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Sample records for junctional terminal cisternae

  1. 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.

  2. 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.

  3. Multi-terminal Josephson junctions as topological matter

    NASA Astrophysics Data System (ADS)

    Riwar, Roman-Pascal; Houzet, Manuel; Meyer, Julia S.; Nazarov, Yuli V.

    2016-04-01

    Topological materials and their unusual transport properties are now at the focus of modern experimental and theoretical research. Their topological properties arise from the bandstructure determined by the atomic composition of a material and as such are difficult to tune and naturally restricted to <=3 dimensions. Here we demonstrate that n-terminal Josephson junctions with conventional superconductors may provide novel realizations of topology in n-1 dimensions, which have similarities, but also marked differences with existing 2D or 3D topological materials. For n>=4, the Andreev subgap spectrum of the junction can accommodate Weyl singularities in the space of the n-1 independent superconducting phases, which play the role of bandstructure quasimomenta. The presence of these Weyl singularities enables topological transitions that are manifested experimentally as changes of the quantized transconductance between two voltage-biased leads, the quantization unit being 4e2/h, where e is the electric charge and h is the Planck constant.

  4. Multi-terminal Josephson junctions as topological matter.

    PubMed

    Riwar, Roman-Pascal; Houzet, Manuel; Meyer, Julia S; Nazarov, Yuli V

    2016-01-01

    Topological materials and their unusual transport properties are now at the focus of modern experimental and theoretical research. Their topological properties arise from the bandstructure determined by the atomic composition of a material and as such are difficult to tune and naturally restricted to ≤3 dimensions. Here we demonstrate that n-terminal Josephson junctions with conventional superconductors may provide novel realizations of topology in n-1 dimensions, which have similarities, but also marked differences with existing 2D or 3D topological materials. For n≥4, the Andreev subgap spectrum of the junction can accommodate Weyl singularities in the space of the n-1 independent superconducting phases, which play the role of bandstructure quasimomenta. The presence of these Weyl singularities enables topological transitions that are manifested experimentally as changes of the quantized transconductance between two voltage-biased leads, the quantization unit being 4e(2)/h, where e is the electric charge and h is the Planck constant. PMID:27040917

  5. Multi-terminal Josephson junctions as topological matter

    PubMed Central

    Riwar, Roman-Pascal; Houzet, Manuel; Meyer, Julia S.; Nazarov, Yuli V.

    2016-01-01

    Topological materials and their unusual transport properties are now at the focus of modern experimental and theoretical research. Their topological properties arise from the bandstructure determined by the atomic composition of a material and as such are difficult to tune and naturally restricted to ≤3 dimensions. Here we demonstrate that n-terminal Josephson junctions with conventional superconductors may provide novel realizations of topology in n−1 dimensions, which have similarities, but also marked differences with existing 2D or 3D topological materials. For n≥4, the Andreev subgap spectrum of the junction can accommodate Weyl singularities in the space of the n−1 independent superconducting phases, which play the role of bandstructure quasimomenta. The presence of these Weyl singularities enables topological transitions that are manifested experimentally as changes of the quantized transconductance between two voltage-biased leads, the quantization unit being 4e2/h, where e is the electric charge and h is the Planck constant. PMID:27040917

  6. Chemical control over the energy-level alignment in a two-terminal junction

    NASA Astrophysics Data System (ADS)

    Yuan, Li; Franco, Carlos; Crivillers, Núria; Mas-Torrent, Marta; Cao, Liang; Sangeeth, C. S. Suchand; Rovira, Concepció; Veciana, Jaume; Nijhuis, Christian A.

    2016-07-01

    The energy-level alignment of molecular transistors can be controlled by external gating to move molecular orbitals with respect to the Fermi levels of the source and drain electrodes. Two-terminal molecular tunnelling junctions, however, lack a gate electrode and suffer from Fermi-level pinning, making it difficult to control the energy-level alignment of the system. Here we report an enhancement of 2 orders of magnitude of the tunnelling current in a two-terminal junction via chemical molecular orbital control, changing chemically the molecular component between a stable radical and its non-radical form without altering the supramolecular structure of the junction. Our findings demonstrate that the energy-level alignment in self-assembled monolayer-based junctions can be regulated by purely chemical modifications, which seems an attractive alternative to control the electrical properties of two-terminal junctions.

  7. Chemical control over the energy-level alignment in a two-terminal junction.

    PubMed

    Yuan, Li; Franco, Carlos; Crivillers, Núria; Mas-Torrent, Marta; Cao, Liang; Sangeeth, C S Suchand; Rovira, Concepció; Veciana, Jaume; Nijhuis, Christian A

    2016-07-26

    The energy-level alignment of molecular transistors can be controlled by external gating to move molecular orbitals with respect to the Fermi levels of the source and drain electrodes. Two-terminal molecular tunnelling junctions, however, lack a gate electrode and suffer from Fermi-level pinning, making it difficult to control the energy-level alignment of the system. Here we report an enhancement of 2 orders of magnitude of the tunnelling current in a two-terminal junction via chemical molecular orbital control, changing chemically the molecular component between a stable radical and its non-radical form without altering the supramolecular structure of the junction. Our findings demonstrate that the energy-level alignment in self-assembled monolayer-based junctions can be regulated by purely chemical modifications, which seems an attractive alternative to control the electrical properties of two-terminal junctions.

  8. Chemical control over the energy-level alignment in a two-terminal junction.

    PubMed

    Yuan, Li; Franco, Carlos; Crivillers, Núria; Mas-Torrent, Marta; Cao, Liang; Sangeeth, C S Suchand; Rovira, Concepció; Veciana, Jaume; Nijhuis, Christian A

    2016-01-01

    The energy-level alignment of molecular transistors can be controlled by external gating to move molecular orbitals with respect to the Fermi levels of the source and drain electrodes. Two-terminal molecular tunnelling junctions, however, lack a gate electrode and suffer from Fermi-level pinning, making it difficult to control the energy-level alignment of the system. Here we report an enhancement of 2 orders of magnitude of the tunnelling current in a two-terminal junction via chemical molecular orbital control, changing chemically the molecular component between a stable radical and its non-radical form without altering the supramolecular structure of the junction. Our findings demonstrate that the energy-level alignment in self-assembled monolayer-based junctions can be regulated by purely chemical modifications, which seems an attractive alternative to control the electrical properties of two-terminal junctions. PMID:27456200

  9. Chemical control over the energy-level alignment in a two-terminal junction

    PubMed Central

    Yuan, Li; Franco, Carlos; Crivillers, Núria; Mas-Torrent, Marta; Cao, Liang; Sangeeth, C. S. Suchand; Rovira, Concepció; Veciana, Jaume; Nijhuis, Christian A.

    2016-01-01

    The energy-level alignment of molecular transistors can be controlled by external gating to move molecular orbitals with respect to the Fermi levels of the source and drain electrodes. Two-terminal molecular tunnelling junctions, however, lack a gate electrode and suffer from Fermi-level pinning, making it difficult to control the energy-level alignment of the system. Here we report an enhancement of 2 orders of magnitude of the tunnelling current in a two-terminal junction via chemical molecular orbital control, changing chemically the molecular component between a stable radical and its non-radical form without altering the supramolecular structure of the junction. Our findings demonstrate that the energy-level alignment in self-assembled monolayer-based junctions can be regulated by purely chemical modifications, which seems an attractive alternative to control the electrical properties of two-terminal junctions. PMID:27456200

  10. Multi-terminal multi-junction dc SQUID for nanoscale magnetometry

    NASA Astrophysics Data System (ADS)

    Meltzer, Alexander Y.; Uri, Aviram; Zeldov, Eli

    2016-11-01

    Miniaturization of superconducting quantum interference devices (SQUIDs) is of major importance for the development of sensitive scanning nanoscale magnetometry tools. The high sensitivity of nanoSQUIDs is restricted, however, to only particular periodic values of the applied magnetic field, making accurate measurements at intermediate values of the field impossible. We present a theoretical investigation of a multi-terminal, multi-junction SQUID (mSQUID) that lifts this limitation by providing electrical means for a continuous shift of the quantum interference pattern with respect to the applied field. Analysis of 4-terminal, 4-junction and 3-terminal, 3-junction mSQUIDs shows that operation at maximum sensitivity can be obtained at any value of the magnetic field by applying control current to the extra terminals. The model describes the variation and the shift of the interference pattern as a function of the control currents, junction asymmetries, and the mSQUID inductance. The mSQUID is also shown to provide a direct measurement of the current-phase relations of superconducting junctions. The derived model provides a quantitative description of the recently developed multi-terminal nanoSQUID-on-tip.

  11. Extension of synaptic extracellular matrix during nerve terminal sprouting in living frog neuromuscular junctions.

    PubMed

    Chen, L; Ko, C P

    1994-02-01

    Remodeling of the synaptic extracellular matrix (ECM) and its dynamic relationship with nerve terminal plasticity have been demonstrated in normal frog neuromuscular junctions (NMJs) in vivo (Chen et al., 1991). Our previous work has led to a hypothesis that extension of synaptic ECM precedes nerve terminal growth during synaptic remodeling. To test this hypothesis, the present study examined the changes of synaptic ECM in frog NMJs that were primarily undergoing nerve terminal growth and sprouting. Frog sartorius muscles were double stained with a fluorescent nerve terminal dye (4-Di-2-Asp) and rhodamine-tagged peanut agglutinin (PNA), which recognizes synaptic ECM. The double-labeled NMJs were visualized in vivo with video-enhanced fluorescence microscopy. Nerve sprouting was then induced in the muscle by grafting segments of the contralateral sciatic nerve. The identified NMJs were restrained and reexamined 2-3 months later. Extensive sprouting was observed in 46% of 167 identified NMJs. At junctional regions that showed extension or formation of new branches, synaptic ECM was commonly seen to have the same shape and distribution as the nerve terminal. However, extension of synaptic ECM beyond the corresponding nerve terminals, often by tens of microns, was observed in 29% of these newly formed junctional regions. This lack of correlation might be transient, as growth of nerve terminals following extended, PNA-stained ECM was seen. Examination with histological staining not only confirmed a lack of nerve terminal at the extended synaptic ECM region but also indicated an absence of AChE and postsynaptic junctional folds. The absence of these postsynaptic specializations at the extended, PNA-stained ECM region makes it unlikely that this region was previously occupied by nerve terminals that had retracted. Thus, the present study provides further findings consistent with the hypothesis that synaptic ECM precedes nerve terminal outgrowth and that the extension of

  12. Laser processing for bevel termination of high voltage pn junction in SiC

    NASA Astrophysics Data System (ADS)

    Kubiak, A.; Ruta, Ł.; Rosowski, A.; French, P.

    2016-04-01

    Proper edge termination of the p-n junction in silicon carbide is a key requirement in the fabrication of discrete devices able to withstand high voltages in reverse polarization. Due to the hardness of SiC the creation of the bevel termination remains difficult using mechanical machining. The use of laser beam sources with medium wavelength (532 nm) gives new possibilities in the machining of the silicon carbide. The paper presents the fabrication of the bevel termination structure in SiC using a green DPSS laser equipped with scanner and dedicated rotating sample holder. Characterization of the resulting structures proves the high potential of the proposed approach.

  13. Dynamical properties of three terminal magnetic tunnel junctions: Spintronics meets spin-orbitronics

    SciTech Connect

    Tomasello, R.; Carpentieri, M.; Finocchio, G.

    2013-12-16

    This Letter introduces a micromagnetic model able to characterize the magnetization dynamics in three terminal magnetic tunnel junctions, where the effects of spin-transfer torque and spin-orbit torque are taken into account. Our results predict that the possibility to separate electrically those two torque sources is very promising from a technological point of view for both next generation of nanoscale spintronic oscillators and microwave detectors. A scalable synchronization scheme based on the parallel connection of those three terminal devices is also proposed.

  14. Novel Nanoelectronic Device Applications Based on the Nonlinearity of Three-Terminal Ballistic Junctions

    NASA Astrophysics Data System (ADS)

    Sun, Jie; Wallin, D.; Brusheim, P.; Maximov, I.; Wang, Z. G.; Xu, H. Q.

    2007-04-01

    Nanometer-scale electron devices containing three-terminal ballistic junctions are fabricated by electron-beam lithography on InP/InGaAs two-dimensional electron gas materials. Based on the intrinsic nonlinearity of the devices, frequency mixer, phase detector and RS flip-flop memory functioning at room temperature are successfully achieved. The devices have simple structure layout and small size, and are expected to function at high speed.

  15. Analysis of Full-Test tools and their limitations as applied to terminal junction blocks

    NASA Technical Reports Server (NTRS)

    Smith, J. L.

    1983-01-01

    Discovery of unlocked contacts in Deutsch Block terminal junctions in Solid Rocket Booster flight hardware prompted an investigation into pull test techniques to help insure against possible failures. Internal frictional forces between socket and pin and between wire and grommet were examined. Pull test force must be greater than internal friction yet less than the crimp strength of the pin or socket. For this reason, a 100 percent accurate test is impossible. Test tools were evaluated. Available tools are adequate for pull testing.

  16. Rectification in tunneling junctions: 2,2'-bipyridyl-terminated n-alkanethiolates.

    PubMed

    Yoon, Hyo Jae; Liao, Kung-Ching; Lockett, Matthew R; Kwok, Sen Wai; Baghbanzadeh, Mostafa; Whitesides, George M

    2014-12-10

    Molecular rectification is a particularly attractive phenomenon to examine in studying structure-property relationships in charge transport across molecular junctions, since the tunneling currents across the same molecular junction are measured, with only a change in the sign of the bias, with the same electrodes, molecule(s), and contacts. This type of experiment minimizes the complexities arising from measurements of current densities at one polarity using replicate junctions. This paper describes a new organic molecular rectifier: a junction having the structure Ag(TS)/S(CH2)11-4-methyl-2,2'-bipyridyl//Ga2O3/EGaIn (Ag(TS): template-stripped silver substrate; EGaIn: eutectic gallium-indium alloy) which shows reproducible rectification with a mean r(+) = |J(+1.0 V)|/|J(-1.0 V)| = 85 ± 2. This system is important because rectification occurs at a polarity opposite to that of the analogous but much more extensively studied systems based on ferrocene. It establishes (again) that rectification is due to the SAM, and not to redox reactions involving the Ga2O3 film, and confirms that rectification is not related to the polarity in the junction. Comparisons among SAM-based junctions incorporating the Ga2O3/EGaIn top electrode and a variety of heterocyclic terminal groups indicate that the metal-free bipyridyl group, not other features of the junction, is responsible for the rectification. The paper also describes a structural and mechanistic hypothesis that suggests a partial rationalization of values of rectification available in the literature.

  17. c-Jun N-terminal kinase mediates disassembly of apical junctions in model intestinal epithelia.

    PubMed

    Naydenov, Nayden G; Hopkins, Ann M; Ivanov, Andrei I

    2009-07-01

    Dynamic remodeling of intercellular junctions is a critical determinant of epithelial barrier function in both physiological and pathophysiological states. While the disassembly of epithelial tight junctions (TJ) and adherens junctions (AJ) has been well-described in response to pathogens and other external stressors, the role of stress-related signaling in TJ/AJ regulation remains poorly understood. The aim of this study was to define the role of stress-activated c-Jun N-terminal kinase (JNK) in disruption of intercellular junctions in model intestinal epithelia. We show that rapid AJ/TJ disassembly triggered by extracellular calcium depletion of T84 and SK-CO15 cell monolayers was accompanied by activation (phosphorylation) of JNK, and prevented by pharmacological inhibitors of JNK. The opposite process, TJ/AJ reassembly, was accelerated by JNK inhibition and suppressed by the JNK activator anisomycin. JNK1 but not JNK2 was found to colocalize with intercellular junctions, and siRNA-mediated downregulation of JNK1 attenuated the TJ/AJ disruption caused by calcium depletion. JNK inhibition also blocked formation of characteristic contractile F-actin rings in calcium-depleted epithelial cells, suggesting that JNK regulates junctions by remodeling the actin cytoskeleton. In this role JNK acts downstream of the actin-reorganizing Rho-dependent kinase (ROCK), since ROCK inhibition abrogated JNK phosphorylation and TJ/AJ disassembly after calcium depletion. Furthermore, JNK acts upstream of F-actin-membrane linker proteins of the ERM (ezrin-radixin-moesin) family, but in a complex relationship yet to be fully elucidated. Taken together, our findings suggest a novel role for JNK in the signaling pathway that links ROCK and F-actin remodeling during disassembly of epithelial junctions.

  18. Conductance through two-terminal graphene junctions with wetting metal contacts

    NASA Astrophysics Data System (ADS)

    Barraza-Lopez, Salvador; Kindermann, Markus; Chou, Mei-Yin

    2012-02-01

    Metallic contacts become a relevant factor for the behavior of nanoscale graphene devices. A thin layer of a wetting metal --a metal that forms covalent bonds to graphene-- is customarily placed in between graphene and bulk leads. The most common choices for this wetting metal are Titanium, Chromium, and Palladium. We will present the equilibrium conductance through crystalline (defect- and impurity-free) two-terminal graphene junctions attached to normal, spin-unpolarized Titanium metal leads. In addition, we discuss the equilibrium potential profile across the junctions, and the presence of Fabry-Perot oscillations. The conductance shows pronounced noise, and the Fano factor near the Dirac point is seen to fluctuate, as in experiment [1]. The distribution of transmission eigenvalues is bimodal, indicating a disordered-metal-like charge transport through nanoscale two-terminal graphene junctions with wetting metals.[4pt] [1] L. DiCarlo, J. R. Williams, Y. Zhang, D. T. McClure, and C. M. Marcus. Phys. Rev. Lett. 100, 156801 (2008).[0pt] [2] S. Barraza-Lopez, M. Kindermann, and M.-Y. Chou. (Manuscript in preparation.)

  19. Performance of a junction termination extension avalanche photodiode for use with scintillators

    NASA Astrophysics Data System (ADS)

    Gramsch, E.; Pcheliakov, O.; Chistokhin, Igor B.

    2008-11-01

    An avalanche photodiode with a ring structure called junction termination extension (JTE) was built and tested. It has three diffused rings around the main junction to avoid early breakdown at the surface. The ITE rings have less doping than the main junction and can be built by well controlled single ion-implantation through a single mask. Avalanche photodiodes with two mm diameter active area have been have been built by implantation of boron with a dose of 2, 3, 4 and 5 × 1012 cm-2, followed by deep diffusion of the junction up to 14 μm. The dark current is strongly dependent on the implantation dose, decreasing with decreasing charge. For the APDs with implanted dose of 5 × 1012 cm-2 a gain of 8 is obtained at 1120 V. The energy resolution from a 137Cs source was measured to be 24.4% FWHM with a 2 × 2 × 2 mm3 BGO scintillator. We have also performed simulations of the gain and breakdown voltage that correlate well with the results.

  20. A 2-terminal perovskite/silicon multijunction solar cell enabled by a silicon tunnel junction

    SciTech Connect

    Mailoa, Jonathan P.; Bailie, Colin D.; Johlin, Eric C.; Hoke, Eric T.; Akey, Austin J.; Nguyen, William H.; McGehee, Michael D.; Buonassisi, Tonio

    2015-03-24

    With the advent of efficient high-bandgap metal-halide perovskite photovoltaics, an opportunity exists to make perovskite/silicon tandem solar cells. We fabricate a monolithic tandem by developing a silicon-based interband tunnel junction that facilitates majority-carrier charge recombination between the perovskite and silicon sub-cells. We demonstrate a 1 cm2 2-terminal monolithic perovskite/silicon multijunction solar cell with a VOC as high as 1.65 V. As a result, we achieve a stable 13.7% power conversion efficiency with the perovskite as the current-limiting sub-cell, and identify key challenges for this device architecture to reach efficiencies over 25%.

  1. Three-terminal magnetic tunneling junction device with perpendicular anisotropy CoFeB sensing layer

    SciTech Connect

    Honjo, H. Nebashi, R.; Tokutome, K.; Miura, S.; Sakimura, N.; Sugibayashi, T.; Fukami, S.; Kinoshita, K.; Murahata, M.; Kasai, N.; Ishihara, K.; Ohno, H.

    2014-05-07

    We demonstrated read and write characteristics of a three terminal memory device with a perpendicular anisotropy-free layer of a strip of [Co/Ni] and a low-switching perpendicular-anisotropy CoFeB/MgO sensing layer. This new design of the cell results in a small cell area. The switching magnetic field of the sensing layer can be decreased by changing sputtering gas for the Ta-cap from Ar to Kr. An electron energy-loss spectroscopy analysis of the cross-section of the magnetic tunneling junction (MTJ) revealed that the boron content in CoFeB with a Kr-sputtered Ta-cap was smaller than that with an Ar-sputtered one. A change in resistance for the MTJ was observed that corresponded to the magnetic switching of the Co/Ni wire and its magnetoresistance ratio and critical current were 90% and 0.8 mA, respectively.

  2. A 2-terminal perovskite/silicon multijunction solar cell enabled by a silicon tunnel junction

    DOE PAGESBeta

    Mailoa, Jonathan P.; Bailie, Colin D.; Johlin, Eric C.; Hoke, Eric T.; Akey, Austin J.; Nguyen, William H.; McGehee, Michael D.; Buonassisi, Tonio

    2015-03-24

    With the advent of efficient high-bandgap metal-halide perovskite photovoltaics, an opportunity exists to make perovskite/silicon tandem solar cells. We fabricate a monolithic tandem by developing a silicon-based interband tunnel junction that facilitates majority-carrier charge recombination between the perovskite and silicon sub-cells. We demonstrate a 1 cm2 2-terminal monolithic perovskite/silicon multijunction solar cell with a VOC as high as 1.65 V. As a result, we achieve a stable 13.7% power conversion efficiency with the perovskite as the current-limiting sub-cell, and identify key challenges for this device architecture to reach efficiencies over 25%.

  3. Partially resummed perturbation theory for multiple Andreev reflections in a short three-terminal Josephson junction

    NASA Astrophysics Data System (ADS)

    Mélin, Régis; Feinberg, Denis; Douçot, Benoît

    2016-03-01

    In a transparent three-terminal Josephson junction, modeling nonequilibrium transport is numerically challenging, owing to the interplay between multiple Andreev reflection (MAR) thresholds and multipair resonances in the pair current. An approximate method, coined as "partially resummed perturbation theory in the number of nonlocal Green's functions", is presented that can be operational on a standard computer and demonstrates compatibility with results existing in the literature. In a linear structure made of two neighboring interfaces (with intermediate transparency) connected by a central superconductor, tunneling through each of the interfaces separately is taken into account to all orders. On the contrary, nonlocal processes connecting the two interfaces are accounted for at the lowest relevant order. This yields logarithmically divergent contributions at the gap edges, which are sufficient as a semi-quantitative description. The method is able to describe the current in the full two-dimensional voltage range, including commensurate as well as incommensurate values. The results found for the multipair (for instance quartet) current-phase characteristics as well as the MAR thresholds are compatible with previous results. At intermediate transparency, the multipair critical current is much larger than the background MAR current, which supports an experimental observation of the quartet and multipair resonances. The paper provides a proof of principle for addressing in the future the interplay between quasiparticles and multipairs in four-terminal structures.

  4. Theoretical efficiency limit for a two-terminal multi-junction "step-cell" using detailed balance method

    NASA Astrophysics Data System (ADS)

    Abdul Hadi, Sabina; Fitzgerald, Eugene A.; Nayfeh, Ammar

    2016-02-01

    Here we present detailed balance efficiency limit for a novel two-terminal dual and triple junction "step-cell" under AM 1.5G and AM 0 incident spectrums. The step-cell is a multi-junction (MJ) solar cell in which part of the top cell is removed, exposing some of the bottom cell area to unfiltered incident light, thus increasing bottom cell's photogenerated current. Optical generation of the bottom cell is modeled in two parts: step part, limited by the bottom cell bandgap, and conventional part, additionally limited by the top cell absorption. Our results show that conventionally designed MJ cell with optimized bandgap combination of 1.64 eV/0.96 eV for dual junction and 1.91 eV/1.37 eV/0.93 eV for triple junction has the highest theoretical efficiency limit. However, the step-cell design provides significant efficiency improvement for cells with non-optimum bandgap values. For example, for 1.41 eV ( ˜GaAs)/Si dual junction under AM 1.5G, efficiency limit increases from ˜21% in a conventional design to 38.7% for optimized step-cell. Similar benefits are observed for three-junction step-cell and for AM 0 spectrum studied here. Step-cell relaxes bandgap requirements for efficient MJ solar cells, providing an opportunity for a wider selection of materials and cost reduction.

  5. Long terminal repeat of murine retroviral DNAs: sequence analysis, host-proviral junctions, and preintegration site.

    PubMed Central

    Van Beveren, C; Rands, E; Chattopadhyay, S K; Lowy, D R; Verma, I M

    1982-01-01

    The nucleotide sequence of the long terminal repeat (LTR) of three murine retroviral DNAs has been determined. The data indicate that the U5 region (sequences originating from the 5' end of the genome) of various LTRs is more conserved than the U3 region (sequences from the 3' end of the genome). The location and sequence of the control elements such as the 5' cap, "TATA-like" sequences, "CCAAT-box," and presumptive polyadenylic acid addition signal AATAAA in the various LTRs are nearly identical. Some murine retroviral DNAs contain a duplication of sequences within the LTR ranging in size from 58 to 100 base pairs. A variant of molecularly cloned Moloney murine sarcoma virus DNA in which one of the two LTRs integrated into the viral DNA was also analyzed. A 4-base-pair duplication was generated at the site of integration of LTR in the viral DNA. The host-viral junction of two molecularly cloned AKR-murine leukemia virus DNAs (clones 623 and 614) was determined. In the case of AKR-623 DNA, a 3- or 4-base-pair direct repeat of cellular sequences flanking the viral DNA was observed. However, AKR-614 DNA contained a 5-base-pair repeat of cellular sequences. The nucleotide sequence of the preintegration site of AKR-623 DNA revealed that the cellular sequences duplicated during integration are present only once. Finally, a striking homology between the sequences flanking the preintegration site and viral LTRs was observed. Images PMID:6281466

  6. Origin of the broad three-terminal Hanle signals in Fe/SiO{sub 2}/Si tunnel junctions

    SciTech Connect

    Sato, Shoichi; Tanaka, Masaaki; Nakane, Ryosho

    2015-07-20

    Lorentzian-shaped broader three-terminal Hanle (B-3TH) signals are observed in Fe/SiO{sub 2}/Si tunnel junction devices at 6–300 K. We propose a spin conducting model, which explains all the characteristics of our experimental results, such as field angle dependence and bias dependence of the B-3TH signals, as well as experimental results reported by other groups. It was found that the shape of the B-3TH signals is determined by the spin depolarization at the Fe/SiO{sub 2} interface caused by local magnetic fields, unlike the conventional understanding. The shape of the B-3TH signals, including narrower and inverted Hanle signals, reflects the magnetic order of an ultrathin paramagnetic layer formed at the Fe/SiO{sub 2} interface. Our model provides a unified explanation of the B-3TH signals observed in three-terminal Hanle measurements.

  7. Microdialysis in cisterna magna during cerebral air embolism in swine.

    PubMed

    Medby, C; Rø, H; Koteng, S; Juul, R; Krossnes, B K; Brubakk, A O

    2002-01-01

    Arterial gas embolism may occur as a consequence of lung rupture, decompression sickness, following operative procedures or as accidental infusion of gas during various diagnostic procedures. It can lead to severe morbidity or even death. Microdialysis is a technique that has been extensively used for evaluating localized changes in the brain. The microdialysis probe is only capable of measuring changes in the immediate adjacent tissue. In arterial gas embolism the changes are multifocal. Thus a probe located in the cerebral cortex will not detect the total amount of damage. We used microdialysis in the cisterna magna of 9 anaesthetized pigs to study the diffuse injury following arterial gas embolism. After injection of 5.0 mL of air in the internal carotid artery, we found a significantly increased lactate-pyruvate ratio in the cerebrospinal fluid, lasting for 2 hours. This indicates anaerobic metabolism. Mean levels of glycerol were significantly increased, indicating membrane disruption. Glutamate levels were also elevated, although not significantly. The injection of air affected carotid flow. Flow in the carotid artery of the side of injection decreased significantly, but returned to baseline in 1 hour. Flow in the contralateral carotid was increased, but not significantly. We conclude that massive air embolism causes ischemia and reduced blood flow in the brain that can be detected in the cisterna magna. PMID:12670124

  8. Four-terminal magneto-transport in graphene p-n junctions created by spatially selective doping.

    PubMed

    Lohmann, Timm; von Klitzing, Klaus; Smet, Jurgen H

    2009-05-01

    In this paper, we describe a graphene p-n junction created by chemical doping. We find that chemical doping does not reduce mobility in contrast to top-gating. The preparation technique has been developed from systematic studies about influences on the initial doping of freshly prepared graphene. We investigated the removal of adsorbates by vacuum treatment, annealing, and compensation doping using NH(3). Hysteretic behavior is observed in the electric field effect due to dipolar adsorbates like water and NH(3). Finally we demonstrate spatially selective doping of graphene using patterned PMMA. Four-terminal transport measurements of the p-n devices reveal edge channel mixing in the quantum hall regime. Quantized resistances of h/e(2), h/3e(2) and h/15e(2) can be observed as expected from theory.

  9. Majorana modes in a triple-terminal Josephson junction with embedded parallel-coupled double quantum dots

    NASA Astrophysics Data System (ADS)

    Yi, Guang-Yu; Wang, Xiao-Qi; Gao, Zhen; Wu, Hai-Na; Gong, Wei-Jiang

    2016-09-01

    We investigate the Josephson effect in one triple-terminal junction with embedded parallel-coupled double quantum dots. It is found that the inter-superconductor supercurrent has opportunities to oscillate in period 4 π, with the adjustment of the phase differences among the superconductors. What is notable is that such a result is robust and independent of fermion parities, intradot Coulomb strength, and the dot-superconductor coupling manner. By introducing the concept of spinful many-particle Majorana modes, we present the analytical definition of the Majorana operator via superposing electron and hole operators. It can be believed that this work provide a simple but feasible proposal for the realization of Majorana modes in a nonmagnetic system.

  10. Simulation and experimental study of 3-step junction termination extension for high-voltage 4H-SiC gate turn-off thyristors

    NASA Astrophysics Data System (ADS)

    Lin, Lei; Zhao, Jian H.

    2013-08-01

    The 4H-SiC NPN structure with a 3-step junction termination extension (JTE), which shows a great capability for control of both the peak surface and bulk electric fields at breakdown, has been investigated and optimized using Synopsys Sentaurus, a two-dimensional (2-D) device simulator. The experimental results show that the NPN structure with an optimized 3-step JTE can accomplish a high breakdown voltage of 7630 V, reaching more than 90% of the ideal parallel plane junction breakdown voltage. A good agreement between simulation and experimental results can be observed. The key step in achieving a high breakdown voltage is controlled etching of the epitaxially grown n-doped layer to reach the optimum depth and balanced charge in the multistep junction termination extension (MJTE) layer.

  11. Nonlinear behavior of three-terminal graphene junctions at room temperature

    NASA Astrophysics Data System (ADS)

    Kim, Wonjae; Pasanen, Pirjo; Riikonen, Juha; Lipsanen, Harri

    2012-03-01

    We demonstrate nonlinear behavior in three-terminal T-branch graphene devices at room temperature. A rectified nonlinear output at the center branch is observed when the device is biased by a push-pull configuration. Nonlinearity is assumed to arise from a difference in charge transfer through the metal-graphene contact barrier between two contacts. The sign of the rectification can be altered by changing the carrier type using the back-gate voltage.

  12. Neuregulin1 displayed on motor axons regulates terminal Schwann cell-mediated synapse elimination at developing neuromuscular junctions.

    PubMed

    Lee, Young Il; Li, Yue; Mikesh, Michelle; Smith, Ian; Nave, Klaus-Armin; Schwab, Markus H; Thompson, Wesley J

    2016-01-26

    Synaptic connections in the nervous system are rearranged during development and in adulthood as a feature of growth, plasticity, aging, and disease. Glia are implicated as active participants in these changes. Here we investigated a signal that controls the participation of peripheral glia, the terminal Schwann cells (SCs), at the neuromuscular junction (NMJ) in mice. Transgenic manipulation of the levels of membrane-tethered neuregulin1 (NRG1-III), a potent activator of SCs normally presented on motor axons, alters the rate of loss of motor inputs at NMJs during developmental synapse elimination. In addition, NMJs of adult transgenic mice that expressed excess axonal NRG1-III exhibited continued remodeling, in contrast to the more stable morphologies of controls. In fact, synaptic SCs of these adult mice with NRG1-III overexpression exhibited behaviors evident in wild type neonates during synapse elimination, including an affinity for the postsynaptic myofiber surface and phagocytosis of nerve terminals. Given that levels of NRG1-III expression normally peak during the period of synapse elimination, our findings identify axon-tethered NRG1 as a molecular determinant for SC-driven neuromuscular synaptic plasticity.

  13. Neuregulin1 displayed on motor axons regulates terminal Schwann cell-mediated synapse elimination at developing neuromuscular junctions

    PubMed Central

    Li, Yue; Mikesh, Michelle; Smith, Ian; Nave, Klaus-Armin; Schwab, Markus H.; Thompson, Wesley J.

    2016-01-01

    Synaptic connections in the nervous system are rearranged during development and in adulthood as a feature of growth, plasticity, aging, and disease. Glia are implicated as active participants in these changes. Here we investigated a signal that controls the participation of peripheral glia, the terminal Schwann cells (SCs), at the neuromuscular junction (NMJ) in mice. Transgenic manipulation of the levels of membrane-tethered neuregulin1 (NRG1-III), a potent activator of SCs normally presented on motor axons, alters the rate of loss of motor inputs at NMJs during developmental synapse elimination. In addition, NMJs of adult transgenic mice that expressed excess axonal NRG1-III exhibited continued remodeling, in contrast to the more stable morphologies of controls. In fact, synaptic SCs of these adult mice with NRG1-III overexpression exhibited behaviors evident in wild type neonates during synapse elimination, including an affinity for the postsynaptic myofiber surface and phagocytosis of nerve terminals. Given that levels of NRG1-III expression normally peak during the period of synapse elimination, our findings identify axon-tethered NRG1 as a molecular determinant for SC-driven neuromuscular synaptic plasticity. PMID:26755586

  14. Aging Drosophila melanogaster display altered pre- and postsynaptic ultrastructure at adult neuromuscular junctions.

    PubMed

    Wagner, Nicole; Laugks, Ulrike; Heckmann, Manfred; Asan, Esther; Neuser, Kirsa

    2015-11-01

    Although age-related changes in synaptic plasticity are an important focus within neuroscience, little is known about ultrastructural changes of synaptic morphology during aging. Here we report how aging affects synaptic ultrastructure by using fluorescence and electron microscopy at the adult Drosophila neuromuscular junction (NMJ) of ventral abdominal muscles. Mainly four striking morphological changes of aging NMJs were revealed. 1) Bouton size increases with proportionally rising number of active zones (AZs). 2) Synaptic vesicle density at AZs is increased in old flies. 3) Late endosomes, cisternae, and multivesicular bodies accumulate in the presynaptic terminal, and vesicles accumulate between membranes of the terminal bouton and the subsynaptic reticulum. 4) The electron-dense pre- and postsynaptic apposition is expanded in aging NMJs, which is accompanied by an expansion of the postsynaptic glutamate receptor fields. These findings suggest that aging is possibly accompanied by impaired synaptic vesicle release and recycling and a potentially compensatory expansion of AZs and postsynaptic densities. PMID:25940748

  15. Logic circuit prototypes for three-terminal magnetic tunnel junctions with mobile domain walls

    NASA Astrophysics Data System (ADS)

    Currivan-Incorvia, J. A.; Siddiqui, S.; Dutta, S.; Evarts, E. R.; Zhang, J.; Bono, D.; Ross, C. A.; Baldo, M. A.

    2016-01-01

    Spintronic computing promises superior energy efficiency and nonvolatility compared to conventional field-effect transistor logic. But, it has proven difficult to realize spintronic circuits with a versatile, scalable device design that is adaptable to emerging material physics. Here we present prototypes of a logic device that encode information in the position of a magnetic domain wall in a ferromagnetic wire. We show that a single three-terminal device can perform inverter and buffer operations. We demonstrate one device can drive two subsequent gates and logic propagation in a circuit of three inverters. This prototype demonstration shows that magnetic domain wall logic devices have the necessary characteristics for future computing, including nonlinearity, gain, cascadability, and room temperature operation.

  16. Logic circuit prototypes for three-terminal magnetic tunnel junctions with mobile domain walls

    PubMed Central

    Currivan-Incorvia, J. A.; Siddiqui, S.; Dutta, S.; Evarts, E. R.; Zhang, J.; Bono, D.; Ross, C. A.; Baldo, M. A.

    2016-01-01

    Spintronic computing promises superior energy efficiency and nonvolatility compared to conventional field-effect transistor logic. But, it has proven difficult to realize spintronic circuits with a versatile, scalable device design that is adaptable to emerging material physics. Here we present prototypes of a logic device that encode information in the position of a magnetic domain wall in a ferromagnetic wire. We show that a single three-terminal device can perform inverter and buffer operations. We demonstrate one device can drive two subsequent gates and logic propagation in a circuit of three inverters. This prototype demonstration shows that magnetic domain wall logic devices have the necessary characteristics for future computing, including nonlinearity, gain, cascadability, and room temperature operation. PMID:26754412

  17. The junction of Hellenic and Cyprus arcs: the Bey Daglari lineament, offshore termination of the Antalya Basin

    NASA Astrophysics Data System (ADS)

    Gogacz, A.; Hall, J.; Çifçi, G.; Yaşar, D.; Küçük, M.; Yaltırak, C.; Aksu, A.

    2009-04-01

    The Antalya Basin is one of a series of basins that sweep along the Cyprus Arc in the forearc region between the (formerly) volcanic Tauride Mountains on Turkey in the north and the subduction zone and associated suture between the African plate and the Aegean-Anatolian microplate in the eastern Mediterranean, south of Cyprus. Miocene contraction occurs widely on southwest verging thrusts. Pliocene-Quaternary structures vary from extension/transtension in the northeast, adjacent to the Turkish coastline, to transpression in the southwest, farther offshore. All these structures are truncated at the northwest end of the Antalya Basin by a broad zone of NNE-SSW-trending transverse structure that appears to represent a prolongation of the extreme easterly transform end of the Hellenic arc. Our mapping suggests that this broad zone links the Hellenic Arc with the Isparta Angle in southern Turkey, which we suggest is an earlier location of the junction of Hellenic and Cyprus Arcs: the junction migrated to the southwest over time, as the Hellenic Arc rolled back. The Turkish coastline turns from parallel to the Antalya Basin structures in the east to a N-S orientation, cutting across the trend of the Antalya Basin. The Antalya Complex and the Bey Dağlari Mountains provide a spectacular backdrop to this edge of the offshore basin. Somewhere offshore lies the structural termination of the Antalya Basin. In 2001, we acquired around 400 km of high-resolution multi-channel seismic reflection data across the western end of the Antalya Basin to explore the nature of the termination, which we call the Bey Dağlari lineament. We present a selection of the seismic profiles with interpretation of the nature and Neogene history of the lineament. Landward of the N-S-trending coastline, ophiolites of the Antalya Complex are exposed in a series of westerly-verging thrust slivers that extend to the carbonate sequences of the Bey Dağlari Mountains. Our seismic data indicate that N

  18. The Junction of Hellenic and Cyprus Arcs: the Bey Daglari Lineament, Offshore Termination of the Antalya Basin

    NASA Astrophysics Data System (ADS)

    Gogacz, A.; Hall, J.; Cifci, G.; Yasar, D.; Kucuk, M.; Yaltirak, C.; Aksu, A.

    2009-05-01

    The Antalya Basin is one of a series of basins that sweep along the Cyprus Arc in the forearc region between the (formerly) volcanic Tauride Mountains on Turkey in the north and the subduction zone and associated suture between the African plate and the Aegean-Anatolian microplate in the eastern Mediterranean, south of Cyprus. Miocene contraction occurs widely on southwest verging thrusts. Pliocene-Quaternary structures vary from extension/transtension in the northeast, adjacent to the Turkish coastline, to transpression in the southwest, farther offshore. All these structures are truncated at the northwest end of the Antalya Basin by a broad zone of NNE-SSW-trending transverse structure that appears to represent a prolongation of the extreme easterly transform end of the Hellenic arc. Our mapping suggests that this broad zone links the Hellenic Arc with the Isparta Angle in southern Turkey, which we suggest is an earlier location of the junction of Hellenic and Cyprus Arcs: the junction migrated to the southwest over time, as the Hellenic Arc rolled back. The Turkish coastline turns from parallel to the Antalya Basin structures in the east to a N-S orientation, cutting across the trend of the Antalya Basin. The Antalya Complex and the Bey Dağları Mountains provide a spectacular backdrop to this edge of the offshore basin. Somewhere offshore lies the structural termination of the Antalya Basin. In 2001, we acquired around 400 km of high-resolution multi-channel seismic reflection data across the western end of the Antalya Basin to explore the nature of the termination, which we call the Bey Dağları lineament. We present a selection of the seismic profiles with interpretation of the nature and Neogene history of the lineament. Landward of the N-S-trending coastline, ophiolites of the Antalya Complex are exposed in a series of westerly-verging thrust slivers that extend to the carbonate sequences of the Bey Dağları Mountains. Our seismic data indicate that N

  19. Cisterna magna cannulated repeated CSF sampling rat model--effects of a gamma-secretase inhibitor on Aβ levels.

    PubMed

    Shapiro, Jennifer S; Stiteler, Mark; Wu, Guoxin; Price, Eric A; Simon, Adam J; Sankaranarayanan, Sethu

    2012-03-30

    Cerebrospinal fluid (CSF) provides a window into central nervous system (CNS) physiology and pathophysiology in human neurodegenerative conditions such as Alzheimer's disease. Changes in CSF bioanalytes also provide a direct readout of target engagement in the CNS following pharmacological interventions in clinical trials. Given the importance of tracking CNS bioanalytes in drug discovery, we have developed a novel cisterna magna cannulated rat model for repeated CSF sampling and used it to assess an amyloid beta (Aβ) lowering agent. The surgically implanted cisterna magna cannula was patent over a period of 1-2 weeks and enabled repeated sampling of CSF (volume of ∼30-50μL/sample) from each rat. CSF Aβ40 levels showed good intra-animal variability across time points and inter-animal variability within a time point. Peripheral treatment with a gamma-secretase inhibitor (GSI) led to a rapid and robust decline in CSF Aβ40 levels that returned to baseline over 24-96h after dosing. Terminal brain, CSF and plasma Aβ levels measured at 24h after dosing demonstrated robust Aβ lowering and showed excellent correlation across these compartments. These results are the first pharmacological validation of the repeated CSF sampling rat model for Aβ lowering agents. This model can have broad applicability in pharmacological evaluation for diverse CNS targets.

  20. Current-induced magnetization switching of a three terminal perpendicular magnetic tunnel junction by spin-orbit torque

    NASA Astrophysics Data System (ADS)

    Cubukcu, Murat; Drouard, Marc; Boulle, Olivier; Garello, Kevin; Miron, Ioan Mihai; Langer, Juergen; Ocker, Berthold; Gambardella, Pietro; Gaudin, Gilles

    2014-03-01

    A current flowing in the plane of a magnetic multilayer with structural inversion asymmetry, such as Pt/Co/AlOx, creates a torque on the magnetization. This torque is due to the strong spin-orbit interaction present in such multilayers and can lead to fast magnetization reversal with a low writing energy.We will present the first proof of concept of a perpendicular spin-orbit torque magnetic random access memory (SOT-MRAM) cell composed of a Ta/FeCoB/MgO/FeCoB magnetic tunnel junction. The basic write and read operations, i.e., the magnetization reversal by current injection in the Ta track and its detection using the high TMR signal, are demonstrated. Our results open a path for the development of a novel class of three terminal MRAM combining fast, reliable and low energy writing. This work was supported by the European Commission under the Seventh Framework Program (Grant Agreement 318144, spot project).

  1. Fuzzy-Logic Based Detection and Characterization of Junctions and Terminations in Fluorescence Microscopy Images of Neurons.

    PubMed

    Radojević, Miroslav; Smal, Ihor; Meijering, Erik

    2016-04-01

    Digital reconstruction of neuronal cell morphology is an important step toward understanding the functionality of neuronal networks. Neurons are tree-like structures whose description depends critically on the junctions and terminations, collectively called critical points, making the correct localization and identification of these points a crucial task in the reconstruction process. Here we present a fully automatic method for the integrated detection and characterization of both types of critical points in fluorescence microscopy images of neurons. In view of the majority of our current studies, which are based on cultured neurons, we describe and evaluate the method for application to two-dimensional (2D) images. The method relies on directional filtering and angular profile analysis to extract essential features about the main streamlines at any location in an image, and employs fuzzy logic with carefully designed rules to reason about the feature values in order to make well-informed decisions about the presence of a critical point and its type. Experiments on simulated as well as real images of neurons demonstrate the detection performance of our method. A comparison with the output of two existing neuron reconstruction methods reveals that our method achieves substantially higher detection rates and could provide beneficial information to the reconstruction process.

  2. C-terminal Src Kinase Gates Homeostatic Synaptic Plasticity and Regulates Fasciclin II Expression at the Drosophila Neuromuscular Junction

    PubMed Central

    Spring, Ashlyn M.; Brusich, Douglas J.; Frank, C. Andrew

    2016-01-01

    Forms of homeostatic plasticity stabilize neuronal outputs and promote physiologically favorable synapse function. A well-studied homeostatic system operates at the Drosophila melanogaster larval neuromuscular junction (NMJ). At the NMJ, impairment of postsynaptic glutamate receptor activity is offset by a compensatory increase in presynaptic neurotransmitter release. We aim to elucidate how this process operates on a molecular level and is preserved throughout development. In this study, we identified a tyrosine kinase-driven signaling system that sustains homeostatic control of NMJ function. We identified C-terminal Src Kinase (Csk) as a potential regulator of synaptic homeostasis through an RNAi- and electrophysiology-based genetic screen. We found that Csk loss-of-function mutations impaired the sustained expression of homeostatic plasticity at the NMJ, without drastically altering synapse growth or baseline neurotransmission. Muscle-specific overexpression of Src Family Kinase (SFK) substrates that are negatively regulated by Csk also impaired NMJ homeostasis. Surprisingly, we found that transgenic Csk-YFP can support homeostatic plasticity at the NMJ when expressed either in the muscle or in the nerve. However, only muscle-expressed Csk-YFP was able to localize to NMJ structures. By immunostaining, we found that Csk mutant NMJs had dysregulated expression of the Neural Cell Adhesion Molecule homolog Fasciclin II (FasII). By immunoblotting, we found that levels of a specific isoform of FasII were decreased in homeostatically challenged GluRIIA mutant animals–but markedly increased in Csk mutant animals. Additionally, we found that postsynaptic overexpression of FasII from its endogenous locus was sufficient to impair synaptic homeostasis, and genetically reducing FasII levels in Csk mutants fully restored synaptic homeostasis. Based on these data, we propose that Csk and its SFK substrates impinge upon homeostatic control of NMJ function by regulating

  3. An investigation of the SNS Josephson junction as a three-terminal device. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Meissner, H.; Prans, G. P.

    1973-01-01

    A particular phenomenon of the SNS Josephson junction was investigated; i.e., control by a current entering the normal region and leaving through one of the superconducting regions. The effect of the control current on the junction was found to be dependent upon the ration of the resistances of the two halves of the N layer. A low frequency, lumped, nonlinear model was proposed to describe the electrical characteristics of the device, and a method was developed to plot the dynamic junction resistance as a function of junction current. The effective thermal noise temperature of the sample was determined. Small signal linearized analysis of the device suggests its use as an impedance transformer, although geometric limitations must be overcome. Linear approximation indicates that it is reciprocal and no power gain is possible. It is felt that, with suitable metallurgical and geometrical improvements, the device has promise to become a superconducting transistor.

  4. Longitudinal continuity of the subrhabdomeric cisternae in the photoreceptors of the compound eye of the drone, Apis mellifera.

    PubMed

    Skalska-Rakowska, J M; Baumgartner, B

    1985-01-15

    It is shown that the subrhabdomeric cisternae of the honey bee drone photoreceptor cell constitute a single structure with a continuous lumen, that extends over at least 15 micron and perhaps the whole length of the cell. In this case, the structure of the cisternae might subserve the propagation of light adaptation along the cell.

  5. 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.

  6. Novel room-temperature functional analogue and digital nanoelectronic circuits based on three-terminal ballistic junctions and planar quantum-wire transistors

    NASA Astrophysics Data System (ADS)

    Sun, J.; Wallin, D.; Brusheim, P.; Maximov, I.; Xu, H. Q.

    2008-03-01

    Three-Terminal ballistic junctions (TBJs) and planar quantum-wire transistors (QWTs) are emerging nanoelectronic devices with various novel electrical properties. In this work, we realize novel nanoelectronic analogue and digital circuits with TBJs and planar QWTs made on In0.75Ga0.25As/InP two-dimensional electron gas (2DEG) material. First we show that a single TBJ can work as a frequency mixer or a phase detector. Second, we fabricate an integrated nanostructure containing two planar QWTs, which can be used as an RS flip-flop element. Third, we make a nanoelectronic circuit by the integration of two TBJs and two planar QWTs. This circuit shows the RS flip-flop functionalities with much larger noise margins in both high and low level inputs. All measurements in this work are done at room temperature.

  7. A chronic cannula for obtaining CSF from the cisterna magna of awake dogs.

    PubMed

    Jennings, D B; Tobin, P

    1979-01-01

    We have designed a cannula system that can be chronically implanted to end above the dura of the cisterna magna of the dog. During experiments in the awake dog, a screw cap with stylet is removed from the cannula and a spinal needle inserted for the withdrawal of samples of cisternal cerebrospinal fluid (CSF) or for making continuous measurements of pressure. The system can be used for repeated experiments extending over several weeks.

  8. Clinical Improvement of Alpha-mannosidosis Cat Following a Single Cisterna Magna Infusion of AAV1.

    PubMed

    Yoon, Sea Young; Bagel, Jessica H; O'Donnell, Patricia A; Vite, Charles H; Wolfe, John H

    2016-02-01

    Lysosomal storage diseases (LSDs) are debilitating neurometabolic disorders for most of which long-term effective therapies have not been developed. Gene therapy is a potential treatment but a critical barrier to treating the brain is the need for global correction. We tested the efficacy of cisterna magna infusion of adeno-associated virus type 1 (AAV1) expressing feline alpha-mannosidase gene in the postsymptomatic alpha-mannosidosis (AMD) cat, a homologue of the human disease. Lysosomal alpha-mannosidase (MANB) activity in the cerebrospinal fluid (CSF) and serum were increased above the control values in untreated AMD cats. Clinical neurological signs were delayed in onset and reduced in severity. The lifespan of the treated cats was significantly extended. Postmortem histopathology showed resolution of lysosomal storage lesions throughout the brain. MANB activity in brain tissue was significantly above the levels of untreated tissues. The results demonstrate that a single cisterna magna injection of AAV1 into the CSF can mediate widespread neuronal transduction of the brain and meaningful clinical improvement. Thus, cisterna magna gene delivery by AAV1 appears to be a viable strategy for treatment of the whole brain in AMD and should be applicable to many of the neurotropic LSDs as well as other neurogenetic disorders.

  9. PREDICTING WATER ACTIVITY IN ELECTROLYTE SOLUTIONS WITH THE CISTERNAS-LAM MODEL

    SciTech Connect

    REYNOLDS JG; GREER DA; DISSELKAMP RL

    2011-03-01

    Water activity is an important parameter needed to predict the solubility of hydrated salts in Hanford nuclear waste supernatants. A number of models available in the scientific literature predict water activity from electrolyte solution composition. The Cisternas-Lam model is one of those models and has several advantages for nuclear waste application. One advantage is that it has a single electrolyte specific parameter that is temperature independent. Thus, this parameter can be determined from very limited data and extrapolated widely. The Cisternas-Lam model has five coefficients that are used for all aqueous electrolytes. The present study aims to determine if there is a substantial improvement in making all six coefficients electrolyte specific. The Cisternas-Lam model was fit to data for six major electrolytes in Hanford nuclear waste supernatants. The model was first fit to all data to determine the five global coefficients, when they were held constant for all electrolytes it yielded a substantially better fit. Subsequently, the model was fit to each electrolyte dataset separately, where all six coefficients were allowed to be electrolyte specific. Treating all six coefficients as electrolyte specific did not make sufficient difference, given the complexity of applying the electrolyte specific parameters to multi-solute systems. Revised water specific parameters, optimized to the electrolytes relevant to Hanford waste, are also reported.

  10. The gap junction inhibitor 2-aminoethoxy-diphenyl-borate protects against acetaminophen hepatotoxicity by inhibiting cytochrome P450 enzymes and c-jun N-terminal kinase activation

    SciTech Connect

    Du, Kuo; Williams, C. David; McGill, Mitchell R.; Xie, Yuchao; Farhood, Anwar; Vinken, Mathieu; Jaeschke, Hartmut

    2013-12-15

    Acetaminophen (APAP) hepatotoxicity is the leading cause of acute liver failure in the US. Although many aspects of the mechanism are known, recent publications suggest that gap junctions composed of connexin32 function as critical intercellular communication channels which transfer cytotoxic mediators into neighboring hepatocytes and aggravate liver injury. However, these studies did not consider off-target effects of reagents used in these experiments, especially the gap junction inhibitor 2-aminoethoxy-diphenyl-borate (2-APB). In order to assess the mechanisms of protection of 2-APB in vivo, male C56Bl/6 mice were treated with 400 mg/kg APAP to cause extensive liver injury. This injury was prevented when animals were co-treated with 20 mg/kg 2-APB and was attenuated when 2-APB was administered 1.5 h after APAP. However, the protection was completely lost when 2-APB was given 4–6 h after APAP. Measurement of protein adducts and c-jun-N-terminal kinase (JNK) activation indicated that 2-APB reduced both protein binding and JNK activation, which correlated with hepatoprotection. Although some of the protection was due to the solvent dimethyl sulfoxide (DMSO), in vitro experiments clearly demonstrated that 2-APB directly inhibits cytochrome P450 activities. In addition, JNK activation induced by phorone and tert-butylhydroperoxide in vivo was inhibited by 2-APB. The effects against APAP toxicity in vivo were reproduced in primary cultured hepatocytes without use of DMSO and in the absence of functional gap junctions. We conclude that the protective effect of 2-APB was caused by inhibition of metabolic activation of APAP and inhibition of the JNK signaling pathway and not by blocking connexin32-based gap junctions. - Highlights: • 2-APB protected against APAP-induced liver injury in mice in vivo and in vitro • 2-APB protected by inhibiting APAP metabolic activation and JNK signaling pathway • DMSO inhibited APAP metabolic activation as the solvent of 2-APB

  11. Iatrogenic Aorto-Cisterna Chyli Fistula During Percutaneous Balloon Aortoplasty in a Patient with Takayasu's Arteritis: A Case Report

    SciTech Connect

    Hwang, Hye Sun; Shin, Sung Wook Kim, Eun Hui; Do, Young Soo; Choo, Sung Wook; Cho, Sung Ki; Park, Kwang Bo

    2007-04-15

    We present a case of iatrogenic aorto-cisterna chyli fistula that developed during percutaneous transluminal aortoplasty in a 16-year old girl with Takayasu's arteritis. The aorto-cisterna chyli fistula was angiographically confirmed and treated using a stent-graft, which successfully occluded the fistula. Her claudication then improved, although follow-up CT angiography at 10 months revealed mild recurrent aortic stenosis.

  12. Interplay of Rashba spin orbit coupling and disorder in the conductance properties of a four terminal junction device

    NASA Astrophysics Data System (ADS)

    Ganguly, Sudin; Basu, Saurabh

    2016-04-01

    We report a thorough theoretical investigation on the quantum transport of a disordered four terminal device in the presence of Rashba spin orbit coupling (RSOC) in two dimensions. Specifically we compute the behaviour of the longitudinal (charge) conductance, spin Hall conductance and spin Hall conductance fluctuation as a function of the strength of disorder and Rashba spin orbit interaction using the Landauer Büttiker formalism via Green's function technique. Our numerical calculations reveal that both the conductances diminish with disorder. At smaller values of the RSOC parameter, the longitudinal and spin Hall conductances increase, while both vanish in the strong RSOC limit. The spin current is more drastically affected by both disorder and RSOC than its charge counterpart. The spin Hall conductance fluctuation does not show any universality in terms of its value and it depends on both disorder as well as on the RSOC strength. Thus the spin Hall conductance fluctuation has a distinct character compared to the fluctuation in the longitudinal conductance. Further one parameter scaling theory is studied to assess the transition to a metallic regime as claimed in literature and we find no confirmation about the emergence of a metallic state induced by RSOC.

  13. AAV9-mediated central nervous system–targeted gene delivery via cisterna magna route in mice

    PubMed Central

    Lukashchuk, Vera; Lewis, Katherine E; Coldicott, Ian; Grierson, Andrew J; Azzouz, Mimoun

    2016-01-01

    Current barriers to the use of adeno-associated virus serotype 9 (AAV9) in clinical trials for treating neurological disorders are its high expression in many off-target tissues such as liver and heart, and lack of cell specificity within the central nervous system (CNS) when using ubiquitous promoters such as human cytomegalovirus (CMV) or chicken-β-actin hybrid (CAG). To enhance targeting the transgene expression in CNS cells, self-complementary (sc) AAV9 vectors, scAAV9-GFP vectors carrying neuronal Hb9 and synapsin 1, and nonspecific CMV and CAG promoters were constructed. We demonstrate that synapsin 1 and Hb9 promoters exclusively targeted neurons in vitro, although their strengths were up to 10-fold lower than that of CMV. In vivo analyses of mouse tissue after scAAV9-GFP vector delivery via the cisterna magna revealed a significant advantage of synapsin 1 promoter over both Hb9 variants in targeting neurons throughout the brain, since Hb9 promoters were driving gene expression mainly within the motor-related areas of the brain stem. In summary, this study demonstrates that cisterna magna administration is a safe alternative to intracranial or intracerebroventricular vector delivery route using scAAV9, and introduces a novel utility of the Hb9 promoter for the targeted gene expression for both in vivo and in vitro applications. PMID:26942208

  14. InP/Ga0.47In0.53As monolithic, two-junction, three-terminal tandem solar cells

    NASA Technical Reports Server (NTRS)

    Wanlaas, M. W.; Gessert, T. A.; Horner, G. S.; Emery, K. A.; Coutts, T. J.

    1991-01-01

    The work presented has focussed on increasing the efficiency of InP-based solar cells through the development of a high-performance InP/Ga(0.47)In(0.53)As two-junction, three-terminal monolithic tandem cell. Such a tandem is particularly suited to space applications where a radiation-hard top cell (i.e., InP) is required. Furthermore, the InP/Ga(0.47)In(0.53)As materials system is lattice matched and offers a top cell/bottom cell bandgap differential (0.60 eV at 300 K) suitable for high tandem cell efficiencies under AMO illumination. A three-terminal configuration was chosen since it allows for independent power collection from each subcell in the monolithic stack, thus minimizing the adverse impact of radiation damage on the overall tandem efficiency. Realistic computer modeling calculations predict an efficiency boost of 7 to 11 percent from the Ga(0.47)In(0.53)As bottom cell under AMO illumination (25 C) for concentration ratios in the 1 to 1000 range. Thus, practical AMO efficiencies of 25 to 32 percent appear possible with the InP/Ga(0.47)In(0.53)As tandem cell. Prototype n/p/n InP/Ga(0.47)In(0.53)As monolithic tandem cells were fabricated and tested successfully. Using an aperture to define the illuminated areas, efficiency measurements performed on a non-optimized device under standard global illumination conditions (25 C) with no antireflection coating (ARC) give 12.2 percent for the InP top cell and 3.2 percent for the Ga(0.47)In(0.53)As bottom cell, yielding an overall tandem efficiency of 15.4 percent. With an ARC, the tandem efficiency could reach approximately 22 percent global and approximately 20 percent AMO. Additional details regarding the performance of individual InP and Ga(0.47)In(0.53)As component cells, fabrication and operation of complete tandem cells and methods for improving the tandem cell performance, are also discussed.

  15. Actin filaments are involved in the maintenance of Golgi cisternae morphology and intra-Golgi pH.

    PubMed

    Lázaro-Diéguez, Francisco; Jiménez, Nuria; Barth, Holger; Koster, Abraham J; Renau-Piqueras, Jaime; Llopis, Juan L; Burger, Koert N J; Egea, Gustavo

    2006-12-01

    Here we examine the contribution of actin dynamics to the architecture and pH of the Golgi complex. To this end, we have used toxins that depolymerize (cytochalasin D, latrunculin B, mycalolide B, and Clostridium botulinum C2 toxin) or stabilize (jasplakinolide) filamentous actin. When various clonal cell lines were examined by epifluorescence microscopy, all of these actin toxins induced compaction of the Golgi complex. However, ultrastructural analysis by transmission electron microscopy and electron tomography/three-dimensional modelling of the Golgi complex showed that F-actin depolymerization first induces perforation/fragmentation and severe swelling of Golgi cisternae, which leads to a completely disorganized structure. In contrast, F-actin stabilization results only in cisternae perforation/fragmentation. Concomitantly to actin depolymerization-induced cisternae swelling and disorganization, the intra-Golgi pH significantly increased. Similar ultrastructural and Golgi pH alkalinization were observed in cells treated with the vacuolar H+ -ATPases inhibitors bafilomycin A1 and concanamycin A. Overall, these results suggest that actin filaments are implicated in the preservation of the flattened shape of Golgi cisternae. This maintenance seems to be mediated by the regulation of the state of F-actin assembly on the Golgi pH homeostasis.

  16. An electrical inspection of the subsurface cisternae of the outer hair cell.

    PubMed

    Song, Lei; Santos-Sacchi, Joseph

    2015-02-01

    The cylindrical outer hair cell (OHC) of Corti's organ drives cochlear amplification by a voltage-dependent activation of the molecular motor, prestin (SLC26a5), in the cell's lateral membrane. The voltage-dependent nature of this process leads to the troublesome observation that the membrane resistor-capacitor filter could limit high-frequency acoustic activation of the motor. Based on cable theory, the unique 30 nm width compartment (the extracisternal space, ECS) formed between the cell's lateral membrane and adjacent subsurface cisternae (SSC) could further limit the influence of receptor currents on lateral membrane voltage. Here, we use dual perforated/whole-cell and loose patch clamp on isolated OHCs to sequentially record currents resulting from excitation at apical, middle, and basal loose patch sites before and after perforated patch rupture. We find that timing of currents is fast and uniform before whole-cell pipette washout, suggesting little voltage attenuation along the length of the lateral membrane. Prior treatment with salicylate, a disrupter of the SSC, confirms the influence of the SSC on current spread. Finally, a cable model of the OHC, which can match our data, indicates that the SSC poses a minimal barrier to current flow across it, thereby facilitating rapid delivery of voltage excitation to the prestin-embedded lateral membrane.

  17. Neogenesis and maturation of transient Golgi-like cisternae in a simple eukaryote.

    PubMed

    Stefanic, Sasa; Morf, Laura; Kulangara, Caroline; Regös, Attila; Sonda, Sabrina; Schraner, Elisabeth; Spycher, Cornelia; Wild, Peter; Hehl, Adrian B

    2009-08-15

    The highly reduced protozoan parasite Giardia lamblia has minimal machinery for cellular processes such as protein trafficking. Giardia trophozoites maintain diverse and regulated secretory pathways but lack an identifiable Golgi complex. During differentiation to cysts, however, they produce specialized compartments termed encystation-specific vesicles (ESVs). ESVs are hypothesized to be unique developmentally regulated Golgi-like organelles dedicated to maturation and export of pre-sorted cyst wall proteins. Here we present a functional analysis of this unusual compartment by direct interference with the functions of the small GTPases Sar1, Rab1 and Arf1. Conditional expression of dominant-negative variants revealed an essential role of Sar1 in early events of organelle neogenesis, whilst inhibition of Arf1 uncoupled morphological changes and cell cycle progression from extracellular matrix export. The latter led to development of ;naked cysts', which lacked water resistance and thus infectivity. Time-lapse microscopy and photobleaching experiments showed that putative Golgi-like cisternae in Giardia develop into a network capable of exchanging soluble cargo at a high rate via dynamic, tubular connections, presumably to synchronize maturation. The minimized and naturally pulsed trafficking machinery for export of the cyst wall biopolymer in Giardia is a simple model for investigating basic principles of neogenesis and maturation of Golgi compartments. PMID:19622633

  18. Syringomyelia without hindbrain herniation: tight cisterna magna. Report of four cases and a review of the literature.

    PubMed

    Kyoshima, Kazuhiko; Kuroyanagi, Takayuki; Oya, Fusakazu; Kamijo, Yukihiro; El-Noamany, Hossam; Kobayashi, Shigeaki

    2002-03-01

    Idiopathic syringomyelia, which is not associated with any definite pathogenic lesions, has been treated mainly by shunting of the syrinx and rarely by craniocervical decompression. The authors report four cases of syringomyelia thought to be idiopathic syringomyelia but treated by craniocervical decompression with favorable results. Syringomyelia was present without hindbrain herniation. In such cases, the subarachnoid space anterior to the brainstem at the level of the foramen magnum is usually open but the cisterna magna is impacted by the tonsils, a condition the authors term "tight cisterna magna." All patients underwent foramen magnum decompression and C-1 laminectomy, and the outer layer of the dura was peeled off. Further intradural exploration was performed when outflow of cerebrospinal fluid (CSF) from the fourth ventricle was deemed to be insufficient. Postoperatively, improvement in symptoms and a reduction in syrinx size were demonstrated in three patients, and a reduction in ventricle size was shown in two. Syringomyelia associated with tight cisterna magna should not be classified as idiopathic syringomyelia; rather, it belongs to the category of organic syringomyelia such as Chiari malformation. A possible pathogenesis of cavitation is obstruction of the CSF outflow from the foramen of Magendie, and the cavity may be a communicating dilation of the central canal. Ventricular dilation may depend on the extent to which CSF drainage is impaired from the foramina of Luschka. These cavities may respond to craniocervical decompression if it results in sufficient CSF outflow from the foramen of Magendie, even in cases with concomitant hydrocephalus.

  19. A technique for cannulating the Cisterna magna and sampling cerebrospinal fluid from socially housed birds.

    PubMed

    Moore, M S; Kuenzel, W J; Mench, J A

    1994-04-01

    The measurement of central levels of neurochemicals is an important approach to the understanding of the neurophysiological basis of behavior patterns in animals. Previous studies have utilized central sampling techniques developed for individually housed animals. The purpose of this study was to develop a cannulation technique and a method for sampling cerebrospinal fluid (CSF) from socially housed birds to facilitate the study of the neurophysiological basis of social behaviors. The cannulation technique involved the surgical implantation of a 22-gauge concentric guide cannula into the cisterna magna of 16-wk-old, feed-restricted male broiler breeders (n = 6). Individual-specific coordinates and optimum angle and depth of implantation of the cannula were determined in order to place the cannula correctly in the designated site. Once implanted, the guide cannula proved to be unobtrusive and secure and did not attract aggressive pecking from other birds in the pen. Two methods of CSF sampling were then examined. The first method required the use of a push-pull perfusion pump to withdraw CSF at a rate of 1 to 2 microL/min. The second method (passive), which did not use a pump, involved simply removing a "dummy" cannula from the guide cannula to release the CSF, which was then collected with a glass Hamilton syringe. Samples ranging from 100 to 500 microL were collected using the passive method. The combination of the cannulation technique described and the passive sampling method proved to be the most simple, efficient, and reliable method for measuring central levels of neurochemicals in socially housed broiler breeder males.

  20. 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.

  1. 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.

  2. Claudin-4 Overexpression in Epithelial Ovarian Cancer Is Associated with Hypomethylation and Is a Potential Target for Modulation of Tight Junction Barrier Function Using a C-Terminal Fragment of Clostridium perfringens Enterotoxin1

    PubMed Central

    Litkouhi, Babak; Kwong, Joseph; Lo, Chun-Min; Smedley, James G; McClane, Bruce A; Aponte, Margarita; Gao, Zhijian; Sarno, Jennifer L; Hinners, Jennifer; Welch, William R; Berkowitz, Ross S; Mok, Samuel C; Garner, Elizabeth I O

    2007-01-01

    Background Claudin-4, a tight junction (TJ) protein and receptor for the C-terminal fragment of Clostridium perfringens enterotoxin (C-CPE), is overexpressed in epithelial ovarian cancer (EOC). Previous research suggests DNA methylation is a mechanism for claudin-4 overexpression in cancer and that C-CPE acts as an absorption-enhancing agent in claudin-4-expressing cells. We sought to correlate claudin-4 overexpression in EOC with clinical outcomes and TJ barrier function, investigate DNA methylation as a mechanism for overexpression, and evaluate the effect of C-CPE on the TJ. Methods Claudin-4 expression in EOC was quantified and correlated with clinical outcomes. Claudin-4 methylation status was determined, and claudin-4-negative cell lines were treated with a demethylating agent. Electric cell-substrate impedance sensing was used to calculate junctional (paracellular) resistance (Rb) in EOC cells after claudin-4 silencing and after C-CPE treatment. Results Claudin-4 overexpression in EOC does not correlate with survival or other clinical endpoints and is associated with hypomethylation. Claudin-4 overexpression correlates with Rb and C-CPE treatment of EOC cells significantly decreased Rb in a dose- and claudin-4-dependent noncytotoxic manner. Conclusions C-CPE treatment of EOC cells leads to altered TJ function. Further research is needed to determine the potential clinical applications of C-CPE in EOC drug delivery strategies. PMID:17460774

  3. Maturation of late Golgi cisternae into RabE(RAB11) exocytic post-Golgi carriers visualized in vivo.

    PubMed

    Pantazopoulou, Areti; Pinar, Mario; Xiang, Xin; Peñalva, Miguel A

    2014-08-15

    The mechanism(s) by which proteins traverse and exit the Golgi are incompletely understood. Using Aspergillus nidulans hyphae, we show that late Golgi cisternae undergo changes in composition to gradually lose Golgi identity while acquiring post-Golgi RabE(RAB11) identity. This behavior of late Golgi cisternae is consistent with the cisternal maturation model. Post-Golgi RabE(RAB11) carriers travel to, and accumulate at, the apex, indicating that fusion is rate limiting for exocytosis. These carriers, which are loaded with kinesin, dynein, and MyoE(MYO5), move on a microtubule-based bidirectional conveyor belt relaying them to actin, which ultimately focuses exocytosis at the apex. Dynein drags RabE(RAB11) carriers away if engagement of MyoE(MYO5) to actin cables fails. Microtubules seemingly cooperating with F-actin capture can sustain secretion if MyoE(MYO5) is absent. Thus, filamentous fungal secretion involving post-Golgi carriers is remarkably similar, mechanistically, to the transport of melanosomes in melanocyte dendrites, even though melanosome biogenesis involves lysosomes rather than Golgi. PMID:24943841

  4. Computed Tomography-Guided Access to the Cisterna Chyli: Introduction of a Technique for Direct Lymphangiography to Evaluate and Treat Chylothorax

    SciTech Connect

    Schoellnast, Helmut; Maybody, Majid; Getrajdman, George I.; Bains, Manjit S.; Finley, David J.; Solomon, Stephen B.

    2011-02-15

    The purpose of this report is to introduce a technique of direct lymphangiography to enable chylothorax treatment. Using a hybrid computed tomography (CT) and fluoroscopy imaging system, a 21-gauge needle was placed under CT guidance into the cisterna chyli to allow contrast lymphangiography and CT lymphangiography in two patients with presumed postoperative chylothorax. Water-soluble contrast media injection demonstrated the thoracic duct anatomy in both patients. Further successful needle disruption of the cisterna chyli was performed in one patient to interrupt lymph flow and stop the chylous leak, with subsequent resolution of the chylothorax.

  5. 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.

  6. 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.

  7. 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

  8. A model for the termination of the Ryukyu subduction zone against Taiwan: A junction of collision, subduction/separation, and subduction boundaries

    USGS Publications Warehouse

    Wu, F.T.; Liang, W.-T.; Lee, J.-C.; Benz, H.; Villasenor, A.

    2009-01-01

    The NW moving Philippine Sea plate (PSP) collides with the Eurasian plate (EUP) in the vicinity of Taiwan, and at the same time, it subducts toward the north along SW Ryukyu. The Ryukyu subduction zone terminates against eastern Taiwan. While the Ryukyu Trench is a linear bathym??trie low about 100 km east of Taiwan, closer to Taiwan, it cannot be clearly identified bathymetrically owing to the deformation related to the collision, making the location of the intersection of the Ryukyu with Taiwan difficult to decipher. We propose a model for this complex of boundaries on the basis of seismicity and 3-D velocity structures. In this model the intersection is placed at the latitude of about 23.7??N, placing the northern part of the Coastal Range on EUP. As PSP gets deeper along the subduction zone it collides with EUP on the Taiwan side only where they are in direct contact. Thus, the Eurasian plate on the Taiwan side is being pushed and compressed by the NW moving Philippine Sea plate, at increasing depth toward the north. Offshore of northeastern Taiwan the wedge-shaped EUP on top of the Ryukyu subducting plate is connected to the EUP on the Ryukyu side and coupled to the NW moving PSP by friction at the plate interface. The two sides of the EUP above the western end of the subduction zone are not subjected to the same forces, and a difference in motions can be expected. The deformation of Taiwan as revealed by continuous GPS measurements, geodetic movement along the east coast of Taiwan, and the formation of the Hoping Basin can be understood in terms of the proposed model. Copyright 2009 by the American Geophysical Union.

  9. Pressor response to L-cysteine injected into the cisterna magna of conscious rats involves recruitment of hypothalamic vasopressinergic neurons.

    PubMed

    Takemoto, Yumi

    2013-03-01

    The sulfur-containing non-essential amino acid L-cysteine injected into the cisterna magna of adult conscious rats produces an increase in blood pressure. The present study examined if the pressor response to L-cysteine is stereospecific and involves recruitment of hypothalamic vasopressinergic neurons and medullary noradrenergic A1 neurons. Intracisternally injected D-cysteine produced no cardiovascular changes, while L-cysteine produced hypertension and tachycardia in freely moving rats, indicating the stereospecific hemodynamic actions of L-cysteine via the brain. The double labeling immunohistochemistry combined with c-Fos detection as a marker of neuronal activation revealed significantly higher numbers of c-Fos-positive vasopressinergic neurons both in the supraoptic and paraventricular nuclei and tyrosine hydroxylase containing medullary A1 neurons, of L-cysteine-injected rats than those injected with D-cysteine as iso-osmotic control. The results indicate that the cardiovascular responses to intracisternal injection of L-cysteine in the conscious rat are stereospecific and include recruitment of hypothalamic vasopressinergic neurons both in the supraoptic and paraventricular nuclei, as well as of medullary A1 neurons. The findings may suggest a potential function of L-cysteine as an extracellular signal such as neuromodulators in central regulation of blood pressure.

  10. [Total proteins of the cerebrospinal fluid obtained by punction of the cisterna magna: normal values. Variations related to sex].

    PubMed

    Vermes, L M; Ferri, R G; Aisen, J; Marlet, J M

    1976-12-01

    The total protein content of CSF collected from the cisterna magna (cisternal fluid) of 98 patients (58 males and 40 females) with no neurological diseases was determined by the colorimetric method devised by Lowry and co-workers. This method has been previously chosen based mainly on it's sensitivity, accuracy and low fluid consumption. The CSF samples were normal with regard to pressure, color, citology and it's content in glucose, chloride and urea. Complement fixation tests for syphilis and cisticercosis, as well as the globulin tests (Pandy, Nonne--Appelt and Takata-Ara) were negative. The average value and the normal range of cisternal fluid total protein was calculated for the mixed population (males and females). The mean protein value was 26.78 mg/100 ml, the lower and upper limits were respectively 13.20 and 40.36 mg/100 ml. These data are higher than those stated in some publications, and factors that could interfere in the different results mentioned in the literature are briefly discussed. Since the statistical analysis of the results showed that the mean total protein concentration in males (28.76 mg/100 ml) was higher than in females (23.91 mg/100 ml), normal limits for each sex were established: 16.96 to 47.13 mg/100 ml for males and 14.76 to 42.76 mg/100 ml for females.

  11. 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.

  12. Theoretical performance of multi-junction solar cells combining III-V and Si materials.

    PubMed

    Mathews, Ian; O'Mahony, Donagh; Corbett, Brian; Morrison, Alan P

    2012-09-10

    A route to improving the overall efficiency of multi-junction solar cells employing conventional III-V and Si photovoltaic junctions is presented here. A simulation model was developed to consider the performance of several multi-junction solar cell structures in various multi-terminal configurations. For series connected, 2-terminal triple-junction solar cells, incorporating an AlGaAs top junction, a GaAs middle junction and either a Si or InGaAs bottom junction, it was found that the configuration with a Si bottom junction yielded a marginally higher one sun efficiency of 41.5% versus 41.3% for an InGaAs bottom junction. A significant efficiency gain of 1.8% over the two-terminal device can be achieved by providing an additional terminal to the Si bottom junction in a 3-junction mechanically stacked configuration. It is shown that the optimum performance can be achieved by employing a four-junction series-connected mechanically stacked device incorporating a Si subcell between top AlGaAs/GaAs and bottom In0.53Ga0.47As cells.

  13. 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

  14. Bone marrow stem cells delivered into the subarachnoid space via cisterna magna improve repair of injured rat spinal cord white matter

    PubMed Central

    Marcol, Wiesław; Slusarczyk, Wojciech; Sieroń, Aleksander L; Koryciak-Komarska, Halina; Lewin-Kowalik, Joanna

    2015-01-01

    The influence of bone marrow stem cells on regeneration of spinal cord in rats was investigated. Young adult male Wistar rats were used (n=22). Focal injury of spinal cord white matter at Th10 level was produced using our original non-laminectomy method by means of high-pressured air stream. Cells from tibial and femoral bone marrow of 1-month old rats (n=3) were cultured, labeled with BrdU/Hoechst and injected into cisterna magna (experimental group) three times: immediately after spinal cord injury and 3 as well as 7 days later. Neurons in brain stem and motor cortex were labeled with FluoroGold (FG) delivered caudally from the injury site a week before the end of experiment. Functional outcome and morphological features of regeneration were analyzed during 12-week follow-up. The lesions were characterized by means of MRI. Maximal distance of expansion of implanted cells in the spinal cord was measured and the number of FG-positive neurons in the brain was counted. Rats treated with stem cells presented significant improvement of locomotor performance and spinal cord morphology when compared to the control group. Distance covered by stem cells was 7 mm from the epicenter of the injury. Number of brain stem and motor cortex FG-positive neurons in experimental group was significantly higher than in control. Obtained data showed that bone marrow stem cells are able to induce the repair of injured spinal cord white matter. The route of cells application via cisterna magna appeared to be useful for their delivery in spinal cord injury therapy. PMID:26628950

  15. Bone marrow stem cells delivered into the subarachnoid space via cisterna magna improve repair of injured rat spinal cord white matter.

    PubMed

    Marcol, Wiesław; Slusarczyk, Wojciech; Sieroń, Aleksander L; Koryciak-Komarska, Halina; Lewin-Kowalik, Joanna

    2015-01-01

    The influence of bone marrow stem cells on regeneration of spinal cord in rats was investigated. Young adult male Wistar rats were used (n=22). Focal injury of spinal cord white matter at Th10 level was produced using our original non-laminectomy method by means of high-pressured air stream. Cells from tibial and femoral bone marrow of 1-month old rats (n=3) were cultured, labeled with BrdU/Hoechst and injected into cisterna magna (experimental group) three times: immediately after spinal cord injury and 3 as well as 7 days later. Neurons in brain stem and motor cortex were labeled with FluoroGold (FG) delivered caudally from the injury site a week before the end of experiment. Functional outcome and morphological features of regeneration were analyzed during 12-week follow-up. The lesions were characterized by means of MRI. Maximal distance of expansion of implanted cells in the spinal cord was measured and the number of FG-positive neurons in the brain was counted. Rats treated with stem cells presented significant improvement of locomotor performance and spinal cord morphology when compared to the control group. Distance covered by stem cells was 7 mm from the epicenter of the injury. Number of brain stem and motor cortex FG-positive neurons in experimental group was significantly higher than in control. Obtained data showed that bone marrow stem cells are able to induce the repair of injured spinal cord white matter. The route of cells application via cisterna magna appeared to be useful for their delivery in spinal cord injury therapy.

  16. 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.

  17. Termination Documentation

    ERIC Educational Resources Information Center

    Duncan, Mike; Hill, Jillian

    2014-01-01

    In this study, we examined 11 workplaces to determine how they handle termination documentation, an empirically unexplored area in technical communication and rhetoric. We found that the use of termination documentation is context dependent while following a basic pattern of infraction, investigation, intervention, and termination. Furthermore,…

  18. 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

  19. 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

  20. 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.

  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. 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.

  3. Bank Terminals

    NASA Technical Reports Server (NTRS)

    1978-01-01

    In the photo, employees of the UAB Bank, Knoxville, Tennessee, are using Teller Transaction Terminals manufactured by SCI Systems, Inc., Huntsville, Alabama, an electronics firm which has worked on a number of space projects under contract with NASA. The terminals are part of an advanced, computerized financial transaction system that offers high efficiency in bank operations. The key to the system's efficiency is a "multiplexing" technique developed for NASA's Space Shuttle. Multiplexing is simultaneous transmission of large amounts of data over a single transmission link at very high rates of speed. In the banking application, a small multiplex "data bus" interconnects all the terminals and a central computer which stores information on clients' accounts. The data bus replaces the maze-of wiring that would be needed to connect each terminal separately and it affords greater speed in recording transactions. The SCI system offers banks real-time data management through constant updating of the central computer. For example, a check is immediately cancelled at the teller's terminal and the computer is simultaneously advised of the transaction; under other methods, the check would be cancelled and the transaction recorded at the close of business. Teller checkout at the end of the day, conventionally a time-consuming matter of processing paper, can be accomplished in minutes by calling up a summary of the day's transactions. SCI manufactures other types of terminals for use in the system, such as an administrative terminal that provides an immediate printout of a client's account, and another for printing and recording savings account deposits and withdrawals. SCI systems have been installed in several banks in Tennessee, Arizona, and Oregon and additional installations are scheduled this year.

  4. 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.

  5. 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

  6. 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.

  7. Magic-T Junction using Microstrip/Slotline Transitions

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

    among all four ports, and to strong parasitic couplings at the microstrip/slotline T junction, where four microstrip lines and a slotline are combined. The present improved broadband magic-T junction (see figure) includes a microstrip ring structure and two microstrip- to-slotline transitions. One of the microstrip/slotline transitions is a small T junction between the ring and a slotline; the other microstrip/slotline transition effects coupling between the slotline and port E. The smallness of the T junction and the use of minimum-size slotline terminations help to minimize radiation loss. An impedance-transformation network that includes multiple quarter-wavelength sections is used to increase the operating bandwidth and minimize the parasitic coupling around the microstrip/slotline T junction. As a result, the improved junction has greater bandwidth and lower phase imbalance at the sum and difference ports than did the prior junction.

  8. The Onecut Transcription Factor HNF-6 Regulates in Motor Neurons the Formation of the Neuromuscular Junctions

    PubMed Central

    Audouard, Emilie; Schakman, Olivier; René, Frédérique; Huettl, Rosa-Eva; Huber, Andrea B.; Loeffler, Jean-Philippe; Gailly, Philippe; Clotman, Frédéric

    2012-01-01

    The neuromuscular junctions are the specialized synapses whereby spinal motor neurons control the contraction of skeletal muscles. The formation of the neuromuscular junctions is controlled by a complex interplay of multiple mechanisms coordinately activated in motor nerve terminals and in their target myotubes. However, the transcriptional regulators that control in motor neurons the genetic programs involved in neuromuscular junction development remain unknown. Here, we provide evidence that the Onecut transcription factor HNF-6 regulates in motor neurons the formation of the neuromuscular junctions. Indeed, adult Hnf6 mutant mice exhibit hindlimb muscle weakness and abnormal locomotion. This results from defects of hindlimb neuromuscular junctions characterized by an abnormal morphology and defective localization of the synaptic vesicle protein synaptophysin at the motor nerve terminals. These defects are consequences of altered and delayed formation of the neuromuscular junctions in newborn mutant animals. Furthermore, we show that the expression level of numerous regulators of neuromuscular junction formation, namely agrin, neuregulin-2 and TGF-ß receptor II, is downregulated in the spinal motor neurons of Hnf6 mutant newborn animals. Finally, altered formation of neuromuscular junction-like structures in a co-culture model of wildtype myotubes with mutant embryonic spinal cord slices is rescued by recombinant agrin and neuregulin, indicating that depletion in these factors contributes to defective neuromuscular junction development in the absence of HNF-6. Thus, HNF-6 controls in spinal motor neurons a genetic program that coordinates the formation of hindlimb neuromuscular junctions. PMID:23227180

  9. Terminal structure

    DOEpatents

    Schmidt, Frank; Allais, Arnaud; Mirebeau, Pierre; Ganhungu, Francois; Lallouet, Nicolas

    2009-10-20

    A terminal structure (2) for a superconducting cable (1) is described. It consists of a conductor (2a) and an insulator (2b) that surrounds the conductor (2a), wherein the superconducting cable (1) has a core with a superconducting conductor (5) and a layer of insulation that surrounds the conductor (5), and wherein the core is arranged in such a way that it can move longitudinally in a cryostat. The conductor (2a) of the terminal structure (2) is electrically connected with the superconducting conductor (5) or with a normal conductor (6) that is connected with the superconducting conductor (5) by means of a tubular part (7) made of an electrically conductive material, wherein the superconducting conductor (5) or the normal conductor (6) can slide in the part (7) in the direction of the superconductor.

  10. 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

  11. Termination unit

    DOEpatents

    Traeholt, Chresten; Willen, Dag; Roden, Mark; Tolbert, Jerry C.; Lindsay, David; Fisher, Paul W.; Nielsen, Carsten Thidemann

    2016-05-03

    Cable end section comprises end-parts of N electrical phases/neutral, and a thermally-insulation envelope comprising cooling fluid. The end-parts each comprises a conductor and are arranged with phase 1 innermost, N outermost surrounded by the neutral, electrical insulation being between phases and N and neutral. The end-parts comprise contacting surfaces located sequentially along the longitudinal extension of the end-section. A termination unit has an insulating envelope connected to a cryostat, special parts at both ends comprising an adapter piece at the cable interface and a closing end-piece terminating the envelope in the end-section. The special parts houses an inlet and/or outlet for cooling fluid. The space between an inner wall of the envelope and a central opening of the cable is filled with cooling fluid. The special part at the end connecting to the cryostat houses an inlet or outlet, splitting cooling flow into cable annular flow and termination annular flow.

  12. 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

  13. 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

  14. 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.

  15. 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.

  16. 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-terminated

  17. 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…

  18. 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

  19. Electrical properties of covalently linked silicon/polypyrrole junctions

    NASA Astrophysics Data System (ADS)

    Vermeir, Inge E.; Kim, Namyong Y.; Laibinis, Paul E.

    1999-06-01

    Electrodeposited polypyrrole films were formed on chemically modified hydrogen-terminated silicon surfaces that expose tethered pyrrole units. Semiconductor/polypyrrole junctions on the native and modified substrates exhibit diode-like characteristics, with those on the latter substrate exhibiting higher current densities and better ideality factors. Impedance measurements revealed that the improved electrical properties of junctions on the modified substrates were not due to a change in barrier height but rather a consequence of incorporating sites on the silicon surface where the polymer and semiconductor have direct contact.

  20. Wire Crimp Termination Verification Using Ultrasonic Inspection

    NASA Technical Reports Server (NTRS)

    Perey, Daniel F.; Cramer, K. Elliott; Yost, William T.

    2007-01-01

    The development of a new ultrasonic measurement technique to quantitatively assess wire crimp terminations is discussed. The amplitude change of a compressional ultrasonic wave propagating through the junction of a crimp termination and wire is shown to correlate with the results of a destructive pull test, which is a standard for assessing crimp wire junction quality. Various crimp junction pathologies such as undercrimping, missing wire strands, incomplete wire insertion, partial insulation removal, and incorrect wire gauge are ultrasonically tested, and their results are correlated with pull tests. Results show that the nondestructive ultrasonic measurement technique consistently (as evidenced with destructive testing) predicts good crimps when ultrasonic transmission is above a certain threshold amplitude level. A physics-based model, solved by finite element analysis, describes the compressional ultrasonic wave propagation through the junction during the crimping process. This model is in agreement within 6% of the ultrasonic measurements. A prototype instrument for applying this technique while wire crimps are installed is also presented. The instrument is based on a two-jaw type crimp tool suitable for butt-splice type connections. Finally, an approach for application to multipin indenter type crimps will be discussed.

  1. Termination unit

    DOEpatents

    Traeholt, Chresten [Frederiksberg, DK; Willen, Dag [Klagshamn, SE; Roden, Mark [Newnan, GA; Tolbert, Jerry C [Carrollton, GA; Lindsay, David [Carrollton, GA; Fisher, Paul W [Heiskell, TN; Nielsen, Carsten Thidemann [Jaegerspris, DK

    2014-01-07

    This invention relates to a termination unit comprising an end-section of a cable. The end section of the cable defines a central longitudinal axis and comprising end-parts of N electrical phases, an end-part of a neutral conductor and a surrounding thermally insulation envelope adapted to comprising a cooling fluid. The end-parts of the N electrical phases and the end-part of the neutral conductor each comprising at least one electrical conductor and being arranged in the cable concentrically around a core former with a phase 1 located relatively innermost, and phase N relatively outermost in the cable, phase N being surrounded by the neutral conductor, electrical insulation being arrange between neighboring electrical phases and between phase N and the neutral conductor, and wherein the end-parts of the neutral conductor and the electrical phases each comprise a contacting surface electrically connected to at least one branch current lead to provide an electrical connection: The contacting surfaces each having a longitudinal extension, and being located sequentially along the longitudinal extension of the end-section of the cable. The branch current leads being individually insulated from said thermally insulation envelope by individual electrical insulators.

  2. The terminal crest: morphological features relevant to electrophysiology

    PubMed Central

    Sánchez-Quintana, D; Anderson, R H; Cabrera, J A; Climent, V; Martin, R; Farré, J; Ho, S Y

    2002-01-01

    Objective: To investigate the detailed anatomy of the terminal crest (crista terminalis) and its junctional regions with the pectinate muscles and intercaval area to provide the yardstick for structural normality. Design: 97 human necropsy hearts were studied from patients who were not known to have medical histories of atrial arrhythmias. The dimensions of the terminal crest were measured in width and thickness from epicardium to endocardium, at the four points known to be chosen as sites of ablation. Results: The pectinate muscles originating from the crest and extending along the wall of the appendage towards the vestibule of the tricuspid valve had a non-uniform trabecular pattern in 80% of hearts. Fine structure of the terminal crest studied using light and scanning electron microscopy consisted of much thicker and more numerous fibrous sheaths of endomysium with increasing age of the patient. 36 specimens of 45 (80%) specimens studied by electron microscopy had a predominantly uniform longitudinal arrangement of myocardial fibres within the terminal crest. In contrast, in all specimens, the junctional areas of the terminal crest with the pectinate muscles and with the intercaval area had crossing and non-uniform architecture of myofibres. Conclusions: The normal anatomy of the muscle fibres and connective tissue in the junctional area of the terminal crest/pectinate muscles and terminal crest/intercaval bundle favours non-uniform anisotropic properties. PMID:12231604

  3. 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

  4. 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.

  5. 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

  6. 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.

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

    PubMed

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

    2012-03-14

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

  8. 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].

  9. Development and fabrication of a solar cell junction processing system

    NASA Technical Reports Server (NTRS)

    1984-01-01

    A processing system capable of producing solar cell junctions by ion implantation followed by pulsed electron beam annealing was developed and constructed. The machine was to be capable of processing 4-inch diameter single-crystal wafers at a rate of 10(7) wafers per year. A microcomputer-controlled pulsed electron beam annealer with a vacuum interlocked wafer transport system was designed, built and demonstrated to produce solar cell junctions on 4-inch wafers with an AMI efficiency of 12%. Experiments showed that a non-mass-analyzed (NMA) ion beam could implant 10 keV phosphorous dopant to form solar cell junctions which were equivalent to mass-analyzed implants. A NMA ion implanter, compatible with the pulsed electron beam annealer and wafer transport system was designed in detail but was not built because of program termination.

  10. 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.

  11. Gate tunable nonlinear rectification effects in three-terminal graphene nanojunctions

    NASA Astrophysics Data System (ADS)

    Zhu, R. J.; Huang, Y. Q.; Kang, N.; Xu, H. Q.

    2014-04-01

    We report on a study of the room-temperature nonlinear charge transport properties of three-terminal junction devices made from graphene. We demonstrate that the graphene three terminal junction devices show a rectification characteristic, namely, when voltages VL = V and VR = -V are applied to the left and the right terminal in a push-pull configuration, the voltage output from the central terminal VC is finite and is scaled approximately with V2. The rectification coefficient can be effectively tuned by a gate voltage and shows a transport carrier polarity dependence. We further show that the nonlinear charge transport characteristics can be used to probe the electronic structure of graphene nanostructures and to study the thermoelectrical power of graphene. These results show that the graphene three-terminal junction devices could be used as novel building blocks for nanoelectronics and as novel devices for the study of the material properties of graphene on the nanoscale.

  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. 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

  18. EAST ELEVATION OF LOWER TRAM TERMINAL WITH SIX FOOT SCALE, ...

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

    EAST ELEVATION OF LOWER TRAM TERMINAL WITH SIX FOOT SCALE, LOOKING NORTHWEST. THE SCALE IS LOCATED AT CENTER RIGHT, AGAINST THE SECOND SUPPORT TIMBER FROM THE RIGHT. - Keane Wonder Mine, Park Route 4 (Daylight Pass Cutoff), Death Valley Junction, Inyo County, CA

  19. OBLIQUE DETAIL VIEW OF LOWER TRAM TERMINAL, LOOKING NORTHWEST. THE ...

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

    OBLIQUE DETAIL VIEW OF LOWER TRAM TERMINAL, LOOKING NORTHWEST. THE JAW CRUSHER FOUNDATION CAN BE CLEARLY SEEN AT CENTER LEFT WITH A CONVEYOR TO CARRY CRUSHED ORE UP TO THE SECONDARY ORE BIN,LEFT. - Keane Wonder Mine, Park Route 4 (Daylight Pass Cutoff), Death Valley Junction, Inyo County, CA

  20. Snake states in graphene quantum dots in the presence of a p-n junction

    NASA Astrophysics Data System (ADS)

    Zarenia, M.; Pereira, J. M., Jr.; Peeters, F. M.; Farias, G. A.

    2013-01-01

    We investigate the magnetic interface states of graphene quantum dots that contain p-n junctions. Within a tight-binding approach, we consider rectangular quantum dots in the presence of a perpendicular magnetic field containing p-n as well as p-n-p and n-p-n junctions. The results show the interplay between the edge states associated with the zigzag terminations of the sample and the snake states that arise at the p-n junction due to the overlap between electron and hole states at the potential interface. Remarkable localized states are found at the crossing of the p-n junction with the zigzag edge having a dumb-bell-shaped electron distribution. The results are presented as a function of the junction parameters and the applied magnetic flux.

  1. Targeting motifs and functional parameters governing the assembly of connexins into gap junctions.

    PubMed Central

    Martin, P E; Steggles, J; Wilson, C; Ahmad, S; Evans, W H

    2000-01-01

    To study the assembly of gap junctions, connexin--green-fluorescent-protein (Cx--GFP) chimeras were expressed in COS-7 and HeLa cells. Cx26-- and Cx32--GFP were targeted to gap junctions where they formed functional channels that transferred Lucifer Yellow. A series of Cx32--GFP chimeras, truncated from the C-terminal cytoplasmic tail, were studied to identify amino acid sequences governing targeting from intracellular assembly sites to the gap junction. Extensive truncation of Cx32 resulted in failure to integrate into membranes. Truncation of Cx32 to residue 207, corresponding to removal of most of the 78 amino acids on the cytoplasmic C-terminal tail, led to arrest in the endoplasmic reticulum and incomplete oligomerization. However, truncation to amino acid 219 did not impair Cx oligomerization and connexon hemichannels were targeted to the plasma membrane. It was concluded that a crucial gap-junction targeting sequence resides between amino acid residues 207 and 219 on the cytoplasmic C-terminal tail of Cx32. Studies of a Cx32E208K mutation identified this as one of the key amino acids dictating targeting to the gap junction, although oligomerization of this site-specific mutation into hexameric hemichannels was relatively unimpaired. The studies show that expression of these Cx--GFP constructs in mammalian cells allowed an analysis of amino acid residues involved in gap-junction assembly. PMID:10861240

  2. 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

  3. 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

  4. 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.

  5. Paradoxical responses to pacing maneuvers differentiating atrioventricular node reentrant tachycardia and junctional tachycardia.

    PubMed

    Tokuda, Michifumi; Yamane, Teiichi; Matsuo, Seiichiro; Tokutake, Kenichi; Yokoyama, Kenichi; Hioki, Mika; Narui, Ryohsuke; Tanigawa, Shin-Ichi; Yamashita, Seigo; Inada, Keiichi; Yoshimura, Michihiro

    2016-02-01

    A 40-year-old female presented at our hospital because of heart palpitations. During an electrophysiological study, atrioventricular (AV) conduction showed dual AV nodal physiology. Three types of supraventricular tachycardia (SVT) were induced. The initiation of SVT was reproducibility dependent on a critical A-H interval prolongation. An early premature atrial contraction during SVT repeatedly advanced the immediate His potential with termination of the tachycardia, indicating AV node reentrant tachycardia (AVNRT). However, after atrial overdrive pacing during SVT without termination of the tachycardia, the first return electrogram resulted in an AHHA response, consistent with junctional tachycardia. The mechanism of paradoxical responses to pacing maneuvers differentiating AVNRT and junctional tachycardia was discussed.

  6. 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.

  7. OVERVIEW OF LOWER TRAM TERMINAL AND STAMP MILL SITE, LOOKING ...

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

    OVERVIEW OF LOWER TRAM TERMINAL AND STAMP MILL SITE, LOOKING NORTHWEST. THE AERIAL TRAMWAY BEGINS AT THE TERMINAL AND CONTINUES NORTH TO THE UPPER RIGHT. THE FIRST SUPPORT TOWER CAN BE SEEN. JUST BELOW THE WATER TANK IS A LOADING PLATFORM AND TRAM TRESTLE USED FOR THE TRANSPORT OF SUPPLIES THAT LEAD UP TO THE TRAM TERMINAL. ALL THREE LEVELS OF THE FORMER 20 STAMP MILL CAN BE SEEN AT CENTER. SEE CA-291-02 FOR IDENTICAL B&W NEGATIVE. - Keane Wonder Mine, Park Route 4 (Daylight Pass Cutoff), Death Valley Junction, Inyo County, CA

  8. OVERVIEW OF LOWER TRAM TERMINAL AND STAMP MILL SITE, LOOKING ...

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

    OVERVIEW OF LOWER TRAM TERMINAL AND STAMP MILL SITE, LOOKING NORTHWEST. THE AERIAL TRAMWAY BEGINS AT THE TERMINAL AND CONTINUES NORTH TO THE UPPER RIGHT. THE FIRST SUPPORT TOWER CAN BE SEEN. JUST BELOW THE WATER TANK IS A LOADING PLATFORM AND TRAM TRESTLE USED FOR THE TRANSPORT OF SUPPLIES THAT LEAD UP TO THE TRAM TERMINAL. ALL THREE LEVELS OF THE FORMER 20 STAMP MILL CAN BE SEEN AT CENTER. SEE CA-291-46( CT) FOR IDENTICAL COLOR TRANSPARENCY. - Keane Wonder Mine, Park Route 4 (Daylight Pass Cutoff), Death Valley Junction, Inyo County, CA

  9. 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

  10. 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

  11. The Mr 28,000 gap junction proteins from rat heart and liver are different but related.

    PubMed

    Nicholson, B J; Gros, D B; Kent, S B; Hood, L E; Revel, J P

    1985-06-10

    The sequence of the amino-terminal 32 residues of the rat heart Mr 28,000 gap junction protein presented here allows, for the first time, a sequence comparison of gap junctional proteins from different tissues (heart and liver). Comparison of the rat heart gap junction protein sequence and that available from rat liver reveals 43% sequence identity and conservative changes at an additional 25% of the positions. Both proteins exhibit a hydrophobic domain which could represent a transmembrane span of the junction. This result unequivocally demonstrates the existence of at least two forms of the gap junction protein. As yet, no homology is evident between the gap junctional proteins of either heart or liver and main intrinsic protein from rat eye lens. PMID:2987225

  12. 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

  13. Structure of the three-way helical junction of the hepatitis C virus IRES element.

    PubMed

    Ouellet, Jonathan; Melcher, Sonya; Iqbal, Asif; Ding, Yiliang; Lilley, David M J

    2010-08-01

    The hepatitis C virus internal ribosome entry site (IRES) element contains a three-way junction that is important in the overall RNA conformation, and for its role in the internal initiation of translation. The junction also illustrates some important conformational principles in the folding of three-way helical junctions. It is formally a 3HS(4) junction, with the possibility of two alternative stacking conformers. However, in principle, the junction can also undergo two steps of branch migration that would form 2HS(1)HS(3) and 2HS(2)HS(2) junctions. Comparative gel electrophoresis and ensemble fluorescence resonance energy transfer (FRET) studies show that the junction is induced to fold by the presence of Mg(2+) ions in low micromolar concentrations, and suggest that the structure adopted is based on coaxial stacking of the two helices that do not terminate in a hairpin loop (i.e., helix IIId). Single-molecule FRET studies confirm this conclusion, and indicate that there is no minor conformer present based on an alternative choice of helical stacking partners. Moreover, analysis of single-molecule FRET data at an 8-msec resolution failed to reveal evidence for structural transitions. It seems probable that this junction adopts a single conformation as a unique and stable fold.

  14. 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

  15. Heterotypic gap junctions at glutamatergic mixed synapses are abundant in goldfish brain

    PubMed Central

    Rash, John E.; Kamasawa, Naomi; Vanderpool, Kimberly G.; Yasumura, Thomas; O'Brien, John; Nannapaneni, Srikant; Pereda, Alberto E.; Nagy, James I.

    2014-01-01

    Gap junctions provide for direct intercellular electrical and metabolic coupling. The abundance of gap junctions at “large myelinated club ending” synapses on Mauthner cells of the teleost brain provided a convenient model to correlate anatomical and physiological properties of electrical synapses. There, presynaptic action potentials were found to evoke short-latency electrical “pre-potentials” immediately preceding their accompanying glutamate-induced depolarizations, making these the first unambiguously identified “mixed” (i.e., chemical plus electrical) synapses in the vertebrate CNS. We recently showed that gap junctions at these synapses exhibit asymmetric electrical resistance (i.e., electrical rectification), which we correlated with total molecular asymmetry of connexin composition in their apposing gap junction hemiplaques, with Cx35 restricted to axon terminal hemiplaques and Cx34.7 restricted to apposing Mauthner cell plasma membranes. We now show that similarly heterotypic neuronal gap junctions are abundant throughout goldfish brain, with labeling exclusively for Cx35 in presynaptic hemiplaques and exclusively for Cx34.7 in postsynaptic hemiplaques. Moreover, the vast majority of these asymmetric gap junctions occur at glutamatergic axon terminals. The widespread distribution of heterotypic gap junctions at glutamatergic mixed synapses throughout goldfish brain and spinal cord implies that pre- vs. postsynaptic asymmetry at electrical synapses evolved early in the chordate lineage. We propose that the advantages of the molecular and functional asymmetry of connexins at electrical synapses that are so prominently expressed in the teleost CNS are unlikely to have been abandoned in higher vertebrates. However, to create asymmetric coupling in mammals, where most gap junctions are composed of Cx36 on both sides, would require some other mechanism, such as differential phosphorylation of connexins on opposite sides of the same gap junction or

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Properties of Edge States at the Graphene P-N Junction Interface

    NASA Astrophysics Data System (ADS)

    Le, Son; Klimov, Nikolai; Newell, David; Yan, Jun; Lee, Ji Ung; Richter, Curt

    The Landau level edge states from the p- and the n-section of a graphene P/N junction (pnJ) interact with each other differently across the junction depending upon the properties of the junction and the graphene. Full equilibration was reported for a two terminal graphene pnJ device in Williams et al.. In our four-terminal device, however, only the lowest Landau level edge state is equilibrated across the pnJ. When the two devices are compared, the LL energy spacings, the length of the edge states along the pnJ interface, and the carrier mobility are similar. Electrostatic simulations for our device geometry and that of contrast the rate of change of the electrostatic potential across the pnJs. Edge states at an electrostatically smooth junction are spatially further apart than those at a relatively abrupt junction, which decreases the probability of edge states mixing. Thus, we attribute the difference in equilibration in our device and that of to the dramatic difference in the shape of the electrostatic junction.

  4. 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

  5. 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.

  6. The PLATO V Terminal.

    ERIC Educational Resources Information Center

    Stifle, J. E.

    This report provides a detailed description of the architecture and programming of the PLATO V terminal, which contains an 8080 microprocessor and is capable of being operated by programs located in a host computer. The terminal contains 8k of memory for storing local programs, a 4k ROM resident program which supervises terminal operation, a 2k…

  7. CAI Terminal Characteristics.

    ERIC Educational Resources Information Center

    Braun, Peter

    The bewildering number of available terminals which are offered to CAI users presents a rather formidable problem of which one to choose. This article surveys what appear to be evolving standards for terminals. The usefulness of these terminals for CAI purposes is discussed, together with the best known prototype exhibiting the particular feature.…

  8. Probe of local impurity states by bend resistance measurements in graphene cross junctions

    NASA Astrophysics Data System (ADS)

    Du, J.; Li, J. Y.; Kang, N.; Lin, Li; Peng, Hailin; Liu, Zhongfan; Xu, H. Q.

    2016-06-01

    We report on low-temperature transport measurements on four-terminal cross junction devices fabricated from high-quality graphene grown by chemical vapor deposition. At high magnetic fields, the bend resistance reveals pronounced peak structures at the quantum Hall plateau transition, which can be attributed to the edge state transport through the junctions. We further demonstrate that the bend resistance is drastically affected by the presence of local impurity states in the junction regions, and exhibits an unusual asymmetric behavior with respect to the magnetic field direction. The observations can be understood in a model taking into account the combination of the edge transport and an asymmetric scatterer. Our results demonstrate that a graphene cross junction may serve as a sensitive probe of local impurity states in graphene at the nanoscale.

  9. Motor nerve terminals on abdominal muscles in larval flesh flies, Sarcophaga bullata: comparisons with Drosophila.

    PubMed

    Feeney, C J; Karunanithi, S; Pearce, J; Govind, C K; Atwood, H L

    1998-12-14

    Motor nerve terminals on abdominal body-wall muscles 6A and 7A in larval flesh flies were investigated to establish their general structural features with confocal microscopy, transmission electron microscopy, and freeze-fracture procedures. As in Drosophila and other dipterans, two motor axons supply these muscles, and two morphologically different terminals were discerned with confocal microscopy: thin terminals with relatively small varicosities (Type Is), and thicker terminals with larger varicosities (Type Ib). In serial electron micrographs, Type Ib terminals were distinguished from Type Is terminals by their larger cross-sectional area, more extensive subsynaptic reticulum, more mitochondrial profiles, and more clear synaptic vesicles. Type Ib terminals possessed larger synapses and more synaptic contact area per unit terminal length. Although presynaptic dense bars of active zones were similar in mean length for the two terminal types, there were almost twice as many dense bars per synapse for Type Ib terminals. Freeze-fractures through the presynaptic membrane showed particle-free areas indicative of synapses on the P-face, within which were localized aggregations of large intramembranous particles indicative of active zones. These particles were similar in number to those found at active zones of several other arthropod neuromuscular junctions. In general, synaptic structural parameters strongly paralleled those of the anatomically homologous muscles in Drosophila melanogaster. In live preparations, simultaneous focal recording from identified varicosities and intracellular recording indicated that the two terminals produced excitatory junction potentials of similar amplitude in a physiological solution similar to that used for Drosophila.

  10. 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.

  11. Snake states and Majorana's in graphene quantum dots in the presence of a p-n junction

    NASA Astrophysics Data System (ADS)

    Peeters, Francois; Zarenia, M.; Pereira, J. M., Jr.; Farias, G. A.

    2013-03-01

    We investigate the magnetic interface states of graphene quantum dots that contain p-n junctions. Within a tight-binding approach, we consider rectangular quantum dots in the presence of a perpendicular magnetic field containing p-n, as well as p-n-p and n-p-n junctions. The results show the interplay between the edge states associated with the zigzag terminations of the sample and the snake states that arise at the p-n junction, due to the overlap between electron and hole states at the potential interface. Remarkable localized states are found at the crossing of the p-n junction with the zigzag edge having a dumb-bell shaped electron distribution. These states are localized Majorana states. The results are presented as function of the junction parameters and the applied magnetic flux.

  12. Three-terminal heterojunction bipolar transistor solar cell for high-efficiency photovoltaic conversion.

    PubMed

    Martí, A; Luque, A

    2015-01-01

    Here we propose, for the first time, a solar cell characterized by a semiconductor transistor structure (n/p/n or p/n/p) where the base-emitter junction is made of a high-bandgap semiconductor and the collector is made of a low-bandgap semiconductor. We calculate its detailed-balance efficiency limit and prove that it is the same one than that of a double-junction solar cell. The practical importance of this result relies on the simplicity of the structure that reduces the number of layers that are required to match the limiting efficiency of dual-junction solar cells without using tunnel junctions. The device naturally emerges as a three-terminal solar cell and can also be used as building block of multijunction solar cells with an increased number of junctions. PMID:25902374

  13. Three-terminal heterojunction bipolar transistor solar cell for high-efficiency photovoltaic conversion

    PubMed Central

    Martí, A.; Luque, A.

    2015-01-01

    Here we propose, for the first time, a solar cell characterized by a semiconductor transistor structure (n/p/n or p/n/p) where the base–emitter junction is made of a high-bandgap semiconductor and the collector is made of a low-bandgap semiconductor. We calculate its detailed-balance efficiency limit and prove that it is the same one than that of a double-junction solar cell. The practical importance of this result relies on the simplicity of the structure that reduces the number of layers that are required to match the limiting efficiency of dual-junction solar cells without using tunnel junctions. The device naturally emerges as a three-terminal solar cell and can also be used as building block of multijunction solar cells with an increased number of junctions. PMID:25902374

  14. 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).

  15. 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.

  16. Charge transport through dicarboxylic-acid-terminated alkanes bound to graphene-gold nanogap electrodes

    NASA Astrophysics Data System (ADS)

    Liu, Longlong; Zhang, Qian; Tao, Shuhui; Zhao, Cezhou; Almutib, Eman; Al-Galiby, Qusiy; Bailey, Steven W. D.; Grace, Iain; Lambert, Colin J.; Du, Jun; Yang, Li

    2016-07-01

    Graphene-based electrodes are attractive for single-molecule electronics due to their high stability and conductivity and reduced screening compared with metals. In this paper, we use the STM-based matrix isolation I(s) method to measure the performance of graphene in single-molecule junctions with one graphene electrode and one gold electrode. By measuring the length dependence of the electrical conductance of dicarboxylic-acid-terminated alkanes, we find that the transport is consistent with phase-coherent tunneling, but with an attenuation factor of βN = 0.69 per methyl unit, which is lower than the value measured for Au-molecule-Au junctions. Comparison with density-functional-theory calculations of electron transport through graphene-molecule-Au junctions and Au-molecule-Au junctions reveals that this difference is due to the difference in Fermi energies of the two types of junction, relative to the frontier orbitals of the molecules. For most molecules, their electrical conductance in graphene-molecule-Au junctions is higher than that in Au-molecule-Au junctions, which suggests that graphene offers superior electrode performance, when utilizing carboxylic acid anchor groups.Graphene-based electrodes are attractive for single-molecule electronics due to their high stability and conductivity and reduced screening compared with metals. In this paper, we use the STM-based matrix isolation I(s) method to measure the performance of graphene in single-molecule junctions with one graphene electrode and one gold electrode. By measuring the length dependence of the electrical conductance of dicarboxylic-acid-terminated alkanes, we find that the transport is consistent with phase-coherent tunneling, but with an attenuation factor of βN = 0.69 per methyl unit, which is lower than the value measured for Au-molecule-Au junctions. Comparison with density-functional-theory calculations of electron transport through graphene-molecule-Au junctions and Au

  17. 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

  18. 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)

  19. OVERVIEW OF UPPER TRAM TERMINAL, TRAM TRESTLE, AND PRIMARY ORE ...

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

    OVERVIEW OF UPPER TRAM TERMINAL, TRAM TRESTLE, AND PRIMARY ORE BIN, LOOKING NORTHEAST. REMAINS OF A BLACKSMITH'S FORGE AND WORK CAN BE SEEN JUST BELOW THE ORE BIN (SEE CA-291-32 FOR DETAIL). ROCK FOUNDATIONS LOCATED JUST ABOVE THE ORE BIN AND ALONG THE FIRST RIDGELINE ARE TENT PADS. SEE CA-291-49 (CT) FOR IDENTICAL COLOR TRANSPARENCY. - Keane Wonder Mine, Park Route 4 (Daylight Pass Cutoff), Death Valley Junction, Inyo County, CA

  20. OVERVIEW OF UPPER TRAM TERMINAL, TRAM TRESTLE, AND PRIMARY ORE ...

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

    OVERVIEW OF UPPER TRAM TERMINAL, TRAM TRESTLE, AND PRIMARY ORE BIN, LOOKING NORTHEAST. REMAINS OF A BLACKSMITH'S FORGE AND WORK CAN BE SEEN JUST BELOW THE ORE BIN (SEE CA-291-32 FOR DETAIL). ROCK FOUNDATIONS LOCATED JUST ABOVE THE ORE BIN AND ALONG THE FIRST RIDGELINE ARE TENT PADS. SEE CA-291-24 FOR IDENTICAL B&W NEGATIVE. - Keane Wonder Mine, Park Route 4 (Daylight Pass Cutoff), Death Valley Junction, Inyo County, CA

  1. EAST ELEVATION OF LOWER TRAM TERMINAL, LOOKING NORTHWEST. TRAM CARS ...

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

    EAST ELEVATION OF LOWER TRAM TERMINAL, LOOKING NORTHWEST. TRAM CARS ENTERED AND EXITED FROM RIGHT,AND DUMPED INTO THE ORE BIN SEEN AT LOWER LEFT. BELOW THE ORE BIN IS A JAW CRUSHER FOUNDATION. THE WOODEN BOX AT CENTER IS FILLED WITH ROCKS, PROVIDING THE COUNTERWEIGHT TO THE TRAMWAY CABLE, WHICH KEEPS IT TAUGHT. - Keane Wonder Mine, Park Route 4 (Daylight Pass Cutoff), Death Valley Junction, Inyo County, CA

  2. 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

  3. Netrin and Frazzled regulate presynaptic gap junctions at a Drosophila giant synapse.

    PubMed

    Orr, Brian O; Borgen, Melissa A; Caruccio, Phyllis M; Murphey, Rodney K

    2014-04-16

    Netrin and its receptor, Frazzled, dictate the strength of synaptic connections in the giant fiber system (GFS) of Drosophila melanogaster by regulating gap junction localization in the presynaptic terminal. In Netrin mutant animals, the synaptic coupling between a giant interneuron and the "jump" motor neuron was weakened and dye coupling between these two neurons was severely compromised or absent. In cases in which Netrin mutants displayed apparently normal synaptic anatomy, half of the specimens exhibited physiologically defective synapses and dye coupling between the giant fiber (GF) and the motor neuron was reduced or eliminated, suggesting that gap junctions were disrupted in the Netrin mutants. When we examined the gap junctions with antibodies to Shaking-B (ShakB) Innexin, they were significantly decreased or absent in the presynaptic terminal of the mutant GF. Frazzled loss of function mutants exhibited similar defects in synaptic transmission, dye coupling, and gap junction localization. These data are the first to show that Netrin and Frazzled regulate the placement of gap junctions presynaptically at a synapse. PMID:24741033

  4. 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.

  5. Terminal Air Flow Planning

    NASA Technical Reports Server (NTRS)

    Denery, Dallas G.; Erzberger, Heinz; Edwards, Thomas A. (Technical Monitor)

    1998-01-01

    The Center TRACON Automation System (CTAS) will be the basis for air traffic planning and control in the terminal area. The system accepts arriving traffic within an extended terminal area and optimizes the flow based on current traffic and airport conditions. The operational use of CTAS will be presented together with results from current operations.

  6. Superconducting Cable Termination

    DOEpatents

    Sinha, Uday K.; Tolbert, Jerry

    2005-08-30

    Disclosed is a termination that connects high temperature superconducting (HTS) cable immersed in pressurized liquid nitrogen to high voltage and neutral (shield) external bushings at ambient temperature and pressure. The termination consists of a splice between the HTS power (inner) and shield (outer) conductors and concentric copper pipes which are the conductors in the termination. There is also a transition from the dielectric tape insulator used in the HTS cable to the insulators used between and around the copper pipe conductors in the termination. At the warm end of the termination the copper pipes are connected via copper braided straps to the conventional warm external bushings which have low thermal stresses. This termination allows for a natural temperature gradient in the copper pipe conductors inside the termination which enables the controlled flashing of the pressurized liquid coolant (nitrogen) to the gaseous state. Thus the entire termination is near the coolant supply pressure and the high voltage and shield cold bushings, a highly stressed component used in most HTS cables, are eliminated. A sliding seal allows for cable contraction as it is cooled from room temperature to ˜72-82 K. Seals, static vacuum, and multi-layer superinsulation minimize radial heat leak to the environment.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Activation of Matrix Metalloproteinase-3 is altered at the frog neuromuscular junction following changes in synaptic activity.

    PubMed

    VanSaun, M; Humburg, B C; Arnett, M G; Pence, M; Werle, M J

    2007-09-15

    The extracellular matrix surrounding the neuromuscular junction is a highly specialized and dynamic structure. Matrix Metalloproteinases are enzymes that sculpt the extracellular matrix. Since synaptic activity is critical to the structure and function of this synapse, we investigated whether changes in synaptic activity levels could alter the activity of Matrix Metalloproteinases at the neuromuscular junction. In particular, we focused on Matrix Metalloproteinase 3 (MMP3), since antibodies to MMP3 recognize molecules at the frog neuromuscular junction, and MMP3 cleaves a number of synaptic basal lamina molecules, including agrin. Here we show that the fluorogenic compound (M2300) can be used to perform in vivo proteolytic imaging of the frog neuromuscular junction to directly measure the activity state of MMP3. Application of this compound reveals that active MMP3 is concentrated at the normal frog neuromuscular junction, and is tightly associated with the terminal Schwann cell. Blocking presynaptic activity via denervation, or TTX nerve blockade, results in a decreased level of active MMP3 at the neuromuscular junction. The loss of active MMP3 at the neuromuscular junction in denervated muscles can result from decreased activation of pro-MMP3, or it could result from increased inhibition of MMP3. These results support the hypothesis that changes in synaptic activity can alter the level of active MMP3 at the neuromuscular junction. PMID:17525979

  12. Kinase programs spatiotemporally regulate gap junction assembly and disassembly: Effects on wound repair.

    PubMed

    Solan, Joell L; Lampe, Paul D

    2016-02-01

    Gap junctions are highly ordered plasma membrane domains that are constantly assembled, remodeled and turned over due to the short half-life of connexins, the integral membrane proteins that form gap junctions. Connexin 43 (Cx43), by far the most widely expressed connexin, is phosphorylated at multiple serine residues in the cytoplasmic, C-terminal region allowing for exquisite cellular control over gap junctional communication. This is evident during epidermal wounding where spatiotemporal changes in connexin expression occur as cells are instructed whether to die, proliferate or migrate to promote repair. Early gap junctional communication is required for initiation of keratinocyte migration, but accelerated Cx43 turnover is also critical for proper wound healing at later stages. These events are controlled via a "kinase program" where sequential phosphorylation of Cx43 leads to reductions in Cx43's half-life and significant depletion of gap junctions from the plasma membrane within several hours. The complex regulation of gap junction assembly and turnover affords several steps where intervention might speed wound healing. PMID:26706150

  13. Recent Progress and Spectral Robustness Study for Mechanically Stacked Multi-junction Solar Cells

    NASA Astrophysics Data System (ADS)

    Zhao, Lu; Flamand, Giovanni; Poortmans, Jef

    2010-10-01

    Multi-terminal mechanically stacked multi-junction solar cells are an attractive candidate for terrestrial concentrator photovoltaics applications. Unlike monolithically integrated multi-junction solar cells which require current matching, all the available photon currents can be fully extracted from each junction of a mechanically stacked solar cell. Therefore, it has a high performance potential, and more importantly is less sensitive to spectrum variations. Lower losses due to current mismatch translate into a higher annual energy output for the mechanical stack. This paper presents the baseline processing developed at imec for the mechanical stacking process, and the most recent cell results by means of this technology. A GaAs-Ge dual-junction mechanically stacked multi-junction solar cell is demonstrated, with 24.7% plus 2.52% under AM1.5g, and 27.7% plus 4.42% under 30Suns concentration. In addition, spectral sensitivity is studied for both monolithically stacked and mechanically stacked solar cells, to learn the influence of spectrum variations on multi-junction solar cell performance. SMARTS model is used to predict the spectral irradiances, with solar radiation and meteorological elements from typical meteorological year 3 (TMY3) data set. The generated spectra are then fed into TCAD numerical simulation tool, to simulate the device performance. The simulation results show a reduced spectral sensitivity for mechanically stacked cell, and there is a 6% relative gain in annual energy production for the site studied (Las Vegas), compared with the monolithic stack.

  14. 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

  15. 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

  16. Phenylethynyl terminated imide oligomers

    NASA Technical Reports Server (NTRS)

    Hergenrother, Paul M. (Inventor); Bryant, Robert G. (Inventor); Jensen, Brian J. (Inventor); Havens, Stephen J. (Inventor)

    1995-01-01

    Four phenylethynyl amine compounds - 3 and 4-aminophenoxy-4'-phenylethynylbenzophenone, and 3 and 4-amino-4'-phenylethynylbenzophenone - were readily prepared and were used to endcap imide oligomers. Phenylethynyl-terminated amide acid oligomers and phenylethynyl-terminated imide oligomers with various molecular weights and compositions were prepared and characterized. These oligomers were cured at 300 to 400 C to provide crosslinked polyimides with excellent solvent resistance, high strength and modulus, and good high temperature properties. Adhesive panels, composites, films, and moldings from these phenylethynyl terminated imide oligomers gave excellent mechanical performance.

  17. Analysis of the Intrinsically Disordered N-Terminus of the DNA Junction-Resolving Enzyme T7 Endonuclease I: Identification of Structure Formed upon DNA Binding.

    PubMed

    Freeman, Alasdair D J; Stevens, Michael; Declais, Anne-Cecile; Leahy, Adam; Mackay, Katherine; El Mkami, Hassane; Lilley, David M J; Norman, David G

    2016-08-01

    The four-way (Holliday) DNA junction of homologous recombination is processed by the symmetrical cleavage of two strands by a nuclease. These junction-resolving enzymes bind to four-way junctions in dimeric form, distorting the structure of the junction in the process. Crystal structures of T7 endonuclease I have been determined as free protein, and the complex with a DNA junction. In neither crystal structure was the N-terminal 16-amino acid peptide visible, yet deletion of this peptide has a marked effect on the resolution process. Here we have investigated the N-terminal peptide by inclusion of spin-label probes at unique sites within this region, studied by electron paramagnetic resonance. Continuous wave experiments show that these labels are mobile in the free protein but become constrained on binding a DNA junction, with the main interaction occurring for residues 7-10 and 12. Distance measurements between equivalent positions within the two peptides of a dimer using PELDOR showed that the intermonomeric distances for residues 2-12 are long and broadly distributed in the free protein but are significantly shortened and become more defined on binding to DNA. These results suggest that the N-terminal peptides become more organized on binding to the DNA junction and nestle into the minor grooves at the branchpoint, consistent with the biochemical data indicating an important role in the resolution process. This study demonstrates the presence of structure within a protein region that cannot be viewed by crystallography. PMID:27387136

  18. Analysis of the Intrinsically Disordered N-Terminus of the DNA Junction-Resolving Enzyme T7 Endonuclease I: Identification of Structure Formed upon DNA Binding.

    PubMed

    Freeman, Alasdair D J; Stevens, Michael; Declais, Anne-Cecile; Leahy, Adam; Mackay, Katherine; El Mkami, Hassane; Lilley, David M J; Norman, David G

    2016-08-01

    The four-way (Holliday) DNA junction of homologous recombination is processed by the symmetrical cleavage of two strands by a nuclease. These junction-resolving enzymes bind to four-way junctions in dimeric form, distorting the structure of the junction in the process. Crystal structures of T7 endonuclease I have been determined as free protein, and the complex with a DNA junction. In neither crystal structure was the N-terminal 16-amino acid peptide visible, yet deletion of this peptide has a marked effect on the resolution process. Here we have investigated the N-terminal peptide by inclusion of spin-label probes at unique sites within this region, studied by electron paramagnetic resonance. Continuous wave experiments show that these labels are mobile in the free protein but become constrained on binding a DNA junction, with the main interaction occurring for residues 7-10 and 12. Distance measurements between equivalent positions within the two peptides of a dimer using PELDOR showed that the intermonomeric distances for residues 2-12 are long and broadly distributed in the free protein but are significantly shortened and become more defined on binding to DNA. These results suggest that the N-terminal peptides become more organized on binding to the DNA junction and nestle into the minor grooves at the branchpoint, consistent with the biochemical data indicating an important role in the resolution process. This study demonstrates the presence of structure within a protein region that cannot be viewed by crystallography.

  19. Analysis of the Intrinsically Disordered N-Terminus of the DNA Junction-Resolving Enzyme T7 Endonuclease I: Identification of Structure Formed upon DNA Binding

    PubMed Central

    2016-01-01

    The four-way (Holliday) DNA junction of homologous recombination is processed by the symmetrical cleavage of two strands by a nuclease. These junction-resolving enzymes bind to four-way junctions in dimeric form, distorting the structure of the junction in the process. Crystal structures of T7 endonuclease I have been determined as free protein, and the complex with a DNA junction. In neither crystal structure was the N-terminal 16-amino acid peptide visible, yet deletion of this peptide has a marked effect on the resolution process. Here we have investigated the N-terminal peptide by inclusion of spin-label probes at unique sites within this region, studied by electron paramagnetic resonance. Continuous wave experiments show that these labels are mobile in the free protein but become constrained on binding a DNA junction, with the main interaction occurring for residues 7–10 and 12. Distance measurements between equivalent positions within the two peptides of a dimer using PELDOR showed that the intermonomeric distances for residues 2–12 are long and broadly distributed in the free protein but are significantly shortened and become more defined on binding to DNA. These results suggest that the N-terminal peptides become more organized on binding to the DNA junction and nestle into the minor grooves at the branchpoint, consistent with the biochemical data indicating an important role in the resolution process. This study demonstrates the presence of structure within a protein region that cannot be viewed by crystallography. PMID:27387136

  20. 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.

  1. 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

  2. Sail intelligent terminal evaluation

    NASA Technical Reports Server (NTRS)

    Pruitt, J. L.

    1977-01-01

    Engineering assessments, recommendations, and equipment necessary to solve the operational problems are described, and operational flexibility of the intelligent terminal facility are extended. The following capabilities were considered: (1) the operation of at least two D/D stations and one remote graphics terminal simultaneously; (2) the capability to run plotter, AIDS and FORTRAN programs simultaneously; (3) simultaneous use of system utility routines of D/D stations and remote graphics terminal; (4) the capability to provide large volume hardcopy of data and graphics; and (5) the capability to eliminate or at least ease the current operation/programming problems with related labor costs. The overall intelligent terminal development, and plans guiding the analysis and equipment acquisitions were studied, and the assessments and analyses performed are also summarized.

  3. Nearest Alignment Space Termination

    2006-07-13

    Near Alignment Space Termination (NAST) is the Greengenes algorithm that matches up submitted sequences with the Greengenes database to look for similarities and align the submitted sequences based on those similarities.

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. Charge transport and rectification in molecular junctions formed with carbon-based electrodes.

    PubMed

    Kim, Taekyeong; Liu, Zhen-Fei; Lee, Chulho; Neaton, Jeffrey B; Venkataraman, Latha

    2014-07-29

    Molecular junctions formed using the scanning-tunneling-microscope-based break-junction technique (STM-BJ) have provided unique insight into charge transport at the nanoscale. In most prior work, the same metal, typically Au, Pt, or Ag, is used for both tip and substrate. For such noble metal electrodes, the density of electronic states is approximately constant within a narrow energy window relevant to charge transport. Here, we form molecular junctions using the STM-BJ technique, with an Au metal tip and a microfabricated graphite substrate, and measure the conductance of a series of graphite/amine-terminated oligophenyl/Au molecular junctions. The remarkable mechanical strength of graphite and the single-crystal properties of our substrates allow measurements over few thousand junctions without any change in the surface properties. We show that conductance decays exponentially with molecular backbone length with a decay constant that is essentially the same as that for measurements with two Au electrodes. More importantly, despite the inherent symmetry of the oligophenylamines, we observe rectification in these junctions. State-of-art ab initio conductance calculations are in good agreement with experiment, and explain the rectification. We show that the highly energy-dependent graphite density of states contributes variations in transmission that, when coupled with an asymmetric voltage drop across the junction, leads to the observed rectification. Together, our measurements and calculations show how functionality may emerge from hybrid molecular-scale devices purposefully designed with different electrodes beyond the so-called "wide band limit," opening up the possibility of assembling molecular junctions with dissimilar electrodes using layered 2D materials.

  9. Charge transport and rectification in molecular junctions formed with carbon-based electrodes

    PubMed Central

    Kim, Taekyeong; Liu, Zhen-Fei; Lee, Chulho; Neaton, Jeffrey B.; Venkataraman, Latha

    2014-01-01

    Molecular junctions formed using the scanning-tunneling-microscope–based break-junction technique (STM-BJ) have provided unique insight into charge transport at the nanoscale. In most prior work, the same metal, typically Au, Pt, or Ag, is used for both tip and substrate. For such noble metal electrodes, the density of electronic states is approximately constant within a narrow energy window relevant to charge transport. Here, we form molecular junctions using the STM-BJ technique, with an Au metal tip and a microfabricated graphite substrate, and measure the conductance of a series of graphite/amine-terminated oligophenyl/Au molecular junctions. The remarkable mechanical strength of graphite and the single-crystal properties of our substrates allow measurements over few thousand junctions without any change in the surface properties. We show that conductance decays exponentially with molecular backbone length with a decay constant that is essentially the same as that for measurements with two Au electrodes. More importantly, despite the inherent symmetry of the oligophenylamines, we observe rectification in these junctions. State-of-art ab initio conductance calculations are in good agreement with experiment, and explain the rectification. We show that the highly energy-dependent graphite density of states contributes variations in transmission that, when coupled with an asymmetric voltage drop across the junction, leads to the observed rectification. Together, our measurements and calculations show how functionality may emerge from hybrid molecular-scale devices purposefully designed with different electrodes beyond the so-called “wide band limit,” opening up the possibility of assembling molecular junctions with dissimilar electrodes using layered 2D materials. PMID:25024198

  10. ACTS broadband aeronautical terminal

    NASA Technical Reports Server (NTRS)

    Agan, M. J.; Densmore, A. C.

    1995-01-01

    This paper discusses the design of, and experiments with, the ACTS Broadband Aeronautical Terminal. As part of the ongoing effort to investigate commercial applications of ACTS technologies, NASA's Jet Propulsion Laboratory and various industry/government partners are developing a broadband mobile terminal for aeronautical applications. The ACTS Broadband Aeronautical Terminal is designed to explore the use of K/Ka-band for high data rate aeronautical satellite communications. Currently available commercial aeronautical satellite communications systems are only capable of achieving data rates on the order of tens of kilobits per second. The broadband terminal used in conjunction with the ACTS mechanically steerable antenna, can achieve data rates of 384 kilobits per second, while use of an ACTS spot beam antenna with this terminal will allow up to T1 data rates (1.544 megabits per second). The aeronautical terminal will be utilized to test a variety of applications that require a high data rate communications link. The use of the K/Ka-band for wideband aeronautical communications has the advantages of spectrum availability and smaller antennas, while eliminating the one major drawback of this frequency band, rain attenuation, by flying above the clouds the majority of the time.

  11. The importance of the N-terminus of T7 endonuclease I in the interaction with DNA junctions.

    PubMed

    Freeman, Alasdair D J; Déclais, Anne-Cécile; Lilley, David M J

    2013-01-23

    T7 endonuclease I is a dimeric nuclease that is selective for four-way DNA junctions. Previous crystallographic studies have found that the N-terminal 16 amino acids are not visible, neither in the presence nor in the absence of DNA. We have now investigated the effect of deleting the N-terminus completely or partially. N-terminal deleted enzyme binds more tightly to DNA junctions but cleaves them more slowly. While deletion of the N-terminus does not measurably affect the global structure of the complex, the presence of the peptide is required to generate a local opening at the center of the DNA junction that is observed by 2-aminopurine fluorescence. Complete deletion of the peptide leads to a cleavage rate that is 3 orders of magnitude slower and an activation enthalpy that is 3-fold higher, suggesting that the most important interaction of the peptide is with the reaction transition state. Taken together, these data point to an important role of the N-terminus in generating a central opening of the junction that is required for the cleavage reaction to proceed properly. In the absence of this, we find that a cruciform junction is no longer subject to bilateral cleavage, but instead, just one strand is cleaved. Thus, the N-terminus is required for a productive resolution of the junction.

  12. 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.

  13. 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.

  14. Formation of electronic junctions on molecularly modified surfaces by lift-and-float electrical contacts.

    PubMed

    Ikram, I Mohamed; Rabinal, M K; Kalasad, M N; Mulimani, B G

    2009-03-01

    Here, we report a simple method of forming electrical contacts on soft surfaces of organic monolayers and organically capped nanoparticles. It is based on the lift of predefined contacts of silver paste on a water surface and their pickup and float on a soft surface by capillary force. Three different surfaces of silicon--hydrogen terminated, covalently bonded organic molecules, and a thin film of organically capped CdSe nanoparticles--were used to constitute electronic junctions by lift and float of individual contacts. Charge transport measurements clearly demonstrate that these junctions are free from shorting and wrinkling of the top contact and damage of molecular films. Hence, the method is simple, effective, nondestructive, and economical to form electronic junctions on molecular surfaces.

  15. Strength and precision of neurotransmission at mammalian presynaptic terminals

    PubMed Central

    TAKAHASHI, Tomoyuki

    2015-01-01

    Classically, the basic concept of chemical synaptic transmission was established at the frog neuromuscular junction, and direct intracellular recordings from presynaptic terminals at the squid giant presynaptic terminal have further clarified principles of neurotransmitter release. More recently, whole-cell patch-camp recordings from the calyx of Held in rodent brainstem slices have extended the classical concept to mammalian synapses providing new insights into the mechanisms underlying strength and precision of neurotransmission and developmental changes therein. This review summarizes findings from our laboratory and others on these subjects, mainly at the calyx of Held, with a particular focus on precise, high-fidelity, fast neurotransmission. The mechanisms by which presynaptic terminals acquire strong, precise neurotransmission during postnatal development are also discussed. PMID:26194855

  16. TOP VIEW OF UPPER TRAM TERMINAL, PRIMARY ORE BIN, AND ...

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

    TOP VIEW OF UPPER TRAM TERMINAL, PRIMARY ORE BIN, AND ORE CHUTE,LOOKING SOUTHWEST. TRAM MACHINERY AND GEARS ARE AT LOWER CENTER. A SMALL ELECTRIC MOTOR AT THE REAR LEFT OF THE TERMINAL PROBABLY WAS ADDED AFTER THE ORIGINAL CONSTRUCTION. THE MOVING CABLE OF THE TRAM WAS DRIVEN BY THESE GEARS AND THE LARGE WHEEL UNDERNEATH (SEE CA-291-31 FOR DETAIL). EMPTY TRAM BUCKETS CAME IN FROM THE LEFT, SWINGING AROUND TO THE CHUTES FROM THE ORE BIN TO BE LOADED FOR THE TRIP DOWN TO THE MILL (SEE CA-291-35 FOR DETAIL). THE BREAK OVER TOWER CAN BE SEEN IN THE DISTANCE AT TOP LEFT. THE SUPPORT TOWER BETWEEN THE UPPER TERMINAL AND THE BREAK OVER TOWER IS COLLAPSED. - Keane Wonder Mine, Park Route 4 (Daylight Pass Cutoff), Death Valley Junction, Inyo County, CA

  17. Documents from malicious terminals

    NASA Astrophysics Data System (ADS)

    Berta, Istvan Z.; Vajda, Istvan

    2003-04-01

    The user wishes to communicate with a remote partner over an insecure network. Since the user is a human being, a terminal is needed for communication. Cryptographic algorithms running on the terminal may provide authenticity for the user's messages. In this paper the problem of sending authentic messages from insecure or untrusted terminals is analyzed. In this case attackers are able to gain total control over the terminal, so the user must consider the terminal a potential attacker. Smart cards are often considered the ultimate tool for secure messaging from untrusted terminals. However, their lack of user interface enables man-in-the middle attack from the terminal. The authors assume, that user is a human being with limited memory and computational power, and also makes mistakes in his calculations. They demnostrate, that only exceptional useres are able to authenticate messages without a trusted device. Several biometric media encapsulate the content of the message and the identity of the sender, such as speech, video and handwriting. The authors suggest, that such media is far more difficult to counterfeit than plaintext. Thus, the user must rely on his other resources, like biometric ones. In the protocol proposed by the authors, the user sends messages in a biometric format, strengthened by simple algorithmic authenticators. The smart card functions as a secure time gate ensuring, that the attacker has extremely little time to counterfeit both the biometric and the algorithmic protection on the message. The authors claim, that with the proper calibration of the biometric method and the time gate of the smart card, their protocol is strong enough for practical use.

  18. 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.

  19. InGaP/GaAs and InGaAs mechanically-stacked triple-junction solar cells

    SciTech Connect

    Takamoto, T.; Ikeda, E.; Agui, T.

    1997-12-31

    Triple-junction cells with AM1.5 efficiencies of over 33% have been demonstrated. A planar type InGaP/GaAs monolithic dual-junction cell was fabricated on a semi-insulating FaAs substrate, which has high infra-red transparency. Then a dual-junction cell, with efficiency of 27--28%, was mechanically stacked on an InGaAs cell fabricated on an InP substrate. The bottom InGaAs cell showed an efficiency of 6.2% under the InGaP/GaAs cell, and a total efficiency of 33--34% was achieved for the four-terminal triple-junction cell.

  20. 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.

  1. In situ Formation of Highly Conducting Covalent Au-C Contacts for Single-Molecule Junctions

    SciTech Connect

    Cheng, Z.L.; Hybertsen, M.; Skouta, R.; Vazquez, H.; Widawsky, J.R.; Schneebeli, S.; Chen, W.; Breslow, R.; Venkataraman, L.

    2011-06-01

    Charge transport across metal-molecule interfaces has an important role in organic electronics. Typically, chemical link groups such as thiols or amines are used to bind organic molecules to metal electrodes in single-molecule circuits, with these groups controlling both the physical structure and the electronic coupling at the interface. Direct metal-carbon coupling has been shown through C60, benzene and {pi}-stacked benzene but ideally the carbon backbone of the molecule should be covalently bonded to the electrode without intervening link groups. Here, we demonstrate a method to create junctions with such contacts. Trimethyl tin (SnMe{sub 3})-terminated polymethylene chains are used to form single-molecule junctions with a break-junction technique. Gold atoms at the electrode displace the SnMe{sub 3} linkers, leading to the formation of direct Au-C bonded single-molecule junctions with a conductance that is {approx}100 times larger than analogous alkanes with most other terminations. The conductance of these Au-C bonded alkanes decreases exponentially with molecular length, with a decay constant of 0.97 per methylene, consistent with a non-resonant transport mechanism. Control experiments and ab initio calculations show that high conductances are achieved because a covalent Au-C sigma ({sigma}) bond is formed. This offers a new method for making reproducible and highly conducting metal-organic contacts.

  2. Snake and Spider Toxins Induce a Rapid Recovery of Function of Botulinum Neurotoxin Paralysed Neuromuscular Junction

    PubMed Central

    Duregotti, Elisa; Zanetti, Giulia; Scorzeto, Michele; Megighian, Aram; Montecucco, Cesare; Pirazzini, Marco; Rigoni, Michela

    2015-01-01

    Botulinum neurotoxins (BoNTs) and some animal neurotoxins (β-Bungarotoxin, β-Btx, from elapid snakes and α-Latrotoxin, α-Ltx, from black widow spiders) are pre-synaptic neurotoxins that paralyse motor axon terminals with similar clinical outcomes in patients. However, their mechanism of action is different, leading to a largely-different duration of neuromuscular junction (NMJ) blockade. BoNTs induce a long-lasting paralysis without nerve terminal degeneration acting via proteolytic cleavage of SNARE proteins, whereas animal neurotoxins cause an acute and complete degeneration of motor axon terminals, followed by a rapid recovery. In this study, the injection of animal neurotoxins in mice muscles previously paralyzed by BoNT/A or /B accelerates the recovery of neurotransmission, as assessed by electrophysiology and morphological analysis. This result provides a proof of principle that, by causing the complete degeneration, reabsorption, and regeneration of a paralysed nerve terminal, one could favour the recovery of function of a biochemically- or genetically-altered motor axon terminal. These observations might be relevant to dying-back neuropathies, where pathological changes first occur at the neuromuscular junction and then progress proximally toward the cell body. PMID:26670253

  3. 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

  4. 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.

  5. 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.

  6. 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.

  7. Phenylethynyl terminated reactive oligomer

    NASA Technical Reports Server (NTRS)

    Bryant, Robert G. (Inventor); Jensen, Brian J. (Inventor); Hergenrother, Paul M. (Inventor)

    1995-01-01

    A composition of matter having the general structure: ##STR1## (wherein X is F, Cl, or NO.sub.2, and Y is CO, SO.sub.2 or C(CF.sub.3).sub.2) is employed to terminate a nucleophilic reagent, resulting in the exclusive production of phenylethynyl terminated reactive oligomers which display unique thermal characteristics. A reactive diluent having the general structure: ##STR2## (wherein R is any aliphatic or aromatic moiety) is employed to decrease the melt viscosity of a phenylethynyl terminated reactive oligomer and to subsequently react therewith to provide a thermosetting material of enhanced density. These materials have features which make them attractive candidates for use as composite matrices and adhesives.

  8. 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.

  9. Electrical termination techniques

    NASA Technical Reports Server (NTRS)

    Oakey, W. E.; Schleicher, R. R.

    1976-01-01

    A technical review of high reliability electrical terminations for electronic equipment was made. Seven techniques were selected from this review for further investigation, experimental work, and preliminary testing. From the preliminary test results, four techniques were selected for final testing and evaluation. These four were: (1) induction soldering, (2) wire wrap, (3) percussive arc welding, and (4) resistance welding. Of these four, induction soldering was selected as the best technique in terms of minimizing operator errors, controlling temperature and time, minimizing joint contamination, and ultimately producing a reliable, uniform, and reusable electrical termination.

  10. ALSEP termination report

    NASA Technical Reports Server (NTRS)

    Bates, J. R.; Lauderdale, W. W.; Kernaghan, H.

    1979-01-01

    The Apollo Lunar Surface Experiments Package (ALSEP) final report was prepared when support operations were terminated September 30, 1977, and NASA discontinued the receiving and processing of scientific data transmitted from equipment deployed on the lunar surface. The ALSEP experiments (Apollo 11 to Apollo 17) are described and pertinent operational history is given for each experiment. The ALSEP data processing and distribution are described together with an extensive discussion on archiving. Engineering closeout tests and results are given, and the status and configuration of the experiments at termination are documented. Significant science findings are summarized by selected investigators. Significant operational data and recommendations are also included.

  11. 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.

  12. 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.

  13. Etch-stop technique for patterning of tunnel junctions for a magnetic field sensor

    NASA Astrophysics Data System (ADS)

    Persson, Anders; Ericson, Fredric; Thornell, Greger; Nguyen, Hugo

    2011-04-01

    Spin-dependent tunnelling devices, e.g. magnetic random access memories and highly sensitive tunnelling magnetoresistance (TMR) sensors, often consist of a large number of magnetic tunnel junctions (MTJs) of uniform quality over the whole device. The uniformity and yield of the fabrication of such a device are therefore very important. A major source of yield loss is the short-circuiting of junctions by redeposition of etch residues. This can be prevented by terminating of the etch in the typically 1 nm thick tunnelling barrier. Here, electron spectroscopy for chemical analysis for monitoring the etching semi-continuously is proposed. The fabrication scheme employs Ar ion milling for etching the MTJs, and photoelectron spectroscopy for analysing the composition of the etched surface in situ. Junctions etched either to or through the barrier were used for this. The quality of the etch stop was investigated using transmission electron microscopy (TEM), and it was confirmed that the etch could be stopped in the MgO barrier. The TEM imaging also showed clear signs of redeposition. Such redeposition was attributed to being partly caused by the reduction of the TMR ratio of the junctions etched through the barrier, which was only 15% as compared with 150% for junctions etched to the barrier. Also, the latter junctions exhibited 2.7 times less noise in the low-frequency regime, resulting in a 27 times improvement of the signal-to-noise ratio with the etch stop. The barrier also proved effective in protecting the bottom contact from oxidation during the capping and contacting of the junctions.

  14. Prematurely terminated slug tests

    SciTech Connect

    Karasaki, K. )

    1990-07-01

    A solution of the well response to a prematurely terminated slug test (PTST) is presented. The advantages of a PTST over conventional slug tests are discussed. A systematized procedure of a PTST is proposed, where a slug test is terminated in the midpoint of the flow point, and the subsequent shut-in data is recorded and analyzed. This method requires a downhole shut-in device and a pressure transducer, which is no more than the conventional deep-well slug testing. As opposed to slug tests, which are ineffective when a skin is present, more accurate estimate of formation permeability can be made using a PTST. Premature termination also shortens the test duration considerably. Because in most cases no more information is gained by completing a slug test to the end, the author recommends that conventional slug tests be replaced by the premature termination technique. This study is part of an investigation of the feasibility of geologic isolation of nuclear wastes being carried out by the US Department of Energy and the National Cooperative for the Storage of Radioactive Waste of Switzerland.

  15. The Versatile Terminal.

    ERIC Educational Resources Information Center

    Evans, C. D.

    This paper describes the experiences of the industrial research laboratory of Kodak Ltd. in finding and providing a computer terminal most suited to its very varied requirements. These requirements include bibliographic and scientific data searching and access to a number of worldwide computing services for scientific computing work. The provision…

  16. Shipboard regasification terminal

    SciTech Connect

    Campbell, G.; Zednik, J.

    1999-07-01

    Mobil Technology Company and Mobil Shipping and Transportation Company have jointly developed a new combination of existing proven equipment to regasify LNG. Advantages of this Shipboard Regasification Terminal (SRT) include accelerated initial gas delivery schedule, low capital cost, delivery of smaller quantities of LNG at a competitive price and shorter term of LNG purchase and improved financing options. These advantages benefit both the supplier of LNG and the purchaser. SRT can be used as an interim supply to developing markets allowing the demand to grow while developing downstream infrastructure. This concept does not involve offshore transfer of cryogenic fluids while delivering near-ambient temperature pipeline quality gas at typical pipeline pressures. During times when gas is not required, the SRT ship can easily be returned to the trade of transporting and delivering LNG to conventional land based terminals. This paper will discuss the merits of Shipboard Regasification Terminals in general, cover the development of this concept and review the factors guiding the use of SRT vs. an onshore terminal.

  17. Modeling Terminal Velocity

    ERIC Educational Resources Information Center

    Brand, Neal; Quintanilla, John A.

    2013-01-01

    Using a simultaneously falling softball as a stopwatch, the terminal velocity of a whiffle ball can be obtained to surprisingly high accuracy with only common household equipment. This classroom activity engages students in an apparently daunting task that nevertheless is tractable, using a simple model and mathematical techniques at their…

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. 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.

  3. Cirrus Crystal Terminal Velocities.

    NASA Astrophysics Data System (ADS)

    Heymsfield, Andrew J.; Iaquinta, Jean

    2000-04-01

    Cirrus crystal terminal velocities are of primary importance in determining the rate of transport of condensate from upper- to middle-tropospheric levels and profoundly influence the earth's radiation balance through their effect on the rate of buildup or decay of cirrus clouds. In this study, laboratory and field-based cirrus crystal drag coefficient data, as well as analytical descriptions of cirrus crystal shapes, are used to derive more physically based expressions for the velocities of cirrus crystals than have been available in the past.Polycrystals-often bullet rosettes-are shown to be the dominant crystal types in synoptically generated cirrus, with columns present in varying but relatively large percentages, depending on the cloud. The two critical parameters needed to calculate terminal velocity are the drag coefficient and the ratio of mass to cross-sectional area normal to their fall direction. Using measurements and calculations, it is shown that drag coefficients from theory and laboratory studies are applicable to crystals of the types found in cirrus. The ratio of the mass to area, which is shown to be relatively independent of the number of bullets in the rosette, is derived from an analytic model that represents bullet rosettes containing one to eight bullets in 19 primary geometric configurations. The ratio is also derived for columns. Using this information, a general set of equations is developed to calculate the terminal velocities and masses in terms of the aspect ratio (width divided by length), ice density, and rosette maximum dimension. Simple expressions for terminal velocity and mass as a function of bullet rosette maximum dimension are developed by incorporating new information on bullet aspect ratios.The general terminal velocity and mass relations are then applied to a case from the First International Satellite Cloud Climatology Project (ISCCP) Research Experiment (FIRE) 2, when size spectra from a balloon-borne ice crystal

  4. Mechanically Stacked Four-Junction Concentrator Solar Cells

    SciTech Connect

    Steiner, Myles A.; Geisz, John F.; Ward, J. Scott; Garcia, Ivan; Friedman, Daniel J.; King, Richard R.; Chiu, Philip T.; France, Ryan M.; Duda, Anna; Olavarria, Waldo J.; Young, Michelle; Kurtz, Sarah R.

    2015-06-14

    Multijunction solar cells can be fabricated by bonding together component cells that are grown separately. Because the component cells are each grown lattice-matched to suitable substrates, this technique allows alloys of different lattice constants to be combined without the structural defects introduced when using metamorphic buffers. Here we present results on the fabrication and performance of four-junction mechanical stacks composed of GaInP/GaAs and GaInAsP/GaInAs tandems, grown on GaAs and InP substrates, respectively. The two tandems were bonded together with a low-index, transparent epoxy that acts as an omni-directional reflector to the GaAs bandedge luminescence, while simultaneously transmitting nearly all of the sub-bandgap light. As determined by electroluminescence measurements and optical modeling, the GaAs subcell demonstrates a higher internal radiative limit and thus higher subcell voltage, compared with GaAs subcells without enhanced internal optics; all four subcells exhibit excellent material quality. The device was fabricated with four contact terminals so that each tandem can be operated at its maximum power point, which raises the cumulative efficiency and decreases spectral sensitivity. Efficiencies exceeding 38% at one-sun have been demonstrated. Eliminating the series resistance is the key challenge for the concentrator cells. We will discuss the performance of one-sun and concentrator versions of the device, and compare the results to recently fabricated monolithic four-junction cells.

  5. Graphics Software For VT Terminals

    NASA Technical Reports Server (NTRS)

    Wang, Caroline

    1991-01-01

    VTGRAPH graphics software tool for DEC/VT computer terminal or terminals compatible with it, widely used by government and industry. Callable in FORTRAN or C language, library program enabling user to cope with many computer environments in which VT terminals used for window management and graphic systems. Provides PLOT10-like package plus color or shade capability for VT240, VT241, and VT300 terminals. User can easily design more-friendly user-interface programs and design PLOT10 programs on VT terminals with different computer systems. Requires ReGis graphics set terminal and FORTRAN compiler.

  6. Direct Conversion from Terminal Borylene into Terminal Phosphinidene.

    PubMed

    Braunschweig, Holger; Jimenez-Halla, J Oscar C; Radacki, Krzysztof; Shang, Rong

    2016-10-01

    The first terminal manganese phosphinidene complex was quantitatively synthesized from a terminal alkylborylene complex. Its structure and bonding, as well as the reaction mechanism, were investigated through a combination of experimental and computational studies. PMID:27621216

  7. Direct Conversion from Terminal Borylene into Terminal Phosphinidene.

    PubMed

    Braunschweig, Holger; Jimenez-Halla, J Oscar C; Radacki, Krzysztof; Shang, Rong

    2016-10-01

    The first terminal manganese phosphinidene complex was quantitatively synthesized from a terminal alkylborylene complex. Its structure and bonding, as well as the reaction mechanism, were investigated through a combination of experimental and computational studies.

  8. [Genetic defects and disorders at the neuromuscular junction].

    PubMed

    Ohno, Kinji

    2011-07-01

    Genetic defects in molecules expressed at the neuromuscular junction (NMJ) cause congenital myasthenic syndromes (CMSs), which are characterized by muscle weakness, abnormal fatigability, amyotrophy, and minor facial anomalies. Muscle weakness mostly develops under 2 years but is also sometimes seen in adults. Mutations identified to date include (i) muscle nicotinic acetylcholine receptor (AChR) subunits, (ii) rapsyn that anchors and clusters AChRs at the neuromuscular junction, (iii) agrin that is released from the nerve terminal and induces AChR clustering by stimulating the downstream LRP4/MuSK/Dok-7/rapsyn/AChR pathway, (iv) muscle-specific kinase (MuSK) that transmits the AChR-clustering signal from agrin/LRP4 to rapsyn/AChR, (v) Dok-7 that transmits the AChR-clustering signal from agrin/LRP4/MuSK to rapsyn/AChR, (vi) skeletal muscle sodium channel type 1.4 (Nav1.4) that spreads the depolarization potential from the endplate throughout muscle fibers, (vii) collagen Q that anchors acetylcholinesterase to the synaptic basal lamina, and (viii) choline acetyltransferase that resynthesizes acetylcholine from recycled choline at the nerve terminal. In addition, mutations in the heparin sulfate proteoglycan perlecan, which binds to many molecules including collagen Q and dystroglycan, causes Schwartz-Jampel syndrome. Interestingly, mutations in LRP4 cause Cenani-Lenz syndactyly syndrome but not CMS. AChR, MuSK, and LRP4 are also targets of auto-antibodies in myasthenia gravis. In addition, molecules at the NMJ are targets of many other disease states AChRs are blocked by the snake toxin alpha-bungarotoxin and the plant poison curare. The presynaptic SNARE complex is attacked by botulinum toxin. Acetylcholinesterase is inhibited by the nerve gas sarin and by organophosphate pesticides. This review focuses on the molecular bases underlying defects of AChR, rapsyn, Nav1.4, collagen Q, and choline acetyltransferase. PMID:21747136

  9. Mobile Phone Terminal

    NASA Technical Reports Server (NTRS)

    1978-01-01

    In the photo, an employee of a real estate firm is contacting his office by means of HICOM, an advanced central terminal for mobile telephones. Developed by the Orlando Division of Martin Marietta Aerospace, Orlando, Florida, and manufactured by Harris Corporation's RF Division, Rochester, N.Y., HICOM upgrades service to users, provides better system management to telephone companies, and makes more efficient use of available mobile telephone channels through a computerized central control terminal. The real estate man, for example, was able to dial his office and he could also have direct-dialed a long distance number. Mobile phones in most areas not yet served by HICOM require an operator's assistance for both local and long distance calls. HICOM improves system management by automatically recording information on all calls for accurate billing, running continual performance checks on its own operation, and reporting any malfunctions to a central office.

  10. Shipboard fisheries management terminals

    NASA Technical Reports Server (NTRS)

    Nagler, R. G.; Sager, E. V.

    1980-01-01

    The needs of the National Marine Fisheries Service (NMGS), National Weather Service, and the U.S. Coast Guard for locational, biological, and environmental data were assessed. The fisheries conservation zones and the yellowfin tuna jurisdiction of the NMFS operates observer programs on foreign and domestic fishing vessels. Data input terminal and data transfer and processing technology are reviewed to establish available capability. A matrix of implementation options is generated to identify the benefits of each option, and preliminary cost estimates are made. Recommendations are made for incremental application of available off the shelf hardware to obtain improved performance and benefits within a well bounded cost. Terminal recommendations are made for three interdependent shipboard units emphasizing: (1) the determination of location and fishing activity; (2) hand held data inputting and formatting in the fishing work areas; and (3) data manipulation, merging, and editing.

  11. Remote terminal system evaluation

    NASA Technical Reports Server (NTRS)

    Phillips, T. L.; Grams, H. L.; Lindenlaub, J. C.; Schwingendorf, S. K.; Swain, P. H.; Simmons, W. R.

    1975-01-01

    An Earth Resources Data Processing System was developed to evaluate the system for training, technology transfer, and data processing. In addition to the five sites included in this project two other sites were connected to the system under separate agreements. The experience of these two sites is discussed. The results of the remote terminal project are documented in seven reports: one from each of the five project sites, Purdue University, and an overview report summarizing the other six reports.

  12. "Terminal" Students Do Transfer.

    ERIC Educational Resources Information Center

    Townsend, Barbara K.

    This report discusses the transfer rate of community college students with A.S. or A.A.S. degrees from vocational or "terminal" programs in Missouri. The study shows that during the 1995-1996 academic year, 6,171 students received an associate degree from a Missouri public two-year college. Of these, 3,169 (51%) earned the A.A. degree and 3,002…

  13. Amine terminated bisaspartimide polymer

    NASA Technical Reports Server (NTRS)

    Kumar, D. (Inventor); Fohlen, G. M. (Inventor); Parker, J. A. (Inventor)

    1986-01-01

    Novel amine terminated bisaspartimides are prepared by a Michael-type reaction of an aromatic bismalteimide and an aromatic diamine in an aprotic solvent. These bisaspartimides are thermally polymerized to yield tough, resinous polymers cross-lined through -NH- groups. Such polymers are useful in applications requiring materials with resistance to change at elevated temperatures, e.g., as lightweight laminates with graphite cloth, molding material prepregs, adhesives and insulating material.

  14. DETAIL VIEW OF UPPER TRAM TERMINAL STRUCTURE, LOOKING NORTHEAST TOWARD ...

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

    DETAIL VIEW OF UPPER TRAM TERMINAL STRUCTURE, LOOKING NORTHEAST TOWARD THE REAR OF THE STRUCTURE. THE WHEELS AT THE TOP OF THE TRAM BUCKETS RODE OFF THE STATIONARY CABLES ONTO THE TRACK SUPPORTED BY THE "C" IRONS SUSPENDED FROM THE TOP TIMBERS, CLEARLY SEEN AT THE TOP OF THE FRAME. THE ANCHOR POINTS FOR THE TWO STATIONARY CABLES ARE AT BOTTOM CENTER, JUST BELOW THE CABLE WHEEL. THE MAIN CABLE WHEEL IS IN THE DISTANCE AT CENTER LEFT. THE ORE CHUTES COMING FROM THE ORE BIN ARE AT LEFT CENTER EDGE. TRAM BUCKETS WERE CHARGED HERE. - Keane Wonder Mine, Park Route 4 (Daylight Pass Cutoff), Death Valley Junction, Inyo County, CA

  15. 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.

  16. Correlation between amplitude of spin accumulation signals investigated by Hanle effect measurement and effective junction barrier height in CoFe/MgO/n{sup +}-Si junctions

    SciTech Connect

    Saito, Y. Ishikawa, M.; Sugiyama, H.; Inokuchi, T.; Hamaya, K.; Tezuka, N.

    2015-05-07

    Correlation between the amplitude of the spin accumulation signals and the effective barrier height estimated from the slope of the log (RA) - t{sub MgO} plot (RA: resistance area product, t{sub MgO}: thickness of MgO tunnel barrier) in CoFe/MgO/n{sup +}-Si junctions was investigated. The amplitude of spin accumulation signals increases with increasing effective barrier heights. This increase of the amplitude of spin accumulation is originated from the increase of the spin polarization (P{sub Si}) in Si. The estimated absolute values of P{sub Si} using three-terminal Hanle signals are consistent with those estimated by four-terminal nonlocal-magnetoresistance (MR) and two-terminal local-MR. To demonstrate large spin accumulation in Si bulk band and enhance the local-MR through Si channel, these results indicate that the increase of the effective barrier height at ferromagnet/(tunnel barrier)/n{sup +}-Si junction electrode is important.

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Effect of disorder on longitudinal resistance of a graphene p-n junction in the quantum Hall regime

    NASA Astrophysics Data System (ADS)

    Chen, Jiang-Chai; Yeung, T. C. Au; Sun, Qing-Feng

    2010-06-01

    The longitudinal resistances of a six-terminal graphene p-n junction under a perpendicular magnetic field are investigated. Because of the chirality of the Hall edge states, the longitudinal resistances on top and bottom edges of the graphene ribbon are not equal. In the presence of suitable disorder, the top-edge and bottom-edge resistances well show the plateau structures in the both unipolar and bipolar regimes, and the plateau values are determined by the Landau filling factors only. These plateau structures are in excellent agreement with the recent experiment. For the unipolar junction, the resistance plateaus emerge in the absence of impurity and they are destroyed by strong disorder. But for the bipolar junction, the resistances are very large without the plateau structures in the clean junction. The disorder can strongly reduce the resistances and leads the formation of the resistance plateaus due to the mixture of the Hall edge states in virtue of the disorder. In addition, the size effect of the junction on the resistances is studied and some extra resistance plateaus are found in the long graphene junction case. This is explained by the fact that only part of the edge states participate in the full mixing.

  3. 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.

  4. Detergent-resistant microdomains determine the localization of sigma-1 receptors to the endoplasmic reticulum-mitochondria junction.

    PubMed

    Hayashi, Teruo; Fujimoto, Michiko

    2010-04-01

    Sigma-1 receptors (Sig-1Rs) that bind diverse synthetic and endogenous compounds have been implicated in the pathophysiology of several human diseases such as drug addiction, depression, neurodegenerative disorders, pain-related disorders, and cancer. Sig-1Rs were identified recently as novel ligand-operated molecular chaperones. Although Sig-1Rs are predominantly expressed at endoplasmic reticulum (ER) subdomains apposing mitochondria [i.e., the mitochondria-associated ER membrane (MAM)], they dynamically change the cellular distribution, thus regulating both MAM-specific and plasma membrane proteins. However, what determines the location of Sig-1R at the MAM and how the receptor translocation is initiated is unknown. Here we report that the detergent-resistant membranes (DRMs) play an important role in anchoring Sig-1Rs to the MAM. The MAM, which is highly capable of accumulating ceramides, is enriched with both cholesterol and simple sphingolipids, thus forming Triton X-114-resistant DRMs. Sig-1Rs associate with MAM-derived DRMs but not with those from microsomes. A lipid overlay assay found that solubilized Sig-1Rs preferentially associate with simple sphingolipids such as ceramides. Disrupting DRMs by lowering cholesterol or inhibiting de novo synthesis of ceramides at the ER largely decreases Sig-1R at DRMs and causes translocation of Sig-1R from the MAM to ER cisternae. These findings suggest that the MAM, bearing cholesterol and ceramide-enriched microdomains at the ER, may use the microdomains to anchor Sig-1Rs to the location; thus, it serves to stage Sig-1R at ER-mitochondria junctions.

  5. DETAIL VIEW OF LOWER TRAM TERMINAL, SECONDARY ORE BIN, CRUSHER ...

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

    DETAIL VIEW OF LOWER TRAM TERMINAL, SECONDARY ORE BIN, CRUSHER FOUNDATION, AND BALL MILL FOUNDATIONS, LOOKING NORTH NORTHWEST. ORE FROM THE MINES WAS DUMPED FROM THE TRAM BUCKETS INTO THE PRIMARY ORE BIN UNDER THE TRAM TERMINAL. A SLIDING CONTROL DOOR INTRODUCED THE INTO THE JAW CRUSHER (FOUNDATIONS,CENTER). THE CRUSHED ORE WAS THEN CONVEYED INTO THE SECONDARY ORE BIN AT CENTER LEFT. A HOLE IN THE FLOOR OF THE ORE BIN PASSED ORE ONTO ANOTHER CONVEYOR THAT BROUGHT IT OUT TO THE BALL MILL(FOUNDATIONS,CENTER BOTTOM). THIS SYSTEM IS MOST LIKELY NOT THE ORIGINAL SET UP, PROBABLY INSTALLED IN THE MINE'S LAST OCCUPATION IN THE EARLY 1940s. - Keane Wonder Mine, Park Route 4 (Daylight Pass Cutoff), Death Valley Junction, Inyo County, CA

  6. 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.

  7. 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.

  8. Role of amino terminus in voltage gating and junctional rectification of Shaking B innexins.

    PubMed

    Marks, William D; Skerrett, I Martha

    2014-03-01

    Rectifying electrical synapses are rare gap junctions that favor transmission of signals in one direction. Such synapses have been identified in neural systems, including those mediating rapid escape responses of arthropods. In the Drosophila giant fiber system, adjacent cells express and contribute different transcript variants of the innexin Shaking B, resulting in heterotypic gap junctions with rectifying properties. When expressed exogenously, variants Shaking B Lethal (ShakBL) and Shaking B neural + 16 (ShakBN16) form heterotypic junctions that gate asymmetrically in response to transjunctional voltage. To determine whether the amino terminus confers properties of gating and rectification, amino-terminal domains were exchanged between ShakBL and ShakBN16, creating chimeric proteins SBL NTN16 and SBN16 NTL. The properties were analyzed in paired Xenopus oocytes. Our results suggest that the amino terminus plays an important role in establishing rectifying properties inherent to heterotypic junctions composed of ShakBL and ShakBN16. ShakBL/SBL NTN16 junctions behaved similarly to ShakBL/ShakBN16 junctions, gating in response to transjunctional voltage of one polarity and inducing a highly asymmetric conductance-voltage relationship. However, the amino terminus did not act independently to confer sensitivity to transjunctional voltage. The complementary pairing ShakBN16/SBN16 NTL displayed little sensitivity to voltage of either polarity, and in homotypic pairings SBL NTN16 was strongly gated by transjunctional voltage. We propose a model in which the amino terminus induces gating only when matched with an accommodating innexin body.

  9. MicroRNA-205 Targets Tight Junction-related Proteins during Urothelial Cellular Differentiation *

    PubMed Central

    Chung, Pei-Jung Katy; Chi, Lang-Ming; Chen, Chien-Lun; Liang, Chih-Lung; Lin, Chung-Tzu; Chang, Yu-Xun; Chen, Chun-Hsien; Chang, Yu-Sun

    2014-01-01

    The mammalian bladder urothelium classified as basal, intermediate, and terminally differentiated umbrella cells offers one of the most effective permeability barrier functions known to exist in nature because of the formation of apical uroplakin plaques and tight junctions. To improve our understanding of urothelial differentiation, we analyzed the microRNA (miRNA) expression profiles of mouse urinary tissues and by TaqMan miRNA analysis of microdissected urothelial layers and in situ miRNA-specific hybridization to determine the dependence of these miRNAs on the differentiation stage. Our in situ hybridization studies revealed that miR-205 was enriched in the undifferentiated basal and intermediate cell layers. We then used a quantitative proteomics approach to identify miR-205 target genes in primary cultured urothelial cells subjected to antagomir-mediated knockdown of specific miRNAs. Twenty-four genes were reproducibly regulated by miR-205; eleven of them were annotated as cell junction- and tight junction-related molecules. Western blot analysis demonstrated that antagomir-induced silencing of miR-205 in primary cultured urothelial cells elevated the expression levels of Tjp1, Cgnl1, and Cdc42. Ectopic expression of miR-205 in MDCK cells inhibited the expression of tight junction proteins and the formation of tight junctions. miR-205- knockdown urothelial cells showed alterations in keratin synthesis and increases of uroplakin Ia and Ib, which are the urothelial differentiation products. These results suggest that miR-205 may contribute a role in regulation of urothelial differentiation by modulating the expression of tight junction-related molecules. PMID:24912853

  10. Distributed deformation ahead of the Cocos-Nazca Rift at the Galapagos triple junction

    NASA Astrophysics Data System (ADS)

    Smith, Deborah K.; Schouten, Hans; Zhu, Wen-lu; Montési, Laurent G. J.; Cann, Johnson R.

    2011-11-01

    The Galapagos triple junction is not a simple ridge-ridge-ridge (RRR) triple junction. The Cocos-Nazca Rift (C-N Rift) tip does not meet the East Pacific Rise (EPR). Instead, two secondary rifts form the link: Incipient Rift at 2°40‧N and Dietz Deep volcanic ridge, the southern boundary of the Galapagos microplate (GMP), at 1°10‧N. Recently collected bathymetry data are used to investigate the regional tectonics prior to the establishment of the GMP (∼1.5 Ma). South of C-N Rift a band of northeast-trending cracks cuts EPR-generated abyssal hills. It is a mirror image of a band of cracks previously identified north of C-N Rift on the same age crust. In both areas, the western ends of the cracks terminate against intact abyssal hills suggesting that each crack initiated at the EPR spreading center and cut eastward into pre-existing topography. Each crack formed a short-lived triple junction until it was abandoned and a new crack and triple junction initiated nearby. Between 2.5 and 1.5 Ma, the pattern of cracking is remarkably symmetric about C-N Rift providing support for a crack interaction model in which crack initiation at the EPR axis is controlled by stresses associated with the tip of the westward-propagating C-N Rift. The model also shows that offsets of the EPR axis may explain times when cracking is not symmetric. South of C-N Rift, cracks are observed on seafloor as old as 10.5 Ma suggesting that this triple junction has not been a simple RRR triple junction during that time.

  11. Terminal weather information management

    NASA Technical Reports Server (NTRS)

    Lee, Alfred T.

    1990-01-01

    Since the mid-1960's, microburst/windshear events have caused at least 30 aircraft accidents and incidents and have killed more than 600 people in the United States alone. This study evaluated alternative means of alerting an airline crew to the presence of microburst/windshear events in the terminal area. Of particular interest was the relative effectiveness of conventional and data link ground-to-air transmissions of ground-based radar and low-level windshear sensing information on microburst/windshear avoidance. The Advanced Concepts Flight Simulator located at Ames Research Center was employed in a line oriented simulation of a scheduled round-trip airline flight from Salt Lake City to Denver Stapleton Airport. Actual weather en route and in the terminal area was simulated using recorded data. The microburst/windshear incident of July 11, 1988 was re-created for the Denver area operations. Six experienced airline crews currently flying scheduled routes were employed as test subjects for each of three groups: (1) A baseline group which received alerts via conventional air traffic control (ATC) tower transmissions; (2) An experimental group which received alerts/events displayed visually and aurally in the cockpit six miles (approx. 2 min.) from the microburst event; and (3) An additional experimental group received displayed alerts/events 23 linear miles (approx. 7 min.) from the microburst event. Analyses of crew communications and decision times showed a marked improvement in both situation awareness and decision-making with visually displayed ground-based radar information. Substantial reductions in the variability of decision times among crews in the visual display groups were also found. These findings suggest that crew performance will be enhanced and individual differences among crews due to differences in training and prior experience are significantly reduced by providing real-time, graphic display of terminal weather hazards.

  12. 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

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. 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

  19. 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

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. Radiation effects on bipolar junction transistors induced by 25 MeV carbon ions

    NASA Astrophysics Data System (ADS)

    Liu, Chaoming; Li, Xingji; Geng, Hongbin; Zhao, Zhiming; Yang, Dezhuang; He, Shiyu

    2010-12-01

    The characteristic degradation in silicon NPN bipolar junction transistors (BJTs) of 3DG112 type is examined under the irradiation with 25 MeV carbon (C) ions and various bias conditions. Different electrical parameters were measured in-situ during the exposure under each bias condition. From the experimental data, larger variation of base current ( IB) is observed after irradiation at a given value of base-emitter voltage ( VBE), while the collector current is only slightly affected by irradiation at a given VBE. The gain degradation is mostly affected by the behavior of the base current. The change in the reciprocal of current gain (Δ(1/ β)) increases linearly with increasing the C ions fluence. The degradation of the NPN BJTs under various bias conditions during irradiation was studied. Compared to the case where the terminals are grounded, at a given fluence, the change in the reciprocal of current gain varies slightly less when the base-emitter junction is forward biased. On the other hand, there is no distinction for the change in the reciprocal of current gain between the case of reverse-biased base-emitter junction and that of all terminals grounded for the NPN BJTs at a given fluence.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Role of rut adenylyl cyclase in the ensemble regulation of presynaptic terminal excitability: reduced synaptic strength and precision in a Drosophila memory mutant.

    PubMed

    Ueda, Atsushi; Wu, Chun-Fang

    2009-01-01

    Although modulation of presynaptic terminal excitability can profoundly affect transmission efficacy, how excitability along axonal terminal branches is regulated requires further investigations. We performed focal patch recording in Drosophila larval neuromuscular junctions (NMJs) to monitor the activity of individual synaptic boutons along the presynaptic terminal. Analysis of the learning mutant rutabaga (rut) suggests a tight regulation of presynaptic terminal excitability by rut adenylyl cyclase (AC) that is responsible for Ca2+/calmodulin-dependent cAMP synthesis. Focal excitatory junctional currents (ejcs) demonstrated that disrupted cAMP metabolism in rut mutant boutons leads to decreased transmitter release, coupled with temporal dispersion and amplitude fluctuation of ejcs during repetitive activity. Strikingly, rut motor terminals displayed greatly increased variability among corresponding terminal branches of identified NMJs in different preparations. However, boutons throughout single terminal branches were relatively uniform in either WT or rut mutant larvae. The use of electrotonic depolarization to directly evoke transmitter release from axonal terminals revealed that variability in neurotransmission originated from varying degrees of weakened excitability in rut terminals. Pharmacological treatments and axonal action potential recordings raised the possibility that defective rut AC resulted in reduced Ca2+ currents in the nerve terminal. Thus, our data indicate that rut AC not only affects transmitter release machinery, but also plays a previously unsuspected role in local excitability control, both contributing to transmission level and precision along the entire axonal terminal. PMID:19101836

  11. Termination: A Case Study.

    PubMed

    Friedberg, Ahron L

    2015-12-01

    In this article I posit and examine certain criteria and qualities for ending an analysis. The case study describes the end phase of a four-year psychoanalysis in which the patient's decision to move to another area forced the end of his analysis. We continued to explore and work through his core neurotic conflicts that included issues of competitive rivalry, dominance and submission, control, and anxiety about birth and death. A shift in the transference from me as a negative father to me as a supportive but competitive older brother was also examined in the context of ending treatment as well as other aspects of the transference. In addition, we analyzed the meaning of his ending treatment based on an extra-analytic circumstance. In discussing this phase of treatment, the definition and history of the term "termination" and its connotations are reviewed. Various criteria for completing an analysis are examined, and technical observations about this phase of treatment are investigated. It was found that while a significant shift in the transference occurred in this phase of the patient's analysis, conflicts related to the transference were not "resolved" in the classical sense. Terminating treatment was considered as a practical matter in which the patient's autonomy and sense of choice were respected and analyzed. PMID:26583444

  12. Imaging of terminal myelocystoceles.

    PubMed Central

    Byrd, S. E.; Harvey, C.; McLone, D. G.; Darling, C. F.

    1996-01-01

    This article presents a retrospective analysis of the presentation, imaging studies, and associated findings in 20 children with surgically and histologically proven terminal myelocystoceles. All 20 children presented at birth with a black mass; 13 had cloacal extrophy. The patient population was comprised of 15 girls and 5 with ambiguous genitalia: Of the imaging studies, 8 had plain radiographs, 6 myelography-computed tomography, 11 ultrasound, and 14 magnetic resonance. The associated findings included Chiari I (eight patients), Chiari II (one patient), hydromyelia (three patients), hydrocephalus (three patients), and vertebral segmentation anomalies (six patients). Magnetic resonance imaging was the best imaging modality to diagnose and evaluate children with a myelocystocele. Magnetic resonance imaging demonstrated the classic findings: a terminal cyst of the central canal of the spinal cord that is tethered and herniated with arachnoid and cerebrospinal fluid through an area of spinal dysphria onto the back as a mass. Images Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 PMID:8803433

  13. Acetylene terminated matrix resins

    NASA Technical Reports Server (NTRS)

    Goldfarb, I. J.; Lee, Y. C.; Arnold, F. E.; Helminiak, T. E.

    1985-01-01

    The synthesis of resins with terminal acetylene groups has provided a promising technology to yield high performance structural materials. Because these resins cure through an addition reaction, no volatile by-products are produced during the processing. The cured products have high thermal stability and good properties retention after exposure to humidity. Resins with a wide variety of different chemical structures between the terminal acetylene groups are synthesized and their mechanical properties studied. The ability of the acetylene cured polymers to give good mechanical properties is demonstrated by the resins with quinoxaline structures. Processibility of these resins can be manipulated by varying the chain length between the acetylene groups or by blending in different amounts of reactive deluents. Processing conditions similar to the state-of-the-art epoxy can be attained by using backbone structures like ether-sulfone or bis-phenol-A. The wide range of mechanical properties and processing conditions attainable by this class of resins should allow them to be used in a wide variety of applications.

  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. Mode of action of claudin peptidomimetics in the transient opening of cellular tight junction barriers.

    PubMed

    Staat, Christian; Coisne, Caroline; Dabrowski, Sebastian; Stamatovic, Svetlana M; Andjelkovic, Anuska V; Wolburg, Hartwig; Engelhardt, Britta; Blasig, Ingolf E

    2015-06-01

    In epithelial/endothelial barriers, claudins form tight junctions, seal the paracellular cleft, and limit the uptake of solutes and drugs. The peptidomimetic C1C2 from the C-terminal half of claudin-1's first extracellular loop increases drug delivery through epithelial claudin-1 barriers. However, its molecular and structural mode of action remains unknown. In the present study, >100 μM C1C2 caused paracellular opening of various barriers with different claudin compositions, ranging from epithelial to endothelial cells, preferentially modulating claudin-1 and claudin-5. After 6 h incubation, C1C2 reversibly increased the permeability to molecules of different sizes; this was accompanied by redistribution of claudins and occludin from junctions to cytosol. Internalization of C1C2 in epithelial cells depended on claudin-1 expression and clathrin pathway, whereby most C1C2 was retained in recyclosomes >2 h. In freeze-fracture electron microscopy, C1C2 changed claudin-1 tight junction strands to a more parallel arrangement and claudin-5 strands from E-face to P-face association - drastic and novel effects. In conclusion, C1C2 is largely recycled in the presence of a claudin, which explains the delayed onset of barrier and junction loss, the high peptide concentration required and the long-lasting effect. Epithelial/endothelial barriers are specifically modulated via claudin-1/claudin-5, which can be targeted to improve drug delivery. PMID:25907035

  19. Interface states, negative differential resistance, and rectification in molecular junctions with transition-metal contacts

    NASA Astrophysics Data System (ADS)

    Dalgleish, Hugh; Kirczenow, George

    2006-06-01

    We present a theory of nonlinear transport phenomena in molecular junctions where single thiolated organic molecules bridge transition metal nanocontacts whose densities of states have strong d orbital components near the Fermi level. At moderate bias, we find electron transmission between the contacts to be mediated by interface states within the molecular highest-occupied-molecular-orbital-lowest-unoccupied-molecular-orbital gap that arise from hybridization between the thiol-terminated ends of the molecules and the d orbitals of the transition metals. Because these interface states are localized mainly within the metal electrodes, we find their energies to accurately track the electrochemical potentials of the contacts when a variable bias is applied across the junction. We predict resonant enhancement and reduction of the interface state transmission as the applied bias is varied, resulting in negative differential resistance (NDR) in molecular junctions with Pd nanocontacts. We show that these nonlinear phenomena can be tailored by suitably choosing the nanocontact materials: If a Rh electrode is substituted for one Pd contact, we predict enhancement of these NDR effects. The same mechanism is also predicted to give rise to rectification in Pd/molecule/Au junctions. The dependences of the interface state resonances on the orientation of the metal interface, the adsorption site of the molecule, and the separation between the thiolated ends of the molecule and the metal contacts are also discussed.

  20. The Zinc Finger Protein Zfr1p Is Localized Specifically to Conjugation Junction and Required for Sexual Development in Tetrahymena thermophila

    PubMed Central

    Xu, Jing; Tian, Huaru; Wang, Wei; Liang, Aihua

    2012-01-01

    Conjugation in Tetrahymena thermophila involves a developmental program consisting of three prezygotic nuclear divisions, pronuclear exchange and fusion, and postzygotic and exconjugant stages. The conjugation junction structure appears during the initiation of conjugation development, and disappears during the exconjugant stage. Many structural and functional proteins are involved in the establishment and maintenance of the junction structure in T. thermophila. In the present study, a zinc finger protein-encoding gene ZFR1 was found to be expressed specifically during conjugation and to localize specifically to the conjugation junction region. Truncated Zfr1p localized at the plasma membrane in ordered arrays and decorated Golgi apparatus located adjacent to basal body. The N-terminal zinc finger and C-terminal hydrophobic domains of Zfr1p were found to be required for its specific conjugation junction localization. Conjugation development of ZFR1 somatic knockout cells was aborted at the pronuclear exchange and fusion conjugation stages. Furthermore, Zfr1p was found to be important for conjugation junction stability during the prezygotic nuclear division stage. Taken together, our data reveal that Zfr1p is required for the stability and integrity of the conjugation junction structure and essential for the sexual life cycle of the Tetrahymena cell. PMID:23251712

  1. 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.

  2. 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.

  3. Correlation between quantal secretion and vesicle loss at the frog neuromuscular junction.

    PubMed

    Hurlbut, W P; Iezzi, N; Fesce, R; Ceccarelli, B

    1990-06-01

    1. We measured the rate of occurrence of miniature endplate potentials (MEPPs) at identified endplates in frog cutaneous pectoris muscles treated with crude black widow spider venom (BWSV) or purified alpha-latrotoxin (alpha-LTX) in calcium-free solutions, and we examined the relationship between the length of the nerve terminal and the total number of quanta secreted, and the relationship between the number of quanta secreted and the number of vesicles remaining at different times. 2. The venom, or toxin, was applied in a modified Ringer solution with tetrodotoxin, 1 mM-EGTA and no divalent cations, and quantal secretion was started by applying Ca2(+)-free solutions with Mg2+. This was done to synchronize the quantal discharge at the various junctions in a muscle. Ringer solution was applied after the MEPP rate had declined to low levels, and then the muscle fibre was injected with Lucifer Yellow, the endplate stained for acetylcholinesterase and the length of the nerve terminal and the length of a sarcomere were measured on the fluorescent fibre. 3. The total number of quanta secreted by a terminal was measured under a wide variety of experimental conditions: the weights of the frogs ranged from 13 to 68 g, the temperature from 9 to 28 degrees C, and the concentration of Mg2+ from 2 to 10 mM. In one series of experiments the Mg2+ was withdrawn after 3-4 min and reapplied 35-40 min later in order to divide the total output of quanta into two approximately equal bouts of secretion that were well separated in time. 4. The total number of MEPPs recorded at a junction was loosely correlated with the length of its nerve terminal, but it was not affected by the temperature, the concentration of Mg2+ or the division of secretion into well-separated bouts of quantal release. The average total secretion per unit length was about 3700 quanta/sarcomere or about 1200 quanta/microns. 5. The average time course of quantal secretion per micrometre of terminal was determined at

  4. Correlation between quantal secretion and vesicle loss at the frog neuromuscular junction.

    PubMed Central

    Hurlbut, W P; Iezzi, N; Fesce, R; Ceccarelli, B

    1990-01-01

    1. We measured the rate of occurrence of miniature endplate potentials (MEPPs) at identified endplates in frog cutaneous pectoris muscles treated with crude black widow spider venom (BWSV) or purified alpha-latrotoxin (alpha-LTX) in calcium-free solutions, and we examined the relationship between the length of the nerve terminal and the total number of quanta secreted, and the relationship between the number of quanta secreted and the number of vesicles remaining at different times. 2. The venom, or toxin, was applied in a modified Ringer solution with tetrodotoxin, 1 mM-EGTA and no divalent cations, and quantal secretion was started by applying Ca2(+)-free solutions with Mg2+. This was done to synchronize the quantal discharge at the various junctions in a muscle. Ringer solution was applied after the MEPP rate had declined to low levels, and then the muscle fibre was injected with Lucifer Yellow, the endplate stained for acetylcholinesterase and the length of the nerve terminal and the length of a sarcomere were measured on the fluorescent fibre. 3. The total number of quanta secreted by a terminal was measured under a wide variety of experimental conditions: the weights of the frogs ranged from 13 to 68 g, the temperature from 9 to 28 degrees C, and the concentration of Mg2+ from 2 to 10 mM. In one series of experiments the Mg2+ was withdrawn after 3-4 min and reapplied 35-40 min later in order to divide the total output of quanta into two approximately equal bouts of secretion that were well separated in time. 4. The total number of MEPPs recorded at a junction was loosely correlated with the length of its nerve terminal, but it was not affected by the temperature, the concentration of Mg2+ or the division of secretion into well-separated bouts of quantal release. The average total secretion per unit length was about 3700 quanta/sarcomere or about 1200 quanta/microns. 5. The average time course of quantal secretion per micrometre of terminal was determined at

  5. Channel and terminal description of the ACTS mobile terminal

    NASA Technical Reports Server (NTRS)

    Abbe, B. S.; Agan, M. J.; Girardey, C. C.; Jedrey, T. C.

    1994-01-01

    The Advanced Communications Technology Satellite (ACTS) Mobile Terminal (AMT) is a proof-of-concept K/Ka-band mobile satellite communications terminal under development by NASA at JPL. Currently the AMT is undergoing systems integration and testing in preparation for a July 1993 ACTS launch and the subsequent commencement of mobile experiments in the fall of 1993. The AMT objectives are presented, followed by a discussion of the AMT communications channel and the mobile terminal's design and performance.

  6. Channel and terminal description of the ACTS mobile terminal

    NASA Technical Reports Server (NTRS)

    Abbe, B. S.; Agan, M. J.; Girardey, C. C.; Jedrey, T. C.

    1993-01-01

    The Advanced Communications Technology Satellite (ACTS) Mobile Terminal (AMT) is a proof-of-concept K/Ka-band mobile satellite communications terminal under development by NASA at JPL. Currently the AMT is undergoing system integration and test in preparation for a July 1993 ACTS launch and the subsequent commencement of mobile experiments in the fall of 1993. The AMT objectives are presented followed by a discussion of the AMT communications channel and mobile terminal design and performance.

  7. [Terminal ballistics. 3].

    PubMed

    Marini, F; Mangiante, G; Dagradi, V; Radin, S; Carolo, F; Giarolli, M; Della Giacoma, G; Tosi, D; Merico, G; Tenci, A

    1993-01-01

    This brief chapter, focusing essentially on a single topic, has been written in homage to Emile Theodor Kocker, a masterful exponent of the art of surgery and founder of the culture of terminal ballistics. For most of the literature we are indebted to Fackler and Dougherty, who, with the particular grasp, and fair of historians, act as guides on a trial which is only apparently retrograde, but which actually bears eloquent witness to the fact that even in the most physically tangible of arts, namely the art of surgery, inspired curiosity may help us to go well beyond the limits of our day and age. This chapter is also dedicated to the memory of another great surgeon, Vittorio Pettinari, who for one of the authors was an incomparable mentor and past-master of such curiosity.

  8. Electron Transport, Energy Transfer, and Optical Response in Single Molecule Junctions

    NASA Astrophysics Data System (ADS)

    White, Alexander James

    interactions quantum mechanically within nonequilibrium molecular junctions. Finally we perform preliminary calculations of the Raman spectrum of a three-ring oligophenylene vinylene terminating in amine functional groups molecule in a molecular junction and compare our results to experimental measurements. This work is the rst steps towards full calculations of the optical response of current-carrying molecular junction, which should combine classical calculations of the plasmon enhanced electric field with quantum calculations for the plasmon-molecular exciton interaction and nonequilibrium Raman scattering.

  9. Slow pathway modification for atrioventricular node re-entrant tachycardia: fast junctional tachycardia predicts adverse prognosis

    PubMed Central

    Lipscomb, K; Zaidi, A; Fitzpatrick, A; LEFROY, D

    2001-01-01

    D LEFROY Deputy Editor OBJECTIVE—To examine the cycle length of the junctional tachycardia often seen during successful slow pathway ablation for atrioventricular (AV) node re-entrant tachycardia, to determine whether shorter cycle lengths predict imminent atrioventricular block.
DESIGN—Retrospective analysis of consecutive patients undergoing slow pathway modification. Intracardiac recordings were analysed after digital storage to determine the development of junctional tachycardia, its duration and maximum, minimum, and mean cycle length, occurrence of heart block, persistent slow pathway conduction, or later confirmed recurrence of AV node re-entrant tachycardia.
SETTING—Regional cardiac centre.
PATIENTS—136 consecutive patients undergoing electrophysiological study found to have typical "slow-fast" AV node re-entrant tachycardia and subject to 137 slow pathway modification procedures.
RESULTS—During successful temperature feedback controlled radiofrequency energy application, junctional tachycardia developed in 133 of 137 procedures. During ablation, 10 patients had evidence of AV block (first degree in seven patients and third degree in three), and 17 others had retrograde junctional atrial (JA) block. In these 27 patients, the junctional tachycardia was rapid, with a minimum (SD) cycle length 291 (47) ms. Conduction recovered quickly in all but two patients, one of whom required permanent pacing. Junctional tachycardia with normal AV and JA conduction in the other 111 patients was of a significantly slower minimum cycle length (537 (123) ms; p < 0.0001).
CONCLUSIONS—Fast junctional tachycardia with cycle lengths under 350 ms seen during slow pathway modification is a predictor of conduction block, suggesting proximity to the compact node. Radiofrequency energy application should be terminated immediately to prevent development of AV block. An "auto cut off" facility for cycle lengths shorter than 350 ms could be built into

  10. A General Method for Insertion of Functional Proteins within Proteins via Combinatorial Selection of Permissive Junctions.

    PubMed

    Peng, Yingjie; Zeng, Wenwen; Ye, Hui; Han, Kyung Ho; Dharmarajan, Venkatasubramanian; Novick, Scott; Wilson, Ian A; Griffin, Patrick R; Friedman, Jeffrey M; Lerner, Richard A

    2015-08-20

    A major goal of modern protein chemistry is to create new proteins with different functions. One approach is to amalgamate secondary and tertiary structures from different proteins. This is difficult for several reasons, not the least of which is the fact that the junctions between secondary and tertiary structures are not degenerate and usually affect the function and folding of the entire complex. Here, we offer a solution to this problem by coupling a large combinatorial library of about 10(7) different N- and C-terminal junctions to a powerful system that selects for function. Using this approach, the entire Leptin and follicle-stimulating hormone (FSH) were inserted into an antibody. Complexes with full retention of function in vivo and in vitro, although rare, were found easily by using an autocrine selection system to search for hormonal activity. Such large diversity systems, when coupled to robust selection systems, should enable construction of novel therapeutic proteins.

  11. Quantum Hall effect in a gate-controlled p-n junction of graphene.

    PubMed

    Williams, J R; Dicarlo, L; Marcus, C M

    2007-08-01

    The unique band structure of graphene allows reconfigurable electric-field control of carrier type and density, making graphene an ideal candidate for bipolar nanoelectronics. We report the realization of a single-layer graphene p-n junction in which carrier type and density in two adjacent regions are locally controlled by electrostatic gating. Transport measurements in the quantum Hall regime reveal new plateaus of two-terminal conductance across the junction at 1 and 32 times the quantum of conductance, e(2)/h, consistent with recent theory. Beyond enabling investigations in condensed-matter physics, the demonstrated local-gating technique sets the foundation for a future graphene-based bipolar technology.

  12. 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…

  13. 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

  14. 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

  15. Molecular junctions of self-assembled monolayers with conducting polymer contacts.

    PubMed

    Neuhausen, Alexander B; Hosseini, Ali; Sulpizio, Joseph A; Chidsey, Christopher E D; Goldhaber-Gordon, David

    2012-11-27

    We present a method to fabricate individually addressable junctions of self-assembled monolayers (SAMs) that builds on previous studies which have shown that soft conductive polymer top contacts virtually eliminate shorts through the SAMs. We demonstrate devices with nanoscale lateral dimensions, representing an order of magnitude reduction in device area, with high yield and relatively low device-to-device variation, improving several features of previous soft contact devices. The devices are formed in pores in an inorganic dielectric layer with features defined by e-beam lithography and dry etching. We replace the aqueous PEDOT:PSS conductive polymer used in prior devices with Aedotron P, a low-viscosity, amphiphilic polymer, allowing incorporation of self-assembled monolayers with either hydrophobic or hydrophilic termination with the same junction geometry and materials. We demonstrate the adaptability of this new design by presenting transport measurements on SAMs composed of alkanethiols with methyl, thiol, carboxyl, and azide terminations. We establish that the observed room-temperature tunnel barrier is primarily a function of monolayer thickness, independent of the terminal group's hydrophilicity. Finally, we investigate the temperature dependence of transport and show that the low-temperature behavior is based on the energy distribution of sites from which carriers can tunnel between the polymer and gold contacts, as described by a model of variable-range hopping transport in a disordered conductor.

  16. Molecular junctions of self-assembled monolayers with conducting polymer contacts.

    PubMed

    Neuhausen, Alexander B; Hosseini, Ali; Sulpizio, Joseph A; Chidsey, Christopher E D; Goldhaber-Gordon, David

    2012-11-27

    We present a method to fabricate individually addressable junctions of self-assembled monolayers (SAMs) that builds on previous studies which have shown that soft conductive polymer top contacts virtually eliminate shorts through the SAMs. We demonstrate devices with nanoscale lateral dimensions, representing an order of magnitude reduction in device area, with high yield and relatively low device-to-device variation, improving several features of previous soft contact devices. The devices are formed in pores in an inorganic dielectric layer with features defined by e-beam lithography and dry etching. We replace the aqueous PEDOT:PSS conductive polymer used in prior devices with Aedotron P, a low-viscosity, amphiphilic polymer, allowing incorporation of self-assembled monolayers with either hydrophobic or hydrophilic termination with the same junction geometry and materials. We demonstrate the adaptability of this new design by presenting transport measurements on SAMs composed of alkanethiols with methyl, thiol, carboxyl, and azide terminations. We establish that the observed room-temperature tunnel barrier is primarily a function of monolayer thickness, independent of the terminal group's hydrophilicity. Finally, we investigate the temperature dependence of transport and show that the low-temperature behavior is based on the energy distribution of sites from which carriers can tunnel between the polymer and gold contacts, as described by a model of variable-range hopping transport in a disordered conductor. PMID:23035989

  17. Mitochondrial alarmins released by degenerating motor axon terminals activate perisynaptic Schwann cells

    PubMed Central

    Duregotti, Elisa; Negro, Samuele; Scorzeto, Michele; Zornetta, Irene; Dickinson, Bryan C.; Chang, Christopher J.; Montecucco, Cesare; Rigoni, Michela

    2015-01-01

    An acute and highly reproducible motor axon terminal degeneration followed by complete regeneration is induced by some animal presynaptic neurotoxins, representing an appropriate and controlled system to dissect the molecular mechanisms underlying degeneration and regeneration of peripheral nerve terminals. We have previously shown that nerve terminals exposed to spider or snake presynaptic neurotoxins degenerate as a result of calcium overload and mitochondrial failure. Here we show that toxin-treated primary neurons release signaling molecules derived from mitochondria: hydrogen peroxide, mitochondrial DNA, and cytochrome c. These molecules activate isolated primary Schwann cells, Schwann cells cocultured with neurons and at neuromuscular junction in vivo through the MAPK pathway. We propose that this inter- and intracellular signaling is involved in triggering the regeneration of peripheral nerve terminals affected by other forms of neurodegenerative diseases. PMID:25605902

  18. 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.

  19. Single-molecule conductance of functionalized oligoynes: length dependence and junction evolution.

    PubMed

    Moreno-García, Pavel; Gulcur, Murat; Manrique, David Zsolt; Pope, Thomas; Hong, Wenjing; Kaliginedi, Veerabhadrarao; Huang, Cancan; Batsanov, Andrei S; Bryce, Martin R; Lambert, Colin; Wandlowski, Thomas

    2013-08-21

    We report a combined experimental and theoretical investigation of the length dependence and anchor group dependence of the electrical conductance of a series of oligoyne molecular wires in single-molecule junctions with gold contacts. Experimentally, we focus on the synthesis and properties of diaryloligoynes with n = 1, 2, and 4 triple bonds and the anchor dihydrobenzo[b]thiophene (BT). For comparison, we also explored the aurophilic anchor group cyano (CN), amino (NH2), thiol (SH), and 4-pyridyl (PY). Scanning tunneling microscopy break junction (STM-BJ) and mechanically controllable break junction (MCBJ) techniques are employed to investigate single-molecule conductance characteristics. The BT moiety is superior as compared to traditional anchoring groups investigated so far. BT-terminated oligoynes display a 100% probability of junction formation and possess conductance values which are the highest of the oligoynes studied and, moreover, are higher than other conjugated molecular wires of similar length. Density functional theory (DFT)-based calculations are reported for oligoynes with n = 1-4 triple bonds. Complete conductance traces and conductance distributions are computed for each family of molecules. The sliding of the anchor groups leads to oscillations in both the electrical conductance and the binding energies of the studied molecular wires. In agreement with experimental results, BT-terminated oligoynes are predicted to have a high electrical conductance. The experimental attenuation constants βH range between 1.7 nm(-1) (CN) and 3.2 nm(-1) (SH) and show the following trend: βH(CN) < βH(NH2) < βH(BT) < βH(PY) ≈ βH(SH). DFT-based calculations yield lower values, which range between 0.4 nm(-1) (CN) and 2.2 nm(-1) (PY).

  20. 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.

  1. Understanding electronic structure and transport properties in nanoscale junctions

    NASA Astrophysics Data System (ADS)

    Dhungana, Kamal B.

    Understanding the electronic structure and the transport properties of nanoscale materials are pivotal for designing future nano-scale electronic devices. Nanoscale materials could be individual or groups of molecules, nanotubes, semiconducting quantum dots, and biomolecules. Among these several alternatives, organic molecules are very promising and the field of molecular electronics has progressed significantly over the past few decades. Despite these progresses, it has not yet been possible to achieve atomic level control at the metal-molecule interface during a conductance measurement, which hinders the progress in this field. The lack of atomic level information of the interface also makes it much harder for theorist to interpret the experimental results. To identify the junction configuration that possibly exists during the experimental measurement of conductance in molecular junction, we created an ensemble of Ruthanium-bis(terpyridine) molecular devices, and studied the transport behavior in these molecular junctions. This helps us identifying the junction geometry that yields the experimentally measured current-voltage characteristics. Today's electronic devices mostly ignore the spin effect of an electron. The inclusion of spin effect of an electron on solid-state transistor allows us to build more efficient electronic devices; this also alleviates the problem of huge heat dissipation in the nanoscale electronic devices. Different materials have been utilized to build three terminals spin transistor since its inception in 1950. In search of suitable candidates for the molecular spin transistor, we have recently designed a spin-valve transistor based on an organometallic molecule; a large amplification (320 %) in tunnel magneto-resistance (TMR) is found to occur at an experimentally accessible gate field. This suggests that the organic molecules can be utilized for making the next generation three terminal spintronic devices. Similarly, we have designed a

  2. 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

  3. 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

  4. 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).

  5. 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.

  6. 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

  7. Is Lake Tahoe Terminal?

    NASA Astrophysics Data System (ADS)

    Coats, R. N.; Reuter, J.; Heyvaert, A.; Lewis, J.; Sahoo, G. B.; Schladow, G.; Thorne, J. H.

    2014-12-01

    ) the climatic water deficit will increase, especially at high elevations that will be most affected by the loss of snow, with likely consequences for existing vegetation and fire frequency. Hydrologically, Lake Tahoe is intermittently terminal; in a medical sense it is not yet terminal, but its condition—especially its valued clarity and deep blue color--is serious.

  8. Probing the nature and resistance of the molecule-electrode contact in SAM-based junctions

    NASA Astrophysics Data System (ADS)

    Suchand Sangeeth, C. S.; Wan, Albert; Nijhuis, Christian A.

    2015-07-01

    It is challenging to quantify the contact resistance and to determine the nature of the molecule-electrode contacts in molecular two-terminal junctions. Here we show that potentiodynamic and temperature dependent impedance measurements give insights into the nature of the SAM-electrode interface and other bottlenecks of charge transport (the capacitance of the SAM (CSAM) and the resistance of the SAM (RSAM)), unlike DC methods, independently of each other. We found that the resistance of the top-electrode-SAM contact for junctions with the form of AgTS-SCn//GaOx/EGaIn with n = 10, 12, 14, 16 or 18 is bias and temperature independent and hence Ohmic (non-rectifying) in nature, and is orders of magnitude smaller than RSAM. The CSAM and RSAM are independent of the temperature, indicating that the mechanism of charge transport in these SAM-based junctions is coherent tunneling and the charge carrier trapping at the interfaces is negligible.It is challenging to quantify the contact resistance and to determine the nature of the molecule-electrode contacts in molecular two-terminal junctions. Here we show that potentiodynamic and temperature dependent impedance measurements give insights into the nature of the SAM-electrode interface and other bottlenecks of charge transport (the capacitance of the SAM (CSAM) and the resistance of the SAM (RSAM)), unlike DC methods, independently of each other. We found that the resistance of the top-electrode-SAM contact for junctions with the form of AgTS-SCn//GaOx/EGaIn with n = 10, 12, 14, 16 or 18 is bias and temperature independent and hence Ohmic (non-rectifying) in nature, and is orders of magnitude smaller than RSAM. The CSAM and RSAM are independent of the temperature, indicating that the mechanism of charge transport in these SAM-based junctions is coherent tunneling and the charge carrier trapping at the interfaces is negligible. Electronic supplementary information (ESI) available: Detailed experimental procedure, Nyquist

  9. 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.

  10. 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.

  11. 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.

  12. 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).

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. [Terminal ballistics. 1].

    PubMed

    Mangiante, G; Dagradi, V; Radin, S; Carolo, F; Giarolli, M; Tenci, A; Merico, G; Tosi, D; Acerbi, A; Della Giacoma, G

    1993-01-01

    We have chosen to conceive of terminal ballistics as a violent and extremely rapid confrontation between two forms of resistance before the final state of rest is reached. This definition, which cannot help but don the admittedly loud and outlandish garb of physics, is the most promising for the purposes of biological interpretation. The main characters on this stage are two, but only one of these really plays the lead, namely the human target, which acts out the basic roles inherent in its physical make-up; the other, the bullet, remains a background figure, frozen in its walk-on part, and ready for the next performance. This modus operandi, which is no simplification, but rather an academic necessity, enables us to focus on images which stand out more clearly as a result of an intensive macroscopic spotlight which brings out the features of the individual phenomena, broken down into a succession of close-ups, and subtracts them from the cold physical nature of this or that form of inert matter, which here is merely an occasional, disagreeable witness, or even more, a standing from time to time for but one of the infinite facets of the biological composite being. Here, then, faced with a kind of exploded macrophotograph of a complex kaleidoscope, we see the animal universe, of which we capture so far the plasticity, the subdivisibility, the anisotropy and the cavitation.

  20. Impedance Analysis of Ovarian Cancer Cells upon Challenge with C-terminal Clostridium Perfringens Enterotoxin

    NASA Astrophysics Data System (ADS)

    Gordon, Geoffrey; Lo, Chun-Min

    2007-03-01

    Both in vitro and animal studies in breast, prostate, and ovarian cancers have shown that clostridium perfringens enterotoxin (CPE), which binds to CLDN4, may have an important therapeutic benefit, as it is rapidly cytotoxic in tissues overexpressing CLDN4. This study sought to evaluate the ability of C-terminal clostridium perfringens enterotoxin (C-CPE), a CLDN4-targetting molecule, to disrupt tight junction barrier function. Electric cell-substrate impedance sensing (ECIS) was used to measure both junctional resistance and average cell-substrate separation of ovarian cancer cell lines after exposure to C-CPE. A total of 14 ovarian cancer cell lines were used, and included cell lines derived from serous, mucinous, and clear cells. Our results showed that junctional resistance increases as CLDN4 expression increases. In addition, C-CPE is non-cytotoxic in ovarian cancer cells expressing CLDN4. However, exposure to C-CPE results in a significant (p<0.05) dose- and CLDN4-dependent decrease in junctional resistance and an increase in cell-substrate separation. Treatment of ovarian cancer cell lines with C-CPE disrupts tight junction barrier function.

  1. Side mount universal battery terminal

    SciTech Connect

    Byfield, D. Jr.

    1987-06-16

    An automobile battery is described of the type having side mounted, threaded bolt hole terminal connectors, battery cables having bored disc shaped terminals with peripheral insulating covers and, an improved terminal connector bolt adapted to accommodate the battery cable terminals and other electrical accessory terminals comprising: an elongated body of electrically conducting material having a longitudinal axis and an inner end and an outer end; a first generally cylindrical threaded stud formed on the inner end of the body. The first stud has a length and diameter disposed to permit thread engagement of the stud with one of the side mounted terminal connectors on the battery in electrical connection therewith, and pass through the bore in one of the battery cable terminals; a central portion on the body adjacent to and outwardly from the first stud, the central portion has a peripheral diameter greater than the first stud portion and has a first shoulder surface generally normal to the longitudinal axis of the body facing toward the inner end of the body and disposed to engage the face surface of one of the battery cable terminals in an electrically conducting relationship.

  2. Terminal System for Photovoltaic Arrays

    NASA Technical Reports Server (NTRS)

    Maloney, T. J.

    1984-01-01

    Quick-connect terminal system provides electrical contact and physical alinement between adjacent photovoltaic modules. Dual-ended plugs connect adjacent modules; single-ended plugs connect bus cables. No tools required to insert plugs and no live terminals exposed before, during, or after connection.

  3. Good Endings: Managing Employee Terminations.

    ERIC Educational Resources Information Center

    Finnie, Robert A., Jr.; Sniffin, Paul B.

    A guide to managing employee terminations and resulting changes is presented for administrators. Three reasons for termination that are legitimate, nondiscriminatory, and acceptable in today's marketplace and courts are: cause (serious misconduct, dishonesty, unethical, or dangerous behavior); job elimination (reduction in force, economic…

  4. The PLATO IV Student Terminal.

    ERIC Educational Resources Information Center

    Stifle, Jack

    This report describes the remote computer terminal designed for student use in the PLATO IV computer-assisted instruction system. The terminal features a plasma display panel, self-contained character and line generators, and the ability to communicate over voice grade telephone circuits. Operating modes and control characters are described in…

  5. 49 CFR 1242.27 - Coal marine terminals, ore marine terminals, TOFC/COFC terminals, other marine terminals, motor...

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    .../COFC terminals, other marine terminals, motor vehicle loading and distribution facilities, and facilities for other specialized service operations (accounts XX-13-29 to XX-13-35, inclusive). 1242.27..., motor vehicle loading and distribution facilities, and facilities for other specialized...

  6. Communicating with terminal cancer patients.

    PubMed

    Anderson, J L

    Communication between doctors and terminal cancer patients has been identified as a problem area in medical care. There have been attempts to overcome this problem by establishing new teaching programs; however, the most effective teaching methods are costly. A model is described that requires minimal staff involvement in teaching about communicating with terminal cancer patients.

  7. 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

  8. 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.

  9. Molecular Conductance through a Quadruple-Hydrogen-Bond-Bridged Supramolecular Junction.

    PubMed

    Wang, Lin; Gong, Zhong-Liang; Li, Shu-Ying; Hong, Wenjing; Zhong, Yu-Wu; Wang, Dong; Wan, Li-Jun

    2016-09-26

    A series of self-complementary ureido pyrimidinedione (UPy) derivatives modified with different aurophilic anchoring groups were synthesized. Their electron transport properties through the quadruple hydrogen bonds in apolar solvent were probed employing the scanning tunneling microscopy break junction (STMBJ) technique. The molecule terminated with a thiol shows the optimal electron transport properties, with a statistical conductance value that approaches 10(-3)  G0 . The (1) H NMR spectra and control experiments verify the formation of quadruple hydrogen bonds, which can be effectively modulated by the polarity of the solvent environment. These findings provide a new design strategy for supramolecular circuit elements in molecular electronics. PMID:27576570

  10. Magnetic electron focusing and tuning of the electron current with a pn-junction

    SciTech Connect

    Milovanović, S. P. Ramezani Masir, M. Peeters, F. M.

    2014-01-28

    Transverse magnetic focusing properties of graphene using a ballistic four terminal structure are investigated. The electric response is obtained using the semiclassical billiard model. The transmission exhibits pronounced peaks as a consequence of skipping orbits at the edge of the structure. When we add a pn-junction between the two probes, snake states along the pn-interface appear. Injected electrons are guided by the pn-interface to one of the leads depending on the value of the applied magnetic field. Oscillations in the resistance are found depending on the amount of particles that end up in each lead.

  11. 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.

  12. 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.

  13. 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}

  14. 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.

  15. 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.

  16. 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.

  17. TMEM184b Promotes Axon Degeneration and Neuromuscular Junction Maintenance

    PubMed Central

    Geisler, Stefanie; Pittman, Sara K.; Doan, Ryan A.; Weihl, Conrad C.; Milbrandt, Jeffrey; DiAntonio, Aaron

    2016-01-01

    Complex nervous systems achieve proper connectivity during development and must maintain these connections throughout life. The processes of axon and synaptic maintenance and axon degeneration after injury are jointly controlled by a number of proteins within neurons, including ubiquitin ligases and mitogen activated protein kinases. However, our understanding of these molecular cascades is incomplete. Here we describe the phenotype resulting from mutation of TMEM184b, a protein identified in a screen for axon degeneration mediators. TMEM184b is highly expressed in the mouse nervous system and is found in recycling endosomes in neuronal cell bodies and axons. Disruption of TMEM184b expression results in prolonged maintenance of peripheral axons following nerve injury, demonstrating a role for TMEM184b in axon degeneration. In contrast to this protective phenotype in axons, uninjured mutant mice have anatomical and functional impairments in the peripheral nervous system. Loss of TMEM184b causes swellings at neuromuscular junctions that become more numerous with age, demonstrating that TMEM184b is critical for the maintenance of synaptic architecture. These swellings contain abnormal multivesicular structures similar to those seen in patients with neurodegenerative disorders. Mutant animals also show abnormal sensory terminal morphology. TMEM184b mutant animals are deficient on the inverted screen test, illustrating a role for TMEM184b in sensory-motor function. Overall, we have identified an important function for TMEM184b in peripheral nerve terminal structure, function, and the axon degeneration pathway. SIGNIFICANCE STATEMENT Our work has identified both neuroprotective and neurodegenerative roles for a previously undescribed protein, TMEM184b. TMEM184b mutation causes delayed axon degeneration following peripheral nerve injury, indicating that it participates in the degeneration process. Simultaneously, TMEM184b mutation causes progressive structural

  18. Electronic transport in graphene: p-n junctions, shot noise, and nanoribbons

    NASA Astrophysics Data System (ADS)

    Williams, James Ryan

    2009-12-01

    Novel, two-dimensional materials have allowed for the inception and elucidation of a plethora of physical phenomena. On such material, a hexagonal lattice of carbon atoms called graphene, is a unique, truly two-dimensional molecular conductor. This thesis describes six experiments that elucidate some interesting physical properties and technological applications of graphene, with an emphasis on graphene-based p-n junctions. A technique for the creation of high-quality p-n junctions of graphene is described. Transport measurements at zero magnetic field demonstrate local control of the carrier type and density bipolar graphene-based junctions. In the quantum Hall regime, new plateaus in the conductance are observed and explained in terms of mode mixing at the p-n interface. Shot noise in unipolar and bipolar graphene devices is measured. A density-independent Fano factor is observed, contrary to theoretical expectations. Further, an independence on device geometry is also observed. The role of disorder on the measured Fano factor is discussed, and comparison to recent theory for disordered graphene is made. The effect of a two-terminal geometry, where the device aspect ratio is different from unity, is measured experimentally and analyzed theoretically. A method for extracting layer number from the conductance extrema is proposed. A method for a conformal mapping of a device with asymmetric contacts to a rectangle is demonstrated. Finally, possible origins of discrepancies between theory and experiment are discussed. Transport along p-n junctions in graphene is reported. Enhanced transport along the junction is observed and attributed to states that exist at the p-n interface. A correspondence between the observed phenomena at low-field and in the quantum Hall regime is observed. An electric field perpendicular to the junction is found to reduce the enhanced conductance at the p-n junction. A corollary between the p-n interface states and "snake states" in an

  19. 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.

  20. 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.

  1. 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

  2. DBS terminals - A Canadian perspective

    NASA Astrophysics Data System (ADS)

    Molozzi, A. R.; Douville, R. J.; Chouinard, G.

    1984-03-01

    Factors determining the design of DBS terminals and their development in Canada are described. Early experience indicated the acceptability of terminals with 1.2 to 1.8m diameter reflectors capable of receiving signals in Ku-band with 47-50 dBW satellite ERIP. This experience, the perception that the Canadian customer base consisted of a few million widely dispersed inhabitants, and the possibility of using Anik C in the 11.7 to 12.2 GHz band led to emphasis in studies of medium power systems (50-57 dBW). Accordingly Ku band terminal development has been strongly influenced towards medium power systems. The desirability of uniform standards in terminal design, at least for North America, is also recognized. In the absence of suitable Ku band signals Canadian industrial activity in Ku band terminals is relatively small compared to C-band terminal activity where the emergence of inexpensive home terminals for reception of the numerous available unscrambled C-band signals has opened up an immediate market. The direction and the timing of an introduction of a Ku band DBS system in Canada is uncertain at this time.

  3. 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.

  4. Color tunable monolithic InGaN/GaN LED having a multi-junction structure.

    PubMed

    Kong, Duk-Jo; Kang, Chang-Mo; Lee, Jun-Yeob; Kim, James; Lee, Dong-Seon

    2016-03-21

    In this study, we have fabricated a blue-green color-tunable monolithic InGaN/GaN LED having a multi-junction structure with three terminals. The device has an n-p-n structure consisting of a green and a blue active region, i.e., an n-GaN / blue-MQW / p-GaN / green-MQW / n-GaN / Al2O3 structure with three terminals for independently controlling the two active regions. To realize this LED structure, a typical LED consisting of layers of n-GaN, blue MQW, and p-GaN is regrown on a conventional green LED by using a metal organic chemical vapor deposition (MOCVD) method. We explain detailed mechanisms of three operation modes which are the green, blue, and cyan mode. Moreover, we discuss optical properties of the device. PMID:27136884

  5. Color tunable monolithic InGaN/GaN LED having a multi-junction structure.

    PubMed

    Kong, Duk-Jo; Kang, Chang-Mo; Lee, Jun-Yeob; Kim, James; Lee, Dong-Seon

    2016-03-21

    In this study, we have fabricated a blue-green color-tunable monolithic InGaN/GaN LED having a multi-junction structure with three terminals. The device has an n-p-n structure consisting of a green and a blue active region, i.e., an n-GaN / blue-MQW / p-GaN / green-MQW / n-GaN / Al2O3 structure with three terminals for independently controlling the two active regions. To realize this LED structure, a typical LED consisting of layers of n-GaN, blue MQW, and p-GaN is regrown on a conventional green LED by using a metal organic chemical vapor deposition (MOCVD) method. We explain detailed mechanisms of three operation modes which are the green, blue, and cyan mode. Moreover, we discuss optical properties of the device.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. 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

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. 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

  2. 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 §...

  3. 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 §...

  4. 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 §...

  5. 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 §...

  6. 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 §...

  7. 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.

  8. Endomicroscopy and electromyography of neuromuscular junctions in situ

    PubMed Central

    Brown, Rosalind; Dissanayake, Kosala N; Skehel, Paul A; Ribchester, Richard R

    2014-01-01

    Objective Electromyography (EMG) is used routinely to diagnose neuromuscular dysfunction in a wide range of peripheral neuropathies, myopathies, and neuromuscular degenerative diseases including motor neuron diseases such as amyotrophic lateral sclerosis (ALS). Definitive neurological diagnosis may also be indicated by the analysis of pathological neuromuscular innervation in motor-point biopsies. Our objective in this study was to preempt motor-point biopsy by combining live imaging with electrophysiological analysis of slow degeneration of neuromuscular junctions (NMJs) in vivo. Methods We combined conventional needle electromyography with fiber-optic confocal endomicroscopy (CEM), using an integrated hand-held, 1.5-mm-diameter probe. We utilized as a test bed, various axotomized muscles in the hind limbs of anaesthetized, double-homozygous thy1.2YFP16: WldS mice, which coexpress the Wallerian-degeneration Slow (WldS) protein and yellow fluorescent protein (YFP) in motor neurons. We also tested exogenous vital stains, including Alexa488-α-bungarotoxin; the styryl pyridinium dye 4-Di-2-Asp; and a GFP conjugate of botulinum toxin Type A heavy chain (GFP-HcBoNT/A). Results We show that an integrated EMG/CEM probe is effective in longitudinal evaluation of functional and morphological changes that take place over a 7-day period during axotomy-induced, slow neuromuscular synaptic degeneration. EMG amplitude declined in parallel with overt degeneration of motor nerve terminals. EMG/CEM was safe and effective when nerve terminals and motor endplates were selectively stained with vital dyes. Interpretation Our findings constitute proof-of-concept, based on live imaging in an animal model, that combining EMG/CEM may be useful as a minimally invasive precursor or alternative to motor-point biopsy in neurological diagnosis and for monitoring local administration of potential therapeutics. PMID:25540801

  9. Low Earth Orbiter: Terminal

    NASA Technical Reports Server (NTRS)

    Kremer, Steven E.; Bundick, Steven N.

    1999-01-01

    In response to the current government budgetary environment that requires the National Aeronautics and Space Administration (NASA) to do more with less, NASA/Goddard Space Flight Center's Wallops Flight Facility has developed and implemented a class of ground stations known as a Low Earth Orbiter-Terminal (LEO-T). This development thus provides a low-cost autonomous ground tracking service for NASA's customers. More importantly, this accomplishment provides a commercial source to spacecraft customers around the world to purchase directly from the company awarded the NASA contract to build these systems. A few years ago, NASA was driven to provide more ground station capacity for spacecraft telemetry, tracking, and command (TT&C) services with a decreasing budget. NASA also made a decision to develop many smaller, cheaper satellites rather than a few large spacecraft as done in the past. In addition, university class missions were being driven to provide their own TT&C services due to the increasing load on the NASA ground-tracking network. NASA's solution for this ever increasing load was to use the existing large aperture systems to support those missions requiring that level of performance and to support the remainder of the missions with the autonomous LEO-T systems. The LEO-T antenna system is a smaller, cheaper, and fully autonomous unstaffed system that can operate without the existing NASA support infrastructure. The LEO-T provides a low-cost, reliable space communications service to the expanding number of low-earth orbiting missions around the world. The system is also fostering developments that improve cost-effectiveness of autonomous-class capabilities for NASA and commercial space use. NASA has installed three LEO-T systems. One station is at the University of Puerto Rico, the second system is installed at the Poker Flat Research Range near Fairbanks, Alaska, and the third system is installed at NASA's Wallops Flight Facility in Virginia. This paper

  10. Terminal means for electrochemical cells

    SciTech Connect

    Seiger, H.N.

    1988-03-29

    This patent describes an assembly of reactive metal electrochemical cells which includes bipolar electrodes connected in series between a pair of spaced conductive end plates, terminal means of higher conductive material than the end plates on each end plate comprising an array of interconnected terminal segment means disposed outwardly of a center point of the respective end plate in a generally uniform pattern with respect to the area configuration of the end plate to thereby enlarge the terminal area and to provide more uniform current distribution and active metal consumption over the areas of the bipolar electrodes.

  11. 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....

  12. 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....

  13. 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....

  14. 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....

  15. 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....

  16. 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...

  17. 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

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. 77 FR 38128 - Withdrawal of TORP Terminal LP, Bienville Offshore Energy Terminal Liquefied Natural Gas (LNG...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-26

    ... Maritime Administration Withdrawal of TORP Terminal LP, Bienville Offshore Energy Terminal Liquefied... Terminal LP's (TORP) withdrawal of the deepwater port license application for the proposed Bienville Offshore Energy Terminal (BOET). All actions related to the processing and agency coordination...

  4. Balanced Branching in Transcription Termination

    NASA Technical Reports Server (NTRS)

    Harrington, K. J.; Laughlin, R. B.; Liang, S.

    2001-01-01

    The theory of stochastic transcription termination based on free-energy competition requires two or more reaction rates to be delicately balanced over a wide range of physical conditions. A large body of work on glasses and large molecules suggests that this should be impossible in such a large system in the absence of a new organizing principle of matter. We review the experimental literature of termination and find no evidence for such a principle but many troubling inconsistencies, most notably anomalous memory effects. These suggest that termination has a deterministic component and may conceivably be not stochastic at all. We find that a key experiment by Wilson and von Hippel allegedly refuting deterministic termination was an incorrectly analyzed regulatory effect of Mg(2+) binding.

  5. Terminal attractors in neural networks

    NASA Technical Reports Server (NTRS)

    Zak, Michail

    1989-01-01

    A new type of attractor (terminal attractors) for content-addressable memory, associative memory, and pattern recognition in artificial neural networks operating in continuous time is introduced. The idea of a terminal attractor is based upon a violation of the Lipschitz condition at a fixed point. As a result, the fixed point becomes a singular solution which envelopes the family of regular solutions, while each regular solution approaches such an attractor in finite time. It will be shown that terminal attractors can be incorporated into neural networks such that any desired set of these attractors with prescribed basins is provided by an appropriate selection of the synaptic weights. The applications of terminal attractors for content-addressable and associative memories, pattern recognition, self-organization, and for dynamical training are illustrated.

  6. [Endoscopic therapy for cancer of the esophagogastric junction].

    PubMed

    Fujisaki, Junko; Omae, Masami; Shimizu, Tomoki; Morishige, Kenjiro; Miyamoto, Yuji; Taniguchi, Chika; Horiuchi, Yusuke; Yoshio, Toshiyuki; Ishiyama, Akiyoshi; Hirasawa, Toshiaki; Yamamoto, Yorimasa; Tsuchida, Tomohiro; Igarashi, Masahiro

    2015-01-01

    In Japan, the criteria for cancer of the esophagogastric junction (EGJ) are that the center of the lesions are located within 2cm from the EGJ orally and anally. The main histology of these lesions are squamous cell carcinoma and adenocarcinoma. Squamous cell carcinoma of the esophagus is treated following the guidelines published by the Japan Esophageal Society. This paper focuses on EGJ adenocarcinomas, which include cardiac gastric cancer and Barrett's cancer originating from the short-segment Barrett's esophagus. EGJ cancer is resected endoscopically at the termination of the palisade vessels or upper end of the gastric fold. The various types of cancer involving the EGJ are treated following the guidelines published by each medical specialist society in Japan. The main endoscopic treatment is endoscopic submucosal dissection. The EGJ is a narrow space, and therefore lesions are approached from the oral approach or anal approach using a reverse endoscope. Bleeding, perforation, and stenosis are major complications. When two-thirds or more of the wall is resected, stenosis occurs. Endoscopic therapy for cancer originating in the EGJ has not yet been fully established. PMID:25842810

  7. [Molecular mechanisms underlying the formation of neuromuscular junction].

    PubMed

    Higuchi, Osamu; Yamanashi, Yuji

    2011-07-01

    The neuromuscular junction (NMJ) is a synapse between a motor neuron and skeletal muscle. The contraction of skeletal muscle is controlled by the neurotransmitter acetylcholine (ACh), which is released from the motor nerve terminal. To achieve efficient neuromuscular transmission, acetylcholine receptors (AChRs) must be densely clustered on the muscle membrane of the NMJ. Failure of AChR clustering is associated with disorders of neuromuscular transmission such as congenital myasthenic syndromes (CMS) and myasthenia gravis (MG). Motoneuronal agrin and muscle-specific receptor tyrosine kinase (MuSK) are known to play essential roles in the formation and maintenance of NMJs in the central region of each muscle. However, it had been unclear how agrin activates MuSK. Recent studies have elucidated the roles of several key molecules, including the cytoplasmic adaptor protein Dok-7 and LDL receptor-related protein 4 (Lrp4), in agrin-induced MuSK activation. Moreover, new evidence indicates that cyclin-dependent kinase 5 (Cdk5) regulates postsynaptic differentiation. In this review, we summarize the latest developments in molecular mechanisms underlying NMJ formation in vertebrates. PMID:21747134

  8. Age-associated alterations of the neuromuscular junction.

    PubMed

    Jang, Youngmok C; Van Remmen, Holly

    2011-01-01

    Age-related loss of muscle mass and function greatly affects quality of life in the elderly population. Several hypotheses have been proposed but accumulating evidence point to alterations in neuromuscular system during aging as a key event that leads to functional denervation, muscle wasting, and weakness. Over the past few decades, age-associated degeneration of the neuromuscular junction (NMJ) and its components have been well documented. With advancing age, pre-terminal portions of motor axons exhibit regions of abnormal thinning, distension, and sprouting whereas postsynaptic endplates decrease in size and reduce in number, length, and density of postsynaptic folds. Although the exact underlying mechanisms are still lacking, recent studies provided direct evidence that age-associated increase in oxidative stress plays a crucial role in NMJ degeneration and progression of sarcopenia. Homozygous deletion of an important antioxidant enzyme, Cu,Zn superoxide dismutase (CuZnSOD, SOD1) leads to acceleration of age-dependent muscle atrophy, with a significant NMJ degeneration similar to that seen in old wild-type sarcopenic animals. In this short review, we briefly summarize the current understanding of some of the cellular and molecular changes in the NMJ during aging and suggest a role for oxidative stress and mitochondrial dysfunction in age-related changes in the maintenance of neuromuscular innervation.

  9. Terminal Model Of Newtonian Dynamics

    NASA Technical Reports Server (NTRS)

    Zak, Michail

    1994-01-01

    Paper presents study of theory of Newtonian dynamics of terminal attractors and repellers, focusing on issues of reversibility vs. irreversibility and deterministic evolution vs. probabilistic or chaotic evolution of dynamic systems. Theory developed called "terminal dynamics" emphasizes difference between it and classical Newtonian dynamics. Also holds promise for explaining irreversibility, unpredictability, probabilistic behavior, and chaos in turbulent flows, in thermodynamic phenomena, and in other dynamic phenomena and systems.

  10. Propagation Terminal Design and Measurements

    NASA Technical Reports Server (NTRS)

    Nessel, James

    2015-01-01

    The NASA propagation terminal has been designed and developed by the Glenn Research Center and is presently deployed at over 5 NASA and partner ground stations worldwide collecting information on the effects of the atmosphere on Ka-band and millimeter wave communications links. This lecture provides an overview of the fundamentals and requirements of the measurement of atmospheric propagation effects and, specifically, the types of hardware and digital signal processing techniques employed by current state-of-the-art propagation terminal systems.

  11. Negative differential conductance in molecular junctions: an overview of experiment and theory

    NASA Astrophysics Data System (ADS)

    Xu, Bingqian; Dubi, Yonatan

    2015-07-01

    One of the ultimate goals of molecular electronics is to create technologies that will complement—and eventually supersede—Si-based microelectronics technologies. To reach this goal, electronic properties that mimic at least some of the electrical behaviors of today’s semiconductor components must be recognized and characterized. An outstanding example for one such behavior is negative differential conductance (NDC), in which an increase in the voltage across the device terminals results in a decrease in the electric current passing through the device. This overview focuses on the NDC phenomena observed in metal-single molecule-metal molecular junctions, and is roughly divided into two parts. In the first part, the central experiments which demonstrate NDC in single-molecule junctions are critically reviewed, with emphasis on the main observations and their possible physical origins. The second part is devoted to the theory of NDC in single-molecule junctions, where simple models are employed to shed light on the different possible mechanisms leading to NDC.

  12. 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

  13. The apical disposition of the Caenorhabditis elegans intestinal terminal web is maintained by LET-413.

    PubMed

    Bossinger, Olaf; Fukushige, Tetsunari; Claeys, Myriam; Borgonie, Gaetan; McGhee, James D

    2004-04-15

    We wish to understand how organ-specific structures assemble during embryonic development. In the present paper, we consider what determines the subapical position of the terminal web in the intestinal cells of the nematode Caenorhabditis elegans. The terminal web refers to the organelle-depleted, intermediate filament-rich layer of cytoplasm that underlies the apical microvilli of polarized epithelial cells. It is generally regarded as the anchor for actin rootlets protruding from the microvillar cores. We demonstrate that: (i) the widely used monoclonal antibody MH33 reacts (only) with the gut-specific intermediate filament protein encoded by the ifb-2 gene; (ii) IFB-2 protein accumulates near the gut lumen beginning at the lima bean stage of embryogenesis and remains associated with the gut lumen into adulthood; and (iii) as revealed by immunoelectron microscopy, IFB-2 protein is confined to a discrete circumferential subapical layer within the intestinal terminal web (known in nematodes as the "endotube"); this layer joins directly to the apical junction complexes that connect adjacent gut cells. To investigate what determines the disposition of the IFB-2-containing structure as the terminal web assembles during development, RNAi was used to remove the functions of gene products previously shown to be involved in the overall apicobasal polarity of the developing gut cell. Removal of dlg-1, ajm-1, or hmp-1 function has little effect on the overall position or continuity of the terminal web IFB-2-containing layer. In contrast, removal of the function of the let-413 gene leads to a basolateral expansion of the terminal web, to the point where it can now extend around the entire circumference of the gut cell. The same treatment also leads to concordant basolateral expansion of both gut cell cortical actin and the actin-associated protein ERM-1. LET-413 has previously been shown to be basolaterally located and to prevent the basolateral expansion of several

  14. 7 CFR 1206.22 - Terminate.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE MANGO PROMOTION, RESEARCH, AND INFORMATION Mango Promotion, Research, and Information Order Definitions § 1206.22 Terminate. Terminate...

  15. 7 CFR 1206.22 - Terminate.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

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  16. 7 CFR 1206.22 - Terminate.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE MANGO PROMOTION, RESEARCH, AND INFORMATION Mango Promotion, Research, and Information Order Definitions § 1206.22 Terminate. Terminate...

  17. 7 CFR 1206.22 - Terminate.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE MANGO PROMOTION, RESEARCH, AND INFORMATION Mango Promotion, Research, and Information Order Definitions § 1206.22 Terminate. Terminate...

  18. 7 CFR 1206.22 - Terminate.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE MANGO PROMOTION, RESEARCH, AND INFORMATION Mango Promotion, Research, and Information Order Definitions § 1206.22 Terminate. Terminate...

  19. Hereditary mucoepithelial dysplasia: a disease apparently of desmosome and gap junction formation.

    PubMed Central

    Witkop, C J; White, J G; King, R A; Dahl, M V; Young, W G; Sauk, J J

    1979-01-01

    A previously unrecognized autosomal dominant syndrome affecting oral, nasal, vaginal, urethral, anal, bladder, and conjunctival mucosa with cataracts, follicular keratosis, nonscarring alopecia, and terminal lung disease is described in a four-generation kindred of German extraction. Severe photophobia, tearing, and nystagmus in infancy heralds the development of keratitis, corneal vascularization, and lens cataracts. Repeated corneal transplants have failed. Red, periorificial mucosal lesions involving the above structures are noted by 1 year of age and may persist throughout life. Chronic rhinorrhea and repeated upper respiratory infections frequently progress to bilateral pneumonia accompanied by loss of hair, diarrhea, occasional melena, enuresis, pyuria, and hematuria. Spontaneous pneumothorax is frequent, terminating in fibrocystic-type lung disease and cor pulmonale. Women have had repeated abnormal vaginal PAP smears. Histologically the mucosal epithelium shows dyshesion, thinning of the epithelial layer, and dyskeratosis. Mucosal PAP smears show lack of epithelial maturation, cytoplasmic vacuoles and inclusions, and individual cell dyskeratosis. Histochemically there is a lack of cornification and keratinization. Ultrastructural studies show lack of keratohyalin granules, a paucity of desmosomes, intercellular accumulations, cytoplasmic vacuolization, and formation of bands and aggregates of filamentous fibers and structures in the cytoplasm resembling desmosomes and gap junctions. The condition is probably a panepithelial cell defect of desmosomal and gap junction structure most prominently affecting mucosal epithelia associated with an increased susceptibility to a variety of adventitious organisms. Images Fig. 2-5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 10 PMID:484550

  20. Tunneling magnetoresistance and electroresistance in Fe/PbTiO3/Fe multiferroic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Dai, Jian-Qing

    2016-08-01

    We perform first-principles electronic structure and spin-dependent transport calculations for a Fe/PbTiO3/Fe multiferroic tunnel junction with asymmetric TiO2- and PbO-terminated interfaces. We demonstrate that the interfacial electronic reconstruction driven by the in situ screening of ferroelectric polarization, in conjunction with the intricate complex band structure of barrier, play a decisive role in controlling the spin-dependent tunneling. Reversal of ferroelectric polarization results in a transition from insulating to half-metal-like conducting state for the interfacial Pb 6pz orbitals, which acts as an atomic-scale spin-valve by releasing the tunneling current in antiparallel magnetization configuration as the ferroelectric polarization pointing to the PbO-terminated interface. This effect produces large change in tunneling conductance. Our results open an attractive avenue in designing multiferroic tunnel junctions with excellent performance by exploiting the interfacial electronic reconstruction originated from the in situ screening of ferroelectric polarization.

  1. DETAIL VIEW OF UPPER TRAM TERMINAL STRUCTURE, LOOKING SOUTH TOWARD ...

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

    DETAIL VIEW OF UPPER TRAM TERMINAL STRUCTURE, LOOKING SOUTH TOWARD THE FRONT OF THE STRUCTURE. THE WHEELS AT THE TOP OF THE TRAM BUCKETS RODE OFF THE STATIONARY CABLES ONTO THE TRACK SUPPORTED BY THE "C" IRONS SUSPENDED FROM THE TOP TIMBERS ON THE LEFT AND RIGHT. THE BUCKET OPENING MECHANISM IS ON THE LEFT, AND PART OF THE CLOSING MECHANISM ON THE RIGHT EDGE OF THE FRAME. THE TWO CABLES AT CENTER ARE THE STATIONARY TRAM CABLES THAT RUN ALONG THE TOP OF THE SUPPORT TOWERS ON WHICH THE WHEELS OF THE TRAM BUCKETS RODE. THEY ARE ANCHORED AT GROUND LEVEL JUST OFF FRAME TO THE LOWER LEFT. - Keane Wonder Mine, Park Route 4 (Daylight Pass Cutoff), Death Valley Junction, Inyo County, CA

  2. Calpains participate in nerve terminal degeneration induced by spider and snake presynaptic neurotoxins.

    PubMed

    Duregotti, Elisa; Tedesco, Erik; Montecucco, Cesare; Rigoni, Michela

    2013-03-15

    α-latrotoxin and snake presynaptic phospholipases A2 neurotoxins target the presynaptic membrane of axon terminals of the neuromuscular junction causing paralysis. These neurotoxins display different biochemical activities, but similarly alter the presynaptic membrane permeability causing Ca(2+) overload within the nerve terminals, which in turn induces nerve degeneration. Using different methods, here we show that the calcium-activated proteases calpains are involved in the cytoskeletal rearrangements that we have previously documented in neurons exposed to α-latrotoxin or to snake presynaptic phospholipases A2 neurotoxins. These results indicate that calpains, activated by the massive calcium influx from the extracellular medium, target fundamental components of neuronal cytoskeleton such as spectrin and neurofilaments, whose cleavage is functional to the ensuing nerve terminal fragmentation.

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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).

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. SLO BK Potassium Channels Couple Gap Junctions to Inhibition of Calcium Signaling in Olfactory Neuron Diversification.

    PubMed

    Alqadah, Amel; Hsieh, Yi-Wen; Schumacher, Jennifer A; Wang, Xiaohong; Merrill, Sean A; Millington, Grethel; Bayne, Brittany; Jorgensen, Erik M; Chuang, Chiou-Fen

    2016-01-01

    The C. elegans AWC olfactory neuron pair communicates to specify asymmetric subtypes AWCOFF and AWCON in a stochastic manner. Intercellular communication between AWC and other neurons in a transient NSY-5 gap junction network antagonizes voltage-activated calcium channels, UNC-2 (CaV2) and EGL-19 (CaV1), in the AWCON cell, but how calcium signaling is downregulated by NSY-5 is only partly understood. Here, we show that voltage- and calcium-activated SLO BK potassium channels mediate gap junction signaling to inhibit calcium pathways for asymmetric AWC differentiation. Activation of vertebrate SLO-1 channels causes transient membrane hyperpolarization, which makes it an important negative feedback system for calcium entry through voltage-activated calcium channels. Consistent with the physiological roles of SLO-1, our genetic results suggest that slo-1 BK channels act downstream of NSY-5 gap junctions to inhibit calcium channel-mediated signaling in the specification of AWCON. We also show for the first time that slo-2 BK channels are important for AWC asymmetry and act redundantly with slo-1 to inhibit calcium signaling. In addition, nsy-5-dependent asymmetric expression of slo-1 and slo-2 in the AWCON neuron is necessary and sufficient for AWC asymmetry. SLO-1 and SLO-2 localize close to UNC-2 and EGL-19 in AWC, suggesting a role of possible functional coupling between SLO BK channels and voltage-activated calcium channels in AWC asymmetry. Furthermore, slo-1 and slo-2 regulate the localization of synaptic markers, UNC-2 and RAB-3, in AWC neurons to control AWC asymmetry. We also identify the requirement of bkip-1, which encodes a previously identified auxiliary subunit of SLO-1, for slo-1 and slo-2 function in AWC asymmetry. Together, these results provide an unprecedented molecular link between gap junctions and calcium pathways for terminal differentiation of olfactory neurons.

  18. SLO BK Potassium Channels Couple Gap Junctions to Inhibition of Calcium Signaling in Olfactory Neuron Diversification

    PubMed Central

    Schumacher, Jennifer A.; Wang, Xiaohong; Merrill, Sean A.; Millington, Grethel; Bayne, Brittany; Jorgensen, Erik M.; Chuang, Chiou-Fen

    2016-01-01

    The C. elegans AWC olfactory neuron pair communicates to specify asymmetric subtypes AWCOFF and AWCON in a stochastic manner. Intercellular communication between AWC and other neurons in a transient NSY-5 gap junction network antagonizes voltage-activated calcium channels, UNC-2 (CaV2) and EGL-19 (CaV1), in the AWCON cell, but how calcium signaling is downregulated by NSY-5 is only partly understood. Here, we show that voltage- and calcium-activated SLO BK potassium channels mediate gap junction signaling to inhibit calcium pathways for asymmetric AWC differentiation. Activation of vertebrate SLO-1 channels causes transient membrane hyperpolarization, which makes it an important negative feedback system for calcium entry through voltage-activated calcium channels. Consistent with the physiological roles of SLO-1, our genetic results suggest that slo-1 BK channels act downstream of NSY-5 gap junctions to inhibit calcium channel-mediated signaling in the specification of AWCON. We also show for the first time that slo-2 BK channels are important for AWC asymmetry and act redundantly with slo-1 to inhibit calcium signaling. In addition, nsy-5-dependent asymmetric expression of slo-1 and slo-2 in the AWCON neuron is necessary and sufficient for AWC asymmetry. SLO-1 and SLO-2 localize close to UNC-2 and EGL-19 in AWC, suggesting a role of possible functional coupling between SLO BK channels and voltage-activated calcium channels in AWC asymmetry. Furthermore, slo-1 and slo-2 regulate the localization of synaptic markers, UNC-2 and RAB-3, in AWC neurons to control AWC asymmetry. We also identify the requirement of bkip-1, which encodes a previously identified auxiliary subunit of SLO-1, for slo-1 and slo-2 function in AWC asymmetry. Together, these results provide an unprecedented molecular link between gap junctions and calcium pathways for terminal differentiation of olfactory neurons. PMID:26771544

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. 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}.

  10. Wave reflections from duct terminations.

    PubMed

    Selamet, A; Ji, Z L; Kach, R A

    2001-04-01

    The reflection coefficients and inertial end corrections of several duct terminations, including finite length duct extensions perpendicular to an infinite wall, as well as at a number of angles, curved interface surfaces, and annular cavities, are determined and analyzed in the absence of flow by employing the boundary element method. Predictions for the classical unflanged and flanged circular ducts show good agreement with analytical and computational results available in the literature. The predictions for curved interface surfaces (bellmouth or horn) are also consistent with the available experimental data. In view of its high reflection coefficient, the duct termination with an annular cavity may be suggested for the suppression of noise radiation in a specific frequency band or for an effective wave reflection from the termination. PMID:11325101

  11. Digital autonomous terminal access communications

    NASA Technical Reports Server (NTRS)

    Novacki, S.

    1987-01-01

    A significant problem for the Bus Monitor Unit is to identify the source of a given transmission. This problem arises from the fact that the label which identifies the source of the transmission as it is put into the bus is intercepted by the Digital Autonomous Terminal Access Communications (DATAC) terminal and removed from the transmission. Thus, a given subsystem will see only data associated with a label and never the identifying label itself. The Bus Monitor must identify the source of the transmission so as to be able to provide some type of error identification/location in the event that some problem with the data transmission occurs. Steps taken to alleviate this problem by modifications to the DATAC terminal are discussed.

  12. 32 CFR 34.51 - Termination.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 32 National Defense 1 2011-07-01 2011-07-01 false Termination. 34.51 Section 34.51 National Defense Department of Defense OFFICE OF THE SECRETARY OF DEFENSE DoD GRANT AND AGREEMENT REGULATIONS... Termination and Enforcement § 34.51 Termination. (a) Awards may be terminated in whole or in part only...

  13. 12 CFR 611.1220 - Termination resolution.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 12 Banks and Banking 6 2010-01-01 2010-01-01 false Termination resolution. 611.1220 Section 611... Institution Status § 611.1220 Termination resolution. No more than 1 week before you submit your plan of termination to us, your board of directors must adopt a termination resolution stating its support...

  14. Airborne Satcom Terminal Research at NASA Glenn

    NASA Technical Reports Server (NTRS)

    Hoder, Doug; Zakrajsek, Robert

    2002-01-01

    NASA Glenn has constructed an airborne Ku-band satellite terminal, which provides wideband full-duplex ground-aircraft communications. The terminal makes use of novel electronically-steered phased array antennas and provides IP connectivity to and from the ground. The satcom terminal communications equipment may be easily changed whenever a new configuration is required, enhancing the terminal's versatility.

  15. Preparation of a hole transport layer tethered to ITO surface via a self-assembled monolayer with reactive terminal group

    NASA Astrophysics Data System (ADS)

    Hagihara, Yuya; Kim, Seong-Ho; Tanaka, Kuniaki; Advincula, Rigoberto C.; Usui, Hiroaki

    2014-01-01

    Characteristics of a junction between a polymer thin film and an indium-tin oxide (ITO) substrate was controlled by forming covalent chemical bonds at the interface through self-assembled monolayers (SAMs) with reactive terminal groups. For this purpose, SAMs with vinyl, epoxide, and benzophenone terminal groups were formed on ITO substrates, on which a vinyl derivative of a hole transport molecule was vapor-deposited, and then annealed in vacuum. This procedure produced a polymer layer strongly attached to the substrate surface. It was also found that the charge injection from the ITO electrode to the polymer layer can be improved by chemically tethering the interface via the SAMs.

  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. Bifunctional DNA architectonics: three-way junctions with sticky perylene bisimide caps and a central metal lock.

    PubMed

    Stubinitzky, Claudia; Bijeljanin, Andrea; Antusch, Linda; Ebeling, Daniel; Hölscher, Hendrik; Wagenknecht, Hans-Achim

    2014-09-15

    A new type of a bifunctional DNA architecture based on a three way junction is developed that combines the structural motif of sticky perylene bisimide caps with a tris-bipyridyl metal ion lock in the center part. A clear stabilizing effect was observed in the presence of Fe(3+), Ni(2+) and Zn(2+) by the formation of corresponding bipyridyl complexes in the branching part of the DNA three way junctions. The dimerization of the 5'-terminally attached perylene diimides (PDI) chromophores by hydrophobic interactions can be followed by significant changes in the UV/Vis absorption and steady-state fluorescence. The PDI-mediated DNA assembly occurs at temperatures below the melting temperature and is not influenced by the metal-ion bipyridyl locks in the central part. The corresponding AFM images revealed the formation of higher-ordered structures as the result of DNA assemblies mediated by the PDI interactions.

  5. Power generation of series and series/parallel triple junction tandem solar cells derived from measured spectra in Japan

    NASA Astrophysics Data System (ADS)

    Naito, Shunya; Okada, Yoshitaka

    2013-09-01

    A limiting efficiency of a solar cell changes according to the incident solar spectrum. With respect to a two-terminal triple junction tandem solar cell and interconnection of individual cells within it, the variation of limiting efficiency of a modified triple-tandem solar cell, in which two series-connected bottom cells are connected in parallel to the top cell, is lower than that of a conventional fully series-connected tandem cell. We calculate limiting efficiency of these two structures using measured solar spectra and meteorological condition at four different locations in Japan. It is shown that a triple junction tandem cell in a combination of series and parallel connections generates 7% larger amount of power than a series-connected cell does in average if these cells are optimized at airmass (AM) 1.5.

  6. Do Twelfths Terminate or Repeat?

    ERIC Educational Resources Information Center

    Ambrose, Rebecca; Burnison, Erica

    2015-01-01

    When finding the decimal equivalent of a fraction with 12 in the denominator, will it terminate or repeat? This question came from a seventh grader in author Erica Burnison's class as the student was pondering a poster generated by one of her classmates. Not only was the question intriguing, but it also affirmed the belief in the power of…

  7. Novel terminal strips for transformers

    NASA Technical Reports Server (NTRS)

    Wiler, E. M.

    1969-01-01

    Spacing tinned terminal leads between two tapes of woven glass fiber that are sandwich-bonded with pliable epoxy adhesive alleviates problems of taped leads pulling away from the transformer and shorting due to crossover of wires. Individual leads may or may not be enclosed in glass-fiber sleeves.

  8. Video Display Terminals: Radiation Issues.

    ERIC Educational Resources Information Center

    Murray, William E.

    1985-01-01

    Discusses information gathered in past few years related to health effects of video display terminals (VDTs) with particular emphasis given to issues raised by VDT users. Topics covered include radiation emissions, health concerns, radiation surveys, occupational radiation exposure standards, and long-term risks. (17 references) (EJS)

  9. Transfer terminal for offshore production

    SciTech Connect

    Arnaudeau, M.

    1983-02-01

    A mooring station and transfer terminal for offshore hydrocarbon production is provided, comprising a coaxial riser linking underwater production and safety manifolds to surface lines. An underwater connector and quick release means are provided to facilitate rapid connection and disconnection of the riser pipes.

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. The tight junction protein ZO-2 and Janus kinase 1 mediate intercellular communications in vascular smooth muscle cells

    SciTech Connect

    Tkachuk, Natalia; Tkachuk, Sergey; Patecki, Margret; Kusch, Angelika; Korenbaum, Elena; Haller, Hermann; Dumler, Inna

    2011-07-08

    Highlights: {yields} The tight junction protein ZO-2 associates with Jak1 in vascular smooth muscle cells via ZO-2 N-terminal fragment. {yields} Jak1 mediates ZO-2 tyrosine phosphorylation and ZO-2 localization to the sites of homotypic intercellular contacts. {yields} The urokinase receptor uPAR regulates ZO-2/Jak1 functional association. {yields} The ZO-2/Jak1/uPAR signaling complex is required for vascular smooth muscle cells functional network formation. -- Abstract: Recent evidence points to a multifunctional role of ZO-2, the tight junction protein of the MAGUK (membrane-associated guanylate kinase-like) family. Though ZO-2 has been found in cell types lacking tight junction structures, such as vascular smooth muscle cells (VSMC), little is known about ZO-2 function in these cells. We provide evidence that ZO-2 mediates specific homotypic cell-to-cell contacts between VSMC. Using mass spectrometry we found that ZO-2 is associated with the non-receptor tyrosine kinase Jak1. By generating specific ZO-2 constructs we further found that the N-terminal fragment of ZO-2 molecule is responsible for this interaction. Adenovirus-based expression of Jak1 inactive mutant demonstrated that Jak1 mediates ZO-2 tyrosine phosphorylation. By means of RNA silencing, expression of Jak1 mutant form and fluorescently labeled ZO-2 fusion protein we further specified that active Jak1, but not Jak1 inactive mutant, mediates ZO-2 localization to the sites of intercellular contacts. We identified the urokinase receptor uPAR as a pre-requisite for these cellular events. Functional requirement of the revealed signaling complex for VSMC network formation was confirmed in experiments using Matrigel and in contraction assay. Our findings imply involvement of the ZO-2 tight junction independent signaling complex containing Jak1 and uPAR in VSMC intercellular communications. This mechanism may contribute to vascular remodeling in occlusive cardiovascular diseases and in arteriogenesis.

  17. Stability junction at a common mutation site in the collagenous domain of the mannose binding lectin.

    PubMed

    Mohs, Angela; Li, Yingjie; Doss-Pepe, Ellen; Baum, Jean; Brodsky, Barbara

    2005-02-15

    Missense mutations in the collagen triple-helix that replace one of the required Gly residues in the (Gly-Xaa-Yaa)(n)() repeating sequence have been implicated in various disorders. Although most hereditary collagen disorders are rare, a common occurrence of a Gly replacement mutation is found in the collagenous domain of mannose binding lectin (MBL). A Gly --> Asp mutation at position 54 in MBL is found at a frequency as high as 30% in certain populations and leads to increased susceptibility to infections. The structural and energetic consequences of this mutation are investigated by comparing a triple-helical peptide containing the N-terminal Gly-X-Y units of MBL with the homologous peptide containing the Gly to Asp replacement. The mutation leads to a loss of triple-helix content but only a small decrease in the stability of the triple-helix (DeltaT(m) approximately 2 degrees C) and no change in the calorimetric enthalpy. NMR studies on specifically labeled residues indicate the portion of the peptide C-terminal to residue 54 is in a highly ordered triple-helix in both peptides, while residues N-terminal to the mutation site have a weak triple-helical signal in the parent peptide and are completely disordered in the mutant peptide. These results suggest that the N-terminal triplet residues are contributing little to the stability of this peptide, a hypothesis confirmed by the stability and enthalpy of shorter peptides containing only the region C-terminal to the mutation site. The Gly to Asp replacement at position 54 in MBL occurs at the boundary of a highly stable triple-helix region and a very unstable sequence. The junctional position of this mutation minimizes its destabilizing effect, in contrast with the significant destabilization seen for Gly replacements in peptides modeling collagen diseases.

  18. 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

  19. 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).

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. 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

  17. Wnt4 Participates in the Formation of Vertebrate Neuromuscular Junction

    PubMed Central

    Strochlic, Laure; Falk, Julien; Goillot, Evelyne; Sigoillot, Séverine; Bourgeois, Francine; Delers, Perrine; Rouvière, Jérôme; Swain, Amanda; Castellani, Valérie; Schaeffer, Laurent; Legay, Claire

    2012-01-01

    Neuromuscular junction (NMJ) formation requires the highly coordinated communication of several reciprocal signaling processes between motoneurons and their muscle targets. Identification of the early, spatially restricted cues in target recognition at the NMJ is still poorly documented, especially in mammals. Wnt signaling is one of the key pathways regulating synaptic connectivity. Here, we report that Wnt4 contributes to the formation of vertebrate NMJ in vivo. Results from a microarray screen and quantitative RT-PCR demonstrate that Wnt4 expression is regulated during muscle cell differentiation in vitro and muscle development in vivo, being highly expressed when the first synaptic contacts are formed and subsequently downregulated. Analysis of the mouse Wnt4−/− NMJ phenotype reveals profound innervation defects including motor axons overgrowing and bypassing AChR aggregates with 30% of AChR clusters being unapposed by nerve terminals. In addition, loss of Wnt4 function results in a 35% decrease of the number of prepatterned AChR clusters while Wnt4 overexpression in cultured myotubes increases the number of AChR clusters demonstrating that Wnt4 directly affects postsynaptic differentiation. In contrast, muscle structure and the localization of several synaptic proteins including acetylcholinesterase, MuSK and rapsyn are not perturbed in the Wnt4 mutant. Finally, we identify MuSK as a Wnt4 receptor. Wnt4 not only interacts with MuSK ectodomain but also mediates MuSK activation. Taken together our data reveal a new role for Wnt4 in mammalian NMJ formation that could be mediated by MuSK, a key receptor in synaptogenesis. PMID:22253844

  18. 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.

  19. 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…

  20. 29 CFR 4041.43 - Notice of intent to terminate.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... TERMINATION OF SINGLE-EMPLOYER PLANS Distress Termination Process § 4041.43 Notice of intent to terminate. (a... chapter). (c) Spin-off/termination transactions. In the case of a spin-off/termination transaction...

  1. 48 CFR 49.105 - Duties of termination contracting officer after issuance of notice of termination.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... Regulations System FEDERAL ACQUISITION REGULATION CONTRACT MANAGEMENT TERMINATION OF CONTRACTS General Principles 49.105 Duties of termination contracting officer after issuance of notice of termination. (a... principles relating to the settlement of any settlement proposal, including obligations of the...

  2. Pharmacological elevation of cyclic AMP and transmitter release at the mouse neuromuscular junction.

    PubMed

    Dryden, W F; Singh, Y N; Gordon, T; Lazarenko, G

    1988-03-01

    Intracellular recordings of spontaneous and evoked end-plate potentials have been made at the neuromuscular junction of mouse hemidiaphragms to determine a possible role of cyclic AMP (cAMP) in the release of acetylcholine from presynaptic terminals. Spontaneous release, as determined from the frequency of miniature end-plate potentials, was increased by drugs that inhibit phosphodiesterase: isobutylmethylxanthine (IBMX), SQ 20,009, theophylline, and caffeine; drugs that stimulate adenylate cyclase: forskolin, fluoride, and cholera toxin, and the stable analogue of cAMP: 8-bromo-cAMP but not dibutyryl cAMP. Release increased with time during maintained exposure to the drugs and generally followed a simple exponential time course with time constants ranging from 8 to 17 min at 20 degrees C, except for SQ 20,009 and cholera toxin which required longer exposure times for effect. The order of potency of the phosphodiesterase inhibitors was IBMX = SQ 20,009 greater than theophylline = caffeine. This is consistent with an effect mediated by an increase in cAMP concentrations within the nerve terminal. Evoked release, determined from the quantal content of the end-plate potential, was increased to a lesser extent than spontaneous release. The results are discussed with reference to the possible involvement of second messengers in the release of vesicles from nerve terminals in vertebrate synapses.

  3. Proximity induced vortices and long-range triplet supercurrents in ferromagnetic Josephson junctions and spin valves

    SciTech Connect

    Alidoust, Mohammad; Halterman, Klaus

    2015-03-28

    Using a spin-parameterized quasiclassical Keldysh-Usadel technique, we theoretically study supercurrent transport in several types of diffusive ferromagnetic (F)/superconducting (S) configurations with differing magnetization textures. We separate out the even- and odd-frequency components of the supercurrent within the low proximity limit and identify the relative contributions from the singlet and triplet channels. We first consider inhomogeneous one-dimensional Josephson structures consisting of a uniform bilayer magnetic S/F/F/S structure and a trilayer S/F/F/F/S configuration, in which case the outer F layers can have either a uniform or conical texture relative to the central uniform F layer. Our results demonstrate that for supercurrents flowing perpendicular to the F/F interfaces, incorporating a conical texture yields the most effective way to observe the signatures of long-ranged spin-triplet supercurrents. We also consider three different types of finite-sized two-dimensional magnetic structures subjected to an applied magnetic field normal to the junction plane: a S/F/S junction with uniform magnetization texture and two S/F/F/S configurations with differing F/F bilayer arrangements. In one case, the F/F interface is parallel with the S/F junction interfaces while in the other case, the F/F junction is oriented perpendicular to the S/F interfaces. We then discuss the proximity vortices and corresponding spatial maps of currents inside the junctions. For the uniform S/F/S junction, we analytically calculate the magnetic field induced supercurrent and pair potential in both the narrow and wide junction regimes, thus providing insight into the variations in the Fraunhofer diffraction patterns and proximity vortices when transitioning from a wide junction to a narrow one. Our extensive computations demonstrate that the induced long-range spin-triplet supercurrents can deeply penetrate uniform F/F bilayers when spin-singlet supercurrents flow parallel to the

  4. Transient alteration of the vestibular calyceal junction and synapse in response to chronic ototoxic insult in rats

    PubMed Central

    Sedó-Cabezón, Lara; Jedynak, Paulina; Boadas-Vaello, Pere; Llorens, Jordi

    2015-01-01

    ABSTRACT Ototoxicity is known to cause permanent loss of vestibule function through degeneration of sensory hair cells (HCs). However, functional recovery has been reported during washout after chronic ototoxicity, although the mechanisms underlying this reversible dysfunction are unknown. Here, we study this question in rats chronically exposed to the ototoxic compound 3,3′-iminodipropionitrile (IDPN). Pronounced alterations in vestibular function appeared before significant loss of HCs or stereociliary coalescence became evident by ultrastructural analyses. This early dysfunction was fully reversible if the exposure was terminated promptly. In cristae and utricles, the distinct junctions formed between type I HCs (HCI) and calyx endings were completely dismantled at these early stages of reversible dysfunction, and completely rebuilt during washout. Immunohistochemical observations revealed loss and recovery of the junction proteins CASPR1 and tenascin-C and RT-PCR indicated that their loss was not due to decreased gene expression. KCNQ4 was mislocalized during intoxication and recovered control-like localization after washout. At early stages of the intoxication, the calyces could be classified as showing intact or lost junctions, indicating that calyceal junction dismantlement is triggered on a calyx-by-calyx basis. Chronic toxicity also altered the presence of ribeye, PSD-95 and GluA2 puncta in the calyces. These synaptic alterations varied between the two types of calyx endings (formed by calyx-only or dimorphic afferents) and some persisted at the end of the washout period. The present data reveal new forms of plasticity of the calyx endings in adult mammals, including a robust capacity for rebuilding the calyceal junction. These findings contribute to a better understanding of the phenomena involved in progressive vestibular dysfunction and its potential recovery during and after ototoxic exposure. PMID:26398945

  5. Characterization and Comparison of Intercellular Adherent Junctions Expressed by Human Corneal Endothelial Cells in Vivo and in Vitro

    PubMed Central

    Ying-Ting, Zhu; Hayashida, Yasutaka; Kheirkhah, Ahmad; He, Hua; Sue-Yue, Chen; Tseng, Scheffer C. G.

    2008-01-01

    Purpose Human corneal endothelial cell (HCEC) proliferation is controlled by their cell junctions, of which the mechanism remains unknown. We sought to characterize adherent junction components of in vivo HCECs, and compare their gene expression and their proliferative potential to those of in vitro counterparts. Methods Stripped human Descemet’s membranes were digested with collagenase A, and the resultant HCEC aggregates were cultured for 7, 14, and 21 days in supplemented hormonal epithelial medium (SHEM). Growth of HCEC monolayers was monitored by BrdU labeling performed 24 h before termination. Both in vivo and in vitro HCECs were subjected to immunostaining to FITC-phalloidin and antibodies to different junction components and BrdU. Their mRNA expressions were determined by RT-PCR. Results In vivo HCECs expressed transcripts of N-, VE-, E-, and P-cadherins, α-, β-, γ-, and p120-catenins, and p190. In vitro HCEC counterparts also expressed all these mRNAs except P-cadherin. In vivo HCECs displayed continuous circular F-actin, N-cadherin, β- and p120-catenins, and p190, discontinuous circular VE-cadherin bands at/close to cell junctions, and E-cadherin in the cytoplasm. Such an in vivo pattern was gradually achieved by in vitro HCECs at day 21 and was correlated with a progressive decline of BrdU labeling. Conclusions Both in vivo and in vitro HCECs displayed distinct protein cytolocalization of N-, VE-, and E-cadherins, β- and p120-catenins, and p190. Progressive maturation of adherent junctions was associated with a decline of the proliferative potential. This information allows us to devise new strategies to engineer in vitro HCECs by targeting these components. PMID:18502989

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. 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

  17. 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.

  18. 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

  19. 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.

  20. Scientific ballooning payload termination loads

    NASA Astrophysics Data System (ADS)

    Robbins, E.

    1993-02-01

    NASA's high altitude balloon borne scientific payloads are typically suspended from a deployed flat circular parachute. At flight termination, the recovery train is pyrotechnically separated at the parachute apex and balloon nadir interface. The release of elastic energy stored in the parachute at zero initial virtical velocity in the rarefied atmosphere produces high canopy opening forces that subject the gondola to potentially damaging shock loads. Data from terminations occuring at altitudes to 40 km with payloads up to 2500 kg on parachutes up to 40 m in diameter are presented. Measured loads are markedly larger than encountered via packed parachute deployment for similar canopy loadings. Canopy inflation is significantly surpressed in the early stages and then accelerated during final blossoming. Data interpretation and behavioral phenomena are discussed along with proposed shock attenuation techniques.