Medium-size polarized basis sets for high-level-correlated calculations of molecular electric properties

Summary The first-order polarized basis sets for the use in high-level-correlated investigations of molecular electric properties have been generated for Pb, Bi, Po, and At. The performance of the standard [10.17.14.5/13.11.8.2] and extended [20.17.14.9/13.11.8.4] basis sets has been examined in nonrelativistic and quasirelativistic calculations for atoms and simple closed-shell hydrides. The relativistic contributions to electric dipole properties of those systems have been evaluated by using the recently developed quasirelativistic scheme. The predicted dipole polarizability of At is in good agreement with the results of other relativistic calculations. The calculated quasirelativistic dipole moments of BiH₃ (–0.499 a.u.), PoH₂ (–0.207 a.u.), and AtH (+0.036 a.u.) involve a significant relativistic contribution which amounts to —0.230 a.u., –0.177 a.u., and –0.097 a.u., respectively. The basis set details append this paper. They are also available as a part of the basis set library of the MOLCAS system.     

Fluorinated compounds for advanced IC interconnect applications: a survey of chemistries and processes

The semiconductor industry is now in the early stages of an unprecedented change in materials set for the integrated circuit (IC) interconnect structure. The traditional layers of aluminum conductors and silicon dioxide dielectrics are being replaced by copper thin films and a variety of low k candidates, respectively. In many cases, fluorine confers desirable properties on either the precursors or the final films. At the same time, fluorine presents some potentially adverse effects, which have led to a so-called “fear-of-fluorine” in interconnect applications. This paper will review the proposed uses of fluorinated compounds in the interconnect structures, covering both precursors and the resulting thin films. Both the status of technical studies, and the prospects for commercial implementation, will be addressed.     

压电石英晶体在电解质水溶液中的振荡性能研究(Ⅱ)——频率、频移特性

根据两面电极浸入液体中的压电晶体等效电路模型和Pierce振荡器振荡方程的解,得到晶体在电解质溶液中的振荡频率(F_1)与溶液电导率(x)的关系式:F_1=(1/2π)(1/C_1+1/C_2)(1/X_e)[(R_e~2+X_e~2)x~2+2R_ex+1]。以自行设计的Pierce晶体振荡器。研究了晶体和主振电路参数、输入电压及检测池外壳屏蔽接地对AT切9MHz石英晶体在KCl、Na_2SO_4水溶液中的频率、相对于纯水频移随溶液电导率变化的影响规律,结果与上式相符。     

Chemical mass shifts in resonance ejection experiments in the quadrupole ion trap

Chemical mass shifts were measured in a Paul ion trap operated in the mass-selective instability scan with resonance ejection using a custom-built instrument. These shifts, which can be as much as 2%, decrease with increasing endcap electrode separation owing to changes in the higher order contributions to the electric field. They also decrease with decreasing helium buffer gas pressure. Both of these effects are analogous to those found with boundary ejection. This suggests that the previously proposed chemical mass shift mechanism based on compound-dependent collisional modification of the ejection delay produced by field faults near the endcap electrode apertures holds true also for resonance ejection. The influence of the resonance frequency on chemical mass shifts was also investigated and it is shown that at certain working points (values of the Mathieu parameter q(z) and a(z)) non-linear resonances greatly reduce the ejection delay for all ions, regardless of their chemical structures, and thus reduce the magnitude of the chemical mass shift. Energetic collisions leading to dissociation can take place at an earlier stage during the ejection process in the mass analysis scan when using resonance ejection compared with boundary ejection. This leads to even larger chemical mass shifts of fragile ions in resonance ejection. Increasing the resonance voltage amplitude can enhance this effect. The chemical mass shifts of fragile ions increase with increase in the resonance voltage amplitude, whereas negligible changes occur for structurally stable ions.     

Redox and Conformational Equilibria and Dynamics of Cytochrome c at High Electric Fields

Cytochrome c (Cyt‐c) adsorbed in the electrical double layer of the Ag electrode/electrolyte interface has been studied by stationary and time‐resolved surface‐enhanced resonance Raman spectroscopy to analyse the effect of strong electric fields on structure and reaction equilibria and dynamics of the protein. In the potential range between +0.1 and ?0.55 V (versus saturated calomel electrode), the adsorbed Cyt‐c forms a potential‐dependent reversible equilibrium between the native state B1 and a conformational state B2. The redox potentials of the bis‐histidine‐coordinated six‐coordinated low‐spin and five‐coordinated high‐spin substates of B2 were determined to be ?0.425 and ?0.385 V, respectively, whereas the additional six‐coordinated aquo‐histidine‐coordinated high‐spin substate was found to be redox‐inactive. The redox potential for the conformational state B1 was found to be the same as in solution in agreement with the structural identity of the adsorbed B1 and the native Cyt‐c. For all three redox‐active species, the formal heterogeneous electron transfer rate constants are small and of the same order of magnitude (3–13 s^?1), which implies that the rate‐limiting step is largely independent of the redox‐site structure. These findings, as well as the slow and potential‐dependent transitions between the various conformational (sub‐)states, can be rationalized in terms of an electric field‐induced increase of the activation energy for proton‐transfer steps linked to protein structural reorganisation. Further increasing the electric field strength by shifting the electrode potential above +0.1 V leads to irreversible structural changes that are attributed to an unfolding of the polypeptide chain.     

Application of relaxation periods during electrodialysis of a casein solution: Impact on anion-exchange membrane fouling

Electrodialysis (ED) is a membrane process used on a large scale. However, one of the common problems is fouling of ion-exchange membranes stacked in the cell. The use of pulsed power, consisting in applying a constant current density during a fixed time of application (T_on) followed by a pause duration (T_off), was demonstrated recently as an effective fouling mitigation method for electrodialysis. Up until now, no work has investigated the potential of electrodialysis using pulsed electric field on protein fouling. The aim of the present work was to study the influence of pulsed electric field (PEF) with a low frequency square shaped periodic signal (T_on = 10 s–T_off = 10 s, T_on = 10 s–T_off = 40 s) in comparison with dc current during electrodialysis of a casein solution at different current densities (10, 20 and 30 mA/cm²) on membrane fouling. It appeared from these results that PEF, under certain conditions of pulse, would avoid fouling on anion-exchange membranes. For 10 s–40 s pulsed electric field conditions, no fouling was observed with any density, while for 10 s–10 s PEF conditions, fouling appeared only at current density over 10 mA/cm². dc current, whatever the current density conditions, led to a fouling on the diluate side of the AEM. Furthermore, when fouling occurred, magnitude layer thickness and dry weight increased with the applied current density. The nature of the fouling was identified as 97% protein. The protein fouling would be due to the dissociation of water molecules and/or heat increase at the anion-exchange membrane interface. The relaxation time of the pulse would limit both phenomena on the membrane.     

脉冲激光引信用PFM和PWM式LD驱动电路的研究

 在激光引信的通讯系统中，针对引信用脉冲式半导体激光器驱动电路的脉冲宽度、频率、功率可调的需要，根据LD驱动电路的工作原理，建立了LD驱动电路的一般模型。然后用电子多频振荡器提供驱动信号，用双MOS驱动器来驱动半导体激光器，通过大量的实验、仿真、分析、比较，设计出了方便可调的大功率LD的驱动电路，该电路的脉冲频率和脉冲宽度可方便调整。并且该驱动电路的频率调节范围大（10Hz~20kHz）；脉冲宽度可以从几ns到几百ns进行调节，大大提高了激光引信通讯系统的性能与可靠性。     

基于开关控制的兴趣实验设计

设计了开关控制实验,专门对常见的开关特点及使用进行探讨,根据开关特点搭建相应的控制电路,用近似于工程项目的形式锻炼学生对开关的灵活应用,激发了学生实验的兴趣和积极性.     

A micro/nanocasting method for replicating soft micro/nanosurface structures using a dynamic electrical field

We propose a new electric field-induced micro/nanocasting method to replicate soft patterns using micro/nanocasting techniques without pressure. The process uses an alternating current (AC) electrical field and rotation of one electrode, generating a dynamic electrical field that induces electrokinetic flow motion in a dielectric solution (polydimethylsilane, PDMS). We used a lotus leaf as a replication template and characterised the PDMS flow motion to observe the effects of various process parameters (e.g., electrical field strength, rotation speed of an electrode, and electrode shape). The unstable flow motion was significantly dependent on the processing parameters, especially the rotation speed of the electrode. Using the optimised processing conditions, the replication efficiency was about 88%. We believe that this method has potential for fabricating soft micro/nanosized structures.     

Zero Current Potentiometry for Measuring the Interface Potential at the Electrode/Solution Interface. Theoretical and Experimental Study

A novel electrochemical approach has been proposed to measure the interface potential at the electrode/solution interface based on reconstructing the three‐electrode system of a potentiostat. In this work, the method was investigated both theoretically and experimentally. Mathematical expressions, describing current? potential characteristics, were derived. Zero current potential E_zcp was defined as the potential at which the current is zero based on linear sweep voltammetry, and was determined from the I? E curve to measure the interface potential. The experimental results obtained with the couples Fe(CN)₆^3?/Fe(CN)₆^4? and Co(NH₃)₆³⁺/Co(NH₃)₆²⁺ as examples agreed well with the theory. The proposed approach exhibits an excellent performance for measuring the interface potential due to the advantages of rapidity, high stability and accuracy.