Interpretation of infrared spectra for ion-exchange systems

Analytical expressions for the frequencies of stretching OH vibrations of hydrated ions are obtained. The expressions are applied to the interpretation of the experimental IR spectra of cation exchanger KU-2, heterogeneous cation-exchange membrane MK-40, and to the Nafion membrane. The comparison of the experimental and theoretical spectra gives evidence of the existence of water molecules located between fixed and mobile ions, i.e., of the dissociation of ion pairs.     

Electrochemical impedance of ion-exchange systems with weakly charged membranes

The aim of this work was to investigate the effect of the membrane fixed-charge concentration on the electrochemical impedance of ion-exchange membrane systems and the specific properties of the impedance of ion-exchange systems with weakly charged membranes. The systems under study are constituted by a membrane with a homogeneous distribution of negative fixed-charge and two diffusion boundary layers on both sides of the membrane. The ionic transport processes of a binary electrolyte are theoretically described by the Nernst–Planck and Poisson equations not only in the ion-exchange membrane but also in the two diffusion boundary layers. The electrochemical impedance for different values of the anion diffusion coefficients and the direct component of the applied electric current has been obtained by using the network simulation method as a function of the membrane fixed-charge concentration. New results are presented in relation with the evolution of the characteristic frequency of the diffusion impedance and the dc resistance of the system with the uniform concentration of the fixed-charge inside the membrane.     

Detecting the Transient ENDOR Response

Free radicals at low temperature are sometimes difficult to study by electron-nuclear double-resonance spectroscopy with the commonly available detection schemes. In some cases, slow nuclear spin relaxation limits the steady-state ENDOR response. A detection scheme optimized for transient signals is described that circumvents this limitation on signal amplitude. The apparatus employs pulsed radiofrequency fields with advance of the radiofrequency between pulses. Some spectra of semiquinone and tyrosine radicals are presented to illustrate the utility of the technique.     

Proton ENDOR of dimethylnitramine free radicals

Electron nuclear double resonance (ENDOR) spectra of free radicals produced by ultraviolet (UV) photolysis of polycrystalline and single crystal dimethylnitramine (or N-methyl-N-nitromethanamine) [DMN; (CH₃)₂NNO₂ were studied atca. ?30°C. Results suggest that multiple radical species are formed during UV photolysis of DMN, perdeutero-DMN-d₆, and¹⁵N-labeled DMN. Proton ENDOR spectra are consistent with assignment of a cation radical (CH₃)₂NNO ₂ ⁺ as the major DMN radical species. Proton hyperfine coupling anisotropy, which is observed from the ENDOR spectra, is attributed to inequivalence of the two DMN methyl groups.     

A Proton ENDOR Study of Azurin

As part of our ongoing project that aims at the optimum characterization of the electronic structure of the blue-copper site of azurin from Pseudomonas aeruginosa, we present the complete hyperfine tensors of the protons bound to the Cβ atom of the copper-bound cysteine 112. These tensors have been obtained from a 95 GHz pulsed electron-nuclear double resonance study of a single crystal of the protein.     

ENDOR investigation of tellurium doped GaP

The hyperfine interactions of⁶⁹Ga,⁷¹Ga and³¹P nuclei with donor electrons in tellurium doped GaP have been measured by means of electron nuclear double resonance (ENDOR). Three groups of neighbour nuclei have been identified. Values of |(r)|², r ^–3, and the electric field gradient at the sites of the neighbour nuclei have been determined, and compared with those from ENDOR measurements on sulphur doped GaP.     

ENDOR spectroscopy at 275 GHz

A pulsed ENDOR spectrometer operating at a microwave frequency of 275 GHz is described. The results demonstrate that this type of spectroscopy can now be performed routinely at this high microwave frequency. The advantages compared to conventional EPR frequencies are the high spectral resolution, time resolution, and sensitivity.     

ENDOR investigations of Ge doped GaP

ENDOR measurements of germanium doped gallium phosphide show a SHF-interaction with one neighbour shell strong enough to resolve the splitting of lines caused by the mutual interaction of the different nuclei of the same shell. The symmetry and hyperfine parameters of four other neighbour shells have also been determined.     

ENDOR investigations of sulphur doped GaP

From ENDOR measurements on GaP:S the symmetries and hyperfine parameters of four groups of neighbour nuclei have been investigated. The values of ||², r ^–3 and the electric field gradient at the sites of the neighbour nuclei have been determined.     

Matrix methods in treating decentred optical systems

A set of matrix methods treating decentred optical systems in the paraxial approximation is reviewed. Misalignment phenomena of optical systems can generally be described by an augmented 4×4 matrix; propagation of optical rays in an asymmetric, inhomogeneous medium by a 3×3 matrix. In order to simplify the operations with these matrices, ray transfer flow graphs are introduced.A lot of optical problems can be solved in a clear and simple manner, including optical arrays. Some examples are given.     

EPR and ENDOR study of carbon-mineral sorbents

A character of carbon ordering in carbon mineral systems, such as γ-Al₂O₃ and TiO₂ has been investigated using EPR and ENDOR methods. The experimental data have been interpreted at the assumption that a spatial distribution of paramagnetic centers on the surface of aluminum-oxide is 2-dimensional. The results of ENDOR measurements show that no stable covalent bond is formed between the mineral support surface and coke upon carbonization of aluminum oxide by divinyl. The interaction has mainly the ionic character and is easily affected by water.     

非对称光学系统的矩阵分解与等效变换

使用矩阵光学方法研究了非对称光学系统的矩阵分解和等效变换。将Arsenault提出的分解方法推广应用于分块矩阵行列式为零的4×4矩阵的分解,并以用于光束对称化的光学系统为例说明该方法的应用。     

The ups and downs of Feher-style ENDOR

A new transient variation of the “Feher-style” electron-nuclear double resonance (ENDOR) method is examined. In this technique, the passage-mode electron paramagnetic resonance (EPR) signal is monitored following the application of a pulsed radio frequency (RF). Continuous-wave and transient proton ENDOR experiments have been conducted on the nonheme iron center from the protein nitrile hydratase. These experiments show that the transient ENDOR signal response exhibits a complex response with multiple phases in the time evolution of the ENDOR signal. Both increases and decreases in the passage-mode EPR signals are observed at different times following the RF pulse that induces an ENDOR transition. A simple model based on a packet-shifting ENDOR mechanism for a nonadiabatic passage EPR signal is proposed. This model describes many of the features seen in the transient ENDOR experiments and provides new insight into the traditional Feher-style ENDOR measurements. This new model shows that a packet-shifting mechanism can account for many of the “negative ENDOR” effects commonly seen in Feher-style ENDOR, which suggests that more exotic ENDOR mechanisms may not be required to explain these observations.     

Matrix representation of Gaussian Schell-model beams in optical systems

The behaviour of a Gaussian Schell-model beam at a spherical boundary is investigated in detail, and transformation laws for its propagation parameters are obtained. These laws are used to extend the classic ABCD-matrix method into the context of partially coherent beams. The matrix formalism is useful in designing and analysing real optical systems, which consist of spherical boundaries and uniform media of finite thickness. Explicit relations are derived that couple the input and output beam parameters in general optical systems of that type. The closed-form imaging equations ensuing for a single thin lens are discussed as an illustrative example.     

非对称光学系统的矩阵分解与等效变换

 使用矩阵光学方法研究了非对称光学系统的矩阵分解和等效变换。将Arsenault提出的分解方法推广应用于分块矩阵行列式为零的4×4矩阵的分解，并以用于光束对称化的光学系统为例说明该方法的应用。     

Nuclear relaxation effects in Davies ENDOR variants

A recent article by Yang and Hoffman [T.-C. Yang, B.M. Hoffman, J. Magn. Reson., 181 (2006) 280] presents a ‘Davies/Hahn ENDOR multi-sequence’ in which the α and β peaks of an electron-nuclear double resonance (ENDOR) spectrum can be distinguished. This represents one instance of a family of ENDOR sequences which have no initial microwave inversion pulse, and which can reveal information about nuclear relaxation rates and the signs of hyperfine coupling constants. Here we discuss the more general set of such sequences, which we refer to as Saturated Pulsed ENDOR, and show how signal sensitivity can be optimised within the context of this new technique. Through simulations, we compare its performance to other techniques based on Davies ENDOR, and experimentally illustrate its properties using the non-heme Fe enzyme anthranilate dioxygenase AntDO. Finally, we suggest a protocol for extracting both the magnitude and sign of the hyperfine tensor using a combination of ENDOR techniques.     

一维大气边界层光学折射率结构常数数值模式的实验检验

提出了一种大气光学折射率结构常数的数值模式。一次输入日期、时间、经纬度、温度、湿度、风速、粗糙度、土壤参数，云量等相关参数，可得到24h内的温度、湿度、风场、折射率结构常数等量。通过与实测对比表明，无论是月平均折射率结构常数还是某天的折射率结构常数，模式计算与实测数据都符合得很好。模式计算的向下总辐射通量与实测数据基本一致。     

Matrix factorization method for the Hamiltonian structure of integrable systems

We demonstrate that the process of matrix factorization provides a systematic mathematical method to investigate the Hamiltonian structure of non-linear evolution equations characterized by hereditary operators with Nijenhuis property.     

失调复光学系统的矩阵描述与等效变换

基于复光线概念,采用矩阵光学方法研究了3×3复光线矩阵的分解问题,并以失调高斯透镜和失调傅里叶变换系统为例,说明失调复光学系统的等效变换。研究表明,失调光学系统的增广矩阵可用三个基本矩阵的有序乘积表示。