On the evaluation of measurements of small changes in electric resistance

The measurement of small changes in resistance, caused in metal wires by non-equilibrium point defects, meets with many difficulties caused inter alia by changes in temperature, instability of the voltage source and irreversible changes in the electric resistance due to the thermal treatment of the samples. In the first part of the paper, dealing with the d-c bridge method of measurement, the conditions under which the relations given in the literature can be used for calculating small changes in resistance are quantitatively determined on the basis of a detailed analysis of such relations. The second part describes a method of measurement permitting the elimination of irreversible changes in the resistance of thermally treated samples and relations are derived for calculating reversible changes.     

Topology and numerical simulation of phase separation in sodium silicate glasses

Liquid/liquid phase separation in glasses may lead to heterogeneities in the nanometer scale. The droplet phase can be nucleated from a homogeneous liquid. The chemical composition of the nanoscale phase separation changes with temperature in contrast to the nanocrystallization. The understanding of topological changes in the glass networks is of importance for the changes in viscosity and the microscopic changes in the growth rate during the course of the phase separation process. This work considers a glass system in which one of the separated phases is much more rigid than the other and the formed new phase possesses a lower viscosity in comparison to the matrix phase. The chemical composition of the matrix changes only in a thin layer around the growing droplets. A shell with increased rigidity is formed which decelerates the growth by encapsulation.     

Separation of changes in light scattering and chromophore concentrations during cortical spreading depression in rats

We used near-infrared spectroscopy to separate tissue scattering changes from changes in cerebral oxyhemoglobin and deoxyhemoglobin and the redox state of cytochrome- c -oxidase. A separate term of the transport scattering coefficient (micro(s)(?)) was included in a modified Lambert-Beer equation. It is shown by diffusion equation analysis that there is a simple relationship between the differential path-length factor (D(a)) and its scattering equivalent (D(s)) . The method was applied to cortical spreading depression (CSD) data recorded through the skulls of rats. Biphasic changes in micro(s)(?)of +/-0.1mm(-1)were observed during CSD's that spread with a velocity of ~5mm/min . The method proposed has the promise to permit monitoring of scattering changes noninvasively in humans during cortical activation or pathophysiological conditions.     

WDM光网中虚拓扑重构的优化设计

采用优化方法来研究光网络业务发生改变时的虚拓扑重构问题,并提出了相应的混合整数线性规划算法.主要的思路是当业务发生改变时,寻找既能保证网络性能又对现有业务中断最小的虚拓扑.对影响虚拓扑重构的因素进行了研究,发现,如果使网络性能达到次优而不是最优可以大大减少对现有业务的中断.     

Morse势阱中线性和三阶非线性光折射率的改变

利用量子力学中的密度矩阵算符理论和迭代方法,导出莫尔斯（Morse）势阱中线性和三阶非线性光折射率改变的解析表达式,并以典型的GaAs／AlGaAs Morse势阱为例进行数值计算。数值结果表明,随着入射光强度增强,总的折射率改变将减少;随着势阱参数a的增大,总的折射率改变将减小;而随着载流子浓度的增加,总的折射率改变将增加。结果表明要获得较大的折射率改变,则需选取较小的入射光强度,较小的参数a,较大的载流子浓度,从而为实验研究提供理论依据。     

Laser heterodyne measurements of photo-induced refractive-index changes in amorphous As-S films

A differential-type heterodyne interferometer has been successfully utilized for studying the refractive-index changes in As-S films under illumination. The measuring system can detect phase changes down to 1° in angle in accuracy and sensitivity. It is confirmed that illumination of the films involves two distinct factors: a thermal and an optical one. The index changes are caused only by the optical effect. The time-dependent characteristics of the index changes are explained to be closely related to the photo-darkening effect.     

Dynamic ground compliance in multistorey buildings

A study is presented of the changes in the characteristics of the natural modes of vibration for multistorey structures which are founded on flexible foundations. First a standard eigenvalue problem is formulated for the proportionally damped case. Then general relationships of changes in natural frequencies and mode shapes are derived for the linear vibration theory. By means of an example problem it is demonstrated, however, that only the first mode obeys the predicted changes of frequencies and mode shapes over a wide range of foundation stiffness. The higher modes are shown to deviate substantially from the linear behaviour. This deviation is ascribed to geometric changes in mode shapes.     

北京城市公园冬季声景特征

北京地区冬季气候寒冷干燥,植被郁闭度降低,地球物理声增加,生物声减少。为探测北京冬季声景变化基本特征,根据地图“十字型”筛选10个城市公园,记录分析绿地内冬季声景的构成情况和昼夜变化规律。结果表明：城市公园冬季声景中人工声较多,生物声明显著少于其他季节,而且人工声昼间少于夜间,生物声昼间多于夜间;在公园人工声源分类中,机械电子声最多,其次是话语声,活动声最少;冬季人工声峰值普遍存在于清晨6:00–7:00时,在昼间的波动变化明显,于夜间趋于稳定,生物声峰值出现在上午8:00–9:00时,谷值出现在凌晨3:00时左右;人工声与公园面积、公园年龄和时刻变化未见显著相关性,生物声与公园面积呈显著负相关。实验发现城市公园冬季声景呈现出与其他季节声景的显著不同,生物的节律性变化导致冬季声景产生了较为显著的变化。     

Perturbation theory in terms of electron density

When an inhomogeneous electron gas is subjected to a perturbation, its energy and density both change by small amounts. We calculate the changes in the energy explicitly in terms of the density changes within the density-functional theory of many-electron systems. We also derive the equations for the induced densities, and using these show that a density correct up to order n in terms of the perturbation parameter is sufficient to give energy changes up to order (2n + 1). As a corollary, the even-order energy changes E⁽²ⁿ⁾ are variational with respect to the density changes ?⁽ⁿ⁾. The equations for the induced densities also follow from this corollary. The even-order corollary also gives a variational method of calculating the induced densities. The theory is demonstrated by applying it to calculate the polarizability and hyperpolarizability of the hydrogen, helium and neon atoms.     

Thermal diffusion of hydrogen in ferromagnetic materials

The thermal diffusion of hydrogen dissolved in a ferromagnetic material is investigated. It is shown that the coefficient of thermal diffusion changes when the material changes into the ferromagnetic state. The possibility of a change in the sign of the thermal diffusion flow when passing through the Curie point is discussed.     

The Acoustic Effects of Vowel Equalization Training in Singers

Vowel equalization is a technique that can be used by singers to achieve a more balanced vocal resonance, or chiaroscuro, by balancing corresponding front and back vowels, which share approximate tongue heights, and also high and low vowels by means of a more neutral or centralized lingual posture. The goal of this single group study was to quantify acoustic changes in vowels after a brief training session in vowel equalization. Fifteen young adults with amateur singing experience sang a passage and sustained isolated vowels both before and after a 15-minute training session in vowel equalization. The first two formants of the target vowels /e, i, ɑ, o, u/ were measured from microphone recordings. An analysis of variance was used to test for changes in formant values after the training session. These formant values mostly changed in a manner reflective of a more central tongue posture. For the sustained vowels, all formant changes suggested a more neutral tongue position after the training session. The vowels in the singing passage mostly changed in the expected direction, with exceptions possibly attributable to coarticulation. The changes in the vowel formants indicated that even a brief training session can result in significant changes in vowel acoustics. Further work to explore the perceptual consequences of vowel equalization is warranted.     

青藏高原东北部闪电M变化多参量观测

利用闪电光通道高速摄像、 地面电场变化和峰值辐射强度同步资料, 对比分析了负地闪连续电流阶段和人工触发闪电放电过程中M变化特征. 结果表明, 通道亮度资料能够辅助地面电场波形来准确判断是否为真实的M过程. 在经典M变化产生前及其过程中会产生很多快速电场变化MP(称为预M变化)变化, 大量MP促成了M变化. MP变化和K变化在脉冲特征上没有太多差别, 产生的物理机制是相似的. MP变化是连续电流阶段快速电场变化, 是击穿过程引起的电荷快速流动的结果, 并伴有通道突然增亮和高强度辐射. M变化脉冲波形多数为单极性, 有正有负, 少数呈现不规则变化, 持续时间在0.1 ms之内.而经典M变化的U 形结构只适用于近闪, 波形是静电场所致, 持续时间约0.2–0.8 ms. MP和K变化都是击穿所致, 只是MP变化有电荷流入原回击通道, 而K变化没有. 关键词： 青藏高原 M变化')" href="#">M变化 MP变化')" href="#">MP变化 K变化')" href="#">K变化     

利用酪氨酸残基的共振瑞利散射研究溶液中蛋白质构象

基于酪氨酸残基K带激发峰在较高浓度的蛋白质溶液中表现出特征散射峰,通过Δλ＝0同步荧光扫描识别,建立用荧光分光光度法测定酪氨残基K带的共振散射峰强度及其波长位移来推测溶液中蛋白质构象变化的新方法。方法不受蛋白质色氨酸残基的干扰,图谱简单明了直观。文章叙述了方法建立的实验基础,并用构建的方法研究了盐效应、酸碱性效应对蛋白质构象变化的影响,最后通过测定不同温度下酶活性的实验验证了方法对温度影响酶蛋白质构象变化的分析的正确性。     

Changes in isotopic composition of metals enriched in hydrogen

We have studied changes in the isotopic composition of niobium and palladium as well as of titanium film structures over ceramics enriched in deuterium. We have also investigated changes in the isotopic composition of copper under thermally activated copper diffusion into nickel. An intense isotope exchange between the atoms of the matrices and impurities enriched in deuterium and changes in the isotopic composition of copper during diffusion into nickel were observed. The relationships seen in the experiments lead us to suggest that the changes in the isotope ratio may be caused (along with plausible nuclear transformations) by a strong isotopic effect involved in cold diffusion induced by hydrogen migration. Institute of Strength Physics and Materials Science of the SB RAS. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 61–65, April, 1999.     

Sodium and proton diffusion MRI as biomarkers for early therapeutic response in subcutaneous tumors

The ability to quantitate early effects of tumor therapeutic response using noninvasive imaging would have a major impact in clinical oncology. One area of active research interest is the ability to use MR techniques to detect subtle changes in tumor cellular density. In this study, sodium and proton diffusion MRI were compared for their ability to detect early cellular changes in tumors treated with a cytotoxic chemotherapy. Subcutaneous 9L gliosarcomas were treated with a single dose of 1,3-bis(2-chloroethyl)-1-nitrosourea. Both sodium and diffusion imaging modalities were able to detect changes in tumor cellularity as early as 2 days after treatment, which continued to evolve as increased signal intensities reached a maximum approximately 8 days posttreatment. Early changes in tumor sodium and apparent diffusion coefficient values were predictive of subsequent tumor shrinkage, which occurred approximately 10 days later. Overall, therapeutical induced changes in sodium and diffusion values were found to have similar dynamic and spatial changes. These findings suggest that these imaging modalities detected similar early cellular changes after treatment. The results of this study support the continued clinical testing of diffusion MRI for evaluation of early tumor treatment response and demonstrate the complementary insights of sodium MRI for oncology applications.     

The effect of a longitudinal magnetic field on the plasma-dust structures in strata in a glow discharge

The plasma-dust structures in strata in a glow discharge exposed to a longitudinal magnetic field are studied in detail. In a weakly ordered structure, the angular velocity has a vertical gradient. A reversal of rotation of the structure in a magnetic field corresponding to the magnetization of electrons is found. With the help of the pair distribution function of particles, changes in the degree of order of the structure in the magnetic field are revealed. These changes correlate with changes in the angular velocity of rotation. To explain this effect, it is assumed that the dust structure is subjected to the action of ions in crossed electric and magnetic fields.     

GdFeCo/DyFeCo交换耦合两层薄膜磁化方向转变的研究

用磁控溅射法制备了GdFeCo/DyFeCo交换耦合两层薄膜，对交换耦合两层薄膜变温磁化方向进行了研究.结果表明读出层GdFeCo随温度上升从平面磁化转变成垂直磁化，转变过程中主要受饱和磁矩(M_s)的影响.在GdFeCo的补偿温度附近，读出层的磁化强度近于零，退磁场能减小，并在交换耦合的作用下，使读出层的磁化方向发生转变，制备的交换耦合两层薄膜具有中心孔磁超分辨效应. 关键词： 磁光记录 交换耦合两层薄膜 磁化     

Fluorescent eosin probe in investigations of structural changes in glycated proteins

The possibility of using the luminescent-kinetic probe method to investigate structural changes in bovine serum albumin (BSA) upon nonenzymatic thermal glycation is studied. An increase in the glycation time lead to a decrease in the intensity of the probe (eosin) fluorescence and to a long-wavelength shift of its maximum, as well as to an increase in the eosin phosphorescence intensity, which indicates that eosin binds to hydrophobic regions of protein at any times of incubation of BSA with glucose. From a decrease in the rate constant of the triplet-triplet energy transfer between the donor (eosin) and acceptor (anthracene) bound to proteins, it is found that the changes observed in the spectral characteristics of eosin are caused by structural changes in albumin globules as a result of glycosylation.     

Statistical fluctuations in hot rotating nuclei

Thermal fluctuations in angular momentum due to excitation is investigated. Shape changes or structural rearrangement are observed as a consequence of fluctuation in second moment of spin. The uncertainty in angular momentum is considerably enhanced due to thermal fluctuation and is strongly dependent on spin and structural changes.     

The effect of dexamethasone on tissue water distribution and proton relaxation in Panc02 tumors

The present experiments were conducted to determine the effects of dexamethasone mediated changes in tumor water distribution on proton relaxation times (T1, T2) in a murine pancreatic adenocarcinoma (Panc02). Spin lattice (T1) and spin-spin (T2) relaxation times were determined by ex vivo methods (10MHz) and by in vivo imaging techniques (6.25 MHz) at various intervals after single or multiple dexamethasone treatments. In complementary studies, dexamethasone mediated changes in tumor capillary permeability, tumor water distribution, relative tumor blood flow and tumor cell proliferation were also determined.

Proton spin lattice (T1) and spin-spin (T2 relaxation times for Panc02 tumors shortened within two hours of a single dexamethasone treatment. The time course and magnitude of this response was dexamethasone dose dependent. The time dependent changes in T1 and T2 after dexamethasone were similar at 10 MHz (ex vivo) and 6.25 MHz (in vivo imaging). Although dexamethasone produced little or no change in total tumor water content and tumor cell proliferation, transient changes in the physiologic distribution of tumor water were clearly demonstrated.

The data supports the idea that dexamethasone induced changes in the distribution of tumor water were mediated by changes in capillary permeability and tumor blood flow. These physiologic responses produced serial changes in tumor extracellular extravascular water content that were consistent with the observed changes in tumor T1 and T2. The results from these experiments might imply that therapy associated changes in tumor proton relaxation times may not only reflect changes in tissue water content, but may also reflect physiologic responses which alter the distribution of tissue water and solute.