Resolution of binary mixtures of cephalothin and clavulanic acid by using first derivative spectrophotometry

First-derivative spectrophotometric method with a “zero-crossing” technique of measurement has been used for the quantification of two-components mixtures of cephalothin and clavulanic acid. As the absorption bands of these drugs overlap, both direct and derivative spectrophotometric methods have been investigated and evaluated by a rigorous statistical analysis of the experimental data. The first-derivative spectrophotometric method was found to be more accurate, direct and reproducible. Beer's law was valid over the concentration range 2.0–28.0 mg/l for both compounds. The detection limits of cephalothin and clavulanic acid, at a 0.05 level of significance, were calculated to be 0.13 and 0.15 mg/l. The method was applied for determining these antibiotics in mixtures, some of them containing inject-able dosage forms of cephalothin, and so to determine both compounds in saline and glucosed physiological sera.     

Synthesis and Crystal Structure of Di-n-butyltin(IV) Complex with 2-Oxo-propionic Acid (4-Pyridinecarbonyl) Hydrazone

Introduction The studies of diorganotin(IV) complexes are of current interest owing to their wide range of applica-tions such as biocides and homogeneous catalysts in industry.1 In recent years there have been more and more reports on the synthesis, antitumour activities and structural elucidation of various diorganotin(IV) deriva-tives of carboxylic acid.2-5 In particular, people take considerable interest in structural studies of diorgano-tin(IV) complexes of carboxylic acid, because there…     

Formulation of N- and ν-representable density functional theory. V. Exchange-only self-consistent field

The concept of a self-consistent field is developed within the version of density functional theory based on local-scaling transformations. It is shown that in this context there arise two types of consistency: one relating to the charge-consistency within an orbit and another to “orbit jumping.” The latter is analyzed in terms of one-particle equations. The connection with other methods is discussed. © 1992 John Wiley & Sons, Inc.     

Local solution for the Kadomtsev-Petviashvili equation with periodic conditions

In this article we prove a local existence and uniqueness theorem for the Kadomtsev-Petviashvili Equation (u _t +u _xxx +uu _x ) _x −u _yy =0) in the Sobolev spaces of orders≥3, with initial values in the same spaces, and periodic boundary conditions. This theorem improves previous results based upon the application of singular perturbation techniques.     

Schiff碱水杨醛苯甲酰腙的特性

研究了 Schiff碱水杨醛苯甲酰腙 (简称 SBH)晶体在 DMSO及其 DMSO- H2 O的混合溶剂中的红外光谱 ,通过 SBH氘代前后的 IR对比发现 ,羟基氢质子与混合溶剂 DMSO- H2 O(3∶ 1 ,V/ V)产生较大的相互作用。向溶有 SBH的 75 % DMSO- 2 5 % H2 O的溶液滴加 KOH发现 ,SBH分子上的 C O羰基基团先与 KOH作用 ,其后与 O H 羟基基团作用     

利用电泳技术在不锈钢和铁基底上制备MgB2带材

本文首次报道了利用电泳技术在铁和不锈钢基底上制备MgB2超导带材.电阻测量表明,沉积在铁和不锈钢基底上MgB2带材的超导零电阻转变温度分别为37.5K和31K,超导转变宽度分别为0.3K和1K.磁测量表明,(5K,OT)时不锈钢基底上带材的临界电流密度为6×105(A/cm2).X射线衍射谱和扫描电子显微镜图象表明样品结晶良好,晶粒生长致密.本工艺制备MgB2带材时不受系统真空度的限制,生长迅速,成本低廉,并且可以根据不同的需要任意选择基底的形状和大小.     

S-烯丙基硫赶磷酸酯在SiO2上的合成

探讨了O 烯丙基硫逐磷酸酯热重排制备S 烯丙基硫赶磷酸酯的反应条件 ,结果表明 :反应在SiO2 上进行几乎可定量地完成 .运用这一合成方法 ,制备了 14个不对称结构的新型硫赶磷酸酯 ,所有的化合物均经IR ,1HNMR ,3 1PNMR及元素分析表征 .生物活性试验显示 5a ,5e ,5h ,5i及 5k有良好的杀虫活性 .     

Inorganic Sol-Gel Preparation of Medium Sized Microparticles of Li2TiO3 from TiCl4 as Tritium Breeding Material for Fusion Reactors

Microspheres of Li₂TiO₃ were fabricated by a classical, inorganic sol-gel process from commercially available TiCl₄. Elaborated process consists of the following main steps: (1) dissolving of TiCl₄ in concentrated aqueous HCl and addition of LiOH; (2) formation of sol emulsion in 2-ethylhexanol-1 containing the surfactant SPAN-80 (EH); (3) gelation of emulsion drops by extraction of water with partially dehydrated EH; (4) impregnation of gel to Li:Ti molar ratio MR = 2; (5) thermal treatment at 1200°C in order to receive chloride free product. This temperature can be significantly lowered (to 750°C) by dechlorination starting solution TiCl₄ by chemical treatment of the with nitric acid to form of nitrate-stabilized titania sols. Tritium release from sol-gel made Li₂TiO₃ microspheres were found very close to that observed for other traditional materials, however for the first sample process starts slightly earlier.     

Testing goodness of fit for the distribution of errors in multivariate linear models

In this paper, to test goodness of fit to any fixed distribution of errors in multivariate linear models, we consider a weighted integral of the squared modulus of the difference between the empirical characteristic function of the residuals and the characteristic function under the null hypothesis. We study the limiting behaviour of this test statistic under the null hypothesis and under alternatives. In the asymptotics, the rank of the design matrix is allowed to grow with the sample size.     

Textural changes during CO2 activation of chars: A fractal approach

In this paper two series of active carbons obtained at different flow rates of the activating agent, CO₂, are characterized in order to establish the different mechanisms of pore development during the activation step. This study complements previous works on textural development during the different steps in the process of obtaining active carbons: coal oxidation, coal pyrolysis and char gasification. As the characteristics of the original and intermediate materials are of capital importance in the pore development of active carbons, the properties of the active carbons, precursor chars and coals were considered and analyzed together. Mercury porosimetry and helium picnometry were used to determine classical textural parameters as well as to perform a more detailed study of the pore volume generation during the different conditions of the activation step. Data obtained from the mercury porosimetry determinations was also employed for fractal determinations according to the methodologies proposed by Friesen and Mikula, Zhang and Li and the procedure of Neimark. Average surface fractal dimensions as well as fractal profiles and local surface fractal dimensions were calculated. The use of different flow rates during the activation step produces changes not only in the ordinary textural parameters but also in the fractal characteristics of the active carbons. Activation at higher flow rates leads to smoother fractal profiles and also to lower values of the average surface fractal dimensions of the active carbons.