A practical approach to the preparative purification of peptides using analytical instrumentation with analytical and semipreparative columns

Summary We have examined the effect of particle size of silica-based reversed-phase packings and column packing techniques on the reversed-phase analytical separation of a peptide mixture. A C₁₈ packing of 15–20 μm average particle size produced satisfactory peptide resolution, allowing a relatively inexpensive scale up to the preparative purification of peptides. A shallow gradient (0.1% acetonitrile/min) elution procedure was developed for the preparative purification of closely related decapeptides (differing by one methyl group) on analytical (250×4.1 mm I.D.) and semipreparative (250×10 mm I.D.) columns. Up to 30 mg and 225 mg of the two-peptide mixture was efficiently resolved, with high yields of homogeneous peptides, on analytical and semipreparative columns, respectively, containing the 15–20 μm packing. We have also demonstrated the potential of our purification procedure for resolving more complex multicomponent mixtures by efficiently separating a total of 22 mg of three closely-related peptides on analytical columns containing 7 μm or 15–20 μm particle size reversed-phase packings. The use of the inexpensive 15–20 μm packing, coupled with the ability to pack efficient columns with analytical HPLC instrumentation, offers great cost saving potential.     

Evaluation of the quality of clinical laboratories in the Slovak Republic: conceptual and contextual remarks

The paper demonstrates conceptual parallels and relationships between intellectual capital measurement methods and the evaluation of quality in clinical laboratories in the Slovak Republic. It explores further the contextual links of those parallels with the tangibility (or intangibility) of quality indicators of laboratory diagnostics. It also highlights the problems which laboratory staff in Slovakia are confronted with. Presented at the conference Quality in the Spotlight, March 2007, Antwerp, Belgium.     

高寒地区浅基础埋深问题

运用工程实例论述了影响高寒地区浅基础埋深的重要因素, 提出了基础埋深的具体计算方法。     

Structural modeling of beams on elastic foundations with elasticity couplings

A new simplified structural model and its governing equations for beams on elastic foundations with elastic coupling are proposed. This modeling system is simple but appropriate for the initial structural design of large-scale submerged floating-beam structures moored by tension legs spaced at uniform interval along the beam. The model is actually for beam on discrete elastic supports rather than on continuous elastic foundations. Therefore, the governing equations are based on finite difference calculus and solutions for beams on discrete elastic supports with elasticity coupling are also proposed. To clarify the applicability limit of the proposed model, the equivalence between a beam on discrete elastic supports and that on continuous elastic foundation is investigated by comparisons of characteristic solutions.     

文克勒地基上弹性薄板受有限长弹性杆冲击的动力分析

对具有初速的有限长弹性杆与文克勒地基上弹性薄板的冲击问题进行了研究，用伽辽金原理求出了冲击力及薄板位移响应的近似公式，并对计算结果作了分析讨论     

水泥土搅拌桩复合地基承载力公式中折减系数β取值的分析

水泥土搅拌桩复合地基承载力设计公式中的桩间土承载力折减系数 β值需根据经验确定,且取值范围较大。因此,要准确计算出复合地基承载力有一定难度。本文根据桩土共同作用机理,探讨了折减系数 β的各种影响因素。在比较研究了一些典型工程静载试验的实测资料之后,对系数 β的取值作了具体分析并给出了合理的建议值。     

独立学院数学课程体系的探索

为解决独立学院数学教学中能力强的学生"吃不饱",能力欠佳的学生"吃不消"的问题,提出了"基础+提高"统筹优化的数学课程体系."基础"模块的教学坚持为后续专业课服务,并穿插教书中"育人"理念;"提高"模块作为公共选修范畴,具有自主性、多元化特点,并突出人才培养的阶梯式发展.通过近5年的教学改革与实践,新课程体系有效地提高了学生学习数学的兴趣,降低了期末考试的不通过率,并造就一批有创新意识的人才.     

Effect of hydrogen doping in ZnO thin films by pulsed DC magnetron sputtering

This study examined the role of hydrogen impurities in highly oriented ZnO thin films. Hydrogen intentionally incorporated was found to play an important role as a donor in n-type conduction, improving the free carrier concentration. The increase in the conductivity of ZnO thin films was attributed to the two centers assigned to isolated hydrogen atoms in the anti-bonding sites as well as bond-centered interstitial hydrogen located between the Zn–O bonds and Zn vacancy passivated by one or two hydrogen atoms. Micro Raman spectroscopy showed two additional modes at approximately 501 and 573 cm⁻¹. These two peaks were attributed to damage to the crystal lattice, which could be explained by the optical-phonon branch at the zone boundary and host lattice defects, such as vacancy clusters, respectively.     

Meshing Requirements for Tidal Modeling in the Western North Atlantic

This paper presents an a posteriori approach to unstructured mesh generation via a localized truncation error analysis and applies it to the Western North Atlantic Tidal (WNAT) model domain. The WNAT model domain encompasses the Gulf of Mexico, the Caribbean Sea, and the North Atlantic Ocean east to the 60°W Meridian. Herein, we pay particular attention to the area surrounding the Bahamas.

A bathymetric data set with fine resolution is employed in seven separate linear, harmonic simulations of shallow water tidal flow for seven different tidal-forcing constituents. Each set of simulation results is used to perform a truncation error analysis of a linear, harmonic form of the depth-averaged momentum equations for each of the seven different tidal-forcing frequencies. Truncation error is then driven to a more uniform, domain-wide value by solving for local node spacing requirements. The process is built upon successful research aiming to produce unstructured grids for large-scale domains that can be used in the accurate and efficient modeling of shallow water flow. The methodology described herein can also be transferred to other modeling applications.     

A simple finite volume method for the shallow water equations

We present a new finite volume method for the numerical solution of shallow water equations for either flat or non-flat topography. The method is simple, accurate and avoids the solution of Riemann problems during the time integration process. The proposed approach consists of a predictor stage and a corrector stage. The predictor stage uses the method of characteristics to reconstruct the numerical fluxes, whereas the corrector stage recovers the conservation equations. The proposed finite volume method is well balanced, conservative, non-oscillatory and suitable for shallow water equations for which Riemann problems are difficult to solve. The proposed finite volume method is verified against several benchmark tests and shows good agreement with analytical solutions.