Neural Wave Representation in Early Vision

The neural wave representation which describes spatiotemporal information in early vision is proposed in terms of extended Gabor functions in this paper. Its reasonability, completeness and uncertainty in spatiotemporal domains and their frequency domains were investigated. The ranges of these parameters in this representation were estimated on electrophysiological and psychophysical data. We derived the partial differential equations which the neural wave satisfied. The general significance of 3D neural wave representation has been explored.     

Ab initio melting curve of copper by the phase coexistence approach

Ab initio calculations of the melting properties of copper in the pressure range 0-100 GPa are reported. The ab initio total energies and ionic forces of systems representing solid and liquid copper are calculated using the projector augmented wave implementation of density functional theory with the generalized gradient approximation for exchange-correlation energy. An initial approximation to the melting curve is obtained using an empirical reference system based on the embedded-atom model, points on the curve being determined by simulations in which solid and liquid coexist. The approximate melting curve so obtained is corrected using calculated free energy differences between the reference and ab initio system. It is shown that for system-size errors to be rendered negligible in this scheme, careful tuning of the reference system to reproduce ab initio energies is essential. The final melting curve is in satisfactory agreement with extrapolated experimental data available up to 20 GPa, and supports the validity of previous calculations of the melting curve up to 100 GPa.     

Extended equation for the coexistence curve of molecular liquids in the vicinity of a critical point

An extended equation of state for substances along a phase interface, based on the Van der Waals model of a gas with fluctuations of the order parameter is confirmed by experimental data along the coexistence curve of a wide class of homogeneous and inhomogeneous molecular liquids under the Earth’s field of gravity. It is shown that the parameters of the extended equation for the coexistence curve of homogeneous and spatially inhomogeneous molecular liquids are linear functions of the compressibility factor. This allows us to predict the parameters of the equations of state of molecular liquids that are difficult to investigate experimentally.     

COMPUTER SIMULATIONS OF FIGURE-GROUND DISCRIMINATION IN THE VISUAL SYSTEM OF THE FLY

Figure-ground discrimination and pattern discrimination represent one of the most important problems in computer vision. Based on computational neuronal network model proposed by Reichardt et al. for figure-ground discrimination in the visual system of the fly, entire systematic computer simulations were carried out under nonstationary conditions. Results show that the model network and simulations have predictive power for behavioural experimental results. This paper proposes that motion perception and elementary pattern discrimination in human visual system may be mediated by some kind of figure-ground system with movement detectors as input layer.     

Tunable Photoluminescence of CdTe Nanocrystals over Wide Spectral Range via Microwave-assisted Surface Modiˉcation

An easy and fast microwave-assisted method of tuning the photoluminescence properties of CdTe nanocrystals in aqueous phase is presented. The photoluminescence could be tuned covering almost the whole visual spectral range (537-680 nm), and even partially extending to the near-infrared spectral range. The e?ect is probably related to the formation of core/shell structure and complex nano-assemblies. These results provide a promising means of tuning the photoluminescence of CdTe nanocrystals, leading to potential applications in biomedical labeling, solar cells, lasers, and other ˉelds.     

Cloud-Point Curve for the System Copoly(Ethylene-Vinyl Acetate) Plus Methyl Acetate. Measurement and Prediction by Continuous Thermodynamics

The cloud-point curve for the system copoly(ethylene-vinyl acetate) plus methyl acetate has been measured by a simple visual method. The critical point was determined by using the phase volume ratio method. The method of continuous thermodynamics was applied for thermodynamic treatment. The composition of the copolymer is described by a divariate distribution function assumed as a generalized Stockmayer distribution. The activity coefficients were obtained with the aid of the Huggins Chi -parameter concept assuming Chi to be a quadratic polynomial with respect to the weight-average chemical composition of the copolymer. The three model parameters were calculated from the critical point and the slope of the cloud-point curve at the critical point. The cloud-point curve and the shadow curve were predicted from these parameters. The cloud-point curve shows qualitative agreement with experimental data.     

The Wolf method applied to the liquid-vapor interface of water

The Wolf method for the calculation of electrostatic interactions is applied in a liquid phase and at the liquid-vapor interface of water and its results are compared with those from the Ewald sums method. Molecular dynamics simulations are performed to calculate the radial distribution functions at room temperature. The interface simulations are used to obtain the coexisting densities and surface tension along the coexistence curve. The water model is a flexible version of the extended simple point charge model. The Wolf method gives good structural results, fair coexistence densities, and poor surface tensions as compared with those obtained using the Ewald sums method.     

Tuning the Cellular Uptake and Retention of Rhodamine Dyes by Molecular Engineering for High-Contrast Imaging of Cancer Cells

Probes allowing high-contrast discrimination of cancer cells and effective retention are powerful tools for the early diagnosis and treatment of cancer. However, conventional small-molecule probes often show limited performance in both aspects. Herein, we report an ingenious molecular engineering strategy for tuning the cellular uptake and retention of rhodamine dyes. Introduction of polar aminoethyl leads to the increased brightness and reduced cellular uptake of dyes, and this change can be reversed by amino acetylation. Moreover, these modifications allow cancer cells to take up more dyes than normal cells (16-fold) through active transport. Specifically, we further improve the signal contrast (56-fold) between cancer and normal cells by constructing activatable probes and confirm that the released fluorophore can remain in cancer cells with extended time, enabling long-term and specific tumor imaging.     

角度重叠模型的应用 Ⅰ.计算过渡金属配合物电子光谱的微机程序

按照角度重叠模型,用FORTRAN语言编写了计算过渡金属配合物电子光谱的微机程序。     

熔融CaF2的径向分布函数

熔融CaF_2是一种典型的离子液体,又是一种重要的冶金熔体.径向分布函数不仅是描述熔体结构的重要物理量,而且是计算熔体热力学性质的基础.实验上可以通过X 射线、中子衍射测得结构因子经Fourier 变换得到径向分布函数.已有使用X 射线衍射方法实验测定熔融CaF_2结构因子的报导.但由于实验上分解三种离子对Ca~(2+)-Ca~(2+),Ca~(2+)-F~-、F~--F~-偏结构因子的困难,未能给出相应的三种径向分布函数g++(r)、g+-(r)、g--(r),仅估计出三种径     

耗散粒子动力学研究双层膜线张力与抗弯刚度的关系

利用耗散力粒子动力学模拟方法研究了拉伸状态下双层膜的抗弯刚度与膜孔线张力之间的关系.通过对双层膜在不同投影面积约束下的系统模拟,观察到3个区域:自由振动膜、伸展膜和穿孔膜.由前两个区域的应力张量计算得到的膜的面张力(σΣ)与拟合膜波动性质得到的面张力(σfluc)吻合的很好,除去在两区域的转变点附近σfluc略大于σΣ.当考虑在经典Helfrich弹性膜模型中被忽略的膜厚度时,线张力可以和抗弯刚度用一个简单的模型联系起来.通过对穿孔膜区域的数据进行分析,证明由本模型得到的抗弯刚度与拟合膜波动性质得到的抗弯刚度符合的很好.由此提出一种简便的测量方法,通过计算拉伸膜孔的面张力和统计膜厚度,拟合这个简单模型来测量膜的抗弯刚度.     

GPC-[η]测定聚碳酸酯的长支链

本文的目的在于,在没有相同化学组成的线型待测聚合物试样的情况下,以普适标定线为基础,得到试样的 log[η]～logM 曲线,或从实验直接得到log[η]～V_e曲线,由此计算出G和G_v。 实验说明,支化对M[η]有影响,经修正之后,由GPC-[η]数据计算的?和[η]_b更接近光散射法和经典法测得的和[η]_b值。     

Extended range Zeeman atomic absorption spectrometry based on a 3-field a.c. magnet

The dynamic range of a.c. Zeeman atomic absorption (ZAA) analytical curves can be extended 10 times when intensity measurements are performed at three different field strengths, i.e. zero, maximum and intermediate field strength during each modulation cycle of the magnet, rather than at zero and maximum field strength only.The conventional ZAA analytical curve and the extended range curve are obtained simultaneously from one series of standards.The power supply of the magnet is described. In the extended range system the background correction frequency is 50 Hz, whereas the system operates at 100 Hz in the conventional ZAA mode.     

Surface Polarization Matters: Enhancing the Hydrogen‐Evolution Reaction by Shrinking Pt Shells in Pt–Pd–Graphene Stack Structures

Surface charge state plays an important role in tuning the catalytic performance of nanocrystals in various reactions. Herein, we report a synthetic approach to unique Pt–Pd–graphene stack structures with controllable Pt shell thickness. These unique hybrid structures allow us to correlate the Pt thickness with performance in the hydrogen‐evolution reaction (HER). The HER activity increases with a decrease in the Pt thickness, which is well explained by surface polarization mechanism as suggested by first‐principles simulations. In this hybrid system, the difference in work functions of Pt and Pd results in surface polarization on the Pt surface, tuning its charge state for hydrogen reduction. Meanwhile, the supporting graphene provides two‐dimensional channels for efficient charge transport, improving the HER activities. This work opens up possibilities of reducing Pt usage while achieving high HER performance.     

QUANTUM EFFICIENCIES OF THE REVERSIBLE PHOTOREACTION OF OCTOPUS RHODOPSIN

The classic method of photometric curves for photosensitivity determination has been extended to the case of photoreversible reactions and applied to the octopus rhodopsin --> acid metarhodopsin photoreaction. In such cases, measurements at one irradiation wavelength yield the sum of the photosensitivities of the forward and reverse processes. However, by using different irradiation wavelengths, together with appropriate molar extinction coefficients, the quantum efficiencies for both reactions may be resolved. For detergent-solubilized octopus rhodopsin at room temperature, pH 7, the quantum yields are found to be 0.69 (+/- 0.03) for rhodopsin --> metarhodopsin, in line with values observed in a range of vertebrate visual pigments, and 0.43 (+/- 0.02) for the reverse photoregeneration process. The similarities in overall photosensitivities of the forward and reverse reactions in the visible region are consistent with a significant physiological role for photoreversal in the cephalopod visual cycle.     

Generalized composite degradation kinetics for polymeric systems under isothermal and nonisothermal conditions

A composite degradation methodology is extended to the conversion-dependence function in order to explain the importance of multiple reaction mechanisms which might be considered to be involved in degradation processes. Based on two elementary reaction mechanisms, a specific form of the model equation is derived, which is capable of describing various types of degradation behavior showing sigmoidal rate as well as deceleratory rate. The conversion-dependence function is derived to be independent of the Arrhenius-type reaction constant or temperature, and thus the kinetic parameters are determined by analytic methods that have been developed for isothermal and dynamic-heating experiments without any modification or additional assumptions. The developed model equation is tested by predicting the isothermal master curve of polyether-ether-ketone (PEEK), which is used as a model system in this study. The activation energies of the model system are analyzed using comparable methods for isothermal and dynamic experiments, which compare favorably in terms of the activation energy as a function of conversion. The resulting model equation, based on the kinetic parameters determined by isothermal experiments, can accurately predict both isothermal and dynamic-heating thermogravimetry utilizing the same constants and identical reaction mechanisms without additional assumption.     

Hydroxyl radical in aqueous solution: Computer simulation

Molecular dynamics simulations of hydroxyl radical in water are carried out by use of a classical simple point charge extended (SPC/E) water model and a similar point charge model for hydroxyl radical. Structural and dynamical properties are studied along the coexistence curve of SPC/E water at 298, 373, 473, 573, and 633 K and above its critical point at 683, 733, 783, and 833 K with density fixed at 0.3 g/cm3. Dramatic changes in the diffusion dynamics of water and hydroxyl radical near the critical point are related to the reorganization of the three-dimensional structure of water around hydroxyl radical, as revealed by the study of the spatial distribution functions. This study helps us understand the kinetics of oxidation reactions in high-temperature water.     

Tuning the HOMO and LUMO energy levels of organic chromophores for dye sensitized solar cells

A series of organic chromophores have been synthesized in order to approach optimal energy level composition in the TiO2-dye-iodide/triiodide system in the dye-sensitized solar cells. HOMO and LUMO energy level tuning is achieved by varying the conjugation between the triphenylamine donor and the cyanoacetic acid acceptor. This is supported by spectral and electrochemical experiments and TDDFT calculations. These results show that energetic tuning of the chromophores was successful and fulfilled the thermodynamic criteria for dye-sensitized solar cells, electrical losses depending on the size and orientation of the chromophores were observed.     

分光光度法测定金属硅中铁的线性校正与受控下的不确定度评估

用分光光度法测定金属硅中铁量,来分析讨论如何采用基本方法和控制方法技术,进行校正函数的残差齐性方差检验和有效期间的受控分析。研究结果表明,采用控制方法可以确保测量不确定度尽可能小,以达到检测的最终要求。     

Computerized methods for analyzing two-dimensional agarose gel electropherograms

Previous methods interpret zonal or polydisperse gel patterns of two-dimensional Serwer-type gels in terms of size and free mobility (surface net charge density). These two parameters have been determined for each component without quantitatively measuring the abundance of the components. The present study advances these previous methods by determining the relative concentration of each component by computer evaluation of densitometrically analyzed gel patterns. Suitable procedures and their underlying algorithms are presented. The mathematical routines are implemented in a user-friendly software package, called GelFit and designed for a Macintosh personal computer. The program input consists of digitized images of gel staining patterns exemplified by those obtained from electrophoresis of native subcellular-sized particles. The data are processed through the following steps: (i) Noise reduction and calibration. (ii) Geometrical transformation of the pattern onto a rectangular size/free mobility coordinate system using rationales of the extended Ogston model. (iii) Analysis of the transformed image to determine density maxima, density profiles along iso-free-mobility or iso-size lines, curve fitting of one-dimensional profiles or two-dimensional surfaces using Gaussian functions and curve stripping of surfaces to determine the possible number of particle populations.