利用光子统计概率测量单分子光子源的信号背景比

理论上研究了基于Hanbury Brown Twiss 探测方式，利用单光子和双光子统计概率P RS(1),PRS(2),直接测量单分子光子源的信号背景比.在研究过程中同时考 虑到单分子布居于暂稳态和探测器量子效率对测量结果的影响.在满足PRS(1)2 PRS(2)-3PRS(2)的条件时，研究给出了一种有效测量信号背景比的方 法SBR=P2RS(1)/2PRS(2).另外，分析讨论了Mandel参数Q 与信号背景比之间的关系. 关键词： 单分子光子源 信号背景比 光子统计 暂稳态 Mandel参数     

The effective area of a collimator for gamma rays from Co 60 and Cs 137

Numerical values of correction coefficients due to the penetration of gamma radiation of Co 60 and Cs 137 through the edges of a collimator are given.Na Truhláce 2a, Praha 8, Czechoslovakia.     

Preliminary investigations of Monte Carlo simulations of neutron energy and let spectra for fast neutron therapy facilities

No fast neutron therapy facility has been built with optimized beam quality based on a thorough understanding of the neutron spectrum and its resulting biological effectiveness. A study has been initiated to provide the information necessary for such an optimization. Monte Carlo studies will be used to simulate neutron energy spectra and LET spectra. These studies will be bench-marked with data taken at existing fast neutron therapy facilities. Results will also be compared with radiobiological studies to further support beam quality optimization. These simulations, anchored by this data, will then be used to determine what parameters might be optimized to take full advantage of the unique LET properties of fast neutron beams.This paper will present preliminary work in generating energy and LET spectra for the Fermilab fast neutron therapy facility.     

Determination of thiophanate-methyl using UV absorption spectra based on multiple linear regression

As one worldwide used agent for fungi control in the fruit and vegetable field, thiophanate-methyl has been constituted a significant health risk. To determinate thiophanate-methyl, the method using UV absorption spectra based on multiple liner regression is used. Principal absorption wavelengths related closely with thiophanate-methyl ethanol solution are confirmed through analyzing the absorption spectra of thiophanate-methyl. Utilizing multiple linear regression, mathematical model between absorbance obtained from fourteen absorption wavelengths and thiophanate-methyl concentration is established. The result shows concentrations between the predicted values and measured values are well coincident and the related coefficient is 0.9853 over the concentration range 2–35 ppm.     

Interpretation of the electronic spectra of Fe and Co porphyrins based on quantum-chemical calculations by the density functional method

Using the time-dependent formalism of the density functional theory (time-dependent density functional theory (TDDFT)), the energies and intensities of the electronic transitions of some Fe and Co porphyrins and their anionic forms with different electron localization are studied quantum chemically. It is shown that, in the majority of the considered cases, the calculations performed with the B3LYP functional with a comparatively narrow basis set (6-31G) are quite consistent with previous calculations of these objects by the ZINDO/S-CI semiempirical method taking into account double excitations. Furthermore, the level of agreement of the B3LYP calculations with experiment is the same as that obtained with the ZINDO/S-CI method.     

Determination of the kinetic coefficients of a gas in a supersonic jet from Brillouin spontaneous scattering spectra

The mean free path and the shear viscosity of molecular nitrogen are determined in a rarefied supersonic jet using the Brillouin spontaneous scattering technique. By examples of sub-and supersonic jets, the measured kinetic coefficients are shown to agree with the tabulated values of these parameters. These results are obtained using laser radiation, whose output power, which restricts the signal-to-noise ratio, is as low as 50 mW.     

Determination of the energy diagram of a dielectric-semiconductor structure from the photocharging spectra of the dielectric

The Ge-GeO₂ and Si-SiO₂ structures are investigated by the method of optical charging of traps in the dielectric. It is shown that by measuring the photocharging spectrum in a wide temperature range, one may obtain information on the boundaries of delocalized states of the dielectric as well as on the dimensions of the tails of fluctuation localized states.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 36–40, May, 1982.     

Determination of the positions of impurity centers in a dislocation core in a NaCl crystal from magnetoplasticity spectra

The spectra of the mean free paths l(ν) of edge dislocations have been studied in NaCl crystals exposed in the electron paramagnetic resonance scheme to the crossed magnetic fields: the Earth’s field (50 μT) and the pump field (2.5 μT, 5–440 kHz). The spectra have been measured for a series of angles θ = 0°–5° of rotation of the sample around its edge [100] with respect to the Earth’s field. The fine structure of the spectra contains a series of peaks whose resonance frequencies are described by the empirical expression v _i ^± = Asin(θ ± Δθ _i ) ≈ A(θ ± Δθ _i ). The parameters Δθ _i are independent of the angle θ within the experimental errors. Within the model of “frozen” magnetic moments associated with impurity center Ca⁺-Cl⁰, the angles Δθ _i characterize the deviation of the axis of the center from the 〈100〉 direction in the core of a dislocation. These angles can be expressed in terms of the spectra obtained: Δθ _i = (? _i ⁺ ? v _i ^? )/2A. The computer simulation of the edge dislocation core provides the set of the angles Δθ _i close to the measured values. The spin-lattice relaxation time of the center on dislocation has been estimated from the low-frequency edge of the spectrum l(ν) as τ _{s ? l} ～ 10^?4 s.     

Collision of a comet with Jupiter: Determination of fragment penetration depths from the molecular spectra

After the fragments of comet Shoemaker-Levy 9 fell onto Jupiter, some molecules which were formed as a result of chemical reactions in the shock-compressed gas during the explosion of the comet fragments and ejected into the upper atmosphere by the shock wave were observed in the upper atmosphere. As the initially hot gas expanded, these molecules were quenched. Therefore they represent a kind of “memory” of the shock processes which occurred in the region of generation of the strong shock wave. The radiation from such molecules was registered by both ground-based observers and the Hubble space telescope. In the present paper we estimate the penetration depth and energy of the largest comet fragments on the basis of data on the content of shock-synthesized molecules in Jupiter’s upper atmosphere. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 6, 387–391 (25 March 1996)     

Effects of 60Co gamma-ray irradiation on the optical properties of natural and synthetic quartz from 85 to 300 K

Optical absorption and luminescence measurements have been made between 85 and 300 K on natural and synthetic quartz during and after ⁶⁰Co gamma-ray irradiation. Absorption vs. dose curves can be resolved into the sum of a saturating exponential and a linear component. At 85 K the slope of the linear component is small, while at 300 K the linear term dominates the growth curves. The coloring induced by irradiation at 85 K decreased in a complex manner during anneal at a linear rate to 300 K. During this annealing process multiple-peak thermoluminescent (TL) glow curves were observed and recorded. The TL emission spectra are described accurately by single Gaussian-shaped bands, whereas the gamma-ray induced luminescence is comprised of several poorly resolved bands. All recorded TL glow curves are characterized by a set of four first order glow peaks between 150 and 220 K. The temperature dependence of radioluminescence intensity is described by a classical model in which a temperature-independent radiative transition competes with a thermally activated non-radiative process.     

Determination of the chemical parameters and manufacturer of divins from their broadband transmission spectra

Analysis of multiparametric data on transmission spectra of 24 divins (Moldovan cognacs) in the 190–2600 nm range allows identification of outliers and their removal from a sample under study in the following consideration. The principal component analysis and classification tree with a single-rank predictor constructed in the 2D space of principal components allow classification of divin manufacturers. It is shown that the accuracy of syringaldehyde, ethyl acetate, vanillin, and gallic acid concentrations in divins calculated with the regression to latent structures depends on the sample volume and is 3, 6, 16, and 20%, respectively, which is acceptable for the application.     

Structure and diffusion in aluminium and gallium trihalide melts from simulations based on intramolecular force laws

Diffraction studies of the liquid structure of AlCl₃, AlBr₃, GaBr₃ and GaI₃ close to their respective freezing points have revealed fourfold coordination of the trivalent metal ions, consistent with dimeric M₂X₆ molecules being the dominant species. We evaluate the species-resolved pair distribution functions and liquid structure factors in all these melts by carrying out classical molecular-dynamics simulations, based on polarizable-halogen force laws that were determined on isolated molecular monomers and dimers in the gaseous phase. We also report results for mean-square displacements and diffusion coefficients of the two species in each melt. The model reproduces the main features of the total neutron-diffraction structure factors, showing peaks due to intermediate-range order and to charge and density short-range order, and accounts for the experimental data at a good quantitative level. Direct simulation of the pair distribution functions yields agreement with the diffraction data on metal–halogen and halogen–halogen bond lengths in the melt and on the stability of the first-neighbour shell of the metal ions. We examine the temperature dependence of the liquid structure in our models for GaBr₃ and AlCl₃ and emphasize the structural role of van der Waals interactions between the halogens.     

Calibration of a germanium well-detector using 60Co: The effects of the angular correlation of the two gamma rays emitted in cascade,quantified with Monte Carlo simulations

Radiation sources of ⁶⁰Co are commonly measured by means of HPGe gamma spectrometers, either as unknown sources or as calibration sources. However, the two gamma rays that are emitted by this nuclide, at 1.17 MeV and 1.33 MeV respectively, follow each other so rapidly that in the cases where both photons interact with the crystal, the electronics will record a single additive pulse. This is a cascade or coincidence summing effect. Such effect induces in the gamma spectra a “sum-peak”, appearing at 2.5 MeV on the energy axis, generated by the pair of photons which have both been entirely absorbed by the detector. Also, the second photon is correlated for direction to the first one, i.e., it will not be emitted at random, with an isotropic probability. Then the question arises of to what extent the two effects, cascade and correlation, might affect the count rates for the three peaks. Various answers have already been published, but without practical solutions. In this context, the present work was devoted to further explore the question by means of Monte Carlo simulation, in the case of a welltype detector. As a result, inside the well the sum peak only is not affected and it allows accurate evaluation of the detector efficiency at 1.25 MeV. Outside the well, near the detector, none of the three peaks can be directly used for efficiency evaluation, unless the relevant corrections can be evaluated. At a distance from the detector, the two single peaks can be used, but with the drawback of a low efficiency.     

Comparison of simulations and data from a seismo-acoustic tank experiment

A tank experiment was carried out to investigate underwater sound propagation over an elastic bottom in flat and sloping configurations. The purpose of the experiment was to evaluate range-dependent propagation models with high-quality experimental data. The sea floor was modeled as an elastic medium by a polyvinyl chloride slab. The relatively high rigidity of the slab requires accounting for shear waves in this environment. Acoustic measurements were obtained along virtual arrays in the water column using a robotic apparatus. Elastic parabolic equation solutions are in excellent agreement with data.     

Analysis of one-and two-particle spectra at RHIC based on a hydrodynamical model

We calculate the one-particle hadronic spectra and correlation functions of pions based on a hydrodynamical model. Parameters in the model are so chosen that the one-particle spectra reproduce experimental results of √s= 130 AGeV Au + Au collisions at RHIC. Based on the numerical solution, we discuss the space-time evolution of the fluid. Two-pion correlation functions are also discussed. Our numerical solution suggests the formation of the quark-gluon plasma with large volume and low net baryon density.     

CMOS器件60Coγ射线、电子和质子电离辐射损伤比较

利用TRIM95蒙特卡罗软件计算了质子在二氧化硅中的质量阻止本领和能量沉积,比较了质子在二氧化硅中的电离阻止本领与核阻止本领,分析了质子在材料的表面吸收剂量与灵敏区实际吸收剂量的关系.利用60Coγ射线、1MeV电子和2-9 MeV质子对CC4007RH和CC4011器件进行辐照实验,比较60Coγ射线和带电粒子的电离辐射损伤情况.实验结果表明,60Coγ射线、1MeV电子和2-7MeV质子辐照损伤效应中,在0V栅压下可以相互等效;在5V栅压下,以60Coγ射线损伤最为严重,1MeV电子的辐射损伤与60Coγ射线差别不大,9MeV以下质子辐射损伤总是小于60Coγ射线,能量越低,损伤越小.     

The dose kernels of pencil and differential pencil photon beams with the spectrum of treatment machines with a <Superscript>60</Superscript>Co source in water and their analytical approximation

This article presents the results of calculations by the Monte-Carlo method in the EGSnrc toolkit of the spatial distributions of absorbed energy or dose kernels in water for a pencil beam or differential pencil beam (point spread function) with the spectrum of ROKUS-M treatment machines. The photon spectrum of the ROKUS-M machines was also calculated by the Monte-Carlo method. The calculated dose-kernel results were approximated separately for the radial distribution of the primary and the scattered component of dose kernels by sums of exponential functions divided by the squared radius for a differential pencil beam and by the radius for a pencil beam. This approximation makes direct implementation possible for wellknown model-based techniques for finding 3D dose distributions in external radiation therapy. A simple analytical procedure to verify approximation formulas is proposed. It is also applicable in independent checks of dose distributions along the treat beam axis, which is an important guideline of the Radiation Therapy Quality Assurance Program.     

Determination of the angular separation and the spectra of two-point sources from spectral coherence measurements

We present a novel method not only for determining the angular separation of unknown two-point spectral sources but also for obtaining each of their spectral profiles from measurements of both their complex degree of spectral coherence and their spectra across an observation area in the space-frequency domain. The theoretical predictions are fully proved by an experimental demonstration with a pair of uncorrelated two-point spectral sources.