Occurrence of a distortive transition at a temperature higher than the magnetic one: Case of CeAg

In order to explain the recently observed distortive transition in CeAg which occurs at a higher temperature than the magnetic one, a symmetry- adapted spin-Hamiltonian involving dipolar and quadrupolar interactions is given. The two successive phase transitions observed at low temperature in compounds like CeAg are reproduced in the molecular field approximation.     

On the nature of exponential decrease of boson peak intensity tail, at increasing frequency higher than the peak position

In the present Letter, an exponential decrease of a boson peak intensity tail, at increasing frequency higher than the peak position, is predicted in the soft-mode model of low-energy glass dynamics for a series of glasses which exhibit a high-frequency sound above the peak. A similar theoretical interpretation is suggested for recent experimental data which show for some glasses a resembling behavior of the peak intensity tail.     

Toward a Logic of the Organism: A Process Philosophical Consideration

Mathematical models applied in contemporary theoretical and systems biology are based on some implicit ontological assumptions about the nature of organisms. This article aims to show that real organisms reveal a logic of internal causality transcending the tacit logic of biological modeling. Systems biology has focused on models consisting of static systems of differential equations operating with fixed control parameters that are measured or fitted to experimental data. However, the structure of real organisms is a highly dynamic process, the internal causality of which can only be captured by continuously changing systems of equations. In addition, in real physiological settings kinetic parameters can vary by orders of magnitude, i.e., organisms vary the value of internal quantities that in models are represented by fixed control parameters. Both the plasticity of organisms and the state dependence of kinetic parameters adds indeterminacy to the picture and asks for a new statistical perspective. This requirement could be met by the arising Biological Statistical Mechanics project, which promises to do more justice to the nature of real organisms than contemporary modeling. This article concludes that Biological Statistical Mechanics allows for a wider range of organismic ontologies than does the tacitly followed ontology of contemporary theoretical and systems biology, which are implicitly and explicitly based on systems theory.     

Entropy calculated from the frequency of states of individual particles

Entropy is related to the frequency of states for individual particles. Taking the Ising lattice as an example, a local state for an individual spin is defined by the orientation of the spin and of its neighbors. The ratio of the frequencies of two local states involved in a spin-flipping conflgurational transition is related to an entropy change. Implementation is by computer simulation. A stochastic process is used to construct an initial lattice configuration, corresponding to state of known entropy. This configuration is subsequently relaxed to a desired equilibrium state, with the help of a (uniform Metropolis) Monte Carlo spin flipping and the attendant entropy change is calculated from the sequence of frequency ratios for all transitions. The calculation is approximate since it treats a process that can be described by a hypothetical sequence of states at internal equilibrium, which cannot be true for a relaxation at finite rate. Nonetheless, the results obtained have been quite accurate. The theory, therefore, provides an additional method for measuring the entropy of systems simulated with the help of a computer. It also indicates a practical way for bridging the Boltzmann entropy of individual particle states (which Jaynes has shown to be incorrect, in its original form, for strongly interacting particles), to the Gibbs entropy ofN-particle configurations.     

显微光谱研究半绝缘GaAs带边以上E0+Δ0光学性质

通过显微光致发光技术和显微拉曼(Raman)技术研究了半绝缘GaAs (SI-GaAs)晶体的带边附近的发光. 在光荧光谱中，观察到在高于GaAs带边0.348eV处有一个新的荧光峰. 结合Raman谱指认此发光峰来源于GaAs的E₀＋Δ₀能级的非平衡荧光发射. 同时, 通过研究E₀＋Δ₀能级的偏振、激发光强度依赖关系，以及温度依赖关系说明E₀＋Δ₀能级与带边E₀共享了共同的导带位置Γ₆，同时这也说明在GaAs中主要是导带的性质决定了材料的光学行为.同时，通过与n-GaAs和δ掺杂GaAs相比较，半绝缘GaAs晶体的E₀＋Δ₀能级的发光峰更能反映GaAs电子能级高临界点E₀＋Δ₀的能量位置和物理性质. 研究结果说明显微光致发光技术是研究半导体材料带边以上能级光学性质的一种非常有力的研究工具. 关键词： 半绝缘GaAs 显微光致发光 自旋轨道分裂     

Vocal aging and the impact on daily life: a longitudinal study

Longitudinal studies on vocal aging are scarce, and information on the impact of age-related voice changes on daily life is lacking. This longitudinal study reports on age-related voice changes and the impact on daily life over a time period of 5 years on 11 healthy male speakers, age ranging from 50 to 81 years. All males completed a questionnaire on vocal performance in daily life, and perceptual and acoustical analyses of vocal quality and analyses of maximum performance tasks of vocal function (voice range profile) were performed. Results showed a significant deterioration of the acoustic voice signal as well as increased ratings on vocal roughness judged by experts after the time period of 5 years. An increase of self-reported voice instability and the tendency to avoid social parties supported these findings. Smoking males had a lower speaking fundamental frequency compared with nonsmoking males, and this seemed reversible for males who stop smoking. This study suggests a normal gradual vocal aging process with clear consequences in daily life, which should be taken into consideration in clinical practice as well as in studies concerning communication in social life.     

The individual success of musicians, like that of physicists, follows a stretched exponential distribution by J.A. Davies

Comment on Eur. Phys. J. B 27, 445 (2002) We analyze the distribution of success of musicians, comparing a stretched exponential (found by J.A. Davies [Eur. Phys. J. B 27, 445 (2002)]) with a distribution of the family of the q-exponential (presenting an intermediate power-law regime with a crossover to an exponential tail). We find that both assumptions yield comparable results, within the available range of data, hence a definite conclusion cannot yet be taken. But this example joins many others that has been found to be fairly described by q-exponentials (or variations of it), which may be indicative that there is a (significantly large) class of systems described by nonextensive statistical mechanics, from where q-exponentials naturally appear. Received 17 October 2002 Published online 31 December 2002     

Study of in fiber Mach–Zehnder interferometer based on two spaced 3-dB long period gratings surrounded by a refractive index higher than that of silica

The paper deals with the response of a Mach–Zehnder interferometer composed by two 3-dB long period gratings (LPG) with different external refractive indices higher than that of silica (leaky configuration). A rough analysis of the cladding propagation arising in leaky configuration has allowed us to establish a model that is sufficient to describe the interferometer couplings evolution at the resonance. In particular, we have shown that the interferometer sensitivity depends strongly on its phase-shift Δ and is optimized for Δ equal to π [2π] or 3π/4 [2π]. An experimental study was undertaken and allowed us to validate our model. Finally, a comparison with a single LPG demonstrated an increased sensitivity to the external index, suggesting the conception of a new fiber sensor operating with external refractive indices higher than that of silica.     

Detection of sulphur dioxide at,and below,the part per billion level using a tunable diode laser

A laser absorption spectrometer is described which employs a wavelength tunable diode laser in conjunction with a multipass White cell. The instrument uses absorption lines in the ₃ band of SO₂ to monitor atmospheric SO₂ concentrations with sensitivities as high as 0.2 parts per billion (ppb) in a laboratory system. A portable instrument with a fast response time and a sensitivity of 1 ppb is described, and the development of a highly practical field instrument, based on pyroelectric detectors, is discussed.Work supported by the Department of National Health and Welfare, Environment Canada, Ontario Ministry of the Environment, and Atmospheric Service, Environment Canada.     

Thermosonication as an alternative method for processing,extending the shelf life,and conserving the quality of pulque: A non-dairy Mexican fermented beverage

The aim of this study was to evaluate thermosonication as an alternative method for the pasteurization of pulque in order to improve its shelf life and retain its quality parameters.Thermosonication was carried out at 50 °C using amplitudes of 75% (for 6 and for 9 min), 85% (for 4 and for 6 min), and 95% (for 3 and for 5 min). These were the optimal conditions found for processing pulque by thermosonication. Physicochemical (acidity, color, alcohol content, and sensory analysis) and microbiological (lactic acid bacteria and yeasts) parameters were determined during 30 days for storage at 4 ± 1 °C. Conventional pasteurization (63 °C, 30 min) and raw pulque were used as controls. According to the results, the shelf life of pulque was extended up to 24 days storage at 4 °C. After this time, the quality of beverage decreased, due that the microbial load increases. Thermosonication treatments at 75% and 85% showed a higher content of LAB (6.58–6.77 log CFU/mL) and yeasts (7.08–7.27 log CFU/mL) than conventional pasteurization (3.64 log CFU/mL of LAB and 3.97 log CFU/mL of yeasts) at 24 days of storage. Raw pulque demonstrated up to 7.77 log CFU/mL of yeasts and 7.51 log CFU/mL of LAB. Pulque processed by thermosonication exhibited greater lightness, sensory acceptance, a maximal acidity of 0.83 g/lactic acid, and an alcohol content of 4.48–4.95% v/v. The thermosonication process preserves sensory and physicochemical properties better than conventional pasteurization. Lactic acid bacteria such as Lactobacillus kefiri, Lactobacillus acidophilus, and Lactobacillus hilgardii and yeasts such as Saccharomyces cereviasiae were identified in thermosonicated pulque.     

天体运动中介质的阻力和推力与超光速运动的粒子

行星在太阳风中运动受太阳介质阻力和推力的作用。阻力使行星公转速率逐渐变小。推力使行星逐渐远离太阳并使行星的温度在长期内逐渐降低。推力是太阳系、银河系和宇宙膨胀的原因。除非粒子和介质发生碰撞,否则粒子的运动不受介质的阻碍可以超光速运动。证明宇宙射线中的粒子是超光速运动的粒子。     

Design of a higher harmonic cavity for the SSRF storage ring

Higher harmonic cavity used in the third generation synchrotron light source increases the Touschek lifetime.The higher harmonic cavity of Shanghai Synchrotron Radiation Facility(SSRF)is a 1.5 GHz passive superconducting cavity.Its higher order modes(HOM)are extracted by a ferrite HOM damper out of the cryostat.Multi-cell cavity is chosen concerning the voltage.The harmonic cavity dynamics,beam dynamics with passive harmonic cavity and the design of single cell cavity are included in this paper.     

Testing the accuracy of a Bayesian central-dose model for single-grain OSL,using known-age samples

While reviews of comparisons between multi-grain OSL ages and independent chronological information are available in the literature, there is hardly any such performance test for single-grain OSL ages. And yet, this is all the more needed as the interpretation of single-grain dose distributions remains a difficult task, given the typically considerable dispersion in equivalent dose values measured by OSL – and the numerous sources of such dispersion in measurements. Here, we present the study of 19 samples for which independent age control is available, and whose ages range from 2 to 46 ka. Based on multi-grain OSL age estimates, these samples are presumed to have been both well-bleached at burial, and unaffected by mixing after deposition. Two ways of estimating single-grain ages are then compared: the standard approach on the one hand, consisting of applying the Central Age Model to D_e values determined with the Analyst software; on the other hand, the central dose model recently proposed by Combès et al. (Combès, B., Philippe, A., Lanos, P., Mercier, N., Tribolo, C., Guerin, G., Guibert, P., Lahaye, C., in press. Quaternary Geochronology). The median of the relative discrepancy between single-grain OSL and reference ages is about twice as large for the standard approach (12%) as with the Bayesian model (7%). Statistical tests show that, based on our (limited) dataset, the difference between the two models seems to be significant for samples in the age range 4–46 ka. Finally, the influence of various factors on the (in-)accuracy of single grain OSL ages is discussed; it appears that the accuracy of ages estimated in a standard way decreases when age is increased, while the Bayesian model seems more robust. This study also shows that (i) there is no 20% limit on the CAM overdispersion parameter for well-bleached samples; (ii) dose recovery experiments do not seem to be a very reliable tool to estimate the accuracy of a SAR measurement protocol for age determination.     

Type of lattice strain alteration,the reducing agent of activation energy of titania loading on the silica matrix than that of pure titania

Nanosized titania and silica-supported titania (SST) were prepared by the sol–gel method using titanium tetrachloride as a titania precursor. An opposite behavior was observed in the lattice strain of titania and SST before and after transition onset point (TOP). The effect of the changes of the lattice strain on the size of nanocrystallites, the TOP, and activation energy of phase transformation from anatase to rutile is investigated. It is shown that under identical synthesis conditions, the average size of nanocrystallites in SST was less than that of pure titania. Moreover, TOP of titania was lower in pure titania sample than that of SST due to the tensile strain of pure titania vs. the compressive strain of SST at low calcination temperature. However, the activation energy of pure titania due to the compressive strain and the exponential leap of the tensile strain of SST, after TOP, was higher than that of SST.     

有源抗噪声护耳器H2/H∞优化方法研究

研究了一种基于人因参数几何模型的声学通路辨识策略, 可用于有源降噪技术中的通路辨识环节, 以降低因人体姿态改变而导致的降噪性能退化。该策略利用深度相机输出的点云数据提取人因参数并构建几何模型, 通过仿真和人工神经网络预测声学通路的传递函数矩阵。结果表明, 人因参数几何模型的降噪性能与点云模型接近, 适用于参数化扫描仿真。进一步通过实验验证了仿真的准确性以及所提策略的可行性。实验结果还表明, 人体姿态改变会导致声学通路传递函数发生复杂且显著的变化, 说明实际应用应考虑人体姿态改变所带来的影响。