The Edge Electric Field of a Pyroelectric and its Applications

Following a change of temperature of a pyroelectric (PE), a depolarizing electric field appears both inside the PE, as well as outside its edges, the edge depolarizing electric field (EDEF). The EDEF extends outwards up to a distance of the order of magnitude of the PE width. The mapping and the strength of the EDEF have been calculated and analyzed for the case of a semi-infinite pyroelectric plate. This strong EDEF (104-105 V/cm), when penetrating into the surrounding medium, creates a variety of physical effects: inducing electrical current in a semiconductor and affecting its resistance, accelerating charged and neutral particles in vacuum or in a gas, generating electromagnetic waves, modifying optical characteristics by electrooptical and photoelasic effects, generating piezoelectric deformation and more. We show that these EDEF induced effects could serve as a basis for the development of various applications and devices.Comment: 27 pages including 13 figure

Electric Field Effect Analysis of Thin PbTe films on high-epsilon SrTiO3 Substrate

Thin PbTe films (thickness 500 - 600 angstrom), deposited on SrTiO3, have been investigated by electric field effect (EFE). The high resistivity of such thin films warrants a high sensitivity of the EFE method. The SrTiO3 substrate serves as the dielectric layer in the Gate-Dielectric-PbTe structure. Due to the large dielectric constant of SrTiO3, particularly at low temperatures, the electric displacement D in the film reaches the high value of about 10^8 V/cm, and the EFE introduced charge into the PbTe film amounts to ~ 8 microC/cm2. The high D permits to measure the EFE resistance and Hall constant over a wide region of D, revealing the characteristic features of their D-dependence. An appropriate theoretical model has been formulated, showing that, for such films, one can measure the dependence of the Fermi level on D. In fact, we demonstrate that shifting the Fermi level across the gap by varying D, the density-of-states of the in-gape states can be mapped out. Our results show, that the PbTe layers studied, possess a mobility gap exceeding the gap of bulk PbTe.Comment: 27 pages, 12 figure

Characterization of high-temperature PbTe p-n junctions prepared by thermal diffusion and by ion-implantation

We describe here the characteristics of two types of high-quality PbTe p-n-junctions, prepared in this work: (1) by thermal diffusion of In4Te3 gas (TDJ), and (2) by ion implantation (implanted junction, IJ) of In (In-IJ) and Zn (Zn-IJ). The results, as presented here, demonstrate the high quality of these PbTe diodes. Capacitance-voltage and current-voltage characteristics have been measured. The measurements were carried out over a temperature range from ~ 10 K to ~ 180 K. The latter was the highest temperature, where the diode still demonstrated rectifying properties. This maximum operating temperature is higher than any of the earlier reported results. The saturation current density, J0, in both diode types, was ~ 10^-5 A/cm2 at 80 K, while at 180 K J0 ~ 10^-1 A/cm2 in TDJ and ~ 1 A/cm2 in both ion-implanted junctions. At 80 K the reverse current started to increase markedly at a bias of ~ 400 mV for TDJ, and at ~550 mV for IJ. The ideality factor n was about 1.5-2 for both diode types at 80 K. The analysis of the C-V plots shows that the junctions in both diode types are linearly graded. The analysis of the C-V plots allows also determining the height of the junction barrier, the concentrations and the concentration gradient of the impurities, and the temperature dependence of the static dielectric constant. The zero-bias-resistance x area products (R0Ae) at 80 K are: 850 OHMcm2 for TDJ, 250 OHMcm2 for In-IJ, and ~ 80 OHMcm2 for Zn-IJ, while at 180 K R0Ae ~ 0.38 OHMcm2 for TDJ, and ~ 0.1 OHMcm2 for IJ. The estimated detectivity is: D* ~ 10^10 cmHz^(1/2)/W up to T=140 K, determined mainly by background radiation, while at T=180 K, D* decreases to 108-107 cmHz^(1/2)/W, and is determined by the Johnson noise

Evaluation of ambipolar potential barrier in the gas dynamic trap by Doppler spectroscopy

The recently developed Doppler spectroscopy diagnostic has been used to evaluate the height of the ambipolar potential barrier forming in the gas dynamic trap (GDT) plasma between the central cell and the region with a large magnetic expansion ratio beyond the mirror. The diagnostic technique based on the gas jet charge exchange target, allowed to measure the potential profile along the line of sight covering the radial range from the axis to the limiter. The on-axis potential drop was found to be $2.6 \div 3.1$ in units of the central plane electron temperature, which supports the existing theoretical understanding of suppression of electron thermal conductivity in the GDT expander

Effect of low temperatures and ionizing irradiation upon physical-mechanical properties and connective-tissue structures of porcine fibrous pericardium and aortic valve leaflets

Xenogeneic tissue devitalization is one of the creating methods of the tissuereplacing the biocompatible cell-free shells for the regenerative surgery. The work describes the possibility of applying the complex approach based on the continuous usage of cryo and radioactive (electron irradiation exposure) biological tissue damage effects. The pre-implant treatment provides sterilization and a possibility for the low temperature preservation of xenografts. After the transplantation such a cell-free xenoscaffold can be gradually replaced with the autogenic extracellular matrix from the recipient’s cells and forms a stable long-term structure of the biological prosthesis. Fibrous pericardium (FP) and aortic valve leaflets (AVLs) were extracted from the mature pig. The prepared tissues were rinsed with the sterile normal saline solution and frozen down to the liquid-nitrogen temperature. After one time placing on water-bath (37°C) they were exposed to electron irradiation within dosage range of 25-30 kGray and submerged into the liquid nitrogen vapors. After influence of low temperature and ionizing radiation, tissue morphological structure was assessed using the optical microscopy. Deformations, i.e. longitudinal and transverse monoaxial strength were performed to calculate the physical and mechanical properties of FP and AVLs. Such a devitalization method of the FP and AVLs causes significant destructive changes in cell elements, however the spatial arrangement and structural integrity of the connective tissue fiber are preserved. Joint impact of low temperatures and ionizing radiation gives the synergetic effect, increasing the strength and elastic tissue properties. Freezing down to –196 °C and electron irradiation initiate formation of the intra- and intermolecular transverse cross-linking due to the binding activity of fibrous proteins. It leads to a more dense arrangement of the collagen fiber, adds strength to the implant and provides the structural tissue stabilization. The authors believe that during the remodeling in the recipient organism, the biomaterial structure modified in such a manner can successfully prevent physiological tension

Organospecific influence of the extract of cryopreserved piglets’ skin fragments

Researching mechanisms of peptides’ tissue-specific effect is an important task of modern molecular biology, physiology and medicine. In previous studies it was shown that extracts of cryopreserved piglets’ skin fragments and pigs’ spleen fragments accelerate and normalise the healing of skin wound in experiment. Fibroblasts culture is an appropriate model for studying tissue-specific biological activity of peptide complexes on relevant type of cells. This research was aimed to establish the influence of the extract of cryopreserved newborn piglets’ skin fragments (cNPSE) and the extract of cryopreserved pigs’ spleen fragments (cPSE) on proliferative and metabolic activity of skin fibroblasts in culture. Extracts were obtained from cryopreserved skin fragments and cryopreserved spleen fragments. Primary culture of neonatal rat skin fibroblasts was obtained by free cell transfer from skin fragments and subsequent reseeding. Metabolic activity of cells in culture was defined using non-toxic redox indicator AlamarBlue. The number of cells in a well was measured by counting the quantity of cells in wells. On the 7th day the metabolic activity of fibroblasts, cultured with cNPSE (1 μg/ml final peptide concentration), was higher than control by 1.3 times. Adding of cPSE (in the same concentration of peptides) increased cell metabolic activity by 1.2 times. While incubating fibroblasts in the medium with 2% FBS, a decrease of metabolic activity of cells was observed on the 5th day, and by the 7th day it was 51.2% of the control. At 1 and 1.5 μg/ml final peptide concentration of cNPSE, the metabolic activity of fibroblasts remained at the level observed in the control samples with 10% FBS. Adding cPSE to the incubation medium did not affect the metabolic activity of cells. Increased metabolic activity of cells (initially kept for 30 minutes at 4°C) was observed on the 5th and 7th day in cNPSE presence. Thus, it was found that adding cNPSE and cPSE to the culture medium of rats’ skin fibroblasts increase the metabolic activity of cells. A dose-dependent effect is observed. The addition of cNPSE to the medium with 2% FBS maintains the metabolic activity of fibroblasts at the level observed in the control samples incubated with 10% FBS. Adding extract also increases the metabolic activity of fibroblasts after hypothermic impact on the cells

Ignatzschineria species Bacteremia: A Case Report and Review of the Literature

Ignatzschineria species, a member of the Gammaproteobacteria class of bacteria, is a gram-negative, aerobic, non-spore forming rod. This emerging human pathogen has been found in the digestive tract of the parasitic Wohlfarhtia magnifica fly. Infections in humans are uncommon and are usually associated with maggot infestation (wound myiasis). Rare cases of Ignatzschineria species bacteremia have been reported in individuals with myiasis of chronic skin wounds. Current literature describes 4 known species of Ignatzschineria: I. indica, I. larvae, I. ureiclastica, and I. cameli. An additional 2 cases of Ignatzachineria bacteremia were caused by Ignatzschineria species that were “unable to be identified;” they appeared to be closely related to I. larvae and I. ureclastica culture type. This case discusses Ignatzschineria bacteremia in a 66-year-old undomiciled male from the United States with myiasis of a chronic leg ulcer and reviews the literature on Ignatzschineria bacteremia