Properties and structures of porphyrexides

The molecular and crystal structures of porphyrexides, viz., 4-amino-2-imino-(1) and (Z)-2-amino-4-bromoimino-5,5-dimethyl-4,5-dihydro-1H-imidazole 1-oxyls (7), and their diamagnetic precursors were determined. Compound 1 is kinetically unstable because it is oxidized with atmospheric oxygen to form (E)-1,2-bis[1-amino-1-(cyanoimino)-2-methyl-propan-2-yl]diazene 1,2-dioxide. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 441–447, March, 2006.     

Comparative Evaluation of CE and HPLC for Determination of Cotinine in Human Urine

Two rapid and popular methods—capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC) have been compared for analysis of cotinine in human urine. Cotinine was analyzed in less than 7 min, with detection limits of 5 and 3.2 ng mL⁻¹ for CE and HPLC, respectively. The performance of the methods was evaluated in terms of sensitivity, specificity, precision, accuracy, and limits of detection and quantification. Calibration plots were linear in the range 50–4,000 ng mL⁻¹, at least, and mean recoveries were satisfactory for both techniques. The methods were successfully used for quantification of cotinine in urine.     

Reduction of Chemical Reactions in Nitrogen and Nitrogen–Hydrogen Plasma Jets Flowing into Atmospheric Air

The large number of possible chemical reactions represents a severe burdenfor modeling of even relatively simple plasma systems. Reduced sets ofchemical reactions have been obtained for numerical simulations of nitrogenand nitrogen-hydrogen plasma jets flowing into an atmospheric airenvironment. The important or active reactions are determined based on asimplified reduction method. A reaction is considered active if it leadsto higher sensitivities than a specified cutoff sensitivity of 1%. Theactive reactions exert a significant influence on main plasma parameters,such as velocity, temperature, and species concentrations. The sensitivityanalysis for the specified systems shows that two NO reactions, known asZel'dovich reactions (N₂+ONO+N andNO+OO₂+N),⁽¹⁾ are both active in a nitrogenplasma jet. On the other hand, the latter is not active and may be omittedin a nitrogen–hydrogen plasma jet. A nitrogen–hydrogen plasmajet requires contribution of two active charge exchange reactions:N₂+N⁺N⁺ ₂+N andN+H+N+ +H, while only the former is needed in a nitrogen plasmajet. The dissociation reactions are all active in both plasma jets, exceptthe dissociation of OH.     

Synthesis, characterization and antifungal activity of copper (II) complexes of sterically hindered o-diphenol derivatives

Cu (II) complexes with 3,5-di(tert-butyl)-1,2-benzenediol (I), 4,6-di(tert-butyl)-1,2,3-benzentriol (II) and sulfur-containing sterically hindered o-diphenol derivatives such as 4,6-di(tert-butyl)-3-(2-hydroxyethylsulfanyl)-1,2-benzenediol (III) and 2-[4,6-di(tert-butyl)-2,3-dihydroxyphenylsulfanyl]acetic acid (IV) have been synthesized and characterized by means of elemental analysis, TG/DTA, FT-IR, ESR, XPS, XPD and conductivity measurements. Antifungal activities of these ligands and their respective Cu (II) complexes have been determined against Aspergillus niger, Fusarium sp., Penicillium lividum, Mucor sp. and Botrytis cinerea. Most of the compounds (both the free ligands and the complexes) exert pronounced antifungal activities (RI  70%), and virtually all of them (apart from the Cu(L^II)₂ complex) have the highest inhibitory properties (RI = 100%) against B. cinerea.     

Preservation of sensitive CRMs and monitoring their stability at IRMM

Over the years, the nature of CRMs has changed considerably. Recently, more and more CRMs have been certified in their "natural" form, that is processed as little as possible, with analytes at their natural concentration level. This and the trend towards certified properties other than the concentrations of clearly defined molecules/elements have made guaranteeing stability of CRMs and estimating a shelf life an even more important issue for reference material producers than it has been before. One way to meet this challenge is to take more care in processing, storage and dispatch of CRMs. At IRMM, approximately 20 % of the RMs are stored at –20 °C or below and about 10% require cooled transportation. In addition, increased efforts for assessing stability are needed. Shelf lives are estimated using addition of an uncertainty component based on real-temperature stability studies rather than by accelerated stability studies. These pre-certification efforts are complemented by a stability-monitoring program, which at IRMM includes 80 % of the non-nuclear and non-isotopic materials. Although the costs for these efforts are high in absolute terms, they are only a minor and indispensable contribution to the total costs of CRM production.     

Synthesis, structure, and electrochemical properties of 12,42-dioxo-21,31-diphenyl-7,10,13-trioxa-1,4(3,1)-diquinoxalina-2(2,3),3(3,2)-diindolizinacyclopentadecaphane

The oxidative dehydrocyclization of the 3-(indolizin-2′-yl)-2-oxoquinoxaline monopodand performed either electrochemically or under the action of molecular iodine affords new redox-active heterocyclophane consisting of the redox-switchable biindolizine fragment combined with the polyether-bridged π-deficient quinoxaline systems. The single-crystal X-ray diffraction study showed that the trioxaundecane chain of heterocyclophane adopts an extended conformation, and one of the phenyl substituents of the molecule closes the pseudocavity formed by the spacer from one of the sides. The cyclic voltammetric study of heterocyclophane in MeCN and DMF showed the three-step oxidation of the indolizine fragments accompanied by the single-electron transfer in each step. The first and third steps are reversible, and the second step is irreversible. The oxidation at potentials of the first peak gives rise to stable radical cations detected by the ESR method (g = 2.0024, a _2N = 0.26 mT). Dedicated to Professor E. A. Berdnikov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1991–2003, October, 2007.     

A differential microcalorimetric study of whey proteins and their behaviour in oil-in-water emulsions

Oil-in-water emulsions (20% soya oil, 1% protein) have been prepared containing lysozyme or isolates of -lactalbumin and β-lactoglobulin from whey protein. The structural characteristics of these proteins adsorbed at an oil/water interface were determined by following their thermal transitions using differential scanning microcalorimetry. Thermograms of the proteins in the adsorbed state differed markedly from the corresponding transitions seen for the proteins in solution. This suggests that the proteins underwent substantial changes in secondary and tertiary structure upon adsorption. In general, for all the proteins studied, a net decrease in the total energy absorbed during denaturation was found when the proteins were in an adsorbed state. Both lysozyme and -lactalbumin were in part “surface denatured”, and they showed a certain degree of reversibility between solution and the adsorbed state. β-Lactoglobulin showed the highest degree of denaturation upon adsorption and the conformational change was irreversible.     

组合桥面板疲劳荷载后剩余承载力试验研究

为了研究高性能混凝土组合桥面板经历疲劳荷载后的剩余承载力,设计制作了两个足尺的正交异性高性能混凝土组合桥面板,通过疲劳和静力加载试验测试了正交异性组合桥面板的静力承载能力、破坏形态与疲劳后剩余极限承载力。试验结果表明：正交异性高性能混凝土组合桥面板经历疲劳荷载后的静力破坏形态为受弯破坏,试件达到极限状态时中支点截面U肋屈曲,受拉钢筋屈服,负弯矩区混凝土板开裂严重,组合桥面板的受力性能发生退化。经过疲劳加载后的桥面板的剩余极限承载力较没有经过疲劳加载的桥面板承载力下降了约11.6%。基于钢筋混凝土黏结滑移理论推导了适用于疲劳荷载作用后的高性能混凝土组合桥面板平均裂缝间距计算公式。对比试验结果,所提出的平均裂缝间距计算公式具有良好的精度,可为实际工程应用提供理论参考。     

地面突风对通航飞行器的影响及数值模拟研究

突风一直以来都是危及飞行安全的重要气象要素之一,造成国民经济和人民生命财产的损失。利用常规观测资料、ADWR-X多普勒气象雷达资料和ERA5逐小时再分析资料,对四川盆地西部一次爆发性大风过程中风场的精细化特征、成因及对飞行的影响进行诊断和模拟研究,结果表明：此次大风过程风速增长快,爆发性强。地面风速自午后开始出现4次波动,且每一次波动期间风速峰值呈增加趋势,时间呈缩短趋势。由于第4次波动风速呈爆发性增加,最大瞬时风达到了16.1 m/s,地面风速脉动值超过5 m/s,致使跑道区域内流场的不稳定性增加,起降跑道侧风值超过了中小型飞行器的起降标准。高空动量下传对本次大风过程中风速的爆发性增加起主导作用。中层强偏南气流与低层偏北急流配和,中层辐合以及低层辐散下沉的垂直结构使得低层下沉气流异常强劲,将900～850 hPa的大风核快速向地面传导。通过天气研究与预报(weather research and forecasting, WRF)模式四重嵌套对本次过程进行模拟,表明WRF对盆地西部冷空气补充南下引起的在风速演变趋势、风速最大值和大风影响时段的风向有较好的模拟能力,对飞行起飞和着陆有一...     

Study of the Optimal Integrated Control of a Dengue Transmission Model北大核心CSCD

建立了一个登革热在蚊子和人之间传播的模型,引入了Wolbachia、自我保护和杀虫剂三种控制措施,分别从常数控制和时变控制两个方面进行探讨。首先,分析了常数控制对模型基本再生数的影响,研究发现:Wolbachia有助于减小基本再生数,且基本再生数与自我保护和杀虫剂呈负相关。其次,以使得感染数最少且实施成本最低为目标,使用Pontryagin极值原理讨论最优控制。最后,通过数值模拟展示了最优控制的效果。