Bender–Wu formulas and classical trajectories: Higher dimensions and degeneracies

A method for the asymptotics of the perturbation series (Bender-Wu formulas) which is not restricted to one dimension is outlined. The method has a classical mechanic flavor and involves computing classical trajectories using classical perturbation methods. The method applies also when the unperturbed eigenvalues are degenerate. It is illustrated for the Hydrogen Zeeman Hamiltonian which is not separable and has degeneracies.     

A Sensitive and Specific Resin-Bead Test for Histidine and Its Spectrophotometric Determination Using KBr-KBrO3 Reagent

Abstract

A new, sensitive and specific spot test has been developed for histidine on resin beads. Also, a spectrophotometric method has been devised improving the old Knoop method, which is quite precise and applicable in clinical and biomedical analysis. A tentative mechanism has been proposed for the reaction.     

Reliable and efficient reaction path and transition state finding for surface reactions with the growing string method

The computational challenge of fast and reliable transition state and reaction path optimization requires new methodological strategies to maintain low cost, high accuracy, and systematic searching capabilities. The growing string method using internal coordinates has proven to be highly effective for the study of molecular, gas phase reactions, but difficulties in choosing a suitable coordinate system for periodic systems has prevented its use for surface chemistry. New developments are therefore needed, and presented herein, to handle surface reactions which include atoms with large coordination numbers that cannot be treated using standard internal coordinates. The double‐ended and single‐ended growing string methods are implemented using a hybrid coordinate system, then benchmarked for a test set of 43 elementary reactions occurring on surfaces. These results show that the growing string method is at least 45% faster than the widely used climbing image‐nudged elastic band method, which also fails to converge in several of the test cases. Additionally, the surface growing string method has a unique single‐ended search method which can move outward from an initial structure to find the intermediates, transition states, and reaction paths simultaneously. This powerful explorative feature of single ended‐growing string method is demonstrated to uncover, for the first time, the mechanism for atomic layer deposition of TiN on Cu(111) surface. This reaction is found to proceed through multiple hydrogen‐transfer and ligand‐exchange events, while formation of H‐bonds stabilizes intermediates of the reaction. Purging gaseous products out of the reaction environment is the driving force for these reactions. © 2017 Wiley Periodicals, Inc.     

Orthogonal method development using hydrophilic interaction chromatography and reversed-phase high-performance liquid chromatography for the determination of pharmaceuticals and impurities

A hydrophilic interaction chromatography (HILIC) method has been developed and validated as a secondary or orthogonal method complementary to a reversed-phase HPLC (RP-HPLC) method for quantitation of a polar active pharmaceutical ingredient and its three degradation products. The HILIC method uses a diol column and a mobile phase consisting of acetonitrile/water and ammonium chloride. The compounds of interest show significant differences in retention behaviors with the two very different chromatographic systems, which are desired in developing orthogonal methods. The HILIC method is validated and has met all validation acceptance criteria for the support of drug development activities.     

Degenerate states perturbation theory and continued fractions

An extension is made for degenerate levels of a recently proposed method for calculating higher-order terms of eigenvalues in a perturbation system with discrete energy levels. The method is used for calculating ground-state energy eigenvalue corrections for a rigid rotator which has a dipole ajid interacts with an applied electric field.     

A combination of the tree-code and IPS method to simulate large scale systems by molecular dynamics

An IPS/Tree method which is a combination of the isotropic periodic sum (IPS) method and tree-based method was developed for large-scale molecular dynamics simulations, such as biological and polymer systems, that need hundreds of thousands of molecules. The tree-based method uses a hierarchical tree structure to reduce the calculation cost of long-range interactions. IPS/Tree is an efficient method like IPS/DFFT, which is a combination of the IPS method and FFT in calculating large-scale systems that require massively parallel computers. The IPS method has two different versions: IPSn and IPSp. The basic idea is the same expect for the fact that the IPSn method is applied to calculations for point charges, while the IPSp method is used to calculate polar molecules. The concept of the IPS/Tree method is available for both IPSn and IPSp as IPSn/Tree and IPSp/Tree. Even though the accuracy of the Coulomb forces with tree-based method is well known, the accuracy for the combination of the IPS and tree-based methods is unclear. Therefore, in order to evaluate the accuracy of the IPS/Tree method, we performed molecular dynamics simulations for 32,000 bulk water molecules, which contains around 10(5) point charges. IPSn/Tree and IPSp/Tree were both applied to study the interaction calculations of Coulombic forces. The accuracy of the Coulombic forces and other physical properties of bulk water systems were evaluated. The IPSp/Tree method not only has reasonably small error in estimating Coulombic forces but the error was almost the same as the theoretical error of the ordinary tree-based method. These facts show that the algorithm of the tree-based method can be successfully applied to the IPSp method. On the other hand, the IPSn/Tree has a relatively large error, which seems to have been derived from the interaction treatment of the original IPSn method. The self-diffusion and radial distribution functions of water were calculated each by both the IPSn/Tree and IPSp/Tree methods, where both methods showed reasonable agreement with the Ewald method. In conclusion, the IPSp/Tree method is a potentially fast and sufficiently accurate technique for predicting transport coefficients and liquid structures of water in a homogeneous system.     

A liquid chromatographic method for the simultaneous determination of promethazine and three of its metabolites in plasma using electrochemical and UV detectors

A new assay method has been developed for the quantitation of promethazine (PMZ) with a sensitivity and reproducibility as good as any previously reported method. This method is also capable of quantitatively determining three metabolites of PMZ (monodemethylated, sulphoxidated, and monodemethylated sulphoxidated PMZ), which has not been previously described. The method uses high-performance liquid chromatography with amperometric and UV detection simultaneously and requires only one extraction step from serum with chloroform. The method uses trifluoperazine as the internal standard. The limit of detection level for PMZ is 1.0 ng/ml when a 0.2-mL specimen of plasma is assayed. A validation study is also conducted for evaluating the recovery, precision, linearity of response, sensitivity, and selectivity of the method.     

Requirements and tests for HPLC apparatus and methods in pharmaceutical quality control

Summary One possible method has been demonstrated for pharmaceutical quality control which is not restricted to this field and fulfils and documents the prerequisites for reliable, accurate and precise HPLC analysis. This includes validation which shows that the method is able in principle to fulfil the requirements, the apparatus test which shows that the apparatus generally works correctly and precisely and the system suitability test which shows that the method provides accurate and precise results on this apparatus and with this column for the analysis in question when other non-equipment and non-method-induced errors are excluded.     

Contribution to the radionuclide X-ray fluorescence analysis of human blood and plasma

A photon-induced X-ray fluorescence method, which allows the simultaneous determination of iron, copper, zinc, bromine and rubidium in human blood and blood plasma samples is described. The method is reliable and has a good sensitivity for a wide range of elements.     

点击化学法修饰氧化石墨烯及其在高分子中的应用研究

点击化学是一种操作简单方便、灵活高效的化学合成方法,对石墨烯的改性具有高效和活性位点可控等特点,是一种新型高效修饰石墨烯的改性法。本文结合点击化学改性石墨烯的特点及在高分子中的应用,将点击化学功能化修饰石墨烯分为共价键点击功能化和非共价键点击功能化,其中共价键结合又可细分为边缘点击功能化改性和表面点击功能化改性。本文介绍了叠氮功能改性剂的制备方法及其修饰石墨烯的点击反应原理,总结了点击功能化石墨烯及氧化石墨烯高分子复合材料的功能特性和应用前景。     

Colorimetric method for the determination of captafol (difolatan) in commercial formulations and residues on grains and apples.

A simple and rapid colorimetric method for the microdetermination of captafol (difolatan), based on its reaction with a dithiocarbamate, has been developed. The bright yellow colour which develops instantaneously on mixing the fungicide with the reagent is stable for at least 12 h. The method has been successfully adapted to the determination of captafol in its formulated products and residues on grains and apples.     

Determination of90Sr in soil and sediment using lithium-borate fusion and extraction chromatography

A rapid and reliable method for determination of⁹⁰Sr in soil and sediment has been developed. The method is based on lithium-borate fusion and extraction chromatography with a Sr-resin. The samples can be dissolved and separated for Sr in approximately 5 hours of which the fusion and dissolution requires 20 minutes. The method has been applied to four reference materials, two soils and two sediments, and the results agree well with the recommended values. The mean recovery of Sr was 71%.     

The extraction and spectrophotometric determination of niobium with tetraphenylarsonium chloride

A rapid and accurate spectrophotometric method for niobium is described. Tetraphenylarsonium chloride is used to form an aqueous insoluble ion-pair, tetraphenylarsonium thiocyanato-niobate, which upon extraction into 9:2 chloroformacetone solution has a molar absorptivity of 36,000/M/cm at 390 nm. Niobium is masked with fluoride before a separation step in which the interferences of molybdenum, tungsten, and iron are removed by reduction and extraction. Niobium is subsequently extracted after being demasked with boric acid. The method has been applied successfully to 3 NBS steels and 2 heat-resisting alloys.     

A generalized method for calculation and prediction of vapour-liquid equilibria at high pressures

A generalized method for prediction of vapour-liquid equilibria in hydrocarbon mixtures containing some nonhydrocarbon gases at high pressures has been developed following the approach of Chao and Seader (1961) and Lee et al. (1973). The method proposed is based on three equations: (1) a generalized equation of state for vapour phase calculations, (2) a generalized expression for the pure liquid fugacity coefficient suggested by Lee et al. (1973), and (3) an activity coefficient expression based on a surface modification of the regular solution model. The equations used contain only one partially generalized binary parameter, which has been evaluated from experimental K-value data. The method proposed has been tested by computing K-values and pressures in binary and multicomponent systems consisting of 13 hydrocarbons and three nonhydrocarbon gases. The results have shown that the proposed method can be applied over a wide range of conditions with a good degree of accuracy, which is comparable with that of more complicated methods.     

Colorimetric Determination of Terbutaline and Orciprenaline Through Nitration and Subsequent Treatment with Acetyl Acetone in Alkaline Medium

Abstract

A colorimetric method is proposed for the determination of terbutaline sulphate, orciprenaline sulphate and their dosage forms. The procedure is based on the formation of trinitroderivatives of the drug which are subsequently subjected to a charge transfer complexation reaction with a donor, acetyl acetone. Concentration ranges adhering to Beer's Law are 4–32 μg/ml for both. The proposed method has been applied to pharmaceutical preparations and has proven to be accurate and precise.     

Determination of cefotaxime and desacetylcefotaxime in plasma and urine by high-performance liquid chromatography

A high-performance liquid chromatographic method is described for the analysis of the anti-bacterial agent cefotaxime and desacetylcefotaxime in physiological fluids. Plasma or serum samples were mixed with chloroform--acetone to remove proteins and most lipid material. The aqueous phase was then freeze-dried, reconstituted in mobile phase and chromatographed on a reversed-phase column using UV detection at 262 nm. Urine was analysed directly after centrifugation to remove particulate matter. The detection limit was 0.5--1.0 micrograms/ml for serum and 5 micrograms/ml for urine. The method has been applied to the analyses of cefotaxime and desacetylcefotaxime in plasma, serum, urine, cerebrospinal fluid, saliva, and pus from infected wound secretions. Two additional metabolites, which are lactones in which the beta-lactam ring has been opened, could be separated by this method.     

Isolation and Recovery From Water of Selected Chlorophenoxy Acid Herbicides and Similar Weak Acid Herbicides by Solid-Phase Extraction HPLC and Photodiode Array Detection

Abstract

Solid-Phase Extraction (SPE) has been combined with High Performance Liquid Chromatography using a Photodiode Array Detector to isolate, recover and quantitate selected Chlorophenoxy acid herbicides, dicamba and dinoseb from spiked deionized water and a drinking water sample. Percent recoveries have been determined for spiked water and the precision for replicate SPEs has been determined. the capability of photodiode array detection in providing qualitative analysis and in increasing sensitivity via wavelength programming has been demonstrated. A method is proposed which eliminates non-polar matrix interferences. Recoveries for selected Chlorophenoxy acid herbicides were not influenced using this method.     

常温凝胶渗透色谱法分析C5加氢石油树脂的相对分子量及分布

通过凝胶渗透色谱（GPC）,采用普适校准法对C5加氢石油树脂的相对分子质量及分布进行测定.方法选取适合有效的小分子物质作为标准物质,测得样品的数均分子量约Mn=500,重均分子量约Mw=900。结果表明,方法不仅数据准确、可靠、重现性好,而且精密度高,绘出的图谱具有直观性,这对研究石油树脂的机械性能、流动性和成型加工性等有着极其重要的意义,为C5加氢石油树脂生产工艺提供了行之有效的分析方法。     

Multiple gamma-ray detection method and its application to nuclear chemistry

A new radionuclide quantification method is proposed on the basis of multiple gamma-ray detection, which is two or higher fold gamma-ray coincidence method. The coincidence method has so far been used for nuclear structure study. We apply this method for quantification of radioactive nuclei. The advantage of this method consists of high energy resolution and high sensitivity. It is successfully applied to nuclear waste analysis, neutron activation analysis and prompt gamma-ray analysis. The principle of the multiple gamma-ray detection method and future perspectives for an innovative pulsed neutron source and a new detector system will be presented.     

Size distribution analysis of polymer latex systems by use of extrema in the angular scattering intensity

The angular position of the extrema of the vertically polarized scattering intensity has previously been utilized for a method of particle size analysis for systems of monodisperse, spherical, isotropic particles which conform to the Rayleigh-Gans-Debye theory. The consequences of a finite polydispersity, which is always present in real systems, was not assessed and the application of the method has resulted in erroneous characterization of some latex systems. This work is concerned with (1) reporting the effects of finite polydispersity on the method of analysis, (2) pointing out previous misuse of the method, and (3) introducing a method of analysis which is based on the position of the extrema but which also considers polydispersity and the exact Mie calculation. This method enables one to characterize a scattering system in terms of a modal diameter and a distribution-width parameter by utilizing prepared diagrams for a particular relative refractive index.