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1

Laser thermal processing using an optical coating for ultra shallow junction formation  

Microsoft Academic Search

Semiconductor doping is a critical step in microelectronic device fabrication. Particularly, ultra-shallow junction formation for the CMOS 45-nm node is today intensively studied. Laser thermal processing (LTP) has already shown potentiality to achieve abrupt and ultra-shallow junctions, with a very low resistivity. However, the laser process has to be integrated in the conventional process flow of a real CMOS device

M. Hernandez; J. Venturini; D. Berard; G. Kerrien; T. Sarnet; D. Débarre; J. Boulmer; C. Laviron; D. Camel; J.-L. Santailler; H. Akhouayri

2004-01-01

2

Integration of a long pulse laser thermal process for ultra shallow junction formation of CMOS devices  

Microsoft Academic Search

We present results on ultra-shallow junction formation for the sub 65 nm CMOS node by means of a long pulse laser thermal process (LP-LTP). This method achieve to form abrupt and ultra-shallow junctions with low resistivities, but the different irradiated structures like transistor gates need to be preserved. To assess the integration of the laser process in the fabrication of

J. Venturini; M. Hernandez; K. Huet; C. Laviron; H. Akhouayri; T. Sarnet; J. Boulmer

2004-01-01

3

Formation of Co-implanted Silicon Ultra-Shallow Junctions for Low Thermal Budget Applications  

NASA Astrophysics Data System (ADS)

We present a systematic study to create ultra-shallow junctions in n-type silicon substrates and investigate both pre- and post-annealing processes to create a processing strategy for potential applications in nano-devices. Starting wafers were co-implanted with indium and C atoms at energies of 70 keV and 10 keV, respectively. A carefully chosen implantation schedule provides an abrupt ultra-shallow junction between 17 and 43 nm with suppressed sheet resistance and appropriate retained sheet carrier concentration at low thermal budget. A defect doping matrix, primarily the behavior and movement of co-implant generated interstitials at different annealing temperatures, may be engineered to form sufficiently activated ultra-shallow devices.

Rehana, Mustafa; S., Ahmed; U. Khan, E.

2013-01-01

4

Ultra-shallow junction formation by spike annealing in a lamp-based or hot-walled rapid thermal annealing system: effect of ramp-up rate  

Microsoft Academic Search

Ultra-shallow p-type junction formation has been investigated using 1050°C spike anneals in lamp-based and hot-walled rapid thermal processing (RTP) systems. A spike anneal may be characterized by a fast ramp-up to temperature with only a fraction of a second soak-time at temperature. The effects of the ramp-up rate during a spike anneal on junction depth and sheet resistance were measured

Aditya Agarwal; Anthony T. Fiory; Hans-Joachim L. Gossmann; Conor S. Rafferty; Peter Frisella

1998-01-01

5

Formation of Ultra-Shallow Junctions by Advanced Plasma Doping Techniques  

SciTech Connect

The fabrication of advanced CMOS devices calls for production worthy doping solutions to address requirements for increasingly shallow and abrupt junctions, while maintaining high dopant activation to meet series resistance requirements. Plasma Doping (PLAD), which has already been adopted in high volume manufacturing in the ultra high dose, low energy regime for advanced DRAM technology nodes, is now being investigated for source drain extension (SDE) implants, where precise and repeatable dopant placement is critical for maintaining control over device parameters. In this article, we investigate the process performance of SDE implants carried out in a VIISta registered PLAD system using p- type dopant precursors. Key metrics, such as junction depth, profile abruptness and sheet resistance are reported for as-implanted junctions, as well as samples processed with low thermal budget anneal techniques. Device performance data demonstrating the feasibility of the approach are presented. The advanced control features in the PLAD system are critical in enabling the process performance required for SDE implants.

Papasouliotis, G. D.; Godet, L.; Singh, V.; Miura, R.; Ito, H. [Varian Semiconductor Equipment Associates, 35 Dory Road, Gloucester, MA, 01930 (United States)

2011-01-07

6

Formation of ultra-shallow p +\\/n junctions in silicon-on-insulator (SOI) substrate using laser annealing  

Microsoft Academic Search

Laser annealing (LA), in which the laser melts the surface layer of silicon and causes the dopants to be distributed uniformly within the melted region, produces abrupt, highly activated and ultrashallow junctions. The degree of melting is determined by the extent of laser absorption and rate of heat dissipation, which are dependent on the substrate properties. When applying LA on

K. K. Ong; K. L. Pey; P. S. Lee; A. T. S. Wee; Y. F. Chong; K. L. Yeo; X. C. Wang

2004-01-01

7

Defect Engineering for Ultra-Shallow Junctions Using Surfaces  

Microsoft Academic Search

Formation of extremely shallow pn junctions with very low electrical resistance is a maj or stumbling block to the continued down scaling of microelectronic devices. Recent work in our laboratory has shown that the behavior of defects within silicon (and therefore dopants) can be changed significantly by controlling the chemical state of the surface. Certain chemical treatments of the surface

E. G. Seebauer; C. T. M. Kwok; R. Vaidyanathan; Y. V. Kondratenko; S. H. Yeong; M. P. Srinivasan; Benjamin Colombeau; Lap Chan

2008-01-01

8

Down to 2 nm Ultra Shallow Junctions : Fabrication by IBS Plasma Immersion Ion Implantation Prototype PULSION registered  

SciTech Connect

Classical beam line implantation is limited in low energies and cannot achieve P+/N junctions requirements for <45nm node. Compared to conventional beam line ion implantation, limited to a minimum of about 200 eV, the efficiency of Plasma Immersion Ion Implantation (PIII) is no more to prove for the realization of Ultra Shallow Junctions (USJ) in semiconductor applications: this technique allows to get ultimate shallow profiles (as implanted) thanks to no lower limitation of energy and offers high dose rate. In the field of the European consortium NANOCMOS, Ultra Shallow Junctions implanted on a semi-industrial PIII prototype (PULSION registered ) designed by the French company IBS, have been studied. Ultra shallow junctions implanted with BF3 at acceleration voltages down to 20V were realized. Contamination level, homogeneity and depth profile are studied. The SIMS profiles obtained show the capability to make ultra shallow profiles (as implanted) down to 2nm.

Torregrosa, Frank; Etienne, Hasnaa; Mathieu, Gilles; Roux, Laurent [ION BEAM SERVICES, ZI Peynier-Rousset, rue Gaston Imbert Prolongee, 13790 Peynier (France)

2006-11-13

9

Ultra-shallow junctions produced by plasma doping and flash lamp annealing  

Microsoft Academic Search

The capabilities of plasma doping (PLAD) and flash lamp annealing (FLA) for use in ultra-shallow junction (USJ) fabrication have been evaluated. Silicon wafers have been doped in a BF3 plasma using wafer biases ranging from 0.6 to 1kV and a dose of 4 × 1015cm?2. The wafers so implanted have been heat-treated by FLA using pre-heating temperatures in the range

Wolfgang Skorupa; Rossen A. Yankov; Wolfgang Anwand; Matthias Voelskow; Thoralf Gebel; Daniel F. Downey; Edwin A. Arevalo

2004-01-01

10

Defect Engineering for Ultra-Shallow Junctions Using Surfaces  

NASA Astrophysics Data System (ADS)

Formation of extremely shallow pn junctions with very low electrical resistance is a maj or stumbling block to the continued down scaling of microelectronic devices. Recent work in our laboratory has shown that the behavior of defects within silicon (and therefore dopants) can be changed significantly by controlling the chemical state of the surface. Certain chemical treatments of the surface induce it to act as an active ``sink'' for point defects that removes diffusing Si interstitials selectively over impurity interstitials, leading to less dopant diffusion and better electrical activation. The present work demonstrates such effects experimentally for dopants such as boron and arsenic in both crystalline and Ge pre-amorphized silicon wafers. Surface-based defect engineering was studied by annealing implanted Si according to various protocols with varying degrees of surface activity toward point defects. After implantation, specimens were heated to stimulate diffusive spreading of the implanted profile, with SIMS employed after annealing to monitor the spreading. SIMS measurements showed that the active surface caused less diffusion for boron and arsenic in crystalline silicon (c-Si). However, the boron dose loss in the case of the active surface was significantly higher than for the native oxide surface. This caused higher sheet resistance for the clean surface. Yet the percentage of activated boron was also higher for the clean surface. Thus, the atomically clean surface reduced transient enhanced diffusion and improved the percentage of dopant activation despite higher sheet resistance. Similar trends were observed in Ge preamorphized silicon. Additionally, the active surface dramatically reduced the number of end-of-range defects observed by electron microscopy.

Seebauer, E. G.; Kwok, C. T. M.; Vaidyanathan, R.; Kondratenko, Y. V.; Yeong, S. H.; Srinivasan, M. P.; Colombeau, Benjamin; Chan, Lap

2008-11-01

11

Ultra-shallow junctions and the effect of ramp-up rate during spike anneals in lamp-based and hot-walled RTP systems  

Microsoft Academic Search

Ultra-shallow p-type junction formation has been investigated using 1050°C spike anneals in lamp-based and hot-walled rapid thermal processing (RTP) systems. A spike anneal may be characterized by a fast ramp-up to temperature with only a fraction of a second soak-time at temperature. The effects of the ramp-up rate during a spike anneal on junction depth and sheet resistance were measured

Aditya Agarwal; Anthony T. Fiory; H.-J. Gossmann; C. Rafferty; P. Frisella; J. Hebb; J. Jackson

1999-01-01

12

Carrier Density Profiling of Ultra-Shallow Junction Layers Through Corrected C-V Plotting  

SciTech Connect

The aim of this report is to present and justify a new approach for carrier density profiling in ultra-shallow junction (USJ) layer. This new approach is based on a capacitance measurement model, which takes series impedance, shunt resistance and the presence of a boron skin on the USJ layer into account. It allows us to extract the depletion layer capacitances in the USJ layer from C-V plotting more accurately and hence to obtain better carrier density profiles. Based on this new approach the carrier density profiles of different USJ layers with and without halo-style implants are obtained and discussed.

Chen, James; Dimitrov, Dimitar; Dimitrova, Tatiana [Four Dimensions, Inc., 3140 Diablo Ave, Hayward, California, 94545 (United States); Timans, Paul [Mattson Technology, Inc. Fremont, California (United States); Gelpey, Jeff; McCoy, Steve [Mattson Technology Canada, Inc., Vancouver (Canada); Lerch, Wilfried; Paul, Silke [Mattson Thermal Products GmbH, Dornstadt (Germany); Bolze, Detlef [IHP, Frankfurt (Oder) (Germany)

2008-11-03

13

Advanced Use of Therma-Probe for Ultra-Shallow Junction Monitoring  

NASA Astrophysics Data System (ADS)

Therma-Probe® (TP) is widely used in the semiconductor industry for the Statistical Process Control (SPC) monitoring of the various ion implantation steps included in the Complementary Metal Oxide Semiconductor process. This fully optical, hence non-destructive and fast, pump-probe technique measures the probe laser reflectance (DC reflectance) as well as the pump-laser-induced changes in probe reflectance (AC reflectance, also called TW signal). In this paper, we report on the latest advances in the use of TP for the monitoring of ultra-shallow junctions both before and after annealing of the implanted layers.

Bogdanowicz, Janusz; Clarysse, Trudo; Smets, Gerrit; Rosseel, Erik; Vandervorst, Wilfried

2011-11-01

14

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

NASA Astrophysics Data System (ADS)

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.

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

2005-08-01

15

Multi-technique characterization of arsenic ultra shallow junctions in silicon within the ANNA consortium  

NASA Astrophysics Data System (ADS)

The use of ultra shallow distributions of dopant in silicon to realize source and drain extensions in CMOS devices requires the development of analytical techniques able to provide their quantitative characterization. Information like retained dopant fluence, depth distribution and damage evolution are of fundamental importance to tailor the ultra shallow p/n junctions. In this work a summary of a complementary approach developed within an European multi-laboratories consortium (ANNA) is reported. Results obtained with several techniques on arsenic ultra low energy (0.5-5 keV) implants in Si are described. The employed techniques were secondary ion mass spectrometry, grazing incidence x-ray fluorescence (with either conventional or synchrotron radiation excitation), neutron activation analysis, medium energy ion scattering, Z-contrast annular dark field scanning transmission electron microscopy and spectroscopic ellipsometry. The cross comparisons of dose measurements, dopant distribution and damage build-up behavior enabled a detailed characterization of the implanted samples and identified the overlap of information from each analytical techniques.

Giubertoni, D.; Pepponi, G.; Beckhoff, B.; Hoenicke, P.; Gennaro, S.; Meirer, F.; Ingerle, D.; Steinhauser, G.; Fried, M.; Petrik, P.; Parisini, A.; Reading, M. A.; Streli, C.; van den Berg, J. A.; Bersani, M.

2009-09-01

16

A comprehensive solution for simulating ultra-shallow junctions: From high dose\\/low energy implant to diffusion annealing  

Microsoft Academic Search

This paper presents a global approach permitting accurate simulation of the process of ultra-shallow junctions. Physically based models of dopant implantation (BCA) and diffusion (including point and extended defects coupling) are integrated within a unique simulation tool. A useful set of the relevant parameters has been obtained through an original calibration methodology. It is shown that this approach provides an

F. Boucard; F. Roger; I. Chakarov; V. Zhuk; M. Temkin; X. Montagner; E. Guichard; D. Mathiot

2005-01-01

17

Characterization of ultra-shallow junctions with tapered groove profilometry and other techniques  

NASA Astrophysics Data System (ADS)

The tapered groove profilometry (TGP) technique was applied to a series of activated ultra-shallow junctions produced by implants of 1×1015 B cm-2 at 0.25, 0.50 and 1.0 keV, by implants of 1×1015 As cm-2 at 2.0 keV, and by implants of 1×1015 BF2 cm-2 at 2.0, 3.5, 4.25 and 5.0 keV. The values obtained were compared to SIMS and SRP measurements made on the identical wafer. It was found that the TGP measurements tracked the SIMS values but at a lower level. For the B implants this was approximately 200Å, for the As and BF2 implants it was approximately 100Å. The TGP measurements tracked the SRP values much more closely.

Prussin, S.; Bil, Christiaan A.; Downey, Daniel F.; Meloni, M. L.; Osburn, Carlton M.

1998-11-01

18

Dopant Activation and Defect Analysis of Ultra-Shallow Junctions Made by Gas Cluster Ion Beams  

SciTech Connect

A long-standing problem in the fabrication of junctions by ion implantation is the enhanced diffusion caused by interstitial agglomeration and dissolution on annealing. Another side effect is residual damage that leads to junction leakage. The gas cluster ion beam technique (GCIB) offers a means of introducing dopant atoms without the creation of interstitials due to the low energy non-ballistic nature of the individual atoms and the localized thermal spike associated with the collision event between the large cluster and the silicon surface. We have employed cluster ion beams to infuse B into Si substrates to fabricate ultra-shallow junctions. Various annealing techniques were used to investigate GCIB B activation. We find that annealing at temperatures around 950 deg. C results in profiles that do not exhibit the extended tail characteristic of enhanced diffusion. This is in contrast to profiles in ion implanted samples, which inevitably result in enhanced diffusion. For laser and flash anneal, because the time scale of process is short, multiple anneal passes are needed in order to achieve low sheet resistance with little diffusion. We have shown that control of interfacial and surface smoothness is critical in improving junction characteristics.

Shao Yan; Hautala, John [TEL Epion, 37 Manning Rd., Billerica, MA 01821 (United States); Larson, Larry [FEP Division, SEMATECH, 2706 Montopolis Drive, Austin TX 78741 (United States); Jain, Amitabh [External Development and Manufacturing, Texas Instruments, 13121 TI Boulevard, MS 365 Dallas, TX 75243 (United States)

2008-11-03

19

Non-contact sheet resistance and leakage current monitoring of multi-implant, ultra-shallow junctions: Doping and damage effects for ms-anneals  

NASA Astrophysics Data System (ADS)

Junction photo-voltage methods are used to measure sheet resistance and recombination leakage current effects in ultra-shallow junctions formed with low-energy Boron implants annealed with ms-timescale thermal cycles at ~1300 C. The impact of sub-junction doping and implant damage levels present before the ms-anneal is studied.

Current, M. I.; Faifer, V. N.; Wong, T. M. H.; Nguyen, T.; Koo, A.

2006-11-01

20

Improvement of heavy dopant doped Ni-silicide using ytterbium interlayer for nano-scale MOSFETS with an ultra shallow junction.  

PubMed

In this paper, a novel Ni silicide with Yb interlayer (Yb/Ni/TiN) on a boron cluster (B18H22) implanted source/drain junction is proposed for the first time, and its thermal stability characteristics are analyzed in depth. The proposed Ni-silicide exhibits a wider RTP temperature window for uniform sheet resistance, surface roughness and better thermal stability than the conventional structure (Ni/TiN). In addition, the cross-sectional profile of the proposed Ni-silicide showed less agglomeration despite the high temperature post-silicidation annealing, and it can be said that the proposed structure was little dependence on the temperature post-silicidation annealing. The improvement of Ni silicide properties is analyzed and found to be due to the formation of the rare earth metal--NiSi (YbNi2Si2), whose peaks were confirmed by XRD. The junction leakage current of the p + -n junction with Yb/Ni/TiN and B18H22 implantation is smaller than that with Ni/TiN by almost one order of magnitude as well as improving the thermal stability of ultra shallow junction. PMID:22121582

Shin, Hong-Sik; Oh, Se-Kyung; Kang, Min-Ho; Li, Shi-Guang; Lee, Ga-Won; Lee, Hi-Deok

2011-07-01

21

A 0.05 ?m-CMOS with ultra shallow source\\/drain junctions fabricated by 5 keV ion implantation and rapid thermal annealing  

Microsoft Academic Search

A 0.05 ?m-PMOSFET has been fabricated for the first time, together with a 0.05 ?m-NMOSFET. For this process, ultra shallow source\\/drain junctions were developed on the basis of 5 keV ion implantation technology and rapid thermal annealing. The short channel effect was suppressed and Gm max reaches 460 mS\\/mm for NMOS and 380 mS\\/mm for PMOS. The delay time per

Atsushi HORI; Hiroaki NAKAOKA; Hiroyuki UMIMOTO; Kyoji YAMASHITA; Michihiko TAKASE; Norisato SHIMIZU; B. Mizuno; S. Odanaka

1994-01-01

22

Process advances to achieve ultra-shallow junctions for 0.10 ?m technology requirements  

NASA Astrophysics Data System (ADS)

Ion implants of 11B+, 49BF2+, 31P+ and 75As+ at energies as low as 0.25 keV at various doses were implanted and rapid thermal annealed (RTA) with controlled O2 levels in N2 ambient to investigate the effects of oxygen during anneal. For each of these implant species, an optimal RTA ambient of O2 in N2 is established which maximizes retained dose and uniformity while minimizing oxidation enhanced diffusion (OED) and other oxygen related diffusion effects. TEM analysis was performed for all species and energy thresholds identified (at 1e15/cm2), below which no extended-defects or loops were observed to form and hence a regime where transient enhanced diffusion (TED) should not affect dopant diffusion. In this energy regime with anneals in a low ppm O2 in N2 ambient, the contributions from TED, OED, BED (boridation enhanced diffusion or other dopant enhanced diffusion effects) are minimized/eliminated. With these enhanced diffusion mechanisms under control, the effects of minimizing the thermal diffusion by controlled ``slow'' and ``fast'' spike anneals (<0.1s) are investigated. Taking advantage of these various processing techniques, source/drain extension requirements to satisfy the National Technology Roadmap (NTRS) requirements at the 0.10 ?m node are satisfied for the p-extension by both B (0.25 to 0.5 keV) and BF2 (1.1 to 2.2 keV). In addition, n-extension requirements are meet for As+ (1.0 to 2.0 keV), and P+ (1.0 to 5.0 keV) for contact junctions are reviewed for the NTRS requirements at 0.10?m geometries.

Bertuch, Adam F.; Zhao, Zhiyong; Downey, Daniel F.; Falk, Scott W.

1999-06-01

23

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

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.

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

24

Estimation of ultra-shallow implants using SIMS, NRA and chemical analysis  

Microsoft Academic Search

Estimation methods for ultra-shallow implants (boron and arsenic) were investigated. SIMS analysis enables accurate junction depth estimation for ultra-shallow junctions, when concentration and depth calibration methods using bulk-doped samples and multi-delta-structure samples are used together. Even with this advanced SIMS measurement, accurate implant doses cannot be estimated for ultra-shallow implants. NRA and chemical analyses have been developed for accurate measurements

M. Tomita; M Suzuki; T Tachibe; S Kozuka; A Murakoshi

2003-01-01

25

Flash lamp annealing with millisecond pulses for ultra-shallow boron profiles in silicon  

Microsoft Academic Search

In this paper we report on recent results obtained from flash lamp annealing (FLA) for the formation of ultra-shallow junctions. Si(100) wafers were implanted at ultra-low energy (500 eV) with boron to a fluence of 1015ions\\/cm2. FLA was carried out at temperatures of 1100 and 1200 °C with a soak time of 20 ms. For comparison conventional rapid thermal annealing

T. Gebel; M. Voelskow; W. Skorupa; G. Mannino; V. Privitera; F. Priolo; E. Napolitani; A. Carnera

2002-01-01

26

Laser thermal processing for ultra shallow junction formation: numerical simulation and comparison with experiments  

Microsoft Academic Search

In the last few years, laser thermal processing (LTP) has become a potential solution for sub-0.1?m technology requirements, as focused by the international technology roadmap for semiconductors (ITRS).This paper presents a numerical simulation of the propagation of the melting front and regrowth of Si-based structures during excimer (XeCl-308nm) laser irradiation. The influence of the pulse duration is highlighted in the

M. Hernandez; J. Venturini; D. Zahorski; J. Boulmer; D. Débarre; G. Kerrien; T. Sarnet; C. Laviron; M. N. Semeria; D. Camel; J. L. Santailler

2003-01-01

27

Ultra shallow P+\\/N junctions using plasma immersion ion implantation and laser annealing for sub 0.1 ?m CMOS devices  

Microsoft Academic Search

Classical beam line ion implantation is limited to low energies and cannot achieve P+\\/N junctions requested for <45nm ITRS node. RTA (rapid thermal annealing) needs to be improved for dopants activation and damage reductions. Spike annealing process also induces a large diffusion mainly due to TED (transient enhanced diffusion).Compared to conventional beam line ion implantation limited to a minimum energy

Frank Torregrosa; Cyrille Laviron; Frédéric Milesi; Miguel Hernandez; Hasna Faïk; Julien Venturini

2005-01-01

28

Ultra shallow P+/N junctions using plasma immersion ion implantation and laser annealing for sub 0.1 ?m CMOS devices  

NASA Astrophysics Data System (ADS)

Classical beam line ion implantation is limited to low energies and cannot achieve P+/N junctions requested for <45 nm ITRS node. RTA (rapid thermal annealing) needs to be improved for dopants activation and damage reductions. Spike annealing process also induces a large diffusion mainly due to TED (transient enhanced diffusion). Compared to conventional beam line ion implantation limited to a minimum energy implantation of 200 eV, plasma immersion ion implantation (PIII) is an emerging technique to get ultimate shallow profiles (as-implanted) due to no lower limitation of energy and high dose rate. On the another hand, laser thermal processing (LTP) allows to obtain very shallow junction with no TED, abrupt profile and activated depth control. In this paper, we show the implementation of the BF3 PIII associated with the LTP. Ions from BF3+ plasma have been implanted in 200 mm n-type silicon wafers with energies from 100 eV to 1 keV and doses from 3E14 to 5E15 at/cm2 using PULSION® (IBS PIII prototype). Then, wafers have been annealed using SOPRA VEL 15 XeCl excimer lasers (l = 308 nm, 200 ns, 15 J/pulse) with energy density from 1 to 2.5 J/cm2 and 1, 3 or 10 shots. The samples have been characterized at CEA LETI by secondary ion mass spectrometry (SIMS) combined with four points probe sheet resistance measurements.

Torregrosa, Frank; Laviron, Cyrille; Milesi, Frédéric; Hernandez, Miguel; Faïk, Hasna; Venturini, Julien

2005-08-01

29

Junction formation during desiccation cracking  

NASA Astrophysics Data System (ADS)

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

Toga, K. B.; Alaca, B. Erdem

2006-08-01

30

Junction formation during desiccation cracking.  

PubMed

In order to provide a sound physical basis for the understanding of the formation of desiccation crack networks, an experimental study is presented addressing junction formation. Focusing on junctions, basic features of the network determining the final pattern, provides an elemental approach and imparts conceptual clarity to the rather complicated problem of the evolution of crack patterns. Using coffee-water mixtures a clear distinction between junction formation during nucleation and propagation is achieved. It is shown that for the same drying suspension, one can switch from the well-known symmetric triple junctions that are unique to the nucleation phase to propagation junctions that are purely dictated by the variations of the stress state. In the latter case, one can even manipulate the path of a propagating crack in a deterministic fashion by changing the stress state within the suspension. Clear microscopic evidence is provided for the formation of propagation junctions, and material inhomogeneity is observed to be reflected by a broad distribution of angles, in stark contrast to shrinkage cracks in homogeneous solid films. PMID:17025423

Toga, K B; Alaca, B Erdem

2006-08-09

31

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

SciTech Connect

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.

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

32

70 nm MOSFET with ultra-shallow, abrupt, and super-doped S\\/D extension implemented by laser thermal process (LTP)  

Microsoft Academic Search

For the first time, a sub-100 nm gate length CMOS transistor is demonstrated with the source\\/drain extension implemented by laser thermal process (LTP). Ultra-shallow (<30 nm), abrupt, and highly-doped n+ and p+ junctions are formed by low-keV implant and 308 nm XeCl excimer laser anneal. Locally selective melting and recrystallization of silicon under the laser beam results in excellent dopant

Bin Yu; Yun Wang; Haihong Wang; Qi Xiang; C. Riccobene; S. Talwar; Ming-Ren Lin

1999-01-01

33

Method for shallow junction formation  

DOEpatents

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

Weiner, Kurt H. (San Jose, CA)

1996-01-01

34

PLAsma Doping For P+ Junction Formation In 90 nm NOR Flash Memory Technology  

SciTech Connect

For MOS devices belonging to 65 nm technology node and beyond, ultra-shallow LDD junctions are needed in order to match requirements in terms of sheet resistance and doping profile. PLAsma Doping has been proposed and developed as an effective and viable technology capable to produce such junctions, while keeping high productivity. Furthermore, as the equipment is simpler and smaller than a common implanter, PLAsma Doping can be considered, from the cost of ownership point of view, an attractive solution also for those applications whose requirements are not so demanding; an example can be the junctions of a Flash Memory. Aim of this study is to evaluate, electrically, the compatibility of PLAsma Doping with a NOR Flash Memory belonging to 90 nm technology node. Results of PLAsma Doping experiment concerning the matching of the device parameters will be here presented. Further investigation is needed in order to exclude any possible effect on device reliability.

Bigarella, Dario; Soncini, Valter [STMicroelectronics srl, Via C. Olivetti 2, 20041 Agrate Brianza (Italy); Raj, Deven; Singh, Vikram; Walther, Steve [VSEA Varian Semiconductor Equipment Associates, 35 Dory Road, Gloucester, MA 01930-2297 (United States)

2006-11-13

35

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

Microsoft Academic Search

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

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

2010-01-01

36

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

SciTech Connect

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...)

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)

2008-11-03

37

Tunneling in quantum confined GaAs ultrashallow sidewall tunnel junctions  

NASA Astrophysics Data System (ADS)

Temperature dependence of current-voltage (I -V ) characteristics of quantum-confined GaAs ultra-shallow sidewall p +n + tunnel junctions has been investigated. The sidewall tunnel junctions with junction depths ranging from 5 nm to 50 nm were achieved by the combination of intermittent injection of TEG/AsH3 in an ultra high vacuum and a wet etching process of the GaAs growth layer. From the I -V results, abrupt negative differential resistances (NDR) were observed, which relate to direct/indirect tunneling and sub-band formation. The change in the number instances of NDR and their voltage positions also depended on the junction depth. Mechanisms of tunneling in the present sidewall tunnel junction will be discussed from the point of the sub-band formation in conduction bands.

Ohno, Takeo; Oyama, Yutaka; Nishizawa, Jun-Ichi

2006-03-01

38

Boron-enhanced-diffusion of boron: The limiting factor for ultra-shallow junctions  

SciTech Connect

Reducing implant energy is an effective way to eliminate transient enhanced diffusion (TED) due to excess interstitials from the implant. It is shown that TED from a fixed Si dose implanted at energies from 0.5 to 20 keV into boron doping-superlattices decreases linearly with decreasing Si ion range, virtually disappearing at sub-keV energies. However, for sub-keV B implants diffusion remains enhanced and x{sub j} is limited to {ge} 100 nm at 1,050 C. The authors term this enhancement, which arises in the presence of B atomic concentrations at the surface of {approx} 6%, Boron-Enhanced-Diffusion (BED).

Agarwal, A. [Lucent Technologies, Murray Hill, NJ (United States). Bell Labs.]|[Oak Ridge National Lab., TN (United States). Solid State Div.; Eaglesham, D.J.; Gossmann, H.J.; Pelaz, L.; Herner, S.B.; Jacobson, D.C. [Lucent Technologies, Murray Hill, NJ (United States). Bell Labs.; Haynes, T.E. [Oak Ridge National Lab., TN (United States); Erokhin, Y.; Simonton, R. [Eaton Corp., Beverly, MA (United States). Semiconductor Equipment Operations

1997-12-01

39

Excimer laser thermal processing of ultra-shallow junction: laser pulse duration  

Microsoft Academic Search

According to the International Technology Roadmap for Semiconductors (ITRS), source and drain extensions thickness for 65 nm and below technology nodes MOSFET lead to a major challenge. Rapid thermal processing (RTP) tools reach the limit of their physical abilities in term of temperature cycle and pulsed laser thermal processing (LTP) tool arise as a major potential candidates to solve the

J. Venturini; M. Hernandez; G. Kerrien; C. Laviron; D. Camel; J. L. Santailler; T. Sarnet; J. Boulmer

2004-01-01

40

Laser activation of Ultra Shallow Junctions (USJ) doped by Plasma Immersion Ion Implantation (PIII)  

Microsoft Academic Search

Today, the main challenges for the realization of the source\\/drain extensions concern the ultra-low energy implantation and the activation of the maximum amount of dopants with a minimized diffusion. Among the different annealing processes, one solution is the laser thermal annealing. Many studies [F. Torregrosa, C. Laviron, F. Milesi, M. Hernandez, H. Faik, J. Venturini, Proc. 14th International Conference on

Vanessa Vervisch; Yannick Larmande; Philippe Delaporte; Thierry Sarnet; Marc Sentis; Hasnaa Etienne; Frank Torregrosa; Fuccio Cristiano; Pier Francesco Fazzini

2009-01-01

41

Semiconductor junction formation by directed heat  

DOEpatents

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.

Campbell, Robert B. (Pittsburgh, PA)

1988-03-24

42

Ultra-shallow imaging using two-dimensional and three-dimensional seismic reflection methods  

NASA Astrophysics Data System (ADS)

The research presented in this dissertation focuses on the survey design, acquisition, processing, and interpretation of ultra-shallow seismic reflection (USR) data in two and three dimensions. The application of 3D USR methods to image multiple reflectors less than 20 m deep, including the top of the saturated zone (TSZ), a paleo-channel, and bedrock, are presented using conventional acquisition methods and a new automated method of acquiring 3D data using hydraulically planted geophones. Processing techniques that focus on near-surface problems, such as intersecting reflection hyperbolae caused by large vertical velocity changes and processing pitfalls, are also discussed. The application of AVO analysis of 2D USR data collected during a pumping test yielded amplitude variations related to the thickness of the partially saturated zone that correlated spatially and with changes in pumping. USR methods were also used to image the TSZ less than one meter deep, the shallowest TSZ reflection to date.

Sloan, Steven Daniel

43

Formation of Graphene p-n Junction via Complementary Doping  

Microsoft Academic Search

We demonstrate the formation of a p-n junction in 2-D graphene through complementary doping. A shift of the Dirac point is observed with increased electrical stressing voltage, indi- cating the modification of electrostatic charge distribution in the material system. Both graphene and graphene\\/metal contact resis- tances show significant decrease after electrical stressing. Carrier mobility is affected due to the charge

Tianhua Yu; Changdong Kim; Chen-Wei Liang; Bin Yu

2011-01-01

44

Titanium nitride barrier formation and junction leakage characterization  

Microsoft Academic Search

Rapid thermal processing (RTP) of Titanium in an NH3 ambient results in the formation of a bilayer TiNx\\/TiSiy diffusion barrier to aluminum spiking and junction leakage. Auger electron spectroscopy and Rutherford backscattering spectrometry were used to characterize the bilayer film properties as a function of starting titanium thickness, RTP temperature, metal deposition degas temperature and substrate doping. It has been

J. Hill; S. Gonzales; R. Keating; R. Gregory

1995-01-01

45

Quantitative prediction of junction leakage in bulk-technology CMOS devices  

Microsoft Academic Search

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

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

2010-01-01

46

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

PubMed Central

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

Audouard, Emilie; Schakman, Olivier; Rene, Frederique; Huettl, Rosa-Eva; Huber, Andrea B.; Loeffler, Jean-Philippe; Gailly, Philippe; Clotman, Frederic

2012-01-01

47

Field Theoretical Approach to the Formation of Junctions of Cosmic Strings  

SciTech Connect

Superstring theory predicts the potential formation of string networks with junctions. Kinematic constraints for junction formation were derived in [1], based on Nambu-Goto action. Here we test these constraints numerically within the framework of Abelian-Higgs model and report on good agreement with the analytical predictions.

Salmi, Petja [Instituut-Lorentz, Universiteit Leiden, P. O. Box 9506, 2300 RA Leiden (Netherlands)

2007-11-20

48

Gap and tight junctions in the formation of feather branches: A descriptive ultrastructural study.  

PubMed

The present study has focused on the distribution and ultrastructure of gap and tight junctions responsible for the formation of the barb/barbule branching in developing feathers using immunocytochemical detection. Apart from desmosomes, both tight and gap junctions are present between differentiating barb/barbule cells and during keratinization. While gap junctions are rare along the perimeter of these cells, tight junctions tend to remain localized in nodes joining barbule cells and between barb cells of the ramus. Occludin and connexin-26 but not connexin-43 have been detected between barb medullary, barb cortical and barbule cells during formation of barbs. Gap junctions are present in supportive cells located in the vicinity of barbule cells and destined to degenerate, but no close junctions are present between supportive and barb/barbule cells. Close junctions mature into penta-laminar junctions that are present between mature barb/barbule cells. Immunolabeling for occludin and Cx26 is rare along these cornified junctions. The junctions allow barb/barbule cells to remain connected until feather-keratin form the mature corneous syncytium that constitutes the barbs. A discussion of the role of gap and tight junctions during feather morphogenesis is presented. PMID:20691576

Alibardi, Lorenzo

2010-07-13

49

Leakage Current and Dopant Activation Characterization of SDE/Halo CMOS Junctions with Non-Contact Junction Photo-Voltage Metrology  

NASA Astrophysics Data System (ADS)

Sheet resistance and leakage current of spike rapid thermal processed (RTP), millisecond flash (fRTP) annealed and chemical vapor deposition (CVD) grown ultra-shallow junctions (USJ) are compared with a non-contact junction photovoltage, RsL, technique. Theoretical reverse-biased diode and non-contact leakage currents are compared. A significant leakage current increase for spike RTP and fRTP processed USJ formed in halo-implanted profiles is described by high electron and hole recombination-generation in the end-of-range (EOR) damage layer enhanced by trap assisted and band-to-band tunneling. The reduced thermal budget of fRTP allows junction formation with reduced dopant diffusion and with lower sheet resistance. However when strong halo doping is employed, there is often a significant increase in junction leakage relative to that for junctions formed in lightly-doped test wafers. This increased leakage current can be reduced by annealing the halo implants before implanting the USJ or by lowering the halo dose. USJ grown with CVD demonstrate low leakage current due to localization of recombination centers at the edge of the depletion layer, where recombination (generation) is small. This study demonstrates the importance of characterizing USJ formed in halo profile for advanced ULSI.

Faifer, V. N.; Schroder, D. K.; Current, M. I.; Clarysse, T.; Timans, P. J.; Zangerle, T.; Vandervorst, W.; Wong, T. M. H.; Moussa, A.; McCoy, S.; Gelpey, J.; Lerch, W.; Paul, S.; Bolze, D.

2007-09-01

50

Benefits of Damage Engineering for PMOS Junction Stability  

SciTech Connect

As CMOS devices continue to shrink, the formation of ultra shallow junction (USJ) in the source/drain extension remains to be a key challenge requiring high dopant activation, shallow dopant profile and abrupt junctions. The next generations of sub nano-CMOS devices impose a new set of challenges such as elimination of residual defects resulting in higher leakage, difficulty to control lateral diffusion, junction stability post anneal and junction formation in new materials. To address these challenges for advanced technological nodes beyond 32 nm, it is imperative to explore novel species and techniques. Molecular species such as Carborane (C{sub 2}B{sub 10}H{sub 12}), a novel doping species and a promising alternative to monomer Boron is of considerable interest due to the performance boost for 22 nm low power and high performance devices. Also, to reduce residual defects, damage engineering methodologies have generated a lot of attention as it has demonstrated significant benefits in device performance. Varian proprietary techniques to perform implants at cold temperatures (PTC II) have demonstrated lower junction leakage, enhanced activation, reduced dopant diffusion and less dopant deactivation due to the reduction of self-interstitial atoms present at the end-of-range (EOR) with low implant temperatures. In this paper, for the first time, there is a comprehensive study of the effect of implant temperature on defect engineering affecting deactivation/reactivation, and it is well established in this paper that colder the implant temperature the better it is for damage engineering with reduced EOR defects and better amorphization. The effect has been studied over a wide range of implant temperature. To understand any difference in deactivation between molecular and monomer Boron and to provide direct comparison equivalent Boron implants, co-implanted with Carbon were also studied. Implants with wide range of temperatures are implemented using PTC II. This paper will also show how damage reduction correlates with optimum junction formation and stability.

Khaja, Fareen; Colombeau, Benjamin; Thanigaivelan, Thirumal; Ramappa, Deepak; Henry, Todd [Varian Semiconductor Equipment Associates, Inc. 35 Dory Road, Gloucester, MA 01930 (United States)

2011-01-07

51

Wnt4 Participates in the Formation of Vertebrate Neuromuscular Junction  

PubMed Central

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.

Strochlic, Laure; Falk, Julien; Goillot, Evelyne; Sigoillot, Severine; Bourgeois, Francine; Delers, Perrine; Rouviere, Jerome; Swain, Amanda; Castellani, Valerie; Schaeffer, Laurent; Legay, Claire

2012-01-01

52

Numerical Simulation on the Horseshoe Vortex Formation Around the Hull-Sail Junction of Submarine  

Microsoft Academic Search

The horseshoe vortex is typical flow characteristic around the appendage-body junction. The horseshoe vortex formation around the hull-said junction has important influence on the submarine hydrodynamics performance. The origination process of the submarine horseshoe vertex and its influence on submarine flow is analyzed. The numerical simulation on the horseshoe vortex is carried out using DES method (Detached Eddies Simulation); the

Liu Zhihua; Xiong Ying

2010-01-01

53

Innexin2 gap junctions in somatic support cells are required for cyst formation and for egg chamber formation in Drosophila.  

PubMed

Germ cells require intimate associations with surrounding somatic cells during gametogenesis. During oogenesis, gap junctions mediate communication between germ cells and somatic support cells. However, the molecular mechanisms by which gap junctions regulate the developmental processes during oogenesis are poorly understood. We have identified a female sterile allele of innexin2 (inx2), which encodes a gap junction protein in Drosophila. In females bearing this inx2 allele, cyst formation and egg chamber formation are impaired. In wild-type germaria, Inx2 is strongly expressed in escort cells and follicle cells, both of which make close contact with germline cells. We show that inx2 function in germarial somatic cells is required for the survival of early germ cells and promotes cyst formation, probably downstream of EGFR pathway, and that inx2 function in follicle cells promotes egg chamber formation through the regulation of DE-cadherin and Bazooka (Baz) at the boundary between germ cells and follicle cells. Furthermore, genetic experiments demonstrate that inx2 interacts with the zero population growth (zpg) gene, which encodes a germline-specific gap junction protein. These results indicate a multifunctional role for Inx2 gap junctions in somatic support cells in the regulation of early germ cell survival, cyst formation and egg chamber formation. Inx2 gap junctions may mediate the transfer of nutrients and signal molecules between germ cells and somatic support cells, as well as play a role in the regulation of cell adhesion. PMID:22001874

Mukai, Masanori; Kato, Hirotaka; Hira, Seiji; Nakamura, Katsuhiro; Kita, Hiroaki; Kobayashi, Satoru

2011-10-05

54

Binding between the Junctional Proteins Afadin and PLEKHA7 and Implication in the Formation of Adherens Junction in Epithelial Cells.  

PubMed

Adherens junction (AJ) is a specialized cell-cell junction structure that plays a role in mechanically connecting adjacent cells to resist strong contractile forces and to maintain tissue structure, particularly in the epithelium. AJ is mainly comprised of cell adhesion molecules cadherin and nectin and their associating cytoplasmic proteins including ?-catenin, ?-catenin, p120(ctn), and afadin. Our series of studies have revealed that nectin first forms cell-cell adhesion and then recruits cadherin to form AJ. The recruitment of cadherin by nectin is mediated by the binding of ?-catenin and p120(ctn) to afadin. Recent studies showed that PLEKHA7 binds to p120(ctn), which is associated with E-cadherin, and maintains the integrity of AJ in epithelial cells. In this study, we showed that PLEKHA7 bound to afadin in addition to p120(ctn) and was recruited to the nectin-3?-based cell-cell adhesion site in a manner dependent on afadin, but not on p120(ctn). The binding of PLEKHA7 to afadin was required for the proper formation of AJ, but not for the formation of tight junction, in EpH4 mouse mammary gland epithelial cells. These results indicate that PLEKHA7 plays a cooperative role with nectin and afadin in the proper formation of AJ in epithelial cells. PMID:23990464

Kurita, Souichi; Yamada, Tomohiro; Rikitsu, Etsuko; Ikeda, Wataru; Takai, Yoshimi

2013-08-29

55

The cytoskeletal mechanisms of cell-cell junction formation in endothelial cells  

PubMed Central

The actin cytoskeleton and associated proteins play a vital role in cell–cell adhesion. However, the procedure by which cells establish adherens junctions remains unclear. We investigated the dynamics of cell–cell junction formation and the corresponding architecture of the underlying cytoskeleton in cultured human umbilical vein endothelial cells. We show that the initial interaction between cells is mediated by protruding lamellipodia. On their retraction, cells maintain contact through thin bridges formed by filopodia-like protrusions connected by VE-cadherin–rich junctions. Bridges share multiple features with conventional filopodia, such as an internal actin bundle associated with fascin along the length and vasodilator-stimulated phosphoprotein at the tip. It is striking that, unlike conventional filopodia, transformation of actin organization from the lamellipodial network to filopodial bundle during bridge formation occurs in a proximal-to-distal direction and is accompanied by recruitment of fascin in the same direction. Subsequently, bridge bundles recruit nonmuscle myosin II and mature into stress fibers. Myosin II activity is important for bridge formation and accumulation of VE-cadherin in nascent adherens junctions. Our data reveal a mechanism of cell–cell junction formation in endothelial cells using lamellipodia as the initial protrusive contact, subsequently transforming into filopodia-like bridges connected through adherens junctions. Moreover, a novel lamellipodia-to-filopodia transition is used in this context.

Hoelzle, Matthew K.; Svitkina, Tatyana

2012-01-01

56

V(D)J recombination coding junction formation without DNA homology: processing of coding termini.  

PubMed Central

Coding junction formation in V(D)J recombination generates diversity in the antigen recognition structures of immunoglobulin and T-cell receptor molecules by combining processes of deletion of terminal coding sequences and addition of nucleotides prior to joining. We have examined the role of coding end DNA composition in junction formation with plasmid substrates containing defined homopolymers flanking the recombination signal sequence elements. We found that coding junctions formed efficiently with or without terminal DNA homology. The extent of junctional deletion was conserved independent of coding ends with increased, partial, or no DNA homology. Interestingly, G/C homopolymer coding ends showed reduced deletion regardless of DNA homology. Therefore, DNA homology cannot be the primary determinant that stabilizes coding end structures for processing and joining.

Boubnov, N V; Wills, Z P; Weaver, D T

1993-01-01

57

Formation of an inverted repeat junction in the transposition of insertion sequence ISLC3 isolated from Lactobacillus casei  

Microsoft Academic Search

An insertion sequence, ISLC3, of 1351 bp has been isolated from Lactobacillus casei. Formation of IS circles containing a 3 bp spacer (complete junction) or deletion of 25 bp at the left inverted repeat (IRL) between the abutted IS ends of the ISLC3 junction region (deleted junction) was also discovered in the lactobacilli and Escherichia coli system studied. We found

Ta-Chun Lo; Hung-Wen Chen; Yu-Kuo Tsai; Yang-Cheng Kuo; Chao-Fen Lin; Ssu-Ying Kuo; Thy-Hou Lin

2008-01-01

58

Materials and device issues in the formation of sub-100-nm junctions  

NASA Astrophysics Data System (ADS)

This paper compares the materials and device issues associated with two alternative techniques for the formation of ultrashallow junctions: 1) the use of preamorphization and low energy dopant implantation, combined with rapid, low-temperature annealing; and 2) the use of metal suicides as a diffusion source (SADS) where dopants are implanted into CoSi2 and subsequently diffused into silicon. For conventionally-formed, ultrashallow junctions, preamorphization with either silicon or germanium does not result in shallower junctions. The enhanced diffusion associated with the preamorphization implant damage compensates for the reduction in channeling. Preamorphization does, however, give low sheet resistance junctions and high dopant activation after recrystallization at 550°C. Considerable dopant motion (~ 50 nm) is observed in the tail region, near the junction, after 10 s of annealing at a relatively low temperature (800°C). The SADS process is seen to produce low leakage n+ and p+ diodes with less than 10 nm of dopant diffusion beyond the silicide/silicon interface, using a very low thermal budget process. By confining the implantation to within the suicide, no crystal defects are created in the underlying silicon. With the SADS process, the limitation on scaling the junction depth lies in producing thin, stable suicide films. Agglomeration of the silicide and pullback along feature edges restrict the maximum thermal cycle and the minimum allowable film thickness.

Osburn, C. M.; Chevacharoenkul, S.; Wang, Q. F.; Markus, K.; McGuire, G. E.; Smith, P. L.

1993-04-01

59

The TRPV4 Channel Contributes to Intercellular Junction Formation in Keratinocytes*?  

PubMed Central

Transient receptor potential vanilloid 4 (TRPV4) channel is a physiological sensor for hypo-osmolarity, mechanical deformation, and warm temperature. The channel activation leads to various cellular effects involving Ca2+ dynamics. We found that TRPV4 interacts with ?-catenin, a crucial component linking adherens junctions and the actin cytoskeleton, thereby enhancing cell-cell junction development and formation of the tight barrier between skin keratinocytes. TRPV4-deficient mice displayed impairment of the intercellular junction-dependent barrier function in the skin. In TRPV4-deficient keratinocytes, extracellular Ca2+-induced actin rearrangement and stratification were delayed following significant reduction in cytosolic Ca2+ increase and small GTPase Rho activation. TRPV4 protein located where the cell-cell junctions are formed, and the channel deficiency caused abnormal cell-cell junction structures, resulting in higher intercellular permeability in vitro. Our results suggest a novel role for TRPV4 in the development and maturation of cell-cell junctions in epithelia of the skin.

Sokabe, Takaaki; Fukumi-Tominaga, Tomoko; Yonemura, Shigenobu; Mizuno, Atsuko; Tominaga, Makoto

2010-01-01

60

INTERACTION BETWEEN CYTOCHALASIN B-TREATED MALARIAL PARASITES AND ERYTHROCYTES Attachment and Junction Formation  

Microsoft Academic Search

Malaria parasites develop within erythrocytes (RBCs), 1 and at full maturation infected RBCs rupture, releasing individual merozoites that invade other RBCs. Invasion, the process by which the extracellular merozoite becomes established as an intracellular parasite occurs through a sequence of events that includes recognition and attachment (1), junction formation (2), invagination of the RBC membrane around the merozoite (2), and

LOUIS H. MILLER; MASAMICHI AIKAWA; JAMES G. JOHNSON; TSUGIYE SHIROISHI

61

Involvement of Actinin4 in the Recruitment of JRAB\\/MICAL-L2 to Cell-Cell Junctions and the Formation of Functional Tight Junctions  

Microsoft Academic Search

Tight junctions (TJs) are cell-cell adhesive structures that undergo continuous remodeling. We previously demonstrated that Rab13 and a junctional Rab13-binding protein (JRAB)\\/molecule interacting with CasL-like 2 (MICAL-L2) localized at TJs and mediated the endocytic recycling of the integral TJ protein occludin and the formation of functional TJs. Here, we investigated how JRAB\\/MICAL-L2 was targeted to TJs. Using a series of

Hiroyoshi Nakatsuji; Noriyuki Nishimura; Rie Yamamura; Hiro-omi Kanayama; Takuya Sasaki

2008-01-01

62

Non-Contact and Non-Destructive Characterization of Shallow Implanted Silicon PN Junctions using Ultra-Violet Raman Spectroscopy  

NASA Astrophysics Data System (ADS)

Ultra-shallow boron implanted (B+ 1 keV 1×1015 cm-2) n-type Si wafers were prepared and characterized by four point probe, SIMS and 363.8 nm excited ultra-violet (UV) Raman spectroscopy before and after rapid thermal annealing (RTA). The penetration depth of 363.8 nm laser radiation in a backscattering Raman configuration, is approximately 5 nm. As junction depth increases from high temperature RTA, sheet resistance decreases. Raman peaks shift in the lower wavenumber direction and its full-width-at-half-maximum (FWHM) broadens. There is clear correlation between junction depth and Raman spectra data. UV Raman spectroscopy can be used as a very powerful non-contact, non-destructive, in-line characterization and monitoring technique for ultra-shallow junctions (USJs).

Fukumoto, Masashi; Hasuike, Noriyuki; Harima, Hiroshi; Yoshimoto, Masahiro; Yoo, Woo Sik

2011-01-01

63

Junction leakage measurements with micro four-point probes  

NASA Astrophysics Data System (ADS)

We present a new, preparation-free method for measuring the leakage current density on ultra-shallow junctions. The junction leakage is found by making a series of four-point sheet resistance measurements on blanket wafers with variable electrode spacings. The leakage current density is calculated using a fit of the measured four-point resistances to an analytical two-sheet model. The validity of the approximation involved in the two-sheet model is verified by a comparison to finite element model calculations.

Lin, Rong; Petersen, Dirch H.; Wang, Fei; Yates, Bradley R.; Jones, Kevin S.; Hansen, Ole; Kontos, Alex; Nielsen, Peter F.

2012-11-01

64

tal1 regulates the formation of intercellular junctions and the maintenance of identity in the endocardium.  

PubMed

The endocardium forms the inner lining of the heart tube, where it enables blood flow and also interacts with the myocardium during the formation of valves and trabeculae. Although a number of studies have identified regulators in the morphogenesis of the myocardium, relatively little is known about the molecules that control endocardial morphogenesis. Prior work has implicated the bHLH transcription factor Tal1 in endocardial tube formation: in zebrafish embryos lacking Tal1, endocardial cells form a disorganized mass within the ventricle and do not populate the atrium. Through blastomere transplantation, we find that tal1 plays a cell-autonomous role in regulating endocardial extension, suggesting that Tal1 activity influences the behavior of individual endocardial cells. The defects in endocardial behavior in tal1-deficient embryos originate during the earliest steps of endocardial morphogenesis: tal1-deficient endocardial cells fail to generate a cohesive monolayer at the midline and instead pack tightly together into a multi-layered aggregate. Moreover, the tight junction protein ZO-1 is mislocalized in the tal1-deficient endocardium, indicating a defect in intercellular junction formation. In addition, we find that the tal1-deficient endocardium fails to maintain its identity; over time, a progressively increasing number of tal1-deficient endocardial cells initiate myocardial gene expression. However, the onset of defects in intercellular junction formation precedes the onset of ectopic myocardial gene expression in the tal1-deficient endocardium. We therefore propose a model in which Tal1 has distinct roles in regulating the formation of endocardial intercellular junctions and maintaining endocardial identity. PMID:24075907

Schumacher, Jennifer A; Bloomekatz, Joshua; Garavito-Aguilar, Zayra V; Yelon, Deborah

2013-09-25

65

In-situ formation of p-n junctions in semiconducting TiO 2  

Microsoft Academic Search

Application of small voltages in the range from 0.5 V to 1 V to an originally homogeneously Fe-doped (0.5 mol-%) TiO2 semiconductor at temperatures between 700° C and 750° C caused the formation of a p-n junction within the sample. This is indicated by a change of the U-I characteristics from a symmetrical to a diode type behavior. By inversion

M. Klingler; W. Weppner

1994-01-01

66

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

Microsoft Academic Search

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

Amit Gupta; Ranganathan Kumar

2010-01-01

67

PATJ regulates tight junction formation and polarity in mammalian epithelial cells.  

PubMed

Recent studies have revealed an important role for tight junction protein complexes in epithelial cell polarity. One of these complexes contains the apical transmembrane protein, Crumbs, and two PSD95/discs large/zonula occludens domain proteins, protein associated with Lin seven 1 (PALS1)/Stardust and PALS1-associated tight junction protein (PATJ). Although Crumbs and PALS1/Stardust are known to be important for cell polarization, recent studies have suggested that Drosophila PATJ is not essential and its function is unclear. Here, we find that PATJ is targeted to the apical region and tight junctions once cell polarization is initiated. We show using RNAi techniques that reduction in PATJ expression leads to delayed tight junction formation as well as defects in cell polarization. These effects are reversed by reintroduction of PATJ into these RNAi cells. This study provides new functional information on PATJ as a polarity protein and increases our understanding of the Crumbs-PALS1-PATJ complex function in epithelial polarity. PMID:15738264

Shin, Kunyoo; Straight, Sam; Margolis, Ben

2005-02-28

68

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

PubMed Central

Intercellullar junctions formed by cadherins, including desmosomes and adherens junctions, comprise two dimensional arrays of “trans” dimers formed between monomers emanating from opposing cell surfaces. Lateral “cis” interfaces between cadherins from the same cell surface have been proposed to play a role in cadherin clustering. Although the molecular details of cis interactions remain uncertain, they must define an anisotropic arrangement where binding is favorable only in certain orientations. Here we report Monte Carlo simulations performed on a 2D lattice constructed to account for the anisotropy in cadherin cis interactions. A crucial finding is that the “phase transition” between freely diffusing cadherin monomers and dimers and a condensed ordered 2D junction formed by dimers alone is a cooperative process involving both trans and cis interactions. Moreover, cis interactions, despite being too weak to be measured in solution, are critical to the formation of an ordered junction structure. We discuss these results in light of available experimental information on cadherin binding free energies that are transformed from their bulk solution values to interaction energies on a 2D lattice.

Wu, Yinghao; Jin, Xiangshu; Harrison, Oliver; Shapiro, Lawrence; Honig, Barry H.; Ben-Shaul, Avinoam

2010-01-01

69

High Dopant Activation And Low Damage P+ USJ Formation  

NASA Astrophysics Data System (ADS)

High dopant activation and low damage p+ ultra-shallow junctions (USJ) 15-20nm deep for 45nm node applications have been realized using B10H14 & B18H22 implant species along with flash, laser or SPE diffusion-less activation annealing techniques. New USJ metrology techniques were employed to determine: 1) dopant activation level and 2) junction quality (residual implant damage) using both contact and non-contact methods.

Borland, John; Shishiguchi, Seiichi; Mineji, Akira; Krull, Wade; Jacobson, Dale; Tanjyo, Masayasu; Lerch, Wilfried; Paul, Silke; Gelpey, Jeff; McCoy, Steve; Venturini, Julien; Current, Michael; Faifer, Vladimir; Hillard, Robert; Benjamin, Mark; Walker, Tom; Buczkowski, Andrzej; Li, Zhiqiang; Chen, James

2006-11-01

70

High Dopant Activation And Low Damage P+ USJ Formation  

Microsoft Academic Search

High dopant activation and low damage p+ ultra-shallow junctions (USJ) 15-20nm deep for 45nm node applications have been realized using B10H14 & B18H22 implant species along with flash, laser or SPE diffusion-less activation annealing techniques. New USJ metrology techniques were employed to determine: 1) dopant activation level and 2) junction quality (residual implant damage) using both contact and non-contact methods.

John Borland; Seiichi Shishiguchi; Akira Mineji; Wade Krull; Dale Jacobson; Masayasu Tanjyo; Wilfried Lerch; Silke Paul; Jeff Gelpey; Steve McCoy; Julien Venturini; Vladimir Faifer; Robert Hillard; Mark Benjamin; Tom Walker; Andrzej Buczkowski; Zhiqiang Li; James Chen

2006-01-01

71

Ultrashallow Junction Formation Using Low-Temperature Selective Si1-xGex Chemical Vapor Deposition  

NASA Astrophysics Data System (ADS)

In situ B doping and selective epitaxy on Si at 550° C in Si1- xGe x chemical vapor deposition (CVD) have been investigated for forming high-performance ultrashallow junctions. It was found that the incorporation rate of B increased proportionally with increasing B2H6 partial pressure, and was higher for the film with a higher Ge fraction x. Using Si3N4, thermal SiO2, phosphosilicate glass (PSG) and borophosphosilicate glass (BPSG) as mask film materials, about 40-nm-, 100-nm-, 150-nm- and 150-nm-thick B-doped Si0.5Ge0.5 films, respectively, were grown selectively on Si(100). Using this low-temperature selective Si1- xGe x CVD, a high-performance self-aligned ultrashallow junction formation has been achieved with a very low reverse current density, in the range of 10-10 A/cm2, without heat treatment.

Honma, Fumitaka; Murota, Junichi; Goto, Kinya; Maeda, Takahiro; Sawada, Yasuji

1994-04-01

72

Connexin43 Associated with an N-cadherin-containing Multiprotein Complex Is Required for Gap Junction Formation in NIH3T3 Cells  

Microsoft Academic Search

Previous studies have indicated an intimate linkage between gap junction and adherens junction formation. It was suggested this could reflect the close membrane- membrane apposition required for junction formation. In NIH3T3 cells, we observed the colocalization of con- nexin43 (Cx431) gap junction protein with N-cadherin, p120, and other N-cadherin-associated proteins at re- gions of cell-cell contact. We also found that

Chih-Jen Wei; Richard Francis; Xin Xu; Cecilia W. Lo

2005-01-01

73

A Drosophila neurexin is required for septate junction and blood-nerve barrier formation and function.  

PubMed

Septate and tight junctions are thought to seal neighboring cells together and to function as barriers between epithelial cells. We have characterized a novel member of the neurexin family, Neurexin IV (NRX), which is localized to septate junctions (SJs) of epithelial and glial cells. NRX is a transmembrane protein with a cytoplasmic domain homologous to glycophorin C, a protein required for anchoring protein 4.1 in the red blood cell. Absence of NRX results in mislocalization of Coracle, a Drosophila protein 4.1 homolog, at SJs and causes dorsal closure defects similar to those observed in coracle mutants. nrx mutant embryos are paralyzed, and electrophysiological studies indicate that the lack of NRX in glial-glial SJs causes a breakdown of the blood-brain barrier. Electron microscopy demonstrates that nrx mutants lack the ladder-like intercellular septa characteristic of pleated SJs (pSJs). These studies identify NRX as the first transmembrane protein of SJ and demonstrate a requirement for NRX in the formation of septate-junction septa and intercellular barriers. PMID:8978610

Baumgartner, S; Littleton, J T; Broadie, K; Bhat, M A; Harbecke, R; Lengyel, J A; Chiquet-Ehrismann, R; Prokop, A; Bellen, H J

1996-12-13

74

Ultra-shallow fluorine and nitrogen implantation from r.f. plasma and its effect on electro-physical parameters of Al/HfO2/Si MOS structures  

NASA Astrophysics Data System (ADS)

This study described a novel and original method of ultra-shallow fluorine and nitrogen implantation from radio frequency (RF = 13,56MHz) CF4 and NH3 plasmas, performed in classical RIE / PECVD reactors. The performed experiments indicate that ultra-shallow implantation of high concentration of fluorine and nitrogen ions by using r.f. plasma reactors (PECVD ad RIE) is feasible. It is also possible to control the implantation process parameters, ie implantation depth and maximum concentration, by controlling the parameters of the plasma processes. Electrical characterization of MOS structures with HfO2 layer as a gate dielectric, shows that samples implanted with nitrogen, have the best insulating properties, better even the reference sample. Samples prepared by fluorine implantation, exhibit much worse I-V behavior for low, medium and high electric fields, than all samples studied in this article. This samples exhibit the highest leakage currents, too.

Kalisz, M.; Mroczy?ski, R.; Szyma?ska, M.

2013-07-01

75

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

PubMed Central

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.

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

2012-01-01

76

High-resolution ultra-shallow subsurface imaging by integrating near-surface seismic reflection and ground-penetrating radar data in the depth domain  

NASA Astrophysics Data System (ADS)

This study presents the integration of complementary near-surface geophysical methods for high-resolution ultra-shallow imaging of the subsurface. Shallow-seismic reflection (SSR) and ground-penetrating radar (GPR) data of approximately the same wavelength were collected along a coincident survey line. The top of the saturated zone was successfully imaged using both techniques, but no significant reflectors were imaged above the water table using SSR or below the water table using GPR. The SSR and GPR data sets were depth converted and merged into a single data set, resulting in a more complete image of the subsurface than either method can provide alone. Instead of having two sections representing depths of ˜ 0 5 m (GPR) and ˜ 4 30 m (SSR), the combined section includes the near-surface stratigraphy, water table, and bedrock, among other geologic features. It is important to note that this method of data merging is intended only for qualitative interpretation of layers of differing electrical and elastic properties. In the case shown here, the two geophysical methods image comparable features in depth, but they respond to different physical properties.

Sloan, Steven D.; Tsoflias, Georgios P.; Steeples, Don W.; Vincent, Paul D.

2007-07-01

77

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

PubMed Central

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

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

1979-01-01

78

Electrical stimulation accelerates neuromuscular junction formation through ADAM19/neuregulin/ErbB signaling in vitro.  

PubMed

The mechanism by which electrical stimulation affects formation of neuromuscular junctions (NMJs) remains unknown. NG108-15, a neural cell line, is commonly used in in vitro co-culture models of myotubes to observe synapse formation; therefore, we employed this model to observe the effects of electrical stimulation on NMJ formation. Initially, L6 cells were differentiated and NG108-15 cells were then added to the same culture dish. After 2 and 3 days of co-culture, the cells were electrically stimulated at 50 V and 0.5 Hz for 0, 5, 30, and 60 min (C, ES5, ES30, and ES60 groups, respectively) and were analyzed after co-culture for 4 days. Immunofluorescence experiments showed significantly increased aggregation of acetylcholine receptors and inhibition of neural outgrowth in the ES30 and ES60 groups. Furthermore, ADAM19 and phospho-ErbB3 were found to be specifically localized in co-cultured NG108-15 cells. Immunoblotting demonstrated that synapsin 1, ADAM19 precursor and its activated form, phospho-ErbB3, and ERK1 protein levels had increased in an electrical stimulation period-dependent manner. Thus, we found that electrical stimulation accelerated NMJ formation, possibly through activation of ADAM19/neuregulin/ErbB signaling in NG108-15 cells. PMID:23603262

Fukazawa, Takahiro; Matsumoto, Masaya; Imura, Takeshi; Khalesi, Elham; Kajiume, Teruyuki; Kawahara, Yumi; Tanimoto, Keiji; Yuge, Louis

2013-04-19

79

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

PubMed Central

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.

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

1981-01-01

80

Local electrical stress-induced doping and formation of monolayer graphene P-N junction  

SciTech Connect

We demonstrated doping in monolayer graphene via local electrical stressing. The doping, confirmed by the resistance-voltage transfer characteristics of the graphene system, is observed to continuously tunable from N-type to P-type as the electrical stressing level (voltage) increases. Two major physical mechanisms are proposed to interpret the observed phenomena: modifications of surface chemistry for N-type doping (at low-level stressing) and thermally-activated charge transfer from graphene to SiO{sub 2} substrate for P-type doping (at high-level stressing). The formation of P-N junction on two-dimensional graphene monolayer is demonstrated with complementary doping based on locally applied electrical stressing.

Yu Tianhua; Liang Chenwei; Kim, Changdong; Yu Bin [College of Nanoscale Science and Engineering, State University of New York, Albany, New York 12203 (United States)

2011-06-13

81

Tetraspanin Protein CD9 Is a Novel Paranodal Component Regulating Paranodal Junctional Formation  

Microsoft Academic Search

The axoglial paranodal junction is essential for the proper localization of ion channels around the node of Ranvier. The integrity of this junction is important for nerve conduction. Although recent studies have made significant progress in understanding the molecular composition of the paranodal junction, it is not known how these membrane components are distributed to the appropriate sites and interact

Tomoko Ishibashi; Lei Ding; Kazuhiro Ikenaka; Yoshiro Inoue; Kenji Miyado; Eisuke Mekada; Hiroko Baba

2004-01-01

82

Physical understanding of cryogenic implant benefits for electrical junction stability  

SciTech Connect

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.

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

83

Electrical current induced pinhole formation and insulator-metal transition in tunnel junctions.  

PubMed

Current induced resistance switching (CIS) was recently observed in thin tunnel junctions (TJs) with ferromagnetic (FM) electrodes and was attributed to electromigration of metallic atoms in nanoconstrictions in the insulating barrier. Here the CIS effect is studied in TJs with two thin (20 Å) non-magnetic (NM) Ta electrodes inserted above and below the insulating barrier. We observe resistance (R) switching for positive applied electrical current (flowing from the bottom to the top lead), characterized by a continuous decrease in resistance and associated with current-driven displacement of metallic ions from the bottom electrode into the barrier (thin barrier state). For negative currents, displaced ions return to their initial positions in the electrode and the electrical resistance gradually increases (thick barrier state). We measured the temperature (T) dependence of the electrical resistance of both thin- and thick-barrier states (R(b) and R(B), respectively). Experiments showed a weaker R(T) variation when the tunnel junction is in the R(b) state, associated with a smaller tunnel contribution. By applying large enough electrical currents we induced large irreversible R decreases in the studied TJs, associated with barrier degradation. We then monitored the evolution of the R(T) dependence for different stages of barrier degradation. In particular, we observed a smooth transition from tunnel- to metallic-dominated transport. The initial degradation stages are related to irreversible decreases in barrier thickness (without the formation of pinholes). Only for later stages of barrier degradation do we have the appearance of metallic paths between the two electrodes that, however, do not lead to metallic-dominated transport for small enough pinhole radius. PMID:21690953

Ventura, J; Zhang, Z; Liu, Y; Sousa, J B; Freitas, P P

2007-03-28

84

Formation and propagation of p-n junction in p-(HgCd)Te caused by dry etching  

Microsoft Academic Search

The extended model describing the formation and propagation of a converted n-type layer in p-(HgCd)Te during dry etching (DE)\\u000a based on the ultrafast diffusion of Hg interstitials and their recombination with Hg vacancies is presented. A couple of one-\\u000a and two-dimensional equations are solved numerically to characterize the kinetics of the p-n junction. The time dependence\\u000a of the p-n junction

E. Belas; R. Grill; J. Franc; H. Sitter; P. Moravec; P. Höschl; A. L. Toth

2002-01-01

85

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

NASA Astrophysics Data System (ADS)

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

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

86

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

PubMed Central

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

Iden, Sandra; Misselwitz, Steve; Peddibhotla, Swetha S.D.; Tuncay, Huseyin; Rehder, Daniela; Gerke, Volker; Robenek, Horst; Suzuki, Atsushi

2012-01-01

87

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

PubMed

The PAR-3-atypical protein kinase C (aPKC)-PAR-6 complex has been implicated in the development of apicobasal polarity and the formation of tight junctions (TJs) in vertebrate epithelial cells. It is recruited by junctional adhesion molecule A (JAM-A) to primordial junctions where aPKC is activated by Rho family small guanosine triphosphatases. In this paper, we show that aPKC can interact directly with JAM-A in a PAR-3-independent manner. Upon recruitment to primordial junctions, aPKC phosphorylates JAM-A at S285 to promote the maturation of immature cell-cell contacts. In fully polarized cells, S285-phosphorylated JAM-A is localized exclusively at the TJs, and S285 phosphorylation of JAM-A is required for the development of a functional epithelial barrier. Protein phosphatase 2A dephosphorylates JAM-A at S285, suggesting that it antagonizes the activity of aPKC. Expression of nonphosphorylatable JAM-A/S285A interferes with single lumen specification during cyst development in three-dimensional culture. Our data suggest that aPKC phosphorylates JAM-A at S285 to regulate cell-cell contact maturation, TJ formation, and single lumen specification. PMID:22371556

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

2012-02-27

88

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

NASA Astrophysics Data System (ADS)

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.

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

2012-08-01

89

A Drosophila Neurexin Is Required for Septate Junction and Blood-Nerve Barrier Formation and Function  

Microsoft Academic Search

Septate and tight junctions are thought to seal neighboring cells together and to function as barriers between epithelial cells. We have characterized a novel member of the neurexin family, Neurexin IV (NRX), which is localized to septate junctions (SJs) of epithelial and glial cells. NRX is a transmembrane protein with a cytoplasmic domain homologous to glycophorin C, a protein required

Stefan Baumgartner; J. Troy Littleton; Kendal Broadie; Manzoor A. Bhat; Ruth Harbecke; Judith A. Lengyel; Ruth Chiquet-Ehrismann; Andreas Prokop; Hugo J Bellen

1996-01-01

90

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

PubMed Central

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

Snow, Chelsi J.; Henry, Clarissa A.

2009-01-01

91

Axonal ensheathment and septate junction formation in the peripheral nervous system of Drosophila.  

PubMed

Axonal insulation is critical for efficient action potential propagation and normal functioning of the nervous system. In Drosophila, the underlying basis of nerve ensheathment is the axonal insulation by glial cells and the establishment of septate junctions (SJs) between glial cell membranes. However, the details of the cellular and molecular mechanisms underlying axonal insulation and SJ formation are still obscure. Here, we report the characterization of axonal insulation in the Drosophila peripheral nervous system (PNS). Targeted expression of tau-green fluorescent protein in the glial cells and ultrastructural analysis of the peripheral nerves allowed us to visualize the glial ensheathment of axons. We show that individual or a group of axons are ensheathed by inner glial processes, which in turn are ensheathed by the outer perineurial glial cells. SJs are formed between the inner and outer glial membranes. We also show that Neurexin IV, Contactin, and Neuroglian are coexpressed in the peripheral glial membranes and that these proteins exist as a complex in the Drosophila nervous system. Mutations in neurexin IV, contactin, and neuroglian result in the disruption of blood-nerve barrier function in the PNS, and ultrastructural analyses of the mutant embryonic peripheral nerves show loss of glial SJs. Interestingly, the murine homologs of Neurexin IV, Contactin, and Neuroglian are expressed at the paranodal SJs and play a key role in axon-glial interactions of myelinated axons. Together, our data suggest that the molecular machinery underlying axonal insulation and axon-glial interactions may be conserved across species. PMID:16554482

Banerjee, Swati; Pillai, Anilkumar M; Paik, Raehum; Li, Jingjun; Bhat, Manzoor A

2006-03-22

92

Nedd4-2 interacts with occludin to inhibit tight junction formation and enhance paracellular conductance in collecting duct epithelia.  

PubMed

Nedd4-2, a E3 ubiquitin ligase, regulates epithelial sodium channel-mediated transcellular Na(+) transport in the collecting duct. We investigated the effect of Nedd4-2 on the junctional complex and paracellular conductance in mpkCCD(c14) cells, a collecting duct cell line. We demonstrate that Nedd4-2 coimmunoprecipitated with and reduced the expression of transfected occludin in HEK293 cells. This interaction was mediated via a conserved PY motif in the COOH terminus of occludin and mutation of this PY motif increased the half-life of transfected occludin in HEK293 cells from 6.4 to 11.4 h. We demonstrate that Nedd4-2 ubiquitinates occludin, which was not seen when a catalytically inactive form of Nedd4-2 was used. Overexpression of Nedd4-2 in mpkCCD(c14) cells reduced occludin at the tight junction and transiently increased paracellular conductance in a Ca(2+) switch assay consistent with a delay in the formation of tight junctions. Conversely, siRNA-mediated knockdown of Nedd4-2 increased occludin levels and reduced paracellular conductance. In summary, we demonstrate that Nedd4-2 plays a role in tight junction assembly and the regulation of paracellular conductance in the collecting duct. PMID:20504882

Raikwar, Nandita S; Vandewalle, Alain; Thomas, Christie P

2010-05-26

93

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

NASA Astrophysics Data System (ADS)

The principal enigma of large obducted ophiolite slabs is that they clearly must have been generated by some form of organized sea-floor spreading/plate-accretion, such as may be envisioned for the oceanic ridges, yet the volcanics commonly have arc affinity (Miyashiro) with boninites (high-temperature/low-pressure, high Mg and Si andesites), which are suggestive of a forearc origin. PT conditions under which boninites and metamorphic soles form and observations of modern forearc systems lead us to the conclusion that ophiolite formation is associated with overidding plate spreading centers that intersect the trench to form ridge-trench-trench of ridge-trench-tranform triple junctions. The spreading centers extend and lengthen the forearc parallel to the trench and by definition are in supra-subduction zone (SSZ) settings. Many ophiolites likewise have complexly-deformed associated mafic-ultramafic assemblages that suggest fracture zone/transform t along their frontal edges, which in turn has led to models involving the nucleation of subduction zones on fracture zones or transpressional transforms. Hitherto, arc-related sea-floor-spreading has been considered to be either pre-arc (fore-arc boninites) or post-arc (classic Karig-style back arc basins that trench-parallell split arcs). Syn-arc boninites and forearc oceanic spreading centers that involve a stable ridge/trench/trench triple or a ridge-trench-transform triple junction, the ridge being between the two upper plates, are consistent with large slab ophiolite formation in a readied obduction settting. The direction of subduction must be oblique with a different sense in the two subduction zones and the oblique subduction cannot be partitioned into trench orthogonal and parallel strike-slip components. As the ridge spreads, new oceanic lithosphere is created within the forearc, the arc and fore-arc lengthen significantly, and a syn-arc ophiolite forearc complex is generated by this mechanism. The ophiolite ages along arc-strike; a distinctive diachronous MORB-like to boninitic to arc volcanic stratigraphy develops vertically in the forearc and eruption centers progressively migrate from the forearc back to the main arc massif with time. Dikes in the ophiolite are highly oblique to the trench (as are back-arc magnetic anomalies. Boninites and high-mg andesites are generated in the fore-arc under the aqueous, low pressure/high temperature, regime at the ridge above the instantaneously developed subducting and dehydrating slab. Subducted slab refrigeration of the hanging wall ensues and accretion of MORB metabasites to the hanging wall of the subduction channel initiates. Mafic protolith garnet/two pyroxene granulites to greenschists accrete and form the inverted P and T metamorphic sole prior to obduction. Sole accretion of lithosphere begins at about 1000°C and the full retrogressive sole may be fully formed within ten to fifteen million years of accretion, at which time low grade subduction melanges accrete. Obduction of the SSZ forearc ophiolite with its subjacent metamorphic sole occurs whenever the oceanic arc attempts subduction of a stable buoyant continental or back arc margin.

Casey, John; Dewey, John

2013-04-01

94

Incorporation of CC Steps into Z-DNA: Interplay Between B/Z Junction and Z-DNA Helical Formation  

PubMed Central

The left-handed DNA structure, Z-DNA, is believed to play important roles in gene expression and regulation. Z-DNA forms sequence-specifically with a preference for sequences rich in pyrimidine/purine dinucleotide steps. In vivo, Z-DNA is generated in the presence of negative supercoiling or upon binding proteins that absorb the high energetic cost of the B-to-Z transition including the creation of distorted junctions between B-DNA and Z-DNA. To date, the sequence-preferences for the B-to-Z transition have primarily been studied in the context of sequence repeats lacking B/Z junctions. Here, we develop a method to characterize sequence-specific preferences for Z-DNA formation and B/Z junction localization within heterogeneous DNA duplexes that is based on combining 2-aminopurine fluorescence measurements with a new quantitative application of CD spectroscopy for determining the fraction of B- versus Z-DNA. Using this approach, we show that at least three consecutive CC dinucleotide steps, traditionally thought to disfavor Z-DNA, can be incorporated within heterogeneous Z-DNA containing B/Z junctions upon binding to the Z? domain of the RNA adenosine deaminase (ADAR1) protein. Our results indicate that the incorporation of CC steps into Z-DNA is driven by favorable sequence-specific Z/Z and B/Z stacking interactions as well as by sequence-specific energetics that localize the distorted B/Z junction at flexible sites. Together, our results expose higher order complexities in the Z-DNA code within heterogeneous sequences and suggest that Z-DNA can in principle propagate into a wider range of genomic sequence elements than previously thought.

Bothe, Jameson R.; Lowenhaupt, Ky; Al-Hashimi, Hashim M.

2013-01-01

95

Sub-100 mn p+/n junction formation using plasma immersion ion implantation  

NASA Astrophysics Data System (ADS)

Using plasma immersion ion implantation (PIII), sub-100 nm p+/n junctions were fabricated with SiF4 preamorphization followed by BF3 doping. With this technique, the dose rate can be as high as 1016/cm2 per second. The silicon wafer was immersed in SiF4 or BF3 plasma and biased with a negative voltage. The positively charged ions were accelerated by the electric field in the plasma sheath and implanted into the wafer. The junction depth can be controlled by varying the negative voltage applied to the wafer holder and thermal annealing conditions.

Qian, X. Y.; Cheung, N. W.; Lieberman, M. A.; Current, M. I.; Chu, P. K.; Harrington, W. L.; Magee, C. W.; Botnick, E. M.

1991-04-01

96

A new approach to photovoltaic junction formation by using pulse implantation doping technique  

Microsoft Academic Search

The paper presents the first demonstration of a new method of forming photovoltaic p-n junction in silicon by the « Pulse Implantation Doping (PID) » technique. In this technique, an intense ion pulse provides both the dose necessary for doping and the portion of energy required to recrystallize a damage-free, doped surface layer. The ion beam pulses within the range

J. Piekoszewski; J. Langner; Z. Werner; G. C. Huth

1982-01-01

97

The SARS coronavirus E protein interacts with PALS1 and alters tight junction formation and epithelial morphogenesis.  

PubMed

Intercellular tight junctions define epithelial apicobasal polarity and form a physical fence which protects underlying tissues from pathogen invasions. PALS1, a tight junction-associated protein, is a member of the CRUMBS3-PALS1-PATJ polarity complex, which is crucial for the establishment and maintenance of epithelial polarity in mammals. Here we report that the carboxy-terminal domain of the SARS-CoV E small envelope protein (E) binds to human PALS1. Using coimmunoprecipitation and pull-down assays, we show that E interacts with PALS1 in mammalian cells and further demonstrate that the last four carboxy-terminal amino acids of E form a novel PDZ-binding motif that binds to PALS1 PDZ domain. PALS1 redistributes to the ERGIC/Golgi region, where E accumulates, in SARS-CoV-infected Vero E6 cells. Ectopic expression of E in MDCKII epithelial cells significantly alters cyst morphogenesis and, furthermore, delays formation of tight junctions, affects polarity, and modifies the subcellular distribution of PALS1, in a PDZ-binding motif-dependent manner. We speculate that hijacking of PALS1 by SARS-CoV E plays a determinant role in the disruption of the lung epithelium in SARS patients. PMID:20861307

Teoh, Kim-Tat; Siu, Yu-Lam; Chan, Wing-Lim; Schlüter, Marc A; Liu, Chia-Jen; Peiris, J S Malik; Bruzzone, Roberto; Margolis, Benjamin; Nal, Béatrice

2010-09-22

98

Lindane, a gap junction blocker, suppresses FSH and transforming growth factor  1-induced connexin43 gap junction formation and steroidogenesis in rat granulosa cells  

Microsoft Academic Search

The present study was designed to explore the role of gap junctions in follicle-stimulating hormone (FSH) and trans- forming growth factor 1 (TGF1)-stimulated steroido- genesis in ovarian granulosa cells of gonadotropin-primed immature rats. There were three specific aims. First, we investigated the effect of FSH and TGF1 as well as lindane (a general gap junction blocker) on the level of

Ferng-Chun Ke; Su-Huan Fang; Ming-Ting Lee; Shiow-Yhu Sheu; Si-Yi Lai; Yun Ju Chen; Fore-Lien Huang; Paulus S Wang; Douglas M Stocco; Jiuan-Jiuan Hwang

2005-01-01

99

Formation and Disassembly of Adherens and Tight Junctions in the Corneal Endothelium: Regulation by Actomyosin Contraction  

PubMed Central

Purpose. To determine the role of actin cytoskeleton in the disassembly and reformation of adherens junctions (AJs) and tight junctions (TJs) in bovine corneal endothelial monolayers. Methods. Disassembly and reformation of AJs and TJs were induced by extracellular Ca2+ depletion and subsequent add-back of Ca2+, respectively. Resultant changes in the transendothelial electrical resistance (TER), an indicator of integrity of TJs, were measured based on electrical cell-substrate impedance. Phosphorylated myosin light chain (ppMLC), a biochemical measure of actomyosin contraction, and activation of its upstream regulatory molecule RhoA-GTP were assessed by Western blot analysis. Results. Extracellular Ca2+ depletion led to activation of RhoA, increase in ppMLC, decrease in TER, contraction of the perijunctional actomyosin ring (PAMR), and redistribution of zonula occludens-1 (ZO-1) and cadherins. These effects were reversed on Ca2+ add-back. Pretreatment with Y-27632 and blebbistatin (as inhibitors of actomyosin contraction) reduced the rate of decline in TER, opposed the contraction of the PAMR, and blocked the redistribution of ZO-1 and cadherins. Both drugs reduced the recovery in TER and opposed the normal redistribution of ZO-1 and cadherins on Ca2+ add-back. Cytochalasin D, which led to dissolution of the PAMR, also reduced the recovery of TER on Ca2+ add-back. Conclusions. The (Ca2+ depletion)-induced disassembly of AJs accelerates the breakdown of TJs through a concomitant increase in the actomyosin contraction of the PAMR. However, these data on reassembly show that a contractile tone of the PAMR is essential for assembly of the apical junctional complex.

Ramachandran, Charanya

2010-01-01

100

Spatial Pattern of Hotspot Dispersion in Plume-Triple Junction Interaction: Numerical Models of the Azores and Implications for the Formation of LIPs  

NASA Astrophysics Data System (ADS)

The interaction between a mantle plume and tectonic plate boundaries can produce excess magmatism and create an oceanic plateau. This study investigates how the spatial pattern of plume dispersion differs when a plume upwells underneath a triple junction as opposed to a single ridge. Model results are presented for the Azores triple junction, and general inferences are drawn about the importance of triple junction configuration in the generaton of large igneous provinces. The Azores hotspot is located near a plate boundary triple junction consisting of the Terceira Rift (TER) and two branches of the Mid-Atlantic Ridge (MAR). The seafloor expression of the Azores hotspot has a complex spatial pattern. Latitudinal anomalies along the MAR extend farther to the south of the inferred location of the mantle heterogeneity than to the north. Longitudinal anomalies span a greater distance to the east of the MAR (along the TER) than to the west. A finite element model is used to calculate the dispersion of thermally-buoyant material simulating a mantle plume for two contrasting cases. In one case, model-prescribed plate motion vectors approximate the kinematics of the Azores triple junction during a main phase of plateau formation ~7 Ma. In this case, divergence of the three plates tends to drive plume material preferentially southward and eastward, consistent with observed anomalies. In a second numerical experiment, spreading is "turned off" for the TER, resulting in focused plume expression along the MAR only, less consistent with patterns of volcanism across the plateau. Thus, the intersection of two ridge systems at a triple junction may be important for increasing the spatial extent of seafloor anomalies created by a near-ridge plume. By analogy, triple junction plate boundary geometry may amplify the expression of a mantle heterogeneity, a potentially important process in the formation of a large igneous province.

Georgen, J. E.

2011-12-01

101

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

Microsoft Academic Search

The formation of DNA three-way junction (3WJ) structures has been utilised to develop a novel isothermal nucleic acid amplification assay (SMART) for the detection of specific DNA or RNA targets. The assay consists of two oligonucleotide probes that hybridise to a specific target sequence and, only then, to each other forming a 3WJ structure. One probe (template for the RNA

Susan D. Wharam; Peter Marsh; John S. Lloyd; Trevor D. Ray; Graham A. Mock; René Assenberg; Julie E. McPhee; Philip Brown; Anthony Weston; Donald L. N. Cardy

2001-01-01

102

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

NASA Astrophysics Data System (ADS)

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

Urban, Alexander; Ermentrout, Bard

2012-07-01

103

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

PubMed Central

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

Saez, Pablo J.; Shoji, Kenji F.; Retamal, Mauricio A.; Harcha, Paloma A.; Ramirez, Gigliola; Jiang, Jean X.; von Bernhardi, Rommy; Saez, Juan C.

2013-01-01

104

Regulation of axonal growth and neuromuscular junction formation by neuronal phosphatase and tensin homologue signaling  

PubMed Central

During the development of the vertebrate neuromuscular junction (NMJ), motor axon tips stop growing after contacting muscle and transform into presynaptic terminals that secrete the neurotransmitter acetylcholine and activate postsynaptic ACh receptors (AChRs) to trigger muscle contraction. The neuron-intrinsic signaling that retards axonal growth to facilitate stable nerve–muscle interaction and synaptogenesis is poorly understood. In this paper, we report a novel function of presynaptic signaling by phosphatase and tensin homologue (PTEN) in mediating a growth-to-synaptogenesis transition in neurons. In Xenopus nerve–muscle cocultures, axonal growth speed was halved after contact with muscle, when compared with before contact, but when cultures were exposed to the PTEN blocker bisperoxo (1,10-phenanthroline) oxovanadate, axons touching muscle grew ?50% faster than their counterparts in control cultures. Suppression of neuronal PTEN expression using morpholinos or the forced expression of catalytically inactive PTEN in neurons also resulted in faster than normal axonal advance after contact with muscle cells. Significantly, interference with PTEN by each of these methods also led to reduced AChR clustering at innervation sites in muscle, indicating that disruption of neuronal PTEN signaling inhibited NMJ assembly. We thus propose that PTEN-dependent slowing of axonal growth enables the establishment of stable nerve–muscle contacts that develop into NMJs.

Li, Pan P.; Peng, H. Benjamin

2012-01-01

105

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

PubMed

The junctional epithelium (JE) adheres to the tooth surface, and seals off periodontal tissues from the oral environment. This incompletely differentiated epithelium is formed initially by the fusion of the reduced enamel organ with the oral epithelium (OE). Two proteins, odontogenic ameloblast-associated (ODAM) and amelotin (AMTN), have been identified in the JE. The objective of this study was to evaluate their expression pattern during formation and regeneration of the JE. Cytokeratin 14 was used as a differentiation marker for oral epithelial cells, and Ki67 for cell proliferation. Immunohistochemistry was carried out on erupting rat molars, and in regenerating JE following gingivectomy. In the reducing enamel organ and in established JE, ODAM and AMTN were present at the cell-tooth interface while only ODAM and CK14 were found throughout the JE. Both were also conspicuously present in cell clusters situated between the erupting tooth and OE. During JE regeneration, ODAM was detected first at the leading wound edge and then in the regenerating JE. Some cell clusters in the subjacent connective tissue were also positive for ODAM. AMTN appeared later and both AMTN and ODAM accumulated at the interface with the tooth. Cytokeratin 14 gradually appeared in the regenerating JE but the cell clusters showed variable labeling. Cells associated with JE formation and regeneration exhibited higher division activity than adjacent epithelial cells. These findings suggest that ODAM and AMTN have a role at the cell-tooth interface, and that ODAM is likely also implicated in cellular events during formation and regeneration of the JE. PMID:21154245

Nishio, Clarice; Wazen, Rima; Kuroda, Shingo; Moffatt, Pierre; Nanci, Antonio

2010-12-10

106

Myosins in cell junctions  

PubMed Central

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.

Liu, Katy C.; Cheney, Richard E.

2012-01-01

107

Rab3Gap1 mediates exocytosis of Claudin-1 and tight junction formation during epidermal barrier acquisition.  

PubMed

Epidermal barrier acquisition during late murine gestation is accompanied by an increase in Akt kinase activity and cJun dephosphorlyation. The latter is directed by the Ppp2r2a regulatory subunit of the Pp2a phosphatase. This was accompanied by a change of Claudin-1 localisation to the cell surface and interaction between Occludin and Claudin-1 which are thought to be required for tight junction formation. The aim of this study was to determine the nature of the barrier defect caused by the loss of AKT/Ppp2r2a function. There was a paracellular barrier defect in rat epidermal keratinocytes expressing a Ppp2r2a siRNA. In Ppp2r2a knockdown cells, Claudin-1 was located to the cytoplasm and its expression was increased. Inhibiting cJun phosphorylation restored barrier function and plasma membrane localisation of Claudin-1. Expression of the Rab3 GTPase activating protein, Rab3Gap1, was restored in Ppp2r2a siRNA cells when cJun phosphorylation was inhibited. During normal mouse epidermal development, Claudin-1 plasma membrane localisation and Rab3Gap1 cell surface expression were co-incident with Akt activation in mouse epidermis, strongly suggesting a role of Rab3Gap1 in epidermal barrier acquisition. Supporting this hypothesis, siRNA knockdown of Rab3Gap1 prevented plasma membrane Claudin-1 expression and the formation of a barrier competent epithelium. Replacing Rab3Gap1 in Ppp2r2a knockdown cells was sufficient to rescue Claudin-1 transport to the cell surface. Therefore these data suggest Rab3Gap1 mediated exocytosis of Claudin-1 is an important component of epidermal barrier acquisition during epidermal development. PMID:23685254

Youssef, G; Gerner, L; Naeem, A S; Ralph, O; Ono, M; O'Neill, C A; O'Shaughnessy, R F L

2013-05-16

108

Clathrin Dependence of Synaptic Vesicle Formation at the Drosophila Neuromuscular Junction  

PubMed Central

SUMMARY Background Among the most prominent molecular constituents of a recycling synaptic vesicle is the clathrin triskelion, composed of clathrin light chain (Clc) and clathrin heavy chain (Chc). Remarkably, it remains unknown whether clathrin is strictly necessary for the stimulus-dependent re-formation of a synaptic vesicle and, conversely, whether clathrin-independent vesicle endocytosis exists at the neuronal synapse. Results We employ FlAsH-FALI mediated protein photoinactivation to rapidly (3 minutes) and specifically disrupt Clc function at the Drosophila NMJ. We first demonstrate that Clc photoinactivation does not impair synaptic vesicle fusion. We then provide electrophysiological and ultrastructural evidence that synaptic vesicles, once fused with the plasma membrane, cannot be re-formed following Clc photoinactivation. Finally, we demonstrate that stimulus-dependent membrane internalization occurs following Clc photoinactivation. However, newly internalized membrane fails to resolve into synaptic vesicles. Rather, newly internalized membrane forms large and extensive internal membrane compartments that are never observed at a wild-type synapse. Conclusions We make three major conclusions. 1) FlAsH-FALI mediated protein photoinactivation rapidly and specifically disrupts Clc function with no effect on synaptic vesicle fusion. 2) Synaptic vesicle reformation does not occur following Clc photoinactivation. By extension, clathrin-independent “kiss-and-run” endocytosis does not sustain synaptic transmission during a stimulus train at this synapse. 3) Stimulus-dependent, clathrin-independent membrane internalization exists at this synapse, but it is unable to generate fusion competent, small-diameter synaptic vesicles.

Heerssen, Heather; Fetter, Richard D.

2009-01-01

109

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

SciTech Connect

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.

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

110

Sub-Gap Currents in Nb\\/Al\\/AlOx\\/Nb Josephson Junctions and Their Dependence on the Method of Barrier Formation  

Microsoft Academic Search

Josephson tunnel-junctions have been fabricated using two different methods of barrier formation. Both types of devices start with single-crystal Nb\\/Al bi-layers grown by molecular beam epitaxy on A-plane sapphire. It is found that complete wetting of the Nb layer is achieved with 20 nm of Al evaporated at room temperature. The barrier is then formed either by thermal oxidation of

Paul B. Welander; Tim J. McArdle; Stephanie Law; James N. Eckstein

2008-01-01

111

Junctional adhesion molecule-A participates in the formation of apico-basal polarity through different domains  

Microsoft Academic Search

Junctional adhesion molecule (JAM)-A is an integral membrane protein at tight junctions of epithelial cells which associates with the cell polarity protein PAR-3. Here, we demonstrate that downregulation of JAM-A impairs the ability of MDCK II cells to form cysts in a three-dimensional matrix indicating the requirement of JAM-A for the development of apico-basal polarity. To define the regions of

Daniela Rehder; Sandra Iden; Ines Nasdala; Joachim Wegener; Maria-Katharina Meyer Zu Brickwedde; Dietmar Vestweber; Klaus Ebnet

2006-01-01

112

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

PubMed

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

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

2013-09-16

113

Josephson junction  

DOEpatents

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

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

1995-05-02

114

Effects of substrate and Na concentration on device properties, junction formation, and film microstructure in CuInSe2 PV devices  

NASA Astrophysics Data System (ADS)

Different concentrations of Na were systematically introduced into CuInSe2 (CIS) photovoltaic solar cell absorber material on different substrates (SLG, SiO2/SLG, 7059, alumina) to: 1) determine the resultant effects on device properties, junction formation, and material microstructure; and 2) determine the optimal range of Na concentrations in the CIS films per specific substrate. In general, finished devices show improved Voc, Jsc, and device efficiency, improved charge-collection efficiency and, possibly, increased grain size as a result of the coevaporation of 4 to 100 mg of Na2Se during film deposition. However, a dramatic devolution set in with the addition of 235 mg of Na2Se, and all the aforementioned parameters were either at, or worse than, their pre-Na-addition levels. Meanwhile, although the device microstructure improves with Na addition and, more importantly, the junction (as characterized by electron-beam-induced current) has become much more uniform and closer to the heteroface, all that reverses with the ``Na overdose.''

Matson, R. J.; Granata, J. E.; Asher, S. E.; Young, M. R.

1999-03-01

115

Time-dependent effects of low-temperature atmospheric-pressure argon plasma on epithelial cell attachment, viability and tight junction formation in vitro  

NASA Astrophysics Data System (ADS)

The application of physical plasma to living tissues is expected to promote wound healing by plasma disinfection and stimulation of tissue regeneration. However, the effects of plasma on healthy cells must be studied and understood. In our experiments we used an argon plasma jet (kINPen®09) to gain insights into time-dependent plasma effects on cell attachment, viability and tight junction formation in vitro. Murine epithelial cells mHepR1 were suspended in complete cell culture medium and were irradiated with argon plasma (direct approach) for 30, 60 and 120 s. Suspecting that physical plasma may exert its effect via the medium, cell culture medium alone was first treated with argon plasma (indirect approach) and immediately afterwards, cells were added and also cultured for 24 h. Cell morphology and vitality were verified using light microscopy and an enzyme-linked immunosorbent assay. Already after 30 s of treatment the mHepR1 cells lost their capability to adhere and the cell vitality decreased with increasing treatment time. Interestingly, the same inhibitory effect was observed in the indirect approach. Furthermore, the argon plasma-treated culture medium-induced large openings of the cell's tight junctions, were verified by the zonula occludens protein ZO-1, which we observed for the first time in confluently grown epithelial cells.

Hoentsch, Maxi; von Woedtke, Thomas; Weltmann, Klaus-Dieter; Nebe, J. Barbara

2012-01-01

116

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

NASA Astrophysics Data System (ADS)

The large number and distribution of rollback systems in Mediterranean orogens infer the possibility of interacting extensional back-arc deformation driven by different slabs. The formation of the Pannonian back-arc basin is generally related to the rapid Miocene rollback of a slab attached to the European continent. A key area of the entire system that is neglected by kinematic studies is the connection between the South Carpathians and Dinarides. In order to derive an evolutionary model, we interpreted regional seismic lines traversing the entire Serbian part of the Pannonian Basin. The observed deformation is dominantly expressed by the formation of Miocene extensional detachments and (half) grabens. The extensional geometries and associated synkinematic sedimentation that migrated in time and space allow the definition of a continuous and essentially asymmetric early to late Miocene extensional evolution. This evolution was followed by the formation of few uplifted areas during the subsequent latest Miocene-Quaternary inversion. The present-day extensional geometry changing the strike across the basin is an effect of the clockwise rotation of the South Carpathians and Apuseni Mountains in respect to the Dinarides. Our study infers that the Carpathian rollback is not the only mechanism responsible for the formation of the Pannonian Basin; an additional middle Miocene rollback of a Dinaridic slab is required to explain the observed structures. Furthermore, the study provides constraints for the pre-Neogene orogenic evolution of this junction zone, including the affinity of major crustal blocks, obducted ophiolitic sequences and the Sava suture zone.

Matenco, L.; Radivojevi?, D.

2012-12-01

117

Endothelial cell–cell junctions: happy together  

Microsoft Academic Search

Junctional structures maintain the integrity of the endothelium. Recent studies have shown that, as well as promoting cell–cell adhesion, junctions might transfer intracellular signals that regulate contact-induced inhibition of cell growth, apoptosis, gene expression and new vessel formation. Moreover, modifications of the molecular organization and intracellular signalling of junctional proteins might have complex effects on vascular homeostasis.

Elisabetta Dejana

2004-01-01

118

Electron scattering effects at physisorbed hydrogen molecules on break-junction electrodes and nanowires formation in hydrogen environment  

NASA Astrophysics Data System (ADS)

Physisorption of hydrogen molecules on the surface of gold and other coinage metals has been studied using distance tunneling spectroscopy. We have observed that the distance dependence of the tunnel current (resistance) displays a strong N-shaped deviation from exponential behavior. Such deviations are difficult to explain within the Tersoff-Hamann approximation. We suggest the scattering of tunneling electrons by H2 molecules as an origin for the observed effect. We have found that this phenomenon is also common for strongly adsorbed organic molecules with a single anchoring group. Pulling Au, Cu and Pt nanowires at 22 K in hydrogen environment shows that the break-junction electrodes are still connected through hydrogen-metal monoatomic chains down to very low conductance values of 10-4-10-6 G0.

van der Maas, M.; Vasnyov, S.; Hendriksen, B. L. M.; Shklyarevskii, O. I.; Speller, S.

2012-06-01

119

Signaling from the podocyte intercellular junction to the actin cytoskeleton.  

PubMed

Observations of hereditary glomerular disease support the contention that podocyte intercellular junction proteins are essential for junction formation and maintenance. Genetic deletion of most of these podocyte intercellular junction proteins results in foot process effacement and proteinuria. This review focuses on the current understanding of molecular mechanisms by which podocyte intercellular junction proteins such as the nephrin-neph1-podocin-receptor complex coordinate cytoskeletal dynamics and thus intercellular junction formation, maintenance, and injury-dependent remodeling. PMID:22958485

George, Britta; Holzman, Lawrence B

2012-07-01

120

Hemicentin 2 and Fibulin 1 are required for epidermal-dermal junction formation and fin mesenchymal cell migration during zebrafish development  

PubMed Central

Summary Hemicentin 1 (Hmcn1) and Hemicentin 2 (Hmcn2) belong to the fibulin family of extracellular matrix (ECM) proteins that play pivotal roles during development and homeostasis of a variety of vertebrate tissues. Recently, we have shown that mutations in zebrafish Hmcn1, also called Fibulin 6, lead to massive fin blistering, similar to the defects caused by the Fraser syndrome gene Fras1. In contrast, the role of Hmcn2 during vertebrate development has thus far been uncharacterized. In zebrafish, hmcn2, like fibulin 1 (fbln1), another member of the fibulin family, is predominantly expressed in fin mesenchymal cells and developing somites, contrasting the strict epithelial expression of hmcn1. While antisense morpholino oligonucleotide (MO) – based knockdown of hmcn2 did not yield any discernable defects, hmcn2/fbln1 double knockdown fish displayed blistering in the trunk, pointing to an essential contribution of these proteins from mesodermal sources for proper epidermal-dermal junction formation. In contrast, and unlike hmcn1 mutants, epidermal-dermal junctions in the fin folds of hmcn2/fbln1 double knockdown fish were only moderately affected. Instead, they displayed impaired migration of fin mesenchymal cells into the fin folds, pointing to a crucial role of Hmcn2 and Fbln1 to remodel the ECM of the fin fold interepidermal space, which is a prerequisite for fibroblast ingrowth. TEM analyses suggest that this ECM remodeling occurs at the level of actinotrichia, the collageneous migration substrate of mesenchymal cells, and at the level of cross fibers, which resemble mammalian microfibers. This work provides first insights into the role of Hmcn2 during vertebrate development, identifying it as an evolutionary conserved protein that acts in functional redundancy with Fbln1C and/or Fbln1D isoforms to regulate tissue adhesion and cell migration, while extending current knowledge of the functions of vertebrate Fbln1.

Feitosa, Natalia Martins; Zhang, Jinli; Carney, Thomas J.; Metzger, Manuel; Korzh, Vladimir; Bloch, Wilhelm; Hammerschmidt, Matthias

2012-01-01

121

Analogues of Y27632 increase gap junction communication and suppress the formation of transformed NIH3T3 colonies  

Microsoft Academic Search

Background:Constitutive activation of RhoA-dependent RhoA kinase (ROCK) signalling is known to promote cellular transformation and the ROCK inhibitor Y-27632 has the ability to suppress focus formation of RhoA transformed NIH3T3 cells.Methods:Sixty-four novel structural analogues of Y27632 were synthesised and tested for their ability to persistently inhibit the transformation of NIH3T3 cells by Rho guanidine exchange factor 16 (ARHGEF16) or Ras.

L Hampson; X T He; A W Oliver; J A Hadfield; T Kemp; J Butler; A McGown; H C Kitchener; I N Hampson

2009-01-01

122

The formation, stability, and suitability of n-type junctions in germanium formed by solid phase epitaxial recrystallization  

NASA Astrophysics Data System (ADS)

Design and optimization of n-type doped regions in germanium by solid phase epitaxial recrystallization (SPER) have been studied by the authors. A systematic study is presented of process variables that influence activation and thermal stability, including preamorphization, coimplants, recrystallization temperature, and postrecrystallization thermal treatments. Unlike silicon, activation after recrystallization in germanium is not optimum where the postrecrystallization thermal budget is kept to a minimum. With the aid of modeling, a maximum peak activation of 7×1019 cm-3 was extracted. A steady increase in sheet resistance during postrecrystallization anneals confirms the formation of metastable activation by SPER. It is predicted that active concentrations of 6-8×1019 cm-3 are sufficient to meet targets for sub-20 nm technologies.

Duffy, R.; Shayesteh, M.; White, M.; Kearney, J.; Kelleher, A.-M.

2010-06-01

123

Reevaluation of magnetic chrons in the North Atlantic between 35°N and 47°N: Implications for the formation of the Azores Triple Junction and associated plateau  

NASA Astrophysics Data System (ADS)

In this paper we present a new magnetic compilation for an area of the North Atlantic located between 35°N and 47°N and up to anomaly 33r. We also present a strategy to pick magnetic isochrones and compute finite rotation poles. This technique is based on a continuous reduction to the pole technique and some basic assumptions regarding the direction of the remanent magnetization vector. A cost function that measures the misfit between interpreted and rotated isochrones and the systematic exploitation of the parameter space is used to compute the best set of finite Eulerian rotations for the chrons 5, 6, 6C, 11-12, 13, 18, 20, 21, 22, 23, 24, 25, 26, 28, 29, 30, 32, 33, and 33r. This set of chrons and poles is used to discuss the evolution of the North Atlantic close to Iberia and, in particular, the onset and early development of the Azores Triple Junction area. We show that the relative motion between the Eurasian and the African plates can be coherently described in terms of rigid plate kinematics, respecting both the anomalies shapes and the precise location of the main structural elements of the area: the Pico Fracture Zone, the East Azores Fracture Zone, and the Gloria Fault. We distinguish from the magnetic point of view two different areas of the Azores plateau: the South Azores domain where almost undisturbed NNW magnetic lineations can be found and the Azores domain close to the topographic highs and with no systematic magnetic stripping with the exception of a few recent lineations, probably Matuyama and Brunhes. We present an approximate reconstruction of the plate configuration after chron 18 to conclude that the attachment of Iberia to Eurasia was younger than previously thought (lower Miocene), triggering the formation of the Azores domain, in which stretching took place essentially in the last 20 Ma at an average rate of ˜3.8 mm/a, and progressively attaching the South Azores domain to the African plate by a northward progression of the triple junction.

Luis, J. F.; Miranda, J. M.

2008-10-01

124

The leading edge during dorsal closure as a model for epithelial plasticity: Pak is required for recruitment of the Scribble complex and septate junction formation.  

PubMed

Dorsal closure (DC) of the Drosophila embryo is a model for the study of wound healing and developmental epithelial fusions, and involves the sealing of a hole in the epidermis through the migration of the epidermal flanks over the tissue occupying the hole, the amnioserosa. During DC, the cells at the edge of the migrating epidermis extend Rac- and Cdc42-dependent actin-based lamellipodia and filopodia from their leading edge (LE), which exhibits a breakdown in apicobasal polarity as adhesions are severed with the neighbouring amnioserosa cells. Studies using mammalian cells have demonstrated that Scribble (Scrib), an important determinant of apicobasal polarity that functions in a protein complex, controls polarized cell migration through recruitment of Rac, Cdc42 and the serine/threonine kinase Pak, an effector for Rac and Cdc42, to the LE. We have used DC and the follicular epithelium to study the relationship between Pak and the Scrib complex at epithelial membranes undergoing changes in apicobasal polarity and adhesion during development. We propose that, during DC, the LE membrane undergoes an epithelial-to-mesenchymal-like transition to initiate epithelial sheet migration, followed by a mesenchymal-to-epithelial-like transition as the epithelial sheets meet up and restore cell-cell adhesion. This latter event requires integrin-localized Pak, which recruits the Scrib complex in septate junction formation. We conclude that there are bidirectional interactions between Pak and the Scrib complex modulating epithelial plasticity. Scrib can recruit Pak to the LE for polarized cell migration but, as migratory cells meet up, Pak can recruit the Scrib complex to restore apicobasal polarity and cell-cell adhesion. PMID:20501591

Bahri, Sami; Wang, Simon; Conder, Ryan; Choy, Juliana; Vlachos, Stephanie; Dong, Kevin; Merino, Carlos; Sigrist, Stephan; Molnar, Cristina; Yang, Xiaohang; Manser, Edward; Harden, Nicholas

2010-06-01

125

Challenges and current status in 300 mm rapid thermal processing  

Microsoft Academic Search

Rapid Thermal Processing (RTP) will be indispensable to meet the process requirements of future device and integrated circuit (IC) generations. The paper reviews several approaches to manage the challenges of single-wafer 300 mm heat treatment, including the most important issues in RTP system technology: temperature measurement and accuracy, fast ramp capability, process repeatability, ultra-shallow junction formation and process uniformity for

M Glück; W Lerch; D Löffelmacher; M Hauf; U Kreiser

1999-01-01

126

Electrical and Structural Characterization of Boron Implanted Silicon Following Laser Thermal Processing  

Microsoft Academic Search

One alternative to conventional rapid thermal annealing (RTA) of implants for ultra-shallow junction formation is that of laser annealing. Laser thermal processing (LTP) incorporates an excimer pulsed laser capable of melting the near surface region of the silicon (Si) substrate. The melt depth is dependent upon the energy density supplied by the irradiation source and the melting temperature of the

K. A. Gable; K. S. Jones; M. E. Law; L. S. Robertson; S. Talwar

127

Advanced thermal processing of semiconductor materials in the msec-range  

Microsoft Academic Search

This paper reviews the advances that flash lamp annealing brings to the processing of the most frequently used semiconductor materials, namely silicon and silicon carbide, thus enabling the fabrication of novel microelectronic structures and materials. The paper describes how such developments can translate into important practical applications leading to a wide range of technological benefits. Opportunities in ultra-shallow junction formation,

W. Skorupa; R. A. Yankov; M. Voelskow; W. Anwand; D. Panknin; R. A. McMahon; M. Smith; T. Gebel; L. Rebohle; R. Fendler; W. Hentsch

2005-01-01

128

Science Junction  

NSDL National Science Digital Library

Science Junction is a cybercommunity of researchers, educators, and students, and a center for teaching, learning, and integrating science into daily life. The website features collaborative experiments that allow classes of students to participate jointly with other classes across the state, collect and upload data, then analyze, look for patterns, and make models. The teacher's page features web-based lesson plans organized by topic: life sciences, Earth and space sciences, chemistry, and physics. There are also games and home experiments for students, information on research groups, graduate students, and their projects, an online forum for teachers, and information on professional development programs on using and teaching with technology.

129

Post-translational integration and oligomerization of connexin 26 in plasma membranes and evidence of formation of membrane pores: implications for the assembly of gap junctions.  

PubMed

Gap-junction channels provide a widespread intercellular signalling mechanism. They are constructed of a family of connexin membrane proteins that thread across the membrane four times and oligomerize to generate hexameric gap-junction hemichannels. Using an in vitro cell-free transcription/translation system, we demonstrate that connexin (Cx) 26, one of the smallest connexins, is integrated directly in a post-translational manner into plasma membranes. Protein-cleavage studies of Cx26 integrated into plasma membranes indicate a similar native transmembrane topography to that of Cx26 integrated co-translationally into microsomes. Cx26 integrated post-translationally into plasma membranes oligomerizes and, when incorporated into liposomes, provides permeability to ascorbic acid, suggesting that gap-junction hemichannels are generated. The results provide the basis of a novel alternative mechanism for spontaneous assembly in plasma membranes of Cx26 gap-junction hemichannels that occurs independently of the conventional biogenesis of gap junctions involving connexin trafficking and oligomerization via membrane components of the secretory pathway. PMID:11985493

Ahmad, Shoeb; Evans, W Howard

2002-08-01

130

Assembly of tight junctions during early vertebrate development  

Microsoft Academic Search

Tight junction formation during development is critical for embryonic patterning and organization. We consider mechanisms of junction biogenesis in cleaving mouse and Xenopus eggs. Junction assembly follows the establishment of cell polarity at 8-cell (mouse) or 2-cell (Xenopus) stages, characterized by sequential membrane delivery of constituents, coordinated by embryonic (mouse) or maternal (Xenopus) expression programmes. Cadherin adhesion is permissive for

Tom P. Fleming; Tom Papenbrock; Irina Fesenko; Peter Hausen; Bhavwanti Sheth

2000-01-01

131

Instability of a junction vortex  

Microsoft Academic Search

The flow field in the region where a moving wall, started from rest, slides under a stationary one, produces an interesting flow phenomena with relatively simple generation geometry. Experiments show that if the wall speed is high enough a vortex forms close to the junction of the moving wall with the stationary one. Vortex formation was observed for the range

Takashi Naitoh; James Allen

2005-01-01

132

Growth sequence and interface formation in the Fe/MgO/Fe(001) tunnel junction analyzed by surface x-ray diffraction  

SciTech Connect

We present a surface x-ray diffraction study of the interface geometric structure in the Fe/MgO/Fe(001) magnetic tunnel junction (MTJ). While the lower MgO/Fe(001) interface is characterized by a substoichiometric FeO{sub x} (x=0.6{+-}0.1) layer in agreement with previous studies, growth of Fe on the MgO spacer and the upper Fe/MgO interface structure strongly depends on the preparation method. If 0.4 monolayers of Fe are initially deposited in ambient oxygen atmosphere (p=10{sup -7} mbar) followed by Fe deposition under ultrahigh-vacuum (UHV) conditions, structural coherence across the trilayer junction is observed. In this case, substoichiometric FeO{sub x} layers are present at both Fe/MgO interfaces corresponding to a symmetric MTJ structure. In contrast, lattice registry is not preserved if Fe deposition is carried out solely under UHV conditions. Our results might have important implications for the preparation of magnetic tunnel junctions optimized to achieve giant tunneling-magnetoresistance amplitudes.

Tusche, C.; Meyerheim, H. L.; Kirschner, J. [Max-Planck-Institut fuer Mikrostrukturphysik, Weinberg 2, D-06120 Halle (Germany); Jedrecy, N. [Institut des NanoSciences de Paris, Universites Paris 6 et 7 et CNRS-UMR 7588, 4 place Jussieu, F-75252 Paris Cedex 05 (France); Renaud, G. [CEA-Grenoble, 17 rue des Martyrs, F-38054 Grenoble (France)

2006-11-15

133

Gap junction and hemichannel functions in osteocytes.  

PubMed

Cell-to-cell and cell-to-matrix communication in bone cells mediated by gap junctions and hemichannels, respectively, maintains bone homeostasis. Gap junctional communication between cells permits the passage of small molecules including calcium and cyclic AMP. This cell-to-cell communication occurs between bone cells including osteoblasts, osteoclasts and osteocytes, and is important in both bone formation and bone resorption. Connexin (Cx) 43 is the predominant gap junction protein in bone cells, and facilitates the communication of cellular signals either through docking of gap junctions between two cells, or through the formation of un-paired hemichannels. Systemic deletion of Cx43 results in perinatal lethality, so conditional deletion models are necessary to study the postnatal role of gap junctions in bone. These models provide the opportunity to determine the role of gap junctions in specific bone cells, notably the osteocyte. In this review, we summarize the key roles that gap junctions and hemichannels in osteocytes play in bone cell response to many stimuli including mechanical loading, intracellular and extracellular stimuli, such as parathyroid hormone, PGE2, plasma calcium levels and pH, as well as in maintaining osteocyte survival. PMID:23069374

Loiselle, Alayna E; Jiang, Jean X; Donahue, Henry J

2012-10-13

134

Microtubules regulate disassembly of epithelial apical junctions  

PubMed Central

Background Epithelial tight junction (TJ) and adherens junction (AJ) form the apical junctional complex (AJC) which regulates cell-cell adhesion, paracellular permeability and cell polarity. The AJC is anchored on cytoskeletal structures including actin microfilaments and microtubules. Such cytoskeletal interactions are thought to be important for the assembly and remodeling of apical junctions. In the present study, we investigated the role of microtubules in disassembly of the AJC in intestinal epithelial cells using a model of extracellular calcium depletion. Results Calcium depletion resulted in disruption and internalization of epithelial TJs and AJs along with reorganization of perijunctional F-actin into contractile rings. Microtubules reorganized into dense plaques positioned inside such F-actin rings. Depolymerization of microtubules with nocodazole prevented junctional disassembly and F-actin ring formation. Stabilization of microtubules with either docetaxel or pacitaxel blocked contraction of F-actin rings and attenuated internalization of junctional proteins into a subapical cytosolic compartment. Likewise, pharmacological inhibition of microtubule motors, kinesins, prevented contraction of F-actin rings and attenuated disassembly of apical junctions. Kinesin-1 was enriched at the AJC in cultured epithelial cells and it also accumulated at epithelial cell-cell contacts in normal human colonic mucosa. Furthermore, immunoprecipitation experiments demonstrated association of kinesin-1 with the E-cadherin-catenin complex. Conclusion Our data suggest that microtubules play a role in disassembly of the AJC during calcium depletion by regulating formation of contractile F-actin rings and internalization of AJ/TJ proteins.

Ivanov, Andrei I; McCall, Ingrid C; Babbin, Brian; Samarin, Stanislav N; Nusrat, Asma; Parkos, Charles A

2006-01-01

135

comK Prophage Junction Fragments as Markers for Listeria monocytogenes Genotypes Unique to Individual Meat and Poultry Processing Plants and a Model for Rapid Niche-Specific Adaptation, Biofilm Formation, and Persistence ? †  

PubMed Central

Different strains of Listeria monocytogenes are well known to persist in individual food processing plants and to contaminate foods for many years; however, the specific genotypic and phenotypic mechanisms responsible for persistence of these unique strains remain largely unknown. Based on sequences in comK prophage junction fragments, different strains of epidemic clones (ECs), which included ECII, ECIII, and ECV, were identified and shown to be specific to individual meat and poultry processing plants. The comK prophage-containing strains showed significantly higher cell densities after incubation at 30°C for 48 h on meat and poultry food-conditioning films than did strains lacking the comK prophage (P < 0.05). Overall, the type of strain, the type of conditioning film, and the interaction between the two were all highly significant (P < 0.001). Recombination analysis indicated that the comK prophage junction fragments in these strains had evolved due to extensive recombination. Based on the results of the present study, we propose a novel model in which the concept of defective comK prophage was replaced with the rapid adaptation island (RAI). Genes within the RAI were recharacterized as “adaptons,” as these genes may allow L. monocytogenes to rapidly adapt to different food processing facilities and foods. If confirmed, the model presented would help explain Listeria's rapid niche adaptation, biofilm formation, persistence, and subsequent transmission to foods. Also, comK prophage junction fragment sequences may permit accurate tracking of persistent strains back to and within individual food processing operations and thus allow the design of more effective intervention strategies to reduce contamination and enhance food safety.

Verghese, Bindhu; Lok, Mei; Wen, Jia; Alessandria, Valentina; Chen, Yi; Kathariou, Sophia; Knabel, Stephen

2011-01-01

136

Plasmodium falciparum Adhesion on Human Brain Microvascular Endothelial Cells Involves Transmigration-Like Cup Formation and Induces Opening of Intercellular Junctions  

PubMed Central

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.

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

2010-01-01

137

Holographic Josephson Junctions  

SciTech Connect

We construct a gravitational dual of a Josephson junction. Calculations on the gravity side reproduce the standard relation between the current across the junction and the phase difference of the condensate. We also study the dependence of the maximum current on the temperature and size of the junction and reproduce familiar results.

Horowitz, Gary T.; Santos, Jorge E.; Way, Benson [Department of Physics, University of California, Santa Barbara, California 93106-4030 (United States)

2011-06-03

138

Solar cell junction processing system  

Microsoft Academic Search

An integrated system and process for the continuous formation of p-n junctions in solar cells in a cost-effective manner and under computer control. The integrated system essentially comprises an ion beam implanter, an electron beam annealer and a combination vacuum lock-and-wafer transport system, all disposed within a unitary housing maintained under a common vacuum environment. The integrated system employs no

A. J. Armini; R. G. Little

1982-01-01

139

Dislocation Dynamics Simulations of Junctions in Hexagonal Close-Packed Crystals.  

National Technical Information Service (NTIS)

The formation and strength of dislocations in the hexagonal closed packed material beryllium are studied through dislocation junctions and the critical stress required to break them. Dislocation dynamics calculations (using the code ParaDiS) of junction m...

A. Arsenlis C. Wu P. Chung S. Aubry

2011-01-01

140

Chemically doped radial junction characteristics in silicon nanowires.  

PubMed

We evaluate the boron (B) and phosphorus (P) core-surface codoped radial p-n junction characteristics in silicon nanowires (SiNWs) using density functional theory calculations. We find that the formation of radial p-n junction is energetically favorable. The stability depends on the diameter of SiNWs and the dopant concentration. Generally, a higher concentration of B-P pair dopants results in a more stable nanowire. More importantly, we predict that the radial p-n junction can evolve into a Schottky-like junction in relatively highly doped SiNWs when the diameter increases, attributing to the change of the core p-doping characteristic, that is, the core p-junction becomes metallic, while the n-junction near the surface remains semiconducting. The interfacial contact between the junctions is found to be the key for such change. Our calculated results support an experimental observation in SiNW solar cells. PMID:23137035

Ng, Man-Fai; Tong, Shi Wun

2012-11-09

141

The Bouvet Triple Junction.  

National Technical Information Service (NTIS)

The boundaries of three plates, South America, Africa, and Antarctica, Meet in a triple junction 250 km west of Bouvet Island. In the vicinity of the triple junction the most striking features of the Antarctica/South America and Africa/Antarctica plate bo...

J. G. Sclater C. Bowin R. Hey H. Hoskins J. Peirce

1975-01-01

142

Tunneling in mesoscopic junctions  

Microsoft Academic Search

We have applied the Numerical Renormalization Group method to study a mesoscopic system consisting of two samples of metal separated by an insulating barrier, with nanometer dimensions, which allows the tunnelling of a single electron from one to the other side of the junction. The junction is represented by a generalized orthodox model, taking into account the electronic scattering interaction

H. O. Frota

2004-01-01

143

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

144

Multiferroic tunnel junctions  

NASA Astrophysics Data System (ADS)

Magnetic tunnel junctions with ferroelectric barriers, often referred to as multiferroic tunnel junctions, have been proposed recently to display new functionalities and new device concepts. One of the notable predictions is that the combination of two charge polarizing states and the parallel and antiparallel magnetic states could make it a four resistance state device. We have recently studied the ferroelectric tunneling using a scanning probe technique and multiferroic tunnel junctions using ferromagnetic La0.7Ca0.3MnO3 and La0.7Sr0.3MnO3 as the electrodes and ferroelectric (Ba, Sr)TiO3 as the barrier in trilayer planner junctions. We show that very thin (Ba, Sr)TiO3 films can sustain ferroelectricity up till room temperature. The multiferroic tunnel junctions show four resistance states as predicted and can operate at room temperatures.

Yin, Yue-Wei; Raju, Muralikrishna; Hu, Wei-Jin; Weng, Xiao-Jun; Zou, Ke; Zhu, Jun; Li, Xiao-Guang; Zhang, Zhi-Dong; Li, Qi

2012-08-01

145

Endothelial adherens junctions at a glance.  

PubMed

Adherens junctions have an important role in the control of vascular permeability. These structures are located at cell-to-cell contacts, mediate cell adhesion and transfer intracellular signals. Adhesion is mediated by cadherins, which interact homophilically in trans and form lateral interactions in cis. VE-cadherin (also known as CDH5 and CD144) is the major component of endothelial adherens junctions and is specific to endothelial cells. Endothelial cells from different types of vessels, such as lymphatic vessels, arteries and veins, show differences in junction composition and organization. Vascular permeability is increased by modifications in the expression and function of adherens junction components. In some cases these defects might be cause of pathology. In this Cell Science at a Glance article, we present the example of the so-called cerebral cavernous malformation (CCM), where adherens junctions are dismantled in the vessels contributing to brain microcirculation. This causes the loss of endothelial cell apical-basal polarity and the formation of cavernomas, which are fragile and hemorrhagic. Other diseases are accompanied by persistent alterations of vascular morphology and permeability, such as seen in tumors. It will be important to achieve a better understanding of the relationship between vascular fragility, malformations and junctional integrity in order to develop more effective therapies. PMID:23781019

Dejana, Elisabetta; Orsenigo, Fabrizio

2013-06-18

146

Primary Tunnel Junction Thermometry  

SciTech Connect

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.

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

2008-11-14

147

The Bouvet triple junction  

Microsoft Academic Search

The boundaries of three plates, South America, Africa, and Antarctica, meet in a triple junction 250 km west of Bouvet Island. In the vicinity of the triple junction the most striking features of the Antarctica\\/South America and Africa\\/Antarctica plate boundaries are the Conrad and Bouvet fracture zones which trend N85°E and N45°E, respectively. We show by matching synthetic and observed

J. G. Sclater; C. Brown; R. Hey; H. Hoskins; J. Peirce; J. AUI; C. Tapscott

1976-01-01

148

Tunneling in mesoscopic junctions  

Microsoft Academic Search

We have applied the Numerical Renormalization Group method to study a\\u000amesoscopic system consisting of two samples of metal separated by an insulating\\u000abarrier, with nanometer dimensions, which allows the tunnelling of a single\\u000aelectron from one to the other side of the junction. The junction is\\u000arepresented by a generalized orthodox model, taking into account the electronic\\u000ascattering interaction

H. O. Frota

2004-01-01

149

Quantum junction solar cells.  

PubMed

Colloidal quantum dot solids combine convenient solution-processing with quantum size effect tuning, offering avenues to high-efficiency multijunction cells based on a single materials synthesis and processing platform. The highest-performing colloidal quantum dot rectifying devices reported to date have relied on a junction between a quantum-tuned absorber and a bulk material (e.g., TiO(2)); however, quantum tuning of the absorber then requires complete redesign of the bulk acceptor, compromising the benefits of facile quantum tuning. Here we report rectifying junctions constructed entirely using inherently band-aligned quantum-tuned materials. Realizing these quantum junction diodes relied upon the creation of an n-type quantum dot solid having a clean bandgap. We combine stable, chemically compatible, high-performance n-type and p-type materials to create the first quantum junction solar cells. We present a family of photovoltaic devices having widely tuned bandgaps of 0.6-1.6 eV that excel where conventional quantum-to-bulk devices fail to perform. Devices having optimal single-junction bandgaps exhibit certified AM1.5 solar power conversion efficiencies of 5.4%. Control over doping in quantum solids, and the successful integration of these materials to form stable quantum junctions, offers a powerful new degree of freedom to colloidal quantum dot optoelectronics. PMID:22881834

Tang, Jiang; Liu, Huan; Zhitomirsky, David; Hoogland, Sjoerd; Wang, Xihua; Furukawa, Melissa; Levina, Larissa; Sargent, Edward H

2012-08-16

150

Immunoglobulin superfamily receptors and adherens junctions.  

PubMed

The immunogroblin (Ig) superfamily proteins characterized by the presence of Ig-like domains are involved in various cellular functions. The properties of the Ig-like domains to form rod-like structures and to bind specifically to other proteins make them ideal for cell surface receptors and cell adhesion molecules (CAMs). Ig-CAMs, nectins in mammals and Echinoid in Drosophila, are crucial components of cadherin-based adherens junctions in the epithelium. Nectins form cell-cell adhesion by their trans-interactions and recruit cadherins to the nectin-initiated cell-cell adhesion site to establish adherens junctions. Thereafter junction adhesion molecules, occludin, and claudins, are recruited to the apical side of adherens junctions to establish tight junctions. The recruitment of these molecules by nectins is mediated both by the direct and indirect interactions of afadin with many proteins, such as catenins, and zonula occludens proteins, and by the nectin-induced reorganization of the actin cytoskeleton. Nectins contribute to the formation of both homotypic and heterotypic types of cell-cell junctions, such as synapses in the brain, contacts between pigment and non-pigment cell layers of the ciliary epithelium in the eye, Sertoli cell-spermatid junctions in the testis, and sensory cells and supporting cells in the sensory organs. In addition, cis- and trans-interactions of nectins with various cell surface proteins, such as integrins, growth factor receptors, and nectin-like molecules (Necls) play important roles in the regulation of many cellular functions, such as cell polarization, movement, proliferation, differentiation, survival, and cell sorting. Furthermore, the Ig-CAMs are implicated in many human diseases including viral infections, ectodermal dysplasia, cancers, and Alzheimer's disease. PMID:22674071

Shimono, Yohei; Rikitake, Yoshiyuki; Mandai, Kenji; Mori, Masahiro; Takai, Yoshimi

2012-01-01

151

Intracytoplasmic junctions in cardiac muscle cells.  

PubMed

JUNCTIONAL STRUCTURES FORMED BY TWO PARTS OF THE PLASMA MEMBRANE OF THE SAME CARDIAC MUSCLE CELL WERE OBSERVED IN VENTRICULAR MYOCARDIUM OF: a) patients with neoplasms, aortic valvular disease or idiopathic hypertrophic subaortic stenosis and b) dogs subjected to prolonged normothermic anoxic cardiac arrest. Most of these structures had features of desmosomes; other, more complex structures had components with features of desmosomes, fasciae adherentes and nexuses, and, therefore, resembled intercalated discs. These intracytoplasmic junctions were localized to: a) the peripheral cytoplasm at the sides or ends of cells, b) narrow invaginations of plasma membranes, c) narrow zones of deep, broad plasmalemmal invaginations and d) narrow branches of T tubules. In patients with idiopathic hypertrophic subaortic stenosis or aortic valvular disease and in the dogs subjected to anoxic cardiac arrest, intracytoplasmic junctions were observed in hypertrophied or degenerated muscle cells which were located in areas of fibrosis and which showed loss of contact with adjacent cells. In patients with neoplasms, intracyto-plasmic junctions were found in degenerated cells which were located in areas of interstitial edema and which also showed loss of contact with adjacent cells. Our observations suggest that remodeling of cell surfaces following loss of intercellular contact is the most likely mechanism of formation of intracytoplasmic junctions. PMID:4856036

Buja, L M; Ferrans, V J; Maron, B J

1974-03-01

152

Expression of the gap junction protein connexin43 in embryonic chick lens: Molecular cloning, ultrastructural localization, and post-translational phosphorylation  

Microsoft Academic Search

Summary Lens epithelial cells are physiologically coupled to each other and to the lens fibers by an extensive network of intercellular gap junctions. In the rat, the epithelial-epithelial junctions appear to contain connexin43, a member of the connexin family of gap junction proteins. Limitations on the use of rodent lenses for the study of gap junction formation and regulation led

Linda S. Musil; Eric C. Beyer; Daniel A. Goodenough

1990-01-01

153

The dynamic organic p-n junction  

NASA Astrophysics Data System (ADS)

Static p-n junctions in inorganic semiconductors are exploited in a wide range of today's electronic appliances. Here, we demonstrate the in situ formation of a dynamic p-n junction structure within an organic semiconductor through electrochemistry. Specifically, we use scanning kelvin probe microscopy and optical probing on planar light-emitting electrochemical cells (LECs) with a mixture of a conjugated polymer and an electrolyte connecting two electrodes separated by 120?m. We find that a significant portion of the potential drop between the electrodes coincides with the location of a thin and distinct light-emission zone positioned >30?m away from the negative electrode. These results are relevant in the context of a long-standing scientific debate, as they prove that electrochemical doping can take place in LECs. Moreover, a study on the doping formation and dissipation kinetics provides interesting detail regarding the electronic structure and stability of the dynamic organic p-n junction, which may be useful in future dynamic p-n junction-based devices.

Matyba, Piotr; Maturova, Klara; Kemerink, Martijn; Robinson, Nathaniel D.; Edman, Ludvig

2009-08-01

154

Stereoscopic occlusion junctions.  

PubMed

Portions of surfaces in a binocularly viewed scene may be 'half occluded', that is, visible in only one eye. The human visual system uses zones of half occlusion to help segment the visual scene and infer figure-ground relationships at object boundaries. We developed a quantitative model of the depth-discontinuity cue provided by half occlusion. Half occlusions are revealed by two-dimensional interocular displacements of binocularly viewed occlusion junctions, such as T junctions. We derived a formula relating this two-dimensional displacement, or 'pseudodisparity', to binocular disparities and orientations of occluding and occluded contours. In human psychophysical experiments, perceived depth and contour orientation quantitatively depended on pseudodisparity, as predicted by our model, implying that the visual system senses quantitative variations in interocular junction position to reconstruct occlusion geometry. PMID:10461224

Malik, J; Anderson, B L; Charowhas, C E

1999-09-01

155

Junctional epidermolysis bullosa.  

PubMed

Epidermolysis bullosa (EB) encompasses a heterogeneous group of genodermatoses, characterized by fragility and blistering of the skin, often associated with extracutaneous manifestations. The level of vesiculation within the skin defines 3 major subtypes of EB: EB simplex, junctional EB, and dystrophic EB. We present the case of a male neonate of 36 weeks of gestation, who was born with a few blisters with erosions and who rapidly developed extensive blistering of the skin. Histopathology revealed subepidermal blistering. Electron microscopy confirmed the cleavage of epidermis from dermis within the lamina lucida. Junctional EB was the diagnosis. The patient was discharged after hospitalization for 28 days. The development of new blisters with erosions were gradually improved after AQUACEL Ag dressing, and the general condition was much better than at admission. The patient likely has a subtype of junctional EB termed generalized atrophic benign EB that clinically improves with age. He has the potential to father children and has a normal life expectancy. PMID:17098678

Kao, Chuan-Hong; Chen, Sue-Jen; Hwang, Betau; Yang, An-Hang; Hsu, Chih-Yi; Huang, Cheng-Hung

2006-10-01

156

PERMEABLE JUNCTIONAL COMPLEXES  

PubMed Central

Ionic lanthanum has been used to study transepithelial ion permeation in in vitro rabbit gallbladder and intestine (ileum) by adding 1 mM La3+ to only the mucosal bathing solution. Transepithelial fluid transport electrical potential differences (p.d.), and resistances were measured. During La3+ treatment the gallbladder's rate of active solute-coupled fluid transport remained constant, the resistance increased, and the 2:1 NaCl diffusion p.d. decreased. Mucosa-to-serosa fluxes of 140La3+ were measured and indicate a finite permeability of the gallbladder to La3+. La3+ also increased the transepithelial resistance and p d. of ileum. Electron microscopic examination of La3+-treated gallbladder showed: (a) good preservation of the fine structure, (b) electron-opaque lanthanum precipitates in almost every lateral intercellular space, most frequently near the apical end of the lateral spaces close to or within the junctional complex, (c) lanthanum among the subjacent muscle and connective tissue layers, and (d) lanthanum filling almost the entire length of so-called "tight" junctions. No observations were made which unequivocally showed the penetration of lanthanum into the gallbladder cells. Electron micrographs of similar La3+-treated ilea showed lanthanum deposits penetrating the junctional complexes. These results coupled with other physiological studies indicate that the low resistance pathway for transepithelial ion permeation in gallbladder and ileum is through the tight junctions A division of salt-transporting epithelia into two main groups, those with "leaky" junctional complexes and those with tight junctional complexes, has been proposed.

Machen, Terry E.; Erlij, David; Wooding, F. B. P.

1972-01-01

157

Spin-polarized proximity effect in superconducting junctions  

NASA Astrophysics Data System (ADS)

We study spin dependent phenomena in superconducting junctions in both ballistic and diffusive regimes. For ballistic junctions we study both ferromagnet/s- and d-wave superconductor junctions and two-dimensional electron gas/s-wave superconductor junctions with Rashba spin-orbit coupling. It is shown that the exchange field always suppresses the conductance while the Rashba spin-orbit coupling can enhance it. In the latter part of the article we study the diffusive ferromagnet/insulator/s- and d-wave superconductor (DF/I/S) junctions, where the proximity effect can be enhanced by the exchange field in contrast to common belief. This resonant proximity effect in these junctions is studied for various situations: conductance of the junction and density of states of the DF are calculated by changing the heights of the insulating barriers at the interfaces, the magnitudes of the resistance in DF, the exchange field in DF, the transparencies of the insulating barriers and the angle between the normal to the interface and the crystal axis of d-wave superconductors ?. It is shown that the resonant proximity effect originating from the exchange field in DF strongly influences the tunneling conductance and density of states. We clarify the followings: for s-wave junctions, a sharp zero bias conductance peak (ZBCP) appears due to the resonant proximity effect. The magnitude of this ZBCP can exceed its value in normal states in contrast to that observed in diffusive normal metal/superconductor junctions. We find similar structures to the conductance in the density of states. For d-wave junctions at ?=0, we also find a result similar to that in s-wave junctions. The magnitude of the resonant ZBCP at ?=0 can exceed that at ?/?=0.25 due to the formation of the mid gap Andreev resonant states. To cite this article: T. Yokoyama, Y. Tanaka, C. R. Physique 7 (2006).

Yokoyama, Takehito; Tanaka, Yukio

2006-01-01

158

Superconducting tunnel junctions  

NASA Astrophysics Data System (ADS)

The development of superconducting detectors well suited for X-ray spectroscopy in the energy range below 10 keV is considered. Detectors equipped with superconducting thin film absorbers, which are well suited for X-ray spectroscopy in this range, are investigated. Superconducting tunnel junctions are discussed in general and the results along with superconducting X-ray detectors, exploiting quasi particle trapping, are presented. The relative charge output of superconducting tunnel junctions is considered. The epitaxial growth of vanadium absorbers, necessary to obtain detectors of long term stability is also considered.

Kraus, H.; Jochum, J.; Kemmather, B.; Gutsche, M.; Feilitzsch, F. V.; Moessbauer, R. L.

1991-11-01

159

Adherens junction assembly.  

PubMed

Classical cadherins are a family of transmembrane proteins that mediate cell-cell adhesion at adherens junctions. A complex chain of cis- and trans- interactions between cadherin ectodomains establishes a cadherin adhesive cluster. A principal adhesive interaction in such clusters is an exchange of ? strands between the first extracellular cadherin domains (EC1). The structure of cadherin adhesive clusters can be modified by other adherens junction proteins including additional transmembrane proteins, nectins and various intracellular proteins that directly or indirectly interact with the intracellular cadherin region. These interactions determine the dynamics and stability of cadherin adhesive structures. PMID:22674069

Troyanovsky, Sergey

2012-01-01

160

Conductance of Molecular Junctions Formed with Silver Electrodes.  

PubMed

We compare the conductance of a series of amine-terminated oligophenyl and alkane molecular junctions formed with Ag and Au electrodes using the scanning tunneling microscope based break-junction technique. For these molecules that conduct through the highest occupied molecular orbital, junctions formed with Au electrodes are more conductive than those formed with Ag electrodes, consistent with the lower work function for Ag. The measured conductance decays exponentially with molecular backbone length with a decay constant that is essentially the same for Ag and Au electrodes. However, the formation and evolution of molecular junctions upon elongation are very different for these two metals. Specifically, junctions formed with Ag electrodes sustain significantly longer elongation when compared with Au due to a difference in the initial gap opened up when the metal point-contact is broken. Using this observation and density functional theory calculations of junction structure and conductance we explain the trends observed in the single molecule junction conductance. Our work thus opens a new path to the conductance measurements of a single molecule junction in Ag electrodes. PMID:23731268

Kim, Taekyeong; Vázquez, Héctor; Hybertsen, Mark S; Venkataraman, Latha

2013-06-01

161

Junction Detection for Linear Structures  

NASA Astrophysics Data System (ADS)

This paper presents a method for detecting junctions in an image with linear structures. The candidate junction points are selected through the combination of correlation matrix and Hessian information; then the branches of the junctions are found according to the intensity information and the correlation value between intensity profile of cross sections and a Gaussian-shaped template. Junction detection results for neurite images are provided.

Su, Ran; Sun, Changming; Pham, Tuan D.

2011-06-01

162

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

NASA Astrophysics Data System (ADS)

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.

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

2013-11-01

163

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

PubMed

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. PMID:24129428

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

2013-10-15

164

Electromagnetic topology - Junction characterization methods  

Microsoft Academic Search

The electrical characterization of topological network junctions using a formalism in accordance with electromagnetic topology is discussed. It is shown how the characteristic impedance of the network in which the junction is located can be chosen to treat several physical cable connection and termination configurations. Junctions which represent the separation of a conductor into other conductors are used as an

J. P. Parmantier; G. Labaume; J. C. Alliot; P. Degauque

1990-01-01

165

Lightness and junctions.  

PubMed

The lightness of a test patch completely surrounded by an inducing field can be predicted by variants of Wallach's ratio rule. When a patch is surrounded by two or more regions with different luminances, a plausible extension of the ratio rule would predict that the effect of the surrounding regions should correlate with the length of the border they share with the test patch. However, as shown by the Wertheimer-Benary and White effects, lightness of such patches can depart appreciably from these predictions. It is argued that a fruitful approach toward the explanation of such effects is based on the analysis of junctions (such as T-junctions and X-junctions) between regions. Several new displays and variations of old displays involving such junctions are used to illustrate this approach. An alternative analysis of a lightness effect introduced by Adelson is provided, and the role of depth effects in achromatic perception is discussed. A number of limitations of the approach and possible ways to overcome them are noted. PMID:9404489

Todorovi?, D

1997-01-01

166

Victory Junction Gang Camp  

ERIC Educational Resources Information Center

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

Shell, Ryan

2007-01-01

167

Ultrastructural pathology of endothelial tight junctions in human brain oedema.  

PubMed

Cortical biopsies of patients with the diagnosis of complicated brain trauma, congenital hydrocephalus, brain vascular anomaly, and brain tumour are studied with the electron microscope using cortical biopsies of different cortical brain regions to analyze the alterations of endothelial junctions, and their participation in the pathogenesis of human brain oedema. In moderate oedema, most endothelial tight junctions are structurally closed and intact, while in some cases of severe oedema, the opening of tight endothelial junctions is observed. In very severe brain oedema, a considerable enlargement of interjunctional pockets of extracellular space is also seen suggesting that in highly increased cerebrovascular permeability, the endothelial junctions are open in their entire extent, and that an intercellular or paracellular route through interendothelial clefts for transferring haematogenous oedema fluid from blood to the capillary basement membrane and the brain parenchyma is formed, contributing to the formation of brain oedema. High intensity brain trauma, seizures, osmotic forces, hypoxic conditions, and alteration of tight junctions proteins would explain the opening of endothelial junctions in severe and complicated brain oedema. In congenital hydrocephalus, the capillary wall shows evident signs of blood-brain barrier dysfunction characterized by closed and open interendothelial junctions, increased endothelial vesicular and vacuolar transport, thin and fragmented basement membrane with areas of focal thickening, and discontinuous perivascular astrocytic end-feet. The perivascular space is notably dilated and widely communicated with the enlarged extracellular space in the neuropil, showing the contribution of damaged endothelial junction to the formation of interstitial or hydrocephalic brain oedema. Altered expression of tight junction proteins could cause a blood-brain barrier breakdown following brain injury and hypoxic conditions leading to brain oedema. The results are compared with those found in experimental brain oedema. Some controversial results are also described. PMID:22773457

Castejón, Orlando J

2012-01-01

168

Gliotactin, a novel marker of tricellular junctions, is necessary for septate junction development in Drosophila.  

PubMed

Septate junctions (SJs), similar to tight junctions, function as transepithelial permeability barriers. Gliotactin (Gli) is a cholinesterase-like molecule that is necessary for blood-nerve barrier integrity, and may, therefore, contribute to SJ development or function. To address this hypothesis, we analyzed Gli expression and the Gli mutant phenotype in Drosophila epithelia. In Gli mutants, localization of SJ markers neurexin-IV, discs large, and coracle are disrupted. Furthermore, SJ barrier function is lost as determined by dye permeability assays. These data suggest that Gli is necessary for SJ formation. Surprisingly, Gli distribution only colocalizes with other SJ markers at tricellular junctions, suggesting that Gli has a unique function in SJ development. Ultrastructural analysis of Gli mutants supports this notion. In contrast to other SJ mutants in which septa are missing, septa are present in Gli mutants, but the junction has an immature morphology. We propose a model, whereby Gli acts at tricellular junctions to bind, anchor, or compact SJ strands apically during SJ development. PMID:12782681

Schulte, Joost; Tepass, Ulrich; Auld, Vanessa J

2003-06-02

169

The esophagogastric junction  

PubMed Central

The following discussion of the esophagogastric junctions includes commentaries on the three component structures of the sphincteric segment between the stomach and the esophagus; the pressure contributions from the three sphincteric components in normal subjects and in gastroesophageal reflux (GERD) patients; the mechanism of action of endoscopic plication to determine the underlying pathophysiology of GERD; and in vitro muscle strip studies of defects within the gastroesophageal sphincteric segment potentially leading to GERD.

Miller, Larry S.; Vegesna, Anil K.; Brasseur, James G.; Braverman, Alan S.; Ruggieri, Michael R.

2012-01-01

170

Spin-Flip Effects on Current in a Quantum Dot with a Josephson Junction System  

NASA Astrophysics Data System (ADS)

In this study, we consider the current in a system composed of a superconductor/quantum dot/superconductor junction and a Josephson junction in a parallel configuration. In the model, the spin-flip and the Coulomb interaction in the quantum dot are taken into consideration. The effects of direct tunneling, the spin-flip, and the Coulomb interaction on current and the relation between the current jump and the formation of the ?-junction are examined. The dependence of the current on the quantum dot energy level shows the Fano characteristics. The spin-flip causes the splitting of the Andreev bound state, thereby resulting in a current jump. The region of the ?-junction is spread along the current jump positions. We conclude that the spin-flip causes the formation of the ?-junction but direct tunneling suppresses it. For large values of spin-flip, the Coulomb interaction shifts the central position of the formed region of the ?-junction.

Kawaguchi, Satoshi

2012-03-01

171

Intracytoplasmic Junctions in Cardiac Muscle Cells  

PubMed Central

Junctional structures formed by two parts of the plasma membrane of the same cardiac muscle cell were observed in ventricular myocardium of: a) patients with neoplasms, aortic valvular disease or idiopathic hypertrophic subaortic stenosis and b) dogs subjected to prolonged normothermic anoxic cardiac arrest. Most of these structures had features of desmosomes; other, more complex structures had components with features of desmosomes, fasciae adherentes and nexuses, and, therefore, resembled intercalated discs. These intracytoplasmic junctions were localized to: a) the peripheral cytoplasm at the sides or ends of cells, b) narrow invaginations of plasma membranes, c) narrow zones of deep, broad plasmalemmal invaginations and d) narrow branches of T tubules. In patients with idiopathic hypertrophic subaortic stenosis or aortic valvular disease and in the dogs subjected to anoxic cardiac arrest, intracytoplasmic junctions were observed in hypertrophied or degenerated muscle cells which were located in areas of fibrosis and which showed loss of contact with adjacent cells. In patients with neoplasms, intracyto-plasmic junctions were found in degenerated cells which were located in areas of interstitial edema and which also showed loss of contact with adjacent cells. Our observations suggest that remodeling of cell surfaces following loss of intercellular contact is the most likely mechanism of formation of intracytoplasmic junctions. ImagesFig 25Fig 11Figs 12-13Fig 14Fig 15Fig 16Fig 17Fig 18Fig 19Fig 20Fig 21Fig 1Fig 2Fig 3Fig 22Fig 4Fig 5Fig 6Fig 23Fig 7Fig 8Fig 9Fig 24Fig 10

Buja, L. Maximilian; Ferrans, Victor J.; Maron, Barry J.

1974-01-01

172

Ferromagnetic planar Josephson junction with transparent interfaces: a ? junction proposal.  

PubMed

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

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

2013-05-02

173

Ferromagnetic planar Josephson junction with transparent interfaces: a ? junction proposal  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

174

Defect-Free Junction TFT for Improving Reliability under Hot Carrier Stress  

Microsoft Academic Search

A new polycrystalline silicon thin film transistor (poly-Si TFTs) called 'Defect-Free Junction TFT (DFJ-TFT)', which exhibits improved stability under hot carrier stress, has been proposed and fabricated. In order to remove residual junction defects due to ion implantation, source\\/drain doping was carried out prior to gate formation. During excimer laser annealing (ELA), large lateral grains are grown near the junction

Sang-Hoon Jung; Hee-Sun Shin; Min-Koo Han

2004-01-01

175

Local gate effect of mechanically deformed crossed carbon nanotube junction.  

PubMed

In this work, we have demonstrated that the local deformation at the crossed carbon nanotube (CNT) junctions can introduce significant tunable local gate effect under ambient environment. Atomic force microscope (AFM) manipulation of the local deformation yielded a variation in transconductance that was retained after removing the AFM tip. Application of a large source-drain voltage and pressing the CNT junction above a threshold pressure can respectively erase and recover the transconductance modulation reversibly. The local gate effect is found to be independent of the length of the crossed CNT and attributed to the charges residing at the deformed junctions due to formation of localized states. The number of localized charges is estimated to be in the range of 10(2) to 10(3). These results may find potential applications in electromechanical sensors and could have important implications for designing nonvolatile devices based on crossed CNT junctions. PMID:20945929

Qing, Quan; Nezich, Daniel A; Kong, Jing; Wu, Zhongyun; Liu, Zhongfan

2010-10-14

176

GUARD RING SEMICONDUCTOR JUNCTION  

DOEpatents

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

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

1963-12-01

177

Changes in Gap Junction Distribution and Connexin Expression Pattern During Human Fetal Skin Development  

Microsoft Academic Search

SUMMARY Gap junctions are intercellular channels composed of connexin subunits that mediate cell-cell communication. The functions of gap junctions are believed to be associ- ated with cell proliferation and differentiation and to be important in maintaining tissue homeostasis. We therefore investigated the expression of connexins (Cx)26 and 43, the two major connexins in human epidermis, and examined the formation of

Ken Arita; Masashi Akiyama; Yukiko Tsuji; James R. McMillan; Robin A. J. Eady; Hiroshi Shimizu

2002-01-01

178

Two gap junction channel (innexin) genes of the Bombyx mori and their expression  

Microsoft Academic Search

Gap junctions are clusters of intercellular channels that are associated with embryonic development and neural signaling. Innexins, invertebrate gap junction proteins, have been identified in Drosophila and Caenorhabditis. Here, we report the isolation and characterization of two novel members of the insect innexin family, Bm inx2 and Bm inx4, from embryos of the silkworm, Bombyx mori, during the germ-band formation

Sun-Mee Hong; Seok-Woo Kang; Tae-Won Goo; Nam-Soon Kim; Jin-Sung Lee; Kyung-A Kim; Si-Kab Nho

2008-01-01

179

Charge Tunneling Rates in Ultrasmall Junctions  

Microsoft Academic Search

1. Introduction 2. Description of the environment 3. Electron tunneling rates for single tunnel junctions 4. Examples of electromagnetic environments 5. Tunneling rates in Josephson junctions 6. Double junction and single electron transistor 7. Microscopic foundation

Gert-Ludwig Ingold; Yu. V. Nazarov

2005-01-01

180

Relaxation Oscillations in Josephson Junctions.  

National Technical Information Service (NTIS)

Investigation of the characteristics of Josephson tunneling in tin/tin oxide/tin junctions showed that pulse voltages with sharp rise times were being generated. Pulse amplitude across the junction remained constant and equal to the energy gap voltage V s...

F. L. Vernon R. J. Pedersen

1968-01-01

181

Gap junction structures after experimental alteration of junctional channel conductance  

PubMed Central

Gap junctions are known to present a variety of different morphologies in electron micrographs and x-ray diffraction patterns. This variation in structure is not only seen between gap junctions in different tissues and organisms, but also within a given tissue. In an attempt to understand the physiological meaning of some aspects of this variability, gap junction structure was studied following experimental manipulation of junctional channel conductance. Both physiological and morphological experiments were performed on gap junctions joining stage 20-23 chick embryo lens epithelial cells. Channel conductance was experimentally altered by using five different experimental manipulations, and assayed for conductance changes by observing the intercellular diffusion of Lucifer Yellow CH. All structural measurements were made on electron micrographs of freeze-fracture replicas after quick-freezing of specimens from the living state; for comparison, aldehyde-fixed specimens were measured as well. Analysis of the data generated as a result of this study revealed no common statistically significant changes in the intrajunctional packing of connexons in the membrane plane as a result of experimental alteration of junctional channel conductance, although some of the experimental manipulations used to alter junctional conductance did produce significant structural changes. Aldehyde fixation caused a dramatic condensation of connexon packing, a result not observed with any of the five experimental uncoupling conditions over the 40-min time course of the experiments.

1985-01-01

182

Ion bipolar junction transistors  

PubMed Central

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.

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

2010-01-01

183

THE APPEARANCE AND STRUCTURE OF INTERCELLULAR CONNECTIONS DURING THE ONTOGENY OF THE RABBIT OVARIAN FOLLICLE WITH PARTICULAR REFERENCE TO GAP JUNCTIONS  

Microsoft Academic Search

Lanthanum tracer and freeze-fracture electron microscope techniques were used to study junctional complexes between granulosa cells during the differentiation of the rabbit ovarian follicle. For convenience we refer to cells encompassing the oocyte, before antrum and gap junction formation, as follicle cells. After the appearance of an antrum and gap junctions we call the cells granulosa cells. Maculae adherentes are

DAVID F. ALBERTINI; EVERETT ANDERSON

1974-01-01

184

Epidermolysis bullosa hereditaria with Junctional Blistering in an Adult  

Microsoft Academic Search

A 38-year-old patient with epidermolysis bullosa is described, in whom junctional blister formation is revealed by electron microscopy. Clinical and ultrastructural differences from the recessive dystrophic type (Hallopeau-Siemens) and from the lethal type (Herlitz) of epidermolysis bullosa are discussed in detail.Copyright © 1976 S. Karger AG, Basel

I. Hashimoto; U. W. Schnyder; I. Anton-Lamprecht

1976-01-01

185

Neural tube closure: the curious case of shrinking junctions.  

PubMed

Your brain and spinal cord began as a flat sheet, which narrowed, elongated, and rolled up to form a tube. A new study identifies a key molecular link underlying vertebrate neural tube formation, connecting planar cell polarity patterning to contraction of specific cell-cell junctions. PMID:22835793

Sullivan-Brown, Jessica; Goldstein, Bob

2012-07-24

186

Current–voltage relation for Josephson junctions with ferromagnetic insulator  

Microsoft Academic Search

We calculate the current–voltage relation for planar superconducting d-wave junctions including a ferromagnetic insulating layer. The height of the current peak near zero-bias voltage due to the formation of zero energy states is reduced with the increase of the magnitude of the exchange interaction in ferromagnetic insulator.

Nobukatsu Yoshida; Yukio Tanaka; Satoshi Kashiwaya; Junichiro Inoue

2000-01-01

187

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

PubMed

Electronic factors in molecules such as quantum interference and cross-conjugation can lead to dramatic modulation and suppression of conductance in single-molecule junctions. Probing such effects at the single-molecule level requires simultaneous measurements of independent junction properties, as conductance alone cannot provide conclusive evidence of junction formation for molecules with low conductivity. Here, we compare the mechanics of the conducting para-terminated 4,4'-di(methylthio)stilbene and moderately conducting 1,2-bis(4-(methylthio)phenyl)ethane to that of insulating meta-terminated 3,3'-di(methylthio)stilbene single-molecule junctions. We simultaneously measure force and conductance across single-molecule junctions and use force signatures to obtain independent evidence of junction formation and rupture in the meta-linked cross-conjugated molecule even when no clear low-bias conductance is measured. By separately quantifying conductance and mechanics, we identify the formation of atypical 3,3'-di(methylthio)stilbene molecular junctions that are mechanically stable but electronically decoupled. While theoretical studies have envisaged many plausible systems where quantum interference might be observed, our experiments provide the first direct quantitative study of the interplay between contact mechanics and the distinctively quantum mechanical nature of electronic transport in single-molecule junctions. PMID:22352939

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

2012-02-24

188

The Drosophila Claudin Kune-kune Is Required for Septate Junction Organization and Tracheal Tube Size Control  

PubMed Central

The vertebrate tight junction is a critical claudin-based cell–cell junction that functions to prevent free paracellular diffusion between epithelial cells. In Drosophila, this barrier is provided by the septate junction, which, despite being ultrastructurally distinct from the vertebrate tight junction, also contains the claudin-family proteins Megatrachea and Sinuous. Here we identify a third Drosophila claudin, Kune-kune, that localizes to septate junctions and is required for junction organization and paracellular barrier function, but not for apical-basal polarity. In the tracheal system, septate junctions have a barrier-independent function that promotes lumenal secretion of Vermiform and Serpentine, extracellular matrix modifier proteins that are required to restrict tube length. As with Sinuous and Megatrachea, loss of Kune-kune prevents this secretion and results in overly elongated tubes. Embryos lacking all three characterized claudins have tracheal phenotypes similar to any single mutant, indicating that these claudins act in the same pathway controlling tracheal tube length. However, we find that there are distinct requirements for these claudins in epithelial septate junction formation. Megatrachea is predominantly required for correct localization of septate junction components, while Sinuous is predominantly required for maintaining normal levels of septate junction proteins. Kune-kune is required for both localization and levels. Double- and triple-mutant combinations of Sinuous and Megatrachea with Kune-kune resemble the Kune-kune single mutant, suggesting that Kune-kune has a more central role in septate junction formation than either Sinuous or Megatrachea.

Nelson, Kevin S.; Furuse, Mikio; Beitel, Greg J.

2010-01-01

189

Novel tunnelling barriers for spin tunnelling junctions  

NASA Astrophysics Data System (ADS)

A tunnel junction consists of two metal electrodes separated by an insulating barrier thin enough for electrons to tunnel across. With ferromagnetic electrodes, a spin-dependent tunnelling (SDT) effect, electrons of one spin tunnelling preferentially over those of the other, is observed. When the electrodes are switched from a parallel to an anti-parallel alignment, the tunnelling current changes and gives rise to tunnelling magnetoresistance (TMR). Since 1995, interest in SDT junctions has increased as TMR in excess of 15% has been achieved, making viable their use in non-volatile memory and magnetic sensors applications. In this work, two key issues of SDT junctions are addressed: spin polarization of the electrode and the tunnel barrier. Spin polarization, a measure of electron states of up and down spins, is widely believed to be an intrinsic property of the electrode. In junctions with barriers formed by plasma oxidation of composite Ta/Al films, the surprising effect of the resistance being lower with the electrodes aligned antiparallel was observed. Junctions with Ta/Al barriers and those with Al/Ta barriers behave opposite to each other and exhibit an inversion only when the Ta side of the barrier is biased positive. This demonstrates the spin polarization is also influenced by the barrier material. Half-metallic materials such as magnetite (Fe3O4) have a gap in one of the spins' states at the fermi level, thus having a theoretical spin polarization of 100%. In this work, an ultrathin Fe3O 4 layer was added between the Al2O3 barrier and the NiFe electrode. The TMR increased sharply from 4% to 16% for thicknesses less than 0.5nm. As the tunnel barrier must be thinner than 2nm, choice of the barrier material becomes critical. Presently, Al2O3 is the best known barrier. In looking for alternative materials, AlN and AlON were formed by plasma nitridation and oxy-nitridation of deposited Al films. TMR results of up to 18% and resistance-area products down to 3.5kO · mum 2 were achieved. AlN and AlON thus work as well as Al2O 3. X-ray photoelectron spectroscopy (XPS) was used to determine relative proportions of different oxidation states of the insulating barrier, understand the effect of plasma formation of the barrier on the underlying electrode, and the oxidation state of ion-beam deposited magnetite films. With a nanometer-scale oxide between two ferromagnetic electrodes, an SDT junction is a tiny capacitor. Presence of static charge in the ambient makes it susceptible to electrostatic discharge (ESD). Results from ESD testing on SDT junctions are presented and a useful model is discussed. Results obtained clearly show that the effects of the electrode/barrier interface are prominent in influencing the observed values of spin polarization and hence the TMR. The materials investigated show promise for use as alternate barrier materials in SDT junctions.

Sharma, Manish

190

Kinetic power model of junction losses  

SciTech Connect

Losses across diverging and converging flow junctions can be modeled as a linear combination of kinetic powers, allowing the prediction of total pressure changes across junctions. The efficacy of the model is demonstrated from experimental data on a wide variety of converging flow junctions. An equivalent model should also apply to diverging flow junctions.

Guffey, S.E. (Dept. of Environmental Health, Univ. of Washington, Seattle, WA (US)); Fraser, D.A. (Univ. of North Carolina, Chapel Hill, NC (US))

1989-01-01

191

Molecular Components of the Adherens Junction  

PubMed Central

Adherens junctions serve to couple individual cells into various arrangements required for tissue structure and function. The central structural components of adherens junctions are transmembrane adhesion receptors, and their associated actin-binding/regulatory proteins. The molecular machineries that organize these adhesion receptor complexes into higher order junction structures, and the functional consequences of this junctional organization will be discussed.

Niessen, Carien M.; Gottardi, Cara J.

2008-01-01

192

Solute and dislocation junction interactions  

SciTech Connect

In this study, the role of solute segregation on the strength and the evolution behavior of dislocation junctions is studied by utilizing kinetic Monte Carlo and three-dimensional dislocation dynamics simulations. The different solute concentrations and the character of the junctions are all included in the simulations in an effort to make a parametric investigation. The results indicate that the solutes have a profound effect on the strength of the junctions. Solute segregation can lead to both strengthening and weakening behavior, depending upon the evolution of the dislocation junctions. The local solute concentration seems to be the more relevant parameter to characterizing the solute and dislocation interactions, due to the short-range stress field of solutes; and its bounds are set by the unconstrained volume dilatation.

Chen, Q.; Liu, X.-Y.; Biner, S. B.

2008-03-19

193

Gap Junctions and Heart Development  

Microsoft Academic Search

\\u000a The function of gap junctions in propagation of the cardiac action potential is one of the best characterized roles for intercellular\\u000a communication. Comprehending the part played by cell-to-cell dialogue in embryological processes, including development of\\u000a the heart, has proven to be a more complex problem. Nonetheless, research at the conjunction of cardiac development and gap\\u000a junctions is a diverse and

Robert G. Gourdie; Wanda H. Litchenberg; Leonard M. Eisenberg

194

Neuromuscular junctional disorders.  

PubMed

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

Girija, A S; Ashraf, V V

2008-08-21

195

Octagonal Defects at Carbon Nanotube Junctions  

PubMed Central

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.

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

2013-01-01

196

Mtss1 Promotes Cell-Cell Junction Assembly and Stability through the Small GTPase Rac1  

PubMed Central

Cell-cell junctions are an integral part of epithelia and are often disrupted in cancer cells during epithelial-to-mesenchymal transition (EMT), which is a main driver of metastatic spread. We show here that Metastasis suppressor-1 (Mtss1; Missing in Metastasis, MIM), a member of the IMD-family of proteins, inhibits cell-cell junction disassembly in wound healing or HGF-induced scatter assays by enhancing cell-cell junction strength. Mtss1 not only makes cells more resistant to cell-cell junction disassembly, but also accelerates the kinetics of adherens junction assembly. Mtss1 drives enhanced junction formation specifically by elevating Rac-GTP. Lastly, we show that Mtss1 depletion reduces recruitment of F-actin at cell-cell junctions. We thus propose that Mtss1 promotes Rac1 activation and actin recruitment driving junction maintenance. We suggest that the observed loss of Mtss1 in cancers may compromise junction stability and thus promote EMT and metastasis.

Dawson, John C.; Bruche, Susann; Spence, Heather J.; Braga, Vania M. M.; Machesky, Laura M.

2012-01-01

197

Abl regulates planar polarized junctional dynamics through ?-catenin tyrosine phosphorylation  

PubMed Central

Summary Interactions between epithelial cells are mediated by adherens junctions that are dynamically regulated during development. Here we show that the turnover of ?-catenin is increased at cell interfaces that are targeted for disassembly during Drosophila axis elongation. The Abl tyrosine kinase is concentrated at specific planar junctions and is necessary for polarized ?-catenin localization and dynamics. abl mutant embryos have decreased ?-catenin turnover at shrinking edges, and these defects are accompanied a reduction in multicellular rosette formation and axis elongation. Abl promotes ?-catenin phosphorylation on the conserved tyrosine 667 and expression of an unphosphorylatable ?-catenin mutant recapitulates the defects of abl mutants. Notably, a phosphomimetic ?-cateninY667E mutation is sufficient to increase ?-catenin turnover and rescues axis elongation in abl deficient embryos. These results demonstrate that the asymmetrically localized Abl tyrosine kinase directs planar polarized junctional remodeling during Drosophila axis elongation through the tyrosine phosphorylation of ?-catenin.

Tamada, Masako; Farrell, Dene L.; Zallen, Jennifer A.

2012-01-01

198

High-voltage planar p-n junctions  

Microsoft Academic Search

A concentric ring junction has been devised to prevent surface breakdown of a planar junction. By properly choosing the spacing between the main junction and the ring, the ring junction acts like a voltage divider at the surface. In addition, the ring junction minimizes the effect of the junction curvature at the periphery of a planar junction. Devices fabricated with

Y. C. Kao; E. D. Wolley

1967-01-01

199

Highly conducting ?-conjugated molecular junctions covalently bonded to gold electrodes.  

PubMed

We measure electronic conductance through single conjugated molecules bonded to Au metal electrodes with direct Au-C covalent bonds using the scanning tunneling microscope based break-junction technique. We start with molecules terminated with trimethyltin end groups that cleave off in situ, resulting in formation of a direct covalent ? bond between the carbon backbone and the gold metal electrodes. The molecular carbon backbone used in this study consist of a conjugated ? system that has one terminal methylene group on each end, which bonds to the electrodes, achieving large electronic coupling of the electrodes to the ? system. The junctions formed with the prototypical example of 1,4-dimethylenebenzene show a conductance approaching one conductance quantum (G(0) = 2e(2)/h). Junctions formed with methylene-terminated oligophenyls with two to four phenyl units show a 100-fold increase in conductance compared with junctions formed with amine-linked oligophenyls. The conduction mechanism for these longer oligophenyls is tunneling, as they exhibit an exponential dependence of conductance on oligomer length. In addition, density functional theory based calculations for the Au-xylylene-Au junction show near-resonant transmission, with a crossover to tunneling for the longer oligomers. PMID:21939263

Chen, Wenbo; Widawsky, Jonathan R; Vázquez, Héctor; Schneebeli, Severin T; Hybertsen, Mark S; Breslow, Ronald; Venkataraman, Latha

2011-10-07

200

Junctional membrane uncoupling. Permeability transformations at a cell membrane junction.  

PubMed

The permeability of the membrane surfaces where cells are in contact (junctional membranes) in Chironomus salivary glands depends on Ca(++) and Mg(++). When the concentration of these ions at the junctional membranes is raised sufficiently, these normally highly permeable membranes seal off; their permeability falls one to three orders, as they approach the nonjunctional membranes in conductance. This permeability transformation is achieved in three ways: (a) by iontophoresis of Ca(++) into the cell; (b) by entry of Ca(++) and/or Mg(++) from the extracellular fluid into the cell through leaks in the cell surface membrane (e.g., injury); or (c) by entry of these ions through leaks arising, probably primarily in the perijunctional insulation, due to trypsin digestion, anisotonicity, alkalinity, or chelation. Ca(++) and Mg(++) appear to have three roles in the junctional coupling processes: (a) in the permeability of the junctional membranes; (b) in the permeability of the perijunctional insulation; and (c) a role long known- in the mechanical stability of the cell junction. The two latter roles may well be closely interdependent, but the first is clearly independent of the others. PMID:6050971

Loewenstein, W R; Nakas, M; Socolar, S J

1967-08-01

201

Dislocation Dynamics Simulations of Junctions in Hexagonal Close-Packed Crystals  

SciTech Connect

The formation and strength of dislocations in the hexagonal closed packed material beryllium are studied through dislocation junctions and the critical stress required to break them. Dislocation dynamics calculations (using the code ParaDiS) of junction maps are compared to an analytical line tension approximation in order to validate our model. Results show that the two models agree very well. Also the critical shear stress necessary to break 30{sup o} - 30{sup o} and 30{sup o} - 90{sup o} dislocation junctions is computed numerically. Yield surfaces are mapped out for these junctions to describe their stability regions as function of resolved shear stresses on the glide planes. The example of two non-coplanar binary dislocation junctions with slip planes [2-1-10] (01-10) and [-12-10] (0001) corresponding to a prismatic and basal slip respectively is chosen to verify and validate our implementation.

Wu, C; Aubry, S; Chung, P; Arsenlis, A

2011-12-05

202

The extracellular architecture of adherens junctions revealed by crystal structures of type I cadherins.  

PubMed

Adherens junctions, which play a central role in intercellular adhesion, comprise clusters of type I classical cadherins that bind via extracellular domains extended from opposing cell surfaces. We show that a molecular layer seen in crystal structures of E- and N-cadherin ectodomains reported here and in a previous C-cadherin structure corresponds to the extracellular architecture of adherens junctions. In all three ectodomain crystals, cadherins dimerize through a trans adhesive interface and are connected by a second, cis, interface. Assemblies formed by E-cadherin ectodomains coated on liposomes also appear to adopt this structure. Fluorescent imaging of junctions formed from wild-type and mutant E-cadherins in cultured cells confirm conclusions derived from structural evidence. Mutations that interfere with the trans interface ablate adhesion, whereas cis interface mutations disrupt stable junction formation. Our observations are consistent with a model for junction assembly involving strong trans and weak cis interactions localized in the ectodomain. PMID:21300292

Harrison, Oliver J; Jin, Xiangshu; Hong, Soonjin; Bahna, Fabiana; Ahlsen, Goran; Brasch, Julia; Wu, Yinghao; Vendome, Jeremie; Felsovalyi, Klara; Hampton, Cheri M; Troyanovsky, Regina B; Ben-Shaul, Avinoam; Frank, Joachim; Troyanovsky, Sergey M; Shapiro, Lawrence; Honig, Barry

2011-02-01

203

Fabrication and Characterization of SUB-0.25 Micrometer CMOS P-N Junctions by Low Energy Gallium Ion Focused Ion Beam Implantation.  

NASA Astrophysics Data System (ADS)

The main thrust of this thesis is the investigation of a Focused Ion Beam (FIB)-based approach for fabricating p^+-n shallow junctions approaching the nanometer scale (15-50 nm) which will be compatible with future generation CMOS technology. Ultra shallow junctions are formed by directly implanting low energy (3-25 keV) Ga ions into a crystalline Si substrate using a FIB implanter. Secondary ion mass spectrometry (SIMS) was employed as an analytical tool to measure the depth distribution of low energy Ga ions between 2keV to 10keV implanted into crystalline Si. The issue of ion channeling was investigated by implanting low-energy off-axis Ga ions at various tilt angles. The Ga atomic depth profile was measured using SIMS and the fractions of the Ga dose found in the tail of distribution when compared to a pure Gaussian profile for the 5keV implant were ~16% and 10% for the 0^circ and 15^circ off-axis implantation, respectively. Cross-sectional TEM was used to characterize the resulting structure of the implanted layer. For 5keV Ga ^+ implantation, the xTEM measurement yielded an amorphous layer thickness of 9 nm and a line of end-of-range defects 16nm below the surface (after RTA). SRP measurements were performed to characterize the junction depths and to obtain the activated Ga depth profile. At 4keV an electrical junction depth of 15nm is obtained from spreading resistance profiling (SRP). Effects of rapid thermal annealing on sub-100nm p^+-n Si junctions fabricated using 10keV FIB Ga^+ implantation at doses ranging from 10^{13} to 10^{15}cm^ {-2} were reported. Electrical properties of the diodes fabricated on n-Si with N_{rm b} = (5-10) times 10^ {15} by on-axis Ga^+ FIB implantation at 4 to 25keV were obtained from I-V characteristics. p^+-n junction diodes for sub-0.25mum CMOS circuits were fabricated using FIB Ga implantation into n-Si N_{rm b} = (1-10) times 10^{17 }cm^3. Implant energy was varied from 2 to 50keV at doses ranging 1 times 10^{13} to 1 times 10^{15 }cm^{-2} with different scan speeds. FIB Ga^+ implantation through Ti metal (ITM) and TiSi_2 (ITS) layers, followed by rapid thermal annealing (RTA) has been investigated for application in self-aligned silicide technology. Electrochemical capacitance-voltage (ECV) profiling technique was employed to measure the active carrier concentration in nanoscale layers fabricated by focused ion beam (FIB) implantation of 3 to 10keV Ga^+ ions into crystalline Si. (Abstract shortened by UMI.).

Mogul, Homyar Cavas

204

Method of making semiconductor junctions  

DOEpatents

A p-n junction on a silicon substrate doped with boron ions (d- dopant) is made in following manner. A shallow silicon surface layer including a n-type dopant is first obtained by ion implantation of the substrate with arsenic atoms. The arsenic-doped silicon layer at the surface has a relatively low initial reflectivity. Then, radiation from a pulsed carbon dioxide laser is directed onto the doped surface. A portion of the pulsed radiation causes melting of the thin arsenic-doped layer at the solid surface, giving the shallow melted surface a reflectivity greater than the initial reflectivity of the solid surface. The increased reflectivity of the melted surface prevents an additional portion of the pulsed radiation from causing further melting, thus controlling the depth of melting. The melted surface is then allowed to cool and solidify to form a p-n junction at a thin (less than 200 angstrom) junction depth. 6 figs.

James, R.B.

1990-12-31

205

Spin-filter Josephson junctions.  

PubMed

Josephson junctions with ferromagnetic barriers have been intensively investigated in recent years. Of particular interest has been the realization of so called ?-junctions with a built-in phase difference, and induced triplet pairing. Such experiments have so far been limited to systems containing metallic ferromagnets. Although junctions incorporating a ferromagnetic insulator (I(F)) have been predicted to show a range of unique properties including ?-shifts with intrinsically low dissipation and an unconventional temperature dependence of the critical current I(c), difficulties with the few known I(F) materials have prevented experimental tests. Here we report supercurrents through magnetic GdN barriers and show that the field and temperature dependence of I(c)is strongly modified by the I(F). In particular we show that the strong suppression of Cooper pair tunnelling by the spin filtering of the I(F) barrier can be modified by magnetic inhomogeneity in the barrier. PMID:21909111

Senapati, Kartik; Blamire, Mark G; Barber, Zoe H

2011-09-11

206

Josephson junctions in SPICE3  

SciTech Connect

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

Whiteley, S.R.

1991-03-01

207

Fabrication of rhenium Josephson junctions  

NASA Astrophysics Data System (ADS)

Rhenium is a superconductor with a relatively weak tendency to oxidize, which is advantageous in superconducting quantum circuit and qubit applications. In this work, Re/Al—AlOx/Re Josephson tunnel junctions were fabricated using a selective film-etching process similar to that developed in Nb trilayer technology. The Re films had a superconducting transition temperature of 4.8 K and a transition width of 0.2 K. The junctions were found to be highly reproducible using the fabrication process and their characteristics had good quality with a low leakage current and showed a superconducting gap of 0.55 meV.

Xue, Guang-Ming; Yu, Hai-Feng; Tian, Ye; Liu, Wei-Yang; Yu, Hong-Wei; Ren, Yu-Feng; Zhao, Shi-Ping

2013-09-01

208

Interconverting conformations of slipped-DNA junctions formed by trinucleotide repeats affect repair outcome.  

PubMed

Expansions of (CTG)·(CAG) repeated DNAs are the mutagenic cause of 14 neurological diseases, likely arising through the formation and processing of slipped-strand DNAs. These transient intermediates of repeat length mutations are formed by out-of-register mispairing of repeat units on complementary strands. The three-way slipped-DNA junction, at which the excess repeats slip out from the duplex, is a poorly understood feature common to these mutagenic intermediates. Here, we reveal that slipped junctions can assume a surprising number of interconverting conformations where the strand opposite the slip-out either is fully base paired or has one or two unpaired nucleotides. These unpaired nucleotides can also arise opposite either of the nonslipped junction arms. Junction conformation can affect binding by various structure-specific DNA repair proteins and can also alter correct nick-directed repair levels. Junctions that have the potential to contain unpaired nucleotides are repaired with a significantly higher efficiency than constrained fully paired junctions. Surprisingly, certain junction conformations are aberrantly repaired to expansion mutations: misdirection of repair to the non-nicked strand opposite the slip-out leads to integration of the excess slipped-out repeats rather than their excision. Thus, slipped-junction structure can determine whether repair attempts lead to correction or expansion mutations. PMID:23339280

Slean, Meghan M; Reddy, Kaalak; Wu, Bin; Nichol Edamura, Kerrie; Kekis, Mariana; Nelissen, Frank H T; Aspers, Ruud L E G; Tessari, Marco; Schärer, Orlando D; Wijmenga, Sybren S; Pearson, Christopher E

2013-01-22

209

Habituation: Occurrence at a Neuromuscular Junction.  

National Technical Information Service (NTIS)

At the neuromuscular junctions between the motor giant axon and fast flexor muscle fibers in crayfish, stimulation at frequencies of one per minute produces a large decline in the amplitude of excitatory junctional potentials. Recovery (dishabituation) ca...

D. Kennedy J. Bruner

1970-01-01

210

Wave Tunneling and Hysteresis in Nonlinear Junctions  

SciTech Connect

We consider the nonlinear tunneling of a plane wave through a small barrier potential in a medium with self-defocusing, or repulsive, interactions. We show that nonlinearity can either suppress or enhance transmission rates, determined by whether the initial kinetic energy is above or below the barrier height. Associated with this threshold is the appearance of two distinct hysteresis loops, going clockwise or counterclockwise, respectively. Spatial dynamics upon reflection and transmission reveals the formation of dispersive shock waves (dark soliton trains) due to phase jumps at the interfaces and wave steepening during propagation. The results are demonstrated experimentally for optical wave tunneling through a refractive index defect but will hold for any Schroedinger system that contains a nonlinear junction.

Wan Wenjie; Muenzel, Stefan; Fleischer, Jason W. [Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544 (United States); Princeton Institute for the Science and Technology of Materials, Princeton University, Princeton, New Jersey 08544 (United States)

2010-02-19

211

Wave Tunneling and Hysteresis in Nonlinear Junctions  

NASA Astrophysics Data System (ADS)

We consider the nonlinear tunneling of a plane wave through a small barrier potential in a medium with self-defocusing, or repulsive, interactions. We show that nonlinearity can either suppress or enhance transmission rates, determined by whether the initial kinetic energy is above or below the barrier height. Associated with this threshold is the appearance of two distinct hysteresis loops, going clockwise or counterclockwise, respectively. Spatial dynamics upon reflection and transmission reveals the formation of dispersive shock waves (dark soliton trains) due to phase jumps at the interfaces and wave steepening during propagation. The results are demonstrated experimentally for optical wave tunneling through a refractive index defect but will hold for any Schrödinger system that contains a nonlinear junction.

Wan, Wenjie; Muenzel, Stefan; Fleischer, Jason W.

2010-02-01

212

Wave tunneling and hysteresis in nonlinear junctions.  

PubMed

We consider the nonlinear tunneling of a plane wave through a small barrier potential in a medium with self-defocusing, or repulsive, interactions. We show that nonlinearity can either suppress or enhance transmission rates, determined by whether the initial kinetic energy is above or below the barrier height. Associated with this threshold is the appearance of two distinct hysteresis loops, going clockwise or counterclockwise, respectively. Spatial dynamics upon reflection and transmission reveals the formation of dispersive shock waves (dark soliton trains) due to phase jumps at the interfaces and wave steepening during propagation. The results are demonstrated experimentally for optical wave tunneling through a refractive index defect but will hold for any Schrödinger system that contains a nonlinear junction. PMID:20366886

Wan, Wenjie; Muenzel, Stefan; Fleischer, Jason W

2010-02-18

213

Vinculin associates with endothelial VE-cadherin junctions to control force-dependent remodeling  

PubMed Central

To remodel endothelial cell–cell adhesion, inflammatory cytokine- and angiogenic growth factor–induced signals impinge on the vascular endothelial cadherin (VE-cadherin) complex, the central component of endothelial adherens junctions. This study demonstrates that junction remodeling takes place at a molecularly and phenotypically distinct subset of VE-cadherin adhesions, defined here as focal adherens junctions (FAJs). FAJs are attached to radial F-actin bundles and marked by the mechanosensory protein Vinculin. We show that endothelial hormones vascular endothelial growth factor, tumor necrosis factor ?, and most prominently thrombin induced the transformation of stable junctions into FAJs. The actin cytoskeleton generated pulling forces specifically on FAJs, and inhibition of Rho-Rock-actomyosin contractility prevented the formation of FAJs and junction remodeling. FAJs formed normally in cells expressing a Vinculin binding-deficient mutant of ?-catenin, showing that Vinculin recruitment is not required for adherens junction formation. Comparing Vinculin-devoid FAJs to wild-type FAJs revealed that Vinculin protects VE-cadherin junctions from opening during their force-dependent remodeling. These findings implicate Vinculin-dependent cadherin mechanosensing in endothelial processes such as leukocyte extravasation and angiogenesis.

Oldenburg, Joppe; Spanjaard, Emma; van der Krogt, Gerard; Grigoriev, Ilya; Akhmanova, Anna; Rehmann, Holger

2012-01-01

214

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

PubMed Central

In this study, we demonstrate that fluid shear stress (FSS)-induced actin cytoskeletal reorganization and junctional formation in renal epithelial cells are nearly completely opposite the corresponding changes in vascular endothelial cells (ECs) [Thi MM et al. (2004) Proc Natl Acad Sci USA 101:16483–16488]. Mouse proximal tubule cells (PTCs) were subjected to 5 h of FSS (1 dyn/cm2) to investigate the dynamic responses of the cytoskeletal distribution of filamentous actin (F-actin), ZO-1, E-cadherin, vinculin, and paxillin to FSS. Immunofluorescence analysis revealed that FSS caused basal stress fiber disruption, more densely distributed peripheral actin bands (DPABs), and the formation of both tight junctions (TJs) and adherens junctions (AJs). A dramatic reinforcement of vinculin staining was found at the cell borders as well as the cell interior. These responses were abrogated by the actin-disrupting drug, cytochalasin D. To interpret these results, we propose a “junctional buttressing” model for PTCs in which FSS enables the DPABs, TJs, and AJs to become more tightly connected. In contrast, in the “bumper-car” model for ECs, all junctional connections were severely disrupted by FSS. This “junctional buttressing” model explains why a FSS of only 1/10 of that used in the EC study can cause a similarly dramatic, cytoskeletal response in these tall, cuboidal epithelial cells; and why junctional buttressing between adjacent cells may benefit renal epithelium in maximizing flow-activated, brush border-dependent, transcellular salt and water reabsorption.

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

2008-01-01

215

The development of the myotendinous junction. A review.  

PubMed

The myotendinous junction (MTJ) is a complex specialized region located at the muscle-tendon interface that represents the primary site of force transmission. Despite their different embryologic origins, muscle and tendon morphogenesis occurs in close spatial and temporal association. After muscle attachment, muscle and tendon constitute a dynamic and functional integrated unit that transduces muscle contraction force to the skeletal system. We review here the current understanding of MTJ formation describing changes during morphogenesis and focusing on the crosstalk between muscle and tendon cells that leads to the development of a functional MTJ. Molecules involved in the formation of the linkage, both at the tendon side and at the muscle side of the junction are described. Much of this knowledge comes from studies using different animal models such as mice, zebrafish and Drosophila where powerful methods for in vivo imaging and genetic manipulations can be used to enlighten this developmental process. PMID:23738275

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

2012-09-10

216

The development of the myotendinous junction. A review  

PubMed Central

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

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

2012-01-01

217

Fabrication of high quality ferromagnetic Josephson junctions  

Microsoft Academic Search

We present ferromagnetic Nb\\/Al2O3\\/Ni60Cu40\\/Nb Josephson junctions (SIFS) with an ultrathin Al2O3 tunnel barrier. The junction fabrication was optimized regarding junction insulation and homogeneity of current transport. Using ion-beam-etching and anodic oxidation we defined and insulated the junction mesas. The additional 2nm thin Cu-layer below the ferromagnetic NiCu (SINFS) lowered interface roughness and ensured very homogeneous current transport. A high yield

M. Weides; K. Tillmann; H. Kohlstedt

2006-01-01

218

High-temperature cubic boron nitride p-N junction diode made at high pressure.  

PubMed

A p-n junction diode of cubic boron nitride was made by growing an n-type crystal epitaxially on a p-type seed crystal at a pressure of 55 kilobars and a temperature of about 1700 degrees C. A temperature-difference solvent method was used for the crystal growth, and beryllium and silicon were doped as acceptors and donors, respectively. Formation of the p-n junction was clearly confirmed at 1 bar by rectification characteristics and by existence of a space charge layer of the junction as observed by electron beam induced current measurement. This diode operated at 530 degrees C. PMID:17800457

Mishima, O; Tanaka, J; Yamaoka, S; Fukunaga, O

1987-10-01

219

Expression and functions of neuronal gap junctions  

Microsoft Academic Search

Gap junctions are channel-forming structures in contacting plasma membranes that allow direct metabolic and electrical communication between almost all cell types in the mammalian brain. At least 20 connexin genes and 3 pannexin genes probably code for gap junction proteins in mice and humans. Gap junctions between murine neurons (also known as electrical synapses) can be composed of connexin 36,

Goran Söhl; Stephan Maxeiner; Klaus Willecke

2005-01-01

220

Cadherin Junctions in Mammary Tumors  

Microsoft Academic Search

Cadherins are the transmembrane component of adherens junctions found between interacting cells in tissues. The cadherins bind cells to one another in a specific manner and link to the actin cytoskeleton through intracellular catenins. In addition to promoting strong cell-cell adhesion, cadherins appear to initiate and modify intracellular signaling pathways. The loss of E-cadherin function in epithelial cells is thought

Margaret J. Wheelock; Alejandro Peralta Soler; Karen A. Knudsen

2001-01-01

221

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...

222

Operation Junction City, Vietnam, 1967.  

National Technical Information Service (NTIS)

Operation JUNCTION CITY was the largest search and destroy operation of the Viet Nam war as of the spring of 1967 when the battle took place. Forces of the United States Army and Air Force, in conjunction with elements of the Army of the Republic of Viet ...

B. L. Crittenden D. H. Petraeus G. C. Lorenz J. H. Willbanks P. A. Stuart

1983-01-01

223

The Yolla Bolly junction revisited  

SciTech Connect

West of Red Bluff, California, rocks of the northern Coast Ranges, Klamath-Sierra Nevada, and Great Valley provinces come together at what has been called the Yolla Bolly junction. Mapping of the Red Bluff and Willows 1:100,000 quadrangles has greatly clarified the enigmatic features of this complex area. Terranes of the Klamath Mountains and their Cretaceous sedimentary cover have been thrust northwestward over the Elder Creek terrane and Franciscan rocks, north of the left-lateral Cold Fork fault zone. The Condrey Mountain window (Franciscan Pickett Peak terrane) provides a measure of the magnitude of this thrusting (ca 90 km). South of the Cold Fork fault zone, the Franciscan and Elder Creek terranes were driven southeastward as tectonic wedges onto Sierran-Klamath basement. Timing of this scissor-tectonics is not constrained near the junction, but further north in southwest Oregon, Lower Eocene strata were deformed by overthrusting of the Klamath block whereas Upper Eocene strata overlap the thrust, indicating that thrusting occurred between about 52 and 60 Ma. Plate reconstructions for this time interval indicate the close proximity of the Kula-Farallon-North America triple junction and that old (ca 100 m.y.) Farallon lithosphere was being subducted north of the junction whereas to the south, very young (ca 10 m.y.) Kula plate was presumably obducted onto North America.

Blake, M.C.; Jayko, A.S. (Geological Survey, Menlo Park, CA (United States)); Jones, D.L. (Univ. of California, Berkeley, CA (United States). Dept. of Geology and Geophysics); Engebretson, D.C. (Western Washington Univ., Bellingham, WA (United States). Dept. of Geology)

1993-04-01

224

Acetylcholinesterase Clustering at the Neuromuscular Junction Involves Perlecan and Dystroglycan  

Microsoft Academic Search

Formation of the synaptic basal lamina at vertebrate neuromuscular junction involves the accu- mulation of numerous specialized extracellular matrix molecules including a specific form of acetylcholines- terase (AChE), the collagenic-tailed form. The mecha- nisms responsible for its localization at sites of nerve— muscle contact are not well understood. To understand synaptic AChE localization, we synthesized a fluores- cent conjugate of

H. Benjamin Peng; Hongbo Xie; Susanna G. Rossi; Richard L. Rotundo

2010-01-01

225

JUNCTIONAL COMPLEXES IN VARIOUS EPITHELIA  

PubMed Central

The epithelia of a number of glands and cavitary organs of the rat and guinea pig have been surveyed, and in all cases investigated, a characteristic tripartite junctional complex has been found between adjacent cells. Although the complex differs in precise arrangement from one organ to another, it has been regularly encountered in the mucosal epithelia of the stomach, intestine, gall bladder, uterus, and oviduct; in the glandular epithelia of the liver, pancreas, parotid, stomach, and thyroid; in the epithelia of pancreatic, hepatic, and salivary ducts; and finally, between the epithelial cells of the nephron (proximal and distal convolution, collecting ducts). The elements of the complex, identified as zonula occludens (tight junction), zonula adhaerens (intermediary junction), and macula adhaerens (desmosome), occupy a juxtaluminal position and succeed each other in the order given in an apical-basal direction. The zonula occludens (tight junction) is characterized by fusion of the adjacent cell membranes resulting in obliteration of the intercellular space over variable distances. Within the obliterated zone, the dense outer leaflets of the adjoining cell membranes converge to form a single intermediate line. A diffuse band of dense cytoplasmic material is often associated with this junction, but its development varies from one epithelium to another. The zonula adhaerens (intermediate junction) is characterized by the presence of an intercellular space (?200 A) occupied by homogeneous, apparently amorphous material of low density; by strict parallelism of the adjoining cell membranes over distances of 0.2 to 0.5 µ; and by conspicuous bands of dense material located in the subjacent cytoplasmic matrix. The desmosome or macula adhaerens is also characterized by the presence of an intercellular space (?240 A) which, in this case, contains a central disc of dense material; by discrete cytoplasmic plaques disposed parallel to the inner leaflet of each cell membrane; and by the presence of bundles of cytoplasmic fibrils converging on the plaques. The zonula occludens appears to form a continuous belt-like attachment, whereas the desmosome is a discontinuous, button-like structure. The zomula adhaerens is continuous in most epithelia but discontinuous in some. Observations made during experimental hemoglobinuria in rats showed that the hemoglobin, which undergoes enough concentration in the nephron lumina to act as an electron-opaque mass tracer, does not penetrate the intercellular spaces beyond the zonula occludens. Similar observations were made in pancreatic acini and ducts where discharged zymogen served as a mass tracer. Hence the tight junction is impervious to concentrated protein solutions and appears to function as a diffusion barrier or "seal." The desmosome and probably also the zonula adhaerens may represent intercellular attachment devices.

Farquhar, Marilyn G.; Palade, George E.

1963-01-01

226

The lateral mobility of cell adhesion molecules is highly restricted at septate junctions in Drosophila  

Microsoft Academic Search

BACKGROUND: A complex of three cell adhesion molecules (CAMs) Neurexin IV(Nrx IV), Contactin (Cont) and Neuroglian (Nrg) is implicated in the formation of septate junctions between epithelial cells in Drosophila. These CAMs are interdependent for their localization at septate junctions and e.g. null mutation of nrx IV or cont induces the mislocalization of Nrg to the baso-lateral membrane. These mutations

Monique Laval; Christophe Bel; Catherine Faivre-Sarrailh

2008-01-01

227

Specific localisation of gap junction protein connexin 32 in the gastric mucosa of horses  

Microsoft Academic Search

In the glandular stomach, gap junctional intercellular communication (GJIC) plays an important role in the gastric mucosal\\u000a defense system, and loss of GJIC is associated with ulcer formation. In spite of the high incidence of gastric ulcers in horses,\\u000a particularly at pars nonglandularis, the presence of gap junctions in the equine stomach has not yet been studied. The objective\\u000a was

Cornelia Fink; Tanja Hembes; Ralph Brehm; Roswitha Weigel; Cornelia Heeb; Christiane Pfarrer; Martin Bergmann; Monika Kressin

2006-01-01

228

High-temperature cubic boron nitride p-n junction diode made at high pressure  

Microsoft Academic Search

A p-n junction diode of cubic boron nitride was made by growing an n-type crystal epitaxially on a p-type seed crystal at a pressure of 55 kilobars and a temperature of about 1700 C. A temperature-difference solvent method was used for the crystal growth, and beryllium and silicon were doped as acceptors and donors, respectively. Formation of the p-n junction

Osamu Mishima; Junzo Tanaka; Shinobu Yamaoka; Osamu Fukunaga

1987-01-01

229

Neurexin in Embryonic Drosophila Neuromuscular Junctions  

PubMed Central

Background Neurexin is a synaptic cell adhesion protein critical for synapse formation and function. Mutations in neurexin and neurexin-interacting proteins have been implicated in several neurological diseases. Previous studies have described Drosophila neurexin mutant phenotypes in third instar larvae and adults. However, the expression and function of Drosophila neurexin early in synapse development, when neurexin function is thought to be most important, has not been described. Methodology/Principal Findings We use a variety of techniques, including immunohistochemistry, electron microscopy, in situ hybridization, and electrophysiology, to characterize neurexin expression and phenotypes in embryonic Drosophila neuromuscular junctions (NMJs). Our results surprisingly suggest that neurexin in embryos is present both pre and postsynaptically. Presynaptic neurexin promotes presynaptic active zone formation and neurotransmitter release, but along with postsynaptic neurexin, also suppresses formation of ectopic glutamate receptor clusters. Interestingly, we find that loss of neurexin only affects receptors containing the subunit GluRIIA. Conclusions/Significance Our study extends previous results and provides important detail regarding the role of neurexin in Drosophila glutamate receptor abundance. The possibility that neurexin is present postsynaptically raises new hypotheses regarding neurexin function in synapses, and our results provide new insights into the role of neurexin in synapse development.

Chen, Kaiyun; Gracheva, Elena O.; Yu, Szi-Chieh; Sheng, Qi; Richmond, Janet; Featherstone, David E.

2010-01-01

230

TEM4 is a junctional Rho GEF required for cell-cell adhesion, monolayer integrity and barrier function.  

PubMed

Signaling events mediated by Rho family GTPases orchestrate cytoskeletal dynamics and cell junction formation. The activation of Rho GTPases is tightly regulated by guanine-nucleotide-exchange factors (GEFs). In this study, we identified a novel Rho-specific GEF called TEM4 (tumor endothelial marker 4) that associates with multiple members of the cadherin-catenin complex and with several cytoskeleton-associated proteins. Depending on confluence, TEM4 localized to either actin stress fibers or areas of cell-cell contact. The junctional localization of TEM4 was independent of actin binding. Depletion of endogenous TEM4 by shRNAs impaired Madin-Darby canine kidney (MDCK) and human umbilical vein endothelial cell (HUVEC) cell junctions, disrupted MDCK acini formation in 3D culture and negatively affected endothelial barrier function. Taken together, our findings implicate TEM4 as a novel and crucial junctional Rho GEF that regulates cell junction integrity and epithelial and endothelial cell function. PMID:23729734

Ngok, Siu P; Geyer, Rory; Kourtidis, Antonis; Mitin, Natalia; Feathers, Ryan; Der, Channing; Anastasiadis, Panos Z

2013-05-31

231

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

NSDL National Science Digital Library

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.

Thomas Krupinski (Department of Biochemistry, Molecular Biology, and Cell Biology); Greg J Beitel (Northwestern University)

2009-06-01

232

Signaling the Junctions in Gut Epithelium  

NSDL National Science Digital Library

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.

Frederic Hollande (CNRS France;Functional Genomics Institute (IGF) and Cellular and Molecular Oncology Department REV); Arthur Shulkes (University of Melbourne Department of Surgery and Austin Health; REV); Graham S. Baldwin (University of Melbourne Department of Surgery and Austin Health; REV)

2005-03-29

233

Dark energy and Josephson junctions  

NASA Astrophysics Data System (ADS)

It has been recently claimed that dark energy can be (and has been) observed in laboratory experiments by measuring the power spectrum SI(?) of the noise current in a resistively shunted Josephson junction and that in new dedicated experiments, which will soon test a higher frequency range, SI(?) 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 SI(?). 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 SI(?) will be observed in forthcoming experiments. Our findings provide new (we believe definite) arguments which strongly support previous criticisms.

Branchina, Vincenzo; Di Liberto, Marco; Lodato, Ivano

2009-08-01

234

Dynamics of accelerated Josephson junctions  

NASA Astrophysics Data System (ADS)

The behavior of large-area Josephson tunneling junctions (JTJ) is analyzed theoretically, taking the theory of general relativity into account. The covariant sine-Gordon equation for a large-area JTJ of undefined contour is established and adapted to the specific case of a rotating ring-shaped JTJ. The dynamics of the soliton as rotation rate is varied are investigated. It is shown that soliton angular velocity, conserved with respect to the inertial reference frame in an ideal, vacuum-barrier ring JTJ when ring angular velocity is changed, will be decreased in a real ring JTJ due to permeability/permittivity variation and junction inhomogeneity, resulting in possible soliton pinning. The difficulties implied for the construction of a Josephson inertial rotation sensor (analogous to optical rotation sensors based on the Sagnac effect) and possible techniques for overcoming them are discussed.

Russer, P.

1983-06-01

235

Management of craniocervical junction dislocation  

Microsoft Academic Search

The discovery of a craniocervical junction malformation requires management in three steps: (1) The patterns must be recognized\\u000a using tomographic measurements (Chamberlain’s line, Wackenheim’s line). Dynamic flexion–extension studies are necessary to\\u000a assess stability or instability. Stable patterns range from platybasia to basilar invagination, with gradual deformation,\\u000a and are frequently associated with Chiari malformation. Unstable patterns characterized by odontoid instability are

J. P. Chirossel; J. G. Passagia; E. Gay; O. Palombi

2000-01-01

236

Fusions at the craniovertebral junction  

Microsoft Academic Search

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

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

2008-01-01

237

JUNCTIONAL COMPLEXES IN VARIOUS EPITHELIA  

Microsoft Academic Search

ABSTRACT The epithelia of a number,of glands and,cavitary organs of the rat and,guinea,pig have been surveyed, and in all cases investigated, a characteristic tripartite junctional complex has been found,between,adjacent,cells. Although,the complex,differs in precise arrange- ment from one organ to another, it has been regularly encountered in the mucosal epi- thelia of the stomach, intestine, gall bladder, uterus, and oviduct; in

Marilyn G. Farquhar; George E. Palade

1963-01-01

238

New functions for gap junctions  

Microsoft Academic Search

The most significant finding of the past year in gap junction research has been the association of connexin defects with human diseases. Connexin32 mutations cause X-linked Charcot-Marie-Tooth disease, a demyelinating peripheral neuropathy. Mutations in connexin43 may underlie cardiac malformations in visceroatrial heterotaxia syndromes. Genetic approaches and gene targeting have provided new insights, but also raise new questions concerning connexin function,

David L Paul

1995-01-01

239

THE EPIDERMAL-DERMAL JUNCTION  

Microsoft Academic Search

Ultrastructurally, the epidermal-dermal junction is composed of four component areas: (1) the basal cell plasma membrane with its specialized attachment devices or hemidesmosomes, (2) an electron-lucent area, the lamina lucida, (3) the basal lamina, and (4) the sub-basal lamina fibrous components, including anchoring fibrils, dermal microfibril bundles, and collagen fibers. The light microscopic “basement membrane” comprises only the sub-basal lamina

Robert A. Briggaman; Clayton E. Wheeler Jr.

1975-01-01

240

An approach to measure electromechanical properties of atomic and molecular junctions.  

PubMed

We describe a new setup for simultaneous measurements of force and current in conductive nanocontacts in a liquid environment with a high sampling rate and resolution. A lab-built current-to-voltage converter allows measurements of the current over seven orders of magnitude. As examples, we studied conductances and mechanical forces upon formation and breaking of gold atomic contacts and of two molecular junctions containing 1,2-di(4-pyridyl)ethyne (M1) and 1,4-di(4-pyridyl)buta-1,3-diyne (M2). We found that the forces required to deform or break gold atomic contacts depend critically on the surrounding medium. Further, they show non-linear behaviour in dependence of the number N of gold atoms detached. The electromechanical properties of the two types of molecular junctions upon stretching were analysed by correlating breaking forces with simultaneously measured junction conductances. A rather complex behaviour in a wide range of forces was discovered. Comparison of the current-probe atomic force microscopy experiments on the rupture of molecular junctions with STM-based break junction experiments enables the assignment of breaking forces of molecular junctions to the corresponding junction conductances. PMID:22466399

Pobelov, Ilya V; Mészáros, Gábor; Yoshida, Koji; Mishchenko, Artem; Gulcur, Murat; Bryce, Martin R; Wandlowski, Thomas

2012-03-30

241

The adherens junction: a mosaic of cadherin and nectin clusters bundled by actin filaments.  

PubMed

Cadherin and nectin are distinct transmembrane proteins of adherens junctions. Their ectodomains mediate adhesion, whereas 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, as 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

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

2013-05-02

242

The fine structure of polychaete septate junctions.  

PubMed

Epidermal septate junctions of Nereis sp. and Cirriformia sp. fixed with OsO4 or glutaraldehyde/OsO4 display variable structure in electron micrographs. In transverse section the septa are often indistinct and obscured by opaque material that fills the junctional cleft. Septa (spaced at 180--280 A) are more clearly defined in slightly oblique transverse section; they exhibit an electron lucent center and appear to be linked by arms. En face views of the junction show a honeycomb pattern. Cytoplasmic faces of junctional membranes are backed with plaques opposite the septa. Lanthanum used as a tracer delineates junctional structure in negative contrast. In transverse section a chain-like lattice is present in the junctional cleft. En face vies show parallel rows of pleated elements often linked by arms into honeycomb arrays. Oblique sections demonstrate that these pleated elements are continuous with the chain-like lattice seen in transverse sections. Lanthanum does not pass entirely through the junction. Lanthanum reveals that the septa have a very intricate substructure, but it is difficult to visualize the architecture that could generate the various images presented by these junctions when seen in different orientations. However, it is clear that these junctions possess some features that are diagnostic of several supposedly different types of septate junctions in invertebrates. PMID:991260

Baskin, D G

1976-10-22

243

The pseudoblastema in the wound healing process of the leech Hirudo medicinalis L. (Hirudinea): changes in cell junctions.  

PubMed

The role of the connective tissue cells and their migratory behavior have been investigated in the formation and evolution of the pseudoblastema during wound healing in the leech Hirudo medicinalis. In H. medicinalis the healing process shows first a flow of cells that effectively seal the wound and form a temporary cellular clump, the pseudoblastema, which contributes to the phagocytotic process and apparently regenerates the extracellular matrix. The migratory cells forming the pseudoblastema are connective tissue cells known as vasocentral cells, which, when in a resting state, are associated with the vasofibrous cells. During the formation and evolution of the pseudoblastema several changes affect vasocentral cell junctions. At rest, vasocentral cells do not show cell to cell junctions but they show adhering junctions in contact with the extracellular matrix. These junctions disrupt during the migratory phase. When vasocentral cells regroup in the pseudoblastema, adhering junctions are formed between them, and adhering junctions making contact with the matrix appear again. As the pseudoblastema evolves, cell to cell adhering junctions become more conspicuous and undergo other changes. During the next stage of retraction, close contacts develop between pseudoblastema cells and neighboring nondamaged muscle fibers, which probably serve as points of anchorage for the approaching movement of the wound edges. Finally, cell to cell and cell to matrix junctions disappear and the pseudoblastema disintegrates. PMID:8207379

Huguet, G; Molinas, M

1994-05-15

244

ARHGAP10 is necessary for alpha-catenin recruitment at adherens junctions and for Listeria invasion.  

PubMed

E-cadherin mediates the formation of adherens junctions between epithelial cells. It serves as a receptor for Listeria monocytogenes, a bacterial pathogen that enters epithelial cells. The L. monocytogenes surface protein, InlA, interacts with the extracellular domain of E-cadherin. In adherens junctions, this ectodomain is involved in homophilic interactions whereas the cytoplasmic domain binds beta-catenin, which then recruits alpha-catenin. alpha-catenin binds to actin directly, or indirectly, thus linking E-cadherin to the actin cytoskeleton. Entry of L. monocytogenes into cells and adherens junction formation are dynamic events that involve actin and membrane rearrangements. To understand these processes better, we searched for new ligands of alpha-catenin. Using a two-hybrid screen, we identified a new partner of alpha-catenin: ARHGAP10. This protein colocalized with alpha-catenin at cell-cell junctions and was recruited at L. monocytogenes entry sites. In ARHGAP10-knockdown cells, L. monocytogenes entry and alpha-catenin recruitment at cell-cell contacts were impaired. The GAP domain of ARHGAP10 has GAP activity for RhoA and Cdc42. Its overexpression disrupted actin cables, enhanced alpha-catenin and cortical actin levels at cell-cell junctions and inhibited L. monocytogenes entry. Altogether, our results show that ARHGAP10 is a new component of cell-cell junctions that controls alpha-catenin recruitment and has a key role during L. monocytogenes uptake. PMID:16184169

Sousa, Sandra; Cabanes, Didier; Archambaud, Cristel; Colland, Frédéric; Lemichez, Emmanuel; Popoff, Michel; Boisson-Dupuis, Stéphanie; Gouin, Edith; Lecuit, Marc; Legrain, Pierre; Cossart, Pascale

2005-09-25

245

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

Microsoft Academic Search

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

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

2009-01-01

246

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

NASA Astrophysics Data System (ADS)

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 (<=10-7 A/cm2), large breakdown voltage (>7 V), and ultrahigh rectification (>2×104) in the bias voltage <=2.0 V and temperature range from 5 to 300 K. 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.

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

247

Physiological and physiopathological aspects of connexins and communicating gap junctions in spermatogenesis  

PubMed Central

Spermatogenesis is a highly regulated process of germ cell proliferation and differentiation, starting from spermatogonia to spermatocytes and giving rise to spermatids, the future spermatozoa. In addition to endocrine regulation, testicular cell–cell interactions are essential for spermatogenesis. This precise control is mediated through paracrine/autocrine pathways, direct intercellular contacts and through intercellular communication channels, consisting of gap junctions and their constitutive proteins, the connexins. Gap junctions are localized between adjacent Leydig cells, between Sertoli cells and between Sertoli cells and specific germ cells. This review focuses on the distribution of connexins within the seminiferous epithelium, their participation in gap junction channel formation, the control of their expression and the physiological relevance of these junctions in both the Sertoli–Sertoli cell functional synchronization and the Sertoli–germ cell dialogue. In this review, we also discuss the potential implication of disrupted connexin in testis cancer, since impaired expression of connexin has been described as a typical feature of tumoral proliferation.

Pointis, Georges; Gilleron, Jerome; Carette, Diane; Segretain, Dominique

2010-01-01

248

Defect-Free Junction TFT for Improving Reliability under Hot Carrier Stress  

NASA Astrophysics Data System (ADS)

A new polycrystalline silicon thin film transistor (poly-Si TFTs) called 'Defect-Free Junction TFT (DFJ-TFT)', which exhibits improved stability under hot carrier stress, has been proposed and fabricated. In order to remove residual junction defects due to ion implantation, source/drain doping was carried out prior to gate formation. During excimer laser annealing (ELA), large lateral grains are grown near the junction of the proposed TFT due to the different melting conditions between implanted source/drain region and non-implanted channel region. Our TEM image shows that there are large grains near the source/drain junction instead of residual implanted damage. The DFJ-TFT exhibits improved reliability compared with conventional TFT under hot carrier stress.

Jung, Sang-Hoon; Shin, Hee-Sun; Han, Min-Koo

2004-01-01

249

Optimizing boron junctions through point defect and stress engineering using carbon and germanium co-implants  

SciTech Connect

We report the fabrication of p{sup +}/n junctions using Ge{sup +}, C{sup +}, and B{sup +} co-implantation and a spike anneal. The best junction exhibits a depth of 26 nm, vertical abruptness of 3 nm/decade, and sheet resistance of 520 Ohm/square. The junction location is defined by where the boron concentration drops to 10{sup 18} cm{sup -3}. These junctions are close to the International Technology Roadmap specifications for the 65 nm technology node and are achieved by careful engineering of amorphization, stresses, and point defects. Advanced simulation of boron diffusion is used to understand and optimize the process window. The simulations show that the optimum process completely suppresses the transient-enhanced diffusion of boron and the formation of boron-interstitial clusters. This increases the boron solubility to 20% above the equilibrium solid-state solubility.

Moroz, Victor; Oh, Yong-Seog; Pramanik, Dipu; Graoui, Houda; Foad, Majeed A. [Synopsys, Incorporated, 700 East Middlefield Road, Mountain View, California 94043 (United States); Applied Materials Incorporated, 974 East Arques Avenue, Sunnyvale, California 94086 (United States)

2005-08-01

250

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

PubMed Central

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.

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

2010-01-01

251

ABERRANT DEVELOPMENT OF NEUROMUSCULAR JUNCTIONS IN GLYCOSYLATION-DEFECTIVE LARGEMYD MICE  

PubMed Central

Mice deficient in the glycosyltransferase Large are characterized by severe muscle and central nervous system abnormalities. In this study, we show that the formation and maintenance of neuromuscular junctions in Largemyd mice are greatly compromised. Neuromuscular junctions are not confined to the muscle endplate zone but are widely spread and are frequently accompanied by exuberant nerve sprouting. Nerve terminals are highly fragmented and binding of ?-bungarotoxin to postsynaptic acetylcholine receptors (AChRs) is greatly reduced. In vitro, Largemyd myotubes are responsive to agrin but produce aberrant AChR clusters, which are larger in area and less densely packed with AChRs. In addition, AChR expression on the cell surface is diminished suggesting that AChR assembly or transport is defective. These results together with the finding that O-linked glycosylation at neuromuscular junctions of Largemyd mice is compromised indicate that the action of Large is necessary for proper neuromuscular junction development.

Herbst, Ruth; Iskratsch, Thomas; Unger, Ewald; Bittner, Reginald E.

2010-01-01

252

Physics and applications of NIS junctions  

NASA Astrophysics Data System (ADS)

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, ?, of the superconducting electrode. For junction voltages comparable to ?/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. .

Ullom, J. N.

2002-02-01

253

Modulated microwave absorption spectra from Josephson junctions on a scratched niobium wire  

NASA Astrophysics Data System (ADS)

Modulated microwave absorption (MMA) spectra from Josephson junction formations on a scratched Nb wire have been studied at 9.3 GHz and 4 K. The peak-to-peak separation, ?H of the Josephson lines was found to vary linearly with P1/2, where P is the applied microwave power, in contrast to a recent interpretation of junction formation in pressed lead pieces by Rubins, Drumheller, and Trybula. The interpretation of the MMA data on Nb are given in terms of the theory of Vichery, Beuneu, and Lejay for superconducting loops containing weak links.

Rubins, R. S.; Hutton, S. L.; Ravindran, K.; Subbaraman, K.; Drumheller, John E.

1997-05-01

254

Modulated microwave absorption spectra from Josephson junctions on a scratched niobium wire  

SciTech Connect

Modulated microwave absorption (MMA) spectra from Josephson junction formations on a scratched Nb wire have been studied at 9.3 GHz and 4 K. The peak-to-peak separation, {delta}H of the Josephson lines was found to vary linearly with P{sup 1/2}, where P is the applied microwave power, in contrast to a recent interpretation of junction formation in pressed lead pieces by Rubins, Drumheller, and Trybula. The interpretation of the MMA data on Nb are given in terms of the theory of Vichery, Beuneu, and Lejay for superconducting loops containing weak links. {copyright} {ital 1997} {ital The American Physical Society}

Rubins, R.S. [Department of Physics, Montana State University, Bozeman, Montana 59717 (United States)]|[University of Texas at Arlington, Box 19059, Arlington, Texas 76019 (United States); Hutton, S.L.; Ravindran, K.; Subbaraman, K.; Drumheller, J.E. [Department of Physics, Montana State University, Bozeman, Montana 59717 (United States)

1997-05-01

255

Do conformational biases of simple helical junctions influence RNA folding stability and specificity?  

SciTech Connect

Structured RNAs must fold into their native structures and discriminate against a large number of alternative ones, an especially difficult task given the limited information content of RNA's nucleotide alphabet. The simplest motifs within structured RNAs are two helices joined by nonhelical junctions. To uncover the fundamental behavior of these motifs and to elucidate the underlying physical forces and challenges faced by structured RNAs, we computationally and experimentally studied a tethered duplex model system composed of two helices joined by flexible single- or double-stranded polyethylene glycol tethers, whose lengths correspond to those typically observed in junctions from structured RNAs. To dissect the thermodynamic properties of these simple motifs, we computationally probed how junction topology, electrostatics, and tertiary contact location influenced folding stability. Small-angle X-ray scattering was used to assess our predictions. Single- or double-stranded junctions, independent of sequence, greatly reduce the space of allowed helical conformations and influencing the preferred location and orientation of their adjoining helices. A double-stranded junction guides the helices along a hinge-like pathway. In contrast, a single-stranded junction samples a broader set of conformations and has different preferences than the double-stranded junction. In turn, these preferences determine the stability and distinct specificities of tertiary structure formation. These sequence-independent effects suggest that properties as simple as a junction's topology can generally define the accessible conformational space, thereby stabilizing desired structures and assisting in discriminating against misfolded structures. Thus, junction topology provides a fundamental strategy for transcending the limitations imposed by the low information content of RNA primary sequence.

Chu, Vincent B.; Lipfert, Jan; Bai, Yu; Pande, Vijay S.; Doniach, Sebastian; Herschlag, Daniel; (Stanford); (Houston); (DUT)

2010-02-11

256

Propagating, evanescent, and localized states in carbon nanotube-graphene junctions  

NASA Astrophysics Data System (ADS)

We study the electronic structure of the junctions between a single graphene layer and carbon nanotubes, using a tight-binding model and the continuum theory based on Dirac fermion fields. The latter provides a unified description of different lattice structures with curvature, which is always localized at six heptagonal carbon rings around each junction. When these are evenly spaced, we find that it is possible to curve the planar lattice into armchair (6n,6n) as well as zigzag (6n,0) nanotubes. We show that the junctions fall into two different classes, regarding the low-energy electronic behavior. One of them, constituted by the junctions made of the armchair nanotubes and the zigzag (6n,0) geometries when n is a multiple of 3, is characterized by the presence of two quasibound states at the Fermi level, which are absent for the rest of the zigzag nanotubes. These states, localized at the junction, are shown to arise from the effective gauge flux induced by the heptagonal carbon rings, which has a direct reflection in the local density of states around the junction. Furthermore, we also analyze the band structure of the arrays of junctions, finding out that they can also be classified into two different groups according to the low-energy behavior. In this regard, the arrays made of armchair and (6n,0) nanotubes with n equal to a multiple of 3 are characterized by the presence of a series of flat bands, whose number grows with the length of the nanotubes. We show that such flat bands have their origin in the formation of states confined to the nanotubes, with little overlap in the region between the junctions. This is explained in the continuum theory from the possibility of forming standing waves in the mentioned nanotube geometries, as a superposition of modes with opposite momenta and the same quantum numbers under the C6v symmetry of the junction.

González, J.; Guinea, F.; Herrero, J.

2009-04-01

257

Structural Aspects of Adherens Junctions and Desmosomes  

Microsoft Academic Search

\\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.

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

258

Resonant tunneling in short Josephson SFS junctions  

Microsoft Academic Search

Josephson effect in short ballistic SINIS and SIFIS double-tunnel junctions,\\u000aconsisting of clean superconductors (S), a normal metal (N) or metallic\\u000aferromagnet (F), and insulating interfaces (I) is studied. For SINIS\\u000adouble-tunnel junctions, sharp peaks in the critical Josephson current as a\\u000afunction of the junction width result from the resonant amplification of the\\u000aAndreev process when the quasi-bound states

Z. Radovi?; I. Petkovi?; N. M. Chtchelkatchev

2005-01-01

259

String junction as a baryonic constituent  

NASA Astrophysics Data System (ADS)

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

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

1996-02-01

260

Breakup of microdroplets in asymmetric T junctions  

NASA Astrophysics Data System (ADS)

Symmetric T junctions have been used widely in microfluidics to generate equal-sized microdroplets, which are applicable in drug delivery systems. A newly proposed method for generating unequal-sized microdroplets at a T junction is investigated theoretically and experimentally. Asymmetric T junctions with branches of identical lengths and different cross sections are utilized for this aim. An equation for the critical breakup of droplets at asymmetric T junctions and one for determining the breakup point of droplets are developed. A good agreement was observed between the theories (present and previous) and the experiments.

Samie, Milad; Salari, Alinaghi; Shafii, Mohammad Behshad

2013-05-01

261

Dielectric breakdown of ferromagnetic tunnel junctions  

NASA Astrophysics Data System (ADS)

The time-dependent dielectric breakdown of Co/Al2O3/Co(-Fe) magnetic tunnel junctions is investigated. At voltages larger than 1.2 V, almost immediate breakdown of the junction is observed, leading to a decreased (magneto)resistance. The shorts, which are local hot spots, were visualized by making use of a liquid crystal film on top of the junction. The breakdown voltages of a series of nominally identical tunnel junctions measured in a voltage-ramp experiment are shown to increase with increasing ramp speed. The results are analyzed in the framework of several models for the voltage dependent breakdown probability.

Oepts, W.; Verhagen, H. J.; de Jonge, W. J. M.; Coehoorn, R.

1998-10-01

262

Gap Junctions Couple Astrocytes and Oligodendrocytes  

PubMed Central

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

Orthmann-Murphy, Jennifer L.; Abrams, Charles K.; Scherer, Steven S.

2009-01-01

263

Inhibition of gap junction and adherens junction assembly by connexin and A-CAM antibodies  

Microsoft Academic Search

We examined the roles of the extracellular domains of a gap junction protein and a cell adhesion molecule in gap junction and adherens junction forma- tion by altering cell interactions with antibody Fab fragments. Using immunoblotting and immunocyto- chemistry we demonstrated that Novikoff cells con- tained the gap junction protein, cormexin43 (Cx43), and the cell adhesion molecule, A-CAM (N-cadherin). Cells

Rita A. Meyer; Dale W. Laird; Jean-Paul Revel; Ross G. Johnson

1992-01-01

264

Thermoelectric effects in nanoscale junctions.  

PubMed

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

Dubi, Yonatan; Di Ventra, Massimiliano

2009-01-01

265

Characterization of ultrashallow junctions using frequency-dependent junction photovoltage and its lateral attenuation  

NASA Astrophysics Data System (ADS)

A contactless method for ultrashallow junction (USJ) characterization is described based on analysis of frequency-dependent junction photovoltages from illuminated and nonilluminated areas. Relevant equations for junction photovoltages are derived. It is shown that the measured leakage current in USJ formed in halo profiles is related to space-charge region recombination.

Faifer, V. N.; Current, M. I.; Schroder, D. K.

2006-10-01

266

Ca2+ signalling and PKC? activate increased endothelial permeability by disassembly of VE--cadherin junctions  

PubMed Central

The role of intracellular Ca2+ mobilization in the mechanism of increased endothelial permeability was studied. Human umbilical vein endothelial cells (HUVECs) were exposed to thapsigargin or thrombin at concentrations that resulted in similar increases in intracellular Ca2+ concentration ([Ca2+]i). The rise in [Ca2+]i in both cases was due to release of Ca2+ from intracellular stores and influx of extracellular Ca2+.Both agents decreased endothelial cell monolayer electrical resistance (a measure of endothelial cell shape change) and increased transendothelial 125I-albumin permeability. Thapsigargin induced activation of PKC? and discontinuities in VE-cadherin junctions without formation of actin stress fibres. Thrombin also induced PKC? activation and similar alterations in VE-cadherin junctions, but in association with actin stress fibre formation.Thapsigargin failed to promote phosphorylation of the 20 kDa myosin light chain (MLC20), whereas thrombin induced MLC20 phosphorylation consistent with formation of actin stress fibres.Calphostin C pretreatment prevented the disruption of VE-cadherin junctions and the decrease in transendothelial electrical resistance caused by both agents. Thus, the increased [Ca2+]i elicited by thapsigargin and thrombin may activate a calphostin C-sensitive PKC pathway that signals VE-cadherin junctional disassembly and increased endothelial permeability.Results suggest a critical role for Ca2+ signalling and activation of PKC? in mediating the disruption of VE-cadherin junctions, and thereby in the mechanism of increased endothelial permeability.

Sandoval, Raudel; Malik, Asrar B; Minshall, Richard D; Kouklis, Panos; Ellis, Chad A; Tiruppathi, Chinnaswamy

2001-01-01

267

Electron transport through molecular junctions  

NASA Astrophysics Data System (ADS)

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

Zimbovskaya, Natalya A.; Pederson, Mark R.

2011-12-01

268

Roles of gap junctions and hemichannels in bone cell functions and in signal transmission of mechanical stress  

PubMed Central

Gap junctions formed by connexins (Cx) play an important role in transmitting signals between bone cells such as osteoblasts and osteoclasts, cells responsible for bone formation and bone remodeling, respectively. Gap junction intercellular communication (GJIC) has been demonstrated to mediate the process of osteoblast differentiation and bone formation. Furthermore, GJIC propagates Ca2+ signaling, conveys anabolic effects of hormones and growth factors, and regulates gene transcription of osteoblast differentiation markers. GJIC is also implicated to regulate osteoclast formation, survival and apoptosis. Compared with other bone cells, the most abundant type are osteocytes, which express large amounts of connexins. Mechanosensing osteocytes connect and form gap junctions with themselves and other cells only through the tips of their dendritic processes, a relatively small percent of the total cell surface area compared to other cells. Recent studies show that in addition to gap junctions, osteoblasts and osteocytes express functional hemichannels, the un-opposed halves of gap junction channels. Hemichannels are localized at the cell surface and function independently of gap junctions. Hemichannels in osteocytes mediate the immediate release of prostaglandins in response to mechanical stress. The major challenges remaining in the field are how the functions of these two types of channels are coordinated in bone cells and what the asserted, distinct effects of these channels are on bone formation and remodeling processes, and on conveying signals elicited by mechanical loading.

Jiang, Jean Xin; Siller-Jackson, Arlene Janel; Burra, Sirisha

2007-01-01

269

Exon Junction Sequences as Cryptic Splice Sites  

Microsoft Academic Search

Introns are flanked by a partially conserved coding sequence that forms the immediate exon junction sequence following intron removal from pre-mRNA. Phylogenetic evidence indicates that these sequences have been targeted by numerous intron insertions during evolution, but little is known about this process. Here, we test the prediction that exon junction sequences were functional splice sites that existed in the

Terrie Sadusky; Andrew J Newman; Nicholas J Dibb

2004-01-01

270

Ge-Sn barrier Josephson tunnel junctions  

Microsoft Academic Search

A new form of superconducting Josephson tunnel junction has been developed in which superconducting electrons tunnel through thick (?600 A?) barriers formed by evaporated Ge-Sn mixtures. By varying barrier composition and thickness a wide range of junction I-V characteristics can be obtained. For thick barriers, or barriers with low Sn content, high tunneling resistances and no supercurrent result. Barriers of

E. L. Hu; L. D. Jackel; A. R. Strnad; R. W. Epworth; R. F. Lucey; C. A. Zogg; E. Gornik

1978-01-01

271

Diverse functions of vertebrate gap junctions  

Microsoft Academic Search

Gap junctions are clusters of intercellular channels between adjacent cells. The channels are formed by the direct apposition of oligomeric transmembrane proteins, permitting the direct exchange of ions and small molecules (<1kDa) between cells without involvement of the extracellular space. Vertebrate gap junction channels are composed of oligomers of connexins, an enlarging family of proteins consisting of perhaps >20 members.

Alexander M Simon; Daniel A Goodenough

1998-01-01

272

Shadow Evaporated Josephson Junctions for superconducting qubits  

Microsoft Academic Search

Superconducting circuits are a promising system for the implementation of quantum computing. At present two-level system defects in junctions create a formidable obstacle for superconducting qubits. As shown previously, juctions of reduced size have fewer defects. Making high quality utra-small Josephson junctions is crucial for futher progress. In this talk we will discuss how we define and assess the quality

Fabio Altomare; José Aumentado; Kevin Osborn; Joshua Strong; Raymond Simmonds

2007-01-01

273

Self-assembly of membrane junctions.  

PubMed Central

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

Bruinsma, R; Goulian, M; Pincus, P

1994-01-01

274

Structure and Dynamics of Supported Intermembrane Junctions  

Microsoft Academic Search

Supported intermembrane junctions, formed by rupture of giant unilamellar vesicles onto conventional supported lipid membranes, have recently emerged as model systems for the study of biochemical processes at membrane interfaces. Using intermembrane fluorescence resonance energy transfer and optical standing wave fluorescence interferometry, we characterize the nanometer-scale topography of supported intermembrane junctions and find two distinct association states. In one state,

Yoshihisa Kaizuka; Jay T. Groves

2004-01-01

275

ESD phenomena in graded junction devices  

Microsoft Academic Search

The current very large-scale integration (VLSI) chips for sub-2-?m processes use some form of graded junction devices for process reliability. Electrostatic discharge (ESD) performance for these graded junction processes is examined by studying the process variations. The results show that the ESD protection level can be optimized without significantly compromising the hot carrier reliability or the circuit drive current. The

C. Duvvury; R. N. Rountree; H. J. Stiegler; T. Polgreen; D. Corum

1989-01-01

276

Infantile myofibromatosis of the craniovertebral junction.  

PubMed

Infantile myofibromatosis (IM) is a rare pathological entity characterized by solitary or multiple nodular skin, soft tissues or bony lesions. Craniovertebral (CV) junction lesions are rare. We report the successful management of a solitary IM involving the posterior elements of the CV junction in a 6-month-old child. PMID:18661320

Sinha, A K; Jesudason, E C; Mallucci, C L; Losty, P D; Kokai, G; Pizer, B L

2008-08-01

277

Illegitimate recombination in Xenopus: characterization of end-joined junctions.  

PubMed Central

When linear DNAs are injected into Xenopus laevis eggs, they are converted into several different kinds of recombination products. Some molecules undergo homologous recombination by a resection-annealing mechanism; some ends are precisely ligated; and some ends are joined by illegitimate means. The homologous and illegitimate products are also generated in nuclear extracts from stage VI Xenopus oocytes. In order to gain insight into the mechanism(s) of illegitimate end joining, we amplified, cloned and sequenced a number of junctions from eggs and from oocyte extracts. The egg junctions fell into three categories: some with no homology at the join point that may have been produced by blunt-end ligation; some based on small, but significant homologies (5-10 bp); and some with matches of only 1 or 2 nucleotides at the joint. Junctions made in oocyte extracts were largely of the latter type. In the extracts, formation of illegitimate joints required the addition of all four deoxyribonucleoside triphosphates and was inhibited by aphidicolin. This indicates that this process involves DNA synthesis, and mechanisms incorporating this feature are considered. The spectrum of recombination products formed in Xenopus eggs is very reminiscent of those produced from DNA introduced into mammalian cells. Images

Lehman, C W; Trautman, J K; Carroll, D

1994-01-01

278

The Ly6 Protein Coiled Is Required for Septate Junction and Blood Brain Barrier Organisation in Drosophila  

PubMed Central

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

Hijazi, Assia; Haenlin, Marc; Waltzer, Lucas; Roch, Fernando

2011-01-01

279

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

SciTech Connect

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

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

2012-06-01

280

Tight junctions: molecular structure meets function.  

PubMed

Tight junctions of epithelial and endothelial cells form selective barriers that regulate paracellular transport of solutes, immune cells, and drugs. Tight junctions consist of proteins that physically "seal" the tight junction but also form channels that allow for permeation between the cells, resulting in epithelial surfaces of different tightness. The tight junction proteins occludin, tricellulin, and at least 24 members of the claudin family are characterized by four transmembranal domains and two extracellular loops that, like teeth of a zipper, contact the appropriate loops from opposing cell membranes. Tight junctions are regulated in their molecular composition, ultrastructure, and function by intracellular scaffolding proteins and the cytoskeleton; such regulation serves normal, physiologic adaptation but also occurs in numerous diseases. PMID:19538280

Schulzke, Jörg-Dieter; Fromm, Michael

2009-05-01

281

Substrate effects in superconducting tunnel junction detectors  

NASA Astrophysics Data System (ADS)

Superconducting Nb/AlOx/Nb tunnel junction detectors on bulk Si substrates show a spatially inhomogeneous detector response when part of the energy of an ionizing particle is deposited in the substrate. Nb/AlOx/Nb tunnel junctions with V(sub m) = 24 mV were prepared on 1 to 2 micrometer thick Si membranes. The spatial homogeneity of the response signal for the detection of 35 keV electrons improves significantly for junctions on Si membranes as compared to junctions on bulk silicon. The signal decay time for the membrane detector is about 450 microseconds at T = 5K, reducing the minimum energy (e) required to generate and count a single excess quasiparticle to (e) less than 6 meV. Constraints for the spectroscopy of X-rays with high energy resolution in superconducting tunnel junction detectors are discussed.

Lemke, S.; Hebrank, F.; Gross, R.; Huebener, R. P.; Weimann, T.; Poepel, R.; Niemeyer, J.; Schnakenberg, U.; Benecke, W.

1992-12-01

282

Permeability of a Cell Membrane Junction  

PubMed Central

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++.

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

1969-01-01

283

STRUCTURE OF COUPLED AND UNCOUPLED CELL JUNCTIONS  

PubMed Central

Cells of Chironomus salivary glands and Malpighian tubules have junctions of the "septate" kind. This is the only kind of junction discerned which is large enough to effect the existing degree of intercellular communication. The electron microscopic observations of the "septate" junction conform to a honeycomb structure, with 80-A-thick electron-opaque walls and 90-A-wide transparent cores, connecting the cellular surface membranes. A projection pattern of light and dark bands (the "septa") with a 150-A periodicity results when the electron beam is directed normal to any set of honeycomb walls. Treatment of the salivary gland cells with media, which interrupt cellular communication (without noticeable alteration of cellular adhesion) by reducing junctional membrane permeability or perijunctional insulation, produces no alterations in the junctional structure discernible in electron micrographs of glutaraldehyde-fixed cell material.

Bullivant, Stanley; Loewenstein, Werner R.

1968-01-01

284

Spin accumulation in triplet Josephson junction.  

PubMed

We employ a Hamiltonian method to study the equal-spin pairing triplet Josephson junction with different orbital symmetries of pair potentials. Both the spin/charge supercurrent and possible spin accumulation at the interface of the junction are analyzed by means of the Keldysh Green's function. It is found that a spontaneous angle-resolved spin accumulation can form at the junction's interface when the orbital symmetries of Cooper pairs in two triplet superconductors are different, the physical origin is the combined effect of the different orbital symmetries and different spin states of Cooper pairs due to the misalignment of two d vectors in triplet leads. An abrupt current reversal effect induced by misalignment of d vectors is observed and can survive in a strong interface barrier scattering because the zero-energy state appears at the interface of the junction. These properties of the p-wave Josephson junction may be helpful for identifying the order parameter symmetry. PMID:21411901

Yang, Zhi Hong; Wang, J; Chan, K S

2011-02-08

285

Quantum synchronization effects in intrinsic Josephson junctions  

NASA Astrophysics Data System (ADS)

We investigate quantum dynamics of the superconducting phase in intrinsic Josephson junctions of layered high-Tc superconductors motivated by a recent experimental observation for the switching rate enhancement in the low temperature quantum regime. We pay attention to only the capacitive coupling between neighboring junctions and perform large-scale simulations for the Schrödinger equation derived from the Hamiltonian considering the capacitive coupling alone. The simulation focuses on an issue whether the switching of a junction induces those of the other junctions or not. The results reveal that the superconducting phase dynamics show synchronous behavior with increasing the quantum character, e.g., decreasing the junction plane area and effectively the temperature. This is qualitatively consistent with the experimental result.

Machida, M.; Kano, T.; Yamada, S.; Okumura, M.; Imamura, T.; Koyama, T.

2008-04-01

286

Flux creep in Josephson junction arrays  

SciTech Connect

This paper reports that, in order to analyze the diamagnetic properties of weakly coupled structures in high T{sub c} ceramic superconductors, the Josephson junction array model is used. The authors suppose that the coupling is strong enough to allow magnetic flux trappings inside non superconducting regions surrounded by superconducting loops closed by Josephson junctions. The authors remark that the presence of currents flowing through the junctions has to be taken explicitly into account in the Hamiltonian. This description leads to a creep model of the Josephson junction array. Indeed the authors have: pinning centers generated by non superconducting regions into the loops, pinning potentials determined by fluxon motion barriers due to the Josephson junctions, absence of degeneracy of the states corresponding to a different number of fluxons in the loops, a reduction of the barrier height due to measuring currents or to diamagnetic shielding currents.

Pace, S.; Saggese, A.; DeLuca, R. (Dept. of Physics, Univ. of Salerno, 84100 Salerno (IT)); Celani, F.; Liberatori, L. (INFN-LNF, 00044 Frascati (IT))

1991-03-01

287

Epac1 and PDZ-GEF cooperate in Rap1 mediated endothelial junction control.  

PubMed

Epac1 and its effector Rap1 are important mediators of cAMP induced tightening of endothelial junctions and consequential increased barrier function. We have investigated the involvement of Rap1 signalling in basal, unstimulated, barrier function of a confluent monolayer of HUVEC using real time Electric Cell-substrate Impedance Sensing. Depletion of Rap1, but not Epac1, results in a strong decrease in barrier function. This decrease is also observed when cells are depleted of the cAMP independent Rap exchange factors PDZ-GEF1 and 2, showing that PDZ-GEFs are responsible for Rap1 activity in control of basal barrier function. Monolayers of cells depleted of PDZ-GEF or Rap1 show an irregular, zipper-like organization of VE-cadherin and live imaging of VE-cadherin-GFP reveals enhanced junction motility upon depletion of PDZ-GEF or Rap1. Importantly, activation of Epac1 increases the formation of cortical actin bundles at the cell-cell junctions, inhibits junction motility and restores barrier function of PDZ-GEFs depleted, but not Rap1 depleted cells. We conclude that PDZ-GEF activates Rap1 under resting conditions to stabilize cell-cell junctions and maintain basal integrity. Activation of Rap1 by cAMP/Epac1 induces junctional actin to further tighten cell-cell contacts. PMID:21840392

Pannekoek, Willem-Jan; van Dijk, Jantine J G; Chan, On Ying A; Huveneers, Stephan; Linnemann, Jelena R; Spanjaard, Emma; Brouwer, Patricia M; van der Meer, Anne Jan; Zwartkruis, Fried J T; Rehmann, Holger; de Rooij, Johan; Bos, Johannes L

2011-08-04

288

Proliferation of sharp kinks on cosmic (super)string loops with junctions  

SciTech Connect

Motivated by their effect on the gravitational wave signal emitted by cosmic strings, we study the dynamics of kinks on strings of different tensions meeting at junctions. The propagation of a kink through a Y junction leads to the formation of three 'daughter' kinks. Assuming a uniform distribution of the incoming wave vectors at the junction, we find there is a significant region of configuration space in which the sharpness of at least one of the daughter kinks is enhanced relative to the sharpness of the initial kink. For closed loops with junctions we show this leads to an exponential growth in time of very sharp kinks. Using numerical simulations of realistic, evolving cosmic string loops with junctions to calculate the distribution of kink amplitudes as a function of time, we show that loops of this kind typically develop several orders of magnitude of very sharp kinks before the two junctions collide. This collision, or other effects such as gravitational backreaction, may end the proliferation.

Binetruy, P.; Bohe, A.; Hertog, T.; Steer, D. A. [APC, 10 rue Alice Domon et Leonie Duquet, 75205 Paris Cedex 13 (France) and Universite Paris-Diderot, CNRS/IN2P3, CEA/IRFU and Observatoire de Paris (France)

2010-10-15

289

Direct interaction of two polarity complexes implicated in epithelial tight junction assembly.  

PubMed

Tight junctions help establish polarity in mammalian epithelia by forming a physical barrier that separates apical and basolateral membranes. Two evolutionarily conserved multi-protein complexes, Crumbs (Crb)-PALS1 (Stardust)-PATJ (DiscsLost) and Cdc42-Par6-Par3-atypical protein kinase C (aPKC), have been implicated in the assembly of tight junctions and in polarization of Drosophila melanogaster epithelia. Here we identify a biochemical and functional link between these two complexes that is mediated by Par6 and PALS1 (proteins associated with Lin7). The interaction between Par6 and PALS1 is direct, requires the amino terminus of PALS1 and the PDZ domain of Par6, and is regulated by Cdc42-GTP. The transmembrane protein Crb can recruit wild-type Par6, but not Par6 with a mutated PDZ domain, to the cell surface. Expression of dominant-negative PALS1-associated tight junction protein (PATJ) in MDCK cells results in mis-localization of PALS1, members of the Par3-Par6-aPKC complex and the tight junction marker, ZO-1. Similarly, overexpression of Par6 in MDCK cells inhibits localization of PALS1 to the tight junction. Our data highlight a previously unrecognized link between protein complexes that are essential for epithelial polarity and formation of tight junctions. PMID:12545177

Hurd, Toby W; Gao, Lin; Roh, Michael H; Macara, Ian G; Margolis, Ben

2003-02-01

290

Trafficking of gap junction channels at a vertebrate electrical synapse in vivo.  

PubMed

Trafficking and turnover of transmitter receptors required to maintain and modify the strength of chemical synapses have been characterized extensively. In contrast, little is known regarding trafficking of gap junction components at electrical synapses. By combining ultrastructural and in vivo physiological analysis at identified mixed (electrical and chemical) synapses on the goldfish Mauthner cell, we show here that gap junction hemichannels are added at the edges of GJ plaques where they dock with hemichannels in the apposed membrane to form cell-cell channels and, simultaneously, that intact junctional regions are removed from centers of these plaques into either presynaptic axon or postsynaptic dendrite. Moreover, electrical coupling is readily modified by intradendritic application of peptides that interfere with endocytosis or exocytosis, suggesting that the strength of electrical synapses at these terminals is sustained, at least in part, by fast (in minutes) turnover of gap junction channels. A peptide corresponding to a region of the carboxy terminus that is conserved in Cx36 and its two teleost homologs appears to interfere with formation of new gap junction channels, presumably by reducing insertion of hemichannels on the dendritic side. Thus, our data indicate that electrical synapses are dynamic structures and that their channels are turned over actively, suggesting that regulated trafficking of connexons may contribute to the modification of gap junctional conductance. PMID:22323580

Flores, Carmen E; Nannapaneni, Srikant; Davidson, Kimberly G V; Yasumura, Thomas; Bennett, Michael V L; Rash, John E; Pereda, Alberto E

2012-02-07

291

Dynamic control of slow water transport by aquaporin 0: Implications for hydration and junction stability in the eye lens  

PubMed Central

Aquaporin 0 (AQP0), the most abundant membrane protein in mammalian lens fiber cells, not only serves as the primary water channel in this tissue but also appears to mediate the formation of thin junctions between fiber cells. AQP0 is remarkably less water permeable than other aquaporins, but the structural basis and biological significance of this low permeability remain uncertain, as does the permeability of the protein in a reported junctional form. To address these issues, we performed molecular dynamics (MD) simulations of water transport through membrane-embedded AQP0 in both its (octameric) junctional and (tetrameric) nonjunctional forms. From our simulations, we measured an osmotic permeability for the nonjunctional form that agrees with experiment and found that the distinct dynamics of the conserved, lumen-protruding side chains of Tyr-23 and Tyr-149 modulate water passage, accounting for the slow permeation. The junctional and nonjunctional forms conducted water equivalently, in contrast to a previous suggestion based on static crystal structures that water conduction is lost on junction formation. Our analysis suggests that the low water permeability of AQP0 may help maintain the mechanical stability of the junction. We hypothesize that the structural features leading to low permeability may have evolved in part to allow AQP0 to form junctions that both conduct water and contribute to the organizational structure of the fiber cell tissue and microcirculation within it, as required to maintain transparency of the lens.

Jensen, Morten ?.; Dror, Ron O.; Xu, Huafeng; Borhani, David W.; Arkin, Isaiah T.; Eastwood, Michael P.; Shaw, David E.

2008-01-01

292

Electroluminescence in an Oxygen-Doped ZnSe p-n Junction Grown by Molecular Beam Epitaxy  

Microsoft Academic Search

Blue electroluminescence has been obtained from ZnSe p-n junctions. ZnSe films were grown on n-type GaAs(100) substrates by molecular beam epitaxy. The dopants used for n-and p-type ZnSe were Ga and O, respectively. The electron-beam-induced current strongly suggests the formation of a p-n junction. The built-in Potential of the p-n junction and carrier concentration of p-type ZnSe layer estimated from

Katsuhiro Akimoto; Takao Miyajima; Yoshifumi Mori

1989-01-01

293

The folding of the hairpin ribozyme: dependence on the loops and the junction.  

PubMed Central

In its natural context, the hairpin ribozyme is constructed around a four-way helical junction. This presents the two loops that interact to form the active site on adjacent arms, requiring rotation into an antiparallel structure to bring them into proximity. In the present study we have compared the folding of this form of the ribozyme and subspecies lacking either the loops or the helical junction using fluorescence resonance energy transfer. The complete ribozyme as a four-way junction folds into an antiparallel structure by the cooperative binding of magnesium ions, requiring 20-40 microM for half-maximal extent of folding ([Mg2+]1/2) and a Hill coefficient n = 2. The isolated junction (lacking the loops) also folds into a corresponding antiparallel structure, but does so noncooperatively (n = 1) at a higher magnesium ion concentration ([Mg2+]1/2 = 3 mM). Introduction of a G + 1A mutation into loop A of the ribozyme results in a species with very similar folding to the simple junction, and complete loss of ribozyme activity. Removal of the junction from the ribozyme, replacing it either with a strand break (serving as a hinge) or a GC5 bulge, results in greatly impaired folding, with [Mg2+]1/2 > 20 mM. The results indicate that the natural form of the ribozyme undergoes ion-induced folding by the cooperative formation of an antiparallel junction and loop-loop interaction to generate the active form of the ribozyme. The four-way junction thus provides a scaffold in the natural RNA that facilitates the folding of the ribozyme into the active form.

Zhao, Z Y; Wilson, T J; Maxwell, K; Lilley, D M

2000-01-01

294

Junction Devices Based On Polydiphenylamine  

NASA Astrophysics Data System (ADS)

Polydiphenylamine (PolyDPA) was synthesized by chemical oxidation of diphenylamine monomer. Thin films of PolyDPA were prepared using spin coating technique. The absorption spectrum of this material was studied using a UV-2000 spectrophotometer and it showed a band gap of about 2.2eV. Schottky as well as p-n junction diodes have been fabricated from these thin films and the resultingI-V measurements have indicated that the diodes have good stability and high rectification ratio. Silicon-gated field-effect transistors have also been fabricated using PolyDPA as the active semiconducting layer and the resulting I-V characteristics have been measured. The carrier mobility at room temperaturehas been found to be around 0.02 cm^2/Volt-sec and the on-off ratio was about 10^4.

Ramamoorthy, Anand; Camaratta, Vince; Thakur, Mrinal

1998-03-01

295

Lymphocytes Accelerate Epithelial Tight Junction Assembly: Role of AMP-Activated Protein Kinase (AMPK)  

Microsoft Academic Search

The tight junctions (TJs), characteristically located at the apicolateral borders of adjacent epithelial cells, are required for the proper formation of epithelial cell polarity as well as for sustaining the mucosal barrier to the external environment. The observation that lymphocytes are recruited by epithelial cells to the sites of infection [1] suggests that they may play a role in the

Xiao Xiao Tang; Hao Chen; Sidney Yu; Li Zhang; Michael J. Caplan; Hsiao Chang Chan; Wen-Liang Zhou

2010-01-01

296

Non-genotoxic carcinogens: early effects on gap junctions, cell proliferation and apoptosis in the rat  

Microsoft Academic Search

Non-genotoxic carcinogens are thought to induce tumour formation by disturbing the balance between cell growth and cell death. Gap junctions (GJ) contribute to the maintenance of tissue homeostasis by allowing the intercellular exchange of growth regulatory signals and potential inhibition of GJ intercellular communication through loss of connexin (Cx) plaques has been shown to be involved in the cancer process.

Angela Mally; James Kevin Chipman

2002-01-01

297

ADHERENS JUNCTIONS AND THE ACTOMYOSIN NETWORK REGULATE ORGAN GROWTH BY MODULATING HIPPO PATHWAY ACTIVITY IN DROSOPHILA  

Microsoft Academic Search

Adherens junctions (AJs) and basolateral modules are important for the establishment and maintenance of apico-basal polarity. Loss of AJs and basolateral module members lead to tumor formation, as well as poor prognosis for metastasis. Recently, in mammalian studies it has been shown that loss of either AJ or basolateral module members deregulate Yorkie activity, the downstream transcriptional effector of the

Chih-Chao Yang

2012-01-01

298

Three-dimensional modeling and simulation of p-n junction spherical silicon solar cells  

Microsoft Academic Search

A three-dimensional numerical model is presented to simulate spherical p-n junction silicon solar cells, which is a promising new technology for photovoltaic (PV) energy conversion for terrestrial applications. Material properties imposed by the sphere formation method, geometry of the device, and the specific device structure stemming from the fabrication technology are taken into account in the optical and electrical models

Majid Gharghi; Hua Bai; Gary Stevens; Siva Sivoththaman

2006-01-01

299

Nonparametric generalized belief propagation based on pseudo-junction tree for cooperative localization in wireless networks  

NASA Astrophysics Data System (ADS)

Non-parametric belief propagation (NBP) is a well-known message passing method for cooperative localization in wireless networks. However, due to the over-counting problem in the networks with loops, NBP's convergence is not guaranteed, and its estimates are typically less accurate. One solution for this problem is non-parametric generalized belief propagation based on junction tree. However, this method is intractable in large-scale networks due to the high-complexity of the junction tree formation, and the high-dimensionality of the particles. Therefore, in this article, we propose the non-parametric generalized belief propagation based on pseudo-junction tree (NGBP-PJT). The main difference comparing with the standard method is the formation of pseudo-junction tree, which represents the approximated junction tree based on thin graph. In addition, in order to decrease the number of high-dimensional particles, we use more informative importance density function, and reduce the dimensionality of the messages. As by-product, we also propose NBP based on thin graph (NBP-TG), a cheaper variant of NBP, which runs on the same graph as NGBP-PJT. According to our simulation and experimental results, NGBP-PJT method outperforms NBP and NBP-TG in terms of accuracy, computational, and communication cost in reasonably sized networks.

Savic, Vladimir; Zazo, Santiago

2013-12-01

300

Method of junction formation for CIGS photovoltaic devices  

SciTech Connect

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.

Delahoy, Alan E. (Rocky Hill, NJ)

2010-01-26

301

Acoustic hybrid junction in a rectangular waveguide  

PubMed

Acoustic scattering from a hybrid junction in a rectangular waveguide is studied. The Fourier transform and mode matching is used to represent the scattered wave and the simultaneous equations for the modal coefficients are formulated. A residue calculus is utilized to obtain a solution to the simultaneous equations in fast-converging series. Numerical computations are performed to show the behavior of transmission in terms of junction geometry and operating frequency. The utility of acoustic hybrid junction is discussed in terms of its decoupling characteristics. PMID:10790010

Kwon; Eom

2000-04-01

302

Bioavailability and efficacy of a gap junction enhancer (PQ7) in a mouse mammary tumor model.  

PubMed

The loss of gap junctional intercellular communication is characteristic of neoplastic cells, suggesting that the restoration with a gap junction enhancer may be a new therapeutic treatment option with less detrimental effects than traditional antineoplastic drugs. A gap junction enhancer, 6-methoxy-8-[(2-furanylmethyl) amino]-4-methyl-5-(3-trifluoromethylphenyloxy) quinoline (PQ7), on the normal tissue was evaluated in healthy C57BL/6J mice in a systemic drug distribution study. Immunoblot analysis of the vital organs indicates a reduction in Cx43 expression in PQ7-treated animals with no observable change in morphology. Next the transgenic strain FVB/N-Tg(MMTV-PyVT) 634Mul/J (also known as PyVT) was used as a spontaneous mammary tumor mouse model to determine the biological and histological effects of PQ7 on tumorigenesis and metastasis at three stages of development: Pre tumor, Early tumor, and Late tumor formation. PQ7 was assessed to have a low toxicity through intraperitoneal administration, with the majority of the compound being detected in the heart, liver, and lungs six hours post injection. The treatment of tumor bearing animals with PQ7 had a 98% reduction in tumor growth, while also decreasing the total tumor burden compared to control mice during the Pre stage of development. PQ7 treatment increased Cx43 expression in the neoplastic tissue during Pre-tumor formation; however, this effect was not observed in Late stage tumor formation. This study shows that the gap junction enhancer, PQ7, has low toxicity to normal tissue in healthy C57BL/6J mice, while having clinical efficacy in the treatment of spontaneous mammary tumors of PyVT mice. Additionally, gap junctional intercellular communication and neoplastic cellular growth are shown to be inversely related, while treatment with PQ7 inhibits tumor growth through targeting gap junction expression. PMID:23776708

Shishido, Stephanie N; Prasain, Keshar; Beck, Amanda; Nguyen, Thi D T; Hua, Duy H; Nguyen, Thu Annelise

2013-06-12

303

Bioavailability and Efficacy of a Gap Junction Enhancer (PQ7) in a Mouse Mammary Tumor Model  

PubMed Central

The loss of gap junctional intercellular communication is characteristic of neoplastic cells, suggesting that the restoration with a gap junction enhancer may be a new therapeutic treatment option with less detrimental effects than traditional antineoplastic drugs. A gap junction enhancer, 6-methoxy-8-[(2-furanylmethyl) amino]-4-methyl-5-(3-trifluoromethylphenyloxy) quinoline (PQ7), on the normal tissue was evaluated in healthy C57BL/6J mice in a systemic drug distribution study. Immunoblot analysis of the vital organs indicates a reduction in Cx43 expression in PQ7-treated animals with no observable change in morphology. Next the transgenic strain FVB/N-Tg(MMTV-PyVT) 634Mul/J (also known as PyVT) was used as a spontaneous mammary tumor mouse model to determine the biological and histological effects of PQ7 on tumorigenesis and metastasis at three stages of development: Pre tumor, Early tumor, and Late tumor formation. PQ7 was assessed to have a low toxicity through intraperitoneal administration, with the majority of the compound being detected in the heart, liver, and lungs six hours post injection. The treatment of tumor bearing animals with PQ7 had a 98% reduction in tumor growth, while also decreasing the total tumor burden compared to control mice during the Pre stage of development. PQ7 treatment increased Cx43 expression in the neoplastic tissue during Pre-tumor formation; however, this effect was not observed in Late stage tumor formation. This study shows that the gap junction enhancer, PQ7, has low toxicity to normal tissue in healthy C57BL/6J mice, while having clinical efficacy in the treatment of spontaneous mammary tumors of PyVT mice. Additionally, gap junctional intercellular communication and neoplastic cellular growth are shown to be inversely related, while treatment with PQ7 inhibits tumor growth through targeting gap junction expression.

Shishido, Stephanie N.; Prasain, Keshar; Beck, Amanda; Nguyen, Thi D. T.; Hua, Duy H.; Nguyen, Thu Annelise

2013-01-01

304

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

PubMed

Much of our current knowledge about the physiological and pathophysiological role of gap junctions is based on experiments where coupling has been reduced by either chemical agents or genetic modification. This has brought evidence that gap junctions are important in many physiological processes. In a number of cases, gap junctions have been implicated in the initiation and progress of disease, and experimental uncoupling has been used to investigate the exact role of coupling. The inverse approach, i.e., to increase coupling, has become possible in recent years and represents a new way of testing the role of gap junctions. The aim of this review is to summarize the current knowledge obtained with agents that selectively increase gap junctional intercellular coupling. Two approaches will be reviewed: increasing coupling by the use of antiarrhythmic peptide and its synthetic analogs and by interfering with the gating of gap junctional channels. PMID:17568971

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

2007-06-14

305

Neural Mechanisms for the Robust Representation of Junctions  

Microsoft Academic Search

Junctions provide important cues in various perceptual tasks, such as the determination of occlusion relationships for figure-ground separation, transparency perception, and object recognition, among others. In computer vision, junctions are used in a number of tasks, like point matching for image tracking or correspondence analysis. We propose a biologically motivated approach to junction representation in which junctions are implicitly characterized

Thorsten Hansen; Heiko Neumann

2004-01-01

306

Accuracy of junction temperature measurement in silicon power transistor  

Microsoft Academic Search

This paper reports experimental measurements of junction temperature obtained by various electrical and thermal methods. Electrical measurements were based on temperature-sensitive junction parameters including pulse sampling of CCBFand VBE, steady state hFE, and pulsed ?VCBF. Direct measurement of peak junction temperature was made using an infrared microradiometer. Junction temperature measurements were obtained as a function of device operating conditions, since

H. R. Plumlee; D. A. Peterman

1966-01-01

307

Regulation of Gap Junctions by Phosphorylation of Connexins  

Microsoft Academic Search

Gap junctions are a unique type of intercellular junction found in most animal cell types. Gap junctions permit the intercellular passage of small molecules and have been implicated in diverse biological processes, such as development, cellular metabolism, and cellular growth control. In vertebrates, gap junctions are composed of proteins from the “connexin” gene family. The majority of connexins are modified

Paul D. Lampe; Alan F. Lau

2000-01-01

308

ZnO based organic-inorganic hybrid p-n junction diode  

NASA Astrophysics Data System (ADS)

We have fabricated zinc oxide and metal phthalocyanine based hybrid p-n junction diodes using aluminum doped zinc oxide film as transparent conducting electrode. The current rectifying behavior of these hybrid diodes is similar to those of inorganic p-n junction diodes. The current-voltage measurement gives a rectification ratio of the order of 104 and a current density of 0.6mA/cm2. The formation of depletion region at the inorganic-organic interface has been established by the capacitance-voltage measurements.

Singh, Budhi; Ghosh, Subhasis

2013-02-01

309

Silicon p-i-n junction fibers.  

PubMed

Flexible Si p-i-n junction fibers made by high pressure chemical vapor deposition offer new opportunities in textile photovoltaics and optoelectronics, as exemplified by their photovoltaic properties, gigahertz bandwidth for photodetection, and ability to waveguide light. PMID:23212830

He, Rongrui; Day, Todd D; Krishnamurthi, Mahesh; Sparks, Justin R; Sazio, Pier J A; Gopalan, Venkatraman; Badding, John V

2012-12-04

310

Heat transport through a Josephson junction  

NASA Astrophysics Data System (ADS)

We discuss heat transport through a Josephson tunnel junction under various bias conditions. We first derive the formula for the cooling power of the junction valid for arbitrary time dependence of the Josephson phase. Combining it with the classical equation of motion for the phase, we find the time-averaged cooling power as a function of bias current or bias voltage. We also find the noise of the heat current and, more generally, the full counting statistics of the heat transport through the junction. We separately consider the metastable superconducting branch of the current-voltage characteristics allowing quantum fluctuations of the phase in this case. This regime is experimentally attractive since the junction has low power dissipation, low impedance, and therefore may be used as a sensitive detector.

Golubev, Dmitry; Faivre, Timothé; Pekola, Jukka P.

2013-03-01

311

Chirality effect in disordered graphene ribbon junctions.  

PubMed

We investigate the influence of edge chirality on the electronic transport in clean or disordered graphene ribbon junctions. By using the tight-binding model and the Landauer-Büttiker formalism, the junction conductance is obtained. In the clean sample, the zero-magnetic-field junction conductance is strongly chirality-dependent in both unipolar and bipolar ribbons, whereas the high-magnetic-field conductance is either chirality-independent in the unipolar or chirality-dependent in the bipolar ribbon. Furthermore, we study the disordered sample in the presence of magnetic field and find that the junction conductance is always chirality-insensitive for both unipolar and bipolar ribbons with adequate disorders. In addition, the disorder-induced conductance plateaus can exist in all chiral bipolar ribbons provided the disorder strength is moderate. These results suggest that we can neglect the effect of edge chirality in fabricating electronic devices based on the magnetotransport in a disordered graphene ribbon. PMID:22469635

Long, Wen

2012-04-03

312

Intercellular Junction Assembly, Dynamics, and Homeostasis  

PubMed Central

Intercellular anchoring junctions are highly specialized regions of the plasma membrane where members of the cadherin family of transmembrane adhesion molecules on opposing cells interact through their extracellular domains, and through their cytoplasmic domains serve as a platform for organizing cytoskeletal anchors and remodelers. Here we focus on assembly of so-called “anchoring” or “adhering” junctions—adherens junctions (AJs) and desmosomes (DSMs), which associate with actin and intermediate filaments, respectively. We will examine how the assembly and function of AJs and DSMs are intimately connected during embryogenesis and in adult cells and tissues, and in some cases even form specialized “mixed” junctions. We will explore signaling and trafficking machineries that drive assembly and remodeling and how these mechanisms are co-opted in human disease.

Green, Kathleen J.; Getsios, Spiro; Troyanovsky, Sergey; Godsel, L.M.

2010-01-01

313

Intercellular junction assembly, dynamics, and homeostasis.  

PubMed

Intercellular anchoring junctions are highly specialized regions of the plasma membrane where members of the cadherin family of transmembrane adhesion molecules on opposing cells interact through their extracellular domains, and through their cytoplasmic domains serve as a platform for organizing cytoskeletal anchors and remodelers. Here we focus on assembly of so-called "anchoring" or "adhering" junctions-adherens junctions (AJs) and desmosomes (DSMs), which associate with actin and intermediate filaments, respectively. We will examine how the assembly and function of AJs and DSMs are intimately connected during embryogenesis and in adult cells and tissues, and in some cases even form specialized "mixed" junctions. We will explore signaling and trafficking machineries that drive assembly and remodeling and how these mechanisms are co-opted in human disease. PMID:20182611

Green, Kathleen J; Getsios, Spiro; Troyanovsky, Sergey; Godsel, L M

2010-02-01

314

Local Frame Junction Trees in SLAM  

NASA Astrophysics Data System (ADS)

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

Kuehnel, Frank O.

2005-11-01

315

Chirality effect in disordered graphene ribbon junctions  

NASA Astrophysics Data System (ADS)

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

Long, Wen

2012-05-01

316

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

Microsoft Academic Search

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

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

1982-01-01

317

Mechanically controllable break junctions for molecular electronics.  

PubMed

A mechanically controllable break junction (MCBJ) represents a fundamental technique for the investigation of molecular electronic junctions, especially for the study of the electronic properties of single molecules. With unique advantages, the MCBJ technique has provided substantial insight into charge transport processes in molecules. In this review, the techniques for sample fabrication, operation and the various applications of MCBJs are introduced and the history, challenges and future of MCBJs are discussed. PMID:23913697

Xiang, Dong; Jeong, Hyunhak; Lee, Takhee; Mayer, Dirk

2013-08-02

318

Semiconductor tunnel junction with enhancement layer  

DOEpatents

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.

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

1997-01-01

319

Semiconductor tunnel junction with enhancement layer  

DOEpatents

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

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

1997-10-21

320

BPS nature of 3-string junctions  

Microsoft Academic Search

We study BPS-saturated classical solutions for the world-sheet theory of a D-string in the presence of a point charge. These solutions are interpreted as describing planar 3-string junctions, which arise because the original D-string is deformed by the presence of the inserted charge. We compute the angles of the junctions and show that the vector sum of string tensions is

Keshav Dasgupta; Sunil Mukhi

1998-01-01

321

Ge-Sn barrier Josephson tunnel junctions  

Microsoft Academic Search

A new form of superconducting Josephson tunnel junction has been developed in which superconducting electrons tunnel through thick (~600 A˚) barriers formed by evaporated Ge-Sn mixtures. By varying barrier composition and thickness a wide range of junction I-V characteristics can be obtained. For thick barriers, or barriers with low Sn content, high tunneling resistances and no supercurrent result. Barriers of

E. L. Hu; L. D. Jackel; A. R. Strnad; R. W. Epworth; R. F. Lucey; C. A. Zogg; E. Gornik

1978-01-01

322

Possible curvature effects in the Josephson junction  

NASA Astrophysics Data System (ADS)

The large area Josephson junction with one compact dimension is considered. A geometry that increases the velocity of the kink propagating along the junction is considered. The geometry described in this paper can be used in order to increase or decrease the speed of the signal in the transmission elements in electronic devices. Reflection of the kink front from the large curvature areas is also confirmed.

Dobrowolski, Tomasz

2013-08-01

323

Quantum Coherence in a Superfluid Josephson Junction  

SciTech Connect

We report a new kind of experiment in which we take an array of nanoscale apertures that form a superfluid {sup 4}He Josephson junction and apply quantum phase gradients directly along the array. We observe collective coherent behaviors from aperture elements, leading to quantum interference. Connections to superconducting and Bose-Einstein condensate Josephson junctions as well as phase coherence among the superfluid aperture array are discussed.

Narayana, Supradeep; Sato, Yuki [Rowland Institute at Harvard, Harvard University, Cambridge, Massachusetts 02142 (United States)

2011-02-04

324

Heat dissipation in atomic-scale junctions.  

PubMed

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

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

2013-06-13

325

Multi-junction solar cell device  

DOEpatents

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.

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

2007-12-18

326

Isolation and characterisation of arthropod gap junctions  

PubMed Central

Gap junctions have been isolated from the hepatopancreas of the crustacean arthropod, Nephrops norvegicus (Norway lobster). SDS-PAGE of these preparations shows two major protein bands, mol. wt. 18 000 (18 K) and mol. wt. 28 000 (28 K). The 18-K and 28-K proteins are interconvertible, cannot be distinguished by two dimensional tryptic and chymotryptic peptide mapping, and therefore appear to be different (most likely monomeric and dimeric) forms of the same protein. The protein can also aggregate to higher multimeric forms mol. wt. 38 000 (presumed trimer), and mol. wt. 52 000 (presumed tetramer). The buoyant density of the isolated gap junctions in continuous potassium iodide gradients is 1.260 g/cm3. The junctions are progressively solubilized in increasing SDS concentrations, mostly between 0.1% and 0.2% SDS, and this is accompanied by the release of the 18-K and 28-K forms of the junctional protein. The Nephrops hepatopancreas 18-K junctional protein has antigenic determinants in common with the vertebrate 16-K junctional protein as shown by cross-reactivity with two different affinity purified antibody preparations. However, no detectable similarity can be seen between the major 125I-labelled tryptic and chymotrytpic peptides of the Nephrops hepatopancreas 18-K protein and the mouse liver 16-K protein. ImagesFig. 1.Fig. 2, 3.Fig. 4.Fig. 5.Fig. 7.Fig. 9.Fig. 10.

Finbow, Malcolm E.; Buultjens, T. Eldridge J.; Lane, Nancy J.; Shuttleworth, John; Pitts, John D.

1984-01-01

327

Triple junction motion and grain microstructure evolution  

SciTech Connect

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

Gottstein, G. [Institut fuer Metallkunde und Metallphysik, RWTH Aachen, Kopernikusstr. 14, D-52056 Aachen (Germany)]. E-mail: gottstein@imm.rwth-aachen.de; Ma, Y. [Institut fuer Metallkunde und Metallphysik, RWTH Aachen, Kopernikusstr. 14, D-52056 Aachen (Germany); Shvindlerman, L.S. [Institut fuer Metallkunde und Metallphysik, RWTH Aachen, Kopernikusstr. 14, D-52056 Aachen (Germany); Institute of Solid State Physics, Russian Academy of Sciences, Chernogolovka, Moscow Distr. 142432 (Russian Federation)

2005-03-01

328

Exercise regulation of intestinal tight junction proteins.  

PubMed

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

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

2012-11-01

329

N-cadherin adherens junctions mediate osteogenesis through PI3K signaling.  

PubMed

During endochondral ossification, the cartilage is surrounded by a layer of cells that constitute the perichondrium. Communication between osteoblasts in the perichondrium via N-cadherin adherens junctions is essential for endochondral bone growth. We observed that adherens junction molecule N-cadherin and its interacting partners p120, ?-catenin and PTEN are expressed by cells present in the perichondrium. To study if N-cadherin mediated adherens junctions play a role in mediating signal transduction events during bone development, we utilized MC3T3E1 preosteoblasts plated at sub confluent (low) and confluent (high) densities to mimic adherens junction formation. When MC3T3E1 cells were plated at high density we observed an increase in phosphorylation of AKTSer473 and its downstream target GSK3Ser9, which coincided with an increase in Osterix, Osteomodulin and Osteoglycin gene expression. Using immunofluorescence, we identified N-cadherin, p120 and ?-catenin localized at the membrane of MC3T3E1 cells. Treatment of confluent MC3T3E1 cells with an N-cadherin junction inhibitor-EGTA and a PI3K inhibitor LY294002 resulted in reduction of phosphorylation levels of AKT and GSK3 and expression of Osterix, Osteomodulin and Osteoglycin. Furthermore, utilizing an N-cadherin blocking antibody resulted in reduced AKT signaling and Osterix gene expression, suggesting that osteoblast junction formation is linked to activation of PI3K signaling, which leads to osteoblast differentiation. To further explore the strength of this linkage, we utilized a conditional knockout approach using Dermo1cre to delete ?-catenin and PTEN, two important proteins known to be essential for adherens junctions and PI3K signaling, respectively. In the absence of ?-catenin, we observed a decrease in adherens junctions and AKT signaling in the perichondrium. PTEN deletion, on the other hand, increased the number of cells expressing N-cadherin in the perichondrium. These observations show that N-cadherin mediated junctions between osteoblasts are needed for osteoblast gene transcription. PMID:21964322

Guntur, Anyonya R; Rosen, Clifford J; Naski, Michael C

2011-09-16

330

N-cadherin adherens junctions mediate osteogenesis through PI3K signaling  

PubMed Central

During endochondral ossification, the cartilage is surrounded by a layer of cells that constitute the perichondrium. Communication between osteoblasts in the perichondrium via N-cadherin adherens junctions is essential for endochondral bone growth. We observed that adherens junction molecule N-cadherin and its interacting partners p120, ?-catenin and PTEN are expressed by cells present in the perichondrium. To study if N-cadherin mediated adherens junctions play a role in mediating signal transduction events during bone development, we utilized MC3T3E1 preosteoblasts plated at sub confluent (low) and confluent (high) densities to mimic adherens junction formation. When MC3T3E1 cells were plated at high density we observed an increase in phosphorylation of AKTSer473 and its downstream target GSK3Ser9, which coincided with an increase in Osterix, Osteomodulin and Osteoglycin gene expression. Using immunofluorescence, we identified N-cadherin, p120 and ?-catenin localized at the membrane of MC3T3E1 cells. Treatment of confluent MC3T3E1cells with an N-cadherin junction inhibitor-EGTA and a PI3K inhibitor LY294002 resulted in reduction of phosphorylation levels of AKT and GSK3 and expression of Osterix, Osteomodulin and Osteoglycin. Furthermore, utilizing an N-cadherin blocking antibody resulted in reduced AKT signaling and Osterix gene expression, suggesting that osteoblast junction formation is linked to activation of PI3K signaling, which leads to osteoblast differentiation. To further explore the strength of this linkage, we utilized a conditional knockout approach using Dermo1cre to delete ?-catenin and PTEN, two important proteins known to be essential for adherens junctions and PI3K signaling, respectively. In the absence of ?-catenin, we observed a decrease in adherens junctions and AKT signaling in the perichondrium. PTEN deletion, on the other hand, increased the number of cells expressing N-cadherin in the perichondrium. These observations show that N-cadherin mediated junctions between osteoblasts are needed for osteoblast gene transcription.

Guntur, Anyonya R; Rosen, Clifford J; Naski, Michael C

2011-01-01

331

Structural, chemical and electronic properties of superconducting thin films and junctions. Final report  

SciTech Connect

Ba(1-x)K(x)BiO3 (BKBO) has a transition temperature, T(sub c), of 34 K and is unique among the high-temperature oxide superconductors because it is isotropic. It has been little studied and it is desirable to understand its behavior from the perspectives of both potential electronic applications and fundamental understanding of superconductivity. This study has involved a determination of the structural, electronic, and chemical properties of BKBO films and junctions deposited by rf magnetron sputtering. It was found that films with the highest T(sub c) and lowest rocking curve widths were consistently grown on SrTiO3. This material was therefore used as a buffer layer for growing high-quality BKBO films on the more practical substrates LaAlO3 and NdGaO3. SrTiO3 was also used as a barrier to fabricate BKBO/SrTiO3/BKBO SIS junctions for the first time. These junctions exhibited tunneling behavior. Modelling based on electrical measurements and electron diffraction observations of surface structure indicated island-type growth of the barrier material. The thickness variation in the tunnel barrier as a result of island formation limits the practical potential of such junctions in most applications where tunneling current uniformity and junction reproducibility are required.

McHenry, M.E.

1994-05-01

332

Impaired tight junction sealing and precocious involution in mammary glands of PKN1 transgenic mice.  

PubMed

The mammary gland undergoes a complex set of changes to establish copious milk secretion at parturition. To test the hypothesis that signaling through the Rho pathway plays a role in secretory activation, transgenic mice expressing a constitutively activated form of the Rho effector protein PKN1 in the mammary epithelium were generated. PKN1 activation had no effect in late pregnancy but inhibited milk secretion after parturition, diminishing the ability of transgenic dams to support a litter. Mammary gland morphology as well as increased apoptosis and expression of IFGBP5 and TGFbeta3 suggest precocious involution in these animals. Furthermore, tight junction sealing at parturition was impaired in transgenic mammary glands as demonstrated by intraductal injection of [14C]sucrose. Consistent with this finding, tight junction sealing in response to glucocorticoid stimulation was highly impaired in EpH4 mammary epithelial cells expressing constitutively activated PKN1, whereas expression of a dominant-negative PKN1 mutant resulted in accelerated tight junction sealing in vitro. Tight junction formation was not impaired as demonstrated by the correct localization of occludin and ZO1 at the apical cell borders. Our results provide evidence that PKN1 participates in the regulation of tight junction sealing in the mammary gland by interfering with glucocorticoid signaling. PMID:17591691

Fischer, Andreas; Stuckas, Heiko; Gluth, Markus; Russell, Tanya D; Rudolph, Michael C; Beeman, Neal E; Bachmann, Sebastian; Umemura, Shinobu; Ohashi, Yasuhiro; Neville, Margaret C; Theuring, Franz

2007-07-01

333

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

PubMed

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

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

2011-05-25

334

Nb Surface Effects on the Properties of Nb Oxide Barrier Junctions Prepared Using a CF4 Cleaning Process  

NASA Astrophysics Data System (ADS)

The Nb surface effects on junction characteristics were investigated in Nb/oxide/Pb junctions in which the base electrode was cleaned by an Ar+CF4 mixture plasma. The oxide barrier was grown by rf plasma oxidation on polycrystalline and single-crystal Nb films (RRR{=}4--135). It was confirmed that Nb grain size affected Nb penetration depth, transition temperature, and junction gap structure. However, high junction quality (Vm>30 mV) and high barrier height (?˜ 1.0 eV) were obtained independent of the existence of Nb grain boundaries. Based on these results and previous XPS findings, that is, the formation of a thin Nb-F-O layer on a CF4 cleaned Nb surface, it is surmised that this thin layer deactivates the grain boundary region and reduces the problems associated with this region.

Asano, Hidefumi; Michikami, Osamu

1986-04-01

335

Electron trap level in a GaN nanorod p-n junction grown by molecular-beam epitaxy  

SciTech Connect

We have studied the electrical properties of a GaN nanorod p-n junction diode by deep level transient spectroscopy measurements. The p-n junction nanorods were patterned on a SiO{sub 2} substrate by using e-beam lithography. In order to confirm the formation of p-n junction, cathodoluminescence and current-voltage measurements, as a function of temperature, were made. The current-voltage curve exhibits strong temperature dependence, suggesting that thermionic emission over a barrier dominates. This barrier most likely corresponds to emission from a deep level in the band. The deep level appears to be an electron trap at Ec-0.40 eV below the conduction band with a capture cross section of 2.22x10 cm{sup 2} near the depletion region of the p-n junction.

Park, Y.S.; Park, C.M.; Park, C.J.; Cho, H.Y.; Lee, Seung Joo; Kang, T.W.; Lee, S.H.; Oh, Jae-Eung; Yoo, Kyung-Hwa; Son, Min-Soo [Quantum Functional Semiconductor Research Center, Dongguk University, Seoul 100-715 (Korea, Republic of) and Department of Physics, Dongguk University, Seoul 100-715 (Korea); School of Electrical and Computer Engineering, Hanyang University, Ansan 425-791 (Korea, Republic of); Department of Physics, Yeonse University, Seoul 120-749 (Korea, Republic of)

2006-05-08

336

Performance analysis of AlGaAs/GaAs tunnel junctions for ultra-high concentration photovoltaics  

NASA Astrophysics Data System (ADS)

An n++-GaAs/p++-AlGaAs tunnel junction with a peak current density of 10?100 A cm-2 is developed. This device is a tunnel junction for multijunction solar cells, grown lattice-matched on standard GaAs or Ge substrates, with the highest peak current density ever reported. The voltage drop for a current density equivalent to the operation of the multijunction solar cell up to 10?000 suns is below 5 mV. Trap-assisted tunnelling is proposed to be behind this performance, which cannot be justified by simple band-to-band tunnelling. The metal-organic vapour-phase epitaxy growth conditions, which are in the limits of the transport-limited regime, and the heavy tellurium doping levels are the proposed origins of the defects enabling trap-assisted tunnelling. The hypothesis of trap-assisted tunnelling is supported by the observed annealing behaviour of the tunnel junctions, which cannot be explained in terms of dopant diffusion or passivation. For the integration of these tunnel junctions into a triple-junction solar cell, AlGaAs barrier layers are introduced to suppress the formation of parasitic junctions, but this is found to significantly degrade the performance of the tunnel junctions. However, the annealed tunnel junctions with barrier layers still exhibit a peak current density higher than 2500 A cm-2 and a voltage drop at 10?000 suns of around 20 mV, which are excellent properties for tunnel junctions and mean they can serve as low-loss interconnections in multijunction solar cells working at ultra-high concentrations.

García, I.; Rey-Stolle, I.; Algora, C.

2012-02-01

337

Clathrin and Cx43 gap junction plaque endoexocytosis  

SciTech Connect

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.

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

338

Role of tight junction proteins in gastroesophageal reflux disease  

PubMed Central

Background Gastroesophageal reflux disease (GERD) is associated with impaired epithelial barrier function that is regulated by cell-cell contacts. The aim of the study was to investigate the expression pattern of selected components involved in the formation of tight junctions in relation to GERD. Methods Eighty-four patients with GERD-related symptoms with endoscopic signs (erosive: n?=?47) or without them (non-erosive: n?=?37) as well as 26 patients lacking GERD-specific symptoms as controls were included. Endoscopic and histological characterization of esophagitis was performed according to the Los Angeles and adapted Ismeil-Beigi criteria, respectively. Mucosal biopsies from distal esophagus were taken for analysis by histopathology, immunohistochemistry and quantitative reverse-transcription polymerase chain reaction (RT-PCR) of five genes encoding tight junction components [Occludin, Claudin-1, -2, Zona occludens (ZO-1, -2)]. Results Histopathology confirmed GERD-specific alterations as dilated intercellular spaces in the esophageal mucosa of patients with GERD compared to controls (P?junction-related components and histomorphological GERD-specific alterations does not support a major role of the five proteins studied in the pathogenesis of GERD.

2012-01-01

339

Quantum phase slips in Josephson junction rings  

NASA Astrophysics Data System (ADS)

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.

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

2013-05-01

340

Gap Junctions and Hemichannels in Signal Transmission, Function and Development of Bone  

PubMed Central

Gap junctional intercellular communication (GJIC) mediated by connexins, in particular connexin 43 (Cx43), plays important roles in regulating signal transmission among different bone cells and thereby regulates development, differentiation, modeling and remodeling of the bone. GJIC regulates osteoblast formation, differentiation, survival and apoptosis. Osteoclast formation and resorptive ability are also reported to be modulated by GJIC. Furthermore, osteocytes utilize GJIC to coordinate bone remodeling in response to anabolic factors and mechanical loading. Apart from gap junctions, connexins also form hemichannels, which are localized on the cell surface and function independently of the gap junction channels. Both these channels mediate the transfer of molecules smaller than 1.2 kDa including small ions, metabolites, ATP, prostaglandin and IP3. The biological importance of the communication mediated by connexin-forming channels in bone development is revealed by the low bone mass and osteoblast dysfunction in the Cx43-null mice and the skeletal malformations observed in occulodentodigital dysplasia (ODDD) caused by mutations in the Cx43 gene. The current review summarizes the role of gap junctions and hemichannels in regulating signaling, function and development of bone cells.

Batra, Nidhi; Kar, Rekha; Jiang, Jean X.

2012-01-01

341

Tunnel junctions, cantilevers, and potentials  

NASA Astrophysics Data System (ADS)

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

Tanner, Shawn

342

Spin-polarized edge and transport in graphene nanoscale junctions  

NASA Astrophysics Data System (ADS)

By simulating spin transport through graphene nanoscale junctions, which have been fabricated recently, we show that the junction can conduct a spin-polarized current even without an external field. Conduction through the conduction subband results in an opposite type of spin filtering from conduction through the valence subband. The junction is magnetic with a nonzero total spin that depends on the junction geometry. The qualitative conclusions remain the same no matter a one-side armchair edge junction or a zigzag edge junction is considered.

Guo, Jing; Ouyang, Yijian

2009-06-01

343

Currents induced by injected charge in junction detectors.  

PubMed

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

Gaubas, Eugenijus; Ceponis, Tomas; Kalesinskas, Vidas

2013-09-12

344

Epithelial junctions maintain tissue architecture by directing planar spindle orientation.  

PubMed

During epithelial cell proliferation, planar alignment of the mitotic spindle coordinates the local process of symmetric cell cleavage with the global maintenance of polarized tissue architecture. Although the disruption of planar spindle alignment is proposed to cause epithelial to mesenchymal transition and cancer, the in vivo mechanisms regulating mitotic spindle orientation remain elusive. Here we demonstrate that the actomyosin cortex and the junction-localized neoplastic tumour suppressors Scribbled and Discs large 1 have essential roles in planar spindle alignment and thus the control of epithelial integrity in the Drosophila imaginal disc. We show that defective alignment of the mitotic spindle correlates with cell delamination and apoptotic death, and that blocking the death of misaligned cells is sufficient to drive the formation of basally localized tumour-like masses. These findings indicate a key role for junction-mediated spindle alignment in the maintenance of epithelial integrity, and also reveal a previously unknown cell-death-mediated tumour-suppressor function inherent in the polarized architecture of epithelia. PMID:23873041

Nakajima, Yu-ichiro; Meyer, Emily J; Kroesen, Amanda; McKinney, Sean A; Gibson, Matthew C

2013-07-21

345

Bunched fluxons in coupled Josephson junctions  

SciTech Connect

The nature of bunched fluxons on coupled long Josephson junctions is investigated theoretically by means of a coupled set of sine-Gordon equations. For cases of inductive and capacitive coupling between the junctions, we analyze the stability of the bunched states for different velocities and perturbation parameters, damping and bias. The internal oscillation frequency is found for the bunched modes and the origin of the stability is discussed for the different types of bound states. Extensive numerical simulations are carried out in order to validate the analytical results against the dynamical behavior of the full system. Excellent agreement between the analysis and the simulations is obtained for all values of coupling parameters and velocities. Finally, we demonstrate numerically that the stability of the bound states can persist even when the two systems are not exactly identical, and we conclude that both inductive and capacitive coupling can give rise to large-locking regimes in synchronization experiments on coupled Josephson junctions.

Gronbech-Jensen, N.; Cai, D.; Bishop, A.R.; Lau, A.W.C.; Lomdahl, P.S. (Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States))

1994-09-01

346

Time-dependent transport through molecular junctions  

NASA Astrophysics Data System (ADS)

We investigate transport properties of molecular junctions under two types of bias-a short time pulse or an ac bias-by combining a solution for Green's functions in the time domain with electronic structure information coming from ab initio density functional calculations. We find that the short time response depends on lead structure, bias voltage, and barrier heights both at the molecule-lead contacts and within molecules. Under a low frequency ac bias, the electron flow either tracks or leads the bias signal (resistive or capacitive response) depending on whether the junction is perfectly conducting or not. For high frequency, the current lags the bias signal due to the kinetic inductance. The transition frequency is an intrinsic property of the junctions.

Ke, San-Huang; Liu, Rui; Yang, Weitao; Baranger, Harold U.

2010-06-01

347

Energy barriers in carbon nanotube junctions  

NASA Astrophysics Data System (ADS)

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.

Tamura, Ryo; Tsukada, Masaru

2001-03-01

348

Tunneling magnetothermopower in magnetic tunnel junction nanopillars.  

PubMed

We study tunneling magnetothermopower (TMTP) in CoFeB/MgO/CoFeB magnetic tunnel junction nanopillars. Thermal gradients across the junctions are generated by an electric heater line. Thermopower voltages up to a few tens of ?V between the top and bottom contact of the nanopillars are measured which scale linearly with the applied heating power and hence the thermal gradient. The thermopower signal varies by up to 10???V upon reversal of the relative magnetic configuration of the two CoFeB layers from parallel to antiparallel. This signal change corresponds to a large spin-dependent Seebeck coefficient of the order of 100???V/K and a large TMTP change of the tunnel junction of up to 90%. PMID:22107572

Liebing, N; Serrano-Guisan, S; Rott, K; Reiss, G; Langer, J; Ocker, B; Schumacher, H W

2011-10-17

349

Mathematical classification of tight junction protein images.  

PubMed

We present the rationale for the development of mathematical features used for classification of images stained for selected tight junction proteins. The project examined localization of zonula occludens-1, claudin-1 and F-actin in a model epithelium, Madin-Darby canine kidney II cells. Cytochalasin D exposure was used to perturb junctional localization by actin cytoskeleton disruption. Mathematical features were extracted from images to reliably reveal characteristic information of the pattern of protein localization. Features, such as neighbourhood standard deviation, gradient of pixel intensity measurement and conditional probability, provided meaningful information to classify complex image sets. The newly developed mathematical features were used as input to train a neural network that provided a robust method of individual image classification. The ability for researchers to make determinations concerning image classification while minimizing human bias is an important advancement for the field of tight junction cellular biology. PMID:23889324

Ogawa, K H; Troyer, C M; Doss, R G; Aminian, F; Balreira, E C; King, J M

2013-07-25

350

Tunnel electroresistance in ferroelectric tunnel junctions  

NASA Astrophysics Data System (ADS)

In tunnel junctions with a ferroelectric barrier, large resistance changes can arise upon switching the ferroelectric polarization direction. This tunnel electroresistance (TER) effect has recently been observed by scanning probe techniques on electrode/barrier bilayers (e.g. LSMO/BaTiO3), yielding giant TER values in the 50000% range at room temperature. Beside their fundamental interest to elucidate the interplay between electrostatic effects, changes in the interfacial density of states, piezoelectricity and quantum-mechanical tunneling, ferroelectric tunnel junctions undoubtedly present a great potential for application as memory devices with simple, non-destructive readout and low-power write operations. We will present our progress towards the realization of solid-state ferroelectric tunnel junctions and discuss their potential as next-generation non-volatile memories.

Chanthbouala, A.; Crassous, A.; Garcia, V.; Bouzehouane, K.; Fusil, S.; Grollier, J.; Deranlot, C.; Moya, X.; Mathur, N.; Bibes, M.; Barthelemy, A.

2011-03-01

351

Junction area scaling and statistical description of dc breakdown of ferromagnetic tunnel junctions  

NASA Astrophysics Data System (ADS)

Magnetoresistive random access memory (MRAM) with ferromagnetic tunnel junctions (MTJs) has been recognized as a successful candidate for next generation solid-state memory. There are, however, still significant problems to realize MRAM. In particular, reliability of an ultrathin dielectric layer composing tunnel junctions is of great importance for MRAM developments. In this article, we performed systematical studies of the dielectric breakdown of MTJs. The samples have a double tunnel barrier structure with IrMn/CoFe/AlOx/CoFe/AlOx/CoFe/IrMn. Its width is ranging from 0.4 to 30 ?m. Different from previous reports, the breakdown voltage gradually decrease with decreasing junction area. The breakdown voltage only shows weak dependence on junction area in the sub-?m region. In addition, the breakdown voltage is inversely proportional to the junction perimeter. Results of time-dependent failure measurements demonstrate that, within the limit of this experiment, the failure function of the MTJs obeys a Weibull distribution. The shape parameter of the Weibull distribution is less than unity, indicating early device to failure. We consider that process-induced defects at the sidewall of the junctions may serve a certain role in their early failure and lead the failure of the junction area scaling of the breakdown voltage.

Nakajima, K.; Asao, Y.; Saito, Y.

2003-06-01

352

On the derivative discontinuity in molecular junctions  

NASA Astrophysics Data System (ADS)

Both the wave and particle aspects of the electron play essential roles in transport through single-molecule junctions. The wave character is implicit both in the Landauer formula used to understand nanoscale transport and in the very chemical bonds holding the junction together, while the particle aspect is manifested in phenomena such as Coulomb blockade and shot noise. The dominant computational paradigm for transport in single-molecule junctions involves local or semilocal approximations to density functional theory combined with nonequilibrium Green's functions. This approach does exceptionally well at describing the wave aspect of the electron, but fails to describe the particle aspect---due to the omission of the derivative discontinuity in the exchange-correlation potential that arises in the limit of vanishing lead-molecule coupling. To understand the role of the derivative discontinuity in molecular junctions, we investigated the transport and occupancy of a simple Anderson model of a molecular junction. We showedootnotetextJustin P. Bergfield, Zhenfei Liu, Kieron Burke, Charles A. Stafford, arXiv:1106.3104v2 that the exact single-particle Kohn-Sham potential of density functional theory reproduces the linear-response transport of the Anderson model exactly, despite the lack of a Kondo peak in its spectral function. Using Bethe ansatz techniques, we calculated this potential exactly for all coupling strengths, including the cross-over from mean-field behavior to charge quantization caused by the derivative discontinuity. The implications of our results for more complex molecular junctions will be discussed.

Stafford, Charles

2012-02-01

353

Electrostatic model of radial pn junction nanowires  

NASA Astrophysics Data System (ADS)

Poisson's equation is solved for a radial pn junction nanowire (NW) with surface depletion. This resulted in a model capable of giving radial energy band and electric field profiles for any arbitrary core/shell doping density, core/shell dimensions, and surface state density. Specific cases were analyzed to extract pertinent underlying physics, while the relationship between NW specifications and the depletion of the NW were examined to optimize the built-in potential across the junction. Additionally, the model results were compared with experimental results in literature to good agreement. Finally, an optimum device design is proposed to satisfy material, optical, and electrostatic constraints in high efficiency NW solar cells.

Chia, A. C. E.; LaPierre, R. R.

2013-08-01

354

Surface morphology of epitaxial magnetic tunnel junctions.  

PubMed

The surface morphology of epitaxial Fe(001)/MgO(001)/Fe(001) magnetic tunnel junctions, which show the giant tunneling magnetoresistance effect, was investigated by in situ scanning tunneling microscopy. It was observed that an epitaxial MgO barrier layer forms flat surface structures. The surface was flatter with distinct steps and terraces after annealing, which would lead to an increase of the tunneling magnetoresistance ratio. Examination of the local electronic structures of 1.05-nm-thick MgO barrier layers by scanning tunneling spectroscopy revealed no pinholes in the layers, so they would be perfect barriers in magnetic tunnel junctions. PMID:17455489

Mizuguchi, M; Suzuki, Y; Nagahama, T; Yuasa, S

2007-01-01

355

Craniovertebral junction neoplasms in the pediatric population  

Microsoft Academic Search

Introduction  The incidence of tumors at the craniovertebral junction in the pediatric population is low. Because of the variable pathology\\u000a and the rarity of these tumors, ideal therapies are only now being defined.\\u000a \\u000a \\u000a \\u000a Materials and methods  Thirty-eight children with tumors affecting the craniocervical junction were encountered between 1991 and 2006. These comprised\\u000a neoplasms of osseous origin and neural extramedullary tumors.\\u000a \\u000a \\u000a \\u000a Results and

Arnold H. Menezes

2008-01-01

356

Real-space microscopic electrical imaging of n+-p junction beneath front-side Ag contact of multicrystalline Si solar cells  

NASA Astrophysics Data System (ADS)

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.

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

2012-04-01

357

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

SciTech Connect

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.

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

2012-04-15

358

Nuclear Radiation Silicon Detectors with Silicide-Silicon Junctions.  

National Technical Information Service (NTIS)

It is shown that in order to increase the reliability of nuclear radiation detectors silicide-silicon junctions could be used. The thickness of input windows, leakage current and energy resolution of detectors with palladium silicide-silicon junction are ...

I. Brylowska K. Paprocki M. Walerian Kim Chan Khvan Nguen Thanh Hanh

1986-01-01

359

Role of Gap Junctions in Adverse Reproductive Outcome.  

National Technical Information Service (NTIS)

Several toxicants were evaluated for their effects on junctional communication between cells. Various techniques were used to measure junctional communication, including a new, rapid and sensitive dye coupling assay. The V79 cell line was used in most of ...

R. L. Caruso

1988-01-01

360

Ongelijkvloerse Kruispunten in Enkelbaanswegen (Split Level Junctions in Single Carriageways).  

National Technical Information Service (NTIS)

In conformity with the directives, in Holland rural single carriageways are usually provided with grade junctions. However, quite a number of split level junctions were built in the past in certain areas, especially in the northeastern part of the country...

1993-01-01

361

Non Traditional Transport Processes in Tunneling and Proximity Junctions.  

National Technical Information Service (NTIS)

Several project aimed at dealing with fundamental limitations in the present superconducting electronics technology based on Josephson junctions were carried out. The need for high resistance superconductor/normal metal/ superconductor Josephson junctions...

M. R. Beasley

2001-01-01

362

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

363

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

364

Characterization of discontinuous buffer junctions using pH indicators in capillary electrophoresis for protein preconcentration.  

PubMed

An effective sample preconcentration technique for proteins and peptides was recently developed using capillary electrophoresis (CE) with discontinuous buffers [C.A. Nesbitt, J.T.-M. Lo, K.K.-C. Yeung, J. Chromatogr. A 1073 (2005) 175]. Two buffers of different pH created a junction to trap the sample molecules at their isoelectric points and resulted in over 1000-fold preconcentration for myoglobin within 30 min. To study the formation of pH junctions in CE, a pH indicator, bromothymol blue, is used in this work to reveal the pH changes at the discontinuous buffer boundary. Bromothymol blue (BTB) exhibits a drastic change in its visible absorption spectrum (300-600 nm) going from the acidic to basic pH conditions, and is therefore ideal for visualizing the changes in pH at the junctions created by various buffer combinations. Preconcentration of myoglobin was performed in discontinuous buffers containing BTB. Major differences in the BTB absorption profiles were identified from buffer systems that differ significantly in preconcentration performance, which in turn, allowed for the identification of ideal buffers for sample preconcentration. Up to 2000-fold preconcentrations of myoglobin were achieved in the buffer systems studied in this work. In addition, the role of the electroosmotic flow (EOF) on the preconcentration performance was investigated. A low EOF was found to be desirable, as the pH junction could stay longer in the capillary for accumulation of proteins. The pH junction also displayed characteristics to resist bandbroadening. Potential laminar flow resulted from the mismatched residual EOFs under the two pH conditions within the discontinuous buffers appeared to have minimal effect on the preconcentration. In fact, external applied pressure can be used to control the migration of the pH junction without compromising the protein preconcentration. PMID:17022988

Jurcic, Kristina; Nesbitt, Chandra A; Yeung, Ken K-C

2006-10-04

365

Modulating Neuromuscular Junction Density Changes in Botulinum Toxin-Treated Orbicularis Oculi Muscle  

PubMed Central

Purpose. Botulinum toxin A is the most commonly used treatment for blepharospasm, hemifacial spasm, and other focal dystonias. Its main drawback is its relatively short duration of effect. The goal of this study was to examine the ability of corticotropin releasing factor (CRF) or antibody to insulin growth factor I–receptor (anti-IGFIR) to reduce the up-regulation of neuromuscular junctions that are associated with return of muscle function after botulinum toxin treatment. Methods. Eyelids of adult rabbits were locally injected with either botulinum toxin alone or botulinum toxin treatment followed by injection of either CRF or anti-IGFIR. After one, two, or four weeks, the orbicularis oculi muscles within the treated eyelids were examined for density of neuromuscular junctions histologically. Results. Injection of botulinum toxin into rabbit eyelids resulted in a significant increase in the density of neuromuscular junctions at one and two weeks, and an even greater increase in neuromuscular junction density by four weeks after treatment. Treatment with either CRF or anti-IGFIR completely prevented this increase in neuromuscular junction density. Conclusions. The return of function after botulinum toxin–induced muscle paralysis is due to terminal sprouting and formation of new neuromuscular junctions within the paralyzed muscles. Injection with CRF or anti-IGFIR after botulinum toxin treatment prevents this sprouting, which in turn should increase the duration of effectiveness of single botulinum toxin treatments. Future physiology studies will address this. Prolonging botulinum toxin's clinical efficacy should decrease the number of injections needed for patient muscle spasm relief, decreasing the risk of negative side effects and changes in drug effectiveness that often occurs over a lifetime of botulinum toxin exposure.

Harrison, Andrew R.; Berbos, Zachary; Zaldivar, Renzo A.; Anderson, Brian C.; Semmer, Mollie; Lee, Michael S.

2011-01-01

366

Microcrystalline silicon tunnel junctions for amorphous silicon-based multijunction solar cells  

SciTech Connect

The formation of tunnel junctions for applications in amorphous silicon (a-Si:H) based multijunction n-i-p solar cells has been studied using real time optics. The junction structure investigated in detail here consists of a thin ({approximately} 200 {angstrom}) layer of n-type microcrystalline silicon ({micro}c-Si:H) on top of an equally thin layer of p-type {micro}c-Si:H, the latter deposited on thick ({approximately} 2,000 {angstrom}) intrinsic a-Si:H. Such a structure has been optimized in an attempt to obtain single-phase {micro}c-Si:H with a high crystallite packing density and large grain size for both layers of the tunnel junction. They have explored the conditions under which grain growth is continuous across the p/n junction and conditions under which renucleation of n-layer grains can be ensured at the junction. one important finding of this study is that the optimum conditions for single-phase, high-density {micro}c-Si:H n-layers are different depending on whether the substrate is a {micro}c-Si:H p-layer or is a H{sub 2}-plasma treated or untreated a-Si:H i-layer. Thus, the top-most {micro}c-Si:H layer of the tunnel junction must be optimized in the multijunction device configuration, rather than in single cell configurations on a-Si:H i-layers. The observations are explained using an evolutionary phase diagram for a-Si:H and {micro}c-Si:H film growth versus thickness and H{sub 2}-dilution ratio, in which the boundary between the two phases is strongly substrate-dependent.

Ferlauto, A.S.; Koh, J.; Rovira, P.I.; Wronski, C.R.; Collins, R.W.

1999-07-01

367

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

NASA Astrophysics Data System (ADS)

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

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

2010-06-01

368

Novel germanium photodetectors fabricated with a diffused junction  

NASA Astrophysics Data System (ADS)

Germanium (Ge) photodetectors are fabricated by growing epitaxial III-V compounds on Ge substrates and by in-situ formation of the PN junction by MOVPE. After material growth, Ge photodetectors are mesa-etched using conventional optoelectronic device processing techniques. By varying the Ge substrate resistivity and the device area, Ge photodetector properties such as reverse leakage current, capacitance, and shunt resistance have been engineered. Such devices have demonstrated leakage currents below 50(mu) A/cm2 at -0.1 V bias. For optoelectronic applications that require high temperature operation, high shunt resistance detectors exhibit leakage currents below (mu) A/cm2 at 80 degree(s)C. Low capacitance devices have measured as little as 275 pF at 0V bias for a 1 mm diameter detector. High shunt resistance devices are a low cost alternative to conventional InGaAs photodiodes in applications such as laser monitor diodes.

Morrison, Charles B.; Sudharsanan, Rengarajan; Haddad, Moran; Boisvert, Joseph C.; Krut, Dmitri D.; King, Richard R.; Karam, Nasser H.

2002-05-01

369

Lipid Polarity Is Maintained in Absence of Tight Junctions*  

PubMed Central

The role of tight junctions (TJs) in the establishment and maintenance of lipid polarity in epithelial cells has long been a subject of controversy. We have addressed this issue using lysenin, a toxin derived from earthworms, and an influenza virus labeled with a fluorescent lipid, octadecylrhodamine B (R18). When epithelial cells are stained with lysenin, lysenin selectively binds to their apical membranes. Using an artificial liposome, we demonstrated that lysenin recognizes the membrane domains where sphingomyelins are clustered. Interestingly, lysenin selectively stained the apical membranes of epithelial cells depleted of zonula occludens proteins (ZO-deficient cells), which completely lack TJs. Furthermore, the fluorescent lipid inserted into the apical membrane by fusion with the influenza virus did not diffuse to the lateral membrane in ZO-deficient epithelial cells. This study revealed that sphingomyelin-cluster formation occurs only in the apical membrane and that lipid polarity is maintained even in the absence of TJs.

Ikenouchi, Junichi; Suzuki, Mayu; Umeda, Kazuaki; Ikeda, Kazutaka; Taguchi, Ryo; Kobayashi, Tetsuyuki; Sato, Satoshi B.; Kobayashi, Toshihide; Stolz, Donna B.; Umeda, Masato

2012-01-01

370

Perlecan regulates bidirectional Wnt signaling at the Drosophila neuromuscular junction.  

PubMed

Heparan sulfate proteoglycans (HSPGs) play pivotal roles in the regulation of Wnt signaling activity in several tissues. At the Drosophila melanogaster neuromuscular junction (NMJ), Wnt/Wingless (Wg) regulates the formation of both pre- and postsynaptic structures; however, the mechanism balancing such bidirectional signaling remains elusive. In this paper, we demonstrate that mutations in the gene of a secreted HSPG, perlecan/trol, resulted in diverse postsynaptic defects and overproduction of synaptic boutons at NMJ. The postsynaptic defects, such as reduction in subsynaptic reticulum (SSR), were rescued by the postsynaptic activation of the Frizzled nuclear import Wg pathway. In contrast, overproduction of synaptic boutons was suppressed by the presynaptic down-regulation of the canonical Wg pathway. We also show that Trol was localized in the SSR and promoted postsynaptic accumulation of extracellular Wg proteins. These results suggest that Trol bidirectionally regulates both pre- and postsynaptic activities of Wg by precisely distributing Wg at the NMJ. PMID:23319599

Kamimura, Keisuke; Ueno, Kohei; Nakagawa, Jun; Hamada, Rie; Saitoe, Minoru; Maeda, Nobuaki

2013-01-14

371

Molecular Basis of the Core Structure of Tight Junctions  

PubMed Central

The morphological feature of tight junctions (TJs) fits well with their functions. The core of TJs is a fibril-like proteinaceous structure within the lipid bilayer, the so-called TJ strands. TJ strands in apposing plasma membranes associate with each other to eliminate the intercellular space. A network of paired TJ strands generates a continuous belt that circumscribes each cell to establish the diffusion barrier to the solutes in the paracellular pathway throughout the cellular sheet. Identification and characterization of TJ-associated proteins during the last two decades has unveiled the nature of TJ strands and how they are spatially organized. The interplay between integral membrane proteins, claudins, and cytoplasmic plaque proteins, ZO-1/ZO-2, is critical for TJ formation and function.

Furuse, Mikio

2010-01-01

372

Junctions between i-motif tetramers in supramolecular structures  

PubMed Central

The symmetry of i-motif tetramers gives to cytidine-rich oligonucleotides the capacity to associate into supramolecular structures (sms). In order to determine how the tetramers are linked together in such structures, we have measured by gel filtration chromatography and NMR the formation and dissociation kinetics of sms built by oligonucleotides containing two short C stretches separated by a non-cytidine-base. We show that a stretch of only two cytidines either at the 3?- or 5?-end is long enough to link the tetramers into sms. The analysis of the properties of sms formed by oligonucleotides differing by the length of the oligo-C stretches, the sequence orientation and the nature of the non-C base provides a model of the junction connecting the tetramers in sms.

Guittet, Eric; Renciuk, Daniel; Leroy, Jean-Louis

2012-01-01

373

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

SciTech Connect

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.

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

374

Spin-polarized proximity effect in superconducting junctions  

Microsoft Academic Search

We study spin dependent phenomena in superconducting junctions in both ballistic and diffusive regimes. For ballistic junctions we study both ferromagnet\\/s- and d-wave superconductor junctions and two-dimensional electron gas\\/s-wave superconductor junctions with Rashba spin-orbit coupling. It is shown that the exchange field always suppresses the conductance while the Rashba spin-orbit coupling can enhance it. In the latter part of the

Takehito Yokoyama; Yukio Tanaka

2006-01-01

375

Effect of Laser Thermal Processing on Defect Evolution in Silicon  

Microsoft Academic Search

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

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

376

Analyzing the thermal annealing behavior of laser thermal processed silicon  

Microsoft Academic Search

Laser thermal processing (LTP) is one of several novel processes being studied as a replacement to conventional thermal annealing for silicon processing. It involves laser melting of an ion implantation induced pre-amorphized layer to form highly doped ultra shallow junctions. In theory, a supersaturation of interstitials created by the implantation step remains just below the laser-formed junction. Additionally, the possibility

Erik Adam Kuryliw

2003-01-01

377

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

PubMed

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

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

2013-05-17

378

Studies on Gold\\/Porous Silicon\\/Crystalline Silicon Junctions  

Microsoft Academic Search

Electrical transport in Gold\\/porous silicon\\/crystalline silicon junctions has been studied. The junctions are found to improve when the porous silicon is exposed to a hydrogen plasma before depositing the top metal. The hydrogen passivated junctions exhibited higher current levels and emitted light at lower voltages as compared to the unhydrogenated ones. Internal photoemission measurements were carried out to investigate the

Enakshi Bhattacharya; P. Ramesh; C. Suresh Kumar

2000-01-01

379

Groundwater Heat Pump Project - Junction City High School, Oregon  

Microsoft Academic Search

Junction City School District and Pacific Power & Light are co-sponsors for the Groundwater Heat Pump Project installed at Junction City High School in 1988. Like most school districts in the nation, Junction City School District makes every effort to keep expenses at a minimum; while, still providing top quality education and a comfortable environment. Conserving energy dollars is one

1994-01-01

380

A power balance model for converging and diverging flow junctions  

SciTech Connect

The authors propose that pressures across a junction of flows are best described by potential, kinetic, and dissipated (lost) power. It is demonstrated that differences in Bernoulli constants up- and downstream of junctions are not proportional to energy losses even in the trivial case of zero junction losses.

Guffey, S.E. (Dept. of Environmental Health, Univ. of Washington, Seattle, WA (US)); Fraser, D.A. (Univ. of North Carolina, Chapel Hill, NC (US))

1989-01-01

381

Resonant amplification of the Andreev process in ballistic Josephson junctions  

Microsoft Academic Search

We study the Josephson effect in ballistic SINIS and SIFIS double-barrier junctions, consisting of superconductors (S) , a clean normal (N) or ferromagnetic (F) metal, and insulating interfaces (I) . For short SINIS double-tunnel junctions with one channel open for quasiparticle propagation, the critical Josephson current as a function of the junction width shows sharp peaks because of a resonant

Ivana Petkovic; Nikolai M. Chtchelkatchev; Zoran Radovic

2006-01-01

382

Conductance Asymmetry of Graphene p-n Junction  

Microsoft Academic Search

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.

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

2009-01-01

383

The epithelial tight junction: Structure, function and preliminary biochemical characterization  

Microsoft Academic Search

The tight junction, or zonula occludens (ZO), forms a semi-permeable barrier in the paracellular pathway in most vertebrate epithelia. The ZO is the apical-most member of a series of intercellular junctions, collectively known as the junctional complex, found at the interface of the apical and lateral cell surface. This structure not only restricts movement of substances around the cells, but

Bruce R. Stevenson; James Melvin Anderson; Stanley Bullivant

1988-01-01

384

Propagation of electromagnetic waves in spatially modulated Josephson junctions  

Microsoft Academic Search

The propagation of small amplitude (linear) electromagnetic waves in periodically spatially modulated finite Josephson junctions is studied using the transfer matrix approach. The transmittance of a finite length Josephson junction with thick, identical, periodic defects is presented. The linear wave spectrum consists of pass- and stop-bands, whose width may vary with the geometrical and\\/or the physical parameters of the junction.

N. Lazarides

2005-01-01

385

Influence of nonuniform magnetic field on a ferrite junction circulator  

Microsoft Academic Search

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

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

1999-01-01

386

Temperature control of electromigration to form gold nanogap junctions  

Microsoft Academic Search

Controlled electromigration of gold nanowires of different cross-sectional areas to form nanogap junctions is studied using a feedback method. A linear correlation between the cross-sectional area of the gold nanowires and the power dissipated in the junction during electromigration is observed, indicating that the feedback mechanism operates primarily by controlling the temperature of the junction during electromigration. We also show

G. Esen; M. S. Fuhrer

2005-01-01

387

All-carbon molecular tunnel junctions.  

PubMed

This Article explores the idea of using nonmetallic contacts for molecular electronics. Metal-free, all-carbon molecular electronic junctions were fabricated by orienting a layer of organic molecules between two carbon conductors with high yield (>90%) and good reproducibility (rsd of current density at 0.5 V <30%). These all-carbon devices exhibit current density-voltage (J-V) behavior similar to those with metallic Cu top contacts. However, the all-carbon devices display enhanced stability to bias extremes and greatly improved thermal stability. Completed carbon/nitroazobenzene(NAB)/carbon junctions can sustain temperatures up to 300 °C in vacuum for 30 min and can be scanned at ±1 V for at least 1.2 × 10(9) cycles in air at 100 °C without a significant change in J-V characteristics. Furthermore, these all-carbon devices can withstand much higher voltages and current densities than can Cu-containing junctions, which fail upon oxidation and/or electromigration of the copper. The advantages of carbon contacts stem mainly from the strong covalent bonding in the disordered carbon materials, which resists electromigration or penetration into the molecular layer, and provides enhanced stability. These results highlight the significance of nonmetallic contacts for molecular electronics and the potential for integration of all-carbon molecular junctions with conventional microelectronics. PMID:22017204

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

2011-11-08

388

Severely Symptomatic Craniovertebral Junction Abnormalities in Children  

Microsoft Academic Search

Objectives: The treatment of symptomatic cranio-vertebral junction (CVJ) instability in children affected by CVJ abnormalities is a challenge. A series of severely symptomatic children has been reviewed to understand the controversial long-term effectiveness of the aggressive management of CVJ abnormalities, in terms of clinical improvement, spinal stability and growth. Methods: Three Down syndrome patients, 1 with mucopolysaccharidosis and 1 with

Carlo Giussani; Franck-Emmanuel Roux; Paolo Guerra; David Pirillo; Marco Grimaldi; Giuseppe Citerio; Erik P. Sganzerla

2009-01-01

389

Novel tunnelling barriers for spin tunnelling junctions  

Microsoft Academic Search

A tunnel junction consists of two metal electrodes separated by an insulating barrier thin enough for electrons to tunnel across. With ferromagnetic electrodes, a spin-dependent tunnelling (SDT) effect, electrons of one spin tunnelling preferentially over those of the other, is observed. When the electrodes are switched from a parallel to an anti-parallel alignment, the tunnelling current changes and gives rise

Manish Sharma

2000-01-01

390

WNTs tune up the neuromuscular junction.  

PubMed

Although WNTs have been long thought of as regulators of cell fate, recent studies highlight their involvement in crucial aspects of synaptic development in the nervous system. Particularly compelling are recent studies of the neuromuscular junction in nematodes, insects, fish and mammals. These studies place WNTs as major determinants of synapse differentiation and neurotransmitter receptor clustering. PMID:19693027

Korkut, Ceren; Budnik, Vivian

2009-09-01

391

Permanent junctional reciprocating tachycardia misdiagnosed as 'cardiomyopathy'.  

PubMed

In a nine-year-old female, cardiac failure was erroneously attributed to idiopathic cardiomyopathy and cardiac transplantation was planned. The actual cause of cardiac failure was permanent junctional reciprocating tachycardia (PJRT), a rare form of supraventricular tachycardia. The diagnostic error was discovered before transplantation was performed and the arrhythmia was treated surgically. This resulted in return of near normal cardiac function. PMID:1872752

McGuire, M A; Lau, K C; Davis, L M; Knight, P; Uther, J B; Ross, D L

1991-04-01

392

Gap Junctions: Basic Structure and Function  

Microsoft Academic Search

Gap junctions allow the exchange of ions, second messengers, and small metabolites between adjacent cells and are formed by two unrelated protein families, the pannexins and connexins. Mutations in connexin genes cause a variety of genetic disorders, implicating a critical role in tissue homeostasis. Association of congenital skin disorders to mutations in different connexins has underscored the importance of gap

Gülistan Me?e; Gabriele Richard; Thomas W White

2007-01-01

393

Electronic properties of electrodeposited semiconductor junctions  

Microsoft Academic Search

This thesis describes the synthesis, structural properties, optical properties, and electronic properties of semiconductor junctions based on electrochemically deposited ZnO and CU2O thin films. The first focus is characterizing the effect of deposition conditions (including applied potential and electrolyte composition) on the fundamental properties of these materials (including carrier concentration, band gap, and microstructure). Subsequent discussion addresses electrical conduction to

Shawn Michael Edward Chatman

2009-01-01

394

Structure of gap junction intercellular channels  

Microsoft Academic Search

Gap junctions are formed by a multigene family of polytopic membrane channel proteins, connexins, that have four hydrophobic transmembrane domains and their N and C termini located on the cytoplasmic membrane face. The C-terminal tail plays important roles in channel regulation by pH and phosphorylation. Conserved cysteine residues stabilize the conformation of the extracellular loops that mediate the ‘docking’ between

Mark Yeager; Bruce J Nicholson

1996-01-01

395

Heteromeric Connexons in Lens Gap Junction Channels  

Microsoft Academic Search

Gap junction channels are formed by paired oligomeric membrane hemichannels called connexons, which are composed of proteins of the connexin family. Experiments with transfected cell lines and paired Xenopus oocytes have demonstrated that heterotypic intercellular channels which are formed by two connexons, each composed of a different connexin, can selectively occur. Studies by Stauffer [Stauffer, K. A. (1995) J. Biol.

Jean X. Jiang; Daniel A. Goodenough

1996-01-01

396

Silicon p-n Junction Radiation Detectors  

Microsoft Academic Search

Silicon p-n junction particle detectors have been fabricated by diffusing phosphorus to various depths between 0.1 and 2.0 ¿ into high resistivity p-type silicon. Various base material resistivities have been employed, ranging from 100 ¿ cms to 13,000 ¿ cms. Diffusions have been carried out both by the \\

G. L. Miller; W. L. Brown; P. F. Donovan; I. M. Mackintosh

1960-01-01

397

Junction of Tomonaga–Luttinger liquids  

Microsoft Academic Search

Low-energy physics of one-dimensional electron systems can be generally described in terms of the Tomonaga–Luttinger liquid, instead of the Fermi liquid. We give a nontechnical review for nonspecialists on this intriguing subject. As an example of physical consequences, we discuss junction of two and three Tomonaga–Luttinger liquids.

Masaki Oshikawa

2005-01-01

398

The dynamics of mesoscopic normal tunnel junctions  

NASA Astrophysics Data System (ADS)

We first review the dynamics of mesoscopic tunnel junctions within the semiclassical approach, outlining the method and its assumptions. We examine the case of a single junction driven by a constant current source, and its non-linear I-V characteristic. We then consider a single junction driven by a direct and an alternating current source, and show that it can be used as a phase-voltage converter. We also apply the approach to two junctions in series, showing that such a configuration has a non-linear I-V characteristic that can be used in electronic devices. We subsequently investigate the dynamics of such systems when the phase breaking time is large and the semiclassical approach does not apply. We first review the standard Zener tunneling calculations, and then show the effect of dissipation. We define and calculate the Zener time, a measure of the width of non-adiabatic transitions. We investigate the dynamics of systems whose energy spectrum consists of a set of periodic bands, for the cases where the phase breaking time is larger and smaller than the period of the band, but larger than the Zener time.

Mullen, Kieran; Gefen, Yuval; Ben-Jacob, Eshel

1988-08-01

399

Asymptotic solution for the resistively shunted junction (RSJ) model of the Josephson junction  

SciTech Connect

Using the method developed by Bogolyubov et al., we find analytically a steady-state solution for the resistively shunted junction (RSJ) model of the Josephson junction that is driven by a constant current source. This solution explains how the relative amplitude of the voltage oscillation depends on the junction parameters such as I/sub o/ (the critical current), R (the resistance), C (the capacitance), and the external current I/sub e/. The validity of the analytical solution is assessed by comparing it with numerical results. We find that this solution is useful for normal tunnel junction with I/sub e//I/sub o/ of order 1 or larger, and for any other weak links with I/sub e//I/sub o/ much larger than 1.

Liu, I.; Lee, Y.C.

1981-07-01

400

Relics of a complex triple junction in the Weddell Sea embayment, Antarctica  

Microsoft Academic Search

Interpretation of an airborne magnetic data compilation containing a key, new survey, together with re-tracked satellite gravity data from the Weddell Sea embayment (WSE), West Antarctica, suggests Rift–Rift–Rift triple junction formation at the onset of Gondwana breakup in the Early Middle Jurassic. A complex system of northwest–southeast rifts was active contemporaneously with an east–west trending rift. This rift activity led

J. K Ferris; A. P. M Vaughan; B. C Storey

2000-01-01

401

Relics of a complex triple junction in the Weddell Sea embayment, Antarctica  

Microsoft Academic Search

Interpretation of an airborne magnetic data compilation containing a key, new survey, together with re-tracked satellite gravity data from the Weddell Sea embayment (WSE), West Antarctica, suggests Rift-Rift-Rift triple junction formation at the onset of Gondwana breakup in the Early Middle Jurassic. A complex system of northwest-southeast rifts was active contemporaneously with an east-west trending rift. This rift activity led

J. K. Ferris; A. P. M. Vaughan; B. C. Storey

2000-01-01

402

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

Microsoft Academic Search

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

F. Sarubbi

2010-01-01

403

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

Microsoft Academic Search

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

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

1977-01-01

404

Preventive effect of germanium dioxide on the inhibition of gap junctional intercellular communication by TPA  

Microsoft Academic Search

Gap junctional intercellular communication (GJIC) is thought to be essential for maintaining cellular homeostasis and growth control. In order to detect any protective agent against tumor formation, we examined the anticarcinogenic effect of a germanium dioxide (GeO2) using a model system of GJIC in F344 rat liver epithelial cells, named WB cells. 12-O-tetradecanoylphorbol-13-acetate (TPA), known as tumor promoters, inhibited GJIC

Kyung-Sun Kang; Jun-Won Yun; ByoungSu Yoon; Yoon-Kyu Lim; Yong-Soon Lee

2001-01-01

405

A Silicon Nanocrystal Schottky Junction Solar Cell produced from Colloidal Silicon Nanocrystals  

Microsoft Academic Search

Solution-processed semiconductors are seen as a promising route to reducing the cost of the photovoltaic device manufacture.\\u000a We are reporting a single-layer Schottky photovoltaic device that was fabricated by spin-coating intrinsic silicon nanocrystals\\u000a (Si NCs) from colloidal suspension. The thin-film formation process was based on Si NCs without any ligand attachment, exchange,\\u000a or removal reactions. The Schottky junction device showed

Chin-Yi Liu; Uwe R. Kortshagen

2010-01-01

406

Electrochemiluminescence from porous silicon in formic acid liquid-junction cells  

Microsoft Academic Search

Visible light emission from porous silicon can be stimulated by applying a positive bias to a formic acid\\/sodium formate liquid junction cell. The emission lasts for 45 min at +2.75 V applied potential (<5 mA\\/cm2, power conversion efficiency ?10?2%) and is reliably generated from n- or p-type porous silicon. An applied voltage as low as 1.3 V is capable of

Will H. Green; Eric J. Lee; Jeffrey M. Lauerhaas; Theodore W. Bitner; Michael J. Sailor

1995-01-01

407

Mechanism of Filament Nucleation and Branch Stability Revealed by the Structure of the Arp2\\/3 Complex at Actin Branch Junctions  

Microsoft Academic Search

Actin branch junctions are conserved cytoskeletal elements critical for the generation of protrusive force during actin polymerization-driven cellular motility. Assembly of actin branch junctions requires the Arp2\\/3 complex, upon activation, to initiate a new actin (daughter) filament branch from the side of an existing (mother) filament, leading to the formation of a dendritic actin network with the fast growing (barbed)

Coumaran Egile; Isabelle Rouiller; Xiao-Ping Xu; Niels Volkmann; Rong Li; Dorit Hanein

2005-01-01

408

Single molecule junction conductance and binding geometry  

NASA Astrophysics Data System (ADS)

This Thesis addresses the fundamental problem of controlling transport through a metal-organic interface by studying electronic and mechanical properties of single organic molecule-metal junctions. Using a Scanning Tunneling Microscope (STM) we image, probe energy-level alignment and perform STM-based break junction (BJ) measurements on molecules bound to a gold surface. Using Scanning Tunneling Microscope-based break-junction (STM-BJ) techniques, we explore the effect of binding geometry on single-molecule conductance by varying the structure of the molecules, metal-molecule binding chemistry and by applying sub-nanometer manipulation control to the junction. These experiments are performed both in ambient conditions and in ultra high vacuum (UHV) at cryogenic temperatures. First, using STM imaging and scanning tunneling spectroscopy (STS) measurements we explore binding configurations and electronic properties of an amine-terminated benzene derivative on gold. We find that details of metal-molecule binding affect energy-level alignment at the interface. Next, using the STM-BJ technique, we form and rupture metal-molecule-metal junctions ˜104 times to obtain conductance-vs-extension curves and extract most likely conductance values for each molecule. With these measurements, we demonstrated that the control of junction conductance is possible through a choice of metal-molecule binding chemistry and sub-nanometer positioning. First, we show that molecules terminated with amines, sulfides and phosphines bind selectively on gold and therefore demonstrate constant conductance levels even as the junction is elongated and the metal-molecule attachment point is modified. Such well-defined conductance is also obtained with paracyclophane molecules which bind to gold directly through the pi system. Next, we are able to create metal-molecule-metal junctions with more than one reproducible conductance signatures that can be accessed by changing junction geometry. In the case of pyridine-linked molecules, conductance can be reliably switched between two distinct conductance states using sub-nanometer mechanical manipulation. Using a methyl sulfide linker attached to an oligoene backbone, we are able to create a 3-nm-long molecular potentiometer, whose resistance can be tuned exponentially with Angstom-scale modulations in metal-molecule configuration. These experiments points to a new paradigm for attaining reproducible electrical characteristics of metal-organic devices which involves controlling linker-metal chemistry rather than fabricating identically structured metal-molecule interfaces. By choosing a linker group which is either insensitive to or responds reproducibly to changes in metal-molecule configuration, one can design single molecule devices with functionality more complex than a simple resistor. These ambient temperature experiments were combined with UHV conductance measurements performed in a commercial STM on amine-terminated benzene derivatives which conduct through a non-resonant tunneling mechanism, at temperatures varying from 5 to 300 Kelvin. Our results indicate that while amine-gold binding remains selective irrespective of environment, conductance is not temperature independent, in contrast to what is expected for a tunneling mechanism. Furthermore, using temperature-dependent measurements in ambient conditions we find that HOMO-conducting amines and LUMO-conducting pyridines show opposite dependence of conductance on temperature. These results indicate that energy-level alignment between the molecule and the electrodes changes as a result of varying electrode structure at different temperatures. We find that temperature can serve as a knob with which to tune transport properties of single molecule-metal junctions.

Kamenetska, Maria

409

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

Microsoft Academic Search

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

Stacy L Waksmonski; Richard I Woodruff

2002-01-01

410

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

Microsoft Academic Search

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

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

2005-01-01

411

Hormonal regulation of hepatocyte tight junctional permeability  

SciTech Connect

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

Lowe, P.J.; Miyai, K.; Steinbach, J.H.; Hardison, W.G.M. (Veterans Administration Medical Center, San Diego, CA (USA) Univ. of California, San Diego (USA))

1988-10-01

412

?2-syntrophin and Par-3 promote an apicobasal Rac activity gradient at cell-cell junctions by differentially regulating Tiam1 activity.  

PubMed

Although Rac and its activator Tiam1 are known to stimulate cell-cell adhesion, the mechanisms regulating their activity in cell-cell junction formation are poorly understood. Here, we identify ?2-syntrophin as a Tiam1 interactor required for optimal cell-cell adhesion. We show that during tight-junction (TJ) assembly ?2-syntrophin promotes Tiam1-Rac activity, in contrast to the function of the apical determinant Par-3 whose inhibition of Tiam1-Rac activity is necessary for TJ assembly. We further demonstrate that ?2-syntrophin localizes more basally than Par-3 at cell-cell junctions, thus generating an apicobasal Rac activity gradient at developing cell-cell junctions. Targeting active Rac to TJs shows that this gradient is required for optimal TJ assembly and apical lumen formation. Consistently, ?2-syntrophin depletion perturbs Tiam1 and Rac localization at cell-cell junctions and causes defects in apical lumen formation. We conclude that ?2-syntrophin and Par-3 fine-tune Rac activity along cell-cell junctions controlling TJ assembly and the establishment of apicobasal polarity. PMID:23103911

Mack, Natalie A; Porter, Andrew P; Whalley, Helen J; Schwarz, Juliane P; Jones, Richard C; Khaja, Azharuddin Sajid Syed; Bjartell, Anders; Anderson, Kurt I; Malliri, Angeliki

2012-10-28

413

The anatomical locus of T-junction processing.  

PubMed

Inhomogeneous surrounds can produce either asymmetrical or symmetrical increment/decrement induction by orienting T-junctions to selectively group a test patch with surrounding regions [Melfi, T., & Schirillo, J. (2000). T-junctions in inhomogeneous surrounds. Vision Research, 40, 3735-3741]. The current experiments aimed to determine where T-junctions are processed by presenting each eye with a different image so that T-junctions exist only in the fused percept. Only minor differences were found between retinal and cortical versus cortical-only conditions, indicating that T-junctions are processed cortically. PMID:19464313

Schirillo, James A

2009-05-21

414

Bistability in superconducting rings containing an inhomogeneous Josephson junction  

NASA Astrophysics Data System (ADS)

We investigate the magnetic response of a superconducting Nb ring containing a ferromagnetic PdNi Josephson junction and a tunnel junction in parallel. Doubling of the switching frequency is observed within certain intervals of the external magnetic field. For sinusoidal current-phase relations in both junctions, our model of a double superconducting quantum interference device (a small two-junction loop that interrupts the larger ring) explains this feature by a sequence of current reversals in the ferromagnetic section of the junction in these field intervals. The switching anomalies are induced by the coupling between the magnetic fluxes in the two superconducting loops.

Gaass, M.; Nadj-Perge, S.; Radovi?, Z.; Bauer, A.; Aprili, M.; Wegscheider, W.; Strunk, C.

2008-01-01

415

Tight junctions and the modulation of barrier function in disease  

PubMed Central

Tight junctions create a paracellular barrier in epithelial and endothelial cells protecting them from the external environment. Two different classes of integral membrane proteins constitute the tight junction strands in epithelial cells and endothelial cells, occludin and members of the claudin protein family. In addition, cytoplasmic scaffolding molecules associated with these junctions regulate diverse physiological processes like proliferation, cell polarity and regulated diffusion. In many diseases, disruption of this regulated barrier occurs. This review will briefly describe the molecular composition of the tight junctions and then present evidence of the link between tight junction dysfunction and disease.

2008-01-01

416

Development and fabrication of a solar cell junction processing system. Quarterly report No. 2, July 1980  

SciTech Connect

The basic objectives of the program are the following: (1) to design, develop, construct and deliver a junction processing system which will be capable of producing solar cell junctions by means of ion implantation followed by pulsed electron beam annealing; (2) to include in the system a wafer transport mechanism capable of transferring 4-inch-diameter wafers into and out of the vacuum chamber where the ion implantation and pulsed electron beam annealing processes take place; (3) to integrate, test and demonstrate the system prior to its delivery to JPL along with detailed operating and maintenance manuals; and (4) to estimate component lifetimes and costs, as necessary for the contract, for the performance of comprehensive analyses in accordance with the Solar Array Manufacturing Industry Costing Standards (SAMICS). Under this contract the automated junction formation equipment to be developed involves a new system design incorporating a modified, government-owned, JPL-controlled ion implanter into a Spire-developed pulsed electron beam annealer and wafer transport system. When modified, the ion implanter will deliver a 16 mA beam of /sup 31/P/sup +/ ions with a fluence of 2.5 x 10/sup 15/ ions per square centimeter at an energy of 10 keV. The throughput design goal rate for the junction processor is 10/sup 7/ four-inch-diameter wafers per year.

Siesling, R.

1980-07-01

417

Coherent transmission of nodal Dirac fermions through a graphene-based superconducting double barrier junction  

NASA Astrophysics Data System (ADS)

Transport characteristics of relativistic electrons through graphene-based d-wave superconducting double barrier junction and ferromagnet/ d-wave superconductor/normal metal double junction have been investigated based on the Dirac-Bogoliubov-de Gennes equation. We have first presented the results of superconducting double barrier junction. In the subgap regime, both the crossed Andreev and nonlocal tunneling conductance all oscillate with the bias voltage due to the formation of Andreev bound states in the normal metal region. Moreover, the critical voltage beyond which the crossed Andreev conductance becomes to zero decreases with increasing value of superconducting pair potential ?. In the presence of the ferromagnetism, the MR through graphene-based ferromagnet/ d-wave superconductor/normal metal double junction has been investigated. It is shown that the MR increases from exchange splitting h 0=0 to h 0= E F (Fermi energy), and then it goes down. At h 0= E F, MR reaches its maximum 100. In contrast to the case of a single superconducting barrier, Andreev bound states also manifest itself in the zero bias MR, which result in a series of peaks except the maximum one at h 0= E F. Besides, the resonance peak of the MR can appear at certain bias voltage and structure parameter. Those phenomena mean that the coherent transmission can be tuned by superconducting pair potential, structure parameter, and external bias voltage, which benefits the spin-polarized electron device based on the graphene materials.

Bai, Chunxu; Wei, Ke-Wei; Yang, Gui; Yang, Yanling

2013-05-01

418

De novo-generated small palindromes are characteristic of amplicon boundary junction of double minutes  

PubMed Central

Double minutes (DMs) are hallmarks of gene amplification. However, their molecular structure and the mechanisms of formation are largely unknown. To elucidate the structure and underlying molecular mechanism of DMs, we obtained and cloned DMs using microdissection; and degenerated oligonucleotide primed polymerase chain reaction (DOP-PCR) from the ovarian cancer cell line UACC-1598. Two large amplicons, the 284 kb AmpMYCN, originating from locus 2p24.3 and the 391 kb AmpEIF5A2, from locus 3q26.2, were found co-amplified on the same DMs. The two amplicons are joined through a complex 7 kb junction DNA sequence. Analysis of the junction has revealed three de novo created small palindromes surrounding the six breakpoints. Consistent with these observations, we further found that 70% of the 57 reported DM junction sequences have de novo creation of small palindromic sequences surrounding the breakpoints. Together, our findings indicate that de novo-generated small palindromic sequences are characteristic of amplicon boundary junctions on DMs. It is possible that the de novo-generated small palindromic sequences, which may be generated through non-homologous end joining in concert with a novel DNA repair machinery, play a common role in amplicon rejoining and gene amplification.

Zhu, Jing; Yu, Yang; Meng, Xiangning; Fan, Yihui; Zhang, Yu; Zhou, Chunshui; Yue, Zhichao; Jin, Yan; Zhang, Chunyu; Yu, Lisa; Ji, Wei; Jia, Xueyuan; Guan, Rongwei; Wu, Jie; Yu, Jingcui; Bai, Jing; Guan, Xin-Yuan; Wang, Mingrong; Lee, Ki-Young; Sun, Wenjing; Fu, Songbin

2013-01-01

419

Specific localisation of gap junction protein connexin 32 in the gastric mucosa of horses.  

PubMed

In the glandular stomach, gap junctional intercellular communication (GJIC) plays an important role in the gastric mucosal defense system, and loss of GJIC is associated with ulcer formation. In spite of the high incidence of gastric ulcers in horses, particularly at pars nonglandularis, the presence of gap junctions in the equine stomach has not yet been studied. The objective was to obtain basic data on the distribution of gap junction protein connexin 32 (Cx32) in the different regions of normal equine gastric mucosa. Samples of mucosa were taken from seven horses at cardiac, fundic, and pyloric region and pars nonglandularis. To detect Cx32, immunohistochemical staining and Western blot analysis were performed. Corresponding mRNA was shown by RT-PCR and localised in tissue sections by in situ hybridisation. Cx32 was found in the glandular regions, whereas it was not detectable in squamous mucosa. Within the glandular epithelium, Cx32 was abundant in surface and foveolar cells and decreased towards the proliferative zone of the glands. These results suggest that gap junctions develop during the maturation of surface cells. Whether the lack of Cx32 at pars nonglandularis contributes to its susceptibility for developing ulcers, has to be further elucidated. PMID:16205941

Fink, Cornelia; Hembes, Tanja; Brehm, Ralph; Weigel, Roswitha; Heeb, Cornelia; Pfarrer, Christiane; Bergmann, Martin; Kressin, Monika

2005-10-05

420

Indium oxide thin-film homo-junctions: Morphology and electrical properties  

NASA Astrophysics Data System (ADS)

Indium oxide shows an unusual combination of electrical and optical properties that give rise to a broad range of applications in optoelectronic devices. Here, we report results of structural, x-ray photoelectron spectroscopy, and electrical transport studies of transparent homo-junctions, obtained by sequential growth of polycrystalline thin layers of indium oxide under O2-rich and O2-poor conditions. We find that the growth temperature, which affects significantly film morphology, is critical for the rectifying behavior of the junctions. Only junctions grown at about 350 °C are rectifying. We also find that p-type-like layers have higher concentration of inter-grain oxygen than n-type layers, presumably coming from oxygen-rich deposition conditions and from much larger number of grain boundaries than in n-type layers. We conjecture that the segregation of oxygen ions at grain boundaries is responsible for the formation of inversion layers in O2-rich films and their apparent p-type dc conduction. This mechanism significantly modifies the capacitance-voltage characteristics of the junctions. However, the rectifying mechanism can be accounted for by a space-charge layer at the p-n interface. Such behavior might be important in other polycrystalline thin films with a large number of interface defects at grain boundaries.

Stankiewicz, Jolanta; Villuendas, Francisco; Pilar Lozano, María; Díez, Isabel

2013-08-01

421

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

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

422

Observation of molecular level behavior in molecular electronic junction device  

NASA Astrophysics Data System (ADS)

In this dissertation, I utilize AFM based scanning probe measurement and surface enhanced Raman scattering based vibrational spectroscopic analysis to directly characterize topographic, electronic, and chemical properties of molecules confined in the local area of M3 junction to elucidate the molecular level behavior of molecular junction electronic devices. In the introduction, the characterization of molecular electronic devices with different types of metal-molecule-metal (M3) structures based upon self-assembled monolayers (SAMs) is reviewed. A background of the characterization methods I use in this dissertation, conducting probe atomic force microscopy (cp-AFM) and surface enhanced Raman spectroscopy (SERS), is provided in chapter 1. Several attempts are performed to create the ideal top metal contacts on SAMs by metal vapor phase deposition in order to prevent the metal penetration inducing critical defects of the molecular electronic devices. The scanning probe microscopy (SPM), such as cp-AFM, contact mode (c-) AFM and non-contact mode (nc-) AFM, in ultra high vacuum conditions are utilized to study the process of the metal-SAM interface construction in terms of the correlation between the morphological and electrical properties including the metal nucleation and filament generation as a function of the functionalization of long-chain alkane thiolate SAMs on Au. In chapter 2, the nascent condensation process of vapor phase Al deposition on inert and reactive SAMs are studied by SPM. The results of top deposition, penetration, and filament generation of deposited Al are discussed and compared to the results previously observed by spectroscopic measurements. Cp-AFM was shown to provide new insights into Al filament formation which has not been observed by conventional spectroscopic analysis. Additionally, the electronic characteristics of individual Al filaments are measured. Chapter 3 reveals SPM characterization of Au deposition onto --COOH terminated SAMs utilized with strong surface dipole-dipole intermolecular interaction based on hydrogen bonding and ionic bonding potentially preventing the metal penetration. The observed results are discussed with kinetic paths of metal atoms on each SAM including temporal vacancies controlled by the intermolecular interactions in SAM upon the comparison with the spectroscopic results previously reported. The results in chapter 2 and 3 strongly suggests that AFM based characterization technique is powerful tool especially for detecting molecular-size local phenomena in vapor phase metal deposition process, especially, the electric short-circuit filaments growing through SAMs, which may induce critical misinterpretation of M3 junction device properties. In Chapter 4, an altered metal deposition process on inert SAM with using a buffer layer is performed to diminish the kinetic energy of impinging metal atoms. SPM characterization reveals an abrupt metal-SAM interface without any metal penetration. Examined electric characteristics also revealed typical non-resonant tunneling characteristics of long chain alkane thiolate SAMs. In chapter 5, the buffer layer assisted growth process is used to prepare a nano particles-SAM pristine interface on SAMs to control the metal-SAM interaction in order to study the fundamental issue of chemical enhancement mechanism of SERS. Identical Au nanoparticles-SAM-Au M3 structures with different Au-SAM interactions reveal a large discrepancy of enhancement factors of ˜100 attributed to the chemical interaction. In chapter 6, Raman spectroscopy of M3 junction is applied to the characterization of molecular electronics devices. A crossed nanowire junction (X-nWJ) device is employed for in-situ electronic-spectroscopic simultaneous characterization using Raman spectroscopy. A detailed study reveals the multi-probe capability of X-nWJ for in-situ Raman and in-elastic electron tunneling spectroscopy (IETS) as vibrational spectroscopies to diagnose molecular electronic devices. In chapter 7, aniline oligomer (OAn) based redox SAMs are characterized b

Maitani, Masato

423

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

NASA Astrophysics Data System (ADS)

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.

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

2011-08-01

424

Direct imaging of GaN p-n junction by cross-sectional scanning photoelectron microscopy and spectroscopy  

SciTech Connect

We demonstrate that formation of p-n junction in gallium nitride (GaN) can be directly visualized on cleavage surfaces in a cross-sectional geometry, where the focused synchrotron radiation (soft x-ray) images the different doping layers on the nonpolar a-plane surface perpendicular to the polar growth direction. In contrast to the as-grown GaN polar surface, the in situ cleaved GaN a-plane surface is shown by using photoelectron spectroscopy to be under the flatband conditions. This unique surface property opens up the way to image and identify p-n junctions in III-nitride semiconductors.

Kuo, C.-T.; Lee, H.-M.; Gwo Shangjr [Department of Physics, National Tsing-Hua University, Hsinchu 30013, Taiwan (China); Shiu, H.-W. [Department of Physics, National Tsing-Hua University, Hsinchu 30013, Taiwan (China); National Synchrotron Radiation Research Center (NSRRC), Hsinchu 30076, Taiwan (China); Chen, C.-H. [National Synchrotron Radiation Research Center (NSRRC), Hsinchu 30076, Taiwan (China)

2009-03-23

425

Crooked, Coiled and Crimpled are three Ly6-like proteins required for proper localization of septate junction components  

PubMed Central

Cellular junction formation is an elaborate process that is dependent on the regulated synthesis, assembly and membrane targeting of constituting components. Here, we report on three Drosophila Ly6-like proteins essential for septate junction (SJ) formation. SJs provide a paracellular diffusion barrier and appear molecularly and structurally similar to vertebrate paranodal septate junctions. We show that Crooked (Crok), a small GPI-anchored Ly6-like protein, is required for septa formation and barrier functions. In embryos that lack Crok, SJ components are produced but fail to accumulate at the plasma membrane. Crok is detected in intracellular puncta and acts tissue-autonomously, which suggests that it resides in intracellular vesicles to assist the cell surface localization of SJ components. In addition, we demonstrate that two related Ly6 proteins, Coiled (Cold) and Crimpled (Crim), are required for SJ formation and function in a tissue-autonomous manner, and that Cold also localizes to intracellular vesicles. Specifically, Crok and Cold are required for correct membrane trafficking of Neurexin IV, a central SJ component. The non-redundant requirement for Crok, Cold, Crim and Boudin (Bou; another Ly6 protein that was recently shown to be involved in SJ formation) suggests that members of this conserved family of proteins cooperate in the assembly of SJ components, possibly by promoting core SJ complex formation in intracellular compartments associated with membrane trafficking.

Nilton, Anna; Oshima, Kenzi; Zare, Fariba; Byri, Sunitha; Nannmark, Ulf; Nyberg, Kevin G.; Fehon, Richard G.; Uv, Anne E.

2010-01-01

426

Andreev magnetointerferometry in topological hybrid junctions  

NASA Astrophysics Data System (ADS)

We investigate the fate of topological edge states in the quantum Hall (QH) regime when they experience tunneling processes through a narrow superconducting (S) strip. By computing the charge conductance flowing through a graphene-based QH/S/QH junction, the S strip is shown to act as an Andreev interferometer, giving rise to spectacular conductance oscillations as a function of the Landau level filling factor. We provide a semiclassical analysis allowing for a natural interpretation of these oscillations in terms of interferences between electron and hole trajectories propagating along the QH/S interfaces. Our results suggest that nontrivial junctions between topologically distinct phases could offer a highly tunable means of partitioning the flow of edge states.

Carmier, Pierre

2013-10-01

427

Topological ? Josephson junction in superconducting Rashba wires  

NASA Astrophysics Data System (ADS)

In this Rapid Communication we show that Rashba-based topological superconductor nanowires, where the spin-orbit coupling may change its sign, support three topological phases protected by chiral symmetry. When a superconducting phase gradient is applied over the interface of the two nontrivial phases, the Andreev spectrum is qualitatively phase shifted by ? compared to usual Majorana weak links. The topological ? junction has the striking property of exhibiting a maximum supercurrent in the vicinity of vanishing phase difference. Qualitative features of the junction are robust against disorder and magnetic fields violating chiral symmetry. The studied system could be realized by local gating of the wire or by an appropriate stacking of permanent magnets in synthetic Rashba systems.

Ojanen, Teemu

2013-03-01

428

Spontaneous Supercurrent Induced by Ferromagnetic ? Junctions  

NASA Astrophysics Data System (ADS)

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

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

2004-05-01

429

Interface composition in magnetic tunnel junctions  

SciTech Connect

The magnetoresistance of magnetic tunnel junctions critically depends on the exact composition at the interfaces. As such the completeness of the oxidation process of the Al layer (used to produce Al{sub 2}O{sub 3}-based tunnel junctions) plays an essential role in the magnetoresistance. We studied the chemical properties of ferromagnet/Al{sub 2}O{sub 3} interfaces as a function of original Al layer thickness. We have studied the concentrations of elementary and oxidized Al, Co, Ni, and Fe for varying roughness of the ferromagnetic layer. The oxidation process critically depends on the roughness of the underlying ferromagnetic (FM) layer. Al layers grown onto smooth FM layers oxidize homogeneously whereas Al layers grown on rough FM layers show a complicated oxidation behavior. Within the sensitivity of the analysis technique, we did not observe oxidation of the ferromagnetic layers, even for the overoxidized part of the samples. {copyright} 2001 American Institute of Physics.

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

2001-06-01

430

Probing molecular electronics with mechanical break junctions  

NASA Astrophysics Data System (ADS)

We will report on experiments with single molecule junctions, performed with the mechanically controlled break-junction technique. A review is given on the capabilities of the technique and the results obtained so far. The importance of the molecular structure, the local environment, the contacts, and of the electronic polarizability will be elucidated. As a particular example, we will present an experiment with a molecule that was designed to form a single-molecule diode when contacted from two sides. The concept is closely related to Aviram-Ratner's Gedankenexperiment. Indeed, the IVs show a pronounced asymmetry, whereas a blind experiment with symmetric molecules resulted in symmetric IVs. A closer analysis of the data, involving theoretical models, suggests that the bias-dependent charge reconfiguration of the electronic structure is responsible for the diode-like characteristics.

Weber, Heiko

2006-03-01

431

Spin Valves and Magnetic Tunnel Junctions  

NASA Astrophysics Data System (ADS)

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.

Iversen, Kurt; Pufall, Matthew; Heindl, Ranko

2011-10-01

432

Spin transfer torque in ferroelectric tunnel junctions  

NASA Astrophysics Data System (ADS)

The worldwide interest for spintronics grows up every year, magnetic oscillators and resistance switchers became an important part of electronics with promising applications such as tunable microwave radiation, magnetic memory cells, magnetic field sensors, etc. A non-equilibrium spin-dependent transport in magnetic tunnel junctions</