Determination of the relative power density distribution in a heterogeneous reactor from the results of measurements of the reactivity effects and the neutron importance function

A method for experimental determination of the relative power density distribution in a heterogeneous reactor based on measurements of fuel reactivity effects and importance of neutrons from a californium source is proposed. The method was perfected on two critical assembly configurations at the NARCISS facility of the Kurchatov Institute, which simulated a small-size heterogeneous nuclear reactor. The neutron importance measurements were performed on subcritical and critical assemblies. It is shown that, along with traditionally used activation methods, the developed method can be applied to experimental studies of special features of the power density distribution in critical assemblies and reactors.     

Estimation of Qualitative and Quantitative Parameters of Air Cleaning by a Pulsed Corona Discharge Using Multicomponent Standard Mixtures

The efficiency of removal of volatile organic impurities in air by a pulsed corona discharge is investigated using model mixtures. Based on the method of competing reactions, an approach to estimating the qualitative and quantitative parameters of the employed electrophysical technique is proposed. The concept of the “toluene coefficient” characterizing the relative reactivity of a component as compared to toluene is introduced. It is proposed that the energy efficiency of the electrophysical method be estimated using the concept of diversified yield of the removal process. Such an approach makes it possible to substantially intensify the determination of energy parameters of removal of impurities and can also serve as a criterion for estimating the effectiveness of various methods in which a nonequilibrium plasma is used for air cleaning from volatile impurities.     

Consideration of spatial effects in reactivity measurements

Various methods of considering spatial effects in reactivity measurements are presented. These methods are employed both at the critical (mainly fast-neutron) facilities and at the BN-600 reactor.     

Quantitative assessment of reparameterized PM6 (rPM6) for hydrogen abstraction reactions

In the present study, the usability of semiempirical quantum mechanical methods for calculating bond dissociation energy (BDE) was investigated systematically. Density functional theory (DFT) methods with the B3LYP and B97-1 functionals were used for comparison. We introduced a new test set for BDE, called BDE200, which covers a wide range of compounds including large aromatic compounds. The use of BDE200 test set revealed that the accuracy of the methods studied was ordered from best to worst as: B97-1 > B3LYP > rPM6 >> PM7 > PM6 > AM1 > PM3. In addition to the improved accuracy of rPM6 for predicting BDE, it was found that rPM6 can provide a quantitative correlation between BDE values and reactivity. The rPM6 calculated activation enthalpies for C–H hydroxylation catalysed by the compound I of cytochrome P450 were proportional to the calculated and experimental C–H BDE values, in line with the results of previous DFT studies. We believe that rPM6 can help develop a database, for instance, for the determination of site of metabolism.     

Some methods for calculation of perturbations in nuclear reactors

Some methods for calculation of local perturbations of neutron fields and reactivity effects accompanying them are considered. Existence, uniqueness, properties and methods for finding solutions to the considered problems are discussed.     

生物组织光学特性参数的无创检测理论与技术

无创定量确定生物组织的光学特性在医学诊断和治疗领域中有着很重要的意义和广泛的应用前景。作为生物组织光学特性参数无创检测技术的理论基础 ,首先简要介绍了描述散射介质中光传播及分布的漫散射理论及蒙特卡罗模拟算法 ;然后分别介绍了用漫散射理论和蒙特卡罗模拟算法无创定量确定生物组织光学特性参数的具体方法 ;最后总结了到目前为止无创定量确定生物组织光学特性参数的研究成果 ,并对今后的工作作了展望     

The influence of singular field dominance on the caustic methods

The caustic method as applied to fracture mechanics for measuring the stress intensity factor, contains several approximations which limit its applicability and accuracy. The accuracy of the caustic method for the determination of the stress intensity factor is based on the restriction that the K-dominant singular field is fully established at which the experimental data are taken. In this paper, we attempt to identify the regions in which experimental measurements by caustic methods can be performed with confidence. The reliability of the method of caustics applied to the static problem and the case of a stationary crack subjected to dynamic loading are investigated in detail. The results demonstrate that significant deviation can occur in the determination of the stress intensity factor from shadow spot measurements. Conclusions regarding the method of caustics in the determination of the stress intensity factor are extracted from these results.     

Investigation of the dipolar dephasing NMR on organic solids

We present a method based on integro-differential equations describing the¹³C?¹H dipolar dephasing behaviour of carbon magnetization which results from monoprotonated carbons, non-protonated carbons as well as rapidly rotating methyl groups. Good agreement with theoretical calculations and experiment is obtained in ammonium tartrate and durene. The frequently applied empirical methods for determination the ratio of protonated and non-protonated carbons are analyzed. The dipolar dephasing time constants of non-protonated carbons vary substantially as a result, of variation in their heteronuclear second moments and thus in structure. Two different methods are performed for determination heteronuclear second moments from dipolar dephasing data.     

Photothermal methods for determination of thermal properties of bulk materials and thin films

Information on the thermal properties of materials is very important both in fundamental physical research and in engineering applications. The development of materials with desirable heat transport properties requires methods for their experimental determination. In this paper basic concepts of the measurement of parameters describing the heat transport in solids are discussed. Attention is paid to methods utilizing nonstationary temperature fields, especially to photothermal methods in which the temperature disturbance in the investigated sample is generated through light absorption. Exemplary photothermal measuring techniques, which can be realized using common experimental equipment, are described in detail. It is shown that using these techniques it is possible to determine the thermal diffusivity of bulk transparent samples, opaque and semi-transparent plate-form samples, and the thermal conductivity of thin films deposited on thick substrates. Results of the investigation of thermal diffusivity of the ground in the polar region, which is based on the analysis of the propagation of the thermal wave generated by sun-light, are also presented. Based on chosen examples one can state that photothermal techniques can be used for determination of the thermal properties of very different materials.     

Differential cross sections from quantum calculations on coupled Ab initio potential energy surfaces and scattering experiments for Cl(2P)+H2 reactions

To assess the relative reactivity of the spin-orbit excited state of atomic Cl with molecular hydrogen, we have measured differential cross sections using an atomic Cl beam with a known concentration of the ground and excited spin-orbit states. These are compared with the first determination of the cross sections from quantum mechanical scattering calculations on a set of coupled ab initio potential energy surfaces. The comparison suggests that these surfaces may underestimate the degree of rotational excitation of the HCl products and that the excited spin-orbit state plays a minor role in the reaction.     

Determination of Hansen Parameters of Nanoparticles: A Comparison of Two Methods Using Titania,Carbon Black,and Silicon/Carbon Composite Materials

Hansen solubility parameters (HSPs), for particles understood as Hansen similarity parameters, can provide valuable information about the surface behavior of nanoparticles. In the past years, several methodologies are developed for scoring and ranking of probe liquids for HSP determination. Two methods available to carry out this determination in a structured way are based on integral extinctions (IE) by Süß et al. and particle size determinations by Anwar et al., respectively. In this study, these two methods of HSP determination are applied on titania, carbon black, and silicon/carbon composites. The differences in scoring and subsequent ranking of a probe liquid list are compared between both methods. Comparable HSPs from both methods are reported as a best-practice example and additional considerations that need to be considered to properly derive HSPs from the IE-based method are emphasized.     

Molecular modelling in structural biology

Molecular modelling is a powerful methodology for analysing the three dimensional structure of biological macromolecules. There are many ways in which molecular modelling methods have been used to address problems in structural biology. It is not widely appreciated that modelling methods are often an integral component of structure determination by NMR spectroscopy and X-ray crystallography. In this review we consider some of the numerous ways in which modelling can be used to interpret and rationalise experimental data and in constructing hypotheses that can be tested by experiment. Genome sequencing projects are producing a vast wealth of data describing the protein coding regions of the genome under study. However, only a minority of the protein sequences thus identified will have a clear sequence homology to a known protein. In such cases valuable three-dimensional models of the protein coding sequence can be constructed by homology modelling methods. Threading methods, which used specialised schemes to relate protein sequences to a library of known structures, have been shown to be able to identify the likely protein fold even in cases where there is no clear sequence homology. The number of protein sequences that cannot be assigned to a structural class by homology or threading methods, simply because they belong to a previously unidentified protein folding class, will decrease in the future as collaborative efforts in systematic structure determination begin to develop. For this reason, modelling methods are likely to become increasingly useful in the near future. The role of the blind prediction contests, such as the Critical Assessment of techniques for protein Structure Prediction (CASP), will be briefly discussed. Methods for modelling protein-ligand and protein-protein complexes are also described and examples of their applications given.     

Methodical Aspects of Creation and Calculation of the Space Kinetics Benchmarks

The problems arising at creation and calculation of the space kinetics benchmarks are considered by three tasks. The connection between the nonstationary diffusion equation and the inverse solution of the kinetics equation (ISKE) is considered with the different methods of preparation and presentation of kinetic parameters. The following benchmarks are considered: the nondiffusion Small LWR benchmark from the series of Takeda’s tasks, complemented by modeling the motion of control rods; Ferguson’s benchmark, enlarged by calculation of the reactivity change with ISKE; TWIGL benchmark—2D LWR model with insertion of positive reactivity.     

堆振荡器法测量反应性的误差因素分析

为合理选择堆振荡器法实验条件,利用数值求解和公式推导,对影响测量精度的几项主要因素进行了分析。研究表明,通过选择合适的反应性振荡幅度及频率,可以提高堆振荡器法测量反应性的精度。由分析结果可知,对于中子代时间较短的反应堆,要使用堆振荡器法测量小反应性,在测量条件允许的情况下,应尽可能选择高频率的反应性振荡。     

Statistical and neural net methods for automatic glaucoma diagnosis determination

Two new computer diagnostic methods for the automatic determination of glaucoma diagnosis are presented and compared in this paper: the statistical method and the neural net method. Both introduced methods evaluate colour glaucomatous changes within the optic disc area. The mentioned colour changes are numerically represented using a suitable image analysis process. Next, the investigated eye is classified to three defined glaucoma-risk classes with different reliability of the diagnosis determination. The verification and the reliability comparison of both studied methods are performed by virtue of the application of this methods to a set of normal healthy optic disc images and a set of glaucomatous optic disc images.     

尿素检测方法的研究进展及其快速检测产品现状

进入21世纪,随着生活水平的提高,人们对生活质量的要求越来越高,食品或环境中有害物质的检测成为大众关注的重要部分,尿素的检测就是其中之一.本文介绍了目前国内外对某些行业尿素的一些检测方法,包括直接比色法、间接比色法、色谱法、中红外光谱法等,并讨论了快速检测产品在尿素含量测试方面的应用,对未来尿素的快速检测分析手段进行了展望.     

The Application of 7-Chloro-4-nitrobenzoxadiazole (NBD-Cl) for the Analysis of Pharmaceutical-Bearing Amine Group Using Spectrophotometry and Spectrofluorimetry Techniques

Abstract

Many papers have been presented in recent years regarding the field of application of 7-chloro-4-nitrobenzoxadiazole (NBD-Cl) as a fluorogenic and chromogenic reagent for the determination of pharmaceutical amines using spectrophotometry and spectrofluorimetry techniques. In this review article, various spectrophotometric and spectrofluorimetric methods using NBD-Cl as a labeling reagent for determination of pharmaceutical amines are covered. The application of these methods for the determination of drugs in pharmaceutical and real samples is also discussed.     

Die optischen Eigenschaften von Interferenzfiltern bei Messung mit endlich breiten Spektralbereichen

A special procedure of evaluation permits — from measurements of the transmissibility of interference filters possessing a very narrow band width — the very accurate determination of both the half-width and the position of the transmitted spectral range. Using this procedure a method is developped, that permits to eliminate those errors in the determination of the optical properties of the filters which are due to the finite width of the spectral range used for the measurements. Both methods are illustrated by experimental examples.     

JE-TROSY: combined J- and TROSY-spectroscopy for the measurement of one-bond couplings in macromolecules

With the application of RDCs in high-resolution NMR studies of macromolecules, there has been an interest in the development of accurate, sensitive methods for measuring 15N-1H and 13C-1H one-bond coupling constants. Most methods for determining these couplings are based on the measurement of the displacement between cross-peak components in J-coupled spectra. However, for large macromolecules and macromolecular complexes, these methods are often unreliable since differential relaxation can significantly broaden one of the multiplet components (i.e., the anti-TROSY component) and thereby make accurate determination of its position difficult. To overcome this problem, a J-evolved transverse relaxation optimized (JE-TROSY) method is presented for the determination of one-bond couplings that involves J-evolution of the sharpest cross-peak multiplet component selected in a TROSY experiment. Couplings are measured from the displacement of the TROSY component in the additional J-evolution dimension relative to a zero frequency origin. The JE-TROSY method is demonstrated on uniformly labeled 15N, 13C-labeled RNA and peptide samples, as well as with an RNA-protein complex, in which the protein is uniformly 15N, 13C-labeled. In all cases, resolved, sensitive spectra are obtained from which heteronuclear one-bond J-couplings could be accurately and easily measured.     

Thermal wave methods in investigation of thermal properties of solids

A short review of thermal wave measuring methods is presented in the paper. Based on fundamental laws of heat transport, experimental methods for determination of thermal properties of solids are divided into two groups – steady flux techniques and variable flux ones. Special attention is paid to the wave methods belonging to the second group and methods used by the author in his experiments. The idea of ?ngstr?m's method for determination of the thermal diffusivity of metals is reminded. Then different modifications of this classical technique using in investigations of bulk materials and thin films are described. Examples of a few thermal wave measurements are also presented.