Messung der dynamischen Eigenschaften verdünnter Polymerlösungen

Zusammenfassung Ein neuartiges Rheometer zur Ermittlung der rheologischen Eigenschaften von Polymerlösungen im linear-viskoelastischen Bereich wird vorgestellt. Durch Anwendung der Laser-Doppler-Anemometrie, die eine im hydro-dynamischen Sinn störungsfreie Meßmethode darstellt, ist es möglich, niedrig-viskose bis hin zu wasserähnlichen Proben zu vermessen.Zur Bewältigung der in großer Zahl anfallenden Daten und Rechenoperationen findet ein Mikrocomputer-System Verwendung. Es erledigt im einzelnen die Aufgaben Versuchsablauf-Steuerung, Meßwerterfassung, Auswertung, Dokumentation und graphische Darstellung der Ergebnisse.Anhand von Messungen an newtonschen Flüssigkeiten werden der Funktionsnachweis erbracht und die Betriebsbereiche der Ringspaltsysteme unterschiedlichen Durchmessers ermittelt.Die viskoelastischen Eigenschaften von wäßrigen Polyethylenoxid- und Polyacrylamid-Lösungen niedriger Viskosität lassen sich über einen Frequenzbereich von 0,1 bis 100 Hz messen. Die Ergebnisse werden mit Hilfe der komplexen Viskositätsfunktion dargestellt. Daraus läßt sich als gleichwertige Darstellung das diskrete Relaxationsspektrum eines konkreten Stoffgesetzes gewinnen.

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A novel rheometer for determining the elastic characteristics of polymeric solutions in the linear-viscoelastic region is described. Laser-Doppler anemometry, which does not introduce hydrodynamic disturbances, is used to enable low viscosity liquids including water-like samples to be measured.A microcomputer system is utilized to control the experiments, store and analyse the measured data, and provide graphical representations of the results. Measurements on Newtonian liquids verified the validity of the method and allowed the operational regions of the annulus systems with different diameters to be determined.The elastic characteristics of low viscosity aqueous solutions of polyethyleneoxide and polyacrylamide can be measured at frequencies from 0.1 to 100 Hz. The results are presented using the complex viscosity function. As a result the discrete relaxation spectrum of a special material law can be obtained as an equivalent representation.

     

Synthesis and Anti‐HIV Activity of Triazolo‐Fused,Medium‐Sized Cyclic Nucleoside Analogs Prepared by an Intramolecular Huisgen 1,3‐Dipolar Cycloaddition

Medium‐sized cyclic nucleosides containing a fused triazole ring were synthesized via intramolecular Huisgen 1,3‐dipolar cycloadditon reaction. 2′,3′‐seco‐Uridine was employed as the key intermediate for the introduction of azido and alkynyl moieties in the defined positions of the reaction precursors. The cycloaddition reactions were achieved in high yields by heating the precursor in refluxing toluene. The uracil base in these target compounds was successfully transformed to the corresponding cytosine. The synthesized compounds were evaluated in a MAGI assay for their anti‐HIV activities, and in a H9 T lymphocytes assay for their cell toxicities.     

Electrochemical detection of ultratrace nitroaromatic explosives using ordered mesoporous carbon

A sensitive electrochemical sensor has been fabricated to detect ultratrace nitroaromatic explosives using ordered mesoporus carbon (OMC). OMC was synthesized and characterized by scanning electron microscopy, transmission electron microscopy and nitrogen adsorption/desorption measurements. Glassy carbon electrodes functionalized with OMC show high sensitivity of 62.7 μA cm⁻² per ppb towards 2,4,6-trinitrotoluene (TNT). By comparison with other materials such as carbon nanotubes and ordered mesoporous silica, it is found that the high performance of OMC toward sensing TNT is attributed to its large specific surface area and fast electron transfer capability. As low as 0.2 ppb TNT, 1 ppb 2,4-dinitrotoluene and 1 ppb 1,3-dinitrobenzene can be detected on OMC based electrodes. This work renders new opportunities to detect ultratrace explosives for applications of environment protections and home securities against chemical warfare agents.     

Impact of sugar stereochemistry on natural killer T cell stimulation by bacterial glycolipids

Natural killer T (NKT) cells recognize glycolipids produced by Sphingomonas bacteria, and these glycolipids contain C6-oxidized sugars, either glucuronic acid or galacturonic acid, linked to ceramides. Glycolipids with gluco stereochemistry are the most prevalent. Multiple studies have demonstrated that galactosylceramides are more potent stimulators of NKT cells than their glucose isomers. To determine if this stereoselectivity is retained in the context of the C6-oxidized sugars found in bacterial glycolipids, we prepared two sets of gluco and galacto-glycolipids oxidized at their C6 positions and compared their NKT stimulatory properties. In the context of carboxylic acid groups at C6, gluco stereochemistry gave the more potent responses. We also prepared bacterial glycolipids containing more complex ceramide groups to determine if these chains impact NKT cell responses.     

n阶三圈图的补图的谱半径

三圈图是边数等于顶点数加2的简单连通图.在所有n阶三圈图的补图中,哪一个的谱半径最大?文中给出了n阶三圈图的补图的谱半径的上界,并刻画了唯一的达到该上界的图.     

Pharmacokinetic Study of ZS-1, a Targeted Peptide to NCI-H1299, in Rats Following Intravenous Administration

To investigate the pharmacokinetics of ZS-1 following intravenous injection in rats, ZS-1 was administered at doses of 20, 30 and 45 mg kg^?1, respectively. Blood samples were collected at 0.5, 3, 8, 12, 15, 20, 30, 40 and 45 min. ZS-1 in rat plasma was measured by LC. The limit of detection (LOD) was 0.02 μg mL^?1. The relative standard deviation (RSD) of intra- and inter-day precisions were <10%, and the accuracy of intra- and inter-day were >94%. The mean extraction recovery of ZS-1 was 86.1%. After intravenous injection at doses of 20, 30 and 45 mg kg^?1, the concentration–time curves of ZS-1 fitted well to one compartment model. Area under the concentration–time curves (AUC) increased with dose. Clearance rates (CL) and elimination half-lives (T _1/2) had no significant difference between different dose groups (P > 0.05). ZS-1 was stable in plasma after at 25 °C for 2, 4, 6 h, after three freeze–thaw cycles, after ?20 °C for a month, and after ?80 °C for 3 months. The accuracy of ZS-1 was between 96.8 and 106.9%. The results indicated there was no significant degradation. These data indicated that the method for analysis of ZS-1 was reliable and the pharmacokinetic data could guide dosing regimens to be tested in future clinical pharmacokinetic study.     

Organic dye bearing asymmetric double donor-π-acceptor chains for dye-sensitized solar cells

A novel efficient metal free sensitizer containing asymmetric double donor-π-acceptor chains (DC) was synthesized for dye-sensitized solar cells (DSSCs). Comparing to 3.80%, 4.40% and 4.64% for the DSSCs based on the dyes with single chain (SC1, SC2) and cosensitizers (SC1 + SC2), the overall conversion efficiency reaches 6.06% for DC-sensitized solar cells as a result of its longer electron lifetime and higher incident monochromatic photon-to-current conversion efficiency.     

Precursor-directed fungal generation of novel halogenated chaetoglobosins with more preferable immunosuppressive action

Precursor-fed cultivation of endophytic Chaetomium globosum 1C51 afforded nine novel "unnatural" halogenated chaetoglobosins including those with more preferable immunosuppressive activity.     

基于无网格Galerkin法的穿甲侵彻数值模拟

将无网格Galerkin法与LS-DYNA软件相结合,建立了穿甲侵彻的分析模型,对三维球形弹体侵彻双层无限大钢靶板进行了数值模拟,解决了该过程中出现的负体积现象,并将结果与空穴膨胀理论和有限元法进行了对比,所得结果证实了无网格Galerkin法在模拟穿甲侵彻时的可行性与优越性.     

离子束辅助沉积对类金刚石膜结构影响的计算机模拟

采用分子动力学(MD)模拟研究了离子束辅助沉积(1BAD)生长类金刚石(DLC)膜的物理过程.分 别选C₂分子和Ar离子作为沉积源和辅助沉积粒子.改变Ar的入射能量和到达比(A r／C)，研 究了它对DLC膜结构的影响.重点讨论了Ar辅助沉积引起表面原子的瞬间活性变化对薄膜结构 产生的影响.分析表明，由于Ar离子的轰击引起的能量和动量的传递，大大地增强了C原子在 表面的反冲动能及迁移概率，增加了合成薄膜的SP³键含量.研究结果和实验 观察一致，并从合成机理上给出了一些定量解释. 关键词： 类金刚石膜 离子束辅助沉积 分子动力学模拟