Search results for "Conductivity"
showing 10 items of 1988 documents
Photoconductivity in Discotic Liquid Crystals: A New Class of High-Mobility Materials
1994
Abstract Using a time-of-flight technique, different transport mechanisms, deep trapping, multiple shallow trapping and Gaussian transport, can be observed in the different temperature and phase regions of the liquidcrystalline (LC) photoconductor hexapentyloxytriphenylene (HPT). Transient photocurrents and carrier mobilities for various temperatures, electric fields, and sample histories were examined. The ideal intrinsic Gaussian transport, observed for holes in the mesophase, puts HPT into a new class of highmobility materials with both hole mobilities on the order of 1.10−3cm2/Vs and a steplike current decay. These features result from the fact that there is obviously neither a position…
Chitosan-phosphotungstic acid complex as membranes for low temperature H2-O2 fuel cell
2015
Abstract Free-standing Chitosan/phosphotungstic acid polyelectrolyte membranes were prepared by an easy and fast in-situ ionotropic gelation process performed at room temperature. Scanning electron microscopy was employed to study their morphological features and their thickness as a function of the chitosan concentration. The membrane was tested as proton conductor in low temperature H 2 –O 2 fuel cell allowing to get peak power densities up to 350 mW cm −2 . Electrochemical impedance measurements allowed to estimate a polyelectrolyte conductivity of 18 mS cm −1 .
Gibbs' Dividing Surface between a Fixed-Charge Membrane and an Electrolyte Solution. Application to Electrokinetic Phenomena in Charged Pores
1999
The Gibbs model for the boundary between two phases consists of replacing the finite interfacial region, where the properties of the system change gradually, by a dividing surface which acts as a third phase of zero volume in which some magnitudes change abruptly. This thermodynamic concept was recently applied to a planar interface between a fixed charge membrane and an electrolyte solution.1 The continuous decrease of counterions with the distance from the charged surface is replaced by a step function, so that the diffuse double layer is ideally represented by a charged region depleted of all co-ions. Here the cylindrical geometry is analyzed, and the planar case is revisited by proposin…
Thermomagnetic Properties Improved by Self-Organized Flower-Like Phase Separation of Ferromagnetic Co2Dy0.5Mn0.5Sn
2012
A thermodynamically stable phase separation of Co2Dy0.5Mn0.5Sn into the Heusler compound Co2MnSn and Co8Dy3Sn4 is induced by rapid cooling from the liquid phase. The phase separation forms an ordered flower-like structure on the microscale. The increased scattering of phonons at the phase boundaries reduces the thermal conductivity and thus improves thermoelectric and spincaloric properties.
Glucose oxidase as a biocatalytic enzyme-based bio-fuel cell using Nafion membrane limiting crossover
2013
A novel combination for an Enzyme-based Biofuel cell included a Nafion membrane as an ion transporter that maintained a working cell charge and inhibited membrane degradation. The prototype cell chamber used oxygen (O2) in the cathode cell and glucose in the anode. The Nafion membrane stability studied here was evidently in the region of 0% loss of conductivity as the charge was constant and increased after the addition of glucose. The prototype cell chamber used NaCl in the cathode cell and glucose oxidase (GOx) in the anodic chamber was successfully studied for membrane stability showed in this study no evidence of poisoning from membrane leakage in a controlled pH environment. There was …
Effect of storage period under variable conditions on the chemical and physical composition and colour of Spanish refrigerated orange juices
2005
The effects of the physicochemical and quality characteristics of various minimally pasteurized refrigerated orange Spanish juices and their changes with storage time and temperature were investigated. Essential oils, acidity, conductivity, diacetyl index, hydroxymethylfurfural, formol index, viscosity and ascorbic acid varied with storage time more significantly at 10 degrees C than at 4 degrees C. Density, colour and pectinmethylesterase did not vary at 4 degrees C. Some of the parameters could be used as indicators of quality loss or spoilage of the juices. The degradation kinetics of the concentration of remaining ascorbic acid against time follows a straight line whose slope indicates …
The Permeable Concrete: A Low Energy Consumption Solution for Deep Draining Trenches
2018
The reduction of pore water pressures is one of the very effective measures to improve the stability conditions of marginally stable water-bearing slopes or to stabilise landslides. For this purpose the trench drains have been used long since. Like filling material of deep trenches the permeable concrete can be effectively employed. It presents relatively high hydraulic conductivity, filtering capacity in order to prevent the internal erosion of the soil in which the trench drain is installed, enough residual hydraulic conductivity after possible clogging, sufficient shear strength after a short curing time to avoid the instabilisation of adjacent previously built panels or piles. Results o…
Antimonic acid hydrate xerogels as proton electrolytes
1993
Abstract Two high stability types of protonic solid electrolytes based on antimonic acid hydrate xerogels have been obtained by the sol-gel technique: Sb 2 O 5 ·(3–4)H 2 O (colloidal) and Sb 2 O 5 ·5H 2 O (polymeric). The first one is a white compact material with conductivity 0.40 mS/cm (298 K) for n =3.7. The last one is transparent for visible light with a conductivity of 0.80 mS/cm. An electrochromic system based on the colloidal gel electrolyte in the form of paste has good performance-more than 10 7 cycles and a lifetime of more than five years.
The short-circuited everted sac of rat colon mucosa.
1981
A short-circuited preparation of everted rat colon sacs is described. The serosal current electrode is a AgAgCl wire. A cylindrical agar bridge or AgAgCl electrode may be employed on the mucosal side. Effects of Ag+ ions liberated from the electrodes on ion transport could not be demonstrated. Fluid and sodium are absorbed and bicarbonate secreted. Potassium and chloride movements are not significantly different from zero. The preparation remains stable for at least 2 h. Sodium absorption is diminished by 50% and bicarbonate secretion abolished in the absence of glucose. In principle, similar ion transport properties were found as in Ussing-chamber preparations. The advantage of the everted…
Frequency and temperature dependence of the electrical conductivity of KTaO3; Li and PbTiO3; La, Cu: Indication of a low temperature polaron mechanism
2008
Abstract Recently, the concept of polarons has again been at the focus of solid-state research, as it can constitute the basis for understanding the high-temperature superconductivity or the colossal magnetoresistance of materials. More than a decade ago there were some indications that polarons play an important role in explaining low temperature maxima in imaginary part of the dielectric constant e ″ ( T ) in ABO3 perovskites. In the present work we report the ac electrical conductivities of KTaO3; Li and PbTiO3; La, Cu and their frequency and temperature dependence. The real part of the complex ac conductivity was found to follow the universal dielectric response σ ′ ∝ ν s . A detailed t…