Ferromagnetic HfO2/Si/GaAs interface for spin-polarimetry applications

In this letter, we present electrical and magnetic characteristics of HfO2-based metal-oxide-semiconductor capacitors (MOSCAPs), along with the effect of pseudomorphic Si as a passivating interlayer on GaAs(001) grown by molecular beam epitaxy. Ultrathin HfO2 high-k gate dielectric films (3–15 nm) have been grown on Si/GaAs(001) structures through evaporation of a Hf/HfO2 target in NO2 gas. The lowest interface states density Dit at Au/HfO2/Si/GaAs(001) MOS-structures were obtained in the range of (6−13)×101

Fluorine and oxygen adsorption and their coadsorption on the (111) surface of InAs and GaAs

Oxygen and fluorine adsorption and their coadsorption on the (111) unreconstructed surface of semiconductors InAs and GaAs were studied using the projector augmented-wave method with the generalized gradient approximation for the exchange–correlation functional and hybrid functional approach. The energetically preferable adsorbate sites on the surface were determined. It is shown that fluorine adsorption above surface cations on the AIIIBV(111)A-(1 × 1) unreconstructed surface leads to a removal of the surface state formed by cation pz-orbitals and to an unpinning of the Fermi level, whereas oxygen adsorption induces additional surface states in the band gap. The influence of fluorine and oxygen coadsorption and also fluorine concentration on the surface states in the band gap is discussed. It is shown that oxygen-induced surface states are completely or partially removed from the band gap by fluorine coadsorption if it forms bonds with cation surface atoms involved in an interaction with oxygen. The increase of fluorine concentration leads to considerable changes of the near-surface-layer structure due to the penetration of both electronegative adsorbates into the substrate and affects the electron properties of oxygen/AIIIBV(111) interface

Fluorine and oxygen adsorption and their coadsorption on the (111) surface of InAs and GaAs

Oxygen and fluorine adsorption and their coadsorption on the (111) unreconstructed surface of semiconductors InAs and GaAs were studied using the projector augmented-wave method with the generalized gradient approximation for the exchange–correlation functional and hybrid functional approach. The energetically preferable adsorbate sites on the surface were determined. It is shown that fluorine adsorption above surface cations on the AIIIBV(111)A-(1 × 1) unreconstructed surface leads to a removal of the surface state formed by cation pz-orbitals and to an unpinning of the Fermi level, whereas oxygen adsorption induces additional surface states in the band gap. The influence of fluorine and oxygen coadsorption and also fluorine concentration on the surface states in the band gap is discussed. It is shown that oxygen-induced surface states are completely or partially removed from the band gap by fluorine coadsorption if it forms bonds with cation surface atoms involved in an interaction with oxygen. The increase of fluorine concentration leads to considerable changes of the near-surface-layer structure due to the penetration of both electronegative adsorbates into the substrate and affects the electron properties of oxygen/AIIIBV(111) interface

Fast Deflagration-to-Detonation Transition in Helical Tubes

When designing a new type of power plants operating on pulsed detonations of gaseous or liquid fuels, the concept of fast deflagration-to-detonation transition (FDDT) is used. According to the concept, a flame arising from a weak ignition source must accelerate so fast as to form an intense shock wave at a minimum distance from the ignition source so that the intensity of the shock wave is sufficient for fast shock-to-detonation transition by some additional arrangements. Hence, the FDDT concept implies the use of special means for flame acceleration and shock wave amplification. In this work, we study the FDDT using a pulsed detonation tube comprising a Shchelkin spiral and a helical tube section with ten coils as the means for flame acceleration and shock amplification (focusing), respectively. To attain the FDDT at the shortest distances for fuels of significantly different detonability, the diameter of the pulsed detonation tube is taken close to the limiting diameter of detonation propagation for air mixtures of regular hydrocarbon fuels (50 mm). Experiments are conducted with air mixtures of individual gaseous fuels (hydrogen, methane, propane, and ethylene) and binary fuel compositions (methane–hydrogen, propane–hydrogen, and ethylene–hydrogen) at normal pressure and temperature conditions. The use of a helical tube with ten coils is shown to considerably extend the fuel-lean concentration limits of detonation as compared to the straight tube and the tube with a helical section with two coils

Polyethylene Pyrolysis Products: Their Detonability in Air and Applicability to Solid-Fuel Detonation Ramjets

The detonability of polyethylene pyrolysis products (pyrogas) in mixtures with air is determined for the first time in a standard pulsed detonation tube based on the measured values of deflagration-to-detonation transition run-up time. The pyrogas is continuously produced in a gas generator at decomposition temperatures ranging from 650 to 850 °C. Chromatographic analysis shows that at a high decomposition temperature (850 °C) pyrogas consists mainly of hydrogen, methane, ethylene, and ethane, and has a molecular mass of about 10 g/mol, whereas at a low decomposition temperature (650 °C), it mainly consists of ethylene, ethane, methane, hydrogen, propane, and higher hydrocarbons, and has a molecular mass of 24–27 g/mol. In a pulsed detonation mode, the air mixtures of pyrogas with the fuel-to-air equivalence ratio ranging from 0.6 to 1.6 at normal pressure are shown to exhibit the detonability close to that of the homogeneous air mixtures of ethylene and propylene. On the one hand, this indicates a high explosion hazard of pyrogas, which can be formed, e.g., in industrial and household fires. On the other hand, pyrogas can be considered as a promising fuel for advanced propulsion powerplants utilizing the thermodynamic Zel’dovich cycle with detonative combustion, e.g., solid-fuel detonation ramjets. In view of it, the novel conceptual design of the dual-duct detonation ramjet demonstrator intended for operation on pyrogas at the cruising flight speed of Mach 2 at sea level has been developed. The ramjet demonstrator has been manufactured and preliminarily tested in a pulsed wind tunnel at Mach 1.5 and 2 conditions. In the test fires, a short-term onset of continuous detonation of ethylene was registered at both Mach numbers

Development and Modeling of an Onion Harvester with an Automated Separation System

One of the most important problems during the implementation of any technology is to reduce labor costs, energy, and resource conservation while increasing the yield of cultivated crops and, as a result, reducing the cost of production. Despite a significant amount of scientific research devoted to the problem of energy and resource conservation in the cultivation and harvesting of agricultural crops and the development of mechanization tools that ensure the high-quality performance of technological operations, there remain issues that have not been fully resolved to date. In addition, not all the results of known theoretical and experimental studies can be directly applied to intensify the process of harvesting root crops since the quality indicators of marketable products depend on the type and technological parameters of the separating working bodies. This article presents the design of a rod elevator with an adjustable angle of inclination of the web, which reduces damage to commercial products of root crops and bulbs with maximum completeness of separation. A laboratory facility has been developed to substantiate the design and technological parameters of a separating system with an adjustable web inclination angle. Based on the results of theoretical and experimental studies, a machine for harvesting onions with an adjustable blade inclination angle has been developed, which provides an increase in the quality indicators of onion harvesting at optimal values of the parameters: (1) translational speed of movement of the rod elevator with an adjustable web inclination angle of 1.7 m/s with a 98.4% completeness of separation and 1.7% damage to the bulbs; (2) translational speed of the movement of the machine for harvesting root crops and onions 1.0 m/s with a 98.5% separation completeness and 1.1% damage to the bulbs; (3) digging depth of the digging plowshare equal to 0.02 m, with an onion heap separation completeness of more than 98% and product damage of less than 1.4%. The results of theoretical and experimental studies of a rod elevator to substantiate the design and technological parameters during its interaction with a heap of onion are presented. Basic design and technological parameters of the studied rod elevator are substantiated, namely, the distance S1 of the movement of the rod of the actuators, the angle a1 of the longitudinal inclination of the surface of the rod elevator relative to the horizon, and differential equations of motion of the onion-sowing pile element on the surface of the rod elevator with an adjustable angle of inclination of the web

Development and Modeling of an Onion Harvester with an Automated Separation System

One of the most important problems during the implementation of any technology is to reduce labor costs, energy, and resource conservation while increasing the yield of cultivated crops and, as a result, reducing the cost of production. Despite a significant amount of scientific research devoted to the problem of energy and resource conservation in the cultivation and harvesting of agricultural crops and the development of mechanization tools that ensure the high-quality performance of technological operations, there remain issues that have not been fully resolved to date. In addition, not all the results of known theoretical and experimental studies can be directly applied to intensify the process of harvesting root crops since the quality indicators of marketable products depend on the type and technological parameters of the separating working bodies. This article presents the design of a rod elevator with an adjustable angle of inclination of the web, which reduces damage to commercial products of root crops and bulbs with maximum completeness of separation. A laboratory facility has been developed to substantiate the design and technological parameters of a separating system with an adjustable web inclination angle. Based on the results of theoretical and experimental studies, a machine for harvesting onions with an adjustable blade inclination angle has been developed, which provides an increase in the quality indicators of onion harvesting at optimal values of the parameters: (1) translational speed of movement of the rod elevator with an adjustable web inclination angle of 1.7 m/s with a 98.4% completeness of separation and 1.7% damage to the bulbs; (2) translational speed of the movement of the machine for harvesting root crops and onions 1.0 m/s with a 98.5% separation completeness and 1.1% damage to the bulbs; (3) digging depth of the digging plowshare equal to 0.02 m, with an onion heap separation completeness of more than 98% and product damage of less than 1.4%. The results of theoretical and experimental studies of a rod elevator to substantiate the design and technological parameters during its interaction with a heap of onion are presented. Basic design and technological parameters of the studied rod elevator are substantiated, namely, the distance S1 of the movement of the rod of the actuators, the angle a1 of the longitudinal inclination of the surface of the rod elevator relative to the horizon, and differential equations of motion of the onion-sowing pile element on the surface of the rod elevator with an adjustable angle of inclination of the web

Hepatitis C virus core protein transforms murine fibroblasts by promoting genomic instability." Cellular oncology : the official journal of the International Society for Cellular Oncology 28(4

Abstract. The oncogenic potential of hepatitis C virus (HCV) core protein has been demonstrated, but the precise mechanism of cell transformation triggered by HCV core is still unclear. This study shows that constitutive expression of HCV core protein (core) in NIH 3T3 murine fibroblasts triggers malignant transformation. At the preneoplastic stage, clones that expressed HCV core constitutively demonstrated genomic instability seen as disruption of the mitotic spindle cell checkpoint leading to increased ploidy. Transformation was completed by the loss of DNA and resistance to apoptosis induced by serum starvation. Simultaneously, cells acquired a capacity for anchorage independent growth and absence of contact inhibition. Inoculation of these transformed cells into severe combined immune deficiency (SCID) mice led to formation of solid core-expressing tumors. Transformation and tumorigenicity of core-expressing cell lines coincided with a 5-to 10-fold repression of endogenous p53 transactivation. Thus, long-term HCV core expression alone is sufficient for complete transformation of immortal fibroblasts that can then induce tumors in a susceptible host. This data suggests that malignant transformation by HCV core may occur through primary stress, induction of genomic instability, and further HCV core-induced rescue of surviving mutated cells

Hepatitis C Virus Core Protein Transforms Murine Fibroblasts by Promoting Genomic Instability

The oncogenic potential of hepatitis C virus (HCV) core protein has been demonstrated, but the precise mechanism of cell transformation triggered by HCV core is still unclear. This study shows that constitutive expression of HCV core protein (core) in NIH 3T3 murine fibroblasts triggers malignant transformation. At the preneoplastic stage, clones that expressed HCV core constitutively demonstrated genomic instability seen as disruption of the mitotic spindle cell checkpoint leading to increased ploidy. Transformation was completed by the loss of DNA and resistance to apoptosis induced by serum starvation. Simultaneously, cells acquired a capacity for anchorage independent growth and absence of contact inhibition. Inoculation of these transformed cells into severe combined immune deficiency (SCID) mice led to formation of solid core-expressing tumors. Transformation and tumorigenicity of core-expressing cell lines coincided with a 5- to 10-fold repression of endogenous p53 transactivation. Thus, long-term HCV core expression alone is sufficient for complete transformation of immortal fibroblasts that can then induce tumors in a susceptible host. This data suggests that malignant transformation by HCV core may occur through primary stress, induction of genomic instability, and further HCV core-induced rescue of surviving mutated cells