Evaporation of the pancake-vortex lattice in weakly coupled layered superconductors

We calculate the melting line of the pancake-vortex system in a layered superconductor, interpolating between two-dimensional (2D) melting at high fields and the zero-field limit of single-stack evaporation. Long-range interactions between pancake vortices in different layers permit a mean-field approach, the "substrate model, " where each 2D crystal fluctuates in a substrate potential due to the vortices in other layers. We find the thermal stability limit of the 3D solid, and compare the free energy to a 2D liquid to determine the first-order melting transition and its jump in entropy.     

Periodic orbits in glycolytic oscillators: From elliptic orbits to relaxation oscillations

We consider the Sel’kov model of glycolytic oscillator for a quantitative study of the limit cycle oscillations in the system. We identify a region of parameter space where perturbation theory holds and use both Linstedt Poincaré technique and harmonic balance to obtain the shape and frequency of the limit cycle. The agreement with the numerically obtained result is excellent. We also find a different extreme, where the limit cycle is of the relaxation oscillator variety, has a large time period and it is seen that, as a particular parameter in the model is varied, the time period increases indefinitely. We characterize this divergence numerically. A calculational method is devised to capture the divergence approximately.     

Locking bandwidth and birefringence effects for polarized optical injection in vertical-cavity surface-emitting lasers

The aim of this paper is to investigate the effects of external optical injection taking account of polarization and electron spin properties in vertical-cavity surface-emitting lasers (VCSELs). Using external polarized injection we seek the locked phases and amplitudes of specific polarized fields in terms of injection level and frequency detuning, taking account of two kinds of distinguishable carrier density (spin-up and spin-down). For the conventional form of optical injection without taking account of spin-polarized fields there are three fundamental equations describing the carrier density, field amplitude and phase. However, by using the spin flip model (SFM), the combined effect of polarized fields along two perpendicular crystal axes and electron spin properties results in six equations. We analyse the conditions for stable locking and also the influence of birefringence effects on the stability map of detuning versus optical injection for both cases of injection polarized parallel and perpendicular to the lasing mode of the solitary VCSEL. For given values of pumping and spin relaxation rate there is a minimum birefringence rate for orthogonal injection. Above this value three regions of elliptical polarization are found in the stability map, namely “quasi-stability” (QS), “coupled limit cycle” (CLC) and “coupled chaos” (CC). The three regions of linear polarization, namely chaos, limit cycle and stability, are reduced in area compared to the case of parallel injection. For orthogonal injection it is found that increased birefringence or reduced spin relaxation rate causes the stable locking region to begin at higher injected power and frequency detuning.     

Global injected power statistics in a turbulent system: degrees of freedom and aspect ratio effect

The properties of the global energy injection rate of a closed turbulent flow produced between two counter-rotating disks are studied. The statistics of this global quantity are measured when the aspect ratio (defined as the ratio of the disk diameter to the separating distance between both disks) is modified. It is shown that the non-Gaussian statistics obtained at a low aspect ratio becomes Gaussian for a large aspect ratio. This effect is accompanied with a large decrease of the fluctuation rate. These results indicate the total energy injection rate to obey the central limit theorem. It is also shown that the number of degrees of freedom of total injection rate may be related to the number of independent large scale structures present in the flow.     

Skeletal muscle metabolism in Duchenne muscular dystrophy (DMD): an in-vitro proton NMR spectroscopy study

The metabolic differences in the skeletal muscle of patients with Duchenne muscular dystrophy (DMD) and normal subjects (controls) were investigated using in-vitro high-resolution proton NMR spectroscopy. In all, 56 metabolites were unambiguously identified in the perchloric acid extract of muscle tissue using one- and two-dimensional NMR. The concentrations of glycolytic substrate glucose (Glc; p < 0.05), gluconeogenic amino acids such as glutamine (Gln; p < 0.05) and alanine (Ala; p < 0.05) and the glycolytic product lactate (Lac; p < 0.05) were statistically significantly lower in DMD patients as compared to controls. A significant reduction in the concentrations of total creatine (TCr; p < 0.05), glycerophosphoryl choline + phosphoryl choline + carnitine (GPC/PC/Car; p < 0.05), choline (Cho; p < 0.05) and acetate (Ace; p < 0.05) was also observed in these patients. Decrease in the level of glucose may be attributed to the reduction in the concentrations of gluconeogenic substrates or membrane abnormalities in degenerated muscle of DMD patients. Lower levels of choline containing compounds indicate membrane abnormalities. Decrease in the concentration of lactate in the muscle of DMD patients may be due to the reduction in anaerobic glycolytic activity or lower substrate concentration. The decrease in the concentration of acetate may reflect reduced transport of fatty acids into mitochondria due to decreased concentration of carnitine in DMD patients. Kreb's cycle intermediate alpha-ketoglutarate was observed only in the diseased muscle, which is suggestive of predominant oxidative metabolism for energy generation.     

Impact of substrate injected hot electrons on hot carrier degradation in a 180-nm NMOSFET

Although hot carriers induced degradation of NMOSFETs has been studied for decades, the role of hot electron in this process is still debated. In this paper, the additional substrate hot electrons have been intentionally injected into the oxide layer to analyze tile role of hot electron in hot carrier degradation. The enhanced degradation and the decreased time exponent appear with the injected hot electrons increasing, the degradation increases from 21.80% to 62.00% and the time exponent decreases from 0.59 to 0.27 with Vb decreasing from 0 V to -4 V, at the same time, the recovery also becomes remarkable and which strongly depends on the post stress gate bias Vg. Based on the experimental results, more unrecovered interface traps are created by the additional injected hot electron from the breaking Si-H bond, but the oxide trapped negative charges do not increase after a rapid recovery.     

Effect of epitaxial crystallization on packet-like space charge characteristics in low-density polyethylene under multi-field coupling conditions

In order to study the effect of epitaxial crystallization on charge transport in low-density polyethylene (LDPE) under multi-field coupling conditions, three typical epitaxial crystallizations, namely disorder (glass substrate), crossover (isotactic polypropylene substrate), and parallel (polytetrafluoroethylene substrate), were prepared and denoted as LD-G, LD-iPP, and LD-PT, respectively. Packet-like space charge through samples was analyzed by the pulsed electro-acoustic (PEA) method. It is shown that different microscopic surface morphologies appeared in the LDPE samples with different epitaxial crystallizations, which, however, do not change the crystalline structure of the bulk. Packet-like space charge phenomena were observed and the distortion field increased with the temperature which could be attributed to the larger amount of charge injection in a shorter period. The differences of the amount and injection rate of the space charge were explained and verified considering the typical chain alignment of epitaxial crystallization, which, in our opinions, contributes to the pass over of positive charge in LD-iPP samples.     

Mechanical performance of metal-ceramic interfaces produced by laser processing

This paper concentrates on the mechanical performance of various ceramic coatings of Cr₂O₃ on steel (SAF2205), as produced by CO₂ laser processing. The thickness of the coating that can be applied by laser coating is limited to about 200 m setting a limit to the maximum strain energy release rate that can be measured in a 4 point flexure test before severe yielding occurs. In addition, a network of cracks with spacings of the order of 200 m was always present in the laser applied coating preventing steady state crack growth along the interface.It is concluded that a firmly bonded coating of Cr₂O₃ on steel could be produced by high power laser processing. The actual interface strength of a (Fe, Cr)-spinel applied to stainless steel by laser coating depends strongly on the composition of the substrate and coating materials. The energy release rate was extremely high and delamination occurred by fracture through the coating and partially along the interface, indicating that the interface strength is similar to or higher than the fracture strength of (Fe, Cr)-spinel.     

Local production rate of an “enzyme kinetics” based on coupled random walks

Based on the coupled random walk process, a local production rate of an enzyme kinetics is studied. A substrate as a walker is specified by a set of the jumping probabilities between the sites and between the modes. The modes represent the states of the substrate before, in and after the reaction. The local production rate is explicitly given and its position dependence is studied in terms of jumping probabilities. Qualitatively, the deviations from the Michaelis-Menten's expression are discussed.     

Vibrationally resolved fluorescence from organic molecules near metal surfaces in a scanning tunneling microscope

Intrinsic molecular fluorescence from porphyrin molecules on Au(100) has been realized by using a nanoscale multimonolayer decoupling approach with nanoprobe excitation in the tunneling regime. The molecular origin of luminescence is established by the observed well-defined vibrationally resolved fluorescence spectra. The molecules fluoresce at low "turn-on" voltages for both bias polarities, suggesting an excitation mechanism via hot electron injection from either tip or substrate. The excited molecules decay radiatively through Franck-Condon pi(*)-pi transitions.     

在线流动注射N1923萃淋树脂预富集火焰原子吸收法测定痕量金

研究了富集酸度、进样体积、洗脱流速、富集时间、洗脱液的浓度和酸度、共存离子的影响 ,建立了N1 92 3萃淋树脂富集在线流动注射火焰原子吸收法测定痕量金的新方法。富集倍率为 32倍 ,检测限为 1 μg·L- 1 。用于电镀金废液的在线测定 ,方法灵敏度高、操纵简便、结果较好。     

Physical understanding of complex multiscale biochemical models via algorithmic simplification: Glycolysis in Saccharomyces cerevisiae

Large-scale models of cellular reaction networks are usually highly complex and characterized by a wide spectrum of time scales, making a direct interpretation and understanding of the relevant mechanisms almost impossible. We address this issue by demonstrating the benefits provided by model reduction techniques. We employ the Computational Singular Perturbation (CSP) algorithm to analyze the glycolytic pathway of intact yeast cells in the oscillatory regime. As a primary object of research for many decades, glycolytic oscillations represent a paradigmatic candidate for studying biochemical function and mechanisms. Using a previously published full-scale model of glycolysis, we show that, due to fast dissipative time scales, the solution is asymptotically attracted on a low dimensional manifold. Without any further input from the investigator, CSP clarifies several long-standing questions in the analysis of glycolytic oscillations, such as the origin of the oscillations in the upper part of glycolysis, the importance of energy and redox status, as well as the fact that neither the oscillations nor cell-cell synchronization can be understood in terms of glycolysis as a simple linear chain of sequentially coupled reactions.     

The energy injection into a fluid by stochastic volume forces and random stirring forces

The wavenumber spectrum of the stationary energy injection rate into an incompressible fluid described by the Navier-Stokes equations is evaluated for some simple realizations of stochastic volume as well as stirring forces. A general relation between energy injection, fluid's response, and force correlations is derived which was previously shown to be particularly simple for Gaussian distributed forces with white noise frequency spectrum. For two kinds of such model volume forces the energy injection rates are calculated: Fluid volume elements of variable size around randomly chosen positions are forced in one model centralsymmetrically in the other one anti-symmetrically under inversion with various force density profiles. The circumstances under which both models display an energy injection rate k ^–1 into a bandd k around the wavenumberk are discussed. As a simple realization of stochastic stirring forces externally moved hard spheres immersed in the fluid are considered. The equation of motion and energy balance for the velocity field of the combined system is discussed. The spectral distribution of energy injection by stirring is shown to be that of a volume force model.     

Had We But World Enough,and Time... But We Don’t!: Justifying the Thermodynamic and Infinite-Time Limits in Statistical Mechanics

In this paper, I compare the use of the thermodynamic limit in the theory of phase transitions with the infinite-time limit in the explanation of equilibrium statistical mechanics. In the case of phase transitions, I will argue that the thermodynamic limit can be justified pragmatically since the limit behavior (i) also arises before we get to the limit and (ii) for values of N that are physically significant. However, I will contend that the justification of the infinite-time limit is less straightforward. In fact, I will point out that even in cases where one can recover the limit behavior for finite t, i.e. before we get to the limit, one cannot recover this behavior for realistic time scales. I will claim that this leads us to reconsider the role that the rate of convergence plays in the justification of infinite limits and calls for a revision of the so-called Butterfield’s principle.     

Dependence of limited radiative recombination rate of InGaN-based light-emitting diode on lattice temperature with high injection

It is observed that the radiative recombination rate in InGaN-based light-emitting diode decreases with lattice temperature increasing.The effect of lattice temperature on the radiative recombination rate tends to be stable at high injection.Thus,there should be an upper limit for the radiative recombination rate in the quantum well with the carrier concentration increasing,even under the same lattice temperature.A modified and easily used ABC-model is proposed.It describes that the slope of the radiative recombination rate gradually decreases to zero,and further reaches a negative value in a small range of lattice temperature increasing.These provide a new insight into understanding the dependence of the radiative recombination rate on lattice temperature and carrier concentration in InGaN-based light-emitting diode.     

强电磁干扰对达林顿管的损伤效应与机理

建立了PNP型达林顿管的二维电热模型,对处于有源放大区的达林顿管的集电极注入高功率微波(HPM)和强电磁脉冲(EMP)时的瞬态响应进行了仿真。结果表明:HPM注入下,器件内部的峰值温度呈周期性的“下降-上升”,温度升高过程发生在信号的正半周,靠近达林顿管发射极的晶体管发射结边缘是最易毁伤处;EMP注入下,其损伤机理与HPM注入时的正半周时相似,器件内部峰值温度一直上升,易毁伤部位与HPM注入时相同。得到了损伤功率阈值和损伤能量阈值与损伤脉宽的关系,这两种干扰注入下的损伤能量阈值-脉宽关系和损伤功率阈值-脉宽关系公式相似,并且在相同脉宽下,HPM注入下的损伤能量阈值大于EMP注入下的损伤能量阈值。     

Spray method: Dependence of deposition efficiency on substrate temperature

Application of the spray method for the deposition of thin films has shown that the deposition efficiency is a decreasing function of the substrate temperature. The forces which determine the path and the time the droplets take to go from the nozzle to the substrate are analyzed. A theoretical curve of the deposition efficiency as a function of the substrate temperature has been obtained by a successive-approximation method. Experimental values of the efficiency obtained from the growth rate of the films are always a function of the substrate temperature. The good agreement of the theoretical curve with the experimental data confirms the validity of the method applied for our analysis.Work supported by Ministero della Universitá e della Ricerca Scientifica and Centro Regionale Ricerche Nucleari e Struttura della Materia     

核黄素与NADH在紫光波段的激光诱导荧光光谱研究

基于细胞代谢荧光体的激光诱导荧光探测,在生物反应过程监测与生物活性物质探测中具有广泛的应用.本文利用波长可调谐激光光源,结合液体射流进样装置,研究了核黄素与NADH等生物荧光体在紫光波段(389nm～404nm)激发的荧光光谱,并考察了激光强度、样品浓度等参数对荧光光谱特性的影响.实验观察到核黄素的激发光谱在402.5nm处出现“波谷”,具有特征性,选择403.5nm激光激发,核黄素的浓度灵敏度约为NADH的八百分之一.这些结果为发展生物荧光探测与识别技术提供了新的基础数据.     

Models of chemical reaction systems with exactly evaluable limit cycle oscillations

Models of open chemical reaction systems with two variablesx, y and with elliptic limit cycles in concentration space are investigated. Thereby isothermal and homogeneous conditions and the validity of mass-action kinetics are assumed. Though we restrict ourselves to quadratic rate equations a lot of systems with this behaviour is found; all based on the trimolecular reactionA + 2X 3X. Both globally stable and only locally stable limit cycles are possible. The time dependence of the variables on the cycle is exactly evaluated for all these systems. Bifurcations of the limit cycle are described analytically.D 82 (Diss. TH Aachen)     

核黄素与NADH在紫光波段的激光诱导荧光光谱研究

基于细胞代谢荧光体的激光诱导荧光探测,在生物反应过程监测与生物活性物质探测中具有广泛的应用.本文利用波长可调谐激光光源,结合液体射流进样装置,研究了核黄素与NADH等生物荧光体在紫光波段(389 nm～404 nm)激发的荧光光谱,并考察了激光强度、样品浓度等参数对荧光光谱特性的影响.实验观察到核黄素的激发光谱在402.5 nm处出现"波谷",具有特征性,选择403.5 nm激光激发,核黄素的浓度灵敏度约为NADH的八百分之一.这些结果为发展生物荧光探测与识别技术提供了新的基础数据.