Study on the radiation problem caused by electron beam loss in accelerator tubes

The beam dynamic code PARMELA was used to simulate the transportation process of accelerating electrons in S-band SW linacs with different energies of 2.5, 6 and 20 MeV. The results indicated that in the ideal condition, the percentage of electron beam loss was 50% in accelerator tubes. Also we calculated the spectrum, the location and angular distribution of the lost electrons. Calculation performed by Monte Carlo code MCNP demonstrated that the radiation distribution of lost electrons was nearly uniform along the tube axis, the angular distributions of the radiation dose rates of the three tubes were similar, and the highest leaking dose was at the angle of 160° with respect to the axis. The lower the energy of the accelerator, the higher the radiation relative leakage. For the 2.5 MeV accelerator, the maximum dose rate reached 5% of the main dose and the one on the head of the electron gun was 1%, both of which did not meet the eligible protection requirement for accelerators. We adopted different shielding designs for different accelerators. The simulated result showed that the shielded radiation leaking dose rates fulfilled the requirement.     

Analysis of Laser-generated Rayleigh wave on viscoelastic materials

In order to understand the viscoelasticity of material, this research has been conducted to study the propagation characteristics of viscoelastic Rayleigh wave theoretically. A model is presented for the pulsed laser generation of ultrasound on viscoelastic medium surface. Referred to the Kelvin model, the frequency equation and the normal displacement of viscoelastic Rayleigh wave were derived, the influence of the viscoelastic modulus on dispersion and attenuation was discussed. From the theoretical calculation, it is shown that the effect of viscoelasticity on the attenuation of Rayleigh wave is more than that on its dispersion. In the case of a weak viscosity, the attenuation of viscoelastic Rayleigh wave is directly proportional to viscosity modulus; the effect of shear viscosity on the attenuation is much more than that of bulk viscosity. The transient response of viscoelastic Rayleigh wave was also simulated using Laplace and Hankel inversion transform, which are showed in good agreement with the theoretic predictions. The model provides a useful tool for the determination of viscoelastic parameters of medium.     

Influence of purity of HfO2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.     

Region of interest and pixel-by-pixel analysis of dynamic contrast enhanced magnetic resonance imaging parameters and time-intensity curve shapes: a comparison in chondroid tumors

Dynamic contrast enhanced (DCE) MRI is widely acknowledged to be a helpful tool in the diagnosis and differentiation of tumors. In common clinical settings, the dynamic changes described by the time-intensity curves (TICs) are evaluated to find patterns of atypical tissue behavior, i.e., areas characterized by rapid contrast wash-in and wash-out. Despite the ease of this approach, there is no consensus about the specificity of the TIC shapes in discriminating tumor grades. We explore a new way of looking at TICs, where these are not averaged over a selected region of interest (ROI), but rendered pixel-by-pixel. In this way, the characteristic of the tissue is not given as a single TIC classification but as a distribution of the different TIC patterns. We applied this method in a group of patients with chondroid tumors and compared its outcome with the outcome of the standard ROI-based averaged TIC analysis. Furthermore, we focused on the problem of ROI selection in these tumors and how this affects the outcome of the TIC analysis. Finally, we investigated what relationship exists between the "standard" DCE-MRI parameter maximum enhancement (ME) and the TIC shape. CONCLUSIONS: We demonstrate that, where the ROI approach fails to show the presence of areas of rapid contrast wash-in and wash-out, the pixel-by-pixel approach reveals the coexistence of a heterogeneous pattern of TIC shapes. Secondly, we point out the differences in the DCE MRI parameters and tumor volume that can result when selecting the tumor based on DCE parameter maps or post-contrast T1-weighted images. Finally, we show that ME maps and TIC shape maps highlight different tissue areas and, therefore, the use of the ME maps is not appropriate for the correct identification of areas of atypical TICs.     

A study on the best irradiation dose of X-ray for Hep-2 cells by Fourier transform infrared spectroscopy

Fourier transform infrared spectroscopy (FTIR) was employed to study the human epidermis larynx carcinoma cell lines (Hep-2) which were irradiated by different doses of X-ray.The results show that (1) the irradiation of X-ray damages the structure of the CH3 groups of the thymine in DNA,which restrains the reproduction of Hep-2 cells effectively,(2) the 8 Gy dose of X-ray irradiation changes the framework and the relative contents of some proteins,lipids and the nucleic acid molecules intercellular in the greatest degree,and (3) the 8 Gy dose of X-ray irradiation is the best irradiation dose for lowering the degree of the cancerization of Hep-2 cells according to the criteria for the degree of the cancerization reported recently.Meanwhile,the apoptosis of these cells were detected by using flow cytometry (FCM) primarily.It shows that the apoptotic ratio of the Hep-2 cells depends on the irradiation dose to some extent,but is not linearly.And the apoptotic ratio of the 12 Gy dose group is the maximum (20.36%),but the apoptotic ratios of the 2 to 8 Gy dose groups change little.     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Experimental study on SC RF cavities by using China large grain niobium for ILC

Large grain niobium has the potential of simplifying the production sequence and consequently reducing the cost of the superconducting RF cavities for ILC.To investigate the feasibility of fabrication and the possibility to achieve high gradient by large grain cavities,two 1.3 GHz cavities were made of China large grain niobium and a series of vertical tests were carried out following several different surfaces treatment procedures.Two cavities have both reached the high gradient of more than 43 MV/m repeatedly and the maximum accelerating field of 47.9 MV/m has been achieved by China large grain niobium.This paper introduces the features of the fabrication and surface treatments on the large grain cavities and presents the preliminary results of the research.     

Autofluorescence of Plant Secreting Cells as a Biosensor and Bioindicator Reaction

Autofluorescence of intact secretory cell of plants is considered as a possible biosensor for the cellular biomonitoring. The fluorescence of secretory cells was due to the chemical composition of their secretions. This phenomenon could be recommended: 1. for the diagnostics of secretory cells among non-secretory ones; 2. for the express-analysis of the content of secretory cells at norm and under various factors; 3. for the analysis of cell-cell interactions. Identification of intact secretory cells filled with products of secondary metabolism is based on their fluorescence characteristics. The filling of the cells with a secretion and the removing of the secretions are easily observed under the luminescence microscope—from confocal microscope to various microspectrofluorimeters. The cellular fluorescence can serve as an indicator of the cell state in vivo. The following development of the earlier diagnostics based on the autofluorescence may be the area of the remote monitoring of agriculture crops and yields of medicinal plants as well as the remote sensing of the environmental stress.     

Dynamics of a waveguide pulsed-periodic CO2 laser with loss modulation

The nonlinear dynamics of a waveguide CO₂ laser with combined periodic loss and pumping modulation is investigated theoretically and experimentally. The possibilities of controlling time and energy parameters of the output radiation using the corresponding selection of the detuning of the cavity's longitudinal mode from the center of the amplification line, the amplitude, and the frequency of loss modulation are demonstrated. The observed asymmetric dependence of the lasing-radiation density on the detuning of the cavity frequency is explained by the attendant modulation of the refractive index of the loss modulator. To whom correspondence should be addressed. B. I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, 68, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 4, pp. 471–478, July–August, 1999.     

Rotation of the light polarization plane by an ensemble of oriented linear associates: Model representations

In an “oriented gas” model expressions are obtained for the angle of nongyrotropic rotation of the polarization plane (NRPP) of transmitted light by an ensemble of oriented associates consisting of nongyrotropic molecules. The cluster character of the nongyrotropic rotation of the polarization plane and the dependence of its angle on the incident light polarization vector azimuth are noted, which distinguish linear and circular polarization effects. Measurement of linear dichroism by the angle of nongyrotropic rotation of the polarization plane with the use of commercial spectropolarimeters is theoretically justified. Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072 Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 1, pp. 95–101, January–February, 1998.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Influence of microwave radiation on the association processes of rhodamine 6G molecules in aqueous solutions

The influence of the microwave radiation of two frequency ranges (2.0 mm and 6.9 dm) on the absorption spectra of the cationic dye rhodamine 6G has been investigated. A reversible decrease in the quantity of the dimers of the dye molecules after exposure of its aqueous solution to microwave radiation and also the phenomenon of destruction of the associates of the dye molecules under the influence of the microwave field have been revealed. They are discussed from the standpoint of the structural characteristic features of water.__________Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 1, pp. 34–37, January–February, 2005.     

波源和接收者在介质体内的客观运动理论

建立介质体概念并指出介质体的内部独立性和外部相关性。建立双列车模型,对波在介质体内的多普勒效应进行量化分析。建立波源和接收者在介质体内的客观运动理论。把客观运动理论应用于天文学。指出天体介质体的边缘凸透镜特性。明确时间和物理介质空间的客观性。指出相对论的错误。明确波和粒子的区别。     

LM and TEM study of the orthokeratinized and parakeratinized epithelium of the tongue in the domestic duck (Anas platyrhynchos f. domestica)

The previous histological studies of the lingual mucosa in birds characterized two types of keratinized epithelium, i.e. orthokeratinized and parakeratinized. These epithelia are composed of three layers: basal, intermediate and keratinized. The present study showed detailed ultrastructural features of cells in particular layers of two types of keratinized epithelia on the tongue in the domestic duck and defined structural differences.TEM observations showed a gradual reduction in cell organelles in the following layers, at increasing amounts of keratin fibers. The characteristic feature of the ortho- and parakeratinized epithelium is the presence of sub-layers in the intermediate layer, i.e. the upper and lower part, which results from the different shape of cell nuclei and dye affinity of the cytoplasm. The keratinized layer of ortho- and parakeratinized epithelium is built of two types of cells such as electron dark and light cells, which undergo exfoliation. The basic difference between the keratinized epithelia is the presence of flattened cell nuclei in the keratinized layer of the parakeratinized epithelium. The differentiating feature is also an arrangement of keratin fibers in the cell cytoplasm of the keratinized layer. The analysis of the thickness of the epithelium and the keratinized layer, indicated differences between keratinized epithelia, which result from two variants of performing protective functions, either through a thick keratinized layer or by a higher epithelium.Differences in the ultrastructure of the ortho- and parakeratinized epithelium are associated with mechanical functions of the epithelium resulting from different forces acting on the tongue during feeding activities.     

Tropical Monsoon Forest Thermodynamics Based on Remote Sensing Data

This paper addresses thermodynamic variables that characterize the energy balance and structure of the solar energy transformation by the ecosystems of deciduous tropical forests. By analyzing the seasonal dynamics of these variables, two main states of the thermodynamic system are determined: the end of the drought season and the end of the wet season. Two sub-systems of solar energy transformation are also defined: a balance system that is responsible for the moisture transportation between the ecosystem and atmosphere; and a structural bioproductional system responsible for biological productivity. Several types of thermodynamic systems are determined based on the ratio between the invariants of the variables. They match the main classes of the landscape cover. A seasonal change of thermodynamic variables for different types of thermodynamic systems is additionally studied. The study reveals that temperature above the forest ecosystems is about 4° lower than above the open areas during most of the year.     

The effective absorption cross-section of thermal neutrons in a medium containing strongly or weakly absorbing centres

The structure of a heterogeneous system influences diffusion of thermal neutrons. The thermal-neutron absorption in grained media is considered in the paper. A simple theory is presented for a two-component medium treated as grains embedded in the matrix or as a system built of two types of grains (of strongly differing absorption cross-sections). A grain parameter is defined as the ratio of the effective macroscopic absorption cross-section of the heterogeneous medium to the absorption cross-section of the corresponding homogeneous medium (consisting of the same components in the same proportions). The grain parameter depends on the ratio of the absorption cross-sections and contributions of the components and on the size of grains. The theoretical approach has been verified in experiments on prepared dedicated models which have kept required geometrical and physical conditions (silver grains distributed regularly in Plexiglas). The effective absorption cross-sections have been measured and compared with the results of calculations. A very good agreement has been observed. In certain cases the differences between the absorption in the heterogeneous and homogeneous media are very significant. A validity of an extension of the theoretical model on natural, two-component, heterogeneous mixtures has been tested experimentally. Aqueous solutions of boric acid have been used as the strongly absorbing component. Fine- and coarse-grained pure silicon has been used as the second component with well-defined thermal-neutron parameters. Small and large grains of diabase have been used as the second natural component. The theoretical predictions have been confirmed in these experiments.