The effect of radiation on twinning in quartz

The Dauphine twinning behavior of quartz subjected to irradiation was studied at room temperature and elevated temperatures. The presence of defects produced by irradiation was utilized to pin the domain wall motion. Both neutrons and gamma-rays were employed for this investigation. The stress required to nucleate an appreciable volume of twins is about twice as high for irradiated crystals than those unirradiated. However, the coercive stress required for causing a complete orientation switch was not much different between irradiated and unirradiated crystals.     

The effect of radiation on the electron pairing in a multiband system

The possible occurrence of a generalized (l-wave) nonequilibrium superconducting state in a multiband system under certain conditions is studied. In the model the radiation field causes interband mixing, and phonons of an appropriate mode (branch) are involved in the interband scattering of electrons of two conduction bands of the system. The strength of the generalized l-wave pairing interaction between quasiparticles belonging to new radiation admixed states depends on the density (n ₀/V) of quanta in the system. The coupling constant has the form % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaae4UdmaaBa% aaleaacaaIXaaabeaakiabg2da9GGaaiab-bcaGiab-bcaGiab-f5a% bnaaBaaaleaacqWFXaqmaeqaaOGae8NKdiKaamikaiaab6gadaWgaa% WcbaGaaeimaaqabaGccaGGVaGaaeOvaiaadMcacaqGVaGaam4waiaa% boeacaqGRaGaaeOqaiaadIcacaqGUbWaaSbaaSqaaiaabcdaaeqaaO% Gaai4laiaabAfacaWGPaGaamyxaaaa!4CBB!\[{\text{\lambda }}_1 = {\rm A}_1 {\rm B}({\text{n}}_{\text{0}} /{\text{V}}){\text{/}}[{\text{C + B}}({\text{n}}_{\text{0}} /{\text{V}})]\], where A ₁, B, and C are parameters. For C > B(n ₀/V), the transition temperature T ₁ ^* increases with (n ₀/V) in the initial stages. It levels off with higher power. With further increase of power, the transition temperature is expected to drop sharply due to heating effects which cause pair breaking. Estimates show that p-wave (triplet state) pairing may be possible under radiation-induced nonequilibrium situations in appropriate systems. Estimates for lifetimes of various processes (quasiparticle, phonon, pair relaxation, and photon-induced mixing) show that the coherence required for the mixing and pairing effects will be maintained for the temperature range and photon density considered.Supported by the Science Research Council (U.K.).     

The effect of megavoltage radiation on polymeric materials to be used in biomedical devices

For a number of biomedical applications, including the development of phantoms for quality control of radiotherapy treatments and dose determination, it is important to study the radiation response of the used materials, in order to distinguish the relevant dose distribution modifications from the artifacts caused by the phantom material when subjected to high dose irradiation. Beside the radiation response, those materials should have certain physical and chemical properties in order to be able to be used for the purposes described above, i.e., mechanical hardness and inelasticity, chemically stability and nonreactive, among others. In this work, a wide range of polymeric materials were irradiated under megavoltage radiation using a radiotherapy linear accelerator. The irradiated materials were imaged using transmission X-ray tomography to determine if some radiation induced electronic density change could result in altered Hounsfield units. Furthermore, Raman Spectroscopy and X-ray Diffraction (XRD) techniques were used before and after irradiation in order to study any structural modification induced by the radiation. In addition, a special phantom simulating a breast treatment with two tangential beams has been fabricated and tested.     

The effect of optical radiation on the semiconductor conductivity in a thin-film ferroelectric-semiconductor structure

We have studied the effect of optical radiation on the conductivity of a thin-film field-effect transistor based on a multilayer structure of the Si-SiO₂-Pt-PZT-SnO_2−x -Pt type. Within the permissible radiation dose, the conducting channel exhibits a residual photoconductivity, with an optical data storage time of no less than 10⁵ s. The effective quenching of the residual conductivity in the structure studied can be produced only by simultaneous action of an alternating electric field and the temperature.     

The effect of clustering of particles on Rayleigh scattering of radiation in a turbulent flow

The effect of clustering of particles under conditions of homogeneous isotropic turbulence on Rayleigh scattering of radiation is analyzed. It is demonstrated that, similarly to the diagnostics of molecular structure of liquid using X-ray scattering, the radial distribution function of macroscopic particles, which characterizes the clustering phenomenon, may be determined by way of measuring the intensity of scattering of infrared or microwave radiation. An approximate relation for clustering coefficient is obtained, which may be employed for estimating the increase in reflected radiation of microwave radar from cumulus clouds owing to turbulent clustering of water drops in the cloud.     

The effect of thermal radiation on the propagation of temperature waves in a semitransparent medium

The propagation of temperature waves arising as a result of periodic external thermal stimulation is investigated in a plane layer of semitransparent absorbing and radiating medium without scattering. The classification of temperature waves on the basis of two dimensionless parameters is suggested. It is rigorously demonstrated that not more than two temperature waves may simultaneously exist in a gray semi-infinite medium. The relative contribution of radiation to complex heat transfer is estimated. The system of equations of radiative-conductive heat transfer is reduced to a single integral equation on the boundary. The effect of reflection on the boundary is discussed.     

The effect of flux density on the formation of temperature field in alumina under conditions of heating by concentrated laser radiation

A numerical investigation is performed of the effect of the density of a flux of heating concentrated radiation of CO₂ laser on the formation of temperature field in the process of heating and melting of a plane layer of alumina. A mathematical model of unsteady-state radiative-conductive heat transfer is used for considering the process of heating in rigorous formulation in view of the dependence of the thermophysical properties of the solid phase on temperature and of the optical properties—on temperature and wavelength, including the generalized approach to the problem of phase transition in melting in view of formation of an extended two-phase zone. In so doing, the evaporation from the melt surface is taken into account. The presented results relate to flux densities in the range from 200 to 3000 W/cm². It is demonstrated that the special features of formation of temperature fields are due both to the contribution of volumetric radiation and absorption of fluxes of outer and self-radiation and to the specific nature of alumina for which the absorption coefficients of melt and of solid phase in the energetically important spectral region may differ by as much as two orders of magnitude.     

The effect of gamma radiation on hardness evolution in high density polyethylene at elevated temperatures

This research focuses on characterizing hardness evolution in irradiated high density polyethylene (HDPE) at elevated temperatures. Hardness increases with increasing gamma ray dose, annealing temperature and annealing time. The hardness change is attributed to the variation of defects in microstructure and molecular structure. The kinetics of defects that control the hardness are assumed to follow the first order structure relaxation. The experimental data are in good agreement with the predicted model. The rate constant follows the Arrhenius equation, and the corresponding activation energy decreases with increasing dose. The defects that control hardness in post-annealed HDPE increase with increasing dose and annealing temperature. The structure relaxation of HDPE has a lower energy of mixing in crystalline regions than in amorphous regions. Further, the energy of mixing for defects that influence hardness in HDPE is lower than those observed in polycarbonate (PC), poly(methyl methacrylate) (PMMA) and poly (hydroxyethyl methacrylate) (HEMA). This is due to the fact that polyethylene is a semi-crystalline material, while PC, PMMA and PHEMA are amorphous.     

An automatic device for measuring the effect of meteorological factors on radon-222 flux from soils in the long-term

An automatic method for measuring the radon flux at soil surfaces is described. The proposed experimental design minimises the disturbance induced by the accumulator technique widely used to measure radon exhalation from the ground. By exposing the ground surface to the normal weather conditions between two consecutive measurements, this method can be used to study, in the long term, the effects of meteorological factors on the radon flux density at the soil-atmosphere interface.     

The combined effect of radiation and carbonation on the immobilization of Sr and Cs ions in cementitious pastes

In the present study the effect of gamma irradiation on the transport of immobilized Sr and Cs ions in cementitious paste samples is described. During the irradiation process, the samples were exposed to atmospheric conditions. Hence, atmospheric carbonation of samples could takes place. Cementitious pastes, differing in their w/c ratio (0.3, 0.45), were exposed to an integral dose of 10⁷ grays (Gy) of γ irradiation during a period of approximately 6 months. The effect of irradiation on the transport properties of the immobilized Sr and Cs ions was studied by leaching experiments. The carbonation depth of the different samples was measured and found to markedly increase in the case of irradiated samples compared to samples not exposed to irradiation. The enhanced carbonation is associated with the dehydration due to radiolysis of pore water in the paste. It was found that the irradiation resulted in a marked decrease in the leached fraction of Sr ions. This is related to the increased carbonation found for the irradiated samples. On the other hand, a small increase in Cs diffusivity was found for irradiated samples. This increase in leachability might be associated with the formation of microcracks in the irradiated sample.     

The effect of vacuum on the reflectivity of alumina ceramics under conditions of melting by concentrated laser radiation and subsequent free cooling

The results are given of measurements of the normal-hemispherical reflectivity of alumina ceramics in the semitransparency region for the wavelengths of 0.488, 0.6328, 1.15, and 3.39 μm. The measurements are performed in vacuum both in the process of fast heating by concentrated radiation of a CO₂ laser from room temperature to ～2900 K with the formation of a thin layer of melt and in the process of subsequent cooling after the heating radiation is switched off. The heating time is approximately 2.25 s, with the density of heating radiation flux of approximately 1600 W/cm². The effect of abrupt variation of the absorption coefficient during melting and solidification on the thermal-radiation characteristics is analyzed. The results demonstrate that the absorption coefficient of the melt in the semitransparency region is higher in vacuum than in the air.     

The effect of medical care by a helicopter trauma team on the probability of survival and the quality of life of hospitalised victims

In 1995, an experiment was started to give extra medical help by helicopter to patients who needed emergency treatment. The aim of the experiment was not to reduce the transportation time to the hospital, but to bring specialised medical care directly to patients as soon as possible. An evaluation study was carried out to assess the effect of the treatment given by the Helicopter Trauma Team (HTT) on survival and quality of life. The study focused on hospitalised patients suffering from polytrauma. A direct comparison between an experimental and control group was not possible, because the HTT group consisted of more severely injured patients. A refined severity index was constructed on the basis of the Revised Trauma Scale (RTS) and the Injury Severity Scale (ISS) and their sub-scores. Using this index, it was possible to make a clear distinction between three groups of patients, i.e. those with a high probability of survival (with or without special medical treatment), those with a very low probability of survival and the patients in between. It was shown that the HTT-treatment was effective. The survival rate increased for patients in the 'in between' group, but not for patients with a low probability of survival. There was no difference in the quality of life of patients from the HTT and non-HTT groups 15 months after the accident. These findings refute the hypothesis that only the most severely injured patients with a low quality of life profit from HTT-treatment.     

The effect of fluctuations in the lateral period of a multilayer grating on the scattering of hard synchrotron radiation

The effect of fluctuations in the lateral period of a nonideal multilayer grating on the scattering of hard synchrotron radiation (X-ray frequency range) was studied. Maps of the angular distribution of the coherent and diffuse scattering intensity in the reciprocal space are constructed. Theoretical diffraction curves calculated for a Ni/C multilayer grating are compared to the experimental data obtained by high-resolution triple-axis diffractometry. It is shown that good agreement between theory and experiment is observed for a fluctuation dispersion within 3% of the average lateral period of the grating.     

The effect of thin deployable construction elements of the international space station on the probability of its hull penetration by meteoroids and orbital debris

When calculating the probability of hull penetration by meteoroid and orbital debris (M/OD) for some of the International Space Station (ISS) modules (e.g. FGB, Service module, cargo vehicle “Progress”), one has to take into account their additional shielding produced by ISS deployable construction elements (such as solar panels, radiators), which decrease M/OD penetrating probabilities. The lack of developed calculation methods of accounting for this effect has arisen the necessity to investigate the law— governed nature of particle fragmentation process accompanying high velocity penetration of thin barriers, as well as to elaborate techniques for correct calculation of the probability of no penetration (PNP) of module pressure wall. The results of thorough analysis of the theoretical and experime ntal published data as well as of data obtained in joint NASA and RSA experimental program on particle fragmentation are presented in this report in the form of normalized analytical correlation between the fragment maximum size and impact parameters. On the basis of above mentioned particle fragmentation law, the method of module hull ballistic limit curves (BLC's) recalculation is determined, which include the effect of thin barriers greatly distanced from the module hull. This BLC's are used for module PNP calculations with the help of modified version of NASA BUMPER code. The special subroutines accounting for PNP changes due to the particle collisions with ISS deployable construction elements are introduced in the BUMPER algorithm. The results of the Service module PNP calculations with account for its “shadowing” by solar panels and radiators are presented.     

The effect of a space charge of electrons multiply backscattered from the anode on the current in a planar diode

The effect of a space charge of electrons multiply backscattered from the anode on the current in a planar diode was theoretically studied. Spectral distributions of the energy of electrons moving along the electric field were calculated by the Monte Carlo code. It was found that the maximum decrease in the current of diodes with high-Z anodes does not exceed 20%.     

The effect of ionizing radiation on dielectric properties of bovine achilles tendon collagen in the temperature range of thermal denaturation

The effect of -irradiation, with doses from 10²–2×10³ kGy, on the dielectric properties of solid-state collagen was studied. The temperature dependence of the constants and ' revealed a decrease in the denaturation temperature with increasing dose of irradiation. Dielectric dispersion observed in the frequency range 10 Hz to 10 kHz was suggested to be due to Maxwell-Wagner-Sillars polarization. In addition, an increase in the irradiation dose resulted in increasing activation energy of bovine achilles tendon collagen.     

The effect of annealing on Al-doped ZnO films deposited by RF magnetron sputtering method for transparent electrodes

In this study, transparent conducting Al-doped zinc oxide (AZO) films with a thickness of 150 nm were prepared on Corning glass substrates by the RF magnetron sputtering with using a ZnO:Al (Al₂O₃: 2 wt.%) target at room temperature. This study investigated the effects of the post-annealing temperature and the annealing ambient on the structural, electrical and optical properties of the AZO films. The films were annealed at temperatures ranging from 300 to 500 °C in steps of 100 °C by using rapid thermal annealing equipment in oxygen. The thicknesses of the films were observed by field emission scanning electron microscopy (FE-SEM); their grain size was calculated from the X-ray diffraction (XRD) spectra using the Scherrer equation. XRD measurements showed the AZO films to be crystallized with strong (002) orientation as substrate temperature increases over 300 °C. Their electrical properties were investigated by using the Hall measurement and their transmittance was measured by UV-vis spectrometry. The AZO film annealed at the 500 °C in oxygen showed an electrical resistivity of 2.24 × 10^− 3 Ω cm and a very high transmittance of 93.5% which were decreased about one order and increased about 9.4%, respectively, compared with as-deposited AZO film.     

溶胶凝胶制备工艺对电致变色用氧化镍薄膜性能的影响

以四水醋酸镍-无水乙醇-聚乙二醇(PEG6000)前驱液作为溶胶,采用旋涂法制备的电致变色用氧化镍薄膜,用XRD测得的氧化镍薄膜结晶性能不好,SEM观察到的表面形貌是均匀平整致密的;采用电化学腐蚀系统对其进行循环伏安特性的测试,随后又用紫外-可见光谱仪对变色性能进行测试;通过对比热处理时间、溶胶陈化时间、镀膜层数对薄膜变色性能的影响,总结出了四水醋酸镍-无水乙醇-聚乙二醇(PEG6000)体系溶胶-凝胶法制备氧化镍薄膜的工艺条件,即将溶胶陈化15d后旋涂镀膜3次,在250℃下热处理2h制备得到的薄膜在λ=391nm时透射率调节范围达到61%.