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Junction
Kinds of Junction Terms modified by Junction Selected AbstractsENDOSCOPIC DEFINITION OF ESOPHAGOGASTRIC JUNCTION FOR DIAGNOSIS OF BARRETT'S ESOPHAGUS: IMPORTANCE OF SYSTEMATIC EDUCATION AND TRAININGDIGESTIVE ENDOSCOPY, Issue 4 2009Norihisa Ishimura The diagnosis of Barrett's esophagus (BE) requires an accurate recognition of the columnar-lined esophagus at endoscopy. However, a universally accepted standardized endoscopic grading system of BE was lacking prior to the development of the Prague ,circumferential and maximal' criteria. In this system, the landmark for the esophagogastric junction (EGJ) is the proximal end of the gastric folds, not the distal end of the palisade vessels, which are used to endoscopically identify the EGJ in Japan. Although the circumferential and maximal criteria are clinically relevant, an important shortcoming of this system may be failure to identify short-segment BE, a lesion that is found frequently in the Japanese. To compare the diagnostic yield for BE when using the palisade vessels versus gastric folds as a landmark for the EGJ, we evaluated interobserver diagnostic concordance. The endoscopic identification of the EGJ using both landmarks resulted in unacceptably low kappa coefficients of reliability. However, there was a statistically significant improvement after the participants were thoroughly trained in identification of the EGJ during the endoscopic study. Although it remains controversial which landmark is better for the endoscopic diagnosis of BE, it is important to systematically educate and train endoscopists in order to improve diagnostic consistency in patients with BE. [source] DOES NITRIC OXIDE MODULATE TRANSMITTER RELEASE AT THE MAMMALIAN NEUROMUSCULAR JUNCTION?CLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 4 2007Travis J Nickels SUMMARY 1Application of the nitric oxide (NO) donor, sodium nitrite and the NO synthase substrate l -arginine had no effect on nerve-evoked transmitter release in the rat isolated phrenic nerve/hemidiaphragm preparation; however, when adenosine A1 receptors were blocked with the adenosine A1 receptor antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) prior to application of sodium nitrate or l -arginine, a significant increase in transmitter release was observed. In addition, the NO donor s -nitroso- N -acetylpenicillamine (SNAP) significantly increased transmitter release in the presence of DPCPX. In the present study, we have made the assumption that these NO donors elevate the level of NO in the tissue. Future studies should test other NO-donating compounds and also monitor the NO concentrations in the tissue to ensure that these effects are, in fact, NO induced. 2Elevation of cGMP in this preparation with the guanylyl cyclase activator 3-(5,-hydroxymethyl-2,-furyl)-1-benzyl indazole (YC-1) significantly enhanced transmitter release. In the presence of DPCPX and the selective guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), which blocks the production of cGMP, the excitatory effects of sodium nitrite and l -arginine were abolished. 3These results suggest that NO serves to enhance transmitter release at the rat neuromuscular junction (NMJ) via a cGMP pathway and this facilitation of transmitter release can be blocked with adenosine. Previously, we demonstrated that adenosine inhibits N-type calcium channels. Because NO only affects transmitter release when adenosine A1 receptors are blocked, we suggest that NO enhances transmitter release by enhancing calcium influx via N-type calcium channels. Further studies are needed to confirm that NO alters transmitter release via cGMP and that this action involves the N-type calcium channel. 4The results of the present study are consistent with a model of NO neuromodulation that has been proposed for the mammalian vagal,atrial junction. This model suggests that NO acts on NO-sensitive guanylyl cyclase to increase the intracellular levels of cGMP. In turn, cGMP inhibits phosphodiesterase-3, increasing levels of cAMP, which then acts on the N-type calcium channels to enhance calcium influx, leading to an increase in transmitter release. Our only modification to this model for the NMJ is that adenosine serves to block the modulation of transmitter release by NO. [source] ARE GAP JUNCTIONS TRULY INVOLVED IN INHIBITORY NEUROMUSCULAR INTERACTION IN MOUSE PROXIMAL COLON?CLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 8 2006Andrei Sibaev SUMMARY 1Gap junctions exist between circular muscle cells of the colon and between interstitial cells of Cajal (ICC) in the myenteric plexus of the gastrointestinal tract. They also probably couple intramuscular ICC with smooth muscle cells. Recent functional evidence for this was found in dye-coupling and myoelectrical experiments. 2In the present study, we tested the hypothesis of gap junctions putatively being involved in neuromuscular interaction in mouse colon by using different classes of gap junction blockers. 3Electrical field stimulation of the myenteric plexus elicited tetrodotoxin-sensitive and hexamethonium-independent fast and slow inhibitory junction potentials (fIJP and sIJP, respectively) in circular smooth muscle cells, as evaluated by intracellular recording techniques in impaled smooth muscle cells. Heptanol produced a time-dependent hyperpolarization of the membrane potential (MP) and abolished fIJP and sIJP. Octanol had no effect on the MP and abolished fIJP and sIJP. Carbenoxolone produced a time-dependent depolarization of the MP without any effect on fIJP or sIJP. The connexin 43 mimetic gap junction blocker GAP-27 had no effect on MP, fIJP or sIJP. 4Based on the presently available gap junction blockers we found no evidence that gap junctions are involved in neuromuscular transmission in mouse colon, as suggested by morphological studies. [source] The Effect of Carbachol and ,-Bungarotoxin on the Frequency of Miniature Endplate Potentials at the Frog Neuromuscular JunctionEXPERIMENTAL PHYSIOLOGY, Issue 2 2000Ela Bukharaeva The effects of an acetylcholine analogue, carbachol (CCh), and a purified irreversible nicotinic antagonist, ,-bungarotoxin (BTX), on the frequency of the miniature endplate potentials (mEPPs) at the neuromuscular junction of the frog were tested at 20 and 10°C. CCh (5 ± 10-6 m) reduced the frequency of mEPPs to about 60%; this reduction was not affected by 1 ± 10-7 g ml-1 BTX. BTX also reversibly decreased the mEPP frequency by 40%, but not in the presence of CCh or in Ringer solution with 0 or 8 mM Ca2+. The present data show that BTX, which inhibits a class of nicotinic ACh receptors, does not block the decrease of mEPP frequency evoked by CCh and can itself suppress the frequency of spontaneous quantal release. [source] Effects of wildfire and permafrost on soil organic matter and soil climate in interior AlaskaGLOBAL CHANGE BIOLOGY, Issue 12 2006JENNIFER W. HARDEN Abstract The influence of discontinuous permafrost on ground-fuel storage, combustion losses, and postfire soil climates was examined after a wildfire near Delta Junction, AK in July 1999. At this site, we sampled soils from a four-way site comparison of burning (burned and unburned) and permafrost (permafrost and nonpermafrost). Soil organic layers (which comprise ground-fuel storage) were thicker in permafrost than nonpermafrost soils both in burned and unburned sites. While we expected fire severity to be greater in the drier site (without permafrost), combustion losses were not significantly different between the two burned sites. Overall, permafrost and burning had significant effects on physical soil variables. Most notably, unburned permafrost sites with the thickest organic mats consistently had the coldest temperatures and wettest mineral soil, while soils in the burned nonpermafrost sites were warmer and drier than the other soils. For every centimeter of organic mat thickness, temperature at 5 cm depth was about 0.5°C cooler during summer months. We propose that organic soil layers determine to a large extent the physical and thermal setting for variations in vegetation, decomposition, and carbon balance across these landscapes. In particular, the deep organic layers maintain the legacies of thermal and nutrient cycling governed by fire and revegetation. We further propose that the thermal influence of deep organic soil layers may be an underlying mechanism responsible for large regional patterns of burning and regrowth, detected in fractal analyses of burn frequency and area. Thus, fractal geometry can potentially be used to analyze changes in state of these fire prone systems. [source] Stalked crinoids from a Jurassic tidal deposit in western North AmericaLETHAIA, Issue 1 2000CAROL M. TANG This is the first systematic and paleoecological study of a crinoidal limestone (encrinite) from the Jurassic System of North America. The encrinite is part of a shallow-water tidal facies of the Middle Jurassic Carmel Formation located at Mount Carmel Junction (southwestern Utah, U.S.A.) and may represent one of the youngest shallow-water encrinites in the geological record. In the past, the crinoid at this locality was referred to as Pentacrinus asteriscus, a name used to describe almost all of the crinoid columnals found throughout the Jurassic of the U.S. western interior. However, systematic work indicates that the crinoid is Isocrinus nicoleti and is the first non-endemic crinoid to be reported from North American Jurassic strata. Although articulated pinnules and arms have been found, I. nicoleti occurs predominantly as well-preserved, partially articulated columnals. The crinoids occur within a tidal complex consisting of ooid shoal, tidal channel, and lagoonal facies. The unique environmental and ecological conditions which existed in the southernmost end of the Jurassic North America seaway may have allowed for the development of this crinoid colony and subsequent deposition of the encrinite. [source] Synthesis of Polystyrene- block -Poly(methyl methacrylate) with Fluorene at the Junction: Sequential Anionic and Controlled Radical Polymerization from a Single CarbonMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 24 2009Nathan D. Contrella Abstract Polystyrene- block -poly(methyl methacrylate) (PS- b -PMMA) has been synthesized by sequential anionic and reverse atom transfer radical polymerization (ATRP) or a variation of nitroxide mediated polymerization (NMP) from a single initiating site, specifically the 9-carbon on 2,7-dibromofluorene or fluorene. The addition of the second arm (PS) relied on thermal decomposition of 2,2,-azoisobutyronitrile (AIBN) to generate radicals, abstracting the 9-H on the polymer-bound fluorene species to form the initiating radical. Styrene was not present in the reaction mixture when AIBN was decomposed, preventing competition between addition across the monomeric alkene and hydrogen abstraction from the fluorene. After 1,h, styrene was introduced and mediation of the subsequent radical polymerization was achieved by the presence of CuCl2/ligand or TEMPO. Characterization of the diblock copolymers by gel permeation chromatography (GPC) revealed substantial shifts in number average molecular weight () values compared to the anionically prepared PMMA macroinitiator, while polydispersity indices (PDI's) remained relatively low (typically,<,1.5). Characterization by UV detection with GPC (at 310,nm) verified that the diblock polymer is chromophore-bound, which was further verified by UV-vis spectroscopy of the isolated diblock. [source] Synthesis, Characterization and Self-Assembly of Novel Amphiphilic Block Copolymers with a Polyhedral Oligomeric Silsesquioxanes Moiety Attached at the Junction of the Two BlocksMACROMOLECULAR RAPID COMMUNICATIONS, Issue 12 2009Liang Zhang Abstract A novel well-defined amphiphilic block copolymer, with the polyhedral oligomeric silsesquioxane (POSS) moiety at the junction of the two blocks of polystyrene and poly(ethylene oxide) (PEO), was designed and synthesized. First, a macroinitiator containing a POSS moiety and a PEO chain was prepared and then atom transfer radical polymerization of styrene was carried out in the presence of the macroinitiator in bulk. The polymerization results show that the process bears the characteristics of controlled/living free radical polymerizations. The structure and molecular weight of the polymers were characterized by GPC, 1H NMR, and FT-IR spectroscopy. The self-assembly behaviors of the polymers was investigated by TEM and SEM. It was observed that the polymers can self-assemble into vesicles in aqueous solution. [source] Radiofrequency Energy Modification of the Atrioventricular Junction in Patients with Atrial Fibrillation: Modes of Ventricular Response Under Autonomic Blockade and Long-Term EffectPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 9 2001HARALAMPOS D. KRIATSELIS KRIATSELIS, H.D., et al.: Radiofrequency Energy Modification of the Atrioventricular Junction in Patients with Atrial Fibrillation: Modes of Ventricular Response Under Autonomic Blockade and Long-Term Effect. The short- and long-term effect of radiofrequency (RF) modification of the AV junction on ventricular rate and left ventricular function and the different types of ventricular response during energy application under autonomic nervous blockade were assessed in 28 patients with medically refractory atrial fibrillation. During the successful RF application, ventricular rate slowed progressively (type I response, ten patients) or accelerated at first and then slowed (type II response, 11 patients). Type II response was associated with a more anterior ablation site compared to Type I response. A primary successful outcome was achieved in 21 patients. Inadvertent complete AV block developed in three patients, while in four patients AV nodal ablation was performed after an unsuccessful modification attempt. During 6-month follow-up, the ventricular rate was adequately controlled in only four patients. Among the 16 patients with a recurrence of uncontrolled AF were all 10 patients with type I response and 6 of 11 patients with type II response. One patient died suddenly 10 weeks after the procedure. [source] Safety of Pacemaker Implantation Prior to Radiofrequency Ablation of Atrioventricular Junction in a Single Session ProcedurePACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 6 2000ALESSANDRO PROCLEMER RF current delivery may cause acute and chronic dysfunction of previously implanted pacemakers. The aim of this study was to assess prospectively the effects of RF energy on Thera I and Kappa pacemakers in 70 consecutive patients (mean age 70 ± 11 years, mean left ventricular ejection fraction 48 ± 15%) who underwent RF ablation of the AV junction for antiarrhythmic drug refractory atrial fibrillation (permanent in 42 patients, paroxysmal in 28). These pacing systems incorporate protection elements to avoid electromagnetic interference. The pacemakers (Thera DR 7960 I in 20 patients, Thera SR 8960 1 in 30, Kappa DR 600,601 in 8, Kappa SR 700,701 in 12) were implanted prior to RF ablation in a single session procedure and were transiently programmed to VVI mode at a rate of 30 beats/min. Capsure SP and Z unibipolar leads were used. During RF application there was continuous monitoring of three ECG leads, endocavitary electrograms, and event markers. Complete AV block was achieved in all cases after 3.6 ± 2.9 RF pulses and 100 ± 75 seconds of RF energy delivery. The mean time of pacemaker implantation and RF ablation was 60 ± 20 minutes. Transient or permanent pacemaker dysfunction including under/oversensing, reversion to a "noise-mode" pacing, pacing inhibition, reprogramming, or recycling were not observed. Leads impedance, sensing, and pacing thresholds remained in the normal range in the acute and long-term phase (average follow-up 18 ± 12 months). In conclusion, Thera I and Kappa pacemakers exhibit excellent protection against interference produced by RF current. The functional integrity of the pacemakers and Capsure leads was observed in the acute and chronic phases. Thus, the implantation of these pacing systems prior to RF ablation of the AV junction can be recommended. [source] Chronic Actinic Dermatitis to Sesquiterpene Lactones: [2+2] Photoreaction Toward Thymidine of (+) and (,) ,-Methylene-Hexahydrobenzofuranone with a cis Ring JunctionPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 3 2010Sébastien Fuchs (+) and (,) ,-methylene-hexahydrobenzofuranone derivatives with a stereochemically pure cis ring junction were used as models of sesquiterpene lactones to study their photoreactivity toward thymidine. After 313 nm irradiation of a deoxygenated acetone solution of lactone models and thymidine, six [2+2] photoadducts were isolated for each enantiomer and fully characterized by a combination of NMR experiments. A common syn regioselectivity and exo stereoselectivity were observed for photoadducts. This high photoreactivity of ,-methylene-,-butyrolactone ring toward thymidine could be an explanation of the progressive evolution of allergic contact dermatitis toward chronic actinic dermatitis. [source] III-V concentrator solar cell reliability prediction based on quantitative LED reliability data,PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 6 2007Manuel Vázquez Abstract III-V Multi Junction (MJ) solar cells based on Light Emitting Diode (LED) technology have been proposed and developed in recent years as a way of producing cost-competitive photovoltaic electricity. As LEDs are similar to solar cells in terms of material, size and power, it is possible to take advantage of the huge technological experience accumulated in the former and apply it to the latter. This paper analyses the most important parameters that affect the operational lifetime of the device (crystalline quality, temperature, current density, humidity and photodegradation), taking into account experience on the reliability of LEDs. Most of these parameters are less stressed for a III-V MJ solar cell working at 1000 suns than for a high-power LED. From this analysis, some recommendations are extracted for improving the long-term reliability of the solar cells. Compared to high-power LEDs based on compound semiconductors, it is possible to achieve operational lifetimes higher than 105,hours (34 years of real-time operation) for III-V high-concentration solar cells. Copyright © 2007 John Wiley & Sons, Ltd. [source] Expression of Progesterone Receptor in the Utero-tubal Junction After Intra-uterine and Deep Intra-uterine Insemination in SowsREPRODUCTION IN DOMESTIC ANIMALS, Issue 5 2010P Tummaruk Contents The aim of this study was to investigate the expression of progesterone receptor (PR) in the utero-tubal junction (UTJ) of sows at 24 h after intra-uterine insemination (IUI) and deep intra-uterine insemination (DIUI) compared with conventional artificial insemination (AI) in pigs. Fifteen multiparous sows were used: AI (n = 5), IUI (n = 5) and DIUI (n = 5). The sows were inseminated with a single dose of diluted semen during the second oestrus after weaning at 6,8 h prior to ovulation (AI: 3000 × 106 spermatozoa, IUI: 1000 × 106 spermatozoa and DIUI: 150 × 106 spermatozoa). The UTJ was collected and subject to immunohistochemical staining using avidin-biotin immunoperoxidase technique with mouse monoclonal antibody to PR. In the oviductal part of the UTJ, the intensity of PR in the tunica muscularis and the proportion of PR-positive cells in the surface epithelium after DIUI were lower than AI (p < 0.05). The intensity and the proportion of PR-positive cells between AI and IUI in all compartments of the UTJ did not differ significantly (p > 0.05). When comparing between tissue compartments, prominent staining was observed in the muscular layer of the UTJ. It could be concluded that the expression of PR in the UTJ prior to fertilization after DIUI with a reduced number of spermatozoa was lower than that after AI. This might influence sperm transportation and the fertilization process. [source] A Proteomics Approach to Cloning Fenestrin from the Nuclear Exchange Junction of TetrahymenaTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 4 2008ERIC S. COLE ABSTRACT. We set out to find the "fenestrin" gene, a gene whose protein is associated with numerous cellular apertures, including the nuclear exchange junction in mating Tetrahymena thermophila. First we developed protocols for imaging and isolating intact nuclear exchange junctions from conjugating cells. Proteins from these junctions were purified using SDS-PAGE, subjected to limited proteolysis, and precise molecular weights were determined by mass spectrometry. Using Protein Prospector® software and the published Tetrahymena Genome Database, genes for 15 of the most abundant proteins found in our extracts were identified. The most promising candidate was cloned by PCR, fused to yellow fluorescent protein (YFP), and placed under the control of an inducible metallothionein promoter. YFP-localization within live Tetrahymena transformants strongly suggested that one of these genes encoded the fenestrin protein, a result that was subsequently confirmed by Western blotting. [source] Utilization of a Common Pathway for the Synthesis of High Affinity Macrocyclic Grb2 SH2 Domain-Binding Peptide Mimetics That Differ in the Configuration at One Ring JunctionCHEMISTRY & BIODIVERSITY, Issue 4 2005Zhen-Dan Shi As typified by 2-{(9S,10S,14R,18S)-18-(2-amino-2-oxoethyl)-14-[(5-methyl-1H -indol-1-yl)methyl]-8,17,20-trioxo-10-[4-(phosphonomethyl)phenyl]-7,16,19-triazaspiro[5.14]icos-11-en-9-yl}acetic acid ((14R)- 1b), ring-closing methathesis-derived macrocyclic tetrapeptide mimetics have recently been reported that bind with high affinity to Grb2 SH2 domains in both extracellular and whole-cell assays. The synthetic complexity of this class of agents limits further therapeutic development. Although a significant component of this synthetic complexity arises from the presence of three stereogenic centers, C(9) (S), C(10) (S), and C(14) (R), it is unclear whether stereoselective introduction of defined configuration at C(14) is required for high-affinity binding. Reported herein is a synthetic route to these macrocycles lacking stereoselectivity in the formation of the C(14) ring junction, which is four synthetic steps shorter than the original stereoselective synthesis. Separation of C(14)-epimers obtained by this approach was achieved by preparative HPLC. Molecular-dynamics studies of ligands bound to the Grb2 SH2 domain protein indicated that the (14R)-configuration should display more-favorable interactions with the protein relative to the (14S)-epimer. Indeed, although surface-plasmon-resonance-derived binding constants to Grb2 SH2 domain protein indicated that the affinity of the (14R)-epimer (KD=4.8,nM) is greater than that of the (14S)-epimer (KD=11,nM), it is only marginally so. Therefore, little affinity would be lost through a non-stereoselective synthesis of the C(14)-center. Further studies are in progress to explore reduced structural complexity at the C(14)-center. [source] A Possible Role for Gap Junctions in Generation of Very Fast EEG Oscillations Preceding the Onset of, and Perhaps Initiating, SeizuresEPILEPSIA, Issue 2 2001Roger D. Traub Summary: ,Purpose: We propose an experimentally and clinically testable hypothesis, concerning the origin of very fast (>,70 Hz) EEG oscillations that sometimes precede the onset of focal seizures. These oscillations are important, as they may play a causal role in the initiation of seizures. Methods: Subdural EEG recordings were obtained from children with focal cortical dysplasias and intractable seizures. Intra- and extracellular recordings were performed in rat hippocampal slices, with induction of population activity, as follows: (a) bath-applied tetramethylamine (an intracellular alkalinizing agent, that opens gap junctions); (b) bath-applied carbachol, a cholinergic agonist; and (c) focal pressure ejection of hypertonic K+ solution. Detailed network simulations were performed, the better to understand the cellular mechanisms underlying oscillations. A major feature of the simulations was inclusion of axon,axon gap junctions between principal neurons, as supported by recent experimental data. Results: Very fast oscillations were found in children before seizure onset, but also superimposed on bursts during the seizure, and on interictal bursts. In slice experiments, very fast oscillations had previously been seen on interictal-like bursts; we now show such oscillations before, between, and after epileptiform bursts. Very fast oscillations were also seen superimposed on gamma (30,70 Hz) oscillations induced by carbachol or hypertonic K+, and in the latter case, very fast oscillations became continuous when chemical synapses were blocked. Simulations replicate these data, when axonal gap junctions are included. Conclusions: Electrical coupling between principal neurons, perhaps via axonal gap junctions, could underlie very fast population oscillations, in seizure-prone brain, but possibly also in normal brain. The anticonvulsant potential of gap-junction blockers such as carbenoxolone, now in clinical use for treatment of ulcer disease, should be considered. [source] Organization of Organic Molecules with Inorganic Nanoparticles: Hybrid Nanodiodes,ADVANCED FUNCTIONAL MATERIALS, Issue 5 2008Kallol Mohanta Abstract A monolayer of inorganic nanoparticles and a monolayer of organic molecules have been electrostatically assembled in sequence. Such assemblies or organizations exhibit electrical rectification. When the sequence of the organization is reversed, the direction of rectification becomes opposite. In both n-type ZnO/organic and organic/n-ZnO assemblies, electron flow is favorable from the n-ZnO nanoparticle to the (electron-accepting) organic molecule. While the individual components do not show any rectification, substitutes of the organic molecule tune electrical rectification. Junctions between a p-type ZnO nanoparticle and an electron-donating metal phthalocyanine favor current flow in the nanoparticle-to-phthalocyanine direction. The rectification in a junction between a nanoparticle and an organic molecule is due to the parity between free carriers in the former component and the type of carrier-accepting nature in the latter one. By observing electrical rectification with the tip of a scanning tunneling microscope, organic/inorganic hybrid nanodiodes or rectifiers on the molecular/nanoscale have been established. [source] Bacteriorhodopsin-Monolayer-Based Planar Metal,Insulator,Metal Junctions via Biomimetic Vesicle Fusion: Preparation, Characterization, and Bio-optoelectronic Characteristics,ADVANCED FUNCTIONAL MATERIALS, Issue 8 2007D. Jin Abstract A reliable and reproducible method for preparing bacteriorhodopsin (bR)-containing metal,biomolecule,monolayer-metal planar junctions via vesicle fusion tactics and soft deposition of Au top electrodes is reported. Optimum monolayer and junction preparations, including contact effects, are discussed. The electron-transport characteristics of bR-containing membranes are studied systematically by incorporating native bR or artificial bR pigments derived from synthetic retinal analogues, into single solid-supported lipid bilayers. Current,voltage (I,V) measurements at ambient conditions show that a single layer of such bR-containing artificial lipid bilayers pass current in solid electrode/bilayer/solid electrode structures. The current is passed only if retinal or its analogue is present in the protein. Furthermore, the preparations show photoconductivity as long as the retinal can isomerize following light absorption. Optical characterization suggests that the junction photocurrents might be associated with a photochemically induced M-like intermediate of bR. I,V measurements along with theoretical estimates reveal that electron transfer through the protein is over four orders of magnitude more efficient than what would be estimated for direct tunneling through 5,nm of water-free peptides. Our results furthermore suggest that the light-driven proton-pumping activity of the sandwiched solid-state bR monolayer contributes negligibly to the steady-state light currents that are observed, and that the orientation of bR does not significantly affect the observed I,V characteristics. [source] Impact of Defect Distribution on Resistive Switching Characteristics of Sr2TiO4 Thin FilmsADVANCED MATERIALS, Issue 3 2010Keisuke Shibuya The resistive switching properties of Sr2TiO4 thin films with specific defect distribution have been studied. Junctions of Sr2TiO4 thin films containing a high density of defects show well-pronounced resistive switching properties while those with well-ordered microstructure exhibited insignificant hysteresis windows. This work clearly demonstrates the crucial role of defects for the microscopic switching mechanisms in oxide thin films. [source] Carbon Nanotube Junctions: Multibranched Junctions of Carbon Nanotubes via Cobalt Particles (Adv. Mater.ADVANCED MATERIALS, Issue 44 200944/2009) Junctions between different carbon nanotubes (CNTs) created using cobalt particles as central nodes (background) are demonstrated by Ming-Sheng Wang and co-workers on p. 4477. The process involves high-temperature electron irradiation of areas where a metal particle is located at the overlapping region of two CNTs. In situ transmission electron microscopy measurements show that the junctions are electrically conductive and mechanically robust. The extension of this technique towards creating more complicated structures, such as a 3D CNT network, is also depicted in the cover. [source] Multibranched Junctions of Carbon Nanotubes via Cobalt ParticlesADVANCED MATERIALS, Issue 44 2009Julio A. Rodríguez-Manzo Junctions between different carbon nanotubes are created using cobalt particles as central nodes (see image). The process involves high temperature and electron irradiation of areas where a metal particle is located at the overlapping region of two nanotubes. In situ transmission electron microscopy measurements show that the junctions are electrically conductive and mechanically robust. A high breaking strength of 1,5,GPa is found for the junctions. [source] Progress with Molecular Electronic Junctions: Meeting Experimental Challenges in Design and FabricationADVANCED MATERIALS, Issue 43 2009Richard L. McCreery Abstract Molecular electronics seeks to incorporate molecular components as functional elements in electronic devices. There are numerous strategies reported to date for the fabrication, design, and characterization of such devices, but a broadly accepted example showing structure-dependent conductance behavior has not yet emerged. This progress report focuses on experimental methods for making both single-molecule and ensemble molecular junctions, and highlights key results from these efforts. Based on some general objectives of the field, particular experiments are presented to show progress in several important areas, and also to define those areas that still need attention. Some of the variable behavior of ostensibly similar junctions reported in the literature is attributable to differences in the way the junctions are fabricated. These differences are due, in part, to the multitude of methods for supporting the molecular layer on the substrate, including methods that utilize physical adsorption and covalent bonds, and to the numerous strategies for making top contacts. After discussing recent experimental progress in molecular electronics, an assessment of the current state of the field is presented, along with a proposed road map that can be used to assess progress in the future. [source] Comment on "Molecular Transport Junctions: Clearing Mists"ADVANCED MATERIALS, Issue 16 2009Massimiliano Di Ventra No abstract is available for this article. [source] Chemical Interactions at Metal/Molecule Interfaces in Molecular Junctions,A Pathway Towards Molecular Recognition,ADVANCED MATERIALS, Issue 3 2009Mila Manolova A 4-aminothiophenol self-assembled monolayer (see image) is prepared on top of a Au(111) crystal, which is subsequently metallized by a nearly closed Pd overlayer of monoatomic height. Analysis of its structural setup and electronic properties reveals that the monolayer consists of a minimum of two molecular layers, and strong chemical interactions between the metal overlayer and the amino groups are found to play a decisive role in determining the overall electronic, and thus the transport properties, of the layer/metal contact. [source] Electronic Current Transport through Molecular Monolayers: Comparison between Hg/Alkoxy and Alkyl Monolayer/Si(100) Junctions,ADVANCED MATERIALS, Issue 20 2008Florent Thieblemont Electronic current transport through alkoxy and alkyl monolayer-based junctions is presented. Monolayers are prepared on n-Si(100) with sufficiently high quality to reliably investigate the actual molecular effect of each monolayer on their current,voltage characteristics. The results show that extending the Si-binding chemistry from alkene to alcohol is feasible, which should significantly facilitate preparation of monolayers with modified molecules. [source] Molecular Transport Junctions: Clearing Mists,ADVANCED MATERIALS, Issue 1 2007M. Lindsay Abstract Recent progress in the measurement and modeling of transport in molecular junctions has been very significant. Tunnel transport in the Landauer,Imry regime is now broadly understood for several systems, although a detailed understanding of the role of contact geometry is still required. We overview some clear indications from recent research and note the quite reasonable agreement between measured and calculated conductance in metal,molecule,metal junctions. The next challenge lies in obtaining a microscopic understanding of charge transport that involves reduction or oxidation of molecules. [source] Experimental Approaches for Controlling Current Flowing through Metal,Molecule,Metal Junctions,ADVANCED MATERIALS, Issue 10 2006E. Tran Abstract Two experimental approaches that enable control of current flow through metal,molecules,metal junctions are described. A number of studies using two-electrode metal,molecules,metal junctions have shown that the current between the electrodes depends on the structures of the incorporated molecules. When a tunneling mechanism dominates electron transport through organic molecules, the molecules behave similar to resistors with resistivities that can be controlled by changing the structure. Incorporation of molecules with increasing conjugation into Hg-based junctions increases the current flow dramatically. Alternatively, by using four-electrode electrochemical junctions that allow the potential of the electrodes to be controlled with respect to the energy levels of the incorporated molecules, it is possible to change the mechanism of electron transfer and produce abrupt increases in the current flow. These signals, analogous to solid-state diodes, are particularly significant for molecular electronics. Electrochemical junctions also permit prediction of the value of the applied potential at which the current will start taking off and to identify the mechanism of charge transport. New and recently published results obtained using junctions based on Hg electrodes in an "electrochemical" mode show that two junctions incorporating redox centers by different interactions behave as current switches, with the current flow dominated by different charge-transport mechanisms. [source] Erythrokeratodermia variabilis (EKV) , eine Störung der epidermalen Expression von Gap-Junction-ProteinenJOURNAL DER DEUTSCHEN DERMATOLOGISCHEN GESELLSCHAFT, Issue 5 2005Erythrokeratodermia variabilis (EKV), a disorder due to altered epidermal expression of gap junction proteins Connexin,31; Connexin,43; Erythrokeratodermia variabilis; Gap Junctions Zusammenfassung Die Erythrokeratodermia variabilis (EKV) ist eine seltene autosomal-dominant vererbte Genodermatose mit einer epidermalen Verhornungsstörung. Das klinische Bild der EKV wird von zwei Morphen geprägt: transiente, schnell wandernde Erytheme und persistierende braune Hyperkeratosen. Vor kurzem wurde der zugrunde liegende Gendefekt der EKV auf dem kurzen Arm von Chromosom,1 lokalisiert, der für das Gap-Junction-Protein Connexin,31 kodiert. Wir stellen einen 48jährigen Patienten vor, bei dem seit dem dreißigsten Lebensjahr großflächige, scharf begrenzte, randständig schuppende Erytheme an den Extremitäten, Gesäß und Rumpf auftreten. Histologisch fand sich eine orthokeratotische Hyperkeratose mit fokaler Parakeratose bei Akanthose der Epidermis. Immunhistochemisch konnte eine vermindert Expression des Gap-Junction-Proteins Connexin,31 sowie vermehrte Expression von Connexin,43 dargestellt werden. Ultrastrukturell zeigten sich erweiterte Interzellularräume in der oberen Epidermis mit unauffälligen Desmosomen, Adherensjunktionen und regulären Gap Junctions. In der Epidermis wird u. a. die Zellproliferation und -differenzierung über die Gap Junctions reguliert. Die Mutation im Connexin,31 wird daher als ursächlich für das klinische Bild der EKV angesehen. Die Überexpression von Connexin,43, die hier erstmals beschrieben wird, entsteht möglicherweise reaktiv als Folge der CX31-Mutation und kompensiert vorübergehend den Defekt. Summary Erythrokeratodermia variabilis (EKV) is a rare autosomal dominant genodermatosis with disturbed epidermal differentiation. Its clinical picture varies from transient, fast moving erythema to persistent brown hyperkeratoses. The gene defect in EKV was recently located on the short arm of chromosome,1 encoding the gap junction protein connexin,31. We report on a 48-year-old patient with sharply circumscribed, scaling erythema on the extremities, buttocks and trunk starting since 30,years of age. Histological investigation showed orthokeratotic hyperkeratosis with focal parakeratosis overlying an acanthotic epidermis. Immunohistochemistry revealed a decreased expression of the gap junction protein connexin,31 as well as increased expression of connexin,43. At the ultrastructural level, widened intercellular spaces in the upper epidermis were present with regular desmosomes, adherens junctions and gap junctions. Epidermal cell proliferation and differentiation are regulated by gap junctions. The mutation in connexin,31 is regarded therefore as causal for the clinical picture of the EKV. The unique up-regulation of connexin,43 may occur as a consequence of the Cx31 mutation and temporarily compensate for this defect. [source] Consensus Statement from the Cardiac Nomenclature Study Group of Arrhythmias of the European Society of Cardiology, and the Task Force on Cardiac Nomenclature from the North American Society of Pacing and Electrophysiology on Living Anatomy of the Atrioventricular JunctionsJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 11 2000DARLENE K. RACKER PH.D. [source] Consensus Statement from the Cardiac Nomenclature Study Group of Arrhythmias of the European Society of Cardiology, and the Task Force on Cardiac Nomenclature from the North American Society of Pacing and Electrophysiology on Living Anatomy of the Atrioventricular JunctionsJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 11 2000Reply to the Editor [source] | |||||||||||||||||||||||||||||||||||||||||||||||||