Effect of irradiation with low-energy Ar ions on the characteristics of the working and rear sides of single-crystal GaAs substrate

Contactless methods were used to study the characteristics of the front and rear sides of single-crystal GaAs wafers whose rear side was irradiated with low-energy Ar ions. Variations in the optical and photoelectric properties of irradiated and unirradiated sides were detected. A solitonic mechanism for the penetration of defects into the crystal bulk is suggested.     

Consistent estimation of the memory parameter for nonlinear time series

Abstract. For linear processes, semiparametric estimation of the memory parameter, based on the log‐periodogram and local Whittle estimators, has been exhaustively examined and their properties well established. However, except for some specific cases, little is known about the estimation of the memory parameter for nonlinear processes. The purpose of this paper is to provide the general conditions under which the local Whittle estimator of the memory parameter of a stationary process is consistent and to examine its rate of convergence. We show that these conditions are satisfied for linear processes and a wide class of nonlinear models, among others, signal plus noise processes, nonlinear transforms of a Gaussian process ξ_t and exponential generalized autoregressive, conditionally heteroscedastic (EGARCH) models. Special cases where the estimator satisfies the central limit theorem are discussed. The finite‐sample performance of the estimator is investigated in a small Monte Carlo study.     

A High-Precision Time Handling Library

An appropriate assessment of end-to-end network performance presumes highly efficient time tracking and measurement with precise time control of the stopping and resuming of program operation. In this paper, a novel approach to solving the problems of highly efficient and precise time measurements on PC-platforms and on ARM-architectures is proposed. A new unified High Performance Timer and a corresponding software library offer a unified interface to the known time counters and automatically identify the fastest and most reliable time source, available in the user space of a computing system. The research is focused on developing an approach of unified time acquisition from the PC hardware and accordingly substituting the common way of getting the time value through Linux system calls. The presented approach provides a much faster means of obtaining the time values with a nanosecond precision than by using conventional means. Moreover, it is capable of handling the sequential time value, precise sleep functions and process resuming. This ability means the reduction of wasting computer resources during the execution of a sleeping process from 100% （busy-wait） to 1-1.5%, whereas the benefits of very accurate process resuming times on long waits are maintained.     

Reputation management algorithms for DHT-based peer-to-peer environment

This paper addresses the problem of integration of reputation management mechanisms into data look-up and routing processes to cope with some specific security problems in peer-to-peer (P2P) networks based on Distributed Hash Tables (DHT). The goal is to find a mode for “good” peers to cooperate in order to withstand malicious activity of single malevolent peers and their collusions as well.We start from consideration of individual instruments for reputation evaluation that every single peer should be provided with to autonomously define the level of its own trust towards others. We also propose a possible scenario of integration of some existing reputation management techniques and routing mechanisms in a P2P network based on the popular Kademlia algorithm. Then, we present an interaction algorithm that allows peers to obtain the global trust value for each single node through exchanging opinions in the form of local trust values independently calculated by every peer with other members of the community. Such collaboration between peers is indispensable to cope with malicious activity of inconsistent nature specific to DHT-based environment. To render the algorithm resilient to the presence of malicious participants we propose to apply solutions for Byzantine Agreement to exchange opinions among peers. We also provide mathematical evaluations concerning the complexity and computational costs of the proposed algorithm that evidence apparent improvements over the previous one.     

Effect of ion-beam treatment during reactive radio-frequency magnetron sputtering on the concentration and mobility of charge carriers in ITO films

It is shown that ion-beam treatment during the deposition of ITO films by reactive radio-frequency magnetron sputtering induces a decrease in the resistivity of the films even at room temperature. Variations in the Hall mobility and concentration of charge carriers are studied in relation to the condensation temperature and ion-beam treatment current. The resistivity decreases mainly because of an increase in the concentration of majority charge carriers. It is inferred that the change in the concentration of charge carriers is associated with {ie1237-1} defects.     

Multivitamin Analysis of Fruits, Fruit–Vegetable Juices, and Diet Supplements

Vitamins are organic compounds that are required for various biological functions. In general, vitamins are not synthesized in the human body, but lack or deficiency of them may lead to certain diseases. Determinations of 11 vitamins in various products were performed, which included ascorbic acid (C), seven vitamins of the B group (thiamine B₁, riboflavin B₂, nicotinamide B₃, pantothenic acid B₅, pyridoxine B₆, folic acid B₉, and cyanocobalamin B₁₂), as well as three fat-soluble vitamins (retinol A, cholecalciferol D₃, and α-tocopherol E). A column with RP18 stationary phase and a diode array detector with properly selected analytical wavelengths for each compound were used. A gradient of trifluoroacetic acid in water with methanol was used as the mobile phase. Limits of quantification in the range of 0.70–2.90 μg/mL for water-soluble vitamins and 1.85–15.84 μg/mL for fat-soluble vitamins were obtained. Those values are sufficient for determinations of the aforementioned compounds in foodstuff. The developed procedure of sample preparation together with chromatographic system can be used for food quality monitoring in the food industry.     

Modifying the surfaces of fluorocarbon polymer implants in the plasma of a high-voltage nanosecond discharge

The possibility in principle is shown for rapidly and efficiently modifying the surface of medical articles made of polytetrafluoroethylene (PTFE) by placing them in a bulk plasma discharge formed in a highly overvoltage gap. As an example, by processing PTFE films with nanosecond discharges at a frequency of 3 kHz over a few seconds, it is possible to substantially improve the conditions for cytoadherence and increase the permeability of an implant, which is an important factor for its integration into adjacent tissues.     

BLACK MARKET,HYPERINFLATION, AND HUNGER: GREECE 1941–1944

This article deals with the operation of markets during the famine and food crisis that occurred in occupied Greece in the period 1941–1944. Among other factors, the division of the country into three zones of occupation between which no movements of goods and people was allowed and the failed attempt by the government to control prices and production led to the collapse of the normal markets and the gradual but firm establishment of a black market. In the later years of the occupation, and in association with a rampant inflation, the black market was extremely volatile and heavily dependent on “shocks.” Even though the occupation governments, the press, the resistance, and post-war academics fiercely condemned the black market, oral evidence shows that virtually everyone was involved in some way in its dealings.