Search results for " jun"
showing 10 items of 611 documents
Observation of thermally excited charge transport modes in a superconducting single-electron transistor
1997
Experiments on a superconducting single-electron transistor are reported. A new structure in the current-voltage characteristics at subgap voltages was observed when temperature was not too low as compared to the superconducting transition temperature Tc of the sample. The strength of the anomalies increases exponentially with temperature. The dominating features arise from matching of singularities in the density of states on two sides of a tunnel junction, and from the Josephson-quasiparticle cycle. Thermal excitations are essential for the former process, and they also make the latter process possible at low voltages.
Fluxons in Josephson Transmission Lines
1996
The superconducting Josephson junctions (Barone and Paterno 1982; Parmentier 1978; Lomdahl 1985; Likharev 1986; Pedersen 1986) have proven to be one of the most successful testing grounds for nonlinear wave theory; their use for information processing and storage is quite attractive. In the long Josephson junction or transmission line, the physical quantity of interest is a quantum of magnetic flux, or a fluxon, which has a soliton behavior. It is a remarkably robust and stable object, which can be easily manipulated at high speed and stored electronically. Consequently it should be used as a basic bit in information processing systems.
Numerical investigation of one‐dimensional tunnel junction arrays at temperatures above the Coulomb blockade regime
1996
Arrays of tunnel junctions provide simple thermometric parameters in the limit where thermal excitations dominate over charging effects. We present numerical simulations for calculating the current versus voltage characteristics of an arbitrary one‐dimensional array at arbitrary temperatures on the premise of the ‘‘orthodox theory.’’ The purpose of the computer simulations is to investigate the suitability of tunnel junction arrays for thermometry at low temperatures when the analytical formulas do not hold and, specifically, to see the effect of background charges in this regime.
Establishment of a pulmonary epithelial barrier on biodegradable poly-L-lactic-acid membranes
2019
Development of biocompatible and functional scaffolds for tissue engineering is a major challenge, especially for development of polarised epithelia that are critical structures in tissue homeostasis. Different in vitro models of the lung epithelial barrier have been characterized using non-degradable polyethylene terephthalate membranes which limits their uses for tissue engineering. Although poly-L-lactic acid (PLLA) membranes are biodegradable, those prepared via conventional Diffusion Induced Phase Separation (DIPS) lack open-porous geometry and show limited permeability compromising their use for epithelial barrier studies. Here we used PLLA membranes prepared via a modification of the…
Physostigmine and Neuromuscular Transmission
1993
Single channel studies carried out in cultured rat myoballs and cultured hippocampal neurons, and ion flux studies performed on Torpedo electrocyte membrane vesicles, showed that physostigmine (Phy), a well-established acetylcholinesterase inhibitor, interacts directly with nicotinic acetylcholine receptors (nAChR). Low concentrations (0.1 microM) of Phy activate the receptor integral channel, whereas higher concentrations blocked the channel in its opened state. In contrast to channel activation by acetylcholine (ACh) and classical cholinergic agonists, however, Phy was capable of activating the nAChR channel even when the ACh binding sites were blocked by competitive antagonists, such as …
Josephson junctions and SQUIDs based on artificial grain boundaries in Bi 2 Sr 2 Ca 2 Cu 3 O 10 -thin films
1996
ABSTRACT High quality thin films of Bi2 Sr Ca2 Cu3 0 with critical temperatures of 95 K were used to prepare grainboundary josephson junctions on commercial 36.8° SrTiOg-bicrystal substrates. IR-products of 50 pV at 77 Kand 0.7 mV at 4.2 K have been reached. For temperatures higher than 50 K the current-voltage curves of thejunctions can be well described by the resistively shunted junction (RSJ) model and show no hysteresis. Fromthe hysteretic behavior at low temperature we estimate a junction capacitance of 2ljiF/cm2. The Fraunhoferpattern of the critical current in an external applied field shows, that the junctions are inhomogeneous on a pm scale. The SQUID modulation of a 30 x 40 pm2 w…
Unsupervised recognition of retinal vascular junction points.
2014
Landmark points in retinal images can be used to create a graph representation to understand and to diagnose not only different pathologies of the eye, but also a variety of more general diseases. Aim of this paper is the description of a non-supervised methodology to distinguish between bifurcations and crossings of the retinal vessels, which can be used in differentiating between arteries and veins. A thinned representation of the binarized image, is used to identify pixels with three or more neighbors. Junction points are classified into bifurcations or crossovers according to their geometrical and topological properties. The proposed approach is successfully compared with the state-of-t…
Oligodendrocytes in mouse corpus callosum are coupled via gap junction channels formed by connexin47 and connexin32.
2010
According to previously published ultrastructural studies, oligodendrocytes in white matter exhibit gap junctions with astrocytes, but not among each other, while in vitro oligodendrocytes form functional gap junctions. We have studied functional coupling among oligodendrocytes in acute slices of postnatal mouse corpus callosum. By whole-cell patch clamp we dialyzed oligodendrocytes with biocytin, a gap junction-permeable tracer. On average 61 cells were positive for biocytin detected by labeling with streptavidin-Cy3. About 77% of the coupled cells stained positively for the oligodendrocyte marker protein CNPase, 9% for the astrocyte marker GFAP and 14% were negative for both CNPase and GF…
Determination of thermometric parameters from the conductance curve of the normal metal based tunnel junction array
1997
Abstract We propose a method for extracting thermometric parameters from the measured conductance curve, against bias voltage, of a tunnel junction array. Instead of fitting the whole theoretical conductance curve to the experiment, we perform several polynomial fits to selected bias regions. The advantages of this method is that polynomial fits are linear in their fitting parameters whereas the theoretical form for the conductance is inherently nonlinear. This way the proposed method is about three orders of magnitude faster than the nonlinear fit. Optimizing this polynomial fit procedure is discussed.
Dithiothreitol Treatment of Madin-Darby Canine Kidney Cells Reversibly Blocks Export from the Endoplasmic Reticulum but Does Not Affect Vectorial Tar…
1995
Addition of dithiothreitol (DTT) to the culture medium of Madin-Darby canine kidney (MDCK) cells blocks transport of newly synthesized gp80 (clusterin, apolipoprotein J), a soluble marker protein for apical exocytosis in this epithelial cell line. In cells treated with DTT during pulse labeling, gp80 is retained in the endoplasmic reticulum. After removal of the reducing agent, gp80 is posttranslationally oxidized and secreted at the apical surface of MDCK cell monolayers. This demonstrates that when folded and oxidized posttranslationally, gp80 can acquire a conformation that exhibits sorting signals for vectorial targeting. In the continuous presence of DTT, the transepithelial electrical…