分子热运动揭示的传递现象

作者利用三维分子热运动模型统计得到分子热运动平均速度和分子平均自由程,以及分量和总量之间的关系;运用传递通量概念,推导动量通量、热量通量和质量通量表达式,并与牛顿黏性定律、傅立叶导热定律和费克分子扩散定律进行对比,获得了气体动力学理论结论。     

生长温度对激光分子束外延A1N薄膜的影响

采用激光分子束外延法在Al2O3基片上制备AlN薄膜。用反射高能电子衍射、X射线衍射和原子力显微镜研究沉积温度对薄膜微结构的影响,通过光致发光谱和透射光谱对六方AlN薄膜的光学性能进行研究。结果表明：沉积温度为450℃时,沉积的AlN薄膜为非晶态;沉积温度为650℃时,在Al2O3基片上得到c轴单一取向的的六方AlN薄膜,且AlN和Al2O3之间的外延匹配关系为AlN[1210]//Al2O3[1100],AlN[1100]//Al2O3[1210]和AlN（0001）//Al2O3（0001）,这种面内相对旋转30°,可以减小AlN薄膜与Al2O3基片之间的晶格失配度和界面能。此外,650℃沉积的AlN的透射率达到85%,禁带宽度为5.6 eV。沉积温度升高到750℃时,AlN薄膜的透射率和光学能隙变小     

生长温度对激光分子束外延A1N薄膜的影响

采用激光分子束外延法在Al2O3基片上制备AlN薄膜。用反射高能电子衍射、X射线衍射和原子力显微镜研究沉积温度对薄膜微结构的影响,通过光致发光谱和透射光谱对六方AlN薄膜的光学性能进行研究。结果表明：沉积温度为450℃时,沉积的AlN薄膜为非晶态;沉积温度为650℃时,在Al2O3基片上得到c轴单一取向的的六方AlN薄...     

Conformational Changes in the BSA-LT4 Complex Induced by the Presence of Vitamins: Spectroscopic Approach and Molecular Docking

Levothyroxine (LT4) is known for its use in various conditions including hypothyroidism. LT4 interaction with serum albumin may be influenced by the presence of vitamins. For this reason, we investigated the effect of vitamin C, vitamin B12, and folic acid on the complex of Bovine Serum Albumin with LT4 (BSA-LT4). UV-Vis spectroscopy was used to monitor the influence of vitamins on the BSA-LT4 complex. Fluorescence spectroscopy revealed a static quenching mechanism of the fluorescence of BSA-LT4 complex by the vitamin C and folic acid and a combined mechanism for vitamin B12. The interaction of vitamin C and folic acid with BSA-LT4 was moderate, while the binding of vitamin B12 was much stronger, extending the storage time of LT4 in blood plasma. Synchronous fluorescence found that the vitamins were closer to the vicinity of Trp than to Tyr and the effect was more pronounced for the binding of vitamin B12. The thermal stability of the BSA-LT4 complex was more evident, but no influence on the stability of BSA-LT4 complex was obtained for vitamin C. Molecular docking studies showed that vitamin C and folic acid bound the same site of the protein, while vitamin B12 bonded to a different site.     

Quantification of Coating Adhesion Using Laser Induced Decohesion Spectroscopy

We present a new technique, laser induced decohesion spectroscopy (LIDS), which is capable of measuring the practical work of adhesion G between a transparent polymer coating and an opaque coating or substrate. In LIDS, a laser pulse directed onto the sample creates a blister at the transparent/opaque interface. The blister's internal pressure depends on the laser pulse energy, and at a critical pressure the sample fractures, creating an annular debond similar to that obtained in the standard blister test. By measuring physical variables such as the curvature of the blister, and its radius and thickness, it is possible to deduce G, Here we measure G between an automotive clearcoat and four opaque basecoats of various pigmentations (black, white, red, metallic green) as a function of clearcoat thickness. We find that G depends on pigmentation due to the various pigment volume concentrations (PVC's) and specific pigment-binder interactions. Also, G depends on the clearcoat thickness when the thickness is comparable with the size of the plastic zone, R_p.     

Molecular orientation in novolac cured epoxy resins as studied by rheo-optical FTIR spectroscopy

The molecular orientation and relaxation behavior was studied by rheooptical FTIR spectroscopy during the uniaxial deformation of epoxy resins prepared from the diglycidyl ether of butanediol and novolacs on the basis of bisphenol A. The investigation of orientation phenomena was performed in both the rubbery and the glassy state of the epoxies. Results are discussed with regard to the respective mechanism of deformation. Moreover, the effect of temperature, strain rate, and the molecular weight of the novolacs used on the orientation behavior and the mechanical properties was studied. A significant influence of these parameters on the molecular deformation behavior was observed. The reversibility of the orientation at temperatures above and below the glass transition temperature was examined. Epoxy films were subjected to successive loading–unloading cycles including elongation, relaxation, and annealing. The investigations show that the orientation is completely reversible in the rubbery state, but it is only partly reversible below the glass temperature. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 247–259, 1998     

凝胶色谱测定聚丙烯酸钠分子量及其分布的方法研究

采用凝胶色谱法对测定聚丙烯酸钠分子量及其分布的方法进行了研究,考察了流动相、流速、柱温、进样浓度及体积等操作条件对聚丙烯酸钠分离效果的影响.确定了凝胶色谱测定聚丙烯酸钠分子量及其分布的最佳条件为：以0.1 mol/L NaNO3水溶液为流动相,聚丙烯酸钠为标准品,流速1 mL/min,柱温30℃,进样浓度0.1％,进样体积50μL.测定结果相对标准偏差小于1％,可以准确测定聚丙烯酸钠的分子量及其分布系数.     

超声-微波法合成粉煤灰分子筛及吸附性能研究

通过超声-微波法来合成粉煤灰介孔分子筛,通过考察p H值、微波辐射时间和超声陈化时间等对合成工艺条件的影响,得到最佳的合成工艺条件:p H值为11,超声时间为90min,微波时间为10min时合成介孔分子筛样品对Cu2+和Cr6+的去除率可达到92%以上。X射线衍射表明特征峰基本与标准特征峰相似。由扫描电镜可以看出样品颗粒均匀,晶粒分布均匀。     

分子量及其分布对聚羧酸减水剂吸附行为的影响

从分子量及其分布角度研究聚羧酸系减水剂在水泥颗粒表面的吸附行为,分析了聚羧酸减水剂的吸附行为对其分散性、保坍性的影响.结果表明:平均分子量较高的减水剂在水泥表面的吸附量较高,减水剂分子中的高分子量部分优先吸附在水泥颗粒表面;对于同一减水剂,随其在水泥表面的吸附量增加,浆体的流动度增加,两者之间呈正相关性;而对于不同减水...     

合成多异氰酸酯过程中分子量及其分布的GPC表征

应用高效凝胶色谱法测定合成多异氰酸酯过程中分子量及其分布,色谱柱为ＰＬｇｅｌ ＭＩＸＥＤ Ｂ凝胶色谱柱,流动相为四氢呋喃,示差折光检测器来测定分子量及其分布,分子量范围为３２５００００～１０５,方法有较好的精度。     

GPC法测定煤基、石油基聚丙烯分子量及分布

采用GPC法测定神宁化工生产的均聚聚丙烯牌号（1#）及国内市场上两个同类牌号（2#、3#）的分子量大小及其分布,结果表明1#样品分布最窄;三者在三氯苯溶液中,150℃时具有良好的溶解性,在溶液中的分布状态基本一致。与2#、3#相比,1#样品的分子量分布更窄,更适合用做拉丝料,保证丝带不断丝,稳定生产。     

利用蠕变试验研究硫化胶热氧老化过程中的链键断裂和交联特性

利用蠕变试验研究了天然橡胶／顺丁橡胶并用硫化胶在热氧老化过程中的链键断裂和交联特性，并将试验结果与平衡溶胀试验结果进行了比较，实验表明，这是一种切实可行的试验方法，具有设备简单，测试快速而准确的特点。     

CPS微球固载的TEMPO的制备及其对分子氧氧化醇的催化性能

以交联聚苯乙烯(CPS)微球为载体,通过Friedel-Crafts酰基化反应和亲核取代反应化学固载2,2,6,6-四甲基哌啶氮氧自由基(TEMPO),制备了非均相催化剂微球TEMPO/CPS,对其化学结构和形貌进行了表征;考察了主要因素对氯丁酰氯(CBC)与CPS微球Friedel-Crafts酰基化反应的影响,优化了反应条件;将微球与Fe(NO3)3构成共催化剂,用于肉桂醇和1-苯乙醇的分子氧催化氧化. 结果表明,CBC与CPS微球的Friedel-Crafts酰基化反应最适宜的Lewis酸催化剂为AlCl3,最适宜的溶剂为氯仿,反应过程中发生附加交联反应,影响微球强度,适宜的反应温度为75℃,时间为5 h,该条件下制备了TEMPO固载量为1.78 mmol/g的TEMPO/CPS微球. 其与助催化剂Fe(NO3)3构成的共催化剂具有高催化活性,可在75℃、常压氧气条件下反应24 h将1-苯乙醇氧化为苯乙酮,1-苯乙醇转化率为88%,也能有效将肉桂醇氧化为肉桂醛.     

分子蒸馏分离超临界CO2萃取的米槁精油及其成分分析

为了更好地研究米槁精油的化学成分,用分子蒸馏分离超临界CO2流体萃取的米槁精油,通过改变蒸馏温度和压力,共得到12个馏分。用GC-MS分析其化学成分,共鉴定出98个化学成分,在其馏分中首次检测出朱栾倍半萜、榧叶醇等44个新组分。与传统的蒸馏和柱层析分离方法相比,分子蒸馏技术具有分离快、不破坏其化学组成、没有组分流失的优点,是分离米槁精油组分的有效方法。该文报道工作的新颖性,已为贵州省科学技术情报研究所2007年4月30日出具的第200752001178号《科技查新报告》所证实。     

有机氯硅烷修饰的介孔SBA-15及其疏水性

在非极性溶剂(甲苯)中,用三甲基氯硅烷和苯基二甲基氯硅烷对全硅介孔分子筛SBA-15进行了表面修饰.利用傅里叶变换红外光谱(FT IR)、X射线粉末衍射(XRD)和低温N2吸附-脱附等手段对样品进行了结构分析;并通过测定样品在水或正己烷饱和蒸汽中的吸附量,研究了它们的疏水性.结果表明,表面改性后的SBA-15仍保持完好...     

基于选区激光烧结的无机纳米Al2O3粒子增强增韧聚苯乙烯的研究

基于选区激光烧结（SLS）技术，进行了无机纳米Al2O3粒子改性聚苯乙烯（PS）的试验研究。结果表明，在一定的激光烧结工艺参数条件下，激光烧结件中的纳米Al2O3粒子在PS基体中分布均匀，且其冲击强度、拉伸强度最大分别达到了12．1kJ／m^2和31．2MPa，相对于纯PS烧结件提高了60％和380％。同时，冲击断面SEM显示其属典型的韧性断裂，无机纳米Al2O3粒子起到了增强增韧PS的作用。     

超临界CO_2流体萃取糊毛烟净油成分分析及其对卷烟感官质量的影响研究

利用超临界CO2流体萃取技术萃取糊毛烟叶制备糊毛烟净油,所得净油为红褐色澄清透亮的溶液,得率为5%。净油经GC-MS分析鉴定,其中含有大量的烟草特征致香化合物如茄酮、麦斯明、香叶基丙酮、β-紫罗兰酮、2,3-联吡啶、巨豆三烯酮、六氢法尼醇、植酮、新植二烯、法尼基丙酮等,和异戊酸、乳酸、己酸、乙酰丙酸、苯甲酸、苯乙酸、十二酸、十四酸、十六酸等有机酸。卷烟加香评吸结果表明该净油能提升烟草本身香气,增加特征烟香,使烟气质地细腻柔和,抑制刺激性,掩盖杂气,并能赋予卷烟独特的风格特征,可明显提升卷烟的抽吸品质,是一种理想的高品质烟用香料。     

２０%虫螨星乳油防治苹果叶螨田间药效试验

２０%虫螨星乳油对苹果叶螨有良好的防治效果,３５００-４５００倍稀释液的田间防效在９６.４４%以上,可作为苹果叶螨的防治药剂,田间使用浓度３５００-４５００倍释释液为宜.     

Neural Tissue Degeneration in Rosenthal’s Canal and Its Impact on Electrical Stimulation of the Auditory Nerve by Cochlear Implants: An Image-Based Modeling Study

Sensorineural deafness is caused by the loss of peripheral neural input to the auditory nerve, which may result from peripheral neural degeneration and/or a loss of inner hair cells. Provided spiral ganglion cells and their central processes are patent, cochlear implants can be used to electrically stimulate the auditory nerve to facilitate hearing in the deaf or severely hard-of-hearing. Neural degeneration is a crucial impediment to the functional success of a cochlear implant. The present, first-of-its-kind two-dimensional finite-element model investigates how the depletion of neural tissues might alter the electrically induced transmembrane potential of spiral ganglion neurons. The study suggests that even as little as 10% of neural tissue degeneration could lead to a disproportionate change in the stimulation profile of the auditory nerve. This result implies that apart from encapsulation layer formation around the cochlear implant electrode, tissue degeneration could also be an essential reason for the apparent inconsistencies in the functionality of cochlear implants.     

Effect of process water chemistry and particulate mineralogy on model oilsands separation using a warm slurry extraction process simulation

Variability in ore composition and process parameters is known to affect bitumen recovery from natural oilsands. In this work, we extend our earlier investigations with model oilsands systems (MOS) to determine the effects of calcium, magnesium and bicarbonate ion concentrations in the process water and their interactions with ‘active’ solids such as: kaolinite, montmorillonite and ultra-fine silica. Our results demonstrate that solids mineralogy and decreasing particle size produce negative outcomes on bitumen recovery related to concomitant effects on bitumen droplet size during flotation. In some cases, certain process water chemistries were found to restore recovery, but clay concentration was the key factor.Naturally acidic oilsands are known to give poor bitumen recoveries. An MOS prepared with connate water at pH 2 responded in the same way. Comparison with a typical oilsands showed no significant differences in middlings pH and the large, negative effect on bitumen recovery was not reversed by higher caustic loading during separation. This result may be caused by irreversible co-flocculation of bitumen and mineral particles during preparation of the MOS and may reflect similar behavior in comparable natural samples.