207 resultados para Boethius, d. 524.
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研究了环丙烷衍生物在CD3 OD子体系中的H/D换反应产物离子 [M +1]+ 、[M +2 ]+ 和[M +3]+ 的碰撞诱导碎裂 (CID)反应特征。实验结果表明这些产物离子是由反应物与试剂离子之间发生H/D换反应生成的。获得了环丙烷衍生物结构中活泼氢位置及其数量的信息
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It was found for the first time that gramicidin D (GD) molecules can be incorporated into the ODM monolayer which is self-assembled on the surface of the gold electrode and form monovalent cation channels.
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Gramicidin within the lipid bilayer matrix is a well-known channel-forming polypeptide, but the mechanism of the ions across the membrane induced by gramicidin is not well understood. We found that at very low concentration of gramicidin in a bilayer lipid membrane, the channel behavior was controlled by the voltage applied across the membrane. When the voltage is higher than 75 mV, the channel is closing, while lower than 75 mV, the channel is opening. But when the concentration of the gramicidin in the BLMs is high, the channel behavior is changed into voltage-independent. (C) 1998 Elsevier Science Ltd. All rights reserved.
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聚(ε┐己内酯)/聚(d,l┐丙交酯)共混物膜在酶促降解过程中的形态变化张杰甘志华*梁奇志景遐斌(吉林工业大学理学院应用化学系长春)(中国科学院长春应用化学研究所长春130022)关键词聚己酸内酯-聚丙交酯共混物,酶促降解,形态1997-10-30收…
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采用一种新型的稀土配位化合物Y(CF3COO)3/Al(i-Bu)3为催化剂,制备了不同组成的ε-己内酯/d,l-丙交酯共聚物,并用GPC、NMR和DSC表征了共聚物的结构.结果表明通过改变初始投料中两种单体的比例,可以调节共聚酯的化学结构,而共聚物的形态则受结构影响很大.
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用一种全氟代磺酸酯阳离子交换树酯(East-man AQ-55),将D-氨基酸氧化酶(DAAO),辣根过氧化物酶(HRP)以及1,1′-二(α-羟基乙基)二茂铁(BHFc)同时包埋在玻碳电极(GCE)表面,制成双酶D-氨基酸电流式传感器。电极的工作电位为+0.18V(vs.SCE)响应时间小于50s。对于D-丙氨酸来说,测定的最适宜pH为7.8,测定的线性范围为0.05~0.75mmol/L该电极具有良好的重现性,可以连续使用200次。
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The crystal structure of [Mn(thiamine)Cl2(H2O)]2[thiamine]2Cl4.2H2O has been determined by X-ray diffraction methods. The compound contains a cyclic dimer of a complex cation with two thiamine ligands bridged by two Mn(II) ions across a crystallographic center of symmetry. Each Mn(II) is coordinated by two chloride atoms, a water molecule, a N(1') atom of the pyrimidine from a thiamine and an O(53) atom of the hydroxyethyl side chain from another thiamine. There are two free-base thiamine molecules related by a center of symmetry in the unit cell, which form a base-pair through the hydrogen bonds. Both the independent thiamine molecules in the asymmetric unit assume the common F conformation with phi-T = 10.0(9) and 3.6(10) and phi-P = 85.6(7) and 79.6(7), respectively. The compound provides a possible model for a metal-bridged enzyme-coenzyme complex in thiamine catalysis. Crystallographic data: triclinic, space group P1BAR, a = 12.441(4), b = 13.572(4), c = 11.267(3) angstrom, alpha = 103.15(2), beta 89.03(3), gamma = 115.64(2)-degrees, Z = 1, D(calc) = 1.524 g cm-3, and R = 0.050 for 3019 observed reflections with I > 3-sigma(I).
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本文系统地研究了化合物ASm_2I_5(A=K,Rb,Cs,T1)固体粉末的荧光光谱和反射光谱.讨论了Sm~(2+)在立方晶体场中的分裂能随着碱金属离子半径的增大而减小和f-d发能随着A-I(A=Rb,T1)键的共价性增加而明显降低的现象.并从晶场效应和化学键性质两个方面解释了ASm_2I_5(A=K,Rb,Cs)和ASm_2I_5(A=Rb,T1)中的Sm~(2+)荧光光谱分别发生蓝移和红移的现象.
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十五种希土D-葡萄糖酸配合物的红外和拉曼光谱非常相似,结构类同,配合物的糖酸谱带明显展宽,羧酸根的对称和反对称振动谱带相差200cm~(-1),与希土离子单齿配位,糖酸为β构型,吡喃环上的O_1和O_5也参予配位,希土离子配位数是9。
Impact of spatial resolution and spatial difference accuracy on the performance of Arakawa A-D grids
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This paper alms at illustrating the impact of spatial difference scheme and spatial resolution on the performance of Arakawa A-D grids in physical space. Linear shallow water equations are discretized and forecasted on Arakawa A-D grids for 120-minute using the ordinary second-order (M and fourth-order (C4) finite difference schemes with the grid spacing being 100 km, 10 km and I km, respectively. Then the forecasted results are compared with the exact solution, the result indicates that when the grid spacing is I kin, the inertial gravity wave can be simulated on any grid with the same results from C2 scheme or C4 scheme, namely the impact of variable configuration is neglectable; while the inertial gravity wave is simulated with lengthened grid spacing, the effects of different variable configurations are different. However, whether for C2 scheme or for C4 scheme, the RMS is minimal (maximal) on C (D) grid. At the same time it is also shown that when the difference accuracy increases from C2 scheme to C4 scheme, the resulted forecasts do not uniformly decrease, which is validated by the change of the group A velocity relative error from C2 scheme to C4 scheme. Therefore, the impact of the grid spacing is more important than that of the difference accuracy on the performance of Arakawa A-D grid.
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Song and Banner (2002, henceforth referred to as SB02) used a numerical wave tank (developed by Drimer and Agnon, and further refined by Segre, henceforth referred to as DAS) to study the wave breaking in the deep water, and proposed a dimensionless breaking threshold that based on the behaviour of the wave energy modulation and focusing during the evolution of the wave group. In this paper, two modified DAS models are used to further test the SB02's results, the first one (referred to MDAS1) corrected many integral calculation errors appeared in the DAS code, and the second one (referred to MDAS2) replaced the linear boundary element approximation of DAS into the cubic element on the free surface. Researches show that the results of MDAS1 are the same with those of DAS for the simulations of deep water wave breaking, but, the different values of the wavemaker amplitude, the breaking time and the maximum local average energy growth rate delta(max) for the marginal breaking cases are founded by MDAS2 and MDAS1. However, MDAS2 still satisfies the SB02' s breaking threshold. Furthermore, MDAS1 is utilized to study the marginal breaking case in the intermediate water depth when wave passes over a submerged slope, where the slope is given by 1 : 500, 1 : 300, 1 : 150 or 1 : 100. It is found that the maximum local energy density U increases significantly if the slope becomes steeper, and the delta(max) decreases weakly and increases intensively for the marginal recurrence case and marginal breaking case respectively. SB02's breaking threshold is still valid for the wave passing over a submerged slope gentler than 1 : 100 in the intermediate water depth.
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近年来,甲壳质生产发展迅速,但是在生产过程中所产生的废水引发了一系列的环境污染问题,对于该废水的处理,目前尚未有行之有效的方法,大多数生产厂家仍处于无处理排放状态。本文在处理甲壳质、壳聚糖生产废水的同时回收得到了具有多种生物学功能的虾青素以及可以作为饲料添加剂的粗蛋白,这对于我国甲壳质、壳聚糖产业的发展以及保护我国近海环境具有重要的意义;另一方面,壳聚糖因其具有优良的吸附性能、螯合性能、可再生性及生物降解性,在水处理工艺中已经显示出广阔的应用前景,本研究中将壳聚糖应用于甲壳质、壳聚糖生产废水以及海藻工业水处理工艺中,这样既保护了环境又达到了资源综合利用的目的,并且节约了能源和资源。 首先研究了从甲壳质、壳聚糖生产废水中回收提取虾青素以及所得的虾青素对DPPH自由基的清除作用。分别采用单元有机溶剂、二元有机溶剂作为萃取剂从废水中回收虾青素,并确定了有机溶剂萃取的最佳条件,实验结果表明,二元有机溶剂萃取的效果优于单元有机溶剂萃取的效果;将得到的虾青素经HPLC分析,游离虾青素的含量达30.02%;最后,对所得的虾青素进行了有机自由基DPPH的清除作用的测定,结果表明,所得的虾青素具有很强的清除DPPH自由基的能力,IC50可以达到0.84mg/ml。 将得到的虾青素进行了深加工,合成了虾青素-β-环糊精的包合物。结果表明,当虾青素与β-环糊精形成包合物时,虾青素与β-环糊精以1:4的比例进行包合,包合物的水溶性稍好于虾青素(虾青素不溶于水);在水相中,包合物很容易形成超分子结构;包合物中虾青素对温度和光的稳定性明显增强。 其次,研究了甲壳质、壳聚糖生产废水中蛋白质的回收技术,通过实验确定了蛋白质回收的最佳条件;并对所得的蛋白质沉淀进行了氨基酸分析,结果表明,该沉淀中含有丰富的氨基酸,其总量可以达到20.56%,这些结果表明该沉淀可以开发为饲料用蛋白质添加剂。 在回收虾青素和蛋白质的同时,对甲壳质、壳聚糖生产废水处理新工艺的开发,并且确定了最佳实验条件。经过处理后的废水由青岛市环境保护监测站监测结果表明,处理后的废水达到了国家二级排放标准。 利用壳聚糖对海藻工业水进行了处理,结果表明,壳聚糖絮凝海带工业水中“糖胶”的效果明显优于工业生产中通常使用的方法,在此基础上确定了壳聚糖作为絮凝剂对海带工业水进行处理的最佳实验条件。在本研究中还测定了I-浓度的变化,从I-的浓度变化来看,应用本方法处理海带工业水不影响碘的提取。
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本文所述为磷虾声学探测系统的一部分——接收机及高速A/D换器。该系统的设计旨在克服过去南大洋科学考察所用声学评估系统信号补偿不够精确、动态范围较窄、实时处理能力较差等不足。接收机具有宽动态范围及精确的20LoG(R)和40LoG(R)损耗补偿,8位高速A/D换将数据信号送计算机,使得生物量和声物反射能力的计算得以实时进行。
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牦牛的起源与属级分类学地位至今仍然存在一定的争议.我们测定了家养牦牛和野生牦牛线粒体控制区(D-loop)序列,并以此构建牦牛和牛属、野牛属、水牛属以及非洲水牛属相关种的系统发育树.研究结果表明线粒体D-loop区与Cyt b基因序列在构建牛族的系统发育具有同样重要的价值.系统发育关系显示野牛属的灭绝种草原野牛与现存种美洲野牛先聚合为一单系群,然后再和牦牛形成一单系分支,表明牦牛与野牛属的草原野牛、美洲野牛亲缘关系最近,具有最近的共同祖先,而与牛属的其它亚洲物种亲缘关系较远.因此,本研究不支持将牦牛独立为牦牛属--Poephagus,牛属与野牛属在分类上也应合并为一个属.基于上述研究结果和化石证据,我们进一步对牦牛起源的历史背景进行了讨论,认为牦牛与野牛属的分化是由于第四纪气候变化在欧亚大陆发生的,野牛通过白令陆桥进入北美;冰期结束后,由于欧亚大陆其它地区温度升高,牦牛只能局限分布在较为寒冷的青藏高原;而野牛属在北美先后分化为草原野牛和美洲野牛,前者可能是后者的直接祖先.
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针对江河源退化草地治理与示范项目要求,在果洛州玛沁县大武乡格多牧委会人工和半人工草场上,使用D肉毒杀鼠素对高原鼠兔Ochotona curzoniae进行现场药效试验和大面积灭鼠。结果表明,0.1%和0.2%D内毒杀鼠素毒饵时鼠兔具有良好的灭杀效果,且不污染环境,无二次中毒,对保护鼠粪天敌,维持生态平衡,控制害鼠种群数量回升,减少扩散,使治理后的草场植被再次免遭破坏等方面均具良好作用.