Sample records for ultra-shallow junction formation

  1. Ultra shallow p +\\/n junction formation by plasma doping (PD) and long pulse all solid-state laser annealing (ASLA) with selective absorption modulation

    Microsoft Academic Search

    C. G. Jin; Y. Sasaki; K. Okashita; H. Tamura; H. Ito; B. Mizuno; K. Tsutsui; S. Ohmi; H. Iwai

    2005-01-01

    Plasma doping (PD) and long pulse all solid-state laser annealing (ASLA) was combined with the selective absorption modulation using SiO2 layer to form ultra-shallow p+\\/n junction. By depositing a controlled thickness of SiO2 layer on top of the silicon substrate, we were able to confirm the reduction of laser energy density by 400mJ\\/cm2 (29%) and the formation of ultra-shallow junction

  2. CVD Delta-Doped Boron Surface Layers for Ultra-Shallow Junction Formation F. Sarubbi, L. K. Nanver, and T. L. M. Scholtes

    E-print Network

    Technische Universiteit Delft

    atmospheric/low- pressure chemical vapor deposition (AP/LPCVD) to form -doped boron surface layers. Our). This layer has semi-metallic properties with a high resistivity in the range of 106 cm. The as-deposited -BCVD Delta-Doped Boron Surface Layers for Ultra-Shallow Junction Formation F. Sarubbi, L. K. Nanver

  3. Depth profile characterization of ultra shallow junction implants.

    PubMed

    Hönicke, Philipp; Beckhoff, Burkhard; Kolbe, Michael; Giubertoni, Damiano; van den Berg, Jaap; Pepponi, Giancarlo

    2010-04-01

    A need for analysis techniques, complementary to secondary ion mass spectrometry (SIMS), for depth profiling dopants in silicon for ultra shallow junction (USJ) applications in CMOS technologies has recently emerged following the difficulties SIMS is facing there. Grazing incidence X-ray fluorescence (GIXRF) analysis in the soft X-ray range is a high-potential tool for this purpose. It provides excellent conditions for the excitation of the B-K and the As-L(iii,ii) shells. The X-ray standing wave (XSW) field associated with GIXRF on flat samples is used here as a tunable sensor to obtain information about the implantation profile because the in-depth changes of the XSW intensity are dependent on the angle of incidence. This technique is very sensitive to near-surface layers and is therefore well suited for the analysis of USJ distributions. Si wafers implanted with either arsenic or boron at different fluences and implantation energies were used to compare SIMS with synchrotron radiation-induced GIXRF analysis. GIXRF measurements were carried out at the laboratory of the Physikalisch-Technische Bundesanstalt (PTB) at the electron storage ring BESSY II using monochromatized undulator radiation of well-known radiant power and spectral purity. The use of an absolutely calibrated energy-dispersive detector for the acquisition of the B-Kalpha and As-Lalpha fluorescence radiation enabled the absolute determination of the total retained dose. The concentration profile was obtained by ab initio calculation and comparison with the angular measurements of the X-ray fluorescence. PMID:19941133

  4. Laser annealing of plasma implanted boron for ultra-shallow junctions in Silicon

    NASA Astrophysics Data System (ADS)

    Florakis, A.; Tsoukalas, D.; Zergioti, I.; Giannakopoulos, K.; Dimitrakis, P.; Papazoglou, D. G.; Bennassayag, G.; Bourdon, H.; Halimaoui, A.

    2006-12-01

    This work combines plasma doping implantation (PLAD) with laser annealing using excimer laser, for the formation of ultra-shallow junctions. For that purpose, high dose BF 3 was implanted in n-type silicon wafers using PLAD. The as implanted material was investigated by high resolution TEM, measured by SIMS and simulated by Monte-Carlo codes. Subsequently, the samples were annealed using a KrF laser source at 248 nm with a pulse duration 20 ns and different fluence values. Laser annealing completely recrystallizes the amorphous layer as monitored by TEM measurements, fully activates the dopants achieving low sheet resistance values as shown by Van der Pauw measurements and results in box-shaped dopant profiles with movement less than 10 nm at the junction depth as measured using SIMS.

  5. Ultra-shallow junction (USJ) sheet resistance measurements with a non-penetrating four point probe

    NASA Astrophysics Data System (ADS)

    Benjamin, M. C.; Hillard, R. J.; Borland, J. O.

    2005-08-01

    An accurate method to measure the four point probe (4PP) sheet resistance ( RS) of ultra shallow junction (USJ) Source-Drain Extension structures is described. The method utilizes Elastic Material probes (EM-probes) to form non-penetrating contacts to the silicon surface [R.J. Hillard, P.Y. Hung, William Chism, C. Win Ye, W.H. Howland, L.C. Tan, C.E. Kalnas, Characterization and Metrology for ULSI Technology, AIP Conference proceedings 683 (2003) 802.]. The probe design is kinematic and the force is controlled to ensure elastic deformation of the probe material. The probe material is such that large direct tunneling currents can flow through the native oxide thereby forming a low impedance contact. Sheet resistance measurements on USJ implanted P+/N structures with Secondary Ion Mass Spectroscopy (SIMS) junction depths less than 15 nm have been measured. The method is demonstrated on implanted USJ structures and found to be consistent with expectations.

  6. Understanding defect interactions in Si Ultra-shallow p-n junctions formed by very low energy Boron Implantation

    NASA Astrophysics Data System (ADS)

    Vanamurthy, Lakshmanan H.

    One of the biggest challenges in the scaling of CMOS devices is the formation of a highly activated, abrupt, defect free Source drain extension (SDE) region. This is especially difficult with p-FET's because of the (1) Boron diffusion co-efficient enhancement from Transient enhanced diffusion (TED) and (2) low solid solubility of. Boron at the conventional spike annealing temperatures. In addition to the fabrication challenges, the continued development effort on Boron doped silicon ultra-shallow junctions (USJ) has posed a great challenge to materials characterization. Many of the conventional junction characterization techniques like 4 point probe, Secondary Ion Mass Spectroscopy and Transmission Electron Microscopy have great difficulty in the accurate quantification of junctions less than 10 nm. This has increased the gap in understanding the advanced thermal processing techniques like LASER annealing. Such milli-second annealing techniques can solve the fabrication problem by annealing the junctions for a very high temperature at a very short duration. To solve these challenges a new characterization methodology was developed by using ion beam analysis (Rutherford backscattering, ion channeling, nuclear reaction analysis) with room-temperature UV-assisted oxidation and chemical wet etching. The measurements from this technique was able to profile a high-resolution (~ 0.5 nm) depth distributions of total boron atoms, electrically activated boron atoms and silicon lattice defects in silicon ultra-shallow junctions, as shallow as 8 nm. Additionally, the ability for depth profiling Si lattice defects offered by this method has aided in the understanding of the residual defect differences in the Conventional thermal and laser annealing techniques.In the absence of Transmission electron microscopy's ability to directly quantify the point Defect density in USJ's formed by millisecond LASER annealing, Angular Ion channeling measurements were performed to understand the defect dissolution dependence on LASER temperature and Dwell time. These measurements provided a fundamental understanding of the types of Boron interstitial clusters and the defect dissolution mechanism that is dominant during LASER annealing. Finally a pathway to obtain a highly activated, abrupt junction based on the mechanism proposed in this work was identified.

  7. Ultra-shallow junction depth profile analysis using TOF-SIMS and TXRF

    SciTech Connect

    Iltgen, K.; Weiss, C.; Zschech, E. [AMD Saxony Manufacturing GmbH, Dresden (Germany); MacDonald, B.; Hossain, T. [AMD Inc., Austin, Texas (United States); Brox, O.; Benninghoven, A. [Physical Institute, University of Muenster (Germany)

    1998-11-24

    The drive to fabricate ever shallower source/drain and channel junctions in DRAM and microprocessor production constitutes a great challenge for their analytical characterization. Ultra-shallow SIMS profiling requires high depth resolution and a small surface transient region. It also has to account for the interface between the native oxide and the Si bulk. We have investigated the shallow depth profiling capabilities of TOF-SIMS and TXRF. TOF-SIMS is well established for high sensitivity microarea surface analysis. The technique features high mass resolution, high transmission and a parallel mass registration. Depth profiles are performed in the dual beam mode allowing an independent optimization of the analyzing and sputtering ion beam. The application of a low energy SF{sub 5}{sup +} sputtering ion beam provides depth resolution in the 0.5 nm range and minimizes the width of the near surface transient region. When depth profiling silicon, the oxidation state of the receding surface can be derived from the intensities of the positive secondary ion intensities Si{sub 2}O{sub n}{sup +} (n=0....4). This allows the correction of changes in erosion rate and relative sensitivity factors which are caused by a varying surface oxidation state. For instance, such a variation of the surface oxidation state always occurs in the near surface region. The detection of the interface between the native oxide and the Si bulk and constant sputter and ion yields at this interface are accomplished by the incorporation of {sup 18}O. TXRF has proved to be a powerful technique for the analysis of metallic contaminations on wafer surfaces. One of the advanced applications of this technique is the characterization of ultra-shallow implant profiles. In contrast to the SIMS technique, TXRF provides only an integral value of implants for a near surface layer of some nm thickness. But TXRF is non-destructive, and, therefore, it can be used as a rapid in-fab characterization technique. We will report on TOF-SIMS and TXRF depth profiles of shallow B and As implants in Si.

  8. Fabrication of Ultra-Shallow Junctions on 300 mm Wafers Using the Plasma Immersion Implanter PULSION registered Followed by Spike Annealing Using LEVITOR Furnace

    SciTech Connect

    Torregrosa, Frank; Etienne, Hasnaa; Sempere, Guillaume; Mathieu, Gilles; Roux, Laurent [ION BEAM SERVICES, ZI Peynier-Rousset, rue Gaston Imbert Prolongee, 13790 Peynier (France); Milesi, Frederic; Gonzatti, Frederic [CEA LETI-MINATEC, DRT/DPTS/SDOT, 17 rue des Martyrs 38054 Grenoble cedex 9 (France); Pages, Xavier [ASM Europe B. V., Versterkerstraat 8, 1322 AP Almere (Netherlands)

    2008-11-03

    Thanks to the European Project SEA-NET, an industrial version of the IBS Plasma Ion Implantation tool has been installed in LETI for the fabrication of Ultra-Shallow Junction for 45 and 32 nm CMOS on 200 and 300 mm wafers. In this study, we present first doping results on 300 mm wafers using BF{sub 3} plasma. Annealing after PULSION implantation is performed by the ASM furnace LEVITOR. This tool, which works on conduction heating is emissivity independent for temperature control and allows reaching high ramp up and ramp down speeds (up to 900 deg. C/s). Main characteristics of as implanted wafers are presented (metal contamination 2E10/cm{sup 2}, SIMS depth profiles down to 5 nm). Then the effect of convection gas in the annealing process on sheet resistance, junction depth and uniformity is presented.

  9. Local Resistance Profiling of Ultra-Shallow Junction with Spike Lamp and Laser Annealing Using Scanning Spreading Resistance Microscopy

    SciTech Connect

    Abo, Satoshi; Tanaka, Yuji; Nishikawa, Kazuhisa; Wakaya, Fujio; Takai, Mikio [Center for Quantum Science and Technology under Extreme Conditions, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka, 560-8531 (Japan); Iwamatsu, Toshiaki; Oda, Hidekazu [Renesas Technology Corporation, 4-1 Mizuhara, Itami, Hyogo, 664-0005 (Japan)

    2008-11-03

    Local resistance profiles of ultra-shallow arsenic implanted into silicon with an energy of 3.5 keV and a dose of 1.2x10{sup 15} ions/cm{sup 2} activated by conventional spike lamp and laser annealing were measured by SSRM in a nitrogen atmosphere with a depth resolution of less than 10 nm for investigating the combination of the conventional spike lamp and laser annealing. Spike lamp annealing at 1050 deg. C followed by laser annealing at a power density of 0.42 kW/mm{sup 2} was found to give the lowest sheet resistance. The resistance profiles obtained by SSRM also indicated the lowest resistance for the sample after spike lamp annealing at 1050 deg. C followed by laser annealing with a power density of 0.42 kW/mm{sup 2}. Laser annealing alone with a power density of 0.42 kW/mm{sup 2} resulted in the higher sheet resistance, though the shallower resistance profile could be obtained. Spike lamp annealing followed by laser annealing procedures are effective in activating shallow arsenic profiles.

  10. Excimer laser activation of ultra-shallow junctions in doped Si: Modeling, experiments and real time process monitoring

    NASA Astrophysics Data System (ADS)

    Semmar, Nadjib; Darif, Mohamed; Millon, Eric; Petit, Agnès; Etienne, Hasnaa; Delaporte, Philippe

    2012-07-01

    This work concerns the ALDIP (Laser Activation of Doping agents Implanted by Plasma immersion) project that was a successful collaboration with Ion Beam Services (IBS) corporation, the "Lasers, Plasmas and Photonic Processes" (LP3) laboratory and the GREMI laboratory. The aim of this work is to control the melted thickness (i.e. junction thickness in the range 10-100 nm) by the Real Time Reflectivity (TRR) monitoring during the Laser Thermal Processing (LTP). The LTP is achieved by using a KrF laser beam (248 nm, 27 ns) with a homogeneous 'Top-Hat' space distribution to induce a selective melting and the resolidification of the doped Si:B samples on few nanometers. This recrystallization is conducted here after the pre-amorphisation process resulting from the ionic implantation of Si (PIII IBS implanter). Thus, all the studied samples are partially amorphized and boron doped. TRR method allows the accurate evaluation of the melting threshold, the duration of the melting phase, and the maximum melted thickness. Obtained results versus laser fluence are shown in the new case of under vacuum treatment. In order to calibrate the TRR method (to determine the intensity and the profile of the TRR signal versus the melting depth), we have used the secondary ion mass spectrometry (TOF-SIMS) analysis. This technique gives the doping agents profile versus the depth before and after LTP and confirms also the melting kinetics from TRR results.

  11. Local Resistance Profiling of Ultra Shallow Junction Annealed with Combination of Spike Lamp and Laser Annealing Processes using Scanning Spreading Resistance Microscope

    SciTech Connect

    Abo, Satoshi; Nishikawa, Kazuhisa; Ushigome, Naoya; Wakaya, Fujio; Takai, Mikio [Center for Quantum Science and Technology under Extreme Conditions, Osaka University, 1-3, Machikaneyama, Toyonaka, Osaka, 560-8531 (Japan); Iwamatsu, Toshiaki; Oda, Hidekazu [Advanced Device Technology Department, Production and Technology Unit, Devices and Analysis Technology Division, Renesas Electronics Corporation, 751, Horiguchi, Hitachinaka, Ibaraki, 312-8504 (Japan)

    2011-01-07

    Local resistance profiles of ultra shallow boron and arsenic implanted into silicon with energies of 2.0 and 4.0 keV and doses of 2.0x10{sup 15} and 1.0x10{sup 15} ions/cm{sup 2} activated by a combination of conventional spike lamp and laser annealing processes were measured by scanning spreading resistance microscope (SSRM) with a depth resolution of less than 10 nm. The lowest local resistance at the low resistance region in 2.0 keV boron implanted silicon with 1050 deg. C spike lamp annealing followed by 0.35 kW/mm{sup 2} laser annealing was half of that without laser annealing. The lowest local resistance at the low resistance region in the arsenic implanted silicon activated by 1050 deg. C spike lamp annealing followed by 0.39 kW/mm{sup 2} laser annealing was 74% lower than that followed by 0.36 kW/mm{sup 2} laser annealing. The lowest local resistances at the low resistance regions in the arsenic implanted silicon with 0.36 and 0.39 kW/mm{sup 2} laser annealing followed by 1050 deg. C spike lamp annealing were 41 and 33% lower than those with spike lamp annealing followed by laser annealing. Laser annealing followed by spike lamp annealing could suppress the diffusion of the impurities and was suitable for making the ultra shallow and low resistance regions.

  12. Defect detection in recrystallized ultra-shallow implanted silicon by multiwavelength-excited photoluminescence

    NASA Astrophysics Data System (ADS)

    Yoshimoto, Masahiro; Okutani, Masashi; Saikusa, Hiroki; Takashima, Shuhei; Yoo, Woo Sik

    2012-11-01

    Defect formation and annihilation in ultra-shallow junctions (USJs) before and after rapid thermal annealing are characterized by multiwavelength-excited photoluminescence (PL) with probing depths of the excitation light in a range between 1.5 and 45 ?m. Recrystallization of USJs is monitored by transmission microscopy and UV Raman spectroscopy. PL measurements taken at room temperature, enable us to distinguish USJ layers with trap densities (Nt) on the order of 1012 cm-3 or less and those with Nt of 5×1012 - 1014 cm-3, nondestructively, on an in-line basis.

  13. SIMS backside depth profiling of ultra shallow implants

    NASA Astrophysics Data System (ADS)

    Yeo, K. L.; Wee, A. T. S.; See, A.; Liu, R.; Ng, C. M.

    2003-01-01

    In secondary ion mass spectrometry depth profiling, a more accurate junction depth can be acquired by sputtering from the backside of the wafer [J. Vac. Sci. Technol. B 16 (1) (1998) 298]. This technique takes advantage of the better depth resolution of the leading edge as compared to the trailing edge [Nucl. Instrum. Meth. B 47 (1990) 223]. By using silicon-on-insulator (SOI) wafers, we have developed a backside depth profiling technique for studying ultra shallow implants. The abrupt interface of the SOI wafer and the large selectivity in chemical etching result in smooth after-etched surfaces, which facilitate high resolution SIMS profiling. The true dopant distribution of B 1 keV implants was studied by performing front and backside depth profiling using SOI substrates. The 7.5 and 0.5 keV O 2+ primary ions were used at oblique incidence in a Cameca IMS-6f, with and without oxygen flooding and sample rotation. The effectiveness of backside SIMS profiling of the ultra shallow dopant implants using SOI substrates is evaluated.

  14. Plasma Immersion Ion Implantation applied to P+N junction solar cells

    Microsoft Academic Search

    Vanessa Vervisch; D. Barakel; F. Torregrosa; L. Ottaviani; M. Pasquinelli

    2006-01-01

    Plasma immersion ion implantation is an alternative doping technique for the formation of Ultra Shallow Junctions in semiconductor. In this study, we present the PIII technology developed by the company Ion Beam Services and called PULSION®. We explain the advantages of PIII for the conception of thin emitter solar cells and the use of N type silicon in the fabrication

  15. Activation and thermal stability of ultra-shallow B{sup +}-implants in Ge

    SciTech Connect

    Yates, B. R.; Darby, B. L.; Jones, K. S. [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611 (United States); Petersen, D. H. [DTU Nanotech, Department of Micro- and Nanotechnology, Technical University of Denmark, DK-2800 Kgs. Lyngby (Denmark); Hansen, O. [DTU Nanotech, Department of Micro- and Nanotechnology, Technical University of Denmark, DK-2800 Kgs. Lyngby (Denmark); CINF, Center for Individual Nanoparticle Functionality, Technical University of Denmark, DK-2800 Kongens Lyngby (Denmark); Lin, R.; Nielsen, P. F. [CAPRES A/S, Scion-DTU, DK-2800 Kgs. Lyngby (Denmark); Romano, L. [IMM-CNR MATIS and Dipartimento di Fisica e Astronomia, Universita di Catania, Via S. Sofia 64, I-95123 Catania (Italy); Doyle, B. L. [Sandia National Laboratories, MS-1056, Albuquerque, New Mexico 87185 (United States); Kontos, A. [Applied Materials, Gloucester, Massachusetts 01930 (United States)

    2012-12-15

    The activation and thermal stability of ultra-shallow B{sup +} implants in crystalline (c-Ge) and preamorphized Ge (PA-Ge) following rapid thermal annealing was investigated using micro Hall effect and ion beam analysis techniques. The residual implanted dose of ultra-shallow B{sup +} implants in Ge was characterized using elastic recoil detection and was determined to correlate well with simulations with a dose loss of 23.2%, 21.4%, and 17.6% due to ion backscattering for 2, 4, and 6 keV implants in Ge, respectively. The electrical activation of ultra-shallow B{sup +} implants at 2, 4, and 6 keV to fluences ranging from 5.0 Multiplication-Sign 10{sup 13} to 5.0 Multiplication-Sign 10{sup 15} cm{sup -2} was studied using micro Hall effect measurements after annealing at 400-600 Degree-Sign C for 60 s. For both c-Ge and PA-Ge, a large fraction of the implanted dose is rendered inactive due to the formation of a presumable B-Ge cluster. The B lattice location in samples annealed at 400 Degree-Sign C for 60 s was characterized by channeling analysis with a 650 keV H{sup +} beam by utilizing the {sup 11}B(p, {alpha})2{alpha} nuclear reaction and confirmed the large fraction of off-lattice B for both c-Ge and PA-Ge. Within the investigated annealing range, no significant change in activation was observed. An increase in the fraction of activated dopant was observed with increasing energy which suggests that the surface proximity and the local point defect environment has a strong impact on B activation in Ge. The results suggest the presence of an inactive B-Ge cluster for ultra-shallow implants in both c-Ge and PA-Ge that remains stable upon annealing for temperatures up to 600 Degree-Sign C.

  16. Low-resistive and homogenous NiPt-silicide formation using ultra-low temperature annealing with microwave system for 22nm-node CMOS and beyond

    Microsoft Academic Search

    T. Yamaguchi; Y. Kawasaki; T. Yamashita; Y. Yamamoto; Y. Goto; J. Tsuchimoto; S. Kudo; K. Maekawa; M. Fujisawa; K. Asai

    2010-01-01

    A novel NiPt-silicide formation using microwave annealing (MWA) is proposed, and superior properties of NiPt silicide in ultra-shallow junction (USJ) are demonstrated for the first time. MWA is suitable for the thin NiPtSi formation with its stable and ultra-low temperature (less than 250 °C) heating. The anomalous Ni diffusion during the NiPtSi formation is considered to be suppressed because MW

  17. PULSION®: A Versatile 200 to 300 mm Bridge Tool Plasma Immersion Ion Implanter for Ultra-Shallow Doping and Nanotechology Applications.

    NASA Astrophysics Data System (ADS)

    Torregrosa, Frank; Etienne, Hasnaa; Sempere, Guillaume; Mathieu, Gilles; Roux, Laurent; Milesi, Frédéric; Gonzatti, Frédéric

    2008-11-01

    Thanks to the European Projects SEA-NET and PULLNANO, an industrial version of the IBS Plasma Ion Implantation tool has been installed in LETI for the fabrication of Ultra-Shallow Junctions for 45 and 32 nm CMOS on 200 and 300 mm wafers. In this paper, we present the main machine characteristics (layout, contamination, homogeneity, reproducibility, uptime) and we show that implanted wafers are compatible with the 32 nm nodes requirements. Then doping results (sheet resistance vs junction depth and leakage current) using several annealing technics are presented (laser, flash and spike anneals). In the second part of the paper, versatility of the tool is demonstrated with its use for other applications (3D doping, hydrogenation, solar cells…)

  18. Semiconductor junction formation by directed heat

    DOEpatents

    Campbell, Robert B. (Pittsburgh, PA)

    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.

  19. Medium energy ion scattering analysis of the evolution and annealing of damage and associated dopant redistribution of ultra shallow implants in Si

    NASA Astrophysics Data System (ADS)

    van den Berg, J. A.; Reading, M. A.; Armour, D. G.; Carter, G.; Zalm, P. C.; Bailey, P.; Noakes, T. C. Q.

    As junction depths in advanced semiconductor devices move to below 20 nm, the process of disorder evolution during ion implantation at ultra low energies becomes increasingly influenced by the surface. This may also hold for shallow regrowth and dopant redistribution processes during subsequent thermal annealing of the substrate. The investigation of these near-surface processes requires analytical techniques with a depth resolution of?1 nm. Medium energy ion scattering (MEIS) has the unique capability of simultaneously providing quantitative, high-resolution depth distributions of implant disorder (displaced Si lattice atoms) and of implanted atoms, albeit not of light species. We report here a comparative MEIS investigation into the growth mode of shallow disordered/amorphised layers during?1 keV B+ and 2.5 keV As+ ion implantation into Si. In both cases the growth of the damage depth profiles differs significantly from the energy deposition function, as it is strongly determined on the one hand by the proximity of the surface acting as a nucleation site for migrating point defects formed during implantation, which results in planar growth of the amorphous layer, and on the other by the dynamic annealing processes operating at room temperature. When such defect recombination processes are inhibited, e.g. for low dose, ultra shallow 200 eV B+ implants, MEIS shows that defect production yields exceeding the Kinchin-Pease model predictions are achieved. For As implants, a correlation is observed between the movement of the As and the depth of the growing, planar amorphous layer. Thermal annealing of As implanted samples at different temperatures and durations leads to solid phase epitaxial regrowth. During regrowth, MEIS shows that there is a close correlation between damage dissolution, the movement of nearly half of the As dopant into substitutional sites and the snowploughing of a fraction of the As in front of the advancing amorphous/crystalline interface leading to the formation of a less than 1 nm wide As pile-up layer trapped under the oxide.

  20. Low-Frequency Noise Characterization of Ultra-shallow Gate N-channel Junction Field

    E-print Network

    Technische Universiteit Delft

    high. No G-R noise was detected, but the devices yielded a high flicker noise component in noise onset the lowest limit of sensitivity. A large part of electronic systems operate in the RF frequency range, where noise sources are fully known, characterized, and their effect can be properly

  1. Fabrication of sub-40-nm p-n junctions for 0.18 micron MOS device applications using a cluster-tool-compatible, nanosecond thermal doping technique

    NASA Astrophysics Data System (ADS)

    Weiner, K. H.; McCarthy, A. M.

    1993-09-01

    In this paper, we introduced an alternative deep-submicrometer doping technology, Projection Gas Immersion Laser Doping (P-GILD). Representing the marriage of lithography and diffusion, P-GILD is a resistless, step-and-repeat doping process that utilizes excimer laser light patterned by a dielectric reticle to selectively heat and, thereby, dope regions of an integrated circuit. Results of physical and electrical characterization are presented for ultra-shallow p(sup +) (minus)n and n(sup +) (minus)p junctions produced by gas immersion laser doping (GILD), a phenomenologically identical technique that utilizes an aluminum contact mask rather than a dielectric reticle to pattern the beam. Junctions produced using GILD exhibit uniformly-doped, abrupt impurity profiles with no apparent defect formation in the silicon. Electrically, sheet and contact resistivities of the ultra-shallow junctions are less than 100(Omega)/sheet and 1 x 10(exp -6) (Omega)*sq cm, respectively, while n(sup +) (minus)p and p(sup +) (minus)n diodes exhibit nearly ideal forward bias behavior and reverse leakage current densities less than 5 nA/sq cm at -5V. Uniformity of both diode characteristics and sheet resistance for junctions produced by the step-and-repeat process is also shown to be better than (plus minus)5% across a 4-inch wafer.

  2. Fabrication of sub-40-nm p-n junctions for 0.18 {mu}m MOS device applications using a cluster-tool-compatible, nanosecond thermal doping technique

    SciTech Connect

    Weiner, K.H.; McCarthy, A.M.

    1993-09-20

    In this paper, we introduced an alternative deep-submicrometer doping technology, Projection Gas Immersion Laser Doping (P-GILD). Representing the marriage of lithography and diffusion, P-GILD is a resistless, step-and-repeat doping process that utilizes excimer laser light patterned by a dielectric reticle to selectively heat and, thereby, dope regions of an integrated circuit. Results of physical and electrical characterization are presented for ultra-shallow p{sup +} {minus}n and n{sup +} {minus}p junctions produced by gas immersion laser doping (GILD), a phenomenologically identical technique that utilizes an aluminum contact mask rather than a dielectric reticle to pattern the beam. Junctions produced using GILD exhibit uniformly-doped, abrupt impurity profiles with no apparent defect formation in the silicon. Electrically, sheet and contact resistivities of the ultra-shallow junctions are less than 100{Omega}/sheet and 1 {times} 10{sup {minus}6} {Omega}{sm_bullet}cm{sup 2}, respectively, while n{sup +} {minus}p and p{sup +} {minus}n diodes exhibit nearly ideal forward bias behavior and reverse leakage current densities less than 5 nA/cm{sup 2} at {minus}5V. Uniformity of both diode characteristics and sheet resistance for junctions produced by the step-and-repeat process is also shown to be better than {plus_minus}5% across a 4-inch wafer.

  3. Plasminogen activator inhibitor-1 regulates myoendothelial junction formation

    PubMed Central

    Heberlein, Katherine; Straub, Adam C.; Best, Angela K.; Greyson, Mark A.; Looft-Wilson, Robin C.; Sharma, Poonam R.; Meher, Akshaya; Leitinger, Norbert; Isakson, Brant E

    2010-01-01

    Rationale Plasminogen activator inhibitor-1 (PAI-1) is a biomarker for several vascular disease states; however, its target of action within the vessel wall is undefined. Objective Determine the ability of PAI-1 to regulate myoendothelial junction (MEJ) formation. Methods and Results Myoendothelial junctions are found throughout the vasculature linking endothelial cells (EC) and vascular smooth muscle cells (VSMC). Using a vascular cell co-culture (VCCC) we isolated MEJ fractions and performed two-dimensional differential gel electrophoresis. Mass spectrometry identified PAI-1 as being enriched within MEJ fractions, which we confirmed in vivo. In the VCCC, recombinant PAI-1 (rPAI-1) added to the EC monolayer significantly increased MEJs. Conversely, addition of a PAI-1 monoclonal antibody to the EC monolayer reduced the number of MEJs. This was also observed in vivo where mice fed a high fat diet had increased PAI-1 and MEJs and the number of MEJs in coronary arterioles of PAI-1?/? mice was significantly reduced when compared to C57Bl/6 mice. The presence of MEJs in PAI-1?/? coronary arterioles was restored when their hearts were transplanted into and exposed to the circulation of C57Bl/6 mice. Application of biotin-conjugated PAI-1 to the EC monolayer in vitro confirmed the ability of luminal PAI-1 to translocate to the MEJ. Functionally, phenylephrine-induced heterocellular calcium communication in the VCCC was temporally enhanced when rPAI-1 was present, and prolonged when PAI-1 was absent. Conclusion Our data implicate circulating PAI-1 as a key regulator of MEJ formation and a potential target for pharmacological intervention in diseases with vascular abnormalities (e.g., diabetes mellitus). PMID:20133900

  4. Rap1: a key regulator in cell-cell junction formation.

    PubMed

    Kooistra, Matthijs R H; Dubé, Nadia; Bos, Johannes L

    2007-01-01

    Rap1 is a Ras-like small GTPase that is activated by many extracellular stimuli and strongly implicated in the control of integrin-mediated cell adhesion. Recent evidence indicates that Rap1 also plays a key role in formation of cadherin-based cell-cell junctions. Indeed, inhibition of Rap1 generates immature adherens junctions, whereas activation of Rap1 tightens cell-cell junctions. Interestingly, Rap1 guanine nucleotide exchange factors, such as C3G and PDZ-GEF, are directly linked to E-cadherin or to other junction proteins. Furthermore, several junction proteins, such as afadin/AF6 and proteins controlling the actin cytoskeleton, function as effectors of Rap1. These findings point to a role of Rap1 in spatial and temporal control of cell-cell junction formation. PMID:17182900

  5. Adherens Junction Formation Inhibits Lentivirus Entry and Gene Transfer

    PubMed Central

    Padmashali, Roshan; You, Hui; Karnik, Nikhila; Lei, Pedro; Andreadis, Stelios T.

    2013-01-01

    Although cellular signaling pathways that affect lentivirus infection have been investigated, the role of cell-cell interactions in lentiviral gene delivery remains elusive. In the course of our studies we observed that lentiviral gene transfer was a strong function of the position of epithelial cells within colonies. While peripheral cells were transduced efficiently, cells in the center of colonies were resistant to gene transfer. In addition, gene delivery was enhanced significantly under culture conditions that disrupted adherens junctions (AJ) but decreased upon AJ formation. In agreement, gene knockdown and gain-of-function approaches showed that ?-catenin, a key component of the AJ complex prevented lentivirus gene transfer. Using a doxycycline regulatable system we showed that expression of dominant negative E-cadherin enhanced gene transfer in a dose-dependent manner. In addition, dissolution of AJ by doxycycline increased entry of lentiviral particles into the cell cytoplasm in a dose-dependent manner. Taken together our results demonstrate that AJ formation renders cells non-permissive to lentiviral gene transfer and may facilitate development of simple means to enhance gene delivery or combat virus infection. PMID:24236116

  6. Excess noise in MWIR photovoltaic detectors fabricated using a new junction formation technology

    Microsoft Academic Search

    Muhammad H. Rais; Charles A. Musca; John M. Dell; Jaroslaw Antoszewski; Brett D. Nener; Lorenzo Faraone

    1999-01-01

    The current-voltage characteristics measured over a wide temperature range are reported for HgCdTe mid-wavelength IR n-on-p photodiodes fabricated using a novel junction formation technology. The planar homojunction device junctions were formed on LPE grown vacancy doped HgCdTe using a reactive ion etching (RIE) plasma induced conversion process. The zero bias dynamic resistance - junction area product, RoA, was 4.6 X

  7. HgCdTe photovoltaic detectors fabricated using a new junction formation technology

    Microsoft Academic Search

    M. H Rais; C. A Musca; J. M Dell; J Antoszewski; B. D Nener; L Faraone

    2000-01-01

    The current–voltage characteristics measured over a wide temperature range are reported for HgCdTe mid-wavelength infrared n-on-p photodiodes fabricated using a novel junction formation technology. The planar homojunction device junctions were formed on LPE grown vacancy doped HgCdTe using a reactive ion etching (RIE) plasma induced conversion process. The zero bias dynamic resistance–junction area product, RoA, was 4.6×107?cm2 at 80K and

  8. Wnt4 participates in the formation of vertebrate neuromuscular junction.

    PubMed

    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

  9. Extremely Ultra-Shallow p+ -n Boron-Deposited Silicon Diodes

    E-print Network

    Technische Universiteit Delft

    targeting nm-shallow, ultra-abrupt, and highly-doped junctions with damage-free properties. Current nm radiation detection, which are demanded for advanced (double-exposure) lithography. High.e. the current level is the same as for deep junction counterparts. The B-deposition has very high selectivity

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

    PubMed

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

    2015-02-20

    During the self-assembly of different numbers of oligonucleotides comprising junctional DNA nanostructures, a change in environmental variables (e.g., temperature or salt concentration) has a substantial influence on the final products. Further, distinctive annealing temperatures of oligonucleotides are observed depending on the state of hybridization. Here, we present an evaluation of the annealing characteristics of oligonucleotides for the formation of a simple junctional DNA nanostructure using an annealing curve analysis. This method may be useful for analyzing the formation of complex junctional DNA nanostructures. PMID:25597993

  11. Estrogen and cyclic amp action, and the involvement of the cytoskeleton on gap junction formation in rat myometrium

    E-print Network

    Gaddy, Dana

    1985-01-01

    the synchronized contractions resulting in parturition. The basis for understanding the action of drugs and hormones on coordinated labor contractions must take into account not only the appearance of myometrial cell gap junctions, but also the effects... of the cytoskeleton (CSK) on rat myometrial gap junction formation was examined. A model was proposed and tested for the control of gap junction formation involving 1) estrogen- induced gap junction protein precursor synthesis and insertion into the plasma...

  12. Tight junction formation in cultured epithelial cells (MDCK)

    Microsoft Academic Search

    L. Gonzalez-Mariscal; B. Chfivez de Ramfrez; M. Cereijido

    1985-01-01

    Summary Synthesis and assembly of tight junctions are studied in monolayers of MDCK cells plated at a density sufficient for confluence, allowed to attach for 1 hr, and transferred to fresh media without cells containing or not Ca2+, 20 hr later, while monolayers with Ca2+ have fully developed junctions that confer an electrical resistance across of 346±51 O cm2, those

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

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Gerya, Taras; Burov, Evgueni

    2015-04-01

    Triple junctions are probably the most remarkable features of plate boundaries since their presence constitutes one of the major demonstrations of plate tectonics theory. Divergent (R-R-R) triple junctions (at 120° and T junctions) are particular ones since their stability depends on the exact values of the relative velocities of plate divergence and hence is strongly affected by plate rheology and processes of crustal accretion. The mechanisms of their formation and long-term steadiness are not well understood even though it is commonly accepted, generally based on common sense, that the geometry and stability of triple junctions should be related to the intuitively acceptable geometric considerations that 3-branch configurations should be "stable" over the time on a 3D Earth surface. That said, most plate boundaries are in fact 2D in terms that they involve only two plates, while junctions with 3 and more branches, if even mechanically not excluded, are generally short-lived and hence rarely observed at tectonic scale. Indeed, it has been long-time suggested that triple junctions result from evolution of short-lived quadruple junctions, yet, without providing a consistent mechanical explanation or experimental demonstration of this process, due to the rheological complexity of the lithosphere and that of strain localization and crustal accretion processes. For example, it is supposed that R-R-R junctions form as result of axisymmetric mantle upwellings. However, impingement of buoyant fluid on a non-pre-stressed lithosphere should result in multiple radial cracks, as is well known from previous analog and numerical experiments. In case of uni-directionally pre-stressed lithosphere, it has also shown that linear 2D rift structures should be formed. Therefore, a complete 3D thermos-mechanically consistent approach is needed to understand the processes of formation of multi-branch junctions. With this goal we here reproduce and study the processes of multi-branch junction formation and evolution by using high-resolution 3D numerical mechanical experiments that take into account realistic thermo-rheological structure and rheology of the lithosphere. We find that two major types of quadruple and triple junctions are formed under bi-directional or multidirectional far-field stress field: (i) plate rifting junctions are formed by the initial plate fragmentation and can be subsequently re-arranged into (ii) oceanic spreading junctions controlled by the new oceanic crust accretion. In particular, we document initial formation and destabilization of quadruple R-R-R-R junctions as initial plate rifting structures under bi-directional extension. In most cases, quadruple plate rifting junctions rapidly (typically within 1-2 Myr) evolve towards formation of two diverging triple oceanic spreading junctions connected by a linear spreading center lengthening with time. This configuration remains stable over long time scales. However, under certain conditions, quadruple junctions may also remain relatively stable. Asymmetric stretching results in various configurations, for example formation of "T-junctions" with trans-extensional components and combination of fast and slow spreading ridges. Combined with plume impingement, this scenario evolves in realistic patterns closely resembling observed plate dynamics. In particular, opening of the Red Sea and of the Afar rift system find a logical explanation within a single model. Numerical experiments also suggest that several existing oceanic spreading junctions form as the result of plate motions rearrangements after which only one of two plates spreading along the ridge become subjected to bi-directional spreading.

  15. Electrochemical formation of stable p-i-n junction in conjugated polymer thin films.

    PubMed

    Yu, Zhibin; Sun, Mingliang; Pei, Qibing

    2009-06-25

    Stable p-i-n junction was formed in polymer thin films by a facile electrochemical method. The polymer thin films contained an alkoxyphenyl substituted poly(1,4-phenylene vinylene), a cross-linkable liquid trimethylolpropane trimethacrylate (TMPTMA), and lithium trifluoromethane sulfonate at a weight ratio of 20:10:1. The thin films were sandwiched between an indium tin oxide anode and an aluminum cathode. During initial charging at 12 V, a p-i-n junction was formed in a similar fashion as reported in the polymer light-emitting electrochemical cells except that the junction did not relax during subsequent idling without external bias. TMPTMA was responsible in conducting the ions (dopants) during the formation of the junction. The junction stabilized as TMPTMA cured and lost its ionic conductivity. This mechanism is supported by the measurements of the electroluminescence behavior, the photovoltaic response and the AC impedance of the charged devices. The formation of the stable p-i-n junction improves the electroluminescence performance and photovoltaic efficiency compared to similar devices without such a junction. The polymer p-i-n junction devices exhibited current-voltage response characteristic of light-emitting diodes with turn-on time<5 mS. The luminance efficiency was 3.0 cd/A, and brightness was 450 Cd/m2 at 10 V. The same junction devices under 100 mW/cm(-2) AM1.5 solar illumination had an open-circuit voltage of 1.5 V and a short circuit current of 6 microA/cm2 with an over 460% enhancement on efficiency compared to the device without the junction. PMID:19485402

  16. Estrogen and cyclic amp action, and the involvement of the cytoskeleton on gap junction formation in rat myometrium 

    E-print Network

    Gaddy, Dana

    1985-01-01

    specialization known as the gap junction ( 12-14). There is an excellent correlation between the presence of gap junctions and physiological properties of cells including metabolic and electrotonic coupling ( 14). Without physiological measurements... in hypophysectomized rat myometrium. The role of cAI'iP in myometrial gap junction formation appears to be different than that reported for all other cell types. Disruption of microtubu les and microfi laments increased estradiol benzoate (E2B)-induced gap junction...

  17. Simultaneous junction formation using a directed energy light source

    Microsoft Academic Search

    R. B. Campbell; D. L. Meier

    1986-01-01

    A novel method has been devised for fabricating the emitter and back surface field junctions in solar cells. In this technique, dopants derived from liquid precursors are driven into the material using short time-high temperature heat pulses such as are obtained from rapid thermal annealing systems (''flash diffusion''). Solar cells, both p-base and n-base, have been produced using this method.

  18. Y-junction carbon nanocoils: synthesis by chemical vapor deposition and formation mechanism

    PubMed Central

    Ding, Er-Xiong; Wang, Jing; Geng, Hong-Zhang; Wang, Wen-Yi; Wang, Yan; Zhang, Ze-Chen; Luo, Zhi-Jia; Yang, Hai-Jie; Zou, Cheng-Xiong; Kang, Jianli; Pan, Lujun

    2015-01-01

    Y-junction carbon nanocoils (Y-CNCs) were synthesized by thermal chemical vapor deposition using Ni catalyst prepared by spray-coating method. According to the emerging morphologies of Y-CNCs, several growth models were advanced to elucidate their formation mechanisms. Regarding the Y-CNCs without metal catalyst in the Y-junctions, fusing of contiguous CNCs and a tip-growth mechanism are considered to be responsible for their formation. However, as for the Y-CNCs with catalyst presence in the Y-junctions, the formation can be ascribed to nanoscale soldering/welding and bottom-growth mechanism. It is found that increasing spray-coating time for catalyst preparation generates agglomerated larger nanoparticles strongly adhering to the substrate, resulting in bottom-growth of CNCs and appearance of the metal catalyst in the Y-junctions. In the contrary case, CNCs catalyzed by isolated smaller nanoparticles develop Y-junctions with an absence of metal catalyst by virtue of weaker adhesion of catalyst with the substrate and tip-growth of CNCs. PMID:26063127

  19. Y-junction carbon nanocoils: synthesis by chemical vapor deposition and formation mechanism.

    PubMed

    Ding, Er-Xiong; Wang, Jing; Geng, Hong-Zhang; Wang, Wen-Yi; Wang, Yan; Zhang, Ze-Chen; Luo, Zhi-Jia; Yang, Hai-Jie; Zou, Cheng-Xiong; Kang, Jianli; Pan, Lujun

    2015-01-01

    Y-junction carbon nanocoils (Y-CNCs) were synthesized by thermal chemical vapor deposition using Ni catalyst prepared by spray-coating method. According to the emerging morphologies of Y-CNCs, several growth models were advanced to elucidate their formation mechanisms. Regarding the Y-CNCs without metal catalyst in the Y-junctions, fusing of contiguous CNCs and a tip-growth mechanism are considered to be responsible for their formation. However, as for the Y-CNCs with catalyst presence in the Y-junctions, the formation can be ascribed to nanoscale soldering/welding and bottom-growth mechanism. It is found that increasing spray-coating time for catalyst preparation generates agglomerated larger nanoparticles strongly adhering to the substrate, resulting in bottom-growth of CNCs and appearance of the metal catalyst in the Y-junctions. In the contrary case, CNCs catalyzed by isolated smaller nanoparticles develop Y-junctions with an absence of metal catalyst by virtue of weaker adhesion of catalyst with the substrate and tip-growth of CNCs. PMID:26063127

  20. Formation of Y-junction carbon nanotubes by catalytic CVD of methane

    NASA Astrophysics Data System (ADS)

    Chai, Siang-Piao; Zein, Sharif Hussein Sharif; Mohamed, Abdul Rahman

    2006-11-01

    Y-junction carbon nanotubes were grown by catalytic CVD of methane at 700 ?C on NiO-CuO-MoO(7:2:1) (w/w/w)/SiO 2 catalyst. For comparison, NiO-CuO(8:2) (w/w)/SiO 2 and NiO-MoO(8:2) (w/w)/SiO 2 catalysts were tested for carbon nanotube formation. TEM analysis indicates that no Y-junction structures were formed with the latter two catalysts. This finding elucidates why the addition of a small amount of MoO to NiO-CuO/SiO 2 catalyst is crucial for enhancing the formation of Y-junction carbon nanotubes.

  1. From Plaque to Pretzel: Fold Formation and Acetylcholine Receptor Loss at the Developing Neuromuscular Junction

    Microsoft Academic Search

    Maria Julia Marques; Jeff W. Lichtman

    2000-01-01

    Although there has been progress in understanding the initial steps in the formation of synapses, less is known about their subsequent maturation (Sanes and Lichtman, 1999). Two alter- ations on the postsynaptic side of the mammalian neuromus- cular junction occur during early postnatal life: acetylcholine receptors (AChRs) disappear from parts of the developing junc- tion as all but one axonal

  2. IQGAP1 controls tight junction formation through differential regulation of claudin recruitment.

    PubMed

    Tanos, Barbara E; Perez Bay, Andres E; Salvarezza, Susana; Vivanco, Igor; Mellinghoff, Ingo; Osman, Mahasin; Sacks, David B; Rodriguez-Boulan, Enrique

    2015-03-01

    IQGAP1 is a scaffolding protein previously implicated in adherens junction formation. However, its role in the establishment or maintenance of tight junctions (TJs) has not been explored. We hypothesized that IQGAP1 could regulate TJ formation by modulating the expression and/or localization of junctional proteins, and we systematically tested this hypothesis in the model Madin-Darby canine kidney (MDCK) cell line. We find that IQGAP1 silencing enhances a transient increase in transepithelial electrical resistance (TER) observed during the early stages of TJ formation (Cereijido et al., 1978). Quantitative microscopy and biochemical experiments suggest that this effect of IQGAP1 on TJ assembly is accounted for by reduced expression and TJ recruitment of claudin 2, and increased TJ recruitment of claudin 4. Furthermore, we show that IQGAP1 also regulates TJ formation through its interactor CDC42, because IQGAP1 knockdown increases the activity of the CDC42 effector JNK and dominant-negative CDC42 prevents the increase in TER caused by IQGAP1 silencing. Hence, we provide evidence that IQGAP1 modulates TJ formation by a twofold mechanism: (1) controlling the expression and recruitment of claudin 2 and recruitment of claudin 4 to the TJ, and (2) transient inhibition of the CDC42-JNK pathway. PMID:25588839

  3. Effect of geometry on droplet formation in the squeezing regime in a microfluidic T-junction

    Microsoft Academic Search

    Amit Gupta; Ranganathan Kumar

    2010-01-01

    In the surface tension-dominated microchannel T-junction, droplets can be formed as a result of the mixing of two dissimilar,\\u000a immiscible fluids. This article presents results for very low Capillary numbers and different flow rates of the continuous\\u000a and dispersed phases. Through three-dimensional lattice Boltzmann-based simulations, the mechanism of the formation of “plugs”\\u000a in the squeezing regime has been examined and

  4. The Triple-Repeat Protein Anakonda Controls Epithelial Tricellular Junction Formation in Drosophila.

    PubMed

    Byri, Sunitha; Misra, Tvisha; Syed, Zulfeqhar A; Bätz, Tilmann; Shah, Jimit; Boril, Lukas; Glashauser, Jade; Aegerter-Wilmsen, Tinri; Matzat, Till; Moussian, Bernard; Uv, Anne; Luschnig, Stefan

    2015-06-01

    In epithelia, specialized tricellular junctions (TCJs) mediate cell contacts at three-cell vertices. TCJs are fundamental to epithelial biology and disease, but only a few TCJ components are known, and how they assemble at tricellular vertices is not understood. Here we describe a transmembrane protein, Anakonda (Aka), which localizes to TCJs and is essential for the formation of tricellular, but not bicellular, junctions in Drosophila. Loss of Aka causes epithelial barrier defects associated with irregular TCJ structure and geometry, suggesting that Aka organizes cell corners. Aka is necessary and sufficient for accumulation of Gliotactin at TCJs, suggesting that Aka initiates TCJ assembly by recruiting other proteins to tricellular vertices. Aka's extracellular domain has an unusual tripartite repeat structure that may mediate self-assembly, directed by the geometry of tricellular vertices. Conversely, Aka's cytoplasmic tail is dispensable for TCJ localization. Thus, extracellular interactions, rather than TCJ-directed intracellular transport, appear to mediate TCJ assembly. PMID:25982676

  5. Dopant Dose Metrology for Ultra-Shallow Implanted Wafers using Electron-Induced X-Ray Spectrometry at Pattern-Size Scale

    SciTech Connect

    Staub, Pierre-F.; Hombourger, Chrystel [CAMECA, 103 Bd. St-Denis, 92403, Courbevoie cedex (France)

    2005-09-09

    In the past few years a new technique has been developed and optimized at Cameca to achieve the precise dose monitoring of ultra-shallow implants thanks to Low Energy X-Ray Emission Spectrometry. An instrument is now proposed, called Shallow Probe, for both Factory and Laboratory applications, allying high throughput (a few wafers per hour for full 300mm-200mm wafer mapping), high precision and stability (sub 1%) as well as high spatial resolution to address cheap-size measurements (<60{mu}m)

  6. Dopant Dose Metrology for Ultra-Shallow Implanted Wafers using Electron-Induced X-Ray Spectrometry at Pattern-Size Scale

    NASA Astrophysics Data System (ADS)

    Staub, Pierre-F.; Hombourger, Chrystel

    2005-09-01

    In the past few years a new technique has been developed and optimized at Cameca to achieve the precise dose monitoring of ultra-shallow implants thanks to Low Energy X-Ray Emission Spectrometry. An instrument is now proposed, called Shallow Probe, for both Factory and Laboratory applications, allying high throughput (a few wafers per hour for full 300mm-200mm wafer mapping), high precision and stability (sub 1%) as well as high spatial resolution to address cheap-size measurements (<60?m).

  7. An intact connexin N-terminus is required for function but not gap junction formation

    PubMed Central

    Kyle, John W.; Minogue, Peter J.; Thomas, Bettina C.; Lopez Domowicz, Denise A.; Berthoud, Viviana M.; Hanck, Dorothy A.; Beyer, Eric C.

    2009-01-01

    Summary The cytoplasmic N-termini of connexins have been implicated in protein trafficking, oligomerization and channel gating. To elucidate the role of the N-terminus in connexin37 (CX37), we studied mutant constructs containing partial deletions of its 23 N-terminal amino acids and a construct with a complete N-terminus in which residues 2–8 were replaced with alanines. All mutants containing nine or more N-terminal amino acids form gap junction plaques in transiently transfected HeLa cells, whereas most of the longer deletions do not. Although wild-type CX37 allowed intercellular transfer of microinjected neurobiotin in HeLa cells and formed conducting hemichannels in Xenopus oocytes, none of the mutant constructs tested show evidence of channel function. However, in coexpression experiments, N-terminal mutants that formed gap junction plaques potently inhibit hemichannel conductance of wild-type CX37 suggesting their co-oligomerization. We conclude that as much as half the length of the connexin N-terminus can be deleted without affecting formation of gap junction plaques, but an intact N-terminus is required for hemichannel gating and intercellular communication. PMID:18664489

  8. Conserved Domains of the Nullo Protein Required for Cell-Surface Localization and Formation of Adherens Junctions

    PubMed Central

    Hunter, Christine; Sung, Patricia; Schejter, Eyal D.; Wieschaus, Eric

    2002-01-01

    During cellularization, the Drosophila melanogaster embryo undergoes a transition from syncytial to cellular blastoderm with the de novo generation of a polarized epithelial sheet in the cortex of the embryo. This process couples cytokinesis with the establishment of apical, basal, and lateral membrane domains that are separated by two spatially distinct adherens-type junctions. In nullo mutant embryos, basal junctions fail to form at the onset of cellularization, leading to the failure of cleavage furrow invagination and the generation of multinucleate cells. Nullo is a novel protein that appears to stabilize the initial accumulation of cadherins and catenins as they form a mature basal junction. In this article we characterize a nullo homologue from D. virilis and identify conserved domains of Nullo that are required for basal junction formation. We also demonstrate that Nullo is a myristoylprotein and that the myristate group acts in conjunction with a cluster of basic amino acids to target Nullo to the plasma membrane. The membrane association of Nullo is required in vivo for its role in basal junction formation and for its ability to block apical junction formation when ectopically expressed during late cellularization. PMID:11809829

  9. Formation of adherens junctions leads to the emergence of a tissue-level tension in epithelial monolayers

    PubMed Central

    Harris, Andrew R.; Daeden, Alicia; Charras, Guillaume T.

    2014-01-01

    ABSTRACT Adherens junctions and desmosomes integrate the cytoskeletons of adjacent cells into a mechanical syncitium. In doing so, intercellular junctions endow tissues with the strength needed to withstand the mechanical stresses encountered in normal physiology and to coordinate tension during morphogenesis. Though much is known about the biological mechanisms underlying junction formation, little is known about how tissue-scale mechanical properties are established. Here, we use deep atomic force microscopy (AFM) indentation to measure the apparent stiffness of epithelial monolayers reforming from dissociated cells and examine which cellular processes give rise to tissue-scale mechanics. We show that the formation of intercellular junctions coincided with an increase in the apparent stiffness of reforming monolayers that reflected the generation of a tissue-level tension. Tension rapidly increased, reaching a maximum after 150?min, before settling to a lower level over the next 3?h as monolayers established homeostasis. The emergence of tissue tension correlated with the formation of adherens junctions but not desmosomes. As a consequence, inhibition of any of the molecular mechanisms participating in adherens junction initiation, remodelling and maturation significantly impeded the emergence of tissue-level tension in monolayers. PMID:24659804

  10. Phase segregation, Cu migration and junction formation in Cu(In, Ga)Se{_2}

    NASA Astrophysics Data System (ADS)

    Herberholz, R.; Rau, U.; Schock, H. W.; Haalboom, T.; Gödecke, T.; Ernst, F.; Beilharz, C.; Benz, K. W.; Cahen, D.

    1999-05-01

    A reinvestigation of the phase diagram of the Cu In Se system along the quasi-binary cut In2Se3 Cu2Se reveals an existence range of the chalcopyrite ?-phase that is much narrower than commonly accepted. The presence of 0.1% of Na or replacement of In by Ga at the at.% level widens the existence range of the ?-phase, towards In- and Ga-rich compositions. We also investigate the interplay between phase segregation and junction formation in polycrystalline Cu(In, Ga)Se2 films. Here, we attribute the band bending observed at bare surfaces of the films to a positively charged surface acting as a driving force for the formation of a Cu-poor surface defect layer via Cu-electromigration. The electrical properties of this defect layer are different from those found for the bulk ?-phase. We suggest that Cu-depletion is self-limited at the observed In/(In+Cu) surface composition of 0.75 because further Cu-depletion would require a structural transformation. Capacitance measurements reveal two types of junction metastabilities: one resulting from local defect relaxation, invoked to explain a light-induced increase of the open-circuit voltage of Cu(In, Ga)Se2 solar cells, and one due to Cu-electromigration.

  11. Quantitative prediction of junction leakage in bulk-technology CMOS devices

    NASA Astrophysics Data System (ADS)

    Duffy, R.; Heringa, A.; Venezia, V. C.; Loo, J.; Verheijen, M. A.; Hopstaken, M. J. P.; van der Tak, K.; de Potter, M.; Hooker, J. C.; Meunier-Beillard, P.; Delhougne, R.

    2010-03-01

    Junction leakage becomes more significant as metal-oxide-semiconductor (MOS) technologies scale down in bulk-silicon. In this work we quantify the four key elements to junction leakage generation through a combination of experiment and device simulation. These elements are: (i) ultra-shallow junction steepness, (ii) channel and pocket concentrations, (iii) junction curvature, and (iv) the presence of residual defects. We first characterize n +/p and p +/n diodes to quantify how changes in doping profiles affect reverse bias leakage. Diodes with end-of-range (EOR) silicon defects intentionally located in the junction depletion region are also characterized to quantify their contribution. This feeds into a device simulation study to gain insight in the experimental results and in the capabilities of available physical models. Thereafter simulation is used to predict leakage in future generation bulk-silicon MOS devices. In summary, band-to-band tunneling (BBT) due to aggressively scaled doping profiles and trap-assisted tunneling (TAT) due to the increased presence of defects make off-state low-standby-power leakage targets difficult to meet. With the increase of junction leakage from aggressively scaled ultra-shallow junctions, the assumption that the subthreshold leakage component dominates off-state current is no longer valid.

  12. Epithelial junction formation requires confinement of Cdc42 activity by a novel SH3BP1 complex

    PubMed Central

    Elbediwy, Ahmed; Zihni, Ceniz; Terry, Stephen J.; Clark, Peter

    2012-01-01

    Epithelial cell–cell adhesion and morphogenesis require dynamic control of actin-driven membrane remodeling. The Rho guanosine triphosphatase (GTPase) Cdc42 regulates sequential molecular processes during cell–cell junction formation; hence, mechanisms must exist that inactivate Cdc42 in a temporally and spatially controlled manner. In this paper, we identify SH3BP1, a GTPase-activating protein for Cdc42 and Rac, as a regulator of junction assembly and epithelial morphogenesis using a functional small interfering ribonucleic acid screen. Depletion of SH3BP1 resulted in loss of spatial control of Cdc42 activity, stalled membrane remodeling, and enhanced growth of filopodia. SH3BP1 formed a complex with JACOP/paracingulin, a junctional adaptor, and CD2AP, a scaffolding protein; both were required for normal Cdc42 signaling and junction formation. The filamentous actin–capping protein CapZ also associated with the SH3BP1 complex and was required for control of actin remodeling. Epithelial junction formation and morphogenesis thus require a dual activity complex, containing SH3BP1 and CapZ, that is recruited to sites of active membrane remodeling to guide Cdc42 signaling and cytoskeletal dynamics. PMID:22891260

  13. PAR6B is required for tight junction formation and activated PKC? localization in breast cancer.

    PubMed

    Cunliffe, Heather E; Jiang, Yuan; Fornace, Kimberly M; Yang, Fan; Meltzer, Paul S

    2012-01-01

    Dysregulation of mechanisms that govern the control of epithelial cell polarity, morphology and plasticity are emerging as key processes in tumor progression. In this study we report amplification and overexpression of PAR6B, an essential component in epithelial cell tight junction (TJ) formation and maintenance of apico-basal polarity, in breast cancer cell lines. Analysis of chromosome 20q13.13 in 11 breast cancer cell lines by fluorescence in situ hybridization (FISH) identified a novel small amplicon centered at PARD6B in 5 cell lines, with copy number ranging from 7 to 27. The presence of the PARD6B amplicon correlated with PARD6B transcript and PAR6B protein abundance. Expression of related isoforms PARD6A and PARD6G were detectable at significantly lower levels. PARD6B overexpression correlated with TJ network formation in cultured cell monolayers. SiRNA-mediated inhibition of PAR6B in MCF7 resulted in loss of TJ assembly and membrane localization of atypical PKC? (aPKC), but did not affect adherens junction formation. SiRNA-mediated inhibition of CDC42 in MCF7 also resulted in loss of TJ networks, confirming the requirement of a complete PAR6-aPKC-CDC42-PAR3 complex to activate and stabilize TJs. Immunohistochemical analysis of PAR6B expression on breast tumor microarrays indicated exquisite epithelial cell-specificity. Few quantitative differences in staining were observed between normal epithelium and adjacent tumor margins. However staining appeared reduced and cytoplasmic in more poorly differentiated tumors. We propose that quantitative imbalances in the components of pathways governing normal epithelial cell polarity arising from gain or loss of function may radically alter epithelial cell architecture and contribute to tumor progression. PMID:22957302

  14. MuSK frizzled-like domain is critical for mammalian neuromuscular junction formation and maintenance.

    PubMed

    Messéant, Julien; Dobbertin, Alexandre; Girard, Emmanuelle; Delers, Perrine; Manuel, Marin; Mangione, Francesca; Schmitt, Alain; Le Denmat, Dominique; Molgó, Jordi; Zytnicki, Daniel; Schaeffer, Laurent; Legay, Claire; Strochlic, Laure

    2015-03-25

    The muscle-specific kinase MuSK is one of the key molecules orchestrating neuromuscular junction (NMJ) formation. MuSK interacts with the Wnt morphogens, through its Frizzled-like domain (cysteine-rich domain [CRD]). Dysfunction of MuSK CRD in patients has been recently associated with the onset of myasthenia, common neuromuscular disorders mainly characterized by fatigable muscle weakness. However, the physiological role of Wnt-MuSK interaction in NMJ formation and function remains to be elucidated. Here, we demonstrate that the CRD deletion of MuSK in mice caused profound defects of both muscle prepatterning, the first step of NMJ formation, and synapse differentiation associated with a drastic deficit in AChR clusters and excessive growth of motor axons that bypass AChR clusters. Moreover, adult MuSK?CRD mice developed signs of congenital myasthenia, including severe NMJs dismantlement, muscle weakness, and fatigability. We also report, for the first time, the beneficial effects of lithium chloride, a reversible inhibitor of the glycogen synthase kinase-3, that rescued NMJ defects in MuSK?CRD mice and therefore constitutes a novel therapeutic reagent for the treatment of neuromuscular disorders linked to Wnt-MuSK signaling pathway deficiency. Together, our data reveal that MuSK CRD is critical for NMJ formation and plays an unsuspected role in NMJ maintenance in adulthood. PMID:25810523

  15. Formation of the A/B cis ring junction of ecdysteroids in the locust, Schistocerca gregaria.

    PubMed Central

    Davies, T G; Dinan, L N; Lockley, W J; Rees, H H; Goodwin, T W

    1981-01-01

    1. The mechanism of formation of the A/B cis ring junction of ecdysteroids in the locust Schistocerca gregaria, was investigated by incorporation of [4-14C,3 alpha-3H], [4-14C,4 alpha-3H] and [4-14C,4 beta-3H]cholesterol into 20-hydroxyecdysone in fifth-instar larvae and into ecdysteroid conjugates in ovaries of maturing adult females. 2. In both systems there was retention of the 4 alpha-3H atom in the ecdysteroid and elimination of the 3 alpha- and 4 beta-3H atoms. 3. The 3H retained in the ecdysone formed from [4 alpha-3H]cholesterol in the ovarian system was probably located at C-4. The results are interpreted by postulating the involvement of a 3-oxo-delta 4 intermediate in ecdysteroid biosynthesis in insects. PMID:7305992

  16. Laser annealing of ion implanted CZ silicon for solar cell junction formation

    NASA Technical Reports Server (NTRS)

    Katzeff, J. S.

    1981-01-01

    The merits of large spot size pulsed laser annealing of phosphorus implanted, Czochralski grown silicon for function formation of solar cells are evaluated. The feasibility and requirements are also determined to scale-up a laser system to anneal 7.62 cm diameter wafers at a rate of one wafer/second. Results show that laser annealing yields active, defect-free, shallow junction devices. Functional cells with AM 1 conversion efficiencies up to 15.4% for 2 x 2 cm and 2 x 4 cm sizes were attained. For larger cells, 7.62 cm dia., conversion efficiencies ranged up to 14.5%. Experiments showed that texture etched surfaces are not compatible with pulsed laser annealing due to the surface melting caused by the laser energy. When compared with furnace annealed cells, the laser annealed cells generally exhibited conversion efficiencies which were equal to or better than those furnace annealed. In addition, laser annealing has greater throughput potential.

  17. Nonreceptor Tyrosine Kinase c-Yes Interacts with Occludin during Tight Junction Formation in Canine Kidney Epithelial Cells

    PubMed Central

    Chen, Yan-Hua; Lu, Qun; Goodenough, Daniel A.; Jeansonne, Beverly

    2002-01-01

    Occludin is an integral membrane protein that is tyrosine phosphorylated when localized at tight junctions. When Ca2+ was depleted from the culture medium, occludin tyrosine phosphorylation was diminished from Madin-Darby canine kidney epithelial cells in 2 min. This dephosphorylation was correlated with a significant reduction in transepithelial electrical resistance (TER), indicating a global loss of the tight junction barrier function. Reconstitution of Ca2+ resulted in a robust tyrosine rephosphorylation of occludin that was temporally associated with an increase in TER. Moreover, we demonstrate in this study that occludin was colocalized with the nonreceptor tyrosine kinase c-Yes at cell junction areas and formed an immunoprecipitable complex with c-Yes in vivo. This complex dissociated when the cells were incubated in medium without Ca2+ or treated with a c-Yes inhibitor, CGP77675. In the presence of CGP77675 after Ca2+ repletion, occludin tyrosine phosphorylation was completely abolished and both tight junction formation and the increase of the TER were inhibited. Our study thus provides strong evidence that occludin tyrosine phosphorylation is tightly linked to tight junction formation in epithelial cells, and that the nonreceptor tyrosine kinase c-Yes is involved in the regulation of this process. PMID:11950934

  18. Cell-cell junction formation: the role of Rap1 and Rap1 guanine nucleotide exchange factors.

    PubMed

    Pannekoek, Willem-Jan; Kooistra, Matthijs R H; Zwartkruis, Fried J T; Bos, Johannes L

    2009-04-01

    Rap proteins are Ras-like small GTP-binding proteins that amongst others are involved in the control of cell-cell and cell-matrix adhesion. Several Rap guanine nucleotide exchange factors (RapGEFs) function to activate Rap. These multi-domain proteins, which include C3G, Epacs, PDZ-GEFs, RapGRPs and DOCK4, are regulated by various different stimuli and may function at different levels in junction formation. Downstream of Rap, a number of effector proteins have been implicated in junctional control, most notably the adaptor proteins AF6 and KRIT/CCM1. In this review, we will highlight the latest findings on the Rap signaling network in the control of epithelial and endothelial cell-cell junctions. PMID:19159611

  19. Regional changes of AQP0-dependent square array junction and gap junction associated with cortical cataract formation in the Emory mutant mouse.

    PubMed

    Biswas, Sondip K; Brako, Lawrence; Gu, Sumin; Jiang, Jean X; Lo, Woo-Kuen

    2014-10-01

    The Emory mutant mouse has been widely used as an animal model for human senile cataract since it develops late-onset hereditary cataract. Here, we focus on the regional changes of aquaporin-0 (AQP0) and connexins that are associated with the cortical cataract formation in the Emory mutant mice. Emory mutant and CFW wild-type mice at age 1-16 months were used in this study. By using an established photography system with dissecting microscopy, the opacities were first detected at the anterior or posterior lens center surface in Emory mice at age 7 months, and gradually extended toward the equator during the 16 months examined. Scanning EM verified that disorganized and fragmented fiber cells were associated with the areas of opacities within approximately 200 ?m from the lens surface, indicating that Emory mouse cataracts belong to the cortical cataracts. Freeze-fracture TEM further confirmed that cortical cataracts exhibited extensive wavy square array junctions, small gap junctions and globules. Immunofluorescence analysis showed that in contrast to the high labeling intensity of AQP0-loop antibody, the labeling of AQP0 C-terminus antibody was decreased considerably in superficial fibers in Emory cataracts. Similarly, a significant decrease in the labeling of the antibody against Cx50 C-terminus, but not Cx46 C-terminus, occurred in superficial and outer cortical fibers in Emory cataracts. Western blotting further revealed that the C-termini of both AQP0 and Cx50 in Emory cataracts were decreased to over 50% to that of the wild-type. Thus, this systematic study concludes that the Emory mouse cataract belongs to the cortical cataract which is due to regional breakdown of superficial fibers associated with formation of AQP0-dependent wavy square array junctions, small gap junctions and globules. The marked decreases of the C-termini of both AQP0 and Cx50 in the superficial fibers may disturb the needed interaction between these two proteins during fiber cell differentiation and thus play a role in the cortical cataract formation in Emory mutant mice. PMID:25088353

  20. New doping technology-plasma doping-for next generation CMOS process with ultra shallow junction-LSI yield and surface contamination issues

    Microsoft Academic Search

    M. Takase; B. Mizuno

    1997-01-01

    Plasma doping method as a candidate to alternate conventional ion implantation has been proposed. LSI yield and surface contamination were confirmed for realizing mass production. This method has ultra low energy capability with very high throughput

  1. Nano-welding and junction formation in hydrogen titanate nanowires by low-energy nitrogen ion irradiation

    NASA Astrophysics Data System (ADS)

    Dhal, Satyanarayan; Chatterjee, Shyamal; Sarkar, Subhrangsu; Tribedi, Lokesh C.; Bapat, Rudheer; Ayyub, Pushan

    2015-06-01

    Crystalline hydrogen titanate (H2Ti3O7) nanowires were irradiated with N+ ions of different energies and fluences. Scanning electron microscopy reveals that at relatively lower fluence the nanowires are bent and start to adhere strongly to one another as well as to the silicon substrate. At higher fluence, the nanowires show large-scale welding and form a network of mainly ‘X’ and ‘Y’ junctions. Transmission electron microscopy and Raman scattering studies confirm a high degree of amorphization of the nanowire surface after irradiation. We suggest that while ion-irradiation induced defect formation and dangling bonds may lead to chemical bonding between nanowires, the large scale nano-welding and junction network formation can be ascribed to localized surface melting due to heat spike. Our results demonstrate that low energy ion irradiation with suitable choice of fluence may provide an attractive route to the formation and manipulation of large-area nanowire-based devices.

  2. Physical understanding of cryogenic implant benefits for electrical junction stability

    SciTech Connect

    Adeni Khaja, Fareen; Colombeau, Benjamin; Thanigaivelan, Thirumal; Ramappa, Deepak; Henry, Todd [Applied Materials-Varian Semiconductor Equipment, 35 Dory Road, Gloucester, Massachusetts 01930 (United States)

    2012-03-12

    We investigate the effect of cryogenic temperature implants on electrical junction stability for ultra shallow junction applications for sub-32 nm technology nodes and beyond. A comprehensive study was conducted to gain physical understanding of the impact of cryogenic temperature implants on dopant-defect interactions. Carborane (C{sub 2}B{sub 10}H{sub 12}) molecule, a potential alternative to monomer boron was implanted in carbon preamorphized silicon substrates at cryogenic implant temperatures. Results indicate implants at cryogenic temperatures increase dopant activation with reduced diffusion, resulting in lower sheet resistance for a lower junction depth. Further, this study emphasizes the benefits of co-implants performed at cryogenic temperatures as alternative to traditional preamorphizing implants.

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    Aims: For many years feedback processes generated by OB-stars in molecular clouds, including expanding ionization fronts, stellar winds, or UV-radiation, have been proposed to trigger subsequent star formation. However, hydrodynamic models including radiation and gravity show that UV-illumination has little or no impact on the global dynamical evolution of the cloud. Instead, gravitational collapse of filaments and/or merging of filamentary structures can lead to building up dense high-mass star-forming clumps. However, the overall density structure of the cloud has a large influence on this process, and requires a better understanding. Methods: The Rosette molecular cloud, irradiated by the NGC 2244 cluster, is a template region for triggered star-formation, and we investigated its spatial and density structure by applying a curvelet analysis, a filament-tracing algorithm (DisPerSE), and probability density functions (PDFs) on Herschel column density maps, obtained within the HOBYS key program. Results: The analysis reveals not only the filamentary structure of the cloud but also that all known infrared clusters except one lie at junctions of filaments, as predicted by turbulence simulations. The PDFs of sub-regions in the cloud show systematic differences. The two UV-exposed regions have a double-peaked PDF we interprete as caused by shock compression, while the PDFs of the center and other cloud parts are more complex, partly with a power-law tail. A deviation of the log-normal PDF form occurs at AV ? 9m for the center, and around 4m for the other regions. Only the part of the cloud farthest from the Rosette nebula shows a log-normal PDF. Conclusions: The deviations of the PDF from the log-normal shape typically associated with low- and high-mass star-forming regions at AV ? 3-4m and 8-10m, respectively, are found here within the very same cloud. This shows that there is no fundamental difference in the density structure of low- and high-mass star-forming regions. We conclude that star-formation in Rosette - and probably in high-mass star-forming clouds in general - is not globally triggered by the impact of UV-radiation. Moreover, star formation takes place in filaments that arose from the primordial turbulent structure built up during the formation of the cloud. Clusters form at filament mergers, but star formation can be locally induced in the direct interaction zone between an expanding H II-region and the molecular cloud. Figures 4-6 and Appendices A-C are available in electronic form at http://www.aanda.org

  4. Controlled formation of GaAs pn junctions during hydride vapor phase epitaxy of GaAs

    NASA Astrophysics Data System (ADS)

    Schulte, Kevin L.; Rance, William L.; Reedy, Robert C.; Ptak, Aaron J.; Young, David L.; Kuech, Thomas F.

    2012-08-01

    Interface formation in HVPE GaAs was investigated through the growth of multilayer test structures with alternately doped and undoped layers and subsequently, pn diode devices. Two growth procedures were used in device formation: continuous growth of all layers, and a growth interruption with simultaneous equilibration of new gas flows for subsequent layers. These junctions were probed using SIMS to determine the doping profiles and impurity incorporation near the interfaces and throughout the bulk of the layers. The junction I-V characteristics were measured with and without illumination to correlate the junction properties with the measured photovoltaic performance. It was discovered that the use of a growth interruption leads to doping transitions up to 6x narrower than samples grown without interruption. The growth interruption leads to an interfacial Si spike that is not observed in the uninterrupted samples during growth of GaAs doped with silane. This spike does not appear to degrade either the material quality or pn junction quality, and pn diodes grown with interruption have exhibited enhanced device efficiencies under solar simulation compared with devices grown without interruption, reaching efficiencies of up to 9.2% without the use of antireflective coatings.

  5. Cooperativity between trans and cis interactions in cadherin-mediated junction formation

    E-print Network

    Ben-Shaul, Avinoam

    , 10032; and e Institute of Chemistry and the Fritz Haber Research Center, Hebrew University, Jerusalem and a condensed ordered 2D junction formed by dimers alone is a cooperative process involving both trans and cis of cadherins into junctions. To elu- cidate the physical principles underlying this process, we present

  6. New aspects of phase segregation and junction formation in CuInSe{sub 2}

    SciTech Connect

    Herberholz, R.; Schock, H.W.; Rau, U. [Univ. Stuttgart (Germany). Inst. fuer Physikalische Elektronik] [and others

    1997-12-31

    A reinvestigation of the phase diagram on the quasi-binary Cu{sub 2}-Se-In{sub 2}Se{sub 3} cut reveals a much narrower existence range of the chalcopyrite {alpha}-phase as compared to previous phase diagrams towards In- and Ga-rich compositions. The presence of Na or replacement of In by Ga inhibits defect ordering and widens the existence range of the {alpha}-phase. Capacitance measurements reveal two types of junction metastabilities in Cu (In,Ga)Se{sub 2} solar cells. An increase of the capacitance after electron injection into the space charge region most likely relates to a local defect reaction. A change of the spatial distribution of charges after annealing under applied bias points to Cu-electromigration. The authors suggest that the potential determined by a positive surface charge and Cu-migration assist the formation of the Cu-poor (ODC) surface. This mechanism also causes distinct differences in the properties of the Cu-poor surface and the bulk {beta}-phase.

  7. Atomistic mechanics and formation mechanism of metal-molecule-metal junctions.

    PubMed

    Tsutsui, Makusu; Taniguchi, Masateru; Kawai, Tomoji

    2009-06-01

    The present Letter reports a quantitative analysis of contact mechanics in metal-molecule-metal junctions at a single atom/molecule level through investigating their lifetime at cryogenic temperature. We elucidated that the force breaking mechanism of atomic/molecular junctions is stretching speed dependent, attributed to suppression of contact structure relaxation processes at high strain rate conditions. We also provide solid evidence that strain exerted in the preformation stage of molecular junctions poses extra strain energy that accelerates their eventual fracture. Nonetheless, we find that single-molecule junctions subjected to mechanical stretching at 0.6 pm/s can be held for approximately 100 s on average at 77 K and for a much prolonged period when freezing the elongation after forming the molecular junctions by virtue of moderate thermal destabilizations, the fluctuation-free condition of which provides optimal experimental platform for performing reliable measurements of single molecule electron transport properties. PMID:19507890

  8. 1\\/f Noise in HgCdTe MWIR Photovoltaic Detectors Fabricated Using a Novel Junction Formation Technology

    Microsoft Academic Search

    M. H. Rais; C. A. Musca; J. M. Dell; J. Antoszewski; B. D. Nener; L. Faraone

    1999-01-01

    Extensive temperature dependent noise measurements for mid-wavelength infrared (MWIR) Hg1_xCdxTe photodiodes fabricated using a new junction formation process are presented for the first time. The planar n­ on-p photodiodes were fabricated using a new reactive ion etching (RIE) based p-to-n type conversion process_ The fabricated de­ vices show state of the art performance with RoA=4.6xl0 7 Qcm2 at 80K. Low

  9. Cell–cell junction formation: The role of Rap1 and Rap1 guanine nucleotide exchange factors

    Microsoft Academic Search

    Willem-Jan Pannekoek; Matthijs R. H. Kooistra; Fried J. T. Zwartkruis; Johannes L. Bos

    2009-01-01

    Rap proteins are Ras-like small GTP-binding proteins that amongst others are involved in the control of cell–cell and cell–matrix adhesion. Several Rap guanine nucleotide exchange factors (RapGEFs) function to activate Rap. These multi-domain proteins, which include C3G, Epacs, PDZ-GEFs, RapGRPs and DOCK4, are regulated by various different stimuli and may function at different levels in junction formation. Downstream of Rap,

  10. Junction formation of CuInSe 2 with CdS: A comparative study of “dry” and “wet” interfaces

    Microsoft Academic Search

    R. Hunger; M. V. Lebedev; K. Sakurai; T. Schulmeyer; Th. Mayer; A. Klein; S. Niki; W. Jaegermann

    2007-01-01

    The junction formation of polycrystalline CuInSe2 absorbers (CIS) with thermally evaporated CdS was investigated by high-resolution synchrotron X-ray photoelectron spectroscopy. The chemistry and electronics of the interfaces of Cd partial electrolyte treated CIS (“wet” processed) and clean, decapped CIS (“dry” processed) were compared. A valence band offset of 0.96(10) eV was determined in both cases. The Cd(Se,OH) surface layer induced by

  11. Interface dynamics during the formation of bubbles and droplets at microfluidic junctions

    NASA Astrophysics Data System (ADS)

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

    2008-11-01

    We describe how the size of bubbles and droplets -- created at microfluidic T-junctions -- scales with the shape of the junction. The shape of the junction plays a crucial role as it sets the shape of the bubble. Due to interfacial tensions, the bubble cannot conform to the channel walls. Hence, fluid upstream and downstream of the bubble communicates via so-called gutters between the wall and the bubble. In this work, we show that -- depending on the Capillary number and the ratio between the height and width of the main channel -- significant flows of carrier liquid by-pass the bubble during its growth. We compared our experiments, in which we measured the interface evolution from high-speed micrographs for junctions with different shapes operated at Capillary numbers below 0.01, with a simple model. In this model, a geometrical description of the interface was coupled to a continuity and momentum balance. We balanced the pressure drop over the emerging bubble due to the difference in radii of curvature at the front and rear with the pressure drop due to the flow through the gutters. This model shows good agreement with the experiments, explains the rapid 3-D pinch-off, and shows how the size of bubbles and droplets scales with the T-junction geometry.

  12. Critical Issues in Silicon Shallow Junction Formation - or - Laser Annealing Revisited

    Microsoft Academic Search

    J. M. Poate

    2000-01-01

    For over thirty years, the dominant technology for introducing dopant atoms into Si MOS transistors has been ion implantation, followed by furnace or rapid thermal annealing to remove lattice damage and incorporate dopant atoms on lattice sites. As device dimensions shrink, these processing technologies face severe physical challenges. In the past five years, as junction depths approached 0.1 microns, the

  13. Junction formation during desiccation cracking K. B. Toga and B. Erdem Alaca*

    E-print Network

    Alaca, B. Erdem

    problem of the evolution of crack patterns. Using coffee-water mixtures a clear distinction between suspension, one can switch from the well-known symmetric triple junctions that are unique to the nucleation­18 . The dependence of crack patterns on suspension thickness and interfacial properties is a point that is generally

  14. Medium energy ion scattering for the characterisation of damage profiles of ultra shallow B implants in Si

    NASA Astrophysics Data System (ADS)

    van den Berg, J. A.; Zhang, S.; Whelan, S.; Armour, D. G.; Goldberg, R. D.; Bailey, P.; Noakes, T. C. Q.

    2001-07-01

    High depth resolution medium energy ion scattering (MEIS) in the double alignment mode has been used to determine the pre- and post-annealing damage distributions following 0.1-2.5 keV B + implantation into Si(1 0 0) at different substrate temperatures. Samples were irradiated to doses ranging from 1×10 14 to 2×10 16 cm-2 at substrate temperatures of -150°C, 25°C and 300°C. Rapid thermal processing (RTP) was carried out to temperatures ranging from 400°C to 1000°C for 10 s, to monitor the annealing of damage caused by the B + implant. For the room temperature (RT) implants, two distinct damage distributions were observed. The first was a narrow, near-surface damage peak which grows out from the virgin Si surface peak to a maximum depth of 3 nm, much shallower than the TRIM predicted mean projected range of e.g. 1 keV B + ions ( Rp?5.3 nm). The width of this damage layer showed only a weak dependence on the B + ion energy and strong dependence on the dose. The number of displaced atoms in this layer for dilute damage conditions is in good agreement with modified Kinchin Pease predictions. For 1 keV B +, a second, deeper damage peak appeared only after a B dose of 1×10 15 cm-2, having a maximum at a depth of ?7.5 nm, well beyond the Rp of 5.3 nm. MEIS showed that this post-implant damage structure which develops for irradiations performed at 25°C and 300°C, is the result of dynamic annealing processes that are highly effective in the region in between the two peaks, in which Frenkel defects have their maximum production rates. The observed growth of the surface damage layer with implant dose is ascribed to the migration of point defects, created along the bombardment cascade, to the Si/SiO 2 interface. For 500 eV B + implants, due to proximity of this surface sink, the residual damage is greater even at 300°C. Implantations at -120°C resulted in a single, heavily damaged layer stretching from the surface to the position of the deep damage. These damage profiles show a direct correlation between the displaced Si and the implanted B distributions. MEIS yields approached random level, showing near or total amorphisation of the Si lattice; epitaxial regrowth, even after 30 s RTP at 600°, was however only partial, apparently arrested at B containing I clusters formed near Rp of the B distribution. RTP at 400°C and 500°C of the samples implanted at room temperature leads to substantial reduction in the Si damage, especially in the width of the near-surface peak. It suggests a substantial rearrangement of Si atoms in the lattice that occurs without the release of Si interstitials, in view of the absence of TED at these temperatures and may involve a degree of realignment of the damage structure with the channelling direction. The annealing behaviour measured by MEIS at higher temperatures is consistent with XTEM observations, showing the formation and growth in size of extended interstitial defects and their ultimate dissolution at high temperature. As well as moving into the bulk where they cause TED, a fraction of the released interstitials migrate to the surface and increase the width of the surface damage region. MEIS studies also indicates the occurrence of reverse annealing for high temperature implant conditions.

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

    PubMed Central

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

    2012-01-01

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

  16. Formation of three-particle clusters in hetero-junctions and MOSFET structures

    E-print Network

    E. P. Nakhmedov; K. Morawetz

    2004-03-05

    A novel interaction mechanism in MOSFET structures and $GaAs/AlGaAs$ hetero-junctions between the zone electrons of the two-dimensional (2D) gas and the charged traps on the insulator side is considered. By applying a canonical transformation, off-diagonal terms in the Hamiltonian due to the trapped level subsystem are excluded. This yields an effective three-particle attractive interaction as well as a pairing interaction inside the 2D electronic band. A type of Bethe- Goldstone equation for three particles is studied to clarify the character of the binding and the energy of the three-particle bound states. The results are used to offer a possible explanation of the Metal-Insulator transition recently observed in MOSFET and hetero-junctions.

  17. Dlg3 Trafficking and Apical Tight Junction Formation Is Regulated by Nedd4 and Nedd4-2 E3 Ubiquitin Ligases

    PubMed Central

    Van Campenhout, Claude A.; Eitelhuber, Andrea; Gloeckner, Christian J.; Giallonardo, Patrizia; Gegg, Moritz; Oller, Heide; Grant, Seth G.N.; Krappmann, Daniel; Ueffing, Marius; Lickert, Heiko

    2011-01-01

    Summary The Drosophila Discs large (Dlg) scaffolding protein acts as a tumor suppressor regulating basolateral epithelial polarity and proliferation. In mammals, four Dlg homologs have been identified; however, their functions in cell polarity remain poorly understood. Here, we demonstrate that the X-linked mental retardation gene product Dlg3 contributes to apical-basal polarity and epithelial junction formation in mouse organizer tissues, as well as to planar cell polarity in the inner ear. We purified complexes associated with Dlg3 in polarized epithelial cells, including proteins regulating directed trafficking and tight junction formation. Remarkably, of the four Dlg family members, Dlg3 exerts a distinct function by recruiting the ubiquitin ligases Nedd4 and Nedd4-2 through its PPxY motifs. We found that these interactions are required for Dlg3 monoubiquitination, apical membrane recruitment, and tight junction consolidation. Our findings reveal an unexpected evolutionary diversification of the vertebrate Dlg family in basolateral epithelium formation. PMID:21920314

  18. Improved junction formation procedure for low temperature deposited CdS CdTe solar cells

    Microsoft Academic Search

    T. Takamoto; T. Agui; H. Kurita; M. Ohmori

    1997-01-01

    Thin film CdSCdTe solar cells with high efficiencies above 15% were produced by vacuum evaporation at substrate temperatures lower than 400°C. The junction quality was found to be improved by introducing an In (or Sn)-oxide buffer layer on the transparent conducting oxide film, and Voc greater than 0.84 V and FF greater than 75% could be obtained. Furthermore, the two-step

  19. Fully-depleted Ge interband tunnel transistor: Modeling and junction formation

    Microsoft Academic Search

    Qin Zhang; Surajit Sutar; Thomas Kosel; Alan Seabaugh

    2009-01-01

    Complementary fully-depleted Ge interband-tunneling field-effect transistors (TFETs) and static inverters are modeled to quantify TFET performance relative to Si MOSFETs. SYNOPSYS TCAD is used to compute the two-dimensional electrostatics and determine the tunnel junction electric field. This electric field is used in an analytic expression to compute the tunnel current. The speed and power performance of TFETs are compared with

  20. Role of grainyhead-like 2 in the formation of functional tight junctions.

    PubMed

    Tanimizu, Naoki; Mitaka, Toshihiro

    2013-01-01

    Epithelial cells develop intercellular junctions, including tight junctions (TJs) and adherens junctions (AJs). In epithelial tissues, TJs act as barriers that protect bodies from dehydration, infection and toxic substances. However, the molecular mechanisms regulating the establishment of functional TJs during organogenesis remain largely unknown. Recently, we identified grainyhead-like 2 (Grhl2) as a transcription factor that is specifically expressed in cholangiocytes, which are epithelial cells lining the bile duct tubules in the liver. Using our three-dimensional (3D) culture system of hepatic progenitor cells, we demonstrated that Grhl2 enhanced barrier functions of hepatic progenitor cells by upregulating claudin (Cldn) 3 and Cldn4, thereby promoting epithelial morphogenesis. In addition, we identified Rab25 as another target of Grhl2, which promotes the localization of Cldn4 at TJs. Our results indicate that a transcription factor promotes epithelial morphogenesis by establishing functional TJs by not only regulating the transcription of Cldns but also affecting their localization at TJs. PMID:24665375

  1. The Peptidoglycan-Binding Protein SjcF1 Influences Septal Junction Function and Channel Formation in the Filamentous Cyanobacterium Anabaena

    PubMed Central

    Rudolf, Mareike; Tetik, Nalan; Ramos-León, Félix; Flinner, Nadine; Ngo, Giang; Stevanovic, Mara; Burnat, Mireia; Pernil, Rafael; Flores, Enrique

    2015-01-01

    ABSTRACT Filamentous, heterocyst-forming cyanobacteria exchange nutrients and regulators between cells for diazotrophic growth. Two alternative modes of exchange have been discussed involving transport either through the periplasm or through septal junctions linking adjacent cells. Septal junctions and channels in the septal peptidoglycan are likely filled with septal junction complexes. While possible proteinaceous factors involved in septal junction formation, SepJ (FraG), FraC, and FraD, have been identified, little is known about peptidoglycan channel formation and septal junction complex anchoring to the peptidoglycan. We describe a factor, SjcF1, involved in regulation of septal junction channel formation in the heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120. SjcF1 interacts with the peptidoglycan layer through two peptidoglycan-binding domains and is localized throughout the cell periphery but at higher levels in the intercellular septa. A strain with an insertion in sjcF1 was not affected in peptidoglycan synthesis but showed an altered morphology of the septal peptidoglycan channels, which were significantly wider in the mutant than in the wild type. The mutant was impaired in intercellular exchange of a fluorescent probe to a similar extent as a sepJ deletion mutant. SjcF1 additionally bears an SH3 domain for protein-protein interactions. SH3 binding domains were identified in SepJ and FraC, and evidence for interaction of SjcF1 with both SepJ and FraC was obtained. SjcF1 represents a novel protein involved in structuring the peptidoglycan layer, which links peptidoglycan channel formation to septal junction complex function in multicellular cyanobacteria. Nonetheless, based on its subcellular distribution, this might not be the only function of SjcF1. PMID:26126850

  2. Planar Be-implanted GaAs junction formation using swept-line electron beam annealing

    SciTech Connect

    Banerjee, S.K.; De Jule, R.Y.; Soda, K.J.

    1983-12-01

    Comparative studies of swept-line electron beam annealing and furnace annealing of Be implanted in n-GaAs doped with Si are presented. Electron beam annealing causes less Be redistribution and results in fewer traps than furnace annealing, but causes site mixing of amphoteric Si. Planar Be-implanted junctions result in a p(+)-nu-n structure for the electron beam annealed samples, similar to thermally quenched samples. It is believed that this is caused by the incorporation of amphoteric Si on Ga and As sites during transient annealing, which produces results similar to thermal quenching. 14 references.

  3. Bubble Formation in Yield Stress Fluids Using Flow-Focusing and T-Junction Devices.

    PubMed

    Laborie, Benoit; Rouyer, Florence; Angelescu, Dan E; Lorenceau, Elise

    2015-05-22

    We study the production of bubbles inside yield stress fluids (YSFs) in axisymmetric T-junction and flow-focusing devices. Taking advantage of yield stress over capillary stress, we exhibit a robust break-up mechanism reminiscent of the geometrical operating regime in 2D flow-focusing devices for Newtonian fluids. We report that when the gas is pressure driven, the dynamics is unsteady due to hydrodynamic feedback and YSF deposition on the walls of the channels. However, the present study also identifies pathways for potential steady-state production of bubbly YSFs at large scale. PMID:26047231

  4. Bubble Formation in Yield Stress Fluids Using Flow-Focusing and T -Junction Devices

    NASA Astrophysics Data System (ADS)

    Laborie, Benoit; Rouyer, Florence; Angelescu, Dan E.; Lorenceau, Elise

    2015-05-01

    We study the production of bubbles inside yield stress fluids (YSFs) in axisymmetric T -junction and flow-focusing devices. Taking advantage of yield stress over capillary stress, we exhibit a robust break-up mechanism reminiscent of the geometrical operating regime in 2D flow-focusing devices for Newtonian fluids. We report that when the gas is pressure driven, the dynamics is unsteady due to hydrodynamic feedback and YSF deposition on the walls of the channels. However, the present study also identifies pathways for potential steady-state production of bubbly YSFs at large scale.

  5. Characterization of Nanometer Step Structure Formation During the Fabrication of Large-Scale Superconducting-Tunnel-Junction Array Detectors

    Microsoft Academic Search

    Masahiro Ukibe; Akira Kurokawa; Masataka Ohkubo

    2009-01-01

    Superconducting-tunnel-junction (STJ) array detectors with an effective sensitive area of 4 mm2 were fabricated for mass spectrometry. An array detector has one hundred Nb\\/Al\\/AlOx\\/Al\\/Nb junctions with a 200 mum-square sensitive area. The junctions are quasi-horizontally arranged on a 10 mm-square chip. In the course of fabrication processes, we have found that an anomalous nanometer-step structure appears within the junctions located

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

    SciTech Connect

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

    1998-11-18

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

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

    SciTech Connect

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

    1999-03-01

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

  8. Effect of annealing temperature on formation of superparamagnetism in CoFeB/MgO/CoFeB magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Cao, Jiangwei; Liu, Yan; Ren, Yang; Wei, Fulin; Freitas, P. P.

    2014-09-01

    We report the annealing effect of CoFeB/MgO/CoFeB magnetic tunnel junctions with a thin free layer. For the junctions with CoFeB free layer below the critical thickness, the MR transfer curves are always hysteresis-free and TMR ratio decreases with increasing annealing temperature. For the junctions with CoFeB free layer above the critical thickness, with increasing annealing temperature, both TMR ratio and coercivity increase firstly and then decrease, and finally hysteresis-free MR transfer curves are obtained. The MR loops without hysteresis can be well fitted by using the Langevin equation, suggesting the formation of superparamagnetic particles in the free layer during the high temperature annealing. This behavior originates from the transformation of the ultra-thin CoFeB free layer during annealing: crystallization process of CoFeB and diffusion at MgO/CoFeB and CoFeB/Ru interfaces.

  9. Myosins in cell junctions

    PubMed Central

    Liu, Katy C.; Cheney, Richard E.

    2012-01-01

    The development of cell-cell junctions was a fundamental step in metazoan evolution, and human health depends on the formation and function of cell junctions. Although it has long been known that actin and conventional myosin have important roles in cell junctions, research has begun to reveal the specific functions of the different forms of conventional myosin. Exciting new data also reveals that a growing number of unconventional myosins have important roles in cell junctions. Experiments showing that cell junctions act as mechanosensors have also provided new impetus to understand the functions of myosins and the forces they exert. In this review we will summarize recent developments on the roles of myosins in cell junctions. PMID:22954512

  10. The influence of porous silicon on junction formation in silicon solar cells

    Microsoft Academic Search

    Kazimierz Drabczyk; Piotr Panek; Marek Lipi?ski

    2003-01-01

    In this work the results of a structural investigation by SEM of porous silicon (PS) before and after diffusion processes are reported. The formation of PS n+\\/p structures were carried out on PS p\\/p silicon wafers with two methods: from POCl3 in a conventional furnace and from a phosphorous doped paste in an infrared furnace. Sheet resistance was found to

  11. Gap junction assembly: roles for the formation plaque and regulation by the C-terminus of connexin43

    PubMed Central

    Johnson, Ross G.; Reynhout, James K.; TenBroek, Erica M.; Quade, Bradley J.; Yasumura, Thomas; Davidson, Kimberly G. V.; Sheridan, Judson D.; Rash, John E.

    2012-01-01

    Using an established gap junction (GJ) assembly system with experimentally reaggregated cells, we analyzed “formation plaques” (FPs), apparent sites of GJ assembly. Employing freeze-fracture electron microscopy methods combined with filipin labeling of sterols and immunolabeling for connexin43 (Cx43), we demonstrated that FPs constitute distinct membrane “domains” and that their characteristic 10-nm particles contain connexin43, thus representing precursors (i.e., GJ hemichannels) engaged in assembly. Analysis of FPs in new systems—HeLa and N2A cells—resolved questions surrounding several key but poorly understood steps in assembly, including matching of FP membranes in apposed cells, reduction in the separation between FP membranes during assembly, and the process of particle aggregation. Findings also indicated that “docking” of GJ hemichannels occurs within FP domains and contributes to reduction of intermembrane separation between FPs. Other experiments demonstrated that FPs develop following a major C-terminal truncation of Cx43 (M257), although assembly was delayed. Particle aggregation also occurred at lower densities, and densities of particles within developing GJ aggregates failed to achieve full-length levels. With regard to regulation, inhibition of assembly following protein kinase C activation failed to occur in the M257 truncation mutants, as measured by intercellular dye transfer. However, several C-terminal serine mutations failed to disrupt inhibition. PMID:22049024

  12. Long-term Forskolin Stimulation Induces AMPK Activation and Thereby Enhances Tight Junction Formation in Human Placental Trophoblast BeWo Cells

    Microsoft Academic Search

    M. Egawa; H. Kamata; A. Kushiyama; H. Sakoda; M. Fujishiro; N. Horike; M. Yoneda; Y. Nakatsu; Guo Ying; Zhang Jun; Y. Tsuchiya; K. Takata; H. Kurihara; T. Asano

    2008-01-01

    BeWo cells, derived from human choriocarcinoma, have been known to respond to forskolin or cAMP analogues by differentiating into multinucleated cells- like syncytiotrophoblasts on the surfaces of chorionic villi of the human placenta. In this study, we demonstrated that long-term treatment with forskolin enhances the tight junction (TJ) formation in human placental BeWo cells. Interestingly, AMPK activation and phosphorylation of

  13. Pre-annealing effects of n+/p and p+/n junction formed by plasma doping (PLAD) and laser annealing

    SciTech Connect

    Heo, Sungho; Baek, Sungkweon; Lee, Dongkyu; Hasan, Musarrat; Hwang, Hyunsang [Department of Materials Science and Engineering, Gwangju Institute of Science and Technology, no. 1, Oryong-dong, Buk-gu, Gwangju, 500-712 (Korea, Republic of)

    2006-11-13

    In this paper, we demonstrated ultra-shallow junction formed by plasma doping (PLAD) and laser annealing. PLAD may be considered as an alternative doping method for the sub 45 technology node due to the possibility of low energy doping and high throughput. However, PLAD has various problems due to the incorporated hydrogen or fluorine. Incorporated hydrogen generally increases damage in the Si substrate and junction depth. Incorporated fluorine also retards dopant activation and increases deactivation behavior after post-annealing. In order to improve the effect of incorporated ions, we applied pre-annealing prior to laser annealing in PLAD samples. By employing low temperature pre-annealing, we can improve electrical characteristics such as low sheet resistance and high activation rates, and also reduce the junction depth after laser annealing.

  14. Massive formation of square array junctions dramatically alters cell shape but does not cause lens opacity in the cav1-KO mice.

    PubMed

    Biswas, Sondip K; Brako, Lawrence; Lo, Woo-Kuen

    2014-08-01

    The wavy square array junctions are composed of truncated aquaporin-0 (AQP0) proteins typically distributed in the deep cortical and nuclear fibers in wild-type lenses. These junctions may help maintain the narrowed extracellular spaces between fiber cells to minimize light scattering. Herein, we investigate the impact of the cell shape changes, due to abnormal formation of extensive square array junctions, on the lens opacification in the caveolin-1 knockout mice. The cav1-KO and wild-type mice at age 1-22 months were used. By light microscopy examinations, cav1-KO lenses at age 1-18 months were transparent in both cortical and nuclear regions, whereas some lenses older than 18 months old exhibited nuclear cataracts. Scanning EM consistently observed the massive formation of ridge-and-valley membrane surfaces in young fibers at approximately 150 ?m deep in all cav1-KO lenses studied. In contrast, the typical ridge-and-valleys were only seen in mature fibers deeper than 400 ?m in wild-type lenses. The resulting extensive ridge-and-valleys dramatically altered the overall cell shape in cav1-KO lenses. Remarkably, despite dramatic shape changes, these deformed fiber cells remained intact and made close contact with their neighboring cells. By freeze-fracture TEM, ridge-and-valleys exhibited the typical orthogonal arrangement of 6.6 nm square array intramembrane particles and displayed the narrowed extracellular spaces. Immunofluorescence analysis showed that AQP0 C-terminus labeling was significantly decreased in outer cortical fibers in cav1-KO lenses. However, freeze-fracture immunogold labeling showed that the AQP0 C-terminus antibody was sparsely distributed on the wavy square array junctions, suggesting that the cleavage of AQP0 C-termini might not yet be complete. The cav1-KO lenses with nuclear cataracts showed complete cellular breakdown and large globule formation in the lens nucleus. This study suggests that despite dramatic cell shape changes, the massive formation of wavy square array junctions in intact fibers may provide additional adhesive support for maintaining the narrowed extracellular spaces that are crucial for the transparency of cav1-KO lenses. PMID:24877741

  15. The Apical Junctional Complex in Respiratory Diseases

    PubMed Central

    2014-01-01

    The epithelium, including the respiratory system, acts as a selective gate between the outside environment and underlying tissue. Epithelial cells are polarized due to the formation of the apical junctional complex, which includes adherent junctions and tight junctions. Endothelial cells are one of the most important cellular constituents of blood vessels. Endothelial junctional proteins play important roles in tissue integrity as well as in vascular permeability, leukocyte extravasation, and angiogenesis. This review focuses on the apical junctional complex in respiratory diseases. PMID:24855600

  16. High second-order nonlinearity by p-n junction formation in plasma enhanced chemical vapor deposition deposited hydrogenated amorphous silicon thin films

    NASA Astrophysics Data System (ADS)

    Liu, Qiming; Wu, Guoxing; Wang, Mingliang; Zhao, Xiujian; Du, Jincheng

    2015-02-01

    High second-order nonlinearity as high as 115.9 pm/V was obtained through the formation of p-n junction using plasma-enhanced CVD deposition of hydrogenated amorphous silicon thin films on fused silica substrate without additional electrical poling to induce second harmonic generation in the isotropic amorphous materials. No second harmonic generation was observed for films deposited with only p or n type amorphous silicon. The built-in electrostatic field Edc of p-n junction was observed by measuring the I-V curve of the designed p-i-n layered films, and was found to be the main source of high second-order nonlinearity.

  17. Ultrastructural studies on neuromuscular contacts and the formation of junctions in the flight muscle of Antheraea polyphemus (Lep.) I. Normal adult development.

    PubMed

    Stocker, R F; Nüesch, H

    1975-06-01

    The ultrastructure of neuromuscular connections on developing dorsolongitudinal flight muscles were studied in the moth Antheraea polyphemus. Undifferentiated membrane contacts between axon terminals and muscle-fiber anlagen are present in the diapause pupa. They persist during the period of nerve outgrowth, which probably provides a pathway of contact guidance. By the 4th day of adult development some of these contact areas have differentiated into structures similar to neuromuscular junctions although differentiation of muscle structure does not start earlier than the eighth day. Dense-cored vesicles are abundant in many axon terminals at the beginning of development. They later decrease in number quite rapidly. The significance of the above-mentioned early junctions, their possible mode of action and the role of the dense-cored vesicles are discussed. It is proposed that they exercise a stimulating (trophic) influence on the growth of the undifferentiated muscular tissue. The imaginal neuromuscular junctions are formed during the second half of adult development. Clusters of vesicles and electron-dense depositions along the inner face of the axo- and lemma seem to initiate junction formation. Glial processes then grow between the axo- and sarcolemma and divide the large contact area into several small segments. Mutual invaginations and protrusions of the sarcolemma and the glial cell membrane subsequently form an extensive "rete synapticum." Six days before eclosion the glial and sarcoplasmic parts of the rete synapticum are similar in size. Up to eclosion, all glial processes shrink and increase in electron density. Most of the observations are discussed also in relation to findings in vertebrates. PMID:1149098

  18. Effects of rapid thermal annealing on the formation of shallow p+n junction by implanting BF2+ ions into thin metal films on Si substrate. I. Thin titanium films

    Microsoft Academic Search

    M. H. Juang; H. C. Cheng

    1992-01-01

    High-quality Ti-silicided shallow p+n junctions have been fabricated by implanting BF+2 ions into thin Ti films on Si substrate and subsequent silicidation\\/drive-in by rapid thermal annealing (RTA) or conventional furnace annealing (CFA) under proper implant and anneal conditions. For both the RTA and CFA techniques, annealing temperatures higher than 800 °C degrade the junction formation because of more severe dopant

  19. 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.

  20. Nanotube junctions

    DOEpatents

    Crespi, Vincent Henry (Darien, IL); Cohen, Marvin Lou (Berkeley, CA); Louie, Steven Gwon Sheng (Berkeley, CA); Zettl, Alexander Karlwalter (Kensington, CA)

    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.

  1. Combined evaluation of grazing incidence X-ray fluorescence and X-ray reflectivity data for improved profiling of ultra-shallow depth distributions.

    PubMed

    Ingerle, D; Meirer, F; Pepponi, G; Demenev, E; Giubertoni, D; Wobrauschek, P; Streli, C

    2014-09-01

    The continuous downscaling of the process size for semiconductor devices pushes the junction depths and consequentially the implantation depths to the top few nanometers of the Si substrate. This motivates the need for sensitive methods capable of analyzing dopant distribution, total dose and possible impurities. X-ray techniques utilizing the external reflection of X-rays are very surface sensitive, hence providing a non-destructive tool for process analysis and control. X-ray reflectometry (XRR) is an established technique for the characterization of single- and multi-layered thin film structures with layer thicknesses in the nanometer range. XRR spectra are acquired by varying the incident angle in the grazing incidence regime while measuring the specular reflected X-ray beam. The shape of the resulting angle-dependent curve is correlated to changes of the electron density in the sample, but does not provide direct information on the presence or distribution of chemical elements in the sample. Grazing Incidence XRF (GIXRF) measures the X-ray fluorescence induced by an X-ray beam incident under grazing angles. The resulting angle dependent intensity curves are correlated to the depth distribution and mass density of the elements in the sample. GIXRF provides information on contaminations, total implanted dose and to some extent on the depth of the dopant distribution, but is ambiguous with regard to the exact distribution function. Both techniques use similar measurement procedures and data evaluation strategies, i.e. optimization of a sample model by fitting measured and calculated angle curves. Moreover, the applied sample models can be derived from the same physical properties, like atomic scattering/form factors and elemental concentrations; a simultaneous analysis is therefore a straightforward approach. This combined analysis in turn reduces the uncertainties of the individual techniques, allowing a determination of dose and depth profile of the implanted elements with drastically increased confidence level. Silicon wafers implanted with Arsenic at different implantation energies were measured by XRR and GIXRF using a combined, simultaneous measurement and data evaluation procedure. The data were processed using a self-developed software package (JGIXA), designed for simultaneous fitting of GIXRF and XRR data. The results were compared with depth profiles obtained by Secondary Ion Mass Spectrometry (SIMS). PMID:25202165

  2. Combined evaluation of grazing incidence X-ray fluorescence and X-ray reflectivity data for improved profiling of ultra-shallow depth distributions?

    PubMed Central

    Ingerle, D.; Meirer, F.; Pepponi, G.; Demenev, E.; Giubertoni, D.; Wobrauschek, P.; Streli, C.

    2014-01-01

    The continuous downscaling of the process size for semiconductor devices pushes the junction depths and consequentially the implantation depths to the top few nanometers of the Si substrate. This motivates the need for sensitive methods capable of analyzing dopant distribution, total dose and possible impurities. X-ray techniques utilizing the external reflection of X-rays are very surface sensitive, hence providing a non-destructive tool for process analysis and control. X-ray reflectometry (XRR) is an established technique for the characterization of single- and multi-layered thin film structures with layer thicknesses in the nanometer range. XRR spectra are acquired by varying the incident angle in the grazing incidence regime while measuring the specular reflected X-ray beam. The shape of the resulting angle-dependent curve is correlated to changes of the electron density in the sample, but does not provide direct information on the presence or distribution of chemical elements in the sample. Grazing Incidence XRF (GIXRF) measures the X-ray fluorescence induced by an X-ray beam incident under grazing angles. The resulting angle dependent intensity curves are correlated to the depth distribution and mass density of the elements in the sample. GIXRF provides information on contaminations, total implanted dose and to some extent on the depth of the dopant distribution, but is ambiguous with regard to the exact distribution function. Both techniques use similar measurement procedures and data evaluation strategies, i.e. optimization of a sample model by fitting measured and calculated angle curves. Moreover, the applied sample models can be derived from the same physical properties, like atomic scattering/form factors and elemental concentrations; a simultaneous analysis is therefore a straightforward approach. This combined analysis in turn reduces the uncertainties of the individual techniques, allowing a determination of dose and depth profile of the implanted elements with drastically increased confidence level. Silicon wafers implanted with Arsenic at different implantation energies were measured by XRR and GIXRF using a combined, simultaneous measurement and data evaluation procedure. The data were processed using a self-developed software package (JGIXA), designed for simultaneous fitting of GIXRF and XRR data. The results were compared with depth profiles obtained by Secondary Ion Mass Spectrometry (SIMS). PMID:25202165

  3. Vacuolar symplast formation is due to highly permeable gap junctions between the tonoplast and endoplasmic reticulum membrane

    Microsoft Academic Search

    G. A. Velikanov; L. P. Belova; V. Yu. Levanov

    2008-01-01

    An NMR method with a pulsed magnetic field gradient was applied to study changes in water permeability of the vacuolar symplast\\u000a in maize (Zea mays L.) seedling roots treated with various inhibitors of cell metabolism. The results were qualitatively analogous to literature\\u000a data on conductivity changes of intercellular gap junctions in animal cells exposed to similar treatments. Electron microscopy\\u000a examination

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

    NASA Astrophysics Data System (ADS)

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

    1986-10-01

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

  5. Actin-related protein2/3 complex regulates tight junctions and terminal differentiation to promote epidermal barrier formation

    PubMed Central

    Zhou, Kang; Muroyama, Andrew; Underwood, Julie; Leylek, Rebecca; Ray, Samriddha; Soderling, Scott H.; Lechler, Terry

    2013-01-01

    The epidermis provides an essential seal from the external environment and retains fluids within the body. To form an effective barrier, cells in the epidermis must form tight junctions and terminally differentiate into cornified envelopes. Here, we demonstrate that the branched actin nucleator, the actin-related protein (Arp)2/3 complex, is unexpectedly required for both these activities. Loss of the ArpC3 subunit of the Arp2/3 complex resulted in minimal changes in the morphogenesis and architecture of this stratified squamous epithelium, but resulted in profound defects in its physiology. Mutant embryos did not develop an effective barrier to the external environment and died within hours of birth. We discovered two underlying causes for these effects. First, ArpC3 was essential for robust assembly and function of tight junctions, specialized cell–cell adhesions that restrict water loss in the epidermis. Second, there were defects in differentiation of the epidermis and the production of cornified envelopes, structures essential for barrier activity. Underlying this defect, we found that YAP was inappropriately active not only in the ArpC3 mutant tissue, but also in cultured cells. Inhibition of YAP activity rescued the differentiation and barrier defects caused by loss of ArpC3. These results demonstrate previously unappreciated roles for the Arp2/3 complex and highlight the functions of branched actin networks in a complex tissue. PMID:24043783

  6. Actin-related protein2/3 complex regulates tight junctions and terminal differentiation to promote epidermal barrier formation.

    PubMed

    Zhou, Kang; Muroyama, Andrew; Underwood, Julie; Leylek, Rebecca; Ray, Samriddha; Soderling, Scott H; Lechler, Terry

    2013-10-01

    The epidermis provides an essential seal from the external environment and retains fluids within the body. To form an effective barrier, cells in the epidermis must form tight junctions and terminally differentiate into cornified envelopes. Here, we demonstrate that the branched actin nucleator, the actin-related protein (Arp)2/3 complex, is unexpectedly required for both these activities. Loss of the ArpC3 subunit of the Arp2/3 complex resulted in minimal changes in the morphogenesis and architecture of this stratified squamous epithelium, but resulted in profound defects in its physiology. Mutant embryos did not develop an effective barrier to the external environment and died within hours of birth. We discovered two underlying causes for these effects. First, ArpC3 was essential for robust assembly and function of tight junctions, specialized cell-cell adhesions that restrict water loss in the epidermis. Second, there were defects in differentiation of the epidermis and the production of cornified envelopes, structures essential for barrier activity. Underlying this defect, we found that YAP was inappropriately active not only in the ArpC3 mutant tissue, but also in cultured cells. Inhibition of YAP activity rescued the differentiation and barrier defects caused by loss of ArpC3. These results demonstrate previously unappreciated roles for the Arp2/3 complex and highlight the functions of branched actin networks in a complex tissue. PMID:24043783

  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. Long-term forskolin stimulation induces AMPK activation and thereby enhances tight junction formation in human placental trophoblast BeWo cells.

    PubMed

    Egawa, M; Kamata, H; Kushiyama, A; Sakoda, H; Fujishiro, M; Horike, N; Yoneda, M; Nakatsu, Y; Ying, Guo; Jun, Zhang; Tsuchiya, Y; Takata, K; Kurihara, H; Asano, T

    2008-12-01

    BeWo cells, derived from human choriocarcinoma, have been known to respond to forskolin or cAMP analogues by differentiating into multinucleated cells- like syncytiotrophoblasts on the surfaces of chorionic villi of the human placenta. In this study, we demonstrated that long-term treatment with forskolin enhances the tight junction (TJ) formation in human placental BeWo cells. Interestingly, AMPK activation and phosphorylation of acetyl-CoA carboxylase (ACC), a molecule downstream from AMPK, were induced by long-term incubation (>12h) with forskolin, despite not being induced by acute stimulation with forskolin. In addition, co-incubation with an AMPK inhibitor, compound C, as well as overexpression of an AMPK dominant negative mutant inhibited forskolin-induced TJ formation. Thus, although the molecular mechanism underlying AMPK activation via the forskolin stimulation is unclear, the TJ formation induced by forskolin is likely to be mediated by the AMPK pathway. Taking into consideration that TJs are present in the normal human placenta, this mechanism may be important for forming the placental barrier system between the fetal and maternal circulations. PMID:18950855

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    This paper is concerned with focal plane array (FPA) data and use of analytical and three-dimensional numerical simulation methods to determine the physical effects and processes limiting performance. For shallow homojunction P+n designs the temperature dependence of dark current for T < 300 K depends on the intrinsic carrier concentration of the In0.53Ga0.47As material, implying that the dominant dark currents are generation and recombination (G-R) currents originating in the depletion regions of the double layer planar heterostructure (DLPH) photodiode. In the analytical model differences from bulk G-R behavior are modeled with a G-R like perimeter-dependent shunt current conjectured to originate at the InP/InGaAs interface. In this description the fitting property is the effective conductivity, ? eff(T), in mho cm-1. Variation in the data suggests ? eff (300 K) values of 1.2 × 10-11-4.6 × 10-11 mho cm-1). Substrate removal extends the quantum efficiency (QE) spectral band into the visible region. However, dead-layer effects limit the QE to 10% at a wavelength of 0.5 ?m. For starlight-no moon illumination conditions, the signal-to-noise ratio is estimated to be 50 at an operating temperature of 300 K. A major result of the 3D numerical simulation of the device is the prediction of a perimeter G-R current not associated with the properties of the metallurgical interface. Another is the prediction that for a junction positioned in the larger band gap InP cap layer the QE is bias-dependent and that a relatively large reverse bias ?0.9 V is needed for the QE to saturate to the shallow homojunction value. At this higher bias the dark current is larger than the shallow homojunction value. The 3D numerical model and the analytical model agree in predicting and explaining the measured radiatively limited diffusion current originating at the n-side of the junction. The calculations of the area-dependent G-R current for the condition studied are also in agreement. Unique advantages of the 3D numerical simulation are the ability to mimic real device structures, achieve deeper understanding of the real physical effects associated with the various methods of junction formation, and predict how device designs will function.

  10. The C-terminal domain of Fcj1 is required for formation of crista junctions and interacts with the TOB/SAM complex in mitochondria

    PubMed Central

    Körner, Christian; Barrera, Miguel; Dukanovic, Jovana; Eydt, Katharina; Harner, Max; Rabl, Regina; Vogel, Frank; Rapaport, Doron; Neupert, Walter; Reichert, Andreas S.

    2012-01-01

    Crista junctions (CJs) are tubular invaginations of the inner membrane of mitochondria that connect the inner boundary with the cristae membrane. These architectural elements are critical for mitochondrial function. The yeast inner membrane protein Fcj1, called mitofilin in mammals, was reported to be preferentially located at CJs and crucial for their formation. Here we investigate the functional roles of individual domains of Fcj1. The most conserved part of Fcj1, the C-terminal domain, is essential for Fcj1 function. In its absence, formation of CJ is strongly impaired and irregular, and stacked cristae are present. This domain interacts with full-length Fcj1, suggesting a role in oligomer formation. It also interacts with Tob55 of the translocase of outer membrane ?-barrel proteins (TOB)/sorting and assembly machinery (SAM) complex, which is required for the insertion of ?-barrel proteins into the outer membrane. The association of the TOB/SAM complex with contact sites depends on the presence of Fcj1. The biogenesis of ?-barrel proteins is not significantly affected in the absence of Fcj1. However, down-regulation of the TOB/SAM complex leads to altered cristae morphology and a moderate reduction in the number of CJs. We propose that the C-terminal domain of Fcj1 is critical for the interaction of Fcj1 with the TOB/SAM complex and thereby for stabilizing CJs in close proximity to the outer membrane. These results assign novel functions to both the C-terminal domain of Fcj1 and the TOB/SAM complex. PMID:22496419

  11. The Relationships of Plate Triple-junction Evolution, Trench-Arc Lengthening, Boninite Generation, and SSZ Spreading Centers to Ophiolite Formation, High-Temperature Soles, and Obduction

    NASA Astrophysics Data System (ADS)

    Casey, J.; Dewey, J. F.

    2014-12-01

    A review of modern-day island arcs, the locations of boninite eruptions, the conditions necessary for hot upper plate spreading, potential regions of shallow SSZ flux melting, and formation of high-temperature metamorphic soles along the subduction channels indicates that many future, recent and ancient large slab ophiolite obduction events can be related to triple junctions that link SSZ spreading centers with trenches. These subduction systems leading to large slab ophiolite obduction events typically face stable continental margins. Boninitic melt generation requires hydrous melting of refractory mantle peridotite under an extremely high-temperature and low-pressure condition. This condition is generally explained by the addition of slab-derived fluids into a hot young oceanic mantle asthenosphere and lithosphere, which previously likely experienced melt extraction. Metamorphic conditions associated with metamorphic soles formation likewise require a hot upper plate lithosphere that, based on sole protolith, geochronologic and thermochronologic data, rapidly heats and then refrigerates and decompresses MORB-OIB type subcreted lithosphere. Numerous examples of present-day and recent SSZ spreading centers that link with two trenches or a trench and transform are considered ideal sites for ophiolite and boninite generation. The SZZ fore-arc spreading centers that link to the trench lines and triple junctions at the front of the arc may also continue towards the arc and back arc, creating no distinction between fore-arc and back-arc spreading episodes or to the transform-linked spreading centers from fore-arc to back arc. These SSZ spreading centers, which may be transiently produced during arc evolution over short or protracted time periods, act to open gaps in the arc massif and lengthen the trench, fore-arc and the arc crustal massif. They lead to an evolving arc magmatic front that begins in the infant fore-arc where ophiolite generation occurs at, near or in the trench, followed then by migration to sites distal from the trench line where a new arc massif is established on newly created oceanic lithosphere. Modern and ancient analogues of these setting are reviewed.

  12. Doped semiconductor nanocrystal junctions

    SciTech Connect

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

    2013-11-28

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

  13. Cardiotonic steroid ouabain stimulates expression of blood-testis barrier proteins claudin-1 and -11 and formation of tight junctions in Sertoli cells.

    PubMed

    Dietze, Raimund; Shihan, Mazen; Stammler, Angelika; Konrad, Lutz; Scheiner-Bobis, Georgios

    2015-04-15

    The interaction of ouabain with the sodium pump induces signalling cascades resembling those triggered by hormone/receptor interactions. In the rat Sertoli cell line 93RS2, ouabain at low concentrations stimulates the c-Src/c-Raf/Erk1/2 signalling cascade via its interaction with the ?4 isoform of the sodium pump expressed in these cells, leading to the activation of the transcription factor CREB. As a result of this signalling sequence, ouabain stimulates expression of claudin-1 and claudin-11, which are also controlled by a CRE promoter. Both of these proteins are known to be essential constituents of tight junctions (TJ) between Sertoli cells, and as a result of the ouabain-induced signalling TJ formation between neighbouring Sertoli cells is significantly enhanced by the steroid. Thus, ouabain-treated cell monolayers display higher transepithelial resistance and reduced free diffusion of FITC-coupled dextran in tracer diffusion assays. Taking into consideration that the formation of TJ is indispensable for the maintenance of the blood-testis barrier (BTB) and therefore for male fertility, the actions of ouabain described here and the fact that this and other related cardiotonic steroids (CTS) are produced endogenously suggest a direct influence of ouabain/sodium pump interactions on the maintenance of the BTB and thereby an effect on male fertility. Since claudin-1 and claudin-11 are also present in other blood-tissue barriers, one can speculate that ouabain and perhaps other CTS influence the dynamics of these barriers as well. PMID:25666991

  14. Junction formation at the interface of CdS/CuInxGa(1 - x)Se2

    NASA Astrophysics Data System (ADS)

    Park, Soon Mi; Kim, Tae Gun; Duck Chung, Yong; Cho, Dae-Hyung; Kim, Jeha; Kim, Kyung Joong; Yi, Yeonjin; Kim, Jeong Won

    2014-08-01

    The interfacial band alignment and chemical composition at the cadmium sulfide (CdS)/copper indium gallium diselenide (CuInx Ga1-x Se2?:?CIGS) heterojunction was investigated by photoelectron spectroscopy. Over the two different interfaces made by either thermal deposition of CdS on a CIGS film or step-by-step etching of a chemical-bath deposited (CBD)-CdS/CIGS film by Ar+ ions, the valence band maximum and conduction band minimum were determined using ultraviolet photoelectron spectroscopy and inverse photoemission spectroscopy, respectively. Concurrently, x-ray photoelectron spectroscopy was used to trace chemical changes across the interface. Both interfaces showed a In-rich and Cu-deficient profile. The thermal deposition of CdS on CIGS induces Cd-Cu intermixing and nonstoichiometric CdS formation associated with a strong band bending and high electron injection barrier. However, the CBD-CdS layer shows a rather sharp interface and negligible electron injection barrier in the conduction band, which will show better solar cell characteristics.

  15. Materials Science and Engineering B 114115 (2004) 390396 Fundamental characterization of the effect of nitride sidewall spacer

    E-print Network

    Dunham, Scott

    2004-01-01

    ­6] and thereby enhances the amount of B dose loss into the oxide from the Si. Lesser retained dose leads of the effect of nitride sidewall spacer process on boron dose loss in ultra-shallow junction formation P complementary metal oxide semiconductor (CMOS) process flows. In this work, we have investigated the effect

  16. p-n junction formation in InSb and InAs(1-x)Sb(x) by metalorganic chemical vapor deposition

    NASA Technical Reports Server (NTRS)

    Chiang, P. K.; Bedair, S. M.

    1985-01-01

    p-n junctions have been fabricated in InSb and InAs(1-x)Sb(x)(0.4 less than x less than 0.7) using metalorganic chemical vapor deposition. These junctions showed soft breakdown in addition to forward characteristics with a diode factor greater than 2. The ternary alloy has a cut-off wavelength in the 8-11-micron range, thus providing a potential material system for detectors covering the 8-12-micron range.

  17. Science Junction

    NSDL National Science Digital Library

    North Carolina State University has made available the Science Junction website. The goal of this website is to create an interaction between the researchers and educators at North Carolina State University and the teachers, children, and parents of North Carolina. In addition, the website aims to provide a center for teaching as well as learning and integrating science into people's daily lives. Sections provided at the website are: Data Depot, Student Station, and Teacher Terminal, among others. In the Game Room section, within the Student Station, users can "try their hand at hitting a space vehicle through a special track in space" in the game Space Track. This offers users a fun way to learn more about Newton's Laws while testing their skills and knowledge in physics. Although the website has been launched, some sections are still under construction.

  18. Lactobacillus plantarum MB452 enhances the function of the intestinal barrier by increasing the expression levels of genes involved in tight junction formation

    Microsoft Academic Search

    Rachel C Anderson; Adrian L Cookson; Warren C McNabb; Zaneta Park; Mark J McCann; William J Kelly; Nicole C Roy

    2010-01-01

    BACKGROUND: Intestinal barrier function is important for preserving health, as a compromised barrier allows antigen entry and can induce inflammatory diseases. Probiotic bacteria can play a role in enhancing intestinal barrier function; however, the mechanisms are not fully understood. Existing studies have focused on the ability of probiotics to prevent alterations to tight junctions in disease models, and have been

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

    Microsoft Academic Search

    Brian G. Rash; Elizabeth A. Grove

    2011-01-01

    In human holoprosencephaly (HPE), the forebrain does not separate fully into two hemispheres. Further, the border between the telencephalon and diencephalon, the telencephalic\\/diencephalic junction (TDJ), is often indistinct, and the ventricular system can be blocked at the third ventricle, creating a forebrain ‘holosphere’. Mice deficient in Sonic Hedgehog (Shh) have previously been described to show HPE and associated cyclopia. Here

  20. Solitons in Josephson junctions

    NASA Astrophysics Data System (ADS)

    Ustinov, A. V.

    1998-11-01

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

  1. Plasmodium falciparum adhesion on human brain microvascular endothelial cells involves transmigration-like cup formation and induces opening of intercellular junctions.

    PubMed

    Jambou, Ronan; Combes, Valery; Jambou, Marie-Jose; Weksler, Babeth B; Couraud, Pierre-Olivier; Grau, Georges E

    2010-01-01

    Cerebral malaria, a major cause of death during malaria infection, is characterised by the sequestration of infected red blood cells (IRBC) in brain microvessels. Most of the molecules implicated in the adhesion of IRBC on endothelial cells (EC) are already described; however, the structure of the IRBC/EC junction and the impact of this adhesion on the EC are poorly understood. We analysed this interaction using human brain microvascular EC monolayers co-cultured with IRBC. Our study demonstrates the transfer of material from the IRBC to the brain EC plasma membrane in a trogocytosis-like process, followed by a TNF-enhanced IRBC engulfing process. Upon IRBC/EC binding, parasite antigens are transferred to early endosomes in the EC, in a cytoskeleton-dependent process. This is associated with the opening of the intercellular junctions. The transfer of IRBC antigens can thus transform EC into a target for the immune response and contribute to the profound EC alterations, including peri-vascular oedema, associated with cerebral malaria. PMID:20686652

  2. High precision micro-scale Hall effect characterization method using in-line micro four-point probes

    Microsoft Academic Search

    D. H. Petersena; O. Hansen; R. Lin; P. F. Nielsen; T. Clarysse; J. Goossens; E. Rosseel; W. Vandervorst

    2008-01-01

    Accurate characterization of ultra shallow junctions (USJ) is important in order to understand the principles of junction formation and to develop the appropriate implant and annealing technologies. We investigate the capabilities of a new micro-scale Hall effect measurement method where Hall effect is measured with collinear micro four-point probes (M4PP). We derive the sensitivity to electrode position errors and describe

  3. Matrix readout scheme for superconducting tunnel junction arrays

    Microsoft Academic Search

    D. D. E. Martin; A. Peacock; P. Verhoeve; A. Poelaert; R. Venn

    2000-01-01

    We report on the design and testing of a new readout scheme for superconducting tunnel junction (STJ) arrays. By grouping the electrodes in rows and columns, this method drastically reduces the number of connections and electronic circuits required for reading out a large format array of pixelated detectors. Using charge sensitive amplifiers with junction field-effect transistors we verify that the

  4. Behavior of tight-junction, adherens-junction and cell polarity proteins during HNF-4{alpha}-induced epithelial polarization

    SciTech Connect

    Satohisa, Seiro [Department of Pathology, Sapporo Medical University School of Medicine, South-1, West-17, Chuo-ku, Sapporo 060-8556, (Japan); Department of Obstetrics and Gynecology, Sapporo Medical University School of Medicine, Sapporo 060-8556, (Japan); Chiba, Hideki [Department of Pathology, Sapporo Medical University School of Medicine, South-1, West-17, Chuo-ku, Sapporo 060-8556 (Japan)]. E-mail: hidchiba@sapmed.ac.jp; Osanai, Makoto [Department of Pathology, Sapporo Medical University School of Medicine, South-1, West-17, Chuo-ku, Sapporo 060-8556, (Japan); Ohno, Shigeo [Department of Molecular Biology, Yokohama City University School of Medicine, Yokohama 236-0004 (Japan); Kojima, Takashi [Department of Pathology, Sapporo Medical University School of Medicine, South-1, West-17, Chuo-ku, Sapporo 060-8556, (Japan); Saito, Tsuyoshi [Department of Obstetrics and Gynecology, Sapporo Medical University School of Medicine, Sapporo 060-8556 (Japan); Sawada, Norimasa [Department of Pathology, Sapporo Medical University School of Medicine, South-1, West-17, Chuo-ku, Sapporo 060-8556 (Japan)

    2005-10-15

    We previously reported that expression of tight-junction molecules occludin, claudin-6 and claudin-7, as well as establishment of epithelial polarity, was triggered in mouse F9 cells expressing hepatocyte nuclear factor (HNF)-4{alpha} [H. Chiba, T. Gotoh, T. Kojima, S. Satohisa, K. Kikuchi, M. Osanai, N. Sawada. Hepatocyte nuclear factor (HNF)-4{alpha} triggers formation of functional tight junctions and establishment of polarized epithelial morphology in F9 embryonal carcinoma cells, Exp. Cell Res. 286 (2003) 288-297]. Using these cells, we examined in the present study behavior of tight-junction, adherens-junction and cell polarity proteins and elucidated the molecular mechanism behind HNF-4{alpha}-initiated junction formation and epithelial polarization. We herein show that not only ZO-1 and ZO-2, but also ZO-3, junctional adhesion molecule (JAM)-B, JAM-C and cell polarity proteins PAR-3, PAR-6 and atypical protein kinase C (aPKC) accumulate at primordial adherens junctions in undifferentiated F9 cells. In contrast, CRB3, Pals1 and PATJ appeared to exhibit distinct subcellular localization in immature cells. Induced expression of HNF-4{alpha} led to translocation of these tight-junction and cell polarity proteins to beltlike tight junctions, where occludin, claudin-6 and claudin-7 were assembled, in differentiated cells. Interestingly, PAR-6, aPKC, CRB3 and Pals1, but not PAR-3 or PATJ, were also concentrated on the apical membranes in differentiated cells. These findings indicate that HNF-4{alpha} provokes not only expression of tight-junction adhesion molecules, but also modulation of subcellular distribution of junction and cell polarity proteins, resulting in junction formation and epithelial polarization.

  5. Cell junctions in early embryos of squid (Loligo pealei).

    PubMed

    Ginzberg, R D; Morales, E A; Spray, D C; Bennett, M V

    1985-01-01

    Squid embryos examined by freeze-fracture and thin-section electron microscopy exhibit identifiable gap junctions during mid-cleavage stages (stages 7-8), and junctional complexes composed of adherent appositions, elaborate septate junctions and gap junctions at slightly later stages (stages 12-13). During germinal layer establishment (stages 12-13) cytoplasmic bridges frequently link the embryonic cells. The presence of gap junctions in cleavage-stage embryos provides the morphological substrate for a demonstrated pathway of direct cell-cell communication that is modifiable by experimental treatments and may be physiologically regulatable. The existence of septate junctions and adherent contacts at later stages suggests that some functional specialization, perhaps the establishment of a strongly joined framework of cells at the surface of the embryo, accompanies the formation of germinal layers. PMID:3986876

  6. DEVELOPMENT OF THE VERTEBRATE NEUROMUSCULAR JUNCTION

    Microsoft Academic Search

    Joshua R. Sanes; Jeff W. Lichtman

    1999-01-01

    We describe the formation, maturation, elimination, maintenance, and regen- eration of vertebrate neuromuscular junctions (NMJs), the best studied of all synapses. The NMJ forms in a series of steps that involve the exchange of signals among its three cellular components—nerve terminal, muscle fiber, and Schwann cell. Although essentially any motor axon can form NMJs with any muscle fiber, an additional

  7. Matrix readout for superconducting tunnel junction arrays

    Microsoft Academic Search

    Didier D. Martin; Peter Verhoeve; Anthony J. Peacock; D. J. Goldie

    2000-01-01

    We report on the design and testing of a new readout scheme for Superconducting Tunnel Junction (STJ) arrays. By grouping the electrodes in rows and columns, this method drastically reduces the number of connections and electronic circuits required for reading out a large format array of pixelated detectors. It is a generic scheme in that it could be applied to

  8. Three-junction solar cell

    DOEpatents

    Ludowise, Michael J. (Cupertino, CA)

    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.

  9. Ultrastructural studies on neuromuscular contacts and the formation of junctions in the flight muscle of Antheraea polyphemus (Lep.). II. Changes after motor nerve section.

    PubMed

    Nüesch, H; Stocker, R F

    1975-12-10

    In the moth Antheraea polyphemed at the onset of adult development. The subsequent breakdown of the isolated motor stulongated vesicles similar in structure to channels of smooth ER, appear in large numbers in the axoplasm. Their nature as well as the functional aspects of early axonal changes are discussed. From the 7th day onward two types of axonal breakdown become prominent. The first is characterized 0y swelling axon profiles, distorted vesicles and strongly shrunken mitochondria, uhile shrinking axon profiles containing tightly packed mitochondria and unaltered vesicles are typical of the second. Both types presumably take place independently of each other in different axon terminals. Axons and the contents of at least the first type are finally removed by transformation into lamellar bodies. Glial processes obviously behave independently of degenerating terminals; they loose any contact with them and never act as phagocytes for axon remnants. During the whole period of breakdown undifferentiated contacts between nerve fibers and muscle anlagen are present but synaptic structures as in normal developing dlm have never been observed. This fact, in comparison with earlier studies, suggests a lack of trophic nervous activity on the muscle anlagen tissue. A short time after removal of the isolated stumps new nerve tracts appear between dlm-fibers (which are, of course, strongly retarded in development). They are presumably sensory wing nerves which lack a guide structure to the central target, due to axotomy. Neuromuscular contacts or even junctions formed by axons of these nerves have occasionally been detected on the dlm. Their nature is discussed. Wallerian axon degeneration is compared to the normal, metamorphic breakdown of the innervation of the larval dlm-precursor. In contrast to the former, glial processes here remain in contact with the terminals. Glia and axons first swell. Then most glial processes are transformed into lamellar bodies whereas neurites shrink and become electron-dense. Axonal organelles remain intact for a long period. PMID:1201608

  10. Interface states and Schottky barrier formation at metal/GaAs junctions R. E. Viturro, c. Mailhiot, J. L. Shaw, and L. J. Brillson

    E-print Network

    Woodall, Jerry M.

    model of metal-semiconductor interfaces. Our low-temperature measurements and analyses show the validity and the formation of two reaction-induced interface states are obtained upon metallization of GaAs (100) surfaces semiconductor interfaces which reveal Fermi-level (Ej) sta- bilizations energies distributed over a range

  11. SMALLCAPACITANCE JOSEPHSON JUNCTIONS: ONEDIMENSIONAL ARRAYS AND SINGLE JUNCTIONS

    E-print Network

    Haviland, David

    SMALL­CAPACITANCE JOSEPHSON JUNCTIONS: ONE­DIMENSIONAL ARRAYS AND SINGLE JUNCTIONS MICHIO WATANABE tunnel junctions provide an ideal system for studying the interplay between the Josephson phase have modeled the films as 2D arrays of small­capacitance Josephson junctions (JJs) [8

  12. A Kinetic Monte Carlo model for material aging: Simulations of second phase formation at Au/Bi{sub 2}Te{sub 3} junction in oxygen environments

    SciTech Connect

    Zhou, X. W., E-mail: xzhou@sandia.gov [Mechanics of Materials Department, Sandia National Laboratories, Livermore, California 94550 (United States); Yang, N. Y. C. [Energy Nanomaterials Department, Sandia National Laboratories, Livermore, California 94550 (United States)

    2014-03-14

    Electronic properties of semiconductor devices are sensitive to defects such as second phase precipitates, grain sizes, and voids. These defects can evolve over time especially under oxidation environments and it is therefore important to understand the resulting aging behavior in order for the reliable applications of devices. In this paper, we propose a kinetic Monte Carlo framework capable of simultaneous simulation of the evolution of second phases, precipitates, grain sizes, and voids in complicated systems involving many species including oxygen. This kinetic Monte Carlo model calculates the energy barriers of various events based directly on the experimental data. As a first step of our model implementation, we incorporate the second phase formation module in the parallel kinetic Monte Carlo codes SPPARKS. Selected aging simulations are performed to examine the formation of second phase precipitates at the eletroplated Au/Bi{sub 2}Te{sub 3} interface under oxygen and oxygen-free environments, and the results are compared with the corresponding experiments.

  13. Oxidative Stress, Lens Gap Junctions, and Cataracts

    PubMed Central

    Beyer, Eric C.

    2009-01-01

    Abstract The eye lens is constantly subjected to oxidative stress from radiation and other sources. The lens has several mechanisms to protect its components from oxidative stress and to maintain its redox state, including enzymatic pathways and high concentrations of ascorbate and reduced glutathione. With aging, accumulation of oxidized lens components and decreased efficiency of repair mechanisms can contribute to the development of lens opacities or cataracts. Maintenance of transparency and homeostasis of the avascular lens depend on an extensive network of gap junctions. Communication through gap junction channels allows intercellular passage of molecules (up to 1?kDa) including antioxidants. Lens gap junctions and their constituent proteins, connexins (Cx43, Cx46, and Cx50), are also subject to the effects of oxidative stress. These observations suggest that oxidative stress-induced damage to connexins (and consequent altered intercellular communication) may contribute to cataract formation. Antioxid. Redox Signal. 11, 339–353. PMID:18831679

  14. Primary tunnel junction thermometry.

    PubMed

    Pekola, Jukka P; Holmqvist, Tommy; Meschke, Matthias

    2008-11-14

    We describe the concept and experimental demonstration of primary thermometry based on a four-probe measurement of a single tunnel junction embedded within four arrays of junctions. We show that in this configuration random sample specific and environment-related errors can be avoided. This method relates temperature directly to Boltzmann constant, which will form the basis of the definition of temperature and realization of official temperature scales in the future. PMID:19113365

  15. Primary Tunnel Junction Thermometry

    SciTech Connect

    Pekola, Jukka P.; Holmqvist, Tommy; Meschke, Matthias [Low Temperature Laboratory, Helsinki University of Technology, P.O. Box 3500, 02015 TKK (Finland)

    2008-11-14

    We describe the concept and experimental demonstration of primary thermometry based on a four-probe measurement of a single tunnel junction embedded within four arrays of junctions. We show that in this configuration random sample specific and environment-related errors can be avoided. This method relates temperature directly to Boltzmann constant, which will form the basis of the definition of temperature and realization of official temperature scales in the future.

  16. Gene expression regulating epithelial intercellular junction biogenesis during human blastocyst development in vitro

    Microsoft Academic Search

    M. Reza Ghassemifar; Judith J. Eckert; Franchesca D. Houghton; Helen M. Picton; Henry J. Leese; Tom P. Fleming

    2003-01-01

    We investigated gene expression associated with trophectoderm epithelial intercellular junction formation in single human embryos at different stages of cleavage using RT-PCR methods based upon magnetic bead separation of polyA+ RNA. Trophectoderm tight junction (TJ) and desmosome biogenesis contribute to intercellular sealing and tissue integrity, critical for vectorial transport and blastocoel cavity formation. Expression of the various genes throughout human

  17. Early events in neuromuscular junction formation in vitro: induction of acetylcholine receptor clusters in the postsynaptic membrane and morphology of newly formed synapses

    PubMed Central

    1979-01-01

    The development of clusters of acetylcholine (ACh) receptors at newly formed synapses between embryonic chick spinal cord and muscle cells grown in vitro has been studied by iontophoretic mapping with ACh. A semi-automated technique using on-line computer analysis of ACh responses and a photographic system to record the position of each ACh application permit the rapid construction of extensive and detailed maps of ACh sensitivity. Clusters of receptors, evident as peaks of ACh sensitivity, are present on many uninnervated myotubes. The distribution of ACh sensitivity closely parallels the distribution of 125I-alpha-bungarotoxin binding sites on the same muscle cell. In all cases where individual myotubes were adequately mapped before and after synapse formation, ingrowing axons induced new clusters of receptors rather than seeking out preexisting clusters. Synapses can form at active growth cones within 3 h of nerve-muscle contact. New receptor clusters can appear beneath neurites within a few hours. Many of the uninnervated clusters on innervated myotubes disappear with time. In contrast, receptor clusters on uninnervated myotubes remain in the same location for many hours. Synaptic clusters and clusters on uninervated myotubes are stable even though individual receptors are metabolized rapidly. The morphology of several identified sites of transmitter release was examined. At the scanning EM level, synapses appeared as small, rough-surfaced varicosities with filopodia that radiated outwards over the muscle surface. One synapse was studied by transmission EM. Acetylcholinesterase and a basement lamina were present within the synaptic cleft. PMID:511937

  18. Metal-free molecular junctions on ITO via amino-silane binding—towards optoelectronic molecular junctions

    NASA Astrophysics Data System (ADS)

    Sergani, S.; Furmansky, Y.; Visoly-Fisher, I.

    2013-11-01

    Light control over currents in molecular junctions is desirable as a non-contact input with high spectral and spatial resolution provided by the photonic input and the molecular electronics element, respectively. Expanding the study of molecular junctions to non-metallic transparent substrates, such as indium tin oxide (ITO), is vital for the observation of molecular optoelectronic effects. Non-metallic electrodes are expected to decrease the probability of quenching of molecular photo-excited states, light-induced plasmonic effects, or significant electrode expansion under visible light. We have developed micron-sized, metal free, optically addressable ITO molecular junctions with a conductive polymer serving as the counter-electrode. The electrical transport was shown to be dominated by the nature of the self-assembled monolayer (SAM). The use of amino-silane (APTMS) as the chemical binding scheme to ITO was found to be significant in determining the transport properties of the junctions. APTMS allows high junction yields and the formation of dense molecular layers preventing electrical short. However, polar amino-silane binding to the ITO significantly decreased the conductance compared to thiol-bound SAMs, and caused tilted geometry and disorder in the molecular layer. As the effect of the molecular structure on transport properties is clearly observed in our junctions, such metal-free junctions are suitable for characterizing the optoelectronic properties of molecular junctions.

  19. Tight Junctions\\/Adherens Junctions: Basic Structure and Function

    Microsoft Academic Search

    Carien M Niessen

    2007-01-01

    Adherens and tight junctions are intercellular junctions crucial for epithelial adhesion and barrier function in a wide variety of tissues and organisms. In stratifying epithelia, such as the epidermis, the role of adherens and tight junctions was considered less important owing to the abundance of desmosomes, mediating firm mechanical stability between the cells, and to the barrier function of the

  20. [Gap junctions and secretion].

    PubMed

    Haefliger, Jacques-Antoine; Allagnat, Florent; Krattinger, Nathalie; Martin, David; Waeber, Gérard; Nicod, Pascal; Meda, Paolo

    2005-04-27

    The emergence of multicellular organisms has necessitated the development of mechanisms for interactions between adjacent and distant cells. A consistent feature of this network is the expression of gap junction channels between the secretory cells of all glands so far investigated in vertebrates. Here, we reviewed the distribution of the gap junctions proteins, named connexins, in a few mammalian glands, and discussed the recent evidence pointing to the participation of these proteins in the functioning of endocrine and exocrine cells. Specifically, available data indicate the importance of gap junctions for the proper control of glucose-induced insulin secretion. Understanding the functions of beta-cell connexins are crucial for the engineering of surrogate cells, which is necessary for implementation of a replacement cell therapy in diabetic patients. PMID:15943000

  1. Phase diagrams of particles with dissimilar patches: X-junctions and Y-junctions

    NASA Astrophysics Data System (ADS)

    Tavares, J. M.; Teixeira, P. I. C.

    2012-07-01

    We use Wertheim’s first-order perturbation theory to investigate the phase behaviour and the structure of coexisting fluid phases for a model of patchy particles with dissimilar patches (two patches of type A and fB patches of type B). A patch of type ? = {A,B} can bond to a patch of type ? = {A,B} in a volume v??, thereby decreasing the internal energy by ???. We analyse the range of model parameters where AB bonds, or Y-junctions, are energetically disfavoured (?AB < ?AA/2) but entropically favoured (vAB ? v??), and BB bonds, or X-junctions, are energetically favoured (?BB > 0). We show that, for low values of ?BB/?AA, the phase diagram has three different regions: (i) close to the critical temperature a low-density liquid composed of long chains and rich in Y-junctions coexists with a vapour of chains; (ii) at intermediate temperatures there is coexistence between a vapour of short chains and a liquid of very long chains with X- and Y-junctions; (iii) at low temperatures an ideal gas coexists with a high-density liquid with all possible AA and BB bonds formed. It is also shown that in region (i) the liquid binodal is reentrant (its density decreases with decreasing temperature) for the lower values of ?BB/?AA. The existence of these three regions is a consequence of the competition between the formation of X- and Y-junctions: X-junctions are energetically favoured and thus dominate at low temperatures, whereas Y-junctions are entropically favoured and dominate at higher temperatures.

  2. Atomically wired molecular junctions: Connecting a single organic molecule by chains of metal atoms

    E-print Network

    Yelin, Tamar; Kuritz, Natalia; Korytár, Richard; Bagrets, Alexei; Evers, Ferdinand; Kronik, Leeor; Tal, Oren

    2015-01-01

    Using a break junction technique, we find a clear signature for the formation of conducting hybrid junctions composed of a single organic molecule (benzene, naphthalene or anthracene) connected to chains of platinum atoms. The hybrid junctions exhibit metallic-like conductance (~0.1-1G0), which is rather insensitive to further elongation by additional atoms. At low bias voltage the hybrid junctions can be elongated significantly beyond the length of the bare atomic chains. Ab initio calculations reveal that benzene based hybrid junctions have a significant binding energy and high structural flexibility that may contribute to the survival of the hybrid junction during the elongation process. The fabrication of hybrid junctions opens the way for combining the different properties of atomic chains and organic molecules to realize a new class of atomic scale interfaces.

  3. Tight junction, selective permeability, and related diseases.

    PubMed

    Krug, Susanne M; Schulzke, Jörg D; Fromm, Michael

    2014-12-01

    The tight junction forms a barrier against unlimited paracellular passage but some of the tight junction proteins just do the opposite, they form extracellular channels zigzagging between lateral membranes of neighboring cells. All of these channel-forming proteins and even some of the barrier formers exhibit selectivity, which means that they prefer certain substances over others. All channel formers exhibit at least one of the three types of selectivity: for cations (claudin-2, -10b, -15), for anions (claudin-10a, -17) or for water (claudin-2). Also some, but not all, barrier-forming claudins are charge-selective (claudin-4, -8, -14). Moreover, occludin and tricellulin turned out to be relevant for barrier formation against macromolecule passage. Tight junction proteins are dysregulated or can be genetically defective in numerous diseases, which may lead to three effects: (i) impaired paracellular transport e.g. causing magnesium loss in the kidney, (ii) increased paracellular transport of solutes and water e.g. causing leak-flux diarrhea in the intestine, and (iii) increased permeability to large molecules e.g. unwanted intestinal pathogen uptake fueling inflammatory processes. This review gives an overview on the properties of tight junction proteins featuring selective permeability, and in this context explains how these proteins induce or aggravate diseases. PMID:25220018

  4. Superconducting tunnel junctions

    Microsoft Academic Search

    Didier D. E. Martin; Peter Verhoeve

    2010-01-01

    Superconducting tunnel junctions (STJ) are a class of cryogenic detectors that rely on the generation of free charge carriers by breaking Cooper pairs in a superconducting material with the use of absorbed photon energy. In an STJ, consisting of two superconducting films separated by a thin insulating barrier, the charge carriers can be detected through the tunnel-current pulse they produce

  5. Laterally proximized aluminum tunnel junctions

    NASA Astrophysics Data System (ADS)

    Koski, J. V.; Peltonen, J. T.; Meschke, M.; Pekola, J. P.

    2011-05-01

    This letter presents experiments on junctions fabricated by a technique that enables the use of high-quality aluminum oxide tunnel barriers with normal metal electrodes at low temperatures. Inverse proximity effect is applied to diminish the superconductivity of an aluminum dot through a clean lateral connection to a normal metal electrode. To demonstrate the effectiveness of this method, fully normal-state single electron transistors (SETs) and normal metal-insulator-superconductor (NIS) junctions applying proximized Al junctions were fabricated. The transport characteristics of the junctions were similar to those obtained from standard theoretical models of regular SETs and NIS junctions.

  6. Parity effect in Josephson junction arrays

    NASA Astrophysics Data System (ADS)

    Cole, Jared H.; Heimes, Andreas; Duty, Timothy; Marthaler, Michael

    2015-05-01

    We study the parity effect and transport due to quasiparticles in circuits comprised of many superconducting islands. We develop a general approach and show that it is equivalent to previous methods for describing the parity effect in their more limited regimes of validity. As an example we study transport through linear arrays of Josephson junctions in the limit of negligible Josephson energy and observe the emergence of the parity effect with decreasing number of nonequilibrium quasiparticles. Due to the exponential increase in the number of relevant charge states with increasing length, in multijunction arrays the parity effect manifests in qualitatively different ways to the two-junction case. The role of charge disorder is also studied as this hides much of the parity physics that would otherwise be observed. Nonetheless, we see that the current through a multijunction array at low bias is limited by the formation of metastable even-parity states.

  7. A bosonic Josephson junction

    Microsoft Academic Search

    R Gati; M K Oberthaler

    2007-01-01

    We review the experimental realization of a single bosonic Josephson junction for ultracold gases, which was made possible by the generation of a precisely controllable double-well potential for Bose–Einstein condensates. We will focus on the comparison of the experimentally obtained data with the predictions of a many-body two-mode model and a mean-field description and show that the observed static, thermal

  8. Effect of edge junction isolation on the performance of laser doped selective emitter solar cells

    Microsoft Academic Search

    Brett Hallam; Stuart Wenham; Haeseok Lee; Eunjoo Lee; Hyunwoo Lee; Jisun Kim; Jeoungeun Shin

    2011-01-01

    The effect of laser and chemical edge junction isolation on electrical performance of industrially manufactured laser doped selective emitter solar cells with light induced plated n-type contacts is investigated in this work. Directly after the formation of the aluminium back surface field, photoluminescence images indicates that laser edge junction isolation causes substantial damage around the perimeter of the cell, extending

  9. 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

  10. Organic single-crystalline p-n junction nanoribbons.

    PubMed

    Zhang, Yajie; Dong, Huanli; Tang, Qingxin; Ferdous, Sunzida; Liu, Feng; Mannsfeld, Stefan C B; Hu, Wenping; Briseno, Alejandro L

    2010-08-25

    This article focuses on the growth and transport properties of organic single-crystalline p-n junction nanoribbons. The development of organic nanoelectronics requires the fabrication of organic nanometer-sized p-n junctions for high-performance devices and integrated circuits. Here we demonstrate the formation of single-crystalline p-n junction nanoribbons of organic semiconductors by selective crystallization of copper hexadecafluorophthalocyanine (F(16)CuPc, n-type) on copper phthalocyanine (CuPc, p-type) single-crystalline nanoribbons. The crystallization of F(16)CuPc onto CuPc requires several parameters, including similar molecular structures, similar lattice constants, and pi-stacking along the nanoribbon axis. Ambipolar transport of the p-n junction nanoribbons was observed in field-effect transistors with balanced carrier mobilities of 0.05 and 0.07 cm(2) V(-1) s(-1) for F(16)CuPc and CuPc, respectively. A basic p-n junction nanoribbon photovoltaic device showed current rectification under AM 1.5 simulated light. The discrete p-n junction nanoribbons may serve as ideal systems for understanding basic charge-transport and photovoltaic behaviors at organic-organic interfaces. PMID:20681577

  11. Cadherin controls nectin recruitment into adherens junctions by remodeling the actin cytoskeleton.

    PubMed

    Troyanovsky, Regina B; Indra, Indrajyoti; Chen, Chi-Shuo; Hong, Soonjin; Troyanovsky, Sergey M

    2015-01-01

    The mechanism that coordinates activities of different adhesion receptors is poorly understood. We investigated this mechanism by focusing on the nectin-2 and E-cadherin adherens junction receptors. We found that, cadherin was not required for the basic process of nectin junction formation because nectin-2 formed junctions in cadherin-deficient A431D cells. Formation of nectin-2 junctions in these cells, however, became regulated by cadherin as soon as E-cadherin was re-expressed. E-cadherin recruited nectin-2 into adherens junctions, where both proteins formed distinct but tightly associated clusters. Live-cell imaging showed that the appearance of E-cadherin clusters often preceded that of nectin-2 clusters at sites of junction assembly. Inactivation of E-cadherin clustering by different strategies concomitantly suppressed the formation of nectin clusters. Furthermore, cadherin significantly increased the stability of nectin clusters, thereby making them resistant to the BC-12 antibody, which targets the nectin-2 adhesion interface. By testing different E-cadherin-?-catenin chimeras, we showed that the recruitment of nectin into chimera junctions is mediated by the actin-binding domain of ?-catenin. Our data suggests that E-cadherin regulates assembly of nectin junctions through ?-catenin-induced remodeling of the actin cytoskeleton around the cadherin clusters. PMID:25395582

  12. Self-Similarity of a Junction Vortex

    NASA Astrophysics Data System (ADS)

    Naitoh, Takashi; Allen, James; Smits, Alexander

    2001-11-01

    This paper details experimental results examining the development of a vortical structure at the junction where one plate slides under another. The mechanism for the generation of this structure is the separation of the boundary layer, which forms on the moving plate, at the junction with the stationary one. This type of flow structure is of interest because of its appearance in situations where rigid surfaces slide across one another, such as the case of a piston moving through an internal combustion engine. The current experiment has been configured such that the external experimental length scales are always an order of magnitude larger than the size of the vortical structure that is generated at the junction. Data relating to the growth and strength of the structure for a range of Reynolds number, based on wall speed and distance traveled by the moving wall, from 400 to 100,000 show the initial formation of a viscous structure, a period of inviscid growth with an eventual transition to turbulence and breakdown of the vortex. The development of spawise instabilities on the outer turn of vortex structure have been recorded with dye visualizations and represent the precursor to turbulent breakdown.

  13. JUNCTION FORMATION AND ITS DEVICE IMPAC TT HROUGH THE NODES: FROM SINGLE T OC O-IMPLANTS, FROM BEAM-LINE TO PLASMA, FROM SINGLE IONS T OC LUSTERS, FROM RTA T OL TP

    Microsoft Academic Search

    Hans-Joachim L. Gossmann

    The fundamental design goals for a high-perf or mance logic technology ,m aximizing speed while minimizing power, d rive t he design of the junctions and in tur nt he require- ments on dopant placement and activation. In the early nodes implant energies of 10's ke Va nd furnace anneals sufficed. Scaling into the deep-sub-micron regime brought Tr a nsient

  14. Molecular analysis of the recombination junctions of ? bio transducing phases

    Microsoft Academic Search

    Michiyo Kumagai; Hideo Ikeda

    1991-01-01

    To examine the mechanism of recombination involved in the formation of specialized transducing phage during the induction of bacteriophage ? we have determined the nucleotide sequences of the recombination junctions of ?bio phages. The results indicate that abnormal excision takes place at many sites on both bacterial and phage genomes and that the recombination sites have short regions of homology

  15. Bile duct epithelial tight junctions and barrier function

    PubMed Central

    Rao, R.K.; Samak, G.

    2013-01-01

    Bile ducts play a crucial role in the formation and secretion of bile as well as excretion of circulating xenobiotic substances. In addition to its secretory and excretory functions, bile duct epithelium plays an important role in the formation of a barrier to the diffusion of toxic substances from bile into the hepatic interstitial tissue. Disruption of barrier function and toxic injury to liver cells appear to be involved in the pathogenesis of a variety of liver diseases such as primary sclerosing cholangitis, primary biliary cirrhosis and cholangiocarcinoma. Although the investigations into understanding the structure and regulation of tight junctions in gut, renal and endothelial tissues have expanded rapidly, very little is known about the structure and regulation of tight junctions in the bile duct epithelium. In this article we summarize the current understanding of physiology and pathophysiology of bile duct epithelium, the structure and regulation of tight junctions in canaliculi and bile duct epithelia and different mechanisms involved in the regulation of disruption and protection of bile duct epithelial tight junctions. This article will make a case for the need of future investigations toward our understanding of molecular organization and regulation of canalicular and bile duct epithelial tight junctions. PMID:24665411

  16. The Junction Diode Basic Operation

    E-print Network

    Leach Jr.,W. Marshall

    The Junction Diode Basic Operation The diode is fabricated of a semiconductor material, usually section of the diode. The junction is the dividing line between the n-type and p-type sides. Thermal the electric field sweeps them out. Figure 1: (a) Diode cross section. (b) Reverse biased diode. (c) Forward

  17. Pcbs and tight junction expression.

    PubMed

    Eum, Sung Yong; András, Ibolya E; Couraud, Pierre-Olivier; Hennig, Bernhard; Toborek, Michal

    2008-03-01

    Polychlorinated biphenyl (PCB) congeners exhibit a broad range of adverse biological effects including neurotoxicity. The mechanisms by which PCBs cause neurotoxic effects are still not completely understood. The blood-brain barrier (BBB) is a physical and metabolic barrier separating brain microenvironment from the peripheral circulation and is mainly composed of endothelial cells connected by tight junctions. We examined the effects of several highly-chlorinated PCB congeners on expression of tight junction proteins in human brain endothelial cells. Treatment for 24 h with selective PCB congeners disrupted expression of the cytosolic scaffold proteins of tight junctions, such as zonula occludens (ZO)-1, ZO-2, and AF6. In contrast, PCB exposure did not alter expression of integral membrane proteins, junctional adhesion molecule-A (JAM-A), and claudin-1. Based on these data, we suggest that PCB-mediated selective alterations of tight junction protein expression may contribute to their neurotoxic effects in the central nervous system. PMID:18438464

  18. Bipolar Junction Transistors

    NSDL National Science Digital Library

    Kuphaldt, Tony R.

    All About Circuits is a website that â??provides a series of online textbooks covering electricity and electronics.â? Written by Tony R. Kuphaldt, the textbooks available here are wonderful resources for students, teachers, and anyone who is interested in learning more about electronics. This specific section, Bipolar Junction Transistors, is the fourth chapter in Volume III â??Semiconductors. A few of the topics covered in this chapter include: The Transistor as a Switch, Active Mode Operation, and Input and Output Coupling. Diagrams and detailed descriptions of concepts are included throughout the chapter to provide users with a comprehensive lesson. Visitors to the site are also encouraged to discuss concepts and topics using the All About Circuits discussion forums (registration with the site is required to post materials).

  19. 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

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

    SciTech Connect

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

    2008-05-01

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

  1. Multi-junction solar cell designs

    Microsoft Academic Search

    Mahieddine Emziane; Adam Sleiman

    2011-01-01

    In this paper the designs of multi- junction solar cells for very high energy conversion efficiencies are reviewed. We highlight the importance of the concept of multi-junction solar devices and its superiority compared to other photovoltaic technologies. We present different types of multi-junction structures, and address the different electrical configurations used in various multi- junction designs.

  2. 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].

  3. 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

  4. 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.

  5. Thermal conductance of superlattice junctions

    NASA Astrophysics Data System (ADS)

    Lu, Simon; McGaughey, Alan J. H.

    2015-05-01

    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.

  6. Josephson junction Q-spoiler

    DOEpatents

    Clarke, John (Berkeley, CA); Hilbert, Claude (Austin, TX); Hahn, Erwin L. (Berkeley, CA); Sleator, Tycho (Berkeley, CA)

    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.

  7. Critical current uniformity and stability of Nb/Al-oxide-Nb Josephson junctions

    SciTech Connect

    Gates, J.V.; Washington, M.A.; Gurvitch, M.

    1984-03-01

    The critical current stability of Nb Josephson junctions using thin Al oxide layers as the tunneling barrier has been investigated with respect to repeated thermal cycling, aging, and annealing at elevated temperatures as a function of time. The Nb electrodes and in situ thermally oxidized Al barriers were deposited by dc magnetron sputtering prior to the lithographic formation of the individual junctions. The arrays of junctions were formed by standard photolithography techniques, reactive ion etching, and anodization. A population of 400 20-..mu..m-square junctions were thermally cycled from room temperature to 6 K 4880 times with no failures due to shorts and no change in the average critical currents. These same unpassivated junctions were annealed at elevated temperatures for various periods of time until the critical currents had decreased by 50% at temperatures near 275 /sup 0/C.

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

    PubMed

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

    2013-07-12

    Silicon nanowires (SiNWs) grown on low-cost substrates provide an ideal framework for the monolithic fabrication of radial junction photovoltaics. However, the quality of junction formation over a random matrix of SiNWs, fabricated via a vapor-liquid-solid (VLS) mechanism, has never been assessed in a realistic context. To address this, we probe the current response of individual radial junction solar cells under electron-beam and optical-beam excitations. Excellent current generation from the radial junction units, compared to their planar counterparts, has been recorded, indicating a high junction quality and effective doping in the ultra-thin SiNWs with diameters thinner than 20 nm. Interestingly, we found that the formation of radial junctions by plasma deposition can be quite robust against geometrical disorder and even the crossings of neighboring cell units. These results provide a strong support to the feasibility of building high-quality radial junction solar cells over high-throughput VLS-grown SiNWs on low-cost substrates. PMID:23764545

  9. Electric breakdown in ultrathin MgO tunnel barrier junctions for spin-transfer torque switching

    SciTech Connect

    Schaefers, M.; Drewello, V.; Reiss, G.; Thomas, A. [Department of Physics, Thin Films and Physics of Nanostructures, Bielefeld University, 33501 Bielefeld (Germany); Thiel, K. [Fraunhofer Institut fuer Fertigungstechnik und Angewandte Materialforschung, Wiener Str. 12, 28359 Bremen (Germany); Eilers, G.; Muenzenberg, M.; Schuhmann, H.; Seibt, M. [I. and IV. Physikalisches Institut and Sonderforschungsbereich 602, Friedrich-Hund-Platz 1, Georg-August-Universitaet Goettingen, 37077 Goettingen (Germany)

    2009-12-07

    Magnetic tunnel junctions for spin-transfer torque (STT) switching are prepared to investigate the dielectric breakdown. Intact and broken tunnel junctions are characterized by transport measurements prior to transmission electron microscopy analysis. The comparison to our previous model for thicker MgO tunnel barriers reveals a different breakdown mechanism arising from the high current densities in a STT device: instead of local pinhole formation at a constant rate, massive electromigration and heating leads to displacement of the junction material and voids are appearing. This is determined by element resolved energy dispersive x-ray spectroscopy and three dimensional tomographic reconstruction.

  10. Unexpected Roles of the Na-K-ATPase and Other Ion Transporters in Cell Junctions and Tubulogenesis

    NSDL National Science Digital Library

    Thomas Krupinski (Department of Biochemistry, Molecular Biology, and Cell Biology)

    2009-06-01

    Recent work shows that transport-independent as well as transport-dependent functions of ion transporters, and in particular the Na-K-ATPase, are required for formation and maintenance of several intercellular junctions. Furthermore, these junctional and other nonjunctional functions of ion transporters contribute to development of epithelial tubes. Here, we consider what has been learned about the roles of ion pumps in formation of junctions and epithelial tubes in mammals, zebrafish, Drosophila, and C. elegans. We propose that asymmetric association of the Na-K-ATPase with cell junctions early in metazoan evolution enabled vectorial transcellular ion transport and control of intraorganismal environment. Ion transport-independent functions of the Na-K-ATPase arose as junctional complexes evolved.

  11. The kidney tight junction (Review)

    PubMed Central

    HOU, JIANGHUI

    2014-01-01

    The tight junction is an important subcellular organelle which plays a vital role in epithelial barrier function. Claudin, as the integral membrane component of tight junctions, creates a paracellular transport pathway for various ions to be reabsorbed by the kidneys. This review summarizes advances in claudin structure, function and pathophysiology in kidney diseases. Different claudin species confer selective paracellular permeability to each of three major renal tubular segments: the proximal tubule, the thick ascending limb of Henle’s loop and the distal nephron. Defects in claudin function can cause a wide spectrum of kidney diseases, such as hypomagnesemia, hypercalciuria, kidney stones and hypertension. Studies using transgenic mouse models with claudin mutations have recapitulated several of these renal disease phenotypes and have elucidated the underlying biological mechanisms. Modern recording approaches based upon scanning ion conductance microscopy may resolve the biophysical nature of claudin transport function and provide novel insight into tight junction architecture. PMID:25319473

  12. Glial ankyrins facilitate paranodal axoglial junction assembly.

    PubMed

    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

    2014-12-01

    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, and they 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 are important for membrane domain establishment and maintenance in many cell types. Here we show that ankyrin-B, expressed by Schwann cells, and ankyrin-G, 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 CNS. PMID:25362471

  13. 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

  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. Gap junctions in cardiovascular disease.

    PubMed

    Jongsma, H J; Wilders, R

    2000-06-23

    Connexins, the protein molecules forming gap junction channels, are reduced in number or redistributed from intercalated disks to lateral cell borders in a variety of cardiac diseases. This "gap junction remodeling" is considered to be arrhythmogenic. Using a simple model of human ventricular myocardium, we found that quantitative remodeling data extracted from the literature gave rise to only small to moderate changes in conduction velocity and the anisotropy ratio. Especially for longitudinal conduction, cytoplasmic resistivity (and thus cellular geometry) is much more important than commonly realized. None of the remodeling data gave rise to slow conduction on the order of a few centimeters per second. PMID:10864907

  16. Multi-junction solar cell device

    Microsoft Academic Search

    Daniel J. Friedman; John F. Geisz

    2007-01-01

    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

  17. Precision measurement with an optical Josephson junction

    E-print Network

    H. T. Ng; K. Burnett; J. A. Dunningham

    2006-11-18

    We study a new type of Josephson device, the so-called "optical Josephson junction" as proposed in Phys. Rev. Lett. {\\bf 95}, 170402 (2005). Two condensates are optically coupled through a waveguide by a pair of Bragg beams. This optical Josephson junction is analogous to the usual Josephson junction of two condensates weakly coupled via tunneling. We discuss the use of this optical Josephson junction, for making precision measurements.

  18. 27 CFR 9.164 - River Junction.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...2014-04-01 2014-04-01 false River Junction. 9.164 Section 9.164...American Viticultural Areas § 9.164 River Junction. (a) Name. The name of...viticultural area described in this section is “River Junction.” (b) Approved...

  19. 27 CFR 9.164 - River Junction.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...2012-04-01 2012-04-01 false River Junction. 9.164 Section 9.164...American Viticultural Areas § 9.164 River Junction. (a) Name. The name of...viticultural area described in this section is “River Junction.” (b) Approved...

  20. 27 CFR 9.164 - River Junction.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...2013-04-01 2013-04-01 false River Junction. 9.164 Section 9.164...American Viticultural Areas § 9.164 River Junction. (a) Name. The name of...viticultural area described in this section is “River Junction.” (b) Approved...

  1. 27 CFR 9.164 - River Junction.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...2011-04-01 2011-04-01 false River Junction. 9.164 Section 9.164...American Viticultural Areas § 9.164 River Junction. (a) Name. The name of...viticultural area described in this section is “River Junction.” (b) Approved...

  2. Josephson tunnel junctions on niobium films

    Microsoft Academic Search

    T. Wiik

    1976-01-01

    A method of fabricating stable Josephson tunnel junctions with reproducible characteristics is described. The junctions have a sandwich structure consisting of a vacuum evaporated niobium film, a niobium oxide layer produced by the glow discharge method and a lead film deposited by vacuum evaporation. Difficulties in producing thin-film Josephson junctions are discussed. Experimental results suggest that the lower critical field

  3. Promoting RNA helical stacking via A-minor junctions

    PubMed Central

    Geary, Cody; Chworos, Arkadiusz; Jaeger, Luc

    2011-01-01

    RNA molecules take advantage of prevalent structural motifs to fold and assemble into well-defined 3D architectures. The A-minor junction is a class of RNA motifs that specifically controls coaxial stacking of helices in natural RNAs. A sensitive self-assembling supra-molecular system was used as an assay to compare several natural and previously unidentified A-minor junctions by native polyacrylamide gel electrophoresis and atomic force microscopy. This class of modular motifs follows a topological rule that can accommodate a variety of interchangeable A-minor interactions with distinct local structural motifs. Overall, two different types of A-minor junctions can be distinguished based on their functional self-assembling behavior: one group makes use of triloops or GNRA and GNRA-like loops assembling with helices, while the other takes advantage of more complex tertiary receptors specific for the loop to gain higher stability. This study demonstrates how different structural motifs of RNA can contribute to the formation of topologically equivalent helical stacks. It also exemplifies the need of classifying RNA motifs based on their tertiary structural features rather than secondary structural features. The A-minor junction rule can be used to facilitate tertiary structure prediction of RNAs and rational design of RNA parts for nanobiotechnology and synthetic biology. PMID:20876687

  4. INVESTIGATION Multiple Pathways of Duplication Formation

    E-print Network

    Roth, John R.

    INVESTIGATION Multiple Pathways of Duplication Formation with and Without Recombination (Rec to "unequal recombination" between separated, directly repeated sequence elements (.100 bp), events that leave a recombinant element at the duplication junction. However, in the bacterial chromosome, duplications form

  5. GAP JUNCTION FUNCTION AND CANCER

    EPA Science Inventory

    Gap Junctions (GJs) provide cell-to-cell communication (GJIC) of essential metabolites and ions. Js allow tissues to average responses, clear waste products, and minimize the effects of xenobiotics by dilution and allowing steady-state catabolism. any chemicals can adversely affe...

  6. 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.

  7. Signaling the Junctions in Gut Epithelium

    NSDL National Science Digital Library

    Frederic Hollande (CNRS France; Functional Genomics Institute (IGF) and Cellular and Molecular Oncology Department REV)

    2005-03-29

    This Perspective summarizes recent developments in our understanding of the signaling pathways involved in the regulation of epithelial cell adhesion in the gut. The role of phosphatidylinositol 3-kinase signaling in the modulation of adherens junctions, and the connections between tight junctions and nuclear transcription factors, are discussed. The effect of gastrins on adherens and tight junctions is presented as an example of the regulation of adhesion by growth factors. The consequences of dysregulation of adherens junctions and tight junctions for human pathology are also considered.

  8. The Adherens Junction: A Mosaic of Cadherin and Nectin Clusters Bundled by Actin Filaments

    PubMed Central

    Indra, Indrajyoti; Hong, Soonjin; Troyanovsky, Regina; Kormos, Bernadett; Troyanovsky, Sergey

    2013-01-01

    Summary Cadherin and nectin are distinct transmembrane proteins of adherens junctions. Their ectodomains mediate adhesion while their cytosolic regions couple the adhesive contact to the cytoskeleton. Both these proteins are essential for adherens junction formation and maintenance. However, some basic aspects of these proteins, such as their organization in adherence junctions, have remained open. Therefore, using super-resolution microscopy and live-imaging, we focused on the subjunctional distribution of these proteins. We showed that cadherin and nectin in the junctions of A431 cells and human keratinocytes are located in separate clusters. The size of each cluster is independent of that of the adjacent clusters and can significantly fluctuate over time. Several nectin and cadherin clusters that constitute an individual adherens junction are united by the same actin filament bundle. Surprisingly, interactions between each cluster and F-actin are not uniform since neither vinculin nor LIM domain actin-binding proteins match the boundaries of cadherin or nectin clusters. Thus, the adherens junction is not a uniform structure but a mosaic of different adhesive units with very diverse modes of interaction with the cytoskeleton. We propose that such a mosaic architecture of adherence junctions is important for the fast regulation of their dynamics. PMID:23639974

  9. Tight junction protein MAGI1 is up-regulated by transfection with connexin 32 in an immortalized mouse hepatic cell line: cDNA microarray analysis

    Microsoft Academic Search

    Masaki Murata; Takashi Kojima; Toshinobu Yamamoto; Mitsuru Go; Ken-ichi Takano; Hideki Chiba; Takashi Tokino; Norimasa Sawada

    2005-01-01

    Gap junctions are considered to play a crucial role in differentiation of epithelial cells, including hepatocytes. Recently, we found that Cx32 but not Cx26 was closely related to tight junctional proteins in primary cultured rat hepatocytes (Kojima et al., Exp Cell Res 263:193–201, 2001) and that Cx32 formation and\\/or Cx32-mediated intercellular communication could induce expression and function of tight junctions

  10. Structure and characteristics of the high-temperature SiC detectors based on Al ion-implanted p+-n junctions

    Microsoft Academic Search

    E. V. Kalinina; A. M. Ivanov; N. B. Strokan; A. A. Lebedev

    2011-01-01

    Al ion implantation of chemical-vapor deposition (CVD)-grown n-type films has been used to fabricate p+-n junctions for nuclear particle detectors. The junction formation mode is characterized by a high dose of Al ions and a short-duration (15 s) activating annealing. Specific structural features of the implanted p+-n junctions, revealed using modern analytical techniques, are accounted for by the joint action

  11. The Small GTPase Rab13 Regulates Assembly of Functional Tight Junctions in Epithelial Cells

    PubMed Central

    Marzesco, Anne-Marie; Dunia, Irene; Pandjaitan, Rudy; Recouvreur, Michel; Dauzonne, Daniel; Benedetti, Ennio Lucio; Louvard, Daniel; Zahraoui, Ahmed

    2002-01-01

    Junctional complexes such as tight junctions (TJ) and adherens junctions are required for maintaining cell surface asymmetry and polarized transport in epithelial cells. We have shown that Rab13 is recruited to junctional complexes from a cytosolic pool after cell–cell contact formation. In this study, we investigate the role of Rab13 in modulating TJ structure and functions in epithelial MDCK cells. We generate stable MDCK cell lines expressing inactive (T22N mutant) and constitutively active (Q67L mutant) Rab13 as GFP-Rab13 chimeras. Expression of GFP-Rab13Q67L delayed the formation of electrically tight epithelial monolayers as monitored by transepithelial electrical resistance (TER) and induced the leakage of small nonionic tracers from the apical domain. It also disrupted the TJ fence diffusion barrier. Freeze-fracture EM analysis revealed that tight junctional structures did not form a continuous belt but rather a discontinuous series of stranded clusters. Immunofluorescence studies showed that the expression of Rab13Q67L delayed the localization of the TJ transmembrane protein, claudin1, at the cell surface. In contrast, the inactive Rab13T22N mutant did not disrupt TJ functions, TJ strand architecture nor claudin1 localization. Our data revealed that Rab13 plays an important role in regulating both the structure and function of tight junctions. PMID:12058051

  12. Investigation of modified p-n junctions in crystalline silicon on glass solar cells

    NASA Astrophysics Data System (ADS)

    Lausch, D.; Werner, M.; Naumann, V.; Schneider, J.; Hagendorf, C.

    2011-04-01

    In this paper various methods for studying p-n junctions in thin film solar cells are applied with the aim to localize and investigate defects on a microscopic scale. Different electron and ion beam characterization methods are introduced to determine the p-n junction position using two different examples from crystalline silicon on glass thin film technology. In a first example, planview and cross section electron beam induced current measurements revealed that oxygen rich columnar growth at textured substrates strongly disturbs the p-n junction. In a second example, diffusion from glass substrate is identified by ToF-SIMS to influence the electrical and structural characteristics of the thin Si layer resulting in a modified p-n junction. A model describing the formation of both defect structures is introduced.

  13. Organization of Cellular Receptors into a Nanoscale Junction during HIV-1 Adhesion

    PubMed Central

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

    2010-01-01

    The fusion of the human immunodeficiency virus type 1 (HIV-1) with its host cell is the target for new antiretroviral therapies. Viral particles interact with the flexible plasma membrane via viral surface protein gp120 which binds its primary cellular receptor CD4 and subsequently the coreceptor CCR5. However, whether and how these receptors become organized at the adhesive junction between cell and virion are unknown. Here, stochastic modeling predicts that, regarding binding to gp120, cellular receptors CD4 and CCR5 form an organized, ring-like, nanoscale structure beneath the virion, which locally deforms the plasma membrane. This organized adhesive junction between cell and virion, which we name the viral junction, is reminiscent of the well-characterized immunological synapse, albeit at much smaller length scales. The formation of an organized viral junction under multiple physiopathologically relevant conditions may represent a novel intermediate step in productive infection. PMID:20657663

  14. Metallic oxide p-I-n junctions with ferroelectric as the barrier

    NASA Astrophysics Data System (ADS)

    Yuan, J.; Wu, H.; Cao, L. X.; Zhao, L.; Jin, K.; Zhu, B. Y.; Zhu, S. J.; Zhong, J. P.; Miao, J.; Xu, B.; Qi, X. Y.; Qiu, X. G.; Duan, X. F.; Zhao, B. R.

    2007-03-01

    The authors report the formation of the metallic oxide p-I-n junctions with the ferroelectric (Ba ,Sr)TiO3 (BST) as the barrier. The junctions with different thicknesses of BST are investigated. With appropriate thickness, the junctions possess definite parameters, such as the negligible reversed current density (?10-7A/cm2), large breakdown voltage (>7V), and ultrahigh rectification (>2×104) in the bias voltage ?2.0V and temperature range from 5to300K. It is under consideration that the built-in field V0, the ferroelectric reversed polarized field Vrp, and the resistivity of the BST layer together decide the transport properties of the junctions.

  15. Organization of cell junctions in the peritoneal mesothelium

    Microsoft Academic Search

    Maya Simionescu; Nicolae Simionescu

    1977-01-01

    ABSTRACT Intercellular junctions in the mesothelium,of the visceral (mesentery and omen- turn), and parietal (diaphragm, pre-aortic, and iliac region) peritoneum were examined,in rats and mice by using freeze-cleaved preparations. In addition to usual intercellular junctions (cell body junctions), special junctions are found between,cell processes,and,the surface of the neighboring,cell (cell process junctions). Cell body junctions are provided,with tight junctions and communicat-

  16. 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(-?1d1 - ?2d2), where J(V) is the current density (A/cm(2)) at applied voltage V and ?i 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 ?. PMID:25871745

  17. Correlated charge transport in bilinear tunnel junction arrays

    NASA Astrophysics Data System (ADS)

    Walker, Kelly A.; Cole, Jared H.

    2013-12-01

    We study theoretically the nature of correlations in space and time of the current in a one-dimensional bilinear array of tunnel junctions in the normal conduction limit, using the kinetic Monte Carlo method. The bilinear array consists of two parallel rows of tunnel junctions, capacitively coupled in a ladder configuration. The electrostatic potential landscape and the charge-charge interaction length both depend on the circuit capacitances, which in turn influence transport and charge correlations in the array. We observe the formation of stationary charge states when only one rail is voltage biased. When a symmetric bias is applied to both rails, the site at which the positive and negative charge carriers recombine can drift throughout the array. We also calculate charge densities and auto- and cross-correlation functions.

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

    Microsoft Academic Search

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

    2009-01-01

    Immunocytochemical, electron-, and immunoelectron-microscopical studies have revealed that, in addition to the four major\\u000a “textbook categories” of cell-cell junctions (gap junctions, tight junctions, adherens junctions, and desmosomes), a broad\\u000a 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\\u000a transformed

  19. Thermocouple, multiple junction reference oven

    NASA Technical Reports Server (NTRS)

    Leblanc, L. P. (inventor)

    1981-01-01

    An improved oven for maintaining the junctions of a plurality of reference thermocouples at a common and constant temperature is described. The oven is characterized by a cylindrical body defining a heat sink with axially extended-cylindrical cavity a singularized heating element which comprises a unitary cylindrical heating element consisting of a resistance heating coil wound about the surface of metallic spool with an axial bore defined and seated in the cavity. Other features of the oven include an annular array of radially extended bores defined in the cylindrical body and a plurality of reference thermocouple junctions seated in the bores in uniformly spaced relation with the heating element, and a temperature sensing device seated in the axial bore for detecting temperature changes as they occur in the spool and circuit to apply a voltage across the coil in response to detected drops in temperatures of the spool.

  20. Fabrication of Tunnel Junctions For Direct Detector Arrays With Single-Electron Transistor Readout Using Electron-Beam Lithography

    NASA Technical Reports Server (NTRS)

    Stevenson, T. R.; Hsieh, W.-T.; Li, M. J.; Stahle, C. M.; Rhee, K. W.; Teufel, J.; Schoelkopf, R. J.

    2002-01-01

    This paper will describe the fabrication of small aluminum tunnel junctions for applications in astronomy. Antenna-coupled superconducting tunnel junctions with integrated single-electron transistor readout have the potential for photon-counting sensitivity at sub-millimeter wavelengths. The junctions for the detector and single-electron transistor can be made with electron-beam lithography and a standard self-aligned double-angle deposition process. However, high yield and uniformity of the junctions is required for large-format detector arrays. This paper will describe how measurement and modification of the sensitivity ratio in the resist bilayer was used to greatly improve the reliability of forming devices with uniform, sub-micron size, low-leakage junctions.

  1. Fusions at the craniovertebral junction

    Microsoft Academic Search

    Raheel Ahmed; Vincent C. Traynelis; Arnold H. Menezes

    2008-01-01

    Introduction  The surgical management of craniovertebral junction instability in pediatric patients has unique challenges. While the indications\\u000a for internal fixation in children are similar to those of adults, the data concerning techniques, complications, and outcomes\\u000a of spinal instrumentation comes from experience with adult patients. Diminutive osseous and ligamentous structures and anatomical\\u000a variations associated with syndromic craniovertebral abnormalities frequently complicates the approaches

  2. Magnetic switching and magnetoresistance in nanoscale spin tunnel junctions

    E-print Network

    Haviland, David

    Magnetic switching and magneto­resistance in nano­scale spin tunnel junctions D. B. Haviland, M, Sweden. haviland@nanophys.kth.se, www.nanophys.kth.se Co/AlO x /Co magnetic tunnel junctions in both multi­junction arrays and double­tunnel junction geometries have been studied. The junctions ex­ hibit

  3. 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.

  4. Structural Aspects of Adherens Junctions and Desmosomes

    Microsoft Academic Search

    H.-J. Choi; W. I. Weis

    \\u000a The cadherin-containing intercellular junctions, adherens junctions and desmosomes share an overall logical organization in\\u000a which the extracellular regions of the cadherins on opposing cells interact, while their cytoplasmic domains are linked to\\u000a the cytoskeleton through protein assemblies. In adherens junctions, ?-catenin binds to the cytoplasmic domain of cadherins and to ?-catenin, which links the cadherin\\/?-catenin complex to the actin cytoskeleton.

  5. Geometry and Topology of String Junctions

    E-print Network

    Antonella Grassi; James Halverson; Julius L. Shaneson

    2014-10-24

    We study elliptic fibrations by analyzing suitable deformations of the fibrations and vanishing cycles. We introduce geometric string junctions and describe some of their properties. We show how the structure of the geometric string junctions is naturally related to the Lie algebra structures of the associated singularities. One application in physics is in F-theory, where our novel approach connecting deformations and Lie algebras describes the structure of generalized type IIB seven-branes and string junction states which end on them.

  6. Geometry and Topology of String Junctions

    E-print Network

    Grassi, Antonella; Shaneson, Julius L

    2014-01-01

    We study elliptic fibrations by analyzing suitable deformations of the fibrations and vanishing cycles. We introduce geometric string junctions and describe some of their properties. We show how the structure of the geometric string junctions is naturally related to the Lie algebra structures of the associated singularities. One application in physics is in F-theory, where our novel approach connecting deformations and Lie algebras describes the structure of generalized type IIB seven-branes and string junction states which end on them.

  7. Quantum shot noise in tunnel junctions

    NASA Technical Reports Server (NTRS)

    Ben-Jacob, E.; Mottola, E.; Schoen, G.

    1983-01-01

    The current and voltage fluctuations in a normal tunnel junction are calculated from microscopic theory. The power spectrum can deviate from the familiar Johnson-Nyquist form when the self-capacitance of the junction is small, at low temperatures permitting experimental verification. The deviation reflects the discrete nature of the charge transfer across the junction and should be present in a wide class of similar systems.

  8. Submillimeter wave generation using Josephson junction arrays

    Microsoft Academic Search

    K.-L. Wan; A. K. Jain; J. E. Lukens

    1989-01-01

    A submillimeter-wave oscillator using a phase-locked array of Josephson junctions is demonstrated. With an array of 40 shunted tunnel junctions, the oscillator delivers 1 microW of power at 350 GHz into a 60-Ohm load on the chip. The operating frequency of the oscillator is tunable over a range of about 10 percent. Experiments on two coupled lead alloy tunnel junctions

  9. Investigation of Nd-Ce-Cu-O planar tunnel junctions and bicrystal grain boundary junctions

    Microsoft Academic Search

    S. I. Woods; A. S. Katz; T. L. Kirk; M. C. de Andrade; M. B. Maple; R. C. Dynes

    1999-01-01

    We have fabricated planar c-axis Pb\\/NCCO junctions and in-plane NCCO bicrystal grain boundary junctions. The Pb\\/NCCO junctions exhibit single-step elastic tunneling and sustain hysteretic Josephson supercurrents, evidence that NCCO has an s-wave component to its superconducting order parameter. Tunneling spectroscopy on high-resistance Pb\\/NCCO junctions reveals a semi-gap of 3-4 meV in the density of states of NCCO and evidence for

  10. Thermal activation of superconducting Josephson junctions

    E-print Network

    Devalapalli, Aditya P. (Aditya Prakash)

    2007-01-01

    Superconducting quantum circuits (SQCs) are being explored as model systems for scalable quantum computing architectures. Josephson junctions are extensively used in superconducting quantum interference devices (SQUIDs) ...

  11. UTE MRI of the Osteochondral Junction

    PubMed Central

    Biswas, Reni; Chen, Karen; Chang, Eric Y.; Chung, Christine B.

    2014-01-01

    The osteochondral junction is composed of numerous tissue components and serves important functions relating to structural stability and proper nutrition in joints such as the knee and spine. Conventional MR techniques have been inadequate at imaging the tissues of the osteochondral junction primarily because of the intrinsically short T2 nature of these tissues, rendering them “invisible” with the standard acquisitions. Ultrashort time to echo (UTE) MR techniques acquire sufficient MR signal of osteochondral tissues, thereby allowing direct evaluation. This article reviews the anatomy of the osteochondral junction of the knee and the spine, technical aspects of UTE MRI, and the application of UTE MRI for evaluation of the osteochondral junction. PMID:25061547

  12. Endothelial adherens junctions control tight junctions by VE-cadherin-mediated upregulation of claudin-5

    Microsoft Academic Search

    Andrea Taddei; Costanza Giampietro; Annarita Conti; Fabrizio Orsenigo; Ferruccio Breviario; Valentina Pirazzoli; Michael Potente; Christopher Daly; Stefanie Dimmeler; Elisabetta Dejana

    2008-01-01

    Intercellular junctions mediate adhesion and communication between adjoining cells. Although formed by different molecules, tight junctions (TJs) and adherens junctions (AJs) are functionally and structurally linked, but the signalling pathways behind this interaction are unknown. Here we describe a cell-specific mechanism of crosstalk between these two types of structure. We show that endothelial VE-cadherin at AJs upregulates the gene encoding

  13. Extended description of tunnel junctions for distributed modeling of concentrator multi-junction solar cells

    Microsoft Academic Search

    P. Espinet; I. García; I. Rey-Stolle; C. Algora; M. Baudrit

    2011-01-01

    One of the key components of highly efficient multi-junction concentrator solar cells is the tunnel junction interconnection. In this paper, an improved 3D distributed model is presented that considers real operation regimes in a tunnel junction. This advanced model is able to accurately simulate the operation of the solar cell at high concentrations at which the photogenerated current surpasses the

  14. Ag2S-AgInS2: p-n junction heteronanostructures with quasi type-II band alignment.

    PubMed

    Bose, Riya; Manna, Goutam; Jana, Santanu; Pradhan, Narayan

    2014-03-21

    We report here the fabrication of a p-n junction diode in a single nanostructure by synthesizing a heterostructure involving n-type AgInS2 and p-type Ag2S. The quasi type-II band alignment between these ternary-binary semiconductors in the p-n junction heterostructures also slows down the carrier recombination rate and the heterostructures show rectification behavior. Hence, they can be used as an active material for fabrication of bulk heterojunction photovoltaic devices without any additional semiconductor material or dye required for charge separation or formation of a p-n junction. PMID:24516862

  15. Superconducting tunnel-junction refrigerator

    SciTech Connect

    Melton, R.G.; Paterson, J.L.; Kaplan, S.B.

    1980-03-01

    The dc current through an S/sub 1/-S/sub 2/ tunnel junction, with ..delta../sub 2/ greater than ..delta../sub 1/, when biased with eV<..delta../sub 1/+..delta../sub 2/, will lower the energy in S/sub 1/. This energy reduction will be shared by the phonons and electrons. This device is shown to be analogous to a thermoelectric refrigerator with an effective Peltier coefficient ..pi..* approx. ..delta../sub 1//e. Tunneling calculations yield the cooling power P/sub c/, the electrical power P/sub e/ supplied by the bias supply, and the cooling efficiency eta=P/sub c//P/sub e/. The maximum cooling power is obtained for eV= +- (..delta../sub 2/-..delta../sub 1/) and t/sub 1/=T/sub 1//T/sub c/1 approx. 0.9. Estimates are made of the temperature difference T/sub 2/-T/sub 1/ achievable in Al-Pb and Sn-Pb junctions with an Al/sub 2/O/sub 3/ tunneling barrier. The performance of this device is shown to yield a maximum cooling efficiency eta approx. = ..delta../sub 1//(..delta../sub 2/-..delta../sub 1/) which can be compared with that available in an ideal Carnot refrigerator of eta=T/sub 1//(T/sub 2/-T/sub 1/). The development of a useful tunnel-junction refrigerator requires a tunneling barrier with an effective thermal conductance per unit area several orders of magnitude less than that provided by the A1/sub 2/O/sub 3/ barrier in the Al-Pb and Sn-Pb systems.

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

    PubMed

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

    2012-02-01

    The formation of gold-gold junction electrodes for application in electroanalysis is described here based on electro-deposition from a non-cyanide gold plating bath. Converging growth of two hemispherical gold deposits on two adjacent platinum microelectrodes (both 100 µm diameter in glass, ca. 45 µm gap) followed by careful etching in aqueous chloride solution was employed. During growth both gold hemispheres "connect" and during etching "disconnection" is evident in a drop in current. Gold-gold junctions with sub-micron gaps are formed and applied for the electroanalytical detection of sub-micromolar concentrations of hydroquinone in 0.1 M phosphate buffer pH 7 (E(rev) = 0.04 V vs. SCE) and sub-micromolar concentration of dopamine in 0.1 M phosphate buffer pH 7 (E(rev) = 0.14 V vs. SCE). The potential future uses in analysis and limitations of gold-gold junction electrodes are discussed. PMID:21898774

  17. Occipitocervical junction: imaging, pathology, instrumentation.

    PubMed

    Benke, Michael; Yu, Warren D; Peden, Sean C; O'Brien, Joseph R

    2011-10-01

    The occipitocervical junction (OCJ) is a highly specialized area of the spine. Understanding the unique anatomy, imaging, and craniometry of this area is paramount in recognizing and managing the potentially devastating effects that pathology has on it. Instrumentation techniques continue to evolve, the goal being to safely obtain durable, rigid constructs that allow immediate stability, anatomical alignment, and osseous fusion. This article reviews the pathologic conditions at the OCJ and the current instrumentation and fusion options available for treatment. The general orthopedist needs to recognize the pathology common in this region and appropriately refer patients for treatment. PMID:22263204

  18. 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

  19. Conductance of a Molecular Junction M. A. Reed,* C. Zhou, C. J. Muller, T. P. Burgin,

    E-print Network

    Zhou, Chongwu

    in formation of a self-assembled monolayer (SAM) on the gold electrodes that was nearly perpendicular* Molecules of benzene-1,4-dithiol were self-assembled onto the two facing gold elec- trodes of a mechanically controllable break junction to form a statically stable gold- sulfur-aryl-sulfur-gold system, allowing

  20. Tight Junction Regulation in the Mammary Gland

    Microsoft Academic Search

    Duy-Ai D. Nguyen; Margaret C. Neville

    1998-01-01

    Tight junctions form a narrow, continuous sealthat surrounds each endothelial and epithelial cell atthe apical border, and act to regulate the movement ofmaterial through the paracellular pathway. In the mammary gland, the tight junctions of thealveolar epithelial cells are impermeable duringlactation, and thus allow milk to be stored betweennursing periods without leakage of milk components from the lumen. Nonetheless mammary

  1. Far infrared detection with Josephson junctions

    Microsoft Academic Search

    C. K. So

    1977-01-01

    The response of Josephson junctions to microwave and far infrared radiation was studied. Junctions were formed by pressing a Nb-Ti pointed wire onto a Nb or Nb-Ti pointed wire onto a Nb thin film which in turn was pressed against the open end of a waveguide. Electromagnetic radiation was applied through the back of the films so that only the

  2. Self-assembly of membrane junctions.

    PubMed Central

    Bruinsma, R; Goulian, M; Pincus, P

    1994-01-01

    We present a mechanism for the aggregation of mobile intermembrane junctions, such as the connexon dyad of gap junctions. The model demonstrates that intermembrane repulsion provides a powerful self-assembly pressure. If the membrane repulsion is strong enough to prevent membrane adhesion, then the self-assembly pressure is of effective infinite range. Images FIGURE 1 PMID:7948688

  3. Some properties of Cosmic String Junctions

    NASA Astrophysics Data System (ADS)

    Karouby, Johanna

    2011-07-01

    Cosmic strings are linear concentrations of energy of macroscopic size. Since cosmic superstrings can form junctions, observing them would give some support to string theory. In the following, we study the lensing cosmic string junctions create, the shift in photons' wavelength passing through (leading to the Kaiser-Stebbins effect), and the gravitational radiation they emit.

  4. Gap Junctions: Structure, Functions, and Regulation

    Microsoft Academic Search

    E. A. Tsvetkov

    2001-01-01

    The review presents data on the role of gap junctions in intercellular communication. The review includes information on history of the appearance of this problem. Data are presented on ultrastructure and function of gap junctions as well as on the mechanisms providing for their activity. A part of the review deals with the problem of regulation of intercellular communication realized

  5. 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.

  6. Submillimeter wave generation using Josephson junction arrays

    SciTech Connect

    Wan, K.L.; Jain, A.K.; Lukens, J.E.

    1989-03-01

    A submillimeter wave oscillator using a phase-locked array of Josephson junctions is demonstrated. With an array of 40 shunted tunnel junctions, the oscillator delivered 1..mu..W of power at 350 GHz into a 60..cap omega.. load on the chip. The operating frequency of the oscillator is tunable over a range of about 10%.

  7. Josephson junctions as microwave heterodyne detectors

    Microsoft Academic Search

    Y. Taur

    1974-01-01

    The properties of point contact Josephson junctions operated as 36 GHz heterodyne detectors have been extensively studied. The measured performance is in good agreement with the theory developed for microwave coupling, conversion efficiency, and intrinsic noise based on the resistively shunted junction model. A tunable cavity matching structure was designed to obtain good RF coupling to the point contact. By

  8. Vertical Junction Type Organic Photovoltaic Cells

    Microsoft Academic Search

    Kouji Suemori; Takahiro Miyata; Masahiro Hiramoto; Masaaki Yokoyama

    2004-01-01

    Vertical junction type organic photovoltaic cells having a pn junction formed perpendicularly to a light irradiated surface were fabricated. Short-circuit photocurrent density of 8.5 mA\\\\cdotcm-2 and power conversion efficiency of 0.54% were observed under simulated solar illumination. The large photocurrent density is attributed to the light collection effect via the transparent vertical layer.

  9. 75 FR 6094 - Modification of Class E Airspace; Grand Junction, CO

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-08

    ...Modification of Class E Airspace; Grand Junction, CO AGENCY: Federal Aviation Administration...Grand Junction Regional, Grand Junction, CO, to accommodate the vectoring of Instrument...Grand Junction Regional, Grand Junction, CO to en route airspace, and changes the...

  10. Dark energy and Josephson junctions

    SciTech Connect

    Branchina, Vincenzo [Department of Physics, University of Catania, Via Santa Sofia 64, I-95123, Catania (Italy); Liberto, Marco Di; Lodato, Ivano, E-mail: vincenzo.branchina@ct.infn.it, E-mail: madiliberto@ssc.unict.it, E-mail: ivlodato@ssc.unict.it [Scuola Superiore di Catania, Via S. Nullo 5/i, Catania (Italy)

    2009-08-01

    It has been recently claimed that dark energy can be (and has been) observed in laboratory experiments by measuring the power spectrum S{sub I}(?) of the noise current in a resistively shunted Josephson junction and that in new dedicated experiments, which will soon test a higher frequency range, S{sub I}(?) should show a deviation from the linear rising observed in the lower frequency region because higher frequencies should not contribute to dark energy. Based on previous work on theoretical aspects of the fluctuation-dissipation theorem, we carefully investigate these issues and show that these claims are based on a misunderstanding of the physical origin of the spectral function S{sub I}(?). According to our analysis, dark energy has never been (and will never be) observed in Josephson junctions experiments. We also predict that no deviation from the linear rising behavior of S{sub I}(?) will be observed in forthcoming experiments. Our findings provide new (we believe definite) arguments which strongly support previous criticisms.

  11. Mechanisms controlling neuromuscular junction stability.

    PubMed

    Bloch-Gallego, Evelyne

    2015-03-01

    The neuromuscular junction (NMJ) is the synaptic connection between motor neurons and muscle fibers. It is involved in crucial processes such as body movements and breathing. Its proper development requires the guidance of motor axons toward their specific targets, the development of multi-innervated myofibers, and a selective synapse stabilization. It first consists of the removal of excessive motor axons on myofibers, going from multi-innervation to a single innervation of each myofiber. Whereas guidance cues of motor axons toward their specific muscular targets are well characterized, only few molecular and cellular cues have been reported as clues for selecting and stabilizing specific neuromuscular junctions. We will first provide a brief summary on NMJ development. We will then review molecular cues that are involved in NMJ stabilization, in both pre- and post-synaptic compartments, considering motor neurons and Schwann cells on the one hand, and muscle on the other hand. We will provide links with pathologies and highlight advances that can be brought both by basic research on NMJ development and clinical data resulting from the analyses of neurodegeneration of synaptic connections to obtain a better understanding of this process. The goal of this review is to highlight the findings toward understanding the roles of poly- or single-innervations and the underlying mechanisms of NMJ stabilization. PMID:25359233

  12. 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.

  13. Permeability of a Cell Membrane Junction

    PubMed Central

    Politoff, A. L.; Socolar, S. J.; Loewenstein, W. R.

    1969-01-01

    The ion permeability of the membrane junctions between Chironomus salivary gland cells is strongly depressed by treatments that are generally known to inhibit energy metabolism. These treatments include prolonged cooling at 6°–8°C, and exposure to dinitrophenol, cyanide, oligomycin, and N-ethylmaleimide. Intracellular injection of ATP appears to prevent depression of junctional permeability by dinitrophenol or to reverse it. Ouabain, azide, p-chloromercuriphenylsulfonic acid, reserpine, and acetazolamide fail to depress junctional permeability. Thus the ion permeability of the junctional membranes appears to depend on energy provided by oxidative phosphorylation. Possible energy-linked processes for maintaining junctional permeability are discussed, including processes involving transport of permeability-modifying species such as Ca++. PMID:5778320

  14. Bves Modulates Tight Junction Associated Signaling

    PubMed Central

    Russ, Patricia K.; Pino, Christopher J.; Williams, Christopher S.; Bader, David M.; Haselton, Frederick R.; Chang, Min S.

    2011-01-01

    Blood vessel epicardial substance (Bves) is a transmembrane adhesion protein that regulates tight junction (TJ) formation in a variety of epithelia. The role of TJs within epithelium extends beyond the mechanical properties. They have been shown to play a direct role in regulation of RhoA and ZONAB/DbpA, a y-box transcription factor. We hypothesize that Bves can modulate RhoA activation and ZONAB/DbpA activity through its regulatory effect on TJ formation. Immortalized human corneal epithelial (HCE) cells were stably transfected with Flag-tagged full length chicken Bves (w-Bves) or C-terminus truncated Bves (t-Bves). We found that stably transfected w-Bves and t-Bves were interacting with endogenous human Bves. However, interaction with t-Bves appeared to disrupt cell membrane localization of endogenous Bves and interaction with ZO-1. w-Bves cells exhibited increased TJ function reflected by increased trans-epithelial electrical resistance, while t-Bves cells lost TJ protein immunolocalization at cell-cell contacts and exhibited decreased trans-epithelial electrical resistance. In parental HCE and w-Bves cells ZONAB/DbpA and GEF-H1 were seen at cell borders in the same pattern as ZO-1. However, expression of t-Bves led to decreased membrane localization of both ZONAB/DbpA and GEF-H1. t-Bves cells had increased RhoA activity, as indicated by a significant 30% increase in FRET activity compared to parental HCE cells. ZONAB/DbpA transcriptional activity, assessed using a luciferase reporter probe, was increased in t-Bves cells. These studies demonstrate that Bves expression and localization can regulate RhoA and ZONAB/DbpA activity. PMID:21283798

  15. Is Reelin the Answer to Synapse Elimination at the Neuromuscular Junction?

    NSDL National Science Digital Library

    Ben Chih (Columbia University; Department of Physiology and Cellular Biophysics, and Center for Neurobiology and Behavior REV)

    2003-10-21

    The formation of mature neuronal circuits during development involves elimination of a large number of synapses by activity-dependent processes. A recent study suggests that synapse elimination at the neuromuscular junction is impaired in reeler mutant mice, which are lacking the extracellular matrix protein Reelin. In this process, Reelin acts through an unexpected, proteolytic mechanism that is independent of Disabled 1, a cytoplasmic factor that mediates Reelin signaling in the central nervous system. This Perspective discusses possible models for Reelin function in the framework of activity-dependent synapse elimination at the neuromuscular junction.

  16. 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

  17. Modulation of tight junction structure and function by cytokines

    Microsoft Academic Search

    Shaun V Walsh; Ann M Hopkins; Asma Nusrat

    2000-01-01

    Dynamic regulation of tight junction function is fundamental to many physiologic processes. Disruption of tight junction function drastically alters paracellular permeability and is a hallmark of many pathologic states. Recently, an increasing number of cytokines have been shown to influence tight junction function both in vitro and in vivo. Cytokine-induced effects on tight junction barrier function have also been correlated

  18. Tunnel junction multiple wavelength light-emitting diodes

    DOEpatents

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

    1992-11-24

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

  19. On the reserve capacities of priority junctions and roundabouts

    Microsoft Academic Search

    S. C. Wong

    1996-01-01

    The concept of reverse capacity of a whole junction has been used extensively in the design of signal-controlled junctions. This concept, however, has not been applied to priority junctions and roundabouts, probably because of the complicated demand and supply relationship. When the demands on the approaches to the junction increase, the capacities of those non-priority approaches reduce at different rates.

  20. Magnetic switching and magnetoresistance in nanoscale spin tunnel junctions

    E-print Network

    Haviland, David

    Magnetic switching and magnetoresistance in nanoscale spin tunnel junctions M. Urech,a) V magnetic tunnel junctions in both multijunction arrays and double-tunnel junction geometries have been on the relative magnetic orientation of the tunnel junction electrodes. MR measurements show a strong dependence

  1. Modeling Social Network Relationships via t-Cherry Junction Trees

    E-print Network

    Reisslein, Martin

    Modeling Social Network Relationships via t-Cherry Junction Trees Brian Proulx and Junshan Zhang the underlying structure therein. In this paper, we employ the t-cherry junction tree, a very recent advancement in this approach: 1) the best approximation possible via junction trees belongs to the class of t-cherry junction

  2. Novel design of foam core junctions in sandwich panels

    Microsoft Academic Search

    E. Bozhevolnaya; A. Lyckegaard; O. T. Thomsen

    2008-01-01

    An improved design of core junctions in sandwich panels\\/beams is proposed. The improved\\/novel design consists of a specific geometrical shaping of the boundary of the adjoined core materials, which substantially diminishes the local stress concentrations at core junctions subjected to transverse shear loading. Two groups of the beams with conventional butt junctions and modified (spline shaped) junctions are manufactured and

  3. 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.

  4. 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.

  5. Silicon fiber with p-n junction

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

    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 ?m and core diameters of 20-800 ?m. 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.

  6. Supercurrent decay in extremely underdamped Josephson junctions

    SciTech Connect

    Ruggiero, B. [Istituto di Cibernetica del CNR, I-80072 Arco Felice (Italy)] [Istituto di Cibernetica del CNR, I-80072 Arco Felice (Italy); [Istituto Nazionale di Fisica Nucleare, Sezione di Napoli, Naples I-80125 (Italy); Granata, C. [Istituto di Cibernetica del CNR, I-80072 Arco Felice (Italy)] [Istituto di Cibernetica del CNR, I-80072 Arco Felice (Italy); [AtB Advanced Technologies Biomagnetics, I-66013 Chieti Scalo (Italy); Palmieri, V.G.; Esposito, A. [Istituto di Cibernetica del CNR, I-80072 Arco Felice (Italy)] [Istituto di Cibernetica del CNR, I-80072 Arco Felice (Italy); Russo, M.; Silvestrini, P. [Istituto di Cibernetica del CNR, I-80072 Arco Felice (Italy)] [Istituto di Cibernetica del CNR, I-80072 Arco Felice (Italy); [Istituto Nazionale di Fisica Nucleare, Sezione di Napoli, Naples I-80125 (Italy)

    1998-01-01

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

  7. Carbon nanotube based magnetic tunnel junctions

    PubMed

    Mehrez; Taylor; Guo; Wang; Roland

    2000-03-20

    Spin-coherent quantum transport in carbon nanotube magnetic tunnel junctions is investigated theoretically. A spin-valve effect is found for metallic, armchair tubes, with a magnetoconductance ratio ranging up to 20%. Because of the finite length of the nanotube junctions, transport is dominated by resonant transmission. The magnetic tunnel junctions are found to have distinctly different transport behavior depending on whether or not the length of the tubes is commensurate with a 3N+1 rule, with N the number of basic carbon repeat units along the nanotube length. PMID:11017299

  8. Tunable THz source using superconducting tunnel junctions

    NASA Astrophysics Data System (ADS)

    Boussaha, F.; Féret, A.; Chaumont, C.; Loukitch, L.; Vacelet, T.

    2013-09-01

    We report on tunable submillimeter-wave radiation sources based on micrometer-sized superconducting tunnel junction arrays optimized within a bandwidth of 350-520 GHz. The arrays consist of 10, 20 and 40 Superconductor-Insulator- Superconductor (SIS) parallel-connected Nb/AlOx/Nb junctions embedded in superconducting microstrip lines. A SIS twin-junction is integrated along with each array to detect output signals. The pumped detector's I-V characteristic exhibits clearly photon-assisted quasiparticule steps when the arrays are biased upon corresponding Josephson resonances ranging from 370 to 520 GHz.

  9. Silicon fiber with p-n junction

    SciTech Connect

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

    2014-09-22

    In this study, we fabricated a p-n junction in a fiber with a phosphorous doped silicon core and fused silica cladding. The fibers were fabricated via a hybrid process of the core-suction and melt-draw techniques and maintained overall diameters ranging from 200 to 900??m and core diameters of 20–800??m. 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.

  10. 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.

  11. Bias and temperature dependence on junction magnetoresistance in manganite/magnetite based magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Chopdekar, Rajesh; Hu, Guohan; Suzuki, Yuri

    2005-03-01

    Studies of the bias and temperature dependence of junction magnetoresistance (JMR) in manganite/magnetite trilayer junctions have revealed non-monotonic dependence on both quantities. Such junctions were constructed to probe the spin-polarization of magnetite using the well-established majority spin-polarized oxide (La,Sr)MnO3 as a counter-electrode. We have found that using an isostructural oxide cobalt chromite tunnel barrier reduces disorder at the chromite-magnetite interface as compared to junctions with a rocksalt structure MgO barrier. An order of magnitude increase in JMR for these junctions is strongly peaked as a function of bias magnitude and sign, but has weak temperature dependence. The Verwey transition in magnetite, the paramagnetic-ferrimagnetic transition in cobalt chromite, and the interface roughness in the junctions all play a role in determining the temperature and bias dependence of the measured magnetoresistance.

  12. Electron transport characteristics of the dimeric 1,4-benzenedithiol junction.

    PubMed

    Wang, Lin; Li, Shu-Ying; Yuan, Jing-He; Gu, Jing-Ying; Wang, Dong; Wan, Li-Jun

    2014-08-01

    Understanding the electron transport between single molecules connected through weak interaction is of great importance for molecular electronics. In this paper, we report measurements of the conductivity of the dimeric 1,4-benzenedithiol (BDT) junction using the scanning tunneling microscopy (STM)-based current-displacement I(s) method. The conductance was measured to be 6.14×10(-6) ?G0 , a value almost two orders of magnitude lower than that of the monomer BDT junction. In control experiments, the probability of junction formation decreased with the presence of tris(2-chloroethyl) phosphate (TCEP), a reducing reagent for the disulfide bond. According to theoretical computations, the dihedral angle of the S?S bond tends to take a perpendicular conformation. This non-conjugated structure localizes the electron distribution and accounts for the low conductivity of the disulfide linkage. PMID:24909757

  13. Increasing Gap Junctional Coupling: A Tool for Dissecting the Role of Gap Junctions

    Microsoft Academic Search

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

    2007-01-01

    Much of our current knowledge about the physiological and pathophysiological role of gap junctions is based on experiments\\u000a where coupling has been reduced by either chemical agents or genetic modification. This has brought evidence that gap junctions\\u000a are important in many physiological processes. In a number of cases, gap junctions have been implicated in the initiation\\u000a and progress of disease,

  14. The effects of junction depth and impurity concentration on ion-implanted, junction solar cells

    Microsoft Academic Search

    Neville

    1980-01-01

    This paper presents data resulting from tests on the experimental optimization of the ion-implanted region of horizontal junction, silicon, ion-implanted P+N and N+P solar cells. The experimental data are compared to theoretical predictions based on a simple model and to data obtained with diffused junction solar cells (1). Optimum junction depth and average ion-implanted layer concentration for ion-implanted, silicon, PN

  15. Bias and temperature dependence on junction magnetoresistance in manganite\\/magnetite based magnetic tunnel junctions

    Microsoft Academic Search

    Rajesh Chopdekar; Guohan Hu; Yuri Suzuki

    2005-01-01

    Studies of the bias and temperature dependence of junction magnetoresistance (JMR) in manganite\\/magnetite trilayer junctions have revealed non-monotonic dependence on both quantities. Such junctions were constructed to probe the spin-polarization of magnetite using the well-established majority spin-polarized oxide (La,Sr)MnO3 as a counter-electrode. We have found that using an isostructural oxide cobalt chromite tunnel barrier reduces disorder at the chromite-magnetite interface

  16. Equivalent junction method to predict 3-D effect of curved-abrupt p-n junctions

    Microsoft Academic Search

    Jin He; Xuemei Xi; Mansun Chan; Chenming Hu; Yingxue Li; Xing Zhang; Ru Huang; Yangyuan Wang

    2002-01-01

    In this brief, an equivalent junction method is proposed to study three-dimensional (3-D) effect of the lateral curvature on curved-abrupt junctions. Analytical expressions including 3-D effect are derived to calculate the breakdown voltage, peak electrical field, and maximum depletion layer width of curved-abrupt junctions. The breakdown voltages calculated from the new analytic expression have been verified by the numerical simulation

  17. Method of junction formation for CIGS photovoltaic devices

    DOEpatents

    Delahoy, Alan E.

    2006-03-28

    Sulfur is used to improve the performance of CIGS devices prepared by the evaporation of a single source ZIS type compound to form a buffer layer on the CIGS. The sulfur may be evaporated, or contained in the ZIS type material, or both. Vacuum evaporation apparatus of many types useful in the practice of the invention are known in the art. Other methods of delivery, such as sputtering, or application of a thiourea solution, may be substituted for evaporation.

  18. Method of junction formation for CIGS photovoltaic devices

    DOEpatents

    Delahoy, Alan E. (Rocky Hill, NJ)

    2010-01-26

    Sulfur is used to improve the performance of CIGS devices prepared by the evaporation of a single source ZIS type compound to form a buffer layer on the CIGS. The sulfur may be evaporated, or contained in the ZIS type material, or both. Vacuum evaporation apparatus of many types useful in the practice of the invention are known in the art. Other methods of delivery, such as sputtering, or application of a thiourea solution, may be substituted for evaporation.

  19. Correlation between Types of Junction and Submillimeter-Wave Responses in Point-Contact Josephson Junctions

    NASA Astrophysics Data System (ADS)

    Morita, Seizo; Noguchi, Takashi; Takaki, Satoru; Horii, Shinichi; Imai, Syozo; Takeuti, Yosihisa; Mikoshiba, Nobuo

    1982-01-01

    It has been found that point-contact Josephson junctions can be clearly classified into bridge-type and tunnel-type by introducing new parameters characterizing their I-V curves. Nearly-ideal tunnel-type junctions with Nb-SnOx-Sn (Film) point-contacts were obtained. Tunnel-type junctions showed larger gap energies than bridge-type junctions in Nb-SnOx-Sn and Nb-NbOx-NbN point-contacts. The submillimeter-wave responses were measured in Nb-Nb point-contacts, and it was found that the contacts with the best performance were bridge-type junctions with a sharp gap structure; tunnel-type junctions showed rather bad performance. On irradiation with laser light, the center of the Shapiro step moved to the lower-current side in bridge-type junctions but to the higher-current side in tunnel-type junctions. These differences can be explained by differences in the heating effects between bridge-type and tunnel-type junctions.

  20. Magnetic switching and magnetoresistance in nanoscale spin tunnel junctions

    Microsoft Academic Search

    M. Urech; V. Korenivski; D. B. Haviland

    2002-01-01

    Co\\/AlOx\\/Co magnetic tunnel junctions in both multijunction arrays and double-tunnel junction geometries have been studied. The junctions exhibit magnetoresistance (MR) and change their resistance by ~10% depending on the relative magnetic orientation of the tunnel junction electrodes. MR measurements show a strong dependence on the device geometry. We find that it is necessary to form tunnel junctions with electrode width

  1. Efficiency limits for space multi-junction concentrator solar cells

    Microsoft Academic Search

    Ma Shaodong; Peng Hongling; Chen Wei; Jiang Bin; Zheng Wanhua

    2011-01-01

    Efficiency limits of single-junction and multi-junction concentrator solar cells are established from the thermodynamic principle of detailed balance. The maximum efficiency limit of single-junction solar cells is 35% at 500 suns, while that of 2-junction solar cells which meet the current matching condition is 46%. At the same condition, the maximum efficiency limit of 3-junction solar cells with GaAs as

  2. Mitotic inter-homologue junctions accumulate at damaged DNA replication forks in recQ mutants.

    PubMed

    Carotenuto, Walter; Liberi, Giordano

    2010-06-01

    Mitotic homologous recombination is utilised to repair DNA breaks using either sister chromatids or homologous chromosomes as templates. Because sister chromatids are identical, exchanges between sister chromatids have no consequences for the maintenance of genomic integrity unless they involve repetitive DNA sequences. Conversely, homologous chromosomes might differ in genetic content, and exchanges between homologues might lead to loss of heterozygosity and subsequent inactivation of functional genes. Genomic instability, caused by unscheduled recombination events between homologous chromosomes, is enhanced in the absence of RecQ DNA helicases, as observed in Bloom's cancer-prone syndrome. Here, we used two-dimensional gel electrophoresis to analyse budding yeast diploid cells that were modified to distinguish replication intermediates originating from each homologous chromosome. Therefore, these cells were suitable for analysing the formation of inter-homologue junctions. We found that Rad51-dependent DNA structures resembling inter-homologue junctions accumulate together with sister chromatid junctions at damaged DNA replication forks in recQ mutants, but not in the absence of Srs2 or Mph1 DNA recombination helicases. Inter-homologue joint molecules in recQ mutants are less abundant than sister chromatid junctions, but they accumulate with similar kinetics after origin firing under conditions of DNA damage. We propose that unscheduled accumulation of inter-homologue junctions during DNA replication might account for allelic recombination defects in recQ mutants. PMID:20346738

  3. Helical stacking in DNA three-way junctions containing two unpaired pyrimidines: proton NMR studies.

    PubMed Central

    Leontis, N B; Hills, M T; Piotto, M; Ouporov, I V; Malhotra, A; Gorenstein, D G

    1995-01-01

    The proton NMR spectra of DNA three-way junction complexes (TWJ) having unpaired pyrimidines, 5'-TT- and 5'-TC- on one strand at the junction site were assigned from 2D NOESY spectra acquired in H2O and D2O solvents and homonuclear 3D NOESY-TOCSY and 3D NOESY-NOESY in D2O solvent. TWJ are the simplest branched structures found in biologically active nucleic acids. Unpaired nucleotides are common features of such structures and have been shown to stabilize junction formation. The NMR data confirm that the component oligonucleotides assemble to form conformationally homogeneous TWJ complexes having three double-helical, B-form arms. Two of the helical arms stack upon each other. The unpaired pyrimidine bases lie in the minor groove of one of the helices and are partly exposed to solvent. The coaxial stacking arrangement deduced is different from that determined by Rosen and Patel (Rosen, M.A., and D.J. Patel. 1993. Biochemistry. 32:6576-6587) for a DNA three-way junction having two unpaired cytosines, but identical to that suggested by Welch et al. (Welch, J. B., D. R. Duckett, D. M. J. Lilley. 1993. Nucleic Acids Res. 21:4548-4555) on the basis of gel electrophoretic studies of DNA three-way junctions containing unpaired adenosines and thymidines. Images FIGURE 2 FIGURE 4 FIGURE 5 FIGURE 6 FIGURE 7 PMID:7711249

  4. Helical stacking in DNA three-way junctions containing two unpaired pyrimidines: proton NMR studies.

    PubMed

    Leontis, N B; Hills, M T; Piotto, M; Ouporov, I V; Malhotra, A; Gorenstein, D G

    1995-01-01

    The proton NMR spectra of DNA three-way junction complexes (TWJ) having unpaired pyrimidines, 5'-TT- and 5'-TC- on one strand at the junction site were assigned from 2D NOESY spectra acquired in H2O and D2O solvents and homonuclear 3D NOESY-TOCSY and 3D NOESY-NOESY in D2O solvent. TWJ are the simplest branched structures found in biologically active nucleic acids. Unpaired nucleotides are common features of such structures and have been shown to stabilize junction formation. The NMR data confirm that the component oligonucleotides assemble to form conformationally homogeneous TWJ complexes having three double-helical, B-form arms. Two of the helical arms stack upon each other. The unpaired pyrimidine bases lie in the minor groove of one of the helices and are partly exposed to solvent. The coaxial stacking arrangement deduced is different from that determined by Rosen and Patel (Rosen, M.A., and D.J. Patel. 1993. Biochemistry. 32:6576-6587) for a DNA three-way junction having two unpaired cytosines, but identical to that suggested by Welch et al. (Welch, J. B., D. R. Duckett, D. M. J. Lilley. 1993. Nucleic Acids Res. 21:4548-4555) on the basis of gel electrophoretic studies of DNA three-way junctions containing unpaired adenosines and thymidines. PMID:7711249

  5. Calcium-dependent dynamics of cadherin interactions at cell-cell junctions.

    PubMed

    Kim, Sally A; Tai, Chin-Yin; Mok, Lee-Peng; Mosser, Eric A; Schuman, Erin M

    2011-06-14

    Cadherins play a key role in the dynamics of cell-cell contact formation and remodeling of junctions and tissues. Cadherin-cadherin interactions are gated by extracellular Ca(2+), which serves to rigidify the cadherin extracellular domains and promote trans junctional interactions. Here we describe the direct visualization and quantification of spatiotemporal dynamics of N-cadherin interactions across intercellular junctions in living cells using a genetically encodable FRET reporter system. Direct measurements of transjunctional cadherin interactions revealed a sudden, but partial, loss of homophilic interactions (? = 1.17 ± 0.06 s(-1)) upon chelation of extracellular Ca(2+). A cadherin mutant with reduced adhesive activity (W2A) exhibited a faster, more substantial loss of homophilic interactions (? = 0.86 ± 0.02 s(-1)), suggesting two types of native cadherin interactions--one that is rapidly modulated by changes in extracellular Ca(2+) and another with relatively stable adhesive activity that is Ca(2+) independent. The Ca(2+)-sensitive dynamics of cadherin interactions were transmitted to the cell interior where ?-catenin translocated to N-cadherin at the junction in both cells. These data indicate that cadherins can rapidly convey dynamic information about the extracellular environment to both cells that comprise a junction. PMID:21613566

  6. Mix and match: Investigating heteromeric and heterotypic gap junction channels in model systems and native tissues

    PubMed Central

    Koval, Michael; Molina, Samuel A.; Burt, Janis M.

    2014-01-01

    This review is based in part on a roundtable discussion session: “Physiological roles for heterotypic/heteromeric channels” at the 2013 International Gap Junction Conference (IGJC 2013) in Charleston, South Carolina. It is well recognized that multiple connexins can specifically co-assemble to form mixed gap junction channels with unique properties as a means to regulate intercellular communication. Compatibility determinants for both heteromeric and heterotypic gap junction channel formation have been identified and associated with specific connexin amino acid motifs. Hetero-oligomerization is also a regulated process; differences in connexin quality control and monomer stability are likely to play integral roles to control interactions between compatible connexins. Gap junctions in oligodendrocyte:astrocyte communication and in the cardiovascular system have emerged as key systems where heterotypic and heteromeric channels have unique physiologic roles. There are several methodologies to study heteromeric and heterotypic channels that are best applied to either heterologous expression systems, native tissues or both. There remains a need to use and develop different experimental approaches in order to understand the prevalence and roles for mixed gap junction channels in human physiology. PMID:24561196

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

    PubMed Central

    Yu, Xuechao; Shen, Youde; Liu, Tao; Wu, Tao (Tom); Jie Wang, Qi

    2015-01-01

    Graphene has been considered as an attractive material for optoelectronic applications such as photodetectors owing to its extraordinary properties, e.g. broadband absorption and ultrahigh mobility. However, challenges still remain in fundamental and practical aspects of the conventional graphene photodetectors which normally rely on the photoconductive mode of operation which has the drawback of e.g. high dark current. Here, we demonstrated the photovoltaic mode operation in graphene p-n junctions fabricated by a simple but effective electron irradiation method that induces n-type doping in intrinsic p-type graphene. The physical mechanism of the junction formation is owing to the substrate gating effect caused by electron irradiation. Photoresponse was obtained for this type of photodetector because the photoexcited electron-hole pairs can be separated in the graphene p-n junction by the built-in potential. The fabricated graphene p-n junction photodetectors exhibit a high detectivity up to ~3?×?1010 Jones (cm Hz1/2 W?1) at room temperature, which is on a par with that of the traditional III–V photodetectors. The demonstrated novel and simple scheme for obtaining graphene p-n junctions can be used for other optoelectronic devices such as solar cells and be applied to other two dimensional materials based devices. PMID:26152225

  8. Correlation of interfacial bonding mechanism and equilibrium conductance of molecular junctions

    NASA Astrophysics Data System (ADS)

    Ning, Zhan-Yu; Qiao, Jing-Si; Ji, Wei; Guo, Hong

    2014-12-01

    We report theoretical investigations on the role of interfacial bonding mechanism and its resulting structures to quantum transport in molecular wires. Two bonding mechanisms for the Au-S bond in an Au(111)/1,4-benzenedithiol(BDT)/Au(111) junction were identified by ab initio calculation, confirmed by a recent experiment, which, we showed, critically control charge conduction. It was found, for Au/BDT/Aujunctions, the hydrogen atom, bound by a dative bond to the Sulfur, is energetically non-dissociativeafter the interface formation. The calculated conductance and junction breakdown forces of H-non-dissociative Au/BDT/Au devices are consistent with the experimental values, while the H-dissociated devices, with the interface governed by typical covalent bonding, give conductance more than an order of magnitude larger. By examining the scattering states that traverse the junctions, we have revealed that mechanical and electric properties of a junction have strong correlation with the bonding configuration. This work clearly demonstrates that the interfacial details, rather than previously believed many-body effects, is of vital importance for correctly predicting equilibrium conductance of molecular junctions; and manifests that the interfacial contact must be carefully understood for investigating quantum transport properties of molecular nanoelectronics.

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

    PubMed

    Yu, Xuechao; Shen, Youde; Liu, Tao; Wu, Tao Tom; Jie Wang, Qi

    2015-01-01

    Graphene has been considered as an attractive material for optoelectronic applications such as photodetectors owing to its extraordinary properties, e.g. broadband absorption and ultrahigh mobility. However, challenges still remain in fundamental and practical aspects of the conventional graphene photodetectors which normally rely on the photoconductive mode of operation which has the drawback of e.g. high dark current. Here, we demonstrated the photovoltaic mode operation in graphene p-n junctions fabricated by a simple but effective electron irradiation method that induces n-type doping in intrinsic p-type graphene. The physical mechanism of the junction formation is owing to the substrate gating effect caused by electron irradiation. Photoresponse was obtained for this type of photodetector because the photoexcited electron-hole pairs can be separated in the graphene p-n junction by the built-in potential. The fabricated graphene p-n junction photodetectors exhibit a high detectivity up to ~3?×?10(10) Jones (cm Hz(1/2) W(-1)) at room temperature, which is on a par with that of the traditional III-V photodetectors. The demonstrated novel and simple scheme for obtaining graphene p-n junctions can be used for other optoelectronic devices such as solar cells and be applied to other two dimensional materials based devices. PMID:26152225

  10. Induction of stable ER-plasma-membrane junctions by Kv2.1 potassium channels.

    PubMed

    Fox, Philip D; Haberkorn, Christopher J; Akin, Elizabeth J; Seel, Peter J; Krapf, Diego; Tamkun, Michael M

    2015-06-01

    Junctions between cortical endoplasmic reticulum (cER) and the plasma membrane are a subtle but ubiquitous feature in mammalian cells; however, very little is known about the functions and molecular interactions that are associated with neuronal ER-plasma-membrane junctions. Here, we report that Kv2.1 (also known as KCNB1), the primary delayed-rectifier K(+) channel in the mammalian brain, induces the formation of ER-plasma-membrane junctions. Kv2.1 localizes to dense, cell-surface clusters that contain non-conducting channels, indicating that they have a function that is unrelated to membrane-potential regulation. Accordingly, Kv2.1 clusters function as membrane-trafficking hubs, providing platforms for delivery and retrieval of multiple membrane proteins. Using both total internal reflection fluorescence and electron microscopy we demonstrate that the clustered Kv2.1 plays a direct structural role in the induction of stable ER-plasma-membrane junctions in both transfected HEK 293 cells and cultured hippocampal neurons. Glutamate exposure results in a loss of Kv2.1 clusters in neurons and subsequent retraction of the cER from the plasma membrane. We propose Kv2.1-induced ER-plasma-membrane junctions represent a new macromolecular plasma-membrane complex that is sensitive to excitotoxic insult and functions as a scaffolding site for both membrane trafficking and Ca(2+) signaling. PMID:25908859

  11. Splice junctions are constrained by protein disorder

    PubMed Central

    Smithers, Ben; Oates, Matt E.; Gough, Julian

    2015-01-01

    We have discovered that positions of splice junctions in genes are constrained by the tolerance for disorder-promoting amino acids in the translated protein region. It is known that efficient splicing requires nucleotide bias at the splice junction; the preferred usage produces a distribution of amino acids that is disorder-promoting. We observe that efficiency of splicing, as seen in the amino-acid distribution, is not compromised to accommodate globular structure. Thus we infer that it is the positions of splice junctions in the gene that must be under constraint by the local protein environment. Examining exonic splicing enhancers found near the splice junction in the gene, reveals that these (short DNA motifs) are more prevalent in exons that encode disordered protein regions than exons encoding structured regions. Thus we also conclude that local protein features constrain efficient splicing more in structure than in disorder. PMID:25934802

  12. Superconducting switch made of graphene nanoribbon junctions

    NASA Astrophysics Data System (ADS)

    Liang, Qifeng; Dong, Jinming

    2008-09-01

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

  13. Quantum limited detection in tunnel junction mixers

    Microsoft Academic Search

    JOHN R. TUCKER

    1979-01-01

    A complete quantum generalization of microwave mixer theory is constructed for nonlinear single-particle tunnel junctions. The result represents a unification of the concepts used to describe these \\

  14. Optoelectronic switching of addressable molecular crossbar junctions

    E-print Network

    J. C. Li

    2006-11-22

    This letter reports on the observation of optoelectronic switching in addressable molecular crossbar junctions fabricated using polymer stamp-printing method. The active medium in the junction is a molecular self-assembled monolayer softly sandwiched between gold electrodes. The molecular junctions are investigated through currentvoltage measurements at varied temperature (from 95 to 300 K) in high vacuum condition. The junctions show reversible optoelectronic switching with the highest on/off ratio of 3 orders of magnitude at 95 K. The switching behavior is independent of both optical wavelength and molecular structure, while it strongly depends on the temperature. Initial analysis indicates that the distinct binding nature of the molecule/electrode interfaces play a dominant role in the switching performance.

  15. Co-culture of two MDCK strains with distinct junctional protein expression: a model for intercellular junction rearrangement and cell sorting

    Microsoft Academic Search

    Carla B. Collares-Buzato; Mark A. Jepson; Gordon T. A. McEwan; Barry H. Hirst; Nicholas L. Simmons

    1998-01-01

    Distinct epithelial MDCK cell strains displaying extremes in transepithelial electrical resistance (paracellular permeability) have been established in co-culture and the subsequent cellular behaviour and formation of junctional complexes investigated. After high-density seeding, MDCK strain I and II cells in co-culture are initially randomly distributed but subsequently sort themselves out in a time-dependent manner to form separate homotypic aggregates. The final

  16. Two Classes of Gap Junction Channels Mediate Soma-Germline Interactions Essential for Germline Proliferation and Gametogenesis in Caenorhabditis elegans

    PubMed Central

    Starich, Todd A.; Hall, David H.; Greenstein, David

    2014-01-01

    In all animals examined, somatic cells of the gonad control multiple biological processes essential for germline development. Gap junction channels, composed of connexins in vertebrates and innexins in invertebrates, permit direct intercellular communication between cells and frequently form between somatic gonadal cells and germ cells. Gap junctions comprise hexameric hemichannels in apposing cells that dock to form channels for the exchange of small molecules. Here we report essential roles for two classes of gap junction channels, composed of five innexin proteins, in supporting the proliferation of germline stem cells and gametogenesis in the nematode Caenorhabditis elegans. Transmission electron microscopy of freeze-fracture replicas and fluorescence microscopy show that gap junctions between somatic cells and germ cells are more extensive than previously appreciated and are found throughout the gonad. One class of gap junctions, composed of INX-8 and INX-9 in the soma and INX-14 and INX-21 in the germ line, is required for the proliferation and differentiation of germline stem cells. Genetic epistasis experiments establish a role for these gap junction channels in germline proliferation independent of the glp-1/Notch pathway. A second class of gap junctions, composed of somatic INX-8 and INX-9 and germline INX-14 and INX-22, is required for the negative regulation of oocyte meiotic maturation. Rescue of gap junction channel formation in the stem cell niche rescues germline proliferation and uncovers a later channel requirement for embryonic viability. This analysis reveals gap junctions as a central organizing feature of many soma–germline interactions in C. elegans. PMID:25195067

  17. 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. PMID:23765496

  18. Semiconductor tunnel junction with enhancement layer

    DOEpatents

    Klem, John F. (Sandia Park, NM); Zolper, John C. (Albuquerque, NM)

    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.

  19. Thermometry by arrays of tunnel junctions

    Microsoft Academic Search

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

    1994-01-01

    We show that arrays of tunnel junctions between normal metal electrodes exhibit features suitable for primary thermometry in an experimentally adjustable temperature range where thermal and charging effects compete. I-V and dI\\/dV vs V have been calculated for two junctions including a universal analytic high temperature result. Experimentally the width of the conductance minimum in this regime scales with T

  20. Large-Signal Behavior of Junction Transistors

    Microsoft Academic Search

    J. J. Ebers; J. L. Moll

    1954-01-01

    In the consideration of the junction transistor as a switch there are three characteristics of primary interest, the open impedance, the closed impedance, and the switching-time. A generalized two-terminal-pair theory of junction transistors is presented which is applicable, on a dc basis, in all regions of operation. Using this theory, the open and closed impedances of the transistor switch are

  1. Multi-junction solar cell device

    DOEpatents

    Friedman, Daniel J. (Lakewood, CO); Geisz, John F. (Wheat Ridge, CO)

    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.

  2. Exercise regulation of intestinal tight junction proteins.

    PubMed

    Zuhl, Micah; Schneider, Suzanne; Lanphere, Katherine; Conn, Carole; Dokladny, Karol; Moseley, Pope

    2014-06-01

    Gastrointestinal distress, such as diarrhoea, cramping, vomiting, nausea and gastric pain are common among athletes during training and competition. The mechanisms that cause these symptoms are not fully understood. The stress of heat and oxidative damage during exercise causes disruption to intestinal epithelial cell tight junction proteins resulting in increased permeability to luminal endotoxins. The endotoxin moves into the blood stream leading to a systemic immune response. Tight junction integrity is altered by the phosphoylation state of the proteins occludin and claudins, and may be regulated by the type of exercise performed. Prolonged exercise and high-intensity exercise lead to an increase in key phosphorylation enzymes that ultimately cause tight junction dysfunction, but the mechanisms are different. The purpose of this review is to (1) explain the function and physiology of tight junction regulation, (2) discuss the effects of prolonged and high-intensity exercise on tight junction permeability leading to gastrointestinal distress and (3) review agents that may increase or decrease tight junction integrity during exercise. PMID:23134759

  3. Gap junctions and blood-tissue barriers.

    PubMed

    Li, Michelle W M; Mruk, Dolores D; Cheng, C Yan

    2012-01-01

    Gap junction is a cell-cell communication junction type found in virtually all mammalian epithelia and endothelia and provides the necessary "signals" to coordinate physiological events to maintain the homeostasis of an epithelium and/or endothelium under normal physiological condition and following changes in the cellular environment (e.g., stimuli from stress, growth, development, inflammation, infection). Recent studies have illustrated the significance of this junction type in the maintenance of different blood-tissue barriers, most notably the blood-brain barrier and blood-testis barrier, which are dynamic ultrastructures, undergoing restructuring in response to stimuli from the environment. In this chapter, we highlight and summarize the latest findings in the field regarding how changes at the gap junction, such as the result of a knock-out, knock-down, knock-in, or gap junction inhibition and/or its activation via the use of inhibitors and/or activators, would affect the integrity or permeability of the blood-tissue barriers. These findings illustrate that much research is needed to delineate the role of gap junction in the blood-tissue barriers, most notably its likely physiological role in mediating or regulating the transport of therapeutic drugs across the blood-tissue barriers. PMID:23397629

  4. Lateral assembly of N-cadherin drives tissue integrity by stabilizing adherens junctions.

    PubMed

    Garg, S; Fischer, S C; Schuman, E M; Stelzer, E H K

    2015-03-01

    Cadherin interactions ensure the correct registry and anchorage of cells during tissue formation. Along the plasma membrane, cadherins form inter-junctional lattices via cis- and trans-dimerization. While structural studies have provided models for cadherin interactions, the molecular nature of cadherin binding in vivo remains unexplored. We undertook a multi-disciplinary approach combining live cell imaging of three-dimensional cell assemblies (spheroids) with a computational model to study the dynamics of N-cadherin interactions. Using a loss-of-function strategy, we demonstrate that each N-cadherin interface plays a distinct role in spheroid formation. We found that cis-dimerization is not a prerequisite for trans-interactions, but rather modulates trans-interfaces to ensure tissue stability. Using a model of N-cadherin junction dynamics, we show that the absence of cis-interactions results in low junction stability and loss of tissue integrity. By quantifying the binding and unbinding dynamics of the N-cadherin binding interfaces, we determined that mutating either interface results in a 10-fold increase in the dissociation constant. These findings provide new quantitative information on the steps driving cadherin intercellular adhesion and demonstrate the role of cis-interactions in junction stability. PMID:25589573

  5. Clathrin and Cx43 gap junction plaque endoexocytosis

    SciTech Connect

    Nickel, Beth M.; DeFranco, B. Hewa; Gay, Vernon L. [Department of Cell Biology and Physiology, University of Pittsburgh, School of Medicine, 324 South Biomedical Science Tower, Pittsburgh, PA 15261 (United States); Murray, Sandra A. [Department of Cell Biology and Physiology, University of Pittsburgh, School of Medicine, 324 South Biomedical Science Tower, Pittsburgh, PA 15261 (United States)], E-mail: smurray@pitt.edu

    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.

  6. Real-Space Microscopic Electrical Imaging of n+-p Junction Beneath Front-Side Ag Contact of Multicrystalline Si Solar Cells

    SciTech Connect

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

    2012-04-15

    We investigated the quality of the n+-p diffused junction beneath the front-side Ag contact of multicrystalline Si solar cells by characterizing the uniformities of electrostatic potential and doping concentration across the junction using the atomic force microscopy-based electrical imaging techniques of scanning Kelvin probe force microscopy and scanning capacitance microscopy. We found that Ag screen-printing metallization fired at the over-fire temperature significantly degrades the junction uniformity beneath the Ag contact grid, whereas metallization at the optimal- and under-fire temperatures does not cause degradation. Ag crystallites with widely distributed sizes were found at the Ag-grid/emitter-Si interface of the over-fired cell, which is associated with the junction damage beneath the Ag grid. Large crystallites protrude into Si deeper than the junction depth. However, the junction was not broken down; instead, it was reformed on the entire front of the crystallite/Si interface. We propose a mechanism of junction-quality degradation, based on emitter Si melting at the temperature around the Ag-Si eutectic point during firing, and subsequent re-crystallization with incorporation of Ag and other impurities and with formation of crystallographic defects during quenching. The effect of this junction damage on solar cell performance is discussed.

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

    PubMed

    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 5mm. 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. PMID:24913466

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

    DOEpatents

    Chang, Y. Austin (Middleton, WI); Yang, Jianhua J. (Madison, WI); Ladwig, Peter F. (Hutchinson, MN)

    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.

  9. A peptidomimetic tight junction modulator to improve regional analgesia.

    PubMed

    Zwanziger, Denise; Hackel, Dagmar; Staat, Christian; Böcker, Alexander; Brack, Alexander; Beyermann, Michael; Rittner, Heike; Blasig, Ingolf E

    2012-06-01

    The paracellular flux of solutes through tissue barriers is limited by transmembrane tight junction proteins. Within the family of tight junction proteins, claudin-1 seems to be a key protein for tightness formation and integrity. In the peripheral nervous system, the nerve fibers are surrounded with a barrier formed by the perineurium which expresses claudin-1. To enhance the access of hydrophilic pharmaceutical agents via the paracellular route, a claudin-1 specific modulator was developed. For this purpose, we designed and investigated the claudin-1 derived peptide C1C2. It transiently increased the paracellular permeability for ions and high and low molecular weight compounds through a cellular barrier model. Structural studies revealed a ?-sheet potential for the functionality of the peptide. Perineurial injection of C1C2 in rats facilitated the effect of hydrophilic antinociceptive agents and raised mechanical nociceptive thresholds. The mechanism is related to the internalization of C1C2 and to a vesicle-like distribution within the cells. The peptide mainly colocalized with intracellular claudin-1. C1C2 decreased membrane-localized claudin-1 of cells in culture and in vivo in the perineurium of rats after perineurial injection. In conclusion, a novel tool was developed to improve the delivery of pharmaceutical agents through the perineurial barrier by transient modulation of claudin-1. PMID:22524793

  10. P-cresol induces disruption of cardiomyocyte adherens junctions.

    PubMed

    Peng, Yu-Sen; Lin, Yen-Tung; Wang, Sheng-De; Hung, Kuan-Yu; Chen, Ying; Wang, Seu-Mei

    2013-04-01

    Higher serum levels of p-cresol in chronic kidney disease populations have been associated with increased cardiovascular mortality. However, studies on how p-cresol affects intercellular junctions between cardiomyocytes were limited. This study investigated the effect of p-cresol on adherens junction (AJ) of neonatal cultured cardiomyocytes and its underlying mechanism. A loss of N-cadherin and p120-catenin (p120ctn) immunostaining from cell-cell contact sites was noted by p-cresol treatment. In addition, p-cresol disrupted AJs by inducing formation of intercellular gaps. Our previous study has revealed that p-cresol increased intracellular calcium levels and activated protein kinase C? (PKC?) by phosphorylation. The PKC? activation was involved in the p-cresol-mediated AJ disassembly, since pharmacological inhibition of PKC? abolished the above-mentioned p-cresol effect. This PKC? activation also led to the serine dephosphorylation of p120ctn and caused the dissociation of p120ctn from N-cadherin. This hypothesis was further confirmed in H9c2 cells by siRNA approach. SiRNA knockdown of PKC? prevented p-cresol-induced serine dephosphorylation of p120ctn and splitting of AJ. In conclusion, p-cresol caused PKC?-dependent AJ disassembly of cardiomyocytes, which might be related to asychronized contraction. PMID:23466501

  11. Exploring Hot Gas at Junctions of Galaxy Filaments

    NASA Astrophysics Data System (ADS)

    Mitsuishi, Ikuyuki; Yamasaki, Noriko; Kawahara, Hajime; Sekiya, Norio; Sasaki, Shin; Sousbie, Thierry

    Because galaxies are forced to follow the strong gravitational potential created by the underlying cosmic web of the dark matter, their distribution reflects its filamentary structures. By identifying the filamentary structures, one can therefore recover a map of the network that drives structure formation. Filamentary junctions are regions of particular interest as they identify places where mergers and other interesting astrophysical phenomena have high chances to occur. We identified the galaxy filaments by our original method (Sousbie (2011) & Sousbie et al. (2011)) and X-ray pointing observations were conducted for the six fields locating in the junctions of the galaxy filaments where no specific diffuse X-ray emissions had previously been detected so far. We discovered significant X-ray signals in their images and spectra of the all regions. Spectral analysis demonstrated that six sources originate from diffuse emissions associated with optically bright galaxies, group-scale, or cluster-scale X-ray halos with kT˜1-4 keV, while the others are compact object origin. Interestingly, all of the newly discovered three intracluster media show peculiar features such as complex or elongated morphologies in X-ray and/or optical and hot spot involved in ongoing merger events (Kawahara et al. (2011) & Mitsuishi et al. (2014)). In this conference, results of follow-up radio observations for the merging groups as well as the details of the X-ray observations will be reported.

  12. Exploring Hot Gas at Junctions of Galaxy Filaments with Suzaku

    NASA Astrophysics Data System (ADS)

    Mitsuishi, I.; Kawahara, H.; Sekiya, N.; Sasaki, S.; Sousbie, T.; Y. Yamasaki, N.

    2014-07-01

    Galaxies are forced to form filamentary structure reflecting the underlying cosmic web of the dark matter. In particular, at junctions of galaxy filaments, one can naturally expect that intense structure formation has high chances to occur. We identified the galaxy filaments by making use of our original method (Sousbie (2011) & Sousbie et al. (2011)) in conjunction with SDSS spectroscopic galaxies. We performed X-ray pointing observations for six fields locating in the junctions of the galaxy filaments where no specific diffuse X-ray emissions had previously been detected so far. We discovered significant X-ray signals in their images and spectra of the all regions compared to a background region. Spectral analysis revealed that six sources originate from diffuse emissions associated with optically bright galaxies, group-scale, or cluster-scale X-ray halos with temperautres of 1-4 keV, while the others are compact object origin. Interestingly, the observed three intracluster media possess peculiar signatures such as complex or elongated morphologies in X-ray and/or optical and hot spot, suggesting that all of the systems are experiencing an ongoing merger (Kawahara et al. (2011) & Mitsuishi et al. (2014)). In this conference, results of follow-up radio observations to search for merger-induced diffuse radio emissions will be reported.

  13. Currents Induced by Injected Charge in Junction Detectors

    PubMed Central

    Gaubas, Eugenijus; Ceponis, Tomas; Kalesinskas, Vidas

    2013-01-01

    The problem of drifting charge-induced currents is considered in order to predict the pulsed operational characteristics in photo- and particle-detectors with a junction controlled active area. The direct analysis of the field changes induced by drifting charge in the abrupt junction devices with a plane-parallel geometry of finite area electrodes is presented. The problem is solved using the one-dimensional approach. The models of the formation of the induced pulsed currents have been analyzed for the regimes of partial and full depletion. The obtained solutions for the current density contain expressions of a velocity field dependence on the applied voltage, location of the injected surface charge domain and carrier capture parameters. The drift component of this current coincides with Ramo's expression. It has been illustrated, that the synchronous action of carrier drift, trapping, generation and diffusion can lead to a vast variety of possible current pulse waveforms. Experimental illustrations of the current pulse variations determined by either the rather small or large carrier density within the photo-injected charge domain are presented, based on a study of Si detectors. PMID:24036586

  14. Quantum phase slips in Josephson junction rings

    NASA Astrophysics Data System (ADS)

    Rastelli, G.; Pop, I. M.; Hekking, F. W. J.

    2013-05-01

    We study quantum phase-slip (QPS) processes in a superconducting ring containing N Josephson junctions and threaded by an external static magnetic flux ?B. In such a system, a QPS consists of a quantum tunneling event connecting two distinct classical states of the phases with different persistent currents [Matveev , Phys. Rev. Lett.10.1103/PhysRevLett.89.096802 89, 096802 (2002)]. When the Josephson coupling energy EJ of the junctions is larger than the charging energy EC=e2/2C, where C is the junction capacitance, the quantum amplitude for the QPS process is exponentially small in the ratio EJ/EC. At given magnetic flux, each QPS can be described as the tunneling of the phase difference of a single junction of almost 2?, accompanied by a small harmonic displacement of the phase difference of the other N-1 junctions. As a consequence, the total QPS amplitude ?ring is a global property of the ring. Here, we study the dependence of ?ring on the ring size N, taking into account the effect of a finite capacitance C0 to ground, which leads to the appearance of low-frequency dispersive modes. Josephson and charging effects compete and lead to a nonmonotonic dependence of the ring's critical current on N. For N??, the system converges either towards a superconducting or an insulating state, depending on the ratio between the charging energy E0=e2/2C0 and the Josephson coupling energy EJ.

  15. 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

  16. Electrical characteristics and interface structure of magnetic tunnel junctions with hafnium oxyfluoride barrier

    SciTech Connect

    Yu, Y.Y.; Kim, D.S.; Char, K. [Center for Strongly Correlated Materials Research and School of Physics, Seoul National University, Seoul 151-742 (Korea, Republic of)

    2004-12-01

    We have studied the effects of fluorine inclusion on the electrical transport characteristics and interface structure of the hafnium oxide barrier in a magnetic tunnel junction. The tunneling magnetoresistance (TMR) and resistance-area (RA) as a function of oxidation time show that the TMR ratio of the hafnium oxyfluoride barrier is higher (8.3%) than that of the hafnium oxide barrier (5.7%) at their optimum conditions, and the oxyfluoride barrier junctions maintain a high TMR ratio even when the RA product increases by three orders of magnitude. X-ray photoelectron spectroscopy analysis shows that the fluorine atoms in the oxyfluoride barrier play an important role in the formation of a barrier with uniform composition. We believe that the initial fluoride layer is causing the subsequent oxygen diffusion to slow down, resulting in the formation of a defect-free hafnium oxide layer. These results are consistent with what we have found for aluminum oxyfluoride barriers.

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

    PubMed

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

    2013-07-15

    Gap junctions are unique intercellular channels formed by the proper docking of two hemichannels from adjacent cells. Each hemichannel is a hexamer of connexins (Cxs) - the gap junction subunits, which are encoded by 21 homologous genes in the human genome. The docking of two hemichannels to form a functional gap junction channel is only possible between compatible Cxs, but the underlying molecular mechanism is unclear. On the basis of the crystal structure of the Cx26 gap junction, we developed homology models for homotypic and heterotypic channels from Cx32 and/or Cx26; these models predict six hydrogen bonds at the docking interface of each pair of the second extracellular domain (E2). A Cx32 mutation N175H and a human-disease-linked mutant N175D were predicted to lose the majority of the hydrogen bonds at the E2 docking-interface; experimentally both mutations failed to form morphological and functional gap junctions. To restore the lost hydrogen bonds, two complementary Cx26 mutants - K168V and K168A were designed to pair with the Cx32 mutants. When docked with Cx26K168V or K168A, the Cx32N175H mutant was successfully rescued morphologically and functionally in forming gap junction channels, but not Cx32 mutant N175Y. By testing more homotypic and heterotypic Cx32 and/or Cx26 mutant combinations, it is revealed that a minimum of four hydrogen bonds at each E2-docking interface are required for proper docking and functional channel formation between Cx26 and Cx32 hemichannels. Interestingly, the disease-linked Cx32N175D could be rescued by Cx26D179N, which restored five hydrogen bonds at the E2-docking interface. Our findings not only provide a mechanism for gap junction docking for Cx26 and Cx32 hemichannels, but also a potential therapeutic strategy for gap junction channelopathies. PMID:23687377

  18. Inverse models of gravity data from the Red Sea-Aden-East African rifts triple junction zone

    Microsoft Academic Search

    Christel Tiberi; Cynthia Ebinger; Valérie Ballu; Graham Stuart; Befekadu Oluma

    2005-01-01

    The combined effects of stretching and magmatism permanently modify crustal structure in continental rifts and volcanic passive margins. The Red Sea-Gulf of Aden-Ethiopian rift triple junction zone provides a unique opportunity to examine incipient volcanic margin formation above or near an asthenospheric upwelling. We use gravity inversions and forward modelling to examine lateral variations in crust and upper mantle structure

  19. Energy barriers in carbon nanotube junctions

    NASA Astrophysics Data System (ADS)

    Tamura, Ryo; Tsukada, Masaru

    2001-03-01

    Recently Yao et al. observed a junction connecting a metallic nanotube and a semiconducting nanotube by a pair of a pentagonal defect and a heptagonal defect and rectification of the junction due to the Schottky barrier. (Z. Yao, H.W.Ch.Postma, L. Balents and C. Dekker, Nature 402), (1999) 273. A. A. Odintsov investigated such a hetero-junction theoretically, but his discussion is based on the semi-classical model and does not include the atomic structures . ( A. A. Odintsov, Phys. Rev. Lett. 85), (2000) 150. To consider the effects of the atomic structures, we use Hartree-Fock approximation and tight binding model. Green's function method is also utilized because it is useful tool to calculate the transmission rate.( Electronic Transport in Mesoscopic Systems, edited by S. Datta (Cambridge University Press, 1995).)We will discuss dependence of the electronic current on the bias, the gate voltage, and radii of the tubes.

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

    Microsoft Academic Search

    F. Sarubbi

    2010-01-01

    Doping technologies for formation of ultrashallow and highly-doped p+ junctions are continuously demanded to face the challenges in front-end processing that have emerged due to the aggressive downscaling of vertical dimensions for future semiconductor devices. As an alternative to implantations, current solutions are based on in-situ boron (B) doping during Si\\/SiGe chemical vapor deposition (CVD) by using diborane (B2H6) as

  1. Stable semiconductor liquid junction cell with 9% solar to electrical conversion efficiency

    Microsoft Academic Search

    K. C. Chang; A. Heller; B. Schwartz; S. Menezes; B. Miller

    1977-01-01

    The semiconductor liquid junction cell n-GaAs\\/0.8F K2Se2-1F KOH\\/C has been shown to deliver 9% photovoltaic power conversion efficiency in sunlight. Accelerated tests under 3100 K light sources of several solar intensities indicate very low photocorrosion currents and high output stability. Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts: Use: Authors Title Keywords (in

  2. 30 CFR 56.12007 - Junction box connection procedures.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Electricity § 56.12007 Junction box connection procedures. Trailing cable and power-cable connections to junction boxes...

  3. 30 CFR 56.12007 - Junction box connection procedures.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Electricity § 56.12007 Junction box connection procedures. Trailing cable and power-cable connections to junction boxes...

  4. 30 CFR 56.12007 - Junction box connection procedures.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Electricity § 56.12007 Junction box connection procedures. Trailing cable and power-cable connections to junction boxes...

  5. 6. View northeast, junction of SR 141 and Rockland Road, ...

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

    6. View northeast, junction of SR 141 and Rockland Road, western estate wall and tree lines to right - A. I. Du Pont Estate, Junction of State Route 141 & Rockland Road, Wilmington, New Castle County, DE

  6. 8. Vidw southwest, junction of SR 141 and Rockland Road, ...

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

    8. Vidw southwest, junction of SR 141 and Rockland Road, northern estate wall and tree lines to left - A. I. Du Pont Estate, Junction of State Route 141 & Rockland Road, Wilmington, New Castle County, DE

  7. Magnetic Josephson junctions with noncentrosymmetric superconductors

    NASA Astrophysics Data System (ADS)

    Rahnavard, Yousef; Manske, Dirk; Annunziata, Gaetano

    2014-06-01

    We study the dc Josephson effect in a clean noncentrosymmetric superconductor/ferromagnet/noncentro-symmetric superconductor junction within the quasiclassical theory of superconductivity. By considering charge and spin currents, we show that in such junctions an exotic Josephson effect can take place, depending on the superconducting pairing state and spin polarization direction. We focus on the importance of spin-triplet/spin-singlet gaps ratio in such systems showing that its value is related to the existence of even and odd high-order harmonics in the charge and spin current-phase relations, and to the possibility of 0-? transitions.

  8. Axion physics in a Josephson junction environment

    E-print Network

    Christian Beck

    2011-11-23

    We show that recent experiments based on Josephson junctions, SQUIDS, and coupled Josephson qubits have a cosmological interpretation in terms of axionic dark matter physics, in the sense that they allow for analogue simulation of early-universe axion physics. We propose new experimental setups in which SQUID-like axionic interactions in a resonant Josephson junction environment can be tested, similar in nature to recent experiments that test for quantum entanglement of two coupled Josephson qubits. We point out that the parameter values relevant for early-universe axion cosmology are accessible with present day's achievements in nanotechnology.

  9. Method of making a Josephson Junction

    SciTech Connect

    Ohta, H.

    1984-02-14

    Disclosed is an improved Josephson Junction comprising a superconductor-separator-superconductor laminar deposition on a substrate, the overlying and underlying superconductor layers being laid offset to each other, and a weak link extending from one of the superconductor layers to the other across the thickness of the intervenient separator. A triple layer superconducting device according to this invention has as short barrier length and as low capacitance as possible, and is characteristic of a large product of junction resistance and critical current. Also, the geometrical configuration of the device is most appropriate for the purpose of massproduction.

  10. Junction area dependence of tunneling magnetoresistance

    NASA Astrophysics Data System (ADS)

    Lee, S. S.; Wang, S. X.; Park, C. M.; Rhee, J. R.; Yoon, C. S.; Chang, P. J.; Kim, C. K.

    2002-02-01

    Spin dependent tunneling devices Ta/NiFe/Ta/NiFe/FeMn/NiFe/CoFe/Al 2O 3/CoFe/NiFe/Al with in-situ naturally oxidized Al 2O 3 barrier were fabricated using ion beam deposition and DC sputtering. The as-deposited and post-annealing junctions showed tunneling magnetoresistance of 8-18% with resistance-area products ( R× A) of 340-60 ? ?m 2, which were dependent on the junction area (81-4 ?m 2).

  11. The clinical anatomy of the sinutubular junction.

    PubMed

    Loukas, Marios; Wartmann, Christopher T; Tubbs, R Shane; Apaydin, Nihal; Louis, Robert G; Easter, Laurie; Black, Brandie; Jordan, Robert

    2009-04-01

    Specific sites of atherosclerotic processes due to hemodynamic changes and resultant stress, including how these normal anatomical structures become problematic in certain individuals, have yet to be acknowledged. One of these areas of the cardiovascular system occurs at the sinutubular junction (SJ), causing altercation in an otherwise normal flow status. The anatomy of the SJ was examined in 100 adult human hearts during the gross anatomy course at St George's University, during the years 2006-2007. All hearts were examined in situ, using a General Electric model 3200S ultrasound machine with a 5 MHz linear probe. The aforementioned cadavers were also examined using a Stryker laparoscopic unit. Serial transverse histological sections were made through the SJ perpendicular to its axis, and stained with eosin-hematoxylin, van Gieson, Masson trichrome, and Orcein methods. In addition, an immunohistochemical analysis was performed for the detection of positive smooth muscle cells stained areas. During gross and endoscopic examination we were able to identify the SJ in all adult heart specimens. Neonatal and fetal hearts did not exhibit any gross evident SJ; however, a SJ was evident histologically. Ultrasonographically we were able to identify the SJ in all adult heart specimens examined, and a sinutubular ridge in 62%. A significant association was present between the thickness of the ridge and the age of the specimens. The SJ was found to exhibit atherosclerotic changes and plaque formation in an age-related manner. In older subjects, the SJ was marked with local calcification and hemorrhages. In contrast, the SJ of neonatal hearts appeared to have intimal thickening with focal fragmentation and absent or duplicate internal elastic lamina. Intuitively speaking, the presence of a sinutubular ridge, an inevitable fate in humans based on the results of this study, provides an irreversible atherosclerotic process as there is no evidence that the promoting ridge regresses. This is an alarming situation in those individuals who will eventually develop cardiovascular risk factors, whether through inevitable genetic manifestations or by means of exogenous environmental causes. PMID:19224331

  12. 76 FR 40293 - Proposed Amendment of Class D and Modification of Class E Airspace; Grand Junction, CO

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-08

    ...Modification of Class E Airspace; Grand Junction, CO AGENCY: Federal Aviation Administration...Junction Regional Airport, Grand Junction, CO. Additional controlled airspace is necessary...Junction Regional Airport, Grand Junction, CO. Additional controlled airspace...

  13. Fluctuations of critical current and phase slippage in Josephson junctions

    SciTech Connect

    Simanek, E. (Department of Physics, University of California, Riverside, California 92521(US))

    1989-06-01

    The effect of critical current noise on the phase-slip- rate in an overdamped Josephson junction is calculated. A significant increase of the Kramers escape rate is predicted for submicron metal-insulator-metal junctions. The temperature dependence of the rate shows deviations from the Arrhenius law at low temperatures if the junction conductance fluctuations are produced by quantum ionic tunneling processes in the junction barrier. Implications for magnetization decay in high-T/sub c/ superconductors are discussed.

  14. Expression of JAM-A, AF-6, PAR-3 and PAR-6 during the assembly and remodeling of RPE tight junctions.

    PubMed

    Luo, Yan; Fukuhara, Masayuki; Weitzman, Matthew; Rizzolo, Lawrence J

    2006-09-19

    The tight junctions of the endothelial and epithelial regions of the blood-brain barrier are regulated by interactions with the neighboring tissue. We examined how the neural retina regulates the assembly of tight junctions in the retinal pigment epithelium (RPE). The proteins JAM-A, AF-6, PAR-3 and PAR-6 have been implicated in the assembly of other epithelial tight junctions. Using chick embryos and primary cell culture, we examined gene expression of these proteins during embryonic development, and whether retinal secretions regulate their expression. Three highly conserved RNA splice sites of AF-6 were identified in chick ocular tissues, but only two were expressed in RPE. JAM-A and AF-6 were expressed at relatively high levels early in development when adherens junctions form, but before tight junctions form. Expression of JAM-A and the AF-6 isoforms actually decreased when tight junctions were forming and expanding. The expression of PAR-3 and PAR-6 was constant. Despite the expression of these proteins in vitro (along with claudins, occludin, ZO-1 and ZO-2), the tight junctional networks that form were discontinuous (Rahner, C., Fukuhara, M., Peng, S., Kojima, S., Rizzolo, L.J., 2004. The apical and basal environments of the retinal pigment epithelium regulate the maturation of tight junctions during development. J. Cell Sci. 117, 3307-3318). The expression of these assembly proteins was unaffected by a retinal conditioned medium that induced the completion of tight junction formation. These data indicate that the early expression of the assembly proteins corresponds to the initial establishment of the adherens and tight junctions, but secretory products of the neural retina must induce the expression of additional proteins to complete the maturation process. PMID:16859655

  15. Modulation of gap junction transcript and protein expression during pregnancy in the rat

    PubMed Central

    1990-01-01

    The expression of three different gap junction transcripts, alpha 1 (Cx43), beta 1 (Cx32), and beta 2 (Cx26) was examined in several organs during pregnancy in the rat. In all of the organs that were examined-- uterus, ovary, heart, and liver--there was a strong correlation between levels of gap junction mRNA and gap junction antigens that were detected at different stages of pregnancy. A striking change in alpha 1 transcript levels (a 5.5-fold increase) was detected in the uterine myometrium on the day before parturition. This elevation of the alpha 1 transcript is thought to be associated with the formation of gap junctions that are required for synchronizing the contractility of the myometrial cells during parturition. 2 d before parturition, there was a detectable elevation of beta 2 transcripts and protein in the endometrial epithelium, which was then followed by a dramatic decrease in beta 2 gap junctional protein on the day before parturition. There was also a substantial elevation of alpha 1 transcripts (a 6.7-fold increase) in the stromal regions of the ovary on the day before parturition that was identical to the temporal pattern of alpha 1 expression in the myometrium. In all three instances--the alpha 1 transcripts in the myometrium, beta 2 transcripts in the endometrium, and alpha 1 transcripts in the ovary--the transcript modulation appeared to be cell specific, because the changes in transcript levels of these three gene products occurred independently of the poly(A) + RNA concentrations at the same pregnancy stages in the respective organs. There were no specific changes detected in gap junction transcript levels in the heart and liver during pregnancy. These observations indicate that a cell-specific modulation of gap junction expression occurs in two regions of the uterus and the ovary during pregnancy. Further, it appears that the same gap junction gene in different organs, such as the alpha 1 gene in the uterine myometrium and the heart, can be differentially regulated. PMID:1688855

  16. Influence of nonuniform magnetic field on a ferrite junction circulator

    Microsoft Academic Search

    H. How; S. A. Oliver; S. W. McKnight; P. M. Zavracky; N. E. McGruer; C. Vittoria; R. Schmidt

    1999-01-01

    We have analytically formulated the problem that a ferrite circulator junction is biased by a nonuniform magnetic field. Interport impedances of the junction can, therefore, be solved numerically. Nonuniform-bias field will reduce the transmission bandwidth, and the circulation condition is apt to be altered if the bias field shows nonuniformity near the center of the junction. Our calculation compares very

  17. Achieving the Threshold Regime with an Overscreened Josephson Junction

    Microsoft Academic Search

    Eugene V. Sukhorukov; Andrew N. Jordan

    2009-01-01

    We demonstrate that by utilizing an overscreened Josephson junction as a noise detector it is possible to achieve the threshold regime, whereby the tails of the fluctuating current distribution are measured. This situation is realized by placing the Josephson junction and mesoscopic conductor in an external circuit with very low impedance. In the underdamped limit, overscreening the junction inhibits the

  18. VORTEX PROPAGATION AND RADIATION EMISSION IN JOSEPHSON TUNNEL JUNCTIONS

    E-print Network

    Boyer, Edmond

    emission by large-critical-current junctions are also considered. REVUE DE PHYSIQUE APPLIQUÉE TOME 9299 VORTEX PROPAGATION AND RADIATION EMISSION IN JOSEPHSON TUNNEL JUNCTIONS T. A. FULTON and L. N radiation from a Josephson tunnel junction biased on a « zero-field step » is measured and found to obey

  19. 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

  20. Superconductive tunnel junction device and method of manufacture

    Microsoft Academic Search

    Kroger

    1983-01-01

    A Josephson tunnel junction device having niobium nitride superconductive electrodes includes a polycrystalline semiconductor tunneling barrier therebetween comprised of silicon, germanium, or an alloy thereof preferably deposited on the lower superconductive electrodes by vapor deposition. The barrier thickness of the junction is controlled by precision doping of the semiconductor material. The active junction is defined after the interfaces between the

  1. Spin Dependent Transport in Co Nano-Scale Tunnel Junctions

    E-print Network

    Haviland, David

    Spin Dependent Transport in Co Nano-Scale Tunnel Junctions Mattias Urech Section of Nanostructure, Chalmers #12;Abstract Ferromagnetic tunnel junctions have been fabricated, measured and theoretically de-resistors-in-series model. Single-, triple-, and five- junction arrays were fabricated and measured. In or- der to analyze

  2. Arrays of Josephson tunnel junctions as parametric amplifiers

    Microsoft Academic Search

    S. Wahlsten; S. Rudner; T. Claeson

    1978-01-01

    Single junctions and arrays of 10 or 40 series-connected small densely packed Josephson tunnel junctions are studied. The basic equations governing the response of a tunnel junction are presented, a short account of the theoretical model for a SUPARAMP (Superconducting Unbiased PARametric AMPlifier) is given, including modifications due to a finite magnetic field, and a discussion of relevant circuit parameters

  3. Performance of arrays of SIS junctions in heterodyne mixers

    Microsoft Academic Search

    Denis-Gerard Crete; William R. McGrath; Paul L. Richards; Frances L. Lloyd

    1987-01-01

    A systematic experimental study has been made of the performance of millimeter-wave quasiparticle heterodyne mixers which use arrays of SIS tunnel junctions. Sets of arrays with N = 1, 5, 10, 25, and 50 junctions in series were fabricated by photolithography. Junction areas were scaled so that the total impedance was the same for each array in a set. Sets

  4. Conductance Asymmetry of Graphene p-n Junction

    Microsoft Academic Search

    Tony Low; Seokmin Hong; Joerg Appenzeller; Supriyo Datta; Mark S. Lundstrom

    2009-01-01

    We use the nonequilibrium Green function method in the ballistic limit to provide a quantitative description of the conductance of graphene p-n junctions - an important building block for graphene electronics devices. In this paper, recent experiments on graphene junctions are explained by a ballistic transport model, but only if the finite junction transition width D w is accounted for.

  5. Structurally graded core junctions in sandwich beams: fatigue loading conditions

    Microsoft Academic Search

    Elena Bozhevolnaya; Ole Thybo Thomsen

    2005-01-01

    Sandwich beams with inclusion of different core materials were the subject of the experimental study [Bozhevolnaya E, Thomsen OT. Structurally graded core junctions in sandwich beams: quasi-static analysis. Compos Struct, in press], which focused on the static performance of such sandwich elements. The concept of structurally graded core junctions, suggested in [Bozhevolnaya E, Thomsen OT. Structurally graded core junctions in

  6. The tight junction protein claudin-1 influences cranial neural crest cell emigration

    PubMed Central

    Fishwick, Katherine J.; Neiderer, Theresa; Jhingory, Sharon; Bronner, Marianne; Taneyhill, Lisa A.

    2012-01-01

    The neural crest is a population of migratory cells that follows specific pathways during development, eventually differentiating to form parts of the face, heart, and peripheral nervous system, the latter of which includes contributions from placodal cells derived from the ectoderm. Stationary, premigratory neural crest cells acquire the capacity to migrate by undergoing an epithelial-to-mesenchymal transition that facilitates their emigration from the dorsal neural tube. This emigration involves, in part, the dismantling of cell-cell junctions, including apically localized tight junctions in the neuroepithelium. In this study, we have characterized the role of the transmembrane tight junction protein claudin-1 during neural crest and placode ontogeny. Our data indicate that claudin-1 is highly expressed in the developing neuroepithelium but is down-regulated in migratory neural crest cells, although expression persists in the ectoderm from which the placode cells arise. Depletion or overexpression of claudin-1 augments or reduces neural crest cell emigration, respectively, but does not impact the development of several cranial placodes. Taken together, our results reveal a novel function for a tight junction protein in the formation of migratory cranial neural crest cells in the developing vertebrate embryo. PMID:22771518

  7. Nonredundant roles of cytoplasmic ?- and ?-actin isoforms in regulation of epithelial apical junctions

    PubMed Central

    Baranwal, Somesh; Naydenov, Nayden G.; Harris, Gianni; Dugina, Vera; Morgan, Kathleen G.; Chaponnier, Christine; Ivanov, Andrei I.

    2012-01-01

    Association with the actin cytoskeleton is critical for normal architecture and dynamics of epithelial tight junctions (TJs) and adherens junctions (AJs). Epithelial cells express ?-cytoplasmic (?-CYA) and ?-cytoplasmic (?-CYA) actins, which have different cellular localization and functions. This study elucidates the roles of cytoplasmic actins in regulating structure and remodeling of AJs and TJs in model intestinal epithelia. Immunofluorescence labeling and latrunculin B treatment reveal affiliation of dynamic ?-CYA filaments with newly assembled and mature AJs, whereas an apical ?-CYA pool is composed of stable perijunctional bundles and rapidly turning-over nonjunctional filaments. The functional effects of cytoplasmic actins on epithelial junctions are examined by using isoform-specific small interfering RNAs and cell-permeable inhibitory peptides. These experiments demonstrate unique roles of ?-CYA and ?-CYA in regulating the steady-state integrity of AJs and TJs, respectively. Furthermore, ?-CYA is selectively involved in establishment of apicobasal cell polarity. Both actin isoforms are essential for normal barrier function of epithelial monolayers, rapid AJ/TJ reassembly, and formation of three-dimensional cysts. Cytoplasmic actin isoforms play unique roles in regulating structure and permeability of epithelial junctions. PMID:22855531

  8. Theoretical consideration of III-V nanowire/Si triple-junction solar cells.

    PubMed

    Wen, Long; Li, Xinhua; Zhao, Zhifei; Bu, Shaojiang; Zeng, XueSong; Huang, Jin-hua; Wang, Yuqi

    2012-12-21

    In this paper, we report theoretical consideration and simulation of a proposed III-V nanowire (NW)/Si triple-junction solar cell. The cell consists of two axially connected III-V NW subcells that are grown and electrically integrated on an active Si substrate. The optical properties of the cell are thoroughly analyzed by using the finite-difference time-domain method. It is found that NW subcells with optimized geometry have high absorption throughout their absorption region. Meanwhile, beyond the absorption edge of the top and middle NW subcells, the NWs act as an efficient antireflection coating for the bottom Si subcell due to the formation of an optical cavity within the NW layer. The physics responsible for the enhanced light harvesting process is qualitatively explained through modal analysis. In addition, we have shown that the condition of current matching in a III-V NW/Si multi-junction can be fulfilled by adjusting the diameter of the NWs. In order to study the current-voltage characteristics of the proposed cell, the optical generation profiles under AM1.5G illumination are incorporated into an electrical modeling. Our optoelectrical simulations indicate that, with an excellent current matching between subcells, the performance of the proposed structure is comparable with state-of-the-art multi-junction cells. The results presented here indicate that semiconductor NWs may provide a promising route toward high efficiency multi-junction solar cells. PMID:23182996

  9. Theoretical consideration of III-V nanowire/Si triple-junction solar cells

    NASA Astrophysics Data System (ADS)

    Wen, Long; Li, Xinhua; Zhao, Zhifei; Bu, Shaojiang; Zeng, XueSong; Huang, Jin-hua; Wang, Yuqi

    2012-12-01

    In this paper, we report theoretical consideration and simulation of a proposed III-V nanowire (NW)/Si triple-junction solar cell. The cell consists of two axially connected III-V NW subcells that are grown and electrically integrated on an active Si substrate. The optical properties of the cell are thoroughly analyzed by using the finite-difference time-domain method. It is found that NW subcells with optimized geometry have high absorption throughout their absorption region. Meanwhile, beyond the absorption edge of the top and middle NW subcells, the NWs act as an efficient antireflection coating for the bottom Si subcell due to the formation of an optical cavity within the NW layer. The physics responsible for the enhanced light harvesting process is qualitatively explained through modal analysis. In addition, we have shown that the condition of current matching in a III-V NW/Si multi-junction can be fulfilled by adjusting the diameter of the NWs. In order to study the current-voltage characteristics of the proposed cell, the optical generation profiles under AM1.5G illumination are incorporated into an electrical modeling. Our optoelectrical simulations indicate that, with an excellent current matching between subcells, the performance of the proposed structure is comparable with state-of-the-art multi-junction cells. The results presented here indicate that semiconductor NWs may provide a promising route toward high efficiency multi-junction solar cells.

  10. The tight junction protein claudin-1 influences cranial neural crest cell emigration.

    PubMed

    Fishwick, Katherine J; Neiderer, Theresa E; Jhingory, Sharon; Bronner, Marianne E; Taneyhill, Lisa A

    2012-01-01

    The neural crest is a population of migratory cells that follows specific pathways during development, eventually differentiating to form parts of the face, heart, and peripheral nervous system, the latter of which includes contributions from placodal cells derived from the ectoderm. Stationary, premigratory neural crest cells acquire the capacity to migrate by undergoing an epithelial-to-mesenchymal transition that facilitates their emigration from the dorsal neural tube. This emigration involves, in part, the dismantling of cell-cell junctions, including apically localized tight junctions in the neuroepithelium. In this study, we have characterized the role of the transmembrane tight junction protein claudin-1 during neural crest and placode ontogeny. Our data indicate that claudin-1 is highly expressed in the developing neuroepithelium but is down-regulated in migratory neural crest cells, although expression persists in the ectoderm from which the placode cells arise. Depletion or overexpression of claudin-1 augments or reduces neural crest cell emigration, respectively, but does not impact the development of several cranial placodes. Taken together, our results reveal a novel function for a tight junction protein in the formation of migratory cranial neural crest cells in the developing vertebrate embryo. PMID:22771518

  11. OPTIMAL NORMAL TISSUE SPARING in Craniospinal Axis Irradiation Using IMRT with Daily Intrafractionally Modulated Junction(s)

    Microsoft Academic Search

    Johannes M. A. M. Kusters; Rob J. W. Louwe; Peter G. M. van Kollenburg; Martina C. Kunze-Busch; Corrie E. M. Gidding; Erik J. van Lindert; Johannes H. A. M. Kaanders; Geert O. R. J. Janssens

    2011-01-01

    PURPOSE: To develop a treatment technique for craniospinal irradiation using intensity-modulated radiotherapy (IMRT) with improved dose homogeneity at the field junction(s), increased target volume conformity, and minimized dose to the organs at risk (OARs). METHODS AND MATERIALS: Five patients with high-risk medulloblastoma underwent CT simulation in supine position. For each patient, an IMRT plan with daily intrafractionally modulated junction(s) was

  12. Rectifying Characteristics and Transport Behavior in a Schottky Junction of CaCu3Ti4O12 and Pt

    NASA Astrophysics Data System (ADS)

    Chen, Cong; Ning, Ting-Yin; Wang, Can; Zhou, Yue-Liang; Zhang, Dong-Xiang; Wang, Pei; Ming, Hai; Yang, Guo-Zhen

    2011-08-01

    CaCu3Ti4O12 (CCTO) thin films were fabricated on ITO-covered MgO (100) substrates. The rectification characteristics were observed in the CCTO capacitance structure with Pt top electrodes at temperatures ranging from 150 K to 330 K, which are attributed to the formation of a Schottky junction between n-type semiconducting CCTO and Pt due to the difference of their work functions. At low forward-bias voltage, the current-voltage characteristics of the Schottky junction follow . A strong decrease in ideality factor with the increasing temperature is obtained by linear fitting at the low bias voltage.

  13. Fe\\/MgO\\/FeCo(100) epitaxial magnetic tunnel junctions prepared by using in situ plasma oxidation

    Microsoft Academic Search

    S. Mitani; T. Moriyama; K. Takanashi

    2003-01-01

    Fe\\/MgO\\/FeCo epitaxial magnetic tunnel junctions (MTJs) were prepared on MgO(100) single crystal substrates by using in situ plasma oxidation for the formation of MgO barriers. The epitaxial relationship of Fe(001)\\/MgO(001)\\/FeCo(001) and Fe[100]\\/\\/MgO[110]\\/\\/FeCo[100] in the junctions was observed by reflection high-energy electron diffraction. Tunneling transport was clearly observed at low temperatures below about 150 K, and the barrier height of MgO

  14. Macroscopic Refrigeration Using Superconducting Tunnel Junctions

    NASA Astrophysics Data System (ADS)

    Lowell, Peter; O'Neil, Galen; Underwood, Jason; Zhang, Xiaohang; Ullom, Joel

    2014-03-01

    Sub-kelvin temperatures are often a prerequisite for modern scientific experiments, such as quantum information processing, astrophysical missions looking for dark energy signatures and tabletop time resolved x-ray spectroscopy. Existing methods of reaching these temperatures, such as dilution refrigerators, are bulky and costly. In order to increase the accessibility of sub-Kelvin temperatures, we have developed a new method of refrigeration using normal-metal/insulator/superconductor (NIS) tunnel junctions. NIS junctions cool the electrons in the normal metal since the hottest electrons selectively tunnel from the normal metal into the superconductor. By extending the normal metal onto a thermally isolated membrane, the cold electrons can cool the phonons through the electron-phonon coupling. When these junctions are combined with a pumped 3He system, they provide a potentially inexpensive method of reaching these temperatures. Using only three devices, each with a junction area of approximately 3,500 ?m2, we have cooled a 2 cm3 Cu plate from 290 mK to 256 mK. We will present these experimental results along with recent modeling predictions that strongly suggest that further refinements will allow cooling from 300 mK to 120 mK. This work is supported by the NASA APRA program.

  15. Axion mass estimates from resonant Josephson junctions

    NASA Astrophysics Data System (ADS)

    Beck, Christian

    2015-03-01

    Recently it has been proposed that dark matter axions from the galactic halo can produce a small Shapiro step-like signal in Josephson junctions whose Josephson frequency resonates with the axion mass (Beck, 2013). Here we show that the axion field equations in a voltage-driven Josephson junction environment allow for a nontrivial solution where the axion-induced electrical current manifests itself as an oscillating supercurrent. The linear change of phase associated with this nontrivial solution implies the formal existence of a large magnetic field in a tiny surface area of the weak link region of the junction which makes incoming axions decay into microwave photons. We derive a condition for the design of Josephson junction experiments so that they can act as optimum axion detectors. Four independent recent experiments are discussed in this context. The observed Shapiro step anomalies of all four experiments consistently point towards an axion mass of (110±2) ?eV. This mass value is compatible with the recent BICEP2 results and implies that Peccei-Quinn symmetry breaking was taking place after inflation.

  16. Transport Through Junctions of Quantum Wires

    Microsoft Academic Search

    Sumathi Rao; P. Fuoss; D. Mills; B. Stephenson; L. Young; S. Southworth; L. Chen; B. Adams; K. Moffat; R. Pahl; A. Cavalieri; D. Fritz; S. Lee; A. Lindenberg; K. Gaffney; P. Krejcik; K. Luening; J. Arthur; S. Brenna; J. Hastings; P. Emma; R. Tatchyn; H. Ishii; R. Ischebeck; H. Schlarb; J. Schneider; T. Tschentscher; S. Techert; C. Blome; H. Schulte-Schrepping; Deutsches Elektronen-Synchrotron; F. Settle; D. Lowney; T. Matthews; R. Falcone

    2005-01-01

    Using a renormalization group method valid for weak interactions, we study the effect of electron-electron interactions on the conductance of three or more one-dimensional quantum wires that meet at a junction. We show how the Landauer-Buttiker conductances of various systems depend on the temperature and lengths in a nontrivial way when interelectron interactions are taken into account.

  17. 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??m, 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

  18. Fluorescent window for liquid junction solar cells

    Microsoft Academic Search

    M. S. Kazacos; E. J. McHenry; A. Heller; B. Miller

    1980-01-01

    To recover part of the often substantial fraction of the sunlight lost in practical semiconductor-liquid junction solar cells by solution absorption, two designs incorporating fluorescent windows are analyzed and tested. In these schemes the luminescers absorb incident light in regions of electrolyte absorption and re-emit at wavelengths both within the semiconductor band gap and the transparent range of the solution.

  19. 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.

  20. Fast algorithms for triangular Josephson junction arrays

    SciTech Connect

    Datta, S.; Sahdev, D. [Indian Institute of Technology, Kanpur (India)] [Indian Institute of Technology, Kanpur (India)

    1997-04-01

    We develop fast algorithms for the numerical study of two-dimensional triangular Josephson junction arrays. The Dirac bra-ket formalism is introduced in the context of such arrays. We note that triangular arrays can have both hexagonal and rectangular periodicity and develop algorithms for each. Boundaries are next introduced and fast algorithms for finite arrays are developed. 40 refs., 4 figs.

  1. Quantum wells in multiple junction photovoltaics

    Microsoft Academic Search

    Thomas N. D. Tibbits; Matthew P. Lumb; Alison Dobbin

    2011-01-01

    Triple-junction (3J) solar cells are the world's most efficient photovoltaic conversion devices, hero cells operating >41% under concentration between 300 and 500 suns. The typical 3J approach has a bandgap combination that limits the cell efficiency at approximately 49%. Different combinations of bandgaps can increase the theoretical efficiency to closer to 60%, and use of metamorphic materials has attempted to

  2. Interfacial capacitance effects in magnetic tunneling junctions

    Microsoft Academic Search

    G. Landry; X. Xiang; J. Du; John Q. Xiao

    2001-01-01

    We have investigated the AC transport properties of magnetic tunnel junctions (MTJ) in order to characterize interfacial properties. One such property is interfacial charge accumulation, which leads to a voltage drop in the electrodes of the MTJ and the measured capacitance differing from the geometrical capacitance. Through measurement of capacitance spectra, we have extracted an interfacial capacitance of 16?F\\/cm2 per

  3. Lycopene oxidation product enhances gap junctional communication

    Microsoft Academic Search

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

    2003-01-01

    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

  4. RESEARCH ARTICLE Sustainable correction of junctional epidermolysis

    E-print Network

    Ford, James

    of severe human genetic disorders of self-renewing tissues, such as the blistering skin disease junctional to integrate the LAMB3 cDNA into genomes of epidermal holoclones from six unrelated JEB patients. These cells regenerate human JEB skin that is normalized at the level of laminin 5 protein expression, hemidesmosome

  5. Optimizing Josephson junction performance and nonlinear effects

    E-print Network

    Freericks, Jim

    to the metal-insulator transition, with the goal of minimizing the junction switching speed and maintaining all forms of transport (ballistic, diffusive, incoherent, and correlated) on an equal footing · We program review, 2005 #12;Our model · The superconducting leads are composed of a ballistic metal

  6. Superconductive convolver with junction ring mixers

    SciTech Connect

    Reible, S.A.

    1985-03-01

    A superconductive convolver with tunnel-junction ring mixers was developed and demonstrated as a programmable matched filter for near 1-GHz-bandwidth chirped waveforms. A low-loss, 14-ns-long superconductive striplines circuit provides temporary storage and relative shifting of signal and reference waveforms. These waveforms are sampled by 25 proximity tap pairs and local multiplication is performed by 25 junction ring mixers. Two short transmission lines coherently sum the local products and deliver the convolution output. The output power level of the convolver was increased 18 dB by the incorporation of ring mixers and other output circuit improvements. These mixers employ series arrays of niobium/niobium oxide/lead junctions driven by delay-line taps in a quasi-balanced manner. The ring mixer provides higher-output power levels (to -58 dBm), improved suppression of undesired mixing products and higher if impedances than did the single-junction mixers used in the previous device.

  7. Thermometry by Arrays of Small Tunnel Junctions

    Microsoft Academic Search

    G. Y. Hu; R. F. O'Connell; Young Bong Kang; Jai Yon Ryu

    1998-01-01

    A theoretical treatment is presented which demonstrates the importance of including the effects of stray capacitances and the environment in the analysis of accurate thermometry by arrays of N tunnel junctions. By using the exact solution for the free energy of a one-dimensional array, we calculate the full width at half minimum of the conductance peak and find that due

  8. Magnetotransport in exchange-coupled magnetite junctions

    Microsoft Academic Search

    Rajesh V. Chopdekar; Guohan Hu; Alexandra C. Ford; Yuri Suzuki

    2004-01-01

    Epitaxial magnetic junctions of theoretically half-metallic electrode material magnetite were fabricated with a cobalt chromite paramagnetic insulating tunnel barrier. This spinel structure barrier was chosen to be isostructural to the magnetite electrodes. Highly crystalline trilayers with low surface roughness were grown. Strong exchange coupling between the electrodes is observed across the barrier. Magnetoresistance measurements are reminiscent of a single ferromagnetic

  9. Gallium nitride junction field-effect transistor

    DOEpatents

    Zolper, John C. (Albuquerque, NM); Shul, Randy J. (Albuquerque, NM)

    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.

  10. p-n junction heterostructure device physics model of a four junction solar cell

    Microsoft Academic Search

    Melissa J. Griggs; Brendan M. Kayes; Harry A. Atwater

    2006-01-01

    We present results from a p-n junction device physics model for GaInP\\/GaAs\\/GaInAsP\\/GaInAs four junction solar cells. The model employs subcells whose thicknesses have an upper bound of 5mum and lower bound of 200nm, which is just above the fully depleted case for the assumed doping of NA = 1 x 1018 cm-3 and ND = 1 x 1017 cm-3. The

  11. p-n Junction Heterostructure Device Physics Model of a Four Junction Solar Cell

    Microsoft Academic Search

    Melissa J. Griggs; Brendan M. Kayes; Harry A. Atwater

    We present results from a p-n junction device physics model for GaInP\\/GaAs\\/GaInAsP\\/GaInAs four junction solar cells. The model employs subcells whose thicknesses have an upper bound of 5µm and lower bound of 200nm, which is just above the fully depleted case for the assumed doping of NA = 1 x 10 18 cm-3 and ND = 1 x 10 17

  12. Modeling Germanium p-n Junctions for Multi-junction Solar Cell Applications

    Microsoft Academic Search

    P. Espinet; I. Rey-Stolle; B. Galiana; M. Baudrit; C. Algora

    2007-01-01

    An efficient germanium cell is a key element for attaining high efficiency in state-of-the-art triple junction solar cells. This work summarizes our efforts in the field of modeling of the quantum efficiency of germanium p\\/n junctions for photovoltaic applications. An analytic tool is presented and the most relevant parameters are discussed and modeled. Finally, some hints for the optimum design

  13. Tellurium doping of InGaP for tunnel junction applications in triple junction solar cells

    Microsoft Academic Search

    C. Ebert; Z. Pulwin; D. Byrnes; A. Paranjpe; W. Zhang

    2011-01-01

    Tellurium doped InGaP is an ideal material for the n side of a tunnel junction for triple junction solar cell structures grown by MOCVD. In this paper, we discuss the growth process for abrupt turn-on and turn-off of tellurium in InGaP when InGaP must be highly doped and uniformly doped with tellurium to provide for epitaxial films suitable for tunnel

  14. Minimum performance criteria for quantum well based junctions in multi-junction solar cells

    Microsoft Academic Search

    N. J. Ekins-Daukes; R. P. Raffaelle; K. W. J. Barnham; I. M. Ballard; A. Freundlich; M. Yamaguchi

    2005-01-01

    A systematic survey of the opportunities for incorporating quantum well structures into multi-junction space cells is presented. The quantum well solar cell provides a means for extending the absorption edge of a conventional p\\/n cell, but normally at the cost of a reduction in the open circuit voltage. However, in a current limited multi-junction solar cell, an increased efficiency can

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

    PubMed Central

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

    2014-01-01

    Sertoli cell tight junctions (SCTJs) of the seminiferous epithelium create a specialized microenvironment in the testis to aid differentiation of spermatocytes and spermatids from spermatogonial stem cells. SCTJs must be chronically broken and rebuilt with high fidelity to allow the transmigration of preleptotene spermatocytes from the basal to adluminal epithelial compartment. Impairment of androgen signaling in Sertoli cells perturbs SCTJ remodeling. Claudin (CLDN) 3, a tight junction component under androgen regulation, localizes to newly forming SCTJs and is absent in Sertoli cell androgen receptor knockout (SCARKO) mice. We show here that Cldn3-null mice do not phenocopy SCARKO mice: Cldn3?/? mice are fertile, show uninterrupted spermatogenesis, and exhibit fully functional SCTJs based on imaging and small molecule tracer analyses, suggesting that other androgen-regulated genes must contribute to the SCARKO phenotype. To further investigate the SCTJ phenotype observed in SCARKO mutants, we generated a new SCARKO model and extensively analyzed the expression of other tight junction components. In addition to Cldn3, we identified altered expression of several other SCTJ molecules, including down-regulation of Cldn13 and a noncanonical tight junction protein 2 isoform (Tjp2iso3). Chromatin immunoprecipitation was used to demonstrate direct androgen receptor binding to regions of these target genes. Furthermore, we demonstrated that CLDN13 is a constituent of SCTJs and that TJP2iso3 colocalizes with tricellulin, a constituent of tricellular junctions, underscoring the importance of androgen signaling in the regulation of both bicellular and tricellular Sertoli cell tight junctions. PMID:24825397

  16. 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.

  17. Multiphase Flow in Micro-fracture Junctions

    NASA Astrophysics Data System (ADS)

    Basagaoglu, H.; Meakin, P.; Succi, S.; Wildenschild, D.

    2005-12-01

    A two-dimensional two-phase lattice-Boltzmann model was used to simulate immiscible fluid flow in four micro-fracture geometries closely related to geological fractured systems: (1) a fracture junction with fractal surfaces embedded in a non-porous matrix; (2) a fracture junction embedded in a heterogeneous porous matrix; (3) a heterogeneous porous medium overlying a fracture with fractal surfaces; and (4) a fracture network with fractal surfaces enclosed by a non-porous medium. The spatio-temporal distributions of fluids in fracture junctions were controlled by interplays between velocity-dependent contact angle dynamics, mediated by surface roughness, and pore-scale gravitational, viscous, and capillary forces. All simulations were conducted with actual physical units. Sensitivities of lateral and vertical spreads of fluids in the fracture junctions to the orientation of fracture junctions (tilted vs. vertical) and the wetting strength of fluids were analyzed via temporal moment analyses for the first two geometries. The simulation results revealed that the receding and advancing contact angles varied strongly with the transient fluid velocity. The patterns and distributions of thin films (continuous vs. discontinuous) on rough fracture walls were largely controlled by the wetting strength of the fluids. The spatio-temporal distributions of fluids were highly sensitive to the domain size and boundary conditions (periodic, no-flow, constant density, and flux-type). Single- and two-sided wetting of fracture aperture walls and long-term entrapment of a nonwetting less-dense fluid by a wetting dense fluid were observed in the simulations. These numerical results are useful for the design of experiments and for analyzing the relative strengths of pore-scale processes in more complex and realistic fracture systems such as those encountered at the Yucca Mountain and Idaho National Laboratory sites.

  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 dynamic electronic and magnetic response of the materials in a wide frequency range.

  19. Depletion of E-Cadherin Disrupts Establishment but Not Maintenance of Cell Junctions in Madin-Darby Canine Kidney Epithelial Cells

    PubMed Central

    Capaldo, Christopher T.

    2007-01-01

    E-cadherin forms calcium-dependent homophilic intercellular adhesions between epithelial cells. These contacts regulate multiple aspects of cell behavior, including the organization of intercellular tight junctions (TJs). To distinguish between the roles of E-cadherin in formation versus maintenance of junctions, Madin-Darby canine kidney (MDCK) cells were depleted of E-cadherin by RNA interference. Surprisingly, reducing E-cadherin expression had little effect on the protein levels or localization of adherens junction (AJ) or TJ markers. The cells underwent morphological changes, as the normally flat apical surface swelled into a dome. However, apical–basal polarity was not compromised, transmembrane resistance was normal, and zonula occludin protein 1 dynamics at the TJs were unchanged. Additionally, an E-cadherin/Cadherin-6 double knockdown also failed to disrupt established TJs, although ?-catenin was lost from the cell cortex. Nevertheless, cells depleted of E-cadherin failed to properly reestablish cell polarity after junction disassembly. Recovery of cell–cell adhesion, transepithelial resistance, and the localization of TJ and AJ markers were all delayed. In contrast, depletion of ?-catenin caused long-term disruption of junctions. These results indicate that E-cadherin and Cadherin-6 function as a scaffold for the construction of polarized structures, and they become largely dispensable in mature junctions, whereas ?-catenin is essential for the maintenance of functional junctions. PMID:17093058

  20. Gap Junctional Conductance and Permeability are Linearly Related

    NASA Astrophysics Data System (ADS)

    Verselis, V.; White, R. L.; Spray, D. C.; Bennett, M. V. L.

    1986-10-01

    The permeability of gap junctions to tetraethylammonium ions was measured in isolated pairs of blastomeres from Rana pipiens L. and compared to the junctional conductance. In this system, the junctional conductance is voltage-dependent and decreases with moderate transjunctional voltage of either sign. The permeability to tetraethylammonium ions was determined by injecting one cell of a pair with tetraethylammonium and monitoring its changing concentration in the prejunctional and postjunctional cells with ion-selective electrodes. Junctional conductance was determined by current-clamp and voltage-clamp techniques. For different cell pairs in which the transjunctional voltage was small and the junctional conductance at its maximum value, the permeability to tetraethylammonium ions was proportional to the junctional conductance. In individual cell pairs, a reduction in the junctional conductance induced by voltage was accompanied by a proportional reduction in the permeability of the gap junction over a wide range. The diameter of the tetraethylammonium ion (8.0 to 8.5 angstrom, unhydrated) is larger than that of the potassium ion (4.6 angstrom, hydrated), the predominant current-carrying species. The proportionality between the permeability to tetraethylammonium ions and the junctional conductance, measured here with exceptionally fine time resolution, indicates that a common gap junctional pathway mediates both electrical and chemical fluxes between cells, and that closure of single gap junction channels by voltage is all or none.

  1. Measuring twin dependent triple junctions from a single section plane

    NASA Astrophysics Data System (ADS)

    Hardy, G. B.; Field, D. P.

    2015-04-01

    Given that polycrystalline triple junctions are significant contributors to material properties, they are frequently becoming the focus of emerging research. Despite this interest, the tools to quickly and quantitatively analyze triple junction textures remain severely limited. To enable characterization of triple junctions on a large scale, the parameters, space, and conventions of twin dependent triple junction distributions have been developed. In addition, by adopting grain boundary stereological techniques, triple junction distributions have been generated from a single section plane for triple junctions containing a coherent twin boundary. This methodology has been validated using simulated microstructures and, with further experimental development, will provide insight into actual triple junction structures. This technique also establishes the foundation for a generalized non-twin dependent approach in the future.

  2. Microfluidics Formation of Bubbles in a Multisection Flow-Focusing

    E-print Network

    Prentiss, Mara

    Microfluidics Formation of Bubbles in a Multisection Flow-Focusing Junction Michinao Hashimoto the stable formation of trains of mono-, bi-, and tri-disperse bubbles in microfluidic flow- focusing (FF-assembly through the patterns of flow created by the bubbles. 1.1 Bubbles and Droplets in Microfluidics

  3. New advances in on-line sample preconcentration by capillary electrophoresis using dynamic pH junction.

    PubMed

    Ptolemy, Adam S; Britz-McKibbin, Philip

    2008-12-01

    The small injection volumes and narrow dimensions characteristic of microseparation techniques place constraints on concentration sensitivity that is required for trace chemical analyses. On-line sample preconcentration techniques using dynamic pH junction and its variants have emerged as simple yet effective strategies for enhancing concentration sensitivity of weakly ionic species by capillary electrophoresis (CE). Dynamic pH junction offers a convenient format for electrokinetic focusing of dilute sample plugs directly in-capillary for improved detection without off-line sample pretreatment. In this report, we highlight new advances in dynamic pH junction which have been reported to enhance method performance while discussing challenges for future research. PMID:19082065

  4. The apical and basal environments of the retinal pigment epithelium regulate the maturation of tight junctions during development.

    PubMed

    Rahner, Christoph; Fukuhara, Masayuki; Peng, Shaomin; Kojima, Shota; Rizzolo, Lawrence J

    2004-07-01

    A culture model has been established to study the gradual development of tight junctions during the embryogenesis of the chick retinal pigment epithelium. This study asks how closely the culture model reflects normal development and how the composition, structure and function of embryonic tight junctions are affected by the apical and basal environments. The study focused on the expression of claudins, the fine-structure of tight junctional strands and the transepithelial electrical resistance. Between embryonic days 7 and 14, patches of junctional strands gradually expanded and coalesced to form a continuous junction, in vivo. Although there was a corresponding increase in claudin expression, different claudins appeared at different times. In culture, the apical and basal environments acted synergistically to promote a continuous network of tight junctions with higher electrical resistance. Independently, pituitary extract or the secretory products of either embryonic fibroblasts or the retina promoted the formation of tight junctions. In combination, three effects were identified. With basally placed fibroblast conditioned medium, apical retinal medium increased transepithelial electrical resistance by affecting structure alone. With basally placed pituitary extract, apical retinal conditioned medium increased transepithelial electrical resistance by affecting structure and by modulating claudin expression in a manner that was consistent with development in vivo. Although embryonic day 7 and 14 cultures in retinal medium exhibited similar structure, the transepithelial electrical resistance of the embryonic day 14 cultures was higher. This higher transepithelial electrical resistance correlated with differences in claudin expression and localization. Therefore, this experimental model can isolate the effects of retinal secretions on structure and claudin expression, and can help us to determine how claudins affect function when structure is held constant. PMID:15226402

  5. Anillin regulates cell-cell junction integrity by organizing junctional accumulation of Rho-GTP and actomyosin

    PubMed Central

    Reyes, Ciara C.; Jin, Meiyan; Breznau, Elaina B.; Espino, Rhogelyn; Delgado-Gonzalo, Ricard; Goryachev, Andrew B.; Miller, Ann L.

    2014-01-01

    Summary Anillin is a scaffolding protein that organizes and stabilizes actomyosin contractile rings and was previously thought to function primarily in cytokinesis [1–10]. Using Xenopus laevis embryos as a model system to examine Anillin’s role in the intact vertebrate epithelium, we find that a population of Anillin surprisingly localizes to epithelial cell-cell junctions throughout the cell cycle, whereas it was previously thought to be nuclear during interphase [5, 11]. Further, we show that Anillin plays a critical role in regulating cell-cell junction integrity. Both tight junctions and adherens junctions are disrupted when Anillin is knocked down, leading to altered cell shape and increased intercellular spaces. Anillin interacts with Rho, F-actin, and Myosin II [3, 8, 9], all of which regulate cell-cell junction structure and function. When Anillin is knocked down, active Rho (Rho-GTP), F-actin, and Myosin II are misregulated at junctions. Indeed, increased dynamic “flares” of Rho-GTP are observed at cell-cell junctions, while overall junctional F-actin and Myosin II accumulation is reduced when Anillin is depleted. We propose that Anillin is required for proper Rho-GTP distribution at cell-cell junctions and for maintenance of a robust apical actomyosin belt, which is required for cell-cell junction integrity. These results reveal a novel role for Anillin in regulating epithelial cell-cell junctions. PMID:24835458

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

    PubMed

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

    2015-07-01

    Rho kinase mediates the effects of inflammatory permeability factors by increasing actomyosin-generated traction forces on endothelial adherens junctions, resulting in disassembly of intercellular junctions and increased vascular leakage. In vitro, this is accompanied by the Rho kinase-driven formation of prominent radial F-actin fibers, but the in vivo relevance of those F-actin fibers has been debated, suggesting other Rho kinase-mediated events to occur in vascular leak. Here, we delineated the contributions of the highly homologous isoforms of Rho kinase (ROCK1 and ROCK2) to vascular hyperpermeability responses. We show that ROCK2, rather than ROCK1 is the critical Rho kinase for regulation of thrombin receptor-mediated vascular permeability. Novel traction force mapping in endothelial monolayers, however, shows that ROCK2 is not required for the thrombin-induced force enhancements. Rather, ROCK2 is pivotal to baseline junctional tension as a novel mechanism by which Rho kinase primes the endothelium for hyperpermeability responses, independent from subsequent ROCK1-mediated contractile stress-fiber formation during the late phase of the permeability response. PMID:25869521

  7. Septate Junctions are Required for Ommatidial Integrity and Blood-Eye Barrier Function in Drosophila

    PubMed Central

    Banerjee, Swati; Bainton, Roland J.; Mayer, Nasima; Beckstead, Robert; Bhat, Manzoor A.

    2008-01-01

    The anatomical organization of the Drosophila ommatidia is achieved by specification and contextual placement of photoreceptors, cone and pigment cells. The photoreceptors must be sealed from high ionic concentrations of the hemolymph by a barrier to allow phototransduction. In vertebrates, a blood-retinal barrier (BRB) is established by tight junctions (TJs) present in the retinal pigment epithelium and endothelial membrane of the retinal vessels. In Drosophila ommatidia, the junctional organization and barrier formation is poorly understood. Here we report that septate junctions (SJs), the vertebrate analogs of TJs, are present in the adult ommatidia and are formed between and among the cone and pigment cells. We show that the localization of Neurexin IV (Nrx IV), a SJ-specific protein, coincides with the location of SJs in the cone and pigment cells. Somatic mosaic analysis of nrx IV null mutants shows that loss of Nrx IV leads to defects in ommatidial morphology and integrity. nrx IV hypomorphic allelic combinations generated viable adults with defective SJs and displayed a compromised blood-eye barrier (BEB) function. These findings establish that SJs are essential for ommatidial integrity and in creating a BEB around the ion and light sensitive photoreceptors. Our studies may provide clues towards understanding the vertebrate BEB formation and function. PMID:18407259

  8. Effect of Laser Thermal Processing on Defect Evolution in Silicon

    Microsoft Academic Search

    Erik Kuryliw; Kevin S. Jones; David Sing; Michael J. Rendon; Somit Talwar

    Laser Thermal Processing (LTP) involves laser melting of an implantation induced pre- amorphized layer to form highly doped ultra shallow junctions in silicon. In theory, a large number of interstitials remain in the end of range (EOR) just below the laser-formed junction. There is also the possibility of quenching in point defects during the liquid phase epitaxial regrowth of the

  9. FilGAP, a Rho-ROCK-regulated GAP for Rac, controls adherens junctions in MDCK cells.

    PubMed

    Nakahara, Shinichiro; Tsutsumi, Koji; Zuinen, Takuya; Ohta, Yasutaka

    2015-06-01

    Rho family small GTPases are essential for the formation of adherens junctions in epithelial cells. Here, we found that FilGAP (also known as ARHGAP24), a Rac-specific Rho GTPase-activating protein, promoted the formation of adherens junctions in Madin-Darby canine kidney (MDCK) cells. Knockdown of FilGAP by siRNA stimulated the disassembly and migration of MDCK cells induced by hepatocyte growth factor (HGF). By contrast, forced expression of FilGAP induced accumulation of E-cadherin at adherens junctions. Endogenous FilGAP colocalized with E-cadherin at adherens junctions, and depletion of FilGAP reduced the amount of E-cadherin expressed at the surface. The Rac GAP domain of FilGAP was necessary for the suppression of cell scattering induced by HGF. In agreement with this, siRNA-mediated knockdown of both Rac1 and FilGAP suppressed cell scattering induced by HGF. Forced expression of Rho kinase (ROCK, of which there are two isoforms ROCK1 and ROCK2) induced the accumulation of E-cadherin at the adherens junction, and depletion of FilGAP prevented the accumulation of E-cadherin. Moreover, wild-type FilGAP but not a non-phosphorylatable FilGAP mutant rescued the accumulation of E-cadherin at adherens junctions. These results suggest that FilGAP might regulate cell-cell adhesion through inactivation of Rac downstream of Rho-ROCK-signaling in MDCK cells. PMID:25908853

  10. Electron microscopic single particle analysis of a tetrameric RuvA/RuvB/Holliday junction DNA complex

    SciTech Connect

    Mayanagi, Kouta [Nagahama Institute of Bio-Science and Technology, 1266 Tamura-cho, Nagahama, Shiga 526-0829 (Japan); Takara-Bio Endowed Division, Institute for Protein Research, Osaka University, 6-2-3 Furuedai, Suita, Osaka 565-0874 (Japan); BIRD, JST (Japan)], E-mail: maya@protein.osaka-u.ac.jp; Fujiwara, Yoshie [Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531 (Japan); Miyata, Tomoko [Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871 (Japan); Morikawa, Kosuke [The Takara-Bio Endowed Division, Institute for Protein Research, Osaka University, 6-2-3 Furuedai, Suita, Osaka 565-0874 (Japan); CREST, JST (Japan)], E-mail: morikako@protein.osaka-u.ac.jp

    2008-01-11

    During the late stage of homologous recombination in prokaryotes, RuvA binds to the Holliday junction intermediate and executes branch migration in association with RuvB. The RuvA subunits form two distinct complexes with the Holliday junction: complex I with the single RuvA tetramer on one side of the four way junction DNA, and complex II with two tetramers on both sides. To investigate the functional roles of complexes I and II, we mutated two residues of RuvA (L125D and E126K) to prevent octamer formation. An electron microscopic analysis indicated that the mutant RuvA/RuvB/Holliday junction DNA complex formed the characteristic tripartite structure, with only one RuvA tetramer bound to one side of the Holliday junction, demonstrating the unexpected stability of this complex. The novel bent images of the complex revealed an intriguing morphological similarity to the structure of SV40 large T antigen, which belongs to the same AAA+ family as RuvB.

  11. For uptake of yolk precursors, epithelial cell-oocyte gap junctional communication is required by insects representing six different orders.

    PubMed

    Waksmonski, Stacy L.; Woodruff, Richard I.

    2002-06-01

    For uptake of vitellogenin protein into nascent yolk spheres, communication through open gap junction channels between the follicle epithelium and oocyte is required by six different insects representing six different orders. It was recently shown in the hemipteran, Oncopeltus fasciatus, that endocytic uptake of yolk protein resulting in the formation of nascent yolk spheres depended upon an intact epithelium communicating with the oocyte through patent gap junctions. Following treatment with octanol, which down-regulated gap junctions below the level of dye coupling, vitellogenin uptake was terminated. Yet, for another hemipteran, Dysdercus intermedius, it has been shown that yolk spheres can form even when all epithelial cells have been stripped from the oocyte. To determine if the mechanism seen in Oncopeltus is present in other insects, we utilized the same techniques to study nascent yolk sphere production in a dipteran, Drosophila melanogaster, a lepidopteran, Actias luna, a hymenopteran, Xylocopa virginica, a coleopteran, Tenebrio molitor and an orthopteran, Acheta domesticus. In each of these, when gap junctions were down-regulated yolk uptake quickly stopped. That six different insects from six different orders all required a gap junctionally transmitted chemical signal of epithelial cell origin suggests that this mechanism is widespread throughout the insects. PMID:12770077

  12. Realization of radial p-n junction silicon nanowire solar cell based on low-temperature and shallow phosphorus doping.

    PubMed

    Dong, Gangqiang; Liu, Fengzhen; Liu, Jing; Zhang, Hailong; Zhu, Meifang

    2013-01-01

    A radial p-n junction solar cell based on vertically free-standing silicon nanowire (SiNW) array is realized using a novel low-temperature and shallow phosphorus doping technique. The SiNW arrays with excellent light trapping property were fabricated by metal-assisted chemical etching technique. The shallow phosphorus doping process was carried out in a hot wire chemical vapor disposition chamber with a low substrate temperature of 250°C and H2-diluted PH3 as the doping gas. Auger electron spectroscopy and Hall effect measurements prove the formation of a shallow p-n junction with P atom surface concentration of above 1020 cm-3 and a junction depth of less than 10 nm. A short circuit current density of 37.13 mA/cm2 is achieved for the radial p-n junction SiNW solar cell, which is enhanced by 7.75% compared with the axial p-n junction SiNW solar cell. The quantum efficiency spectra show that radial transport based on the shallow phosphorus doping of SiNW array improves the carrier collection property and then enhances the blue wavelength region response. The novel shallow doping technique provides great potential in the fabrication of high-efficiency SiNW solar cells. PMID:24369781

  13. Vezatin, an integral membrane protein of adherens junctions, is required for the sound resilience of cochlear hair cells

    PubMed Central

    Bahloul, Amel; Simmler, Marie-Christine; Michel, Vincent; Leibovici, Michel; Perfettini, Isabelle; Roux, Isabelle; Weil, Dominique; Nouaille, Sylvie; Zuo, Jian; Zadro, Cristina; Licastro, Danilo; Gasparini, Paolo; Avan, Paul; Hardelin, Jean-Pierre; Petit, Christine

    2009-01-01

    Loud sound exposure is a significant cause of hearing loss worldwide. We asked whether a lack of vezatin, an ubiquitous adherens junction protein, could result in noise-induced hearing loss. Conditional mutant mice bearing non-functional vezatin alleles only in the sensory cells of the inner ear (hair cells) indeed exhibited irreversible hearing loss after only one minute exposure to a 105 dB broadband sound. In addition, mutant mice spontaneously underwent late onset progressive hearing loss and vestibular dysfunction related to substantial hair cell death. We establish that vezatin is an integral membrane protein with two adjacent transmembrane domains, and cytoplasmic N- and C-terminal regions. Late recruitment of vezatin at junctions between MDCKII cells indicates that the protein does not play a role in the formation of junctions, but rather participates in their stability. Moreover, we show that vezatin directly interacts with radixin in its actin-binding conformation. Accordingly, we provide evidence that vezatin associates with actin filaments at cell–cell junctions. Our results emphasize the overlooked role of the junctions between hair cells and their supporting cells in the auditory epithelium resilience to sound trauma. PMID:20049712

  14. Nb and Nb-based A15 compound tunnel junctions fabricated using a new CF/sub 4/ cleaning process

    SciTech Connect

    Michikami, O.; Kato, Y.; Takenaka, H.; Tanabe, K.

    1985-03-01

    A new surface cleaning technique, the CF/sub 4/ Cleaning Process (CFCP), is proposed for the fabrication of Nb and Nb-based A15 compound tunnel junctions with native oxide barriers. The effects of fabrication conditions and these superconducting material properties on the characteristics of these junctions with Pb or Pb alloy counterelectrodes are investigated. High-quality junctions with a well-defined gap, no knee and very low excess conductance are successfully fabricated through the conventional lift-off technique for A15 compounds (Nb/sub 3/A1, Nb/sub 3/Ge and Nb/sub 3/Si) as well as Nb. Arrays of 100 series-connected 2 ..mu..m/phi/ Nb/PbBi junctions are fabricated with the standard deviation (sigma) of critical current (J /SUB c/ = 15.1 KA/cm/sup 2/) equal to 2.5%. The CFCP mechanism that contributes to the formation of such good junctions is studied using in-situ X-ray photoelectron spectroscopy (XPS). Chemical shifts of the Nb 3d levels on the CF/sub 4/ plasma-cleaned Nb surfaces indicate the presence of an Nb-F layer. These XPS spectra show that the tunnel barrier is composed of mixed Nb/sub 2/O/sub 5/ and Nb-F-O compounds.

  15. Morphological and functional characteristics of human gingival junctional epithelium

    PubMed Central

    2014-01-01

    Background This study aims to observe the morphological characteristics and identify the function characteristics of junctional epithelium (JE) tissues and cultured JE cells. Methods Paraffin sections of human molar or premolar on the gingival buccolingual side were prepared from 6 subjects. HE staining and image analysis were performed to measure and compare the morphological difference among JE, oral gingival epithelium (OGE) and sulcular epithelium (SE). Immunohistochemistry was applied to detect the expression pattern of cytokeratin 5/6, 7, 8/18, 10/13, 16, 17, 19, and 20 in JE, OGE and SE. On the other hand, primary human JE and OGE cells were cultured in vitro. Cell identify was confirmed by histology and immunohistochemistry. In a co-culture model, TEM was used to observe the attachment formation between JE cells and tooth surface. Results Human JE was a unique tissue which was different from SE and OGE in morphology. Similarly, morphology of JE cells was also particular compared with OGE cells cultured in vitro. In addition, JE cells had a longer incubation period than OGE cells. Different expression of several CKs illustrated JE was in a characteristic of low differentiation and high regeneration. After being co-cultured for 14 d, multiple cell layers, basement membrane-like and hemidesmosome-like structures were appeared at the junction of JE cell membrane and tooth surface. Conclusions JE is a specially stratified epithelium with low differentiation and high regeneration ability in gingival tissue both in vivo and in vitro. In co-culture model, human JE cells can form basement membrane-like and hemidesmosome-like structures in about 2 weeks. PMID:24708739

  16. LRP4 Is Critical for Neuromuscular Junction Maintenance

    PubMed Central

    Barik, Arnab; Lu, Yisheng; Sathyamurthy, Anupama; Bowman, Andrew; Shen, Chengyong; Li, Lei; Xiong, Wen-cheng

    2014-01-01

    The neuromuscular junction (NMJ) is a synapse between motor neurons and skeletal muscle fibers, and is critical for control of muscle contraction. Its formation requires neuronal agrin that acts by binding to LRP4 to stimulate MuSK. Mutations have been identified in agrin, MuSK, and LRP4 in patients with congenital myasthenic syndrome, and patients with myasthenia gravis develop antibodies against agrin, LRP4, and MuSK. However, it remains unclear whether the agrin signaling pathway is critical for NMJ maintenance because null mutation of any of the three genes is perinatal lethal. In this study, we generated imKO mice, a mutant strain whose LRP4 gene can be deleted in muscles by doxycycline (Dox) treatment. Ablation of the LRP4 gene in adult muscle enabled studies of its role in NMJ maintenance. We demonstrate that Dox treatment of P30 mice reduced muscle strength and compound muscle action potentials. AChR clusters became fragmented with diminished junctional folds and synaptic vesicles. The amplitude and frequency of miniature endplate potentials were reduced, indicating impaired neuromuscular transmission and providing cellular mechanisms of adult LRP4 deficiency. We showed that LRP4 ablation led to the loss of synaptic agrin and the 90 kDa fragments, which occurred ahead of other prejunctional and postjunctional components, suggesting that LRP4 may regulate the stability of synaptic agrin. These observations demonstrate that LRP4 is essential for maintaining the structural and functional integrity of the NMJ and that loss of muscle LRP4 in adulthood alone is sufficient to cause myasthenic symptoms. PMID:25319686

  17. Morphology, properties, and performance of electrodeposited n-CdSe in liquid junction solar cells

    SciTech Connect

    Tomkiewicz, M.; Ling, I.; Parsons, W.S.

    1982-09-01

    The authors describe the mechanisms for galvanostatic electrodeposition of CdSe in terms of competition between chemical reactions that lead to Se formation and electrochemical reduction of Se as polyselenide, at the interfaces between selenium and selenide. This mechanism leads to a cauliflower morphology for the resulting film. This morphology is ideal for a photoanode in the liquid junction solar cell configuration, and the authors describe the performance of such an electrode. In spite of the unique morphology, solid-state properties of the film can be evaluated and the methodology for these evaluations is presented. The performance of the liquid junction solar cells is limited by the dark current and the dielectric properties of the material. The authors also describe the effects of metal ions such as Zn/sup +2/, Ru/sup +3/, and Ga/sup +3/ on the various electrode properties.

  18. An intercellular polyamine transfer via gap junctions regulates proliferation and response to stress in epithelial cells

    PubMed Central

    Desforges, Bénédicte; Curmi, Patrick A.; Bounedjah, Ouissame; Nakib, Samir; Hamon, Loic; De Bandt, Jean-Pascal; Pastré, David

    2013-01-01

    In the organism, quiescent epithelial cells have the potential to resume cycling as a result of various stimuli, including wound healing or oxidative stress. Because quiescent cells have a low polyamine level, resuming their growth requires an increase of their intracellular polyamine levels via de novo polyamine synthesis or their uptake from plasma. Another alternative, explored here, is an intercellular exchange with polyamine-rich cycling cells via gap junctions. We show that polyamines promote gap junction communication between proliferating cells by promoting dynamical microtubule plus ends at the cell periphery and thus allow polyamine exchange between cells. In this way, cycling cells favor regrowth in adjacent cells deprived of polyamines. In addition, intercellular interactions mediated by polyamines can coordinate the translational response to oxidative stress through the formation of stress granules. Some putative in vivo consequences of polyamine-mediated intercellular interactions are also discussed regarding cancer invasiveness and tissue regeneration. PMID:23515223

  19. An intercellular polyamine transfer via gap junctions regulates proliferation and response to stress in epithelial cells.

    PubMed

    Desforges, Bénédicte; Curmi, Patrick A; Bounedjah, Ouissame; Nakib, Samir; Hamon, Loic; De Bandt, Jean-Pascal; Pastré, David

    2013-05-01

    In the organism, quiescent epithelial cells have the potential to resume cycling as a result of various stimuli, including wound healing or oxidative stress. Because quiescent cells have a low polyamine level, resuming their growth requires an increase of their intracellular polyamine levels via de novo polyamine synthesis or their uptake from plasma. Another alternative, explored here, is an intercellular exchange with polyamine-rich cycling cells via gap junctions. We show that polyamines promote gap junction communication between proliferating cells by promoting dynamical microtubule plus ends at the cell periphery and thus allow polyamine exchange between cells. In this way, cycling cells favor regrowth in adjacent cells deprived of polyamines. In addition, intercellular interactions mediated by polyamines can coordinate the translational response to oxidative stress through the formation of stress granules. Some putative in vivo consequences of polyamine-mediated intercellular interactions are also discussed regarding cancer invasiveness and tissue regeneration. PMID:23515223

  20. Spin Valves and Magnetic Tunnel Junctions

    NASA Astrophysics Data System (ADS)

    Iversen, Kurt; Pufall, Matthew; Heindl, Ranko

    2011-10-01

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

  1. Stereoelectronic switching in single-molecule junctions

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    A new intersection between reaction chemistry and electronic circuitry is emerging from the ultraminiaturization of electronic devices. Over decades chemists have developed a nuanced understanding of stereoelectronics to establish how the electronic properties of molecules relate to their conformation; the recent advent of single-molecule break-junction techniques provides the means to alter this conformation with a level of control previously unimagined. Here we unite these ideas by demonstrating the first single-molecule switch that operates through a stereoelectronic effect. We demonstrate this behaviour in permethyloligosilanes with methylthiomethyl electrode linkers. The strong ? conjugation in the oligosilane backbone couples the stereoelectronic properties of the sulfur–methylene ? bonds that terminate the molecule. Theoretical calculations support the existence of three distinct dihedral conformations that differ drastically in their electronic character. We can shift between these three species by simply lengthening or compressing the molecular junction, and, in doing so, we can switch conductance digitally between two states.

  2. Stereoelectronic switching in single-molecule junctions.

    PubMed

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

    2015-03-01

    A new intersection between reaction chemistry and electronic circuitry is emerging from the ultraminiaturization of electronic devices. Over decades chemists have developed a nuanced understanding of stereoelectronics to establish how the electronic properties of molecules relate to their conformation; the recent advent of single-molecule break-junction techniques provides the means to alter this conformation with a level of control previously unimagined. Here we unite these ideas by demonstrating the first single-molecule switch that operates through a stereoelectronic effect. We demonstrate this behaviour in permethyloligosilanes with methylthiomethyl electrode linkers. The strong ? conjugation in the oligosilane backbone couples the stereoelectronic properties of the sulfur-methylene ? bonds that terminate the molecule. Theoretical calculations support the existence of three distinct dihedral conformations that differ drastically in their electronic character. We can shift between these three species by simply lengthening or compressing the molecular junction, and, in doing so, we can switch conductance digitally between two states. PMID:25698330

  3. 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, ?3, ?3 and ?2, 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

  4. Tight junction physiology of pleural mesothelium

    PubMed Central

    Markov, Alexander G.; Amasheh, Salah

    2014-01-01

    Pleura consists of visceral and parietal cell layers, producing a fluid, which is necessary for lubrication of the pleural space. Function of both mesothelial cell layers is necessary for the regulation of a constant pleural fluid volume and composition to facilitate lung movement during breathing. Recent studies have demonstrated that pleural mesothelial cells show a distinct expression pattern of tight junction proteins which are known to ubiquitously determine paracellular permeability. Most tight junction proteins provide a sealing function to epithelia, but some have been shown to have a paracellular channel function or ambiguous properties. Here we provide an in-depth review of the current knowledge concerning specific functional contribution of these proteins determining transport and barrier function of pleural mesothelium. PMID:25009499

  5. Conductance spectroscopy of topological superconductor wire junctions

    NASA Astrophysics Data System (ADS)

    Setiawan, F.; Brydon, P. M. R.; Sau, Jay D.; Das Sarma, S.

    2015-06-01

    We study the zero-temperature transport properties of one-dimensional normal metal-superconductor (NS) junctions with topological superconductors across their topological transitions. Working within the Blonder-Tinkham-Klapwijk (BTK) formalism generalized for topological NS junctions, we analytically calculate the differential conductance for tunneling into two models of a topological superconductor: a spinless intrinsic p -wave superconductor and a spin-orbit-coupled s -wave superconductor in a Zeeman field. In both cases we verify that the zero-bias conductance is robustly quantized at 2 e2/h in the topological regime, while it takes nonuniversal values in the nontopological phase. The conductance spectra in the topological state develops a peak at zero bias for certain parameter regimes, with the peak width controlled by the strength of spin-orbit coupling and barrier transparency.

  6. Vibrating Suspended Carbon Nanotube Josephson Junctions

    NASA Astrophysics Data System (ADS)

    Keijzers, C. J. H.; Padurariu, C.; Nazarov, Y. V.; Kouwenhoven, L. P.

    2012-02-01

    We study a Josephson junction with an embedded high-frequency and high-quality mechanical resonator, made from a suspended carbon nanotube. Good transparency of the superconductor-nanotube interface allows for the observation of supercurrent through the suspended nanotube, owing to the Josephson effect. The magnitude of the supercurrent is dependent on the charge on the nanotube and can be periodically modulated by a gate electrode, similar to previously reported experiments in unsuspended carbon nanotube Josephson junctions. In such a device we find a 1GHz mechanical resonance frequency and a Q factor of 500000. In the regime where the AC Josephson current and charge oscillations induced by the nanotube motion are resonant, we observe a signal of the mechanical resonator, that can be contributed to the interplay of Josephson dynamics and mechanical dynamics. Our work is motivated by the search for a new and sensitive vibration detector, ultimately to measure the ground state motion of the nanotube resonator.

  7. Laminin 332 in junctional epidermolysis bullosa

    PubMed Central

    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, ?3, ?3 and ?2, 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

  8. Single-electron tunnel junction array

    SciTech Connect

    Likharev, K.K.; Bakhvalov, N.S.; Kazacha, G.S.; Serdyukova, S.I.

    1989-03-01

    The authors have carried out an analysis of statics and dynamics of uniform one-dimensional arrays of ultrasmall tunnel junctions. The correlated single-electron tunneling in the junctions of the array results in its behavior qualitatively similar to that of the Josephson transmission line. In particular, external electric fields applied to the array edges can inject single-electron-charged solitons into the array interior. Shape of such soliton and character of its interactions with other solitons and the array edges are very similar to those of the Josephson vortices (sine-Gordon solitons) in the Josephson transmission line. Under certain conditions, a coherent motion of the soliton train along the array is possible, resulting in generation of narrowband SET oscillations with frequency f/sub s/ = /e where is the dc current flowing along the array.

  9. Vascular Lumen Formation

    PubMed Central

    Lammert, Eckhard; Axnick, Jennifer

    2012-01-01

    The vascular system developed early in evolution. It is required in large multicellular organisms for the transport of nutrients, oxygen, and waste products to and from tissues. The vascular system is composed of hollow tubes, which have a high level of complexity in vertebrates. Vasculogenesis describes the de novo formation of blood vessels, e.g., aorta formation in vertebrate embryogenesis. In contrast, angiogenesis is the formation of blood vessels from preexisting ones, e.g., sprouting of intersomitic blood vessels from the aorta. Importantly, the lumen of all blood vessels in vertebrates is lined and formed by endothelial cells. In both vasculogenesis and angiogenesis, lumen formation takes place in a cord of endothelial cells. It involves a complex molecular mechanism composed of endothelial cell repulsion at the cell–cell contacts within the endothelial cell cords, junctional rearrangement, and endothelial cell shape change. As the vascular system also participates in the course of many diseases, such as cancer, stroke, and myocardial infarction, it is important to understand and make use of the molecular mechanisms of blood vessel formation to better understand and manipulate the pathomechanisms involved. PMID:22474612

  10. Anatomy and development of the craniovertebral junction

    Microsoft Academic Search

    Charles Raybaud

    The occipital bone is the upper end of the somatic spine, limited cranially by the tentorium. The bony craniovertebral junction\\u000a (caudal occiput, atlas, and axis) is interposed between the unsegmented occipital and the intersegmental spinal sclerotomes,\\u000a separated from the occiput and C3 by the intrasegmental clefts of O4 and C2 sclerotomes, respectively. It retains a primitive\\u000a segmental hypocentrum (anterior arch

  11. An epitaxial ferroelectric tunnel junction on silicon.

    PubMed

    Li, Zhipeng; Guo, Xiao; Lu, Hui-Bin; Zhang, Zaoli; Song, Dongsheng; Cheng, Shaobo; Bosman, Michel; Zhu, Jing; Dong, Zhili; Zhu, Weiguang

    2014-11-12

    Epitaxially grown functional perovskites on silicon (001) and the ferroelectricity of a 3.2 nm thick BaTiO3 barrier layer are demonstrated. The polarization-switching-induced change in tunneling resistance is measured to be two orders of magnitude. The obtained results suggest the possibility of integrating ferroelectric tunnel junctions as binary data storage media in non-volatile memory cells on a silicon platform. PMID:25200550

  12. Peltier Junction heats and cools car seat

    SciTech Connect

    Gottschalk, M.A.

    1994-10-10

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

  13. Quantum dynamics in the bosonic Josephson junction

    SciTech Connect

    Chuchem, Maya; Cohen, Doron [Department of Physics, Ben-Gurion University of the Negev, P.O.B. 653, Beer-Sheva 84105 (Israel); Smith-Mannschott, Katrina [Department of Physics, Wesleyan University, Middletown, Connecticut 06459 (United States); MPI for Dynamics and Self-Organization, Bunsenstrasse 10, D-37073 Goettingen (Germany); Hiller, Moritz [Physikalisches Institut, Albert-Ludwigs-Universitaet, Hermann-Herder-Strasse 3, D-79104 Freiburg (Germany); Kottos, Tsampikos [Department of Physics, Wesleyan University, Middletown, Connecticut 06459 (United States); Vardi, Amichay [Department of Chemistry, Ben-Gurion University of the Negev, P.O.B. 653, Beer-Sheva 84105 (Israel); Institute for Theoretical Atomic, Molecular and Optical Physics, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138 (United States)

    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.

  14. 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 ? cm) is only slightly greater than in extruded cytoplasm (100 ? 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, 104? 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

  15. Superconducting thin films, composites and junctions

    NASA Astrophysics Data System (ADS)

    Geballe, T. H.

    1986-12-01

    Low energy ion beam cleaning of the substrates prior to deposition has been found to enhance the quality of ultrathin (less than 100A) refractory superconducting Niobium, Vanadium films. Nb film as thin as 7A has been grown from which it has been possible to fabricate good superconducting tunnel junctions. Both the native films and the tunnel junctions can be thermally recycled without any degradation. In-situ surface studies along with transmission electron microscopy (EM) suggest the removal of the carbon atoms from the surface of the substrate and possibly that increased chemical reactivity of the substrate atoms are the causes of the improvement. Electron microscopy (EM) results indicate that the Nb films grow perfectly lattice matched to the sapphire substrate when the substrate is ion-beam cleaned. This strained-layer epitaxy is observed up to 40A, the maximum thickness investigated through EM. Good-quality tunnel junctions have been fabricated on ultrathin films of Nb. Absolute specific-heat measurements have been made through the metal-insulator transition in thin film Molybdenum (X) Germanium (1-X) determining the thermodynamic electronic density of states. Nb/Tantalum multilayered films prepared by magnetron sputtering have been studied by critical field measurements. The effects of substrate orientation and deposition temperature on the properties of the films has been determined. Considerable progress has been made in the design and construction of the new advance electron beam deposition facility.

  16. 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. PMID:23736215

  17. Hemichannel and junctional properties of connexin 50.

    PubMed Central

    Beahm, Derek L; Hall, James E

    2002-01-01

    Lens fiber connexins, cx50 and cx46 (alpha3 and alpha8), belong to a small subset of connexins that can form functional hemichannels in nonjunctional membranes. Knockout of either cx50 or cx46 results in a cataract, so the properties of both connexins are likely essential for proper physiological functioning of the lens. Although portions of the sequences of these two connexins are nearly identical, their hemichannel properties are quite different. Cx50 hemichannels are much more sensitive to extracellular acidification than cx46 hemichannels and differ from cx46 hemichannels both in steady-state and kinetic properties. Comparison of the two branches of the cx50 hemichannel G-V curve with the junctional G-V curve suggests that cx50 gap junctions gate with positive relative polarity. The histidine-modifying reagent, diethyl pyrocarbonate, reversibly blocks cx50 hemichannel currents but not cx46 hemichannel currents. Because cx46 and cx50 have very similar amino acid sequences, one might expect that replacing the two histidines unique to the third transmembrane region of cx50 with the corresponding cx46 residues would produce mutants more closely resembling cx46. In fact this does not happen. Instead the mutant cx50H161N does not form detectable hemichannels but forms gap junctions indistinguishable from wild type. Cx50H176Q is oocyte lethal, and the double mutant, cx50H61N/H176Q, neither forms hemichannels nor kills oocytes. PMID:11916859

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

    DOEpatents

    Chang, Y. Austin (Middleton, WI); Yang, Jianhua Joshua (Madison, WI)

    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.

  19. Kona: A Multi-junction Detector Using Minimum Description Length Principle

    Microsoft Academic Search

    Laxmi Parida; Davi Geiger; Robert A. Hummel

    1997-01-01

    . Corners, T-, Y-, X-junctions give vital depth cues which isa critical aspect of image understanding tasks like object recognition:junctions form an important class of features invaluable in most visionsystems. The three main issues in a junction (or any feature) detectorare: scale, location, and, the junction (feature) parameters. The junctionparameters are (1) the radius, or size, of the junction, (2)

  20. Cell junctions in the subcommissural organ of the rabbit as revealed by use of ruthenium red

    Microsoft Academic Search

    Judith E. Kimble; S. C. Sørensen; K. Møllgaard

    1973-01-01

    Tight junctions were found in the apical junctional complex of the adult rabbit subcommissural organ (SCO) in addition to zonulae adhaerentes and gap junctions of typical ependymal cells. Ventricular perfusion of ruthenium red before fixation was found to give excellent results for distinguishing between gap and tight junctions at the ependymal surface. The implication of tight junctions as a mechanical

  1. Upscaling, integration and electrical characterization of molecular junctions

    NASA Astrophysics Data System (ADS)

    van Hal, Paul A.; Smits, Edsger C. P.; Geuns, Tom C. T.; Akkerman, Hylke B.; de Brito, Bianca C.; Perissinotto, Stefano; Lanzani, Guglielmo; Kronemeijer, Auke J.; Geskin, Victor; Cornil, Jérôme; Blom, Paul W. M.; de Boer, Bert; de Leeuw, Dago M.

    2008-12-01

    The ultimate target of molecular electronics is to combine different types of functional molecules into integrated circuits, preferably through an autonomous self-assembly process. Charge transport through self-assembled monolayers has been investigated previously, but problems remain with reliability, stability and yield, preventing further progress in the integration of discrete molecular junctions. Here we present a technology to simultaneously fabricate over 20,000 molecular junctions-each consisting of a gold bottom electrode, a self-assembled alkanethiol monolayer, a conducting polymer layer and a gold top electrode-on a single 150-mm wafer. Their integration is demonstrated in strings where up to 200 junctions are connected in series with a yield of unity. The statistical analysis on these molecular junctions, for which the processing parameters were varied and the influence on the junction resistance was measured, allows for the tentative interpretation that the perpendicular electrical transport through these monolayer junctions is factorized.

  2. 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.

  3. Single P-N junction tandem photovoltaic device

    DOEpatents

    Walukiewicz, Wladyslaw (Kensington, CA); Ager, III, Joel W. (Berkeley, CA); Yu, Kin Man (Lafayette, CA)

    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. Single P-N junction tandem photovoltaic device

    DOEpatents

    Walukiewicz, Wladyslaw (Kensington, CA); Ager, III, Joel W. (Berkeley, CA); Yu, Kin Man (Lafayette, CA)

    2012-03-06

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

  5. Valley featured electronic transport of pn junction in silicene ribbon

    NASA Astrophysics Data System (ADS)

    Yang, Mou; Song, Xiao-Lei; Chen, Dong-Hai; Bai, Yan-Kui

    2015-06-01

    We calculated the conductance of silicene pn junction in the bipolar region using the non-equilibrium retarded Green's function method. When an electrical field is applied normally, the energy gaps of valleys K and K? become different. The conductance of pn junctions is mainly determined by the transport of electrons of the valley with the smaller gap, and the conductance of the other valley can also be observed for short junctions. For the spin-orbit coupling dominant cases, edge state bands lie in the bulk gap and contribute a unit tunneling conductance plateau, which is independent of the junction length. When changing electrical field continuously, the conductance peaks at a certain position for long junctions but decreases monotonically for short junctions. We explained all these features based on a simple subband tunneling model.

  6. Upscaling, integration and electrical characterization of molecular junctions.

    PubMed

    Van Hal, Paul A; Smits, Edsger C P; Geuns, Tom C T; Akkerman, Hylke B; De Brito, Bianca C; Perissinotto, Stefano; Lanzani, Guglielmo; Kronemeijer, Auke J; Geskin, Victor; Cornil, Jérôme; Blom, Paul W M; De Boer, Bert; De Leeuw, Dago M

    2008-12-01

    The ultimate target of molecular electronics is to combine different types of functional molecules into integrated circuits, preferably through an autonomous self-assembly process. Charge transport through self-assembled monolayers has been investigated previously, but problems remain with reliability, stability and yield, preventing further progress in the integration of discrete molecular junctions. Here we present a technology to simultaneously fabricate over 20,000 molecular junctions-each consisting of a gold bottom electrode, a self-assembled alkanethiol monolayer, a conducting polymer layer and a gold top electrode-on a single 150-mm wafer. Their integration is demonstrated in strings where up to 200 junctions are connected in series with a yield of unity. The statistical analysis on these molecular junctions, for which the processing parameters were varied and the influence on the junction resistance was measured, allows for the tentative interpretation that the perpendicular electrical transport through these monolayer junctions is factorized. PMID:19057596

  7. The critical power to maintain thermally stable molecular junctions.

    PubMed

    Wang, Yanlei; Xu, Zhiping

    2014-01-01

    With the rise of atomic-scale devices such as molecular electronics and scanning probe microscopies, energy transport processes through molecular junctions have attracted notable research interest recently. In this work, heat dissipation and transport across diamond/benzene/diamond molecular junctions are explored by performing atomistic simulations. We identify the critical power Pcr to maintain thermal stability of the junction through efficient dissipation of local heat. We also find that the molecule-probe contact features a power-dependent interfacial thermal resistance RK in the order of 10(9)?kW(-1). Moreover, both Pcr and RK display explicit dependence on atomic structures of the junction, force and temperature. For instance, Pcr can be elevated in multiple-molecule junctions, and streching the junction enhances RK by a factor of 2. The applications of these findings in molecular electronics and scanning probing measurements are discussed, providing practical guidelines in their rational design. PMID:25005801

  8. Modeling of multi-junction solar cells by Crosslight APSYS

    Microsoft Academic Search

    Z. Q. Li; Y. G. Xiao; Z. M. Simon Li

    2006-01-01

    In this work, based on the advanced commercial software, the Crosslight APSYS with improved tunnel junction model, two-dimensional (2D) simulation has been performed on the triple-junction (TJ) GaInP\\/GaAs\\/Ge solar cell devices. The APSYS simulator solves several interwoven equations including the basic Poisson's equation, and drift-diffusion current equations for electrons and holes. The model of tunnel junction with the equivalent mobility

  9. Controlling two-phase flow through pipe junctions

    E-print Network

    Thonsgaard, Jonathan Eric

    1989-01-01

    Major Subject: Petroleum Engineering CONTROLLING TWO-PHASE FLOW THROUGH PIPE JUNCTIONS A Thesis JONATHAN ERIC THONSGAARD Approved as to style and content by: R. A. Sta zman (Chair of Committee) R. A. Wattenbarger (Member) K. R. all (Member... splitting in the network and to develop and test mechanical devices designed to control the unequal phase splitting phenomenon. Through laboratory research a new junction was developed. As indicated by laboratory data, this new junction has the ability...

  10. Single-electron effects in arrays of normal tunnel junctions

    Microsoft Academic Search

    U. Geigenmüller; G. Schön

    1989-01-01

    We study the current-voltage characteristic of a current biased array of normal tunnel junctions with small capacitance, e2\\/2CkBT. It shows a Coulomb gap, which is found to scale with the number of junctions in series and to be independent of the number of junctions in parallel. The probability of single-electron tunneling (SET) depends on the energy difference before and after

  11. An array of SIN tunnel junctions as a sensitive thermometer

    Microsoft Academic Search

    I. J. Agulo; L. Kuzmin

    2008-01-01

    We have fabricated and measured an array of superconductor-insulator-normal metal (SIN) tunnel junctions for the purpose of using it as a sensitive thermometer. An increase in the temperature responsivity of dV\\/dT~5 µV mK-1 for ten junctions is observed from dV\\/dT~1 µV mK-1 for a single junction. We then used such an array thermometer to measure the temperature stability of the

  12. Modeling and Analysis of Multi-junction Solar Cells

    Microsoft Academic Search

    H. Shivaganaik; Suresh. H. Jangamshetti

    2011-01-01

    In this paper a methodology to evolve an analytical design of a high efficiency multi-junction solar cell is presented. The multi-junction selected for the study is a four-junction tandem solar cell structure, ZnO-ZnSe-Si-Ge. These materials have wide range of band gap from 3.33 to 0.67 eV, so as to absorb maximum solar radiation. ZnO is used as top layer to

  13. 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).

  14. Achieving the threshold regime with an overscreened Josephson junction.

    PubMed

    Sukhorukov, Eugene V; Jordan, Andrew N

    2009-02-27

    We demonstrate that by utilizing an overscreened Josephson junction as a noise detector it is possible to achieve the threshold regime, whereby the tails of the fluctuating current distribution are measured. This situation is realized by placing the Josephson junction and mesoscopic conductor in an external circuit with very low impedance. In the underdamped limit, overscreening the junction inhibits the energy diffusion in the junction, effectively creating a tunable activation barrier to the dissipative state. As a result, the activation rate is qualitatively different from the Arrhenius form. PMID:19257771

  15. Electronic simulation of multi-josephson-junction circuits

    SciTech Connect

    Kornev, V.K.; Likharev, K.K.; Platov, Yu.; Yu, K.

    1985-03-01

    A high-speed electronic analog for high-accuracy simulation of complex multi-Josephson-junction circuits has been developed. The analog contains only two types of special circuits, A and B, interconnected with a simple high-frequency commutation circuit and several ordinary operational low-frequency amplifiers. With our present five-junction version of the analog, several problems of urgent interest have been solved, including those of chaos excitation in the double-junction interferometer and mutual phase locking in multi-tunnel-junction arrays.

  16. Flux Soliton Interactions in Coupled Long Josephson Junctions

    NASA Astrophysics Data System (ADS)

    Wustmann, Waltraut; Osborn, Kevin D.

    2015-03-01

    Flux solitons and long Josephson junctions are being studied as structures for energy-conserving reversible computing. The solitons in long Josephson junctions are generally described by the Sine-Gordon equation. Simulations have been performed on discrete long Josephson junctions (DLJJs), where the soliton extends over at least a few unit cells. We will report on the dissipation and mutual interaction from two solitons in separate DLJJs. Single fluxon dissipation in DLJJs is found to arise from junction damping as well as radiation loss created by discreteness and perturbed soliton oscillations. Dissipation of interacting solitons in coupled DLJJs will be compared to the single fluxon case.

  17. Gas flows through shallow microchannel junctions and networks

    NASA Astrophysics Data System (ADS)

    Gat, Amir; Frankel, Itzchak; Weihs, Daniel

    2009-11-01

    We study creeping compressible (and incompressible) flows through micro-channel networks whose depth is small in comparison with all other dimensions. Making use of an extended Hele-Shaw asymptotic scheme together with conformal mapping we obtain the relation between the mass-flow-rate and the entrance and exit pressures of a T-junction, thereby quantifying the effects of the junction on the pressure field. The linearity of the problem in terms of an appropriately defined quadratic form of the pressure allows us to apply the results for a single junction towards the optimization of (inter-digitated) networks of parallel-micro-channels which include multiple T-junctions.

  18. Josephson (001) tilt grain boundary junctions of high temperature superconductors

    NASA Astrophysics Data System (ADS)

    Arnold, Gerald; Klemm, Richard

    2006-03-01

    We calculate the Josephson critical current Ic across in- plane (001) tilt grain boundary junctions of high temperature superconductors. We solve for the electronic states corresponding to the electron-doped cuprates, two slightly different hole-doped cuprates, and an extremely underdoped hole- doped cuprate in each half-space, and weakly connect the two half-spaces by either specular or random Josephson tunnelling. We treat symmetric, straight, and fully asymmetric junctions with s-, extended-s, or dx^2-y^2-wave order parameters. For symmetric junctions with random grain boundary tunnelling, our results are generally in agreement with the Sigrist-Rice form for ideal junctions that has been used to interpret ``phase-sensitive'' experiments consisting of such in- plane grain boundary junctions. For specular grain boundary tunnelling across symmetric junctions, our results depend upon the Fermi surface topology, but are usually rather consistent with the random facet model of Tsuei et al. [Phys. Rev. Lett. 73 593(1994)]. Our results for asymmetric junctions of electron-doped cuprates are in agreement with the Sigrist- Rice form. However, our results for asymmetric junctions of hole- doped cuprates show that the details of the Fermi surface topology and of the tunnelling processes are both very important, so that the ``phase-sensitive'' experiments based upon in-plane Josephson junctions are less definitive than has generally been thought.

  19. Magic-T Junction using Microstrip/Slotline Transitions

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

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

  20. Preparation of a gap junction fraction from uteri of pregnant rats: the 28-kD polypeptides of uterus, liver, and heart gap junctions are homologous

    Microsoft Academic Search

    ANTONIOS S. ZERVOS; JAMES HOPE; W. HOWARD EVANS

    1985-01-01

    A procedure for the preparation of a gap junction fraction from the uteri of pregnant rats is described. The uterine gap junctions, when examined by electron microscopy of thin sections and in negatively stained preparations, were similar to gap junctions isolated from heart and liver. Major proteins of similar apparent molecular weight (Mr 28,000) were found in gap junction fractions

  1. Rap1 Binds Single-stranded DNA at Telomeric Double- and Single-stranded Junctions and Competes with Cdc13 Protein*

    PubMed Central

    Gustafsson, Cecilia; Rhodin Edsö, Jenny; Cohn, Marita

    2011-01-01

    The ends of eukaryotic chromosomes are protected by specialized telomere chromatin structures. Rap1 and Cdc13 are essential for the formation of functional telomere chromatin in budding yeast by binding to the double-stranded part and the single-stranded 3? overhang, respectively. We analyzed the binding properties of Saccharomyces castellii Rap1 and Cdc13 to partially single-stranded oligonucleotides, mimicking the junction of the double- and single-stranded DNA (ds-ss junction) at telomeres. We determined the optimal and the minimal DNA setup for a simultaneous binding of Rap1 and Cdc13 at the ds-ss junction. Remarkably, Rap1 is able to bind to a partially single-stranded binding site spanning the ds-ss junction. The binding over the ds-ss junction is anchored in a single double-stranded hemi-site and is stabilized by a sequence-independent interaction of Rap1 with the single-stranded 3? overhang. Thus, Rap1 is able to switch between a sequence-specific and a nonspecific binding mode of one hemi-site. At a ds-ss junction configuration where the two binding sites partially overlap, Rap1 and Cdc13 are competing for the binding. These results shed light on the end protection mechanisms and suggest that Rap1 and Cdc13 act together to ensure the protection of both the 3? and the 5? DNA ends at telomeres. PMID:22075002

  2. 76 FR 56966 - Amendment of Class D and Modification of Class E Airspace; Grand Junction, CO

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-15

    ...Modification of Class E Airspace; Grand Junction, CO AGENCY: Federal Aviation Administration...modifies Class E airspace at Grand Junction, CO. Additional controlled airspace is necessary...controlled airspace at Grand Junction, CO (76 FR 40293). Interested parties...

  3. CHLORAL HYDRATE DECREASES GAP JUNCTION COMMUNICATION IN RAT LIVER EPITHELIAL CELLS

    EPA Science Inventory

    Chloral hydrate decreases gap junction communication in rat liver epithelial cells Gap junction communication (GJC) is involved in controlling cell proliferation and differentiation. Connexins (Cx) that make up these junctions are composed of a closely related group of m...

  4. Communication Electrical behavior of cement-based junctions including the pn-junction

    E-print Network

    Chung, Deborah D.L.

    , though not perfect, was attained by using a junction (pn or nn + ) between cement pastes with different. All rights reserved. Keywords: Electrical properties; Fiber reinforcement; Cement paste; Silica fume made from cement pastes with different extents of n- or p-type character are reported. Concrete

  5. 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…

  6. 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.

  7. Low resistance junctions in crayfish. Structural changes with functional uncoupling

    PubMed Central

    1976-01-01

    Electrical uncoupling of crayfish septate lateral giant axons is paralleled by structural changes in the gap junctions. The changes are characterized by a tighter aggregation of the intramembrane particles and a decrease in the overall width of the junction and the thickness of the gap. Preliminary measurements indicate also a decrease in particle diameter. The uncoupling is produced by in vitro treatment of crayfish abdominal cords either with a Ca++, Mg++-free solution containing EDTA, followed by return to normal saline (Van Harreveld's solution), or with VAn Harreveld's solution containing dinitrophenol (DNP). The uncoupling is monitored by the intracellular recording of the electrical resistance at a septum between lateral giant axons. The junctions of the same septum are examined in thin sections; those of other ganglia of the same chain used for the electrical measurements are studied by freeze-fracture. In controls, most junctions contain a more or less regular array of particles repeating at a center to center distance of approximately 200 A. The overall width of the junctions is approximately 200 A and the gap thickness is 40-50 A. Vesicles (400-700 A in diameter) are closely apposed to the junctional membranes. In uncoupled axons, most junctions contain a hexagonal array of particles repeating at a center to center distance of 150-155 A. The overall width of the junctions is approximately 180 A and the gap thickness is 20-30 A. These junctions are usually curved and are rarely associated with vesicles. Isolated, PTA-stained junctions, also believed to be uncoupled, display similar structural features. There are reasons to believe that the changes in structure and permeability are triggered by an increase in the intracellular free Ca++ concentration. Most likely, the changes in permeability are caused by conformational changes in some components of the intramembrane particles at the gap junctions. PMID:820701

  8. Role for Traf4 in Polarizing Adherens Junctions as a Prerequisite for Efficient Cell Shape Changes ?

    PubMed Central

    Mathew, Sam J.; Rembold, Martina; Leptin, Maria

    2011-01-01

    Apical constriction of epithelial cells is a widely used morphogenetic mechanism. In the Drosophila embryo, the apical constrictions that internalize the mesoderm are controlled by the transcription factor Twist and require intact adherens junctions and a contractile acto-myosin network. We find that adherens junctions in constricting mesodermal cells undergo extensive remodeling. A Twist target gene encoding a member of the tumor necrosis factor (TNF) receptor-associated factor (TRAF) family, Traf4, is involved in this process. While TRAFs are best known for their functions in inflammatory responses, Traf4 appears to have a different role, and its mechanism of action is poorly understood. We show that Traf4 is required for efficient apical constriction during ventral furrow formation and for proper localization of Armadillo to the apical position in constricting cells. Traf4 and Armadillo interact with each other physically and functionally. Traf4 acts in a TNF receptor- and Jun N-terminal protein kinase (JNK)-independent manner to fine-tune the assembly of adherens junctions in the invaginating mesodermal cells. PMID:21986496

  9. Species-specific voltage-gating properties of connexin-45 junctions expressed in Xenopus oocytes.

    PubMed Central

    Barrio, L C; Capel, J; Jarillo, J A; Castro, C; Revilla, A

    1997-01-01

    Gap junctions composed of connexin-45 (Cx45) homologs from four species, zebrafish, chicken, mouse, and human, were expressed in pairs of Xenopus oocytes. The macroscopic conductance (gj) of all Cx45 junctions was modulated by transjunctional voltage (Vj) and by the inside-outside voltage (Vm), and the modulation was species specific. Although their gating characteristics varied in voltage sensitivity and kinetics, the four Cx45 junctions shared 1) maximum conductance at Vj = 0 and symmetrical gj reduction in response to positive and negative Vj of low amplitude, with little residual conductance; and 2) gj increases in response to simultaneous depolarization of the paired cells. The formation of hybrid channels, comprising Cx45 hemichannels from different species, allowed us to infer that two separate gates exist, one in each hemichannel, and that each Cx45 hemichannel is closed by the negativity of Vj on its cytoplasmic side. Interestingly, the Vm dependence of hybrid channels also suggests the presence of two gates in series, one Vm gate in each hemichannel. Thus the Vj and Vm dependence provides evidence that two independent voltage gates in each Cx45 hemichannel exist, reacting through specific voltage sensors and operating by different mechanisms, properties that have evolved divergently among species. Images FIGURE 2 FIGURE 4 FIGURE 5 FIGURE 6 PMID:9251792

  10. Endocytosis of Cadherin from Intracellular Junctions Is the Driving Force for Cadherin Adhesive Dimer Disassembly

    PubMed Central

    Troyanovsky, Regina B.; Sokolov, Eugene P.

    2006-01-01

    The adhesion receptor E-cadherin maintains cell–cell junctions by continuously forming short-lived adhesive dimers. Here mixed culture cross-linking and coimmunoprecipitation assays were used to determine the dynamics of adhesive dimer assembly. We showed that the amount of these dimers increased dramatically minutes after the inhibition of endocytosis by ATP depletion or by hypertonic sucrose. This increase was accompanied by the efficient recruitment of E-cadherin into adherens junctions. After 10 min, when the adhesive dimer amount had reached a plateau, the assembly of new dimers stalled completely. These cells, in a striking difference from the control, became unable to disintegrate both their intercellular contacts and adhesive dimers in response to calcium depletion. The same effects, but after a slightly longer time course, were obtained using acidic media, another potent approach inhibiting endocytosis. These data suggest that endocytosis is the main pathway for the dissociation of E-cadherin adhesive dimers. Its inhibition blocks the replenishment of the monomeric cadherin pool, thereby inhibiting new dimer formation. This suggestion has been corroborated by immunoelectron microscopy, which revealed cadherin-enriched coated pit-like structures in close association with adherens junctions. PMID:16760429

  11. Rasip1 regulates vertebrate vascular endothelial junction stability through Epac1-Rap1 signaling

    PubMed Central

    Wilson, Christopher W.; Parker, Leon H.; Hall, Christopher J.; Smyczek, Tanya; Mak, Judy; Crow, Ailey; Posthuma, George; De Mazière, Ann; Sagolla, Meredith; Chalouni, Cecile; Vitorino, Philip; Roose-Girma, Merone; Warming, Søren; Klumperman, Judith; Crosier, Philip S.

    2013-01-01

    Establishment and stabilization of endothelial tubes with patent lumens is vital during vertebrate development. Ras-interacting protein 1 (RASIP1) has been described as an essential regulator of de novo lumenogenesis through modulation of endothelial cell (EC) adhesion to the extracellular matrix (ECM). Here, we show that in mouse and zebrafish embryos, Rasip1-deficient vessels transition from an angioblast cord to a hollow tube, permit circulation of primitive erythrocytes, but ultimately collapse, leading to hemorrhage and embryonic lethality. Knockdown of RASIP1 does not alter EC-ECM adhesion, but causes cell-cell detachment and increases permeability of EC monolayers in vitro. We also found that endogenous RASIP1 in ECs binds Ras-related protein 1 (RAP1), but not Ras homolog gene family member A or cell division control protein 42 homolog. Using an exchange protein directly activated by cyclic adenosine monophosphate 1 (EPAC1)-RAP1–dependent model of nascent junction formation, we demonstrate that a fraction of the RASIP1 protein pool localizes to cell-cell contacts. Loss of RASIP1 phenocopies loss of RAP1 or EPAC1 in ECs by altering junctional actin organization, localization of the actin-bundling protein nonmuscle myosin heavy chain IIB, and junction remodeling. Our data show that RASIP1 regulates the integrity of newly formed blood vessels as an effector of EPAC1-RAP1 signaling. PMID:23886837

  12. Effect of phase noise on quantum correlations in Bose-Josephson junctions

    NASA Astrophysics Data System (ADS)

    Ferrini, G.; Spehner, D.; Minguzzi, A.; Hekking, F. W. J.

    2011-10-01

    In a two-mode Bose-Josephson junction the dynamics induced by a sudden quench of the tunnel amplitude leads to the periodic formation of entangled states. For instance, squeezed states are formed at short times and macroscopic superpositions of phase states at later times. In atom interferometry, the two modes of the junction play the role of the two arms of a Mach-Zehnder interferometer; use of multiparticle entangled states allows the enhancement of phase sensitivity with respect to that obtained from uncorrelated atoms. Decoherence due to the presence of noise degrades quantum correlations between atoms, thus reducing phase sensitivity. We consider decoherence due to stochastic fluctuations of the energies of the two modes of the junction. We analyze its effect on squeezed states and macroscopic superpositions and calculate the squeezing parameter and the quantum Fisher information during the quenched dynamics. The latter quantity measures the amount of quantum correlations useful in interferometry. For moderate noise intensities, we show that it increases on time scales beyond the squeezing regime. This suggests multicomponent superpositions of phase states as interesting candidates for high-precision atom interferometry.

  13. Neural differentiation, NCAM-mediated adhesion, and gap junctional communication in neuroectoderm. A study in vitro

    PubMed Central

    1988-01-01

    We studied the development of NCAM and gap junctional communication, and their mutual relationship in chick neuroectoderm in vitro. Expression of NCAM, as detected by monoclonal and polyclonal antibodies, and development of junctional communication, as detected by extensive cell-to-cell transfer of 400-500-D fluorescent tracers, occurred in cultures from stage-2 embryos onward. Both expressions presumably required primary induction. The differentiating cells formed discrete fields of expression on the second to third day in culture, with the NCAM fields coinciding with the junctional communication fields delineated by the tracers. Other neural differentiations developed in the following order: tetanus toxin receptors, neurofilament protein, and neurite outgrowth. Chronic treatment with antibody Fab fragments against NCAM interfered with the development of communication, suggesting that NCAM-mediated adhesion promotes formation of cell-to-cell channels. Temperature-sensitive mutant Rous sarcoma virus blocked (reversibly) communication and the subsequent development of neurofilament protein and neurites, but expression of NCAM continued. PMID:2834404

  14. 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. PMID:25375538

  15. Capacitance extraction in arbitrarily diffused junction 

    E-print Network

    Chung, Tae-Song

    1990-01-01

    -dimensional impurity profile. This simulated result shuws the one- 11 dimensional doping profile after the final diffusion is completed. The simulated result is attached in APPENDIX A. When each first diffusion is performed, the emitter surface doping density is 5...) respec- tively yields equation (3. 10) and equation (3. 11). tl VR I Ec Era Ei ~ ' Efn E&p ~ Reference level Ev N-side neutral region Depletion region P-side neutral region Fig. 8. Energy band diagram for emitter-base junction...

  16. Creating Spin Switches and Junctions on Surfaces

    NASA Astrophysics Data System (ADS)

    Mills, Eric; Stamp, Philip

    2010-03-01

    Inspired by the work of Hirjibehedin et al, (Science 317 1199) creating Heisenberg spin chains on an insulating surface, we examine geometries in which excitations down a spin chain are either blocked or transmitted depending on the state of a central junction, made from a spin dimer. The dimer state can be controlled by excitations down an additional chain, creating a spin switch. In addition to the technological applications of such a switch, the theoretical language developed has application to certain quantum computation schemes.

  17. 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.

  18. Junctional angle of a bihanded helix

    NASA Astrophysics Data System (ADS)

    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.

  19. Capacitance extraction in arbitrarily diffused junction

    E-print Network

    Chung, Tae-Song

    1990-01-01

    -collector junction is at 3fim. The surface doping density of' emitter is lowered to 1. 5E20[cm ]. I'nfortunately the simulated result by SUPREM III does not show the base surface doping density when the final diffusion is completed and the number of data, around... including the carrier terms. d2$ ? = ? -[&d(z) ? &-(z) + p(~ ) ? n(d ). ;dz' (3. 1) where t'ai: Electrostatic potential from reference (reference is the position, z, where the quasi Fermi level and intrinsic Fermi level are crossed in Fig. 8...

  20. Anatomy and biomechanics of the craniovertebral junction.

    PubMed

    Lopez, Alejandro J; Scheer, Justin K; Leibl, Kayla E; Smith, Zachary A; Dlouhy, Brian J; Dahdaleh, Nader S

    2015-04-01

    The craniovertebral junction (CVJ) has unique anatomical structures that separate it from the subaxial cervical spine. In addition to housing vital neural and vascular structures, the majority of cranial flexion, extension, and axial rotation is accomplished at the CVJ. A complex combination of osseous and ligamentous supports allow for stability despite a large degree of motion. An understanding of anatomy and biomechanics is essential to effectively evaluate and address the various pathological processes that may affect this region. Therefore, the authors present an up-to-date narrative review of CVJ anatomy, normal and pathological biomechanics, and fixation techniques. PMID:25828496

  1. Molecular decipherment of Rho effector pathways regulating tight-junction permeability.

    PubMed Central

    Fujita, H; Katoh, H; Hasegawa, H; Yasui, H; Aoki, J; Yamaguchi, Y; Negishi, M

    2000-01-01

    We reported recently that the activation of RhoA induced an increase in transepithelial electrical resistance (TER). To clarify effectors of Rho for this RhoA-induced regulation of tight-junction permeability, we introduced two effector-loop mutants of constitutively active RhoA(V14), RhoA(V14/L40) and RhoA(V14/C42), into Mardin-Darby canine kidney cells in an isopropyl beta-D-thiogalactoside-inducible expression system. RhoA(V14) and the two effector-loop mutants interacted in vitro with the Rho-binding domain of Rho-associated kinase, ROKalpha. Next we examined two parameters of Rho functions, stress-fibre formation and TER elevation, induced by RhoA(V14). Stress-fibre formation was induced by RhoA(V14/C42) but not by RhoA(V14/L40). On the other hand, TER elevation was induced by neither RhoA(V14/L40) nor RhoA(V14/C42). RhoA-associated kinase inhibitor, Y-27632, inhibited both stress-fibre formation and TER elevation induced by RhoA(V14). These results demonstrated that RhoA-induced regulation of tight-junction permeability is mediated by Rho-associated kinase and at least one other unidentified effector, the coupling to RhoA being disrupted by mutation at position 40 or 42 in the effector loop. PMID:10698687

  2. Junction Conditions and Consequences of Quasi-Spherical Space-Time with Electro-Magnetic Field and Vaidya Matric

    E-print Network

    Soma Nath; Ujjal Debnath; Subenoy Chakraborty

    2007-11-07

    In this work the junction conditions between the exterior Reissner-Nordstrom-Vaidya space-time with the interior quasi-spherical Szekeres space-time have been studied for analyzing gravitational collapse in the presence of a magneto-hydrodynamic fluid undergoing dissipation in the form of heat flow. We have discussed about the apparent horizon and have evaluated the time difference between the formation of apparent horizon and central singularity.

  3. Fabrication and characterization of L10-ordered FePt\\/AlO\\/FeCo magnetic tunnel junctions

    Microsoft Academic Search

    S. Mitani; K. Tsukamoto; T. Seki; T. Shima; K. Takanashi; K. Taka

    2005-01-01

    Magnetic tunnel junctions (MTJs) with an L10-ordered FePt alloy were fabricated and characterized. As a bottom electrode, an in-plane magnetized L10 FePt(110) layer was grown epitaxially on an Au buffer layer. A multiple oxidation process was used for the formation of Al oxide barriers. The L10-FePt\\/AlO\\/FeCo MTJ prepared shows tunnel magnetoresistance of 18% and 40% at room temperature (RT) and

  4. A Silicon Nanocrystal Schottky Junction Solar Cell produced from Colloidal Silicon Nanocrystals

    PubMed Central

    2010-01-01

    Solution-processed semiconductors are seen as a promising route to reducing the cost of the photovoltaic device manufacture. We are reporting a single-layer Schottky photovoltaic device that was fabricated by spin-coating intrinsic silicon nanocrystals (Si NCs) from colloidal suspension. The thin-film formation process was based on Si NCs without any ligand attachment, exchange, or removal reactions. The Schottky junction device showed a photovoltaic response with a power conversion efficiency of 0.02%, a fill factor of 0.26, short circuit-current density of 0.148 mA/cm2, and open-circuit voltage of 0.51 V. PMID:20676200

  5. Investigations of Noise in Audio Frequency Amplifiers Using Junction Transistors

    Microsoft Academic Search

    P. M. Bargellini; M. B. Herscher

    1955-01-01

    An investigation of noise from modem junction transistors in audio frequency amplifiers is presented. Different circuit configurations are examined and the effects on noise factor of the input termination and operating point are discussed. At least three distinct sources of noise corresponding to different physical phenomena contributing to total noise are identified. In modem junction transistors shot noise and thermal

  6. Evaluation of competing triple junction concentrator cells by electroluminescence

    Microsoft Academic Search

    Geoffrey Duggan; Ian M. Ballard

    2009-01-01

    Electroluminescence (EL) can provide a valuable insight into the performance of individual junctions in a triple junction cell designed for use in high concentration photovoltaic (HCPV) applications. It has the potential to be used in quality control in cell production as well as providing specific information about the performance of the cell's emitter and metallisation scheme. This paper presents an

  7. Minigap in superconductor-ferromagnet junctions with inhomogeneous magnetization

    E-print Network

    Fominov, Yakov

    Minigap in superconductor-ferromagnet junctions with inhomogeneous magnetization D. Ivanov and Ya: In the superconductor: #12;Calculation of the Thouless minigap In the normal metal: Boundary conditions: - at the SN at #12;Conclusions · Minigap in superconductor-ferromagnet junctions with inhomogeneous magnetization

  8. Minigap in superconductor-ferromagnet junctions with inhomogeneous magnetization

    E-print Network

    Fominov, Yakov

    Minigap in superconductor-ferromagnet junctions with inhomogeneous magnetization Dmitri Ivanov 1: In the superconductor: with real Finding the minigap Eg: maximal energy, at which the Usadel equation has a solution S L F H S 2L S F H #12;· Minigap in superconductor-ferromagnet junctions with inhomogeneous

  9. Ménage a Trois to Form the Tricellular Junction.

    PubMed

    Flores-Benitez, David; Knust, Elisabeth

    2015-06-01

    Tricellular junctions tightly seal epithelia at the corners of three cells. In this issue of Developmental Cell, Byri et al. (2015) show that Anakonda, a novel Drosophila transmembrane protein, contains an unusual tripartite extracellular domain organization, which explains the tripartite septum filling the tricellular junction, previously revealed by ultrastructure analysis. PMID:26058055

  10. Two-junction tuning circuits for submillimeter SIS mixers

    Microsoft Academic Search

    Jonas Zmuidzinas; Henry G. LeDuc; J. A. Stern; Scott R. Cypher

    1994-01-01

    The capacitance of superconducting tunnel junctions can seriously degrade the performance of quasiparticle (SIS) mixers operating in the submillimeter band, so it is essential to provide a circuit for tuning out this capacitance at the operating frequency. In this article, we present two new tuning circuits for SIS mixers which use a pair of SIS junctions connected by an inductance.

  11. Far infrared detection with Josephson junctions. Final report

    Microsoft Academic Search

    C. K. So; W. O. Hamilton

    1976-01-01

    The response of Josephson junctions to microwave and far infrared radiation was studied. Junctions are formed by pressing a Nb or Nb-Ti pointed wire onto a Nb thin film which in turn is pressed against the open end of a waveguide. Electromagnetic radiation is applied through the back of the film so that only the wave magnetic field is coupled

  12. Profiling the Thermoelectric Power of Semiconductor Junctions with

    E-print Network

    Profiling the Thermoelectric Power of Semiconductor Junctions with Nanometer Resolution Ho-Ki Lyeo,3 * We have probed the local thermoelectric power of semiconductor nanostruc- tures with the use of ultrahigh-vacuum scanning thermoelectric microscopy. When applied to a p-n junction, this method reveals

  13. Gap Junctions and Connexon Hemichannels in Human Embryonic Stem Cells

    E-print Network

    Huettner, James E.

    Gap Junctions and Connexon Hemichannels in Human Embryonic Stem Cells JAMES E. HUETTNER,a AIWU LU) cells, the pluripotent cells isolated from the inner cell mass of preimplantation blastocysts. Human ES junctions. Fluorescent dye injections demonstrated exten- sive coupling within human ES cell colonies

  14. Resistance switch employing a simple metal nanogap junction

    Microsoft Academic Search

    Yasuhisa Naitoh; Masayo Horikawa; Hidekazu Abe; Tetsuo Shimizu

    2006-01-01

    In recent years, several researchers have reported the occurrence of reversible resistance switching effects in simple metal nanogap junctions. A large negative resistance is observed in the I-V characteristics of such a junction when high-bias voltages are applied. This phenomenon is characteristic behaviour on the nanometre scale; it only occurs for gap widths slightly under 13 nm. Furthermore, such a

  15. JUNCTIONS BETWEEN INTIMATELY APPOSED CELL MEMBRANES IN THE VERTEBRATE BRAIN

    Microsoft Academic Search

    M. W. Brightman; T. S. REESE

    1969-01-01

    Certain junctions between ependymal cells, between astrocytes, and between some elec- trically coupled neurons have heretofore been regarded as tight, pentalaminar occlusions of the intercellular cleft. These junctions are now redefined in terms of their configuration after treatment of brain tissue in uranyl acetate before dehydration. Instead of a median dense lamina, they are bisected by a median gap 20-30

  16. Chaos synchronization between Josephson junctions coupled with time delays

    E-print Network

    E. M. Shahverdiev; L. H. Hashimova; P. A. Bayramov; R. A. Nuriev

    2015-06-08

    We investigate chaos synchronization between Josephson junctions coupled uni-directionally with time-delay. We demonstrate the possibility of high quality synchronization with numerical simulations of such systems. The results are of certain importance for obtaining the high power system of Josephson junctions, which is promising for practical applications.

  17. TEMPORAL CHANGE IN GAP JUNCTION FUNCTION IN PRIMARY HEPATOCYTES

    EPA Science Inventory

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

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

    PubMed

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

    2013-06-01

    A triple junction polymer solar cell in a novel 1 + 2 type configuration provides photoelectrochemical water splitting in its maximum power point at V ? 1.70 V with an estimated solar to hydrogen energy conversion efficiency of 3.1%. The triple junction cell consists of a wide bandgap front cell and two identical small bandgap middle and back cells. PMID:23625814

  19. Coherent phase slip in arrays of underdamped Josephson tunnel junctions

    SciTech Connect

    van der Zant, H.S.J.; Muller, C.J.; Geerligs, L.J.; Harmans, C.J.P.M.; Mooij, J.E.

    1988-09-01

    In hysteretic I-V characteristics of two-dimensional Josephson junction arrays resistance steps are observed. These steps are explained by switching the whole array into a coherent phase-slip state of rows of junctions across the whole array.

  20. Quantum interference and Coulomb interaction in arrays of tunnel junctions

    Microsoft Academic Search

    I. S. Beloborodov; K. B. Efetov; Alexander Altland; F. W. Hekking

    2001-01-01

    We study the electronic properties of an array of small metallic grains connected by tunnel junctions. Such an array serves as a model for a granular metal. Previous theoretical studies of junction arrays were based on models of quantum dissipation which did not take into account the diffusive motion of electrons within the grains. We demonstrate that these models break

  1. Charge solitons in 1-D array of mesoscopic tunnel junctions

    Microsoft Academic Search

    M. Amman; E. Ben-Jacob; K. Mullen

    1989-01-01

    We study the dynamics of a one-dimensional array of mesoscopic normal tunnel junctions using the semiclassical picture. We show that the charging effect on a single electron tunneling through a single junction together with capacitive coupling to a substrate lead to the existence of soliton-like modes of charge transfer along the array. These modes are manifested by the appearance of

  2. Characterization of NbN films and tunnel junctions

    NASA Technical Reports Server (NTRS)

    Stern, J. A.; Leduc, H. G.

    1991-01-01

    Properties of NbN films and NbN/MgO/NbN tunnel junctions are discussed. NbN junctions are being developed for use in high-frequency, SIS quasiparticle mixers. To properly design mixer circuits, junction and film properties need to be characterized. The specific capacitance of NbN/MgO/NbN junctions has been measured as a function of the product of the normal-state resistance and the junction area (RnA), and it is found to vary by more than a factor of two (35-85 fF/sq microns) over the range of RnA measured (1000-50 ohm sq microns). This variation is important because the specific capacitance determines the RC speed of the tunnel junction at a given RnA value. The magnetic penetration depth of NbN films deposited under different conditions is also measured. The magnetic penetration depth affects the design of microstrip line used in RF tuning circuits. Control of the magnetic penetration depth is necessary to fabricate reproducible tuning circuits. Additionally, the critical current uniformity for arrays of 100 junctions has been measured. Junction uniformity will affect the design of focal-plane arrays of SIS mixers. Finally, the relevance of these measurements to the design of Josephson electronics is discussed.

  3. Phase-locking in a nonuniform array of tunnel junctions

    Microsoft Academic Search

    Nikolai A. Nezlobin; Richard A. Kiehl

    2003-01-01

    A nonuniform, one-dimensional tunnel junction array that is designed to promote phase-locking to an ac pump signal is proposed and theoretically investigated for possible information processing applications. The tunnel resistances of the junctions in one part of the array are tailored to provide phase restoration for electrons tunneling in the array, while the tunnel resistances in the other part of

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

    Microsoft Academic Search

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

    1992-01-01

    'First generation' superconducting tunnel junction X-ray detectors (characterized by a single tunnel junction in direct contact with its substrate, with totally external amplification) remain more than an order of magnitude away from their theoretical energy resolutions which are in the order of eV's. The difficulties that first generation devices are encountering are being attacked by a 'second generation' of superconducting

  5. DETECTION AND EMISSION OF RADIATION BY ARRAYS OF JUNCTIONS (*)

    E-print Network

    Boyer, Edmond

    207 DETECTION AND EMISSION OF RADIATION BY ARRAYS OF JUNCTIONS (*) T. D. CLARK School of Applied the interaction of small regular planar arrays of point contact Josephson junctions with an electromagnetic field is their mechanical instability, at least compa- red with array networks utilising microbridges or tunnel oxide

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

    DOEpatents

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

    1981-01-14

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

  7. Modeling of tunnel junctions for high efficiency solar cells

    Microsoft Academic Search

    John R. Hauser; Zach Carlin; S. M. Bedair

    2010-01-01

    Ultrahigh efficiency, in the range of 40%, can be achieved in multijunction solar cells operating at high solar concentrations, larger than 100 suns. Critical to this approach are high band gap tunnel junctions that serve as electrically low loss interconnections between the cells. The purpose of this work is to theoretically model such wide band gap tunnel junctions and to

  8. Non-synaptic transmission at autonomic neuroeffector junctions Geoffrey Burnstock *

    E-print Network

    Burnstock, Geoffrey

    cells, receptors for neurotransmitters accumulate on cell membranes at close junctions; muscle effectors are bundles rather than single smooth muscle cells, that are connected by gap junctions which allow, the effectors are muscle bundles rather than single smooth muscle cells, which are connected by low

  9. Non-synaptic transmission at autonomic neuroeffector junctions Geoffrey Burnstock *

    E-print Network

    Burnstock, Geoffrey

    on cell membranes at close junctions; muscle effectors are bundles rather than single smooth muscle cells muscle cells, which are connected by low-resistance pathways (gap junctions) that allow electrotonic the varicosities are con- tinuously moving and their special relation with muscle cell membranes changes with time

  10. 7. View eastsoutheast, junction of SR 141 and Rockland Road, ...

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

    7. View east-southeast, junction of SR 141 and Rockland Road, northern estate wall and tree lines left of center and western estate wall right of center - A. I. Du Pont Estate, Junction of State Route 141 & Rockland Road, Wilmington, New Castle County, DE

  11. STRING JUNCTION EFFECTS FOR FORWARD AND CENTRAL BARYON PRODUCTION

    E-print Network

    Siegen, Universität

    STRING JUNCTION EFFECTS FOR FORWARD AND CENTRAL BARYON PRODUCTION IN HADRON­NUCLEUS COLLISIONS F The process of baryon number transfer due to string junction propagation in rapidity space is considered of numerical calculations in the framework of the Quark­Gluon String Model are in reasonable agreement

  12. Low resistance magnetic tunnel junctions and their interface structures

    SciTech Connect

    Fujikata, J.; Ishi, T.; Mori, S.; Matsuda, K.; Mori, K.; Yokota, H.; Hayashi, K.; Nakada, M.; Kamijo, A.; Ohashi, K.

    2001-06-01

    Effects of interface structure and oxidation state were studied in stacked magnetic tunnel junction (MTJ) structures with top and bottom antiferromagnetic layers to obtain optimum resistance and high tunneling magnetoresistance (TMR) ratios for read heads. The roughness of the NiFe surface and the Al coverage were significantly improved by introduction of O{sub 2} surfactant gas on the Ta-seed-layer surface, which increased TMR ratios of the MTJ with low resistance area (RA) products of less than 10 {Omega}{mu}m2. Furthermore, it was found that avoidance of Ni oxidation and Co oxidation at the tunnel barrier interface is essential to obtaining high TMR ratios, and that a good Al coverage and Fe{endash}oxide formation may enhance TMR ratios when Fe-rich magnetic materials are used. For the top-type and bottom-type structures, a TMR ratio of 12%{endash}17% with RA products of 6{endash}7 {Omega}{mu}m2 was obtained, which provides sufficient performance for read heads. {copyright} 2001 American Institute of Physics.

  13. Titration of the gap junction protein Connexin43 reduces atherogenesis.

    PubMed

    Morel, S; Chanson, M; Nguyen, T D; Glass, A M; Richani Sarieddine, M Z; Meens, M J; Burnier, L; Kwak, B R; Taffet, S M

    2014-08-01

    Ubiquitous reduction of the gap junction protein Connexin43 (Cx43) in mice provides beneficial effects on progression and composition of atherosclerotic lesions. Cx43 is expressed in multiple atheroma-associated cells but its function in each cell type is not known. To examine specifically the role of Cx43 in immune cells, we have lethally irradiated low-density lipoprotein receptor-deficient mice and reconstituted with Cx43+/+, Cx43+/- or Cx43-/- haematopoietic fetal liver cells. Progression of atherosclerosis was significantly lower in aortic roots of Cx43+/- chimeras compared with Cx43+/+ and Cx43-/- chimeras, and their plaques contained significantly less neutrophils. The relative proportion of circulating leukocytes was similar between the three groups. Interestingly, the chemoattraction of neutrophils, which did not express Cx43, was reduced in response to supernatant secreted by Cx43+/- macrophages in comparison with the ones of Cx43+/+ and Cx43-/- macrophages. Cx43+/- macrophages did not differ from Cx43+/+ and Cx43-/- macrophages in terms of M1/M2 polarisation but show modified gene expression for a variety chemokines and complement components. In conclusion, titration of Cx43 expression in bone marrow-derived macrophages reduces atherosclerotic plaque formation and chemoattraction of neutrophils to the lesions. PMID:24828015

  14. Negative differential resistance effect in planar graphene nanoribbon break junctions

    NASA Astrophysics Data System (ADS)

    Nguyen, Phuong Duc; Nguyen, Thanh Cong; Hossain, Faruque M.; Huynh, Duc Hau; Evans, Robin; Skafidas, Efstratios

    2014-11-01

    Graphene is an interesting material with a number of desirable electrical properties. Graphene-based negative differential resistance (NDR) devices hold great potential for enabling the implementation of several elements required in electronic circuits and systems. In this article we propose a novel device structure that exhibits NDR using single layer graphene that is able to be fabricated using standard lithography techniques. Using theoretical simulation, we show that graphene nanoribbon (GNR) junctions exhibit NDR effect if a gap is introduced in the structure in the transport direction of the ribbon. Using standard lithography techniques, we produce a GNR and use electro-migration to create a nanogap by breaking the GNR device. Scanning electron microscopy images show the formation of a tunnel gap. The predicted NDR phenomenon is experimentally verified in the current-voltage characteristic of the device. The linear and non-linear characteristics of the I-V responses before and after breakdown confirm that the NDR effect arises from the tunnel gap.

  15. NbN edge junction fabrication

    SciTech Connect

    Meng, X.F.; Amos, R.S.; Lichtenbenger, A.W.; Mattauch, R.J.; Feldman, M.J.

    1989-03-01

    In order to fabricate NbN edge junctions with low parasitic capacitance, an insulator with low dielectric constant, such as SiO/sub 2/, must isolate the base and counterelectrode except on the edge. The authors use reactive ion etching to cut an edge in SiO/sub 2//NbN bilayer films. For this process it is necessary that SiO/sub 2/ be etched more rapidly than NbN to form a suitably sloped edge profile. They have investigated the influence of etching gas composition and other parameters on etching rates and edge profiles, using: (1) CF/sub 4/, (2) CF/sub 4//O/sub 2/, (3) CF/sub 4//CH/sub 4/, (4) CF/sub 4//CHF/sub 3/, and (5) CHF/sub 3/. It was found that CF/sub 4/ and CF/sub 4//O/sub 2/ plasma etching generally yields poor, undercut edge profiles. However, they succeeded in obtaining satisfactory edge profiles using the other three gas combinations. The edge angle can be controlled by changing the proportions of the gasses. Using the process, they have successfully fabricated NbN/oxide/PbBi edge junctions with < 1 ..mu..m/sup 2/ area by standard optical photolithography.

  16. Enterocytes’ tight junctions: From molecules to diseases

    PubMed Central

    Assimakopoulos, Stelios F; Papageorgiou, Ismini; Charonis, Aristidis

    2011-01-01

    Tight junctions (TJs) are structures between cells where cells appear in the closest possible contact. They are responsible for sealing compartments when epithelial sheets are generated. They regulate the permeability of ions, (macro) molecules and cells via the paracellular pathway. Their structure at the electron microscopic level has been well known since the 1970s; however, only recently has their macromolecular composition been revealed. This review first examines the major macromolecular components of the TJs (occludin, claudins, junctional adhesion molecule and tricellulin) and then the associated macromolecules at the intracellular plaque [zonula occludens (ZO)-1, ZO-2, ZO-3, AF-6, cingulin, 7H6]. Emphasis is given to their interactions in order to begin to understand the mode of assembly of TJs. The functional significance of TJs is detailed and several mechanisms and factors involved are discussed briefly. Emphasis is given to the role of intestinal TJs and the alterations observed or speculated in diverse disease states. Specifically, intestinal TJs may exert a pathogenetic role in intestinal (inflammatory bowel disease, celiac disease) and extraintestinal diseases (diabetes type 1, food allergies, autoimmune diseases). Additionally, intestinal TJs may be secondarily disrupted during the course of diverse diseases, subsequently allowing the bacterial translocation phenomenon and promoting the systemic inflammatory response, which is often associated with clinical deterioration. The major questions in the field are highlighted. PMID:22184542

  17. Role of magnetic anisotropy in spin-filter junctions

    NASA Astrophysics Data System (ADS)

    Chopdekar, R. V.; Nelson-Cheeseman, B. B.; Liberati, M.; Arenholz, E.; Suzuki, Y.

    2011-06-01

    We have fabricated oxide-based spin-filter junctions in which we demonstrate that magnetic anisotropy can be used to tune the transport behavior of spin-filter junctions. We have demonstrated spin-filtering behavior in La0.7Sr0.3MnO3/CoCr2O4/Fe3O4 and La0.7Sr0.3MnO3/MnCr2O4/Fe3O4 junctions where the interface anisotropy plays a significant role in determining transport behavior. Detailed studies of chemical and magnetic structure at the interfaces indicate that abrupt changes in magnetic anisotropy across the nonisostructural interface is the cause of the significant suppression of junction magnetoresistance in junctions with MnCr2O4 barrier layers.

  18. Hybrid magnetic tunnel junction/spin filter device

    SciTech Connect

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

    2008-07-10

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

  19. Short chain molecular junctions: Charge transport versus dipole moment

    NASA Astrophysics Data System (ADS)

    Ikram, I. Mohamed; Rabinal, M. K.

    2015-03-01

    The investigation of the influence of dipole moment of short chain organic molecules having three carbon atoms varying in end group on silicon surface was carried on. Here, we use three different molecules of propargyl series varying in dipole moment and its orientation to constitute molecular junctions. The charge transport mechanism in metal-molecules-semiconductor (MMS) junction obtained from current-voltage (I-V) characteristics shows the rectification behavior for two junctions whereas the other junction shows a weak rectification. The electronic properties of the molecules were calculated using Gaussian software package. The observed rectification behavior of these junctions is examined and found to be accounted to the orientation of dipole moment and electron cloud density distribution inside the molecules.

  20. Observation of short ballistic Josephson effect in vertical graphene junctions

    NASA Astrophysics Data System (ADS)

    Lee, Gil-Ho; Lee, Hu-Jong

    2014-03-01

    The current-phase relation (CPR) of vertical graphene Josephson junctions (vGJJs) was measured using phase-sensitive dc-SQUID interferometry. A vGJJ, realized by vertically sandwiching a monolayer graphene between two Al electrodes, had an atomically short channel with transparent contacts for the highly coherent junction nature. The measured CPR was almost perfectly skewed, which rigorously confirmed the short ballisticity of the vGJJs. The short ballistic character of a Josephson junction has been predicted since 1970's but has never been realized in scalable hybrid systems. The CPR also provided energy spectrum of Andreev levels formed inside the junction, which offered a promising prospect for scalable quantum information devices such as Andreev-level qubits. This vertical-junction scheme is also readily applicable to the other cleavable materials such as three-dimensional topological insulators or transition metal dichalcogenides, opening a new pathway for uncovering exotic coherence phenomena arising in an atomic scale.

  1. Quasi-optical Josephson-junction oscillator arrays

    NASA Technical Reports Server (NTRS)

    Stern, J. A.; Leduc, H. G.; Zmuidzinas, J.

    1993-01-01

    Josephson junctions are natural voltage-controlled oscillators capable of generating submillimeter-wavelength radiation, but a single junction usually can produce only 100 nW of power and often has a broad spectral linewidth. The authors are investigating 2D quasi-optical power combining arrays of 103 and 104 NbN/MgO/NbN and Nb/Al-AlO(x)/Nb junctions to overcome these limitations. The junctions are dc-biased in parallel and are distributed along interdigitated lines. The arrays couple to a resonant mode of a Fabry-Perot cavity to achieve mutual phase-locking. The array configuration has a relatively low impedance, which should allow the capacitance of the junctions to be tuned out at the oscillation frequency.

  2. Instabilities in superconducting tunnel junctions in different thermal environments

    SciTech Connect

    Adler, J.G.; Will, T.A.

    1983-05-15

    Instabilities in superconducting tunnel junctions have been studied in three environments: low pressure He gas, normal liquid He I, and superfluid He II. It is demonstrated that the effect arises at a bias voltage V/sub 0/ where junction dissipation is sufficient to drive a region of the electrode(s) normal. The transition is accompanied by a small excess current, which is due to the appearance of electrode resistance and junction heating. For Pb electrode junctions immersed in liquid He the critical junction dissipation marks the outset of film boiling, which shows up as excessive noise in the tunneling curves. This critical heat flux, approx. =1 W/cm/sup 2/ at 4.2 K, limits the useful energy range for tunneling spectroscopy and leads to catastrophic burnout of high density Josephson arrays.

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  4. Emission of Microwave Photon Pairs by a Tunnel Junction

    NASA Astrophysics Data System (ADS)

    Forgues, Jean-Charles; Lupien, Christian; Reulet, Bertrand

    2014-07-01

    We report the observation of photon pairs in the photoassisted shot noise of a tunnel junction in the quantum regime at very high frequency and very low temperature. We have measured the fluctuations of the noise power generated by the junction at two different frequencies, f1=4.4 and f2=7.2 GHz, while driving the junction with a microwave excitation of frequency f0=f1+f2. We observe clear correlations between the fluctuations of the two noise powers even when the mean photon number per measurement is much smaller than one. This is strong evidence for photons being emitted in pairs. We also demonstrate that the electromagnetic field generated by the junction exhibits two-mode amplitude squeezing, a proof of its nonclassicality. The data agree very well with predictions based on the fourth cumulant of the current fluctuations generated by the junction.

  5. Emission of microwave photon pairs by a tunnel junction.

    PubMed

    Forgues, Jean-Charles; Lupien, Christian; Reulet, Bertrand

    2014-07-25

    We report the observation of photon pairs in the photoassisted shot noise of a tunnel junction in the quantum regime at very high frequency and very low temperature. We have measured the fluctuations of the noise power generated by the junction at two different frequencies, f(1) = 4.4 and f(2) = 7.2 GHz, while driving the junction with a microwave excitation of frequency f(0) = f(1) + f(2). We observe clear correlations between the fluctuations of the two noise powers even when the mean photon number per measurement is much smaller than one. This is strong evidence for photons being emitted in pairs. We also demonstrate that the electromagnetic field generated by the junction exhibits two-mode amplitude squeezing, a proof of its nonclassicality. The data agree very well with predictions based on the fourth cumulant of the current fluctuations generated by the junction. PMID:25105619

  6. Fixed-gap tunnel junction for reading DNA nucleotides.

    PubMed

    Pang, Pei; Ashcroft, Brian Alan; Song, Weisi; Zhang, Peiming; Biswas, Sovan; Qing, Quan; Yang, Jialing; Nemanich, Robert J; Bai, Jingwei; Smith, Joshua T; Reuter, Kathleen; Balagurusamy, Venkat S K; Astier, Yann; Stolovitzky, Gustavo; Lindsay, Stuart

    2014-12-23

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

  7. Parametric resonance in the system of long Josephson junctions

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

  8. Rho Kinase Regulates Tight Junction Function and Is Necessary for Tight Junction Assembly in Polarized Intestinal Epithelia

    Microsoft Academic Search

    Shaun V. Walsh; Ann M. Hopkins; Jason Chen; Shuh Narumiya; Charles A. Parkos; Asma Nusrat

    2001-01-01

    Background & Aims: Tight junctions are crucial determinants of barrier function in polarized intestinal epithelia and are regulated by Rho guanosine triphosphatase. Rho kinase (ROCK) is a downstream effector of Rho. Methods: A specific inhibitor of ROCK, Y-27632, was used to examine the role of ROCK in the regulation of tight junctions in model intestinal (T84) cells by electrophysiologic, biochemical,

  9. Junctional Adhesion Molecule, a Novel Member of the Immunoglobulin Superfamily That Distributes at Intercellular Junctions and Modulates Monocyte Transmigration

    Microsoft Academic Search

    I. Martin-Padura; Susan Lostaglio; Markus Schneemann; Lisa Williams; Maria Romano; Paolo Fruscella; Carla Panzeri; Antonella Stoppacciaro; Luigi Ruco; Antonello Villa; David Simmons; Elisabetta Dejana

    1998-01-01

    Tight junctions are the most apical compo- nents of endothelial and epithelial intercellular cleft. In the endothelium these structures play an important role in the control of paracellular permeability to circulating cells and solutes. The only known integral membrane protein localized at sites of membrane-membrane inter- action of tight junctions is occludin, which is linked in- side the cells to

  10. Do ridge^ridge^fault triple junctions exist on Earth? Evidence from the Aden^Owen^Carlsberg junction in

    E-print Network

    Nicolas, Chamot-Rooke

    the transform fault arm of the triple junction has evolved into a divergent boundary before connecting at the southern end of the OFZ, indicating that a divergent plate boundary between Arabia and India is developing at the triple junction.The connection of this boundary with the Carlsberg and Sheba ridges is not clearly

  11. Pallidal gap junctions-triggers of synchrony in Parkinson's disease?

    PubMed Central

    Schwab, Bettina C; Heida, Tjitske; Zhao, Yan; van Gils, Stephan A; van Wezel, Richard J A

    2014-01-01

    Although increased synchrony of the neural activity in the basal ganglia may underlie the motor deficiencies exhibited in Parkinson's disease (PD), how this synchrony arises, propagates through the basal ganglia, and changes under dopamine replacement remains unknown. Gap junctions could play a major role in modifying this synchrony, because they show functional plasticity under the influence of dopamine and after neural injury. In this study, confocal imaging was used to detect connexin-36, the major neural gap junction protein, in postmortem tissues of PD patients and control subjects in the putamen, subthalamic nucleus (STN), and external and internal globus pallidus (GPe and GPi, respectively). Moreover, we quantified how gap junctions affect synchrony in an existing computational model of the basal ganglia. We detected connexin-36 in the human putamen, GPe, and GPi, but not in the STN. Furthermore, we found that the number of connexin-36 spots in PD tissues increased by 50% in the putamen, 43% in the GPe, and 109% in the GPi compared with controls. In the computational model, gap junctions in the GPe and GPi strongly influenced synchrony. The basal ganglia became especially susceptible to synchronize with input from the cortex when gap junctions were numerous and high in conductance. In conclusion, connexin-36 expression in the human GPe and GPi suggests that gap junctional coupling exists within these nuclei. In PD, neural injury and dopamine depletion could increase this coupling. Therefore, we propose that gap junctions act as a powerful modulator of synchrony in the basal ganglia. PMID:25124148

  12. Post-junctional interactions between neuromuscular blocking agents and ethanol at the mouse neuromuscular junction

    PubMed Central

    Searl, TJ; Silinsky, EM

    2010-01-01

    BACKGROUND AND PURPOSE Ethanol is known to have both pre-synaptic and post-synaptic effects at a range of loci in the mammalian nervous system, including the neuromuscular junction. However, the effects of ethanol on evoked synaptic transmission have not been previously studied at the mouse neuromuscular junction. Here, we report on the effects of ethanol on evoked neuromuscular transmission and the interaction of ethanol with non-depolarizing blocking drugs. EXPERIMENTAL APPROACH Electrophysiological techniques to measure synaptic potentials and synaptic currents were employed in this study. KEY RESULTS Ethanol (?100 mM) produced increases in the amplitudes of both spontaneous and evoked synaptic events. Under conditions in which neuromuscular transmission was blocked by (+)-tubocurarine, ethanol (12–100 mM) produced greater increases in evoked response amplitude than in spontaneous response amplitude recorded in the absence of (+)-tubocurarine. Ethanol (100 mM) did not affect evoked neurotransmitter release in low-calcium/high-magnesium solutions. With respect to the clinically used neuromuscular blocking drugs, ethanol (100 mM) interfered with the blocking action of vecuronium, but not cisatracurium. CONCLUSIONS AND IMPLICATIONS Under these conditions, the stimulant effect of ethanol on neuromuscular transmission is exclusively on the post-junctional elements, both to enhance transmission through nicotinic receptors and also via interactions with neuromuscular blocking agents. These actions of ethanol on neuromuscular transmission may affect the dosage of neuromuscular blockers required in patients who have imbibed significant amounts of alcohol. PMID:20880403

  13. Admittance spectroscopy on buried GaSb junctions due to defect distribution in GaAs/GaSb metalorganic vapor phase epitaxy heterostructures

    NASA Astrophysics Data System (ADS)

    Baldini, M.; Gombia, E.; Parisini, A.; Ghezzi, C.; Gorni, M.

    2013-10-01

    Admittance spectroscopy was employed to investigate the electrical properties of buried GaSb homojunctions. A strong p-type surface layer was obtained in n-type GaSb bulk crystals through diffusion of Zn atoms. The acceptor impurities were introduced into Te-doped substrates by epitaxially growing a heavily p(Zn)-doped GaAs layer. Current-voltage investigation, after the removal of the GaAs cap layer, demonstrated the formation of the GaSb p-n homojunction. However, the p-n interface of the junctions resulted to be not due to the presence of Zn. In fact, secondary ion mass spectrometry pointed out only a small penetration depth of Zn atoms in the GaSb substrate (˜100 nm), whereas electron beam induced current investigation demonstrated that the p-n junction interface was located more deeply into the substrate (˜1 ?m). Admittance spectroscopy and capacitance-voltage investigations led to attribute the change of conduction type from n to p of GaSb beyond the Zn penetration depth to the formation of lattice acceptor defects, influenced by the thermal annealing processes during and after the GaAs growth. An attempt to explain the formation of the buried junction in terms of atomic inter-diffusion is provided, in order to justify, from a microscopic point of view, the low diffusivity of Zn in GaSb, and the depth of the p-n junction interface in the substrate.

  14. Ultrafast endocytosis at Caenorhabditis elegans neuromuscular junctions

    PubMed Central

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

    2013-01-01

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

  15. Quantum Fluctuations in Josephson Junction Comparators

    E-print Network

    Thomas J. Walls; Timur V. Filippov; Konstantin K. Likharev

    2002-07-15

    We have developed a method for calculation of quantum fluctuation effects, in particular of the uncertainty zone developing at the potential curvature sign inversion, for a damped harmonic oscillator with arbitrary time dependence of frequency and for arbitrary temperature, within the Caldeira-Leggett model. The method has been applied to the calculation of the gray zone width Delta Ix of Josephson-junction balanced comparators driven by a specially designed low-impedance RSFQ circuit. The calculated temperature dependence of Delta Ix in the range 1.5 to 4.2K is in a virtually perfect agreement with experimental data for Nb-trilayer comparators with critical current densities of 1.0 and 5.5 kA/cm^2, without any fitting parameters.

  16. Studies of silicon pn junction solar cells

    NASA Technical Reports Server (NTRS)

    Lindholm, F. A.; Neugroschel, A.

    1977-01-01

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

  17. Quantum Tunneling Current in Nanoscale Plasmonic Junctions

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  18. Nonlinear nonequilibrium quasiparticle relaxation in Josephson junctions.

    PubMed

    Krasnov, V M

    2009-11-27

    I solve numerically a full set of nonlinear kinetic balance equations for stacked Josephson junctions, which allows analysis of strongly nonequilibrium phenomena. It is shown that nonlinearity becomes significant already at very small disequilibrium. The following new, nonlinear effects are obtained: (i) At even-gap voltages V = 2nDelta/e (n = 2, 3, ...) nonequilibrium bosonic bands overlap. This leads to enhanced emission of Omega = 2Delta bosons and to the appearance of dips in tunnel conductance. (ii) A new type of radiative solution is found at strong disequilibrium. It is characterized by the fast stimulated relaxation of quasiparticles. A stack in this state behaves as a light emitting diode and directly converts electric power to boson emission, without utilization of the ac-Josephson effect. The phenomenon can be used for realization of a new type of superconducting cascade laser in the THz frequency range. PMID:20366121

  19. Ultimately short ballistic vertical graphene Josephson junctions

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  20. Tunable ±? ,?0, and ?0±? Josephson junction

    NASA Astrophysics Data System (ADS)

    Goldobin, E.; Koelle, D.; Kleiner, R.

    2015-06-01

    We study a 0-? dc superconducting quantum interference device (SQUID) with asymmetric inductances and critical currents of the two Josephson junctions (JJs). By considering such a dc SQUID as a black box with two terminals, we calculate its effective current-phase relation Is(? ) and the Josephson energy U (? ) , where ? is the Josephson phase across the terminals. We show that there is a domain of parameters where the black box has the properties of a ? JJ with degenerate ground state phases ? =±? . The ? domain is rather large, so one can easily construct a ? JJ experimentally. We derive the current phase relation and show that it can be tuned in situ by applying an external magnetic flux resulting in a continuous transition between the systems with static solutions ? =±? ,? =?0 (?0?0 ,? ) and even ? =?0±? . The dependence of ?0 on applied magnetic flux is not 2 ? (one flux quantum) periodic.