiple sclerosis (MS). However, little is known about the biochemical mechanisms underlying these changes. We therefore compared NF155 in postmortem tissue of active and chronic inactive MS lesions with white matter from healthy controls. Although NF155 showed a very similar expression in all control white matter samples, a strong individual variation was observed in MS-lesions with NF155-levels reduced in most samples. At the same time an NF155-fragment was increased in MS-lesions, suggesting that NF155 is subject to protein degradation in lesion sites. Interestingly, the association of NF155 to membrane microdomains (rafts) was reduced in all lesions, irrespective of the amount of NF155, indicating that membrane association of NF155 was generally affected. Therefore, myelin fractionation experiments were performed to analyze the fate of paranodal proteins during demyelination. Although NF155 was enriched in heavy myelin from both control white matter and active MS-lesions, association of Caspr1/paranodin with heavy myelin was abolished in MS-lesions, demonstrating that paranodal junctions are disrupted. In conclusion, the data support the hypothesis that efficient raft-association of NF155 is essential for the assembly of the paranodal junction and demonstrate that reduced association of NF155 to lipid rafts is accompanied by the disassembly of the paranodal junction and thus contributes to the demyelination process in MS. PMID:17405145

  12. Paranodal reorganization results in the depletion of transverse bands in the aged central nervous system

    PubMed Central

    Shepherd, Mark N.; Pomicter, Anthony D.; Velazco, Cristine S.; Henderson, Scott C.; Dupree, Jeffrey L.

    2012-01-01

    Paranodal axo-glial junctional complexes anchor the myelin sheath to the axon and breakdown of these complexes presumably facilitates demyelination. Myelin deterioration is also prominent in the aging central nervous system (CNS); however, the stability of the paranodal complexes in the aged CNS has not been examined. Here, we show that transverse bands, prominent components of paranodal junctions, are significantly reduced in the aged CNS; however, the number of paired clusters of both myelin and axonal paranodal proteins is not altered. Ultrastructural analyses also reveal that thicker myelin sheaths display a “piling” of paranodal loops, the cytoplasm-containing sacs that demarcate the paranode. Loops involved in piling are observed throughout the paranode and are not limited to loops positioned in either the nodal- or juxtanodal-most regions. Here, we propose that as myelination continues, previously anchored loops lose their transverse bands and recede away from the axolemma. Newly juxtaposed loops then lose their transverse bands, move laterally to fill in the gap left by the receded loops and finally reform their transverse bands. This paranodal reorganization results in conservation of paranodal length, which may be important in maintaining ion channel spacing and axonal function. Furthermore, we propose that transverse band reformation is less efficient in the aged CNS, resulting in the significant reduction of these junctional components. Although demyelination was not observed, we propose that loss of transverse bands facilitates myelin degeneration and may predispose the aged CNS to a poorer prognosis following a secondary insult. PMID:20888080

  13. Paranodal reorganization results in the depletion of transverse bands in the aged central nervous system.

    PubMed

    Shepherd, Mark N; Pomicter, Anthony D; Velazco, Cristine S; Henderson, Scott C; Dupree, Jeffrey L

    2012-01-01

    Paranodal axo-glial junctional complexes anchor the myelin sheath to the axon and breakdown of these complexes presumably facilitates demyelination. Myelin deterioration is also prominent in the aging central nervous system (CNS); however, the stability of the paranodal complexes in the aged CNS has not been examined. Here, we show that transverse bands, prominent components of paranodal junctions, are significantly reduced in the aged CNS; however, the number of paired clusters of both myelin and axonal paranodal proteins is not altered. Ultrastructural analyses also reveal that thicker myelin sheaths display a "piling" of paranodal loops, the cytoplasm-containing sacs that demarcate the paranode. Loops involved in piling are observed throughout the paranode and are not limited to loops positioned in either the nodal- or juxtanodal-most regions. Here, we propose that as myelination continues, previously anchored loops lose their transverse bands and recede away from the axolemma. Newly juxtaposed loops then lose their transverse bands, move laterally to fill in the gap left by the receded loops and finally reform their transverse bands. This paranodal reorganization results in conservation of paranodal length, which may be important in maintaining ion channel spacing and axonal function. Furthermore, we propose that transverse band reformation is less efficient in the aged CNS, resulting in the significant reduction of these junctional components. Although demyelination was not observed, we propose that loss of transverse bands facilitates myelin degeneration and may predispose the aged CNS to a poorer prognosis following a secondary insult. PMID:20888080

  14. Paranodal dysmyelination in peripheral nerves of Trembler mice.

    PubMed

    Rosenbluth, Jack; Bobrowski-Khoury, Natasha

    2014-04-01

    Subtle defects in paranodes of myelinated nerve fibers can cause significant physiological malfunction. We have investigated myelinated fibers in the peripheral nervous system (PNS) of the Trembler mouse, a model of CMT-1A neuropathy, for evidence of such defects. Ultrastructural analysis shows that the "transverse bands," which attach the myelin sheath to the axon at the paranodal axoglial junction, are grossly diminished in number in Trembler nerve fibers. Although paranodes often appear to be greatly elongated, it is only a short region immediately adjacent to the node of Ranvier that displays transverse bands. Where transverse bands are missing, the junctional gap widens, thus reducing resistance to short circuiting of nodal action currents during saltatory conduction and increasing the likelihood that axonal K(+) channels under the myelin sheath will be activated. In addition, we find evidence that structural domains in Trembler axons are incompletely differentiated, consistent with diminution in nodal Na channel density, which could further compromise conduction. Deficiency of transverse bands may also increase susceptibility to disruption of the paranodal junction and retraction of the myelin sheath. We conclude that Trembler PNS myelinated fibers display subtle defects in paranodal and nodal regions that could contribute significantly to conduction defects and increased risk of myelin detachment.

  15. Contactin-associated protein (Caspr) and contactin form a complex that is targeted to the paranodal junctions during myelination.

    PubMed

    Rios, J C; Melendez-Vasquez, C V; Einheber, S; Lustig, M; Grumet, M; Hemperly, J; Peles, E; Salzer, J L

    2000-11-15

    Specialized paranodal junctions form between the axon and the closely apposed paranodal loops of myelinating glia. They are interposed between sodium channels at the nodes of Ranvier and potassium channels in the juxtaparanodal regions; their precise function and molecular composition have been elusive. We previously reported that Caspr (contactin-associated protein) is a major axonal constituent of these junctions (Einheber et al., 1997). We now report that contactin colocalizes and forms a cis complex with Caspr in the paranodes and juxtamesaxon. These proteins coextract and coprecipitate from neurons, myelinating cultures, and myelin preparations enriched in junctional markers; they fractionate on sucrose gradients as a high-molecular-weight complex, suggesting that other proteins may also be associated with this complex. Neurons express two contactin isoforms that differ in their extent of glycosylation: a lower-molecular-weight phosphatidylinositol phospholipase C (PI-PLC)-resistant form is associated specifically with Caspr in the paranodes, whereas a higher-molecular-weight form of contactin, not associated with Caspr, is present in central nodes of Ranvier. These results suggest that the targeting of contactin to different axonal domains may be determined, in part, via its association with Caspr. Treatment of myelinating cocultures of Schwann cells and neurons with RPTPbeta-Fc, a soluble construct containing the carbonic anhydrase domain of the receptor protein tyrosine phosphatase beta (RPTPbeta), a potential glial receptor for contactin, blocks the localization of the Caspr/contactin complex to the paranodes. These results strongly suggest that a preformed complex of Caspr and contactin is targeted to the paranodal junctions via extracellular interactions with myelinating glia. PMID:11069942

  16. BK Channels Localize to the Paranodal Junction and Regulate Action Potentials in Myelinated Axons of Cerebellar Purkinje Cells

    PubMed Central

    Hirono, Moritoshi; Ogawa, Yasuhiro; Misono, Kaori; Zollinger, Daniel R.; Trimmer, James S.

    2015-01-01

    In myelinated axons, K+ channels are clustered in distinct membrane domains to regulate action potentials (APs). At nodes of Ranvier, Kv7 channels are expressed with Na+ channels, whereas Kv1 channels flank nodes at juxtaparanodes. Regulation of axonal APs by K+ channels would be particularly important in fast-spiking projection neurons such as cerebellar Purkinje cells. Here, we show that BK/Slo1 channels are clustered at the paranodal junctions of myelinated Purkinje cell axons of rat and mouse. The paranodal junction is formed by a set of cell-adhesion molecules, including Caspr, between the node and juxtaparanodes in which it separates nodal from internodal membrane domains. Remarkably, only Purkinje cell axons have detectable paranodal BK channels, whose clustering requires the formation of the paranodal junction via Caspr. Thus, BK channels occupy this unique domain in Purkinje cell axons along with the other K+ channel complexes at nodes and juxtaparanodes. To investigate the physiological role of novel paranodal BK channels, we examined the effect of BK channel blockers on antidromic AP conduction. We found that local application of blockers to the axon resulted in a significant increase in antidromic AP failure at frequencies above 100 Hz. We also found that Ni2+ elicited a similar effect on APs, indicating the involvement of Ni2+-sensitive Ca2+ channels. Furthermore, axonal application of BK channel blockers decreased the inhibitory synaptic response in the deep cerebellar nuclei. Thus, paranodal BK channels uniquely support high-fidelity firing of APs in myelinated Purkinje cell axons, thereby underpinning the output of the cerebellar cortex. PMID:25948259

  17. Connexin-47 and connexin-32 in gap junctions of oligodendrocyte somata, myelin sheaths, paranodal loops and Schmidt-Lanterman incisures: implications for ionic homeostasis and potassium siphoning.

    PubMed

    Kamasawa, N; Sik, A; Morita, M; Yasumura, T; Davidson, K G V; Nagy, J I; Rash, J E

    2005-01-01

    The subcellular distributions and co-associations of the gap junction-forming proteins connexin 47 and connexin 32 were investigated in oligodendrocytes of adult mouse and rat CNS. By confocal immunofluorescence light microscopy, abundant connexin 47 was co-localized with astrocytic connexin 43 on oligodendrocyte somata, and along myelinated fibers, whereas connexin 32 without connexin 47 was co-localized with contactin-associated protein (caspr) in paranodes. By thin-section transmission electron microscopy, connexin 47 immunolabeling was on the oligodendrocyte side of gap junctions between oligodendrocyte somata and astrocytes. By freeze-fracture replica immunogold labeling, large gap junctions between oligodendrocyte somata and astrocyte processes contained much more connexin 47 than connexin 32. Along surfaces of internodal myelin, connexin 47 was several times as abundant as connexin 32, and in the smallest gap junctions, often occurred without connexin 32. In contrast, connexin 32 was localized without connexin 47 in newly-described autologous gap junctions in Schmidt-Lanterman incisures and between paranodal loops bordering nodes of Ranvier. Thus, connexin 47 in adult rodent CNS is the most abundant connexin in most heterologous oligodendrocyte-to-astrocyte gap junctions, whereas connexin 32 is the predominant if not sole connexin in autologous ("reflexive") oligodendrocyte gap junctions. These results clarify the locations and connexin compositions of heterologous and autologous oligodendrocyte gap junctions, identify autologous gap junctions at paranodes as potential sites for modulating paranodal electrical properties, and reveal connexin 47-containing and connexin 32-containing gap junctions as conduits for long-distance intracellular and intercellular movement of ions and associated osmotic water. The autologous gap junctions may regulate paranodal electrical properties during saltatory conduction. Acting in series and in parallel, autologous and

  18. Paranodal permeability in `myelin mutants'

    PubMed Central

    Shroff, S.; Mierzwa, A.; Scherer, S.S.; Peles, E.; Arevalo, J.C.; Chao, M.V.; Rosenbluth, J.

    2011-01-01

    Fluorescent dextran tracers of varying sizes have been used to assess paranodal permeability in myelinated sciatic nerve fibers from control and three `myelin mutant' mice, Caspr-null, cst-null and shaking. We demonstrate that in all of these the paranode is permeable to small tracers (3kDa, 10kDa), which penetrate most fibers, and to larger tracers (40kDa, 70kDa), which penetrate far fewer fibers and move shorter distances over longer periods of time. Despite gross diminution in transverse bands in the Caspr-null and cst-null mice, the permeability of their paranodal junctions is equivalent to that in controls. Thus, deficiency of transverse bands in these mutants does not increase the permeability of their paranodal junctions to the dextrans we used, moving from the perinodal space through the paranode to the internodal periaxonal space. In addition, we show that the shaking mice, which have thinner myelin and shorter paranodes, show increased permeability to the same tracers despite the presence of transverse bands. We conclude that the extent of penetration of these tracers does not depend on the presence or absence of transverse bands but does depend on the length of the paranode and, in turn, on the length of `pathway 3', the helical extracellular pathway that passes through the paranode parallel to the lateral edge of the myelin sheath. PMID:21618613

  19. Paranodal permeability in "myelin mutants".

    PubMed

    Shroff, Seema; Mierzwa, Amanda; Scherer, Steven S; Peles, Elior; Arevalo, Juan C; Chao, Moses V; Rosenbluth, Jack

    2011-10-01

    Fluorescent dextran tracers of varying sizes have been used to assess paranodal permeability in myelinated sciatic nerve fibers from control and three "myelin mutant" mice, Caspr-null, cst-null, and shaking. We demonstrate that in all of these the paranode is permeable to small tracers (3 kDa and 10 kDa), which penetrate most fibers, and to larger tracers (40 kDa and 70 kDa), which penetrate far fewer fibers and move shorter distances over longer periods of time. Despite gross diminution in transverse bands (TBs) in the Caspr-null and cst-null mice, the permeability of their paranodal junctions is equivalent to that in controls. Thus, deficiency of TBs in these mutants does not increase the permeability of their paranodal junctions to the dextrans we used, moving from the perinodal space through the paranode to the internodal periaxonal space. In addition, we show that the shaking mice, which have thinner myelin and shorter paranodes, show increased permeability to the same tracers despite the presence of TBs. We conclude that the extent of penetration of these tracers does not depend on the presence or absence of TBs but does depend on the length of the paranode and, in turn, on the length of "pathway 3," the helical extracellular pathway that passes through the paranode parallel to the lateral edge of the myelin sheath. PMID:21618613

  20. Protein 4.1B associates with both Caspr/paranodin and Caspr2 at paranodes and juxtaparanodes of myelinated fibres.

    PubMed

    Denisenko-Nehrbass, Natalia; Oguievetskaia, Ksénia; Goutebroze, Laurence; Galvez, Thierry; Yamakawa, Hisashi; Ohara, Osamu; Carnaud, Michèle; Girault, Jean-Antoine

    2003-01-01

    Caspr/paranodin, a neuronal transmembrane glycoprotein, is essential for the structure and function of septate-like paranodal axoglial junctions at nodes of Ranvier. A closely related protein, Caspr2, is concentrated in juxtaparanodal regions where it associates indirectly with the shaker-type potassium channels. Although ultrastructural studies indicate that paranodal complexes are linked to the cytoskeleton, the intracellular partners of Caspr/paranodin, as well as those of Caspr2, are poorly characterized. We show that the conserved intracellular juxtamembrane regions (GNP motif) of Caspr/paranodin and Caspr2 bind proteins 4.1R and 4.1B. 4.1B is known to be enriched in paranodal and juxtaparanodal regions. 4.1B immunoreactivity accumulates progressively at paranodes and juxtaparanodes during postnatal development, following the concentration of Caspr/paranodin and Caspr2, respectively, in central and peripheral myelinated axons. These two proteins coimmunoprecipitated with 4.1B in brain homogenates. Our results provide strong evidence for the association of 4.1B with Caspr/paranodin at paranodes and with Caspr2 at juxtaparanodes. We propose that 4.1B anchors these axonal proteins to the actin-based cytoskeleton in these two regions. PMID:12542678

  1. Activated microglia mediate axoglial disruption that contributes to axonal injury in multiple sclerosis.

    PubMed

    Howell, Owain W; Rundle, Jon L; Garg, Anurag; Komada, Masayuki; Brophy, Peter J; Reynolds, Richard

    2010-10-01

    The complex manifestations of chronic multiple sclerosis (MS)are due in part to widespread axonal abnormalities that affect lesional and nonlesional areas in the central nervous system. We describe an association between microglial activation and axon/oligodendrocyte pathology at nodal and paranodal domains in normal-appearing white matter (NAWM) of MS cases and in experimental autoimmune encephalomyelitis (EAE). The extent of paranodal axoglial (neurofascin-155(+)/Caspr1(+)) disruption correlated with local microglial inflammation and axonal injury (expression of nonphosphorylated neurofilaments) in MS NAWM. These changes were independent of demyelinating lesions and did not correlate with the density of infiltrating lymphocytes. Similar axoglial alterations were seen in the subcortical white matter of Parkinson disease cases and in preclinical EAE, at a time point when there is microglial activation before the infiltration of immune cells. Disruption of the axoglial unit in adjuvant-immunized animals was reversible and coincided with the resolution of microglial inflammation; paranodal damage and microglial inflammation persisted in chronic EAE. Axoglial integrity could be preserved by the administration of minocycline, which inhibited microglial activation, in actively immunized animals. These data indicate that, in MS NAWM, permanent disruption to axoglial domains in an environment of microglial inflammation is an early indicator of axonal injury that likely affects nerve conduction and may contribute to physiologic dysfunction.

  2. Protein zero is necessary for E-cadherin-mediated adherens junction formation in Schwann cells.

    PubMed

    Menichella, D M; Arroyo, E J; Awatramani, R; Xu, T; Baron, P; Vallat, J M; Balsamo, J; Lilien, J; Scarlato, G; Kamholz, J; Scherer, S S; Shy, M E

    2001-12-01

    Protein Zero (P0), the major structural protein in the peripheral nervous system (PNS) myelin, acts as a homotypic adhesion molecule and is thought to mediate compaction of adjacent wraps of myelin membrane. E-Cadherin, a calcium-dependent adhesion molecule, is also expressed in myelinating Schwann cells in the PNS and is involved in forming adherens junctions between adjacent loops of membrane at the paranode. To determine the relationship, if any, between P0-mediated and cadherin-mediated adhesion during myelination, we investigated the expression of E-cadherin and its binding partner, beta-catenin, in sciatic nerve of mice lacking P0 (P0(-/-)). We find that in P0(-/-) peripheral myelin neither E-cadherin nor beta-catenin are localized to paranodes, but are instead found in small puncta throughout the Schwann cell. In addition, only occasional, often rudimentary, adherens junctions are formed. Analysis of E-cadherin and beta-catenin expression during nerve development demonstrates that E-cadherin and beta-catenin are localized to the paranodal region after the onset of myelin compaction. Interestingly, axoglial junction formation is normal in P0(-/-) nerve. Taken together, these data demonstrate that P0 is necessary for the formation of adherens junctions but not axoglial junctions in myelinating Schwann cells. PMID:11749037

  3. Defects in myelination, paranode organization and Purkinje cell innervation in the ether lipid-deficient mouse cerebellum

    PubMed Central

    Teigler, Andre; Komljenovic, Dorde; Draguhn, Andreas; Gorgas, Karin; Just, Wilhelm W.

    2009-01-01

    Ether lipids (ELs), particularly plasmalogens, are essential constituents of the mammalian central nervous system. The physiological role of ELs, in vivo, however is still enigmatic. In the present study, we characterized a mouse model carrying a targeted deletion of the peroxisomal dihydroxyacetonephosphate acyltransferase gene that results in the complete lack of ELs. Investigating the cerebellum of these mice, we observed: (i) defects in foliation patterning and delay in precursor granule cell migration, (ii) defects in myelination and concomitant reduction in the level of myelin basic protein, (iii) disturbances in paranode organization by extending the Caspr distribution and disrupting axo-glial septate-like junctions, (iv) impaired innervation of Purkinje cells by both parallel fibers and climbing fibers and (v) formation of axon swellings by the accumulation of inositol-tris-phosphate receptor 1 containing smooth ER-like tubuli. Functionally, conduction velocity of myelinated axons in the corpus callosum was significantly reduced. Most of these phenotypes were already apparent at P20 but still persisted in 1-year-old animals. In summary, these data show that EL deficiency results in severe developmental and lasting structural alterations at the cellular and network level of the cerebellum, and reveal an important role of ELs for proper brain function. Common molecular mechanisms that may underlie these phenotypes are discussed. PMID:19270340

  4. Defects in myelination, paranode organization and Purkinje cell innervation in the ether lipid-deficient mouse cerebellum.

    PubMed

    Teigler, Andre; Komljenovic, Dorde; Draguhn, Andreas; Gorgas, Karin; Just, Wilhelm W

    2009-06-01

    Ether lipids (ELs), particularly plasmalogens, are essential constituents of the mammalian central nervous system. The physiological role of ELs, in vivo, however is still enigmatic. In the present study, we characterized a mouse model carrying a targeted deletion of the peroxisomal dihydroxyacetonephosphate acyltransferase gene that results in the complete lack of ELs. Investigating the cerebellum of these mice, we observed: (i) defects in foliation patterning and delay in precursor granule cell migration, (ii) defects in myelination and concomitant reduction in the level of myelin basic protein, (iii) disturbances in paranode organization by extending the Caspr distribution and disrupting axo-glial septate-like junctions, (iv) impaired innervation of Purkinje cells by both parallel fibers and climbing fibers and (v) formation of axon swellings by the accumulation of inositol-tris-phosphate receptor 1 containing smooth ER-like tubuli. Functionally, conduction velocity of myelinated axons in the corpus callosum was significantly reduced. Most of these phenotypes were already apparent at P20 but still persisted in 1-year-old animals. In summary, these data show that EL deficiency results in severe developmental and lasting structural alterations at the cellular and network level of the cerebellum, and reveal an important role of ELs for proper brain function. Common molecular mechanisms that may underlie these phenotypes are discussed. PMID:19270340

  5. A novel Caspr mutation causes the shambling mouse phenotype by disrupting axoglial interactions of myelinated nerves.

    PubMed

    Sun, Xiao-yang; Takagishi, Yoshiko; Okabe, Erina; Chishima, Yûko; Kanou, Yasuhiko; Murase, Shiori; Mizumura, Kazue; Inaba, Mie; Komatsu, Yukio; Hayashi, Yoshitaka; Peles, Elior; Oda, Sen-ichi; Murata, Yoshiharu

    2009-11-01

    The neurological mouse mutation shambling (shm) exhibits ataxia and hindlimb paresis. Positional cloning of shm showed that it encodes contactin-associated protein (Caspr), which is required for formation of the paranodal junction in myelinated nerves. The shm mutation is a TT insertion in the Caspr gene that results in a frame shift and a premature stop codon at the COOH-terminus. The truncated Caspr protein that is generated lacks the transmembrane and cytoplasmic domains. Here, we found that the nodal/paranodal axoplasm of shm mice lack paranodal junctions and contain large mitochondria and abnormal accumulations of cytoplasmic organelles that indicate altered axonal transport. Immunohistochemical analysis of mutant mice showed reduced expression of Caspr, contactin, and neurofascin 155, which are thought to form a protein complex in the paranodal region; protein 4.1B, however, was normally distributed. The mutant mice had aberrant localization of voltage-gated ion channels on the axolemma of nodal/paranodal regions. Electrophysiological analysis demonstrated that the velocity of saltatory conduction was reduced in sciatic nerves and that the visual response was attenuated in the primary visual cortex. These abnormalities likely contribute to the neurological phenotype of the mutant mice. PMID:19816196

  6. Loss of glial neurofascin155 delays developmental synapse elimination at the neuromuscular junction.

    PubMed

    Roche, Sarah L; Sherman, Diane L; Dissanayake, Kosala; Soucy, Geneviève; Desmazieres, Anne; Lamont, Douglas J; Peles, Elior; Julien, Jean-Pierre; Wishart, Thomas M; Ribchester, Richard R; Brophy, Peter J; Gillingwater, Thomas H

    2014-09-17

    Postnatal synapse elimination plays a critical role in sculpting and refining neural connectivity throughout the central and peripheral nervous systems, including the removal of supernumerary axonal inputs from neuromuscular junctions (NMJs). Here, we reveal a novel and important role for myelinating glia in regulating synapse elimination at the mouse NMJ, where loss of a single glial cell protein, the glial isoform of neurofascin (Nfasc155), was sufficient to disrupt postnatal remodeling of synaptic circuitry. Neuromuscular synapses were formed normally in mice lacking Nfasc155, including the establishment of robust neuromuscular synaptic transmission. However, loss of Nfasc155 was sufficient to cause a robust delay in postnatal synapse elimination at the NMJ across all muscle groups examined. Nfasc155 regulated neuronal remodeling independently of its canonical role in forming paranodal axo-glial junctions, as synapse elimination occurred normally in mice lacking the axonal paranodal protein Caspr. Rather, high-resolution proteomic screens revealed that loss of Nfasc155 from glial cells was sufficient to disrupt neuronal cytoskeletal organization and trafficking pathways, resulting in reduced levels of neurofilament light (NF-L) protein in distal axons and motor nerve terminals. Mice lacking NF-L recapitulated the delayed synapse elimination phenotype observed in mice lacking Nfasc155, suggesting that glial cells regulate synapse elimination, at least in part, through modulation of the axonal cytoskeleton. Together, our study reveals a glial cell-dependent pathway regulating the sculpting of neuronal connectivity and synaptic circuitry in the peripheral nervous system. PMID:25232125

  7. Paranodal interactions regulate expression of sodium channel subtypes and provide a diffusion barrier for the node of Ranvier.

    PubMed

    Rios, Jose C; Rubin, Marina; St Martin, Mary; Downey, Ryan T; Einheber, Steven; Rosenbluth, Jack; Levinson, S Rock; Bhat, Manzoor; Salzer, James L

    2003-08-01

    The node of Ranvier is a distinct domain of myelinated axons that is highly enriched in sodium channels and is critical for impulse propagation. During development, the channel subtypes expressed at the node undergo a transition from Nav1.2 to Nav1.6. Specialized junctions that form between the paranodal glial membranes and axon flank the nodes and are candidates to regulate their maturation and delineate their boundaries. To investigate these roles, we characterized node development in mice deficient in contactin-associated protein (Caspr), an integral junctional component. Paranodes in these mice lack transverse bands, a hallmark of the mature junction, and exhibit progressive disruption of axon-paranodal loop interactions in the CNS. Caspr mutant mice display significant abnormalities at central nodes; components of the nodes progressively disperse along axons, and many nodes fail to mature properly, persistently expressing Nav1.2 rather than Nav1.6. In contrast, PNS nodes are only modestly longer and, although maturation is delayed, eventually all express Nav1.6. Potassium channels are aberrantly clustered in the paranodes; these clusters are lost over time in the CNS, whereas they persist in the PNS. These findings indicate that interactions of the paranodal loops with the axon promote the transition in sodium channel subtypes at CNS nodes and provide a lateral diffusion barrier that, even in the absence of transverse bands, maintains a high concentration of components at the node and the integrity of voltage-gated channel domains. PMID:12904461

  8. Nogo-A at CNS paranodes is a ligand of Caspr: possible regulation of K(+) channel localization.

    PubMed

    Nie, Du-Yu; Zhou, Zhi-Hong; Ang, Beng-Ti; Teng, Felicia Y H; Xu, Gang; Xiang, Tao; Wang, Chao-Yang; Zeng, Li; Takeda, Yasuo; Xu, Tian-Le; Ng, Yee-Kong; Faivre-Sarrailh, Catherine; Popko, Brian; Ling, Eng-Ang; Schachner, Melitta; Watanabe, Kazutada; Pallen, Catherine J; Tang, Bor Luen; Xiao, Zhi-Cheng

    2003-11-01

    We report Nogo-A as an oligodendroglial component congregating and interacting with the Caspr-F3 complex at paranodes. However, its receptor Nogo-66 receptor (NgR) does not segregate to specific axonal domains. CHO cells cotransfected with Caspr and F3, but not with F3 alone, bound specifically to substrates coated with Nogo-66 peptide and GST-Nogo-66. Binding persisted even after phosphatidylinositol- specific phospholipase C (PI-PLC) removal of GPI-linked F3 from the cell surface, suggesting a direct interaction between Nogo-66 and Caspr. Both Nogo-A and Caspr co-immunoprecipitated with Kv1.1 and Kv1.2, and the developmental expression pattern of both paralleled compared with Kv1.1, implicating a transient interaction between Nogo-A-Caspr and K(+) channels at early stages of myelination. In pathological models that display paranodal junctional defects (EAE rats, and Shiverer and CGT(-/-) mice), distances between the paired labeling of K(+) channels were shortened significantly and their localization shifted toward paranodes, while paranodal Nogo-A congregation was markedly reduced. Our results demonstrate that Nogo-A interacts in trans with axonal Caspr at CNS paranodes, an interaction that may have a role in modulating axon-glial junction architecture and possibly K(+)-channel localization during development. PMID:14592966

  9. Contactin-1 regulates myelination and nodal/paranodal domain organization in the central nervous system

    PubMed Central

    Çolakoğlu, Gülsen; Bergstrom-Tyrberg, Ulrika; Berglund, Erik O.; Ranscht, Barbara

    2014-01-01

    Myelin, a multilayered membrane sheath formed by oligodendrocytes around axons in the CNS, enables rapid nerve impulse conduction and sustains neuronal health. The signals exchanged between axons and oligodendrocytes in myelin remain to be fully elucidated. Here we provide genetic evidence for multiple and critical functions of Contactin-1 in central myelin. We document dynamic Contactin-1 expression on oligodendrocytes in vivo, and progressive accumulation at nodes of Ranvier and paranodes during postnatal mouse development. Nodal and paranodal expression stabilized in mature myelin, but overall membranous expression diminished. Contactin-1–deficiency disrupted paranodal junction formation as evidenced by loss of Caspr, mislocalized potassium Kv1.2 channels, and abnormal myelin terminal loops. Reduced numbers and impaired maturation of sodium channel clusters accompanied this phenotype. Histological, electron microscopic, and biochemical analyses uncovered significant hypomyelination in Contactin-1–deficient central nerves, with up to 60% myelin loss. Oligodendrocytes were present in normal numbers, albeit a minor population of neuronal/glial antigen 2-positive (NG2+) progenitors lagged in maturation by postnatal day 18, when the mouse null mutation was lethal. Major contributing factors to hypomyelination were defects in the generation and organization of myelin membranes, as judged by electron microscopy and quantitative analysis of oligodendrocyte processes labeled by GFP transgenically expressed from the proteolipid protein promoter. These data reveal that Contactin-1 regulates both myelin formation and organization of nodal and paranodal domains in the CNS. These multiple roles distinguish central Contactin-1 functions from its specific role at paranodes in the periphery, and emphasize mechanistic differences in central and peripheral myelination. PMID:24385581

  10. Changes in the expression and localization of the paranodal protein Caspr on axons in chronic multiple sclerosis.

    PubMed

    Wolswijk, Guus; Balesar, Rawien

    2003-07-01

    The presence of intact paranodal junctions on myelinated axons in the CNS and PNS is crucial for both myelin sheath attachment and saltatory impulse conduction. The axonal glycoprotein contactin-associated protein (Caspr) is expressed in the paranodal region and plays an important role in the creation and maintenance of these adhesive junctions. In the present study, antibodies to Caspr were used to assess the integrity of paranodal junctions on myelinated axons in brain and spinal cord tissue from subjects with longstanding multiple sclerosis, a neurological disorder that affects both myelin and axons. Triple immunofluorescence combined with confocal laser scanning microscopy showed that axons in the demyelinated centre of the 36 brain and 16 spinal cord multiple sclerosis lesions studied were devoid of Caspr immunoreactivity, suggesting that axons down regulate the expression of Caspr following demyelination. Additional data indicated that Caspr reappears in the paranodal region with the formation of new myelin sheaths. Immuno labelling further revealed that Caspr on myelinated axons in border regions was often no longer concentrated in the paranodal region, but was also present in the internodal region-a phenomenon particularly common in the borders of the more chronic lesions in the collection. Myelinated axons with long Caspr-positive stretches were often present at a considerable distance from the lesion edges. These findings raise the possibility that the aberrant location of Caspr is an early sign of impending myelin loss. This would imply that demyelination continues at a slow rate in established lesions. The diameters of Caspr-positive structures on some myelinated axons near the lesion edges were also increased. Moreover, the gap between individual myelin sheaths on these apparently swollen axons was widened occasionally and a very small myelin sheath plus additional Caspr-positive structures had sometimes formed in the enlarged space. This finding thus

  11. Spatial mapping of juxtacrine axo-glial interactions identifies novel molecules in peripheral myelination

    PubMed Central

    Poitelon, Y.; Bogni, S.; Matafora, V.; Della-Flora Nunes, G.; Hurley, E.; Ghidinelli, M.; Katzenellenbogen, B. S.; Taveggia, C.; Silvestri, N.; Bachi, A.; Sannino, A.; Wrabetz, L.; Feltri, M. L.

    2015-01-01

    Cell–cell interactions promote juxtacrine signals in specific subcellular domains, which are difficult to capture in the complexity of the nervous system. For example, contact between axons and Schwann cells triggers signals required for radial sorting and myelination. Failure in this interaction causes dysmyelination and axonal degeneration. Despite its importance, few molecules at the axo-glial surface are known. To identify novel molecules in axo-glial interactions, we modified the ‘pseudopodia' sub-fractionation system and isolated the projections that glia extend when they receive juxtacrine signals from axons. By proteomics we identified the signalling networks present at the glial-leading edge, and novel proteins, including members of the Prohibitin family. Glial-specific deletion of Prohibitin-2 in mice impairs axo-glial interactions and myelination. We thus validate a novel method to model morphogenesis and juxtacrine signalling, provide insights into the molecular organization of the axo-glial contact, and identify a novel class of molecules in myelination. PMID:26383514

  12. Nodes of Ranvier and Paranodes in Chronic Acquired Neuropathies

    PubMed Central

    Cifuentes-Diaz, Carmen; Dubourg, Odile; Irinopoulou, Theano; Vigny, Marc; Lachkar, Sylvie; Decker, Laurence; Charnay, Patrick; Denisenko, Natalia; Maisonobe, Thierry; Léger, Jean-Marc; Viala, Karine; Hauw, Jean-Jacques; Girault, Jean-Antoine

    2011-01-01

    Chronic acquired neuropathies of unknown origin are classified as chronic inflammatory demyelinating polyneuropathies (CIDP) and chronic idiopathic axonal polyneuropathies (CIAP). The diagnosis can be very difficult, although it has important therapeutic implications since CIDP can be improved by immunomodulating treatment. The aim of this study was to examine the possible abnormalities of nodal and paranodal regions in these two types of neuropathies. Longitudinal sections of superficial peroneal nerves were obtained from biopsy material from 12 patients with CIDP and 10 patients with CIAP and studied by immunofluorescence and in some cases electron microscopy. Electron microscopy revealed multiple alterations in the nodal and paranodal regions which predominated in Schwann cells in CIDP and in axons in CIAP. In CIDP paranodin/Caspr immunofluorescence was more widespread than in control nerves, extending along the axon in internodes where it appeared intense. Nodal channels Nav and KCNQ2 were less altered but were also detected in the internodes. In CIAP paranodes, paranodin labeling was irregular and/or decreased. To test the consequences of acquired primary Schwann cells alteration on axonal proteins, we used a mouse model based on induced deletion of the transcription factor Krox-20 gene. In the demyelinated sciatic nerves of these mice we observed alterations similar to those found in CIDP by immunofluorescence, and immunoblotting demonstrated increased levels of paranodin. Finally we examined whether the alterations in paranodin immunoreactivity could have a diagnosis value. In a sample of 16 biopsies, the study of paranodin immunofluorescence by blind evaluators led to correct diagnosis in 70±4% of the cases. This study characterizes for the first time the abnormalities of nodes of Ranvier in CIAP and CIDP, and the altered expression and distribution of nodal and paranodal proteins. Marked differences were observed between CIDP and CIAP and the alterations

  13. Nodes of ranvier and paranodes in chronic acquired neuropathies.

    PubMed

    Cifuentes-Diaz, Carmen; Dubourg, Odile; Irinopoulou, Theano; Vigny, Marc; Lachkar, Sylvie; Decker, Laurence; Charnay, Patrick; Denisenko, Natalia; Maisonobe, Thierry; Léger, Jean-Marc; Viala, Karine; Hauw, Jean-Jacques; Girault, Jean-Antoine

    2011-01-01

    Chronic acquired neuropathies of unknown origin are classified as chronic inflammatory demyelinating polyneuropathies (CIDP) and chronic idiopathic axonal polyneuropathies (CIAP). The diagnosis can be very difficult, although it has important therapeutic implications since CIDP can be improved by immunomodulating treatment. The aim of this study was to examine the possible abnormalities of nodal and paranodal regions in these two types of neuropathies. Longitudinal sections of superficial peroneal nerves were obtained from biopsy material from 12 patients with CIDP and 10 patients with CIAP and studied by immunofluorescence and in some cases electron microscopy. Electron microscopy revealed multiple alterations in the nodal and paranodal regions which predominated in Schwann cells in CIDP and in axons in CIAP. In CIDP paranodin/Caspr immunofluorescence was more widespread than in control nerves, extending along the axon in internodes where it appeared intense. Nodal channels Nav and KCNQ2 were less altered but were also detected in the internodes. In CIAP paranodes, paranodin labeling was irregular and/or decreased. To test the consequences of acquired primary Schwann cells alteration on axonal proteins, we used a mouse model based on induced deletion of the transcription factor Krox-20 gene. In the demyelinated sciatic nerves of these mice we observed alterations similar to those found in CIDP by immunofluorescence, and immunoblotting demonstrated increased levels of paranodin. Finally we examined whether the alterations in paranodin immunoreactivity could have a diagnosis value. In a sample of 16 biopsies, the study of paranodin immunofluorescence by blind evaluators led to correct diagnosis in 70 ± 4% of the cases. This study characterizes for the first time the abnormalities of nodes of Ranvier in CIAP and CIDP, and the altered expression and distribution of nodal and paranodal proteins. Marked differences were observed between CIDP and CIAP and the

  14. No effect of genetic deletion of contactin-associated protein (CASPR) on axonal orientation and synaptic plasticity.

    PubMed

    Pillai, Anilkumar M; Garcia-Fresco, German P; Sousa, Aurea D; Dupree, Jeffrey L; Philpot, Benjamin D; Bhat, Manzoor A

    2007-08-15

    Myelinated axons are endowed with a specialized domain structure that is essential for saltatory action potential conduction. The paranodal domain contains the axoglial junctions and displays a unique ultrastructure that resembles the invertebrate septate junctions (SJs). Biochemical characterizations of the paranodal axoglial SJs have identified several molecular components that include Caspr and contactin (Cont) on the axonal side and neurofascin 155 kDa (NF155) isoform on the glial side. All these proteins are essential for the formation of the axoglial SJs. Based on the interactions between Caspr and Cont and their colocalization in the CA1 synaptic areas, it was proposed that the synaptic function of Cont requires Caspr. Here we have extended the phenotypic analysis of CASPR mutants to address further the role of Caspr at the axoglial SJs and also in axonal orientation and synaptic plasticity. We report that, in CASPR mutants, the smooth endoplasmic reticulum (SER) forms elongated membranous complexes that accumulate at the nodal/paranodal region and stretch into the juxtaparanodal region, a defect that is consistent with the paranodal disorganization. We show that the cerebellar microorganization is unaffected in CASPR mutants. We also demonstrate that Caspr function is not essential for normal CA1 synaptic transmission and plasticity. Taken together with previous findings, our results highlight that the Caspr/Cont complex is essential for the formation of axoglial SJs, whereas Cont may regulate axonal orientation and synaptic plasticity independent of its association with Caspr. PMID:17549747

  15. Axoglial contacts in the area postrema of the cat - An ultrastructural study

    NASA Technical Reports Server (NTRS)

    Damelio, Fernando E.; Gibbs, Michael A.; Mehler, William R.; Philpott, Delbert E.; Savage, Wayne

    1986-01-01

    Axoglial contacts were observed in an ultrastructural study of the area postrema of the cat. According to the disposition of the electron-dense projections attached to the adjoining membranes these contacts were classified as symmetrical or asymmetrical. The axon profiles contained aggregations of clear vesicles randomly distributed or grouped in clusters adjacent to the electron-dense projections. Dense core vesicles were occasionally seen. The neuroglial profiles were either astrocytic or ependymoglial in nature. The astrocytes showed a clear cytoplasm, polymorphous vesicles, mitochondria, glycogen granules, and bundles of filaments. The ependymal cells, in contrast, had a more electron-dense and granular appearance, tubular structures, irregular vesicular formations, profiles of smooth reticuloendoplasm, and filaments grouped in bundles or isolated in the cytoplasm. The possibility that these contacts might play a role in the chemical transfer from neurons to glial cells is discussed on the basis of existing biochemical data.

  16. HDAC1/2-Dependent P0 Expression Maintains Paranodal and Nodal Integrity Independently of Myelin Stability through Interactions with Neurofascins

    PubMed Central

    Brügger, Valérie; Engler, Stefanie; Pereira, Jorge A.; Ruff, Sophie; Horn, Michael; Welzl, Hans; Münger, Emmanuelle; Vaquié, Adrien; Sidiropoulos, Páris N. M.; Egger, Boris; Yotovski, Peter; Filgueira, Luis; Somandin, Christian; Lühmann, Tessa C.; D’Antonio, Maurizio; Yamaguchi, Teppei; Matthias, Patrick; Suter, Ueli; Jacob, Claire

    2015-01-01

    The pathogenesis of peripheral neuropathies in adults is linked to maintenance mechanisms that are not well understood. Here, we elucidate a novel critical maintenance mechanism for Schwann cell (SC)–axon interaction. Using mouse genetics, ablation of the transcriptional regulators histone deacetylases 1 and 2 (HDAC1/2) in adult SCs severely affected paranodal and nodal integrity and led to demyelination/remyelination. Expression levels of the HDAC1/2 target gene myelin protein zero (P0) were reduced by half, accompanied by altered localization and stability of neurofascin (NFasc)155, NFasc186, and loss of Caspr and septate-like junctions. We identify P0 as a novel binding partner of NFasc155 and NFasc186, both in vivo and by in vitro adhesion assay. Furthermore, we demonstrate that HDAC1/2-dependent P0 expression is crucial for the maintenance of paranodal/nodal integrity and axonal function through interaction of P0 with neurofascins. In addition, we show that the latter mechanism is impaired by some P0 mutations that lead to late onset Charcot-Marie-Tooth disease. PMID:26406915

  17. The paranodal complex of F3/contactin and caspr/paranodin traffics to the cell surface via a non-conventional pathway.

    PubMed

    Bonnon, Carine; Goutebroze, Laurence; Denisenko-Nehrbass, Natasha; Girault, Jean-Antoine; Faivre-Sarrailh, Catherine

    2003-11-28

    During myelination, membrane-specialized domains are generated by complex interactions between axon and glial cells. The cell adhesion molecules caspr/paranodin and F3/contactin play a crucial role in the generation of functional septate-like junctions at paranodes. We have previously demonstrated that association with the glycosylphosphatidylinositol-linked F3/contactin is required for the recruitment of caspr/paranodin into the lipid rafts and its targeting to the cell surface. When transfected alone in neuroblastoma N2a cells, caspr/paranodin is retained in the endoplasmic reticulum (ER). Using chimerical constructs, we show that the cytoplasmic region does not contain any ER retention signal, whereas the ectodomain plays a crucial role in caspr/paranodin trafficking. A series of truncations encompassing the extracellular region of caspr/paranodin was unable to abolish ER retention. We show that N-glycosylation and quality control by the lectin-chaperone calnexin are required for the cell surface delivery of caspr/paranodin. Cell surface transport of F3/contactin and caspr/paranodin is insensitive to brefeldin A and the two glycoproteins are endoglycosidase H-sensitive when associated in complex, recruited into the lipid rafts, and expressed on the cell surface. Our results indicate a Golgi-independent pathway for the paranodal cell adhesion complex that may be implicated in the segregation of axonal subdomains. PMID:12972410

  18. HDAC1/2-Dependent P0 Expression Maintains Paranodal and Nodal Integrity Independently of Myelin Stability through Interactions with Neurofascins.

    PubMed

    Brügger, Valérie; Engler, Stefanie; Pereira, Jorge A; Ruff, Sophie; Horn, Michael; Welzl, Hans; Münger, Emmanuelle; Vaquié, Adrien; Sidiropoulos, Páris N M; Egger, Boris; Yotovski, Peter; Filgueira, Luis; Somandin, Christian; Lühmann, Tessa C; D'Antonio, Maurizio; Yamaguchi, Teppei; Matthias, Patrick; Suter, Ueli; Jacob, Claire

    2015-01-01

    The pathogenesis of peripheral neuropathies in adults is linked to maintenance mechanisms that are not well understood. Here, we elucidate a novel critical maintenance mechanism for Schwann cell (SC)-axon interaction. Using mouse genetics, ablation of the transcriptional regulators histone deacetylases 1 and 2 (HDAC1/2) in adult SCs severely affected paranodal and nodal integrity and led to demyelination/remyelination. Expression levels of the HDAC1/2 target gene myelin protein zero (P0) were reduced by half, accompanied by altered localization and stability of neurofascin (NFasc)155, NFasc186, and loss of Caspr and septate-like junctions. We identify P0 as a novel binding partner of NFasc155 and NFasc186, both in vivo and by in vitro adhesion assay. Furthermore, we demonstrate that HDAC1/2-dependent P0 expression is crucial for the maintenance of paranodal/nodal integrity and axonal function through interaction of P0 with neurofascins. In addition, we show that the latter mechanism is impaired by some P0 mutations that lead to late onset Charcot-Marie-Tooth disease. PMID:26406915

  19. Nodal, paranodal and juxtaparanodal axonal proteins during demyelination and remyelination in multiple sclerosis.

    PubMed

    Coman, I; Aigrot, M S; Seilhean, D; Reynolds, R; Girault, J A; Zalc, B; Lubetzki, C

    2006-12-01

    Saltatory conduction in myelinated fibres depends on the specific molecular organization of highly specialized axonal domains at the node of Ranvier, the paranodal and the juxtaparanodal regions. Voltage-gated sodium channels (Na(v)) have been shown to be deployed along the naked demyelinated axon in experimental models of CNS demyelination and in multiple sclerosis lesions. Little is known about aggregation of nodal, paranodal and juxtaparanodal constituents during the repair process. We analysed by immunohistochemistry on free-floating sections from multiple sclerosis brains the expression and distribution of nodal (Na(v) channels), paranodal (paranodin/Caspr) and juxtaparanodal (K(v) channels and Caspr2) molecules in demyelinated and remyelinated lesions. Whereas in demyelinated lesions, paranodal and juxtaparanodal proteins are diffusely distributed on denuded axons, the distribution of Na(v) channels is heterogeneous, with a diffuse immunoreactivity but also few broad Na(v) channel aggregates in all demyelinated lesions. In contrast to the demyelinated plaques, all remyelinated lesions are characterized by the detection of aggregates of Na(v) channels, paranodin/Caspr, K(v) channels and Caspr2. Our data suggest that these aggregates precede remyelination, and that Na(v) channel aggregation is the initial event, followed by aggregation of paranodal and then juxtaparanodal axonal proteins. Remyelination takes place in multiple sclerosis tissue but myelin repair is often incomplete, and the reasons for this remyelination deficit are many. We suggest that a defect of Na(v) channel aggregation might be involved in the remyelination failure in demyelinated lesions with spared axons and oligodendroglial cells. PMID:16766541

  20. Paranodal myelin retraction in relapsing experimental autoimmune encephalomyelitis visualized by coherent anti-Stokes Raman scattering microscopy

    NASA Astrophysics Data System (ADS)

    Fu, Yan; Frederick, Terra J.; Huff, Terry B.; Goings, Gwendolyn E.; Miller, Stephen D.; Cheng, Ji-Xin

    2011-10-01

    How demyelination is initiated is a standing question for pathology of multiple sclerosis. By label-free coherent anti-Stokes Raman scattering (CARS) imaging of myelin lipids, we investigate myelin integrity in the lumbar spinal cord tissue isolated from naïve SJL mice, and from mice at the onset, peak acute, and remission stages of relapsing experimental autoimmune encephalomyelitis (EAE). Progressive demyelinating disease is initially characterized by the retraction of paranodal myelin both at the onset of disease and at the borders of acute demyelinating lesions. Myelin retraction is confirmed by elongated distribution of neurofascin proteins visualized by immunofluorescence. The disruption of paranodal myelin subsequently exposes Kv1.2 channels at the juxtaparanodes and lead to the displacement of Kv1.2 channels to the paranodal and nodal domains. Paranodal myelin is partially restored during disease remission, indicating spontaneous myelin regeneration. These findings suggest that paranodal domain injury precedes formation of internodal demyelinating lesions in relapsing EAE. Our results also demonstrate that CARS microscopy is an effective readout of myelin disease burden.

  1. Myelin organization in the nodal, paranodal, and juxtaparanodal regions revealed by scanning x-ray microdiffraction.

    PubMed

    Inouye, Hideyo; Liu, Jiliang; Makowski, Lee; Palmisano, Marilena; Burghammer, Manfred; Riekel, Christian; Kirschner, Daniel A

    2014-01-01

    X-ray diffraction has provided extensive information about the arrangement of lipids and proteins in multilamellar myelin. This information has been limited to the abundant inter-nodal regions of the sheath because these regions dominate the scattering when x-ray beams of 100 µm diameter or more are used. Here, we used a 1 µm beam, raster-scanned across a single nerve fiber, to obtain detailed information about the molecular architecture in the nodal, paranodal, and juxtaparanodal regions. Orientation of the lamellar membrane stacks and membrane periodicity varied spatially. In the juxtaparanode-internode, 198-202 Å-period membrane arrays oriented normal to the nerve fiber axis predominated, whereas in the paranode-node, 205-208 Å-period arrays oriented along the fiber direction predominated. In parts of the sheath distal to the node, multiple sets of lamellar reflections were observed at angles to one another, suggesting that the myelin multilayers are deformed at the Schmidt-Lanterman incisures. The calculated electron density of myelin in the different regions exhibited membrane bilayer profiles with varied electron densities at the polar head groups, likely due to different amounts of major myelin proteins (P0 glycoprotein and myelin basic protein). Scattering from the center of the nerve fibers, where the x-rays are incident en face (perpendicular) to the membrane planes, provided information about the lateral distribution of protein. By underscoring the heterogeneity of membrane packing, microdiffraction analysis suggests a powerful new strategy for understanding the underlying molecular foundation of a broad spectrum of myelinopathies dependent on local specializations of myelin structure in both the PNS and CNS.

  2. Mutations in CNTNAP1 and ADCY6 are responsible for severe arthrogryposis multiplex congenita with axoglial defects.

    PubMed

    Laquérriere, Annie; Maluenda, Jérome; Camus, Adrien; Fontenas, Laura; Dieterich, Klaus; Nolent, Flora; Zhou, Jié; Monnier, Nicole; Latour, Philippe; Gentil, Damien; Héron, Delphine; Desguerres, Isabelle; Landrieu, Pierre; Beneteau, Claire; Delaporte, Benoit; Bellesme, Céline; Baumann, Clarisse; Capri, Yline; Goldenberg, Alice; Lyonnet, Stanislas; Bonneau, Dominique; Estournet, Brigitte; Quijano-Roy, Susana; Francannet, Christine; Odent, Sylvie; Saint-Frison, Marie-Hélène; Sigaudy, Sabine; Figarella-Branger, Dominique; Gelot, Antoinette; Mussini, Jean-Marie; Lacroix, Catherine; Drouin-Garraud, Valerie; Malinge, Marie-Claire; Attié-Bitach, Tania; Bessieres, Bettina; Bonniere, Maryse; Encha-Razavi, Ferechte; Beaufrère, Anne-Marie; Khung-Savatovsky, Suonary; Perez, Marie José; Vasiljevic, Alexandre; Mercier, Sandra; Roume, Joelle; Trestard, Laetitia; Saugier-Veber, Pascale; Cordier, Marie-Pierre; Layet, Valérie; Legendre, Marine; Vigouroux-Castera, Adeline; Lunardi, Joel; Bayes, Monica; Jouk, Pierre S; Rigonnot, Luc; Granier, Michèle; Sternberg, Damien; Warszawski, Josiane; Gut, Ivo; Gonzales, Marie; Tawk, Marcel; Melki, Judith

    2014-05-01

    Non-syndromic arthrogryposis multiplex congenita (AMC) is characterized by multiple congenital contractures resulting from reduced fetal mobility. Genetic mapping and whole exome sequencing (WES) were performed in 31 multiplex and/or consanguineous undiagnosed AMC families. Although this approach identified known AMC genes, we here report pathogenic mutations in two new genes. Homozygous frameshift mutations in CNTNAP1 were found in four unrelated families. Patients showed a marked reduction in motor nerve conduction velocity (<10 m/s) and transmission electron microscopy (TEM) of sciatic nerve in the index cases revealed severe abnormalities of both nodes of Ranvier width and myelinated axons. CNTNAP1 encodes CASPR, an essential component of node of Ranvier domains which underlies saltatory conduction of action potentials along the myelinated axons, an important process for neuronal function. A homozygous missense mutation in adenylate cyclase 6 gene (ADCY6) was found in another family characterized by a lack of myelin in the peripheral nervous system (PNS) as determined by TEM. Morpholino knockdown of the zebrafish orthologs led to severe and specific defects in peripheral myelin in spite of the presence of Schwann cells. ADCY6 encodes a protein that belongs to the adenylate cyclase family responsible for the synthesis of cAMP. Elevation of cAMP can mimic axonal contact in vitro and upregulates myelinating signals. Our data indicate an essential and so far unknown role of ADCY6 in PNS myelination likely through the cAMP pathway. Mutations of genes encoding proteins of Ranvier domains or involved in myelination of Schwann cells are responsible for novel and severe human axoglial diseases. PMID:24319099

  3. Rituximab in treatment-resistant CIDP with antibodies against paranodal proteins

    PubMed Central

    Querol, Luis; Rojas-García, Ricard; Diaz-Manera, Jordi; Barcena, Joseba; Pardo, Julio; Ortega-Moreno, Angel; Sedano, Maria Jose; Seró-Ballesteros, Laia; Carvajal, Alejandra; Ortiz, Nicolau; Gallardo, Eduard

    2015-01-01

    Objective: To describe the response to rituximab in patients with treatment-resistant chronic inflammatory demyelinating polyneuropathy (CIDP) with antibodies against paranodal proteins and correlate the response with autoantibody titers. Methods: Patients with CIDP and IgG4 anti–contactin-1 (CNTN1) or anti–neurofascin-155 (NF155) antibodies who were resistant to IV immunoglobulin and corticosteroids were treated with rituximab and followed prospectively. Immunocytochemistry was used to detect anti-CNTN1 and anti-NF155 antibodies and ELISA with human recombinant CNTN1 and NF155 proteins was used to determine antibody titers. Results: Two patients had a marked improvement; another patient improved slightly after 10 years of stable, severe disease; and the fourth patient had an ischemic stroke unrelated to treatment and was lost to follow-up. Autoantibodies decreased in all patients after rituximab treatment. Conclusions: Rituximab treatment is an option for patients with CIDP with IgG4 anti-CNTN1/NF155 antibodies who are resistant to conventional therapies. Classification of evidence: This study provides Class IV evidence that rituximab is effective for patients with treatment-resistant CIDP with IgG4 anti-CNTN1 or anti-NF155 antibodies. PMID:26401517

  4. Molecular alterations underlie nodal and paranodal degeneration in type 1 diabetic neuropathy and are prevented by C-peptide.

    PubMed

    Sima, Anders A F; Zhang, Weixian; Li, Zhen-Guo; Murakawa, Yuichi; Pierson, Christopher R

    2004-06-01

    To explore the molecular abnormalities underlying the degeneration of the node of Ranvier, a characteristic aberration of type 1 diabetic neuropathy, we examined in type 1 BB/Wor and type 2 BBZDR/Wor rats changes in expression of key molecules that make up the nodal and paranodal apparatus of peripheral nerve. Their posttranslational modifications were examined in vitro. Their responsiveness to restored insulin action was examined in type 1 animals replenished with proinsulin C-peptide. In sciatic nerve, the expression of contactin, receptor protein tyrosine phosphatase beta, and the Na(+)-channel beta(1) subunit, paranodal caspr and nodal ankyrin(G) was unaltered in 2-month type 1 diabetic BB/Wor rats but significantly decreased after 8 months of diabetes. These abnormalities were prevented by C-peptide administered to type 1 BB/Wor rats and did not occur in duration- and hyperglycemia-matched type 2 BBZDR/Wor rats. The expression of the alpha-Na(+)-channel subunit was unaltered. In SH-SY5Y cells, only the combination of insulin and C-peptide normalized posttranslational O-linked N-acetylglucosamine modifications and maximized serine phosphorylation of ankyrin(G) and p85 binding to caspr. The beneficial effects of C-peptide resulted in significant normalization of the nerve conduction deficits. These data describe for the first time the progressive molecular aberrations underlying nodal and paranodal degenerative changes in type 1 diabetic neuropathy and demonstrate that they are preventable by insulinomimetic C-peptide. PMID:15161761

  5. Neuro-glial interactions at the nodes of Ranvier: implication in health and diseases

    PubMed Central

    Faivre-Sarrailh, Catherine; Devaux, Jérôme J.

    2013-01-01

    Specific cell adhesion molecules (CAMs) are dedicated to the formation of axo-glial contacts at the nodes of Ranvier of myelinated axons. They play a central role in the organization and maintenance of the axonal domains: the node, paranode, and juxtaparanode. In particular, CAMs are essential for the accumulation of voltage-gated sodium channels at the nodal gap that ensures the rapid and saltatory propagation of the action potentials (APs). The mechanisms regulating node formation are distinct in the central and peripheral nervous systems, and recent studies have highlighted the relative contribution of paranodal junctions and nodal extracellular matrix. In addition, CAMs at the juxtaparanodal domains mediate the clustering of voltage-gated potassium channels which regulate the axonal excitability. In several human pathologies, the axo-glial contacts are altered leading to disruption of the nodes of Ranvier or mis-localization of the ion channels along the axons. Node alterations and the failure of APs to propagate correctly from nodes to nodes along the axons both contribute to the disabilities in demyelinating diseases. This article reviews the mechanisms regulating the association of the axo-glial complexes and the role of CAMs in inherited and acquired neurological diseases. PMID:24194699

  6. Glial and neuronal isoforms of Neurofascin have distinct roles in the assembly of nodes of Ranvier in the central nervous system.

    PubMed

    Zonta, Barbara; Tait, Steven; Melrose, Shona; Anderson, Heather; Harroch, Sheila; Higginson, Jennifer; Sherman, Diane L; Brophy, Peter J

    2008-06-30

    Rapid nerve impulse conduction in myelinated axons requires the concentration of voltage-gated sodium channels at nodes of Ranvier. Myelin-forming oligodendrocytes in the central nervous system (CNS) induce the clustering of sodium channels into nodal complexes flanked by paranodal axoglial junctions. However, the molecular mechanisms for nodal complex assembly in the CNS are unknown. Two isoforms of Neurofascin, neuronal Nfasc186 and glial Nfasc155, are components of the nodal and paranodal complexes, respectively. Neurofascin-null mice have disrupted nodal and paranodal complexes. We show that transgenic Nfasc186 can rescue the nodal complex when expressed in Nfasc(-/-) mice in the absence of the Nfasc155-Caspr-Contactin adhesion complex. Reconstitution of the axoglial adhesion complex by expressing transgenic Nfasc155 in oligodendrocytes also rescues the nodal complex independently of Nfasc186. Furthermore, the Nfasc155 adhesion complex has an additional function in promoting the migration of myelinating processes along CNS axons. We propose that glial and neuronal Neurofascins have distinct functions in the assembly of the CNS node of Ranvier. PMID:18573915

  7. Loss of Glial Neurofascin155 Delays Developmental Synapse Elimination at the Neuromuscular Junction

    PubMed Central

    Roche, Sarah L.; Sherman, Diane L.; Dissanayake, Kosala; Soucy, Geneviève; Desmazieres, Anne; Lamont, Douglas J.; Peles, Elior; Julien, Jean-Pierre; Wishart, Thomas M.; Ribchester, Richard R.; Brophy, Peter J.

    2014-01-01

    Postnatal synapse elimination plays a critical role in sculpting and refining neural connectivity throughout the central and peripheral nervous systems, including the removal of supernumerary axonal inputs from neuromuscular junctions (NMJs). Here, we reveal a novel and important role for myelinating glia in regulating synapse elimination at the mouse NMJ, where loss of a single glial cell protein, the glial isoform of neurofascin (Nfasc155), was sufficient to disrupt postnatal remodeling of synaptic circuitry. Neuromuscular synapses were formed normally in mice lacking Nfasc155, including the establishment of robust neuromuscular synaptic transmission. However, loss of Nfasc155 was sufficient to cause a robust delay in postnatal synapse elimination at the NMJ across all muscle groups examined. Nfasc155 regulated neuronal remodeling independently of its canonical role in forming paranodal axo–glial junctions, as synapse elimination occurred normally in mice lacking the axonal paranodal protein Caspr. Rather, high-resolution proteomic screens revealed that loss of Nfasc155 from glial cells was sufficient to disrupt neuronal cytoskeletal organization and trafficking pathways, resulting in reduced levels of neurofilament light (NF-L) protein in distal axons and motor nerve terminals. Mice lacking NF-L recapitulated the delayed synapse elimination phenotype observed in mice lacking Nfasc155, suggesting that glial cells regulate synapse elimination, at least in part, through modulation of the axonal cytoskeleton. Together, our study reveals a glial cell-dependent pathway regulating the sculpting of neuronal connectivity and synaptic circuitry in the peripheral nervous system. PMID:25232125

  8. Nanotube junctions

    DOEpatents

    Crespi, Vincent Henry; Cohen, Marvin Lou; Louie, Steven Gwon; Zettl, Alexander Karlwalte

    2004-12-28

    The present invention comprises a new nanoscale metal-semiconductor, semiconductor-semiconductor, or metal-metal junction, designed by introducing topological or chemical defects in the atomic structure of the nanotube. Nanotubes comprising adjacent sections having differing electrical properties are described. These nanotubes can be constructed from combinations of carbon, boron, nitrogen and other elements. The nanotube can be designed having different indices on either side of a junction point in a continuous tube so that the electrical properties on either side of the junction vary in a useful fashion. For example, the inventive nanotube may be electrically conducting on one side of a junction and semiconducting on the other side. An example of a semiconductor-metal junction is a Schottky barrier. Alternatively, the nanotube may exhibit different semiconductor properties on either side of the junction. Nanotubes containing heterojunctions, Schottky barriers, and metal-metal junctions are useful for microcircuitry.

  9. Nanotube junctions

    DOEpatents

    Crespi, Vincent Henry; Cohen, Marvin Lou; Louie, Steven Gwon Sheng; Zettl, Alexander Karlwalter

    2003-01-01

    The present invention comprises a new nanoscale metal-semiconductor, semiconductor-semiconductor, or metal-metal junction, designed by introducing topological or chemical defects in the atomic structure of the nanotube. Nanotubes comprising adjacent sections having differing electrical properties are described. These nanotubes can be constructed from combinations of carbon, boron, nitrogen and other elements. The nanotube can be designed having different indices on either side of a junction point in a continuous tube so that the electrical properties on either side of the junction vary in a useful fashion. For example, the inventive nanotube may be electrically conducting on one side of a junction and semiconducting on the other side. An example of a semiconductor-metal junction is a Schottky barrier. Alternatively, the nanotube may exhibit different semiconductor properties on either side of the junction. Nanotubes containing heterojunctions, Schottky barriers, and metal-metal junctions are useful for microcircuitry.

  10. Josephson junction

    DOEpatents

    Wendt, Joel R.; Plut, Thomas A.; Martens, Jon S.

    1995-01-01

    A novel method for fabricating nanometer geometry electronic devices is described. Such Josephson junctions can be accurately and reproducibly manufactured employing photolithographic and direct write electron beam lithography techniques in combination with aqueous etchants. In particular, a method is described for manufacturing planar Josephson junctions from high temperature superconducting material.

  11. Josephson junction

    DOEpatents

    Wendt, J.R.; Plut, T.A.; Martens, J.S.

    1995-05-02

    A novel method for fabricating nanometer geometry electronic devices is described. Such Josephson junctions can be accurately and reproducibly manufactured employing photolithographic and direct write electron beam lithography techniques in combination with aqueous etchants. In particular, a method is described for manufacturing planar Josephson junctions from high temperature superconducting material. 10 figs.

  12. Gap Junctions

    PubMed Central

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

    2013-01-01

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

  13. Making the connection - shared molecular machinery and evolutionary links underlie the formation and plasticity of occluding junctions and synapses.

    PubMed

    Harden, Nicholas; Wang, Simon Ji Hau; Krieger, Charles

    2016-08-15

    The pleated septate junction (pSJ), an ancient structure for cell-cell contact in invertebrate epithelia, has protein components that are found in three more-recent junctional structures, the neuronal synapse, the paranodal region of the myelinated axon and the vertebrate epithelial tight junction. These more-recent structures appear to have evolved through alterations of the ancestral septate junction. During its formation in the developing animal, the pSJ exhibits plasticity, although the final structure is extremely robust. Similar to the immature pSJ, the synapse and tight junctions both exhibit plasticity, and we consider evidence that this plasticity comes at least in part from the interaction of members of the immunoglobulin cell adhesion molecule superfamily with highly regulated membrane-associated guanylate kinases. This plasticity regulation probably arose in order to modulate the ancestral pSJ and is maintained in the derived structures; we suggest that it would be beneficial when studying plasticity of one of these structures to consider the literature on the others. Finally, looking beyond the junctions, we highlight parallels between epithelial and synaptic membranes, which both show a polarized distribution of many of the same proteins - evidence that determinants of apicobasal polarity in epithelia also participate in patterning of the synapse. PMID:27528207

  14. Association of Caspr/paranodin with tumour suppressor schwannomin/merlin and beta1 integrin in the central nervous system.

    PubMed

    Denisenko-Nehrbass, Natalia; Goutebroze, Laurence; Galvez, Thierry; Bonnon, Carine; Stankoff, Bruno; Ezan, Pascal; Giovannini, Marco; Faivre-Sarrailh, Catherine; Girault, Jean-Antoine

    2003-01-01

    Caspr/paranodin is an essential neuronal component of paranodal axoglial junctions, associated with contactin/F3. Its short intracellular domain contains a conserved motif (GNP motif) capable of binding protein 4.1 domains [FERM domains (four point one, ezrin, radixin, moesin)]. Schwannomin/merlin is a tumour suppressor expressed in many cell types, including in neurons, the function and partners of which are still poorly characterized. We show that the FERM domain of schwannomin binds to the paranodin GNP motif in glutathione S-transferase (GST)-pull down assays and in transfected COS-7 cells. The two proteins co-immunoprecipitated in brain extracts. In addition, paranodin and schwannomin were associated with integrin beta1 in transfected cells and in brain homogenates. The presence of paranodin increased the association between integrin beta1 and schwannomin or its N-terminal domain, suggesting that the interactions between these proteins are interdependent. In jimpy mutant mice, which display a severe dysmyelination with deficient paranodal junctions, the interactions between paranodin, schwannomin and integrin beta1 were profoundly altered. Our results show that schwannomin and integrin beta1 can be associated with paranodin in the central nervous system. Since integrin beta1 and schwannomin do not appear to be enriched in paranodes they may be quantitatively minor partners of paranodin in these regions and/or be associated with paranodin at other locations. PMID:12558984

  15. [Molecular Mimicry and Guillain-Barré Syndrome].

    PubMed

    Yuki, Nobuhiro

    2015-11-01

    One-thirds of patients develop Guillain-Barré syndrome subsequent to Campylobacter jejuni enteritis. Molecular mimicry exists between C. jejuni lipo-oligosaccharides and human peripheral nerve gangliosides GM1 and GD1a. IgG antibodies against GM1 or GD1a are produced in one out of 5,000 patients with C. jejuni enteritis. The autoantibodies bind to gangliosides at the nodes of Ranvier in the peripheral motor nerves and activate complement in situ. This is followed by the disappearance of the voltage-gated sodium channel clusters at the nodes and disruption of axo-glial junctions at the paranodes. This results in the development of motor nerve conduction failure and muscle weakness in the four limbs.

  16. Mice lacking sodium channel beta1 subunits display defects in neuronal excitability, sodium channel expression, and nodal architecture.

    PubMed

    Chen, Chunling; Westenbroek, Ruth E; Xu, Xiaorong; Edwards, Chris A; Sorenson, Dorothy R; Chen, Yuan; McEwen, Dyke P; O'Malley, Heather A; Bharucha, Vandana; Meadows, Laurence S; Knudsen, Gabriel A; Vilaythong, Alex; Noebels, Jeffrey L; Saunders, Thomas L; Scheuer, Todd; Shrager, Peter; Catterall, William A; Isom, Lori L

    2004-04-21

    Sodium channel beta1 subunits modulate alpha subunit gating and cell surface expression and participate in cell adhesive interactions in vitro. beta1-/- mice appear ataxic and display spontaneous generalized seizures. In the optic nerve, the fastest components of the compound action potential are slowed and the number of mature nodes of Ranvier is reduced, but Na(v)1.6, contactin, caspr 1, and K(v)1 channels are all localized normally at nodes. At the ultrastructural level, the paranodal septate-like junctions immediately adjacent to the node are missing in a subset of axons, suggesting that beta1 may participate in axo-glial communication at the periphery of the nodal gap. Sodium currents in dissociated hippocampal neurons are normal, but Na(v)1.1 expression is reduced and Na(v)1.3 expression is increased in a subset of pyramidal neurons in the CA2/CA3 region, suggesting a basis for the epileptic phenotype. Our results show that beta1 subunits play important roles in the regulation of sodium channel density and localization, are involved in axo-glial communication at nodes of Ranvier, and are required for normal action potential conduction and control of excitability in vivo. PMID:15102918

  17. Three-junction solar cell

    DOEpatents

    Ludowise, Michael J.

    1986-01-01

    A photovoltaic solar cell is formed in a monolithic semiconductor. The cell contains three junctions. In sequence from the light-entering face, the junctions have a high, a medium, and a low energy gap. The lower junctions are connected in series by one or more metallic members connecting the top of the lower junction through apertures to the bottom of the middle junction. The upper junction is connected in voltage opposition to the lower and middle junctions by second metallic electrodes deposited in holes 60 through the upper junction. The second electrodes are connected to an external terminal.

  18. A Laminin G-EGF-Laminin G module in Neurexin IV is essential for the apico-lateral localization of Contactin and organization of septate junctions.

    PubMed

    Banerjee, Swati; Paik, Raehum; Mino, Rosa E; Blauth, Kevin; Fisher, Elizabeth S; Madden, Victoria J; Fanning, Alan S; Bhat, Manzoor A

    2011-01-01

    Septate junctions (SJs) display a unique ultrastructural morphology with ladder-like electron densities that are conserved through evolution. Genetic and molecular analyses have identified a highly conserved core complex of SJ proteins consisting of three cell adhesion molecules Neurexin IV, Contactin, and Neuroglian, which interact with the cytoskeletal FERM domain protein Coracle. How these individual proteins interact to form the septal arrays that create the paracellular barrier is poorly understood. Here, we show that point mutations that map to specific domains of neurexin IV lead to formation of fewer septae and disorganization of SJs. Consistent with these observations, our in vivo domain deletion analyses identified the first Laminin G-EGF-Laminin G module in the extracellular region of Neurexin IV as necessary for the localization of and association with Contactin. Neurexin IV protein that is devoid of its cytoplasmic region is able to create septae, but fails to form a full complement of SJs. These data provide the first in vivo evidence that specific domains in Neurexin IV are required for protein-protein interactions and organization of SJs. Given the molecular conservation of SJ proteins across species, our studies may provide insights into how vertebrate axo-glial SJs are organized in myelinated axons.

  19. Equivalent Josephson junctions

    NASA Astrophysics Data System (ADS)

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

    2008-01-01

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

  20. Four-junction superconducting circuit

    PubMed Central

    Qiu, Yueyin; Xiong, Wei; He, Xiao-Ling; Li, Tie-Fu; You, J. Q.

    2016-01-01

    We develop a theory for the quantum circuit consisting of a superconducting loop interrupted by four Josephson junctions and pierced by a magnetic flux (either static or time-dependent). In addition to the similarity with the typical three-junction flux qubit in the double-well regime, we demonstrate the difference of the four-junction circuit from its three-junction analogue, including its advantages over the latter. Moreover, the four-junction circuit in the single-well regime is also investigated. Our theory provides a tool to explore the physical properties of this four-junction superconducting circuit. PMID:27356619

  1. Four-junction superconducting circuit.

    PubMed

    Qiu, Yueyin; Xiong, Wei; He, Xiao-Ling; Li, Tie-Fu; You, J Q

    2016-01-01

    We develop a theory for the quantum circuit consisting of a superconducting loop interrupted by four Josephson junctions and pierced by a magnetic flux (either static or time-dependent). In addition to the similarity with the typical three-junction flux qubit in the double-well regime, we demonstrate the difference of the four-junction circuit from its three-junction analogue, including its advantages over the latter. Moreover, the four-junction circuit in the single-well regime is also investigated. Our theory provides a tool to explore the physical properties of this four-junction superconducting circuit. PMID:27356619

  2. Four-junction superconducting circuit.

    PubMed

    Qiu, Yueyin; Xiong, Wei; He, Xiao-Ling; Li, Tie-Fu; You, J Q

    2016-06-30

    We develop a theory for the quantum circuit consisting of a superconducting loop interrupted by four Josephson junctions and pierced by a magnetic flux (either static or time-dependent). In addition to the similarity with the typical three-junction flux qubit in the double-well regime, we demonstrate the difference of the four-junction circuit from its three-junction analogue, including its advantages over the latter. Moreover, the four-junction circuit in the single-well regime is also investigated. Our theory provides a tool to explore the physical properties of this four-junction superconducting circuit.

  3. Magnetic Tunnel Junctions

    NASA Astrophysics Data System (ADS)

    Reiss, Günter; Schmalhorst, Jan; Thomas, Andre; Hütten, Andreas; Yuasa, Shinji

    In magnetoelectronic devices large opportunities are opened by the spin dependent tunneling resistance, where a strong dependence of the tunneling current on the relative orientation of the magnetization of the electrodes is found. Within a short time, the amplitude of the resistance change of the junctions increased dramatically. We will cover Al-O and MgO based junctions and present highly spin-polarized electrode materials such as Heusler alloys. Furthermore, we will give a short overview on applications such as read heads in hard disk drives, storage cells in MRAMs, field programmable logic circuits and biochips. Finally, we will discuss the currently growing field of current induced magnetization switching.

  4. Victory Junction Gang Camp

    ERIC Educational Resources Information Center

    Shell, Ryan

    2007-01-01

    This article describes the Victory Junction Gang Camp, a not-for-profit, NASCAR-themed camp for children with chronic medical conditions that serves 24 different disease groups. The mission of the camp is to give children life-changing camping experiences that are exciting, fun, and empowering in a safe and medically sound environment. While doing…

  5. Brain barriers: Crosstalk between complex tight junctions and adherens junctions

    PubMed Central

    Tietz, Silvia

    2015-01-01

    Unique intercellular junctional complexes between the central nervous system (CNS) microvascular endothelial cells and the choroid plexus epithelial cells form the endothelial blood–brain barrier (BBB) and the epithelial blood–cerebrospinal fluid barrier (BCSFB), respectively. These barriers inhibit paracellular diffusion, thereby protecting the CNS from fluctuations in the blood. Studies of brain barrier integrity during development, normal physiology, and disease have focused on BBB and BCSFB tight junctions but not the corresponding endothelial and epithelial adherens junctions. The crosstalk between adherens junctions and tight junctions in maintaining barrier integrity is an understudied area that may represent a promising target for influencing brain barrier function. PMID:26008742

  6. Holliday Junction Resolvases

    PubMed Central

    Wyatt, Haley D.M.; West, Stephen C.

    2014-01-01

    Four-way DNA intermediates, called Holliday junctions (HJs), can form during meiotic and mitotic recombination, and their removal is crucial for chromosome segregation. A group of ubiquitous and highly specialized structure-selective endonucleases catalyze the cleavage of HJs into two disconnected DNA duplexes in a reaction called HJ resolution. These enzymes, called HJ resolvases, have been identified in bacteria and their bacteriophages, archaea, and eukaryotes. In this review, we discuss fundamental aspects of the HJ structure and their interaction with junction-resolving enzymes. This is followed by a brief discussion of the eubacterial RuvABC enzymes, which provide the paradigm for HJ resolvases in other organisms. Finally, we review the biochemical and structural properties of some well-characterized resolvases from archaea, bacteriophage, and eukaryotes. PMID:25183833

  7. Wireless Josephson Junction Arrays

    NASA Astrophysics Data System (ADS)

    Adams, Laura

    2015-03-01

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

  8. Thermoelectricity in molecular junctions.

    PubMed

    Reddy, Pramod; Jang, Sung-Yeon; Segalman, Rachel A; Majumdar, Arun

    2007-03-16

    By trapping molecules between two gold electrodes with a temperature difference across them, the junction Seebeck coefficients of 1,4-benzenedithiol (BDT), 4,4'-dibenzenedithiol, and 4,4''-tribenzenedithiol in contact with gold were measured at room temperature to be +8.7 +/- 2.1 microvolts per kelvin (muV/K), +12.9 +/- 2.2 muV/K, and +14.2 +/- 3.2 muV/K, respectively (where the error is the full width half maximum of the statistical distributions). The positive sign unambiguously indicates p-type (hole) conduction in these heterojunctions, whereas the Au Fermi level position for Au-BDT-Au junctions was identified to be 1.2 eV above the highest occupied molecular orbital level of BDT. The ability to study thermoelectricity in molecular junctions provides the opportunity to address these fundamental unanswered questions about their electronic structure and to begin exploring molecular thermoelectric energy conversion. PMID:17303718

  9. Fractional order junctions

    NASA Astrophysics Data System (ADS)

    Machado, J. Tenreiro

    2015-01-01

    Gottfried Leibniz generalized the derivation and integration, extending the operators from integer up to real, or even complex, orders. It is presently recognized that the resulting models capture long term memory effects difficult to describe by classical tools. Leon Chua generalized the set of lumped electrical elements that provide the building blocks in mathematical models. His proposal of the memristor and of higher order elements broadened the scope of variables and relationships embedded in the development of models. This paper follows the two directions and proposes a new logical step, by generalizing the concept of junction. Classical junctions interconnect system elements using simple algebraic restrictions. Nevertheless, this simplistic approach may be misleading in the presence of unexpected dynamical phenomena and requires including additional "parasitic" elements. The novel γ -junction includes, as special cases, the standard series and parallel connections and allows a new degree of freedom when building models. The proposal motivates the search for experimental and real world manifestations of the abstract conjectures.

  10. Pathophysiological actions of neuropathy-related anti-ganglioside antibodies at the neuromuscular junction

    PubMed Central

    Plomp, Jaap J; Willison, Hugh J

    2009-01-01

    The outer leaflet of neuronal membranes is highly enriched in gangliosides. Therefore, specific neuronal roles have been attributed to this family of sialylated glycosphingolipids, e.g. in modulation of ion channels and transporters, neuronal interaction and recognition, temperature adaptation, Ca2+ homeostasis, axonal growth, (para)node of Ranvier stability and synaptic transmission. Recent developmental, ageing and injury studies on transgenic mice lacking subsets of gangliosides indicate that gangliosides are involved in maintenance rather than development of the nervous system and that ganglioside family members are able to act in a mutually compensatory manner. Besides having physiological functions, gangliosides are the likely antigenic targets of autoantibodies present in Guillain-Barré syndrome (GBS), a group of neuropathies with clinical symptoms of motor- and/or sensory peripheral nerve dysfunction. Antibody binding to peripheral nerves is thought to either interfere with ganglioside function or activate complement, causing axonal damage and thereby disturbed action potential conduction. The presynaptic motor nerve terminal at the neuromuscular junction (NMJ) may be a prominent target because it is highly enriched in gangliosides and lies outside the blood–nerve barrier, allowing antibody access. The ensuing neuromuscular synaptopathy might contribute to the muscle weakness in GBS patients. Several groups, including our own, have studied the effects of anti-ganglioside antibodies in ex vivo and in vivo experimental settings at mouse NMJs. Here, after providing a background overview on ganglioside synthesis, localization and physiology, we will review those studies, which clearly show that anti-ganglioside antibodies are capable of binding to NMJs and thereby can exert a variety of pathophysiological effects. Furthermore, we will discuss the human clinical electrophysiological and histological evidence produced so far of the existence of a neuromuscular

  11. Signatures of topological Josephson junctions

    NASA Astrophysics Data System (ADS)

    Peng, Yang; Pientka, Falko; Berg, Erez; Oreg, Yuval; von Oppen, Felix

    2016-08-01

    Quasiparticle poisoning and diabatic transitions may significantly narrow the window for the experimental observation of the 4 π -periodic dc Josephson effect predicted for topological Josephson junctions. Here, we show that switching-current measurements provide accessible and robust signatures for topological superconductivity which persist in the presence of quasiparticle poisoning processes. Such measurements provide access to the phase-dependent subgap spectrum and Josephson currents of the topological junction when incorporating it into an asymmetric SQUID together with a conventional Josephson junction with large critical current. We also argue that pump-probe experiments with multiple current pulses can be used to measure the quasiparticle poisoning rates of the topological junction. The proposed signatures are particularly robust, even in the presence of Zeeman fields and spin-orbit coupling, when focusing on short Josephson junctions. Finally, we also consider microwave excitations of short topological Josephson junctions which may complement switching-current measurements.

  12. An induced junction photovoltaic cell

    NASA Technical Reports Server (NTRS)

    Call, R. L.

    1974-01-01

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

  13. Tight junctions and human diseases.

    PubMed

    Sawada, Norimasa; Murata, Masaki; Kikuchi, Keisuke; Osanai, Makoto; Tobioka, Hirotoshi; Kojima, Takashi; Chiba, Hideki

    2003-09-01

    Tight junctions are intercellular junctions adjacent to the apical end of the lateral membrane surface. They have two functions, the barrier (or gate) function and the fence function. The barrier function of tight junctions regulates the passage of ions, water, and various macromolecules, even of cancer cells, through paracellular spaces. The barrier function is thus relevant to edema, jaundice, diarrhea, and blood-borne metastasis. On the other hand, the fence function maintains cell polarity. In other words, tight junctions work as a fence to prevent intermixing of molecules in the apical membrane with those in the lateral membrane. This function is deeply involved in cancer cell biology, in terms of loss of cell polarity. Of the proteins comprising tight junctions, integral membrane proteins occludin, claudins, and JAMs have been recently discovered. Of these molecules, claudins are exclusively responsible for the formation of tight-junction strands and are connected with the actin cytoskeleton mediated by ZO-1. Thus, both functions of tight junctions are dependent on the integrity of the actin cytoskeleton as well as ATP. Mutations in the claudin14 and the claudin16 genes result in hereditary deafness and hereditary hypomagnesemia, respectively. Some pathogenic bacteria and viruses target and affect the tight-junction function, leading to diseases. In this review, the relationship between tight junctions and human diseases is summarized.

  14. GUARD RING SEMICONDUCTOR JUNCTION

    DOEpatents

    Goulding, F.S.; Hansen, W.L.

    1963-12-01

    A semiconductor diode having a very low noise characteristic when used under reverse bias is described. Surface leakage currents, which in conventional diodes greatly contribute to noise, are prevented from mixing with the desired signal currents. A p-n junction is formed with a thin layer of heavily doped semiconductor material disposed on a lightly doped, physically thick base material. An annular groove cuts through the thin layer and into the base for a short distance, dividing the thin layer into a peripheral guard ring that encircles the central region. Noise signal currents are shunted through the guard ring, leaving the central region free from such currents. (AEC)

  15. Cementoenamel junction: An insight.

    PubMed

    Vandana, Kharidi Laxman; Haneet, Ryana Kour

    2014-09-01

    The location and nature of cemento-enamel junction (CEJ) are more than descriptive terms used simply to describe some aspects of tooth morphology; however, CEJ gains a lot of clinical significance due to various measurements dependent on it. It may be necessary to determine the location and pathological changes occurring at CEJ to make a diagnosis and treat diseases pertaining to epithelial attachment and gingival margin. However, the information related to CEJ is not discussed commonly. Hence, the present review paper provides an insight on CEJ in both primary and permanent dentition. PMID:25425813

  16. Cementoenamel junction: An insight

    PubMed Central

    Vandana, Kharidi Laxman; Haneet, Ryana Kour

    2014-01-01

    The location and nature of cemento-enamel junction (CEJ) are more than descriptive terms used simply to describe some aspects of tooth morphology; however, CEJ gains a lot of clinical significance due to various measurements dependent on it. It may be necessary to determine the location and pathological changes occurring at CEJ to make a diagnosis and treat diseases pertaining to epithelial attachment and gingival margin. However, the information related to CEJ is not discussed commonly. Hence, the present review paper provides an insight on CEJ in both primary and permanent dentition. PMID:25425813

  17. Herlitz junctional epidermolysis bullosa.

    PubMed

    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

  18. Ion bipolar junction transistors

    PubMed Central

    Tybrandt, Klas; Larsson, Karin C.; Richter-Dahlfors, Agneta; Berggren, Magnus

    2010-01-01

    Dynamic control of chemical microenvironments is essential for continued development in numerous fields of life sciences. Such control could be achieved with active chemical circuits for delivery of ions and biomolecules. As the basis for such circuitry, we report a solid-state ion bipolar junction transistor (IBJT) based on conducting polymers and thin films of anion- and cation-selective membranes. The IBJT is the ionic analogue to the conventional semiconductor BJT and is manufactured using standard microfabrication techniques. Transistor characteristics along with a model describing the principle of operation, in which an anionic base current amplifies a cationic collector current, are presented. By employing the IBJT as a bioelectronic circuit element for delivery of the neurotransmitter acetylcholine, its efficacy in modulating neuronal cell signaling is demonstrated. PMID:20479274

  19. Quantification of gap junction selectivity.

    PubMed

    Ek-Vitorín, Jose F; Burt, Janis M

    2005-12-01

    Gap junctions, which are essential for functional coordination and homeostasis within tissues, permit the direct intercellular exchange of small molecules. The abundance and diversity of this exchange depends on the number and selectivity of the comprising channels and on the transjunctional gradient for and chemical character of the permeant molecules. Limited knowledge of functionally significant permeants and poor detectability of those few that are known have made it difficult to define channel selectivity. Presented herein is a multifaceted approach to the quantification of gap junction selectivity that includes determination of the rate constant for intercellular diffusion of a fluorescent probe (k2-DYE) and junctional conductance (gj) for each junction studied, such that the selective permeability (k2-DYE/gj) for dyes with differing chemical characteristics or junctions with differing connexin (Cx) compositions (or treatment conditions) can be compared. In addition, selective permeability can be correlated using single-channel conductance when this parameter is also measured. Our measurement strategy is capable of detecting 1) rate constants and selective permeabilities that differ across three orders of magnitude and 2) acute changes in that rate constant. Using this strategy, we have shown that 1) the selective permeability of Cx43 junctions to a small cationic dye varied across two orders of magnitude, consistent with the hypothesis that the various channel configurations adopted by Cx43 display different selective permeabilities; and 2) the selective permeability of Cx37 vs. Cx43 junctions was consistently and significantly lower. PMID:16093281

  20. Thermopower measurements in molecular junctions.

    PubMed

    Rincón-García, Laura; Evangeli, Charalambos; Rubio-Bollinger, Gabino; Agraït, Nicolás

    2016-08-01

    The measurement of thermopower in molecular junctions offers complementary information to conductance measurements and is becoming essential for the understanding of transport processes at the nanoscale. In this review, we discuss the recent advances in the study of the thermoelectric properties of molecular junctions. After presenting the theoretical background for thermoelectricity at the nanoscale, we review the experimental techniques for measuring the thermopower in these systems and discuss the main results. Finally, we consider the challenges in the application of molecular junctions in viable thermoelectric devices. PMID:27277330

  1. Josephson junction Q-spoiler

    DOEpatents

    Clarke, J.; Hilbert, C.; Hahn, E.L.; Sleator, T.

    1986-03-25

    An automatic Q-spoiler comprising at least one Josephson tunnel junction connected in an LC circuit for flow of resonant current therethrough. When in use in a system for detecting the magnetic resonance of a gyromagnetic particle system, a high energy pulse of high frequency energy irradiating the particle system will cause the critical current through the Josephson tunnel junctions to be exceeded, causing the tunnel junctions to act as resistors and thereby damp the ringing of the high-Q detection circuit after the pulse. When the current has damped to below the critical current, the Josephson tunnel junctions revert to their zero-resistance state, restoring the Q of the detection circuit and enabling the low energy magnetic resonance signals to be detected.

  2. Josephson junction Q-spoiler

    DOEpatents

    Clarke, John; Hilbert, Claude; Hahn, Erwin L.; Sleator, Tycho

    1988-01-01

    An automatic Q-spoiler comprising at least one Josephson tunnel junction connected in an LC circuit for flow of resonant current therethrough. When in use in a system for detecting the magnetic resonance of a gyromagnetic particle system, a high energy pulse of high frequency energy irradiating the particle system will cause the critical current through the Josephson tunnel junctions to be exceeded, causing the tunnel junctions to act as resistors and thereby damp the ringing of the high-Q detection circuit after the pulse. When the current has damped to below the critical current, the Josephson tunnel junctions revert to their zero-resistance state, restoring the Q of the detection circuit and enabling the low energy magnetic resonance signals to be detected.

  3. Thermal conductance of superlattice junctions

    SciTech Connect

    Lu, Simon; McGaughey, Alan J. H.

    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.

  4. Tunable φ Josephson junction ratchet

    NASA Astrophysics Data System (ADS)

    Menditto, R.; Sickinger, H.; Weides, M.; Kohlstedt, H.; Koelle, D.; Kleiner, R.; Goldobin, E.

    2016-10-01

    We demonstrate experimentally the operation of a deterministic Josephson ratchet with tunable asymmetry. The ratchet is based on a φ Josephson junction with a ferromagnetic barrier operating in the underdamped regime. The system is probed also under the action of an additional dc current, which acts as a counterforce trying to stop the ratchet. Under these conditions the ratchet works against the counterforce, thus producing a nonzero output power. Finally, we estimate the efficiency of the φ Josephson junction ratchet.

  5. Electronic thermometry in tunable tunnel junction

    DOEpatents

    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.

  6. Confocal Annular Josephson Tunnel Junctions

    NASA Astrophysics Data System (ADS)

    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.

  7. Junction formation during desiccation cracking.

    PubMed

    Toga, K B; Alaca, B Erdem

    2006-08-01

    In order to provide a sound physical basis for the understanding of the formation of desiccation crack networks, an experimental study is presented addressing junction formation. Focusing on junctions, basic features of the network determining the final pattern, provides an elemental approach and imparts conceptual clarity to the rather complicated problem of the evolution of crack patterns. Using coffee-water mixtures a clear distinction between junction formation during nucleation and propagation is achieved. It is shown that for the same drying suspension, one can switch from the well-known symmetric triple junctions that are unique to the nucleation phase to propagation junctions that are purely dictated by the variations of the stress state. In the latter case, one can even manipulate the path of a propagating crack in a deterministic fashion by changing the stress state within the suspension. Clear microscopic evidence is provided for the formation of propagation junctions, and material inhomogeneity is observed to be reflected by a broad distribution of angles, in stark contrast to shrinkage cracks in homogeneous solid films.

  8. Octagonal Defects at Carbon Nanotube Junctions

    PubMed Central

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

    2013-01-01

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

  9. Josephson junctions in SPICE3

    SciTech Connect

    Whiteley, S.R.

    1991-03-01

    This paper reports on SPICE3 which is the most recent version of the venerable circuit simulator SPICE from the University of California, Berkeley. Unlike its predecessors, SPICE3 is written in the C programming language, and is designed for interactive use under a modern multitasking operating system. SPICE3, being an interactive program, offers the user great control and flexibility in performing simulations, and provides a powerful graphics capability for viewing simulation results. A C-shell like control syntax is supported, as well as such features as plotting while simulating, parameter alteration during simulation, and simulation data controlled breakpoints. Unfortunately, the Berkeley distribution of SPICE3 lacks support for Josephson junctions. As a consequence, the author has developed a customize version of SPICE3b.1 which incorporates a Josephson junction model. The model supports control current modulation, as well as a fifth order polynomial description of the quasiparticle current suitable for NbN junctions.

  10. Triple junction distributions in polycrystals

    SciTech Connect

    King, W.E.; Kumar, M.; Schwartz, A.J.

    1999-07-01

    Recently, it has been demonstrated that some material properties can be enhanced by grain boundary engineering, i.e., the systematic modifications in the topology of the microstructure through thermomechanical processing. Experimental observations have shown that the microstructural parameter likely responsible for improved properties is the grain boundary character distribution (GBCD). It has been suggested that improvements in the fractions of special boundaries as defined by the coincident site lattice model (1) are necessary, but not fully sufficient to cause property improvements. For example, it has been observed that cracks propagating along interconnected networks of random grain boundaries can be arrested (2) when intersecting a triple junction where the remaining two pathways are special boundaries. Therefore, it is of interest to characterize microstructures in terms of the distributions of triple junction types. A simple method to describe a triple junction is by the types of grain boundaries intersecting at that junction [special vs. random, as described by the coincident site lattice (CSL) model]. The distribution of 0-CSL, 1-CSL, 2-CSL and 3-CSL triple junctions in the microstructure can then be plotted as a function of the fraction of special boundaries. Such data has been collected using orientation-imaging microscopy (OIM) (3--5) for oxygen-free-electronic (ofe)-Cu and Inconel 600 over a range of special fraction of grain boundaries. These results have been compared with theoretical models considering isolated triple junctions and invoking the {Sigma}-product rule (6) where {Sigma} is the inverse density of coincident lattice sites (7).

  11. Differential clustering of Caspr by oligodendrocytes and Schwann cells.

    PubMed

    Eisenbach, Menahem; Kartvelishvily, Elena; Eshed-Eisenbach, Yael; Watkins, Trent; Sorensen, Annette; Thomson, Christine; Ranscht, Barbara; Barnett, Susan C; Brophy, Peter; Peles, Elior

    2009-11-15

    Formation of the paranodal axoglial junction (PNJ) requires the presence of three cell adhesion molecules: the 155-kDa isoform of neurofascin (NF155) on the glial membrane and a complex of Caspr and contactin found on the axolemma. Here we report that the clustering of Caspr along myelinated axons during development differs fundamentally between the central (CNS) and peripheral (PNS) nervous systems. In cultures of Schwann cells (SC) and dorsal root ganglion (DRG) neurons, membrane accumulation of Caspr was detected only after myelination. In contrast, in oligodendrocytes (OL)/DRG neurons cocultures, Caspr was clustered upon initial glial cell contact already before myelination had begun. Premyelination clustering of Caspr was detected in cultures of oligodendrocytes and retinal ganglion cells, motor neurons, and DRG neurons as well as in mixed cell cultures of rat forebrain and spinal cords. Cocultures of oligodendrocyte precursor cells isolated from contactin- or neurofascin-deficient mice with wild-type DRG neurons showed that clustering of Caspr at initial contact sites between OL processes and the axon requires glial expression of NF155 but not of contactin. These results demonstrate that the expression of membrane proteins along the axolemma is determined by the type of the contacting glial cells and is not an intrinsic characteristic of the axon. PMID:19565653

  12. Caspr regulates the processing of contactin and inhibits its binding to neurofascin.

    PubMed

    Gollan, Leora; Salomon, Daniela; Salzer, James L; Peles, Elior

    2003-12-22

    Three cell adhesion molecules are present at the axoglial junctions that form between the axon and myelinating glia on either side of nodes of Ranvier. These include an axonal complex of contacin-associated protein (Caspr) and contactin, which was proposed to bind NF155, an isoform of neurofascin located on the glial paranodal loops. Here, we show that NF155 binds directly to contactin and that surprisingly, coexpression of Caspr inhibits this interaction. This inhibition reflects the association of Caspr with contactin during biosynthesis and the resulting expression of a low molecular weight (LMw), endoglycosidase H-sensitive isoform of contactin at the cell membrane, which remains associated with Caspr but is unable to bind NF155. Accordingly, deletion of Caspr in mice by gene targeting results in a shift from the LMw- to a HMw-contactin glycoform. These results demonstrate that Caspr regulates the intracellular processing and transport of contactin to the cell surface, thereby affecting its ability to interact with other cell adhesion molecules. PMID:14676309

  13. Repetitive propagation of action potentials destabilizes the structure of the myelin sheath. A dynamic x-ray diffraction study.

    PubMed Central

    Padrón, R; Mateu, L

    1982-01-01

    Time courses of myelin lattice swelling in toad sciatic nerves preexposed to different treatments were determined by x-ray diffraction using a one-dimensional position-sensitive detector. In the nerves supramaximally stimulated for 1 h at 200 Hz, the subsequent process of myelin swelling occurred 45.0 +/- 7.3 min (n = 24) sooner than in resting controls. Sciatic nerves incubated for 1 h in a Ringer's solution deprived of divalent cations (Ca++ and Mg++) exhibited a kinetics of swelling similar to that shown by the stimulated nerves, that is, 52.5 +/- 14.2 min (n = 6) sooner than controls preincubated for the same time in normal Ringer's solution (with divalent cations). The fact that both pretreatments supramaximal stimulation and removal of divalent cations from the perfusion solution produced a similar effect; namely, a decrease of the myelin lattice stability against swelling in distilled water, suggests that the repetitive propagation of action potentials could modify the ionic composition at either the intraperiod channel or the paranodal axoglial junction complexes. PMID:6810970

  14. Conducting polyaniline nanowire electrode junction

    NASA Astrophysics Data System (ADS)

    Gaikwad, Sumedh; Bodkhe, Gajanan; Deshmukh, Megha; Patil, Harshada; Rushi, Arti; Shirsat, Mahendra D.; Koinkar, Pankaj; Kim, Yun-Hae; Mulchandani, Ashok

    2015-03-01

    In this paper, a synthesis of conducting polyaniline nanowires electrode junction (CPNEJ) has been reported. Conducting polyaniline nanowires electrode junction on Si/SiO2 substrate (having 3 μm gap between two gold microelectrodes) is prepared. Polyaniline nanowires with diameter (ca. 140 nm to 160 nm) were synthesized by one step electrochemical polymerization using galvanostatic (constant current) technique to bridge this gap. The surface morphology of CPNEJ was studied by scanning electron microscope (SEM). The synthesized CPNEJ is an excellent platform for biosensor applications.

  15. Simple Electronic Analog of a Josephson Junction.

    ERIC Educational Resources Information Center

    Henry, R. W.; And Others

    1981-01-01

    Demonstrates that an electronic Josephson junction analog constructed from three integrated circuits plus an external reference oscillator can exhibit many of the circuit phenomena of a real Josephson junction. Includes computer and other applications of the analog. (Author/SK)

  16. Layer Engineering of 2D Semiconductor Junctions.

    PubMed

    He, Yongmin; Sobhani, Ali; Lei, Sidong; Zhang, Zhuhua; Gong, Yongji; Jin, Zehua; Zhou, Wu; Yang, Yingchao; Zhang, Yuan; Wang, Xifan; Yakobson, Boris; Vajtai, Robert; Halas, Naomi J; Li, Bo; Xie, Erqing; Ajayan, Pulickel

    2016-07-01

    A new concept for junction fabrication by connecting multiple regions with varying layer thicknesses, based on the thickness dependence, is demonstrated. This type of junction is only possible in super-thin-layered 2D materials, and exhibits similar characteristics as p-n junctions. Rectification and photovoltaic effects are observed in chemically homogeneous MoSe2 junctions between domains of different thicknesses. PMID:27136275

  17. Improved Solar-Cell Tunnel Junction

    NASA Technical Reports Server (NTRS)

    Daud, T.; Kachare, A.

    1986-01-01

    Efficiency of multiple-junction silicon solar cells increased by inclusion of p+/n+ tunnel junctions of highly doped GaP between component cells. Relatively low recombination velocity at GaP junction principal reason for recommending this material. Relatively wide band gap also helps increase efficiency by reducing optical losses.

  18. SIN tunnel junction as a temperature sensor

    NASA Astrophysics Data System (ADS)

    Golubev, D.; Kuzmin, Leonid S.; Willander, Magnus

    1999-04-01

    The current-voltage characteristics of a superconductor-normal metal tunnel junction (SIN) is very sensitive to the temperature of the normal metal. Therefore SIN junction can be used as a thermometer which can be conveniently integrated into more complicated devices, for example bolometers. We estimate the effect of different types of noise on the sensitivity of such a thermometer. Shot noise of the tunnel junction, amplifier noise and the noise related to the fluctuations of the heat flow through the junction are considered. The performance of the bolometer with SIN junction as a temperature sensor is also discussed.

  19. Ferromagnetic Josephson Junctions for Cryogenic Memory

    NASA Astrophysics Data System (ADS)

    Niedzielski, Bethany M.; Gingrich, Eric C.; Khasawneh, Mazin A.; Loloee, Reza; Pratt, William P., Jr.; Birge, Norman O.

    2015-03-01

    Josephson junctions containing ferromagnetic materials are of interest for both scientific and technological purposes. In principle, either the amplitude of the critical current or superconducting phase shift across the junction can be controlled by the relative magnetization directions of the ferromagnetic layers in the junction. Our approach concentrates on phase control utilizing two junctions in a SQUID geometry. We will report on efforts to control the phase of junctions carrying either spin-singlet or spin-triplet supercurrent for cryogenic memory applications. Supported by Northorp Grumman Corporation and by IARPA under SPAWAR Contract N66001-12-C-2017.

  20. Fabrication of high quality ferromagnetic Josephson junctions

    NASA Astrophysics Data System (ADS)

    Weides, M.; Tillmann, K.; Kohlstedt, H.

    2006-05-01

    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 jc spreads less than 2% was obtained.

  1. Molecular series-tunneling junctions.

    PubMed

    Liao, Kung-Ching; Hsu, Liang-Yan; Bowers, Carleen M; Rabitz, Herschel; Whitesides, George M

    2015-05-13

    Charge transport through junctions consisting of insulating molecular units is a quantum phenomenon that cannot be described adequately by classical circuit laws. This paper explores tunneling current densities in self-assembled monolayer (SAM)-based junctions with the structure Ag(TS)/O2C-R1-R2-H//Ga2O3/EGaIn, where Ag(TS) is template-stripped silver and EGaIn is the eutectic alloy of gallium and indium; R1 and R2 refer to two classes of insulating molecular units-(CH2)n and (C6H4)m-that are connected in series and have different tunneling decay constants in the Simmons equation. These junctions can be analyzed as a form of series-tunneling junctions based on the observation that permuting the order of R1 and R2 in the junction does not alter the overall rate of charge transport. By using the Ag/O2C interface, this system decouples the highest occupied molecular orbital (HOMO, which is localized on the carboxylate group) from strong interactions with the R1 and R2 units. The differences in rates of tunneling are thus determined by the electronic structure of the groups R1 and R2; these differences are not influenced by the order of R1 and R2 in the SAM. In an electrical potential model that rationalizes this observation, R1 and R2 contribute independently to the height of the barrier. This model explicitly assumes that contributions to rates of tunneling from the Ag(TS)/O2C and H//Ga2O3 interfaces are constant across the series examined. The current density of these series-tunneling junctions can be described by J(V) = J0(V) exp(-β1d1 - β2d2), where J(V) is the current density (A/cm(2)) at applied voltage V and βi and di are the parameters describing the attenuation of the tunneling current through a rectangular tunneling barrier, with width d and a height related to the attenuation factor β. PMID:25871745

  2. Modulation of adrenal gap junction expression.

    PubMed

    Murray, S A; Shah, U S

    1998-01-01

    To increase our knowledge of the role of peptide hormone stimulation in gap junction protein expression and adrenal cortical cell function, primary rat adrenal cortical cells were treated with adrenocorticotropin, and gap junction proteins were measured. Immunocytochemistry and western blot analysis were used to detect and characterize gap junction type and distribution. The gap junction protein, connexin 43 (alpha 1), was detected. Analysis of six connexin protein types did not reveal gap junction species other than alpha 1. Cells of the inner adrenal cortical zones, zonae fasciculata and reticularis, were demonstrated to have the highest number of gap junctions per cell in the adrenal gland. Adrenal cell cultures enriched for the two inner cortical adrenal zones were established and demonstrated also to express alpha 1 gap junction protein. Adrenocorticotropin (40 mUnits/ml) and dibutyryl cyclic adenosine monophosphate (1 mM) treatments increased alpha 1 gap junction protein levels and decreased cell proliferation rates in the cell cultures. The results are consistent with the hypothesis that gap junction expression can be regulated by adrenocorticotropin acting through the second messenger cyclic adenosine monophosphate. It can be suggested that gap junction expression in the adrenal gland may be under hormonal influence, and that gap junctions serve as passage for movement of molecules involved in control of cell proliferation. PMID:9694574

  3. Seebeck effect in molecular junctions

    NASA Astrophysics Data System (ADS)

    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.

  4. Seebeck effect in molecular junctions.

    PubMed

    Zimbovskaya, Natalya A

    2016-05-11

    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. PMID:27073108

  5. Thermoelectric efficiency of molecular junctions

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  6. Thermoelectric efficiency of molecular junctions.

    PubMed

    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

  7. Thermoelectric efficiency of molecular junctions

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  8. Thermoelectric efficiency of molecular junctions.

    PubMed

    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.

  9. Synchronization in Disordered Josephson Junction Arrays

    NASA Astrophysics Data System (ADS)

    Dissanayake, S. T. M.; Trees, B. R.

    2001-10-01

    There is considerable scientific and technological interest in the time-dependent behavior of arrays of non-identical Josephson junctions, whose voltages oscillate with individual bare frequencies that can be made, through interactions, to renormalize their frequencies to a common value. We have studied the degree of synchronization of a subset of overdamped junctions in a ladder geometry, in which the voltages across the ``rung'' junctions of the ladder oscillate with the same, renormalized frequency and a fixed phase difference. We measure the degree of synchronization of the junctions with an order parameter, r (0<= r<= 1), as a function of the nearest-neighbor junction coupling strength. We also determined that a time-averaged version of the resistively-shunted junction (RSJ) equations could be used as an accurate description of the dynamics of the junctions. The solutions to the averaged equations exhibit phase slips between pairs of junctions for certain ranges of the junction coupling strength and also demonstrated that the relationship between the array size N and the critical coupling strength for all junctions to oscillate with the same frequency scales as N^2. This research was partially funded by a grant to Ohio Wesleyan University from the McGregor Foundation to support student research.

  10. Chaos induced by coupling between Josephson junctions

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

  11. Physics and Applications of NIS Junctions

    SciTech Connect

    Ullom, J N

    2001-08-24

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

  12. String junction as a baryonic constituent

    NASA Astrophysics Data System (ADS)

    Kalashnikova, Yu. S.; Nefediev, A. V.

    1996-02-01

    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. Thermoelectric effects in nanoscale junctions.

    PubMed

    Dubi, Yonatan; Di Ventra, Massimiliano

    2009-01-01

    Despite its intrinsic nonequilibrium origin, thermoelectricity in nanoscale systems is usually described within a static scattering approach which disregards the dynamical interaction with the thermal baths that maintain energy flow. Using the theory of open quantum systems, we show instead that unexpected properties, such as a resonant structure and large sign sensitivity, emerge if the nonequilibrium nature of this problem is considered. Our approach also allows us to define and study a local temperature, which shows hot spots and oscillations along the system according to the coupling of the latter to the electrodes. This demonstrates that Fourier's lawa paradigm of statistical mechanicsis generally violated in nanoscale junctions. PMID:19072125

  14. Multiterminal Coulomb-Majorana junction.

    PubMed

    Altland, Alexander; Egger, Reinhold

    2013-05-10

    We study multiple helical nanowires in proximity to a common mesoscopic superconducting island, where Majorana fermion bound states are formed. We show that a weak finite charging energy of the center island may dramatically affect the low-energy behavior of the system. While for strong charging interactions, the junction decouples the connecting wires, interactions lower than a nonuniversal threshold may trigger the flow towards an exotic Kondo fixed point. In either case, the ideally Andreev reflecting fixed point characteristic for infinite capacitance (grounded) devices gets destabilized by interactions.

  15. Method for shallow junction formation

    DOEpatents

    Weiner, K.H.

    1996-10-29

    A doping sequence is disclosed that reduces the cost and complexity of forming source/drain regions in complementary metal oxide silicon (CMOS) integrated circuit technologies. The process combines the use of patterned excimer laser annealing, dopant-saturated spin-on glass, silicide contact structures and interference effects creates by thin dielectric layers to produce source and drain junctions that are ultrashallow in depth but exhibit low sheet and contact resistance. The process utilizes no photolithography and can be achieved without the use of expensive vacuum equipment. The process margins are wide, and yield loss due to contact of the ultrashallow dopants is eliminated. 8 figs.

  16. Method for shallow junction formation

    DOEpatents

    Weiner, Kurt H.

    1996-01-01

    A doping sequence that reduces the cost and complexity of forming source/drain regions in complementary metal oxide silicon (CMOS) integrated circuit technologies. The process combines the use of patterned excimer laser annealing, dopant-saturated spin-on glass, silicide contact structures and interference effects creates by thin dielectric layers to produce source and drain junctions that are ultrashallow in depth but exhibit low sheet and contact resistance. The process utilizes no photolithography and can be achieved without the use of expensive vacuum equipment. The process margins are wide, and yield loss due to contact of the ultrashallow dopants is eliminated.

  17. Electrodeposited, Transverse Nanowire Electroluminescent Junctions.

    PubMed

    Qiao, Shaopeng; Xu, Qiang; Dutta, Rajen K; Le Thai, Mya; Li, Xiaowei; Penner, Reginald M

    2016-09-27

    The preparation by electrodeposition of transverse nanowire electroluminescent junctions (tn-ELJs) is described, and the electroluminescence (EL) properties of these devices are characterized. The lithographically patterned nanowire electrodeposition process is first used to prepare long (millimeters), linear, nanocrystalline CdSe nanowires on glass. The thickness of these nanowires along the emission axis is 60 nm, and the width, wCdSe, along the electrical axis is adjustable from 100 to 450 nm. Ten pairs of nickel-gold electrical contacts are then positioned along the axis of this nanowire using lithographically directed electrodeposition. The resulting linear array of nickel-CdSe-gold junctions produces EL with an external quantum efficiency, EQE, and threshold voltage, Vth, that depend sensitively on wCdSe. EQE increases with increasing electric field and also with increasing wCdSe, and Vth also increases with wCdSe and, therefore, the electrical resistance of the tn-ELJs. Vth down to 1.8(±0.2) V (for wCdSe ≈ 100 nm) and EQE of 5.5(±0.5) × 10(-5) (for wCdSe ≈ 450 nm) are obtained. tn-ELJs produce a broad EL emission envelope, spanning the wavelength range from 600 to 960 nm.

  18. The Sinai triple junction revisited

    NASA Astrophysics Data System (ADS)

    Courtillot, Vincent; Armijo, Rolando; Tapponnier, Paul

    1987-09-01

    This paper is a summary of a more detailed analysis of the kinematics of the Sinai triple junction (Courtillot et al., 1987). Accurate kinematic data are lacking along the Red Sea and they can be supplemented by bathymetric, topographic and geological data pertaining to the three arms of the entirely continental Sinai triple junction. Motions across the northern Red Sea and along the Gulf of Elat are an order of magnitude larger than across the Gulf of Suez. The direction of motion there remains a major uncertainty. A possible kinematic model is highlighted, in which right-lateral strike-slip motion and small pull-apart basins occur along the Gulf of Suez, in agreement with recent field observations in Egypt. Early Miocene is marked by major geodynamical changes all along the northern boundaries of the African and Indian plates. We suggest that rifting in the Arabian Sea, Gulf of Aden, Red Sea and Gulf of Suez was initiated at the end of the first phase of continental extrusion of Indochina, when the Tibetan plateau began to rise and spreading in the South China Sea came to a halt.

  19. Solar Cells With Multiple Small Junctions

    NASA Technical Reports Server (NTRS)

    Daud, T.; Koliwad, K. M.

    1985-01-01

    Concept for improving efficiency of photovoltaic solar cells based on decreasing p/n junction area in relation to total surface area of cell. Because of reduced junction area, surface leakage drops and saturation current density decreases. Surface passivation helps to ensure short-circuit current remains at high value and response of cells to blue light increases.

  20. Analysis of Tight Junction Formation and Integrity

    SciTech Connect

    Karakaya, Mahmut; Kerekes, Ryan A; Morrell-Falvey, Jennifer L; Foster, Carmen M; Retterer, Scott T

    2012-01-01

    In this paper, we study segmentation of tight junctions and analyze the formation and integrity of tight junctions in large-scale confocal image stacks, a challenging biological problem because of the low spatial resolution images and the presence of breaks in tight junction structure. We present an automated, three-step processing approach for tight junction analysis. In our approach, we first localize each individual nucleus in the image by using thresholding, morphological filters and active contours. By using each nucleus position as a seed point, we automatically segment the cell body based on the active contour. We then use an intensity-based skeletonization algorithm to generate the boundary regions for each cell, and features are extracted from tight junctions associated with each cell to assess tight junction continuity. Based on qualitative results and quantitative comparisons, we show that we are able to automatically segment tight junctions and compute relevant features that provide a quantitative measure of tight junction formation to which the permeability of the cell monolayer can ultimately be correlated.

  1. Zipper and freeway shear zone junctions

    NASA Astrophysics Data System (ADS)

    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

  2. On the auxiliary lattices and dislocation reactions at triple junctions.

    PubMed

    Gertsman, V Y

    2002-03-01

    Coincidence site and displacement shift complete lattices of triple junctions are analysed. Dislocation reactions at triple junctions are considered. It is shown that in alpha=1 junctions no trapped residual triple-junction dislocation is geometrically necessary for dislocation transmission between adjoining grain boundaries. However, the situation is different for alpha (unequal) 1 triple junctions, where in some cases the residual dislocation cannot leave the triple junction for a grain boundary without generating a stacking-fault-like defect.

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

    SciTech Connect

    Cleland, A.N.

    1991-04-01

    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 {approx} 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.

  4. Axon-glia interactions and the domain organization of myelinated axons requires neurexin IV/Caspr/Paranodin.

    PubMed

    Bhat, M A; Rios, J C; Lu, Y; Garcia-Fresco, G P; Ching, W; St Martin, M; Li, J; Einheber, S; Chesler, M; Rosenbluth, J; Salzer, J L; Bellen, H J

    2001-05-01

    Myelinated fibers are organized into distinct domains that are necessary for saltatory conduction. These domains include the nodes of Ranvier and the flanking paranodal regions where glial cells closely appose and form specialized septate-like junctions with axons. These junctions contain a Drosophila Neurexin IV-related protein, Caspr/Paranodin (NCP1). Mice that lack NCP1 exhibit tremor, ataxia, and significant motor paresis. In the absence of NCP1, normal paranodal junctions fail to form, and the organization of the paranodal loops is disrupted. Contactin is undetectable in the paranodes, and K(+) channels are displaced from the juxtaparanodal into the paranodal domains. Loss of NCP1 also results in a severe decrease in peripheral nerve conduction velocity. These results show a critical role for NCP1 in the delineation of specific axonal domains and the axon-glia interactions required for normal saltatory conduction. PMID:11395000

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

    NASA Astrophysics Data System (ADS)

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

    2005-10-01

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

  6. Electrostatic control of thermoelectricity in molecular junctions.

    PubMed

    Kim, Youngsang; Jeong, Wonho; Kim, Kyeongtae; Lee, Woochul; Reddy, Pramod

    2014-11-01

    Molecular junctions hold significant promise for efficient and high-power-output thermoelectric energy conversion. Recent experiments have probed the thermoelectric properties of molecular junctions. However, electrostatic control of thermoelectric properties via a gate electrode has not been possible due to technical challenges in creating temperature differentials in three-terminal devices. Here, we show that extremely large temperature gradients (exceeding 1 × 10(9) K m(-1)) can be established in nanoscale gaps bridged by molecules, while simultaneously controlling their electronic structure via a gate electrode. Using this platform, we study prototypical Au-biphenyl-4,4'-dithiol-Au and Au-fullerene-Au junctions to demonstrate that the Seebeck coefficient and the electrical conductance of molecular junctions can be simultaneously increased by electrostatic control. Moreover, from our studies of fullerene junctions, we show that thermoelectric properties can be significantly enhanced when the dominant transport orbital is located close to the chemical potential (Fermi level) of the electrodes. These results illustrate the intimate relationship between the thermoelectric properties and charge transmission characteristics of molecular junctions and should enable systematic exploration of the recent computational predictions that promise extremely efficient thermoelectric energy conversion in molecular junctions. PMID:25282046

  7. Downregulation of gap junctions in cancer cells.

    PubMed

    Leithe, Edward; Sirnes, Solveig; Omori, Yasufumi; Rivedal, Edgar

    2006-12-01

    Gap junctions are intercellular plasma membrane domains enriched in channels that allow direct exchange of ions and small molecules between adjacent cells. Gap junction channels are composed of a family of transmembrane proteins called connexin. Connexins play important roles in the regulation of cell growth and differentiation. Cancer cells usually have downregulated levels of gap junctions, and several lines of evidence suggest that loss of gap junctional intercellular communication is an important step in carcinogenesis. In support of this hypothesis are studies showing that reexpression of connexins in cancer cells causes normalization of cell growth control and reduced tumor growth. To gain a more detailed understanding of the role of connexins as tumor suppressors, a clearer picture of the mechanisms involved in loss of gap junctions in cancer cells is needed. Furthermore, defining the mechanisms involved in downregulation of connexins in carcinogenesis will be an important step toward utilizing the potential of connexins as targets in cancer prevention and therapy. Various mechanisms are involved in the loss of gap junctions in cancer cells, ranging from loss of connexin gene transcription to aberrant trafficking of connexin proteins. This review will discuss our current knowledge on the molecular mechanisms involved in the downregulation of gap junctions in cancer cells. PMID:17425504

  8. Constraints on string networks with junctions

    SciTech Connect

    Copeland, E. J.; Kibble, T. W. B.; Steer, D. A.

    2007-03-15

    We consider the constraints on string networks with junctions in which the strings may all be different, as may be found, for example, in a network of (p,q) cosmic superstrings. We concentrate on three aspects of junction dynamics. First we consider the propagation of small-amplitude waves across a static three-string junction. Then, generalizing our earlier work, we determine the kinematic constraints on two colliding strings with different tensions. As before, the important conclusion is that strings do not always reconnect with a third string; they can pass straight through one another (or in the case of non-Abelian strings become stuck in an X configuration), the constraint depending on the angle at which the strings meet, on their relative velocity, and on the ratios of the string tensions. For example, if the two colliding strings have equal tensions, then for ultrarelativistic initial velocities they pass through one another. However, if their tensions are sufficiently different they can reconnect. Finally, we consider the global properties of junctions and strings in a network. Assuming that, in a network, the incoming waves at a junction are independently randomly distributed, we determine the root-mean-square (r.m.s.) velocities of strings and calculate the average speed at which a junction moves along each of the three strings from which it is formed. Our findings suggest that junction dynamics may be such as to preferentially remove the heavy strings from the network leaving a network of predominantly light strings. Furthermore the r.m.s. velocity of strings in a network with junctions is smaller than 1/{radical}(2), the result for conventional Nambu-Goto strings without junctions in Minkowski space-time.

  9. Plasticity of single-atom Pb junctions

    NASA Astrophysics Data System (ADS)

    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.

  10. New Phenomena in Josephson SINIS Junctions

    NASA Astrophysics Data System (ADS)

    Volkov, A. F.

    1995-06-01

    We analyze the dc and ac Josephson effects in SaINISb junctions in which an additional bias current flows in the N layer. The case of low temperatures and voltages \\(eV, T<<Δ\\) is considered in the dirty limit. We show that the critical Josephson current may change sign, and the considered SINIS junction may become a π junction if the voltage drop across the N/Sa interface exceeds a certain value \\(eVN>Δ/2\\). The ac Josephson effect may arise even if the current flows only through the N/Sa interface, whereas the current through the Sb/N interface is absent.

  11. Graded junction termination extensions for electronic devices

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

    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. Graded junction termination extensions for electronic devices

    NASA Technical Reports Server (NTRS)

    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.

  13. delta-biased Josephson tunnel junctions

    SciTech Connect

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

    2010-02-01

    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 delta-biased samples having different electrical and geometrical parameters.

  14. Grand Junction Resource Area, Resource Management Plan, Grand Junction, Colorado

    SciTech Connect

    Not Available

    1985-03-01

    Implementation of a resource management plan is proposed for the 2.0-million-acre Grand Junction Planning Area, located in west-central Colorado. Under the preferred alternative, existing withdrawals from mineral location on 124,442 acres would continue and an additional 154,067 acres would be withdrawn. Approximately 14,100 acres would be identified as unsuitable for further coal leasing. Approximately 624,701 acres would be open to oil and gas leasing without stipulations; 685,603 acres would be open to oil and gas leasing with stipulations; and 149,087 acres would be closed to oil and gas leasing. Air quality enhancement, soil stabilization, and watershed protection would be emphasized. Habitats of major wildlife species and of threatened and endangered plants and animals would be actively managed, but no new livestock management actions would be implemented. The wild horse herd would be allowed to expand from 65 to 120 animals. Paleontological sites and 11,685 archaeological sites would be protected. Approximately 1319 acres of commercial forest land would be identified as suitable for management, and 2800 cords of fuel wood would be offered for sale annually. The three existing developed recreation sites would be maintained, and the Mud Springs site would be expanded to accommodate more group use.

  15. 40.8% Efficient Inverted Triple-Junction Solar Cell with Two Independently Metamorphic Junctions

    SciTech Connect

    Geisz, J. F.; Friedman, D. J.; Ward, J. S.; Duda, A.; Olavarria, W. J.; Moriarty, T. E.; Kiehl, J. T.; Romero, M. J.; Norman, A. G.; Jones, K. M.

    2008-01-01

    A photovoltaic conversion efficiency of 40.8% at 326 suns concentration is demonstrated in a monolithically grown, triple-junction III-V solar cell structure in which each active junction is composed of an alloy with a different lattice constant chosen to maximize the theoretical efficiency. The semiconductor structure was grown by organometallic vapor phase epitaxy in an inverted configuration with a 1.83 eV Ga{sub .51}In{sub .49}P top junction lattice-matched to the GaAs substrate, a metamorphic 1.34 eV In{sub .04}Ga{sub .96}As middle junction, and a metamorphic 0.89 eV In{sub .37}Ga{sub .63}As bottom junction. The two metamorphic junctions contained approximately 1 x 10{sup 5} cm{sup -2} and 2-3 x 10{sup 6} cm{sup -2} threading dislocations, respectively.

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

    PubMed

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

    2007-03-01

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

  17. Ferromagnetic planar Josephson junction with transparent interfaces: a φ junction proposal.

    PubMed

    Heim, D M; Pugach, N G; Kupriyanov, M Yu; Goldobin, E; Koelle, D; Kleiner, R

    2013-05-29

    We calculate the current-phase relation of a planar Josephson junction with a ferromagnetic weak link located on top of a thin normal metal film. Following experimental observations we assume transparent superconductor-ferromagnet interfaces. This provides the best interlayer coupling and a low suppression of the superconducting correlations penetrating from the superconducting electrodes into the ferromagnetic layer. We show that this Josephson junction is a promising candidate for experimental φ junction realization. PMID:23636963

  18. Tunnel junction multiple wavelength light-emitting diodes

    DOEpatents

    Olson, J.M.; Kurtz, S.R.

    1992-11-24

    A multiple wavelength LED having a monolithic cascade cell structure comprising at least two p-n junctions, wherein each of said at least two p-n junctions have substantially different band gaps, and electrical connector means by which said at least two p-n junctions may be collectively energized; and wherein said diode comprises a tunnel junction or interconnect. 5 figs.

  19. Tunnel junction multiple wavelength light-emitting diodes

    DOEpatents

    Olson, Jerry M.; Kurtz, Sarah R.

    1992-01-01

    A multiple wavelength LED having a monolithic cascade cell structure comprising at least two p-n junctions, wherein each of said at least two p-n junctions have substantially different band gaps, and electrical connector means by which said at least two p-n junctions may be collectively energized; and wherein said diode comprises a tunnel junction or interconnect.

  20. Adrenocortical Gap Junctions and Their Functions

    PubMed Central

    Bell, Cheryl L.; Murray, Sandra A.

    2016-01-01

    Adrenal cortical steroidogenesis and proliferation are thought to be modulated by gap junction-mediated direct cell–cell communication of regulatory molecules between cells. Such communication is regulated by the number of gap junction channels between contacting cells, the rate at which information flows between these channels, and the rate of channel turnover. Knowledge of the factors regulating gap junction-mediated communication and the turnover process are critical to an understanding of adrenal cortical cell functions, including development, hormonal response to adrenocorticotropin, and neoplastic dedifferentiation. Here, we review what is known about gap junctions in the adrenal gland, with particular attention to their role in adrenocortical cell steroidogenesis and proliferation. Information and insight gained from electrophysiological, molecular biological, and imaging (immunocytochemical, freeze fracture, transmission electron microscopic, and live cell) techniques will be provided. PMID:27445985

  1. Chirality effect in disordered graphene ribbon junctions

    NASA Astrophysics Data System (ADS)

    Long, Wen

    2012-05-01

    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.

  2. Local Frame Junction Trees in SLAM

    NASA Astrophysics Data System (ADS)

    Kuehnel, Frank O.

    2005-11-01

    Junction trees (JT) is a general purpose tool for exact inference on graphical models. Many of the existing algorithms for building junction trees require a fixed static graphical model. The construction process is not unique, finding the one with the best computational structure (smallest clique size) is also a hard problem. For large scale inference problems, such as Geo-referencing using triangular geodetic networks or equivalent, the simultaneous localization and mapping (SLAM) problem in robotics pose some challenges to junction tree applications. Incremental junction tree techniques for dynamic graphical models prescribe heuristic methods for growing the tree structure, and are applicable to large scale graphical models. Of concern are the proliferative widening of the tree, which makes message passing expensive. In the context of SLAM we present a new apporach that exploits the local frame dependence of novel observation variables.

  3. Current trends in salivary gland tight junctions.

    PubMed

    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

  4. Random telegraph signals in molecular junctions.

    PubMed

    Brunner, Jan; González, Maria Teresa; Schönenberger, Christian; Calame, Michel

    2014-11-26

    We investigate conductance fluctuations in molecular junctions using a mechanically controllable break junction setup in a liquid environment. In contrast to conventional break junction measurements, time-dependent conductance signals were recorded while reducing the gap size between the two contact electrodes. Only small amplitude fluctuations of the conductance are observed when measuring in pure solvent. Conductance traces recorded in solutions containing alkanedithiols show significantly larger fluctuations which can take the form of random telegraph signals. Such signals emerge in a limited conductance range, which corresponds well to the known molecular conductance of the compounds investigated. These large-amplitude fluctuations are attributed to the formation and thermally driven breaking of bonds between a molecule and a metal electrode and provide a still poorly explored source of information on the dynamics of molecular junctions formation. The lifetimes of the high and low conductance states are found to vary between 0.1 ms and 0.1 s. PMID:25352489

  5. The Inherent Properties of DNA Four-way Junctions: Comparing the Crystal Structures of Holliday Junctions

    PubMed Central

    Eichman, Brandt F.; Ortiz-Lombardía, Miguel; Aymamí, Joan; Coll, Miquel; Ho, Pui Shing

    2015-01-01

    Holliday junctions are four-stranded DNA complexes that are formed during recombination and related DNA repair events. Much work has focused on the overall structure and properties of four-way junctions in solution, but we are just now beginning to understand these complexes at the atomic level. The crystal structures of two all-DNA Holliday junctions have been determined recently from the sequences d(CCGGGACCGG) and d(CCGGTACCGG). A detailed comparison of the two structures helps to distinguish distortions of the DNA conformation that are inherent to the cross-overs of the junctions in this crystal system from those that are consequences of the mismatched dG·dA base-pair in the d(CCGGGACCGG) structure. This analysis shows that the junction itself perturbs the sequence-dependent conformational features of the B-DNA duplexes and the associated patterns of hydration in the major and minor grooves only minimally. This supports the idea that a DNA four-way junction can be assembled at relatively low energetic cost. Both structures show a concerted rotation of the adjacent duplex arms relative to B-DNA, and this is discussed in terms of the conserved interactions between the duplexes at the junctions and further down the helical arms. The interactions distant from the strand cross-overs of the junction appear to be significant in defining its macroscopic properties, including the angle relating the stacked duplexes across the junction. PMID:12126623

  6. Gravitational wave bursts from cosmic superstrings with Y-junctions

    SciTech Connect

    Binetruy, P.; Bohe, A.; Hertog, T.; Steer, D. A.

    2009-12-15

    Cosmic superstring loops generically contain strings of different tensions that meet at Y-junctions. These loops evolve nonperiodically in time, and have cusps and kinks that interact with the junctions. We study the effect of junctions on the gravitational wave signal emanating from cosmic string cusps and kinks. We find that earlier results on the strength of individual bursts from cusps and kinks on strings without junctions remain largely unchanged, but junctions give rise to additional contributions to the gravitational wave signal coming from strings expanding at the speed of light at a junction and kinks passing through a junction.

  7. Two junction effects in dc SQUID phase qubit

    NASA Astrophysics Data System (ADS)

    Cooper, B. K.; Kwon, H.; Przybysz, A. J.; Budoyo, R.; Anderson, J. R.; Lobb, C. J.; Wellstood, F. C.

    2011-03-01

    The dc SQUID phase qubit was designed to allow one isolation junction to filter bias current noise from a second junction operating as a single junction phase qubit. As junctions shrink to minimize dielectric loss, the Josephson inductances of each junction approach the coupling loop inductance and this single junction picture appears inadequate. We consider a two-junction model of the dc SQUID phase qubit, where the qubit now corresponds to one of the normal oscillatory modes of the full SQUID. We discuss applications of this model to sweet spots in various control parameters and unusual behavior in the tunneling state measurement. Funded by DOD, CNAM and JQI.

  8. Bond resistances in molecular junctions

    NASA Astrophysics Data System (ADS)

    Painelli, Anna

    2006-03-01

    The description of molecular contacts is one of the hardest problems in modeling molecular junctions. In common approaches macroscopic leads ensure a finite potential drop and hence a driving force for the current. Recently, a different strategy is emerging where a steady-state DC current is forced in the molecule, by making resort to Lagrange multipliers, or by drawing a magnetic flux through the molecule. The strategy is promising, but two main problems remain to be solved: (1) the calculation of the potential drop needed to sustain the current, and (2) the definition of the potential profile along the molecule. Here the Joule law is used to evaluate the potential drop from the electrical power spent on the molecule, and continuity constraints for steady-state DC current are implemented to get information on the potential profile. Borrowing powerful concepts from the field of molecular spectroscopy, emphasis is put on the molecule, while clamping information about contacts in the molecular relaxation matrix. The molecule is described in a real-space approach, leading to a suggestive analogy between the molecule and an electrical circuit where resistances are associated with chemical bonds.

  9. Heat dissipation in atomic-scale junctions.

    PubMed

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

    2013-06-13

    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 experimental challenges. Here we use custom-fabricated scanning probes with integrated nanoscale thermocouples to investigate heat dissipation in the electrodes of single-molecule ('molecular') junctions. We find that if the junctions have transmission characteristics that are strongly energy dependent, this heat dissipation is asymmetric--that is, unequal between the electrodes--and also dependent on both the bias polarity and the identity of the majority charge carriers (electrons versus holes). In contrast, junctions consisting of only a few gold atoms ('atomic junctions') whose transmission characteristics show weak energy dependence do not exhibit appreciable asymmetry. Our results unambiguously relate the electronic transmission characteristics of atomic-scale junctions to their heat dissipation properties, establishing a framework for understanding heat dissipation in a range of mesoscopic systems where transport is elastic--that is, without exchange of energy in the contact region. We anticipate that the techniques established here will enable the study of Peltier effects at the atomic scale, a field that has been barely explored experimentally despite interesting theoretical predictions. Furthermore, the experimental advances described here are also expected to enable the study of heat transport in atomic and molecular junctions--an important and challenging scientific and technological goal that has remained elusive.

  10. Photovoltaic device having an extended PN junction

    NASA Technical Reports Server (NTRS)

    D'Aiello, Robert Vincent (Inventor)

    1978-01-01

    A photovoltaic device having essentially only a body of semiconductor material having a first region of one conductivity type in contact with a second region of the opposite conductivity type, forming a portion of the device PN junction therebetween. A plurality of pocket regions of the same conductivity type as the first region extend into the second region thereby further defining a portion of the PN junction in the second region.

  11. Semiconductor tunnel junction with enhancement layer

    DOEpatents

    Klem, John F.; Zolper, John C.

    1997-01-01

    The incorporation of a pseudomorphic GaAsSb layer in a runnel diode structure affords a new degree of freedom in designing runnel junctions for p-n junction device interconnects. Previously only doping levels could be varied to control the tunneling properties. This invention uses the valence band alignment band of the GaAsSb with respect to the surrounding materials to greatly relax the doping requirements for tunneling.

  12. Semiconductor tunnel junction with enhancement layer

    DOEpatents

    Klem, J.F.; Zolper, J.C.

    1997-10-21

    The incorporation of a pseudomorphic GaAsSb layer in a runnel diode structure affords a new degree of freedom in designing runnel junctions for p-n junction device interconnects. Previously only doping levels could be varied to control the tunneling properties. This invention uses the valence band alignment band of the GaAsSb with respect to the surrounding materials to greatly relax the doping requirements for tunneling. 5 figs.

  13. Method of fabrication of Josephson tunnel junction

    SciTech Connect

    Michikami, O.; Katoh, Y.; Takenaka, H.; Tanabe, K.; Yoshii, S.

    1983-11-01

    There is disclosed a method of fabrication of a Josephson tunnel junction device. A surface of a base electrode of Nb or Nb compound is subjected to sputter cleaning and then to plasma oxidation in an atmosphere of a diluent gas and oxygen to form thereon an oxide layer serving as a tunnel barrier. A counter electrode is then formed on the oxide layer to provide the Josephson tunnel junction.

  14. Multi-junction solar cell device

    DOEpatents

    Friedman, Daniel J.; Geisz, John F.

    2007-12-18

    A multi-junction solar cell device (10) is provided. The multi-junction solar cell device (10) comprises either two or three active solar cells connected in series in a monolithic structure. The multi-junction device (10) comprises a bottom active cell (20) having a single-crystal silicon substrate base and an emitter layer (23). The multi-junction device (10) further comprises one or two subsequent active cells each having a base layer (32) and an emitter layer (23) with interconnecting tunnel junctions between each active cell. At least one layer that forms each of the top and middle active cells is composed of a single-crystal III-V semiconductor alloy that is substantially lattice-matched to the silicon substrate (22). The polarity of the active p-n junction cells is either p-on-n or n-on-p. The present invention further includes a method for substantially lattice matching single-crystal III-V semiconductor layers with the silicon substrate (22) by including boron and/or nitrogen in the chemical structure of these layers.

  15. Triple junction motion and grain microstructure evolution

    SciTech Connect

    Gottstein, G. . E-mail: gottstein@imm.rwth-aachen.de; Ma, Y.; Shvindlerman, L.S.

    2005-03-01

    The classical concepts of grain growth in polycrystals are based on the dominant role of grain boundaries. This is reflected by the well known von Neumann-Mullins relation. According to this approach triple junctions do not affect grain boundary motion, and their role in grain growth is reduced to maintaining the thermodynamically prescribed equilibrium angles at the lines where boundaries meet. In the current study the experimental data of triple junction mobility are considered with respect to the process of grain growth in 2D systems, in particular with regard to the controlling kinetics. When boundary kinetics prevails grain growth in a polycrystal complies with the von Neumann-Mullins relation. When grain growth is governed by the mobility of triple junctions the kinetics change, and the von Neumann-Mullins relation does not hold anymore. This is the more pronounced the smaller the triple junction mobility. We present a generalized theory of 2D grain growth including a limited triple junction mobility. In this concept the criterion {lambda} plays a central role. It reflects the ratio of boundary to triple junction mobility but is proportional to the grain size as well. The generalized von Neumann-Mullins relation can be expressed in terms of {lambda}. For small values of {lambda}, conspicuous changes of microstructure evolution during grain growth and of microstructural stability are predicted. The theoretical predictions are compared to results of computer simulations by a virtual vertex model.

  16. Transport Fluctuations in Metal-Molecule Junctions

    NASA Astrophysics Data System (ADS)

    Malen, Jonathan; Baheti, Kanhayalal; Doak, Peter; Segalman, Rachel; Majumdar, Arun

    2008-03-01

    Thermopower of metal-molecule junctions is an alternative transport characteristic to conductance that can be experimentally measured. A scanning tunneling microscope break junction was used to measure the thermopower of such molecular junctions. Temperature bias applied between gold contacts across the bridging molecules generates a thermoelectric voltage. Hitherto, the statistical analysis of the data from both thermopower and conductance measurements has focused on the histogram peaks rather than the spread of the data. We find that the full width half maximums (FWHM) of the voltage histograms are finite at zero temperature bias and increase in proportion to the temperature bias. Johnson Noise is the most likely cause of the zero bias FWHM, and its magnitude is thereby related to the junction conductance. For 1,4,Benzenedithiol (BDT) the junction conductance associated with the zero bias FWHM is 0.02G0, in close agreement with prior conductance measurements of BDT. The dependence of FWHM on temperature bias may provide further insight to the origin of stochastic fluctuations in metal molecule junctions.

  17. Synchronization in Disordered Josephson Junction Arrays

    NASA Astrophysics Data System (ADS)

    Trees, B. R.; Dissanayake, S. T. M.

    2002-03-01

    We have studied the dynamics of a ladder array of overdamped Josephson junctions with periodic boundary conditions. The junctions have critical current and resistive disorder, are current biased above the critical current, and their voltages oscillate with nonidentical bare frequencies. We have been interested in the onset of synchronization in the rung junctions of the ladder, in which nearest neighbor interactions of strength α renormalize the bare frequencies to a common value. The degree of synchronization of the array is measured by an order parameter, r (0<= r<= 1), as a function of α and the spread of bare frequencies. For a given frequency spread, a synchronization phase transition is clearly visible with an increase in α. We have also determined that a time-averaged version of the resistively-shunted junction equations can be used as an accurate description of the dynamics of the junctions. The solutions to the averaged equations exhibit phase slips between pairs of junctions for certain ranges of values of α and also demonstrate that the relationship between the array size, N, and the critical coupling strength for the onset of synchronization scales as N^2. This research was partially funded by a grant to Ohio Wesleyan University from the McGregor Foundation to support student research.

  18. Grain boundary hardening and triple junction hardening in polycrystalline molybdenum

    SciTech Connect

    Kobayashi, Shigeaki . E-mail: skoba@ashitech.ac.jp; Tsurekawa, Sadahiro; Watanabe, Tadao

    2005-02-01

    The grain boundary and triple junction hardenings in molybdenum with different carbon content were studied in connection with the character and the connectivity of grain boundaries at triple junctions by the micro-indentation test. The triple junction hardening is smaller at the junctions composed of low-angle and {sigma} boundaries than at the junctions composed of random boundaries. This difference in the hardening depending on the grain boundary connectivity becomes more significant with a decrease in carbon content in molybdenum.

  19. Charge transport in nanoscale junctions.

    PubMed

    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.

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

    ERIC Educational Resources Information Center

    Selvarajah, Geeta; Selvarajah, Susila

    2016-01-01

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

  1. Junctional Adhesion Molecule A Promotes Epithelial Tight Junction Assembly to Augment Lung Barrier Function

    PubMed Central

    Mitchell, Leslie A.; Ward, Christina; Kwon, Mike; Mitchell, Patrick O.; Quintero, David A.; Nusrat, Asma; Parkos, Charles A.; Koval, Michael

    2016-01-01

    Epithelial barrier function is maintained by tight junction proteins that control paracellular fluid flux. Among these proteins is junctional adhesion molecule A (JAM-A), an Ig fold transmembrane protein. To assess JAM-A function in the lung, we depleted JAM-A in primary alveolar epithelial cells using shRNA. In cultured cells, loss of JAM-A caused an approximately 30% decrease in transepithelial resistance, decreased expression of the tight junction scaffold protein zonula occludens 1, and disrupted junctional localization of the structural transmembrane protein claudin-18. Consistent with findings in other organs, loss of JAM-A decreased β1 integrin expression and impaired filamentous actin formation. Using a model of mild systemic endoxotemia induced by i.p. injection of lipopolysaccharide, we report that JAM-A−/− mice showed increased susceptibility to pulmonary edema. On injury, the enhanced susceptibility of JAM-A−/− mice to edema correlated with increased, transient disruption of claudin-18, zonula occludens 1, and zonula occludens 2 localization to lung tight junctions in situ along with a delay in up-regulation of claudin-4. In contrast, wild-type mice showed no change in lung tight junction morphologic features in response to mild systemic endotoxemia. These findings support a key role of JAM-A in promoting tight junction homeostasis and lung barrier function by coordinating interactions among claudins, the tight junction scaffold, and the cytoskeleton. PMID:25438062

  2. Esophagogastric junction distensibility in hiatus hernia.

    PubMed

    Lottrup, C; McMahon, B P; Ejstrud, P; Ostapiuk, M A; Funch-Jensen, P; Drewes, A M

    2016-07-01

    Hiatus hernia is known to be an important risk factor for developing gastroesophageal reflux disease. We aimed to use the endoscopic functional lumen imaging probe (EndoFLIP) to evaluate the functional properties of the esophagogastric junction. EndoFLIP assessments were made in 30 patients with hiatus hernia and Barrett's esophagus, and in 14 healthy controls. The EndoFLIP was placed straddling the esophagogastric junction and the bag distended stepwise to 50 mL. Cross-sectional areas of the bag and intra-bag pressures were recorded continuously. Measurements were made in the separate sphincter components and hiatus hernia cavity. EndoFLIP measured functional aspects such as sphincter distensibility and pressure of all esophagogastric junction components and visualized all hiatus hernia present at endoscopy. The lower esophageal sphincter in hiatus hernia patients had a lower pressure (e.g. 47.7 ± 13.0 vs. 61.4 ± 19.2 mm Hg at 50-mL distension volume) and was more distensible (all P < 0.001) than the common esophagogastric junction in controls. In hiatus hernia patients, the crural diaphragm had a lower pressure (e.g. 29.6 ± 10.1 vs. 47.7 ± 13.0 mm Hg at 50-mL distension volume) and was more distensible (all P < 0.001) than the lower esophageal sphincter. There was a significant association between symptom scores in patients and EndoFLIP assessment. Conclusively, EndoFLIP was a useful tool. To evaluate the presence of a hiatus hernia and to measure the functional properties of the esophagogastric junction. Furthermore, EndoFLIP distinguished the separate esophagogastric junction components in hiatus hernia patients, and may help us understand the biomechanics of the esophagogastric junction and the mechanisms behind hiatal herniation. PMID:25789842

  3. Clathrin and Cx43 gap junction plaque endoexocytosis

    SciTech Connect

    Nickel, Beth M.; DeFranco, B. Hewa; Gay, Vernon L.; Murray, Sandra A.

    2008-10-03

    In earlier transmission electron microscopic studies, we have described pentilaminar gap junctional membrane invaginations and annular gap junction vesicles coated with short, electron-dense bristles. The similarity between these electron-dense bristles and the material surrounding clathrin-coated pits led us to suggest that the dense bristles associated with gap junction structures might be clathrin. To confirm that clathrin is indeed associated with annular gap junction vesicles and gap junction plaques, quantum dot immuno-electron microscopic techniques were used. We report here that clathrin associates with both connexin 43 (Cx43) gap junction plaques and pentilaminar gap junction vesicles. An important finding was the preferential localization of clathrin to the cytoplasmic surface of the annular or of the gap junction plaque membrane of one of the two contacting cells. This is consistent with the possibility that the direction of gap junction plaque internalization into one of two contacting cells is regulated by clathrin.

  4. A single-gradient junction technique to replace multiple-junction shifts for craniospinal irradiation treatment

    SciTech Connect

    Hadley, Austin; Ding, George X.

    2014-01-01

    Craniospinal irradiation (CSI) requires abutting fields at the cervical spine. Junction shifts are conventionally used to prevent setup error–induced overdosage/underdosage from occurring at the same location. This study compared the dosimetric differences at the cranial-spinal junction between a single-gradient junction technique and conventional multiple-junction shifts and evaluated the effect of setup errors on the dose distributions between both techniques for a treatment course and single fraction. Conventionally, 2 lateral brain fields and a posterior spine field(s) are used for CSI with weekly 1-cm junction shifts. We retrospectively replanned 4 CSI patients using a single-gradient junction between the lateral brain fields and the posterior spine field. The fields were extended to allow a minimum 3-cm field overlap. The dose gradient at the junction was achieved using dose painting and intensity-modulated radiation therapy planning. The effect of positioning setup errors on the dose distributions for both techniques was simulated by applying shifts of ± 3 and 5 mm. The resulting cervical spine doses across the field junction for both techniques were calculated and compared. Dose profiles were obtained for both a single fraction and entire treatment course to include the effects of the conventional weekly junction shifts. Compared with the conventional technique, the gradient-dose technique resulted in higher dose uniformity and conformity to the target volumes, lower organ at risk (OAR) mean and maximum doses, and diminished hot spots from systematic positioning errors over the course of treatment. Single-fraction hot and cold spots were improved for the gradient-dose technique. The single-gradient junction technique provides improved conformity, dose uniformity, diminished hot spots, lower OAR mean and maximum dose, and one plan for the entire treatment course, which reduces the potential human error associated with conventional 4-shifted plans.

  5. The atrioventricular junctions in Ebstein malformation

    PubMed Central

    Ho, S; Goltz, D; McCarthy, K; Cook, A; Connell, M; Smith, A; Anderson, R

    2000-01-01

    OBJECTIVE—To review the anatomical structure of the right atrioventricular junction, including the specialised atrioventricular conduction system, in hearts with Ebstein's malformation, to identify potential substrates for the abnormalities in conduction.
METHODS—Five heart specimens representing the morphological spectrum of Ebstein malformation were examined grossly and histologically.
RESULTS—On the endocardial surface, the atrioventricular junction was marked by a faint line in two hearts, and by a small ridge in the other three. Analysis of the right parietal junction in four hearts revealed only two accessory muscular atrioventricular connections. A plane of fibrofatty tissue separated atrial from ventricular myocardium in the right parietal junction in all hearts. The compact atrioventricular node was closer to the coronary sinus than usual. Accessory nodoventricular connections were present in four hearts, while accessory fasciculo-ventricular connections were found in one. The right bundle branch was hypoplastic or absent in four hearts.
CONCLUSIONS—In this small series, the parietal atrioventricular junction was better developed than previously thought. Structural abnormalities of the atrioventricular conduction system, however, were present. These may account for some of the conduction abnormalities frequently observed with the Ebstein malformation.


Keywords: Ebstein's anomaly; atrioventricular node; bundle branch block; Wolff-Parkinson-White syndrome PMID:10722549

  6. Proximal Junctional Kyphosis: Diagnosis, Pathogenesis, and Treatment

    PubMed Central

    Lee, Jaewon

    2016-01-01

    Proximal junctional kyphosis (PJK) is a common radiographic finding after long spinal fusion. A number of studies on the causes, risk factors, prevention, and treatment of PJK have been conducted. However, no clear definition of PJK has been established. In this paper, we aimed to clarify the diagnosis, prevention, and treatment of PJK by reviewing relevant papers that have been published to date. A literature search was conducted on PubMed using "proximal junctional", "proximal junctional kyphosis", and "proximal junctional failure" as search keywords. Only studies that were published in English were included in this study. The incidence of PJK ranges from 5% to 46%, and it has been reported that 66% of cases occur 3 months after surgery and approximately 80% occur within 18 months. A number of studies have reported that there is no significantly different clinical outcome between PJK patients and non-PJK patients. One study showed that PJK patients expressed more pain than non-PJK patients. However, recent studies focused on proximal junctional failure (PJF), which is accepted as a severe form of PJK. PJF showed significant adverse impact in clinical aspect such as pain, neurologic deficit, ambulatory difficulties, and social isolation. Numerous previous studies have identified various risk factors and reported on the treatment and prevention of PJK. Based on these studies, we determined the clinical significance and impact of PJK. In addition, it is important to find a strategic approach to the proper treatment of PJK. PMID:27340542

  7. Semiconductor Lasers Containing Quantum Wells in Junctions

    NASA Technical Reports Server (NTRS)

    Yang, Rui Q.; Qiu, Yueming

    2004-01-01

    In a recent improvement upon In(x)Ga(1-x)As/InP semiconductor lasers of the bipolar cascade type, quantum wells are added to Esaki tunnel junctions, which are standard parts of such lasers. The energy depths and the geometric locations and thicknesses of the wells are tailored to exploit quantum tunneling such that, as described below, electrical resistances of junctions and concentrations of dopants can be reduced while laser performances can be improved. In(x)Ga(1-x)As/InP bipolar cascade lasers have been investigated as sources of near-infrared radiation (specifically, at wavelengths of about 980 and 1,550 nm) for photonic communication systems. The Esaki tunnel junctions in these lasers have been used to connect adjacent cascade stages and to enable transport of charge carriers between them. Typically, large concentrations of both n (electron-donor) and p (electron-acceptor) dopants have been necessary to impart low electrical resistances to Esaki tunnel junctions. Unfortunately, high doping contributes free-carrier absorption, thereby contributing to optical loss and thereby, further, degrading laser performance. In accordance with the present innovation, quantum wells are incorporated into the Esaki tunnel junctions so that the effective heights of barriers to quantum tunneling are reduced (see figure).

  8. Conductance bistability in metal oxide junctions

    NASA Astrophysics Data System (ADS)

    Tan, Zhongkui; Patel, Vijay; Monge, Esteban; Chang, Shih-Sheng; Pottorf, Shawn; Lukens, James; Likharev, Konstantin

    2009-03-01

    We are exploring conductance bistability (memory) effects in junctions based on metal oxides, in the context of their possible applications in hybrid CMOS/nanoelectronic (e.g., CMOL [1]) circuits. So far, we have investigated CuOx, NbOx and TiOx formed by thermal and plasma oxidation, with or without rapid thermal post-annealing (at 200 to 800^oC for 30 to 300 seconds). Conductance switching effects have been observed for all these materials. Particularly high endurance (over 1000 switching cycles) has been obtained for TiOx junctions plasma oxidized in 15mTorr oxygen and then post-annealed at 700^oC. However, the ON/OFF conductance ratio for these junctions is only about 5, and the sample-to-sample reproducibility is much lower than required for integrated circuit applications. Our plans are to extend our studies to a-Si junctions with one Ag electrode, and multilayer TiOx junctions, with the main goal to improve device reproducibility. The work is supported in part by AFOSR. [3pt] [1] K. K. Likharev, ``Hybrid CMOS/Nanoelectronic Circuits,'' accepted for publication in J. Nanoelectronics and Optoelectronics, Nov. 2008.

  9. Tunnel junctions, cantilevers, and potentials

    NASA Astrophysics Data System (ADS)

    Tanner, Shawn

    We have developed a process for making sub-micrometer dimensional cantilevers, clamped beams, and more complicate electro-mechanical structures that carry integrated electrical leads. Such objects are perhaps useful as test structures for connecting to and measuring the electrical properties of molecular sized objects, as high frequency electromechanical components for radio and microwave frequency applications, and as sensor components for studying the fluctuation physics of small machines. Our process uses two realigned electron-beam lithography steps, a thin film angled deposition system, and differential removal of sacrificial aluminum layers to produce freely suspended sub-micron electromechanical components. We have produced cantilevers and beams on a variety of substrates (silica, silicon, and poly-imide) and have produced insulating, conductive, and multi-layer mechanical structures. We have measured mechanical resonances in the 10 MHz range by electrostatically actuating the cantilevers while in a magnetic field (3500 gauss) and measuring the voltage that results across the front edge of the cantilever. Two structures are fabricated sharing a common ground so that a balanced detection technique can be used to eliminate background signals. Due to the square dependence of the electrostatic force on the voltage, they can be resonated by a drive voltage of 1/2 the natural frequency or at the natural frequency. Two separate attempts have been made to apply these resonators. First, a process was developed to integrate a tunnel junction with the cantilever. These devices can possibly be used for probing small-scale systems such as molecules. We have verified the exponential variation of the tunneling resistance with both substrate flex and electrostatic gating. Second, a novel gate structure was developed to create a double potential well for resonator motion. This is accomplished by placing a multilayer structure in front of the hairpin cantilever consisting two

  10. Methods for the fabrication of thermally stable magnetic tunnel junctions

    DOEpatents

    Chang, Y. Austin; Yang, Jianhua J.; Ladwig, Peter F.

    2009-08-25

    Magnetic tunnel junctions and method for making the magnetic tunnel junctions are provided. The magnetic tunnel junctions are characterized by a tunnel barrier oxide layer sandwiched between two ferromagnetic layers. The methods used to fabricate the magnetic tunnel junctions are capable of completely and selectively oxidizing a tunnel junction precursor material using an oxidizing gas containing a mixture of gases to provide a tunnel junction oxide without oxidizing the adjacent ferromagnetic materials. In some embodiments the gas mixture is a mixture of CO and CO.sub.2 or a mixture of H.sub.2 and H.sub.2O.

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

    NASA Astrophysics Data System (ADS)

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

    2008-08-01

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

  12. Electrostatic Modeling of Vacuum Insulator Triple Junctions

    SciTech Connect

    Tully, L K; Goerz, D A; Houck, T L; Javedani, J B

    2006-10-25

    Triple junctions are often initiation points for insulator flashover in pulsed power devices. The two-dimensional finite-element TriComp [1] modeling software suite was utilized for its electrostatic field modeling package to investigate electric field behavior in the anode and cathode triple junctions of a high voltage vacuum-insulator interface. TriComp enables simple extraction of values from a macroscopic solution for use as boundary conditions in a subset solution. Electric fields computed with this zoom capability correlate with theoretical analysis of the anode and cathode triple junctions within submicron distances for nominal electrode spacing of 1.0 cm. This paper will discuss the iterative zoom process with TriComp finite-element software and the corresponding theoretical verification of the results.

  13. Thermionic refrigeration at CNT-CNT junctions

    NASA Astrophysics Data System (ADS)

    Li, C.; Pipe, K. P.

    2016-10-01

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

  14. Silicon fiber with p-n junction

    SciTech Connect

    Homa, D.; Cito, A.; Pickrell, G.; Hill, C.; Scott, B.

    2014-09-22

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

  15. Junction-side illuminated silicon detector arrays

    DOEpatents

    Iwanczyk, Jan S.; Patt, Bradley E.; Tull, Carolyn

    2004-03-30

    A junction-side illuminated detector array of pixelated detectors is constructed on a silicon wafer. A junction contact on the front-side may cover the whole detector array, and may be used as an entrance window for light, x-ray, gamma ray and/or other particles. The back-side has an array of individual ohmic contact pixels. Each of the ohmic contact pixels on the back-side may be surrounded by a grid or a ring of junction separation implants. Effective pixel size may be changed by separately biasing different sections of the grid. A scintillator may be coupled directly to the entrance window while readout electronics may be coupled directly to the ohmic contact pixels. The detector array may be used as a radiation hardened detector for high-energy physics research or as avalanche imaging arrays.

  16. Tunnel junction based memristors as artificial synapses

    PubMed Central

    Thomas, Andy; Niehörster, Stefan; Fabretti, Savio; Shepheard, Norman; Kuschel, Olga; Küpper, Karsten; Wollschläger, Joachim; Krzysteczko, Patryk; Chicca, Elisabetta

    2015-01-01

    We prepared magnesia, tantalum oxide, and barium titanate based tunnel junction structures and investigated their memristive properties. The low amplitudes of the resistance change in these types of junctions are the major obstacle for their use. Here, we increased the amplitude of the resistance change from 10% up to 100%. Utilizing the memristive properties, we looked into the use of the junction structures as artificial synapses. We observed analogs of long-term potentiation, long-term depression and spike-time dependent plasticity in these simple two terminal devices. Finally, we suggest a possible pathway of these devices toward their integration in neuromorphic systems for storing analog synaptic weights and supporting the implementation of biologically plausible learning mechanisms. PMID:26217173

  17. Synchronized Switching in a Josephson Junction Crystal

    NASA Astrophysics Data System (ADS)

    Leib, Martin; Hartmann, Michael J.

    2014-06-01

    We consider a superconducting coplanar waveguide resonator where the central conductor is interrupted by a series of uniformly spaced Josephson junctions. The device forms an extended medium that is optically nonlinear on the single photon level with normal modes that inherit the full nonlinearity of the junctions but are nonetheless accessible via the resonator ports. For specific plasma frequencies of the junctions, a set of normal modes clusters in a narrow band and eventually becomes entirely degenerate. Upon increasing the intensity of a red detuned drive on these modes, we observe a sharp and synchronized switching from low-occupation quantum states to high-occupation classical fields, accompanied by a pronounced jump from low to high output intensity.

  18. Synchronized switching in a josephson junction crystal.

    PubMed

    Leib, Martin; Hartmann, Michael J

    2014-06-01

    We consider a superconducting coplanar waveguide resonator where the central conductor is interrupted by a series of uniformly spaced Josephson junctions. The device forms an extended medium that is optically nonlinear on the single photon level with normal modes that inherit the full nonlinearity of the junctions but are nonetheless accessible via the resonator ports. For specific plasma frequencies of the junctions, a set of normal modes clusters in a narrow band and eventually becomes entirely degenerate. Upon increasing the intensity of a red detuned drive on these modes, we observe a sharp and synchronized switching from low-occupation quantum states to high-occupation classical fields, accompanied by a pronounced jump from low to high output intensity. PMID:24949766

  19. Studies of silicon PN junction solar cells

    NASA Technical Reports Server (NTRS)

    Lindholm, F. A.

    1975-01-01

    Silicon pn junction solar cells made with low-resistivity substrates show poorer performance than traditional theory predicts. The purpose of this research was to identify and characterize the physical mechanisms responsible for the discrepancy. Attention was concentrated on the open circuit voltage in shallow junction cells of 0.1 ohm-cm substrate resistivity. A number of possible mechanisms that can occur in silicon devices were considered. Two mechanisms which are likely to be of main importance in explaining the observed low values of open-circuit voltage were found: (1) recombination losses associated with defects introduced during junction formation, and (2) inhomogeneity of defects and impurities across the area of the cell. To explore these theoretical anticipations, various diode test structures were designed and fabricated and measurement configurations for characterizing the defect properties and the areal inhomogeneity were constructed.

  20. Vortex structures in exponentially shaped Josephson junctions

    NASA Astrophysics Data System (ADS)

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

    2005-04-01

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

  1. Electronic Properties of Carbon Nanotubes and Junctions

    NASA Technical Reports Server (NTRS)

    Anantram, M. P.; Han, Jie; Yang, Liu; Govindan, T. R.; Jaffe, R.; Saini, Subhash (Technical Monitor)

    1998-01-01

    Metallic and semiconducting Single Wall Carbon Nanotubes (CNT) have recently been characterized using scanning tunneling microscopy (STM) and the manipulation of individual CNT has been demonstrated. These developments make the prospect of using CNT as molecular wires and possibly as electronic devices an even more interesting one. We have been modeling various electronic properties such as the density of states and the transmission coefficient of CNT wires and junctions. These studies involve first calculating the stability of junctions using molecular dynamics simulations and then calculating the electronic properties using a pi-electron tight binding Hamiltonian. We have developed the expertise to calculate the electronic properties of both finite-sized CNT and CNT systems with semi-infinite boundary conditions. In this poster, we will present an overview of some of our results. The electronic application of CNT that is most promising at this time is their use as molecular wires. The conductance can however be greatly reduced because of reflection due to defects and contacts. We have modeled the transmission through CNT in the presence of two types of defects: weak uniform disorder and strong isolated scatterers. We find that the conductance is affected in significantly different manners due to these defects Junctions of CNT have also been imaged using STM. This makes it essential to derive rules for the formation of junctions between tubes of different chirality, study their relative energies and electronic properties. We have generalized the rules for connecting two different CNT and have calculated the transmission and density of states through CNT junctions. Metallic and semiconducting CNT can be joined to form a stable junction and their current versus voltage characteristics are asymmetric. CNT are deformed by the application of external forces including interactions with a substrate or other CNT. In many experiments, these deformation are expected to

  2. Structure and function of gap junction proteins: role of gap junction proteins in embryonic heart development.

    PubMed

    Ahir, Bhavesh K; Pratten, Margaret K

    2014-01-01

    Intercellular (cell-to-cell) communication is a crucial and complex mechanism during embryonic heart development. In the cardiovascular system, the beating of the heart is a dynamic and key regulatory process, which is functionally regulated by the coordinated spread of electrical activity through heart muscle cells. Heart tissues are composed of individual cells, each bearing specialized cell surface membrane structures called gap junctions that permit the intercellular exchange of ions and low molecular weight molecules. Gap junction channels are essential in normal heart function and they assist in the mediated spread of electrical impulses that stimulate synchronized contraction (via an electrical syncytium) of cardiac tissues. This present review describes the current knowledge of gap junction biology. In the first part, we summarise some relevant biochemical and physiological properties of gap junction proteins, including their structure and function. In the second part, we review the current evidence demonstrating the role of gap junction proteins in embryonic development with particular reference to those involved in embryonic heart development. Genetics and transgenic animal studies of gap junction protein function in embryonic heart development are considered and the alteration/disruption of gap junction intercellular communication which may lead to abnormal heart development is also discussed.

  3. Complementary junction heterostructure field-effect transistor

    DOEpatents

    Baca, A.G.; Drummond, T.J.; Robertson, P.J.; Zipperian, T.E.

    1995-12-26

    A complimentary pair of compound semiconductor junction heterostructure field-effect transistors and a method for their manufacture are disclosed. The p-channel junction heterostructure field-effect transistor uses a strained layer to split the degeneracy of the valence band for a greatly improved hole mobility and speed. The n-channel device is formed by a compatible process after removing the strained layer. In this manner, both types of transistors may be independently optimized. Ion implantation is used to form the transistor active and isolation regions for both types of complimentary devices. The invention has uses for the development of low power, high-speed digital integrated circuits. 10 figs.

  4. Complementary junction heterostructure field-effect transistor

    DOEpatents

    Baca, Albert G.; Drummond, Timothy J.; Robertson, Perry J.; Zipperian, Thomas E.

    1995-01-01

    A complimentary pair of compound semiconductor junction heterostructure field-effect transistors and a method for their manufacture are disclosed. The p-channel junction heterostructure field-effect transistor uses a strained layer to split the degeneracy of the valence band for a greatly improved hole mobility and speed. The n-channel device is formed by a compatible process after removing the strained layer. In this manner, both types of transistors may be independently optimized. Ion implantation is used to form the transistor active and isolation regions for both types of complimentary devices. The invention has uses for the development of low power, high-speed digital integrated circuits.

  5. Josephson junctions with alternating critical current density

    SciTech Connect

    Mints, R.G.; Kogan, V.G.

    1997-04-01

    The magnetic-field dependence of the critical current I{sub c}(H) is considered for a short Josephson junction with the critical current density j{sub c} alternating along the tunnel contact. Two model cases, periodic and randomly alternating j{sub c}, are treated in detail. Recent experimental data on I{sub c}(H) for grain-boundary Josephson junctions in YBa{sub 2}Cu{sub 3}O{sub x} are discussed. {copyright} {ital 1997} {ital The American Physical Society}

  6. Fluctuation of heat current in Josephson junctions

    SciTech Connect

    Virtanen, P.; Giazotto, F.

    2015-02-15

    We discuss the statistics of heat current between two superconductors at different temperatures connected by a generic weak link. As the electronic heat in superconductors is carried by Bogoliubov quasiparticles, the heat transport fluctuations follow the Levitov–Lesovik relation. We identify the energy-dependent quasiparticle transmission probabilities and discuss the resulting probability density and fluctuation relations of the heat current. We consider multichannel junctions, and find that heat transport in diffusive junctions is unique in that its statistics is independent of the phase difference between the superconductors.

  7. The multiple junction edge illuminated solar cell

    NASA Technical Reports Server (NTRS)

    Sater, B. I.; Brandhorst, H. W., Jr.; Riley, T. J.; Hart, R. E., Jr.

    1973-01-01

    The multiple junction edge illuminated solar cell was devised for high voltage low current applications. Devices to be flight tested in early 1974 with 96 series connected PNN+ junctions in a 2 cm X 2.3 cm size deliver 36 volts at 1 milliampere. Test data of M-J cells fabricated with resistivities of 10, 50, 100, 200, 450, and 1000 ohm cm silicon are presented and problem areas are discussed. An additional potential application of the M-J cell lies in ultilization of its high intensity performance that has been demonstrated at levels in excess of 100 AMO suns.

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

    NASA Astrophysics Data System (ADS)

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

    2007-09-01

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

  9. Atomic-scaled characterization of graphene PN junctions

    NASA Astrophysics Data System (ADS)

    Zhou, Xiaodong; Wang, Dennis; Dadgar, Ali; Agnihotri, Pratik; Lee, Ji Ung; Reuter, Mark C.; Ross, Frances M.; Pasupathy, Abhay N.

    Graphene p-n junctions are essential devices for studying relativistic Klein tunneling and the Veselago lensing effect in graphene. We have successfully fabricated graphene p-n junctions using both lithographically pre-patterned substrates and the stacking of vertical heterostructures. We then use our 4-probe STM system to characterize the junctions. The ability to carry out scanning electron microscopy (SEM) in our STM instrument is essential for us to locate and measure the junction interface. We obtain both the topography and dI/dV spectra at the junction area, from which we track the shift of the graphene chemical potential with position across the junction interface. This allows us to directly measure the spatial width and roughness of the junction and its potential barrier height. We will compare the junction properties of devices fabricated by the aforementioned two methods and discuss their effects on the performance as a Veselago lens.

  10. Singular PP waves, Junction Conditions and BPS States

    SciTech Connect

    Canfora, Fabrizio; Vilasi, Gaetano

    2005-03-16

    A simple model to study the collision of PP waves via the Israel junction conditions is proposed. The junction conditions are interpreted as topological conservation laws, and the relation with BPS states is shortly described.

  11. Ballistic bipolar junctions in chemically gated graphene ribbons

    PubMed Central

    Baringhaus, Jens; Stöhr, Alexander; Forti, Stiven; Starke, Ulrich; Tegenkamp, Christoph

    2015-01-01

    The realization of ballistic graphene pn-junctions is an essential task in order to study Klein tunneling phenomena. Here we show that intercalation of Ge under the buffer layer of pre-structured SiC-samples succeeds to make truly nano-scaled pn-junctions. By means of local tunneling spectroscopy the junction width is found to be as narrow as 5 nm which is a hundred times smaller compared to electrically gated structures. The ballistic transmission across the junction is directly proven by systematic transport measurements with a 4-tip STM. Various npn- and pnp-junctions are studied with respect to the barrier length. The pn-junctions are shown to act as polarizer and analyzer with the second junction becoming transparent in case of a fully ballistic barrier. This can be attributed to the almost full suppression of electron transmission through the junction away from normal incidence. PMID:25898259

  12. Long-term maintenance of Na+ channels at nodes of Ranvier depends on glial contact mediated by gliomedin and NrCAM.

    PubMed

    Amor, Veronique; Feinberg, Konstantin; Eshed-Eisenbach, Yael; Vainshtein, Anya; Frechter, Shahar; Grumet, Martin; Rosenbluth, Jack; Peles, Elior

    2014-04-01

    Clustering of Na(+) channels at the nodes of Ranvier is coordinated by myelinating glia. In the peripheral nervous system, axoglial contact at the nodes is mediated by the binding of gliomedin and glial NrCAM to axonal neurofascin 186 (NF186). This interaction is crucial for the initial clustering of Na(+) channels at heminodes. As a result, it is not clear whether continued axon-glial contact at nodes of Ranvier is required to maintain these channels at the nodal axolemma. Here, we report that, in contrast to mice that lack either gliomedin or NrCAM, absence of both molecules (and hence the glial clustering signal) resulted in a gradual loss of Na(+) channels and other axonal components from the nodes, the formation of binary nodes, and dysregulation of nodal gap length. Therefore, these mice exhibit neurological abnormalities and slower nerve conduction. Disintegration of the nodes occurred in an orderly manner, starting with the disappearance of neurofascin 186, followed by the loss of Na(+) channels and ankyrin G, and then βIV spectrin, a sequence that reflects the assembly of nodes during development. Finally, the absence of gliomedin and NrCAM led to the invasion of the outermost layer of the Schwann cell membrane beyond the nodal area and the formation of paranodal-like junctions at the nodal gap. Our results reveal that axon-glial contact mediated by gliomedin, NrCAM, and NF186 not only plays a role in Na(+) channel clustering during development, but also contributes to the long-term maintenance of Na(+) channels at nodes of Ranvier.

  13. High voltage series connected tandem junction solar battery

    DOEpatents

    Hanak, Joseph J.

    1982-01-01

    A high voltage series connected tandem junction solar battery which comprises a plurality of strips of tandem junction solar cells of hydrogenated amorphous silicon having one optical path and electrically interconnected by a tunnel junction. The layers of hydrogenated amorphous silicon, arranged in a tandem configuration, can have the same bandgap or differing bandgaps. The tandem junction strip solar cells are series connected to produce a solar battery of any desired voltage.

  14. Electric Field Effect in Intrinsic Josephson Junctions

    NASA Astrophysics Data System (ADS)

    Koyama, T.

    The electric field effect in intrinsic Josephson junction stacks (IJJ's) is investigated on the basis of the capacitively-coupled IJJ model. We clarify the current-voltage characteristics of the IJJ's in the presence of an external electric field. It is predicted that the IJJ's show a dynamical transition to the voltage state as the external electric field is increased.

  15. TOPICAL REVIEW: Intrinsic Josephson junctions: recent developments

    NASA Astrophysics Data System (ADS)

    Yurgens, A. A.

    2000-08-01

    Some recent developments in the fabrication of intrinsic Josephson junctions (IJJ) and their application for studying high-temperature superconductors are discussed. The major advantages of IJJ and unsolved problems are outlined. The feasibility of three-terminal devices based on the stacked IJJ is briefly evaluated.

  16. Gallium nitride junction field-effect transistor

    DOEpatents

    Zolper, John C.; Shul, Randy J.

    1999-01-01

    An all-ion implanted gallium-nitride (GaN) junction field-effect transistor (JFET) and method of making the same. Also disclosed are various ion implants, both n- and p-type, together with or without phosphorous co-implantation, in selected III-V semiconductor materials.

  17. Gallium nitride junction field-effect transistor

    DOEpatents

    Zolper, J.C.; Shul, R.J.

    1999-02-02

    An ion implanted gallium-nitride (GaN) junction field-effect transistor (JFET) and method of making the same are disclosed. Also disclosed are various ion implants, both n- and p-type, together with or without phosphorus co-implantation, in selected III-V semiconductor materials. 19 figs.

  18. Supercurrent in van der Waals Josephson junction.

    PubMed

    Yabuki, Naoto; Moriya, Rai; Arai, Miho; Sata, Yohta; Morikawa, Sei; Masubuchi, Satoru; Machida, Tomoki

    2016-01-01

    Supercurrent flow between two superconductors with different order parameters, a phenomenon known as the Josephson effect, can be achieved by inserting a non-superconducting material between two superconductors to decouple their wavefunctions. These Josephson junctions have been employed in fields ranging from digital to quantum electronics, yet their functionality is limited by the interface quality and use of non-superconducting material. Here we show that by exfoliating a layered dichalcogenide (NbSe2) superconductor, the van der Waals (vdW) contact between the cleaved surfaces can instead be used to construct a Josephson junction. This is made possible by recent advances in vdW heterostructure technology, with an atomically flat vdW interface free of oxidation and inter-diffusion achieved by eliminating all heat treatment during junction preparation. Here we demonstrate that this artificially created vdW interface provides sufficient decoupling of the wavefunctions of the two NbSe2 crystals, with the vdW Josephson junction exhibiting a high supercurrent transparency.

  19. Isolation and purification of gap junction channels.

    PubMed

    Stauffer, K A; Kumar, N M; Gilula, N B; Unwin, N

    1991-10-01

    This paper reports methods we have developed to solubilize gap junction channels, or connexons, from isolated gap junctions and to purify them in milligram quantities. Two sources of material are used: rat liver gap junctions and gap junctions produced by infecting insect cells with a baculovirus containing the cDNA for human liver beta 1 protein (connexin 32). Complete solubilization is obtained with long chain detergents (lauryl dimethyl amineoxide, dodecyl maltoside) and requires high ionic strength and high pH as well as reducing conditions. The purification involves chromatography on hydroxylapatite and gel filtration on Superose 6. A homogeneous product is indicated by a single band on a silver-stained gel and a homogeneous population of doughnut-shaped particles under the electron microscope. These particles have hexameric symmetry. The purified connexons have a tendency to form aggregates: filaments and sheets. The filaments grow by end-to-end association of connexons and are nonpolar, suggesting that the connexons are paired as in the cell-to-cell channel. The sheets grow by lateral association of the filaments.

  20. Tandem junction amorphous silicon solar cells

    DOEpatents

    Hanak, Joseph J.

    1981-01-01

    An amorphous silicon solar cell has an active body with two or a series of layers of hydrogenated amorphous silicon arranged in a tandem stacked configuration with one optical path and electrically interconnected by a tunnel junction. The layers of hydrogenated amorphous silicon arranged in tandem configuration can have the same bandgap or differing bandgaps.

  1. Supercurrent in van der Waals Josephson junction

    PubMed Central

    Yabuki, Naoto; Moriya, Rai; Arai, Miho; Sata, Yohta; Morikawa, Sei; Masubuchi, Satoru; Machida, Tomoki

    2016-01-01

    Supercurrent flow between two superconductors with different order parameters, a phenomenon known as the Josephson effect, can be achieved by inserting a non-superconducting material between two superconductors to decouple their wavefunctions. These Josephson junctions have been employed in fields ranging from digital to quantum electronics, yet their functionality is limited by the interface quality and use of non-superconducting material. Here we show that by exfoliating a layered dichalcogenide (NbSe2) superconductor, the van der Waals (vdW) contact between the cleaved surfaces can instead be used to construct a Josephson junction. This is made possible by recent advances in vdW heterostructure technology, with an atomically flat vdW interface free of oxidation and inter-diffusion achieved by eliminating all heat treatment during junction preparation. Here we demonstrate that this artificially created vdW interface provides sufficient decoupling of the wavefunctions of the two NbSe2 crystals, with the vdW Josephson junction exhibiting a high supercurrent transparency. PMID:26830754

  2. Radiation comb generation with extended Josephson junctions

    SciTech Connect

    Solinas, P.; Bosisio, R.; Giazotto, F.

    2015-09-21

    We propose the implementation of a Josephson radiation comb generator based on an extended Josephson junction subject to a time dependent magnetic field. The junction critical current shows known diffraction patterns and determines the position of the critical nodes when it vanishes. When the magnetic flux passes through one of such critical nodes, the superconducting phase must undergo a π-jump to minimize the Josephson energy. Correspondingly, a voltage pulse is generated at the extremes of the junction. Under periodic driving, this allows us to produce a comb-like voltage pulses sequence. In the frequency domain, it is possible to generate up to hundreds of harmonics of the fundamental driving frequency, thus mimicking the frequency comb used in optics and metrology. We discuss several implementations through a rectangular, cylindrical, and annular junction geometries, allowing us to generate different radiation spectra and to produce an output power up to 10 pW at 50 GHz for a driving frequency of 100 MHz.

  3. Superfluid density through 2D superconductor junctions

    NASA Astrophysics Data System (ADS)

    Nam, Hyoungdo; Shih, Chih-Kang

    As S. Qin et al. reported, two monolayer (2 ML) lead film on a silicon (111) substrate has one of two different atomic structures on the silicon substrate: the unstrained 1x1 and the psedumorphically strained √3x √3 (i.e. the same lattice constant as the Si √3x √3 lattice). Most interestingly, although these two different regions show the same quantum well state features, they have different Tc's (5 K and 4 K). These two different regions of 2 ML film naturally form superconductor-superconductor (SS or SS') junctions along silicon step edges. Physical connection of the junction is only 1 ML thickness because of the step height difference of substrate. We will present this study of SS (or SS') junction system using scanning tunneling microscopy/spectroscopy and in-situ double-coil mutual inductance measurement. The transition of superconducting gaps across either SS or SS' junctions should show how to locally affect each other. Double coil measurement show a global Tc close to the lower Tc region with sizable superfluid density. We will discuss the phase rigidity and its relationship to the superfluid density in this ultra-thin Pb film that is only 2 ML thick.

  4. Costochondral junction osteomyelitis in 3 septic foals

    PubMed Central

    Cesarini, Carla; Macieira, Susana; Girard, Christiane; Drolet, Richard; d’Anjou, Marc-André; Jean, Daniel

    2011-01-01

    The costochondral junction constitutes a potential site of infection in septic foals and it could be favored by thoracic trauma. Standard radiographs and ultrasonography are useful tools for diagnosis of this condition and ultrasound-guided needle aspiration could permit the definitive confirmation of infection. PMID:22210943

  5. PECAM-1: regulator of endothelial junctional integrity.

    PubMed

    Privratsky, Jamie R; Newman, Peter J

    2014-03-01

    PECAM-1 (also known as CD31) is a cellular adhesion and signaling receptor comprising six extracellular immunoglobulin (Ig)-like homology domains, a short transmembrane domain and a 118 amino acid cytoplasmic domain that becomes serine and tyrosine phosphorylated upon cellular activation. PECAM-1 expression is restricted to blood and vascular cells. In circulating platelets and leukocytes, PECAM-1 functions largely as an inhibitory receptor that, via regulated sequential phosphorylation of its cytoplasmic domain, limits cellular activation responses. PECAM-1 is also highly expressed at endothelial cell intercellular junctions, where it functions as a mechanosensor, as a regulator of leukocyte trafficking and in the maintenance of endothelial cell junctional integrity. In this review, we will describe (1) the functional domains of PECAM-1 and how they contribute to its barrier-enhancing properties, (2) how the physical properties of PECAM-1 influence its subcellular localization and its ability to influence endothelial cell barrier function, (3) various stimuli that initiate PECAM-1 signaling and/or function at the endothelial junction and (4) cross-talk of PECAM-1 with other junctional molecules, which can influence endothelial cell function. PMID:24435645

  6. Local trap spectroscopy in superconducting tunnel junctions

    SciTech Connect

    Kozorezov, A. G.; Wigmore, J. K.; Peacock, A.; Poelaert, A.; Verhoeve, P.; den Hartog, R.; Brammertz, G.

    2001-06-04

    We show that thermal activation of quasiparticles from local traps is responsible for the temperature variation of responsivity observed for some superconducting tunneling junction photon detectors. With this model, the depth of the local traps in two different proximized Ta structures was found to be the same, 0.20{+-}0.02 meV. {copyright} 2001 American Institute of Physics.

  7. Limiting process in shallow junction solar cells

    NASA Technical Reports Server (NTRS)

    Meulenberg, A.; Rittner, E.

    1979-01-01

    In extending the violet and nonreflective cell technology to lower resistivities, several processes limiting output power were encountered. The most important was the dark diffusion current due to recombination at the front grid contacts. After removal of this problem by reduction of the silicon metal contact area (to 0.14 percent of the total area), the electric field enhanced junction recombination current J sub r was the main limitation. Alteration of the diffusion profile to reduce the junction field is shown to be an effective means of influencing J sub r. The remaining problems are the bulk recombination in the n+ layer and the surface recombination at the oxide-silicon interface; both of these problems are aggravated by band-narrowing resulting from heavy doping in the diffused layer. Experimental evidence for the main limitations is shown, where increased diffusion temperature is seen to reduce both the influence of the front grid contacts and the junction electric field by increasing the junction depth. The potential for further significant improvement in efficiency appears to be high.

  8. Progress on millimeter wave Josephson junction mixers

    NASA Technical Reports Server (NTRS)

    Taur, Y.; Kerr, A. R.

    1978-01-01

    Preset, recyclable Nb point contacts are tested as low-noise Josephson mixers at a signal frequency of 115 GHz. The best result achieved is a mixer noise temperature (single sideband) of 120 K with unity conversion efficiency (SSB) for a junction at 6 K. Variation of mixer properties with temperature and other parameters is presented.

  9. Polyphosphonium-based ion bipolar junction transistors

    PubMed Central

    Gabrielsson, Erik O.; Berggren, Magnus

    2014-01-01

    Advancements in the field of electronics during the past few decades have inspired the use of transistors in a diversity of research fields, including biology and medicine. However, signals in living organisms are not only carried by electrons but also through fluxes of ions and biomolecules. Thus, in order to implement the transistor functionality to control biological signals, devices that can modulate currents of ions and biomolecules, i.e., ionic transistors and diodes, are needed. One successful approach for modulation of ionic currents is to use oppositely charged ion-selective membranes to form so called ion bipolar junction transistors (IBJTs). Unfortunately, overall IBJT device performance has been hindered due to the typical low mobility of ions, large geometries of the ion bipolar junction materials, and the possibility of electric field enhanced (EFE) water dissociation in the junction. Here, we introduce a novel polyphosphonium-based anion-selective material into npn-type IBJTs. The new material does not show EFE water dissociation and therefore allows for a reduction of junction length down to 2 μm, which significantly improves the switching performance of the ion transistor to 2 s. The presented improvement in speed as well the simplified design will be useful for future development of advanced iontronic circuits employing IBJTs, for example, addressable drug-delivery devices. PMID:25553192

  10. Polyphosphonium-based ion bipolar junction transistors.

    PubMed

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

    2014-11-01

    Advancements in the field of electronics during the past few decades have inspired the use of transistors in a diversity of research fields, including biology and medicine. However, signals in living organisms are not only carried by electrons but also through fluxes of ions and biomolecules. Thus, in order to implement the transistor functionality to control biological signals, devices that can modulate currents of ions and biomolecules, i.e., ionic transistors and diodes, are needed. One successful approach for modulation of ionic currents is to use oppositely charged ion-selective membranes to form so called ion bipolar junction transistors (IBJTs). Unfortunately, overall IBJT device performance has been hindered due to the typical low mobility of ions, large geometries of the ion bipolar junction materials, and the possibility of electric field enhanced (EFE) water dissociation in the junction. Here, we introduce a novel polyphosphonium-based anion-selective material into npn-type IBJTs. The new material does not show EFE water dissociation and therefore allows for a reduction of junction length down to 2 μm, which significantly improves the switching performance of the ion transistor to 2 s. The presented improvement in speed as well the simplified design will be useful for future development of advanced iontronic circuits employing IBJTs, for example, addressable drug-delivery devices. PMID:25553192

  11. 27 CFR 9.164 - River Junction.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false River Junction. 9.164 Section 9.164 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY LIQUORS AMERICAN VITICULTURAL AREAS Approved American Viticultural Areas §...

  12. 27 CFR 9.164 - River Junction.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2012-04-01 2012-04-01 false River Junction. 9.164 Section 9.164 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY LIQUORS AMERICAN VITICULTURAL AREAS Approved American Viticultural Areas §...

  13. 27 CFR 9.164 - River Junction.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2013-04-01 2013-04-01 false River Junction. 9.164 Section 9.164 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY ALCOHOL AMERICAN VITICULTURAL AREAS Approved American Viticultural Areas §...

  14. 27 CFR 9.164 - River Junction.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2014-04-01 2014-04-01 false River Junction. 9.164 Section 9.164 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY ALCOHOL AMERICAN VITICULTURAL AREAS Approved American Viticultural Areas §...

  15. 27 CFR 9.164 - River Junction.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 false River Junction. 9.164 Section 9.164 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY LIQUORS AMERICAN VITICULTURAL AREAS Approved American Viticultural Areas §...

  16. Averaged equations for distributed Josephson junction arrays

    NASA Astrophysics Data System (ADS)

    Bennett, Matthew; Wiesenfeld, Kurt

    2004-06-01

    We use an averaging method to study the dynamics of a transmission line studded by Josephson junctions. The averaged system is used as a springboard for studying experimental strategies which rely on spatial non-uniformity to achieve enhanced synchronization. A reduced model for the near resonant case elucidates in physical terms the key to achieving stable synchronized dynamics.

  17. 30 CFR 57.12007 - Junction box connection procedures.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Junction box connection procedures. 57.12007... Electricity Surface and Underground § 57.12007 Junction box connection procedures. Trailing cable and power-cable connections to junction boxes shall not be made or broken under load....

  18. 30 CFR 57.12007 - Junction box connection procedures.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Junction box connection procedures. 57.12007... Electricity Surface and Underground § 57.12007 Junction box connection procedures. Trailing cable and power-cable connections to junction boxes shall not be made or broken under load....

  19. 30 CFR 57.12007 - Junction box connection procedures.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Junction box connection procedures. 57.12007... Electricity Surface and Underground § 57.12007 Junction box connection procedures. Trailing cable and power-cable connections to junction boxes shall not be made or broken under load....

  20. 30 CFR 57.12007 - Junction box connection procedures.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Junction box connection procedures. 57.12007... Electricity Surface and Underground § 57.12007 Junction box connection procedures. Trailing cable and power-cable connections to junction boxes shall not be made or broken under load....

  1. 30 CFR 57.12007 - Junction box connection procedures.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Junction box connection procedures. 57.12007... Electricity Surface and Underground § 57.12007 Junction box connection procedures. Trailing cable and power-cable connections to junction boxes shall not be made or broken under load....

  2. 30 CFR 75.602 - Trailing cable junctions.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Trailing cable junctions. 75.602 Section 75.602... MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Trailing Cables § 75.602 Trailing cable junctions. When two or more trailing cables junction to the same distribution center, means shall be provided...

  3. Overview of the Grand Junction Office from Bluff east of ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Overview of the Grand Junction Office from Bluff east of facility. Note Buildings #35. #33 and #31A in lower left of photograph. VIEW WEST - Department of Energy, Grand Junction Office, 2597 B3/4 Road, Grand Junction, Mesa County, CO

  4. Ultrafast Nonlinear Optics in the Tunneling Junction

    NASA Astrophysics Data System (ADS)

    Yarotski, Dmitry

    2014-03-01

    Coupling of the electromagnetic radiation to the tip-sample junction of a scanning tunneling microscope (STM) offers exciting opportunities in molecular adsorbate identification, high-resolution dopant profiling, studies of the molecular motion and detection of dynamic changes in the electronic structure of the materials. Microwave spectral region is of particular interest because it encompasses rotational, magnetic and other resonances of molecular and solid state systems. However, previous works have either used external microwave sources or generated microwave radiation by a nonlinear mixing of the outputs from two continuous-wave lasers in a tunneling junction. In both cases, the usable spectrum was limited to a single or few frequencies. On the other hand, the regular train of pulses from a mode-locked ultrafast laser has a spectrum which represents an optical frequency comb, with a series of narrow lines (modes) spaced by the pulse repetition frequency. Here, we will show that the nonlinear response of the tunneling junction of an STM to the field of ultrashort laser pulses results in an intermode mixing that produces microwave frequency comb (MFC) with harmonics up to n = 200 (14.85 GHz) on both semiconducting and metallic surfaces. The observed dependence of the microwave power on the harmonic number reveals adverse effects of the tunneling gap capacitance but also shows that the roll-off at higher microwave frequencies should be negligible within the tunneling junction itself leading to intrinsic MFC spread up to THz region. We also demonstrate that MFC generation on semiconductor surface might have the same origin as THz generation in a surface depletion field. Generation of the broadband microwave signals within the tunneling junction should reduce the extraneous effects and provide significantly higher coupling efficiency. With improved frequency response, the described MFC-STM may find broad range of applications in nanoscale characterization of

  5. Inverted Three-Junction Tandem Thermophotovoltaic Modules

    NASA Technical Reports Server (NTRS)

    Wojtczuk, Steven

    2012-01-01

    An InGaAs-based three-junction (3J) tandem thermophotovoltaic (TPV) cell has been investigated to utilize more of the blackbody spectrum (from a 1,100 C general purpose heat source GPHS) efficiently. The tandem consists of three vertically stacked subcells, a 0.74-eV InGaAs cell, a 0.6- eV InGaAs cell, and a 0.55-eV InGaAs cell, as well as two interconnecting tunnel junctions. A greater than 20% TPV system efficiency was achieved by another group with a 1,040 C blackbody using a single-bandgap 0.6- eV InGaAs cell MIM (monolithic interconnected module) (30 lateral junctions) that delivered about 12 V/30 or 0.4 V/junction. It is expected that a three-bandgap tandem MIM will eventually have about 3 this voltage (1.15 V) and about half the current. A 4 A/cm2 would be generated by a single-bandgap 0.6-V InGaAs MIM, as opposed to the 2 A/cm2 available from the same spectrum when split among the three series-connected junctions in the tandem stack. This would then be about a 50% increase (3xVoc, 0.5xIsc) in output power if the proposed tandem replaced the single- bandgap MIM. The advantage of the innovation, if successful, would be a 50% increase in power conversion efficiency from radioisotope heat sources using existing thermophotovoltaics. Up to 50% more power would be generated for radioisotope GPHS deep space missions. This type of InGaAs multijunction stack could be used with terrestrial concentrator solar cells to increase efficiency from 41 to 45% or more.

  6. Hormonal regulation of hepatocyte tight junctional permeability

    SciTech Connect

    Lowe, P.J.; Miyai, K.; Steinbach, J.H.; Hardison, W.G.M. Univ. of California, San Diego )

    1988-10-01

    The authors have investigated the effects of hormones on the permeability of the hepatocyte tight junction to two probes, ({sup 14}C)sucrose and horseradish peroxidase, using one-pass perfused rat livers. Using a single injection of horseradish peroxidase the authors have demonstrated that this probe can enter bile by two pathways that are kinetically distinct, a fast pathway, which corresponds to the passage of the probe through the hepatocyte tight junctions, and a slow pathway, which corresponds to the transcytotic entry into bile. The passage of horseradish peroxidase through the hepatocyte tight junctions was confirmed by electron microscopic histochemistry. Vasopressin, epinephrine, and angiotensin II, hormones that act in the hepatocyte through the intracellular mediators calcium, the inositol polyphosphates, and diacylglycerol, increased the bile-to-perfusion fluid ratio of ({sup 14}C)sucrose and the rapid entry of horseradish peroxidase into bile, indicating that the permeability of the tight junctions to these probes was increased. The effect of these hormones was dose dependent and in the cases of angiotensin II and epinephrine was inhibited by the specific inhibitors (Sar{sup 1},Thr{sup 8})angiotensin II and prazosin, respectively. Dibutyryl adenosine 3{prime},5{prime}-cyclic monophosphate did not affect the ({sup 14}C)sucrose bile-to-perfusion fluid ratio or the fast entry of horseradish peroxidase into bile. These results suggest that the hepatocyte tight junction can no longer be considered a static system of pores separating blood from bile. It is rather a dynamic barrier potentially capable of influencing the composition of the bile.

  7. Thermopower measurements of atomic and molecular junctions using microheater-embedded mechanically-controllable break junctions

    NASA Astrophysics Data System (ADS)

    Tsutsui, Makusu; Morikawa, Takanori; Arima, Akihide; Taniguchi, Masateru

    2015-03-01

    There has been growing interest in developing high-performance thermoelectric materials for realizing thermoelectric power generation. Quantum confinement effects in low-dimensional structures are expected to provide high electronic density of states for enhanced thermopower, and thus considered as a promising approach for achieving a high figure of merit (M. S. Dresselhaus et al., Adv. Mat. 19 (2007) 1043-1053). From this respect, it is interesting to study thermoelectric properties of atomic and molecular junctions and evaluate their potential as a thermoelectric material. Recently, we have developed a heater-embedded micro-fabricated mechanically-controllable break junction (MCBJ) for investigating the thermoelectric transport in single-atom and -molecule junctions. Using the MCBJ devices, we could repeatedly form stable junctions at room temperatures via a self-breaking mechanism with one side being heated by the adjacent microheater. In my presentation, I will show the results of simultaneous measurements of the thermoelectric voltage and the electrical conductance of atom-sized Au junctions and Au-benzenedithiol-Au junctions and discuss on the geometrical dependence of thermoelectric transport.

  8. Myosin-dependent remodeling of adherens junctions protects junctions from Snail-dependent disassembly

    PubMed Central

    Weng, Mo

    2016-01-01

    Although Snail is essential for disassembly of adherens junctions during epithelial–mesenchymal transitions (EMTs), loss of adherens junctions in Drosophila melanogaster gastrula is delayed until mesoderm is internalized, despite the early expression of Snail in that primordium. By combining live imaging and quantitative image analysis, we track the behavior of E-cadherin–rich junction clusters, demonstrating that in the early stages of gastrulation most subapical clusters in mesoderm not only persist, but move apically and enhance in density and total intensity. All three phenomena depend on myosin II and are temporally correlated with the pulses of actomyosin accumulation that drive initial cell shape changes during gastrulation. When contractile myosin is absent, the normal Snail expression in mesoderm, or ectopic Snail expression in ectoderm, is sufficient to drive early disassembly of junctions. In both cases, junctional disassembly can be blocked by simultaneous induction of myosin contractility. Our findings provide in vivo evidence for mechanosensitivity of cell–cell junctions and imply that myosin-mediated tension can prevent Snail-driven EMT. PMID:26754645

  9. Indentation Tests Reveal Geometry-Regulated Stiffening of Nanotube Junctions.

    PubMed

    Ozden, Sehmus; Yang, Yang; Tiwary, Chandra Sekhar; Bhowmick, Sanjit; Asif, Syed; Penev, Evgeni S; Yakobson, Boris I; Ajayan, Pulickel M

    2016-01-13

    Here we report a unique method to locally determine the mechanical response of individual covalent junctions between carbon nanotubes (CNTs), in various configurations such as "X", "Y", and "Λ"-like. The setup is based on in situ indentation using a picoindenter integrated within a scanning electron microscope. This allows for precise mapping between junction geometry and mechanical behavior and uncovers geometry-regulated junction stiffening. Molecular dynamics simulations reveal that the dominant contribution to the nanoindentation response is due to the CNT walls stretching at the junction. Targeted synthesis of desired junction geometries can therefore provide a "structural alphabet" for construction of macroscopic CNT networks with tunable mechanical response. PMID:26618517

  10. Boson Josephson Junction with Trapped Atoms

    NASA Astrophysics Data System (ADS)

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

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

  11. Magnetoamplification in a bipolar magnetic junction transistor.

    PubMed

    Rangaraju, N; Peters, J A; Wessels, B W

    2010-09-10

    We have demonstrated the first bipolar magnetic junction transistor using a dilute magnetic semiconductor. For an InMnAs p-n-p transistor magnetoamplification is observed at room temperature. The observed magnetoamplification is attributed to the magnetoresistance of the magnetic semiconductor InMnAs heterojunction. The magnetic field dependence of the transistor characteristics confirm that the magnetoamplification results from the junction magnetoresistance. To describe the experimentally observed transistor characteristics, we propose a modified Ebers-Moll model that includes a series magnetoresistance attributed to spin-selective conduction. The capability of magnetic field control of the amplification in an all-semiconductor transistor at room temperature potentially enables the creation of new computer logic architecture where the spin of the carriers is utilized.

  12. Laminin 332 in junctional epidermolysis bullosa.

    PubMed

    Kiritsi, Dimitra; Has, Cristina; Bruckner-Tuderman, Leena

    2013-01-01

    Laminin 332 is an essential component of the dermal-epidermal junction, a highly specialized basement membrane zone that attaches the epidermis to the dermis and thereby provides skin integrity and resistance to external mechanical forces. Mutations in the LAMA3, LAMB3 and LAMC2 genes that encode the three constituent polypeptide chains, α3, β3 and γ2, abrogate or perturb the functions of laminin 332. The phenotypic consequences are diminished dermal-epidermal adhesion and, as clinical symptoms, skin fragility and mechanically induced blistering. The disorder is designated as junctional epidermolysis bullosa (JEB). This article delineates the signs and symptoms of the different forms of JEB, the mutational spectrum, genotype-phenotype correlations as well as perspectives for future molecular therapies. PMID:23076207

  13. Dissipation and traversal time in Josephson junctions

    SciTech Connect

    Cacciari, Ilaria; Ranfagni, Anedio; Moretti, Paolo

    2010-05-01

    The various ways of evaluating dissipative effects in macroscopic quantum tunneling are re-examined. The results obtained by using functional integration, while confirming those of previously given treatments, enable a comparison with available experimental results relative to Josephson junctions. A criterion based on the shortening of the semiclassical traversal time tau of the barrier with regard to dissipation can be established, according to which DELTAtau/tau > or approx. N/Q, where Q is the quality factor of the junction and N is a numerical constant of order unity. The best agreement with the experiments is obtained for N=1.11, as it results from a semiempirical analysis based on an increase in the potential barrier caused by dissipative effects.

  14. Fabrication and characterization of graphene PN junctions

    NASA Astrophysics Data System (ADS)

    Wang, Dennis; Zhou, Xiaodong; Dadgar, Ali; Agnihotri, Pratik; Lee, Ji Ung; Reuter, Mark; Ross, Frances; Pasupathy, Abhay

    Theoretical predictions of relativistic Klein tunneling and Veselago lensing in graphene have inspired efforts to fabricate graphene p-n junctions where such phenomena could be realized and studied via electronic transport or scanning tunneling microscopy (STM). Here we will discuss the interplay between device geometry and our measurements in a 4-probe STM, which allows for simultaneous back gating, biasing, and scanning of a micromechanically exfoliated graphene sample. A sharp p-n junction is essential to the manifestation of these aforementioned effects, and we examine the benefits and drawbacks of several routes toward this goal from a fabrication standpoint. These methods include lithographically pre-patterned substrates and the stacking of vertical heterostructures. Finally, we will describe our subsequent characterization results for each, including information about topography and spatial mapping of the density of states. This work is supported by NSF IGERT (DGE-1069240).

  15. Spontaneous Supercurrent Induced by Ferromagnetic π Junctions

    NASA Astrophysics Data System (ADS)

    Bauer, A.; Bentner, J.; Aprili, M.; della Rocca, M. L.; Reinwald, M.; Wegscheider, W.; Strunk, C.

    2004-05-01

    We present magnetization measurements of mesoscopic superconducting niobium loops containing a ferromagnetic (PdNi) π junction. The loops are prepared on top of the active area of a micro-Hall sensor based on high mobility GaAs/AlGaAs heterostructures. We observe asymmetric switching of the loop between different magnetization states when reversing the sweep direction of the magnetic field. This provides evidence for a spontaneous current induced by the intrinsic phase shift of the π junction. In addition, the presence of the spontaneous current near zero applied field is directly revealed by an increase of the magnetic moment with decreasing temperature, which results in half integer flux quantization in the loop at low temperatures.

  16. Junction between surfaces of two topological insulators

    NASA Astrophysics Data System (ADS)

    Sen, Diptiman; Deb, Oindrila

    2012-02-01

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

  17. Junction conditions in extended Teleparallel gravities

    SciTech Connect

    De la Cruz-Dombriz, Álvaro; Dunsby, Peter K.S.; Sáez-Gómez, Diego E-mail: peter.dunsby@uct.ac.za

    2014-12-01

    In the context of extended Teleparallel gravity theories, we address the issue of junction conditions required to guarantee the correct matching of different regions of spacetime. In the absence of shells/branes, these conditions turn out to be more restrictive than their counterparts in General Relativity as in other extended theories of gravity. In fact, the general junction conditions on the matching hypersurfaces depend on the underlying theory and a new condition on the induced tetrads in order to avoid delta-like distributions in the field equations. This result imposes strict consequences on the viability of standard solutions such as the Einstein-Straus-like construction. We find that the continuity of the scalar torsion is required in order to recover the usual General Relativity results.

  18. Vibrational Heat Transport in Molecular Junctions.

    PubMed

    Segal, Dvira; Agarwalla, Bijay Kumar

    2016-05-27

    We review studies of vibrational energy transfer in a molecular junction geometry, consisting of a molecule bridging two heat reservoirs, solids or large chemical compounds. This setup is of interest for applications in molecular electronics, thermoelectrics, and nanophononics, and for addressing basic questions in the theory of classical and quantum transport. Calculations show that system size, disorder, structure, dimensionality, internal anharmonicities, contact interaction, and quantum coherent effects are factors that combine to determine the predominant mechanism (ballistic/diffusive), effectiveness (poor/good), and functionality (linear/nonlinear) of thermal conduction at the nanoscale. We review recent experiments and relevant calculations of quantum heat transfer in molecular junctions. We recount the Landauer approach, appropriate for the study of elastic (harmonic) phononic transport, and outline techniques that incorporate molecular anharmonicities. Theoretical methods are described along with examples illustrating the challenge of reaching control over vibrational heat conduction in molecules. PMID:27215814

  19. Interface composition in magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Schad, R.; Mayen, K.; McCord, J.; Allen, D.; Yang, D.; Tondra, M.; Wang, D.

    2001-06-01

    The magnetoresistance of magnetic tunnel junctions critically depends on the exact composition at the interfaces. As such the completeness of the oxidation process of the Al layer (used to produce Al2O3-based tunnel junctions) plays an essential role in the magnetoresistance. We studied the chemical properties of ferromagnet/Al2O3 interfaces as a function of original Al layer thickness. We have studied the concentrations of elementary and oxidized Al, Co, Ni, and Fe for varying roughness of the ferromagnetic layer. The oxidation process critically depends on the roughness of the underlying ferromagnetic (FM) layer. Al layers grown onto smooth FM layers oxidize homogeneously whereas Al layers grown on rough FM layers show a complicated oxidation behavior. Within the sensitivity of the analysis technique, we did not observe oxidation of the ferromagnetic layers, even for the overoxidized part of the samples.

  20. Spin Valves and Magnetic Tunnel Junctions

    NASA Astrophysics Data System (ADS)

    Iversen, Kurt; Pufall, Matthew; Heindl, Ranko

    2011-10-01

    This is a presentation of research conducted through the National Institute of Standards and Technology's Summer Undergraduate Research Fellowship program. A spintronic device is one that uses the electron's magnetic moment (its spin) as well as its charge to perform operations, such as data storage or logic. Many of today's spintronic devices are based on the ``tunneling magnetoresistance'' effect of CoFeB/MgO/CoFeB tunnel junctions. The MgO barrier in devices must be highly uniform and only 1-2 nm thick. Relevant background, including electron spin and tunneling, is supplied. The fabrication, operation, and behavior of spin-valves and magnetic tunnel junctions are described, and applications in Hard Disk Drives, Magnetic Random Access Memory, Magnetic Field Sensors, and Spin-Torque Oscillators are discussed.

  1. Refoldable Peptide Barrel -- Carbon Nanotube Junctions

    NASA Astrophysics Data System (ADS)

    Titov, Alexey; Wang, Boyang; Kral, Petr

    2008-03-01

    We design hybrid bio-nano-junctions formed by cylindrical peptide structures covalently attached to carbon nanotubes. The cylinders are composed of 5 pairs of antiparallel peptide strands that are ``one-to-one'' matched and covalently bonded through ester and amide bonds to the terminal C atoms in two (20,0) carbon nanotubes. The remaining terminal carbons in the CNTs are replaced by nitrogens, forming embedded quinoline-like structures. The used peptide strands are composed of charged amino acids that form cylindrical patterns with preferred stable configurations. By applying a torque to the nanotubes, we can reversibly fold and control the overall structure of the peptide barrels. The junctions might allow the collection and delivery of drugs and activation of biological molecules attached to them.

  2. Vibrational Heat Transport in Molecular Junctions

    NASA Astrophysics Data System (ADS)

    Segal, Dvira; Agarwalla, Bijay Kumar

    2016-05-01

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

  3. Cusps on cosmic superstrings with junctions

    SciTech Connect

    Davis, Anne-Christine; Rajamanoharan, Senthooran; Nelson, William; Sakellariadou, Mairi E-mail: william.nelson@kcl.ac.uk E-mail: mairi.sakellariadou@kcl.ac.uk

    2008-11-15

    The existence of cusps on non-periodic strings ending on D-branes is demonstrated and the conditions for which such cusps are generic are derived. The dynamics of F-strings, D-strings and FD-string junctions are investigated. It is shown that pairs of FD-string junctions, such as would form after intercommutations of F-strings and D-strings, generically contain cusps. This new feature of cosmic superstrings opens up the possibility of extra channels of energy loss from a string network. The phenomenology of cusps on such cosmic superstring networks is compared to that of cusps formed on networks of their field theory analogues, the standard cosmic strings.

  4. Lycopene oxidation product enhances gap junctional communication.

    PubMed

    Aust, O; Ale-Agha, N; Zhang, L; Wollersen, H; Sies, H; Stahl, W

    2003-10-01

    Carotenoids as well as their metabolites and oxidation products stimulate gap junctional communication (GJC) between cells, which is thought to be one of the protective mechanisms related to cancer-preventive activities of these compounds. Increased intake of lycopene by consumption of tomatoes or tomato products has been epidemiologically associated with a diminished risk of prostate cancer. Here, we report a stimulatory effect of a lycopene oxidation product on GJC in rat liver epithelial WB-F344 cells. The active compound was obtained by complete in vitro oxidation of lycopene with hydrogen peroxide/osmium tetroxide. For structural analysis high performance liquid chromatography, gas chromatography coupled with mass spectrometry, ultraviolet/visible-, and infrared spectrophotometry were applied. The biologically active oxidation product was identified as 2,7,11-trimethyl-tetradecahexaene-1,14-dial. The present data indicate a potential role of lycopene degradation products in cell signaling enhancing cell-to-cell communication via gap junctions. PMID:12909274

  5. Quantum dynamics in the bosonic Josephson junction

    SciTech Connect

    Chuchem, Maya; Cohen, Doron; Smith-Mannschott, Katrina; Hiller, Moritz; Kottos, Tsampikos; Vardi, Amichay

    2010-11-15

    We employ a semiclassical picture to study dynamics in a bosonic Josephson junction with various initial conditions. Phase diffusion of coherent preparations in the Josephson regime is shown to depend on the initial relative phase between the two condensates. For initially incoherent condensates, we find a universal value for the buildup of coherence in the Josephson regime. In addition, we contrast two seemingly similar on-separatrix coherent preparations, finding striking differences in their convergence to classicality as the number of particles increases.

  6. Josephson Junctions Help Measure Resonance And Dispersion

    NASA Technical Reports Server (NTRS)

    Javadi, Hamid H. S.; Mcgrath, William R.; Bumble, Bruce; Leduc, Henry G.

    1994-01-01

    Electrical characteristics of superconducting microstrip transmission lines measured at millimeter and submillimeter wavelengths. Submicron Josephson (super-conductor/insulator/superconductor) junctions used as both voltage-controlled oscillators and detectors to measure frequencies (in range of hundreds of gigahertz) of high-order resonant electromagnetic modes of superconducting microstrip transmission-line resonators. This oscillator/detector approach similar to vacuum-tube grid dip meters and transistor dip meters used to probe resonances at much lower frequencies.

  7. Semiconductor junction formation by directed heat

    DOEpatents

    Campbell, Robert B.

    1988-03-24

    The process of the invention includes applying precursors 6 with N- and P-type dopants therein to a silicon web 2, with the web 2 then being baked in an oven 10 to drive off excessive solvents, and the web 2 is then heated using a pulsed high intensity light in a mechanism 12 at 1100.degree.-1150.degree. C. for about 10 seconds to simultaneously form semiconductor junctions in both faces of the web.

  8. Ferromagnetic resonance with a magnetic Josephson junction

    NASA Astrophysics Data System (ADS)

    Barnes, S. E.; Aprili, M.; Petković, I.; Maekawa, S.

    2011-02-01

    We show experimentally and theoretically that there is a coupling via the Aharonov-Bohm phase between the order parameter of a ferromagnet and a singlet, s-wave, Josephson super-current. We have investigated the possibility of measuring the dispersion of such spin-waves by varying the magnetic field applied in the plane of the junction and demonstrated the electromagnetic nature of the coupling by the observation of magnetic resonance side-bands to microwave induced Shapiro steps.

  9. Solar-Cell-Junction Processing System

    NASA Technical Reports Server (NTRS)

    Bunker, S. N.; Armini, A. J.

    1986-01-01

    System under development reduces equipment costs. Processing system will produce solar-cell junctions on 4 in. (10.2 cm) round silicon wafers at rate of 10 to seventh power per year. System includes non-mass-analyzed ion implanter, microcomputer-controlled, pulsed-electron-beam annealer, and wafertransport system with vacuum interlock. These features eliminate large, expensive magnet and plates, circuitry, and power source otherwise needed for scanning.

  10. Electron irradiation of tandem junction solar cells

    NASA Technical Reports Server (NTRS)

    Anspaugh, B. E.; Miyahira, T. F.; Scott-Monck, J. A.

    1979-01-01

    The electrical behavior of 100 micron thick tandem junction solar cells manufactured by Texas Instruments was studied as a function of 1 MeV electron fluence, photon irradiation, and 60 C annealing. These cells are found to degrade rapidly with radiation, the most serious loss occurring in the blue end of the cell's spectral response. No photon degradation was found to occur, but the cells did anneal a small amount at 60 C.

  11. Primary thermometry with nanoscale tunnel junctions

    SciTech Connect

    Hirvi, K.P.; Kauppinen, J.P.; Paalanen, M.A.; Pekola, J.P.

    1995-10-01

    We have found current-voltage (I-V) and conductance (dI/dV) characteristics of arrays of nanoscale tunnel junctions between normal metal electrodes to exhibit suitable features for primary thermometry. The current through a uniform array depends on the ratio of the thermal energy k{sub B}T and the electrostatic charging energy E{sub c} of the islands between the junctions and is completely blocked by Coulomb repulsion at T=0 and at small voltages eV/2 {<=} Ec. In the opposite limit, k{sub B}T {much_gt} E{sub c}, the width of the conductance minimum scales linearly and universally with T and N, the number of tunnel junctions, and qualifies as a primary thermometer. The zero bias drop in the conductance is proportional to T{sup -1} and can be used as a secondary thermometer. We will show with Monte Carlo simulations how background charge and nonuniformities of the array will affect the thermometer.

  12. Single-molecule junctions beyond electronic transport.

    PubMed

    Aradhya, Sriharsha V; Venkataraman, Latha

    2013-06-01

    The idea of using individual molecules as active electronic components provided the impetus to develop a variety of experimental platforms to probe their electronic transport properties. Among these, single-molecule junctions in a metal-molecule-metal motif have contributed significantly to our fundamental understanding of the principles required to realize molecular-scale electronic components from resistive wires to reversible switches. The success of these techniques and the growing interest of other disciplines in single-molecule-level characterization are prompting new approaches to investigate metal-molecule-metal junctions with multiple probes. Going beyond electronic transport characterization, these new studies are highlighting both the fundamental and applied aspects of mechanical, optical and thermoelectric properties at the atomic and molecular scales. Furthermore, experimental demonstrations of quantum interference and manipulation of electronic and nuclear spins in single-molecule circuits are heralding new device concepts with no classical analogues. In this Review, we present the emerging methods being used to interrogate multiple properties in single molecule-based devices, detail how these measurements have advanced our understanding of the structure-function relationships in molecular junctions, and discuss the potential for future research and applications.

  13. STUDIES ON AN EPITHELIAL (GLAND) CELL JUNCTION

    PubMed Central

    Loewenstein, Werner R.; Kanno, Yoshinobu

    1964-01-01

    Membrane permeability of an epithelial cell junction (Drosophila salivary gland) was examined with intracellular microelectrodes and with fluorescent tracers. In contrast to the non-junctional cell membrane surface, which has a low permeability to ions (10-4 mho/cm2), the junctional membrane surface is highly permeable. In fact, it introduces no substantial restriction to ion flow beyond that in the cytoplasm; the resistance through a chain of cells (150 Ω cm) is only slightly greater than in extruded cytoplasm (100 Ω cm). The diffusion resistance along the intercellular space to the exterior, on the other hand, is very high. Here, there exists an ion barrier of, at least, 104Ω cm2. As a result, small ions and fluorescein move rather freely from one cell to the next, but do not leak appreciably through the intercellular space to the exterior. The organ here, rather than the single cell, appears to be the unit of ion environment. The possible underlying structural aspects are discussed. PMID:14206423

  14. Josephson Effect in SFNS Josephson Junctions

    NASA Astrophysics Data System (ADS)

    Karminskaya, T. Yu.; Kupriyanov, M. Yu.; Golubov, A. A.; Sidorenko, A. S.

    The critical current, I C, of Josephson junctions both in ramp-type (S-FN-S) and in overlap (SNF-FN-FNS, SN-FN-NS, SNF-N-FNS) geometries has been calculated in the frame of linearized Usadel equations (S-superconductor, F-ferromagnetic, N-normal metal). For the ramp-type structures, in which S electrodes contact directly the end walls of FN bilayer, it is shown that I C may exhibit damping oscillations as a function of both the distance L between superconductors and thicknesses d F,N of ferromagnetic and normal layers. The conditions have been determined under which the decay length and period of oscillation of I C(L) at fixed d F are of the order of decay length of superconducting correlations in the N metal, ξN, that is much larger than in F film. In overlap configurations, in which S films are placed on the top of NF bilayer, the studied junctions have complex SNF or SN electrodes (N or NF bilayer are situated under a superconductor). We demonstrate that in these geometries the critical current can exceed that in ramp-type junctions. Based on these results, the choice of the most practically applicable geometry is discussed.

  15. Josephson junction in a thin film

    SciTech Connect

    Kogan, V. G.; Dobrovitski, V. V.; Clem, J. R.; Mawatari, Yasunori; Mints, R. G.

    2001-04-01

    The phase difference {phi}(y) for a vortex at a line Josephson junction in a thin film attenuates at large distances as a power law, unlike the case of a bulk junction where it approaches exponentially the constant values at infinities. The field of a Josephson vortex is a superposition of fields of standard Pearl vortices distributed along the junction with the line density {phi}'(y)/2{pi}. We study the integral equation for {phi}(y) and show that the phase is sensitive to the ratio l/{Lambda}, where l={lambda}{sub J}{sup 2}/{lambda}{sub L}, {Lambda}=2{lambda}{sub L}{sup 2}/d, {lambda}{sub L}, and {lambda}{sub J} are the London and Josephson penetration depths, and d is the film thickness. For l<<{Lambda}, the vortex ''core'' of the size l is nearly temperature independent, while the phase ''tail'' scales as l{Lambda}/y{sup 2}={lambda}{sub J}2{lambda}{sub L}/d/y{sup 2}; i.e., it diverges as T{yields}T{sub c}. For l>>{Lambda}, both the core and the tail have nearly the same characteristic length l{Lambda}.

  16. The junctions that don't fit the scheme: special symmetrical cell-cell junctions of their own kind.

    PubMed

    Franke, Werner W; Rickelt, Steffen; Barth, Mareike; Pieperhoff, Sebastian

    2009-10-01

    Immunocytochemical, electron-, and immunoelectron-microscopical studies have revealed that, in addition to the four major "textbook categories" of cell-cell junctions (gap junctions, tight junctions, adherens junctions, and desmosomes), a broad range of other junctions exists, such as the tiny puncta adhaerentia minima, the taproot junctions (manubria adhaerentia), the plakophilin-2-containing adherens junctions of mesenchymal or mesenchymally derived cell types including malignantly transformed cells, the composite junctions (areae compositae) of the mature mammalian myocardium, the cortex adhaerens of the eye lens, the interdesmosomal "sandwich" or "stud" junctions in the subapical layers of stratified epithelia and the tumors derived therefrom, and the complexus adhaerentes of the endothelial and virgultar cells of the lymph node sinus. On the basis of their sizes and shapes, other morphological criteria, and their specific molecular ensembles, these junctions and the genes that encode them cannot be subsumed under one of the major categories mentioned above but represent special structures in their own right, appear to serve special functions, and can give rise to specific pathological disorders. PMID:19680692

  17. Aberrant expression and function of gap junctions during carcinogenesis.

    PubMed Central

    Yamasaki, H

    1991-01-01

    Gap junctional intercellular communication plays a key role in the maintenance of homeostasis in multicellular organisms. Reflecting deranged homeostasis in cancer cells, most transformed or cancerous cells show aberrant gap junctional intercellular communication; they have decreased junctional communication between each other and/or with surrounding normal cells. Studies with in vitro cell transformation and animal carcinogenesis models suggest an involvement of blocked intercellular communication in later stages of carcinogenesis. Analysis of expression of gap junction proteins (connexins) and corresponding mRNA indicates that a number of regulation sites are involved in aberrant function of gap junctions during carcinogenesis. Suppression of transformed phenotypes is often seen when transformed cells are physically in contact with their normal counterparts. Some studies suggest that gap junctional intercellular communication is involved in such tumor suppression. PMID:1663449

  18. Coherent diffraction of thermal currents in long Josephson tunnel junctions

    NASA Astrophysics Data System (ADS)

    Guarcello, Claudio; Giazotto, Francesco; Solinas, Paolo

    2016-08-01

    We discuss heat transport in thermally-biased long Josephson tunnel junctions in the presence of an in-plane magnetic field. In full analogy with the Josephson critical current, the phase-dependent component of the heat current through the junction displays coherent diffraction. Thermal transport is analyzed as a function of both the length and the damping of the junction, highlighting deviations from the standard "Fraunhofer" pattern characteristic of short junctions. The heat current diffraction patterns show features strongly related to the formation and penetration of Josephson vortices, i.e., solitons. We show that a dynamical treatment of the system is crucial for the realistic description of the Josephson junction, and it leads to peculiar results. In fact, hysteretic behaviors in the diffraction patterns when the field is swept up and down are observed, corresponding to the trapping of vortices in the junction.

  19. Electron optics with p-n junctions in ballistic graphene

    NASA Astrophysics Data System (ADS)

    Chen, Shaowen; Han, Zheng; Elahi, Mirza M.; Habib, K. M. Masum; Wang, Lei; Wen, Bo; Gao, Yuanda; Taniguchi, Takashi; Watanabe, Kenji; Hone, James; Ghosh, Avik W.; Dean, Cory R.

    2016-09-01

    Electrons transmitted across a ballistic semiconductor junction are expected to undergo refraction, analogous to light rays across an optical boundary. In graphene, the linear dispersion and zero-gap band structure admit highly transparent p-n junctions by simple electrostatic gating. Here, we employ transverse magnetic focusing to probe the propagation of carriers across an electrostatically defined graphene junction. We find agreement with the predicted Snell’s law for electrons, including the observation of both positive and negative refraction. Resonant transmission across the p-n junction provides a direct measurement of the angle-dependent transmission coefficient. Comparing experimental data with simulations reveals the crucial role played by the effective junction width, providing guidance for future device design. Our results pave the way for realizing electron optics based on graphene p-n junctions.

  20. Junction box wiring and connector durability issues in photovoltaic modules

    NASA Astrophysics Data System (ADS)

    Kalejs, Juris

    2014-10-01

    We report here on Photovoltaic (PV) module durability issues associated with junction boxes which are under study in Task 10 of the International PV Quality Assurance Task Force (PVQAT). A number of failure modes are being identified in junction boxes in PV arrays in the field which have less than 5 years outdoor operation. Observed failure modes include melted contacts and plastic walls in the junction boxes, separated external connectors and broken latches. Standard IEC and UL tests for modules are designed to expose early mortality failures due to materials selection and design in the assembled module and their impact on performance and safety. Test standards for individual junction box components, when not part of a PV module, are still in development. We will give an overview of the reported field failures associated with junction boxes, and examine standard development as it may impact on testing for durability of junction box connectors over a 25 year life.

  1. Sub-micrometer epitaxial Josephson junctions for quantum circuits

    NASA Astrophysics Data System (ADS)

    Kline, Jeffrey S.; Vissers, Michael R.; da Silva, Fabio C. S.; Wisbey, David S.; Weides, Martin; Weir, Terence J.; Turek, Benjamin; Braje, Danielle A.; Oliver, William D.; Shalibo, Yoni; Katz, Nadav; Johnson, Blake R.; Ohki, Thomas A.; Pappas, David P.

    2012-02-01

    We present a fabrication scheme and testing results for epitaxial sub-micrometer Josephson junctions. The junctions are made using a high-temperature (1170 K) ‘via process’ yielding junctions as small as 0.8 µm in diameter by use of optical lithography. Sapphire (Al2O3) tunnel-barriers are grown on an epitaxial Re/Ti multilayer base-electrode. We have fabricated devices with both Re and Al top-electrodes. While room temperature (295 K) resistance versus area data are favorable for both types of top-electrodes, the low-temperature (50 mK) data show that junctions with the Al top-electrode have a much higher subgap resistance. The microwave loss properties of the junctions have been measured by use of superconducting Josephson junction qubits. The results show that high subgap resistance correlates with improved qubit performance.

  2. Single P-N junction tandem photovoltaic device

    DOEpatents

    Walukiewicz, Wladyslaw; Ager, III, Joel W.; Yu, Kin Man

    2012-03-06

    A single P-N junction solar cell is provided having two depletion regions for charge separation while allowing the electrons and holes to recombine such that the voltages associated with both depletion regions of the solar cell will add together. The single p-n junction solar cell includes an alloy of either InGaN or InAlN formed on one side of the P-N junction with Si formed on the other side in order to produce characteristics of a two junction (2J) tandem solar cell through only a single P-N junction. A single P-N junction solar cell having tandem solar cell characteristics will achieve power conversion efficiencies exceeding 30%.

  3. Single P-N junction tandem photovoltaic device

    DOEpatents

    Walukiewicz, Wladyslaw; Ager, III, Joel W.; Yu, Kin Man

    2011-10-18

    A single P-N junction solar cell is provided having two depletion regions for charge separation while allowing the electrons and holes to recombine such that the voltages associated with both depletion regions of the solar cell will add together. The single p-n junction solar cell includes an alloy of either InGaN or InAlN formed on one side of the P-N junction with Si formed on the other side in order to produce characteristics of a two junction (2J) tandem solar cell through only a single P-N junction. A single P-N junction solar cell having tandem solar cell characteristics will achieve power conversion efficiencies exceeding 30%.

  4. Macroscopic quantum effects in intrinsic Josephson junction stacks

    NASA Astrophysics Data System (ADS)

    Koyama, T.; Machida, M.

    2008-09-01

    A macroscopic quantum theory for the capacitively-coupled intrinsic Josephson junctions (IJJ’s) is constructed. We clarify the multi-junction effect for the macroscopic quantum tunneling (MQT) to the first resistive branch. It is shown that the escape rate is greatly enhanced by the capacitive coupling between junctions. We also discuss the origin of the N2-enhancement in the escape rate observed in the uniformly switching in Bi-2212 IJJ’s.

  5. Geometrical theory of triple junctions of CSL boundaries.

    PubMed

    Gertsman, V Y

    2001-07-01

    When three grain boundaries having misorientations generating coincidence site lattices (CSLs) meet at a triple junction, a common (triple-junction) CSL is formed. A theory is developed as a set of theorems establishing the relationships between the geometrical parameters of the grain-boundary and triple-junction CSLs. Application of the theory is demonstrated in detail for the case of the cubic crystal system. It is also shown how the theory can be extended to an arbitrary crystal lattice.

  6. Definitive Evidence for the existence of tight junctions in invertebrates

    PubMed Central

    Lane, NJ; Chandler, HJ

    1980-01-01

    Extensive and unequivocal tight junctions are here reported between the lateral borders of the cellular layer that circumscribes the arachnid (spider) central nervous system. This account details the features of these structures, which form a beltlike reticulum that is more complex than the simple linear tight junctions hitherto found in invertebrate tissues and which bear many of the characteristics of vertebrate zonulae occludentes. We also provide evidence that these junctions form the basis of a permeability barrier to exogenous compounds. In thin sections, the tight junctions are identifiable as punctate points of membrane apposition; they are seen to exclude the stain and appear as election- lucent moniliform strands along the lines of membrane fusion in en face views of uranyl-calcium-treated tissues. In freeze-fracture replicas, the regions of close membrane apposition exhibit P-face (PF) ridges and complementary E-face (EF) furrows that are coincident across face transitions, although slightly offset with respect to one another. The free inward diffusion of both ionic and colloidal lanthanum is inhibited by these punctate tight junctions so that they appear to form the basis of a circumferential blood-brain barrier. These results support the contention that tight junctions exist in the tissues of the invertebrata in spite of earlier suggestions that (a) they are unique to vertebrates and (b) septate junctions are the equivalent invertebrate occluding structure. The component tight junctional 8- to 10-nm-particulate PF ridges are intimately intercalated with, but clearly distinct from, inverted gap junctions possessing the 13-nm EF particles typical of arthropods. Hence, no confusion can occur as to which particles belong to each of the two junctional types, as commonly happens with vertebrate tissues, especially in the analysis of developing junctions. Indeed, their coexistance in this way supports the idea, over which there has been some controversy, that

  7. Design of mode-sorting asymmetric Y-junctions.

    PubMed

    Riesen, Nicolas; Love, John D

    2012-05-20

    The theory of mode-sorting in bimodal asymmetric Y-junctions is extended to multimode asymmetric Y-junctions with multiple output arms. This theory allows for the optimization of these mode-sorting planar structures. Asymmetric Y-junctions provide unique opportunities for spatial mode division multiplexing (MDM) of optical fiber. Spatial MDM is considered paramount to overcoming the bandwidth limitations of single-mode fiber. The design criteria presented in this paper facilitate their design.

  8. Classical phase diffusion in small hysteretic Josephson junctions

    SciTech Connect

    Martinis, J.M.; Kautz, R.L. )

    1989-10-02

    The existence of classical phase diffusion in hysteretic junctions is demonstrated by quantitative agreement between experimental and simulated {ital I}-{ital V} curves. The simulations are based on a circuit that accurately models both the junction and its external shunting impedance at microwave frequencies. We show that the bias current at which the junction switches from the phase diffusion state to the voltage state is sensitive to dissipation at microwave frequencies.

  9. Noise characteristics and instabilities of long Josephson junctions

    SciTech Connect

    Han, B.S.; Lee, B.; Symko, O.G.; Yeh, W.J.; Zheng, D.J.

    1989-03-01

    In a magnetic field, current biased long Josephson junctions exhibit the dynamics of fluxon motion which are affected by fluctuations. These consist of telegraph noise at voltage steps and instabilities due to chaotic behavior. Results on long junctions with McCumber number ..beta../sub c/ ranging from 10 to 100 show such behavior. The telegraph noise is driven by thermal fluctuations. Modeling of our junctions using a perturbed sine-Gordon equation shows the chaotic regions and the periodic ones.

  10. Gap Junctions between Photoreceptor Cells in the Vertebrate Retina

    PubMed Central

    Raviola, Elio; Gilula, Norton B.

    1973-01-01

    In the outer plexiform layer of the retina the synaptic endings of cone cells make specialized junctions with each other and with the endings of rod cells. The ultrastructure of these interreceptor junctions is described in retinas of monkeys, rabbits, and turtles, in thin sections of embedded specimens and by the freeze-fracturing technique. Cone-to-rod junctions are ribbon-like areas of close membrane approximation. On either side of the narrowing of the intercellular space, the junctional membranes contain a row of particles located on the fracture face A (cytoplasmic leaflet), while the complementary element, a row of single depressions, is located on fracture face B. The particle rows are surrounded by a membrane region that is devoid of particulate inclusions and bears an adherent layer of dense cytoplasmic material. Cone-to-cone junctions in some places are identical to cone-to-rod junctions, while in other places they closely resemble typical gap junctions (nexus). Interreceptor junctions, therefore, represent a morphological variant of the gap junction, and probably mediate electrotonic coupling between neighboring photoreceptor cells. Images PMID:4198274

  11. The 'depletion layer' of amorphous p-n junctions

    NASA Technical Reports Server (NTRS)

    Von Roos, O.

    1981-01-01

    It is shown that within reasonable approximations for the density of state distribution within the mobility gap of a:Si, a one-to-one correspondence exists between the electric field distribution in the transition region of an amorphous p-n junction and that in the depletion layer of a crystalline p-n junction. Thus it is inferred that the depletion layer approximation which leads to a parabolic potential distribution within the depletion layer of crystalline junctions also constitutes a fair approximation in the case of amorphous junctions. This fact greatly simplifies an analysis of solid-state electronic devices based on amorphous material (i.e., solar cells).

  12. Direct experimental determination of voltage across high-low junctions

    NASA Technical Reports Server (NTRS)

    Daud, T.; Lindholm, F. A.

    1986-01-01

    High-low (HL) junctions form a part of many semiconductor devices, including back surface field solar cells. A first experimental determination and interpretation of the voltage across the HL junction under low- and high-injection conditions is presented as a function of the voltage across a nearby p/n junction. Theoretical analysis from first principles is shown to bear well on the experimental results. In addition, a test structure is proposed for measurement of the effective surface recombination velocity at the HL junctions.

  13. Josephson junction through a disordered topological insulator with helical magnetization

    NASA Astrophysics Data System (ADS)

    Zyuzin, Alexander; Alidoust, Mohammad; Loss, Daniel

    2016-06-01

    We study supercurrent and proximity vortices in a Josephson junction made of disordered surface states of a three-dimensional topological insulator with a proximity induced in-plane helical magnetization. In a regime where the rotation period of helical magnetization is larger than the junction width, we find supercurrent 0 -π crossovers as a function of junction thickness, magnetization strength, and parameters inherent to the helical modulation and surface states. The supercurrent reversals are associated with proximity induced vortices, nucleated along the junction width, where the number of vortices and their locations can be manipulated by means of the superconducting phase difference and the parameters mentioned above.

  14. Craniovertebral Junction Instability: A Review of Facts about Facets

    PubMed Central

    2015-01-01

    Craniovertebral junction surgery involves an appropriate philosophical, biomechanical and anatomical understanding apart from high degree of technical skill and ability of controlling venous and arterial bleeding. The author presents his 30-year experience with treating complex craniovertebral junction instability related surgical issues. The facets of atlas and axis form the primary site of movements at the craniovertebral junction. All craniovertebral junction instability is essentially localized to the atlantoaxial facet joint. Direct manipulation and fixation of the facets forms the basis of treatment for instability. PMID:26240728

  15. Interfacial mixing during annealing of zinc oxide nanoparticle junctions

    NASA Astrophysics Data System (ADS)

    Hu, Ming; Giapis, Konstantinos P.; Poulikakos, Dimos

    2011-05-01

    The process of forming a junction between crystalline zinc oxide (ZnO) nanoparticles during pulsed thermal annealing in liquid tetradecane is studied using molecular dynamics simulation. Pairs of equal and unequal size particles are considered with emphasis on neck growth and atom mixing. The contact area and interface width of the junction are found to increase with heat pulse power albeit at different rates. The results suggest that it is possible to increase the junction area without significant mixing of atoms across the junction interface by tailoring the heat pulse power.

  16. Flow mechanotransduction regulates traction forces, intercellular forces, and adherens junctions

    PubMed Central

    Ting, Lucas H.; Jahn, Jessica R.; Jung, Joon I.; Shuman, Benjamin R.; Feghhi, Shirin; Han, Sangyoon J.; Rodriguez, Marita L.

    2012-01-01

    Endothelial cells respond to fluid shear stress through mechanotransduction responses that affect their cytoskeleton and cell-cell contacts. Here, endothelial cells were grown as monolayers on arrays of microposts and exposed to laminar or disturbed flow to examine the relationship among traction forces, intercellular forces, and cell-cell junctions. Cells under laminar flow had traction forces that were higher than those under static conditions, whereas cells under disturbed flow had lower traction forces. The response in adhesion junction assembly matched closely with changes in traction forces since adherens junctions were larger in size for laminar flow and smaller for disturbed flow. Treating the cells with calyculin-A to increase myosin phosphorylation and traction forces caused an increase in adherens junction size, whereas Y-27362 cause a decrease in their size. Since tugging forces across cell-cell junctions can promote junctional assembly, we developed a novel approach to measure intercellular forces and found that these forces were higher for laminar flow than for static or disturbed flow. The size of adherens junctions and tight junctions matched closely with intercellular forces for these flow conditions. These results indicate that laminar flow can increase cytoskeletal tension while disturbed flow decreases cytoskeletal tension. Consequently, we found that changes in cytoskeletal tension in response to shear flow conditions can affect intercellular tension, which in turn regulates the assembly of cell-cell junctions. PMID:22447948

  17. Specialized membrane junctions between neurons in the vertebrate cerebellar cortex.

    PubMed

    Sotelo, C; Llinás, R

    1972-05-01

    "Gap" junctions, the morphological correlate for low-resistance junctions, are demonstrated between some mossy fiber terminals and granule cell dendrites in some lower vertebrate cerebella (gymnotid and frog). Most of the gap junctions (GJs) seen in the gymnotid-fish cerebellum exhibit an asymmetrical configuration, the electron-opaque cytoplasmic material underlying the junction being more extensive in the dendritic than in the axonal side. In the frog cerebellum, the GJs have a symmetrical distribution of such electron-opaque material. In both species the GJs are encountered at the same synaptic interface as the conventional synaptic zone (CSZ), constituting "mixed synapses" in a morphological sense. The axonal surface covered by CSZs is larger than that covered by GJs. In mammalian cerebellum, GJs are observed only in the molecular layer, between perikarya, dendrites, or perikarya and dendrites of the inhibitory interneurons. These GJs are intermixed with attachment plates and intermediary junctions interpreted as simply adhesive. In the mammalian cerebellum, a new type of junction which resembles the septate junctions (SJs) of invertebrate epithelia is observed between axonal branches forming the tip of the brush of basket fibers around the initial segment of the Purkinje cell axon. It is suggested that such junctions may be modified forms of septate junctions. The physiological implications of the possible existence of high-resistance cross-bridges between basket cell terminals, which may compartmentalize the extracellular space and thus regulate extracellular current flow, must be considered.

  18. Tight junctions and the regulation of gene expression.

    PubMed

    Balda, Maria S; Matter, Karl

    2009-04-01

    Cell adhesion is a key regulator of cell differentiation. Cell interactions with neighboring cells and the extracellular matrix regulate gene expression, cell proliferation, polarity and apoptosis. Apical cell-cell junctions participate in these processes using different types of proteins, some of them exhibit nuclear and junctional localization and are called NACos for Nuclear Adhesion Complexes. Tight junctions are one type of such cell-cell junctions and several signaling complexes have been identified to associate with them. In general, expression of tight junction components suppresses proliferation to allow differentiation in a coordinated manner with adherens junctions and extracellular matrix adhesion. These tight junction components have been shown to affect several signaling and transcriptional pathways, and changes in the expression of tight junction proteins are associated with several disease conditions, such as cancer. Here, we will review how tight junction proteins participate in the regulation of gene expression and cell proliferation, as well as how they are regulated themselves by different mechanisms involved in gene expression and cell differentiation.

  19. Magic-T Junction using Microstrip/Slotline Transitions

    NASA Technical Reports Server (NTRS)

    U-yen, Kongpop; Wollack, Edward J.; Doiron, Terence

    2008-01-01

    An improved broadband planar magic-T junction that incorporates microstrip/slotline transitions has been developed. In comparison with a prior broadband magic-T junction incorporating microstrip/slotline transitions, this junction offers superior broadband performance. In addition, because this junction is geometrically simpler and its performance is less affected by fabrication tolerances, the benefits of the improved design can be realized at lower fabrication cost. There are potential uses for junctions like this one in commercial microwave communication receivers, radar and polarimeter systems, and industrial microwave instrumentation. A magic-T junction is a four-port waveguide junction consisting of a combination of an H-type and an E-type junction. An E-type junction is so named because it includes a junction arm that extends from a main waveguide in the same direction as that of the electric (E) field in the waveguide. An H-type junction is so named because it includes a junction arm parallel to the magnetic (H) field in a main waveguide. A magic-T junction includes two input ports (here labeled 1 and 2, respectively) and two output ports (here labeled E and H, respectively). In an ideal case, (1) a magic-T junction is lossless, (2) the input signals add (that is, they combine in phase with each other) at port H, and (3) the input signals subtract (that is, they combine in opposite phase) at port E. The prior junction over which the present junction is an improvement affords in-phase-combining characterized by a broadband frequency response, and features a small slotline area to minimize in-band loss. However, with respect to isolation between ports 1 and 2 and return loss at port E, it exhibits narrowband frequency responses. In addition, its performance is sensitive to misalignment of microstrip and slotline components: this sensitivity is attributable to a limited number of quarter-wavelength (lambda/4) transmission-line sections for matching impedances

  20. Fabrication of magnetic tunnel junctions with epitaxial and textured ferromagnetic layers

    DOEpatents

    Chang, Y. Austin; Yang, Jianhua Joshua

    2008-11-11

    This invention relates to magnetic tunnel junctions and methods for making the magnetic tunnel junctions. The magnetic tunnel junctions include a tunnel barrier oxide layer sandwiched between two ferromagnetic layers both of which are epitaxial or textured with respect to the underlying substrate upon which the magnetic tunnel junctions are grown. The magnetic tunnel junctions provide improved magnetic properties, sharper interfaces and few defects.

  1. Differences between liver gap junction protein and lens MIP 26 from rat: implications for tissue specificity of gap junctions.

    PubMed

    Nicholson, B J; Takemoto, L J; Hunkapiller, M W; Hood, L E; Revel, J P

    1983-03-01

    Liver gap junctions and gap-junction-like structures from eye lenses are each comprised of a single major protein (Mr 28,000 and 26,000, respectively). These proteins display different two-dimensional peptide fingerprints, distinct amino acid compositions, nonhomologous N-terminal amino acid sequences and different sensitivities to proteases when part of the intact junction. However, the junctional protein of each tissue is well conserved between species, as demonstrated previously for lens and now for liver in several mammalian species. The possiblity of tissue-specific gap junction proteins is discussed in the light of data suggesting that rat heart gap junctions are comprised of yet a third protein. PMID:6299583

  2. Pseudospin dynamics in multimode polaritonic Josephson junctions

    NASA Astrophysics Data System (ADS)

    Pavlovic, G.; Malpuech, G.; Shelykh, I. A.

    2013-03-01

    Using Keldysh-Green function formalism we theoretically analyzed the dynamics of multimode exciton-polariton Josephson junctions. We took into account the spinor nature of polaritons and considered in detail the role of coupling of the fundamental modes with excited states. We demonstrate that the coupling to the reservoir results in a change of the oscillation pattern. In particular, it can lead to renormalization of the oscillation frequency, appearance of higher order harmonics, and induce transition between the regimes of free Josephson oscillations and macroscopic quantum self-trapping.

  3. Nonintrusive Measurement Of Temperature Of LED Junction

    NASA Technical Reports Server (NTRS)

    Leidecker, Henning; Powers, Charles

    1991-01-01

    Temperature inferred from spectrum of emitted light. Method of determining temperature of junction based on two relevant characteristics of LED. Gap between valence and conduction electron-energy bands in LED material decreases with increasing temperature, causing wavelength of emitted photon to increase with temperature. Other, as temperature increases, non-radiative processes dissipate more of input electrical energy as heat and less as photons in band-gap wavelenth region; optical and quantum efficiencies decrease with increasing temperature. In principal, either characteristic alone used to determine temperature. However, desirable to use both to obtain indication of uncertainty.

  4. Elasticity of a soap film junction

    NASA Astrophysics Data System (ADS)

    Elias, F.; Janiaud, E.; Bacri, J.-C.; Andreotti, B.

    2014-03-01

    We investigate the elasticity of an isolated, threefold junction of soap films (Plateau border), which displays static undulations when liquid rapidly flows into it. By analyzing the shape of the Plateau border (thickness R and transverse displacement) as a function of the liquid flow rate Q, we show experimentally and theoretically that the elasticity of the Plateau border is dominated by the bending of the soap films pulling on the Plateau border. In this asymptotic regime, the undulation wavelength obeys the scaling law ˜Q2 R-2 and the decay length ˜Q2 R-4.

  5. Plasmon Enhanced Hetero-Junction Solar Cell

    NASA Astrophysics Data System (ADS)

    Long, Gen; Ching, Levine; Sadoqi, Mostafa; Xu, Huizhong

    2015-03-01

    Here we report a systematic study of plasmon-enhanced hetero-junction solar cells made of colloidal quantum dots (PbS) and nanowires (ZnO), with/without metal nanoparticles (Au). The structure of solar cell devices was characterized by AFM, SEM and profilometer, etc. The power conversion efficiencies of solar cell devices were characterized by solar simulator (OAI TriSOL, AM1.5G Class AAA). The enhancement in the photocurrent due to introduction of metal nanoparticles was obvious. We believe this is due to the plasmonic effect from the metal nanoparticles. The correlation between surface roughness, film uniformity and device performance was also studied.

  6. On-chip Josephson junction microwave switch

    NASA Astrophysics Data System (ADS)

    Naaman, O.; Abutaleb, M. O.; Kirby, C.; Rennie, M.

    2016-03-01

    The authors report on the design and measurement of a reflective single-pole single-throw microwave switch with no internal power dissipation, based on a superconducting circuit containing a single Josephson junction. The data demonstrate the switch operation with 2 GHz instantaneous bandwidth centered at 10 GHz, low insertion loss, and better than 20 dB on/off ratio. The switch's measured performance agrees well with simulations for input powers up to -100 dBm. An extension of the demonstrated circuit to implement a single-pole double-throw switch is shown in simulation.

  7. On Chip Josephson Junction Microwave Switch

    NASA Astrophysics Data System (ADS)

    Naaman, Ofer; Abutaleb, Mohamed; Kirby, Chris; Rennie, Michael

    We report on the design and measurement of a reflective single-pole single-throw microwave switch based on a superconducting circuit containing a single Josephson junction. The device has no internal power dissipation, minimal insertion loss, and is controlled by Φ0-level base-band signals. The data demonstrates the device operation with 2 GHz instantaneous bandwidth centered at 10 GHz and better than 20 dB on/off ratio for input powers up to -100 dBm.

  8. Phonon interference effects in molecular junctions

    SciTech Connect

    Markussen, Troels

    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.

  9. Idiopathic Hypertrophic Pachymeningitis in the Craniocervical Junction

    PubMed Central

    Bang, Jin Hyuk; Kim, Eo Jin

    2015-01-01

    Idiopathic hypertrophic pachymeningitis (IHP) is a rare disease, and it is characterized by chronic progressive inflammatory fibrosis and thickening of the dura mater with resultant compression of the spinal cord or neural structure without any identifiable cause. It can occur in the intracranial or spinal dura mater alone or as a craniospinal form. The spinal form is rarer than the cranial form and the craniospinal form is extremely rare. We report a rare case of IHP in the craniocervical junction involving both the cranial and spinal dura mater and discuss the diagnosis and management of the disease. PMID:26512276

  10. Junctional angle of a bihanded helix.

    PubMed

    Yang, Jing; Wolgemuth, Charles W; Huber, Greg

    2014-10-01

    Helical filaments having sections of reversed chirality are common phenomena in the biological realm. The apparent angle between the two sections of opposite handedness provides information about the geometry and elasticity of the junctional region. In this paper, the governing differential equations for the local helical axis are developed, and asymptotic solutions of the governing equations are solved by perturbation theory. The asymptotic solutions are compared with the corresponding numerical solutions, and the relative error at second order is found to be less than 1.5% over a range of biologically relevant curvature and torsion values from 0 to 1/2 in dimensionless units.

  11. Collisions of strings with Y junctions.

    PubMed

    Copeland, E J; Kibble, T W B; Steer, D A

    2006-07-14

    We study the dynamics of Nambu-Goto strings with junctions at which three strings meet. In particular, we exhibit one simple exact solution and examine the process of intercommuting of two straight strings in which they exchange partners but become joined by a third string. We show that there are important kinematical constraints on this process. The exchange cannot occur if the strings meet with very large relative velocity. This may have important implications for the evolution of cosmic superstring networks and non-Abelian string networks. PMID:16907431

  12. Analysis of atrioventricular junction, ventricular mass, and ventriculoarterial junction in 43 specimens with atrial isomerism.

    PubMed

    De Tommasi, S; Daliento, L; Ho, S Y; Macartney, F J; Anderson, R H

    1981-03-01

    We have analysed the atrioventricular junction, ventricular mass, and ventriculoarterial junction in 43 hearts with isomeric atrial chambers. Of the hearts, 32 had atrial chambers of bilateral right morphology while 11 had atrial chambers with bilateral left atrial characteristics. Among the hearts with right atrial isomerism, there were 13 biventricular hearts, all with ambiguous atrioventricular connection. Eight had a common valve and five had two atrioventricular valves. In the other 19 hearts, the atrial chambers were connected to only one ventricular chamber, 18 having double inlet ventricle through a common valve and the other having absence of the left atrioventricular connection. In these univentricular hearts, all possible types of ventricular morphology were found. The ventriculoarterial junction among these hearts with right isomerism showed great variation. In the hearts with left atrial isomerism, nine hearts had two ventricles and two were univentricular. The biventricular hearts all had ambiguous atrioventricular connection, six via a common valve and three via two valves. The two univentricular hearts both had double inlet via a common valve, one to a chamber of right ventricular type and the other to a chamber of left ventricular type. Both had rudimentary chambers of complementary pattern. The ventriculoarterial junction again showed much variation. Statistical analysis showed that pulmonary obstruction and a univentricular heart were both significantly more frequent in association with right compared with left isomerism. Significant differences were also noted in the two groups in terms of ventriculoarterial connections and infundibular morphology.

  13. Grades 1-8, Apache Junction Unified School District 43, Apache Junction, Arizona. PLATO Evaluation Series.

    ERIC Educational Resources Information Center

    Quinn, David W.; Quinn, Nancy W.

    Apache Junction Unified School District, Arizona, has embarked on a 5-year program of instructional improvement using technology. PLATO Elementary reading and mathematics products were installed in the district's elementary and middle schools at the beginning of the 1999-2000 school year. This evaluation studied the use and preliminary student…

  14. Switching and Rectification in Carbon-Nanotube Junctions

    NASA Technical Reports Server (NTRS)

    Srivastava, Deepak; Andriotis, Antonis N.; Menon, Madhu; Chernozatonskii, Leonid

    2003-01-01

    Multi-terminal carbon-nanotube junctions are under investigation as candidate components of nanoscale electronic devices and circuits. Three-terminal "Y" junctions of carbon nanotubes (see Figure 1) have proven to be especially interesting because (1) it is now possible to synthesize them in high yield in a controlled manner and (2) results of preliminary experimental and theoretical studies suggest that such junctions could exhibit switching and rectification properties. Following the preliminary studies, current-versus-voltage characteristics of a number of different "Y" junctions of single-wall carbon nanotubes connected to metal wires were computed. Both semiconducting and metallic nanotubes of various chiralities were considered. Most of the junctions considered were symmetric. These computations involved modeling of the quantum electrical conductivity of the carbon nanotubes and junctions, taking account of such complicating factors as the topological defects (pentagons, heptagons, and octagons) present in the hexagonal molecular structures at the junctions, and the effects of the nanotube/wire interfaces. A major component of the computational approach was the use of an efficient Green s function embedding scheme. The results of these computations showed that symmetric junctions could be expected to support both rectification and switching. The results also showed that rectification and switching properties of a junction could be expected to depend strongly on its symmetry and, to a lesser degree, on the chirality of the nanotubes. In particular, it was found that a zigzag nanotube branching at a symmetric "Y" junction could exhibit either perfect rectification or partial rectification (asymmetric current-versus-voltage characteristic, as in the example of Figure 2). It was also found that an asymmetric "Y" junction would not exhibit rectification.

  15. Intrinsic Josephson Junctions with Intermediate Damping

    NASA Astrophysics Data System (ADS)

    Warburton, Paul A.; Saleem, Sajid; Fenton, Jon C.; Speller, Susie; Grovenor, Chris R. M.

    2011-03-01

    In cuprate superconductors, adjacent cuprate double-planes are intrinsically Josephson-coupled. For bias currents perpendicular to the planes, the current-voltage characteristics correspond to those of an array of underdamped Josephson junctions. We will discuss our experiments on sub-micron Tl-2212 intrinsic Josephson junctions (IJJs). The dynamics of the IJJs at the plasma frequency are moderately damped (Q ~ 8). This results in a number of counter-intuitive observations, including both a suppression of the effect of thermal fluctuations and a shift of the skewness of the switching current distributions from negative to positive as the temperature is increased. Simulations confirm that these phenomena result from repeated phase slips as the IJJ switches from the zero-voltage to the running state. We further show that increased dissipation counter-intuitively increases the maximum supercurrent in the intermediate damping regime (PRL vol. 103, art. no. 217002). We discuss the role of environmental dissipation on the dynamics and describe experiments with on-chip lumped-element passive components in order control the environment seen by the IJJs. Work supported by EPSRC.

  16. Gap junctions in the nervous system.

    PubMed

    Rozental, R; Giaume, C; Spray, D C

    2000-04-01

    Synapses are classically defined as close connections between two nerve cells or between a neuronal cell and a muscle or gland cell across which a chemical signal (i.e., a neurotransmitter) and/or an electrical signal (i.e., current-carrying ions) can pass. The definition of synapse was developed by Charles Sherrington and by Ramon y Cajal at the beginning of this century and refined by John Eccles and Bernard Katz 50 years later; in this collection of papers, the definition of synapses is discussed further in the chapter by Mike Bennett. who provided the first functional demonstration of electrical transmission via gap junction channels between vertebrate neurons. As is evidenced by the range of topics covered in this issue, research dealing with gap junctions in the nervous system has expanded enormously in the past decade, major findings being that specific cell types in the brain expresses specific types of connexins and that expression patterns coincide with tissue compartmentalization and function and that these compartments change during development.

  17. Vertical-junction solar cells. Final report

    SciTech Connect

    Not Available

    1985-12-20

    The goal of this program was to develop and evaluate an acceptable coversliding technology for vertical-junction solar cells. The technical program was divided into the following sub-tasks: 1.0. to fabricate 80 vertical junction cells of most recent configuration for evaluation as individual samples and for test-module assembly. 2.1. to develop a satisfactory method for coversliding V.J. cells to withstand deep thermal cycle in space. 2.2. to establish welding parameters for V.J. cells and evaluate their weldability. 3.0. Using techniques from 2.1 and 2.2 four modules (4 cell each) to be fabricated and thermal cycled in dry nitrogen (115 c to +125 c 25 cycles) and thermal vacuum tested at 135 c. 4.0. based on results of tasks 2 and 3, two six cell modules to be designed: 1 soldered, 1 welded, and design to be discussed with COTR prior to finalization and 5.0. final design to be fabricated subjected to a thermal vacuum test at +135 c, thermal cycled -115 c to + 125 c, and characterized by I-V measurements and delivered to NRL for testing and evaluation.

  18. Communication Through Gap Junctions in the Endothelium.

    PubMed

    Schmidt, K; Windler, R; de Wit, C

    2016-01-01

    A swarm of fish displays a collective behavior (swarm behavior) and moves "en masse" despite the huge number of individual animals. In analogy, organ function is supported by a huge number of cells that act in an orchestrated fashion and this applies also to vascular cells along the vessel length. It is obvious that communication is required to achieve this vital goal. Gap junctions with their modular bricks, connexins (Cxs), provide channels that interlink the cytosol of adjacent cells by a pore sealed against the extracellular space. This allows the transfer of ions and charge and thereby the travel of membrane potential changes along the vascular wall. The endothelium provides a low-resistance pathway that depends crucially on connexin40 which is required for long-distance conduction of dilator signals in the microcirculation. The experimental evidence for membrane potential changes synchronizing vascular behavior is manifold but the functional verification of a physiologic role is still open. Other molecules may also be exchanged that possibly contribute to the synchronization (eg, Ca(2+)). Recent data suggest that vascular Cxs have more functions than just facilitating communication. As pharmacological tools to modulate gap junctions are lacking, Cx-deficient mice provide currently the standard to unravel their vascular functions. These include arteriolar dilation during functional hyperemia, hypoxic pulmonary vasoconstriction, vascular collateralization after ischemia, and feedback inhibition on renin secretion in the kidney.

  19. Communication Through Gap Junctions in the Endothelium.

    PubMed

    Schmidt, K; Windler, R; de Wit, C

    2016-01-01

    A swarm of fish displays a collective behavior (swarm behavior) and moves "en masse" despite the huge number of individual animals. In analogy, organ function is supported by a huge number of cells that act in an orchestrated fashion and this applies also to vascular cells along the vessel length. It is obvious that communication is required to achieve this vital goal. Gap junctions with their modular bricks, connexins (Cxs), provide channels that interlink the cytosol of adjacent cells by a pore sealed against the extracellular space. This allows the transfer of ions and charge and thereby the travel of membrane potential changes along the vascular wall. The endothelium provides a low-resistance pathway that depends crucially on connexin40 which is required for long-distance conduction of dilator signals in the microcirculation. The experimental evidence for membrane potential changes synchronizing vascular behavior is manifold but the functional verification of a physiologic role is still open. Other molecules may also be exchanged that possibly contribute to the synchronization (eg, Ca(2+)). Recent data suggest that vascular Cxs have more functions than just facilitating communication. As pharmacological tools to modulate gap junctions are lacking, Cx-deficient mice provide currently the standard to unravel their vascular functions. These include arteriolar dilation during functional hyperemia, hypoxic pulmonary vasoconstriction, vascular collateralization after ischemia, and feedback inhibition on renin secretion in the kidney. PMID:27451099

  20. Magnetoelectrics in disordered topological insulator Josephson junctions

    NASA Astrophysics Data System (ADS)

    Bobkova, I. V.; Bobkov, A. M.; Zyuzin, Alexander A.; Alidoust, Mohammad

    2016-10-01

    We study theoretically the coupling of electric charge and spin polarization in an equilibrium and nonequilibrium electric transport across a two-dimensional Josephson configuration comprised of disordered surface channels of a three-dimensional topological insulator. In the equilibrium state of the system, we predict the Edelstein effect, which is much more pronounced than its counterpart in conventional spin-orbit coupled materials. Employing a quasiclassical Keldysh technique, we demonstrate that the ground state of the system can be shifted experimentally into arbitrary macroscopic superconducting phase differences other than the standard "0" or "π ," constituting a ϕ0 junction, solely by modulating a quasiparticle flow injection into the junction. We propose a feasible experiment in which the quasiparticles are injected into the topological insulator surface by means of a normal electrode and voltage gradient so that oppositely oriented stationary spin densities can be developed along the interfaces and allow for direct use of the spin-momentum locking nature of Dirac fermions in the surface channels. The ϕ0 state is proportional to the voltage difference applied between the injector electrode and superconducting terminals that calibrates the injection rate of particles and, therefore, the ϕ0 shift.

  1. Edge currents in frustrated Josephson junction ladders

    NASA Astrophysics Data System (ADS)

    Marques, A. M.; Santos, F. D. R.; Dias, R. G.

    2016-09-01

    We present a numerical study of quasi-1D frustrated Josephson junction ladders with diagonal couplings and open boundary conditions, in the large capacitance limit. We derive a correspondence between the energy of this Josephson junction ladder and the expectation value of the Hamiltonian of an analogous tight-binding model, and show how the overall superconducting state of the chain is equivalent to the minimum energy state of the tight-binding model in the subspace of one-particle states with uniform density. To satisfy the constraint of uniform density, the superconducting state of the ladder is written as a linear combination of the allowed k-states of the tight-binding model with open boundaries. Above a critical value of the parameter t (ratio between the intra-rung and inter-rung Josephson couplings) the ladder spontaneously develops currents at the edges, which spread to the bulk as t is increased until complete coverage is reached. Above a certain value of t, which varies with ladder size (t = 1 for an infinite-sized ladder), the edge currents are destroyed. The value t = 1 corresponds, in the tight-binding model, to the opening of a gap between two bands. We argue that the disappearance of the edge currents with this gap opening is not coincidental, and that this points to a topological origin for these edge current states.

  2. Functional ferroelectric tunnel junctions on silicon

    NASA Astrophysics Data System (ADS)

    Guo, Rui; Wang, Zhe; Zeng, Shengwei; Han, Kun; Huang, Lisen; Schlom, Darrell G.; Venkatesan, T.; Ariando; Chen, Jingsheng

    2015-07-01

    The quest for solid state non-volatility memory devices on silicon with high storage density, high speed, low power consumption has attracted intense research on new materials and novel device architectures. Although flash memory dominates in the non-volatile memory market currently, it has drawbacks, such as low operation speed, and limited cycle endurance, which prevents it from becoming the “universal memory”. In this report, we demonstrate ferroelectric tunnel junctions (Pt/BaTiO3/La0.67Sr0.33MnO3) epitaxially grown on silicon substrates. X-ray diffraction spectra and high resolution transmission electron microscope images prove the high epitaxial quality of the single crystal perovskite films grown on silicon. Furthermore, the write speed, data retention and fatigue properties of the device compare favorably with flash memories. The results prove that the silicon-based ferroelectric tunnel junction is a very promising candidate for application in future non-volatile memories.

  3. Interface Composition in Magnetic Tunnel Junctions

    NASA Astrophysics Data System (ADS)

    Mayen, Kether; McCord, Jeff; Allen, Drew; Schad, Rainer; Wang, Dexin; Tondra, Mark; Yang, Dehua

    2000-03-01

    The magnetoresistance of magnetic tunnel junctions is given by the spin dependence of the electron transfer across the insulator layer. As such, its magnitude critically depends on the spin polarization at the interfaces between the magnetic electrodes and the insulator. These properties will, naturally, depend on the exact composition at the interfaces. The way in which the insulator layers of tunnel junctions are commonly produced (oxidation of a Al layer) leads to ambiguities in the exact interface composition. We studied the chemical properties, using high-resolution XPS, of ferromagnet/AlOx interfaces. The samples had a Al layer the thickness of which varied between 0.6 and 1.8nm. The homogeneous oxidation process applied to those samples resulted in an oxygen overexposure or underexposure for respectively the thin and the thick Al end of the samples. We have studied the concentrations of elementary and oxidized Al, Co, Ni and Fe for various composition and roughness of the ferromagnetic layer. The amount of elementary Al we find as function of the original Al thickness gives insight into the Al oxidation process. However, within the sensitivity of the analysis technique, we did not observe oxidation of the ferromagnetic layers, even for the overoxidized end of the samples.

  4. Functional ferroelectric tunnel junctions on silicon

    PubMed Central

    Guo, Rui; Wang, Zhe; Zeng, Shengwei; Han, Kun; Huang, Lisen; Schlom, Darrell G.; Venkatesan, T.; Ariando, A; Chen, Jingsheng

    2015-01-01

    The quest for solid state non-volatility memory devices on silicon with high storage density, high speed, low power consumption has attracted intense research on new materials and novel device architectures. Although flash memory dominates in the non-volatile memory market currently, it has drawbacks, such as low operation speed, and limited cycle endurance, which prevents it from becoming the “universal memory”. In this report, we demonstrate ferroelectric tunnel junctions (Pt/BaTiO3/La0.67Sr0.33MnO3) epitaxially grown on silicon substrates. X-ray diffraction spectra and high resolution transmission electron microscope images prove the high epitaxial quality of the single crystal perovskite films grown on silicon. Furthermore, the write speed, data retention and fatigue properties of the device compare favorably with flash memories. The results prove that the silicon-based ferroelectric tunnel junction is a very promising candidate for application in future non-volatile memories. PMID:26215429

  5. Metallic Electrode: Semiconducting Nanotube Junction Model

    NASA Technical Reports Server (NTRS)

    Yamada, Toshishige; Biegel, Bryon (Technical Monitor)

    2001-01-01

    A model is proposed for two observed current-voltage (I-V) patterns in an experiment with a scanning tunneling microscope tip and a carbon nanotube [Collins et al., Science 278, 100 ('97)]. We claim that there are two contact modes for a tip (metal) -nanotube semi conductor) junction depending whether the alignment of the metal and semiconductor band structure is (1) variable (vacuum-gap) or (2) fixed (touching) with V. With the tip grounded, the tunneling case in (1) would produce large dI/dV with V > 0, small dI/dV with V < 0, and I = 0 near V = 0 for an either n- or p-nanotube. However, the Schottky mechanism in (2) would result in forward current with V < 0 for an n-nanotube, while with V > 0 for an p-nanotube. The two observed I-V patterns are thus entirely explained by a tip-nanotube contact of the two types, where the nanotube must be n-type. We apply this picture to the source-drain I-V characteristics in a long nanotube-channel field-effect-transistor (Zhou et al., Appl. Phys. Lett. 76, 1597 ('00)], and show that two independent metal-semiconductor junctions connected in series are responsible for the observed behavior.

  6. Mutational analysis of gap junction formation.

    PubMed Central

    Dahl, G; Werner, R; Levine, E; Rabadan-Diehl, C

    1992-01-01

    The paired oocyte cell-cell channel assay was used to investigate the mechanisms involved in the process of formation of gap junction channels. Single oocytes, injected with connexin-specific mRNAs, accumulate a pool of precursors from which cell-cell channels can form rapidly upon pairing. Several lines of evidence, including immunohistochemistry and surface labeling, indicate that part of this precursor pool is located in the cell membrane, probably in the form of closed hemichannels. The homophilic binding of hemichannels to each other can be mimicked by synthetic peptides representing the extracellular loop sequences of connexin32. The peptides specifically suppress channel formation. A crucial role is established for the six cysteines in the extracellular domains that are conserved in all vertebrate gap junction proteins. Change of any of these cysteines into serines results in absolute loss of function of the mutant connexin. The effects of thiol-specific reagents on channel formation suggest that docking and/or opening of channels involves disulfide exchange. Several of the variable amino acids in the extracellular loop sequences were found to determine specificity of connexin-connexin interactions. Images FIGURE 2 PMID:1376165

  7. Fractional Solitons in Excitonic Josephson Junctions

    NASA Astrophysics Data System (ADS)

    Hsu, Ya-Fen; Su, Jung-Jung

    2015-10-01

    The Josephson effect is especially appealing to physicists because it reveals macroscopically the quantum order and phase. In excitonic bilayers the effect is even subtler due to the counterflow of supercurrent as well as the tunneling between layers (interlayer tunneling). Here we study, in a quantum Hall bilayer, the excitonic Josephson junction: a conjunct of two exciton condensates with a relative phase ϕ0 applied. The system is mapped into a pseudospin ferromagnet then described numerically by the Landau-Lifshitz-Gilbert equation. In the presence of interlayer tunneling, we identify a family of fractional sine-Gordon solitons which resemble the static fractional Josephson vortices in the extended superconducting Josephson junctions. Each fractional soliton carries a topological charge Q that is not necessarily a half/full integer but can vary continuously. The calculated current-phase relation (CPR) shows that solitons with Q = ϕ0/2π is the lowest energy state starting from zero ϕ0 - until ϕ0 > π - then the alternative group of solitons with Q = ϕ0/2π - 1 takes place and switches the polarity of CPR.

  8. Tight junctions in the testis: new perspectives

    PubMed Central

    Mruk, Dolores D.; Cheng, C. Y.

    2010-01-01

    In the testis, tight junctions (TJs) are found between adjacent Sertoli cells at the level of the blood–testis barrier (BTB) where they coexist with basal ectoplasmic specializations and desmosome-gap junctions. The BTB physically divides the seminiferous epithelium into two distinct compartments: a basal compartment where spermatogonia and early spermatocytes are found, and an adluminal compartment where more developed germ cells are sequestered from the systemic circulation. In order for germ cells (i.e. preleptotene spermatocytes) to enter the adluminal compartment, they must cross the BTB, a cellular event requiring the participation of several molecules and signalling pathways. Still, it is not completely understood how preleptotene spermatocytes traverse the BTB at stage VIII of the seminiferous epithelial cycle. In this review, we discuss largely how TJ proteins are exploited by viruses and cancer cells to cross endothelial and epithelial cells. We also discuss how this information may apply to future studies investigating the movement of preleptotene spermatocytes across the BTB. PMID:20403874

  9. Improving transition voltage spectroscopy of molecular junctions

    NASA Astrophysics Data System (ADS)

    Markussen, Troels; Chen, Jingzhe; Thygesen, Kristian S.

    2011-04-01

    Transition voltage spectroscopy (TVS) is a promising spectroscopic tool for molecular junctions. The principles in TVS is to find the minimum on a Fowler-Nordheim plot where ln(I/V2) is plotted against 1/V and relate the voltage at the minimum Vmin to the closest molecular level. Importantly, Vmin is approximately half the voltage required to see a peak in the dI/dV curve. Information about the molecular level position can thus be obtained at relatively low voltages. In this work we show that the molecular level position can be determined at even lower voltages, Vmin(α), by finding the minimum of ln(I/Vα) with α<2. On the basis of a simple Lorentzian transmission model we analyze theoretical ab initio as well as experimental I-V curves and show that the voltage required to determine the molecular levels can be reduced by ~30% as compared to conventional TVS. As for conventional TVS, the symmetry/asymmetry of the molecular junction needs to be taken into account in order to gain quantitative information. We show that the degree of asymmetry may be estimated from a plot of Vmin(α) vs α.

  10. 75 FR 76294 - Radio Broadcasting Services: Pacific Junction, IA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-08

    ... Junction, in overcoming objections raised by the FAA to the activation of this allotment. See 75 FR 30756... From the Federal Register Online via the Government Publishing Office FEDERAL COMMUNICATIONS COMMISSION 47 CFR Part 73 Radio Broadcasting Services: Pacific Junction, IA AGENCY: Federal...

  11. Molecular Transport Junctions Created By Self-Contacting Gapped Nanowires.

    PubMed

    Lim, Jong Kuk; Lee, One-Sun; Jang, Jae-Won; Petrosko, Sarah Hurst; Schatz, George C; Mirkin, Chad A

    2016-08-01

    Molecular transport junctions (MTJs) are important components in molecular electronic devices. However, the synthesis of MTJs remains a significant challenge, as the dimensions of the junction must be tailored for each experiment, based on the molecular lengths. A novel methodology is reported for forming MTJs, taking advantage of capillary and van der Waals forces. PMID:27364594

  12. Septal Junctions in Filamentous Heterocyst-Forming Cyanobacteria.

    PubMed

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

    2016-02-01

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

  13. Triple junction polymer solar cells for photoelectrochemical water splitting.

    PubMed

    Esiner, Serkan; van Eersel, Harm; Wienk, Martijn M; Janssen, René A J

    2013-06-01

    A triple junction polymer solar cell in a novel 1 + 2 type configuration provides photoelectrochemical water splitting in its maximum power point at V ≈ 1.70 V with an estimated solar to hydrogen energy conversion efficiency of 3.1%. The triple junction cell consists of a wide bandgap front cell and two identical small bandgap middle and back cells.

  14. Claudins and the Modulation of Tight Junction Permeability

    PubMed Central

    Günzel, Dorothee

    2013-01-01

    Claudins are tight junction membrane proteins that are expressed in epithelia and endothelia and form paracellular barriers and pores that determine tight junction permeability. This review summarizes our current knowledge of this large protein family and discusses recent advances in our understanding of their structure and physiological functions. PMID:23589827

  15. Processing of Superconductor-Normal-Superconductor Josephson Edge Junctions

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

    The electrical behavior of epitaxial superconductor-normal-superconductor (SNS) Josephson edge junctions is strongly affected by processing conditions. Ex-situ processes, utilizing photoresist and polyimide/photoresist mask layers, are employed for ion milling edges for junctions with Yttrium-Barium-Copper-Oxide (YBCO) electrodes and primarily Co-doped YBCO interlayers.

  16. 10. VIEW UPSTREAM OF PIPELINE SECTION AT JUNCTION OF HUME ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    10. VIEW UPSTREAM OF PIPELINE SECTION AT JUNCTION OF HUME CEMENT PIPE AND CAST-IRON (460'). NOTE CYLINDRICAL COLLAR OF CEMENT SECTIONS AND BELL JUNCTIONS OF IRON PIPE. - Kalaupapa Water Supply System, Waikolu Valley to Kalaupapa Settlement, Island of Molokai, Kalaupapa, Kalawao County, HI

  17. Slit diaphragm junctional complex and regulation of the cytoskeleton.

    PubMed

    Garg, Puneet; Verma, Rakesh; Holzman, Lawrence B

    2007-01-01

    In recent years, identification of proteins found at the slit diaphragm has greatly improved our understanding of the molecular mechanisms responsible for forming and maintaining the glomerular filtration barrier. This review examines the function of proteins identified at the podocyte intercellular junction in coordinating podocyte intercellular junction dynamics or cytoskeletal dynamics.

  18. Diencephalic-Mesencephalic Junction Dysplasia: A Novel Recessive Brain Malformation

    ERIC Educational Resources Information Center

    Zaki, Maha S.; Saleem, Sahar N.; Dobyns, William B.; Barkovich, A. James; Bartsch, Hauke; Dale, Anders M.; Ashtari, Manzar; Akizu, Naiara; Gleeson, Joseph G.; Grijalvo-Perez, Ana Maria

    2012-01-01

    We describe six cases from three unrelated consanguineous Egyptian families with a novel characteristic brain malformation at the level of the diencephalic-mesencephalic junction. Brain magnetic resonance imaging demonstrated a dysplasia of the diencephalic-mesencephalic junction with a characteristic "butterfly"-like contour of the midbrain on…

  19. Mapping the Transmission Functions of Single-Molecule Junctions.

    PubMed

    Capozzi, Brian; Low, Jonathan Z; Xia, Jianlong; Liu, Zhen-Fei; Neaton, Jeffrey B; Campos, Luis M; Venkataraman, Latha

    2016-06-01

    Charge transport phenomena in single-molecule junctions are often dominated by tunneling, with a transmission function dictating the probability that electrons or holes tunnel through the junction. Here, we present a new and simple technique for measuring the transmission functions of molecular junctions in the coherent tunneling limit, over an energy range of 1.5 eV around the Fermi energy. We create molecular junctions in an ionic environment with electrodes having different exposed areas, which results in the formation of electric double layers of dissimilar density on the two electrodes. This allows us to electrostatically shift the molecular resonance relative to the junction Fermi levels in a manner that depends on the sign of the applied bias, enabling us to map out the junction's transmission function and determine the dominant orbital for charge transport in the molecular junction. We demonstrate this technique using two groups of molecules: one group having molecular resonance energies relatively far from EF and one group having molecular resonance energies within the accessible bias window. Our results compare well with previous electrochemical gating data and with transmission functions computed from first principles. Furthermore, with the second group of molecules, we are able to examine the behavior of a molecular junction as a resonance shifts into the bias window. This work provides a new, experimentally simple route for exploring the fundamentals of charge transport at the nanoscale. PMID:27186894

  20. Josephson junctions in high-T/sub c/ superconductors

    DOEpatents

    Falco, C.M.; Lee, T.W.

    1981-01-14

    The invention includes a high T/sub c/ Josephson sperconducting junction as well as the method and apparatus which provides the junction by application of a closely controlled and monitored electrical discharge to a microbridge region connecting two portions of a superconducting film.

  1. 4. View of junction from the northwest looking southeast over ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    4. View of junction from the northwest looking southeast over the northwest leg and northwest ramp of the cloverleaf toward the western side of bridge no. 5820. - Cloverleaf Interchange, Junction of Trunk Highways 52, 3, & 55, Inver Grove Heights, Dakota County, MN

  2. TEMPORAL CHANGE IN GAP JUNCTION FUNCTION IN PRIMARY HEPATOCYTES

    EPA Science Inventory

    TEMPORAL CHANGES IN GAP JUNCTION FUNCTION IN PRIMARY *

    The objective of this study was to examine the reduction in gap junction communication (GJC) in primary hepatocytes due to coincident melatonin and magnetic field treatments to determine if these conditions could prov...

  3. Shapiro and parametric resonances in coupled Josephson junctions

    NASA Astrophysics Data System (ADS)

    Gaafar, Ma A.; Shukrinov, Yu M.; Foda, A.

    2012-11-01

    The effect of microwave irradiation on the phase dynamics of intrinsic Josephson junctions in high temperature superconductors is investigated. We compare the current-voltage characteristics for a stack of coupled Josephson junctions under external irradiation calculated in the framework of CCJJ and CCJJ+DC models.

  4. Craniovertebral Junction Instability in the Setting of Chiari I Malformation.

    PubMed

    Goldstein, Hannah E; Anderson, Richard C E

    2015-10-01

    This article addresses the key features, clinical presentation, and radiographic findings associated with craniovertebral junction instability in the setting of Chiari I malformation. It further discusses surgical technique for treating patients with Chiari I malformation with concomitant craniovertebral junction instability, focusing on modern posterior rigid instrumentation and fusion techniques.

  5. Conditions for synchronization in Josephson-junction arrays

    SciTech Connect

    Chernikov, A.A.; Schmidt, G.

    1995-12-31

    An effective perturbation theoretical method has been developed to study the dynamics of Josephson Junction series arrays. It is shown that the inclusion of Junction capacitances, often ignored, has a significant impact on synchronization. Comparison of analytic with computational results over a wide range of parameters shows excellent agreement.

  6. Junction properties of aluminum/polypyrrole (polypyrrole derivatives) Schottky diodes

    NASA Astrophysics Data System (ADS)

    Singh, Ramadhar; Narula, Amarjeet K.

    1997-11-01

    The current-voltage characteristics of Schottky junctions formed by using aluminum on polypyrrole, poly(N-methyl pyrrole) and the copolymer poly(N-methyl pyrrole-pyrrole) have been investigated. The formation of the junctions has been confirmed by capacitance-voltage characteristics and Chot plots. The results have been explained on the basis of thermionic emission theory.

  7. Septal Junctions in Filamentous Heterocyst-Forming Cyanobacteria.

    PubMed

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

    2016-02-01

    In the filaments of heterocyst-forming cyanobacteria, septal junctions that traverse the septal peptidoglycan join adjacent cells, allowing intercellular communication. Perforations in the septal peptidoglycan have been observed, and proteins involved in the formation of such perforations and putative protein components of the septal junctions have been identified, but their relationships are debated. PMID:26748968

  8. Localization of the paranodal protein Caspr in the mammalian retina

    PubMed Central

    Hirano, Arlene A.; Buttermore, Elizabeth D.; Bhat, Manzoor A.; Peles, Elior

    2010-01-01

    Purpose The retina has the demanding task of encoding all aspects of the visual scene within the space of one fixation period lasting only a few hundred milliseconds. To accomplish this feat, information is encoded in specialized parallel channels and passed on to numerous central nuclei via the optic nerve. These parallel channels achieve specialization in at least three ways: the synaptic networks in which they participate, the neurotransmitter receptors expressed and the types and locations of ion channels or transporters used. Subcellular localization of receptors, channels and transporters is made yet more complex in the retina by the double duty many retinal processes serve. In the present work, we show that the protein Caspr (Contactin Associated Protein), best known for its critical role in the localization of voltage-gated ion channels at the nodes of Ranvier, is present in several types of retinal neurons including amacrine, bipolar, horizontal, and ganglion cells. Methods Using standard double label immunofluorescence protocols, we characterized the pattern of Caspr expression in the rodent retina. Results Caspr labeling was observed through much of the retina, including horizontal, bipolar, amacrine, and ganglion cells. Among amacrine cells, Caspr was observed in AII amacrine cells through co-localization with Parvalbumin and Disabled-1 in rat and mouse retinas, respectively. An additional amacrine cell type containing Calretinin also co-localized with Caspr, but did not co-localize with choline-acetyltransferase. Nearly all cells in the ganglion cell layer contain Caspr, including both displaced amacrine and ganglion cells. In the outer retina, Caspr was co-localized with PKC labeling in rod bipolar cell dendrites. In addition, Caspr labeling was found inside syntaxin-4 'sandwiches' in the outer plexiform layer, most likely indicating its presence in cone bipolar cell dendrites. Finally, Caspr was co-localized in segments of horizontal cell dendrites labeled with Calbindin-D28k. Conclusions Caspr is best known for its role in organizing the localization of different voltage-gated ion channels in and around nodes of Ranvier. As neuronal processes in the retina often play a dual role involving both input and output, it is possible that the localization of Caspr in the retina will help us decipher the way retinal cells localize ion channels in their processes to increase computational capacity. PMID:21031018

  9. The effect of triple-junction drag on grain growth

    SciTech Connect

    Gottstein, G.; King, A.H.; Shvindlerman, L.S.

    2000-01-24

    Current theories of grain growth presume that grain boundary migration is the rate-limiting step, and either explicitly or implicitly assume that triple junctions can always move with sufficient speed to accommodate the changing positions of the grain boundaries. Following from some recent observations of triple-junction drag effects in tricrystals of zinc and in molecular dynamics models, an analytical theory is developed to explore the effects of triple-junction drag upon grain growth, for a two-dimensional solid. The theory is developed in the framework of the Von Neumann-Mullins formulation, and demonstrates that drag effects operating exclusively at the triple junctions result in a retardation of grain growth. The stability of six-sided grains in the isotropic, drag-free case of the Von Neumann-Mullins analysis is successively extended to grains of 6 {+-} N sides, where N increases with the strength of the triple-junction drag.

  10. Hybrid magnetic tunnel junction/spin filter device

    SciTech Connect

    Suzuki, Y.; Nelson-Cheeseman, B.; Wong, F.; Chopdekar, R.; Arenholz, E.; Chi, Miaofang; Browning, Nigel

    2008-07-10

    Surfaces and interfaces of complex oxides materials provide a rich playground for the exploration of novel magnetic properties not found in the bulk but also the development of functional interfaces to be incorporated into applications. We have recently been able to demonstrate a new type of hybrid spin filter/ magnetic tunnel junction. Our hybrid spin-filter/magnetic-tunnel junction devices are epitaxial oxide junctions of La{sub 0.7}Sr{sub 0.3}MnO{sub 3} and Fe{sub 3}O{sub 4} electrodes with magnetic NiMn{sub 2}O{sub 4} barrier layers. Depending on whether the barrier is in a paramagnetic or ferromagnetic state, the junction exhibits magnetic tunnel junction behavior where the spin polarized conduction is dominated by the electrode-barrier interface or spin filter behavior where conduction is dominated by barrier layer magnetism.

  11. Temperature dependence of charge transport in conjugated single molecule junctions

    NASA Astrophysics Data System (ADS)

    Huisman, Eek; Kamenetska, Masha; Venkataraman, Latha

    2011-03-01

    Over the last decade, the break junction technique using a scanning tunneling microscope geometry has proven to be an important tool to understand electron transport through single molecule junctions. Here, we use this technique to probe transport through junctions at temperatures ranging from 5K to 300K. We study three amine-terminated (-NH2) conjugated molecules: a benzene, a biphenyl and a terphenyl derivative. We find that amine groups bind selectively to undercoordinate gold atoms gold all the way down to 5K, yielding single molecule junctions with well-defined conductances. Furthermore, we find that the conductance of a single molecule junction increases with temperature and we present a mechanism for this temperature dependent transport result. Funded by a Rubicon Grant from The Netherlands Organisation for Scientific Research (NWO) and the NSEC program of NSF under grant # CHE-0641523.

  12. A multilayered approach to superconducting tunnel junction x ray detectors

    NASA Technical Reports Server (NTRS)

    Rippert, E. D.; Song, S. N.; Ketterson, J. B.; Maglic, S. R.; Lomatch, S.; Thomas, C.; Cheida, M. A.; Ulmer, M. P.

    1992-01-01

    'First generation' superconducting tunnel junction X-ray detectors (characterized by a single tunnel junction in direct contact with its substrate, with totally external amplification) remain more than an order of magnitude away from their theoretical energy resolutions which are in the order of eV's. The difficulties that first generation devices are encountering are being attacked by a 'second generation' of superconducting X-ray detector designs including quasiparticle trapping configurations and Josephson junction arrays. A second generation design concept, the multilayered superconducting tunnel junction X-ray detector, consisting of tens to hundreds of tunnel junctions stacked on top of one another (a superlattice), is presented. Some of the possibilities of this engineered materials approach include the tuning of phonon transmission characteristics of the material, suppression of parasitic quasiparticle trapping and intrinsic amplification.

  13. Subgap conductivity in SIN-junctions of high barrier transparency

    NASA Astrophysics Data System (ADS)

    Lotkhov, S. V.; Balashov, D. V.; Khabipov, M. I.; Buchholz, F.-I.; Zorin, A. B.

    2006-11-01

    We investigate the current-voltage characteristics of high-transparency superconductor-insulator-normal metal (SIN) junctions with the specific tunnel resistance ρ ≲ 30 Ω μm2. The junctions were fabricated from different superconducting and normal conducting materials, including Nb, Al, AuPd and Cu. The subgap leakage currents were found to be appreciably larger than those given by the standard tunnelling model. We explain our results using the model of two-electron tunnelling in the coherent diffusive transport regime. We demonstrate that even in the high-transparency SIN-junctions, a noticeable reduction of the subgap current can be achieved by splitting a junction into several submicron sub-junctions. These structures can be used as nonlinear low-noise shunts in rapid-single-flux-quantum (RSFQ) circuitry for controlling Josephson qubits.

  14. Parametric resonance in the system of long Josephson junctions

    NASA Astrophysics Data System (ADS)

    Rahmonov, I. R.; Shukrinov, Yu. M.; Irie, A.

    2014-08-01

    The phase dynamics of the system of long Josephson junctions whose length exceeds the Josephson penetration depth has been studied. The possibility of the appearance of a longitudinal plasma wave and parametric resonance has been demonstrated. Both inductive and capacitive couplings between Josephson junctions have been taken into account in the calculations. The current-voltage characteristics, as well as time evolution of the spatial distribution of the electric charge in superconducting layers and the magnetic field, have been calculated in all Josephson junctions of the system. The coexistence of the longitudinal plasma wave and fluxon states has been observed in the region of parametric resonance beginning with a certain length of the Josephson junction. This indicates the appearance of a new unique collective excitation in the system of coupled Josephson junctions, namely, a composite state of the Josephson current, electric field, and vortex magnetic field.

  15. Fixed-Gap Tunnel Junction for Reading DNA Nucleotides

    PubMed Central

    2015-01-01

    Previous measurements of the electronic conductance of DNA nucleotides or amino acids have used tunnel junctions in which the gap is mechanically adjusted, such as scanning tunneling microscopes or mechanically controllable break junctions. Fixed-junction devices have, at best, detected the passage of whole DNA molecules without yielding chemical information. Here, we report on a layered tunnel junction in which the tunnel gap is defined by a dielectric layer, deposited by atomic layer deposition. Reactive ion etching is used to drill a hole through the layers so that the tunnel junction can be exposed to molecules in solution. When the metal electrodes are functionalized with recognition molecules that capture DNA nucleotides via hydrogen bonds, the identities of the individual nucleotides are revealed by characteristic features of the fluctuating tunnel current associated with single-molecule binding events. PMID:25380505

  16. Presence of functional gap junctions in human embryonic stem cells.

    PubMed

    Wong, Raymond C B; Pébay, Alice; Nguyen, Linh T V; Koh, Karen L L; Pera, Martin F

    2004-01-01

    Gap junctions are intercellular channels that allow both chemical and electrical signaling between two adjacent cells. Gap junction intercellular communication has been implicated in the regulation of various cellular processes, including cell migration, cell proliferation, cell differentiation, and cell apoptosis. This study aimed to determine the presence and functionality of gap junctions in human embryonic stem cells (hESCs). Using reverse transcription--polymerase chain reaction and immunocytochemistry, we demonstrate that human ES cells express two gap junction proteins, connexin 43 and connexin 45. Western blot analysis revealed the presence of three phosphorylated forms (nonphosphorylated [NP], P1, and P2) of connexin 43, NP being prominent. Moreover, scrape loading/dye transfer assay indicates that human ES cells are coupled through functional gap junctions that are inhibited by protein kinase C activation and extracellular signal-regulated kinase inhibition.

  17. Role of autophagy in the regulation of epithelial cell junctions.

    PubMed

    Nighot, Prashant; Ma, Thomas

    2016-01-01

    Autophagy is a cell survival mechanism by which bulk cytoplasmic material, including soluble macromolecules and organelles, is targeted for lysosomal degradation. The role of autophagy in diverse cellular processes such as metabolic stress, neurodegeneration, cancer, aging, immunity, and inflammatory diseases is being increasingly recognized. Epithelial cell junctions play an integral role in the cell homeostasis via physical binding, regulating paracellular pathways, integrating extracellular cues into intracellular signaling, and cell-cell communication. Recent data indicates that cell junction composition is very dynamic. The junctional protein complexes are actively regulated in response to various intra- and extra-cellular clues by intracellular trafficking and degradation pathways. This review discusses the recent and emerging information on how autophagy regulates various epithelial cell junctions. The knowledge of autophagy regulation of epithelial junctions will provide further rationale for targeting autophagy in a wide variety of human disease conditions. PMID:27583189

  18. Altered patterns of cardiac intercellular junction distribution in hypertrophic cardiomyopathy.

    PubMed Central

    Sepp, R.; Severs, N. J.; Gourdie, R. G.

    1996-01-01

    OBJECTIVE: To examine the distribution pattern of intercellular junctions (the mechanically coupling desmosomes and the electrically coupling gap junctions) in hypertrophic cardiomyopathy (HCM) hearts showing myofibre disarray. DESIGN: Samples from six necropsied hearts were studied, representing the interventricular septum and the free walls of the left and right ventricles. Immunohistochemical labelling of desmoplakin was used as a marker for desmosomes, and of connexin43 as a marker for gap junctions, in single and double stainings. The slides were examined by confocal laser scanning microscopy. RESULTS: Marked disorganisation of intercalated discs was observed in areas featuring myofibre disarray. Besides overall derangement, localised abnormalities in desmosome organisation were evident, which included: (1) the formation of abnormally enlarged megadiscs; (2) the presence of intersecting disc structures; and (3) aberrant side to side desmosomal connections. Gap junctional abnormalities included: (1) random distribution of gap junctions over the surface of myocytes, rather than localisation to intercalated discs; (2) abundant side to side gap junction connections between adjacent myocytes; and (3) formation of abnormally shaped gap junctions. Circles of myocytes continuously interconnected by gap junctions were also observed. Regions of the diseased hearts lacking myofibre disarray, and control hearts of normal patients and patients with other cardiac diseases, did not show these alterations. CONCLUSIONS: The disorganisation of the intercellular junctions associated with myofibre disarray in HCM may play an important role in the pathophysiological manifestations of the disease. The remodelling of gap junction distribution may underlie the formation of an arrhythmogenic substrate, thereby contributing to the generation and maintenance of cardiac arrhythmias associated with HCM. Images PMID:8944586

  19. Scattering form factors for self-assembled network junctions

    NASA Astrophysics Data System (ADS)

    Foster, T.; Safran, S. A.; Sottmann, T.; Strey, R.

    2007-11-01

    The equilibrium microstructures in microemulsions and other self-assembled systems show complex, connected shapes such as symmetric bicontinuous spongelike structures and asymmetric bicontinuous networks formed by cylinders interconnected at junctions. In microemulsions, these cylinder network microstructures may mediate the structural transition from a spherical or globular phase to the bicontinuous microstructure. To understand the structural and statistical properties of such cylinder network microstructures as measured by scattering experiments, models are needed to extract the real-space structure from the scattering data. In this paper, we calculate the scattering functions appropriate for cylinder network microstructures. We focus on such networks that contain a high density of network junctions that connect the cylindrical elements. In this limit, the network microstructure can be regarded as an assembly of randomly oriented, closed packed network junctions (i.e., the cylinder scattering contributions are neglected). Accordingly, the scattering spectrum of the network microstructure can be calculated as the product of the junction number density, the junction form factor, which describes the scattering from the surface of a single junction, and a structure factor, which describes the local correlations of different junctions due to junction interactions (including their excluded volume). This approach is applied to analyze the scattering data from a bicontinuous microemulsion with equal volumes of water and oil. In a second approach, we included the cylinder scattering contribution in the junction form factor by calculating the scattering intensity of Y junctions to which three rods with spherical cross section are attached. The respective theoretical predictions are compared with results of neutron scattering measurements on a water-in-oil microemulsion with a connected microstructure.

  20. Switch in Gap Junction Protein Expression is Associated with Selective Changes in Junctional Permeability During Keratinocyte Differentiation

    NASA Astrophysics Data System (ADS)

    Brissette, Janice L.; Kumar, Nalin M.; Gilula, Norton B.; Hall, James E.; Dotto, G. Paolo

    1994-07-01

    Gap junctional communication provides a mechanism for regulating multicellular activities by allowing the exchange of small diffusible molecules between neighboring cells. The diversity of gap junction proteins may exist to form channels that have different permeability properties. We report here that induction of terminal differentiation in mouse primary keratinocytes by calcium results in a specific switch in gap junction protein expression. Expression of α_1 (connexin 43) and β_2 (connexin 26) gap junction proteins is down-modulated, whereas that of β_3 (connexin 31) and β_4 (connexin 31.1) proteins is induced. Although both proliferating and differentiating keratinocytes are electrically coupled, there are significant changes in the permeability properties of the junctions to small molecules. In parallel with the changes in gap junction protein expression during differentiation, the intercellular transfer of the small dyes neurobiotin, carboxyfluorescein, and Lucifer yellow is significantly reduced, whereas that of small metabolites, such as nucleotides and amino acids, proceeds unimpeded. Thus, a switch in gap junction protein expression in differentiating keratinocytes is accompanied by selective changes in junctional permeability that may play an important role in the coordinate control of the differentiation process.

  1. Switch in gap junction protein expression is associated with selective changes in junctional permeability during keratinocyte differentiation.

    PubMed Central

    Brissette, J L; Kumar, N M; Gilula, N B; Hall, J E; Dotto, G P

    1994-01-01

    Gap junctional communication provides a mechanism for regulating multicellular activities by allowing the exchange of small diffusible molecules between neighboring cells. The diversity of gap junction proteins may exist to form channels that have different permeability properties. We report here that induction of terminal differentiation in mouse primary keratinocytes by calcium results in a specific switch in gap junction protein expression. Expression of alpha 1 (connexin 43) and beta 2 (connexin 26) gap junction proteins is down-modulated, whereas that of beta 3 (connexin 31) and beta 4 (connexin 31.1) proteins is induced. Although both proliferating and differentiating keratinocytes are electrically coupled, there are significant changes in the permeability properties of the junctions to small molecules. In parallel with the changes in gap junction protein expression during differentiation, the intercellular transfer of the small dyes neurobiotin, carboxyfluorescein, and Lucifer yellow is significantly reduced, whereas that of small metabolites, such as nucleotides and amino acids, proceeds unimpeded. Thus, a switch in gap junction protein expression in differentiating keratinocytes is accompanied by selective changes in junctional permeability that may play an important role in the coordinate control of the differentiation process. Images PMID:8022804

  2. Influence of coupling between junctions on breakpoint current in intrinsic Josephson junctions.

    PubMed

    Shukrinov, Yu M; Mahfouzi, F

    2007-04-13

    We study theoretically the current-voltage characteristics of intrinsic Josephson junctions in high-Tc superconductors. An oscillation of the breakpoint current on the outermost branch as a function of coupling alpha and dissipation beta parameters is found. We explain this oscillation as a result of the creation of longitudinal plasma waves at the breakpoint with different wave numbers. We demonstrate the commensurability effect and predict a group behavior of the current-voltage characteristics for the stacks with a different number of junctions. A method to determine the wave number of longitudinal plasma waves from alpha and beta dependence of the breakpoint current is suggested. We model the alpha and beta dependence of the breakpoint current and obtain good agreement with the results of the simulation.

  3. Influence of Coupling between Junctions on Breakpoint Current in Intrinsic Josephson Junctions

    NASA Astrophysics Data System (ADS)

    Shukrinov, Yu. M.; Mahfouzi, F.

    2007-04-01

    We study theoretically the current-voltage characteristics of intrinsic Josephson junctions in high-Tc superconductors. An oscillation of the breakpoint current on the outermost branch as a function of coupling α and dissipation β parameters is found. We explain this oscillation as a result of the creation of longitudinal plasma waves at the breakpoint with different wave numbers. We demonstrate the commensurability effect and predict a group behavior of the current-voltage characteristics for the stacks with a different number of junctions. A method to determine the wave number of longitudinal plasma waves from α and β dependence of the breakpoint current is suggested. We model the α and β dependence of the breakpoint current and obtain good agreement with the results of the simulation.

  4. Artificial Photosynthesis with Semiconductor-Liquid Junctions.

    PubMed

    Guijarro, Néstor; Formal, Florian Le; Sivula, Kevin

    2015-01-01

    Given the urgent need to develop a sustainable, carbon neutral energy storage system on a global scale, intense efforts are currently underway to advance the field of artificial photosynthesis: i.e. solar fuel engineering. In this review we give an overview of the field of artificial photosynthesis using a semiconductor-electrolyte interface employed in a photoelectrochemical device or as a heterogeneous photocatalyst. First we present a basic description of the operation principles of a semiconductor-liquid junction based device. The role of nanotechnology in the recent advances in the field is highlighted and common material systems under current study are briefly reviewed. The importance of the material surfaces are further scrutinized by presenting recent advances in interfacial engineering. Technical challenges and an outlook towards industrialization of the technology are given.

  5. Studies of silicon pn junction solar cells

    NASA Technical Reports Server (NTRS)

    Lindholm, F. A.; Neugroschel, A.

    1977-01-01

    Modifications of the basic Shockley equations that result from the random and nonrandom spatial variations of the chemical composition of a semiconductor were developed. These modifications underlie the existence of the extensive emitter recombination current that limits the voltage over the open circuit of solar cells. The measurement of parameters, series resistance and the base diffusion length is discussed. Two methods are presented for establishing the energy bandgap narrowing in the heavily-doped emitter region. Corrections that can be important in the application of one of these methods to small test cells are examined. Oxide-charge-induced high-low-junction emitter (OCI-HLE) test cells which exhibit considerably higher voltage over the open circuit than was previously seen in n-on-p solar cells are described.

  6. Permanent junctional reciprocating tachycardia in a dog.

    PubMed

    Santilli, Roberto A; Santos, Luis F N; Perego, Manuela

    2013-09-01

    A 5-year-old male English Bulldog was presented with a 1-year history of paroxysmal supraventricular tachycardia (SVT) partially responsive to amiodarone. At admission the surface ECG showed sustained runs of a narrow QRS complex tachycardia, with a ventricular cycle length (R-R interval) of 260 ms, alternating with periods of sinus rhythm. Endocardial mapping identified the electrogenic mechanism of the SVT as a circus movement tachycardia with retrograde and decremental conduction along a concealed postero-septal atrioventricular pathway (AP) and anterograde conduction along the atrioventricular node. These characteristics were indicative of a permanent junctional reciprocating tachycardia (PJRT). Radiofrequency catheter ablation of the AP successfully terminated the PJRT, with no recurrence of tachycardia on Holter monitoring at 12 months follow-up.

  7. Ultrafast endocytosis at Caenorhabditis elegans neuromuscular junctions

    PubMed Central

    Watanabe, Shigeki; Liu, Qiang; Davis, M Wayne; Hollopeter, Gunther; Thomas, Nikita; Jorgensen, Nels B; Jorgensen, Erik M

    2013-01-01

    Synaptic vesicles can be released at extremely high rates, which places an extraordinary demand on the recycling machinery. Previous ultrastructural studies of vesicle recycling were conducted in dissected preparations using an intense stimulation to maximize the probability of release. Here, a single light stimulus was applied to motor neurons in intact Caenorhabditis elegans nematodes expressing channelrhodopsin, and the animals rapidly frozen. We found that docked vesicles fuse along a broad active zone in response to a single stimulus, and are replenished with a time constant of about 2 s. Endocytosis occurs within 50 ms adjacent to the dense projection and after 1 s adjacent to adherens junctions. These studies suggest that synaptic vesicle endocytosis may occur on a millisecond time scale following a single physiological stimulus in the intact nervous system and is unlikely to conform to current models of endocytosis. DOI: http://dx.doi.org/10.7554/eLife.00723.001 PMID:24015355

  8. Wnt Signaling in Neuromuscular Junction Development

    PubMed Central

    Koles, Kate

    2012-01-01

    Wnt proteins are best known for their profound roles in cell patterning, because they are required for the embryonic development of all animal species studied to date. Besides regulating cell fate, Wnt proteins are gaining increasing recognition for their roles in nervous system development and function. New studies indicate that multiple positive and negative Wnt signaling pathways take place simultaneously during the formation of vertebrate and invertebrate neuromuscular junctions. Although some Wnts are essential for the formation of NMJs, others appear to play a more modulatory role as part of multiple signaling pathways. Here we review the most recent findings regarding the function of Wnts at the NMJ from both vertebrate and invertebrate model systems. PMID:22510459

  9. Quantum Tunneling Current in Nanoscale Plasmonic Junctions

    NASA Astrophysics Data System (ADS)

    Zhang, Peng; Lau, Y. Y.; Gilgenbach, R. M.

    2014-10-01

    Recently, electron tunneling between plasmonic resonators is found to support quantum plasmon resonances, which may introduce new regimes in nano-optoelectronics and nonlinear optics. This revelation is of substantial interest to the fundamental problem of electron transport in nano-scale, for example, in a metal-insulator-metal junction (MIM), which has been continuously studied for decades. Here, we present a self-consistent model of electron transport in a nano-scale MIM, by solving the coupled Schrödinger and Poisson equations. The effects of space charge, exchange-correlation, anode emission, and material properties of the electrodes and insulator are examined in detail. The self-consistent calculations are compared with the widely used Simmons formula. Transition from the direct tunneling regime to the space-charge-limited regime is demonstrated. This work was supported by AFOSR.

  10. Functional oesophago-gastric junction imaging

    PubMed Central

    McMahon, Barry P; Drewes, Asbjørn Mohr; Gregersen, Hans

    2006-01-01

    Despite its role in disease there is still no definitive method to assess oesophago-gastric junction competence (OGJ). Traditionally the OGJ has been assessed using manometry with lower oesophageal sphincter pressure as the indicator. More recently this has been shown not to be a very reliable marker of sphincter function and competence against reflux. Disorders such as gastro-oesophageal reflux disease and to a lesser extend achalasia still effects a significant number of patients. This review looks at using a new technique known as impedance planimetry to profile the geometry and pressure in the OGJ during distension of a bag. The data gathered can be reconstructed into a dynamic representation of OGJ action. This has been shown to provide a useful representation of the OGJ and to show changes to the competence of the OGJ in terms of compliance and distensibility as a result of endoluminal therapy. PMID:16718804

  11. Pathology of the uterine tubal junction.

    PubMed

    Biffignandi, F

    1982-01-01

    First the Author reviews briefly the anatomy and the physiology of the Uterine-Tubal Junction (UTJ) with a main concern for the muscular pattern and the secretory activity of this part of the tube, in relation with the hormonal and nervous control. Speaking about the pathology of the UTJ that can impair fertility, different are the causes: chronic infections and their sequelae, salpingitis isthmica nodosa, polyps, iatrogenic lesions (mainly following sterilization procedures), congenital malformations. Other pathologies might be: ectopic pregnancies - 2.5% of all tubal pregnancies - and neoplasms even if not related to infertility. The therapy in most cases for restoring the continuity and hopefully the function of the tube is surgery through a microsurgical approach.

  12. Ultimately short ballistic vertical graphene Josephson junctions

    PubMed Central

    Lee, Gil-Ho; Kim, Sol; Jhi, Seung-Hoon; Lee, Hu-Jong

    2015-01-01

    Much efforts have been made for the realization of hybrid Josephson junctions incorporating various materials for the fundamental studies of exotic physical phenomena as well as the applications to superconducting quantum devices. Nonetheless, the efforts have been hindered by the diffusive nature of the conducting channels and interfaces. To overcome the obstacles, we vertically sandwiched a cleaved graphene monoatomic layer as the normal-conducting spacer between superconducting electrodes. The atomically thin single-crystalline graphene layer serves as an ultimately short conducting channel, with highly transparent interfaces with superconductors. In particular, we show the strong Josephson coupling reaching the theoretical limit, the convex-shaped temperature dependence of the Josephson critical current and the exceptionally skewed phase dependence of the Josephson current; all demonstrate the bona fide short and ballistic Josephson nature. This vertical stacking scheme for extremely thin transparent spacers would open a new pathway for exploring the exotic coherence phenomena occurring on an atomic scale. PMID:25635386

  13. Nonlinear nonequilibrium quasiparticle relaxation in Josephson junctions.

    PubMed

    Krasnov, V M

    2009-11-27

    I solve numerically a full set of nonlinear kinetic balance equations for stacked Josephson junctions, which allows analysis of strongly nonequilibrium phenomena. It is shown that nonlinearity becomes significant already at very small disequilibrium. The following new, nonlinear effects are obtained: (i) At even-gap voltages V = 2nDelta/e (n = 2, 3, ...) nonequilibrium bosonic bands overlap. This leads to enhanced emission of Omega = 2Delta bosons and to the appearance of dips in tunnel conductance. (ii) A new type of radiative solution is found at strong disequilibrium. It is characterized by the fast stimulated relaxation of quasiparticles. A stack in this state behaves as a light emitting diode and directly converts electric power to boson emission, without utilization of the ac-Josephson effect. The phenomenon can be used for realization of a new type of superconducting cascade laser in the THz frequency range.

  14. Terbinafine inhibits gap junctional intercellular communication.

    PubMed

    Lee, Ju Yeun; Yoon, Sei Mee; Choi, Eun Ju; Lee, Jinu

    2016-09-15

    Terbinafine is an antifungal agent that selectively inhibits fungal sterol synthesis by blocking squalene epoxidase. We evaluated the effect of terbinafine on gap junctional intercellular communication (GJIC). Fluorescence recovery after photobleaching (FRAP) and I-YFP GJIC assays revealed that terbinafine inhibits GJIC in a reversible and dose-dependent manner in FRT-Cx43 and LN215 cells. Treatment with terbinafine did not affect Cx43 phosphorylation status or intracellular Ca(2+) concentration, well-known action mechanisms of various GJIC blockers. While a structurally related chemical, naftifine, attenuated GJIC, epigallocatechin gallate, another potent squalene epoxidase inhibitor with a different structure, did not. These results suggest that terbinafine inhibits GJIC with a so far unknown mechanism of action. PMID:27487578

  15. Guiding chemical pulses through geometry: Y junctions.

    PubMed

    Qiao, L; Kevrekidis, I G; Punckt, C; Rotermund, H H

    2006-03-01

    We study computationally and experimentally the propagation of chemical pulses in complex geometries. The reaction of interest, CO oxidation, takes place on single crystal Pt(110) surfaces that are microlithographically patterned; they are also addressable through a focused laser beam, manipulated through galvanometer mirrors, capable of locally altering the crystal temperature and thus affecting pulse propagation. We focus on sudden changes in the domain shape (corners in a Y-junction geometry) that can affect the pulse dynamics; we also show how brief, localized temperature perturbations can be used to control reactive pulse propagation. The computational results are corroborated through experimental studies in which the pulses are visualized using reflection anisotropy microscopy. PMID:16605643

  16. Tight junction modulator and drug delivery.

    PubMed

    Matsuhisa, Koji; Kondoh, Masuo; Takahashi, Azusa; Yagi, Kiyohito

    2009-05-01

    Recent progress in pharmaceutical technology based on genomic and proteomic research has provided many drug candidates, including not only chemicals but peptides, antibodies and nucleic acids. These candidates do not show pharmaceutical activity without their absorption into systemic flow and movement from the systemic flow into the target tissue. Epithelial and endothelial cell sheets play a pivotal role in the barrier between internal and external body and tissues. Tight junctions (TJs) between adjacent epithelial cells limit the movement of molecules through the intercellular space in epithelial and endothelial cell sheets. Thus, a promising strategy for drug delivery is the modulation of TJ components to allow molecules to pass through the TJ-based cellular barriers. In this review, we discuss recent progress in the development of TJ modulators and the possibility of absorption enhancers and drug-delivery systems based on TJ components.

  17. Neuromuscular junction in a microfluidic device.

    PubMed

    Park, Hyun Sung; Liu, Su; McDonald, John; Thakor, Nitish; Yang, In Hong

    2013-01-01

    Malfunctions at the site of neuromuscular junction (NMJ) of post-injuries or diseases are major barriers to recovery of function. The ability to efficiently derive motor neurons (MN) from embryonic stem cells has indicated promise toward the development of new therapies in increasing functional outcomes post injury. Recent advances in micro-technologies have provided advanced culture platforms allowing compartmentalization of sub-cellular components of neurons. In this study, we combined these advances in science and technology to develop a compartmentalized in vitro NMJ model. The developed NMJ system is between mouse embryonic stem cell (mESC)-derived MNs and c2c12 myotubes cultured in a compartmentalized polydimethylsiloxane (PDMS) microfluidic device. While some functional in vitro NMJ systems have been reported, this system would further contribute to research in NMJ-related diseases by providing a system to study the site of action of NMJ aimed at improving promoting better functional recovery. PMID:24110317

  18. Investigation of polycrystalline ferroelectric tunnel junction

    NASA Astrophysics Data System (ADS)

    Hou, Pengfei; Wang, Jinbin; Zhong, Xiangli

    2016-07-01

    Ferroelectric tunnel junction (FTJ) is a breakthrough for addressing the nondestructive read in the ferroelectric random access memories. However, FTJs with nearly ideal characteristics have only been demonstrated on perovskite heterostructures that are deposited on closely lattice-matched and non-silicon substrates, or silicon substrates with epitaxial multilayer. In order to promote the application of FTJs, we develop a polycrystalline FTJ with ultrathin bottom electrode, in which the resistance variations exceed two orders of magnitude. And we achieve two stable logic states written and read easily using voltage pulses. Especially the device integrates with the silicon technology in modern microelectronics. Our results suggest new opportunities for ferroelectrics as nonvolatile resistive switching memory.

  19. Field-effect P-N junction

    DOEpatents

    Regan, William; Zettl, Alexander

    2015-05-05

    This disclosure provides systems, methods, and apparatus related to field-effect p-n junctions. In one aspect, a device includes an ohmic contact, a semiconductor layer disposed on the ohmic contact, at least one rectifying contact disposed on the semiconductor layer, a gate including a layer disposed on the at least one rectifying contact and the semiconductor layer and a gate contact disposed on the layer. A lateral width of the rectifying contact is less than a semiconductor depletion width of the semiconductor layer. The gate contact is electrically connected to the ohmic contact to create a self-gating feedback loop that is configured to maintain a gate electric field of the gate.

  20. Ultimately short ballistic vertical graphene Josephson junctions.

    PubMed

    Lee, Gil-Ho; Kim, Sol; Jhi, Seung-Hoon; Lee, Hu-Jong

    2015-01-01

    Much efforts have been made for the realization of hybrid Josephson junctions incorporating various materials for the fundamental studies of exotic physical phenomena as well as the applications to superconducting quantum devices. Nonetheless, the efforts have been hindered by the diffusive nature of the conducting channels and interfaces. To overcome the obstacles, we vertically sandwiched a cleaved graphene monoatomic layer as the normal-conducting spacer between superconducting electrodes. The atomically thin single-crystalline graphene layer serves as an ultimately short conducting channel, with highly transparent interfaces with superconductors. In particular, we show the strong Josephson coupling reaching the theoretical limit, the convex-shaped temperature dependence of the Josephson critical current and the exceptionally skewed phase dependence of the Josephson current; all demonstrate the bona fide short and ballistic Josephson nature. This vertical stacking scheme for extremely thin transparent spacers would open a new pathway for exploring the exotic coherence phenomena occurring on an atomic scale. PMID:25635386

  1. Controlling local currents in molecular junctions

    NASA Astrophysics Data System (ADS)

    Yadalam, Hari Kumar; Harbola, Upendra

    2016-09-01

    The effects of nonequilibrium constraints and dephasing on the circulating currents in molecular junctions are analyzed. Circulating currents are manifestations of quantum effects and can be induced either by externally applied bias or an external magnetic field through the molecular system. In a symmetric Aharonov-Bohm ring, bond currents have two contributions, bias driven and magnetic field driven. We analyze the competition between these two contributions and show that, as a consequence, current through one of the branches can be completely suppressed. We then study the effect of asymmetry (as a result of chemical substitution) on the current pathways inside the molecule and study asymmetry-induced circulating currents (without magnetic field) by tuning the coupling strength of the substituent (at finite bias).

  2. Optical trapping of microparticles using silicon nitride waveguide junctions and tapered-waveguide junctions on an optofluidic chip.

    PubMed

    Cai, Hong; Poon, Andrew W

    2012-10-01

    We study optical trapping of microparticles on an optofluidic chip using silicon nitride waveguide junctions and tapered-waveguide junctions. We demonstrate the trapping of single 1 μm-sized polystyrene particles using the evanescent field of waveguide junctions connecting a submicrometer-sized input-waveguide and a micrometer-sized output-waveguide. Particle trapping is localized in the vicinity of the junction. We also demonstrate trapping of one and two 1μm-sized polystyrene particles using tapered-waveguide junctions connecting a submicrometer-sized singlemode input-waveguide and a micrometer-sized multimode output-waveguide. Particle trapping occurs near the taper output end, the taper center and the taper input end, depending on the taper aspect ratio.

  3. Are ``Pinholes'' the Cause of Excess Current in Superconducting Tunnel Junctions? A Study of Andreev Current in Highly Resistive Junctions

    NASA Astrophysics Data System (ADS)

    Greibe, Tine; Stenberg, Markku P. V.; Wilson, C. M.; Bauch, Thilo; Shumeiko, Vitaly S.; Delsing, Per

    2011-03-01

    In highly resistive superconducting tunnel junctions, excess subgap current is usually observed and is often attributed to microscopic pinholes in the tunnel barrier. We have studied the subgap current in superconductor-insulator-superconductor (SIS) and superconductor-insulator-normal-metal (SIN) junctions. In Al/AlOx/Al junctions, we observed a decrease of 2 orders of magnitude in the current upon the transition from the SIS to the SIN regime, where it then matched theory. In Al/AlOx/Cu junctions, we also observed generic features of coherent diffusive Andreev transport in a junction with a homogenous barrier. We use the quasiclassical Keldysh-Green function theory to quantify single- and two-particle tunneling and find good agreement with experiment over 2 orders of magnitude in transparency. We argue that our observations rule out pinholes as the origin of the excess current.

  4. The bonded unipolar silicon-silicon junction

    NASA Astrophysics Data System (ADS)

    Bengtsson, Stefan; Andersson, Gert I.; Andersson, Mats O.; Engström, Olof

    1992-07-01

    The electrical and optical properties of wafer bonded unipolar silicon-silicon junctions were investigated. The interfaces, both n-n type and p-p type, were prepared using wafers with hydrophilic surfaces. The current versus voltage characteristics, the current transients following stepwise changes in the applied bias, and the capacitance versus voltage characteristics as well as the temperature dependence of the current and capacitance were experimentally obtained and theoretically modeled. The proposed model assumes two distributions of interface states, one of acceptors and one of donors, causing a potential barrier at the bonded interface. It is argued that the origins of the interface states are impurities and crystallographic defects in the interfacial region. The capacitance of the bonded structures includes contributions from the depletion regions as well as from minority carriers. When bonded n-n type samples were illuminated with light of photon energies larger than the silicon band gap the current across the junction increased. This is caused by the photogenerated increase in the minority carrier concentration in the interfacial region, which results in a lowering of the potential barrier. Illumination of n-n type structures with light of photon energies lower than the band gap caused a considerable photocurrent at low temperatures. In this case the observed behavior cannot be explained by interaction with the interface states. Instead, the mechanism is the change in the occupancy of deep electron traps caused by the illumination. These traps are located in the silicon in a small volume around the bonded interface with energies close to the center of the band gap and with a peak concentration of about 1013 cm-3. Impurities present on the silicon surfaces before bonding and impurities gettered to the bonded interface are possible reasons for the increased concentration of deep electron traps in the vicinity of the bonded interface.

  5. Incompressible Turbulent Wing-Body Junction Flow

    NASA Technical Reports Server (NTRS)

    Krishnamurthy, R.; Cagle, Corey D.; Chandra, S.

    1998-01-01

    The overall objective of this study is to contribute to the optimized design of fan bypass systems in advanced turbofan engines. Increasing the engine bypass ratios have provided a major boost in engine performance improvement over the last fifty years. An engine with high bypass ratio (11-16:1) such as the Advanced Ducted Propulsion (ADP) is being developed and is expected to provide an additional 25% improvement in overall efficiency over the early turbofans. Such significant improvements in overall efficiency would reduce the cost per seat mile, which is a major government and Industry challenge for the 21th century. The research is part of the Advanced Subsonic Technology (AST) program that involves a NASA, U.S. Industry and FAA partnership with the goal of a safe and highly productive global air transportation system. The immediate objective of the study is to perform numerical simulation of duct-strut interactions to elucidate the loss mechanisms associated with this configuration that is typical of advanced turbofan engines such as ADP. However, at present experimental data for a duct-strut configuration are not available. Thus, as a first step a wing-body junction flow would be studied and is the specific objective of the present study. At the outset it is to be recognized that while duct-strut interaction flow is similar to that of wing-body junction flows, there are some differences owing to the presence of a wall at both ends of the strut. Likewise, some differences are due to the sheared inflow (as opposed to a uniform inflow) velocity profile. It is however expected that some features of a wing-body junction flow would persist. Next, some of the salient aspects of the complex flow near a wing-body junction, as revealed by various studies reported in the literature will be reviewed. One of the principle characteristics of the juncture flow, is the presence of the mean flow components in a plane perpendicular to the direction of the oncoming free

  6. Differential effects of diltiazem on glutamate potentials and excitatory junctional potentials at the crayfish neuromuscular junction.

    PubMed Central

    Ishida, M; Shinozaki, H

    1980-01-01

    1. The effects of diltiazem on glutamate potentials and excitatory junctional potentials (e.j.p.s) were investigated in the crayfish neuromuscular junction. 2. When diltiazem (0.3 mM) was added to the perfusion fluid, the ionophoretic glutamate potential was reduced to about half, whereas the peak amplitude of successive e.j.p.s elicited by a train of pulses of 100/sec increased by about 2 times. 3. It was suggested that diltiazem was a non-competitive inhibitor of L-glutamate. The reduction of the response to applied glutamate was not due to the acceleration of desensitization of the glutamate receptor. The rate of recovery from desensitization was delayzed by diltiazem. 4. The increase in amplitude of e.j.p.s caused by diltiazem was due to the increase in membrane resistance. The quantum content and size of extracellular e.j.p.s were not affected by diltiazem. 5. It was substantiated using the micro-electrode technique that the glutamate sensitive area coincided with the neuromuscular junctional area. 6. The pharmacological difference between glutamate potentials and e.j.p.s revealed in the present study is difficult to explain on the glutamate transmitter hypothesis. One explanation worthy to be considered is that there are two pharmacologically different kinds of receptors sensitive to L-glutamate. PMID:7359406

  7. VEGF and Angiopoietin-1 exert opposing effects on cell junctions by regulating the Rho GEF Syx

    PubMed Central

    Ngok, Siu P.; Geyer, Rory; Liu, Miaoliang; Kourtidis, Antonis; Agrawal, Sudesh; Wu, Chuanshen; Seerapu, Himabindu Reddy; Lewis-Tuffin, Laura J.; Moodie, Karen L.; Huveldt, Deborah; Marx, Ruth; Baraban, Jay M.; Storz, Peter

    2012-01-01

    Vascular endothelial growth factor (VEGF) and Ang1 (Angiopoietin-1) have opposing effects on vascular permeability, but the molecular basis of these effects is not fully known. We report in this paper that VEGF and Ang1 regulate endothelial cell (EC) junctions by determining the localization of the RhoA-specific guanine nucleotide exchange factor Syx. Syx was recruited to junctions by members of the Crumbs polarity complex and promoted junction integrity by activating Diaphanous. VEGF caused translocation of Syx from cell junctions, promoting junction disassembly, whereas Ang1 maintained Syx at the junctions, inducing junction stabilization. The VEGF-induced translocation of Syx from EC junctions was caused by PKD1 (protein kinase D1)-mediated phosphorylation of Syx at Ser806, which reduced Syx association to its junctional anchors. In support of the pivotal role of Syx in regulating EC junctions, syx−/− mice had defective junctions, resulting in vascular leakiness, edema, and impaired heart function. PMID:23253477

  8. Spin transport and dynamics in the F/N junction

    NASA Astrophysics Data System (ADS)

    Li, Hua; Bedell, Kevin

    2015-03-01

    We study the spin transport in the low temperature regime (often referred to as the precession-dominated regime) between a ferromagnetic Fermi liquid (FFL) and a normal metal metallic Fermi liquid (NFL), the F/N junction, which is considered one of the basic spintronic devices. In particular, we explore the propagation of spin waves and transport of magnetization through the interface of the F/N junction where non-equilibrium spin polarization is created on the normal metal side of the junction by spin injection. We calculate the probable spin wave modes in the precession-dominated regime on both sides of the junction especially on the NFL side where the system is out of equilibrium. Proper boundary conditions at the interface are introduced to establish the transport of the spin properties through the F/N junction. In the end, a possible transmission conduction electron spin resonance experiment is suggested on the F/N junction to see if the predicted spin wave modes could propagate through the junction.

  9. Gold plasmonic effects on charge transport through single molecule junctions

    NASA Astrophysics Data System (ADS)

    Adak, Olgun; Venkataraman, Latha

    2014-03-01

    We study the impact of surface plasmon polaritons, the coupling of electromagnetic waves to collective electron oscillations on metal surfaces, on the conductance of single-molecule junctions. We use a scanning-tunneling microscope based break junction setup that is built into an optical microscope to form molecular junctions. Coherent 685nm light is used to illuminate the molecular junctions formed with 4,4'-bipyridine with diffraction limited focusing performance. We employ a lock-in type technique to measure currents induced by light. Furthermore, the thermal expansion due to laser heating is mimicked by mechanically modulating inter-electrode separation. For each junction studied, we measure current, and use AC techniques to determine molecular junction resonance levels and coupling strengths. We use a cross correlations analysis technique to analyze and compare the effect of light to that of the mechanical modulation. Our results show that junction transmission characteristics are not altered under illumination, within the resolution of our instrument. We argue that photo-currents measured with lock-in techniques in these kinds of structures are due to thermal effects. This work was funded by the Center for Re-Defining Photovoltaic Efficiency through Molecule Scale Control, an EFRC funded by the US Department of Energy, Office of Basic Energy Sciences under Contract No. DESC0001085.

  10. Organization of multiprotein complexes at cell–cell junctions

    PubMed Central

    2008-01-01

    The formation of stable cell–cell contacts is required for the generation of barrier-forming sheets of epithelial and endothelial cells. During various physiological processes like tissue development, wound healing or tumorigenesis, cellular junctions are reorganized to allow the release or the incorporation of individual cells. Cell–cell contact formation is regulated by multiprotein complexes which are localized at specific structures along the lateral cell junctions like the tight junctions and adherens junctions and which are targeted to these site through their association with cell adhesion molecules. Recent evidence indicates that several major protein complexes exist which have distinct functions during junction formation. However, this evidence also indicates that their composition is dynamic and subject to changes depending on the state of junction maturation. Thus, cell–cell contact formation and integrity is regulated by a complex network of protein complexes. Imbalancing this network by oncogenic proteins or pathogens results in barrier breakdown and eventually in cancer. Here, I will review the molecular organization of the major multiprotein complexes at junctions of epithelial cells and discuss their function in cell–cell contact formation and maintenance. PMID:18365233

  11. Sorin Solo stentless valve: extended adaptability for sinotubular junction mismatch.

    PubMed

    Weltert, Luca; De Paulis, Ruggero; Maselli, Daniele; Scaffa, Raffaele

    2008-08-01

    Stentless valve continence is affected by the implantation technique, annular symmetry and dilatation of the sinotubular junction. We tested in vitro how the Sorin Solo stentless pericardial valve adapts to a slightly dilated sinotubular junction. Stentless Sorin Solo aortic valves (25 mm) were sutured into a 32-mm Valsalva graft suspending the commissures into the expandable region of the graft. The neo-aortic root was pressurized and sinotubular junction size progressively decreased by wrapping the neocommissural ridge with Dacron rings. Direct endoscopic view and ultrasound imaging were used to observe geometry and morphology of leaflets, regurgitation, height and level of leaflets coaptation. Fresh porcine valves of the same annular size were used as controls. Solo valves had mild regurgitation at baseline, became continent at 32 mm sinotubular junction size and remained continent at any size of reduction, with optimal coaptation height and level. Porcine valves had severe regurgitation at baseline, became continent at 30 mm and showed mild insufficiency and reduction of the coaptation level at a sinotubular junction of 28 mm. The Solo valve prevents residual valve regurgitation for a wider range of sinotubular junction mismatch when compared with natural porcine valves. This extended tolerance to sinotubular junction mismatch suggests a safe use of stentless valves even in suboptimal geometry roots.

  12. High electronic couplings of single mesitylene molecular junctions

    PubMed Central

    Komoto, Yuki; Nishino, Tomoaki; Kiguchi, Manabu

    2015-01-01

    Summary We report on an experimental analysis of the charge transport properties of single mesitylene (1,3,5-trimethylbenzene) molecular junctions. The electronic conductance and the current–voltage characteristics of mesitylene molecules wired into Au electrodes were measured by a scanning tunnelling microscopy-based break-junction method at room temperature in a liquid environment. We found the molecular junctions exhibited two distinct conductance states with high conductance values of ca. 10−1 G 0 and of more than 10−3 G 0 (G 0 = 2e 2/h) in the electronic conductance measurements. We further performed a statistical analysis of the current–voltage characteristics of the molecular junctions in the two states. Within a single channel resonant tunnelling model, we obtained electronic couplings in the molecular junctions by fitting the current–voltage characteristics to the single channel model. The origin of the high conductance was attributed to experimentally obtained large electronic couplings of the direct π-bonded molecular junctions (ca. 0.15 eV). Based on analysis of the stretch length of the molecular junctions and the large electronic couplings obtained from the I–V analysis, we proposed two structural models, in which (i) mesitylene binds to the Au electrode perpendicular to the charge transport direction and (ii) mesitylene has tilted from the perpendicular orientation. PMID:26732978

  13. Mechanical deformations of boron nitride nanotubes in crossed junctions

    NASA Astrophysics Data System (ADS)

    Zhao, Yadong; Chen, Xiaoming; Park, Cheol; Fay, Catharine C.; Stupkiewicz, Stanislaw; Ke, Changhong

    2014-04-01

    We present a study of the mechanical deformations of boron nitride nanotubes (BNNTs) in crossed junctions. The structure and deformation of the crossed tubes in the junction are characterized by using atomic force microscopy. Our results show that the total tube heights are reduced by 20%-33% at the crossed junctions formed by double-walled BNNTs with outer diameters in the range of 2.21-4.67 nm. The measured tube height reduction is found to be in a nearly linear relationship with the summation of the outer diameters of the two tubes forming the junction. The contact force between the two tubes in the junction is estimated based on contact mechanics theories and found to be within the range of 4.2-7.6 nN. The Young's modulus of BNNTs and their binding strengths with the substrate are quantified, based on the deformation profile of the upper tube in the junction, and are found to be 1.07 ± 0.11 TPa and 0.18-0.29 nJ/m, respectively. Finally, we perform finite element simulations on the mechanical deformations of the crossed BNNT junctions. The numerical simulation results are consistent with both the experimental measurements and the analytical analysis. The results reported in this paper contribute to a better understanding of the structural and mechanical properties of BNNTs and to the pursuit of their applications.

  14. Mechanical deformations of boron nitride nanotubes in crossed junctions

    SciTech Connect

    Zhao, Yadong; Chen, Xiaoming; Ke, Changhong; Park, Cheol; Fay, Catharine C.; Stupkiewicz, Stanislaw

    2014-04-28

    We present a study of the mechanical deformations of boron nitride nanotubes (BNNTs) in crossed junctions. The structure and deformation of the crossed tubes in the junction are characterized by using atomic force microscopy. Our results show that the total tube heights are reduced by 20%–33% at the crossed junctions formed by double-walled BNNTs with outer diameters in the range of 2.21–4.67 nm. The measured tube height reduction is found to be in a nearly linear relationship with the summation of the outer diameters of the two tubes forming the junction. The contact force between the two tubes in the junction is estimated based on contact mechanics theories and found to be within the range of 4.2–7.6 nN. The Young's modulus of BNNTs and their binding strengths with the substrate are quantified, based on the deformation profile of the upper tube in the junction, and are found to be 1.07 ± 0.11 TPa and 0.18–0.29 nJ/m, respectively. Finally, we perform finite element simulations on the mechanical deformations of the crossed BNNT junctions. The numerical simulation results are consistent with both the experimental measurements and the analytical analysis. The results reported in this paper contribute to a better understanding of the structural and mechanical properties of BNNTs and to the pursuit of their applications.

  15. Development of cell junctions in sea-urchin embryos.

    PubMed

    Spiegel, E; Howard, L

    1983-07-01

    The development of cell junctions in sea-urchin embryos has been investigated using thin sections, lanthanum-tracer and freeze-fracture techniques. Three types of desmosomes are present: belt desmosomes and spot desmosomes, which attach cells to each other, and hemi-desmosomes, which attach cells to the basement membrane. Two types of septate junctions are present: the straight, unbranched, double-septum septate, which is present in epithelial cells throughout embryogenesis, and the pleated, anastomosing, single-septum septate. The latter is formed only on cells that have invaginated to the interior of the embryo to form the digestive tract. The pleated junctions are shown to replace the straight junctions that were originally present before the cells migrated to the interior. It is suggested that these pleated septates may be specialized for digestive processes, since they are developed just prior to feeding and are retained in the adult intestine. Tricellular junctions, which join the bicellular junctions of three adjoining cells, have been identified in the embryo and in the adult intestine. Evidence for the presence of gap junctions was not obtained, but there are indications of their presence.

  16. Epithelial junctions and Rho family GTPases: the zonular signalosome

    PubMed Central

    Citi, Sandra; Guerrera, Diego; Spadaro, Domenica; Shah, Jimit

    2014-01-01

    The establishment and maintenance of epithelial cell-cell junctions is crucially important to regulate adhesion, apico-basal polarity and motility of epithelial cells, and ultimately controls the architecture and physiology of epithelial organs. Junctions are supported, shaped and regulated by cytoskeletal filaments, whose dynamic organization and contractility are finely tuned by GTPases of the Rho family, primarily RhoA, Rac1 and Cdc42. Recent research has identified new molecular mechanisms underlying the cross-talk between these GTPases and epithelial junctions. Here we briefly summarize the current knowledge about the organization, molecular evolution and cytoskeletal anchoring of cell-cell junctions, and we comment on the most recent advances in the characterization of the interactions between Rho GTPases and junctional proteins, and their consequences with regards to junction assembly and regulation of cell behavior in vertebrate model systems. The concept of “zonular signalosome” is proposed, which highlights the close functional relationship between proteins of zonular junctions (zonulae occludentes and adhaerentes) and the control of cytoskeletal organization and signaling through Rho GTPases, transcription factors, and their effectors. PMID:25483301

  17. Josephson radiation from InSb-nanowire junction

    NASA Astrophysics Data System (ADS)

    van Woerkom, David; Proutski, Alexander; Krivachy, Tamas; Bouman, Daniel; van Gulik, Ruben; Gul, Onder; Cassidy, Maja; Car, Diana; Bakkers, Erik; Kouwenhoven, Leo; Geresdi, Attila

    Semiconducting nanowire Josephson junctions has recently gained interest as building blocks for Majorana circuits and gate-tuneable superconducting qubits . Here we investigate the rich physics of the Andreev bound state spectrum of InSb nanowire junctions utilizing the AC Josephson relation 2eV_bias =hf . We designed and characterized an on-chip microwave circuit coupling the nanowire junction to an Al/AlOx/Al tunnel junction. The DC response of the tunnel junction is affected by photon-assisted quasiparticle current, which gives us the possibility to measure the radiation spectrum of the nanowire junction up to several tens of GHz in frequency. Our circuit design allows for voltage or phase biasing of the Josephson junction enabling direct mapping of Andreev bound states. We discuss our fabrication methods and choice of materials to achieve radiation detection up to a magnetic field of few hundred milliTesla, compatible with Majorana states in spin-orbit coupled nanowires. This work has been supported by the Netherlands Foundations FOM, Abstract NWO and Microsoft Corporation Station Q.

  18. Thin-film Josephson junctions with alternating critical current density

    NASA Astrophysics Data System (ADS)

    Moshe, Maayan; Kogan, V. G.; Mints, R. G.

    2009-01-01

    We study the field dependence of the maximum current Im(H) in narrow edge-type thin-film Josephson junctions with alternating critical current density. Im(H) is evaluated within nonlocal Josephson electrodynamics taking into account the stray fields that affect the difference of the order-parameter phases across the junction and therefore the tunneling currents. We find that the phase difference along the junction is proportional to the applied field, depends on the junction geometry, but is independent of the Josephson critical current density gc , i.e., it is universal. An explicit form for this universal function is derived for small currents through junctions of the width W≪Λ , the Pearl length. The result is used to calculate Im(H) . It is shown that the maxima of Im(H)∝1/H and the zeros of Im(H) are equidistant but only in high fields. We find that the spacing between zeros is proportional to 1/W2 . The general approach is applied to calculate Im(H) for a superconducting quantum interference device with two narrow edge-type junctions. If gc changes sign periodically or randomly, as it does in grain boundaries of high- Tc materials and superconductor-ferromagnet-superconductor heterostructures, Im(H) not only acquires the major side peaks, but due to nonlocality the following peaks decay much slower than in bulk junctions.

  19. Epithelial junctions and Rho family GTPases: the zonular signalosome.

    PubMed

    Citi, Sandra; Guerrera, Diego; Spadaro, Domenica; Shah, Jimit

    2014-01-01

    The establishment and maintenance of epithelial cell-cell junctions is crucially important to regulate adhesion, apico-basal polarity and motility of epithelial cells, and ultimately controls the architecture and physiology of epithelial organs. Junctions are supported, shaped and regulated by cytoskeletal filaments, whose dynamic organization and contractility are finely tuned by GTPases of the Rho family, primarily RhoA, Rac1 and Cdc42. Recent research has identified new molecular mechanisms underlying the cross-talk between these GTPases and epithelial junctions. Here we briefly summarize the current knowledge about the organization, molecular evolution and cytoskeletal anchoring of cell-cell junctions, and we comment on the most recent advances in the characterization of the interactions between Rho GTPases and junctional proteins, and their consequences with regards to junction assembly and regulation of cell behavior in vertebrate model systems. The concept of "zonular signalosome" is proposed, which highlights the close functional relationship between proteins of zonular junctions (zonulae occludentes and adhaerentes) and the control of cytoskeletal organization and signaling through Rho GTPases, transcription factors, and their effectors.

  20. Incompressible Turbulent Wing-Body Junction Flow

    NASA Technical Reports Server (NTRS)

    Krishnamurthy, R.; Cagle, Corey D.; Chandra, S.

    1998-01-01

    The overall objective of this study is to contribute to the optimized design of fan bypass systems in advanced turbofan engines. Increasing the engine bypass ratios have provided a major boost in engine performance improvement over the last fifty years. An engine with high bypass ratio (11-16:1) such as the Advanced Ducted Propulsion (ADP) is being developed and is expected to provide an additional 25% improvement in overall efficiency over the early turbofans. Such significant improvements in overall efficiency would reduce the cost per seat mile, which is a major government and Industry challenge for the 21th century. The research is part of the Advanced Subsonic Technology (AST) program that involves a NASA, U.S. Industry and FAA partnership with the goal of a safe and highly productive global air transportation system. The immediate objective of the study is to perform numerical simulation of duct-strut interactions to elucidate the loss mechanisms associated with this configuration that is typical of advanced turbofan engines such as ADP. However, at present experimental data for a duct-strut configuration are not available. Thus, as a first step a wing-body junction flow would be studied and is the specific objective of the present study. At the outset it is to be recognized that while duct-strut interaction flow is similar to that of wing-body junction flows, there are some differences owing to the presence of a wall at both ends of the strut. Likewise, some differences are due to the sheared inflow (as opposed to a uniform inflow) velocity profile. It is however expected that some features of a wing-body junction flow would persist. Next, some of the salient aspects of the complex flow near a wing-body junction, as revealed by various studies reported in the literature will be reviewed. One of the principle characteristics of the juncture flow, is the presence of the mean flow components in a plane perpendicular to the direction of the oncoming free

  1. [The morse taper junction in modular revision hip replacement].

    PubMed

    Gravius, S; Mumme, T; Andereya, S; Maus, U; Müller-Rath, R; Wirtz, D C

    2007-01-01

    Morse taper junctions of modular hip revision replacements are predilection sites for fretting, crevice corrosion, dissociation and breakage of the components. In this report we present the results of a retrieval analysis of a morse taper junction of a MRP-titanium modular revision replacement (MRP-Titanium, Peter Brehm GmbH, Weisendorf, Germany) after 11.5 years of in vivo use. In the context of this case report the significance of morse taper junctions in modular hip revision replacement under consideration of the current literature is also discussed.

  2. Bloch inductance in small-capacitance Josephson junctions.

    PubMed

    Zorin, A B

    2006-04-28

    We show that the electrical impedance of a small-capacitance Josephson junction also includes, in addition to the capacitive term -i/(omega)CB, an inductive term i(omega)LB. Similar to the known Bloch capacitance CB(q), the Bloch inductance LB(q) also depends periodically on the quasicharge, q, and its maximum value achieved at q=e(mod 2e) always exceeds the value of the Josephson inductance of this junction LJ(phi) at fixed phi=0. The effect of the Bloch inductance on the dynamics of a single junction and a one-dimensional array is described.

  3. Two new septate junctions in the phylum Coelenterata.

    PubMed

    Green, C R; Flower, N E

    1980-04-01

    Freeze-fracture of fixed and unfixed tissue, lanthanum tracer and conventional thin-section studies have revealed 2 new types of septate junction in the class Anthozoa, phylum Coelenterata. These new junctions have the 15-18-nm intercellular spacing of all other described septate junctions and are found around the apical circumference of cells lining a lumen or outside edge. However, in freeze-fracture replicas and tangential views of lanthanum-impregnated tissue, they are seen to be quite different from other known septate junction types. One of the new junctions is found in endothelial tissue such as that lining the gut or the inside of the tentacles. In tangential view it is seen to consist of relatively short, straight, double septa, again with lateral projections. In feeeze-fracture of unfixed tissue, the junction consists of double rows of particles on the P face, the particles of one row being rounded, those of the other being elongated at right angles to the line of the septum. This dichotomy in particle size is unexpected, as the 2 halves of the septa as seen in tangential view are symmetrical. In freeze-fracture of fixed material the particle arrays remain on the P face and appear similar to those of unfixed material, but never as clear. In fixed tissue, some distortion had occurred and in extreme cases septa appear as a single broad jumbled row of particles. In this double septa junction, the rows of particles seen in freeze-fracture are occasionally seen to anastomose with a septum dividing into 2 and a third row of particles aligning with the 2 new septa to form their double particle rows. In both fixed and unfixed tissues, the E face of the junction consists of wide, shallow grooves. The second of the new junctions occurs in epithelial tissue, such as around the outer edge of sea-anemone tentacles, and consists of long wavy septa with lateral projections. In views where these projections appear longest, they arise predominantly from one side of the

  4. Effect of current injection into thin-film Josephson junctions

    SciTech Connect

    Kogan, V. G.; Mints, R. G.

    2014-11-11

    New thin-film Josephson junctions have recently been tested in which the current injected into one of the junction banks governs Josephson phenomena. One thus can continuously manage the phase distribution at the junction by changing the injected current. Our method of calculating the distribution of injected currents is also proposed for a half-infinite thin-film strip with source-sink points at arbitrary positions at the film edges. The strip width W is assumed small relative to Λ=2λ2/d;λ is the bulk London penetration depth of the film material and d is the film thickness.

  5. Effect of current injection into thin-film Josephson junctions

    DOE PAGESBeta

    Kogan, V. G.; Mints, R. G.

    2014-11-11

    New thin-film Josephson junctions have recently been tested in which the current injected into one of the junction banks governs Josephson phenomena. One thus can continuously manage the phase distribution at the junction by changing the injected current. Our method of calculating the distribution of injected currents is also proposed for a half-infinite thin-film strip with source-sink points at arbitrary positions at the film edges. The strip width W is assumed small relative to Λ=2λ2/d;λ is the bulk London penetration depth of the film material and d is the film thickness.

  6. Gap junction modulation and its implications for heart function

    PubMed Central

    Kurtenbach, Stefan; Kurtenbach, Sarah; Zoidl, Georg

    2014-01-01

    Gap junction communication (GJC) mediated by connexins is critical for heart function. To gain insight into the causal relationship of molecular mechanisms of disease pathology, it is important to understand which mechanisms contribute to impairment of gap junctional communication. Here, we present an update on the known modulators of connexins, including various interaction partners, kinases, and signaling cascades. This gap junction network (GJN) can serve as a blueprint for data mining approaches exploring the growing number of publicly available data sets from experimental and clinical studies. PMID:24578694

  7. Stabilization of ion concentration polarization using a heterogeneous nanoporous junction

    NASA Astrophysics Data System (ADS)

    Kim, Pilnam; Kim, Sung Jae; Han, Jongyoon; Suh, Kahp Y.

    2009-11-01

    We demonstrate a recycled ion -- flux through heterogeneous nanoporous junctions, which induce stable ion concentration polarization (ICP) with an electric field. The nanoporous junctions are based on integration of ionic hydrogels whose surfaces are negatively- and positively- charged for cationic selectivity and anionic selectivity, respectively. It is shown that a `heterojunction' structure with cationic selective hydrogels (CSH) and anionic selective hydrogels (ASH) can be matched up in a way to achieve continuous ion-flux operation for stable concentration gradient or ionic conductance. Furthermore, the combined junctions can be used to accumulate ions on a specific region of the device.

  8. Nonequilibrium and proximity effects in superconductor-normal metal junctions

    NASA Astrophysics Data System (ADS)

    Kauppila, V. J.; Nguyen, H. Q.; Heikkilä, T. T.

    2013-08-01

    We study the consequences of nonequilibrium heating and inverse proximity effect in normal metal-insulator-superconductor-insulator-normal metal (NISIN) junctions with a simple quasi-one-dimensional model. We especially focus on observables and parameter regions that are of interest in the design of SINIS coolers with quasiparticle traps. We present numerical results calculated by solving the Usadel equation and also present analytical approximations in two limiting cases: a short junction with a non-negligible resistance in both ends and a long junction with a transparent contact at one end.

  9. Junction Temperature Measurement of IGBTs Using Short Circuit Current

    SciTech Connect

    Wang, Fei; Xu, Zhuxian; Ning, Puqi

    2012-01-01

    In this paper, a method is proposed to measure the junction temperatures of IGBT discrete devices and modules using short circuit current. Experimental results show that the short circuit current has good sensitivity, linearity and selectivity, which is suitable to be used as temperature sensitive electrical parameters (TSEP). Test circuit and hardware design are proposed for junction temperature measurement in single phase and three phase convertes. By connecting a temperature measurement unit to the converter and giving a short circuit pulse, the IGBT junction temperature can be measured.

  10. Vortex structure in a long Josephson junction with two inhomogeneities

    NASA Astrophysics Data System (ADS)

    Andreeva, O. Yu.; Boyadjiev, T. L.; Shukrinov, Yu. M.

    2007-09-01

    We study the vortex structure in the long Josephson junctions with one and two rectangular inhomogeneities in the barrier layer. In case of one inhomogeneity we demonstrate the existence of the asymmetric fluxon states. The disappearance of the mixed fluxon-antifluxon states is shown when the position of the inhomogeneity shifted to the end of the junction. In case of two inhomogeneities the change of the amplitude of Josephson current through the inhomogeneity in the end of the junction makes strong effect on the stability of the fluxon states and smoothes the maximums on the dependence “critical current-magnetic field”.

  11. Statistical mechanics of strings with Y-junctions

    SciTech Connect

    Rivers, R. J.; Steer, D. A.

    2008-07-15

    We investigate the Hagedorn transitions of string networks with Y-junctions as may occur, for example, with (p,q) cosmic superstrings. In a simplified model with three different types of string, the partition function reduces to three generalized coupled XY models. We calculate the phase diagram and show that, as the system is heated, the lightest strings first undergo the Hagedorn transition despite the junctions. There is then a second, higher, critical temperature above which infinite strings of all tensions, and junctions, exist. Conversely, on cooling to low temperatures, only the lightest strings remain, but they collapse into small loops.

  12. Compact tunable sub-terahertz oscillators based on Josephson junctions

    NASA Astrophysics Data System (ADS)

    Song, Fengbin; Müller, Franz; Scheller, Thomas; Semenov, Alexei; He, Ming; Fang, Lan; Hübers, Heinz-Wilhelm; Klushin, Alexander M.

    2011-04-01

    Essential applications of terahertz technology are urgently in need of compact, tunable solid-state continuous wave radiation sources. However, no satisfactory solution is yet available for the frequency range of up to approximately 1.0 THz. Here, we present coherent radiation from large series arrays of Josephson junctions between 0.1 and 0.25 THz with off-chip radiation power of 7 μW. Niobium junctions oscillate at 4.2 K and the detection has been done at room temperature. The well-known obstacle to impedance matching is overcome by utilizing the excited resonances in the junction substrates serving as dielectric resonator antennae.

  13. Effect of current injection into thin-film Josephson junctions

    NASA Astrophysics Data System (ADS)

    Kogan, V. G.; Mints, R. G.

    2014-11-01

    New thin-film Josephson junctions have recently been tested in which the current injected into one of the junction banks governs Josephson phenomena. One thus can continuously manage the phase distribution at the junction by changing the injected current. A method of calculating the distribution of injected currents is proposed for a half-infinite thin-film strip with source-sink points at arbitrary positions at the film edges. The strip width W is assumed small relative to Λ =2 λ2/d ;λ is the bulk London penetration depth of the film material and d is the film thickness.

  14. High thermopower of mechanically stretched single-molecule junctions.

    PubMed

    Tsutsui, Makusu; Morikawa, Takanori; He, Yuhui; Arima, Akihide; Taniguchi, Masateru

    2015-01-01

    Metal-molecule-metal junction is a promising candidate for thermoelectric applications that utilizes quantum confinement effects in the chemically defined zero-dimensional atomic structure to achieve enhanced dimensionless figure of merit ZT. A key issue in this new class of thermoelectric nanomaterials is to clarify the sensitivity of thermoelectricity on the molecular junction configurations. Here we report simultaneous measurements of the thermoelectric voltage and conductance on Au-1,4-benzenedithiol (BDT)-Au junctions mechanically-stretched in-situ at sub-nanoscale. We obtained the average single-molecule conductance and thermopower of 0.01 G0 and 15 μV/K, respectively, suggesting charge transport through the highest occupied molecular orbital. Meanwhile, we found the single-molecule thermoelectric transport properties extremely-sensitive to the BDT bridge configurations, whereby manifesting the importance to design the electrode-molecule contact motifs for optimizing the thermoelectric performance of molecular junctions. PMID:26112999

  15. Thermoelectricity in atom-sized junctions at room temperatures.

    PubMed

    Tsutsui, Makusu; Morikawa, Takanori; Arima, Akihide; Taniguchi, Masateru

    2013-01-01

    Atomic and molecular junctions are an emerging class of thermoelectric materials that exploit quantum confinement effects to obtain an enhanced figure of merit. An important feature in such nanoscale systems is that the electron and heat transport become highly sensitive to the atomic configurations. Here we report the characterization of geometry-sensitive thermoelectricity in atom-sized junctions at room temperatures. We measured the electrical conductance and thermoelectric power of gold nanocontacts simultaneously down to the single atom size. We found junction conductance dependent thermoelectric voltage oscillations with period 2e(2)/h. We also observed quantum suppression of thermovoltage fluctuations in fully-transparent contacts. These quantum confinement effects appeared only statistically due to the geometry-sensitive nature of thermoelectricity in the atom-sized junctions. The present method can be applied to various nanomaterials including single-molecules or nanoparticles and thus may be used as a useful platform for developing low-dimensional thermoelectric building blocks. PMID:24270238

  16. Raman scattering in molecular junctions: a pseudoparticle formulation.

    PubMed

    White, Alexander J; Tretiak, Sergei; Galperin, Michael

    2014-02-12

    We present a formulation of Raman spectroscopy in molecular junctions based on a many-body state representation of the molecule. The approach goes beyond the previous effective single orbital formalism and provides a convenient way to incorporate computational methods and tools proven for equilibrium molecular spectroscopy into the realm of current carrying junctions. The presented framework is illustrated by first principle simulations of Raman response in a three-ring oligophenylene vinylene terminating in amine functional groups (OPV3) junction. The calculated shift in Stokes lines and estimate of vibrational heating by electric current agree with available experimental data. In particular, our results suggest that participation of the OPV3 cation in Raman scattering under bias may be responsible for the observed shift, and that the direction of the shift depends on renormalization of normal modes. This work is a step toward atomistic quantum ab initio modeling of the optical response of nonequilibrium electronic dynamics in molecular junctions. PMID:24447295

  17. Triple junction and grain boundary character distributions in metallic materials

    SciTech Connect

    Fortier, P.; Miller, W.A.; Aust, K.T.

    1997-08-01

    Triple junction and grain boundary orientations were obtained by electron backscattered diffraction in high purity aluminium and copper, and in copper-bismuth alloys, and were then characterized using the CSL, CAD and I-line (O-lattice) geometrical models. A computer simulation was also performed and compared to the experimental results. Relationships were established between triple junction and grain boundary character distributions using both experimental and computer simulated results. A general trend was observed which shows an increase in special triple junction character density with increasing special grain boundary character content. An increased frequency of low angle and twin boundaries is shown to lead to an increase in the I-line triple junction density.

  18. 10. DETAIL OF JUNCTION BETWEEN LOWER CHORD, VERTICAL LACED CHANNEL, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    10. DETAIL OF JUNCTION BETWEEN LOWER CHORD, VERTICAL LACED CHANNEL, FLOOR BEAM, EYE BAR, AND U-BOLT. WEST ABUTMENT. - River Road Bridge, Spanning Spring Creek in Spring Creek Township, Hallton, Elk County, PA

  19. Evidence for nonlocal electrodynamics in planar Josephson junctions.

    PubMed

    Boris, A A; Rydh, A; Golod, T; Motzkau, H; Klushin, A M; Krasnov, V M

    2013-09-13

    We study the temperature dependence of the critical current modulation I(c)(H) for two types of planar Josephson junctions: a low-Tc Nb/CuNi/Nb and a high-Tc YBa2Cu3O(7-δ) bicrystal grain-boundary junction. At low T both junctions exhibit a conventional behavior, described by the local sine-Gordon equation. However, at elevated T the behavior becomes qualitatively different: the I(c)(H) modulation field ΔH becomes almost T independent and neither ΔH nor the critical field for the penetration of Josephson vortices vanish at Tc. Such an unusual behavior is in good agreement with theoretical predictions for junctions with nonlocal electrodynamics. We extract absolute values of the London penetration depth λ from our data and show that a crossover from local to nonlocal electrodynamics occurs with increasing T when λ(T) becomes larger than the electrode thickness.

  20. The influence of the instabilities in modelling arteriovenous junction haemodynamics.

    PubMed

    Broderick, Stephen P; Houston, J Graeme; Walsh, Michael T

    2015-10-15

    The arteriovenous junction is characterised by high flow rates, large pressure difference and typically a palpable thrill or audible bruit, associated with turbulent flow. However, the arteriovenous junction is frequently studied with the assumption of streamline flow. This assumption is based on the Reynolds number calculation, although other factors can contribute to turbulent generation. In this study, the presence of instabilities is examined and the influencing factors discussed. This was performed using a pseudo-realistic geometry with adapted graft angles, vein diameter, outflow split ratio and graft inlet velocity values. Correlation was performed between steady and unsteady averaged simulation cases with correlation performance ranked. Overall the arteriovenous junction is capable of possessing highly disturbed flows, in which strict modelling requirements are necessary to capture such instabilities and avoid erroneous conclusions. Vein diameter and flow split ratio contribute to turbulent generation, thus Reynolds number cannot be used as a sole turbulent criterion in the arteriovenous junction. PMID:26315920

  1. View of Highway 140 and Overhang Rock. Location of junction ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View of Highway 140 and Overhang Rock. Location of junction with Old Coulterville Road behind rock. Looking north-northwest - All Year Highway, Between Arch Rock & Yosemite Valley, El Portal, Mariposa County, CA

  2. Macroscopic quantum tunnelling in spin filter ferromagnetic Josephson junctions.

    PubMed

    Massarotti, D; Pal, A; Rotoli, G; Longobardi, L; Blamire, M G; Tafuri, F

    2015-01-01

    The interfacial coupling of two materials with different ordered phases, such as a superconductor (S) and a ferromagnet (F), is driving new fundamental physics and innovative applications. For example, the creation of spin-filter Josephson junctions and the demonstration of triplet supercurrents have suggested the potential of a dissipationless version of spintronics based on unconventional superconductivity. Here we demonstrate evidence for active quantum applications of S-F-S junctions, through the observation of macroscopic quantum tunnelling in Josephson junctions with GdN ferromagnetic insulator barriers. We show a clear transition from thermal to quantum regime at a crossover temperature of about 100 mK at zero magnetic field in junctions, which present clear signatures of unconventional superconductivity. Following previous demonstration of passive S-F-S phase shifters in a phase qubit, our result paves the way to the active use of spin filter Josephson systems in quantum hybrid circuits. PMID:26054495

  3. Manipulating Josephson junctions in thin-films by nearby vortices

    SciTech Connect

    Kogan, V G; Mints, R G

    2014-07-01

    It is shown that a vortex trapped in one of the banks of a planar edge-type Josephson junction in a narrow thin-film superconducting strip can change drastically the dependence of the junction critical current on the applied field, I-c(H). When the vortex is placed at certain discrete positions in the strip middle, the pattern I-c(H) has zero at H = 0 instead of the traditional maximum of '0-type' junctions. The number of these positions is equal to the number of vortices trapped at the same location. When the junction-vortex separation exceeds similar to W, the strip width, I-c(H) is no longer sensitive to the vortex presence. The same is true for any separation if the vortex approaches the strip edges. (C) 2014 Elsevier B.V. All rights reserved.

  4. Macroscopic quantum tunnelling in spin filter ferromagnetic Josephson junctions

    PubMed Central

    Massarotti, D.; Pal, A.; Rotoli, G.; Longobardi, L.; Blamire, M. G.; Tafuri, F.

    2015-01-01

    The interfacial coupling of two materials with different ordered phases, such as a superconductor (S) and a ferromagnet (F), is driving new fundamental physics and innovative applications. For example, the creation of spin-filter Josephson junctions and the demonstration of triplet supercurrents have suggested the potential of a dissipationless version of spintronics based on unconventional superconductivity. Here we demonstrate evidence for active quantum applications of S-F-S junctions, through the observation of macroscopic quantum tunnelling in Josephson junctions with GdN ferromagnetic insulator barriers. We show a clear transition from thermal to quantum regime at a crossover temperature of about 100 mK at zero magnetic field in junctions, which present clear signatures of unconventional superconductivity. Following previous demonstration of passive S-F-S phase shifters in a phase qubit, our result paves the way to the active use of spin filter Josephson systems in quantum hybrid circuits. PMID:26054495

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

    PubMed

    Hashimoto, Michinao; Whitesides, George M

    2010-05-01

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

  6. Studies of silicon p-n junction solar cells

    NASA Technical Reports Server (NTRS)

    Neugroschel, A.; Lindholm, F. A.

    1979-01-01

    To provide theoretical support for investigating different ways to obtain high open-circuit voltages in p-n junction silicon solar cells, an analytical treatment of heavily doped transparent-emitter devices is presented that includes the effects of bandgap narrowing, Fermi-Dirac statistics, a doping concentration gradient, and a finite surface recombination velocity at the emitter surface. Topics covered include: (1) experimental determination of bandgap narrowing in the emitter of silicon p-n junction devices; (2) heavily doped transparent regions in junction solar cells, diodes, and transistors; (3) high-low-emitter solar cell; (4) determination of lifetimes and recombination currents in p-n junction solar cells; (5) MOS and oxide-charged-induced BSF solar cells; and (6) design of high efficiency solar cells for space and terrestrial applications.

  7. Interface Structure and Transport of Complex Oxide Junctions

    SciTech Connect

    Nelson-Cheeseman, B. B.; Wong, F.; Chopdekar, R. V.; Chi, M.; Arenholz, E.; Browning, N. D.; Suzuki, Y.

    2008-02-01

    The interface structure and magnetism of hybrid magnetic tunnel junction-spin filter devices have been investigated and correlated with the transport behavior exhibited. Magnetic tunnel junctions made of theoretically predicted half-metallic electrodes (perovskite La0.7Sr0.3MnO3 and spinel Fe3O4) sandwiching a spinel NiMn2O4 tunnel barrier exhibit very high crystalline quality as observed by transmission electron microscopy. Structurally abrupt interfaces allow for the distinct magnetic switching of the electrodes as well as large junction magnetoresistance. The change in the magnetic anisotropy observed at the spinel-spinel interface supports the presence of limited interdiffusion and the creation of a magnetically soft interfacial layer, whose strong exchange coupling to the Fe3O4 electrode likely accounts for the low background magnetoresistance observed in these junctions, and the successful spin filtering when the barrier layer is ferrimagnetic.

  8. Experimental study of resistive bistability in metal oxide junctions

    NASA Astrophysics Data System (ADS)

    Tan, Zhongkui; Patel, Vijay; Likharev, Konstantin K.; Su, Dong; Zhu, Yimei

    2011-05-01

    We have studied resistive bistability (memory) effects in junctions based on metal oxides, with a focus on sample-to-sample reproducibility, which is necessary for the use of such junctions as crosspoint devices of hybrid CMOS/nanoelectronic circuits. Few-nm-thick layers of NbO x , CuO x and TiO x have been formed by thermal and plasma oxidation, at various deposition and oxidation conditions, both with and without rapid thermal post-annealing. The resistive bistability effect has been observed for all these materials, with particularly high endurance (over 103 switching cycles) obtained for single-layer TiO2 junctions, and the best reproducibility reached for multi-layer junctions of the same material. Fabrication optimization has allowed us to improve the OFF/ON resistance ratio to about 103, but the sample-to-sample reproducibility is so far lower than that required for large-scale integration.

  9. Tunnel junction enhanced nanowire ultraviolet light emitting diodes

    SciTech Connect

    Sarwar, A. T. M. Golam; May, Brelon J.; Deitz, Julia I.; Grassman, Tyler J.; McComb, David W.; Myers, Roberto C.

    2015-09-07

    Polarization engineered interband tunnel junctions (TJs) are integrated in nanowire ultraviolet (UV) light emitting diodes (LEDs). A ∼6 V reduction in turn-on voltage is achieved by the integration of tunnel junction at the base of polarization doped nanowire UV LEDs. Moreover, efficient hole injection into the nanowire LEDs leads to suppressed efficiency droop in TJ integrated nanowire LEDs. The combination of both reduced bias voltage and increased hole injection increases the wall plug efficiency in these devices. More than 100 μW of UV emission at ∼310 nm is measured with external quantum efficiency in the range of 4–6 m%. The realization of tunnel junction within the nanowire LEDs opens a pathway towards the monolithic integration of cascaded multi-junction nanowire LEDs on silicon.

  10. Evidence for Nonlocal Electrodynamics in Planar Josephson Junctions

    NASA Astrophysics Data System (ADS)

    Boris, A. A.; Rydh, A.; Golod, T.; Motzkau, H.; Klushin, A. M.; Krasnov, V. M.

    2013-09-01

    We study the temperature dependence of the critical current modulation Ic(H) for two types of planar Josephson junctions: a low-Tc Nb/CuNi/Nb and a high-Tc YBa2Cu3O7-δ bicrystal grain-boundary junction. At low T both junctions exhibit a conventional behavior, described by the local sine-Gordon equation. However, at elevated T the behavior becomes qualitatively different: the Ic(H) modulation field ΔH becomes almost T independent and neither ΔH nor the critical field for the penetration of Josephson vortices vanish at Tc. Such an unusual behavior is in good agreement with theoretical predictions for junctions with nonlocal electrodynamics. We extract absolute values of the London penetration depth λ from our data and show that a crossover from local to nonlocal electrodynamics occurs with increasing T when λ(T) becomes larger than the electrode thickness.

  11. PAINT SHOP, DETAIL OF FABRICATED COLUMN AT JUNCTION OF WEST ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    PAINT SHOP, DETAIL OF FABRICATED COLUMN AT JUNCTION OF WEST BAY (ORIGINAL) AND CENTER BAYS (SECOND ADDITION), LOOKING NORTHEAST. - Southern Pacific, Sacramento Shops, Paint Shop, 111 I Street, Sacramento, Sacramento County, CA

  12. 17. PRAIRIE CITY DITCH, NEAR ITS JUNCTION WITH RHODES DITCH, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    17. PRAIRIE CITY DITCH, NEAR ITS JUNCTION WITH RHODES DITCH, CUT THROUGH SLATY BEDROCK. VIEW TO NORTHEAST. - Natomas Ditch System, Rhodes Ditch, West of Bidwell Street, north of U.S. Highway 50, Folsom, Sacramento County, CA

  13. 8. VIEW SOUTHWEST, DETAIL OF JUNCTION OF EAST AND NORTH ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    8. VIEW SOUTHWEST, DETAIL OF JUNCTION OF EAST AND NORTH ELEVATIONS AT PORCH ROOF LEVEL SHOWING GLAZED HEADERS AND BELT COURSE - David Sterrett House, State Game Lands Plot No. 169 (Upper Mifflin Township), Newville, Cumberland County, PA

  14. Static vortices in long Josephson junctions of exponentially varying width

    NASA Astrophysics Data System (ADS)

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

    2004-06-01

    A numerical simulation is carried out for static vortices in a long Josephson junction with an exponentially varying width. At specified values of the parameters the corresponding boundary-value problem admits more than one solution. Each solution (distribution of the magnetic flux in the junction) is associated to a Sturm-Liouville problem, the smallest eigenvalue of which can be used, in a first approximation, to assess the stability of the vortex against relatively small spatiotemporal perturbations. The change in width of the junction leads to a renormalization of the magnetic flux in comparison with the case of a linear one-dimensional model. The influence of the model parameters on the stability of the states of the magnetic flux is investigated in detail, particularly that of the shape parameter. The critical curve of the junction is constructed from pieces of the critical curves for the different magnetic flux distributions having the highest critical currents for the given magnetic field.

  15. B & P Junction Substation & Interlocking Tower. Baltimore, Baltimore ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    B & P Junction Substation & Interlocking Tower. Baltimore, Baltimore City, MD. Sec. 1201, MP 95.85. - Northeast Railroad Corridor, Amtrak route between District of Columbia/Maryland state line & Maryland/Delaware state line, Baltimore, Independent City, MD

  16. Union Junction Interlocking Tower. Baltimore, Baltimore City, MD. Sec. 1201, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Union Junction Interlocking Tower. Baltimore, Baltimore City, MD. Sec. 1201, MP 95.49. - Northeast Railroad Corridor, Amtrak route between District of Columbia/Maryland state line & Maryland/Delaware state line, Baltimore, Independent City, MD

  17. High thermopower of mechanically stretched single-molecule junctions

    PubMed Central

    Tsutsui, Makusu; Morikawa, Takanori; He, Yuhui; Arima, Akihide

    2015-01-01

    Metal-molecule-metal junction is a promising candidate for thermoelectric applications that utilizes quantum confinement effects in the chemically defined zero-dimensional atomic structure to achieve enhanced dimensionless figure of merit ZT. A key issue in this new class of thermoelectric nanomaterials is to clarify the sensitivity of thermoelectricity on the molecular junction configurations. Here we report simultaneous measurements of the thermoelectric voltage and conductance on Au-1,4-benzenedithiol (BDT)-Au junctions mechanically-stretched in-situ at sub-nanoscale. We obtained the average single-molecule conductance and thermopower of 0.01 G0 and 15 μV/K, respectively, suggesting charge transport through the highest occupied molecular orbital. Meanwhile, we found the single-molecule thermoelectric transport properties extremely-sensitive to the BDT bridge configurations, whereby manifesting the importance to design the electrode-molecule contact motifs for optimizing the thermoelectric performance of molecular junctions. PMID:26112999

  18. Magnetoanisotropic Andreev reflection in ferromagnet-superconductor junctions.

    PubMed

    Högl, Petra; Matos-Abiague, Alex; Žutić, Igor; Fabian, Jaroslav

    2015-09-11

    Andreev reflection spectroscopy of ferromagnet-superconductor (FS) junctions [corrected] is an important probe of spin polarization. We theoretically investigate spin-polarized transport in FS junctions in the presence of Rashba and Dresselhaus interfacial spin-orbit fields and show that Andreev reflection can be controlled by changing the magnetization orientation. We predict a giant in- and out-of-plane magnetoanisotropy of the junction conductance. If the ferromagnet is highly spin polarized-in the half-metal limit-the magnetoanisotropic Andreev reflection depends universally on the spin-orbit fields only. Our results show that Andreev reflection spectroscopy can be used for sensitive probing of interfacial spin-orbit fields in a FS junction.

  19. Probing Electronic and Thermoelectric Properties of Single Molecule Junctions

    NASA Astrophysics Data System (ADS)

    Widawsky, Jonathan R.

    In an effort to further understand electronic and thermoelectric phenomenon at the nanometer scale, we have studied the transport properties of single molecule junctions. To carry out these transport measurements, we use the scanning tunneling microscope-break junction (STM-BJ) technique, which involves the repeated formation and breakage of a metal point contact in an environment of the target molecule. Using this technique, we are able to create gaps that can trap the molecules, allowing us to sequentially and reproducibly create a large number of junctions. By applying a small bias across the junction, we can measure its conductance and learn about the transport mechanisms at the nanoscale. The experimental work presented here directly probes the transmission properties of single molecules through the systematic measurement of junction conductance (at low and high bias) and thermopower. We present measurements on a variety of molecular families and study how conductance depends on the character of the linkage (metal-molecule bond) and the nature of the molecular backbone. We start by describing a novel way to construct single molecule junctions by covalently connecting the molecular backbone to the electrodes. This eliminates the use of linking substituents, and as a result, the junction conductance increases substantially. Then, we compare transport across silicon chains (silanes) and saturated carbon chains (alkanes) while keeping the linkers the same and find a stark difference in their electronic transport properties. We extend our studies of molecular junctions by looking at two additional aspects of quantum transport -- molecular thermopower and molecular current-voltage characteristics. Each of these additional parameters gives us further insight into transport properties at the nanoscale. Evaluating the junction thermopower allows us to determine the nature of charge carriers in the system and we demonstrate this by contrasting the measurement of amine

  20. Dermal eosinophilic infiltrate in junctional epidermolysis bullosa.

    PubMed

    Saraiya, Ami; Yang, Catherine S; Kim, Jinah; Bercovitch, Lionel; Robinson-Bostom, Leslie; Telang, Gladys

    2015-08-01

    Junctional epidermolysis bullosa (JEB) is a rare genodermatosis characterized by a split in the lamina lucida usually because of mutations in LAMA3, LAMB3 and LAMC2 resulting in absence or reduction of laminin-332. Rare subtypes of JEB have mutations in COL17A1, ITGB4, ITGA6 and ITGA3 leading to reduction or dysfunction of collagen XVII, integrin α6β4 and integrin α3. The classic finding under light microscopy is a paucicellular, subepidermal split. We describe the unusual presence of an eosinophilic infiltrate in the bullae and subjacent dermis in a neonate with JEB, generalized intermediate (formerly known as non-Herlitz-type JEB), discuss the histologic differential diagnosis for a subepidermal blister in a neonate, review the literature regarding cases of epidermolysis bullosa (EB) presenting with inflammatory infiltrates, and discuss mechanisms to explain these findings. This case highlights that eosinophils can rarely be seen in EB and should not mislead the dermatopathologist into diagnosing an autoimmune blistering disorder. PMID:25950805

  1. Parallel Quantum Circuit in a Tunnel Junction.

    PubMed

    Faizy Namarvar, Omid; Dridi, Ghassen; Joachim, Christian

    2016-01-01

    Spectral analysis of 1 and 2-states per line quantum bus are normally sufficient to determine the effective Vab(N) electronic coupling between the emitter and receiver states through the bus as a function of the number N of parallel lines. When Vab(N) is difficult to determine, an Heisenberg-Rabi time dependent quantum exchange process must be triggered through the bus to capture the secular oscillation frequency Ωab(N) between those states. Two different linear and regimes are demonstrated for Ωab(N) as a function of N. When the initial preparation is replaced by coupling of the quantum bus to semi-infinite electrodes, the resulting quantum transduction process is not faithfully following the Ωab(N) variations. Because of the electronic transparency normalisation to unity and of the low pass filter character of this transduction, large Ωab(N) cannot be captured by the tunnel junction. The broadly used concept of electrical contact between a metallic nanopad and a molecular device must be better described as a quantum transduction process. At small coupling and when N is small enough not to compensate for this small coupling, an N(2) power law is preserved for Ωab(N) and for Vab(N). PMID:27453262

  2. Photoinduced carrier annihilation in silicon pn junction

    NASA Astrophysics Data System (ADS)

    Sameshima, Toshiyuki; Motoki, Takayuki; Yasuda, Keisuke; Nakamura, Tomohiko; Hasumi, Masahiko; Mizuno, Toshihisa

    2015-08-01

    We report analysis of the photo-induced minority carrier effective lifetime (τeff) in a p+n junction formed on the top surfaces of a n-type silicon substrate by ion implantation of boron and phosphorus atoms at the top and bottom surfaces followed by activation by microwave heating. Bias voltages were applied to the p+ boron-doped surface with n+ phosphorus-doped surface kept at 0 V. The values of τeff were lower than 1 × 10-5 s under the reverse-bias condition. On the other hand, τeff markedly increased to 1.4 × 10-4 s as the forward-bias voltage increased to 0.7 V and then it leveled off when continuous-wave 635 nm light was illuminated at 0.74 mW/cm2 on the p+ surface. The carrier annihilation velocity S\\text{p + } at the p+ surface region was numerically estimated from the experimental τeff. S\\text{p + } ranged from 4000 to 7200 cm/s under the reverse-bias condition when the carrier annihilation velocity S\\text{n + } at the n+ surface region was assumed to be a constant value of 100 cm/s. S\\text{p + } markedly decreased to 265 cm/s as the forward-bias voltage increased to 0.7 V.

  3. Spin-crossover molecule based thermoelectric junction

    SciTech Connect

    Ghosh, Dibyajyoti; Parida, Prakash; Pati, Swapan K.

    2015-05-11

    Using ab-initio numerical methods, we explore the spin-dependent transport and thermoelectric properties of a spin-crossover molecule (i.e., iron complex of 2-(1H-pyrazol-1-yl)-6-(1H-tetrazole-5-yl)pyridine) based nano-junction. We demonstrate a large magnetoresistance, efficient conductance-switching, and spin-filter activity in this molecule-based two-terminal device. The spin-crossover process also modulates the thermoelectric entities. It can efficiently switch the magnitude as well as spin-polarization of the thermocurrent. We find that thermocurrent is changed by ∼4 orders of magnitude upon spin-crossover. Moreover, it also substantially affects the thermopower and consequently, the device shows extremely efficient spin-crossover magnetothermopower generation. Furthermore, by tuning the chemical potential of electrodes into a certain range, a pure spin-thermopower can be achieved for the high-spin state. Finally, the reasonably large values of figure-of-merit in the presence and absence of phonon demonstrate a large heat-to-voltage conversion efficiency of the device. We believe that our study will pave an alternative way of tuning the transport and thermoelectric properties through the spin-crossover process and can have potential applications in generation of spin-dependent current, information storage, and processing.

  4. Gamma Radiation Tolerance of Magnetic Tunnel Junctions

    NASA Astrophysics Data System (ADS)

    Ren, Fanghui; Jander, Albrecht; Dhagat, Pallavi; Nordman, Cathy

    2011-10-01

    Determining the radiation tolerance of magnetic tunnel junctions (MTJ), which are the storage elements of non-volatile magnetoresistive random access memories (MRAM), is important for investigating their potential application in space. In this effort, the effect of gamma radiation on MTJs with MgO tunnel barriers was studied. Experimental and control groups of samples were characterized by ex situ measurements of the magnetoresistive hysteresis loops and I-V curves. The experimental group was exposed to gamma rays from a ^60Co source. The samples initially received a dose of 5.9 Mrad (Si) after which they were again characterized electrically and magnetically. Irradiation was then continued for a cumulative dose of 10 Mrad and the devices re-measured. The result shows no change in magnetic properties such as coercivity or exchange coupling due to irradiation. After correcting for differences in temperature at the time of testing, the tunneling magnetoresistance was also found to be unchanged. Thus, it has been determined that MgO-based MTJs are highly tolerant of gamma radiation, particularly in comparison to silicon field-effect transistors which have been shown to degrade with gamma ray exposure even as low as 100 Krad [Zhiyuan Hu. et al., IEEE trans. on Nucl. Sci., vol. 58, 2011].

  5. Aeroacoustics of T-junction merging flow.

    PubMed

    Lam, G C Y; Leung, R C K; Tang, S K

    2013-02-01

    This paper reports a numerical study of the aeroacoustics of merging flow at T-junction. The primary focus is to elucidate the acoustic generation by the flow unsteadiness. The study is conducted by performing direct aeroacoustic simulation approach, which solves the unsteady compressible Navier-Stokes equations and the perfect gas equation of state simultaneously using the conservation element and solution element method. For practical flows, the Reynolds number based on duct width is usually quite high (>10(5)). In order to properly account for the effects of flow turbulence, a large eddy simulation methodology together with a wall modeling derived from the classical logarithm wall law is adopted. The numerical simulations are performed in two dimensions and the acoustic generation physics at different ratios of side-branch to main duct flow velocities VR (=0.5,0.67,1.0,2.0) are studied. Both the levels of unsteady interactions of merging flow structures and the efficiency of acoustic generation are observed to increase with VR. Based on Curle's analogy, the major acoustic source is found to be the fluctuating wall pressure induced by the flow unsteadiness occurred in the downstream branch. A scaling between the wall fluctuating force and the efficiency of the acoustic generation is also derived. PMID:23363089

  6. Ferroelectric tunnel junctions with graphene electrodes.

    PubMed

    Lu, H; Lipatov, A; Ryu, S; Kim, D J; Lee, H; Zhuravlev, M Y; Eom, C B; Tsymbal, E Y; Sinitskii, A; Gruverman, A

    2014-01-01

    Polarization-driven resistive switching in ferroelectric tunnel junctions (FTJs)--structures composed of two electrodes separated by an ultrathin ferroelectric barrier--offers new physics and materials functionalities, as well as exciting opportunities for the next generation of non-volatile memories and logic devices. Performance of FTJs is highly sensitive to the electrical boundary conditions, which can be controlled by electrode material and/or interface engineering. Here, we demonstrate the use of graphene as electrodes in FTJs that allows control of interface properties for significant enhancement of device performance. Ferroelectric polarization stability and resistive switching are strongly affected by a molecular layer at the graphene/BaTiO3 interface. For the FTJ with the interfacial ammonia layer we find an enhanced tunnelling electroresistance (TER) effect of 6 × 10(5)%. The obtained results demonstrate a new approach based on using graphene electrodes for interface-facilitated polarization stability and enhancement of the TER effect, which can be exploited in the FTJ-based devices. PMID:25417720

  7. Parallel Quantum Circuit in a Tunnel Junction

    NASA Astrophysics Data System (ADS)

    Faizy Namarvar, Omid; Dridi, Ghassen; Joachim, Christian

    2016-07-01

    Spectral analysis of 1 and 2-states per line quantum bus are normally sufficient to determine the effective Vab(N) electronic coupling between the emitter and receiver states through the bus as a function of the number N of parallel lines. When Vab(N) is difficult to determine, an Heisenberg-Rabi time dependent quantum exchange process must be triggered through the bus to capture the secular oscillation frequency Ωab(N) between those states. Two different linear and regimes are demonstrated for Ωab(N) as a function of N. When the initial preparation is replaced by coupling of the quantum bus to semi-infinite electrodes, the resulting quantum transduction process is not faithfully following the Ωab(N) variations. Because of the electronic transparency normalisation to unity and of the low pass filter character of this transduction, large Ωab(N) cannot be captured by the tunnel junction. The broadly used concept of electrical contact between a metallic nanopad and a molecular device must be better described as a quantum transduction process. At small coupling and when N is small enough not to compensate for this small coupling, an N2 power law is preserved for Ωab(N) and for Vab(N).

  8. Parallel Quantum Circuit in a Tunnel Junction.

    PubMed

    Faizy Namarvar, Omid; Dridi, Ghassen; Joachim, Christian

    2016-07-25

    Spectral analysis of 1 and 2-states per line quantum bus are normally sufficient to determine the effective Vab(N) electronic coupling between the emitter and receiver states through the bus as a function of the number N of parallel lines. When Vab(N) is difficult to determine, an Heisenberg-Rabi time dependent quantum exchange process must be triggered through the bus to capture the secular oscillation frequency Ωab(N) between those states. Two different linear and regimes are demonstrated for Ωab(N) as a function of N. When the initial preparation is replaced by coupling of the quantum bus to semi-infinite electrodes, the resulting quantum transduction process is not faithfully following the Ωab(N) variations. Because of the electronic transparency normalisation to unity and of the low pass filter character of this transduction, large Ωab(N) cannot be captured by the tunnel junction. The broadly used concept of electrical contact between a metallic nanopad and a molecular device must be better described as a quantum transduction process. At small coupling and when N is small enough not to compensate for this small coupling, an N(2) power law is preserved for Ωab(N) and for Vab(N).

  9. Parallel Quantum Circuit in a Tunnel Junction

    PubMed Central

    Faizy Namarvar, Omid; Dridi, Ghassen; Joachim, Christian

    2016-01-01

    Spectral analysis of 1 and 2-states per line quantum bus are normally sufficient to determine the effective Vab(N) electronic coupling between the emitter and receiver states through the bus as a function of the number N of parallel lines. When Vab(N) is difficult to determine, an Heisenberg-Rabi time dependent quantum exchange process must be triggered through the bus to capture the secular oscillation frequency Ωab(N) between those states. Two different linear and regimes are demonstrated for Ωab(N) as a function of N. When the initial preparation is replaced by coupling of the quantum bus to semi-infinite electrodes, the resulting quantum transduction process is not faithfully following the Ωab(N) variations. Because of the electronic transparency normalisation to unity and of the low pass filter character of this transduction, large Ωab(N) cannot be captured by the tunnel junction. The broadly used concept of electrical contact between a metallic nanopad and a molecular device must be better described as a quantum transduction process. At small coupling and when N is small enough not to compensate for this small coupling, an N2 power law is preserved for Ωab(N) and for Vab(N). PMID:27453262

  10. Graphene Josephson Junction Single Photon Detector

    NASA Astrophysics Data System (ADS)

    Walsh, Evan D.; Lee, Gil-Ho; Efetov, Dmitri K.; Heuck, Mikkel; Crossno, Jesse; Taniguchi, Takashi; Watanabe, Kenji; Ohki, Thomas A.; Kim, Philip; Englund, Dirk; Fong, Kin Chung

    Single photon detectors (SPDs) have found use across a wide array of applications depending on the wavelength to which they are sensitive. Graphene, because of its linear, gapless dispersion near the Dirac point, has a flat, wide bandwidth absorption that can be enhanced to near 100 % through the use of resonant structures making it a promising candidate for broadband SPDs. Upon absorbing a photon in the optical to mid-infrared range, a small (~10 μm2) sheet of graphene at cryogenic temperatures can experience a significant increase in electronic temperature due to its extremely low heat capacity. At 1550 nm, for example, calculations show that the temperature could rise by as much as 500 %. This temperature increase could be detected with near perfect quantum efficiency by making the graphene the weak link in a Josephson junction (JJ). We present a theoretical model demonstrating that such a graphene JJ SPD could operate at the readily achievable temperature of 3 K with near zero dark count, sub-50 ps timing jitter, and sub-5 ns dead time and report on the progress toward experimentally realizing the device.

  11. Ouabain modulates epithelial cell tight junction

    PubMed Central

    Larre, Isabel; Lazaro, Amparo; Contreras, Ruben G.; Balda, Maria S.; Matter, Karl; Flores-Maldonado, Catalina; Ponce, Arturo; Flores-Benitez, David; Rincon-Heredia, Ruth; Padilla-Benavides, Teresita; Castillo, Aída; Shoshani, Liora; Cereijido, Marcelino

    2010-01-01

    Epithelial cells treated with high concentrations of ouabain (e.g., 1 μM) retrieve molecules involved in cell contacts from the plasma membrane and detach from one another and their substrates. On the basis of this observation, we suggested that ouabain might also modulate cell contacts at low, nontoxic levels (10 or 50 nM). To test this possibility, we analyzed its effect on a particular type of cell–cell contact: the tight junction (TJ). We demonstrate that at concentrations that neither inhibit K+ pumping nor disturb the K+ balance of the cell, ouabain modulates the degree of sealing of the TJ as measured by transepithelial electrical resistance (TER) and the flux of neutral 3 kDa dextran (JDEX). This modulation is accompanied by changes in the levels and distribution patterns of claudins 1, 2, and 4. Interestingly, changes in TER, JDEX, and claudins behavior are mediated through signal pathways containing ERK1/2 and c-Src, which have distinct effects on each physiological parameter and claudin type. These observations support the theory that at low concentrations, ouabain acts as a modulator of cell–cell contacts. PMID:20534449

  12. Superconducting qubits with semiconductor nanowire Josephson junctions

    NASA Astrophysics Data System (ADS)

    Petersson, K. D.; Larsen, T. W.; Kuemmeth, F.; Jespersen, T. S.; Krogstrup, P.; Nygård, J.; Marcus, C. M.

    2015-03-01

    Superconducting transmon qubits are a promising basis for a scalable quantum information processor. The recent development of semiconducting InAs nanowires with in situ molecular beam epitaxy-grown Al contacts presents new possibilities for building hybrid superconductor/semiconductor devices using precise bottom up fabrication techniques. Here, we take advantage of these high quality materials to develop superconducting qubits with superconductor-normal-superconductor Josephson junctions (JJs) where the normal element is an InAs semiconductor nanowire. We have fabricated transmon qubits in which the conventional Al-Al2O3-Al JJs are replaced by a single gate-tunable nanowire JJ. Using spectroscopy to probe the qubit we observe fluctuations in its level splitting with gate voltage that are consistent with universal conductance fluctuations in the nanowire's normal state conductance. Our gate-tunable nanowire transmons may enable new means of control for large scale qubit architectures and hybrid topological quantum computing schemes. Research supported by Microsoft Station Q, Danish National Research Foundation, Villum Foundation, Lundbeck Foundation and the European Commission.

  13. Fluxon Dynamics in Elliptic Annular Josephson Junctions

    NASA Astrophysics Data System (ADS)

    Monaco, Roberto; Mygind, Jesper

    2016-04-01

    We analyze the dynamics of a magnetic flux quantum (current vortex) trapped in a current-biased long planar elliptic annular Josephson tunnel junction. The system is modeled by a perturbed sine-Gordon equation that determines the spatial and temporal behavior of the phase difference across the tunnel barrier separating the two superconducting electrodes. In the absence of an external magnetic field, the fluxon dynamics in an elliptic annulus does not differ from that of a circular annulus where the stationary fluxon speed merely is determined by the system losses. The interaction between the vortex magnetic moment and a spatially homogeneous in-plane magnetic field gives rise to a tunable periodic non-sinusoidal potential which is strongly dependent on the annulus aspect ratio. We study the escape of the vortex from a well in the tilted potential when the bias current exceeds the depinning current. The smallest depinning current as well as the lowest sensitivity of the annulus to the external field is achieved when the axes ratio is equal to √{2}. The presented extensive numerical results are in good agreement with the findings of the perturbative approach. We also probe the rectifying properties of an asymmetric potential implemented with an egg-shaped annulus formed by two semi-elliptic arcs.

  14. Quantum statistical theory of semiconductor junctions in thermal equilibrium

    NASA Technical Reports Server (NTRS)

    Von Roos, O.

    1977-01-01

    Free carrier and electric field distributions of one-dimensional semiconductor junctions are evaluated using a quantum mechanical phase-space distribution and its corresponding Boltzmann equation. Attention is given to quantum and exchange corrections in cases of high doping concentrations when carrier densities become degenerate. Quantitative differences between degenerate and classical junction characteristics, e.g., maximum electric field and built-in voltage and carrier concentration within the transition region, are evaluated numerically.

  15. Raman Scattering at Plasmonic Junctions Shorted by Conductive Molecular Bridges

    SciTech Connect

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

    2013-04-10

    Intensity spikes in Raman scattering, accompanied by switching between line spectra and band spectra, can be assigned to shorting the junction plasmon through molecular conductive bridges. This is demonstrated through Raman trajectories recorded at a plasmonic junction formed by a gold AFM tip in contact with a silver surface coated either with biphenyl-4,4’-dithiol or biphenyl-4-thiol. The fluctuations are absent in the monothiol. In effect, the making and breaking of chemical bonds is tracked.

  16. Improved High/Low Junction Silicon Solar Cell

    NASA Technical Reports Server (NTRS)

    Neugroschel, A.; Pao, S. C.; Lindholm, F. A.; Fossum, J. G.

    1986-01-01

    Method developed to raise value of open-circuit voltage in silicon solar cells by incorporating high/low junction in cell emitter. Power-conversion efficiency of low-resistivity silicon solar cell considerably less than maximum theoretical value mainly because open-circuit voltage is smaller than simple p/n junction theory predicts. With this method, air-mass-zero opencircuit voltage increased from 600 mV level to approximately 650 mV.

  17. Droplet traffic at a simple junction at low capillary numbers.

    PubMed

    Engl, Wilfried; Roche, Matthieu; Colin, Annie; Panizza, Pascal; Ajdari, Armand

    2005-11-11

    We report that, when a train of confined droplets flowing through a channel reaches a junction, the droplets either are alternately distributed between the different outlets or all collect into the shortest one. We argue that this behavior is due to the hydrodynamic feedback of droplets in the different outlets on the selection process occurring at the junction. A "mean field" model, yielding semiquantitative results, offers a first guide to predict droplet traffic in branched networks.

  18. Craniovertebral junction stenosis in Lenz-Majewski syndrome.

    PubMed

    Mizuguchi, Koichi; Miyazaki, Osamu; Nishimura, Gen; Ishigro, Akira

    2015-09-01

    We report a girl with Lenz-Majewski syndrome associated with craniovertebral junction stenosis that led to communicating hydrocephalus and cervical myelopathy. The life-threatening complication was related to progressive craniovertebral hyperostosis that rapidly exacerbated during early childhood. Despite initial success of surgical intervention at 2 years of age, she developed apneic spells and died suddenly at age 5 years. Close monitoring for craniovertebral junction stenosis is essential to reduce morbidity and mortality in children with Lenz-Majewski syndrome.

  19. Prism-coupled light emission from tunnel junctions

    NASA Technical Reports Server (NTRS)

    Ushioda, S.; Rutledge, J. E.; Pierce, R. M.

    1985-01-01

    Completely p-polarized light emission has been observed from smooth Al-AlO(x)-Au tunnel junctions placed on a prism coupler. The angle and polarization dependence demonstrate unambiguously that the emitted light is radiated by the fast-mode surface plasmon polariton. The emission spectra suggest that the dominant process for the excitation of the fast mode is through conversion of the slow mode to the fast mode mediated by residual roughness on the junction surface.

  20. A rare presentation of lipoma on mandibular mucogingival junction

    PubMed Central

    Sharma, Gaurav; Jain, Kanu; Nagpal, Archna; Baiju, Chandrababu Sudha

    2016-01-01

    Lipoma is the most common tumor of mesenchymal tissues of body, but its occurrence in oral cavity is infrequent. Buccal mucosa is the most common intraoral site of lipoma followed by tongue, floor of the mouth, and buccal vestibule. The involvement of mucogingival junction is rare. We present a unique case report of oral lipoma occurring on mandibular mucogingival junction with review of literature which has emphasis on differential diagnosis. PMID:27143835

  1. Resonance features of coupled Josephson junctions: radiation and shunting

    NASA Astrophysics Data System (ADS)

    Shukrinov, Yu M.; Seidel, P.; Il'ichev, E.; Nawrocki, W.; Grajcar, M.; Plecenik, P. A.; Rahmonov, I. R.; Kulikov, K.

    2012-11-01

    We study the phase dynamics and the resonance features of coupled Josephson junctions in layered superconductors and their manifestations in the current- voltage characteristics and temporal dependence of the electric charge in the superconducting layers. Results on the effect of the external radiation and shunting of the stack of Josephson junctions by LC-elements are presented. We discuss the ideas concerning the experimental observation of these resonances.

  2. Gap Junctions and Biophysical Regulation of Bone Cells

    PubMed Central

    Lloyd, Shane A. J.

    2013-01-01

    Communication between osteoblasts, osteoclasts, and osteocytes is integral to their ability to build and maintain the skeletal system and respond to physical signals. Various physiological mechanisms, including nerve communication, hormones, and cytokines, play an important role in this process. More recently, the important role of direct, cell–cell communication via gap junctions has been established. In this review, we demonstrate the integral role of gap junctional intercellular communication (GJIC) in skeletal physiology and bone cell mechanosensing. PMID:23762015

  3. Gravitational radiation by cosmic strings in a junction

    SciTech Connect

    Brandenberger, R.; Karouby, J.; Firouzjahi, H.; Khosravi, S.

    2009-01-15

    The formalism for computing the gravitational power radiation from excitations on cosmic strings forming a junction is presented and applied to the simple case of co-planar strings at a junction when the excitations are generated along one string leg. The effects of polarization of the excitations and of the back-reaction of the gravitational radiation on the small scale structure of the strings are studied.

  4. Optical switching in a superconductor-semiconductor-superconductor Josephson junction

    NASA Astrophysics Data System (ADS)

    Bastian, G.; Göbel, E. O.; Schmitz, J.; Walther, M.; Wagner, J.

    1999-07-01

    We have fabricated Josephson junctions with a two-dimensional electron gas based on InAs/AlSb/GaSb as the barrier. The behavior of the junction during and after illumination with different wavelengths was studied. Due to a persistent positive and negative photoeffect, depending on the excitation wavelength, the carrier density and hence the critical current as well as the normal resistance could be switched between two different stable states.

  5. In vivo assembly of tight junctions in fetal rat liver.

    PubMed

    Montesano, R; Friend, D S; Perrelet, A; Orci, L

    1975-11-01

    Examination of glutaraldehyde-fixed, freeze-fractured livers from 14-15-day rat fetuses provided the basis for the following observations. Membrane particles align in otherwise poorly particulated areas of the presumptive pericanalicular plasma membrane (A face), frequently forming a discontinuous "honey-comb" network joining small particle islands. Even at this early stage, contiguous B-fracture faces contain furrows, rather than rows of pits, distinguishing the linear particle aggregates on the A face as developing tight junctions rather than gap junctions. Short segments of these linear arrays merge with smooth ridges clearly identifiable as segments of discontinuous tight junctions. With the continuing confluence of particulate and smooth ridge segments, mature tight junctions become fully appreciable. We conclude that tight junctions form de novo by the alignment and fusion of separate particles into beaded ridges which, in turn, become confluent and are transformed into continuous smooth ones. At 21 days of fetal life, most of the images of assembly have disappeared, and the liver reveals well-formed bile canaliculi sealed by mature tight junctions. PMID:1194351

  6. Critical Current Oscillations of Josephson Junctions with Ferromagnetic Layers

    NASA Astrophysics Data System (ADS)

    Glick, Joseph A.; Khasawneh, Mazin A.; Niedzielski, Bethany M.; Loloee, Reza; Pratt, W. P., Jr.; Birge, Norman O.

    Josephson junctions containing ferromagnetic layers are of considerable interest for the development of practical cryogenic memory and superconducting qubits. Such junctions exhibit a phase shift of π for certain ranges of ferromagnetic layer thickness. We present studies of Nb based micron-scale Josephson junctions using ferromagnetic layers of Ni, Ni81Fe19, or Ni65Co20Fe15. By applying an external magnetic field, the critical current of the junctions containing Ni81Fe19 and Ni65Co20Fe15 is found to follow a characteristic Fraunhofer pattern, and displays the clear switching behavior expected of single-domain magnets. However, the junctions containing Ni exhibit more complex behaviors. The maximum value of the critical current, extracted from the Fraunhofer patterns, oscillates as a function of the ferromagnetic layer thickness, indicating transitions in the phase difference across the junction between values of zero and π. We compare the data to previous work and to models of the 0- π transitions based on existing clean and dirty limit theories. This work was supported by IARPA via ARO Contract W911NF-14-C-0115.

  7. Intraepithelial lymphocytes express junctional molecules in murine small intestine

    SciTech Connect

    Inagaki-Ohara, Kyoko . E-mail: INAGAKI@med.miyazaki-u.ac.jp; Sawaguchi, Akira; Suganuma, Tatsuo; Matsuzaki, Goro; Nawa, Yukifumi

    2005-06-17

    Intestinal intraepithelial lymphocytes (IEL) that reside at basolateral site regulate the proliferation and differentiation of epithelial cells (EC) for providing a first line of host defense in intestine. However, it remains unknown how IEL interact and communicate with EC. Here, we show that IEL express junctional molecules like EC. We identified mRNA expression of the junctional molecules in IEL such as zonula occludens (ZO)-1, occludin and junctional adhesion molecule (JAM) (tight junction), {beta}-catenin and E-cadherin (adherens junction), and connexin26 (gap junction). IEL constitutively expressed occludin and E-cadherin at protein level, while other T cells in the thymus, spleen, liver, mesenteric lymph node, and Peyer's patches did not. {gamma}{delta} IEL showed higher level of these expressions than {alpha}{beta} IEL. The expression of occludin was augmented by anti-CD3 Ab stimulation. These results suggest the possibility of a novel role of IEL concerning epithelial barrier and communication between IEL and EC.

  8. Engineering design of artificial vascular junctions for 3D printing.

    PubMed

    Han, Xiaoxiao; Bibb, Richard; Harris, Russell

    2016-06-20

    Vascular vessels, including arteries, veins and capillaries, are being printed using additive manufacturing technologies, also known as 3D printing. This paper demonstrates that it is important to follow the vascular design by nature as close as possible when 3D printing artificial vascular branches. In previous work, the authors developed an algorithm of computational geometry for constructing smooth junctions for 3D printing. In this work, computational fluid dynamics (CFDs) is used to compare the wall shear stress and blood velocity field for the junctions of different designs. The CFD model can reproduce the expected wall shear stress at locations remote from the junction. For large vessels such as veins, it is shown that ensuring the smoothness of the junction and using smaller joining angles as observed in nature is very important to avoid high wall shear stress and recirculation. The issue is however less significant for capillaries. Large joining angles make no difference to the hemodynamic behavior, which is also consistent with the fact that most capillary junctions have large joining angles. The combination of the CFD analysis and the junction construction method form a complete design method for artificial vascular vessels that can be 3D printed using additive manufacturing technologies.

  9. Symplekin, a novel type of tight junction plaque protein

    PubMed Central

    1996-01-01

    Using a monoclonal antibody we have identified and cDNA-cloned a novel type of protein localized, by light and electron microscopy, to the plaque associated with the cytoplasmic face of the tight junction- containing zone (zonula occludens) of polar epithelial cells and of Sertoli cells of testis, but absent from the junctions of vascular endothelia. The approximately 3.7-kb mRNA encodes a polypeptide of 1142 amino acids (calculated molecular weight 126.5 kD, pI 6.25), for which the name "symplekin" (from Greek sigma upsilon mu pi lambda epsilon kappa epsilon iota, nu, to tie together, to weave, to be intertwined) is proposed. However, both the mRNA and the protein can also be detected in a wide range of cell types that do not form tight junctions or are even completely devoid of any stable cell contacts. Careful analyses have revealed that the protein occurs in all these diverse cells in the nucleoplasm, and only in those cells forming tight junctions is it recruited, partly but specifically, to the plaque structure of the zonula occludens. We discuss symplekin as a representative of a group of dual residence proteins which occur and probably function in the nucleus as well as in the plaques exclusive for either tight junctions, adherens junctions, or desmosomes. PMID:8769423

  10. Electronic Transport in Molecular Junction Based on C20 Cages

    NASA Astrophysics Data System (ADS)

    Ouyang, Fang-Ping; Xu, Hui

    2007-04-01

    Choosing closed-ended armchair (5, 5) single-wall carbon nanotubes (CCNTs) as electrodes, we investigate the electron transport properties across an all-carbon molecular junction consisting of C20 molecules suspended between two semi-infinite carbon nanotubes. It is shown that the conductances are quite sensitive to the number of C20 molecules between electrodes for both configuration CF1 and double-bonded models: the conductances of C20 dimers are markedly smaller than those of monomers. The physics is that incident electrons easily pass the C20 molecules and are predominantly scattered at the C20-C20 junctions. Moreover, we study the doping effect of such molecular junction by doping nitrogen atoms substitutionally. The bonding property of the molecular junction with configuration CF1 has been analysed by calculating the Mulliken atomic charges. Our results have revealed that the C atoms in N-doped junctions are more ionic than those in pure-carbon ones, leading to the fact that N-doped junctions have relatively large conductance.

  11. Low-energy theory of transport in Majorana wire junctions

    NASA Astrophysics Data System (ADS)

    Zazunov, A.; Egger, R.; Levy Yeyati, A.

    2016-07-01

    We formulate and apply a low-energy transport theory for hybrid quantum devices containing junctions of topological superconductor (TS) wires and conventional normal (N) or superconducting (S) leads. We model TS wires as spinless p -wave superconductors and derive their boundary Keldysh Green's function, capturing both the Majorana end state and continuum quasiparticle excitations in a unified manner. We also specify this Green's function for a finite-length TS wire. Junctions connecting different parts of the device are described by the standard tunneling Hamiltonian. Using this Hamiltonian approach, one also has the option to include many-body interactions in a systematic manner. For N-TS junctions, we provide the current-voltage (I -V ) characteristics at arbitrary junction transparency and give exact results for the shot-noise power and the excess current. For TS-TS junctions, analytical results for the thermal noise spectrum and for the I -V curve in the high-transparency low-bias regime are presented. For S-TS junctions, we compute the entire I -V curve and clarify the conditions for having a finite Josephson current.

  12. Breakdown of the escape dynamics in Josephson junctions

    NASA Astrophysics Data System (ADS)

    Massarotti, D.; Stornaiuolo, D.; Lucignano, P.; Galletti, L.; Born, D.; Rotoli, G.; Lombardi, F.; Longobardi, L.; Tagliacozzo, A.; Tafuri, F.

    2015-08-01

    We have identified anomalous behavior of the escape rate out of the zero-voltage state in Josephson junctions with a high critical current density Jc. For this study we have employed YBa2Cu3O7 -x grain boundary junctions, which span a wide range of Jc and have appropriate electrodynamical parameters. Such high Jc junctions, when hysteretic, do not switch from the superconducting to the normal state following the expected stochastic Josephson distribution, despite having standard Josephson properties such as a Fraunhofer magnetic field pattern. The switching current distributions (SCDs) are consistent with nonequilibrium dynamics taking place on a local rather than a global scale. This means that macroscopic quantum phenomena seem to be practically unattainable for high Jc junctions. We argue that SCDs are an accurate means to measure nonequilibrium effects. This transition from global to local dynamics is of relevance for all kinds of weak links, including the emergent family of nanohybrid Josephson junctions. Therefore caution should be applied in the use of such junctions in, for instance, the search for Majorana fermions.

  13. Engineering design of artificial vascular junctions for 3D printing.

    PubMed

    Han, Xiaoxiao; Bibb, Richard; Harris, Russell

    2016-06-01

    Vascular vessels, including arteries, veins and capillaries, are being printed using additive manufacturing technologies, also known as 3D printing. This paper demonstrates that it is important to follow the vascular design by nature as close as possible when 3D printing artificial vascular branches. In previous work, the authors developed an algorithm of computational geometry for constructing smooth junctions for 3D printing. In this work, computational fluid dynamics (CFDs) is used to compare the wall shear stress and blood velocity field for the junctions of different designs. The CFD model can reproduce the expected wall shear stress at locations remote from the junction. For large vessels such as veins, it is shown that ensuring the smoothness of the junction and using smaller joining angles as observed in nature is very important to avoid high wall shear stress and recirculation. The issue is however less significant for capillaries. Large joining angles make no difference to the hemodynamic behavior, which is also consistent with the fact that most capillary junctions have large joining angles. The combination of the CFD analysis and the junction construction method form a complete design method for artificial vascular vessels that can be 3D printed using additive manufacturing technologies. PMID:27321286

  14. Anchored PKA as a gatekeeper for gap junctions

    PubMed Central

    Pidoux, Guillaume; Taskén, Kjetil

    2015-01-01

    Anchored protein kinase A (PKA) bound to A Kinase Anchoring Protein (AKAP) mediates effects of localized increases in cAMP in defined subcellular microdomains and retains the specificity in cAMP-PKA signaling to distinct extracellular stimuli. Gap junctions are pores between adjacent cells constituted by connexin proteins that provide means of communication and transfer of small molecules. While the PKA signaling is known to promote human trophoblast cell fusion, the gap junction communication through connexin 43 (Cx43) is a prerequisite for this process. We recently demonstrated that trophoblast fusion is regulated by ezrin, a known AKAP, which binds to Cx43 and delivers PKA in the vicinity gap junctions. We found that disruption of the ezrin-Cx43 interaction abolished PKA-dependent phosphorylation of Cx43 as well as gap junction communication and subsequently cell fusion. We propose that the PKA-ezrin-Cx43 macromolecular complex regulating gap junction communication constitutes a general mechanism to control opening of Cx43 gap junctions by phosphorylation in response to cAMP signaling in various cell types. PMID:26478781

  15. The string-junction picture of multiquark states: an update

    NASA Astrophysics Data System (ADS)

    Rossi, G. C.; Veneziano, G.

    2016-06-01

    We recall and update, both theoretically and phenomenologically, our (nearly) forty-years-old proposal of a string-junction as a necessary complement to the conventional classification of hadrons based just on their quark-antiquark constituents. In that proposal single (though in general metastable) hadronic states are associated with "irreducible" gauge-invariant operators consisting of Wilson lines (visualized as strings of color flux tubes) that may either end on a quark or an antiquark, or annihilate in triplets at a junction J or an anti-junction overline{J} . For the junction-free sector (ordinary qoverline{q} mesons and glueballs) the picture is supported by large- N (number of colors) considerations as well as by a lattice strong-coupling expansion. Both imply the famous OZI rule suppressing quark-antiquark annihilation diagrams. For hadrons with J and/or overline{J} constituents the same expansions support our proposal, including its generalization of the OZI rule to the suppression of J-overline{J} annihilation diagrams. Such a rule implies that hadrons with junctions are "mesophobic" and thus unusually narrow if they are below threshold for decaying into as many baryons as their total number of junctions (two for a tetraquark, three for a pentaquark). Experimental support for our claim, based on the observation that narrow multiquark states typically lie below (well above) the relevant baryonic (mesonic) thresholds, will be presented.

  16. Dynamics of Josephson junctions and single-flux-quantum networks with superconductor-insulator-normal-metal junction shunts

    NASA Astrophysics Data System (ADS)

    Zorin, A. B.; Tolkacheva, E. M.; Khabipov, M. I.; Buchholz, F.-I.; Niemeyer, J.

    2006-07-01

    Within the framework of the microscopic model of tunneling, we modeled the behavior of the Josephson junction shunted by the superconductor-insulator-normal-metal (SIN) tunnel junction. The electromagnetic impedance of the SIN junction includes both the frequency-dependent damping and reactance, which affect the circuit dynamics. We calculated the dc I-V curves and transient characteristics and show their differences to the characteristics obtained within the simpler models. The correct operation of the basic single-flux-quantum circuits, i.e., the Josephson transmission line and the toggle flip-flop, based on such SIN-shunted Josephson junctions with small damping at low frequencies, has also been modeled.

  17. A Three-Isocenter Jagged-Junction IMRT Approach for Craniospinal Irradiation Without Beam Edge Matching for Field Junctions

    SciTech Connect

    Cao, Fred; Ramaseshan, Ramani; Corns, Robert; Harrop, Sheryl; Nuraney, Nimet; Steiner, Peter; Aldridge, Stephanie; Liu, Mitchell; Carolan, Hannah; Agranovich, Alex; Karvat, Anand

    2012-11-01

    Purpose: Traditionally craniospinal irradiation treats the central nervous system using two or three adjacent field sets. We propose a technique using a three-isocenter intensity-modulated radiotherapy (IMRT) plan (jagged-junction IMRT) which overcomes problems associated with field junctions and beam edge matching and improves planning and treatment setup efficiencies with homogenous target dose distribution. Methods and Materials: Treatments for 3 patients with a prescription of 36 Gy in 20 fractions were retrospectively planned with jagged-junction IMRT and compared to conventional treatment plans. Planning target volume (PTV) included the whole brain and spinal canal to the S3 vertebral level. The plan used three field sets, each with a unique isocenter. One field set with seven fields treated the cranium. Two field sets treated the spine, each set using three fields. Fields from adjacent sets were overlapped, and the optimization process smoothly integrated the dose inside the overlapped junction. Results: For jagged-junction IMRT plans vs. conventional technique, the average homogeneity index equaled 0.08 {+-} 0.01 vs. 0.12 {+-} 0.02, respectively, and conformity number equaled 0.79 {+-} 0.01 vs. 0.47 {+-} 0.12, respectively. The 95% isodose surface covered (99.5 {+-} 0.3)% of the PTV vs. (98.1 {+-} 2.0)%, respectively. Both jagged-junction IMRT plans and the conventional plans had good sparing of organs at risk. Conclusions: Jagged-junction IMRT planning provided good dose homogeneity and conformity to the target while maintaining a low dose to organs at risk. Results from jagged-junction IMRT plans were better than or equivalent to those from the conventional technique. Jagged-junction IMRT optimization smoothly distributed dose in the junction between field sets. Because there was no beam matching, this treatment technique is less likely to produce hot or cold spots at the junction, in contrast to conventional techniques. The planning process is also

  18. Optimal Normal Tissue Sparing in Craniospinal Axis Irradiation Using IMRT With Daily Intrafractionally Modulated Junction(s)

    SciTech Connect

    Kusters, Johannes M.A.M.; Louwe, Rob J.W.; Kollenburg, Peter G.M. van; Kunze-Busch, Martina C.; Gidding, Corrie E.M.; Lindert, Erik J. van; Kaanders, Johannes H.A.M.; Janssens, Geert O.R.J.

    2011-12-01

    Purpose: To develop a treatment technique for craniospinal irradiation using intensity-modulated radiotherapy (IMRT) with improved dose homogeneity at the field junction(s), increased target volume conformity, and minimized dose to the organs at risk (OARs). Methods and Materials: Five patients with high-risk medulloblastoma underwent CT simulation in supine position. For each patient, an IMRT plan with daily intrafractionally modulated junction(s) was generated, as well as a treatment plan based on conventional three-dimensional planning (3DCRT). A dose of 39.6 Gy in 22 daily fractions of 1.8 Gy was prescribed. Dose-volume parameters for target volumes and OARs were compared for the two techniques. Results: The maximum dose with IMRT was <107% in all patients. V{sub <95} and V{sub >107} were <1 cm{sup 3} for IMRT compared with 3-9 cm{sup 3} for the craniospinal and 26-43 cm{sup 3} for the spinal-spinal junction with 3DCRT. These observations corresponded with a lower homogeneity index and a higher conformity index for the spinal planning target volume with IMRT. IMRT provided considerable sparing of acute and late reacting tissues. V{sub 75} for the esophagus, gastroesophageal junction, and intestine was 81%, 81%, and 22% with 3DCRT versus 5%, 0%, and 1% with IMRT, respectively. V{sub 75} for the heart and thyroid was 42% and 32% vs. 0% with IMRT. Conclusion: IMRT with daily intrafractionally modulated junction results in a superior target coverage and junction homogeneity compared with 3DCRT. A significant dose reduction can be obtained for acute as well as late-reacting tissues.

  19. Junction-to-Case Thermal Resistance of a Silicon Carbide Bipolar Junction Transistor Measured

    NASA Technical Reports Server (NTRS)

    Niedra, Janis M.

    2006-01-01

    Junction temperature of a prototype SiC-based bipolar junction transistor (BJT) was estimated by using the base-emitter voltage (V(sub BE)) characteristic for thermometry. The V(sub BE) was measured as a function of the base current (I(sub B)) at selected temperatures (T), all at a fixed collector current (I(sub C)) and under very low duty cycle pulse conditions. Under such conditions, the average temperature of the chip was taken to be the same as that of the temperature-controlled case. At increased duty cycle such as to substantially heat the chip, but same I(sub C) pulse height, the chip temperature was identified by matching the V(sub BE) to the thermometry curves. From the measured average power, the chip-to-case thermal resistance could be estimated, giving a reasonable value. A tentative explanation for an observed bunching with increasing temperature of the calibration curves may relate to an increasing dopant atom ionization. A first-cut analysis, however, does not support this.

  20. Reduction of Gap Junctional Conductance by Microinjection of Antibodies against the 27-kDa Liver Gap Junction Polypeptide

    NASA Astrophysics Data System (ADS)

    Hertzberg, E. L.; Spray, D. C.; Bennett, M. V. L.

    1985-04-01

    Antibody raised against isolated rat liver gap junctions was microinjected into coupled cells in culture to assess its influence on gap junctional conductance. A rapid inhibition of fluorescent dye transfer and electrical coupling was produced in pairs of freshly dissociated adult rat hepatocytes and myocardial cells as well as in pairs of superior cervical ganglion neurons from neonatal rats cultured under conditions in which electrotonic synapses form. The antibodies have been shown by indirect immunofluorescence to bind to punctate regions of the plasma membrane in liver. By immunoreplica analysis of rat liver homogenates, plasma membranes, and isolated gap junctions resolved on NaDodSO4/polyacrylamide gels, binding was shown to be specific for the 27-kDa major polypeptide of gap junctions. This and similar antibodies should provide a tool for further investigation of the role of cell-cell communication mediated by gap junctions and indicate that immunologically similar polypeptides comprise gap junctions in adult mammalian cells derived from all three germ layers.

  1. THE CELL JUNCTION IN A LAMELLIBRANCH GILL CILIATED EPITHELIUM

    PubMed Central

    Satir, P.; Gilula, N. B.

    1970-01-01

    The junctional complex in the gill epithelium of the freshwater mussel (Elliptio complanatus) consists of an intermediary junction followed by a 2–3 µ long septate junction. Homologous and heterologous cell pairs are connected by this junction. After fixation with 1% OsO4 containing 1% potassium pyroantimonate, electron microscopy of the gill reveals deposits of electron-opaque precipitate, specifically and consistently localized along cellular membranes. In both junctional and nonjunctional membrane regions, the precipitate usefully outlines the convolutions without obliterating the 150 A intercellular space, which suggests the rarity or absence of either vertebrate-type gap or tight junctions along the entire cell border. The precipitate appears on the cytoplasmic side of the limiting unit membranes of frontal (F), laterofrontal (LF), intermediate (I), lateral (L), and postlateral (PL) cells. The membrane surfaces of certain vesicles of the smooth endoplasmic reticulum, of multivesicular bodies, and of mitochondrial cristae contain precipitate, as does the nucleolus. In other portions of the cell, precipitate is largely absent. The amount of over-all deposition is variable and depends on the treatment of the tissue prior to fixation. Deposition is usually enhanced by pretreatment with 40 mM NaCl as opposed to 40 mM KCl, which suggests that the precipitate is in part sodium pyroantimonate. Treatment with 0.2 mM ouabain does not enhance deposition. Regional differentiation of cell membranes with respect to their ability to precipitate pyroantimonate is found in at least three instances: (a) between the ciliary membranes and other portions of the cell membrane: the precipitate terminates abruptly at the ciliary base, (b) between the LF and I cell borders: the precipitate is asymmetric, favoring the LF side of the junction, and (c) between the septate junctional membrane and adjacent membrane: the precipitate occurs periodically throughout the septate junction

  2. Regeneration of the active zone at the frog neuromuscular junction

    PubMed Central

    1984-01-01

    The active zone is a unique specialization of the presynaptic membrane and is believed to be the site of transmitter release. The formation of the active zone and the relationship of this process to transmitter release were studied at reinnervated neuromuscular junctions in the frog. At different times after a nerve crush, the cutaneous pectoris muscles were examined with intracellular recording recording and freeze- fracture electron microscopy. The P face of a normal active zone typically consists of two double rows of particles lined up in a continuous segment located opposite a junctional fold. In the initial stage of reinnervation, clusters of large intramembrane particles surrounding membrane elevations appeared on the P face of nerve terminals. Like normal active zones, these clusters were aligned with junctional folds. Vesicle openings, which indicate transmitter release, were seen at these primitive active zones, even though intramembrane particles were not yet organized into the normal pattern of two double rows. The length of active zones at this stage was only approximately 15% of normal. During the secondary stage, every junction was reinnervated and most active zones had begun to organize into the normal pattern with normal orientation. Unlike normal, there were often two or more discontinuous short segments of active zone aligned with the same junctional fold. The total length of active zone per junctional fold increased to one-third of normal, mainly because of the greater number of segments. In the third stage, the number of active zone segments per junctional fold showed almost no change when compared with the secondary stage. However, individual segments elongated and increased the total length of all active zone segments per junctional fold to about two-thirds of the normal length. The dynamic process culminated in the final stage, during which elongating active zones appeared to join together and the number of active zone segments per

  3. Tight Junction Defects in Atopic Dermatitis

    PubMed Central

    De Benedetto, Anna; Rafaels, Nicholas M.; McGirt, Laura Y.; Ivanov, Andrei I.; Georas, Steve N.; Cheadle, Chris; Berger, Alan E.; Zhang, Kunzhong; Vidyasagar, Sadasivan; Yoshida, Takeshi; Boguniewicz, Mark; Hata, Tissa; Schneider, Lynda C.; Hanifin, Jon M.; Gallo, Richard L.; Novak, Natalija; Weidinger, Stephan; Beaty, Terri H.; Leung, Donald Y.; Barnes, Kathleen C.; Beck, Lisa A.

    2010-01-01

    Background Atopic dermatitis (AD) is characterized by dry skin and a hyperreactive immune response to allergens, two cardinal features that are caused in part by epidermal barrier defects. Tight junctions (TJ) reside immediately below the stratum corneum and regulate the selective permeability of the paracellular pathway. Objective We evaluated the expression/function of the TJ protein, claudin-1 in epithelium from AD and nonatopic (NA) subjects and screened two American populations for SNPs in CLDN1. Methods Expression profiles of nonlesional epithelium from extrinsic AD, NA and psoriasis subjects were generated using Illumina’s BeadChips. Dysregulated intercellular proteins were validated by tissue staining and qPCR. Bioelectric properties of epithelium were measured in Ussing chambers. Functional relevance of claudin-1 was assessed using a knockdown approach in primary human keratinocytes (PHK). Twenty seven haplotype-tagging SNPs in CLDN1 were screened in two independent AD populations. Results We observed strikingly reduced expression of the TJ proteins claudin-1 and -23 only in AD, which were validated at the mRNA and protein levels. Claudin-1 expression inversely correlated with Th2 biomarkers. We observed a remarkable impairment of the bioelectric barrier function in AD epidermis. In vitro, we confirmed that silencing claudin-1 expression in human keratinocytes diminishes TJ function while enhancing keratinocyte proliferation. Finally, CLDN1 haplotype-tagging single nucleotide polymorphisms revealed associations with AD in two North American populations. Conclusion Taken together, these data suggest that an impaired epidermal TJ is a novel feature of skin barrier dysfunction and immune dysregulation observed in AD, and that CLDN1 may be a new susceptibility gene in this disease. PMID:21163515

  4. Neuromuscular junction channelopathies: a brief overview.

    PubMed

    Newsom-Davis, John

    2005-12-01

    The neuromuscular junction lacks the protection of the blood-nerve barrier and is vulnerable to antibody-mediated disorders. In myasthenia gravis (MG), 85% of patients have IgG antibodies to acetylcholine receptors (AChRs). About half the remaining patients have IgG antibodies to Muscle Specific Kinase (MuSK), an AChR-associated transmembrane post-synaptic protein concerned in AChR aggregation. Bulbar weakness is typically predominant in this form of MG, and females are more often affected. The Lambert-Eaton Myasthenic Syndrome (LEMS) can occur in a paraneoplastic form (P-LEMS) usually with small cell lung cancer, or in a non-paraneoplastic form (NP-LEMS). In both, IgG antibodies to nerve terminal voltage-gated calcium channels (VGCCs), detectable in over 90% of patients, lead to VGCC loss and impaired quantal release of transmitter and may be implicated in the occasionally associated cerebellar ataxia. Neuromyotonia (NMT) and Cramp-Fasciculation syndrome (C-FS) are manifestations of peripheral nerve hyperexcitability and share some clinical and electromyographic features. Antibodies to voltage-gated potassium channels (VGKCs) are present in about 40% of NMT patients, but less frequently in C-FS, and appear to cause loss of functional VGKCs. They may also be implicated in the Maladie de Morvan and limbic encephalitis that can associate with NMT: The antibodies described here provide valuable aids to diagnosis and management. The Congenital Myasthenic Syndromes are a group of genetically determined heterogeneous disorders, usually recessively inherited. The commonest mutation sites appear to be the acetylcholine receptor epsilon-subunit and rapsyn.

  5. Preface: Charge transport in nanoscale junctions

    NASA Astrophysics Data System (ADS)

    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.

  6. Calcium-induced assembly of adherens junctions in keratinocytes

    PubMed Central

    1987-01-01

    Extracellular calcium concentration has been shown to control the stratification of cultured keratinocytes, presumably by regulation of formation of desmosomes. Previous studies have shown that keratinocytes cultured in medium containing 0.1 mM Ca++ form loose colonies without desmosomes. If the Ca++ is raised to 1 mM, desmosomes are assembled and the distribution of keratin filaments is altered. We have examined the disposition of vinculin and actin in keratinocytes under similar conditions. Using immunofluorescence microscopy we show that raising [Ca++] in the medium dramatically alters the distribution of vinculin and actin and results in the formation of adherens-type junctions within 15 min after switching to high calcium medium. Borders of cells at the edge of colonies, which are not proximal to other cells, are not affected, while cells in the interior of the colony form junctions around their periphery. Attachment plaques in keratinocytes grown in low calcium medium are located at the ventral plane of the cell, but junctions formed after switching to high calcium are not, as demonstrated by interference reflection microscopy. In cells colabeled with antibodies against vinculin and desmoplakin, vinculin-containing adherens junctions were visible before desmosomal junctions when cells were switched to high calcium. Although newly formed vinculin- containing structures in high calcium cells, like desmosomes, colocalize with phase-dense structures, superimposition of video fluorescence images using digitized fluorescence microscopy indicates that adherens junctions and desmosomes are discrete structures. Adherens junctions, like desmosomes, may play an essential role in controlling stratification of keratinocytes. PMID:2442175

  7. Effects of aminoglycoside antibiotics on the neuromuscular junction: Part I.

    PubMed

    Yamada, S; Kuno, Y; Iwanaga, H

    1986-03-01

    The effects of aminoglycoside antibiotics (AGA) including streptomycin (SM), kanamycin (KM), gentamicin (GM), dibekacin (DKB), amikacin (AMK) and sisomycin (SISO), on the neuromuscular junction were studied by in vivo and in vitro experiments. In in vitro experiments, no effect of AGA on rat phrenic nerve diaphragm preparations was observed, but the use of the antibiotics at a high concentration exerted a slight blocking effect on the neuromuscular junction. The blocking effect of SISO and DKB on the neuromuscular junction was marked. These antibiotics were definitely found to compete with eserine in terms of the blocking effect on the neuromuscular junction, but did not compete with calcium chloride. In in vitro experiments with frog sciatic nerve and musculus sartorius preparations, DKB and SISO exerted a blocking effect on the NMJ, inducing the disappearance of action potentials and the appearance of endplate potentials (EPPs). In in vitro experiments with the preparations from Rana catesbiana frogs, SM, GM, DKB and SISO exhibited an inhibiting effect on the release of acetylcholine (ACh), a chemical neurotransmitter in neuromuscular junction, resulting in a decrease in the frequency of miniature endplate potentials (mEPPS). In in vivo experiments with rabbit sciatic tibialis anterior muscle preparations, SM, GM, DKB and SISO exerted a blocking effect on the neuromuscular junction. From the facts that the effect was augmented by the use of magnesium chloride combined with these antibiotics and that the antibiotics competed with calcium chloride and potassium chloride in terms of the blocking effect on the neuromuscular junction, the effects seemed to be due to the inhibition of ACh release.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3699939

  8. PASTA: splice junction identification from RNA-Sequencing data

    PubMed Central

    2013-01-01

    Background Next generation transcriptome sequencing (RNA-Seq) is emerging as a powerful experimental tool for the study of alternative splicing and its regulation, but requires ad-hoc analysis methods and tools. PASTA (Patterned Alignments for Splicing and Transcriptome Analysis) is a splice junction detection algorithm specifically designed for RNA-Seq data, relying on a highly accurate alignment strategy and on a combination of heuristic and statistical methods to identify exon-intron junctions with high accuracy. Results Comparisons against TopHat and other splice junction prediction software on real and simulated datasets show that PASTA exhibits high specificity and sensitivity, especially at lower coverage levels. Moreover, PASTA is highly configurable and flexible, and can therefore be applied in a wide range of analysis scenarios: it is able to handle both single-end and paired-end reads, it does not rely on the presence of canonical splicing signals, and it uses organism-specific regression models to accurately identify junctions. Conclusions PASTA is a highly efficient and sensitive tool to identify splicing junctions from RNA-Seq data. Compared to similar programs, it has the ability to identify a higher number of real splicing junctions, and provides highly annotated output files containing detailed information about their location and characteristics. Accurate junction data in turn facilitates the reconstruction of the splicing isoforms and the analysis of their expression levels, which will be performed by the remaining modules of the PASTA pipeline, still under development. Use of PASTA can therefore enable the large-scale investigation of transcription and alternative splicing. PMID:23557086

  9. Occluding junctions and cytoskeletal components in a cultured transporting epithelium

    PubMed Central

    Meza, I; Ibarra, G; Sabanero, M; Martinez-Palomo, A; Cereijido, M

    1980-01-01

    MDCK cells form uninterrupted monolayers and make occluding junctions similar to those of natural epithelia. This aricle explores the relationship between these junctions and the cytoskeleton by combining studies on the distribution of microfilaments and microtubules with the effect of drugs, such as colchicines and cytochalasin B, on the degree of tightness of the occluding junctions. To study the degree of tightness, monolayers were prepared by plating MDCK cells on mylon disks coated with collagen. Disks were mounted as flat sheets between two Lucite chambers, and the sealing capacity of the junctions was evaluated by measuring the electrical resistance across the monolayers. Equivalent monolayers on coverslips were used to study the distribution of microtubules and microfilaments by indirect immunofluorescence staining with antibodies against tubulin and actin. This was done both on complete cells and on cytoskeleton preparations in which the cell membranes had been solubilized before fixation. Staining with antiactin shows a reticular pattern of very fine filaments that spread radially toward the periphery where they form a continuous cortical ring underlying the plasma membrane. Staining with antitubulin depicts fibers that extend radially to form a network that occupies the cytoplasm up to the edges of the cell. Colchicine causes a profound disruption of microtubules but only a 27 percent decrease in the electrical resistance of the resting monolayers. Cytochalasin B, when present for prolonged periods, disrupts the cytoplasmic microfilaments and abolishes the electrical resistance. The cortical ring of filaments remains in place but appears fragmented with time. We find that removal of extracellular Ca(++), which causes the tight junctions to open, also causes the microfilaments and microtubules to retract toward the center of the cells. The process of junction opening and fiber retraction is reversed by the restoration of Ca(++). Colchicine has no effect

  10. Optimization of electron cooling by SIN tunnel junctions

    NASA Astrophysics Data System (ADS)

    Kuzmin, L.; Agulo, I.; Fominsky, M.; Savin, A.; Tarasov, M.

    2004-05-01

    We report on the optimization of electron cooling by SIN tunnel junctions due to the advanced geometry of superconducting electrodes and very effective normal metal traps for more efficient removal of quasiparticles at temperatures from 25 to 500 mK. The maximum decrease in electron temperature of about 200 mK has been observed at bath temperatures 300-350 mK. We used four-junction geometry with Al-AlOx-Cr/Cu tunnel junctions and Au traps. Efficient electron cooling was realized due to the improved geometry of the cooling tunnel junctions (quadrant shape of the superconducting electrode) and optimized Au traps just near the junctions ({\\approx }0.5~\\micmu {\\mathrm {m}} ) to reduce reabsorption of quasiparticles after removing them from normal metal. The maximum cooling effect was increased from a temperature drop of d T = -56 mK (ordinary cross geometry) to -130 mK (improved geometry of superconducting electrodes) and to d T = -200 mK (improved geometry of superconducting electrodes and effective Au traps). The heating peak (instead of cooling) near the zero voltage across cooling junctions has been observed in practice for all samples at temperatures below 150 mK. For higher cooling voltages close to the superconducting gap, the heating was converted to cooling with decreased amplitude. The leakage resistance of the tunnel junctions gives a reasonable explanation of the heating peak. The phonon reabsorption due to the recombination of quasiparticles in superconducting electrodes gives an additional improvement in the theoretical fitting but could not explain the heating peak. An anomalous zero-bias resistance peak has been observed for all tested structures. The peak is explained by Coulomb blockade of tunnelling in transistor-type structures with relatively small tunnel junctions. The work on electron cooling is devoted to the development of a cold-electron bolometer (CEB) with capacitive coupling by SIN tunnel junctions to the antenna for sensitive detection

  11. Thermally assisted vortex motion in intrinsic Josephson junctions

    NASA Astrophysics Data System (ADS)

    Irie, A.; Oya, G.

    2008-02-01

    The vortex dynamics in intrinsic Josephson junctions (IJJs) at finite temperatures has been investigated numerically by taking into account the thermal fluctuations. Our simulations based on the perturbed, coupled sine-Gordon model successfully reproduce the experimental results associated with the Josephson-vortex flow resistance (JVFR) at low bias currents. Depending on the junction length, bias current, and temperature, the JVFR oscillation is changed from the period of half flux quantum per junction to the period of one flux quantum per junction. It is shown that the oscillation is essentially due to the field dependence of the critical current. At currents slightly exceeding the critical current the stationary vortex lattice structure becomes unstable and an irregular vortex flow can be induced by thermal fluctuations in different junctions. Our simulation results strongly suggest that the triangular lattice of vorticies in the dynamical state is more stable rather than the rectangular one even in a submicrometer IJJ stack when IJJs are biased at a low current.

  12. Oxygen adsorption at noble metal/TiO2 junctions

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  13. Hexadecameric structure of an invertebrate gap junction channel.

    PubMed

    Oshima, Atsunori; Matsuzawa, Tomohiro; Murata, Kazuyoshi; Tani, Kazutoshi; Fujiyoshi, Yoshinori

    2016-03-27

    Innexins are invertebrate-specific gap junction proteins with four transmembrane helices. These proteins oligomerize to constitute intercellular channels that allow for the passage of small signaling molecules associated with neural and muscular electrical activity. In contrast to the large number of structural and functional studies of connexin gap junction channels, few structural studies of recombinant innexin channels are reported. Here we show the three-dimensional structure of two-dimensionally crystallized Caenorhabditis elegans innexin-6 (INX-6) gap junction channels. The N-terminal deleted INX-6 proteins are crystallized in lipid bilayers. The three-dimensional reconstruction determined by cryo-electron crystallography reveals that a single INX-6 gap junction channel comprises 16 subunits, a hexadecamer, in contrast to chordate connexin channels, which comprise 12 subunits. The channel pore diameters at the cytoplasmic entrance and extracellular gap region are larger than those of connexin26. Two bulb densities are observed in each hemichannel, one in the pore and the other at the cytoplasmic side of the hemichannel in the channel pore pathway. These findings imply a structural diversity of gap junction channels among multicellular organisms. PMID:26883891

  14. Resolving metal-molecule interfaces at single-molecule junctions

    PubMed Central

    Komoto, Yuki; Fujii, Shintaro; Nakamura, Hisao; Tada, Tomofumi; Nishino, Tomoaki; Kiguchi, Manabu

    2016-01-01

    Electronic and structural detail at the electrode-molecule interface have a significant influence on charge transport across molecular junctions. Despite the decisive role of the metal-molecule interface, a complete electronic and structural characterization of the interface remains a challenge. This is in no small part due to current experimental limitations. Here, we present a comprehensive approach to obtain a detailed description of the metal-molecule interface in single-molecule junctions, based on current-voltage (I-V) measurements. Contrary to conventional conductance studies, this I-V approach provides a correlated statistical description of both, the degree of electronic coupling across the metal-molecule interface, and the energy alignment between the conduction orbital and the Fermi level of the electrode. This exhaustive statistical approach was employed to study single-molecule junctions of 1,4-benzenediamine (BDA), 1,4-butanediamine (C4DA), and 1,4-benzenedithiol (BDT). A single interfacial configuration was observed for both BDA and C4DA junctions, while three different interfacial arrangements were resolved for BDT. This multiplicity is due to different molecular adsorption sites on the Au surface namely on-top, hollow, and bridge. Furthermore, C4DA junctions present a fluctuating I-V curve arising from the greater conformational freedom of the saturated alkyl chain, in sharp contrast with the rigid aromatic backbone of both BDA and BDT. PMID:27221947

  15. Symmetry breaking in SNS junctions: edge transport and field asymmetries

    NASA Astrophysics Data System (ADS)

    Suominen, Henri; Nichele, Fabrizio; Kjaergaard, Morten; Rasmussen, Asbjorn; Danon, Jeroen; Flensberg, Karsten; Levitov, Leonid; Shabani, Javad; Palmstrom, Chris; Marcus, Charles

    We study magnetic diffraction patterns in a tunable superconductor-semiconductor-superconductor junction. By utilizing epitaxial growth of aluminum on InAs/InGaAs we obtain transparent junctions which display a conventional Fraunhofer pattern of the critical current as a function of applied perpendicular magnetic field, B⊥. By studying the angular dependence of the critical current with applied magnetic fields in the plane of the junction we find a striking anisotropy. We attribute this effect to dephasing of Andreev states in the bulk of the junction, leading to SQUID like behavior when the magnetic field is applied parallel to current flow. Furthermore, in the presence of both in-plane and perpendicular fields, asymmetries in +/-B⊥ are observed. We suggest possible origins and discuss the role of spin-orbit and Zeeman physics together with a background disorder potential breaking spatial symmetries of the junction. Research supported by Microsoft Project Q, the Danish National Research Foundation and the NSF through the National Nanotechnology Infrastructure Network.

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

    PubMed

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

    2009-01-01

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

  17. Regulation of Endothelial Adherens Junctions by Tyrosine Phosphorylation

    PubMed Central

    Adam, Alejandro Pablo

    2015-01-01

    Endothelial cells form a semipermeable, regulated barrier that limits the passage of fluid, small molecules, and leukocytes between the bloodstream and the surrounding tissues. The adherens junction, a major mechanism of intercellular adhesion, is comprised of transmembrane cadherins forming homotypic interactions between adjacent cells and associated cytoplasmic catenins linking the cadherins to the cytoskeleton. Inflammatory conditions promote the disassembly of the adherens junction and a loss of intercellular adhesion, creating openings or gaps in the endothelium through which small molecules diffuse and leukocytes transmigrate. Tyrosine kinase signaling has emerged as a central regulator of the inflammatory response, partly through direct phosphorylation and dephosphorylation of the adherens junction components. This review discusses the findings that support and those that argue against a direct effect of cadherin and catenin phosphorylation in the disassembly of the adherens junction. Recent findings indicate a complex interaction between kinases, phosphatases, and the adherens junction components that allow a fine regulation of the endothelial permeability to small molecules, leukocyte migration, and barrier resealing. PMID:26556953

  18. Variability study of Si nanowire FETs with different junction gradients

    NASA Astrophysics Data System (ADS)

    Yoon, Jun-Sik; Kim, Kihyun; Rim, Taiuk; Baek, Chang-Ki

    2016-01-01

    Random dopant fluctuation effects of gate-all-around Si nanowire field-effect transistors (FETs) are investigated in terms of different diameters and junction gradients. The nanowire FETs with smaller diameters or shorter junction gradients increase relative variations of the drain currents and the mismatch of the drain currents between source-drain and drain-source bias change in the saturation regime. Smaller diameters decreased current drivability critically compared to standard deviations of the drain currents, thus inducing greater relative variations of the drain currents. Shorter junction gradients form high potential barriers in the source-side lightly-doped extension regions at on-state, which determines the magnitude of the drain currents and fluctuates the drain currents greatly under thermionic-emission mechanism. On the other hand, longer junction gradients affect lateral field to fluctuate the drain currents greatly. These physical phenomena coincide with correlations of the variations between drain currents and electrical parameters such as threshold voltages and parasitic resistances. The nanowire FETs with relatively-larger diameters and longer junction gradients without degrading short channel characteristics are suggested to minimize the relative variations and the mismatch of the drain currents.

  19. Measure Guideline: Optimizing the Configuration of Flexible Duct Junction Boxes

    SciTech Connect

    Beach, R.; Burdick, A.

    2014-03-01

    This measure guideline offers additional recommendations to heating, ventilation, and air conditioning (HVAC) system designers for optimizing flexible duct, constant-volume HVAC systems using junction boxes within Air Conditioning Contractors of America (ACCA) Manual D guidance (Rutkowski, H. Manual D -- Residential Duct Systems, 3rd edition, Version 1.00. Arlington, VA: Air Conditioning Contractors of America, 2009.). IBACOS used computational fluid dynamics software to explore and develop guidance to better control the airflow effects of factors that may impact pressure losses within junction boxes among various design configurations (Beach, R., Prahl, D., and Lange, R. CFD Analysis of Flexible Duct Junction Box Design. Golden, CO: National Renewable Energy Laboratory, submitted for publication 2013). These recommendations can help to ensure that a system aligns more closely with the design and the occupants' comfort expectations. Specifically, the recommendations described herein show how to configure a rectangular box with four outlets, a triangular box with three outlets, metal wyes with two outlets, and multiple configurations for more than four outlets. Designers of HVAC systems, contractors who are fabricating junction boxes on site, and anyone using the ACCA Manual D process for sizing duct runs will find this measure guideline invaluable for more accurately minimizing pressure losses when using junction boxes with flexible ducts.

  20. Water and suspended sediment division at a stratified tidal junction

    NASA Astrophysics Data System (ADS)

    Buschman, F. A.; Vegt, M.; Hoitink, A. J. F.; Hoekstra, P.

    2013-03-01

    Tidal junctions play a crucial role in the transport of water, salt, and sediment through a delta distributary network. Water, salt and sediment are exchanged at tidal junctions, thereby influencing the transports in the connecting branches and the overall dynamics of the system. This paper presents observations of water, salt and sediment transports in three channels that connect at a stratified tidal junction. Flow variation in one channel was found to lag behind flow variation in a connected channel by more than 1 h, which is largely attributed to channel length differences from the junction to the sea. The water columns in the three channels were periodically stratified during spring tide, whereas the salinity structure represented a salt wedge during neap tide. Salinity differences between the three channels were substantial. The channels contain water bodies of different salinity and act largely independently. Flow velocities in the upper and lower layers differed substantially. Flow in the lower layer was generally in the direction of acceleration produced by the baroclinic pressure gradient. Interestingly, baroclinic pressure gradients were sometimes directed landward, indicating the presence of saltier water at the land side of the estuary. In sharp channel bends close to the junction, secondary flow was strongest at the highest axial flow velocity during spring tide. In one channel bend, these circulations steered the suspended sediment toward the inner bend, which affected the suspended sediment division.

  1. Proximity Effect at Graphene - High Tc Superconductor Junctions

    NASA Astrophysics Data System (ADS)

    Wang, Da; Shih, En-Min; Arefe, Ghidewon; Kim, Youngduck; Edelberg, Drew; Andrade, Erick; Wang, Dennis; Hone, James; Dean, Cory; Pasupathy, Abhay; Department of Physics, Columbia University, New York, NY 10027, USA Collaboration

    The proximity effect is a well-known mesoscopic phenomenon where Cooper pairs from a superconductor (S) enter into a normal metal (N) that is well coupled to it. Since graphene was discovered a decade ago, the proximity effect at superconductor-graphene junctions has been extensively studied and interesting phenomena such as specular Andreev reflection and ballistic transport at graphene Josephson junctions have been observed. However, superconductors used in these experiments to date are of conventional low Tc, such as aluminum(Tc=1.2K), NbSe2(Tc=7K), and MoRe(Tc=8K). Understanding how the proximity effect works between high-Tc superconductors (pnictides and cuprates) and the Dirac Fermions of graphene remains largely unexplored. The chief technical challenge here is to create high-quality junctions between high-Tc superconductors and graphene. In this work, we will introduce a home-made setup that allows us to exfoliate, transfer and encapsulate superconductor-graphene junctions in a well controlled inert atmosphere. Transport measurements of the proximity effect at graphene-iron pnictide(FeSe, FeTeSe) and graphene-cuprate(BSCCO) junctions will be described.

  2. Arrays of Nano Tunnel Junctions as Infrared Image Sensors

    NASA Technical Reports Server (NTRS)

    Son, Kyung-Ah; Moon, Jeong S.; Prokopuk, Nicholas

    2006-01-01

    Infrared image sensors based on high density rectangular planar arrays of nano tunnel junctions have been proposed. These sensors would differ fundamentally from prior infrared sensors based, variously, on bolometry or conventional semiconductor photodetection. Infrared image sensors based on conventional semiconductor photodetection must typically be cooled to cryogenic temperatures to reduce noise to acceptably low levels. Some bolometer-type infrared sensors can be operated at room temperature, but they exhibit low detectivities and long response times, which limit their utility. The proposed infrared image sensors could be operated at room temperature without incurring excessive noise, and would exhibit high detectivities and short response times. Other advantages would include low power demand, high resolution, and tailorability of spectral response. Neither bolometers nor conventional semiconductor photodetectors, the basic detector units as proposed would partly resemble rectennas. Nanometer-scale tunnel junctions would be created by crossing of nanowires with quantum-mechanical-barrier layers in the form of thin layers of electrically insulating material between them (see figure). A microscopic dipole antenna sized and shaped to respond maximally in the infrared wavelength range that one seeks to detect would be formed integrally with the nanowires at each junction. An incident signal in that wavelength range would become coupled into the antenna and, through the antenna, to the junction. At the junction, the flow of electrons between the crossing wires would be dominated by quantum-mechanical tunneling rather than thermionic emission. Relative to thermionic emission, quantum mechanical tunneling is a fast process.

  3. Theoretical exploration of Josephson Plasma Emission in Intrinsic Josephson Junctions

    SciTech Connect

    Tachiki, M.; Machida, M.

    2000-07-18

    In this paper, the authors theoretically predict the best efficient way for electromagnetic wave emission by Josephson plasma excitation in intrinsic Josephson junctions. First, they briefly derive basic equations describing dynamics of phase differences inside junction sites in intrinsic Josephson junctions, and review the nature of Josephson plasma excitation modes based on the equations. Especially, they make an attention to that Josephson plasma modes have much different dispersion relations depending on the propagating directions and their different modes can be recognized as N standing waves propagating along ah-plane in cases of finite stacked systems composed of N junctions. Second, they consider how to excite their modes and point out that excitations of in-phase mode with the highest propagation velocity among their N modes are the most efficient way for electromagnetic wave emissions. Finally, they clarify that in-phase excitations over all junctions are possible by using Josephson vortex flow states. They show simulation results of Josephson vortex flow states resonating with some Josephson plasma modes and predict that superradiance of electromagnetic field may occur in rectangular vortex flow state in which spatiotemporal oscillations of electromagnetic fields are perfectly in-phase.

  4. Electron transport properties of single molecular junctions under mechanical modulations

    NASA Astrophysics Data System (ADS)

    Zhou, Jianfeng; Guo, Cunlan; Xu, Bingqian

    2012-04-01

    Electron transport behaviors of single molecular junctions are very sensitive to the atomic scale molecule-metal electrode contact interfaces, which have been difficult to control. We used a modified scanning probe microscope-break junction technique (SPM-BJT) to control the dynamics of the contacts and simultaneously monitor both the conductance and force. First, by fitting the measured data into a modified multiple tunneling barrier model, the static contact resistances, corresponding to the different contact conformations of single alkanedithiol and alkanediamine molecular junctions, were identified. Second, the changes of contact decay constant were measured under mechanical extensions of the molecular junctions, which helped to classify the different single molecular conductance sets into specific microscopic conformations of the molecule-electrode contacts. Third, by monitoring the changes of force and contact decay constant with the mechanical extensions, the changes of conductance were found to be caused by the changes of contact bond length and by the atomic reorganizations near the contact bond. This study provides a new insight into the understanding of the influences of contact conformations, especially the effect of changes of dynamic contact conformation on electron transport through single molecular junctions.

  5. Controllable 0-π Josephson junctions containing a ferromagnetic spin valve

    NASA Astrophysics Data System (ADS)

    Gingrich, E. C.; Niedzielski, Bethany M.; Glick, Joseph A.; Wang, Yixing; Miller, D. L.; Loloee, Reza; Pratt, W. P., Jr.; Birge, Norman O.

    2016-06-01

    Superconductivity and ferromagnetism are antagonistic forms of order, and rarely coexist. Many interesting new phenomena occur, however, in hybrid superconducting/ferromagnetic systems. For example, a Josephson junction containing a ferromagnetic material can exhibit an intrinsic phase shift of π in its ground state for certain thicknesses of the material. Such `π-junctions' were first realized experimentally in 2001 (refs ,), and have been proposed as circuit elements for both high-speed classical superconducting computing and for quantum computing. Here we demonstrate experimentally that the phase state of a Josephson junction containing two ferromagnetic layers can be toggled between 0 and π by changing the relative orientation of the two magnetizations. These controllable 0-π junctions have immediate applications in cryogenic memory, where they serve as a necessary component to an ultralow power superconducting computer. Such a fully superconducting computer is estimated to be orders of magnitude more energy-efficient than current semiconductor-based supercomputers. Phase-controllable junctions also open up new possibilities for superconducting circuit elements such as superconducting `programmable logic', where they could function in superconducting analogues to field-programmable gate arrays.

  6. Role of magnetic anisotropy in spin-filter junctions

    SciTech Connect

    Chopdekar, R.V.; Wong, F.; Nelson-Cheeseman, B.B.; Liberati, M.; Arenholz, E.; Suzuki, Y.

    2011-01-10

    We have fabricated oxide-based spin-filter junctions in which we demonstrate that magnetic anisotropy can be used to tune the transport behavior of spin-filter junctions. We have demonstrated spin-filtering behavior in La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/CoCr{sub 2}O{sub 4}/Fe{sub 3}O{sub 4} and La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/MnCr{sub 2}O{sub 4}/Fe{sub 3}O{sub 4} junctions where the interface anisotropy plays a significant role in determining transport behavior. Detailed studies of chemical and magnetic structure at the interfaces indicate that abrupt changes in magnetic anisotropy across the nonisostructural interface is the cause of the significant suppression of junction magnetoresistance in junctions with MnCr{sub 2}O{sub 4} barrier layers.

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

    PubMed

    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.

  8. MLN0264 in Previously Treated Asian Patients With Advanced Gastrointestinal Carcinoma or Metastatic or Recurrent Gastric or Gastroesophageal Junction Adenocarcinoma Expressing Guanylyl Cyclase C

    ClinicalTrials.gov

    2016-06-03

    Advanced Gastrointestinal Carcinoma; Gastroesophageal Junction Adenocarcinoma; Recurrent Gastric Adenocarcinoma; Recurrent Gastroesophageal Junction Adenocarcinoma; Metastatic Gastric Adenocarcinoma; Metastatic Gastroesophageal Junction Adenocarcinoma; Recurrent Gastrointestinal Carcinoma

  9. Reciprocal influence of connexins and apical junction proteins on their expressions and functions

    PubMed Central

    Derangeon, Mickaël; Spray, David C.; Bourmeyster, Nicolas; Sarrouilhe, Denis; Hervé, Jean-Claude

    2009-01-01

    Membranes of adjacent cells form intercellular junctional complexes to mechanically anchor neighbour cells (anchoring junctions), to seal the paracellular space and to prevent diffusion of integral proteins within the plasma membrane (tight junctions) and to allow cell-to-cell diffusion of small ions and molecules (gap junctions). These different types of specialised plasma membrane microdomains, sharing common adaptor molecules, particularly zonula occludens proteins, frequently present intermingled relationships where the different proteins co-assemble into macromolecular complexes and their expressions are co-ordinately regulated. Proteins forming gap junction channels (connexins, particularly) and proteins fulfilling cell attachment or forming tight junction strands mutually influence expression and functions of one another. PMID:19046940

  10. Terahertz Responses of Intrinsic Josephson Junctions in High T{sub C} Superconductors

    SciTech Connect

    Wang, H. B.; Wu, P. H.; Yamashita, T.

    2001-09-03

    High frequency responses of intrinsic Josephson junctions up to 2.5THz, including the observation of Shapiro steps under various conditions, are reported and discussed in this Letter. The sample was an array of intrinsic Josephson junctions singled out from inside a high T{sub C} superconducting Bi{sub 2}Sr {sub 2}CaCu{sub 2}O{sub 8+x} single crystal, with a bow-tie antenna integrated to it. The number of junctions in the array was controllable, the junctions were homogeneous, the distribution of applied irradiation among the junctions was even, and the junctions could synchronously respond to high frequency irradiation.

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

    SciTech Connect

    Hybertsen M. S.

    2013-04-11

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

  12. Length and energy gap dependences of thermoelectricity in nanostructured junctions.

    PubMed

    Asai, Yoshihiro

    2013-04-17

    The possibilities of an enhanced thermoelectric figure of merit value, ZT, in a nanostructured junction are examined for a wide range of parameter values in a theoretical model. Our research shows that the figure of merit can take a very large maximum, which depends both on the length and the energy gap values. The maximum of ZT is achieved when the Fermi level of the electrodes is aligned to the edge of the electronic transmission function of the junction, where both the conductance and the Seebeck constant are significantly enhanced. On the basis of our results, we conclude that nanowires and molecular junctions form a special class of systems where a large ZT can be expected in some cases. PMID:23528878

  13. Alloyed 2D Metal-Semiconductor Atomic Layer Junctions.

    PubMed

    Kim, Ah Ra; Kim, Yonghun; Nam, Jaewook; Chung, Hee-Suk; Kim, Dong Jae; Kwon, Jung-Dae; Park, Sang Won; Park, Jucheol; Choi, Sun Young; Lee, Byoung Hun; Park, Ji Hyeon; Lee, Kyu Hwan; Kim, Dong-Ho; Choi, Sung Mook; Ajayan, Pulickel M; Hahm, Myung Gwan; Cho, Byungjin

    2016-03-01

    Heterostructures of compositionally and electronically variant two-dimensional (2D) atomic layers are viable building blocks for ultrathin optoelectronic devices. We show that the composition of interfacial transition region between semiconducting WSe2 atomic layer channels and metallic NbSe2 contact layers can be engineered through interfacial doping with Nb atoms. WxNb1-xSe2 interfacial regions considerably lower the potential barrier height of the junction, significantly improving the performance of the corresponding WSe2-based field-effect transistor devices. The creation of such alloyed 2D junctions between dissimilar atomic layer domains could be the most important factor in controlling the electronic properties of 2D junctions and the design and fabrication of 2D atomic layer devices.

  14. Spin polarized conductance in ferromagnet / insulator / conventional superconductor junctions

    NASA Astrophysics Data System (ADS)

    Shigeta, Iduru; Tanaka, Yukio; Golubov, Alexander A.; Hiroi, Masahiko

    2012-12-01

    A theory of differential conductance in ferromagnet / insulator / conventional superconductor (F/I/CS) junctions is presented and an experimental conductance is analyzed by the theory. With regard to line shapes of calculated differential conductance, as the magnitude of the exchange interaction in ferromagnets is increased, the differential conductance for the half-metallic state below the energy gap is always reduced in contrast to that for the normal metallic state. This is due to the fact that the retro-reflectivity of the Andreev reflection in the case of CS's is broken by the influence from the exchange interaction. The experimental conductance of ferromagnetic Ru2-xFexCrSi Heusler alloy / superconducting Pb junctions was in good agreement with calculational results of the theory for the F/I/CS junctions.

  15. Junction-based field emission structure for field emission display

    DOEpatents

    Dinh, Long N.; Balooch, Mehdi; McLean, II, William; Schildbach, Marcus A.

    2002-01-01

    A junction-based field emission display, wherein the junctions are formed by depositing a semiconducting or dielectric, low work function, negative electron affinity (NEA) silicon-based compound film (SBCF) onto a metal or n-type semiconductor substrate. The SBCF can be doped to become a p-type semiconductor. A small forward bias voltage is applied across the junction so that electron transport is from the substrate into the SBCF region. Upon entering into this NEA region, many electrons are released into the vacuum level above the SBCF surface and accelerated toward a positively biased phosphor screen anode, hence lighting up the phosphor screen for display. To turn off, simply switch off the applied potential across the SBCF/substrate. May be used for field emission flat panel displays.

  16. Advanced materials development for multi-junction monolithic photovoltaic devices

    SciTech Connect

    Dawson, L.R.; Reno, J.L.

    1996-07-01

    We report results in three areas of research relevant to the fabrication of monolithic multi-junction photovoltaic devices. (1) The use of compliant intervening layers grown between highly mismatched materials, GaAs and GaP (same lattice constant as Si), is shown to increase the structural quality of the GaAs overgrowth. (2) The use of digital alloys applied to the MBE growth of GaAs{sub x}Sb{sub l-x} (a candidate material for a two junction solar cell) provides increased control of the alloy composition without degrading the optical properties. (3) A nitrogen plasma discharge is shown to be an excellent p-type doping source for CdTe and ZnTe, both of which are candidate materials for a two junction solar cell.

  17. Fluxons in long and annular intrinsic Josephson junction stacks

    NASA Astrophysics Data System (ADS)

    Clauss, T.; Oehmichen, V.; Mößle, M.; Müller, A.; Weber, A.; Koelle, D.; Kleiner, R.

    2002-12-01

    A promising approach towards a THz oscillator based on intrinsic Josephson junctions in high-temperature superconductors is based on the collective motion of Josephson fluxons, which are predicted to form various configurations ranging from a triangular to a quadratic lattice. Not only for this reason, but certainly also for the sake of basic physics, several experimental and theoretical investigations have been done on the subject of collective fluxon dynamics in stacked intrinsic Josephson junctions. In this paper we will present some experimental results on the fluxon dynamics of long intrinsic Josephson junction stacks made of Bi2Sr2CaCu2O8. The stacks were formed either in an open or in an annular geometry, and clear resonant fluxon modes were observed. Experiments discussed include measurements of current-voltage characteristics in external magnetic fields and in external microwave fields.

  18. Reflectionless tunneling in planar Nb/GaAs hybrid junctions

    NASA Astrophysics Data System (ADS)

    Giazotto, Francesco; Cecchini, Marco; Pingue, Pasqualantonio; Beltram, Fabio; Lazzarino, Marco; Orani, Daniela; Rubini, Silvia; Franciosi, Alfonso

    2001-03-01

    Reflectionless tunneling was observed in Nb/GaAs superconductor/semiconductor junctions fabricated by a two-step procedure. First, periodic δ-doped layers were grown by molecular-beam epitaxy near the GaAs surface, followed by an As cap layer to protect the surface during ex situ transfer. Second, Nb was deposited by dc-magnetron sputtering onto a GaAs(001) 2×4 surface in situ after thermal desorption of the cap layer. The magnetotransport behavior of the resulting hybrid junctions was successfully analyzed within the random matrix theory of phase-coherent Andreev transport. The impact of junction morphology on reflectionless tunneling and the applicability of the fabrication technique to the realization of complex superconductor/semiconductor mesoscopic systems are discussed.

  19. Grain Boundary Junctions in Microstructure Generated by Multiple Twinning

    SciTech Connect

    Gertsman, Valerii Y.; Henager, Charles H.

    2003-10-01

    The microstructure of a Cu-Ni alloy after static recrystallization was investigated using electron backscatter diffraction in a scanning electron microscope and the existence of orientationally related clusters of crystallites formed by multiple twinning has been established. Grain boundary and triple junction character within the clusters are analyzed. While the outer boundaries of the cluster are crystallographically random, all the inner boundaries have sigma 3^n misorientations. A newly developed crystallographic theory of triple junctions and multicrystallite ensembles consisting of CSL boundaries is used to describe the structure of the cluster. The presence of an alpha not egual to 1 triple junction is confirmed. Apparently, the mesostructure of recrystallized materials susceptible to annealing twinning consists

  20. Field-free junctions for surface electrode ion traps

    NASA Astrophysics Data System (ADS)

    Jordens, Robert; Schmied, R.; Blain, M. G.; Leibfried, D.; Wineland, D.

    2015-05-01

    Intersections between transport guides in a network of RF ion traps are a key ingredient to many implementations of scalable quantum information processing with trapped ions. Several junction architectures demonstrated so far are limited by varying radial secular frequencies, a reduced trap depth, or a non-vanishing RF field along the transport channel. We report on the design and progress in implementing a configurable microfabricated surface electrode Y-junction that employs switchable RF electrodes. An essentially RF-field-free pseudopotential guide between any two legs of the junction can be established by applying RF potential to a suitable pair of electrodes. The transport channel's height above the electrodes, its depth and radial curvature are constant to within 15%. Supported by IARPA, Sandia, NSA, ONR, and the NIST Quantum Information Program.