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1

Optically Stimulated Diffusion in Ultra-Shallow Junction Formation  

NASA Astrophysics Data System (ADS)

Formation of pn junctions in advanced Si-based transistors employs rapid thermal annealing after ion-implantation in order to increase the activation of dopants. There has long been suspicion that the strong lamp illumination required for this procedure may nonthermally influence the diffusion of dopants. Identification of such effects is difficult in conventional RTA geometries because lamps provide both heating and photo stimulation, and because the interpretation of conventional dopant diffusion experiments is impeded by complex dopant-defect interactions. We have circumvented these problems with a new experimental design in which heating and illumination can be decoupled. Data interpretation has been simplified by examining the motion of isotopically labelled 30Si tracer in an epitaxial 28Si matrix using SIMS depth profiling, and more recently with dopants such as arsenic in standard ion-implanted Si. Results for self-diffusion show that for n-type Si, self-diffusion rates are increased nonthermally by more than an order of magnitude for modest illumination intensities of roughly 1 W/cm2. Diffusion rates for silicon self-diffusion are shown to change by factors of up to 25 in response to optical fluxes on the order of 1 W/cm2. Results depend on doping type; the rates of both interstitial formation and migration are affected in the case of n-type material. There is no comparable effect for p-type material, however. Significant effects appear for boron as well in standard implantation experiments.

Kondratenko, Y.; Kwok, C. T. M.; Vaidyanathan, R.; Seebauer, E. G.

2008-11-01

2

Stimulated oxygen impurity gettering under ultra-shallow junction formation in silicon  

NASA Astrophysics Data System (ADS)

Ultra-shallow junctions were formed by low-energy As ion implantation followed by furnace annealing. It was found that a significant amount of oxygen is redistributed from the silicon bulk to the As-implanted region. Using a marker layer created by implantation of 18O isotope, it is confirmed that a large number of interstitial oxygen atoms are transferred from the bulk of Si wafer to the surface during dopant activation annealing, which leads to an increase of the surface oxide thickness. Estimation of the oxygen diffusivity in silicon during the 950 °C anneal, yields a value close to 1 × 10?10 cm2 s?1 which is more than an order of magnitude larger than the literature value which is close to 7 × 10?12 cm2 s?1.

Oberemok, O.; Kladko, V.; Litovchenko, V.; Romanyuk, B.; Popov, V.; Melnik, V.; Sarikov, A.; Gudymenko, O.; Vanhellemont, J.

2014-05-01

3

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

NASA Astrophysics Data System (ADS)

Plasma doping (PD) and long pulse all solid-state laser annealing (ASLA) was combined with the selective absorption modulation using SiO 2 layer to form ultra-shallow p +/n junction. By depositing a controlled thickness of SiO 2 layer on top of the silicon substrate, we were able to confirm the reduction of laser energy density by 400 mJ/cm 2 (29%) and the formation of ultra-shallow junction at 12.7 nm (@10 18 cm -3) with Rs of 670 ?/sq., which demonstrated the high feasibility of this new method.

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

2005-08-01

4

Ultra shallow junction formation using excimer laser annealing for ultra small devices  

Microsoft Academic Search

In this paper, novel device structures in order to realize ultra fast and ultra small silicon devices are investigated using ultra-high vacuum chemical vapor deposition (UHVCVD) and excimer laser annealing (ELA). Based on these fundamental technologies for the deep sub-micron device, high speed and low power devices can be fabricated. These junction formation technologies based on damage-free process for replacing

Eun Sik Jung; Ji Chel Bea; Yong Jae Lee

2001-01-01

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 Junctions by Advanced Plasma Doping Techniques  

NASA Astrophysics Data System (ADS)

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® 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.

2011-01-01

7

Continuity in the development of ultra shallow junctions for 130-45 nm CMOS: the tool and annealing methods  

Microsoft Academic Search

The roadmap for ultra-shallow junction formation (USJ) includes implant spike anneal and solid-phase epitaxial re-growth. The roadmap for the junction contacts foresees transition from CoSi2 to NiSi. The processes in the roadmap require extreme capabilities from RTP tools: heat-up and cool-down rates of hundreds of degrees per second, no pattern\\/emissivity dependence, precise temperature control, and operation at low temperature (starting

V. I. Kuznetsov; A. J. M. M. van Zutphen; H. R. Kerp; P. G. Vermont; X. Pages; J. J. van Hapert; K. van der Jeugd; E. H. A. Granneman

2003-01-01

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

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

10

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

11

Buried source and drain (BSD) structure for ultra-shallow junction using selective deposition of highly doped amorphous silicon  

Microsoft Academic Search

A buried source and drain (BSD) structure, that realizes ultra-shallow junctions, is proposed. Regions for source and drain are etched off. An in-situ highly doped amorphous silicon layer is selectively deposited on the etched region and is crystallized by solid phase epitaxy. Junction depth can be reduced to 10 nm without lowering the dopant concentration, because the doped layer can

Y. Mitani; I. Mizushima; S. Kambayashi; H. Koyama; M. T. Takagi; M. Kashiwagi

1996-01-01

12

Simultaneous determination of ultra-shallow junction depth and abruptness using thermal wave technique  

NASA Astrophysics Data System (ADS)

Thermal wave (TW) studies of ultra-shallow junctions (USJ) formed by ion implantation into a semiconductor wafer followed by rapid thermal annealing (RTP) are described. It is shown that using the TW technique allows for a simultaneous determination of the most important USJ parameters-depth and profile abruptness. In a TW-based system, the USJ depth is obtained using the quadrature component of the TW signal while determination of USJ profile abruptness is based on the analysis of the TW quadrature and in-phase components measured at two different pump-probe beam offsets. Experimental results for junction depth and abruptness obtained on a set of B+-implanted, RTP-annealed USJ samples show better than 0.99 correlations to the corresponding secondary ion mass spectroscopy data.

Salnick, Alex; Nicolaides, Lena; Opsal, Jon; Jain, Amitabh; Rogers, Duncan; Robertson, Lance

2004-06-01

13

Ultra-shallow Junction Metrology Using the Therma-Probe Tool  

NASA Astrophysics Data System (ADS)

Therma-Probe tool has long been established to monitor the implant dose. In this work, we demonstrate that the unmodified tool is also capable of meeting the stringent demands of junction depth monitoring for the current and future technology nodes. The ultra-shallow junction (USJ) application development was carried out on the Therma-Probe tool using the wafers provided by the International SEMATECH. The measured Therma-Wave signal varies as a sinusoidal function of the SIMS-based junction depth (at 1E18 ions/cm3) for wafers with various dose and energy conditions annealed around 1000°C. A theoretical model has been proposed to explain the source of the experimental signal response to the junction depth. A correlation table may be set up using the junction depth values provided by a reference method such as SIMS (Secondary Ion Mass Spectrometry) or SRP (Spreading Resistance Profiling) or the sheet resistance obtained using a 4-point probe system. The existing user interface software has been modified to allow reporting the results directly terms of the correlated junction depth. For production-worthy throughput conditions, the short-term precision is found to be <0.5Å, while the long-term stability is shown to be <2 Å for a variety of wafers tested. The USJ application package for the Therma-Probe tool offers a method to monitor wafers using an in-line, fast, and non-destructive metrology in production.

Bakshi, Mira; Nicolaides, Lena; Cherekdjian, Sarko; Tichy, Robin

2003-09-01

14

Characterization of Arsenic Ultra-Shallow Junctions in Silicon Using Photocarrier Radiometry and Spectroscopic Ellipsometry  

NASA Astrophysics Data System (ADS)

Photocarrier radiometry (PCR) and spectroscopic ellipsometry (SE) techniques were employed to measure ultra-shallow junction (USJ) wafers. These USJ wafers were prepared by As+ ion implantation at energies of 0.5 keV to 5 keV, at a dose of 1 × 1015 As+/cm2 and spike annealing. The experimental data showed that the PCR signal versus implantation energy exhibits a monotonic behavior. The damaged layer of the as-implanted wafer and the recrystallization and activation of the post-annealed wafer were evaluated by SE in the spectral range from 0.27 ?m to 20 ?m. PCR and SE were shown to provide non-destructive metrology tools for process monitoring in USJ fabrication.

Huang, Qiuping; Li, Bincheng; Gao, Weidong

2012-11-01

15

Ultra-Shallow Junctions Fabrication by Plasma Immersion Implantation on PULSION registered Followed by Laser Thermal Processing  

SciTech Connect

In order to achieve the requirements for P+/N junctions for <45 nm ITRS nodes, ultra low energy and high dose implantations are needed. Classical beamline implantation is now limited in low energies, compared to Plasma Immersion Ion Implantation (PIII) which efficiency 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) due to no lower limitation of energy and high dose rate. Electrical activation is also a big issue since it has to afford high electrical activation rate with very low diffusion. Laser annealing is one of the candidates for the 45 nm node. This paper presents electrical and physico-chemical characterizations of junctions realized with BF3 PIII followed by laser thermal processing with aim to obtain ultra-shallow junctions. Different implantation conditions (acceleration voltage/dose) and laser conditions (laser types, fluence/number of shots) are used for this study. Pre-amorphization is also used to confine the junction depth, and is shown to have a positive effect on junction depth but leads in higher junction leakage due to the remaining of EOR defects. The characterization is done using Optical characterization tool (SEMILAB) for sheet resistance and junction leakage measurements. SIMS is used for Boron profile and junction depth.

Torregrosa, Frank; Etienne, Hasnaa; Sempere, Guillaume; Mathieu, Gilles; Roux, Laurent [ION BEAM SERVICES, ZI Peynier-Rousset, rue Gaston Imbert Prolongee, 13790 Peynier (France); Vervisch, Vanessa; Delaporte, Philippe; Sarnet, Thierry [UMR CNRS LP3, Universite de la mediterranee, Campus de Luminy, Case 917, 13288 Marseille cedex 9-France (France); Pap, Aron; Kis-Szabo, Krisztian; Pavelka, Tibor [SEMILAB Semilab, Inc., 2 Prielle K. sir., H-1117 Budapest (Hungary); Grosjean, Catherine [CIMPACA Caracterisation Plateform, ZI Peynier Rousset, F13790 Rousset (France)

2008-11-03

16

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

17

Novel Laser Annealing Process for Advanced Complementary Metal Oxide Semiconductor Devices with Suppressed Polycrystalline Silicon Gate Depletion and Ultra shallow Junctions  

NASA Astrophysics Data System (ADS)

One of the major challenges in advanced complementary metal oxide semiconductor (CMOS) technology is to achieve an adequate dopant activation at the polycrystalline silicon (poly-Si) gate/gate oxide interface to minimize the poly-Si depletion effect. We investigated gate pre annealing by laser thermal process (LTP) in conjunction with laser spike annealing (LSA) source/drain (S/D) activation to effectively suppress poly-Si gate depletion while forming highly activated ultra shallow junctions for S/D. We found that carrier concentration at the poly-Si gate/gate oxide interface increases and, accordingly, electrical inversion oxide thickness (Tinv) decreases whereas dopant penetration into the Si substrate is suppressed to a level far below that in conventional rapid thermal annealing (RTA). We realized improved device performance characteristics such as a high drive current, a small threshold voltage (Vth) shift, and a reduced off current (Ioff).

Shima, Akio; Mine, Toshiyuki; Torii, Kazuyoshi

2007-04-01

18

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

NASA Astrophysics Data System (ADS)

Local resistance profiles of ultra-shallow arsenic implanted into silicon with an energy of 3.5 keV and a dose of 1.2×1015 ions/cm2 activated by conventional spike lamp and laser annealing were measured by SSRM in a nitrogen atmosphere with a depth resolution of less than 10 nm for investigating the combination of the conventional spike lamp and laser annealing. Spike lamp annealing at 1050 °C followed by laser annealing at a power density of 0.42 kW/mm2 was found to give the lowest sheet resistance. The resistance profiles obtained by SSRM also indicated the lowest resistance for the sample after spike lamp annealing at 1050 °C followed by laser annealing with a power density of 0.42 kW/mm2. Laser annealing alone with a power density of 0.42 kW/mm2 resulted in the higher sheet resistance, though the shallower resistance profile could be obtained. Spike lamp annealing followed by laser annealing procedures are effective in activating shallow arsenic profiles.

Abo, Satoshi; Tanaka, Yuji; Nishikawa, Kazuhisa; Wakaya, Fujio; Iwamatsu, Toshiaki; Oda, Hidekazu; Takai, Mikio

2008-11-01

19

Enabling Solutions for 28 nm CMOS Advanced Junction Formation  

NASA Astrophysics Data System (ADS)

Controlling short channel effects for further scaled CMOS is required to take full advantage of the introduction of high K/metal gate or stress induced carrier mobility enhancement. Ultra-Shallow junction formation is necessary to minimize the short channel effects. In this paper, we will discuss the challenges for 28 nm Ultra-Shallow Junction formations in terms of figure of merits of Rs/Xj and junction leakage. We will demonstrate that by adopting and integrating Carborane (CBH, C2B10H12) molecular implant and Phosphorus along with co-implantation and PTC II (VSEA Process Temperature Control) technology, sub-32 nm pLDD and nLDD junction targets can be timely achieved using traditional anneals. Those damage engineering solutions can be readily implemented on state-of-the-art 28 nm device manufacturing.

Li, C. I.; Kuo, P.; Lai, H. H.; Ma, K.; Liu, R.; Wu, H. H.; Chan, M.; Yang, C. L.; Wu, J. Y.; Guo, B. N.; Colombeau, B.; Thirumal, T.; Arevalo, E.; Toh, T.; Shim, K. H.; Sun, H. L.; Wu, T.; Lu, S.

2011-01-01

20

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

NASA Astrophysics Data System (ADS)

Local resistance profiles of ultra shallow boron and arsenic implanted into silicon with energies of 2.0 and 4.0 keV and doses of 2.0×1015 and 1.0×1015 ions/cm2 activated by a combination of conventional spike lamp and laser annealing processes were measured by scanning spreading resistance microscope (SSRM) with a depth resolution of less than 10 nm. The lowest local resistance at the low resistance region in 2.0 keV boron implanted silicon with 1050 °C spike lamp annealing followed by 0.35 kW/mm2 laser annealing was half of that without laser annealing. The lowest local resistance at the low resistance region in the arsenic implanted silicon activated by 1050 °C spike lamp annealing followed by 0.39 kW/mm2 laser annealing was 74% lower than that followed by 0.36 kW/mm2 laser annealing. The lowest local resistances at the low resistance regions in the arsenic implanted silicon with 0.36 and 0.39 kW/mm2 laser annealing followed by 1050 °C spike lamp annealing were 41 and 33% lower than those with spike lamp annealing followed by laser annealing. Laser annealing followed by spike lamp annealing could suppress the diffusion of the impurities and was suitable for making the ultra shallow and low resistance regions.

Abo, Satoshi; Nishikawa, Kazuhisa; Ushigome, Naoya; Wakaya, Fujio; Iwamatsu, Toshiaki; Oda, Hidekazu; Takai, Mikio

2011-01-01

21

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

SciTech Connect

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

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

2011-01-07

22

Active dopant profiling of ultra shallow junction annealed with combination of spike lamp and laser annealing processes using scanning spreading resistance microscopy  

NASA Astrophysics Data System (ADS)

Depth profiles of a spreading resistance of ultra-shallow arsenic implanted into silicon with an energy of 3.0 keV and a dose of 1.0 × 1015ions/cm2 activated by a combination of conventional spike lamp and laser annealing processes were measured by scanning spreading resistance microscopy (SSRM) with a depth resolution of less than 5 nm. The lowest resistances at the arsenic activated region annealed by laser followed by spike lamp annealing (a laser first process) were lower than those by spike lamp annealing followed by laser annealing (a spike first process) with the same laser power densities. The lowest resistances at the arsenic activated region annealed by the laser and spike first processes with a laser power density of 0.39 kW/mm2 were lower than those with a laser power density of 0.36kW/mm2. The laser first process was suitable for the lower resistance regions than the spike first process.

Abo, Satoshi; Ushigome, Naoya; Osae, Hidenori; Wakaya, Fujio; Iwamatsu, Toshiaki; Oda, Hidekazu; Takai, Mikio

2012-11-01

23

The effect of plasma exposure and annealing atmosphere on shallow junction formation using plasma source ion implantation  

Microsoft Academic Search

The effect of recoil-implantation and out-diffusion in plasma source ion implantation (PSII) on ultra-shallow p+\\/n junction formation has been studied. Because the wafer is directly exposed to plasma, diborane radicals in the plasma can be adsorbed on the wafer surface. The amount of recoil-implanted boron as an additive dose was measured. In the annealing process, increasing the nitrogen pressure from

Jeonghee Cho; Seunghee Han; Yeonhee Lee; Ok Kyung Kim; Gon-Ho Kim; Young-Woo Kim; Hyuneui Lim

2002-01-01

24

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

25

Reducing ultra-shallow boron diffusion using carbon and fluorine co-implantation  

NASA Astrophysics Data System (ADS)

A method to reduce the diffusion of boron in ultra-shallow junctions (USJ) has been found using the co-implantation of fluorine and carbon. In this 2 4 designed experiment a 40% reduction of B diffusion in the presence of a shallow F and C implant was found over the use of F alone. In addition another 10% reduction of B diffusion can be obtained if a medium dose arsenic implant is preformed before F and B implantation. It has been found that implanting in this order significantly alters the defect structure of the USJ and suggests that F trapped in the lattice after anneal may be tied up in vacancy fluorine clusters which increase B activation.

Vanderpool, Aaron; Taylor, Mitch

2005-08-01

26

Analysis of Tight Junction Formation and Integrity  

SciTech Connect

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

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

2012-01-01

27

Planar SONOS gate power MOSFET with an ultra-shallow body region  

Microsoft Academic Search

In this paper, a planar silicon-oxide-nitride-oxide-silicon (SONOS) gate power MOSFET (SG-MOSFET) with a 0.3 µm ultra-shallow heavily doped p-body region is presented. The ultra-shallow body provides a much reduced parasitic JFET resistance, resulting in a low specific on-resistance of 18 m?·mm2 for a planar device. At the same time, no punch-through problem is caused by the ultra-shallow body, and the

Xianda Zhou; Hao Feng; Johnny K. O. Sin

2012-01-01

28

Method for shallow junction formation  

DOEpatents

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

Weiner, K.H.

1996-10-29

29

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

30

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

31

Study of shallow junction formation by boron-containing cluster ion implantation of silicon and two-stage annealing  

NASA Astrophysics Data System (ADS)

Shallow junction formation made by low energy ion implantation and rapid thermal annealing is facing a major challenge for ULSI (ultra large scale integration) as the line width decreases down to the sub micrometer region. The issues include low beam current, the channeling effect in low energy ion implantation and TED (transient enhanced diffusion) during annealing after ion implantation. In this work, boron containing small cluster ions, such as GeB, SiB and SiB2, was generated by using the SNICS (source of negative ion by cesium sputtering) ion source to implant into Si substrates to form shallow junctions. The use of boron containing cluster ions effectively reduces the boron energy while keeping the energy of the cluster ion beam at a high level. At the same time, it reduces the channeling effect due to amorphization by co-implanted heavy atoms like Ge and Si. Cluster ions have been used to produce 0.65--2keV boron for low energy ion implantation. Two stage annealing, which is a combination of low temperature (550°C) preannealing and high temperature annealing (1000°C), was carried out to anneal the Si sample implanted by GeB, SiBn clusters. The key concept of two-step annealing, that is, the separation of crystal regrowth, point defects removal with dopant activation from dopant diffusion, is discussed in detail. The advantages of the two stage annealing include better lattice structure, better dopant activation and retarded boron diffusion. The junction depth of the two stage annealed GeB sample was only half that of the one-step annealed sample, indicating that TED was suppressed by two stage annealing. Junction depths as small as 30 nm have been achieved by two stage annealing of sample implanted with 5 x 10-4/cm2 of 5 keV GeB at 1000°C for 1 second. The samples were evaluated by SIMS (secondary ion mass spectrometry) profiling, TEM (transmission electron microscopy) and RBS (Rutherford Backscattering Spectrometry)/channeling. Cluster ion implantation in combination with two-step annealing is effective in fabricating ultra-shallow junctions.

Lu, Xin-Ming

32

Nitric oxide enhances de novo formation of endothelial gap junctions  

Microsoft Academic Search

Objective: Gap junctions (formed by connexins, Cx) are important for functional coordination of cells in the vascular wall. However, little is known about their physiological regulation in this tissue. We examined the effects of nitric oxide (NO), an important mediator of vasomotion, wound healing and angiogenesis, on the formation of gap junctions in endothelial cells (human umbilical vein endothelial cells,

Anke Hoffmann; Torsten Gloe; Ulrich Pohl; Stefan Zahler

2003-01-01

33

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

34

Photocarrier Radiometry Characterization of Ultra-shallow Junctions (USJ) in Silicon with Excimer Laser Irradiation  

NASA Astrophysics Data System (ADS)

The activation and recrystallization in arsenic ion-implanted silicon under excimer laser (193 nm) irradiation is investigated using photocarrier radiometry (PCR). Arsenic ion-implanted silicon wafers with a dose of 1 × 10^{15} cm^{-2} and an energy of 1 keV were irradiated at different laser parameters, such as the laser fluence, shot number, and repetition rate. The excimer laser irradiation-induced enhancement of PCR signals of implanted silicon samples showed that the implantation-induced crystalline structural damage was reduced and the implanted ions were effectively activated.

Wang, Qian; Li, Bincheng; Ren, Shengdong; Wang, Qiang

2014-04-01

35

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

36

Opening Hemichannels in Nonjunctional Membrane Stimulates Gap Junction Formation  

PubMed Central

We studied gap junction formation in pairs of Xenopus laevis oocytes expressing connexins that form functional hemichannels and found no correlation between junctional conductance (Gj) and whole-cell hemichannel conductances (Ghemi) within the first few hours of pairing. However, opening hemichannels to a threshold current stimulated a rapid Gj increase. Moreover, cx46 hemichannel current stimulated cx40 Gj even though cx40 and cx46 do not form heteromeric or heterotypic gap junctions. Initial growth rate and final steady-state level of stimulated Gj were proportional to the product of hemichannel conductances. External calcium affected the growth rate of stimulated Gj but not the final steady-state value. Time constants of formation were short in low [Ca2+]out (3 min in 200 ?M Ca2+) and long in high [Ca2+]out (15 min in 1 mM Ca2+), but in oocyte pairs pretreated with lectins to reduce steric hindrance imposed by large membrane glycoproteins the time constant was short and Ca2+-independent. We suggest that hemichannel activity stimulates Gj by collapsing the extracellular volume between membranes to allow the end-to-end binding between hemichannels. These studies suggest the possibility that functional hemichannels could trigger or enhance junctional formation in vivo in response to appropriate stimuli.

Beahm, Derek L.; Hall, James E.

2004-01-01

37

3-D Autojuggie: Automating Deployment of Two-Dimensional Geophone Arrays for Efficient Ultra-Shallow Seismic-Reflection Surveys  

NASA Astrophysics Data System (ADS)

Near-surface seismic reflection methods require dense spatial sampling of the wavefield. Seismic surveys imaging the top ten meters of the subsurface employ geophone spacing on the order of decimeters. Two-dimensional (2-D), ultra-shallow seismic reflection methods have increased in popularity. However, placement of geophones remains a labor-intensive deterrent to the acquisition of near-surface, 3-D seismic data. Although 3-D seismic imaging is a mature hydrocarbon-exploration technique, only a handful of 3-D shallow seismic surveys have been acquired over the last decade. We present the development and field-testing of instrumentation for automatic deployment of a 2-D array of 72 geophones for acquisition of ultra-shallow 3-D reflection seismic data, referred to as the 3-D Autojuggie. The main components of the instrumentation include: a) two vertically stacked rigid steel frames used for positioning, planting, and transporting an array of geophones; b) an hydraulically controlled mechanism for decoupling the geophones from the steel frames during seismic data recording; and c) a 2-D array of seventy-two 100 Hz Mark Products geophones with 20.32 cm long spikes, spaced 20 cm apart in the inline (12 geophones) and crossline (6 rows) orientation. Seismic noise testing (walkaways) conducted at The University of Kansas employing automatically planted 2-D geophone arrays next to conventional hand-planted geophones resulted in equivalent seismic imaging of the subsurface. The geophone planting instrumentation did not degrade the quality of the recorded wavefield. The efficiency of automatically placing a dense 2-D array of geophones on the ground and the ease of moving the array quickly to adjacent positions, along with the ability to acquire comparable quality data to conventional hand-planted geophones, indicate that the 3-D Autojuggie is a viable approach to ultra-shallow 3-D seismic acquisition. Conceptually, the design could accommodate an array of hundreds of geophones at once.

Tsoflias, G. P.; Steeples, D. W.; Czarnecki, G.; Sloan, S. D.; Eslick, R.

2005-12-01

38

Characterization of dopant profiles produced by ultra-shallow As implantation and spike annealing using medium energy ion scattering  

NASA Astrophysics Data System (ADS)

Medium energy ion scattering (MEIS) combining a toroidal electrostatic analyzer with an energy resolution (d E/ E) of 4 × 10 -3 has been used for ultra-shallow depth profiling of As implanted into Si at 1, 2 and 5 keV to a dose of 1.2 × 10 15 ions/cm 2 before and after spike annealing at 1075 °C. Depth profiling results extracted from MEIS spectra were compared with those of simulation and SIMS measurement. The arsenic re-distribution close to the surface after spike annealing was found by MEIS and SIMS measurements.

Ichihara, S.; Nakagawa, T.; Nitta, M.; Abo, S.; Lohner, T.; Angelov, C.; Ohta, K.; Takai, M.

2004-06-01

39

Plasminogen activator inhibitor-1 regulates myoendothelial junction formation  

PubMed Central

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

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

2010-01-01

40

?-Catenin gain of function in muscles impairs neuromuscular junction formation.  

PubMed

Neuromuscular junction (NMJ) formation requires proper interaction between motoneurons and muscle cells. ?-Catenin is required in muscle cells for NMJ formation. To understand underlying mechanisms, we investigated the effect of ?-catenin gain of function (GOF) on NMJ development. In HSA-?-cat(flox(ex3)/+) mice, which express stable ?-catenin specifically in muscles, motor nerve terminals became extensively defasciculated and arborized. Ectopic muscles were observed in the diaphragm and were innervated by ectopic phrenic nerve branches. Moreover, extensive outgrowth and branching of spinal axons were evident in the GOF mice. These results indicate that increased ?-catenin in muscles alters presynaptic differentiation. Postsynaptically, AChR clusters in HSA-?-cat(flox(ex3)/+) diaphragms were distributed in a wider region, suggesting that muscle ?-catenin GOF disrupted the signal that restricts AChR clustering to the middle region of muscle fibers. Expression of stable ?-catenin in motoneurons, however, had no effect on NMJ formation. These observations provide additional genetic evidence that pre- and postsynaptic development of the NMJ requires an intricate balance of ?-catenin activity in muscles. PMID:22627288

Wu, Haitao; Lu, Yisheng; Barik, Arnab; Joseph, Anish; Taketo, Makoto Mark; Xiong, Wen-Cheng; Mei, Lin

2012-07-01

41

?-Catenin gain of function in muscles impairs neuromuscular junction formation  

PubMed Central

Neuromuscular junction (NMJ) formation requires proper interaction between motoneurons and muscle cells. ?-Catenin is required in muscle cells for NMJ formation. To understand underlying mechanisms, we investigated the effect of ?-catenin gain of function (GOF) on NMJ development. In HSA-?-catflox(ex3)/+ mice, which express stable ?-catenin specifically in muscles, motor nerve terminals became extensively defasciculated and arborized. Ectopic muscles were observed in the diaphragm and were innervated by ectopic phrenic nerve branches. Moreover, extensive outgrowth and branching of spinal axons were evident in the GOF mice. These results indicate that increased ?-catenin in muscles alters presynaptic differentiation. Postsynaptically, AChR clusters in HSA-?-catflox(ex3)/+ diaphragms were distributed in a wider region, suggesting that muscle ?-catenin GOF disrupted the signal that restricts AChR clustering to the middle region of muscle fibers. Expression of stable ?-catenin in motoneurons, however, had no effect on NMJ formation. These observations provide additional genetic evidence that pre- and postsynaptic development of the NMJ requires an intricate balance of ?-catenin activity in muscles.

Wu, Haitao; Lu, Yisheng; Barik, Arnab; Joseph, Anish; Taketo, Makoto Mark; Xiong, Wen-Cheng; Mei, Lin

2012-01-01

42

Adherens junction formation inhibits lentivirus entry and gene transfer.  

PubMed

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

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

2013-01-01

43

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

44

Polyamine sensitivity of gap junctions is required for skin pattern formation in zebrafish  

PubMed Central

Gap junctions allow the direct and bidirectional transfer of small molecules between cells. Polyamine sensitivity, which has been observed for a certain gap junction in vitro, confers rectification property to gap junction. Here we report that the polyamine sensitivity of gap junctions in vivo is crucial for skin pattern formation in zebrafish. Transgenic experiments have revealed that several connexin genes were able to rescue the spot phenotype of mutant zebrafish. Mutational analyses of the N-terminal region of connexins revealed that the ExxxE motif, a hypothetical polyamine-binding site, was important for connexin's role in pattern formation. Ectopic expression of spermidine/spermine N1-acetyltransferase (SSAT), a polyamine metabolic enzyme, also caused stripe pattern changes, which further indicates that the polyamine sensitivity of gap junctions is crucial. This is the first report to show that polyamine sensitivity has a physiologically relevant function and is related to skin pattern formation in animals.

Watanabe, Masakatsu; Watanabe, Daisuke; Kondo, Shigeru

2012-01-01

45

junctions  

Microsoft Academic Search

The nonlinear capacitance in doped nanotube junctions is calculated self consistently. A negative differential capacitance is observed when the applied bias becomes larger than the pseudogap of the metallic armchair nanotube. For this device, one can deduce a relaxation time of about 0.1 femtosecond. Because of its negative differential resistance (NDR), a switching time of less than a fs, i.e.

Keivan Esfarjani; Amir A. Farajian; Yoshiyuki Kawazoe; Siu Tat Chui

46

Dopant profiling of ultra shallow As implanted in Si with and without spike annealing using medium energy ion scattering  

NASA Astrophysics Data System (ADS)

Ultra shallow dopant profiles of arsenic implanted into Si with an energy range from 0.5 to 3 keV to a dose of 8 × 10 14 ions/cm 2 with and without spike annealing were measured by medium energy ion scattering (MEIS) with a toroidal electrostatic analyzer (TEA). A shift of the peak of arsenic profile to the surface after spike annealing was observed by MEIS measurement. Most of the implanted arsenic atoms were trapped in the native oxide layer after spike annealing. A recovery of silicon crystal defects induced by arsenic implantation was observed after spike annealing by glancing angle Rutherford back scattering (RBS) measurement with a solid-state detector. The thickness of disordered Si layers down to 1.5 nm was evaluated from glancing angle RBS measurements for implanted sample before and after spike annealing.

Abo, S.; Ichihara, S.; Lohner, T.; Wakaya, F.; Eimori, T.; Inoue, Y.; Takai, M.

2005-08-01

47

Saltatory formation, sliding and dissolution of ER-PM junctions in migrating cancer cells  

PubMed Central

We demonstrated three novel forms of dynamic behaviour of junctions between the ER (endoplasmic reticulum) and the PM (plasma membrane) in migrating cancer cells: saltatory formation, long-distance sliding and dissolution. The individual ER–PM junctions formed near the leading edge of migrating cells (usually within 0.5 ?m of polymerized actin and close to focal adhesions) and appeared suddenly without sliding from the interior of the cell. The long distance sliding and dissolution of ER–PM junctions accompanied the tail withdrawal.

Dingsdale, Hayley; Okeke, Emmanuel; Awais, Muhammad; Haynes, Lee; Criddle, David N.; Sutton, Robert; Tepikin, Alexei V.

2013-01-01

48

Saltatory formation, sliding and dissolution of ER-PM junctions in migrating cancer cells.  

PubMed

We demonstrated three novel forms of dynamic behaviour of junctions between the ER (endoplasmic reticulum) and the PM (plasma membrane) in migrating cancer cells: saltatory formation, long-distance sliding and dissolution. The individual ER-PM junctions formed near the leading edge of migrating cells (usually within 0.5 ?m of polymerized actin and close to focal adhesions) and appeared suddenly without sliding from the interior of the cell. The long distance sliding and dissolution of ER-PM junctions accompanied the tail withdrawal. PMID:23323887

Dingsdale, Hayley; Okeke, Emmanuel; Awais, Muhammad; Haynes, Lee; Criddle, David N; Sutton, Robert; Tepikin, Alexei V

2013-04-01

49

Formation of Silicon Carbide Y Junctions by the Coalescence of Catalysts  

Microsoft Academic Search

We previously reported the formation of crystalline SiC nanocones by the released iron catalytic procedure, where the initially carbon- encapsulated iron nanoparticles escape from their carbon shells and agglomerate while catalyzing 1D SiC growth. Here we show that the coalescence of the iron nanoparticles can lead to Y junctions. Y junctions where the SiC branches are either parallel or inclined

Zhenyu Liu; Judith C. Yang; V. Srot; Peter A. van Aken; M. Rühle

2009-01-01

50

Infrared Semiconductor Laser Annealing Used for Formation of Shallow Junction  

Microsoft Academic Search

We report continuous-wave (CW) infrared-semiconductor laser annealing of silicon implanted with boron atoms with assistance of diamond-like carbon (DLC) films as optical absorption layer in order to form shallow junctions. Boron ions were implanted at 10 keV at concentrations 5x1014, 1x1015 and 2x1015 cm-2. Boron clusters were also implanted at 30 and 6 keV at 1x1015cm-2. The samples were coated

Toshiyuki Sameshima; Yuta Mizutani; Naoki Sano; Masao Naito

51

Application of laser annealing to solar cell junction formation  

NASA Technical Reports Server (NTRS)

The possibility of using high-energy Q-switched Nd:glass lasers to form pn junctions in solar cells by annealing ion-implanted substrates is investigated. The properties of laser annealed cells are analyzed by electrical, transmission electron microscopy, Rutherford backscattering and secondary ion mass spectrometry techniques. Tests indicate the laser annealed substrates to be damage-free and electrically active. Similar reference analysis of ion-implanted furnace-annealed substrates reveals the presence of residual defects in the form of dislocation lines and loops with substantial impurity redistribution evident for some anneal temperature/time regimes. Fabricated laser annealed cells exhibit excellent conversion efficiency. It is noted that additional improvements are anticipated once the anneal parameters for a back surface field are optimized.

Katzeff, J. S.; Lopez, M.; Josephs, R. H.

1981-01-01

52

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

53

Solution Formation of Holliday Junctions in Inverted-Repeat DNA Sequences†  

PubMed Central

The structure of Holliday junctions has now been well characterized at the atomic level through single-crystal X-ray diffraction in symmetric (inverted-repeat) DNA sequences. At issue, however, is whether the formation of these four-stranded complexes in solution is truly sequence dependent in the manner proposed or is an artifact of the crystallization process and, therefore, has no relevance to the behavior of this central intermediate in homologous recombination and recombination-dependent cellular processes. Here, we apply analytical ultracentrifugation to demonstrate that the sequence d(CCGGTAC-CGG), which crystallizes in the stacked-X form of the junction, assembles into four-stranded junctions in solution in a manner that is dependent on the DNA and cation concentrations, with an equilibrium established between the junction and duplex forms at 100–200 ?M DNA duplex. In contrast, the sequence d(CCGCTAGCGG), which has been crystallized as B-DNA, is seen to adopt only the double-helical form at all DNA and salt concentrations that were tested. Thus, the ACC trinucleotide core is now shown to be important for the formation of Holliday junctions in both crystals and in solution and can be estimated to contribute approximately ?4 kcal/mol to stabilizing this recombination intermediate in inverted-repeat sequences.

Hays, Franklin A.; Schirf, Virgil; Ho, P. Shing; Demeler, Borries

2007-01-01

54

Shp2 Is Dispensable in the Formation and Maintenance of the Neuromuscular Junction  

Microsoft Academic Search

SHP2, a protein tyrosine phosphatase with two SH2 domains, has been implicated in regulating acetylcholine receptor (AChR) gene expression and cluster formation in cultured muscle cells. To understand the role of SHP2 in neuromuscular junction (NMJ) formation in vivo, we generated mus cle-specific deficient mice by using a loxP\\/Cre strategy since Shp2 null mutation causes embryonic lethality. Shp2floxed\\/floxed mice were

Xian-Ping Dong; Xiao-Ming Li; Tian-Ming Gao; Eric E. Zhang; Gen-Sheng Feng; Wen C. Xiong; Lin Mei

2006-01-01

55

Effect of Pulse Duration on Formation of Ultrashallow Junction by Excimer Laser Annealing  

NASA Astrophysics Data System (ADS)

An ultrashallow junction (USJ) was formed by KrF excimer laser annealing. The effect of laser pulse duration on USJ formation was discussed through the evaluations of junction depth, sheet resistance and crystal defects. The possibility of reducing crystal defects by long-pulse laser annealing was discussed. A simple one-dimensional thermal diffusion model was used to analyze the results considering the solidification velocity after melting. The calculated results for the relationship between melt depth and laser energy density qualitatively agreed well with the experimental results. The results also showed that longer pulse duration made solidification velocity lower. Lower solidification velocity is the key to reducing the residual defects.

Matsuno, Akira; Shibahara, Kentaro

2006-11-01

56

Study on chemical binding states of silicon in conjunction with ultra-shallow plasma doping by using Hard X-ray Photoelectron spectroscopy (HX-PES)  

NASA Astrophysics Data System (ADS)

We took HX-PES measurement (Si 1s) on ultra shallow plasma doped silicon samples before and after spike RTA, flash lamp anneal (FLA) and all solid-state laser anneal (ASLA) in SPring-8 for the first time. After PD, the carrier density of n-Si substrate decreased to intrinsic Si level due to defect induced carrier traps. After annealing by either spike RTA or FLA, the PD samples showed excellent chemical binding states with high impurity activation and recrystallization. After annealing by ASLA, PD samples showed ultimate high impurity activation at surface several nanometer layer.

Jin, C. G.; Sasaki, Y.; Okashita, K.; Tamura, H.; Ito, H.; Mizuno, B.; Okumura, T.; Kobata, M.; Kim, J. J.; Ikenaga, E.; Kobayashi, K.

2006-11-01

57

Characterization of nano-depth junctions in silicon by using Photo-Carrier Radiometry (PCR)  

NASA Astrophysics Data System (ADS)

Non-contact, non-intrusive Photo-Carrier Radiometry (PCR) was used for monitoring nano-depth junctions in industrial-grade silicon wafers. The silicon wafers were implanted with arsenic to the dose of 5E1014 cm-2. The junction depth was in the 30 nm to 100 nm range. Quantitative results for PCR sensitivity to the junction depth and implantation energies are presented. This laser-based carrier-wave technique monitors harmonically photo-excited and recombining carriers and shows great potential advantages for the characterization of multiple semiconductor processes such as ion implantation, ultra shallow junction (USJ) depth determination and other Si wafer process steps.

Garcia, J. A.; Guo, X.; Mandelis, A.; Shaughnessy, D.; Nicolaides, L.; Salnik, A.

2008-01-01

58

Decreased gap junctional intercellular communication in hexachlorobenzene-induced gender-specific hepatic tumor formation in the rat  

Microsoft Academic Search

Hexachlorobenzene (HCB), an epigenetic carcinogen, HCB induces the formation of liver tumors in female rats, whereas only a small percentage of males are responsive. Intercellular communication via gap junctions is decreased in carcinogenesis. Gap junctions are composed of proteins termed connexins (Cxs). The objectives of this study were (i) to determine if HCB-induced tumor development is associated with a loss

Isabelle Plante; Michel Charbonneau; Daniel G. Cyr

59

Mechanism of formation of the A/B cis ring junction of ecdysteroids in Polypodium vulgare.  

PubMed Central

1. The fates of the alpha-, 4 alpha- and 4 beta-hydrogen atoms of cholesterol during formation of the A/B cis ring junction of ecdysteroids was investigated by administration of [4-14C, 3 alpha-3H], [4-14C, 4 alpha-3H]- and [4-14C, 4 beta-3H]cholesterol species to the fern, Polypodium vulgare, and isolation of the 20-hydroxyecdysone formed in each case. 2. The 3H was retained in the ecdysteroid formed from each substrate. 3. Location of the 3H in the 20-hydroxyecdysone indicated that migration of 3H from the 3 alpha- and 4 beta-positions to C-4 and C-5, respectively, had occurred, whereas the 4 alpha-3H atom was retained at C-4. 4. A possible mechanism for the formation of the A/B cis ring junction of ecdysteroids in P. vulgare is presented.

Davies, T G; Lockley, W J; Boid, R; Rees, H H; Goodwin, T W

1980-01-01

60

Analysis of USJ formation with combined RTA/laser annealing conditions for 28 nm high-k/metal gate CMOS technology using advanced TCAD for process and device simulation  

NASA Astrophysics Data System (ADS)

TCAD process and device simulations are used to gain physical understanding for the integration of laser-annealed junctions into a 28 nm high-k/metal gate first process flow. Spike-RTA (Rapid Thermal Annealing) scaling used for transient enhanced diffusion (TED) suppression and shallow extension formation is investigated. In order to overcome the performance loss due to a reduced RTA, laser anneal (lsa) is introduced after Spike-RTA to form highly activated and ultra shallow junctions (USJs). In this work, the impact of different annealing conditions on the performance of NMOS and PMOS devices is investigated in terms of Vth and Ion/Ioff, considering lateral dopant diffusion and activation.

Bazizi, E. M.; Zaka, A.; Benistant, F.

2013-05-01

61

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

62

Formation of junctions involved in excitation-contraction coupling in skeletal and cardiac muscle.  

PubMed Central

During excitation-contraction (e-c) coupling of striated muscle, depolarization of the surface membrane is converted into Ca2+ release from internal stores. This process occurs at intracellular junctions characterized by a specialized composition and structural organization of membrane proteins. The coordinated arrangement of the two key junctional components--the dihydropyridine receptor (DHPR) in the surface membrane and the ryanodine receptor (RyR) in the sarcoplasmic reticulum--is essential for their normal, tissue-specific function in e-c coupling. The mechanisms involved in the formation of the junctions and a potential participation of DHPRs and RyRs in this process have been subject of intensive studies over the past 5 years. In this review we discuss recent advances in understanding the organization of these molecules in skeletal and cardiac muscle, as well as their concurrent and independent assembly during development of normal and mutant muscle. From this information we derive a model for the assembly of the junctions and the establishment of the precise structural relationship between DHPRs and RyRs that underlies their interaction in e-c coupling. Images Fig. 1 Fig. 2 Fig. 3

Flucher, B E; Franzini-Armstrong, C

1996-01-01

63

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

64

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

SciTech Connect

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

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

2011-06-01

65

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

66

Formation of Schottky-type metal\\/SrTiO 3 junctions and their resistive properties  

Microsoft Academic Search

Motivated by the successful use of strontium titanate with different doping metals for memory cells on the basis of resistive\\u000a switching and the recent findings on the major importance of oxygen vacancy redistribution in this compound, the present work\\u000a shows the possibility of a non-volatile resistance change memory based on vacancy-doped SrTiO3. The formation of corresponding metal\\/SrTiO3??\\u000a junctions (?>0) in

Hartmut Stöcker; Matthias Zschornak; Juliane Seibt; Florian Hanzig; Susi Wintz; Barbara Abendroth; Jens Kortus; Dirk C. Meyer

2010-01-01

67

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

PubMed Central

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

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

2014-01-01

68

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

PubMed

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

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

2014-06-01

69

Afadin Regulates Puncta Adherentia Junction Formation and Presynaptic Differentiation in Hippocampal Neurons  

PubMed Central

The formation and remodeling of mossy fiber-CA3 pyramidal cell synapses in the stratum lucidum of the hippocampus are implicated in the cellular basis of learning and memory. Afadin and its binding cell adhesion molecules, nectin-1 and nectin-3, together with N-cadherin, are concentrated at puncta adherentia junctions (PAJs) in these synapses. Here, we investigated the roles of afadin in PAJ formation and presynaptic differentiation in mossy fiber-CA3 pyramidal cell synapses. At these synapses in the mice in which the afadin gene was conditionally inactivated before synaptogenesis by using nestin-Cre mice, the immunofluorescence signals for the PAJ components, nectin-1, nectin-3 and N-cadherin, disappeared almost completely, while those for the presynaptic components, VGLUT1 and bassoon, were markedly decreased. In addition, these signals were significantly decreased in cultured afadin-deficient hippocampal neurons. Furthermore, the interevent interval of miniature excitatory postsynaptic currents was prolonged in the cultured afadin-deficient hippocampal neurons compared with control neurons, indicating that presynaptic functions were suppressed or a number of synapse was reduced in the afadin-deficient neurons. Analyses of presynaptic vesicle recycling and paired recordings revealed that the cultured afadin-deficient neurons showed impaired presynaptic functions. These results indicate that afadin regulates both PAJ formation and presynaptic differentiation in most mossy fiber-CA3 pyramidal cell synapses, while in a considerable population of these neurons, afadin regulates only PAJ formation but not presynaptic differentiation.

Toyoshima, Daisaku; Mandai, Kenji; Maruo, Tomohiko; Supriyanto, Irwan; Togashi, Hideru; Inoue, Takahito; Mori, Masahiro; Takai, Yoshimi

2014-01-01

70

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

NASA Technical Reports Server (NTRS)

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

Katzeff, J. S.

1981-01-01

71

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

72

Na,K-ATPase Activity Is Required for Formation of Tight Junctions, Desmosomes, and Induction of Polarity in Epithelial Cells  

Microsoft Academic Search

Na,K-ATPase is a key enzyme that regulates a variety of transport functions in epithelial cells. In this study, we demonstrate a role for Na,K-ATPase in the formation of tight junctions, desmo- somes, and epithelial polarity with the use of the calcium switch model in Madin-Darby canine kidney cells. Inhibition of Na,K-ATPase either by ouabain or potassium depletion prevented the formation

Sigrid A. Rajasekaran; Lawrence G. Palmer; Sun Y. Moon; Alejandro Peralta Soler; Gerard L. Apodaca; Jeffrey F. Harper; Yi Zheng; Ayyappan K. Rajasekaran

2001-01-01

73

Gas-liquid slug formation at a rectangular microchannel T-junction: A CFD benchmark case  

NASA Astrophysics Data System (ADS)

Computational fluid dynamics (CFD) is an important tool for development of microfluidic systems based on gasliquid two-phase flow. The formation of Taylor slugs at microchannel T-junctions has been studied both experimentally and numerically, however discrepancies still exist because of difficulties in correctly representing experimental conditions and uncertainties in the physics controlling slug flow, such as contact line and velocity slip. In this paper detailed methods and results are described for the study of Santos and Kawaji [1] on the comparison of experimental results and numerical modeling. The system studied consisted of a rectangular microchannel Tjunction nominally 100 ?m in hydraulic diameter, used to generate Taylor slugs from air-water perpendicular flow. The effect of flow rates on parameters such as slug length, velocity slip, void fraction and two-phase frictional pressure drop were studied. Numerical simulation was performed using FLUENT volume-of-fluid (VOF) model. It is proposed in this paper that this microfluidic problem be taken up by researchers in the field as a benchmark case to test other numeric codes in comparison to FLUENT on the prediction of micro-scale multiphase flow, and also to model in more detail the experimental system described to obtain greater accuracy in prediction of microfluidic slug formation.

Santos, Rafael M.; Kawaji, Masahiro

2011-12-01

74

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

75

Identification, simulation and avoidance of artifacts in ultra-shallow depth profiling by secondary ion mass spectrometry  

SciTech Connect

Distortions and shifts of shallow implantation distributions of B in Si, recently observed in depth profiling by secondary ion mass spectrometry (SIMS) using 1.9 keV O{sub 2}{sup +} ions at oblique incidence ({approx}60 deg.) with oxygen flooding, have been reproduced at a beam energy of 1 keV. Measurements on samples containing a series of delta doping spikes revealed a pronounced initial drop in erosion rate followed by a more gradual decrease extending to at least 200 nm. These changes give rise to severe errors in depth calibration (shift up to 4 nm). The artifacts are due to bombardment-induced oxygen incorporation and surface roughening (ripple formation), the latter effect also causing a pronounced degradation in depth resolution. The essential features of the observed profile distortions can be simulated by a simple model. Ripple formation is not observed with normally incident oxygen beams in vacuum, in which case profiles with excellent resolution and minimum shift can be obtained, notably at ultra-low probe energy.

Wittmaack, K. [GSF-National Research Center for Environment and Health, Institute of Radiation Protection, D-85758 Neuherberg (Germany); Patel, S. B. [ATOMIKA Instruments GmbH, Bruckmannring 4O, D-85764 Oberschleissheim (Germany); Corcoran, S. F. [Intel Components TD Q and R, MS RA1-329, Hillsboro, Oregon 97212 (United States)

1998-11-24

76

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

77

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

78

Molecular and functional analysis of apical junction formation in the gut epithelium of Caenorhabditis elegans  

Microsoft Academic Search

The Caenorhabditis elegans intestine is a simple and accessible model system to analyze the mechanism of junction assembly. In comparison to Drosophila and vertebrates, the C. elegans apical junction is remarkable because a single electron-dense structure is implicated in complex processes such as epithelial tightness, vectorial transport and cell adhesion. Here we present evidence in support of a heterogeneous molecular

Christoph Segbert; Kevin Johnson; Carin Theres; Daniela van Fürden; Olaf Bossinger

2004-01-01

79

Formation of Satellite and subsatellite droplets in a flow-focusing junction for viscoelastic fluids  

NASA Astrophysics Data System (ADS)

The formation of a cascade of satellite and subsatellite oil droplets is observed in a flow-focusing microfluidic junction (250 micrometer of characteristic length) in the presence of surfactant (Sodium Dodecyl Sulfate), and polymer (100 to 1000 ppm of PAAm of high molecular mass). The size and distribution of the satellite and subsatellite droplets is quite reproducible. One and only one satellite droplet is formed in the dripping regime in case of Newtonian fluids [1]. When PAAm is added to the solution, the viscosity becomes viscoelastic and satellite droplets are many. The mechanism of breakup leading to multiple satellite droplets is self-repeating, as observed in previous work [2, 3]. At low frequency, the number of satellite droplet can go up to 7 or more. The distribution is generally very structured: a unique mother satellite droplet is surrounded by two daughter droplets, each of these daughter droplet is surrounded again by two grand-daughter droplets so that there are 4 daughter droplets in total. The ratio in volume between each generation is about 30. [1] Funfschilling D., Debas H., Li H.-Z.and Mason T. G., 2009, Phys. Rev. E, 80, 015301 [2] Muzzio F. J., Tjahjadi M. and Ottino J. M. 1991, Phys. Rev. Lett. 67, 54-57 [3] Tjahjadi M., Stone H. A. and Ottino J. M. 1992, J. Fluid Mech. 243, 297-317

Funfschilling, Denis; Carrier, Odile; Li, Huai-Zhi

2011-11-01

80

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

81

The transmembrane protein Macroglobulin complement-related is essential for septate junction formation and epithelial barrier function in Drosophila.  

PubMed

Occluding cell-cell junctions in epithelia form physical barriers that separate different membrane domains, restrict paracellular diffusion and prevent pathogens from spreading across tissues. In invertebrates, these functions are provided by septate junctions (SJs), the functional equivalent of vertebrate tight junctions. How the diverse functions of SJs are integrated and modulated in a multiprotein complex is not clear, and many SJ components are still unknown. Here we report the identification of Macroglobulin complement-related (Mcr), a member of the conserved ?-2-macroglobulin (?2M) complement protein family, as a novel SJ-associated protein in Drosophila. Whereas ?2M complement proteins are generally known as secreted factors that bind to surfaces of pathogens and target them for phagocytic uptake, Mcr represents an unusual ?2M protein with a predicted transmembrane domain. We show that Mcr protein localizes to lateral membranes of epithelial cells, where its distribution overlaps with SJs. Several SJ components are required for the correct localization of Mcr. Conversely, Mcr is required in a cell-autonomous fashion for the correct membrane localization of SJ components, indicating that membrane-bound rather than secreted Mcr isoforms are involved in SJ formation. Finally, we show that loss of Mcr function leads to morphological, ultrastructural and epithelial barrier defects resembling mutants lacking SJ components. Our results, along with previous findings on the role of Mcr in phagocytosis, suggest that Mcr plays dual roles in epithelial barrier formation and innate immunity. Thus, Mcr represents a novel paradigm for investigating functional links between occluding junction formation and pathogen defense mechanisms. PMID:24496626

Bätz, Tilmann; Förster, Dominique; Luschnig, Stefan

2014-02-01

82

Isoform-specific differences between Rap1A and Rap1B GTPases in the formation of endothelial cell junctions  

PubMed Central

Rap1 is a Ras-like GTPase that has been studied with respect to its role in cadherin-based cell adhesion. Rap1 exists as two separate isoforms, Rap1A and Rap1B, which are 95% identical and yet the phenotype of the isoform-specific knockout mice is different. We and others have previously identified a role for Rap1 in regulating endothelial adhesion, junctional integrity and barrier function; however, these early studies did not distinguish a relative role for each isoform. To dissect the individual contribution of each isoform in regulating the endothelial barrier, we utilized an engineered microRNA-based approach to silence Rap1A, Rap1B or both, then analyzed barrier properties of the endothelium. Electrical impedance sensing experiments show that Rap1A is the predominant isoform involved in endothelial cell junction formation. Quantification of monolayer integrity by VE-cadherin staining revealed that knockdown of Rap1A, but not Rap1B, increased the number of gaps in the confluent monolayer. This loss of monolayer integrity could be rescued by re-expression of exogenous Rap1A protein. Expression of GFP-tagged Rap1A or 1B revealed quantifiable differences in localization of each isoform, with the junctional pool of Rap1A being greater. The junctional protein AF-6 also co-immunoprecipitates more strongly with expressed GFP-Rap1A. Our results show that Rap1A is the more critical isoform in the context of endothelial barrier function, indicating that some cellular processes differentially utilize Rap1A and 1B isoforms. Studying how Rap1 isoforms differentially regulate EC junctions may thus reveal new targets for developing therapeutic strategies during pathological situations where endothelial barrier disruption leads to disease.

Aghajanian, Amir; Burridge, Keith

2011-01-01

83

The crystal structures of psoralen cross-linked DNAs: drug-dependent formation of Holliday junctions.  

PubMed

The single-crystal structures are presented for two DNA sequences with the thymine bases covalently cross-linked across the complementary strands by 4'-hydroxymethyl-4,5',8-trimethylpsoralen (HMT). The HMT-adduct of d(CCGCTAGCGG) forms a psoralen-induced Holliday junction, showing for the first time the effect of this important class of chemotheraputics on the structure of the recombination intermediate. In contrast, HMT-d(CCGGTACCGG) forms a sequence-dependent junction. In both structures, the DNA duplex is highly distorted at the thymine base linked to the six-member pyrone ring of the drug. The psoralen cross-link defines the intramolecular interactions of the drug-induced junction, while the sequence-dependent structure is nearly identical to the native Holliday junction of d(CCGGTACCGG) alone. The two structures contrast the effects of drug- and sequence-dependent interactions on the structure of a Holliday junction, suggesting a role for psoralen in the mechanism to initiate repair of psoralen-lesions in mammalian DNA. PMID:11302703

Eichman, B F; Mooers, B H; Alberti, M; Hearst, J E; Ho, P S

2001-04-20

84

Formation of p-n-p junction with ionic liquid gate in graphene  

NASA Astrophysics Data System (ADS)

Ionic liquid gating is a technique which is much more efficient than solid gating to tune carrier density. To observe the electronic properties of such a highly doped graphene device, a top gate made of ionic liquid has been used. By sweeping both the top and back gate voltage, a p-n-p junction has been created. The mechanism of forming the p-n-p junction has been discussed. Tuning the carrier density by ionic liquid gate can be an efficient method to be used in flexible electronics.

He, Xin; Tang, Ning; Gao, Li; Duan, Junxi; Zhang, Yuewei; Lu, Fangchao; Xu, Fujun; Wang, Xinqiang; Yang, Xuelin; Ge, Weikun; Shen, Bo

2014-04-01

85

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

86

The SARS Coronavirus E Protein Interacts with PALS1 and Alters Tight Junction Formation and Epithelial Morphogenesis  

PubMed Central

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.

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

2010-01-01

87

Droplet formation in microfluidic T-junction generators operating in the transitional regime. III. Dynamic surfactant effects.  

PubMed

This study extends our previous work on droplet generation in microfluidic T-junction generators to include dynamic interfacial tension effects created by the presence of surfactants. In Paper I [T. Glawdel, C. Elbuken, and C. L. Ren, Phys. Rev. E 85, 016322 (2012)], we presented experimental findings regarding the formation process in the squeezing-to-transition regime, and in Paper II [T. Glawdel, C. Elbuken, and C. L. Ren, Phys. Rev. E 85, 016323 (2012)] we developed a theoretical model that describes the performance of T-junction generators without surfactants. Here we study dynamic interfacial tension effects for two surfactants, one with a small molecular weight that adsorbs quickly, and the other with a large molecular weight that adsorbs slowly. Using the force balance developed in Paper II we extract the dynamic interfacial tension from high speed videos obtained during experiments. We then develop a theoretical model to predict the dynamic interfacial tension in microfluidic T-junction generators as a function of the surfactant properties, flow conditions, and generator design. This model is then incorporated into the overall model for generator performance to effectively predict the size of droplets produced when surfactants are present. PMID:23005855

Glawdel, Tomasz; Ren, Carolyn L

2012-08-01

88

The effect of preamorphization energy on ultrashallow junction formation following ultrahigh-temperature annealing of ion-implanted silicon  

NASA Astrophysics Data System (ADS)

High-power arc lamp design has enabled ultrahigh-temperature (UHT) annealing as an alternative to conventional rapid thermal processing (RTP) for ultrashallow junction formation. The time duration of the UHT annealing technique is significantly reduced from those obtained through conventional RTP. This difference in time may offer the ability to maintain a highly activated ultrashallow junction without being subjected to transient enhanced diffusion (TED), which is typically observed during postimplant thermal processing. In this study, two 200-mm (100) n-type Czochralski-grown Si wafers were preamorphized with either a 48- or a 5-keV Ge+ implant to 5×1014 cm2, and subsequently implanted with 3-keV BF2+ molecular ions to 6×1014 cm2. The wafers were sectioned and annealed under various conditions in order to investigate the effects of the UHT annealing technique on the resulting junction characteristics. The main point of the paper is to show that the UHT annealing technique is capable of producing a highly activated p-type source/drain extension without being subjected to TED only when the preamorphization implant is sufficiently deep.

Gable, K. A.; Robertson, L. S.; Jain, Amitabh; Jones, K. S.

2005-02-01

89

Corrosion at the neck-stem junction as a cause of metal ion release and pseudotumour formation.  

PubMed

We present a series of 35 patients (19 men and 16 women) with a mean age of 64 years (36.7 to 75.9), who underwent total hip replacement using the ESKA dual-modular short stem with metal on-polyethylene bearing surfaces. This implant has a modular neck section in addition to the modular head. Of these patients, three presented with increasing post-operative pain due to pseudotumour formation that resulted from corrosion at the modular neck-stem junction. These patients underwent further surgery and aseptic lymphocytic vaculitis associated lesions were demonstrated on histological analysis. Retrieval analysis of two modular necks showed corrosion at the neck-stem taper. Blood cobalt and chromium levels were measured at a mean of nine months (3 to 28) following surgery. These were compared with the levels in seven control patients (three men and four women) with a mean age of 53.4 years (32.1 to 64.1), who had an identical prosthesis and articulation but with a prosthesis that had no modularity at neck-stem junction. The mean blood levels of cobalt in the study group were raised at 50.75 nmol/l (5 to 145) compared with 5.6 nmol/l (2 to 13) in control patients. Corrosion at neck-stem tapers has been identified as an important source of metal ion release and pseudotumour formation requiring revision surgery. Finite element modelling of the dual modular stem demonstrated high stresses at the modular stem-neck junction. Dual modular cobalt-chrome hip prostheses should be used with caution due to these concerns. PMID:22733942

Gill, I P S; Webb, J; Sloan, K; Beaver, R J

2012-07-01

90

Autoregulation of connexin43 gap junction formation by internally translated isoforms  

PubMed Central

During each heartbeat, intercellular electrical coupling via connexin43 (C×43) gap junctions enables synchronous cardiac contraction. In failing hearts, impaired C×43 trafficking reduces gap junction coupling, resulting in arrhythmias. Here we report that internal translation within C×43 (GJA1) mRNA occurs, resulting in truncated isoforms that autoregulate C×43 trafficking. We find at least four truncated C×43 isoforms occur in human heart, with a 20 kDa isoform predominating. In frame AUG codons within GJA1 mRNA are the translation initiation sites and their ablation arrests trafficking of full-length C×43. The 20 kDa isoform is sufficient to rescue this trafficking defect in trans, suggesting it as a trafficking chaperone for C×43. Limiting cap-dependent translation through inhibition of mTOR enhances truncated isoform expression, increasing C×43 gap junction size. The results suggest that internal translation is a mechanism of membrane protein autoregulation, and a potent target for therapies aimed at restoring normal electrical coupling in diseased hearts.

Smyth, James W.; Shaw, Robin M.

2013-01-01

91

Moleskin is essential for the formation of the myotendinous junction in Drosophila  

PubMed Central

It is the precise connectivity between skeletal muscles and their corresponding tendon cells to form a functional myotendinous junction (MTJ) that allows for the force generation required for muscle contraction and organismal movement. The Drosophila MTJ is comprised of secreted extracellular matrix (ECM) proteins deposited between integrin-mediated hemi-adherens junctions on the surface of muscle and tendon cells. In this paper, we have identified a novel, cytoplasmic role for the canonical nuclear import protein Moleskin (Msk) in Drosophila embryonic somatic muscle attachment. Msk protein is enriched at muscle attachment sites in late embryogenesis and msk mutant embryos exhibit a failure in muscle-tendon cell attachment. Although the muscle-tendon attachment sites are reduced in size, components of the integrin complexes and ECM proteins are properly localized in msk mutant embryos. However, msk mutants fail to localize phosphorylated Focal adhesion kinase (pFAK) to the sites of muscle-tendon cell junctions. In addition, the tendon cell specific proteins Stripe (Sr) and activated mitogen-activated protein kinase (MAPK) are reduced in msk mutant embryos. Our rescue experiments demonstrate that Msk is required in the muscle cell, but not in the tendon cells. Moreover, muscle attachment defects due to loss of Msk are rescued by an activated form of MAPK or the secreted Epidermal Growth Factor receptor (Egfr) ligand Vein. Taken together, these findings provide strong evidence that Msk signals non-autonomously through the Vein-Egfr signaling pathway for late tendon cell late differentiation and/or maintenance.

Liu, Ze (Cindy); Geisbrecht, Erika R.

2014-01-01

92

Junction formation of Cu(3)BiS(3) investigated by Kelvin probe force microscopy and surface photovoltage measurements.  

PubMed

Recently, the compound semiconductor Cu(3)BiS(3) has been demonstrated to have a band gap of ~1.4 eV, well suited for photovoltaic energy harvesting. The preparation of polycrystalline thin films was successfully realized and now the junction formation to the n-type window needs to be developed. We present an investigation of the Cu(3)BiS(3) absorber layer and the junction formation with CdS, ZnS and In(2)S(3) buffer layers. Kelvin probe force microscopy shows the granular structure of the buffer layers with small grains of 20-100 nm, and a considerably smaller work-function distribution for In(2)S(3) compared to that of CdS and ZnS. For In(2)S(3) and CdS buffer layers the KPFM experiments indicate negatively charged Cu(3)BiS(3) grain boundaries resulting from the deposition of the buffer layer. Macroscopic measurements of the surface photovoltage at variable excitation wavelength indicate the influence of defect states below the band gap on charge separation and a surface-defect passivation by the In(2)S(3) buffer layer. Our findings indicate that Cu(3)BiS(3) may become an interesting absorber material for thin-film solar cells; however, for photovoltaic application the band bending at the charge-selective contact has to be increased. PMID:22497001

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

2012-01-01

93

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

SciTech Connect

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

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

1983-12-01

94

Optimization of alternate-strand triple helix formation at the 5"-TpA-3" and 5"-ApT-3" junctions.  

PubMed Central

Alternate-strand triple helix formation was optimized at the two junction steps, the 5"-TpA-3" and 5"-ApT-3" junctions. Footprint experiments, gel retardation assays and thermal denaturation measures on a sequence appropriately designed with two adjacent alternate-strand polypurine tracts points out that the addition of an adenine residue and the removal of one nucleotide should facilitate the crossing strands at the 5"-TpA-3" junction and at the 5"-ApT-3" junction, respectively. These results provide a 'switch code' for the construction of alternate-strand triple helix forming oligonucleotides which open new possibilities for extending the range of applications of antigene strategy.

Brodin, P; Sun, J S; Mouscadet, J F; Auclair, C

1999-01-01

95

Shope fibroma virus DNA topoisomerase catalyses holliday junction resolution and hairpin formation in vitro.  

PubMed

The telomeres of poxviral chromosomes comprise covalently closed hairpin structures bearing mismatched bases. These hairpins are formed as concatemeric replication intermediates and are processed into mature, unit-length genomes. The structural transitions and enzymes involved in telomere resolution are poorly understood. Here we show that the type I topoisomerase of Shope fibroma virus (SFV) can promote a recombination reaction which converts cloned SFV replication intermediates into hairpin-ended molecules resembling mature poxviral telomeres. Recombinant SFV topoisomerase linearised a palindromic plasmid bearing 1.5 kb of DNA encoding the SFV concatemer junction, at a site near the centre of inverted-repeat symmetry. Most of these linear reaction products bore hairpin tips as judged by denaturing gel electrophoresis. The resolution reaction required palindromic SFV DNA sequences and was inhibited by compounds which block branch migration (MgCl2) or poxviral topoisomerases. The resolution reaction was also slow, needed substantial quantities of topoisomerase, and required that the palindrome be extruded in a cruciform configuration. DNA cleavage experiments identified a pair of suitably oriented topoisomerase recognition sites, 90 bases from the centre of the cloned SFV terminal inverted repeat, which may mark the resolution site. These data suggest a resolution scheme in which branch migration of a Holliday junction through a site occupied by covalently bound topoisomerase molecules, could lead to telomere resolution. PMID:10074403

Palaniyar, N; Gerasimopoulos, E; Evans, D H

1999-03-19

96

A novel protein complex, Mesh-Ssk, is required for septate junction formation in the Drosophila midgut.  

PubMed

Septate junctions (SJs) are specialized intercellular junctions that restrict the free diffusion of solutes through the paracellular route in invertebrate epithelia. In arthropods, two morphologically different types of SJs have been reported: pleated SJs and smooth SJs (sSJs), which are found in ectodermally and endodermally derived epithelia, respectively. However, the molecular and functional differences between these SJ types have not been fully elucidated. Here, we report that a novel sSJ-specific component, a single-pass transmembrane protein, which we term 'Mesh' (encoded by CG31004), is highly concentrated in Drosophila sSJs. Compromised mesh expression causes defects in the organization of sSJs, in the localizations of other sSJ proteins, and in the barrier function of the midgut. Ectopic expression of Mesh in cultured cells induces cell-cell adhesion. Mesh forms a complex with Ssk, another sSJ-specific protein, and these proteins are mutually interdependent for their localization. Thus, a novel protein complex comprising Mesh and Ssk has an important role in sSJ formation and in intestinal barrier function in Drosophila. PMID:22854041

Izumi, Yasushi; Yanagihashi, Yuichi; Furuse, Mikio

2012-10-15

97

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

SciTech Connect

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

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

1999-03-01

98

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

SciTech Connect

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

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

1998-11-18

99

Endoplasmic Reticulum Export, Subcellular Distribution, and Fibril Formation by Pmel17 Require an Intact N-terminal Domain Junction*  

PubMed Central

Pmel17 is a melanocyte/melanoma-specific protein that subcellularly localizes to melanosomes, where it forms a fibrillar matrix that serves for the sequestration of potentially toxic reaction intermediates of melanin synthesis and deposition of the pigment. As a key factor in melanosomal biogenesis, understanding intracellular trafficking and processing of Pmel17 is of central importance to comprehend how these organelles are formed, how they mature, and how they function in the cell. Using a series of deletion and missense mutants of Pmel17, we are able to show that the integrity of the junction between the N-terminal region and the polycystic kidney disease-like domain is highly crucial for endoplasmic reticulum export, subcellular targeting, and fibril formation by Pmel17 and thus for establishing functional melanosomes.

Leonhardt, Ralf M.; Vigneron, Nathalie; Rahner, Christoph; Van den Eynde, Benoit J.; Cresswell, Peter

2010-01-01

100

Formation of shallow junctions through BGe molecular ion implantation and rapid thermal annealing  

NASA Astrophysics Data System (ADS)

This study investigated the implantation of BGe molecular ions into silicon together with post-annealing. The implantation ion energy and fluence were 77 keV and 5 × 10 14 cm -2, respectively. Secondary ion mass spectrometry (SIMS) results revealed that the effects of radiation-enhanced diffusion (RED) led to a deeper boron depth profile in the as-annealed specimen compared to the as-implanted one. The junction depths for a boron level of 10 17 cm -3 were 129 and 189 nm for the as-implanted and as-annealed specimens, respectively. Rutherford backscattering spectrometry with channeling (RBS/C) revealed an amorphous layer of approximately 70 nm in thickness in the as-implanted specimen, consistent with the cross-sectional transmission electron microscopy (XTEM) observations as well as SRIM simulations. Notably, amorphization was significantly reduced following rapid thermal annealing treatment, a finding confirmed in both the RBS/C and XTEM results. Plan-view transmission electron microscopy (PTEM) observations indicated no visible defects but only germanium precipitations with relatively sparse distribution.

Liang, J. H.; Sang, Y. J.

2004-06-01

101

CYCLOOXYGENASE 2 (COX2) SUPPRESSES FORMATION OF ADHERENS JUNCTIONS AND STRESS FIBERS  

Microsoft Academic Search

INTRODUCTION. Cyclooxygenase 2 (COX-2) is a key enzyme in the production of prostaglandins (PGs) and represents an important target for treatment and prevention of colorectal cancer (1). However, the molecular mechanisms by which COX-2 regulates colon epithelial cell morphology and stress fiber formation are not well understood. The normal morphology of colon epithelial cells is established and maintained by adherens

Yu-Wen E. Chang; Terry W. Chance; Jerry W. Marlin; Rolf Jakobi

102

The Receptor Tyrosine Kinase MuSK Is Required for Neuromuscular Junction Formation In Vivo  

Microsoft Academic Search

Formation of neuromuscular synapses requires a series of inductive interactions between growing motor axons and differentiating muscle cells, culminating in the precise juxtaposition of a highly specialized nerve terminal with a complex molecular structure on the postsynaptic muscle surface. The receptors and signaling pathways mediating these inductive interactions are not known. We have generated mice with a targeted disruption of

Thomas M DeChiara; David C Bowen; David M Valenzuela; Mary V Simmons; William T Poueymirou; Susan Thomas; Erika Kinetz; Debra L Compton; Eduardo Rojas; John S Park; Cynthia Smith; Peter S DiStefano; David J Glass; Steven J Burden; George D Yancopoulos

1996-01-01

103

Palladin, an actin-associated protein, is required for adherens junction formation and intercellular adhesion in HCT116 colorectal cancer cells.  

PubMed

Palladin is a scaffold protein involved in the formation of actin-associated protein complexes. Gene expression array analysis on the poorly metastatic HCT116 colon cancer cell line and a metastatic derivative cell line (E1) with EMT (epithelial-mesenchymal transition) features showed a down-regulation of palladin gene expression in the latter. Knockdown of palladin expression in the HCT116 cells suppressed junctional localization of E-cadherin, reduced intercellular adhesion and collective cell migration, showing that palladin plays an important role in maintaining the integrity of adherens junctions. The acquisition of the EMT features by the E1 cell line was dependent on the Erk pathway. Inhibition of this pathway by U0126 treatment in E1 cells resulted in the re-expression of palladin, relocalization of E-cadherin to the adherens junctions and a reversal of EMT features. The re-establishment of intercellular adhesion was dependent on palladin expression. The down-regulation of palladin was also observed in poorly-differentiated tumor tubules and dissociated tumor cells that have undergone de-differentiation in human primary colon tumors. Our data show that palladin is an integral component of adherens junctions and plays a role in the localization of E-cadherin to the junctions. The loss of palladin may be an integral part of EMT, an early step in the metastatic spread of colon carcinoma. PMID:20811713

Tay, Puei Nam; Tan, Patrick; Lan, Yuhong; Leung, Carol Ho-Wing; Laban, Mirtha; Tan, Tze Chin; Ni, Hongmin; Manikandan, Jayapal; Rashid, Suhaimi Bin Abdul; Yan, Benedict; Yap, Celestial Therese; Lim, Lina Hsiu Kim; Lim, Yaw Chyn; Hooi, Shing Chuan

2010-10-01

104

Junction Photovoltage Metrology and High Resolution Mapping of Ion Implants Electrically Isolated from the Wafer Surface  

NASA Astrophysics Data System (ADS)

Application of the Junction Photovoltage (JPV) method for metrology of ultra-shallow implant (USJ) has been well documented. In this paper we report the application of the JPV method to control implant processes which create an electrically active layer isolated from the surface. In such structures four point probe (4PP) metrology is unreliable or impossible. This paper presents results obtained using a Junction Photo-Voltage (JPV) method optimized for characterization of these two processes, CMOS: Implantation through a screen oxide followed by anneal and also MeV p-type high energy implantation into n-type doped substrate followed by an anneal. Taking errors and necessary corrections into account the JPV method allows accurate high resolution mapping of such structures without the need for an extra process step. Results obtained from the JPV measurements were correlated to destructive off-line analytical measurement tools.

Korsós, Ferenc; Kis-Szabo, Krisztian; Don, Eric; Pap, Aron; Pavelka, Tibor; Laviron, Cyrille; Pfeffer, Marcus

2008-11-01

105

Metrology and High Resolution Mapping of Shallow Junctions Formed by Low Energy Implant Processes  

NASA Astrophysics Data System (ADS)

This paper presents results obtained using a Junction Photo-Voltage (JPV) method optimized for characterization of the combined implant-annealing process. The tool was found to be particularly suited to measurement of ultra-shallow junction sheet resistivity and leakage. In this work the authors also evaluated the benefits of improved spatial resolution compared to previous equipment designs. Current technology USJ monitor wafers were made using a BF2 or Arsenic implant followed by a spike anneal and also R&D USJ wafers were made by Plasma Immersion followed by laser annealing. All the wafers were measured using the non-contact JPV measurement tool. Results obtained from the JPV measurements were correlated to destructive off-line analytical measurement tools.

Don, Eric; Pap, Aron; Tutto, Peter; Pavelka, Tibor; Wyon, Christophe; Laviron, Cyrille; Sotta, David; Oechsner, Richard; Pfeffer, Marcus

2006-11-01

106

Formation of axial metal–semiconductor junctions in GaAs nanowires by thermal annealing  

NASA Astrophysics Data System (ADS)

We demonstrate the formation of nanoscale axial Schottky contacts in GaAs nanowires by thermal annealing of NiGeAu multilayers. Energy dispersive x-ray spectroscopy indicates that in specific annealing conditions a sharply-defined Au-rich phase can be obtained in the vicinity of the metallic contacts. Charge transport characteristics are analyzed for different degrees of diffusion of the Au-rich phase in the wire and indicate that it has a metallic nature. The mechanism behind this local post-growth modification of the nanowire composition and its potential impact on device applications are discussed.

Orrù, Marta; Rubini, Silvia; Roddaro, Stefano

2014-05-01

107

Alpha1-syntrophin-deficient skeletal muscle exhibits hypertrophy and aberrant formation of neuromuscular junctions during regeneration.  

PubMed

Alpha1-syntrophin is a member of the family of dystrophin-associated proteins; it has been shown to recruit neuronal nitric oxide synthase and the water channel aquaporin-4 to the sarcolemma by its PSD-95/SAP-90, Discs-large, ZO-1 homologous domain. To examine the role of alpha1-syntrophin in muscle regeneration, we injected cardiotoxin into the tibialis anterior muscles of alpha1-syntrophin-null (alpha1syn-/-) mice. After the treatment, alpha1syn-/- muscles displayed remarkable hypertrophy and extensive fiber splitting compared with wild-type regenerating muscles, although the untreated muscles of the mutant mice showed no gross histological change. In the hypertrophied muscles of the mutant mice, the level of insulin-like growth factor-1 transcripts was highly elevated. Interestingly, in an early stage of the regeneration process, alpha1syn-/- mice showed remarkably deranged neuromuscular junctions (NMJs), accompanied by impaired ability to exercise. The contractile forces were reduced in alpha1syn-/- regenerating muscles. Our results suggest that the lack of alpha1-syntrophin might be responsible in part for the muscle hypertrophy, abnormal synapse formation at NMJs, and reduced force generation during regeneration of dystrophin-deficient muscle, all of which are typically observed in the early stages of Duchenne muscular dystrophy patients. PMID:12221071

Hosaka, Yukio; Yokota, Toshifumi; Miyagoe-Suzuki, Yuko; Yuasa, Katsutoshi; Imamura, Michihiro; Matsuda, Ryoichi; Ikemoto, Takaaki; Kameya, Shuhei; Takeda, Shin'ichi

2002-09-16

108

Neuromuscular junction formation between human stem cell-derived motoneurons and human skeletal muscle in a defined system.  

PubMed

Functional in vitro models composed of human cells will constitute an important platform in the next generation of system biology and drug discovery. This study reports a novel human-based in vitro Neuromuscular Junction (NMJ) system developed in a defined serum-free medium and on a patternable non-biological surface. The motoneurons and skeletal muscles were derived from fetal spinal stem cells and skeletal muscle stem cells. The motoneurons and skeletal myotubes were completely differentiated in the co-culture based on morphological analysis and electrophysiology. NMJ formation was demonstrated by phase contrast microscopy, immunocytochemistry and the observation of motoneuron-induced muscle contractions utilizing time-lapse recordings and their subsequent quenching by d-Tubocurarine. Generally, functional human based systems would eliminate the issue of species variability during the drug development process and its derivation from stem cells bypasses the restrictions inherent with utilization of primary human tissue. This defined human-based NMJ system is one of the first steps in creating functional in vitro systems and will play an important role in understanding NMJ development, in developing high information content drug screens and as test beds in preclinical studies for spinal or muscular diseases/injuries such as muscular dystrophy, Amyotrophic lateral sclerosis and spinal cord repair. PMID:21944471

Guo, Xiufang; Gonzalez, Mercedes; Stancescu, Maria; Vandenburgh, Herman H; Hickman, James J

2011-12-01

109

Nectin-4 mutations causing ectodermal dysplasia with syndactyly perturb the rac1 pathway and the kinetics of adherens junction formation.  

PubMed

Defective nectin-1 and -4 have been implicated in ectodermal dysplasia (ED) syndromes with variably associated features including orofacial and limb defects. In particular, nectin-1 mutations cause cleft lip/palate ED (CLPED1; OMIM#225060), whereas defective nectin-4 is associated with ED-syndactyly syndrome (EDSS1; OMIM#613573). Although the broad phenotypic overlap suggests a common mode of action of nectin-1 and -4, little is known about the pathogenic mechanisms involved. We report the identification of, to our knowledge, a previously undescribed nectin-4 homozygous p.Val242Met missense mutation in a patient with EDSS1. We used patient skin biopsy and primary keratinocytes, as well as nectin-4 ectopic expression in epithelial cell lines, to characterize functional consequences of p.Val242Met and p.Thr185Met mutations, the latter previously identified in compound heterozygosity with a truncating mutation. We show that nectin-4-altered expression perturbs nectin-1 clustering at keratinocyte contact sites and delays, but does not impede cell-cell aggregation and cadherin recruitment at adherens junctions (AJs). Moreover, trans-interaction of nectin-1 and -4 induces the activation of Rac1, a member of the Rho family of small GTPases, and regulates E-cadherin-mediated cell-cell adhesion. These data outline a synergistic action of nectin-1 and -4 in the early steps of AJ formation and implicate this interaction in modulating the Rac1 signaling pathway. PMID:24577405

Fortugno, Paola; Josselin, Emmanuelle; Tsiakas, Konstantinos; Agolini, Emanuele; Cestra, Gianluca; Teson, Massimo; Santer, René; Castiglia, Daniele; Novelli, Giuseppe; Dallapiccola, Bruno; Kurth, Ingo; Lopez, Marc; Zambruno, Giovanna; Brancati, Francesco

2014-08-01

110

Syringomyelia associated with arachnoid septum at the craniovertebral junction, contradicting the currently prevailing theory of syringomyelia formation.  

PubMed

Despite a number of various hypotheses in the literature, the pathophysiology of syringomyelia is still not well understood. In this article, we report two cases of cervical syringomyelia not associated with Chiari I malformation. Both cases had a septum-like structure in the subarachnoid space on the dorsal side of the cord at the craniovertebral junction. Cardiac-gated phase-contrast cine-mode magnetic resonance imaging (MRI) demonstrated decreased cerebrospinal fluid (CSF) flow on the dorsal side of the spinal cord. Surgical excision of this septum, restoring the CSF flow, resulted in a prompt reduction of the syrinx size in both cases. Findings in these cases contradict the currently prevailing hypothesis of syrinx formation that postulate that the piston-like movement of the cerebellar tonsils enhance the pulsatile CSF flow in the spinal subarachnoid space, driving the CSF into the syrinx through the perivascular space of Virchow and Robin. The authors propose that a mechanism based on the decreased pulsatile CSF flow in the spinal subarachnoid space will be more suitable as a hypothesis in studying the pathophyisiology of syringomyelia. These cases also provide an important lesson in managing the patients with syringomyelia not associated with Chiari I malformation. PMID:22052474

Chang, Han Soo; Tsuchiya, Tsukasa; Fujisawa, Naoaki; Oya, Soichi; Matsui, Toru

2012-01-01

111

Neuromuscular Junction Formation between Human Stem cell-derived Motoneurons and Human Skeletal Muscle in a Defined System  

PubMed Central

Functional in vitro models composed of human cells will constitute an important platform in the next generation of system biology and drug discovery. This study reports a novel human-based in vitro Neuromuscular Junction (NMJ) system developed in a defined serum-free medium and on a patternable non-biological surface. The motoneurons and skeletal muscles were derived from fetal spinal stem cells and skeletal muscle stem cells. The motoneurons and skeletal myotubes were completely differentiated in the co-culture based on morphological analysis and electrophysiology. NMJ formation was demonstrated by phase contrast microscopy, immunocytochemistry and the observation of motoneuron-induced muscle contractions utilizing time lapse recordings and their subsequent quenching by D-Tubocurarine. Generally, functional human based systems would eliminate the issue of species variability during the drug development process and its derivation from stem cells bypasses the restrictions inherent with utilization of primary human tissue. This defined human-based NMJ system is one of the first steps in creating functional in vitro systems and will play an important role in understanding NMJ development, in developing high information content drug screens and as test beds in preclinical studies for spinal or muscular diseases/injuries such as muscular dystrophy, Amyotrophic lateral sclerosis and spinal cord repair.

Guo, Xiufang; Gonzalez, Mercedes; Stancescu, Maria; Vandenburgh, Herman; Hickman, James

2011-01-01

112

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

2013-08-15

113

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

PubMed Central

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.

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

2013-01-01

114

Radiation-induced junction formation behavior of boron-doped Czochralski and float zone silicon crystals under 3 MeV proton irradiation  

Microsoft Academic Search

A comparative study was performed on the junction formation behavior of boron-doped p-type Czochralski (Cz) and float zone (Fz) Si wafers, which differed mainly in interstitial oxygen concentration, upon 3 MeV proton irradiation with fluences of up to 2×1015 cm?2. The region around the projected range in both the Cz and Fz Si wafers converted its conduction type to n

M. D. Chun; D. Kim; J. Y. Huh

2003-01-01

115

Radiation-induced junction formation behavior of boron-doped Czochralski and float zone silicon crystals under 3 MeV proton irradiation  

Microsoft Academic Search

A comparative study was performed on the junction formation behavior of boron-doped p-type Czochralski (Cz) and float zone (Fz) Si wafers, which differed mainly in interstitial oxygen concentration, upon 3 MeV proton irradiation with fluences of up to 2×1015 cm-2. The region around the projected range in both the Cz and Fz Si wafers converted its conduction type to n

M. D. Chun; D. Kim; J. Y. Huh

2003-01-01

116

PAR6 regulates aPKC activity in a novel way and mediates cell-cell contact-induced formation of the epithelial junctional complex  

Microsoft Academic Search

Background :P AR-6, aPKC and PAR-3 are polarity proteins that co-operate in the establishment of cell polarity in Caenorhabditis elegans and Drosophila embryos. We have recently shown that mammalian aPKC is required for the formation of the epithelia-specific cell- cell junctional structure. We have also revealed that a mammalian PAR-6 forms a ternary complex with aPKC and ASIP\\/PAR-3, and localizes

Tomoyuki Yamanaka; Yosuke Horikoshi; Atsushi Suzuki; Yuki Sugiyama; Koichi Kitamura; Rika Maniwa; Yoko Nagai; Akio Yamashita; Tomonori Hirose; Hiroko Ishikawa; Shigeo Ohno

2001-01-01

117

Quantitative cell polarity imaging defines leader-to-follower transitions during collective migration and the key role of microtubule-dependent adherens junction formation.  

PubMed

The directed migration of cell collectives drives the formation of complex organ systems. A characteristic feature of many migrating collectives is a 'tissue-scale' polarity, whereby 'leader' cells at the edge of the tissue guide trailing 'followers' that become assembled into polarised epithelial tissues en route. Here, we combine quantitative imaging and perturbation approaches to investigate epithelial cell state transitions during collective migration and organogenesis, using the zebrafish lateral line primordium as an in vivo model. A readout of three-dimensional cell polarity, based on centrosomal-nucleus axes, allows the transition from migrating leaders to assembled followers to be quantitatively resolved for the first time in vivo. Using live reporters and a novel fluorescent protein timer approach, we investigate changes in cell-cell adhesion underlying this transition by monitoring cadherin receptor localisation and stability. This reveals that while cadherin 2 is expressed across the entire tissue, functional apical junctions are first assembled in the transition zone and become progressively more stable across the leader-follower axis of the tissue. Perturbation experiments demonstrate that the formation of these apical adherens junctions requires dynamic microtubules. However, once stabilised, adherens junction maintenance is microtubule independent. Combined, these data identify a mechanism for regulating leader-to-follower transitions within migrating collectives, based on the relocation and stabilisation of cadherins, and reveal a key role for dynamic microtubules in this process. PMID:24595289

Revenu, Céline; Streichan, Sebastian; Donà, Erika; Lecaudey, Virginie; Hufnagel, Lars; Gilmour, Darren

2014-03-01

118

The Apical Junctional Complex in Respiratory Diseases  

PubMed Central

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

2014-01-01

119

In situ formation of p-n junction: A novel principle for photoelectrochemical sensor and its application for mercury(II) ion detection.  

PubMed

The discovery and development of photoelectrochemical sensors with novel principles are of great significance to realize sensitive and low-cost detection. In this paper, a new photoelectrochemial sensor based on the in situ formation of p-n junction was designed and used for the accurate determination of mercury(II) ions. Cysteine-capped ZnS quantum dots (QDs) was assembled on the surface of indium tin oxide (ITO) electrode based on the electrostatic interaction between Poly(diallyldimethylammonium chloride) (PDDA) and Cys-capped ZnS QDs. The in situ formation of HgS, a p-type semiconductor, on the surface of ZnS facilitated the charge carrier transport and promoted electron-hole separation, triggered an obviously enhanced anodic photocurrent of Cys-capped ZnS QDs. The formation of p-n junction was confirmed by P-N conductive type discriminator measurements and current-voltage (I-V) curves. The photoelectrochemical method was used for the sensing of trace mercuric (II) ions with a linear concentration of 0.01 to 10.0µM and a detection limit of 4.6×10(-9)mol/L. It is expected that the present study can serve as a foundation to the application of p-n heterojunction to photoelectrochemical sensors and it might be easily extended to more exciting sensing systems by photoelectrochemistry. PMID:24832992

Wang, Guang-Li; Liu, Kang-Li; Dong, Yu-Ming; Li, Zai-Jun; Zhang, Chi

2014-05-27

120

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.

Wendt, Joel R. (Albuquerque, NM); Plut, Thomas A. (Albuquerque, NM); Martens, Jon S. (Sunnyvale, CA)

1995-01-01

121

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

2013-10-01

122

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

PubMed Central

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.

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

2013-01-01

123

Effects of Substrate and Na Concentration on Device Properties, Junction Formation, and Film Microstructure in CuInSe2PV Devices  

SciTech Connect

Different concentrations of Na were systematically introduced into CuInSe2 (CIS) photovoltaic solar cell absorber material on different substrates (SLG, Si02/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.

1998-10-22

124

Effects of substrate and Na concentration on device properties, junction formation, and film microstructure in CuInSe{sub 2} PV devices  

SciTech Connect

Different concentrations of Na were systematically introduced into CuInSe{sub 2} (CIS) photovoltaic solar cell absorber material on different substrates (SLG, SiO{sub 2}/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 V{sub oc}, J{sub sc}, and device efficiency, improved charge-collection efficiency and, possibly, increased grain size as a result of the coevaporation of 4 to 100 mg of Na{sub 2}Se during film deposition. However, a dramatic devolution set in with the addition of 235 mg of Na{sub 2}Se, 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 {open_quotes}Na overdose.{close_quotes} {copyright} {ital 1999 American Institute of Physics.}

Matson, R.J.; Granata, J.E.; Asher, S.E.; Young, M.R. [National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, Colorado 80401 (United States)

1999-03-01

125

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

126

Gap Junctions  

PubMed Central

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

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

2013-01-01

127

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

128

Effects of junction formation conditions on the photovoltaic properties of sintered CdS/CdTe solar cells  

NASA Astrophysics Data System (ADS)

The microstructure and electrical properties of sintered CdS/CdTe heterojunction solar cells were examined experimentally. Borosilicate glass substrates were coated with a slurry of calcined CdS, and the combination was sintered at 650 C for an hour. The resulting films were coated with a CdTe slurry to a thickness of 25 microns and the combinations were sintered at temperatures ranging from 585-700 C. The CdS films had grain sizes averaging 15 microns while the CdTe grains averaged just over 5 microns. The sintering process produced p-n junctions. A maximum solar cell efficiency of 7.18 percent was obtained when the final sintering was 625 C for 1 hr. Effective cells were only obtained when the sintering temperature was between 610-625 C.

Lee, J. S.; Im, H. B.

1986-03-01

129

P?N junction formation in 6H?SiC by acceptor implantation into n-type substrate  

NASA Astrophysics Data System (ADS)

A1 and B implantations were performed into n-type 6H-bulk SiC and epitaxial layers at both room temperature and 850°C. Annealings were performed in the temperature range of 1100-1650°C in a SiC crucible. For single-energy implants, the implant gettered to the 0.7 Rp location for annealing temperatures ?1400°C. For the 850°C implanted samples the RBS yield in the annealed material is comparable to the yield in the as-grown material, indicating a good lattice recovery. A maximum activation of 18% for Al-implanted samples was observed. P?N junction diodes were made using Al-implanted material.

Rao, Mulpuri V.; Gardner, Jason; Griffiths, Peter; Holland, O. W.; Kelner, G.; Chi, P. H.; Simons, D. S.

1995-12-01

130

Problems related to the formation of lateral p--n junctions on channeled substrate (100) GaAs for lasers  

SciTech Connect

We shall describe the main steps required for molecular-beam epitaxial (MBE) growth on structured GaAs substrates for lasers, in particular, a reproducible etching process develolped for GaAs which yields well-defined and controllable tilt angles. The main parameters determining morphology and doping behavior on a facet are tilt angle THETA, substrate temperature, and the V:III ratio. The limiting values of these three parameters for obtaining good quality n- and p-type films, using Si as a dopant, will be determined. We conclude that a (311A) facet is best suited to obtain plane selective doping without generating a detrimental (111A) plane. As a result of this study, lateral p--n junctions with light emission will be demonstrated showing promise for new device structures such as lasers.

Meier, H.P.; Broom, R.F.; Epperlein, P.W.; van Gieson, E.; Harder, C.; Jaeckel, H.; Walter, W.; Webb, D.J.

1988-03-01

131

Signaling from the Podocyte Intercellular Junction to the Actin Cytoskeleton  

PubMed Central

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.

George, Britta; Holzman, Lawrence B.

2012-01-01

132

Rectosigmoid Junction  

Microsoft Academic Search

Summary  Physioanatomical aspects of the rectosigmoid junction are scarcely treated in the literature. We studied the anatomy and physiology\\u000a of the rectosigmoid junction in a series of publications aiming at elucidating its function in the light of its anatomical\\u000a structure. The sigmoid colon is a storage organ, and the rectum, apart from being a conduit, proved to be a storage organ,

A. Shafik

1998-01-01

133

Radiation-induced junction formation behavior of boron-doped Czochralski and float zone silicon crystals under 3 MeV proton irradiation  

NASA Astrophysics Data System (ADS)

A comparative study was performed on the junction formation behavior of boron-doped p-type Czochralski (Cz) and float zone (Fz) Si wafers, which differed mainly in interstitial oxygen concentration, upon 3 MeV proton irradiation with fluences of up to 2×1015 cm-2. The region around the projected range in both the Cz and Fz Si wafers converted its conduction type to n type at fluences between 1×1013 and 3×1013 cm-2, which is most probably due to the formation of hydrogen-related donors. The main difference between the Cz and Fz Si wafers was in the susceptibility of the proton track region to type conversion. The proton track region of the Cz Si wafer converted to n type at fluence between 1×1013 and 3×1013 cm-2, whereas that of the Fz Si wafer showed only an increase in resistivity without any type conversion as the fluence increased up to 2×1015 cm-2, which was attributed to oxygen-related donor formation in the case of the Cz Si wafer. The present results are discussed with respect to the radiation-induced failure mechanisms of n+/p/p+-structured Si space solar cells based on boron-doped Cz and Fz Si.

Chun, M. D.; Kim, D.; Huh, J. Y.

2003-11-01

134

DNA models of trinucleotide frameshift deletions: the formation of loops and bulges at the primer-template junction  

PubMed Central

Although mechanisms of single-nucleotide residue deletion have been investigated, processes involved in the loss of longer nucleotide sequences during DNA replication are poorly understood. Previous reports have shown that in vitro replication of a 3?-TGC TGC template sequence can result in the deletion of one 3?-TGC. We have used low-energy circular dichroism (CD) and fluorescence spectroscopy to investigate the conformations and stabilities of DNA models of the replication intermediates that may be implicated in this frameshift. Pyrrolocytosine or 2-aminopurine residues, site-specifically substituted for cytosine or adenine in the vicinity of extruded base sequences, were used as spectroscopic probes to examine local DNA conformations. An equilibrium mixture of four hybridization conformations was observed when template bases looped-out as a bulge, i.e. a structure flanked on both sides by duplex DNA. In contrast, a single-loop structure with an unusual unstacked DNA conformation at its downstream edge was observed when the extruded bases were positioned at the primer–template junction, showing that misalignments can be modified by neighboring DNA secondary structure. These results must be taken into account in considering the genetic and biochemical mechanisms of frameshift mutagenesis in polymerase-driven DNA replication.

Baase, Walter A.; Jose, Davis; Ponedel, Benjamin C.; von Hippel, Peter H.; Johnson, Neil P.

2009-01-01

135

Electron transport in crossed nano-wire junctions  

Microsoft Academic Search

Electron transport in a crossed nano-wire junction is studied using a tight-binding model. Increase in the inter-wire tunneling coupling strength suppresses the transmissions through the junction around the first subband edge. The junction's transport characteristics can be explained by the formation of bound or quasi-bound states at the junction.

J. H. Wei; K. S. Chan

2005-01-01

136

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

PubMed

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 the current knowledge of the functions of vertebrate Fbln1. PMID:22771579

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

2012-09-15

137

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

138

Delayed short-course treatment with teriparatide (PTH(1-34)) improves femoral allograft healing by enhancing intramembranous bone formation at the graft-host junction.  

PubMed

Clinical management of critical bone defects remains a major challenge. Despite preclinical work demonstrating teriparatide (PTH(1-34)) effectiveness in small animals, inconclusive data from clinical trials have raised questions of dose and regimen. To address this, we completed a comprehensive study in the murine femoral allograft model, to assess the effects of dose (0.4, 4, and 40?µg/kg/day) and various treatment regimens on radiographic, histologic, and biomechanical healing at 2, 4, and 9 weeks. Only the high dose (40?µg/kg) of PTH(1-34) demonstrated significant effects when given daily over 9 weeks. Remarkably, equivalent biomechanical results were obtained with delayed, short treatment from 2 to 6 weeks that did not induce a significant increase in endochondral bone formation and callus volume. In contrast, PTH(1-34) treatment from 1 to 5 weeks postop demonstrated similar osteogenic effects as immediate daily treatment for 9 weeks, but failed to achieve a significant increase in biomechanics at 9 weeks. MicroCT and histologic analyses demonstrated that the 2-week delay in treatment allowed for timely completion of the endochondral phase, such that the prominent effects of PTH(1-34) were enhanced intramembranous bone formation and remodeling at the graft-host junction. These findings support the potential use of PTH(1-34) as an adjuvant therapy for massive allograft healing, and suggest that there may be an ideal treatment window in which a short course is administered after the endochondral phase to promote osteoblastic bone formation and remodeling to achieve superior union with modest callus formation. PMID:21956542

Takahata, Masahiko; Schwarz, Edward M; Chen, Tony; O'Keefe, Regis J; Awad, Hani A

2012-01-01

139

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

PubMed Central

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

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

2012-01-01

140

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

PubMed

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

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

2012-06-01

141

Stimulation of chondrocyte hypertrophy by chemokine stromal cell-derived factor 1 in the chondro-osseous junction during endochondral bone formation.  

PubMed

During endochondral bone formation, chondrocytes undergo differentiation toward hypertrophy before they are replaced by bone and bone marrow. In this study, we found that a G-protein coupled receptor CXCR4 is predominantly expressed in hypertrophic chondrocytes, while its ligand, chemokine stromal cell-derived factor 1 (SDF-1) is expressed in the bone marrow adjacent to hypertrophic chondrocytes. Thus, they are expressed in a complementary pattern in the chondro-osseous junction of the growth plate. Transfection of a CXCR4 cDNA into pre-hypertrophic chondrocytes results in a dose-dependent increase of hypertrophic markers including Runx2, Col X, and MMP-13 in response to SDF-1 treatment. In organ culture SDF-1 infiltrates cartilage and accelerates growth plate hypertrophy. Furthermore, a continuous infusion of SDF-1 into the rabbit proximal tibial physis results in early physeal closure, which is accompanied by a transient elevation of type X collagen expression. Blocking SDF-1/CXCR4 interaction suppresses the expression of Runx2. Thus, interaction of SDF-1 and CXCR4 is required for Runx2 expression. Interestingly, knocking down Runx2 gene expression results in a decrease of CXCR4 mRNA levels in hypertrophic chondrocytes. This suggests a positive feedback loop of stimulation of chondrocyte hypertrophy by SDF-1/CXCR4, which is mediated by Runx2. PMID:20206617

Wei, Lei; Kanbe, Katsuaki; Lee, Mark; Wei, Xiaochun; Pei, Ming; Sun, Xiaojuan; Terek, Richard; Chen, Qian

2010-05-01

142

The crystal structures of psoralen cross-linked DNAs: drug-dependent formation of Holliday junctions 1 1 Edited by I. Tinoco  

Microsoft Academic Search

The single-crystal structures are presented for two DNA sequences with the thymine bases covalently cross-linked across the complementary strands by 4?-hydroxymethyl-4,5?,8-trimethylpsoralen (HMT). The HMT-adduct of d(CCGCTAGCGG) forms a psoralen-induced Holliday junction, showing for the first time the effect of this important class of chemotheraputics on the structure of the recombination intermediate. In contrast, HMT-d(CCGGTACCGG) forms a sequence-dependent junction. In both

Brandt F. Eichman; Blaine H. M. Mooers; Marie Alberti; John E. Hearst; P. Shing Ho

2001-01-01

143

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

PubMed Central

Background Intestinal barrier function is important for preserving health, as a compromised barrier allows antigen entry and can induce inflammatory diseases. Probiotic bacteria can play a role in enhancing intestinal barrier function; however, the mechanisms are not fully understood. Existing studies have focused on the ability of probiotics to prevent alterations to tight junctions in disease models, and have been restricted to a few tight junction bridging proteins. No studies have previously investigated the effect of probiotic bacteria on healthy intestinal epithelial cell genes involved in the whole tight junction signalling pathway, including those encoding for bridging, plaque and dual location tight junction proteins. Alteration of tight junction signalling in healthy humans is a potential mechanism that could lead to the strengthening of the intestinal barrier, resulting in limiting the ability of antigens to enter the body and potentially triggering undesirable immune responses. Results The effect of Lactobacillus plantarum MB452 on tight junction integrity was determined by measuring trans-epithelial electrical resistance (TEER) across Caco-2 cell layers. L. plantarum MB452 caused a dose-dependent TEER increase across Caco-2 cell monolayers compared to control medium. Gene expression was compared in Caco-2 cells untreated or treated with L. plantarum MB452 for 10 hours. Caco-2 cell RNA was hybridised to human oligonucleotide arrays. Data was analysed using linear models and differently expressed genes were examined using pathway analysis tools. Nineteen tight junction-related genes had altered expression levels in response to L. plantarum MB452 (modified-P < 0.05, fold-change > 1.2), including those encoding occludin and its associated plaque proteins that anchor it to the cytoskeleton. L. plantarum MB452 also caused changes in tubulin and proteasome gene expression levels which may be linked to intestinal barrier function. Caco-2 tight junctions were visualised by fluorescent microscopy of immuno-stained occludin, zona occludens (ZO)-1, ZO-2 and cingulin. Caco-2 cells treated with L. plantarum MB452 had higher intensity fluorescence of each of the four tight junction proteins compared to untreated controls. Conclusions This research indicates that enhancing the expression of genes involved in tight junction signalling is a possible mechanism by which L. plantarum MB452 improves intestinal barrier function.

2010-01-01

144

Sound Junction  

NSDL National Science Digital Library

It's hard to learn about music without listening to it closely, and this multimedia website created by a group of organizations in Britain (including the Royal Academy of Music), provides a surfeit of music from all genres. Through interactive games, musical excerpts, interviews, and other such devices, the SoundJunction site is a great way for anyone to learn about music. A good place to start is the "What can I do on SoundJunction?" overview feature, which walks users through the layout of the site. After that, visitors may wish to look at the left-hand side of the homepage and click on through such areas as "Explore Music", "How Music Works", "Music in Context", and "Composing and remixing". For budding Beethovens, there is the "Composer Tool", which allows users to create their own music. Music educators and those who are just generally curious will find that this site merits numerous return visits, and it may prove to be quite habit-forming, in the best possible sense of the phrase.

145

Stochastic oscillations in Josephson tunnel junctions  

SciTech Connect

The dynamics of the onset of stochastic oscillations in Josephson tunnel junctions is investigated in a wide range of external microwave fields. The experimental data are compared with analytic and numerical calculations of the conditions of the formation of stochastic oscillations. The calculations are carried out within the framework of the resistive model of the Josephson junction.

Gubankov, V.N.; Ziglin, S.L.; Konstantinyan, K.I.; Koshelets, V.P.; Ovsyannikov, G.A.

1984-01-01

146

Science Junction  

NSDL National Science Digital Library

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

147

Rho GEFs in endothelial junctions  

PubMed Central

Rho GTPases are cytoskeleton-regulating proteins that mediate the formation of intercellular junctions. Their localized activation by Rho GEFs (guanine-nucleotide exchange factors) and the selective activation of downstream effectors have emerged as areas of active research in the cell adhesion field. We reported recently that the Rho-specific GEFs Syx (Synectin-binding RhoA exchange factor) and TEM4 (Tumor Endothelial Marker 4) are both essential for endothelial junction maturation and barrier function. Syx is recruited to cell contacts via its C-terminal PDZ binding motif and it’s interaction with Mupp1 and the Crumbs polarity complex, while the junctional localization of TEM4 requires it’s N-terminal domain and interaction with the cadherin-catenin complex. Our findings support multiple roles for RhoA in junction formation and maintenance. They also suggest that selective coupling of RhoA activation to Dia1 and/or ROCK signaling is critical for determining endothelial junction integrity.

Ngok, Siu P; Anastasiadis, Panos Z

2013-01-01

148

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

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

149

Conductance values of alkanedithiol molecular junctions  

NASA Astrophysics Data System (ADS)

We study the electrical conductance of octanedithiol molecular junctions using a mechanically controllable break-junction setup. The stability of the system allows control of whether the electrodes get into contact before each new molecular junction formation or not (contact and non-contact modes). We find three characteristic conductance values for octanedithiol. Well-defined peaks in the conductance histograms at multiples of 1.2×10-5 G0 suggest that this value corresponds to the conductance of a single molecular junction conductance. Reproducible features are also observed at 4.5×10-5 and 2.3×10-4 G0. The first value has the strongest statistical weight, whereas the second is only observed in the non-contact mode. We propose that these two values reflect the formation of several molecular junctions in parallel between the electrodes.

González, M. Teresa; Brunner, Jan; Huber, Roman; Wu, Songmei; Schönenberger, Christian; Calame, Michel

2008-06-01

150

Formation of the apical pole of epithelial (Madin-Darby canine kidney) cells: polarity of an apical protein is independent of tight junctions while segregation of a basolateral marker requires cell-cell interactions  

PubMed Central

The time course of development of polarity of an apical (184-kD) and a basolateral (63-kD) plasma membrane protein of Madin-Darby canine kidney cells was followed using semiquantitative immunofluorescence on semithin (approximately 0.5-micron) frozen sections and monoclonal antibody probes. The 184-kD protein became highly polarized to the apical pole within the initial 24 h both in normal medium and in 1-5 microM Ca2+, which results in well-spread, dome-shaped cells, lacking tight junctions and other lateral membrane interactions. In contrast, the basolateral 63-kD membrane protein developed full polarity only after incubation in normal Ca2+ concentrations for greater than 72 h, a time much longer than that required for the formation of tight junctions (approximately 18 h) and failed to polarize in 1-5 microM Ca2+. These results demonstrate that intradomain restriction mechanisms independent of tight junctions, such as self-aggregation or specific interactions with the submembrane cytoskeleton, participate in the regionalization of at least some epithelial plasma membrane proteins. The full operation of these mechanisms depends on the presence of normal cell-cell interactions in the case of the basolateral 63-kD antigen but not in the case of the apical 184-kD protein.

1987-01-01

151

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

152

Three-arm nucleic acid junctions are flexible.  

PubMed

Nucleic acid junctions are stable analogs of branched DNA structures which occur transiently in living systems. We show here that junctions which contain three double helical arms can be enzymatically oligomerized, using conventional sticky-ended ligation procedures, to create larger complexes. The products consist of a series of linked junctions separated by 20 base pairs. Junction dimers are formed that have free termini only, whereas trimers and larger species are found to be both unclosed and cyclized. The formation of a series of macrocyclic products which, surprisingly, begins with trimers and tetramers indicates that this junction is flexible about a bending axis, and perhaps twist-wise as well. We have obtained the same results from three different 3-arm junctions, two in which the junction is flanked by a 3 Watson-Crick base pairs, and one in which a G-G base pair flanks the junction. PMID:3808954

Ma, R I; Kallenbach, N R; Sheardy, R D; Petrillo, M L; Seeman, N C

1986-12-22

153

Circuit theory of unconventional superconductor junctions.  

PubMed

We extend the circuit theory of superconductivity to cover transport and proximity effect in mesoscopic systems that contain unconventional superconductor junctions. The approach fully accounts for zero-energy Andreev bound states forming at the surface of unconventional superconductors. As a simple application, we investigate the transport properties of a diffusive normal metal in series with a d-wave superconductor junction. We reveal the competition between the formation of Andreev bound states and proximity effect that depends on the crystal orientation of the junction interface. PMID:12731995

Tanaka, Y; Nazarov, Yu V; Kashiwaya, S

2003-04-25

154

Nanowire transistors without junctions  

Microsoft Academic Search

All existing transistors are based on the use of semiconductor junctions formed by introducing dopant atoms into the semiconductor material. As the distance between junctions in modern devices drops below 10 nm, extraordinarily high doping concentration gradients become necessary. Because of the laws of diffusion and the statistical nature of the distribution of the doping atoms, such junctions represent an

Jean-Pierre Colinge; Chi-Woo Lee; Aryan Afzalian; Nima Dehdashti Akhavan; Ran Yan; Isabelle Ferain; Pedram Razavi; Brendan O'Neill; Alan Blake; Mary White; Anne-Marie Kelleher; Brendan McCarthy; Richard Murphy

2010-01-01

155

Chaos in Josephson tunnel junctions  

SciTech Connect

Experimental data have been obtained confirming the theoretical assumption of chaos existence in superconducting tunnel junctions (STJ) with hysteretic I-V curve (IVC) in the presence of the external microwave radiation for zero bias current. The dynamic of the chaos formation was investigated and the chaos intensity was estimated. Observation of chaotic oscillations for bias current smaller than the critical current are reported and discussed.

Gubankov, V.; Konstantinyan, K.; Koshelets, V.; Ovsyannikov, G.

1983-05-01

156

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

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. PMID:21441318

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

2011-05-01

157

Gel electrophoretic analysis of DNA branched junctions.  

PubMed

Gel electrophoresis has provided much of the detailed information we have about the properties of DNA junctions, stable branched molecules formed from oligonucleotide or polynucleotide strands. Here we review these applications, and present the results of an electrophoretic investigation of conformationally restricted junctions formed by covalently connecting two different pairs of strands in a junction with four arms. Native gel electrophoresis is employed to establish the formation and stoichiometry of the multistrand complexes. Ferguson analysis of native gel mobility shows that junctions have retardation coefficients that are distinct from those of linear DNA duplexes. Denaturing gel electrophoresis is the primary tool for characterizing junctions that have been covalently linked together to form both linear and macrocyclic oligomers of junctions (oligojunctions). Radioactively labelled strands enable one to monitor the progress of the ligation reaction: both linear and closed cyclic molecules result, and these can be distinguished by applying Ferguson analysis to denaturing gels. Combinations of exonuclease III, restriction enzymes and sequencing reactions have been applied to oligojunction molecules, and the results are all analyzed on denaturing gels. Junctions containing intramolecular "tethers" that restrict the conformation freedom of the complex comprise a new system for analyzing the conformations of branched molecules. In these tethered junctions, the ability of arms to move relative to each other is restricted substantially by covalently connecting pairs of arms in the original complex with short, flexible loops. The two tethers used here constrain the helical domains of the structure to be roughly parallel or anti-parallel. In this article, we use Ferguson analysis to compare two tethered junctions with an untethered junction. At high gel concentrations, the mobility of the untethered complex is found to be closer to that of the molecule tethered anti-parallel than to the one tethered parallel. Curvature in the Ferguson plots for all three of these junctions is detected over a range of compositions. At low gel concentrations, differences in electrophoretic mobility persist, suggesting that the untethered junction differs in charge as well as conformational freedom from the tethered analogs. We expect that studies of this kind will be able to define the conformational repertoire of junctions of different kinds, and to explore the effects of electrophoresis on these states. PMID:2548837

Seeman, N C; Chen, J H; Kallenbach, N R

1989-01-01

158

Inducible expression of claudin-1-myc but not occludin-VSV-G results in aberrant tight junction strand formation in MDCK cells.  

PubMed

Occludin and 18 distinct members of the claudin family are tetra-span transmembrane proteins that are localized in cell-specific tight junctions (TJs). A previous study showed that expression of chick occludin in Madin-Darby canine kidney (MDCK) cells raised transepithelial electrical resistance (TER) and, paradoxically, increased mannitol flux. In the present study, we employed epitope tagged canine occludin expression, under the control of the tetracycline repressible transactivator, to determine the extent to which the unexpected parallel increase in TER and mannitol flux was related to a structural mismatch between avian and canine occludins, which are only 50% identical. To determine whether the paradoxical changes in permeability was specific to occludin, we assessed the effect of over-expressing epitope tagged murine claudin-1. Our data revealed that over-expression of either of the epitope tagged mammalian tight junction proteins increased TER, mannitol and FITC-dextran flux. We observed a 2- and up to 5.6-fold over-expression of occludin-VSV-G and claudin-1-myc, respectively, with no change in ZO-1, endogenous occludin or claudin-1 expression. Confocal microscopy revealed that occludin-VSV-G, claudin-1-myc and ZO-1 co-localized at the TJ. In addition, claudin-1-myc formed aberrant strands along the lateral cell surface without an underlying ZO-1 scaffold. In fracture labeled replicas these strands consisted of claudin-1-myc with little accompanying occludin. These observations suggest that in epithelial cells claudin-1 can assemble into TJ strands without the participation of either ZO-1 or occludin. The proximity of the myc tag to the COOH-terminal YV sequence of claudin-1 appeared to interfere with its interaction with ZO-1, since over-expression of non-tagged claudin-1 increased TER but had a minimal effect on solute flux and no aberrant strands formed. From our data we conclude that differences in structure between avian and mammalian occludin do not account for the observed paradoxical increase in mannitol flux. Levels of ZO-1 remained unchanged despite substantial increases in induced TJ integral protein expression, suggesting that an imbalance between levels of ZO-1 and occludin or claudin-1 leads to altered regulation of pores through which non-charged solute flux occurs. We suggest that ion and solute flux are differentially regulated at the TJ. PMID:10984430

McCarthy, K M; Francis, S A; McCormack, J M; Lai, J; Rogers, R A; Skare, I B; Lynch, R D; Schneeberger, E E

2000-10-01

159

Can gap junctions deliver?  

PubMed

In vivo delivery of small interfering RNAs (siRNAs) to target cells via the extracellular space has been hampered by dilution effects and immune responses. Gap junction-mediated transfer between cells avoids the extracellular space and its associated limitations. Because of these advantages cell based delivery via gap junctions has emerged as a viable alternative for siRNA or miRNA delivery. Here we discuss the advantages and disadvantages of extracellular delivery and cell to cell delivery via gap junction channels composed of connexins. This article is part of a Special Issue entitled: The Communicating junctions, composition, structure and characteristics. PMID:21986484

Brink, Peter R; Valiunas, Virginijus; Gordon, Chris; Rosen, Michael R; Cohen, Ira S

2012-08-01

160

Metal Silicides: Active elements of ULSI contacts  

NASA Astrophysics Data System (ADS)

As device dimensions scale to the 0.1 urn regime, the self-aligned suicide (SALICIDE) contact technology increasingly becomes an integral part of both the ultra-shallow junction and the metal oxide semiconductor field-effect transistor device itself. This paper will discuss the effect of suicide materials and formation processes on suicide stability, junction consumption, the ability to accurately profile shallow junctions, and contact resistance in series with the channel. The use of suicides as diffusion sources (SADS) provides an important pathway toward optimization of suicide technology. Diffusion of boron and arsenic from nearly epitaxial layers of CoSi2, formed from bilayers of Ti and Co, offer good suicide stability, ultra-shallow, low-leakage junctions, and low contact resistance.

Osburn, C. M.; Tsai, J. Y.; Sun, J.

1996-11-01

161

SHH AND GLI3 REGULATE FORMATION OF THE TELENCEPHALIC-DIENCEPHALIC JUNCTION AND SUPPRESS AN ISTHMUS-LIKE SIGNALING SOURCE IN THE FOREBRAIN  

PubMed Central

In human holoprosencephaly (HPE), the forebrain does not separate fully into two hemispheres. Further, the border between the telencephalon and diencephalon, the telencephalic/diencephalic junction (TDJ), is often indistinct, and the ventricular system can be blocked at the third ventricle, creating a forebrain ‘holosphere’. Mice deficient in Sonic Hedgehog (Shh) have previously been described to show HPE and associated cyclopia. Here we report that the third ventricle is blocked in Shh null mutants, similar to human HPE, and that characteristic telencephalic and diencephalic signaling centers, the cortical hem and zona limitans intrathalamica (ZLI), are merged, obliterating the TDJ. The resulting forebrain holosphere comprises Foxg1-positive telencephalic- and Foxg1-negative diencephalic territories. Loss of one functional copy of Gli3 in Shh nulls rescues ventricular collapse and substantially restores the TDJ. Characteristic regional gene expression patterns are rescued on the telencephalic side of the TDJ but not in the diencephalon. Further analysis of compound Shh;Gli3 mutants revealed an unexpected type of signaling center deregulation. In Shh;Gli3 mutants, adjacent rings of Fgf8 and Wnt3a expression are induced in the diencephalon at the ZLI, reminiscent of the Fgf8/Wnt1-expressing isthmic organizer. Neither Shh nor Gli3 single mutants show this forebrain double ring of Fgf/Wnt expression; thus both Shh and Gli3 are independently required to suppress it. Adjacent tissue is not respecified to a midbrain/hindbrain fate, but shows overgrowth, consistent with ectopic mitogen expression. Our observations indicate that the separation of the telencephalon and diencephalon depends on interactions between Shh and Gli3, and, moreover, demonstrate that both Shh and Gli3 suppress a potential Fgf/Wnt signaling source in the forebrain. That optional signaling centers are actively repressed in normal development is a striking new insight into the processes of vertebrate brain development.

Grove, Elizabeth A.

2011-01-01

162

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

163

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

SciTech Connect

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

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

2005-10-15

164

Three-junction solar cell  

DOEpatents

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

Ludowise, Michael J. (Cupertino, CA) [Cupertino, CA

1986-01-01

165

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

2013-06-15

166

Junctional adhesion molecules in angiogenesis.  

PubMed

The process of new blood vessel formation from pre-existing vessels is known as angiogenesis. This process is important, both during physiological processes such as development and during wound healing, as well as during pathological processes, such as cancer and arthritis. Understanding the molecular mechanism of the regulation of angiogenesis and the identification of the key players involved in this process may help identify new therapeutic targets to combat and control angiogenesis and hence arthritis and cancer. This review focuses on a recently identified novel cell adhesion molecule, Junctional Adhesion Molecule A, and its role in the process of regulating angiogenesis. PMID:17981544

Naik, Tejal U; Naik, Meghna U; Naik, Ulhas P

2008-01-01

167

Holliday junctions in the eukaryotic nucleus: resolution in sight?  

PubMed

The Holliday junction is a key recombination intermediate whose resolution generates crossovers. Interplay between recombination, repair and replication has moved the Holliday junction to the center stage of nuclear DNA metabolism. Holliday junction resolvases in the eukaryotic nucleus have long eluded identification. The endonucleases Mus81/Mms4-Eme1 and XPF-MEI-9/MUS312 are structurally related to the archaeal resolvase Hjc and were found to be involved in crossover formation in budding yeast and flies, respectively. Although these endonucleases might represent one class of eukaryotic resolvases, their substrate preference opens up the possibility that junctions other than classical Holliday junctions might contribute to crossovers. Holliday junction resolution to non-crossover products can also be achieved topologically, for example, by the action of RecQ-like DNA helicases combined with topoisomerase III. PMID:14559184

Heyer, Wolf Dietrich; Ehmsen, Kirk T; Solinger, Jachen A

2003-10-01

168

Organization of multiprotein complexes at cell-cell junctions  

PubMed Central

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

2008-01-01

169

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

Microsoft Academic Search

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

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

2010-01-01

170

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

Microsoft Academic Search

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

P. Binétruy; A. Bohé; T. Hertog; D. A. Steer

2010-01-01

171

Talin at myotendinous junctions  

PubMed Central

Junctions formed by skeletal muscles where they adhere to tendons, called myotendinous junctions, are sites of tight adhesion and where forces generated by the cell are placed on the substratum. In this regard, myotendinous junctions and focal contacts of fibroblasts in vitro are analogues. Talin is a protein located at focal contacts that may be involved in force transmission from actin filaments to the plasma membrane. This study investigates whether talin is also found at myotendinous junctions. Protein separations on SDS polyacrylamide gels and immunolabeling procedures show that talin is present in skeletal muscle. Immunofluorescence microscopy using anti-talin indicates that talin is found concentrated at myotendinous junctions and in lesser amounts in periodic bands over nonjunctional regions. Electron microscopic immunolabeling shows talin is a component of the digitlike processes of muscle cells that extend into tendons at myotendinous junctions. These findings indicate that there may be similarities in the molecular composition of focal contacts and myotendinous junctions in addition to functional analogies.

1986-01-01

172

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

2012-09-12

173

Oxidative Stress, Lens Gap Junctions, and Cataracts  

PubMed Central

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

Beyer, Eric C.

2009-01-01

174

Studies of silicon PN junction solar cells  

NASA Technical Reports Server (NTRS)

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

Lindholm, F. A.

1975-01-01

175

T-Junction Benchmark  

SciTech Connect

Part 1: Two different volume renderings of fluid temperatures in a turbulent T-junction mixing problem at Reynolds number Re=40,000. Part 2: Volume rendering of fluid temperatures in a turbulent T-junction mixing problem at Reynolds number Re=40,000, simulated using Nek5000 at three different resolutions. Part 3: Temperature distribution for a turbulent T-junction mixing problem at Reynolds number Re=40,000, simulated using Nek5000 with 89056 spectral elements of order N=9 (65 million grid points). Credits: Science: Aleks Obabko and Paul Fisher, Argonne National Laboratory? Visualization: Hank Childs, Lawrence Berkeley National Laboratory?? This research used resources of the Argonne Leadership Computing Facility at Argonne National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under contract DE-AC02-06CH11357

None

2010-01-01

176

Resealing of endothelial junctions by focal adhesion kinase.  

PubMed

Endothelial cell (EC) junctions determine vascular barrier properties and are subject to transient opening to allow liquid flux from blood to tissue. Although EC junctions open in the presence of permeability-enhancing factors, including oxidants, the mechanisms by which they reseal remain inadequately understood. To model opening and resealing of EC junctions in the presence of an oxidant, we quantified changes in H(2)O(2)-induced transendothelial resistance (TER) in monolayers of rat lung microvascular EC. During a 30-min exposure, H(2)O(2) (100 microM) decreased TER for an initial approximately 10 min, indicating junctional opening. Subsequently, despite continuous presence of H(2)O(2), TER recovered to baseline, indicating the activation of junctional resealing mechanisms. These bimodal TER transients matched the time course of loss and then gain of E-cadherin at EC junctions. The timing of the TER decrease matched the onset of focal adhesion formation, while F-actin increase at the cell periphery occurred with a time course that complemented the recovery of peripheral E-cadherin. In monolayers expressing a focal adhesion kinase (FAK) mutant (del-FAK) that inhibits FAK activity, the initial H(2)O(2)-induced junctional opening was present, although the subsequent junctional recovery was blocked. Expression of transfected E-cadherin was evident at the cell periphery of wild-type but not del-FAK-expressing EC. E-cadherin overexpression in del-FAK-expressing EC failed to effect major rescue of the junctional resealing response. These findings indicate that in oxidant-induced EC junction opening, FAK plays a critical role in remodeling the adherens junction to reseal the barrier. PMID:17012369

Quadri, Sadiqa K; Bhattacharya, Jahar

2007-01-01

177

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

178

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

Microsoft Academic Search

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

Carien M Niessen

2007-01-01

179

Electronic Properties of Carbon Nanotubes and Junctions  

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

180

Ubiquitination of Gap Junction Proteins  

Microsoft Academic Search

Gap junctions are plasma membrane domains containing arrays of channels that exchange ions and small molecules between neighboring\\u000a cells. Gap junctional intercellular communication enables cells to directly cooperate both electrically and metabolically.\\u000a Several lines of evidence indicate that gap junctions are important in regulating cell growth and differentiation and for\\u000a maintaining tissue homeostasis. Gap junction channels consist of a family

Edward Leithe; Edgar Rivedal

2007-01-01

181

Dynamics of ?-junction interferometer circuits  

Microsoft Academic Search

The ?-junction superconducting circuit dynamics was studied by means of numerical simulation technique. Parallel arrays consisting of Josephson junctions of both 0- and ?-type were studied as a model of high-Tc grain-boundary Josephson junction. The array dynamics and the critical current dependence on magnetic field are discussed. Experimental results for dc interferometers with 0 and ? high-Tc bi-crystal Josephson junctions

I. V. Borisenko; P. B. Mozhaev; G. A. Ovsyannikov; N. F. Pedersen

2002-01-01

182

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

183

Exogenous Expression of the Amino-Terminal Half of the Tight Junction Protein Zo-3 Perturbs Junctional Complex Assembly  

PubMed Central

The functional characteristics of the tight junction protein ZO-3 were explored through exogenous expression of mutant protein constructs in MDCK cells. Expression of the amino-terminal, PSD95/dlg/ZO-1 domain-containing half of the molecule (NZO-3) delayed the assembly of both tight and adherens junctions induced by calcium switch treatment or brief exposure to the actin-disrupting drug cytochalasin D. Junction formation was monitored by transepithelial resistance measurements and localization of junction-specific proteins by immunofluorescence. The tight junction components ZO-1, ZO-2, endogenous ZO-3, and occludin were mislocalized during the early stages of tight junction assembly. Similarly, the adherens junction proteins E-cadherin and ?-catenin were also delayed in their recruitment to the cell membrane, and NZO-3 expression had striking effects on actin cytoskeleton dynamics. NZO-3 expression did not alter expression levels of ZO-1, ZO-2, endogenous ZO-3, occludin, or E-cadherin; however, the amount of Triton X-100–soluble, signaling-active ?-catenin was increased in NZO-3–expressing cells during junction assembly. In vitro binding experiments showed that ZO-1 and actin preferentially bind to NZO-3, whereas both NZO-3 and the carboxy-terminal half of the molecule (CZO-3) contain binding sites for occludin and cingulin. We hypothesize that NZO-3 exerts its dominant-negative effects via a mechanism involving the actin cytoskeleton, ZO-1, and/or ?-catenin.

Wittchen, Erika S.; Haskins, Julie; Stevenson, Bruce R.

2000-01-01

184

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

2013-11-15

185

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

186

Plasma-assisted Recoil Implantation for Shallow Boron Doping in Silicon  

Microsoft Academic Search

An ion beam mixing technique is used to fabricate ultra-shallow p+\\/n junctions for the application of sub-micron CMOS source\\/drain formation. In this method, a thin boron layer is first sputtered onto the Si wafer. Then -3kV argon Plasma Source Ion Implantation (PSII) drives the boron atoms into the Si substrate by means of ion beam mixing. This process avoids the

H. L. Liu; S. S. Gearhart; J. H. Booske; W. Wang

1997-01-01

187

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

PubMed

We use Wertheim's first-order perturbation theory to investigate the phase behaviour and the structure of coexisting fluid phases for a model of patchy particles with dissimilar patches (two patches of type A and f(B) patches of type B). A patch of type ? = {A,B} can bond to a patch of type ? = {A,B} in a volume v(??), thereby decreasing the internal energy by ?(??). We analyse the range of model parameters where AB bonds, or Y-junctions, are energetically disfavoured (?(AB) < ?(AA)/2) but entropically favoured (v(AB) ? v(??)), and BB bonds, or X-junctions, are energetically favoured (?(BB) > 0). We show that, for low values of ?(BB)/?(AA), the phase diagram has three different regions: (i) close to the critical temperature a low-density liquid composed of long chains and rich in Y-junctions coexists with a vapour of chains; (ii) at intermediate temperatures there is coexistence between a vapour of short chains and a liquid of very long chains with X- and Y-junctions; (iii) at low temperatures an ideal gas coexists with a high-density liquid with all possible AA and BB bonds formed. It is also shown that in region (i) the liquid binodal is reentrant (its density decreases with decreasing temperature) for the lower values of ?(BB)/?(AA). The existence of these three regions is a consequence of the competition between the formation of X- and Y-junctions: X-junctions are energetically favoured and thus dominate at low temperatures, whereas Y-junctions are entropically favoured and dominate at higher temperatures. PMID:22738863

Tavares, J M; Teixeira, P I C

2012-07-18

188

Phosphatase regulation of intercellular junctions  

PubMed Central

Intercellular junctions represent the key contact points and sites of communication between neighboring cells. Assembly of these junctions is absolutely essential for the structural integrity of cell monolayers, tissues and organs. Disruption of junctions can have severe consequences such as diarrhea, edema and sepsis, and contribute to the development of chronic inflammatory diseases. Cell junctions are not static structures, but rather they represent highly dynamic micro-domains that respond to signals from the intracellular and extracellular environments to modify their composition and function. This review article will focus on the regulation of tight junctions and adherens junctions by phosphatase enzymes that play an essential role in preserving and modulating the properties of intercellular junction proteins.

McCole, Declan F

2013-01-01

189

Transverse junction stripe laser  

SciTech Connect

This patent describes a semiconductor laser the structure, comprising in combination: a substrate including first and second surface sections having different crystallographic orientation, a semiconductor laser formed on the substrate and including an active layer extending laterally over the first and second surface sections and having a p-n junction therein extending in a direction substantially transverse to the surface of the active layer, radiation being produced by the presence of an electrical current across the transaverse p-n junction of a magnitude above a threshold value for lasing, the active layer being amphoterically doped to produce by crystal plane dependent doping a first n-type region therein where the active layer is adjacent to the first surface section of the substrate and a second p- type region where the active layer is adjacent the second surface region of the substrate, and electrical means for producing an electrical current across the transverse p-n junction of a magnitude greater than the threshold value to produce lasing radiation in the active layer.

Harder, C.S.; Jaekel, H.; Meier, H.P.

1989-02-14

190

Connexins, gap junctions and tissue invasion.  

PubMed

Formation of metastases negatively impacts the survival prognosis of cancer patients. Globally, if the various steps involved in their formation are relatively well identified, the molecular mechanisms responsible for the emergence of invasive cancer cells are still incompletely resolved. Elucidating what are the mechanisms that allow cancer cells to evade from the tumor is a crucial point since it is the first step of the metastatic potential of a solid tumor. In order to be invasive, cancer cells have to undergo transformations such as down-regulation of cell-cell adhesions, modification of cell-matrix adhesions and acquisition of proteolytic properties. These transformations are accompanied by the capacity to "activate" stromal cells, which may favor the motility of the invasive cells through the extracellular matrix. Since modulation of gap junctional intercellular communication is known to be involved in cancer, we were interested to consider whether these different transformations necessary for the acquisition of invasive phenotype are related with gap junctions and their structural proteins, the connexins. In this review, emerging roles of connexins and gap junctions in the process of tissue invasion are proposed. PMID:24457198

Defamie, Norah; Chepied, Amandine; Mesnil, Marc

2014-04-17

191

Tight junctions in human pancreatic duct epithelial cells  

PubMed Central

Tight junctions of the pancreatic duct are essential regulators of physiologic secretion of the pancreas and disruption of the pancreatic ductal barrier is known to contribute to the pathogenesis of pancreatitis and progression of pancreatic cancer. Various inflammatory mediators and carcinogens can trigger tight junction disassembly and disruption of the pancreatic barrier, however signaling events that mediates such barrier dysfunctions remain poorly understood. This review focuses on structure and regulation of tight junctions in normal pancreatic epithelial cells and mechanisms of junctional disruption during pancreatic inflammation and cancer. We will pay special attention to a novel model of human telomerase reverse transcriptase-transfected human pancreatic ductal epithelial cells and will describe the roles of major signaling molecules such as protein kinase C and c-Jun N-terminal kinase in formation and disassembly of the pancreatic ductal barrier.

Kojima, Takashi; Yamaguchi, Hiroshi; Ito, Tatsuya; Kyuno, Daisuke; Kono, Tsuyoshi; Konno, Takumi; Sawada, Norimasa

2013-01-01

192

Mitochondrial apoptosis is amplified through gap junctions  

PubMed Central

The death of one cell can precipitate the death of nearby cells in a process referred to as the bystander effect. We investigated whether mitochondrial apoptosis generated a bystander effect and, if so, by which pathway. Microinjection with cytochrome c mimicked function of the mitochondrial apoptosis-induced channel MAC and caused apoptosis of both target and nearby osteoblasts. This effect was suppressed by inhibiting gap junction intercellular communication. A bystander effect was also observed after exogenous expression of tBid, which facilitates MAC formation and cytochrome c release. Interestingly, in connexin-43 deficient osteoblasts, microinjection of cytochrome c induced apoptosis only in the target cell. These findings indicate that a death signal was generated downstream of MAC function and was transmitted through gap junctions to amplify apoptosis in neighboring cells. This concept may have implications in development of new therapeutic approaches.

Peixoto, Pablo M.; Ryu, Shin-Young; Pietkiewicz-Pruzansky, Dawn; Kuriakose, Maria; Gilmore, Andrew; Kinnally, Kathleen W.

2009-01-01

193

Assembly of the Escherichia coli RuvABC resolvasome directs the orientation of Holliday junction resolution  

PubMed Central

Genetic recombination can lead to the formation of intermediates in which DNA molecules are linked by Holliday junctions. Movement of a junction along DNA, by a process known as branch migration, leads to heteroduplex formation, whereas resolution of a junction completes the recombination process. Holliday junctions can be resolved in either of two ways, yielding products in which there has, or has not, been an exchange of flanking markers. The ratio of these products is thought to be determined by the frequency with which the two isomeric forms (conformers) of the Holliday junction are cleaved. Recent studies with enzymes that process Holliday junctions in Escherichia coli, the RuvABC proteins, however, indicate that protein binding causes the junction to adopt an open square-planar configuration. Within such a structure, DNA isomerization can have little role in determining the orientation of resolution. To determine the role that junction-specific protein assembly has in determining resolution bias, a defined in vitro system was developed in which we were able to direct the assembly of the RuvABC resolvasome. We found that the bias toward resolution in one orientation or the other was determined simply by the way in which the Ruv proteins were positioned on the junction. Additionally, we provide evidence that supports current models on RuvABC action in which Holliday junction resolution occurs as the resolvasome promotes branch migration.

van Gool, Alain J.; Hajibagheri, Nasser M.A.; Stasiak, Andrzej; West, Stephen C.

1999-01-01

194

Random instability in Josephson junctions  

SciTech Connect

The experimental observation and study of random oscillations in Josephson junction with a IV characteristic exhibiting hysteresis during the application of an external microwave power are reported. (AIP)

Gubankov, V.N.; Konstantinyan, K.I.; Koshelets, V.P.; Ovsyannikov, G.A.

1982-11-01

195

An induced junction photovoltaic cell  

NASA Technical Reports Server (NTRS)

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

Call, R. L.

1974-01-01

196

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

Microsoft Academic Search

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

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

2011-01-01

197

Thermoelectric Properties of Nanotube Junctions  

NASA Astrophysics Data System (ADS)

We calculate the thermoelectric properties of several kinds of carbon nanotube junctions using the Landauer formalism. Several junction geometries are considered, including end-to-end, side-by-side, and crossed tubes. All of these geometries should be present in nanotube mats.

Esfarjani, Keivan; Poorman, Leif

2007-03-01

198

Dynamics of adherens junctions in epithelial establishment, maintenance, and remodeling  

PubMed Central

The epithelial cadherin (E-cadherin)–catenin complex binds to cytoskeletal components and regulatory and signaling molecules to form a mature adherens junction (AJ). This dynamic structure physically connects neighboring epithelial cells, couples intercellular adhesive contacts to the cytoskeleton, and helps define each cell’s apical–basal axis. Together these activities coordinate the form, polarity, and function of all cells in an epithelium. Several molecules regulate AJ formation and integrity, including Rho family GTPases and Par polarity proteins. However, only recently, with the development of live-cell imaging, has the extent to which E-cadherin is actively turned over at junctions begun to be appreciated. This turnover contributes to junction formation and to the maintenance of epithelial integrity during tissue homeostasis and remodeling.

Baum, Buzz

2011-01-01

199

Terahertz pulse driven Josephson junctions  

NASA Astrophysics Data System (ADS)

The voltage response of a Josephson junction to a pulsed terahertz current is evaluated in the limit of a negligible junction capacitance (overdamped limit). The time-dependent superconductor phase difference across the junction is calculated in the framework of the standard resistive shunted junction model by using a perturbative method. The pulsed current bias affects the time average value of the voltage across the junction and current steps are induced in the current-voltage characteristics for voltage values depending on the pulse repetition rate. The current step height is proportional to the square of the pulse time width ( ?) to the period ( T) ratio. A fast response detector for pulsed Terahertz radiation is proposed, with an expected responsivity of the order of 0.1 V/W and an equivalent noise power of about 3 × 10 -10 W/Hz 1/2.

Camerlingo, Carlo

2011-09-01

200

PCBS AND TIGHT JUNCTION EXPRESSION  

PubMed Central

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

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

2008-01-01

201

Organic single-crystalline p-n junction nanoribbons.  

PubMed

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

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

2010-08-25

202

The influence of junction depth on short channel effects in vertical sidewall MOSFETs  

NASA Astrophysics Data System (ADS)

This work addresses a fundamental problem of vertical MOSFETs, that is, inherently deep junctions that exacerbate short channel effects (SCEs). Due to the unconventional asymmetric junction depths in vertical MOSFETs, it is necessary to look separately at the electrostatic influence of each junction. In order to suppress short channel effects better, we explore the formation of a shallow drain junction. This is realized by a self-aligned oxide region, or junction stop (JS) which is formed at the pillar top and acts as a diffusion barrier for shallow junction formation. The benefits of using a JS structure in vertical MOSFETs are demonstrated by simulations which show clearly the effect of asymmetric junctions on SCEs and bulk punch-through. A critical point is identified, where control of SCEs by junction depth is lost and this leads to appropriate junction design in JS vertical sidewall MOSFETs. For a 70 nm channel length the JS structure improves charge sharing by 54 mV and DIBL by 46 mV. For body dopings of 5.0 × 10 17 cm -3 and 6.0 × 10 17 cm -3 the JS gives improvements in Ioff of 58.7% and 37.8%, respectively, for a given Ion. The inclusion of a retrograde channel gives a further increase in Ion of 586 ?A/?m for a body doping of 4.0 × 10 18 cm -3.

Tan, Lizhe; Buiu, Octavian; Hall, Stephen; Gili, Enrico; Uchino, Takashi; Ashburn, Peter

2008-07-01

203

Thermal Stability of Cu/NiSi-Contacted p+n Shallow Junction  

NASA Astrophysics Data System (ADS)

The thermal stability of Cu/NiSi-contacted p+n shallow junction diodes was investigated with respect to their electrical characteristics and metallurgical reactions. The TaN/Cu/NiSi/p+n junction diode remained intact after 30 min thermal annealing at temperatures of up to 350°C. Upon annealing at 375°C, a marked increase in reverse bias leakage current occurred, and secondary ion mass spectrometry (SIMS) analysis indicated that Cu started to penetrate into the NiSi-contacted shallow junction region. After a higher temperature annealing at 425°C, a Cu3Si phase was formed. The failure of the TaN/Cu/NiSi/p+n junction diodes is attributed to the penetration of Cu through the NiSi layer into the junction region, leading to junction degradation by introducing deep-level trap states and the eventual formation of Cu3Si.

Wang, Chao-Chun; Lin, Hsin-Hung; Chen, Mao-Chieh

2004-09-01

204

Discovering the Molecular Components of Intercellular Junctions--A Historical View  

PubMed Central

The organization of metazoa is based on the formation of tissues and on tissue-typical functions and these in turn are based on cell–cell connecting structures. In vertebrates, four major forms of cell junctions have been classified and the molecular composition of which has been elucidated in the past three decades: Desmosomes, which connect epithelial and some other cell types, and the almost ubiquitous adherens junctions are based on closely cis-packed glycoproteins, cadherins, which are associated head-to-head with those of the hemi-junction domain of an adjacent cell, whereas their cytoplasmic regions assemble sizable plaques of special proteins anchoring cytoskeletal filaments. In contrast, the tight junctions (TJs) and gap junctions (GJs) are formed by tetraspan proteins (claudins and occludins, or connexins) arranged head-to-head as TJ seal bands or as paracrystalline connexin channels, allowing intercellular exchange of small molecules. The by and large parallel discoveries of the junction protein families are reported.

Franke, Werner W.

2009-01-01

205

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

206

Microtubule Plus-End-Tracking Proteins Target Gap Junctions Directly from the Cell Interior to Adherens Junctions  

PubMed Central

SUMMARY Gap junctions are intercellular channels that connect the cytoplasms of adjacent cells. For gap junctions to properly control organ formation and electrical synchronization in the heart and the brain, connexin-based hemichannels must be correctly targeted to cell-cell borders. While it is generally accepted that gap junctions form via lateral diffusion of hemichannels following microtubule-mediated delivery to the plasma membrane, we provide evidence for direct targeting of hemichannels to cell-cell junctions through a pathway that is dependent on microtubules; through the adherens-junction proteins N-cadherin and ?-catenin; through the microtubule plus-end-tracking protein (+TIP) EB1; and through its interacting protein p150(Glued). Based on live cell microscopy that includes fluorescence recovery after photobleaching (FRAP), total internal reflection fluorescence (TIRF), deconvolution, and siRNA knockdown, we propose that preferential tethering of microtubule plus ends at the adherens junction promotes delivery of connexin hemichannels directly to the cell-cell border. These findings support an unanticipated mechanism for protein delivery to points of cell-cell contact.

Shaw, Robin M.; Fay, Alex J.; Puthenveedu, Manojkumar A.; von Zastrow, Mark; Jan, Yuh-Nung; Jan, Lily Y.

2007-01-01

207

Aberrant expression of tight junction-related proteins ZO-1, claudin-1 and occludin in synovial sarcoma: an immunohistochemical study with ultrastructural correlation  

Microsoft Academic Search

Synovial sarcoma demonstrates epithelial differentiation, either by light microscopy (biphasic synovial sarcoma) or by immunohistochemical\\/ultrastructural methods only (monophasic) and poorly differentiated synovial sarcoma. Although the glands of synovial sarcoma are known to have tight junction-like structures, far less is known about junction formation in the spindled component of synovial sarcomas. Additionally, it is unknown whether the tight junctions of synovial

Steven D Billings; Shaun V Walsh; Cyril Fisher; Asma Nusrat; Sharon W Weiss; Andrew L Folpe; AL Folpe

2004-01-01

208

Junctional trafficking and epithelial morphogenesis  

PubMed Central

Summary Epithelial monolayers are major determinants of three-dimensional tissue organization and provide the structural foundation for the body plan and all of its component organs. Epithelial cells are connected by junctional complexes containing the cell adhesion molecule E-cadherin. These adherens junctions mediate stable cohesion between cells but must be actively reorganized to allow tissue remodeling during development. Recent studies demonstrate that junctional proteins are dynamically turned over at the cell surface, even in cells that do not appear to be moving. The redistribution of E-cadherin through spatially regulated endocytosis and exocytosis contributes to cell adhesion, cell polarity, and is also involved in cell rearrangement. Here we describe recent progress in understanding the roles of the vesicle transport machinery in regulating cell adhesion and junctional dynamics during epithelial morphogenesis in vivo.

Wirtz-Peitz, Frederik; Zallen, Jennifer A.

2009-01-01

209

Josephson junction Q-spoiler  

DOEpatents

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

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

1986-03-25

210

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

211

Rap1 potentiates endothelial cell junctions by spatially controlling myosin II activity and actin organization  

PubMed Central

Reorganization of the actin cytoskeleton is responsible for dynamic regulation of endothelial cell (EC) barrier function. Circumferential actin bundles (CAB) promote formation of linear adherens junctions (AJs) and tightening of EC junctions, whereas formation of radial stress fibers (RSF) connected to punctate AJs occurs during junction remodeling. The small GTPase Rap1 induces CAB formation to potentiate EC junctions; however, the mechanism underlying Rap1-induced CAB formation remains unknown. Here, we show that myotonic dystrophy kinase–related CDC42-binding kinase (MRCK)-mediated activation of non-muscle myosin II (NM-II) at cell–cell contacts is essential for Rap1-induced CAB formation. Our data suggest that Rap1 induces FGD5-dependent Cdc42 activation at cell–cell junctions to locally activate the NM-II through MRCK, thereby inducing CAB formation. We further reveal that Rap1 suppresses the NM-II activity stimulated by the Rho–ROCK pathway, leading to dissolution of RSF. These findings imply that Rap1 potentiates EC junctions by spatially controlling NM-II activity through activation of the Cdc42–MRCK pathway and suppression of the Rho–ROCK pathway.

Ando, Koji; Moriya, Takahiro; Obara, Yutaro; Nakahata, Norimichi

2013-01-01

212

Wnt Signaling in Neuromuscular Junction Development  

PubMed Central

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

Koles, Kate

2012-01-01

213

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

214

Characterisation of dark current in novel Hg 1? x Cd x Te mid-wavelength infrared photovoltaic detectors based on n-on-p junctions formed by plasma-induced type conversion  

Microsoft Academic Search

This paper reports initial characterisation results for planar mid-wavelength infrared (MWIR) photodiodes fabricated using a novel reactive ion plasma-induced n-on-p junction formation technology on vacancy-doped p-type HgCdTe grown by LPE on CdZnTe substrates. The junction is formed without the need for post-implant annealing typically required by ion implantation junction formation techniques to repair damage or to move the junction away

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

2000-01-01

215

Graphene-based tunnel junction  

NASA Astrophysics Data System (ADS)

The tunneling current in a junction formed by graphene half-planes and bilayer graphene with two possible packing types and two possible orientations of the crystal lattice is calculated by the Green's function technique in the framework of the tight-binding approximation. It is shown that the band structure of graphene oriented toward the junction by the armchair-type edges leads to a power-law dependence of the tunneling current on applied voltage being specific for each specific kind of graphene. The characteristic features of this dependence are determined by the change in the number of transport channels with the growth of the applied voltage. For all junctions under study with zigzag edges oriented toward each other, it is found that the tunneling current exhibits characteristic peaks related to the existence of the localized edge states. The effects induced by the gate voltage are also studied. For the structures with zigzag edges, it is shown that the effect of switching off/on takes place for the junctions. The junctions formed by the graphene armchair edges do not exhibit any pronounced switching phenomena and the growth of the bias voltage results in higher values of the conductivity.

Katkov, V. L.; Osipov, V. A.

2014-02-01

216

The crystal structures of DNA Holliday junctions.  

PubMed

Nearly 40 years ago, Holliday proposed a four-stranded complex or junction as the central intermediate in the general mechanism of genetic recombination. During the past two years, six single-crystal structures of such DNA junctions have been determined by three different research groups. These structures all essentially adopt the antiparallel stacked-X conformation, but can be classified into three distinct categories: RNA-DNA junctions; ACC trinucleotide junctions; and drug-induced junctions. Together, these structures provide insight into how local and distant interactions help to define the detailed and general physical features of Holliday junctions at the atomic level. PMID:11406378

Ho, P S; Eichman, B F

2001-06-01

217

The Extracellular Architecture of Adherens Junctions Revealed by Crystal Structures of Type I Cadherins  

SciTech Connect

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.

O Harrison; X Jin; S Hong; F Bahna; G Ahlsen; J Brasch; Y Wu; J Vendome; K Felsovalyi; et al.

2011-12-31

218

Probing ?-coupling in molecular junctions  

PubMed Central

Charge transport characteristics for metal–molecule–metal junctions containing two structurally related ?-conjugated systems were studied to probe ?–? interactions in molecular junctions. The first molecule contains a typical ?-conjugated framework derived from phenylene vinylene units, whereas the second has the phenylene vinylene structure interrupted by a [2.2]paracyclophane (pCp) core. Electrochemical investigations were used to characterize the defects and packing density of self-assembled monolayers of the two molecules on gold surfaces and to enable quantitative comparison of their transport characteristics. Current–voltage measurements across molecular junctions containing the two species demonstrate that the pCp moiety yields a highly conductive break in through-bond ?-conjugation. The observed high conductivity is consistent with density functional theory calculations, which demonstrate strong through-space ?–? coupling across the pCp moiety.

Seferos, Dwight S.; Trammell, Scott A.; Bazan, Guillermo C.; Kushmerick, James G.

2005-01-01

219

Junction array carbon nanotube bolometer  

NASA Astrophysics Data System (ADS)

Vertically aligned arrays of multi-walled carbon nanotubes (MWNT forests) irradiated with low-intensity near-infrared laser exhibited bolometric response that became significant with decreasing temperature down from room to about 84 K. High responsivity of 42 V/W with signal bandwidth of about 2600 Hz was observed in the region with a surprisingly small temperature coefficient of resistance. This fact along with peculiar current dependences of material differential photoresistance can be explained by lifting Coulomb blockade in carbon nanotube junctions irradiated with light. A combination of significant bolometric response and nonlinear electrical transport are believed to be characteristic features of the nanostructured junction array system. Investigated material also revealed quite substantial noise with equivalent power of 3 * 10-6 WHz-1/2 that can be reduced by optimization of nanotube junction network in the forest structure.

Kozlov, Mikhail E.

2013-04-01

220

Stability and structure of three-way DNA junctions containing unpaired nucleotides.  

PubMed Central

Non-paired nucleotides stabilize the formation of three-way helical DNA junctions. Two or more unpaired nucleotides located in the junction region enable oligomers ten to fifteen nucleotides long to assemble, forming conformationally homogeneous junctions, as judged by native gel electrophoresis. The unpaired bases can be present on the same strand or on two different strands. Up to five extra bases on one strand have been tested and found to produce stable junctions. The formation of stable structures is favored by the presence of a divalent cation such as magnesium and by high monovalent salt concentration. The order-disorder transition of representative three-way junctions was monitored optically in the ultraviolet and analyzed to quantify thermodynamically the stabilization provided by unpaired bases in the junction region. We report the first measurements of the thermodynamics of adding an unpaired nucleotide to a nucleic acid three-way junction. We find that delta delta G degrees (37 degrees C) = +0.5 kcal/mol for increasing the number of unpaired adenosines from two to three. Three-way junctions having reporter arms 40 base-pairs long were also prepared. Each of the three reporter arms contained a unique restriction site 15 base-pairs from the junction. Asymmetric complexes produced by selectively cleaving each arm were analyzed on native gels. Cleavage of the double helical arm opposite the strand having the two extra adenosines resulted in a complex that migrated more slowly than complexes produced by cleavage at either of the other two arms. It is likely that the strand containing the unpaired adenosines is kinked at an acute angle, forming a Y-shaped, rather than a T-shaped junction. Images

Leontis, N B; Kwok, W; Newman, J S

1991-01-01

221

Simple Electronic Analog of a Josephson Junction.  

ERIC Educational Resources Information Center

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

Henry, R. W.; And Others

1981-01-01

222

Millimeter Wave Generation Using Josephson Junction Arrays.  

National Technical Information Service (NTIS)

Studies have been carried out to develop methods to couple Josephson junction oscillators at frequencies near 100GHz so as to demonstrate the feasibility of Josephson effect sources of reasonable power and impedance. Phase-locking of junctions separated b...

J. E. Lukens

1988-01-01

223

Hysteresis Development in Superconducting Josephson Junctions.  

National Technical Information Service (NTIS)

The resistively and capacitive shunted junction model is used to investigate hysteresis development in superconducting Josephson junctions. Two empirical formulas that relate the hysteresis width and the quasi-particle diffusion length in terms of the jun...

T. F. Refai L. N. Shehata

1988-01-01

224

Crystal structure of a junction between two Z-DNA helices  

PubMed Central

The double helix of DNA, when composed of dinucleotide purine-pyrimidine repeats, can adopt a left-handed helical structure called Z-DNA. For reasons not entirely understood, such dinucleotide repeats in genomic sequences have been associated with genomic instability leading to cancer. Adoption of the left-handed conformation results in the formation of conformational junctions: A B-to-Z junction is formed at the boundaries of the helix, whereas a Z-to-Z junction is commonly formed in sequences where the dinucleotide repeat is interrupted by single base insertions or deletions that bring neighboring helices out of phase. B-Z junctions are shown to result in exposed nucleotides vulnerable to chemical or enzymatic modification. Here we describe the three-dimensional structure of a Z-Z junction stabilized by Z?, the Z-DNA binding domain of the RNA editing enzyme ADAR1. We show that the junction structure consists of a single base pair and leads to partial or full disruption of the helical stacking. The junction region allows intercalating agents to insert themselves into the left-handed helix, which is otherwise resistant to intercalation. However, unlike a B-Z junction, in this structure the bases are not fully extruded, and the stacking between the two left-handed helices is not continuous.

de Rosa, Matteo; de Sanctis, Daniele; Rosario, Ana Lucia; Archer, Margarida; Rich, Alexander; Athanasiadis, Alekos; Carrondo, Maria Armenia

2010-01-01

225

Interconverting Conformations of Slipped-DNA Junctions Formed by Trinucleotide Repeats Affect Repair Outcome  

PubMed Central

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.

2013-01-01

226

A moment solution for waveguide junction problems  

NASA Astrophysics Data System (ADS)

A moment procedure for solving waveguide junction problems is given using the generalized network formulation for aperture problems. As an illustration, the procedure is applied to a transverse planar junction between two uniform cylindrical waveguides. The generalized admittance network representation of the junction is first obtained. Its scattering matrix representation is then deduced from the former representation. A discussion shows that the conservation of complex power technique, which handles the same class of junctions, is a specialization of the moment procedure.

Auda, H.; Harrington, R. F.

1983-07-01

227

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

2010-02-19

228

Normal-Metal/Graphene/Superconductor Tunnel Junctions  

NASA Astrophysics Data System (ADS)

We report on progress with lateral tunneling in N/G/S (Normal-metal/Graphene/Superconductor) tunnel junctions. Our primary approach is the study of systems of the form: Au/Graphene/Nb where lateral tunneling occurs across graphene bridges. Gates are also provided for Fermi-level adjustments in the standard ``FET'' format. Samples are created by e-beam lithography on electronic-grade oxidized Si substrates, using commercially prepared graphene flakes. Raman scattering is used to verify the single-layer nature of samples under study. We discuss the current status of studies designed to observe predicted oscillations in the tunnel conductance of samples with the above-described geometry, associated with Klein tunneling in the graphene films and Andreev reflections at graphene interfaces.

Sun, Nan; Tahy, Kristof; Jena, Debdeep; Xing, Huili; Ruggiero, Steven

2009-03-01

229

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

230

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

231

Quantum shot noise in tunnel junctions  

Microsoft Academic Search

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

Eshel Ben-Jacob; Emil Mottola; G. Schoen

1983-01-01

232

27 CFR 9.164 - River Junction.  

Code of Federal Regulations, 2012 CFR

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

2012-04-01

233

27 CFR 9.164 - River Junction.  

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

2014-04-01

234

27 CFR 9.164 - River Junction.  

Code of Federal Regulations, 2011 CFR

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

2011-04-01

235

27 CFR 9.164 - River Junction.  

Code of Federal Regulations, 2013 CFR

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

2013-04-01

236

A moment solution for waveguide junction problems  

Microsoft Academic Search

A moment procedure for solving waveguide junction problems is given using the generalized network formulation for aperture problems. As an illustration, the procedure is applied to a transverse planar junction between two uniform cylindrical waveguides. The generalized admittance network representation of the junction is first obtained. Its scattering matrix representation is then deduced from the former representation. A discussion shows

H. Auda; R. F. Harrington

1983-01-01

237

Gap junctions and chagas disease.  

PubMed

Gap junction channels provide intercellular communication between cells. In the heart, these channels coordinate impulse propagation along the conduction system and through the contractile musculature, thereby providing synchronous and optimal cardiac output. As in other arrhythmogenic cardiac diseases, chagasic cardiomyopathy is associated with decreased expression of the gap junction protein connexin43 (Cx43) and its gene. Our studies of cardiac myocytes infected with Trypanosoma cruzi have revealed that synchronous contraction is greatly impaired and gap junction immunoreactivity is lost in infected cells. Such changes are not seen for molecules forming tight junctions, another component of the intercalated disc in cardiac myocytes. Transcriptomic studies of hearts from mouse models of Chagas disease and from acutely infected cardiac myocytes in vitro indicate profound remodelling of gene expression patterns involving heart rhythm determinant genes, suggesting underlying mechanisms of the functional pathology. One curious feature of the altered expression of Cx43 and its gene expression is that it is limited in both extent and location, suggesting that the more global deterioration in cardiac function may result in part from spread of damage signals from more seriously compromised cells to healthier ones. PMID:21884887

Adesse, Daniel; Goldenberg, Regina Coeli; Fortes, Fabio S; Jasmin; Iacobas, Dumitru A; Iacobas, Sanda; Campos de Carvalho, Antonio Carlos; de Narareth Meirelles, Maria; Huang, Huan; Soares, Milena B; Tanowitz, Herbert B; Garzoni, Luciana Ribeiro; Spray, David C

2011-01-01

238

Defects, vortices, and critical current in Josephson-junction arrays  

Microsoft Academic Search

The breakdown phenomena of a resistively shunted two-dimensional Josephson-junction array with a single defect driven by an external current at zero temperature are studied numerically. The nonlinear Josephson relation causes the formation of vortices at the tips of the defect at i(v) and thus lowers the current enhancement there. Above a higher critical current the vortices depin from the defect

W. Xia; P. L. Leath

1989-01-01

239

Germanium n-type shallow junction activation dependences  

Microsoft Academic Search

A few of the recent unsatisfactory germanium n-channel metal-oxide-semiconductor field-effect transistor MOSFET experimentations are believed to stem from the poor source and drain n+-p junction formations. In order to explain the primary cause and suggest rectifying solutions, we have examined the activation of common n-type dopants in germanium and the related dependences. These dependences include thermal anneal budget, impurity species,

Chi On Chui; Leonard Kulig; Jean Moran; Wilman Tsai; Krishna C. Saraswat

2005-01-01

240

Cancer of the esophagogastric junction.  

PubMed

In the Western world, there has been an alarming rise in the incidence and prevalence of adenocarcinoma arising at the esophagogastric junction during recent decades. Epidemiological, clinical and pathological data support a sub-classification of adenocarcinomas arising in the vicinity of the esophagogastric junction (AEG) into adenocarcinoma of the distal esophagus (Type I), true carcinoma of the cardia (Type II) and subcardial carcinoma (Type III). While most, if not all, adenocarcinomas of the distal esophagus arise from areas with specialized intestinal metaplasia, which develop as a consequence of chronic gastroesophageal reflux, the etiology and pathogenesis of true carcinoma of the gastric cardia and subcardial gastric cancer is not clear at present. Although a subgroup of true carcinomas of the gastric cardia may also develop within short segments of intestinal metaplasia at the esophagogastric junction, a causal relation between these tumors and gastroesophageal reflux has been difficult to establish. Irrespective of the etiology, a complete removal of the primary tumor and its lymphatic drainage has to be the primary goal of any surgical approach to adenocarcinoma of the esophagogastric junction. Our experience in the management of more than 1000 such patients during the past 18 years suggests that an individualized therapeutic strategy oriented by tumor type and stage results in survival rates superior to those reported with a more indiscriminate approach. This individualized strategy prescribes a transmediastinal esophagectomy with lymphadenectomy in the lower posterior mediastinum and along the celiac axis for Type I tumors, extended total gastrectomy with transhiatal resection of the distal esophagus and D2 lymphadenectomy for Type II and Type III tumors, a limited resection of the esophagogastric junction and distal esophagus with interposition of a pedicled jejunal segment for uT1N0 tumors, and neoadjuvant chemotherapy followed by resection for uT3/T4 tumors. Extensive preoperative staging is essential to allow correct selection of the appropriate therapeutic strategy using this tailored approach. PMID:11525305

Stein, H J; Feith, M; Siewert, J R

2000-07-01

241

Contactin Orchestrates Assembly of the Septate-like Junctions at the Paranode in Myelinated Peripheral Nerve  

Microsoft Academic Search

Rapid nerve impulse conduction depends on specialized membrane domains in myelinated nerve, the node of Ranvier, the paranode, and the myelinated internodal region. We report that GPI-linked contactin enables the formation of the paranodal septate-like axo-glial junctions in myelinated peripheral nerve. Contactin clusters at the paranodal axolemma during Schwann cell myelination. Ablation of contactin in mutant mice disrupts junctional attachment

Mary E. T. Boyle; Erik O. Berglund; Keith K. Murai; Lynne Weber; Elior Peles; Barbara Ranscht

2001-01-01

242

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

243

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

244

Gap Junctions and Connexin Hemichannels Underpin Haemostasis and Thrombosis  

PubMed Central

Background Connexins are a widespread family of membrane proteins that assemble into hexameric hemichannels, also known as connexons. Connexons regulate membrane permeability in individual cells or couple between adjacent cells to form gap junctions and thereby provide a pathway for regulated intercellular communication. We have now examined the role of connexins in platelets, blood cells that circulate in isolation, but upon tissue injury adhere to each other and the vessel wall to prevent blood loss and facilitate wound repair. Methods and Results We report the presence of connexins in platelets, notably connexin37, and that the formation of gap junctions within platelet thrombi is required for the control of clot retraction. Inhibition of connexin function modulated a range of platelet functional responses prior to platelet-platelet contact, and reduced laser induced thrombosis in vivo in mice. Deletion of the Cx37 gene (Gja4) in transgenic mice reduced platelet aggregation, fibrinogen binding, granule secretion and clot retraction indicating an important role for Cx37 hemichannels and gap junctions in platelet thrombus function. Conclusions Together, these data demonstrate that platelet gap junctions and hemichannels underpin the control of haemostasis and thrombosis and represent potential therapeutic targets.

Vaiyapuri, Sakthivel; Jones, Chris I.; Sasikumar, Parvathy; Moraes, Leonardo A.; Munger, Stephanie J.; Wright, Joy R.; Ali, Marfoua S.; Sage, Tanya; Kaiser, William J.; Tucker, Katherine L.; Stain, Christopher J.; Bye, Alexander P.; Jones, Sarah; Oviedo-Orta, Ernesto; Simon, Alexander M.; Mahaut-Smith, Martyn P.; Gibbins, Jonathan M.

2012-01-01

245

Rab13 small G protein and junctional Rab13-binding protein (JRAB) orchestrate actin cytoskeletal organization during epithelial junctional development.  

PubMed

During epithelial junctional development, both vesicle transport and reorganization of the actin cytoskeleton must be spatiotemporally regulated. Coordination of these cellular functions is especially important, but the precise mechanism remains elusive. Previously, we identified junctional Rab13-binding protein (JRAB)/molecules interacting with CasL-like 2 (MICAL-L2) as an effector of the Rab13 small G protein, and we found that the Rab13-JRAB system may be involved in the formation of cell-cell adhesions via transport of adhesion molecules. Here, we showed that JRAB interacts with two actin-binding proteins, actinin-1 and -4, and filamentous actin via different domains and regulates actin cross-linking and stabilization through these interactions. During epithelial junctional development, JRAB is prominently enriched in the actin bundle at the free border; subsequently, JRAB undergoes a Rab13-dependent conformational change that is required for maturation of cell-cell adhesion sites. These results suggest that Rab13 and JRAB regulate reorganization of the actin cytoskeleton throughout epithelial junctional development from establishment to maturation of cell-cell adhesion. PMID:23100251

Sakane, Ayuko; Abdallah, Ahmed Alamir Mahmoud; Nakano, Kiyoshi; Honda, Kazufumi; Ikeda, Wataru; Nishikawa, Yumiko; Matsumoto, Mitsuru; Matsushita, Natsuki; Kitamura, Toshio; Sasaki, Takuya

2012-12-14

246

The Liquid Junction Potential in Potentiometric Titrations. XII. The Calculation of Potentials for Emf Cells with Liquid Junctions, of the Type, AY | AY + A 2 MoO 4 +HY, Involving the Formation of Iso-Polymolybdates in the Range ?log? 10 [H + ]?7, at [A + ]= C mol?L ?1 , Constant, and 25?°C  

Microsoft Academic Search

Equations are derived, in a general form, and valid in the range 0.5?C?3 mol?L?1, for the calculation of the total potential anomalies (?E\\u000a H) for emf cells where the formation of iso-polymolybdates takes place, according to the equilibria: \\u000a \\u000a \\u000a \\u000a \\u000a $$p \\\\mathrm{H}^{+} (h) + q \\\\mathrm{MoO}_{4}^{2 -} (b)\\\\rightleftharpoons [(\\\\mathrm{H}^{+})_{p}(\\\\mathrm{MoO}_{4}^{2-})_{q} ] ^{p - 2q} (cpx _{pq})$$\\u000a \\u000a \\u000a \\u000a by measuring [H+]=h, in NaClO4 ionic medium (A+,

Erzsébet Néher-Neumann

2011-01-01

247

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

248

Adenocarcinoma of the Esophagogastric Junction  

PubMed Central

Objective To assess the outcome of surgical therapy based on a topographic/anatomical classification of adenocarcinoma of the esophagogastric junction. Summary Background Data Because of its borderline location between the stomach and esophagus, the choice of surgical strategy for patients with adenocarcinoma of the esophagogastric junction is controversial. Methods In a large single-center series of 1,002 consecutive patients with adenocarcinoma of the esophagogastric junction, the choice of surgical approach was based on the location of the tumor center or tumor mass. Treatment of choice was esophagectomy for type I tumors (adenocarcinoma of the distal esophagus) and extended gastrectomy for type II tumors (true carcinoma of the cardia) and type III tumors (subcardial gastric cancer infiltrating the distal esophagus). Demographic data, morphologic and histopathologic tumor characteristics, and long-term survival rates were compared among the three tumor types, focusing on the pattern of lymphatic spread, the outcome of surgery, and prognostic factors in patients with type II tumors. Results There were marked differences in sex distribution, associated intestinal metaplasia in the esophagus, tumor grading, tumor growth pattern, and stage distribution between the three tumor types. The postoperative death rate was higher after esophagectomy than extended total gastrectomy. On multivariate analysis, a complete tumor resection (R0 resection) and the lymph node status (pN0) were the dominating independent prognostic factors for the entire patient population and in the three tumor types, irrespective of the surgical approach. In patients with type II tumors, the pattern of lymphatic spread was primarily directed toward the paracardial, lesser curvature, and left gastric artery nodes; esophagectomy offered no survival benefit over extended gastrectomy in these patients. Conclusion The classification of adenocarcinomas of the esophagogastric junction into type I, II, and III tumors shows marked differences between the tumor types and provides a useful tool for selecting the surgical approach. For patients with type II tumors, esophagectomy offers no advantage over extended gastrectomy if a complete tumor resection can be achieved.

Rudiger Siewert, J.; Feith, Marcus; Werner, M.; Stein, Hubert J.

2000-01-01

249

Tunneling Phenomena in Mesoscopic Normal Junctions  

NASA Astrophysics Data System (ADS)

Single-electron tunneling effects are studied experimentally and theoretically in a system consisting of two normal ultra-small capacitance junctions in series. A Scanning Tunneling Microscope (STM) tip poised over a small conducting particle lodged in the surface oxide of a metallic substrate provides the physical realization of this system. We demonstrate for the first time, that incremental charging effects are important and observable, not only at cryogenic temperatures but also at room temperature, provided that conditions are such that thermal and quantum fluctuations do not destroy the correlation. With current technologies, STM-formed junctions are the only option allowing these phenomena to persist up to room temperature. At elevated temperatures it is particularly important to precisely control a variety of noise sources which can otherwise mimic or obscure the effect. Substrates and tips are fabricated of granular NbN. We find that dc magnetron sputtering of NbN thin films naturally promotes formation of small surface structures appropriate for a double junction system yielding single -electron effects at room temperature. Performing a semiclassical approximation, an analytic expression valid at finite temperature is derived for the current-voltage characteristic of the system. A number of expressions, useful in fitting experiment to theory are subsequently extracted from this result. The Coulomb blockade and Coulomb staircase (occasioned by incremental charging of the central island in a double capacitor system) were both clearly observed at room temperature. The Coulomb staircase observation provides decisive evidence that the blockade is not being caused by an oxide impurity effect, a gap in the density of states in the tip, or merely a lowering of the effective tunneling barrier with increasing bias voltage. Fits with the developed theory yield capacitances on the order of 10^{-18} F and tunneling resistances from 10 MOmega to 800 MOmega.. A study of the noise at room temperature indicates an enhancement of the shot noise at the current steps of the Coulomb staircase. A dependence of the overall noise on the derivative of the conductance is also observed.

Reeve, Mark Douglas

250

Gap Junctional Communication in Morphogenesis  

PubMed Central

Gap junctions permit the direct passage of small molecules from the cytosol of one cell to that of its neighbor, and thus form a system of cell-cell communication that exists alongside familiar secretion/receptor signaling. Because of the rich potential for regulation of junctional conductance, and directional and molecular gating (specificity), gap junctional communication (GJC) plays a crucial role in many aspects of normal tissue physiology. However, the most exciting role for GJC is in the regulation of information flow that takes place during embryonic development, regeneration, and tumor progression. The molecular mechanisms by which GJC establishes local and long-range instructive morphogenetic cues are just beginning to be understood. This review summarizes the current knowledge of the involvement of GJC in the patterning of both vertebrate and invertebrate systems and discusses in detail several morphogenetic systems in which the properties of this signaling have been molecularly characterized. One model consistent with existing data in the fields of vertebrate left-right patterning and anterior-posterior polarity in flatworm regeneration postulates electrophoretically-guided movement of small molecule morphogens through long-range GJC paths. The discovery of mechanisms controlling embryonic and regenerative GJC-mediated signaling, and identification of the downstream targets of GJC-permeable molecules, represent exciting next areas of research in this fascinating field.

Levin, Michael

2007-01-01

251

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

2013-11-01

252

The catenin/cadherin adhesion system is localized in synaptic junctions bordering transmitter release zones  

PubMed Central

Molecular mechanisms linking pre- and postsynaptic membranes at the interneuronal synapses are little known. We tested the cadherin adhesion system for its localization in synapses of mouse and chick brains. We found that two classes of cadherin-associated proteins, alpha N- and beta-catenin, are broadly distributed in adult brains, colocalizing with a synaptic marker, synaptophysin. At the ultrastructural level, these proteins were localized in synaptic junctions of various types, forming a symmetrical adhesion structure. These structures sharply bordered the transmitter release sites associated with synaptic vesicles, although their segregation was less clear in certain types of synapses. N-cadherin was also localized at a similar site of synaptic junctions but in restricted brain nuclei. In developing synapses, the catenin-bearing contacts dominated their junctional structures. These findings demonstrate that interneuronal synaptic junctions comprise two subdomains, transmitter release zone and catenin-based adherens junction. The catenins localized in these junctions are likely associated with certain cadherin molecules including N-cadherin, and the cadherin/ catenin complex may play a critical role in the formation or maintenance of synaptic junctions.

1996-01-01

253

AII amacrine cells discriminate between heterocellular and homocellular locations when assembling connexin36-containing gap junctions  

PubMed Central

ABSTRACT Electrical synapses (gap junctions) rapidly transmit signals between neurons and are composed of connexins. In neurons, connexin36 (Cx36) is the most abundant isoform; however, the mechanisms underlying formation of Cx36-containing electrical synapses are unknown. We focus on homocellular and heterocellular gap junctions formed by an AII amacrine cell, a key interneuron found in all mammalian retinas. In mice lacking native Cx36 but expressing a variant tagged with enhanced green fluorescent protein at the C-terminus (KO-Cx36-EGFP), heterocellular gap junctions formed between AII cells and ON cone bipolar cells are fully functional, whereas homocellular gap junctions between two AII cells are not formed. A tracer injected into an AII amacrine cell spreads into ON cone bipolar cells but is excluded from other AII cells. Reconstruction of Cx36–EGFP clusters on an AII cell in the KO-Cx36-EGFP genotype confirmed that the number, but not average size, of the clusters is reduced – as expected for AII cells lacking a subset of electrical synapses. Our studies indicate that some neurons exhibit at least two discriminatory mechanisms for assembling Cx36. We suggest that employing different gap-junction-forming mechanisms could provide the means for a cell to regulate its gap junctions in a target-cell-specific manner, even if these junctions contain the same connexin.

Meyer, Arndt; Hilgen, Gerrit; Dorgau, Birthe; Sammler, Esther M.; Weiler, Reto; Monyer, Hannah; Dedek, Karin; Hormuzdi, Sheriar G.

2014-01-01

254

Effect of cAMP derivates on assembly and maintenance of tight junctions in human umbilical vein endothelial cells  

PubMed Central

Background Endothelial tight and adherens junctions control a variety of physiological processes like adhesion, paracellular transport of solutes or trafficking of activated leukocytes. Formation and maintenance of endothelial junctions largely depend on the microenvironment of the specific vascular bed and on interactions of the endothelium with adjacent cell types. Consequently, primary cultures of endothelial cells often lose their specific junctional pattern and fail to establish tight monolayer in vitro. This is also true for endothelial cells isolated from the vein of human umbilical cords (HUVEC) which are widely used as model for endothelial cell-related studies. Results We here compared the effect of cyclic 3'-5'-adenosine monophosphate (cAMP) and its derivates on formation and stabilization of tight junctions and on alterations in paracellular permeability in HUVEC. We demonstrated by light and confocal laser microscopy that for shorter time periods the sodium salt of 8-bromoadenosine-cAMP (8-Br-cAMP/Na) and for longer incubation periods 8-(4-chlorophenylthio)-cAMP (pCPT-cAMP) exerted the greatest effects of all compounds tested here on formation of continuous tight junction strands in HUVEC. We further demonstrated that although all compounds induced protein kinase A-dependent expression of the tight junction proteins claudin-5 and occludin only pCPT-cAMP slightly enhanced paracellular barrier functions. Moreover, we showed that pCPT-cAMP and 8-Br-cAMP/Na induced expression and membrane translocation of tricellulin. Conclusions pCPT-cAMP and, to a lesser extend, 8-Br-cAMP/Na improved formation of continuous tight junction strands and decreased paracellular permeability in primary HUVEC. We concluded that under these conditions HUVEC represent a feasible in vitro model to study formation and disassembly of endothelial tight junctions and to characterize tight junction-associated proteins

2010-01-01

255

Enhancement of ventricular gap-junction coupling by rotigaptide  

PubMed Central

Aims Rotigaptide is proposed to exert its anti-arrhythmic effects by improving myocardial gap-junction communication. To directly investigate the mechanisms of rotigaptide action, we treated cultured neonatal murine ventricular cardiomyocytes with clinical pharmacological doses of rotigaptide and directly determined its effects on gap-junctional currents. Methods and results Neonatal murine ventricular cardiomyocytes were enzymatically isolated and cultured for 1–4 days. Primary culture cell pairs were subjected to dual whole cell patch-clamp procedures to directly measure gap-junctional currents (Ij) and voltage (Vj). Rotigaptide (0–350 nM) was applied overnight or acutely perfused into 35 mm culture dishes. Rotigaptide (35–100 nM) acutely and chronically increased the resting gap-junction conductance (gj), and normalized steady-state minimum gj (Gmin) by 5–20%. Higher concentrations produced a diminishing response, which mimics the observed therapeutic efficacy of the drug. The inactivation kinetics was similarly slowed in a therapeutic concentration-dependent manner without affecting the Vj dependence of inactivation or recovery. The effects of 0–100 nM rotigaptide on ventricular gj during cardiac action potential propagation were accurately modelled by computer simulations which demonstrate that clinically effective concentrations of rotigaptide can partially reverse conduction slowing due to decreases in gj and inactivation. Conclusion These results demonstrate that therapeutic concentrations of rotigaptide increase the resting gap-junction conductance and reduce the magnitude and kinetics of steady-state inactivation in a concentration-dependent manner. Rotigaptide may be effective in treating re-entrant forms of cardiac arrhythmias by improving conduction and preventing the formation of re-entrant circuits in partially uncoupled myocardium.

Lin, Xianming; Zemlin, Christian; Hennan, James K.; Petersen, J?rgen S.; Veenstra, Richard D.

2008-01-01

256

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

PubMed Central

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

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

2002-01-01

257

Direct coupling between magnetism and superconducting current in the Josephson phi0 junction.  

PubMed

We study the proximity effect between conventional superconductor and magnetic normal metal with a spin-orbit interaction of the Rashba type. Using the phenomenological Ginzburg-Landau theory and the quasiclassical Eilenberger approach it is demonstrated that the Josephson junction with such a metal as a weak link has a special nonsinusoidal current-phase relation. The ground state of this junction is characterized by the finite phase difference phi{0}, which is proportional to the strength of the spin-orbit interaction and the exchange field in the normal metal. The proposed mechanism of the phi{0} junction formation gives a direct coupling between the superconducting current and the magnetic moment in the weak link. Therefore the phi{0} junctions open interesting perspectives for the superconducting spintronics. PMID:18851248

Buzdin, A

2008-09-01

258

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

NASA Astrophysics Data System (ADS)

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

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

2011-04-01

259

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

260

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

261

Importin 13 Regulates Neurotransmitter Release at the Drosophila Neuromuscular Junction  

PubMed Central

In an unbiased genetic screen designed to isolate mutations that affect synaptic transmission, we have isolated homozygous lethal mutations in Drosophila importin 13 (imp13). Imp13 is expressed in and around nuclei of both neurons and muscles. At the larval neuromuscular junction (NMJ), imp13 affects muscle growth and formation of the subsynaptic reticulum without influencing any presynaptic structural features. In the absence of imp13, the probability of release of neurotransmitter and quantal content is increased, yet the abundance of the postsynaptic receptors and the amplitude of miniature excitatory junctional potentials are not affected. Interestingly, imp13 is required in the muscles to control presynaptic release. Thus, imp13 is a novel factor that affects neurotransmitter release at the fly NMJ. Its role in the context of synaptic homeostasis is discussed.

Giagtzoglou, Nikolaos; Lin, Yong Qi; Haueter, Claire; Bellen, Hugo J.

2014-01-01

262

Low-high junction theory applied to solar cells  

NASA Technical Reports Server (NTRS)

Recent use of alloying techniques for rear contact formation has yielded a new kind of silicon solar cell, the back surface field (BSF) cell, with abnormally high open circuit voltage and improved radiation resistance. Several analytical models for open circuit voltage based on the reverse saturation current are formulated to explain these observations. The zero SRV case of the conventional cell model, the drift field model, and the low-high junction (LHJ) model can predict the experimental trends. The LHJ model applies the theory of the low-high junction and is considered to reflect a more realistic view of cell fabrication. This model can predict the experimental trends observed for BSF cells. Detailed descriptions and derivations for the models are included. The correspondences between them are discussed. This modeling suggests that the meaning of minority carrier diffusion length measured in BSF cells be reexamined.

Godlewski, M. P.; Baraona, C. R.; Brandhorst, H. W., Jr.

1973-01-01

263

Correlated charge transport in bilinear tunnel junction arrays  

NASA Astrophysics Data System (ADS)

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

Walker, Kelly A.; Cole, Jared H.

2013-12-01

264

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

265

Using Elastic Wave Seismic Data to Image an Ultra-shallow Buried Paleo- channel  

NASA Astrophysics Data System (ADS)

Previously we conducted a set of compressional wave seismic investigations at a groundwater contamination site (Hill Air Force Base, Ogden, UT), in order to better characterize the subsurface environment determined from well data. The seismic target is the bottom of a paleo-channel eroded in a clay layer at a depth of 10-15 m that is overlain by a mix of sands, clays, and gravels with different compaction and water saturation. The channel acts as contaminant trap for dense non-aqueous phase liquids (DNAPLs), therefore a detailed map of its geometry and depth is crucial to the remediation effort. At the same site, we recently performed another experiment using elastic-wave sources, in order to determine subsurface elastic parameters, to complement the P-wave data already acquired and processed, and to exploit the lack of sensitivity of the shear modulus to fluid saturation. The seismic data were acquired along two profiles using 60 groups of three single-component 40 Hz geophones mounted in a Galperin configuration. The length of each profile is 29.5 m. The transverse component was extracted and processed in order to obtain SH- wave images of the subsurface. The SH-wave depth migrated sections show geometry of and depth to the clay layer that are remarkably similar to those derived from well data. Moreover, the sections can be compared to the velocity model previously obtained from P-wave waveform tomography: If one assumes that the 1100 m/s P-wave velocity contour the top of the clay in the waveform tomography, the difference between the channel imaged by the SH- wave data and waveform tomography is insignificant. We have also obtained P-wave and S-wave tomography velocity models along the two lines. By combining the Vp and Vs information, a map of the Vp/Vs ratio and the Poisson's ratio was reconstructed. These parameters can be related to lithology changes in the subsurface. Low Vp/Vs and Poisson's ratio values normally relate to stiff materials (i.e. sands), while high value are generally interpreted to be less rigid materials (i.e. saturated clays). Our study shows that it is possible to image and delineate the geometry of the channel, with fairly high resolution and accuracy, using shear wave sources, as well as the using compressional-wave sources. The images made using the different seismic methods are in good accordance with each other and the well data, and allow a cross-validation of the final results.

Fradelizio, G.; Levander, A.; Zelt, C.

2006-12-01

266

Craniocervical junction abnormalities in dogs.  

PubMed

Craniocervical junction abnormality (CJA) is a term that encompasses a number of developmental anatomical aberrations at the region of the caudal occiput and first two cervical vertebrae. Chiari-like malformation appears to be the most common CJA encountered in dogs, and there has been a tremendous amount of clinical investigation into this disorder in recent years. Other abnormalities in this region include atlanto-occipital overlap, dorsal constriction at C1/C2 and atlantoaxial instability. This review article presents an overview of the current understanding of CJA in dogs, as well as medical and surgical treatment options available. PMID:23556552

Dewey, C W; Marino, D J; Loughin, C A

2013-07-01

267

Dbl3 drives Cdc42 signaling at the apical margin to regulate junction position and apical differentiation  

PubMed Central

Epithelial cells develop morphologically characteristic apical domains that are bordered by tight junctions, the apical–lateral border. Cdc42 and its effector complex Par6–atypical protein kinase c (aPKC) regulate multiple steps during epithelial differentiation, but the mechanisms that mediate process-specific activation of Cdc42 to drive apical morphogenesis and activate the transition from junction formation to apical differentiation are poorly understood. Using a small interfering RNA screen, we identify Dbl3 as a guanine nucleotide exchange factor that is recruited by ezrin to the apical membrane, that is enriched at a marginal zone apical to tight junctions, and that drives spatially restricted Cdc42 activation, promoting apical differentiation. Dbl3 depletion did not affect junction formation but did affect epithelial morphogenesis and brush border formation. Conversely, expression of active Dbl3 drove process-specific activation of the Par6–aPKC pathway, stimulating the transition from junction formation to apical differentiation and domain expansion, as well as the positioning of tight junctions. Thus, Dbl3 drives Cdc42 signaling at the apical margin to regulate morphogenesis, apical–lateral border positioning, and apical differentiation.

Zihni, Ceniz; Munro, Peter M.G.; Elbediwy, Ahmed; Keep, Nicholas H.; Terry, Stephen J.; Harris, John

2014-01-01

268

Voltage induced torque in magnetic tunnel junctions  

Microsoft Academic Search

A mechanism is proposed for a voltage induced torque in magnetic tunnel junctions when the magnetizations on opposite sides of the junction are not parallel to each other. By taking into account the effect of the electron–electron interaction, we found in tunnel structures the possibility of an enhanced spin switching effect that, when normalized with respect to the current, can

Z. F. Lin; S. T. Chui; L. B. Hu

2004-01-01

269

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

270

Flow dynamics past a simplified wing body junction  

NASA Astrophysics Data System (ADS)

Junction flows may suffer from secondary flows such as horseshoe vortices and corner separations that can dramatically impair the performances of aircrafts. The present article brings into focus the unsteady aspects of the flow at the intersection of a wing and a flat plate. The simplified junction flow test case is designed according to a literature review to favor the onset of a corner separation. The salient statistical and fluctuating properties of the flow are scrutinized using large eddy simulation and wind tunnel tests, which are carried out at a Reynolds number based on the wing chord c and the free stream velocity U? of Rec=2.8×105. As the incoming boundary layer at Re?=2100 (? being the boundary layer momentum thickness one-half chord upstream the junction) experiences the adverse pressure gradient created by the wing, a three dimensional separation occurs at the nose of the junction leading to the formation of a horseshoe vortex. The low frequency, large scale bimodal behavior of the horseshoe vortex at the nose of the junction is characterized by multiple frequencies within f.?/U?=[0.05-0.1] (where ? is the boundary layer thickness one-half chord upstream the wing). Downstream of the bimodal region, the meandering of the core of the horseshoe vortex legs in the crossflow planes is scrutinized. It is found that the horseshoe vortex oscillates around a mean location over an area covering almost 10% of the wing chord in the tranverse plane at the trailing edge at normalized frequencies around f.?/U?=0.2-0.3. This so-called meandering is found to be part of a global dynamics of the horseshoe vortex initiated by the bimodal behavior. Within the corner, no separation is observed and it is shown that a high level of anisotropy (according to Lumley's formalism) is reached at the intersection of the wing and the flat plate, which makes the investigated test case challenging for numerical methods. The conditions of apparition of a corner separation are eventually discussed and we assume that the vicinity of the horseshoe vortex suction side leg might prevent the corner separation. It is also anticipated that higher Reynolds number junction flows are more likely to suffer from such separations.

Gand, Fabien; Deck, Sébastien; Brunet, Vincent; Sagaut, Pierre

2010-11-01

271

Computer models of DNA four-way junctions.  

PubMed

A modeling scheme that combines a constrained backbone generating algorithm with simple hard-sphere packing calculations is offered to build the four-stranded structures of DNA found in Holliday junctions. Two standard B-DNA duplexes are oriented side by side with helix axes at different relative inclinations and then systematically rotated and translated to identify closely spaced contact-free states. Attempts are subsequently made to introduce a low-energy sugar-phosphate linkage that serves as the site of strand exchange between the two duplexes. The chemical connection is sought using an algorithm which identifies the possible arrangements of the intervening backbone torsions between arbitrarily positioned bases. The goal is to identify the multiple conformational solutions associated with a particular arrangement of neighboring DNA helices in the four-way junction rather than a single optimum structure. The methodology is general, in terms of accommodating four-way junctions with arms of variable conformation and chain length and of dimensions much greater than treated heretofore. The only deformation in the four-way structures relative to B-DNA occurs at the site of backbone exchange, with base stacking and Watson-Crick pairing completely preserved in all models. The arrangements of neighboring bases at these sites resemble the unusual conformational steps found in a number of small molecule nucleic acid crystal structures. An interesting outcome of the calculations is the formation of sterically acceptable four-arm Holliday junctions over a wide range of angles at the cross. The potential mobility of the Holliday junctions is inferred from visualization and energetic analysis of the various models. Long-range electrostatic energies based on different currently available treatments of the dielectric constant are used to estimate the conformational preferences and flexibility of the four-stranded structures. The various dielectric schemes, however, are not in complete agreement on the likely conformational variability of the four-way junctions. The structures suggest a possible mechanism for branch migration and detail a pathway linking the antiparallel uncrossed Holliday structure inferred from solution measurements and the parallel cross-packed helical arrangements observed in single-crystal X-ray studies. PMID:8068615

Srinivasan, A R; Olson, W K

1994-08-16

272

Synthesis procedures for production of carbon nanotube junctions  

NASA Astrophysics Data System (ADS)

A quite wide brunch of the carbon nanotube science, including the utilization of singlewall nanotube for production of nano-electronic devices has being continuously explored even nowadays. Tuning and modifying the synthesis procedures to obtain nanotube junctions of T, Y, H or X shapes lead to inappropriate results concerning the industrial or large scale production. However, the importance and the demand for these junctions are quite large, since these may be the secondary building units of carbon nanotubes based chips or even more complex nanoelectronic devices. Recently, some novel solutions of their preparation have been published. A Taiwanese group described a method to prepare multi-junctioned carbon nanotubes on mechanically pretreated silicon surface applying chemical vapor deposition (CVD) technology using decomposition of methane at 1373 K. The nanotubes were nucleated following the lines prepared by scratching the surface with 600-grit sand paper. Contrary to the physical pretreatment of a substrate surface, chemical reactions can also be used for the preparation of carbon nanotube junctions. P.W. Chu et al. reported interconnecting reactions between functionalized carbon nanotubes . By the described method, the carboxyl groups on the wall of singlewall carbon nanotubes are converted to carbonyl chloride groups by reaction with SOCl2 at room temperature. The formed COCl groups are very reactive on the outer surface and can be reacted easily with various amines, particularly diamines resulting in the formation of amide bonding. When two functionalized carbon nanotubes react with such an amine molecule interconnection of tubes is generated. The resulted carbon nanotube junctions have been investigated by AFM. In this presentation, we report on the results obtained on the preparation of carbon nanotube junctions applying two different procedures. The first method is similar to Chu"s one, which was mentioned above, i.e. we used functionalized multiwall carbon nanotubes and the successful interconnection of them by propylene diamine has been proven by TEM and AFM. The second method demonstrates a novel principle: catalyst material has been deposited on the outer surface of carbon nanotubes and branches of nanotubes were produced at this contact point by catalytic chemical vapor deposition (CCVD) of acetylene. The product has been characterized by TEM.

Kiricsi, Imre; Kónya, Zoltán; Niesz, Krisztián; Koós, Antal A.; Biró, László P.

2003-04-01

273

Sertoli-sertoli junctions and Sertoli-spermatid junctions after efferent ductule ligation and lanthanum treatment.  

PubMed

Seminiferous tubules, partially dilated by ligation of the efferent ductules, were examined after treatment with lanthanum. Lanthanum penetrated the intercellular spaces of the seminiferous epithelium, but only to the level of the Sertoli-Sertoli junctions. Further penetration from the interstitial surface of the tubule was restricted by membrane fusions (tight junctions) at the junctional complex. Lanthanum also penetrated the epithelium from the luminal surface permeating the adluminal intercellular spaces, including the site of the Sertoli-spermatid junction. The lanthanum occupying the Sertoli-spermatid junctional site appeared as a slightly narrower electron-opaque zone than that found in the non-specialized intercellular areas. The findings clearly reveal that only the Sertoli-Sertoli junctional site forms a restrictive barrier. In contrast to the specializations of plasma membrane which form the tight junction, the associated filaments and cisterna of endoplasmic reticulum may be components more directly related to maintaining and regulating cell adhesion. PMID:842475

Ross, M H

1977-01-01

274

Anti-breast cancer agents, quinolines, targeting gap junction.  

PubMed

Cancer cells exhibit many defects in cell communication that contribute to the loss of tissue homeostasis (excess cell proliferation, invasion, and metastasis). The process of cancer formation causes a disruption in cell homeostasis, affecting the ability to respond to extracellular signals, as well as triggering some intracellular events which alter gap junctional intercellular communication (GJIC). Previous research has shown that the first two generations of substituted quinolines have anti-cancer effects in human breast cancer cells. This report presents the synthesis and bioactivities of third generation substituted quinolines. Scrape load/dye transfer studies showed that 100 nM of PQ15, a third generation substituted quinoline, causes a 4.5-fold increase of gap junction activity in T47D breast cancer cells. Furthermore, a significant decrease of cell proliferation and viability was observed in the presence of 200 nM PQ15 compared to control. The expression of ?-survivin was reduced to <40% in the treatment of 200 nM PQ15 compared to solvent alone. Alpha-survivin expression is upregulated in human cancers and associated with resistance to chemotherapy, suggesting that ?-survivin prolongs the survival of cancer cells. Thus, it has been shown that substituted quinolines stimulate gap junction activity, decrease alpha survivin expression, and subsequently inhibit cancer cell growth. Our findings demonstrate that PQ15 has a promising role in exerting anti-cancer activity in human breast cancer cells. PMID:21801150

Bernzweig, Julie; Heiniger, Brian; Prasain, Keshar; Lu, Jianyu; Hua, Duy H; Nguyen, Thu A

2011-09-01

275

Anti-breast Cancer Agents, Quinolines, Targeting Gap Junction  

PubMed Central

Cancer cells exhibit many defects in cell communication that contribute to the loss of tissue homeostasis (excess cell proliferation, invasion, and metastasis). The process of cancer formation causes a disruption in cell homeostasis, affecting the ability to respond to extracellular signals, as well as triggering some intracellular events which alter gap junctional intercellular communication (GJIC). Previous research has shown that the first two generations of substituted quinolines have anti-cancer effects in human breast cancer cells. This report presents the synthesis and bioactivities of third generation substituted quinolines. Scrape load/dye transfer studies showed that 100 nM of PQ15, a third generation substituted quinoline, causes a 4.5-fold increase of gap junction activity in T47D breast cancer cells. Furthermore, a significant decrease of cell proliferation and viability was observed in the presence of 200 nM PQ15 compared to control. The expression of ?-survivin was reduced to <18% in the treatment of 100 nM PQ15 compared to control without treatment or solvent. Alpha-survivin expression is upregulated in human cancers and associated with resistance to chemotherapy, suggesting that ?-survivin prolongs the survival of cancer cells. Thus, it has been shown that substituted quinolines stimulate gap junction activity, decrease alpha survivin expression, and subsequently inhibit cancer cell growth. Our findings demonstrate that PQ15 has a promising role in exerting anti-cancer activity in human breast cancer cells.

Bernzweig, Julie; Heiniger, Brian; Prasain, Keshar; Lu, Jianyu; Hua, Duy H.; Nguyen, Thu A.

2011-01-01

276

Barrier defect analysis using Josephson junction resonators  

NASA Astrophysics Data System (ADS)

We have designed Josephson junction (JJ) resonators by adding an Al/AlOx/Al Josephson junction in parallel with a coplanar sapphire capacitor and an inductor so that the total loss will be dominated by the junction barrier. JJ resonators couple to individual defects in the junction barrier, causing splittings in the spectroscopy of the resonator when it is excited near single-photon energies, similar to phase and other qubits. Measurements are performed in a dilution refrigerator at 30mK with a drive frequency of approximately 7GHz. By applying a dc flux bias, we can tune the resonance frequency by as much as 1GHz. Analysis of the frequency of splittings as a function of junction area and barrier growth process provides a method for determining the source of the defects. We will use these devices to study amorphous aluminum oxide barriers and will report our progress towards studying novel barrier dielectrics.

Stoutimore, M. J. A.; Sarabi, Bahman; Khalil, Moe; Lobb, C. J.; Osborn, K. D.

2011-03-01

277

Occludin is a functional component of the tight junction.  

PubMed

Occludin's role in mammalian tight junction activity was examined by 'labeling' the occludin pool with immunologically detectable chick occludin. This was accomplished by first transfecting MDCK cell with the Lac repressor gene. HygR clones were then transfected with chick occludin cDNA inserted into a Lac operator construct. The resulting HygR/NeoR clones were plated on porous inserts and allowed to form tight junctions. Once steady state transepithelial electrical resistance was achieved, isopropyl- beta-D-thiogalactoside was added to induce chick occludin expression. Confocal laser scanning microscopy of monolayers immunolabeled with Oc-2 monoclonal antibody revealed that chick occludin localized precisely to the preformed tight junctions. When sparse cultures were maintained in low Ca2+ medium, chick occludin and canine ZO-1 co-localized to punctate sites in the cytoplasm suggesting their association within the same vesicular structures. In low calcium medium both proteins also co-localized to contact sites between occasional cell pairs, where a prominent bar was formed at the plasma membrane. Chick occludin was detectable by western blot within two hours of adding isopropyl- beta-D-thiogalactoside to monolayers that had previously achieved steady state transepithelial electrical resistance; this coincided with focal immunofluorescence staining for chick occludin at the cell membrane of some cells. A gradual rise in transepithelial electrical resistance, above control steady state values, began five hours after addition of the inducing agent reaching new steady state values, which were 30-40% above baseline, 31 hours later. Upon removal of isopropyl- beta-D-thiogalactoside chick occludin expression declined slowly until it was no longer detected in western blots 72 hours later; transepithelial electrical resistance also returned to baseline values during this time. While densitometric analysis of western blots indicated that the presence of chick occludin had no detectable effect on E-cadherin or ZO-1 expression, the possibility cannot be excluded that ZO-1 might be a limiting factor in the expression of chick occludin at the cell surface. To test whether expression of chick occludin affected the process of tight junction assembly, monolayers in low Ca2+ medium were treated with isopropyl- beta-D-thiogalactoside for 24 or 48 hours, before Ca2+ was added to stimulate tight junction assembly. Chick occludin did not alter the rate at which transepithelial electrical resistance developed, however, steady state values were 30-40% above control monolayers not supplemented with the inducing agent. By freeze fracture analysis, the number of parallel tight junction strands shifted from a mode of three in controls to four strands in cells expressing chick occludin and the mean width of the tight junction network increased from 175 +/- 11 nm to 248 +/- 16 nm. Two days after plating confluent monolayers that were induced to express chick occludin, mannitol flux was reduced to a variable degree relative to control monolayers. With continued incubation with the inducing agent, mannitol flux increased on day 11 to 50%, and TER rose to 45% above controls. Both of these changes were reversible upon removal of isopropyl- beta-D-thiogalactoside. These data are consistent with the notion that occludin contributes to the electrical barrier function of the tight junction and possibly to the formation of aqueous pores within tight junction strands. PMID:8886979

McCarthy, K M; Skare, I B; Stankewich, M C; Furuse, M; Tsukita, S; Rogers, R A; Lynch, R D; Schneeberger, E E

1996-09-01

278

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

SciTech Connect

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

Cleland, A.N.

1991-04-01

279

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

280

Rapid electrical stimulation causes alterations in cardiac intercellular junction proteins of cardiomyocytes.  

PubMed

The intercellular junctions contain two complexes, adhesion junctions (AJ) and connexin (Cx) gap junctions (GJs). GJs provide the pathway for intercellular current flow. AJs mediate normal mechanical coupling and play an important role in the stability of GJs. We investigated the effects of rapid electrical stimulation (RES) on cardiac intercellular junctions, especially ?-catenin and Cx43 alterations. We also studied the effects of ANG II receptor blockade on intercellular junction remodeling. Neonatal rats were euthanized by decapitation, and cardiomyocytes were prepared, cultured, and subjected to RES. We used real-time PCR, western blot analysis, and immunohistochemical methods. Conduction properties were examined by an extracellular potential mapping system. Cx43 protein expression in cardiomyocytes was significantly increased after 60 min. ?-Catenin expression in the total cell fraction was significantly increased after 30 min. The expression level of ?-catenin in the nucleus, which functions as a T cell factor/lymphocyte enhancer binding factor transcriptional activator of Cx43 with its degradation regulated by glycogen synthase kinase-3?, was dramatically increased after 10 min. Conduction velocity was increased significantly by RES for 60 min. Olmesartan prevented most these effects of RES. We showed an increase of phosphorylated glycogen synthase kinase-3?, which is phosphorylated by activated MAPKs and inhibits ?-catenin degradation, was attenuated by olmesartan. The changes in ?-catenin precede Cx43 GJ remodeling and might play an important role in the formation and stability of GJs. Olmesartan might be a new upstream arrhythmia therapy by modulating intercellular junction remodeling through the ?-catenin signaling pathway. PMID:24610920

Nakashima, Tadamitsu; Ohkusa, Tomoko; Okamoto, Yoko; Yoshida, Masaaki; Lee, Jong-Kook; Mizukami, Yoichi; Yano, Masafumi

2014-05-01

281

TRF2 promotes, remodels and protects telomeric Holliday junctions  

PubMed Central

The ability of the telomeric DNA-binding protein, TRF2, to stimulate t-loop formation while preventing t-loop deletion is believed to be crucial to maintain telomere integrity in mammals. However, little is known on the molecular mechanisms behind these properties of TRF2. In this report, we show that TRF2 greatly increases the rate of Holliday junction (HJ) formation and blocks the cleavage by various types of HJ resolving activities, including the newly identified human GEN1 protein. By using potassium permanganate probing and differential scanning calorimetry, we reveal that the basic domain of TRF2 induces structural changes to the junction. We propose that TRF2 contributes to t-loop stabilisation by stimulating HJ formation and by preventing resolvase cleavage. These findings provide novel insights into the interplay between telomere protection and homologous recombination and suggest a general model in which TRF2 maintains telomere integrity by controlling the turnover of HJ at t-loops and at regressed replication forks.

Poulet, Anais; Buisson, Remi; Faivre-Moskalenko, Cendrine; Koelblen, Melanie; Amiard, Simon; Montel, Fabien; Cuesta-Lopez, Santiago; Bornet, Olivier; Guerlesquin, Francoise; Godet, Thomas; Moukhtar, Julien; Argoul, Francoise; Declais, Anne-Cecile; Lilley, David M J; Ip, Stephen C Y; West, Stephen C; Gilson, Eric; Giraud-Panis, Marie-Josephe

2009-01-01

282

Regulation of gap junction coupling in bovine ciliary epithelium  

PubMed Central

Aqueous humor is formed by fluid transfer from the ciliary stroma sequentially across the pigmented ciliary epithelial (PE) cells, gap junctions, and nonpigmented ciliary epithelial (NPE) cells. Which connexins (Cx) contribute to PE-NPE gap junctional formation appears species specific. We tested whether small interfering RNA (siRNA) against Cx43 (siCx43) affects bovine PE-NPE communication and whether cAMP affects communication. Native bovine ciliary epithelial cells were studied by dual-cell patch clamping, Lucifer Yellow (LY) transfer, quantitative polymerase chain reaction with reverse transcription (qRT-PCR), and Western immunoblot. qRT-PCR revealed at least 100-fold greater expression for Cx43 than Cx40. siCx43 knocked down target mRNA expression by 55 ± 7% after 24 h, compared with nontargeting control siRNA (NTC1) transfection. After 48 h, siCx43 reduced Cx43 protein expression and LY transfer. The ratio of fluorescence intensity (Rf) in recipient to donor cell was 0.47 ± 0.09 (n = 11) 10 min after whole cell patch formation in couplets transfected with NTC1. siCx43 decreased Rf by ?60% to 0.20 ± 0.07 (n = 13, P < 0.02). Dibutyryl-cAMP (500 ?M) also reduced LY dye transfer by ?60%, reducing Rf from 0.41 ± 0.05 (n = 15) to 0.17 ± 0.05 (n = 20) after 10 min. Junctional currents were lowered by ?50% (n = 6) after 10-min perfusion with 500 ?M dibutyryl-cAMP (n = 6); thereafter, heptanol abolished the currents (n = 5). Preincubation with the PKA inhibitor H-89 (2 ?M) prevented cAMP-triggered current reduction (n = 6). We conclude that 1) Cx43, but not Cx40, is a major functional component of bovine PE-NPE gap junctions; and 2) under certain conditions, cAMP may act through PKA to inhibit bovine PE-NPE gap junctional communication.

Wang, Zhao; Do, Chi Wai; Valiunas, Virginijus; Leung, Chi Ting; Cheng, Angela K. W.; Clark, Abbott F.; Wax, Martin B.; Chatterton, Jon E.

2010-01-01

283

Programmable one-pot multistep organic synthesis using DNA junctions.  

PubMed

A system for multistep DNA-templated synthesis is controlled by the sequential formation of DNA junctions. Reactants are attached to DNA adapters which are brought together by hybridization to DNA template strands. This process can be repeated to allow sequence-controlled oligomer synthesis while maintaining a constant reaction environment, independent of oligomer length, at each reaction step. Synthesis can take place in a single pot containing all required reactive monomers. Different oligomers can be synthesized in parallel in the same vessel, and the products of parallel synthesis can be ligated, reducing the number of reaction steps required to produce an oligomer of a given length. PMID:22276773

McKee, Mireya L; Milnes, Phillip J; Bath, Jonathan; Stulz, Eugen; O'Reilly, Rachel K; Turberfield, Andrew J

2012-01-25

284

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

285

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

286

Junction Termination Extension Implementing Drive-in Diffusion of Boron for High-Voltage SiC Devices  

Microsoft Academic Search

A novel method of graded junction termination extension (JTE) formation for high-voltage 4H-SiC power devices is presented. Unlike conventional multiimplantation or tapered thickness mask approaches utilizing several photolithography steps, the new termination technique utilizes a single mask with window areas varied laterally away from the main junction, a single-step boron implantation, and drive-in diffusion at elevated temperature. Numerical device simulations

Alexander V. Bolotnikov; Peter G. Muzykov; Qingchun Zhang; A. K. Agarwal; T. S. Sudarshan

2010-01-01

287

Angiopoietin 2 regulates the transformation and integrity of lymphatic endothelial cell junctions.  

PubMed

Primitive lymphatic vessels are remodeled into functionally specialized initial and collecting lymphatics during development. Lymphatic endothelial cell (LEC) junctions in initial lymphatics transform from a zipper-like to a button-like pattern during collecting vessel development, but what regulates this process is largely unknown. Angiopoietin 2 (Ang2) deficiency leads to abnormal lymphatic vessels. Here we found that an ANG2-blocking antibody inhibited embryonic lymphangiogenesis, whereas endothelium-specific ANG2 overexpression induced lymphatic hyperplasia. ANG2 inhibition blocked VE-cadherin phosphorylation at tyrosine residue 685 and the concomitant formation of button-like junctions in initial lymphatics. The defective junctions were associated with impaired lymph uptake. In collecting lymphatics, adherens junctions were disrupted, and the vessels leaked upon ANG2 blockade or gene deletion. ANG2 inhibition also suppressed the onset of lymphatic valve formation and subsequent valve maturation. These data identify ANG2 as the first essential regulator of the functionally important interendothelial cell-cell junctions that form during lymphatic development. PMID:25030698

Zheng, Wei; Nurmi, Harri; Appak, Sila; Sabine, Amélie; Bovay, Esther; Korhonen, Emilia A; Orsenigo, Fabrizio; Lohela, Marja; D'Amico, Gabriela; Holopainen, Tanja; Leow, Ching Ching; Dejana, Elisabetta; Petrova, Tatiana V; Augustin, Hellmut G; Alitalo, Kari

2014-07-15

288

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

289

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

290

Barrier and electrode properties of high Tc Josephson junctions formed by a plasma discharge process  

Microsoft Academic Search

The influence of rf discharge in CF4 and O2 gases on the properties of thin YBCO films and edge junctions was investigated by transport measurements and Auger spectroscopy. It was found that oxygen plasma of short duration can serve as a cleaning step before the formation of the barrier. In contrast, CF4 plasma tends to substitute oxygen in the superconducting

E. Aharoni; G. Koren; E. Polturak; D. Cohen

1993-01-01

291

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

292

Mutual phase locking in Josephson junction arrays  

SciTech Connect

Arrays of interacting Josephson junctions have been studied experimentally. The Josephson element in these arrays consisted of indium microbridges having sub-micron dimensions. An external resistive inductor connected across the array provided long range interaction between the junctions. The results of these experiments have been analyzed in light of the theory developed recently for such systems by Likharev, Kuzmin and Ovsyannikov. Detailed experimental results on the simplest such array of two junctions are presented. The interaction leads to frequency pulling and then to phase locking (and voltage locking) as the unperturbed frequencies of the two jucntions are brought closer. The effects of the interaction on the current voltage characteristic of the junctions and the behavior of the radiation linewidth and power in the neighborhood of voltage locking have been studied. These experiments clearly show the differing effects of the junction and coupling loop resistance noise on the locking stability and radiation linewidth for the series and parallel biasing configurations. All these observations are in accordance with the calculations of Likharev, et al. In addition, measurements have also been made on two microbridge arrays coupled by a superconducting loop. In this case, the phase difference between the junction oscillations was dependent on the flux through the loop, and both the radiated power and the linewidth varied periodically with this flux. An additional normal shunt was found to considerably decrease the variation of the phase difference with the flux. Larger linear arrays containing up to 99 junctions have also been studied.

Jain, A.K.

1982-01-01

293

[Gap junctions and cancer: implications and perspectives].  

PubMed

Gap junctions are made of intercellular channels which permit the diffusion from cytoplasm to cytoplasm of small hydrophilic molecules (<1,200 Da) such as ions, sugars, amino acids, nucleotides, second messengers (calcium, inositol triphosphate, etc.). Since their discovery in the early sixties, several groups have described the loss of their function in cancer cells. The accumulation of such data led to the hypothesis that gap junctions are involved in the carcinogenesis process. This assumption has been confirmed by data establishing that gap junctional intercellular communication is inhibited by most of the tumor promoters and that the restoration of such a communication, by transfection of cDNAs encoding gap junction proteins (connexins), inhibits the aberrant growth rates of tumorigenic cells. Despite these important informations, several fundamental questions remain still open. First, we do not know how gap junctions mediate such a tumor suppressor effect and whether it may depend either on the cell type or on the connexin type. Moreover, most of the data concerning a possible involvement of gap junctions in carcinogenesis have been obtained from in vitro and animal models. The very few results which have been currently collected from human tumors are not sufficient to have a clear idea concerning the real involvement of gap junctions in sporadic human cancers. These points as well as other unresolved questions about the role of gap junctional intercellular communication in carcinogenesis are mentioned. To bring some answers, some prospects are proposed with the objective to use gap junctions for increasing the effect of anticancer therapies. PMID:14997440

Mesnil, Marc

2004-02-01

294

Method of junction formation for CIGS photovoltaic devices  

DOEpatents

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

295

Schottky Barrier Formation at a Carbon Nanotube-Scandium Junction  

NASA Astrophysics Data System (ADS)

Recent experiment shows that scandium (Sc) can make a good performance contact with carbon nanotubes (CNTs) to fabricate n-type field effect transistor (n-FET). We study the Schottky barrier (SB) of scandium (Sc) and palladium (Pd) with a (8,0) single-wall CNT (SWCNT) using first-principles calculation. It is found that the p-type SB height (SBH) of the Pd-CNT contact is about 0.34 eV, which is in good agreement with the experimental data. For the Sc-CNT contact, an n-type contact is formed and the SBH is about 0.08 eV in agreement with the experimental observations. Our calculation demonstrates that by contacting CNT with Pd and Sc, p-FET and n-FET can be fabricated, respectively. The dipole effect at the interface is used to explain our result.

He, Yu; Zhang, Ming; Zhang, Jin-Yu; Wang, Yan; Yu, Zhi-Ping

2009-02-01

296

Schottky Barrier Formation at a Carbon Nanotube-Scandium Junction  

Microsoft Academic Search

Recent experiment shows that scandium (Sc) can make a good performance contact with carbon nanotubes (CNTs) to fabricate n-type field effect transistor (n-FET). We study the Schottky barrier (SB) of scandium (Sc) and palladium (Pd) with a (8,0) single-wall CNT (SWCNT) using first-principles calculation. It is found that the p-type SB height (SBH) of the Pd-CNT contact is about 0.34

Yu He; Ming Zhang; Jin-Yu Zhang; Yan Wang; Zhi-Ping Yu

2009-01-01

297

Mutual Phase Locking in Josephson Junction Arrays.  

NASA Astrophysics Data System (ADS)

Arrays of interacting Josephson junctions have been studied experimentally. The Josephson element in these arrays consisted of indium microbridges having sub -micron dimensions. An external resistive inductor connected across the array provided long range interaction between the junctions. The results of these experiments have been analyzed in light of the theory developed recently for such systems by Likharev, Kuzmin and Ovsyannikov. Detailed experimental results on the simplest such array of two junctions are presented. The interaction leads to frequency pulling and then to phase locking (and voltage locking) as the unperturbed frequencies of the two junctions are brought closer. The effects of the interaction on the current voltage characteristic of the junctions and the behavior of the radiation linewidth and power in the neighborhood of voltage locking have been studied. These experiments clearly show the differing effects of the junction and coupling loop resistance noise on the locking stability and radiation linewidth for the series and parallel biasing configurations. All these observations are in accordance with the calculations of Likharev, et al. In addition, measurements have also been made on two microbridge arrays coupled by a superconducting loop. In this case, the phase difference between the junction oscillations was dependent on the flux through the loop, and both the radiated power and the linewidth varied periodically with this flux. An additional normal shunt was found to considerably decrease the variation of the phase difference with the flux. We have also studied larger linear arrays containing up to 99 junctions. A principal requirement for obtaining coherence in these arrays is small dispersion in the junction voltages ((TURN) 10%). Because with current fabrication techniques, the junction parameters vary by about 20%, a biasing scheme using superconducting loops was used to ensure the uniformity of the junction voltages. The external resistive inductor connected across the array provided the long range interaction between the junctions. The effectiveness of this biasing and coupling scheme has been demonstrated. The observed increase in the power ((alpha) N('2)) and the decrease in the linewidth (('1)/N) are in agreement with the theory.

Jain, Aloke Kumar

298

Palladium Electrodes for Molecular Tunnel Junctions  

PubMed Central

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

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

2012-01-01

299

Graded junction termination extensions for electronic devices  

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

300

Graded junction termination extensions for electronic devices  

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

301

Supercurrent decay in extremely underdamped Josephson junctions  

SciTech Connect

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

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

1998-01-01

302

delta-biased Josephson tunnel junctions  

SciTech Connect

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

Monaco, R.; Mygind, J.; Koshelets, V. P.; Dmitriev, P. [Istituto di Cibernetica del CNR, 80078 Pozzuoli (Italy) and Dipartimento di Fisica, Universita di Salerno, 84081 Baronissi (Italy); DTU Physics, Technical University of Denmark, B309, DK-2800 Lyngby (Denmark); Institute of Radio Engineering and Electronics, Russian Academy of Science, Mokhovaya 11, Bldg. 7, 125009 Moscow (Russian Federation)

2010-02-01

303

Molecular mechanism of double Holliday junction dissolution  

PubMed Central

Processing of homologous recombination intermediates is tightly coordinated to ensure that chromosomal integrity is maintained and tumorigenesis avoided. Decatenation of double Holliday junctions, for example, is catalysed by two enzymes that work in tight coordination and belong to the same ‘dissolvasome’ complex. Within the dissolvasome, the RecQ-like BLM helicase provides the translocase function for Holliday junction migration, while the topoisomerase III alpha-RMI1 subcomplex works as a proficient DNA decatenase, together resulting in double-Holliday-junction unlinking. Here, we review the available architectural and biochemical knowledge on the dissolvasome machinery, with a focus on the structural interplay between its components.

2014-01-01

304

Dural Arteriovenous Fistulas of the Craniocervical Junction  

PubMed Central

Dural arteriovenous fistulas (DAVF) involving the craniocervical junction are uncommon lesions that may result in neurological deficits referable to posterior fossa structures and/or the spinal cord. We report on two patients with craniocervical junction DAVF whose venous drainage involved the cervical spinal cord. Both cases presented with progressive quadriparesis and parenchymal magnetic resonance signal abnormality of the cervical spinal cord. Both patients improved following embolization of the fistulas. AVF of the craniocervical junction are an uncommon, but important cause of treatable neurological deficits referable to this region of the nervous system. ImagesFigure 1Figure 2p4-bFigure 3

Hurst, Robert W.; Bagley, Linda J.; Scanlon, Mary; Flamm, Eugene S.

1999-01-01

305

Assembly of the tight junction: the role of diacylglycerol  

PubMed Central

Extracellular Ca2+ triggers assembly and sealing of tight junctions (TJs) in MDCK cells. These events are modulated by G-proteins, phospholipase C, protein kinase C (PKC), and calmodulin. In the present work we observed that 1,2-dioctanoylglycerol (diC8) promotes the assembly of TJ in low extracellular Ca2+, as evidenced by translocation of the TJ-associated protein ZO-1 to the plasma membrane, formation of junctional fibrils observed in freeze-fracture replicas, decreased permeability of the intercellular space to [3H]mannitol, and reorganization of actin filaments to the cell periphery, visualized by fluorescence microscopy using rhodamine-phalloidin. In contrast, diC8 in low Ca2+ did not induce redistribution of the Ca-dependent adhesion protein E-cadherin (uvomorulin). Extracellular antibodies to E-cadherin block junction formation normally induced by adding Ca2+. diC8 counteracted this inhibition, suggesting that PKC may be in the signaling pathway activated by E-cadherin-mediated cell-cell adhesion. In addition, we found a novel phosphoprotein of 130 kD which coimmunoprecipitated with the ZO-1/ZO-2 complex. Although the assembly and sealing of TJs may involve the activation of PKC, the level of phosphorylation of ZO-1, ZO-2, and the 130-kD protein did not change after adding Ca2+ or a PKC agonist. The complex of these three proteins was present even in low extracellular Ca2+, suggesting that the addition of Ca2+ or diC8 triggers the translocation and assembly of preformed TJ subcomplexes.

1993-01-01

306

Tunnel junction multiple wavelength light-emitting diodes  

DOEpatents

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

Olson, Jerry M. (Lakewood, CO); Kurtz, Sarah R. (Golden, CO)

1992-01-01

307

Tunnel junction multiple wavelength light-emitting diodes  

DOEpatents

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

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

1992-11-24

308

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

309

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

Microsoft Academic Search

Holliday junctions are four-stranded DNA complexes that are formed during recombination and related DNA repair events. Much work has focused on the overall structure and properties of four-way junctions in solution, but we are just now beginning to understand these complexes at the atomic level. The crystal structures of two all-DNA Holliday junctions have been determined recently from the sequences

Brandt F. Eichman; Miguel Ortiz-Lombard??a; Joan Aymam??; Miquel Coll; Pui Shing Ho

2002-01-01

310

Electronic transport in molecular junctions  

NASA Astrophysics Data System (ADS)

A combined density functional theory and Green function method is used to study some basics and applications in the field of molecular electronics. We have investigated the effects of lateral interactions on the conductance of two molecules connected in parallel to semi-infinite leads. The system, modeled after a self-assembled monolayer, consists of benzylmercaptane molecules sandwiched between gold electrodes. We find that the conductance increases when intermolecular interaction comes into play. The source of this increase is the indirect interaction through the gold substrate rather than direct molecule-molecule interaction. As for applications, single-molecule spintronic switch and spin valve, rectifier and negative differential resistive (NDR) diode are proposed. Spintronic switch is constructed by a di-cobaltocene containing molecule. The anti-parallel (singlet) configuration blocks electron transport near the Fermi energy, while the spin parallel (triplet) configuration enables a much higher current. The energy difference between the anti-parallel and parallel states depends on the insulating spacer separating the two cobaltocenes, allowing switching through the application of a moderate magnetic field. In addition, single cobaltocene containing molecule can be used as a spin valve. Rectification of current through a single molecule with an intrinsic spatial asymmetry is studied. The molecule contains a cobaltocene moiety in order to take advantage of its relatively localized and high energy d states. A rectifier with large voltage range, high current density, and low threshold voltage can be realized. The evolution of molecular orbitals under both forward and reverse bias reveals the source of rectification being asymmetric potential drop. Our calculations demonstrate the plausibility of making excellent molecular diodes by using metallocenes, pointing to a fruitful class of molecules. Analogous to a quantum double dot system, we found that diblock structured molecules could also show NDR. We show that molecular level crossing in a molecular double dot (MDD) system containing cobaltocene and ferrocene leads to NDR and hysteresis. Time-dependent transport properties of molecular junctions under external perturbation of a short time pulse or an alternative bias is studied by solving Green function in the time domain, combined with electronic structure information coming from ab initio density functional calculations. We found that the short time response depends on lead structure, bias voltage and barrier heights both at molecule-lead contacts and within molecules. Under an alternative current (AC) mode, the electron flow either lags (capacitive response) or leads (inductive response) the bias signal. The critical frequency for this transition is characteristic of a junction, depending on factors such as electronic structure of the leads and capacitance of the contacts.

Liu, Rui

311

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

NSDL National Science Digital Library

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

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

2003-10-21

312

Two junction effects in dc SQUID phase qubit  

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

313

27 CFR 9.164 - River Junction.  

Code of Federal Regulations, 2010 CFR

...Ripon, CA 1969, photorevised 1980; (2) Vernalis, CA 1969, photorevised 1980. (c) Boundaries. The River Junction AVA is located in southern San Joaquin County, California. The boundaries are as follows: (1) Beginning on the...

2010-04-01

314

27 CFR 9.164 - River Junction.  

Code of Federal Regulations, 2010 CFR

...Ripon, CA 1969, photorevised 1980; (2) Vernalis, CA 1969, photorevised 1980. (c) Boundaries. The River Junction AVA is located in southern San Joaquin County, California. The boundaries are as follows: (1) Beginning on the...

2009-04-01

315

URETEROSCOPIC TREATMENT OF URETEROPELVIC JUNCTION OBSTRUCTION  

Microsoft Academic Search

PurposeEndopyelotomy has increasingly become well accepted as the optimal management for primary and secondary ureteropelvic junction obstruction. We report our experience with ureteroscopic endopyelotomy guided by endoluminal ultrasound.

EHAB R. TAWFIEK; JI-BIN LIU; DEMETRIUS H. BAGLEY

1998-01-01

316

Hydraulic Performance of Conflict Junction Boxes.  

National Technical Information Service (NTIS)

This report documents an experimental investigation of the hydraulic performance of typical conflict junctions, installed when utility conduits intersect a stormwater drainage line. The conflict pipe disrupts the jet flow across the box creating additiona...

S. C. Kranc F. Romano K. Cecil D. Olin A. Perez S. Ethier E. Droz

1996-01-01

317

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

318

The inherent properties of DNA four-way junctions: comparing the crystal structures of holliday junctions.  

PubMed

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

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

2002-07-26

319

Junction Plasmon-Induced Molecular Reorientation  

SciTech Connect

Time and frequency dependent intensity variations in sequences of Raman spectra recorded at plasmonic junctions can be assigned to molecular reorientation. This is revealed through Raman trajectories recorded at a nanojunction formed between a silver AFM tip and a corrugated silver surface coated with biphenyl-4,4’-dithiol. Molecular motion is not observed when the tip is retracted and only surface enhancement is operative. In effect, junction plasmon induced molecular reorientation is tracked.

El-Khoury, Patrick Z.; Hu, Dehong; Hess, Wayne P.

2013-10-17

320

Buried junction enhanced Schottky barrier device  

NASA Astrophysics Data System (ADS)

The present invention contemplates a completely submersed Schottky barrier junction in order to enhance collection efficiency of photogenerated carriers. Using a buried active back-to-back thin junction allows collection of carriers generated with momentum vectors in both the forward and reverse directions. Thus, the quantum efficiency and sensitivity of the infrared detector is substantially enhanced. In addition, thicker Schottky metallizations can be used to enhance spectral absorption of incident infrared lights.

Skolnik, L. H.

1984-08-01

321

Shot noise in YBCO bicrystal Josephson junctions  

Microsoft Academic Search

We measured spectral noise density in YBCO symmetric bicrystal Josephson junctions on sapphire substrates at bias voltages up to 100 mV and T=4.2 K. Normal state resistance of the Josephson junctions, RN=20-90 ? and ICRN up to 2.2 mV have been observed in the experimental samples. Noise measurements were carried out within frequency bands of 1-2 GHz and 0.3-300 kHz.

Karen Y. Constantinian; Gennady A. Ovsyannikov; Igor V. Borisenko; Jesper Mygind; Niels F. Pedersen

2003-01-01

322

Large-Signal Behavior of Junction Transistors  

Microsoft Academic Search

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

J. J. Ebers; J. L. Moll

1954-01-01

323

Dorsolateral Approach to the Craniocervical Junction  

Microsoft Academic Search

\\u000a The region of the craniocervical junction is the site of various pathological lesions. Due to the complex topographical anatomy,\\u000a performing surgery within this area requires great experience and knowledge in both spinal and skull-base anatomy. The most\\u000a frequent tumors located within the craniocervical junction area are meningiomas. These lesions may occur in a great variety\\u000a of appearances in terms of

Helmut Bertalanffy; Oliver Bozinov; Oguzkan Sürücü; Ulrich Sure; Ludwig Benes; Christoph Kappus; Niklaus Krayenbühl

324

The crystal structures of DNA Holliday junctions  

Microsoft Academic Search

Nearly 40 years ago, Holliday proposed a four-stranded complex or junction as the central intermediate in the general mechanism of genetic recombination. During the past two years, six single-crystal structures of such DNA junctions have been determined by three different research groups. These structures all essentially adopt the antiparallel stacked-X conformation, but can be classified into three distinct categories: RNA–DNA

P. Shing Ho; Brandt F Eichman

2001-01-01

325

Rho Signaling and Tight Junction Functions  

NSDL National Science Digital Library

Tight junctions are heteromeric protein complexes that act as signaling centers by mediating the bidirectional transmission of information between the environment and the cell interior to control paracellular permeability and differentiation. Insight into tight junction-associated signaling mechanisms is of fundamental importance for our understanding of the physiology of epithelia and endothelia in health and disease. Review of RhoGTPase effector pathways and paracellular permeability

Steve Terry (University College London); Mei Nie (University College London); Karl Matter (University College London); Maria S. Balda (University College London)

2010-02-01

326

Development of Thin-Junction Detector  

Microsoft Academic Search

Two methods to produce a thin-junction sensor covered by a layer of aluminum to substantially attenuate incident visible light are reported here. The first method is a regular boron implant (10's of keV) through a thin oxide layer to form a junction. The aluminum layer was coated in the same vacuum system after back-sputtering to remove oxide on top of

W. Chen; G. Carini; J. Keister; Z. Li; P. Rehak

2006-01-01

327

E-cadherin is essential for in vivo epidermal barrier function by regulating tight junctions  

PubMed Central

Cadherin adhesion molecules are key determinants of morphogenesis and tissue architecture. Nevertheless, the molecular mechanisms responsible for the morphogenetic contributions of cadherins remain poorly understood in vivo. Besides supporting cell–cell adhesion, cadherins can affect a wide range of cellular functions that include activation of cell signalling pathways, regulation of the cytoskeleton and control of cell polarity. To determine the role of E-cadherin in stratified epithelium of the epidermis, we have conditionally inactivated its gene in mice. Here we show that loss of E-cadherin in the epidermis in vivo results in perinatal death of mice due to the inability to retain a functional epidermal water barrier. Absence of E-cadherin leads to improper localization of key tight junctional proteins, resulting in permeable tight junctions and thus altered epidermal resistance. In addition, both Rac and activated atypical PKC, crucial for tight junction formation, are mislocalized. Surprisingly, our results indicate that E-cadherin is specifically required for tight junction, but not desmosome, formation and this appears to involve signalling rather than cell contact formation.

Tunggal, Judith A; Helfrich, Iris; Schmitz, Annika; Schwarz, Heinz; Gunzel, Dorothee; Fromm, Michael; Kemler, Rolf; Krieg, Thomas; Niessen, Carien M

2005-01-01

328

Expression of Tight Junction Protein Claudin-1 in Human Crescentic Glomerulonephritis  

PubMed Central

The origin of crescent forming cells in human glomerulonephritis (GN) remains unknown. Some animal studies demonstrated that parietal epithelial cells of Bowman's capsule (PECs) were the main component of proliferating cells and PEC-specific tight junction protein claudin-1 was expressed in crescentic lesions. We investigated the expression of claudin-1 in human GN. Immunohistochemistry for claudin-1 was performed on 17 kidney biopsy samples with crescent formation. Colocalization of claudin-1 with intracellular tight junction protein ZO-1 was also evaluated by immunofluorescence double staining. Claudin-1 is expressed mainly at the cell to cell contact site of proliferating cells in cellular crescentic lesions in patients with these forms of human GN. Small numbers of crescent forming cells showed extrajunctional localization of claudin-1. Colocalization of claudin-1 with ZO-1 was found at cell to cell contact sites of adjacent proliferating cells. In control samples, staining of claudin-1 was positive in PECs, but not in podocytes. Our findings suggest that claudin-1 contributes to crescent formation as a component of the tight junction protein complex that includes ZO-1. Co-localization of claudin-1 with ZO-1 implies the formation of functional tight junction complexes in crescentic lesions to prevent the interstitial damage caused by penetration of filtered molecules from Bowman's space.

Koda, Ryo; Yoshino, Atsunori; Imanishi, Yuji; Kawamoto, Shinya; Ueda, Yoshihiko; Yaoita, Eishin; Kazama, Junichiro James; Narita, Ichiei; Takeda, Tetsuro

2014-01-01

329

Rectification Properties of Carbon Nanotube ''Y-Junctions''  

SciTech Connect

Quantum conductivity of single-wall carbon nanotube Y-junctions is calculated. The current versus voltage characteristics of these junctions show asymmetry and rectification, in agreement with recent experimental results. Furthermore, rectification is found to be independent of the angle between the branches of these junctions, indicating this to be an intrinsic property of symmetric Y-junctions. The implications for the Y-junction to function as a nanoscale molecular electronic switch are investigated.

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

2001-08-06

330

Capacitively Enhanced Thermal Escape in Underdamped Josephson Junctions  

NASA Astrophysics Data System (ADS)

We have studied experimentally the escape dynamics in underdamped capacitively shunted and unshunted Josephson junctions with submicroampere critical currents below 0.5 K temperatures. In the shunted junctions, thermal activation process was preserved up to the highest temperature where the escape in the unshunted junctions exhibits the phase diffusion. Our observations in the shunted junctions are in good agreement with the standard thermal activation escape, unlike the results in the unshunted junctions.

Yoon, Y.; Gasparinetti, S.; Möttönen, M.; Pekola, J. P.

2011-05-01

331

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

2014-06-01

332

Atomic force microscopy of arthropod gap junctions.  

PubMed

Atomic force microscopy has been used to characterize gap junctions isolated from the hepatopancreas of Nephrops norvegicus. The major polypeptide of these gap junctions is ductin, a highly conserved 16- to 18-kDa protein. The hydrated gap junctions, imaged in phosphate-buffered saline, appeared as membrane plaques with a thickness of 14 nm, consistent with their being a pair of apposing membranes. The upper membrane was removed by force dissection using an increased imaging force. The thickness of the lower membrane was 6 nm, giving a separation or gap between the two membranes of 2 nm. High-resolution images show fine details of the force-dissected extracellular surfaces, as previously reported for vertebrate and heart gap junctions. In addition high-resolution AFM images show for the first time detailed substructure on the cytoplasmic face of hydrated gap junctions of either vertebrate or invertebrate. The plaques had particles on their exposed and force-dissected faces. These particles were packed in a hexagonal lattice (a = b = 8.9 nm on both faces) and had a diameter of approximately 6.5 nm, with a central, pore-like depression. Fourier maps calculated from the AFM data suggested that each particle was composed of six subunits. These images show a marked similarity to the widely accepted structure of the connexon channel of vertebrate gap junctions. PMID:9356288

John, S A; Saner, D; Pitts, J D; Holzenburg, A; Finbow, M E; Lal, R

1997-10-01

333

Gap junctions and blood-tissue barriers.  

PubMed

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

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

2012-01-01

334

Electron transport in manganite bicrystal junctions  

NASA Astrophysics Data System (ADS)

The transport and magnetic properties of junctions created in La0.67Sr0.33MnO3 thin films epitaxially grown on substrates with a bicrystal boundary have been investigated. In tilted neodymium gallate bicrystal substrates, the NdGaO3(110) planes are inclined at angles of 12° and 38°. The temperature dependences of the electrical resistance, magnetoresistance, and differential conductance of the junctions at different voltages have been measured and analyzed. It has been found that the magnetoresistance and electrical resistance of the junction significantly increase with an increase in the misorientation angle, even though the misorientation of the easy magnetization axes remains nearly unchanged. The ratio of the spin-dependent and spin-independent contributions to the conductance of the bicrystal junction increases by almost an order of magnitude with an increase in the misorientation angle from 12° to 38°. The magnetoresistance of the junction increases with decreasing temperature, which is most likely associated with an increase of the magnetic polarization of the electrons. It has been shown that, at low (liquid-helium) temperatures, the conductance depends on the voltage V according to the law V 1/2, which indicates the dominant contribution from the electron-electron interaction to the electrical resistance of the junction. An increase in the temperature leads to a decrease in this contribution and an increase in the contribution proportional to V 3/2, which is characteristic of the mechanism involving inelastic spin scattering by surface antiferromagnetic magnons.

Petrzhik, A. M.; Ovsyannikov, G. A.; Demidov, V. V.; Shadrin, A. V.; Borisenko, I. V.

2013-04-01

335

GAP JUNCTIONS AND BLOOD-TISSUE BARRIERS  

PubMed Central

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

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

2014-01-01

336

Viral oncoprotein-induced mislocalization of select PDZ proteins disrupts tight junctions and causes polarity defects in epithelial cells  

PubMed Central

Summary The development of human cancers is frequently associated with a failure of epithelial cells to form tight junctions and to establish proper apicobasal polarity. Interestingly, the oncogenic potential of the adenovirus E4-ORF1 protein correlates with its binding to the cellular PDZ proteins MUPP1, MAGI-1, ZO-2 and SAP97, the first three of which assemble protein complexes at tight junctions. Given that E4-ORF1 sequesters these three PDZ proteins in the cytoplasm of fibroblasts, we postulated that E4-ORF1 would inhibit tight junction formation in epithelial cells. Providing further support for this idea, we identified MUPP1-related PATJ, a key component of the tight junction-associated CRB3-PALS1-PATJ polarity complex, as a new PDZ-protein target for both the E4-ORF1 and high-risk human papillomavirus type 18 E6 oncoproteins. Moreover, in epithelial cells, E4-ORF1 blocked the tight junction localization of PATJ and ZO-2, as well as their interacting partners, and disrupted both the tight junction barrier and apicobasal polarity. These significant findings expose a direct link between the tumorigenic potential of E4-ORF1 and inactivation of cellular PDZ proteins involved in tight junction assembly and polarity establishment.

Latorre, Isabel J.; Roh, Michael H.; Frese, Kristopher K.; Weiss, Robert S.; Margolis, Ben; Javier, Ronald T.

2012-01-01

337

Differential positioning of adherens junctions is associated with initiation of epithelial folding  

PubMed Central

During tissue morphogenesis, simple epithelial sheets undergo folding to form complex structures. The prevailing model underlying epithelial folding involves cell shape changes driven by Myosin-dependent apical constriction1. Here we describe an alternative mechanism that requires differential positioning of adherens junctions controlled by modulation of epithelial apical-basal polarity. Using live embryo imaging, we show that prior to the initiation of dorsal transverse folds during Drosophila gastrulation, adherens junctions shift basally in the initiating cells, but maintain their original subapical positioning in the neighboring cells. Junctional positioning in the dorsal epithelium depends on the polarity proteins Bazooka and Par-1. In particular, the basal shift that occurs in the initiating cells is associated with a progressive decrease in Par-1 levels. We show that uniform reduction of the activity of Bazooka or Par-1 results in uniform apical or lateral positioning of junctions and in each case dorsal fold initiation is abolished. In addition, an increase in the Bazooka/Par-1 ratio causes formation of ectopic dorsal folds. The basal shift of junctions not only alters the apical shape of the initiating cells, but also forces the lateral membrane of the adjacent cells to bend toward the initiating cells, thereby facilitating tissue deformation. Our data thus establish a direct link between modification of epithelial polarity and initiation of epithelial folding.

Wang, Yu-Chiun; Khan, Zia; Kaschube, Matthias; Wieschaus, Eric F.

2013-01-01

338

Gate-Tunable Superconductor-Insulator Transition in Bilayer-Graphene Josephson Junctions  

NASA Astrophysics Data System (ADS)

Bilayer graphene shows opening of electric-field-induced band gap, the size of which is proportional to the intensity of the electric field. We report electronic transport measurements on superconducting proximity effect in planar dual-gated bilayer-graphene Josephson junction with Pb0.93In0.07 (PbIn) electrodes (?PbIn ˜ 1.1meV, Tc = 7.0 K). The junction resistance along the charge-neutral point (CNP) increases as we modulate top- and back-gate voltages away from the zero-gap CNP. The resistive state near the CNP shows a variable-range-hopping-type insulating behavior in R-T curve with lowering temperature crossing the superconducting transition of PbIn electrodes. However, a highly doped regime shows metallic R-T behavior and junction becomes superconducting below Tc. Moreover, magnetic-field-induced Fraunhofer supercurrent modulation, microwave-induced Shapiro steps, and multiple Andreev reflection (MAR) are observed, which indicate the formation of genuine Josephson coupling across the planar junctions below Tc with sufficiently transparent superconductor-bilayer graphene interface. The separatrix of the superconductor-insulator transition corresponds to the square junction conductance of Gsq˜ 6-8e^2/h.

Jeong, Dongchan; Lee, Gil-Ho; Doh, Yong-Joo; Lee, Hu-Jong

2012-02-01

339

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

PubMed Central

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

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

1995-01-01

340

Correlation between micromagnetism and tunnel magnetoresistance in magnetic tunnel junctions using artificial ferrimagnets  

NASA Astrophysics Data System (ADS)

The impact of the micromagnetic configuration on transport properties of magnetic tunnel junctions is presented. An artificial ferrimagnet system (AFi), made of two ferromagnetic layers with different magnetic moments antiferromagnetically coupled by exchange interactions through a Ru spacer layer, is used as a hard magnetic subsystem of the magnetic junction. Magnetic-force microscopy studies have shown that the magnetization reversal in artificial ferrimagnet systems occurs through the formation of Néel-type 360° domain walls. The stability of these walls is demonstrated to be different in the two magnetic layers of the AFi. These aspects have major effects in magnetic tunnel junction devices, due to the extreme sensitivity of spin tunneling to spatial variations in local magnetic order. The large tunnel magnetoresistance (TMR) of our samples, in the range of 20-30 % at room temperature, makes the tunnel junctions highly sensitive to magnetic fluctuations. A sharp switching of the soft magnetic layer upon field reversal prevents a domain structure from occurring in the soft magnetic layer, in the field window used for our micromagnetic studies. The tunnel device can thus be used as a sensitive probe for measuring small magnetic fluctuations associated with micromagnetic defects, domains, and walls in the AFi system. These fluctuations modulate the resistance of the tunnel junction and are fully reflected in the shape and the amplitude of the TMR signal.

Tiusan, C.; Dimopoulos, T.; Ounadjela, K.; Hehn, M.; van den Berg, H. A. M.; da Costa, V.; Henry, Y.

2000-01-01

341

Optimization of a tunneling barrier in magnetic tunneling junction by tilted-plasma oxidation  

SciTech Connect

Oxidation of an AlO{sub x} insulating barrier in a magnetic tunneling junction (MTJ) was carried out by a tilted-plasma oxidation method. It was found that the tilted-plasma oxidation induced a gradual change in the extent of oxidation of an insulating layer, which consequently led to a gradual change in the tunneling magnetoresistance (TMR) and specific junction resistance (RA) of the MTJ. We found a linear relation in the TMR versus RA curve with positive and negative slopes for less- and overoxidized junctions, respectively, and a parabolic relation for optimally oxidized junctions. The crossover in the TMR versus RA curves provides an effective and useful way to optimize (and monitor) the oxidation condition of a tunneling barrier in MTJs especially of a tunneling barrier less than 10 A thick. The tunneling junctions were also investigated after thermal annealing at various temperatures. The observations after thermal annealing were found to be consistent with transmission electrons microscopy images and a scenario of the partial formation of an additional ultrathin tunneling barrier at the top surface of the bottom magnetic layer.

Nam, C.H.; Shim, Heejae; Kim, K.S.; Cho, B.K. [Center for Frontier Materials, Department of Materials Science and Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju 500-712 (Korea, Republic of)

2004-10-01

342

Highly Conducting pi-Conjugated Molecular Junctions Covalently Bonded to Gold Electrodes  

SciTech Connect

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 {sigma} bond between the carbon backbone and the gold metal electrodes. The molecular carbon backbone used in this study consist of a conjugated {pi} system that has one terminal methylene group on each end, which bonds to the electrodes, achieving large electronic coupling of the electrodes to the {pi} system. The junctions formed with the prototypical example of 1,4-dimethylenebenzene show a conductance approaching one conductance quantum (G{sub 0} = 2e{sup 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.

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

2011-11-02

343

[Screw fixation of craniocervical junction].  

PubMed

In recent years an increase has been observed of the use of screw techniques for the fixation of the craniocervical junction. For clinical use two techniques have been introduced: (1) transarticular screw fixation, and (2) transpedicular screw fixation. In the former the screw is inserted through the C2 lateral mass, the fissure of the C1-C2 joint, and the C1 lateral mass. (2) in the latter the screw is inserted into the C2 pedicle and anchored in C2 vertebral body. Transarticular or pedicle screws can be easily connected to longitudinal elements such as rods or plates, and combined with lateral mass screws of the remaining cervical vertebrae or occipital screws. In comparison to sublaminar wiring or interlaminar clamping the screw techniques: (a) strengthen the stiffness of the construct and speed up fusion, (b) allow fixation in the absence or deficiency of laminae as a result of trauma or laminectomy, and (c) can selectively include only the affected segments. Increased construct stiffness is due to deep anchorage of the screw in bone providing thus a solid grip on the vertebra. Both techniques require preoperative assessment of the course of the vertebral artery using imaging methods. In about 18% of cases abnormal course of the artery precludes screw use. Pedicle screw insertion requires direct control of the medial and superior walls of C2 pedicle with dissector introduced into the vertebral canal, which requires removal of the atlantoaxial ligament. Additional control can be achieved with lateral fluoroscopy. The entry point for transarticular screw is on the lateral mass of the odontoid 2-3 mm laterally to the medial margin of C2 facet and 2-3 mm above the C1/C2 articular fissure. The screw trajectory is 0-10 degrees in horizontal plane and towards the anterior C1 tuberculum in sagittal plane. PMID:10791042

Maciejczak, A; Radek, A

1999-01-01

344

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

345

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

346

Holding Tight: Cell Junctions and Cancer Spread  

PubMed Central

Cell junctions are sites of intercellular adhesion that maintain the integrity of epithelial tissue and regulate signalling between cells. These adhesive junctions are comprised of protein complexes that serve to establish an intercellular cytoskeletal network for anchoring cells, in addition to regulating cell polarity, molecular transport and communication. The expression of cell adhesion molecules is tightly controlled and their downregulation is essential for epithelial-mesenchymal transition (EMT), a process that facilitates the generation of morphologically and functionally diverse cell types during embryogenesis. The characteristics of EMT are a loss of cell adhesion and increased cellular mobility. Hence, in addition to its normal role in development, dysregulated EMT has been linked to cancer progression and metastasis, the process whereby primary tumors migrate to invasive secondary sites in the body. This paper will review the current understanding of cell junctions and their role in cancer, with reference to the abnormal regulation of junction protein genes. The potential use of cell junction molecules as diagnostic and prognostic markers will also be discussed, as well as possible therapies for adhesive dysregulation.

Knights, Alexander J.; Funnell, Alister P. W.; Crossley, Merlin; Pearson, Richard C. M.

2013-01-01

347

Semiconductor Lasers Containing Quantum Wells in Junctions  

NASA Technical Reports Server (NTRS)

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

Yang, Rui Q.; Qiu, Yueming

2004-01-01

348

The discovery of epidermal tight junctions.  

PubMed

It was previously thought that the skin barrier is composed singly by the stratum corneum. However, this concept was overturned by the report of Tsukita's group in 2002. They convinced us that tight junctions exist in the stratum granulosum of the epidermis, with the constituent proteins being occludin, claudin-1 and claudin-4. However, more than 30 years before this, Hashimoto et al. described the possible existence of tight junctions in the epidermis in 'Intercellular spaces of the human epidermis as demonstrated with lanthanum' in 1971. Dr. Hashimoto observed lanthanum nitrate-injected human skin by electron microscopy. He discovered that the injected lanthanum penetrated the intercellular spaces of the basal and spinous layers of the epidermis and then moved towards the skin surface until penetration was halted in the granular cell layer near the stratum corneum. He described the cell-to-cell adhesion structures that blocked the movement of lanthanum as 'truly tight junctions'. Thus, this was the first description of the existence of tight junctions in the epidermis. However, the presence of these structures was denied by others and was forgotten. Thanks to the discovery of claudin, the existence of tight junctions between epidermal keratinocytes was finally confirmed. It is interesting that Hashimoto's finding was eventually proved to be correct three decades later as a result of progress in molecular biology. This article encourages us to recognize the importance of careful observation in the molecular biology era. PMID:24673182

Ozawa, Toshiyuki; Sugawara, Koji; Tsuruta, Daisuke

2014-06-01

349

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

350

Methods for the fabrication of thermally stable magnetic tunnel junctions  

DOEpatents

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

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

2009-08-25

351

Plasticity of Button-Like Junctions in the Endothelium of Airway Lymphatics in Development and Inflammation  

PubMed Central

Endothelial cells of initial lymphatics have discontinuous button-like junctions (buttons), unlike continuous zipper-like junctions (zippers) of collecting lymphatics and blood vessels. Buttons are thought to act as primary valves for fluid and cell entry into lymphatics. To learn when and how buttons form during development and whether they change in disease, we examined the appearance of buttons in mouse embryos and their plasticity in sustained inflammation. We found that endothelial cells of lymph sacs at embryonic day (E)12.5 and tracheal lymphatics at E16.5 were joined by zippers, not buttons. However, zippers in initial lymphatics decreased rapidly just before birth, as buttons appeared. The proportion of buttons increased from only 6% at E17.5 and 12% at E18.5 to 35% at birth, 50% at postnatal day (P)7, 90% at P28, and 100% at P70. In inflammation, zippers replaced buttons in airway lymphatics at 14 and 28 days after Mycoplasma pulmonis infection of the respiratory tract. The change in lymphatic junctions was reversed by dexamethasone but not by inhibition of vascular endothelial growth factor receptor-3 signaling by antibody mF4-31C1. Dexamethasone also promoted button formation during early postnatal development through a direct effect involving glucocorticoid receptor phosphorylation in lymphatic endothelial cells. These findings demonstrate the plasticity of intercellular junctions in lymphatics during development and inflammation and show that button formation can be promoted by glucocorticoid receptor signaling in lymphatic endothelial cells.

Yao, Li-Chin; Baluk, Peter; Srinivasan, R. Sathish; Oliver, Guillermo; McDonald, Donald M.

2012-01-01

352

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

353

Synchronized Switching in a Josephson Junction Crystal  

NASA Astrophysics Data System (ADS)

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

Leib, Martin; Hartmann, Michael J.

2014-06-01

354

Numerical Investigation of Josephson Junction Structures  

NASA Astrophysics Data System (ADS)

Multilayered long Josephson Junction Structures form an interesting physical system where both nonlinearity and interaction between subsystems play an important role. Such systems allow to study physical effects that do not occur in single Josephson junction. The Sakai-Bodin-Pedersen model-a system of perturbed sine-Gordon equations-is used to study the dynamic states of stacks of inductively coupled long Josephson Junctions (LJJs). The corresponding static problem is numerically investigated as well. In order to study the stability of possible static solutions a Sturm-Liouville problem is generated and solved. The transitions from static to dynamic state and the scenario of these transitions are analyzed depending on the model parameters. Different physical characteristics-current-voltage characteristics, individual instant voltages and internal magnetic fields, are calculated and interpreted.

Hristov, I.; Dimova, S.; Boyadjiev, T.

2009-10-01

355

Synchronized switching in a josephson junction crystal.  

PubMed

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

Leib, Martin; Hartmann, Michael J

2014-06-01

356

Brownian refrigeration by hybrid tunnel junctions  

NASA Astrophysics Data System (ADS)

Voltage fluctuations generated in a hot resistor can cause extraction of heat from a colder normal metal electrode of a hybrid tunnel junction between a normal metal and a superconductor. We extend the analysis presented in Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.98.210604 98, 210604 (2007) of this heat rectifying system, bearing resemblance to a Maxwell’s demon. Explicit analytic calculations show that the entropy of the total system is always increasing. We then consider a single-electron transistor configuration with two hybrid junctions in series, and show how the cooling is influenced by charging effects. We analyze also the cooling effect from nonequilibrium fluctuations instead of thermal noise, focusing on the shot noise generated in another tunnel junction. We conclude by discussing limitations for an experimental observation of the effect.

Peltonen, J. T.; Helle, M.; Timofeev, A. V.; Solinas, P.; Hekking, F. W. J.; Pekola, J. P.

2011-10-01

357

Conductance across strain junctions in graphene nanoribbons  

NASA Astrophysics Data System (ADS)

To address the robustness of the transport gap induced by locally strained regions in graphene nanostructures, the effect of disorder and smoothness of the interface region is investigated within the Landauer-Büttiker formalism. The electronic conductance across strained junctions and barriers in graphene nanoribbons is calculated numerically, with and without various types of disorder, and comparing smooth and sharp strain junctions. A smooth strain barrier in graphene is seen to be generically as efficient in suppressing transport at low densities as a sharp one, and the critical density (or energy) for the onset of transmission depends on the strain orientation with respect to the ribbon. In addition, hopping (or strain) inhomogeneity and work function mismatch at the interface region do not visibly degrade the transport gap. These results show that the strain-induced transport gap at a strain junction is robust to more realistic strain conditions.

Bahamon, D. A.; Pereira, Vitor M.

2013-11-01

358

Currents Induced by Injected Charge in Junction Detectors  

PubMed Central

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.

Gaubas, Eugenijus; Ceponis, Tomas; Kalesinskas, Vidas

2013-01-01

359

Non-invasive microfluidic gap junction assay.  

PubMed

Gap junctions are protein channels between cells that allow direct electrical and metabolic coupling via the exchange of biomolecules and ions. Their expression, though ubiquitous in most mammalian cell types, is especially important for the proper functioning of cardiac and neuronal systems. Many existing methods for studying gap junction communication suffer from either unquantifiable data or difficulty of use. Here, we measure the extent of dye spread and effective diffusivities through gap junction connected cells using a quantitative microfluidic cell biology platform. After loading dye by hydrodynamic focusing of calcein/AM, dye transfer dynamics into neighboring, unexposed cells can be monitored via timelapse fluorescent microscopy. By using a selective microfluidic dye loading over a confluent layer of cells, we found that high expression of gap junctions in C6 cells transmits calcein across the monolayer with an effective diffusivity of 3.4 x 10(-13) m(2)/s, which are highly coupled by Cx43. We also found that the gap junction blocker 18alpha-GA works poorly in the presence of serum even at high concentrations (50 microM); however, it is highly effective down to 2.5 microM in the absence of serum. Furthermore, when the drug is washed out, dye spread resumes rapidly within 1 min for all doses, indicating the drug does not affect transcriptional regulation of connexins in these Cx43+ cells, in contrast to previous studies. This integrated microfluidic platform enables the in situ monitoring of gap junction communication, yielding dynamic information about intercellular molecular transfer and pharmacological inhibition and recovery. PMID:20473391

Chen, Sisi; Lee, Luke P

2010-03-01

360

VARIATIONS IN TIGHT AND GAP JUNCTIONS IN MAMMALIAN TISSUES  

PubMed Central

The fine structure and distribution of tight (zonula occludens) and gap junctions in epithelia of the rat pancreas, liver, adrenal cortex, epididymis, and duodenum, and in smooth muscle were examined in paraformaldehyde-glutaraldehyde-fixed, tracer-permeated (K-pyroantimonate and lanthanum), and freeze-fractured tissue preparations. While many pentalaminar and septilaminar foci seen in thin-section and tracer preparations can be recognized as corresponding to well-characterized freeze-fracture images of tight and gap junction membrane modifications, many others cannot be unequivocally categorized—nor can all freeze-etched aggregates of membrane particles. Generally, epithelia of exocrine glands (pancreas and liver) have moderate-sized tight junctions and large gap junctions, with many of their gap junctions basal to the junctional complex. In contrast, the adrenal cortex, a ductless gland, may not have a tight junction but does possess large gap junctions. Mucosal epithelia (epididymis and intestine) have extensive tight junctions, but their gap junctions are not as well developed as those of glandular tissue. Smooth muscle contains numerous small gap junctions The incidence, size, and configuration of the junctions we observed correlate well with the known functions of the junctions and of the tissues where they are found.

Friend, Daniel S.; Gilula, Norton B.

1972-01-01

361

Complementary junction heterostructure field-effect transistor  

DOEpatents

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

Baca, Albert G. (Albuquerque, NM); Drummond, Timothy J. (Albuquerque, NM); Robertson, Perry J. (Albuquerque, NM); Zipperian, Thomas E. (Albuquerque, NM)

1995-01-01

362

Complementary junction heterostructure field-effect transistor  

DOEpatents

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

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

1995-12-26

363

Magnetic Josephson junctions with noncentrosymmetric superconductors  

NASA Astrophysics Data System (ADS)

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

Rahnavard, Yousef; Manske, Dirk; Annunziata, Gaetano

2014-06-01

364

Modeling transport through single-molecule junctions  

Microsoft Academic Search

Non-equilibrium Green's functions (NEGF) formalism combined with extended Hckel (EHT) and charging model are used to study\\u000a electrical conduction through single-molecule junctions. The analyzed molecular complex is composed of the asymmetric 1,4-Bis((2?-para-mercaptophenyl)-ethinyl)-2-acetyl-amino-5-nitrobenzene molecule symmetrically coupled to two gold electrodes. Owing to this\\u000a model, the accurate values of the current flowing through such junctions can be obtained by utilizing basic fundamentals

Kamil Walczak; Sergey Edward Lyshevski

2005-01-01

365

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

366

Pinhole analysis in magnetic tunnel junctions  

NASA Astrophysics Data System (ADS)

Pinholes in the insulating layer of magnetic tunnel junctions are local shortcuts and cause malfunction of such devices. The need for reduction of the tunnel resistance by reduction of the insulator thickness will make this problem even more severe. Therefore, the development of low-resistance magnetic tunnel junctions requires analyzing the pinhole density. We developed a method for pinhole imaging using electrodeposition of copper. Selective nucleation at pinholes produces characteristic structures that can be visualized by conventional microscopy techniques. The experimental conditions were carefully chosen in order to avoid uncontrolled damage of the insulator layer.

Schad, R.; Allen, D.; Zangari, Giovanni; Zana, Iulica; Yang, D.; Tondra, Mark; Wang, Dexin

2000-01-01

367

Astroglial gap junctions shape neuronal network activity  

PubMed Central

Astrocytes, the third element of the tripartite synapse, are active players in neurotransmission. Up to now, their involvement in neuronal functions has primarily been investigated at the single cell level. However, a key property of astrocytes is that they communicate via extensive networks formed by gap junction channels. Recently, we have shown that this networking modulates the moment to moment basal synaptic transmission and plasticity via the regulation of extracellular potassium and glutamate levels. Here we show that astroglial gap junctional communication also regulates neuronal network activity. We discuss these findings and their implications for brain information processing.

Pannasch, Ulrike; Derangeon, Mickael; Chever, Oana; Rouach, Nathalie

2012-01-01

368

Alternating current driven instability in magnetic junctions.  

PubMed

An effect is considered of alternating (high-frequency) current on the spin-valve-type magnetic junction configuration. The stability with respect to small fluctuations is investigated in the macrospin approximation. When the current frequency is close to the eigenfrequency (precession frequency) of the free layer, parametric resonance occurs. Both collinear configurations, antiparallel and parallel, can become unstable under resonance conditions. The antiparallel configuration can also become unstable under non-resonant conditions. The threshold current density amplitude is of the order of the dc current density for switching of the magnetic junction. PMID:21825350

Epshtein, E M; Zilberman, P E

2009-04-01

369

Electronic properties of electrodeposited semiconductor junctions  

NASA Astrophysics Data System (ADS)

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 and through ZnO/substrate junctions as a function of these deposition conditions. Finally, three device applications for these ZnO-based junction are explored: Schottky rectifiers, humidity sensors, and photovoltaic cells. Since electrical conduction to and through heterojunction interfaces is very important for maximizing the functionality of semiconductor devices, this thesis work is an essential step towards increasing the functionality of multi-layer ZnO-based heterojunction devices prepared by electrodeposition. Capacitive Mott-Schottky analyses showed that the carrier concentrations of our ZnO electrodeposits are dependent upon deposition potential, with higher net carrier concentration at more positive potentials. UV/Visible diffuse reflectance data indicates that band gap increases with more positive deposition potentials. Together, these results suggest that hydrogen is the dominant, yet unintentional, Moss-Burstein like dopant in our n-type ZnO. Furthermore, the range of carrier concentrations we can achieve (10 18 -- 1021 cm-3) is comparable to that obtained with intentional doping. This is significant because using deposition potential to change growth rate or morphology will simultaneously change electronic properties. The deposition potential studies evolved into a procedure for selective, one-step production of either ohmic or rectifying (Schottky) ZnO/metal junctions (Chatman et al., Appi.Phys.Lett., 2008, 92, 012103/1-3). Rectifying ratio and soft-breakdown characteristics can be influenced by tuning either deposition potential and pH (Chatman et al., ACS Appl. Mater. Interfaces, 2009, 1, 552-558). (In contrast, our CU2O/metal junctions were always ohmic.) Rectifying ZnO/metal junctions are very susceptible to relative humidity compared with ohmic samples because of protonic conduction at the ZnO/air interface. Hydrophobic coatings applied to ZnO deposits greatly reduce the erratic sensitivity of ZnO at high humidities while retaining humidity sensitivity (Chatman et al., ACS Appl. Mater. Interfaces, 2009, 1, 552-558). ZnO/CU2O pn junctions were prepared with different permutations of a two-step electrodeposition process. ZnO/CU 2O/metal junctions were determined to be light sensitive when the CU 2O layer was deposited using lactate-based electrolytes. Unfortunately, solar conversion efficiencies was too low to determine device efficiencies.

Chatman, Shawn Michael Edward

370

Gap junction- and hemichannel-independent actions of connexins  

PubMed Central

Connexins have been known to be the protein building blocks of gap junctions and mediate cell–cell communication. In contrast to the conventional dogma, recent evidence suggests that in addition to forming gap junction channels, connexins possess gap junction-independent functions. One important gap junction-independent function for connexins is to serve as the major functional component for hemichannels, the un-apposed halves of gap junctions. Hemichannels, as independent functional units, play roles that are different from that of gap junctions in the cell. The other functions of connexins appear to be gap junction- and hemichannel-independent. Published studies implicate the latter functions of connexins in cell growth, differentiation, tumorigenicity, injury, and apoptosis, although the mechanistic aspects of these actions remain largely unknown. In this review, gap junction- and hemichannel-independent functions of connexins are summarized, and the molecular mechanisms underlying these connexin functions are speculated and discussed.

Jiang, Jean X.; Gu, Sumin

2007-01-01

371

Phase-locking in distributed arrays of Josephson junctions  

SciTech Connect

Results from various experimental studies of Josephson junctions in distributed structures composed of superconducting microstriplines are presented. These systems have a physical length comparable to or greater than the electromagnetic wavelength propagating in the microstripline. Distributed arrays of Josephson junctions were fabricated and studied for phase coherence between the junctions. Equivalent-circuit models are introduced for both the microstriplines and the junctions. Chapter 2 describes the techniques utilized for the fabrication of the various devices studied in the experiments. Chapter 3 presents the results from several experiments involving single Josephson junctions in microstripline resonators. Estimates of the attenuation and phase velocity for the microstriplines were obtained from the experimental measurements. Chapter 4 describes the first two junction distributed array structures designed, fabricated and tested. Phase locking between the two junctions was observed and the locking strengths measured. Chapter 5 presents the experimental results from a 40-junction distributed array that was fabricated and tested.

Sauvageau, J.E.

1987-01-01

372

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

373

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

374

1. View east, junction Rockland Road and Old Murphy Road, ...  

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

1. View east, junction Rockland Road and Old Murphy Road, George Murphy House to left and Alfred I. Du Pont Institute gates to right - George Murphy House, Junction of Rockland & Old Murphy Roads, Wilmington, New Castle County, DE

375

30 CFR 56.12007 - Junction box connection procedures.  

Code of Federal Regulations, 2013 CFR

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

2013-07-01

376

Splice Junction Classification Problems for DNA Sequences: Representation Issues.  

National Technical Information Service (NTIS)

Splice junction classification in a Eukaryotic cell is an important problem because the splice junction indicates which part of the DNA sequence carries protein coding information, The major issue in building a classifier for this classification task is h...

M. Sarkar T. Leong

2001-01-01

377

Aberrant chromosome morphology in human cells defective for Holliday junction resolution.  

PubMed

In somatic cells, Holliday junctions can be formed between sister chromatids during the recombinational repair of DNA breaks or after replication fork demise. A variety of processes act upon Holliday junctions to remove them from DNA, in events that are critical for proper chromosome segregation. In human cells, the BLM protein, inactivated in individuals with Bloom's syndrome, acts in combination with topoisomerase III?, RMI1 and RMI2 (BTR complex) to promote the dissolution of double Holliday junctions. Cells defective for BLM exhibit elevated levels of sister chromatid exchanges (SCEs) and patients with Bloom's syndrome develop a broad spectrum of early-onset cancers caused by chromosome instability. MUS81-EME1 (refs 4-7), SLX1-SLX4 (refs 8-11) and GEN1 (refs 12, 13) also process Holliday junctions but, in contrast to the BTR complex, do so by endonucleolytic cleavage. Here we deplete these nucleases from Bloom's syndrome cells to analyse human cells compromised for the known Holliday junction dissolution/resolution pathways. We show that depletion of MUS81 and GEN1, or SLX4 and GEN1, from Bloom's syndrome cells results in severe chromosome abnormalities, such that sister chromatids remain interlinked in a side-by-side arrangement and the chromosomes are elongated and segmented. Our results indicate that normally replicating human cells require Holliday junction processing activities to prevent sister chromatid entanglements and thereby ensure accurate chromosome condensation. This phenotype was not apparent when both MUS81 and SLX4 were depleted from Bloom's syndrome cells, suggesting that GEN1 can compensate for their absence. Additionally, we show that depletion of MUS81 or SLX4 reduces the high frequency of SCEs in Bloom's syndrome cells, indicating that MUS81 and SLX4 promote SCE formation, in events that may ultimately drive the chromosome instabilities that underpin early-onset cancers associated with Bloom's syndrome. PMID:21399624

Wechsler, Thomas; Newman, Scott; West, Stephen C

2011-03-31

378

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

2006-11-17

379

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

380

Modeling of rf-biased overdamped Josephson junctions  

NASA Astrophysics Data System (ADS)

This paper presents a mathematical model for determining the stable phase-lock areas of microwave-biased superconductor-normal metal- superconductor Josephson junctions with low normal state resistance and small junction capacitance. The calculations are based on the resistively shunted junction model. The theoretically determined phase-lock areas are in accordance with the experimental results on Nb/HfTi/Nb junctions.

Karpov, O. V.; Buchstaber, V. M.; Tertychniy, S. I.; Niemeyer, J.; Kieler, O.

2008-11-01

381

High voltage series connected tandem junction solar battery  

DOEpatents

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

Hanak, Joseph J. (Lawrenceville, NJ)

1982-01-01

382

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

383

Perlecan regulates bidirectional Wnt signaling at the Drosophila neuromuscular junction  

PubMed Central

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.

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

2013-01-01

384

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

385

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

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

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

386

Single-channel currents of an intercellular junction  

NASA Astrophysics Data System (ADS)

We have used a double whole-cell patch-clamp system to make the first quantitative recordings of the single-channel current from an intercellular junction, presumably a gap junction. The junctional channel has various conductance states and discriminates poorly between cations and anions. It seems to change slowly from one conductance state to another.

Neyton, Jacques; Trautmann, Alain

1985-09-01

387

Mesoscopic effects in superconductor-ferromagnet-super- conductor junctions  

Microsoft Academic Search

We show that at zero temperature the supercurrent through the superconductor ferromagnetic-metal superconductor (SFS) junctions does not decay exponentially with the thickness L of the junction. At large L it has a random sample-specific sign which can change with a change in temperature. In the case of mesoscopic junctions the phase of the order parameter in the ground state is

A. Yu. Zyuzin; B. Spivak; M. Hruska

2003-01-01

388

Magnetoelectric Properties of Magnetic Tunneling Junctions  

Microsoft Academic Search

Magnetic tunneling junctions(MTJ's) consisting of two ferromagnetic layers separated by a thin insulating barrier show large tunnel magnetoresistive effects when the magnetizations of the ferromagnetic layers change their relative orientation from parallel to antiparallel in an applied field. Tunnel magneto resistance (TMR) is defined as the relative difference in tunnel resistance between parallel and antiparallel oriented magnetizations of electrodes. The

Shilpa Chava; Avishesh Dhakal; Wei Jiang Yeh

2007-01-01

389

CELL JUNCTIONS IN OMMATIDIA OF LIMULUS  

PubMed Central

The intercellular relationships in the ommatidia of the lateral eye of Limulus have been investigated. The distal process of the eccentric cell gives origin to microvilli which interdigitate with the microvilli of the retinular cells. Therefore, both types of visual cells contribute to form the rhabdom and may have an analogous photoreceptor function. Quintuple-layered junctions are found within the rhabdom at the lines of demarcation between adjoining microvilli, whether the microvilli originate from a single retinular cell, from two adjacent retinular cells, or from a retinular cell and the eccentric cell. Furthermore, quintuple-layered junctions between the eccentric cell and the tips of the microvilli of the retinular cells occur at the boundary between the distal process and the rhabdom. These findings are interpreted to indicate that the rhabdom provides an extensive electrotonic junction relating retinular cells to one another and to the eccentric cell. Quintuple-layered junctions between glial and visual cells, as well as other structural features of the ommatidial cells, are also described.

Lasansky, Arnaldo

1967-01-01

390

Ureteropelvic junction obstruction presenting after antireflux surgery  

PubMed Central

Ureteropelvic junction obstruction (UPJO) and vesicoureteral reflux (VUR) are two of the most common urologic problems in children that sometimes coexist simultaneously in a patient. However, presentation of UPJO after VUR treatment is rare. We will present two cases and discuss diagnostic and therapeutic aspects of the condition.

Alizadeh, Farshid; Izadpanahi, Mohammad Hossein; Khorrami, Mohammad Hatef; Nouri-Mahdavi, Kia

2012-01-01

391

Fluorescent window for liquid junction solar cells  

Microsoft Academic Search

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

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

1980-01-01

392

Semiconductor liquid-junction solar cell  

DOEpatents

A semiconductor liquid junction photocell in which the photocell is in the configuration of a light concentrator and in which the electrolytic solution both conducts current and facilitates the concentration of incident solar radiation onto the semiconductor. The photocell may be in the configuration of a non-imaging concentrator such as a compound parabolic concentrator, or an imaging concentrator such as a lens.

Parkinson, B.A.

1982-10-29

393

Anisotropy of p-wave Josephson junction  

NASA Astrophysics Data System (ADS)

The anisotropy of the dc Josephson current in the superconducting junctions of the p-wave equal spin pairing symmetry is theoretically investigated by the Furusaki-Tsukada-like formula. The current phase relations exhibit different oscillation periods and different phase shifts for the current along different directions, respectively.

Wang, Zhen-Yan; Shen, Rui

2010-08-01

394

Polycrystalline Diamond Junction Field Effect Transistors (JFETS).  

National Technical Information Service (NTIS)

The overall objective of this work is to develop a diamond junction field effect transistor (JFET) technology. The JFET transistor design is an approach that takes advantage of diamonds large bandgap and utilizes this property to help overcome the lack of...

D. Moyer M. Landstrass

1990-01-01

395

Magnetotransport in exchange-coupled magnetite junctions  

Microsoft Academic Search

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

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

2004-01-01

396

Overdamped Josephson junctions for digital applications  

NASA Astrophysics Data System (ADS)

An interesting feature of Superconductor-Normal metal-Superconductor Josephson junctions for digital applications is due to their non-hysteretic current-voltage characteristics in a broad temperature range below Tc. This allows to design Single-Flux-Quantum (SFQ) cells without the need of external shunts. Two advantages can be drawn from this property: first the SFQ cells can be more compact which leads to a more integrated solution towards nano-devices and more complex circuits; second the absence of electrical parasitic elements associated with the wiring of resistors external to the Josephson junctions increases the performance of SFQ circuits, in particular regarding the ultimate speed of operation. For this purpose Superconductor-Normal metal-Insulator-Superconductor Nb/Al-AlOx/Nb Josephson junctions have been recently developed at INRiM with aluminum layer thicknesses between 30 and 100 nm. They exhibit non-hysteretic current-voltage characteristics with IcRn values higher than 0.5 mV in a broad temperature range and optimal Stewart McCumber parameters at 4.2 K for RSFQ applications. The main features of obtained SNIS junctions regarding digital applications are presented.

Febvre, P.; De Leo, N.; Fretto, M.; Sosso, A.; Belogolovskii, M.; Collot, R.; Lacquaniti, V.

2013-01-01

397

Magnetoelectric Properties of Magnetic Tunneling Junctions  

NASA Astrophysics Data System (ADS)

Magnetic tunneling junctions(MTJ's) consisting of two ferromagnetic layers separated by a thin insulating barrier show large tunnel magnetoresistive effects when the magnetizations of the ferromagnetic layers change their relative orientation from parallel to antiparallel in an applied field. Tunnel magneto resistance (TMR) is defined as the relative difference in tunnel resistance between parallel and antiparallel oriented magnetizations of electrodes. The larger this TMR effect, the more sensitive the MTJ will be as magnetic read out device. This result has attracted considerable attention due to its potential applicability in digital storage industry and as magnetic field sensors. In this study we present our experimental evidence of magnetoelectric properties of MTJ's. Co(30nm)/Al2O3(1.5nm)/NiFe(30nm) tunnel junctions were fabricated on a Si wafer using DC plasma sputtering deposition with shadow mask technique. We used the RF plasma in-situ oxidation method to oxidize the thin Al layer. We measured the magnetoresistance(MR) ratio of these junctions at room temperature by applying magnetic field in plane and perpendicular to the direction of current. We could obtain MR values of 8% at room temperature and the resistances of these junctions were found to be 500O to 50 KO range. To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2007.NWS07.C1.2

Chava, Shilpa; Dhakal, Avishesh; Jiang Yeh, Wei

2007-05-01

398

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

399

Tandem junction amorphous silicon solar cells  

DOEpatents

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

Hanak, Joseph J. (Lawrenceville, NJ)

1981-01-01

400

Costochondral junction osteomyelitis in 3 septic foals  

PubMed Central

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

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

2011-01-01

401

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

402

Quantum fluctuations in chains of Josephson junctions  

SciTech Connect

We study the effect of quantum fluctuations of the phase on the low-temperature behavior of two models of Josephson junction chains with Coulomb interactions taken into account. The first model, which represents a chain of junctions close to a ground plane, is the Hamiltonian version of the two-dimensional XY model in one space and one time dimension. We demonstrate explicitly how the Nelson-Kosterlitz jump manifests itself in the conduction properties of this system at a critical value of the superconducting grain capacitance. In the second model, the charging energy for a single junction in the chain is just the parallel-plate capacitor energy Q/sup 2//8C, where Q is the charge difference across the junction and C is its capacitance. We show that for any nonzero charging energy (i.e., C

Bradley, R.M.; Doniach, S.

1984-08-01

403

Junction stresses in buried jointed pipelines  

Microsoft Academic Search

An analytical and experimental investigation on the effects of placing flexible joints in the vicinity of buried pipeline junctions evaluated the following important variables: (1) flexibility of rubber-gasketed pipeline joints, (2) bending and axial stiffness of cast-iron pipe barrels and joints, (3) modulus of soil foundation and direct soil shear effects, and (4) variations in the network topology of intersecting

A. C. Singhal; Chian-Lee Meng

1983-01-01

404

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

405

Carrier Generation and Recombination in PN Junctions and PN Junction Characteristics  

Microsoft Academic Search

For certain p-n junctions, it has been observed that the measured current-voltage characteristics deviate from the ideal case of the diffusion model. It is the purpose of this paper to show that the current due to generation and recombination of carriers from generation-recombination centers in the space charge region of a p-n junction accounts for the observed characteristics. This phenomenon

Chih-Tang Sah; Robert Noyce; William Shockley

1957-01-01

406

A Pd\\/Oxide\\/AlGaAs (MOS) junction resistor-type hydrogen sensor  

Microsoft Academic Search

An interesting Pd\\/oxide\\/AlGaAs metal oxide semiconductor (MOS) junction resistor-type hydrogen sensor, based on the current-voltage characteristics in the linear region of an AlGaAs-based PHEMT structure, is fabricated and studied. A simple model is employed to elucidate the hydrogen detection mechanism. The dissociation of H2, diffusion of H atoms and formation of a dipole layer cause a in channel resistance, show

Ching-Wen Hung; Huey-Ing Chen; Kun-Wei Lin; Tsung-Han Tsai; Tzu-Pin Chen; Li-Yang Chen; Kuei-Yi Chu; Wen-Chau Liu

2008-01-01

407

Current status and future prospects of 4H-SiC power RF bipolar junction transistors  

Microsoft Academic Search

This paper reviews the current status of 4H-SiC RF NPN bipolar junction transistors (BJT's). Process developments including precise and uniform SiC etch and low resistance p-type ohmic contact formation on a two inch SiC wafer will be presented. The high temperature operation up to 500degC and radiation hardness up to 1.6 Mrad, as well as RF performance promising for long-pulse

Feng Zhao

2009-01-01

408

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

409

Structure of Three-Way DNA Junctions 1. NonPlanar DNA Geometry  

Microsoft Academic Search

Three-way junctions were obtained by annealing two synthetic DNA-oligomers. One of the strands contains a short palindrome sequence, leading to the formation of a hairpin with four base pairs in the stem and four bases in the loop. Another strand is complementary to the linear arms of the first hairpin-containing strand. Both strands were annealed to form a three-way branched

Luda S. Shlyakhtenko; Dima Rekesh; Stuart M. Lindsay; Igor Kutyavin; Ettore Appella; Rodney E. Harrington; Yuri L. Lyubchenko

1994-01-01

410

Inverted Three-Junction Tandem Thermophotovoltaic Modules  

NASA Technical Reports Server (NTRS)

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

Wojtczuk, Steven

2012-01-01

411

3D maps of RNA interhelical junctions.  

PubMed

More than 50% of RNA secondary structure is estimated to be A-form helices, which are linked together by various junctions. Here we describe a protocol for computing three interhelical Euler angles describing the relative orientation of helices across RNA junctions. 5' and 3' helices, H1 and H2, respectively, are assigned based on the junction topology. A reference canonical helix is constructed using an appropriate molecular builder software consisting of two continuous idealized A-form helices (iH1 and iH2) with helix axis oriented along the molecular Z-direction running toward the positive direction from iH1 to iH2. The phosphate groups and the carbon and oxygen atoms of the sugars are used to superimpose helix H1 of a target interhelical junction onto the corresponding iH1 of the reference helix. A copy of iH2 is then superimposed onto the resulting H2 helix to generate iH2'. A rotation matrix R is computed, which rotates iH2' into iH2 and expresses the rotation parameters in terms of three Euler angles ?(h), ?(h) and ?(h). The angles are processed to resolve a twofold degeneracy and to select an overall rotation around the axis of the reference helix. The three interhelical Euler angles define clockwise rotations around the 5' (-?(h)) and 3' (?(h)) helices and an interhelical bend angle (?(h)). The angles can be depicted graphically to provide a 'Ramachandran'-type view of RNA global structure that can be used to identify unusual conformations as well as to understand variations due to changes in sequence, junction topology and other parameters. PMID:21959236

Bailor, Maximillian H; Mustoe, Anthony M; Brooks, Charles L; Al-Hashimi, Hashim M

2011-10-01

412

Androgen-dependent sertoli cell tight junction remodeling is mediated by multiple tight junction components.  

PubMed

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

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

2014-07-01

413

Characterization of cytoskeletal and junctional proteins expressed by cells cultured from human arachnoid granulation tissue  

PubMed Central

Background The arachnoid granulations (AGs) are projections of the arachnoid membrane into the dural venous sinuses. They function, along with the extracranial lymphatics, to circulate the cerebrospinal fluid (CSF) to the systemic venous circulation. Disruption of normal CSF dynamics may result in increased intracranial pressures causing many problems including headaches and visual loss, as in idiopathic intracranial hypertension and hydrocephalus. To study the role of AGs in CSF egress, we have grown cells from human AG tissue in vitro and have characterized their expression of those cytoskeletal and junctional proteins that may function in the regulation of CSF outflow. Methods Human AG tissue was obtained at autopsy, and explanted to cell culture dishes coated with fibronectin. Typically, cells migrated from the explanted tissue after 7–10 days in vitro. Second or third passage cells were seeded onto fibronectin-coated coverslips at confluent densities and grown to confluency for 7–10 days. Arachnoidal cells were tested using immunocytochemical methods for the expression of several common cytoskeletal and junctional proteins. Second and third passage cultures were also labeled with the common endothelial markers CD-31 or VE-cadherin (CD144) and their expression was quantified using flow cytometry analysis. Results Confluent cultures of arachnoidal cells expressed the intermediate filament protein vimentin. Cytokeratin intermediate filaments were expressed variably in a subpopulation of cells. The cultures also expressed the junctional proteins connexin43, desmoplakin 1 and 2, E-cadherin, and zonula occludens-1. Flow cytometry analysis indicated that second and third passage cultures failed to express the endothelial cell markers CD31 or VE-cadherin in significant quantities, thereby showing that these cultures did not consist of endothelial cells from the venous sinus wall. Conclusion To our knowledge, this is the first report of the in vitro culture of arachnoidal cells grown from human AG tissue. We demonstrated that these cells in vitro continue to express some of the cytoskeletal and junctional proteins characterized previously in human AG tissue, such as proteins involved in the formation of gap junctions, desmosomes, epithelial specific adherens junctions, as well as tight junctions. These junctional proteins in particular may be important in allowing these arachnoidal cells to regulate CSF outflow.

Holman, David W; Grzybowski, Deborah M; Mehta, Bhavya C; Katz, Steven E; Lubow, Martin

2005-01-01

414

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

415

Microwave detector response of the Josephson junction arrays  

SciTech Connect

This paper reports on microwave detector response {eta} for three types of superconducting structures:single edge-type Josephson junction, array of series connected junctions and array of RF series and DC parallel connected junctions investigated in the frequency range 35-120 GHz. Experimental dependence of {eta} vs biasing voltage is mainly determined by the interaction of junctions in array. The Selective response, that means narrow linewidth of Josephson radiation, has been observed for third type of superconducting structures in small magnetic field changing the phase shift between near placed junctions. These arrays have the advantage in coupling with the external microwave system.

Ovsyannikov, G.A.; Babayan, G.E. (Inst. of Radio Engineering and Electronics, Academy of Sciences, Moscow 103907 (SU)); Laptev, V.N.; Makhov, V.I. (Research Inst. of Physical Problems, Moscow 103460 (SU))

1991-03-01

416

Bistable hysteresis and resistance switching in hydrogen-gold junctions  

NASA Astrophysics Data System (ADS)

Current-voltage characteristics of H2-Au molecular junctions exhibit intriguing steps around a characteristic voltage of Vs?40mV . Surprisingly, we find that a hysteresis is connected to these steps with a typical time scale >10ms . This time constant scales linearly with the power dissipated in the junction beyond an off-set power Ps=IVs . We propose that the hysteresis is related to vibrational heating of both the molecule in the junction and a set of surrounding hydrogen molecules. Remarkably, by stretching the junction the hysteresis’ characteristic time becomes >days . We demonstrate that reliable switchable devices can be built from such junctions.

Trouwborst, M. L.; Huisman, E. H.; van der Molen, S. J.; van Wees, B. J.

2009-08-01

417

Differential pathways of claudin oligomerization and integration into tight junctions  

PubMed Central

Tight junctions are the critical intercellular structure required to establish an epithelial barrier. Among the several classes of proteins required to form tight junctions are the tetraspan transmembrane proteins known as claudins that directly determine paracellular permeability. Considerable progress has been made in understanding how incorporation of different claudins into tight junctions increase or decrease paracellular permeability and ion selectivity. However, it has proven difficult to identify discrete steps in claudin assembly and whether claudins exist in distinct oligomerization states prior to tight junction assembly. Studies of homomeric and heteromeric claudin-claudin interactions using complementary techniques suggest a diversity of pathways used by different claudins to oligomerize and integrate into tight junctions.

Koval, Michael

2013-01-01

418

?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

2012-11-01

419