Theoretical analysis of the onset of liquid entrainment for slots of finite width

The onset of liquid entrainment during discharge from large reservoirs containing a stratified mixture of two immiscible fluids through a side slot of a finite width is considered theoretically. A previously reported analysis in which the slot was approximated as a two-dimensional line sink has been extended to account for the finite width of the slot. The model resulting from the present analysis is expressed in terms of two simple algebraic equations suitable for hand calculations. According to the present results, the ratio of the critical height to the slot width is dependent only on the Froude number. Numerical results show that the present model approaches the correct physical limits at low Froude numbers and it converges to the predictions of the previously reported simple model at high Froude numbers.     

炉液倾动重心近似计算的数学分析

为给转炉设计提供依据,需要计算炉液倾动的重心.利用数学方法将实际问题进行简化,通过分析炉液倾动过程中变量间的相互关系,来确定每个倾动角度对应情况下的液面位置.利用数学中三重积分的有关应用,进一步得出转炉在每个倾动角度为α∈(0,π2)时的重心计算方法及相关结论,在理论上为工程计算重心的方法提供参考.     

Characterization of reduced iso‐α‐acids derived from hops (Humulus lupulus) by NMR

Reduced forms of iso‐α‐acids (isohumulones), used in modern beer brewing were separated and characterized by ¹H and ¹³C NMR spectroscopy. Components from mixtures of rho‐iso‐α‐acids, tetrahydro‐iso‐α‐acids, and hexahydro‐iso‐α‐acids were isolated using high‐performance liquid chromatography (HPLC) and analyzed by use of one‐ and two‐dimensional NMR experiments. The data presented assign the identities of the main peaks in the HPLC traces for the reduced iso‐α‐acids. Previous tentative assignments regarding the cis and trans configurations and the structures of the acyl residues of the reduced iso‐α‐acids were confirmed and extensive NMR assignments were made. Furthermore, the previously unknown stereochemistry in the C‐4 side‐chain of the rho‐ and hexahydro‐iso‐α‐acids was assigned. Copyright © 2003 John Wiley & Sons, Ltd.     

液态铅的电阻率

采用精确的结构因数实验数据和Ｂｅｈａｖｉ模型赝势，用Ｚｉｍａｎ理论计算了液态铅的电阻率．计算结果和实验数据符合很好．讨论了Ｚｉｍａｎ理论对液态铅的适用性以及适合于液态铅的赝势的特征．     

高压下液态Ag-20 at%Ge合金的凝固及密排六方亚稳相的形成

 利用高压淬火方法，在液态Ag-20at%Ge合金的凝固过程中，对比液态急冷低四个数量级的冷却速率得到了单相密排六方结构亚稳相，其点阵参数为a=0.289 8 nm，c=0.470 8 nm，c/a=1.625。     

The method of concentrating a substance from a solution in a stationary sorbent layer and its theoretical basis

The principle of concentrating a substance from a mixture flow in a stationary sorbent layer of infinite length that was previously developed for gas chromatography is extended to liquid chromatography. Translated fromIzevestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1063–1065, May, 1997.     

Two new asterosaponins from the starfish Asterias rubens: application of a cryogenic NMR probe head

We report two new asterosaponins from the Baltic starfish Asterias rubens along with their ¹H and ¹³C NMR data. The compounds were isolated after on‐flow liquid chromatography–NMR–mass spectrometry screening indicated that they had not been identified before. The one‐ and two‐dimensional NMR experiments used to elucidate the structures were recorded using a 5 mm cryogenic probe head. The advantages of cryogenic probes for this kind of examination in comparison with conventional probe heads are discussed. Copyright © 2003 John Wiley & Sons, Ltd.     

High-Throughput Screening of Ten Microcystins and Nodularins, Cyanobacterial Peptide Hepatotoxins, by Reversed-Phase Liquid Chromatography-Electrospray Ionisation Mass Spectrometry

Liquid chromatography-electrospray ionisation mass spectrometry was evaluated in the high-throughput analysis of microcystins and nodularins, cyanobacterial peptide hepatotoxins. Extracts originating from cyanobacterial strains and field material were separated on a 30 mm × 4 mm I.D. Merck Purospher STAR RP-18e column using a rapid gradient of aqueous formic acid and acetonitrile, ionised by electrospray technique and analysed on a Micromass Quattro II triple-quadrupole mass spectrometer operated in the selected ion recording (SIR) mode. The total analysis time per sample was 2.8 min corresponding to 514 samples a day. The system showed good robustness during a series of 320 repetitive injections of a field sample containing three major microcystins.     

液态泡沫结构及其稳定性

液态泡沫由大量气泡密集堆积在少量的表面活性剂溶液中形成，是具有高度自组织结构的典型的软物质．文章从泡沫物理学角度简要介绍了液态泡沫的结构特征和稳定性方面的研究．