Solid phase synthesis of hydantoins by thermal cyclization and screening of reaction conditions using APOS 1200

A novel strategy for solid-phase synthesis of hydantoins with highoptical purity is described using a thermal pH-neutral cyclization and simultaneous release from resin. Hereby even hydantoins bearinga pH-sensitive side chain (protection) are available. The reaction conditions are well screened applying the parallel organic synthesizerAPOS 1200.     

Evaluation of Automated ECG Monitoring: Theoretical Model Based upon Point Process Techniques

The development of practical methods of ECG monitoring using dedicated computers has presented problems in the evaluation and comparison of the relative effectiveness of various ECG monitoring systems. A theoretical model based on the application of point process techniques is discussed in this paper.     

Achieving the full performance of highly efficient columns by optimizing conventional benchmark high-performance liquid chromatography instruments

A series of experiments and measurements demonstrate the importance of minimizing the extra-column band broadening contribution of the instrument used. The combination of several measures allowed the achievement of the full potential efficiency of three Kinetex-C₁₈ columns, using a conventional liquid chromatograph. The first measure consists in minimizing the extra-column volume of the instrument, without increasing much its back pressure contribution, by changing the needle seat volume, the inner diameter and length of the capillary connectors, and the volume of the detector cell of a standard instrument (Agilent 1100). The second measure consists in injecting a volume of weak eluent (less than half the elution strength of the mobile phase) right after the sample, before the sample had time to reach the column. Experimental results show that these changes could provide most of the resolution expected from the true column performance. After the changes were made, the resolutions of the 2.1 mm ×$\times$ 50 mm, 4.6 mm ×$\times$ 50 mm, and 4.6 mm ×$\times$ 100 mm Kinetex-C₁₈ columns for compounds having retention factors close to 1 were increased by about 180, 35, and 30%, respectively. The resolutions obtained are then similar to those measured with advanced instruments like the Agilent 1200, the Agilent 1290 Infinity HPLC, and the Acquity chromatographs.     

Highly sensitive capillary electrophoresis-mass spectrometry for rapid screening and accurate quantitation of drugs of abuse in urine

The combination of capillary electrophoresis (CE) and mass spectrometry (MS) is particularly well adapted to bioanalysis due to its high separation efficiency, selectivity, and sensitivity; its short analytical time; and its low solvent and sample consumption. For clinical and forensic toxicology, a two-step analysis is usually performed: first, a screening step for compound identification, and second, confirmation and/or accurate quantitation in cases of presumed positive results. In this study, a fast and sensitive CE-MS workflow was developed for the screening and quantitation of drugs of abuse in urine samples. A CE with a time-of-flight MS (CE-TOF/MS) screening method was developed using a simple urine dilution and on-line sample preconcentration with pH-mediated stacking. The sample stacking allowed for a high loading capacity (20.5% of the capillary length), leading to limits of detection as low as 2 ng mL⁻¹ for drugs of abuse. Compound quantitation of positive samples was performed by CE-MS/MS with a triple quadrupole MS equipped with an adapted triple-tube sprayer and an electrospray ionization (ESI) source. The CE-ESI-MS/MS method was validated for two model compounds, cocaine (COC) and methadone (MTD), according to the Guidance of the Food and Drug Administration. The quantitative performance was evaluated for selectivity, response function, the lower limit of quantitation, trueness, precision, and accuracy. COC and MTD detection in urine samples was determined to be accurate over the range of 10–1000 ng mL⁻¹ and 21–1000 ng mL⁻¹, respectively.     

Biased detection of guanine-rich microRNAs by array profiling: Systematic error or biological phenomenon?

This article describes an unexpected phenomenon which was revealed during the study of microRNA expression profiles of breast tumors. Hierarchical clustering has distinguished two broad groups of microRNAs with different expression patterns. One of these groups, Group Q (“questionable”), was composed mainly of recently discovered microRNAs and contained a large number of viral microRNA species. This microRNA subset was found to be extremely rich in guanine. The above features suggest that the Group Q is an artifact of microRNA expression profiling. However, the latter explanation is not supported by the evidence for biologically relevant associations observed for the Group Q microRNAs.     

Two novel C18-diterpenoid alkaloids,sinomontadine with an unprecedented seven-membered ring A and chloride-containing sinomontanine N from Aconitum sinomontanum

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Membrane transport of dicarboxylic and α-hydroxy carboxylic acids induced by α-amino phosphonates

New -amino phosphonates containing different alkyl and aryl substituents at the -carbon atom were synthesized in high yields by the Kabachnik—Fields and Pudovik reactions. These compounds were studied as carriers of several -hydroxy carboxylic and dicarboxylic acids through liquid impregnated membranes. These -amino phosphonates studied are capable of molecular recognition of oxalic acid among structurally similar -hydroxy carboxylic and dicarboxylic acids. The efficiency and selectivity of mass transfer of oxalic acid increase with an increase in the lipophilicity of the -amino phosphonate.     

基于C#的交流异步电机测试与分析系统开发

针对电机出厂前需进行测试分析这一情况,利用C#语言,开发了一套交流异步电机测试与分析系统。首先,介绍了系统总体结构;其次,给出了系统通讯设计,详细说明了西门子S7-1200PLC与上位机的以太网通讯,及与各测试仪表之间的RS485通讯的具体实现方式;然后根据国标GB/T1032-2012,开发了交流异步电机测试与分析系统,给出了系统功能和数据库设计方法;最后通过测试实例,说明了该系统的实用性和有效性。