Specific absorbed fractions of electrons and photons forRad-HUMAN phantom using Monte Carlo method

The specific absorbed fractions (SAF) for self- and cross-irradiation are effective tools for the internal dose estimation of inhalation and ingestion intakes of radionuclides. A set of SAFs of photons and electrons were calculated using the Rad-HUMAN phantom, which is a computational voxel phantom of a Chinese adult female that was created using the color photographic image of the Chinese Visible Human (CVH) data set by the FDS Team. The model can represent most Chinese adult female anatomical characteristics and can be taken as an individual phantom to investigate the difference of internal dose with Caucasians. In this study, the emission of mono-energetic photons and electrons of 10 keV to 4 MeV energy were calculated using the Monte Carlo particle transport calculation code MCNP. Results were compared with the values from ICRP reference and ORNL models. The results showed that SAF from the Rad-HUMAN have similar trends but are larger than those from the other two models. The differences were due to the racial and anatomical differences in organ mass and inter-organ distance. The SAFs based on the Rad-HUMAN phantom provide an accurate and reliable data for internal radiation dose calculations for Chinese females.     

Specific absorbed fractions of electrons and photons for Rad-HUMAN phantom using Monte Carlo method

The specific absorbed fractions(SAF) for self- and cross-irradiation are effective tools for the internal dose estimation of inhalation and ingestion intakes of radionuclides. A set of SAFs of photons and electrons were calculated using the Rad-HUMAN phantom, which is a computational voxel phantom of a Chinese adult female that was created using the color photographic image of the Chinese Visible Human(CVH) data set by the FDS Team. The model can represent most Chinese adult female anatomical characteristics and can be taken as an individual phantom to investigate the difference of internal dose with Caucasians. In this study, the emission of mono-energetic photons and electrons of 10 ke V to 4 Me V energy were calculated using the Monte Carlo particle transport calculation code MCNP. Results were compared with the values from ICRP reference and ORNL models. The results showed that SAF from the Rad-HUMAN have similar trends but are larger than those from the other two models. The differences were due to the racial and anatomical differences in organ mass and inter-organ distance. The SAFs based on the Rad-HUMAN phantom provide an accurate and reliable data for internal radiation dose calculations for Chinese females.     

Distortion-product otoacoustic-emission suppression tuning in human infants and adults using absorbed sound power

The greatest difference in distortion product otoacoustic emission (DPOAE) suppression tuning curves (STCs) in infant and adult ears occurs at a stimulus frequency of 6 kHz. These infant and adult STCs are much more similar when constructed using the absorbed power level of the stimulus and suppressor tones rather than using sound pressure level. This procedure incorporates age-related differences in forward and reverse transmission of sound power through the ear canal and middle ear. These results support the theory that the cochlear mechanics underlying DPOAE suppression are substantially mature in full-term infants.     

Phase transition for absorbed Brownian motion with drift

We study one-dimensional Brownian motion with constant drift toward the origin and initial distribution concentrated in the strictly positive real line. We say that at the first time the process hits the origin, it is absorbed. We study the asymptotic behavior, ast, ofm _t , the conditional distribution at time zero of the process conditioned on survival up to timet and on the process having a fixed value at timet. We find that there is a phase transition in the decay rate of the initial condition. For fast decay rate (subcritical case)m _t is localized, in the critical casem _t is located around , and for slow rates (supercritical case)m _t is located aroundt. The critical rate is given by the decay of the minimal quasistationary distribution of this process. We also study in each case the asymptotic distribution of the process, scaled by , conditioned as before. We prove that in the subcritical case this distribution is a Brownian excursion. In the critical case it is a Brownian bridge attaining 0 for the first time at time 1, with some initial distribution. In the supercritical case, after centering around the expected value—which is of the order oft—we show that this process converges to a Brownian bridge arriving at 0 at time 1 and with a Gaussian initial distribution.     

Photoswitching microscopy with standard fluorophores

We introduce far-field subdiffraction-resolution fluorescence imaging based on photoswitching of individual standard fluorophores in air-saturated solution. Here, photoswitching microscopy relies on the light-induced switching of organic fluorophores (ATTO 655 and ATTO 680) into long-lived metastable dark states and spontaneous repopulation of the fluorescent state. In the presence of low concentrations (2–10 mM) of reducing, thiol-containing compounds such as ß-mercaptoethylamine or glutathione, the density of fluorescent molecules can be adjusted to enable multiple localizations of individual fluorophores with an experimental accuracy of ～20 nm. The method requires wide-field illumination with only a single laser beam for readout and photoswitching and provides superresolution fluorescence images of intracellular structures under live cell compatible conditions.     

Calculating particle correlators with the account of detector efficiency

The formulae for m-order correlators K _m of a given particle observable (e.g., energy, transverse momentum or a conserved discrete quantum number) accounting for the track reconstruction efficiencies in a real detector are presented. The calculation of second- to fourth-order correlators is considered in some detail. Similar to the case of an ideal detector, the correlators can be expressed through the event-by-event fluctuation measures of the observable single event mean, the pseudocorrelators (determined by the pseudo-central moments of the observable distribution) and their cross terms. It allows one to avoid the combinatorics and essentially reduce the computer time when calculating the higher-order correlators in high multiplicity events. Compared with the case of ideal detector, this reduction is somewhat smaller due to the increased number of pseudocorrelators and additional calculations of the moments of the distribution of the track weights. For a constant track reconstruction efficiency, the correlator formulae reduce to those for an ideal detector. However, in real experiments the efficiencies are usually essentially dependent on particle momenta and may lead to substantial corrections of momentum correlators on the level of tens of percent.     

混沌动力系统小波变换模数的关联维数

关联维数是描述动力系统混沌的重要参数.在仿真计算的基础上,发现尽管小尺度小波变换时,奇异吸引子的整体形状发生了改变,但小波变换模数的关联维数与动力系统本身是一致的.同时仿真计算还表明,随尺度的增加,关联积分与距离的标度关系逐渐变差,但在一定范围内仍可较准确地计算出关联维数. 关键词： 混沌 关联维数 小波分析 尺度 相空间     

用函数计算器计算透镜定中心十字象的计算程序

利用函数计算器的功能,选用适当的光路计算公式快速简便地完成在编制透镜胶合工艺和编制透镜滚边定中心车外圆等装校工艺中的大量球心十字象(通常也称”飞机”象)的光路计算,从而确定出定中心所用的十字象位置尺寸参数。     

基于传递矩阵法的热声发动机频率设计计算

介绍利用传递矩阵法计算热声发动机的工作频率的思路和方法。理论分析表明该方法是切实可行的 ,和其他方法得到了相互的印证。利用该方法的计算结果和已发表的试验结果进行了对比分析。研究结果表明 ,相比已有的计算方法而言 ,传递矩阵法更加简单直观 ,方便于采用计算机编程计算复杂结构的热声系统的工作频率。     

使用示波器测量旋光率

对现有的测旋光度装置加以改进,组成了一套直观测量旋光度的实验装置.本文介绍了该装置的基本原理、结构及使用方法.     

Quartic phase compensation with a standard grating compressor

We demonstrate that, by changing the altitude and the azimuth incident angles on the gratings of the conventional grating-pair compressor used in chirped-pulse amplification, an extra degree of freedom is added. This results in a continuous adjustment of second-, third-, and fourth-order dispersions, which allows one to compensate for those dispersions that originated in the expansor or in the amplifier medium as a result of material dispersion or self-phase modulation, even with small out-of-plane tilts of the expansor and compressor. Analytical calculations of the high-order dispersions introduced by this compressor and examples for a pulse with a central wavelength at 800 nm are presented.     

Enhanced photoluminescence properties of morin and trypsin absorbed on porous alumina films with ordered pores array

For the first time, the photoluminescence (PL) spectra of anodic porous alumina (P-Al) films impregnated with essentially non-fluorescent morin and morin-trypsin (Try) were investigated and compared with those of liquid solutions. It was found that their PL positions are similar to that of dye-Al³⁺ in ethanol solution, and the PL intensity of embedded dye-Try is much higher than that of embedded dye alone. We infer that the appearance of the PL band detected here is due to the formation of morin-Al complex in the holes of P-Al with the inner wall involved, and a likely luminescent mechanism is proposed to elucidate the PL enhancement phenomena due to the coexistence of morin and Try in the P-Al pores, which is confirmed by UV and FTIR measurements. Moreover, it is also found that the PL intensity increases with the pore size.     

Multilayer piezocomposite structures with piezoceramic volume fractions determined by mathematical optimisation

Piezocomposite materials are now widely used in broadband underwater sonar for ultrasound generation and detection because of their recognised advantages over piezoceramic devices. However, it is difficult to make single-layer piezocomposite devices to operate effectively at frequencies below 100 kHz. Instead, multilayer composite stacks can be used. If this solution is adopted, interesting effects can be achieved by choosing appropriate ceramic volume fractions for different layers in the stack, as volume fraction plays a key role in achieving the desired performance. In this paper we describe a theoretical study of 1-3 piezocomposite transducers with five layers each with a different volume fraction. Our work is based mainly on our own special purpose computer code which solves the one-dimensional wave equation by matrix manipulation, with additional support from the PZ Flex finite element analysis package. The choice of volume fractions is difficult because of the multifaceted nature of the problem, with a very large number of possible combinations and complex dependence of material properties, and hence transducer sensitivity and frequency response on the volume fractions. Therefore, we have used the stochastic optimisation technique of simulated annealing implemented in MATLAB code to determine the volume fraction of each layer. The optimisation cost function we have used is maximisation of gain-bandwidth product. We have found that significant increases in gain-bandwidth product can be achieved compared with the use of the same volume fraction in each layer, far exceeding the 35% reported previously with trial-and-error volume fraction adjustment. This suggests that improvements in practical device performance are possible.     

Separation of low-molecular-weight fractions of ultrafine polytetrafluoroethylene with supercritical carbon dioxide

The separation of low-molecular-weight fractions of FORUM® ultrafine polytetrafluoroethylene (UPTFE) in supercritical carbon dioxide (SC-CO₂) was studied under static conditions. The experiments were performed over temperature and pressure ranges of 318–383 K and 10–70 MPa, respectively. Over the entire pressure and temperature ranges covered, a behavior typical of solid substance-SC-CO₂ systems was observed: as the pressure and temperature of the solvent increased, so did the concentrations of low-molecular-weight UPTFE fractions in it. The experimental data were interpreted within the framework of three models establishing a relationship between the solubility of a substance with the supercritical fluid density, those proposed by Chrastil, Bartle, and Mendez-Santiago. The experimental data were closely described by the Bartle and Mendez-Santiago models.     

Auditory backward recognition masking in children with a specific language impairment and children with a specific reading disability

The auditory backward recognition masking (ABRM) and intensity discrimination (ID) thresholds of children with a specific language impairment and poor reading (SLI-poor readers), children with an SLI and average reading (SLI-average readers), children with a specific reading disability and average spoken language skills (SRD-average language), and children with normal spoken and written language (controls) were estimated with "child-friendly" psychophysical tasks. The pattern of ABRM and ID scores suggests that a subset of children with concomitant oral language and reading impairments has poor ABRM thresholds, and that a subgroup of children with an SLI or SRD has poorer ID thresholds than controls. The latter result warns against using rapid auditory processing tasks that do not actively control for auditory discrimination ability. Further, some unusually poor ABRM scores and ID scores question the validity of extreme scores produced by children on psychophysical tasks. Finally, the poor oral language scores of many of the children who had impaired reading highlight the need to test the oral language skills of SRD samples to ascertain how homogeneous and specifically disabled they really are.     

New Approach to Calculating the Double Coaxial Resonator with a Shortening Capacitance

Russian Physics Journal - The double coaxial resonator with a shortening capacitance is calculated by the partial volume method. The double resonator is represented by two single coaxial resonators...