Solvent and electric field dependence of the photocurrent generation in donor：acceptor blend system

This paper reports that the blend films of poly (2-methoxy-5-(2'-ethyl-hexyloxy)-p-phenylene vinylene) (MEH-PPV) and N,N'-bis(1-ethylpropyl)-3,4: 9,10-perylene bis (tetracarboxyl diimide) (EP-PDI) with the weight ratio of 1:2.5 have been prepared by spin-coating from chloroform (CF) and chlorobenzene (CB) solutions respectively. The absorption spectra and the morphology of the blend films show that large crystal-like EP-PDI aggregates are formed in film prepared from CB solution, which corresponds to a new absorption shoulder near 590nm, while there is no shoulder around 590\,nm in the UV--Vis absorption spectra of the blend film from CF solution. The electric-field dependence spectra of the photocurrent generation quantum yield of the film from CB solution shows that at weak electric field the EP-PDI aggregates act as more efficient sensitizers, but at strong electric field the quantum yields become almost invariable over the entire spectral range no matter what the state of EP-PDI, monomer or aggregate. At strong electric field, the photocurrent generation yields of both films from CF and CB solution saturate and their yield spectra become spectrally similar, mentioning that at strong electric field the photoexcitons dissociate efficiently and the free charges are collected by the electrodes almost completely.     

荧光材料Y_2O_3:Eu变温拉曼光谱分析

本文用显微拉曼谱仪在波长为785 nm的激光激发下,对Y2O3:Eu陶瓷在温度83-473 K间进行了系统的变温拉曼实验研究。实验发现Y2O3:Eu的一些振动模在低温下没有出现,只有当温度达到一定值之后才可以被观察到,分析表明这是由于温度变化引起的简并振动模式分裂。此外,Y2O3:Eu的拉曼峰位、半高全峰宽(FWHM)也是温度的非线性函数,且不同的拉曼峰遵循不同的函数关系,本文分析这是由于晶格的各向异性导致的。     

The anomalous spectral dependence of polarization in comets

We have found an anomalous (negative) spectral dependence of polarization for split comet 73P/Schwassmann–Wachmann 3, i.e. polarization degree in the I filter is systematically less (4%) than that in the R filter for both B and C subnuclei of the comet. Earlier we revealed a similar effect for comets 21P/Giacobini–Zinner, C/1999 S4 (LINEAR), and 9P/Tempel 1. Together with comet C/1989 X1 (Austin), for which the similar spectral dependence of polarization was also observed, these comets form a group characterized by some peculiar properties of their dust. Since atypical organic composition is a characteristic feature for all these comets, the anomalous spectral dependence of polarization may indicate specifics of origin of these comets. Really, most of these comets (but not all) originated from the Kuiper Belt. Also, most (but not all) of these comets belong to the group of comets depleted in carbon species in the gas phase, which is typical for comets formed in the giant-planet area of the solar system. On the other hand, all of the comets with negative spectral gradient of polarization have the dust dominated by large particles and most of them belong to the Jupiter family. This may indicate that anomalous spectral dependence of their polarization is a result of their evolution. To identify the reason of anomalous polarization, systematic spectropolarimetric observations of Jupiter-family comets are necessary.     

Investigation of Viscosity and Density Versus Temperature in Comparison with 1H Nmr Relaxation time Results for O,M-, P-Xylenes and α -,β-, γ - Picolines

The paper presents the results of density and viscosity measurements in liquid derivatives of benzene and pyridine, well purified, degassed or aerated, depending on temperature, in the whole liquidity range. Gaseous admixtures were found to affect the viscosity of liquids. From one to three Arrhenius regions were observed, depending on the structure and orientational freedom of the molecules. the results are discussed on the background of 1H NMR relaxation time studies with regard to the effect of dipole interactions on the structure of close packing.     

Schnell-Methode zur Umsetzung von Kohlenwasserstoffen zu Wasserstoff für die Isotopenanalyse

Es wird eine weiterentwickeltes, isotopenanalytisches Verfahren zur probenchemischen Umsetzung von Kohlenwasserstoffen mit Chromium zu Wasserstoff bei 1300 K vorgestellt. Die erzielten Testergebnisse zeigen anhand der gemessenen δD-Werte, daβ Quarzöfen bei diesen Temperaturen noch keine die Isotopenmeβwerte beeinflussende Diffusion von Wasserstoff durch die Wandung zulassen. Auβerdem erfolgte die Reaktion nahezu spontan und vollständig, was die Methode zeitlich sehr effektiv macht.

A modified isotope analytical method is presented for the chemical reaction of hydrocarbons with chromium at 1300 K to form hydrogen. The test results obtained (i.e. the measured δD-values) show that at this temperature quartz heating tubes do not allow hydrogen to diffuse through the wail, which fact would influence the isotopic composition. Furthermore the reaction proceeds nearly spontaneously and quantitatively, which yields an effective method, especially with respect to time.     

Free (open) boundary condition: some experiences with viscous flow simulations

The free (or open) boundary condition (FBC, OBC) was proposed by Papanastasiou et al. (A new outflow boundary condition, International Journal for Numerical Methods in Fluids, 1992; 14:587–608) to handle truncated domains with synthetic boundaries where the outflow conditions are unknown. In the present work, implementation of the FBC has been tested in several benchmark problems of viscous flow in fluid mechanics. The FEM is used to provide numerical results for both cases of planar and axisymmetric domains under laminar, isothermal or non‐isothermal, steady‐state conditions, for Newtonian fluids. The effects of inertia, gravity, compressibility, pressure dependence of the viscosity, slip at the wall, and surface tension are all considered individually in the extrudate‐swell benchmark problem for a wide range of the relevant parameters. The present results extend previous ones regarding the applicability of the FBC and show cases where the FBC is inappropriate, namely in the extrudate‐swell problem with gravity or surface‐tension effects. Particular emphasis has been given to the pressure at the outflow, which is the most sensitive quantity of the computations. In all cases where FBC is appropriate, excellent agreement has been found in comparisons with results from very long domains. The formulation for Picard‐type iterations is given in some detail, and the differences with the Newton–Raphson formulation are highlighted regarding some computational aspects. Copyright © 2011 John Wiley & Sons, Ltd.     

Barrier degradation of tunneling magnetoresistance device with MgO barrier and low resistance-area product

MgO barrier degradation is studied in a tunneling magnetoresistance head with low resistance-area product. As the stress current is increased, the resistance is significantly reduced before the barrier breakdown, while the magnetoresistance ratio remains almost unvaried. At the same time, the bias dependence of the resistance becomes less affected by the bias polarity, suggesting that slight degradation occurs at the interface between MgO and the ferromagnetic electrode. Just before the breakdown, the bias dependence shows an increasing tendency, indicating the defect accumulation inside the MgO barrier. The results are helpful for understanding the mechanisms of barrier degradation, which is critical for developing future magnetic tunneling junction devices.     

An explanation for deviations from the quark number scaling of elliptic flows in low pT region

We carry out a systematic study of the different contributions to the deviations of the elliptic flows from the quark number scaling in high energy heavy ion collision in a quark combination model.The effects that we considered are:the resonance decay,the flavor dependence of the quark elliptic flow and the combination of quarks/antiquarks with slightly different transverse momenta.Our results show that the deviations observed in experiments can be well reproduced within the combination framework if all the three effects are considered. We make a detailed analysis of the different contributions using a Monte-Carlo program and suggest measuring the quark number scaling in intermediate pT range more precisely.     

The Sigmoidal Transfer Function and the Gain-Threshold Exponential Dependence for Neurons from Statistical Mechanics Treatment

Analogy is used to treat the system of non-interacting integrate-and-fire neurons as an ideal Fermi gas. It allows to obtain the nonlinear gain curve in the form of sigmoid in agreement with biological findings. As the by-product the gain-threshold mechanism in neurons is presented. Surprisingly enough, this is in agreement with new biological findings, too. Besides, the application of this mechanism to the dynamics of neurons leads to the non-monotone transfer function.     

A class of differentiable toral maps which are topologically mixing

We show that on the 2-torus there exists a open set of regular maps such that every map belonging to is topologically mixing but is not Anosov. It was shown by Mañé that this property fails for the class of toral diffeomorphisms, but that the property does hold for the class of diffeomorphisms on the 3-torus . Recently Bonatti and Diaz proved that the second result of Mañé is also true for the class of diffeomorphisms on the -torus ().