PARALLEL AUXILIARY SPACE AMG FOR H（curl） PROBLEMS

In this paper we review a number of auxiliary space based preconditioners for the second order definite and semi-definite Maxwell problems discretized with the lowest order Nedelec finite elements. We discuss the parallel implementation of the most promising of these methods, the ones derived from the recent Hiptmair-Xu （HX） auxiliary space decomposition [Hiptmair and Xu, SIAM J. Numer. Anal., 45 （2007）, pp. 2483-2509]. An extensive set of numerical experiments demonstrate the scalability of our implementation on large-scale H（curl） problems.     

Convergent approaches for the synthesis of the antitumoral peptide, Kahalalide F. Study of orthogonal protecting groups

Kahalalide compounds are peptides that are isolated from a Hawaiian herbivorous marine species of mollusc, Elysia rufescens, and its diet, the green alga Bryopsis sp. Kahalalide F and its synthetic analogues are the most promising compounds of the Kahalalide family because they show antitumoral activity. Linear solid-phase syntheses of Kahalalide F have been reported. Here we describe several new improved synthetic routes based on convergent approaches with distinct orthogonal protection schemes for the preparation of Kahaladide analogues. These strategies allow a better control and characterization of the intermediates because more reactions are performed in solution.     

Influence of the Operative Conditions on the Characteristics of Poly(D,L-lactide-co-glycolide) Synthesized in Supercritical Carbon Dioxide

Summary: The co-polymerizations of D,L -lactide and glycolide in supercritical carbon dioxide (scCO₂) using zinc (II) ethylhexanoate (ZnOct₂) as catalyst and methanol as initiator have been investigated. The influence of stirring rate (N), temperature (T), and mass carbon dioxide (m_CO2) on molecular weight distribution (MWD); co-polymer composition; and conversion has been studied by means an experimental factorial design. The stirring rate has the greatest influence on conversion. Due to the heterogeneous nature of the process the mass transfer enhancement, that the grater turbulence produces, favors greatly the incorporation of monomers into the polymer phase. An important decrease of molecular weight is observed independently of reaction conditions for high conversion values because some thermal degradation or rearrangement reactions are taking place. The influence of the initiator, methanol, on the molecular weight has been also studied. Methanol acts as an effective chain transfer agent initiating more growing chains than expected, what also contributes to get low molecular weights.     

Straightforward synthesis of indolizidine alkaloid 167B

The synthetic access to indolizidines, substituted in C-5 position, was reported with good diastereoselectivity. The strategy developed was based on a key step of Michael addition associated with a Clauson-Kaas condensation.     

Corrosion reaction of iron exposed to the open atmosphere in the Antarctic

Within a cooperative program for the elaboration of a Latin American Map of Atmospheric Corrosion, weathering steel and mild steel samples were exposed to the Antarctic atmosphere and the corrosion products analyzed by ICEMS, XPS and XRD. Superparamagnetic -FeOOH was the main corrosion product after 24 h of exposure. Cl^– ions are found on the surface of the corroded samples by XPS.     

Colorimetric determination of iron in infant fortified formulas by sequential injection analysis

 A procedure is described for the colorimetric determination of iron in infant fortified formulas based on sequential injection analysis (SIA). Iron(III) complexation with thiocyanate is used as colour developing reaction. The system enables the determination of iron in the samples (after digestion by dry ashing and treatment with 0.2 mol/L nitric acid in the range of 0.50–20.0 mg/L, consuming 140 μL of the sample and 8 mg thiocyanate per determination. The reactor geometry and the adjustment of the ionic content of the calibration solutions is important for the accuracy of the results. A regression line according to the equation [Fe(III) (mg/L)]_SIA=−0.3(±0.4)+1.03(±0.04) [Fe(III) (mg/L)]_FAAS was obtained after comparative analysis of a set of 12 samples. The measurement rate was 34 s, thus allowing to analyze 100 samples per hour with a relative standard deviation lower than 2%. Received: 30 July 1996/Revised: 1 October 1996/Accepted: 4 October 1996     

YBa2Cu3Ox超导体的光谱研究

能带是决定固体特性的头等重要的因素。我们用光谱方法对单相YBa₂Cu₂O_x高T。超导体进行了研究,测量了样品的反射-吸收谱、Raman光谱和荧光光谱.其350和500nm吸收带以及390nm,560nm荧光峰来自晶格中Cu⁺发光中心,是跃迁过程¹A_1g(3d¹⁰)-¹E_g和~3E_g(3d⁹4s¹)。其720nm和860nm荧光峰来自Cu²⁺发光中心,是由于自由离子光谱项²D在八面体晶场、正交晶系晶场中分裂为5个能级之间的跃迁。此外,还有一些光谱可能来自晶格中Cu³⁺发光中心,其481cm^-1和551cm^-1声子对说明了312cm^-1处声子对与电子系统是强耦合。     

相对论性核与乳胶(Ag)碰撞中灰粒子的系统研究 *

用描写相对论性核 核碰撞的LUCIAE模型和相应的事件产生器系统地研究了 1 4.6 ,6 0和 2 0 0AGeV的O核、2 0 0AGeV的Si和S核以及 1 1 .6AGeV的Au核与乳胶 (Ag)碰撞中灰粒子产生的平均多重数、多重数分布以及角分布 3个物理量同入射能量、射弹质量及碰撞中心度间的关系 ,还研究了再散射在灰粒子产生机制中的作用 .LUCIAE的这些研究结果与相应的EMU0 1乳胶实验结果都相一致 .