Theoretical studies on a new pattern of laser-driven systems: towards elucidation of direct photo-injection in dye-sensitized solar cells

In this paper, we theoretically and numerically investigate a new type of analytically solvable laser-driven systems inspired by electron-injection dynamics in dye-sensitized solar cells. The simple analytical expressions are found to be useful for understanding the difference between dye excitation and direct photo-injection occurring between dye molecule and semiconductor nanoparticles. More importantly, we propose a method for discriminating experimentally dye excitation and direct photo-injection using time-dependent fluorescence. We have found that dye excitation shows no significant quantum beat, whereas the direct photo-injection shows a significant quantum beat.     

Substituent effects on acidity of aryl‐substituted fluoroalkanes: a computational study

The gas‐phase acidities (GA) of various aryl‐substituted fluoroalkanes, XC₆H₄CH(R¹)R², were calculated at the B3LYP/6‐311 + G(d,p)//B3LYP/6‐311 + G(d,p). The acidity values of alkanes having a common substituent X varied significantly with the change of R¹ and R². Their changes in acidity of 1 and 2 having two strong electron‐withdrawing groups (CF₃ or C₂F₅) at the deprotonation site and 8 , 9 , 10 , 11 having no fluorine atom at β‐position were linearly correlated with the corrected number of fluorine atoms contained in the fluorinated alkyl group (R² > 0.999). On the other hand, the GA values of β‐fluorine substituted alkanes ( 3 , 4 , 5 , 6 , 7 ) deviated in a stronger acid direction from the line. The enhanced acidity was attributed to the additional stabilization of the conjugate anion caused by the β‐fluorine negative hyperconjugation. The magnitude of β‐fluorine negative hyperconjugation of the fluorinated alkyl group (ΔG^o_β‐F) given by the deviations from the line decreased with increasing electron‐withdrawing ability of substituent X on the benzene ring, indicating that β‐fluorine negative hyperconjugation competes with the electronic effect of the substituent X. The GA_el values obtained by subtraction ΔG^o_β‐F from the apparent GA value were successfully correlated in terms of the Yukawa–Tsuno equation. The obtained ρ_el and r^?_el values were linearly related to the GA_el value of the respective phenyl‐substituted fluoroalkanes, supporting our previous conclusion that the ρ and r^? values for the substituent effect caused by the electronic effects of the substituent on the acidity are determined by the thermodynamic stability of the parent ion (ring substituent = H). Copyright © 2015 John Wiley & Sons, Ltd.     

电阻式核磁共振测量的最新进展

电阻式核磁共振(RDNMR)测量是1988年由德国马普所的von Klitzing研究小组针对GaAs二维电子气中少量核自旋的探测而提出的一种具有超高灵敏度的实验技术. 目前, RDNMR已经成为研究单层或双层GaAs二维电子气核自旋和电子自旋特性的重要手段. 由于为实现电阻式核磁共振测量所建立的动态核极化方法强烈依赖于GaAs特有的材料属性, 至今这一技术一直没有扩展应用到其他半导体低维系统中. 最近,本研究小组发展了一种动态核极化新方法,成功实现了对典型窄带半导体锑化铟(InSb) 二维电子气的电阻式核磁共振测量.本文在介绍电阻式核磁共振测量工作原理及已建立的典型动态核极化方法的基础上,着重讨论所提出的动态核极化新方法的机理、 实验结果以及对今后研究的展望.     

Status of prediction methods for critical heat fluxes in mini and microchannels

Saturated critical heat flux (CHF) is an important issue during flow boiling in mini and microchannels. To determine the best prediction method available in the literature, 2996 data points from 19 different laboratories have been collected since 1958. The database includes nine different fluids (R-134a, R-245fa, R-236fa, R-123, R-32, R-113, nitrogen, CO₂ and water) for a wide range of experimental conditions. This database has been compared to 6 different correlations and 1 theoretically based model. For predicting the non-aqueous fluids, the theoretical model by Revellin and Thome [Revellin, R., Thome, J.R., 2008. A theoretical model for the prediction of the critical heat flux in heated microchannels. Int. J. Heat Mass Transfer 51, 1216–1225] is the best method. It predicts 86% of the CHF data for non-aqueous fluids within a 30% error band. The data for water are best predicted by the correlation by Zhang et al. [Zhang, W., Hibiki, T., Mishima, K., Mi, Y., 2006. Correlation of critical heat flux for flow boiling of water in minichannels. Int. J. Heat Mass Transfer 49, 1058–1072]. This method predicts 83% of the CHF data for water within a 30% error band. Some suggestions have also been proposed in this paper for the future studies.     

Combination of LFP‐TRIR spectroscopy and DFT computation as a tool to determine the intermediate during the photooxidation of triarylphosphine

Laser flash photolysis‐time‐resolved infrared spectroscopy (LFP‐TRIR) was performed on an acetonitrile or dichloromethane solution of triarylphosphines, Ar₃P, in air. A transient spectrum consisting of several absorption bands appeared in the region of 1050–1300 cm^?1 on the TRIR on a microsecond timescale, which disappeared on a millisecond timescale. To identify the observed transient intermediate, the IR spectra of possible intermediates of the photoreaction were simulated by theoretical calculations based on density functional theory (DFT). The IR spectrum simulated for the phosphine peroxidic radical cation, Ar₃P⁺OO^?, well predicted the observed IR spectrum, showing that Ar₃P⁺OO^? is formed as a transient intermediate upon the LFP of Ar₃P in air. Copyright © 2014 John Wiley & Sons, Ltd.     

Orthogonal-polarization compensation method for measuring unsteady vertical force of a bumblebee in a wind tunnel

It is important to measure the unsteady vertical force of an insect in a wind tunnel for studying the flight performance of insects. Optical method can measure it with high accuracy, but it is affected by air turbulence. An orthogonal-polarization compensation (OPC) method is developed for measuring the beating force of a bumblebee in a wind tunnel and compensating the error due to beam fluctuations induced by air turbulence. The applicability of the OPC method was confirmed by using a piezo translator to generate the tilt angle variation. The results show that by using the OPC method, the error in tilt angle measurement due to air turbulence can be decreased by about 80% compared with that using the conventional angle measurement method. The OPC method was then applied to measure the tilt angle variation caused by the beating motion of a bumblebee attached to one end of a sensor block in a wind tunnel for a wind velocity of 1.1 ms⁻¹. The results confirmed the effectiveness of this new method.     

Flame Emission Spectrometry Using Atomic Absorption Apparatus (I) Determination of Sr In Sea Water

Flame emission determination of Sr in sea water is studied using an ordinary atomic absorption apparatus. The analytical line 4607 A is used with background correction at 4616 A. The ionization is found to be negligible in air acetylene flame with sea water, and the interference of H₂SO₄ is elimentated using the higher part of the flame.     

Synthesis and characterization of proton‐conducting copolyimides bearing pendant sulfonic acid groups

A series of sulfonated copolyimides (co‐SPIs) bearing pendant sulfonic acid groups were synthesized from 1,4,5,8‐naphthalenetetracarboxylic dianhydride (NTDA), bis(3‐sulfopropoxy) benzidines (BSPBs), and common nonsulfonated diamines via statistical or sequenced polycondensation reactions. Membranes were prepared by casting their m‐cresol solutions. The co‐SPI membrane had a microphase‐separated structure composed of hydrophilic and hydrophobic domains, but the connecting behavior of hydrophilic domains was different from that of the homo‐SPIs. The co‐SPI membranes displayed clear anisotropic membrane swelling in water with negligibly small dimensional changes in the plane direction of the membrane. With water uptake values of 39–94 wt %, they showed dimensional changes in membrane thickness of about 0.11–0.58, which were much lower than those of homo‐SPIs. The proton conductivity σ values of co‐SPI membranes with ion exchange capacity values ranging from 1.95–2.32 meq/g increased sigmoidally with increasing relative humidity. They displayed σ values of 0.05–0.16 S/cm at 50 °C in liquid water. Increasing temperature up to 120 °C resulted in further increase in proton conductivity. The co‐SPI membranes showed relatively good conductivity stability during the aging treatment in water at 100 °C for 300 h. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1545–1553, 2005     

Capillary electrophoretic discrimination of single nucleotide polymorphisms using an oligodeoxyribonucleotidepolyacrylamide conjugate as a pseudo-immobilized affinity ligand: optimum ligand length predicted by the melting temperature values.

We developed a weak-affinity separation system for single-nucleotide polymorphisms (SNPs) based on capillary electrophoresis. In this approach, single-stranded DNA (ssDNA)-polyacrylamide (polyAAm) conjugate was used as a pseudo-immobilized affinity ligand to separate the target DNA, cytochrome P450 2C9 (CYP2C9), and its point mutant. The ligand DNA was designed to be complementary to the normal DNA, and the target DNA was electrophoretically separated by the difference in the affinity with the pseudo-immobilized ligand in the capillary. We showed that the separation efficiency was closely associated with the Tm value of double-stranded DNA (dsDNA) consisting of the target and ligand DNA, which depends on the measurement conditions, such as the base number of the ligand DNA and the concentration of Mg2+ in the buffer solution.