溶剂介质对ZnO晶体极性生长的影响

以Zn(NO3)2·6H2O、NaOH为原料,以水、乙醇、液体石蜡和双氧水为溶剂,在不同条件下水热合成不同结构形貌的ZnO.通过X射线衍射(XRD)和扫描电子显微镜(SEM)对其结构形貌进行表征,讨论ZnO在上述介质中的极性生长特性和生长机制.结果表明,溶剂类型可明显改变晶体+c轴方向的生长速率,从而获得不同的结构形态.在水介质中,晶体极性生长习性明显,+c轴 [0001]方向的生长速率明显大于其它方向,晶体生长为六方长柱状结构;以水和乙醇混合物为溶剂时,沿+c轴方向的生长速率明显减小,晶体呈六方片状;在液体石蜡中晶体沿各个晶向都无择优性,极性生长习性不明显,+c轴 [0001]方向的生长速率近似于其它方向,从而形成六方短柱状结构;双氧水的富氧体系则大大促进了晶体沿+c轴方向的极性生长,促使晶体呈针管状结构.     

EDTA对脱硫石膏制备α-半水石膏晶体生长的影响

采用常压盐溶液法工艺以脱硫石膏为原料制备α-半水石膏,研究乙二胺四乙酸(EDTA)对脱水反应速率、产物晶体形貌的影响,并结合多种分析手段从微观角度对转晶机制进行探讨。结果表明:EDTA能显著降低脱硫石膏脱水反应速率,在0.2%~1.0%掺量下,脱水反应时间逐渐延长至4 h;EDTA对α-半水石膏晶体形貌改善作用明显,使之由细长的针棒状转变为短柱状,在1.0%掺量下晶体长径比约为1.5∶1;EDTA在晶体生长过程中会吸附在(111)晶面上,阻碍半水石膏晶体在c轴方向上的生长,但并未掺杂在产物石膏晶格中,不会改变晶体的晶型。     

磷石膏常压水盐法制备高强石膏转晶剂探究

利用化工磷石膏制备高强石膏,通过设定不同的实验条件来考察盐溶液浓度、转晶剂对生成的高强石膏的晶体形貌的影响,探讨最优的水热合成方案。在水热条件下,磷石膏中的二水石膏通过溶解-再结晶的方式生成半水石膏,在没有任何转晶剂加入的条件下,最终会生成针状的半水石膏晶体。转晶剂会选择性地吸附在半水石膏的(111)晶面上,降低该晶面能,削弱该晶面在C轴的生长速率,改变半水石膏的晶体生长习性和形貌,获得短柱状的半水石膏晶体。实验结果表明:在磷石膏浓度20%、加热时间2h、Na Cl浓度12%、丁二酸浓度0.05%的条件下,获得高强石膏晶体的长径比为2∶1至3∶1,晶型为最优。     

缓凝剂在磷石膏水化进程中的影响

通过缓凝剂对磷石膏凝结时间、强度、水化率、水化温升与液相离子浓度测定,结合扫描电镜观察,研究了缓凝剂对磷石膏水化进程的影响。结果表明:SG-10、柠檬酸缓凝剂与磷石膏适应性较好;pH值对缓凝剂缓凝效果有很大影响,SG-10和柠檬酸在磷石膏浆体中最佳pH值分别为5.1和6.0时:柠檬酸掺量不宜超过0.1%,SG-10掺量不宜超过0.2%;SG-10、柠檬酸在水化初期使水化放热明显变缓,早期水化率显著降低,最终水化率有所降低,一定程度上改变了磷石膏水化动力学过程;缓凝剂掺入后,石膏初始液相离子浓度和过饱和度低于空白样,水化反应过程中液相离子浓度和过饱和度降低速率大幅降低;SG-10的掺加使二水石膏晶体尺度增大,但对二水石膏晶体形貌影响较小,掺柠檬酸时,硬化体晶体形貌改变较大。     

复合型缓凝剂对脱硫建筑石膏水化进程的影响及缓凝机理

研究了复合型缓凝剂P粉对脱硫建筑石膏水化进程、液相离子浓度与过饱和度及二水石膏晶体形貌的影响,结合扫描电镜对其缓凝机理进行了分析。结果表明:P粉能抑制脱硫建筑石膏的早期水化,使其水化放热减缓,早期水化率降低,凝结时间延长;P粉对二水石膏晶体形貌影响较大,并且使二水石膏晶体尺寸明显增大;P粉通过多种途径对石膏产生了缓凝作用,其中羟基羧酸钙盐钙离子的电离对早期半水石膏的溶解起到一定的阻碍作用,延缓了晶核的形成,同时羧基和羟基组成的基团的选择性吸附抑制了晶核的生长,另外蛋白质也对石膏起到了胶体包裹的作用,抑制了     

愈创木酚甘油醚晶习的影响因素

通过改变溶剂、过饱和度以及原料杂质3个条件，得到了愈创木酚甘油醚的不同的晶习．利用扫描电子显微镜对所得到的晶体进行了测定，从而确定了溶剂、过饱和度和杂质对愈创木酚甘油醚晶习的影响．研究结果表明，它们主要通过影响各个晶面的生长速率来改变晶习．当改变溶剂和初始过饱和度时（110）面和（-↑110）面之间的晶棱也随之改变甚至消失．随着过程过饱和度的减少晶体生长沿z轴方向趋于长度增加，并且晶体的（001）面和（0-↑01）面由四边形向六边形发展．没有杂质时晶体的晶习为长方体．     

丁二酸对α半水脱硫石膏晶体生长习性与晶体形貌的影响

采用扫描电镜、显微红外分析仪和X光电子能谱研究了丁二酸对α半水脱硫石膏晶体生长习性与形貌的影响,从晶体生长角度分析了丁二酸的晶形调节作用机理.结果表明:丁二酸显著改变了α半水脱硫石膏晶体的生长习性,使其由长棒状转变为短柱状或片状,且晶体发育更完整,晶体尺度变大;控制丁二酸的掺量,可制备长径比为1:1的短柱状α半水脱硫石...     

柠檬酸镁和广金钱草对草酸钙晶体生长的影响

研究了水溶液体系中广金钱草和柠檬酸镁存在下对草酸钙结晶及晶体生长的影响.XRD谱图分析表明,广金钱草对草酸钙晶型基本无影响,柠檬酸镁浓度较高时可诱导二水合草酸钙的形成;SEM图像分析表明,广金钱草可抑制大颗粒草酸钙晶体的形成,从而产生大量的小尺寸草酸钙晶体,柠檬酸镁可改变草酸钙晶体的形貌,使其形成片状或层状的晶体.实验结果表明,广金钱草和柠檬酸镁的存在或者有利于阻止草酸钙晶体变大形成尿石,或者诱导二水合草酸钙(COD)的形成.该结论可为临床上治疗CaOxa结石提供参考.     

谷氨酸阴离子和晶种对晶体成核与生长的影响

研究了谷氨酸阴离子（Ｇ－）和晶种对其晶体二次成核与生长的影响．结果表明成核速率随晶种粒度和晶种量减少而减少；在高过饱和度时Ｇ－对成核有促进作用，而在低过饱和度时则有抑制作用；晶体生长速率随粒度减小而增大；Ｇ－对晶体生长有抑制作用；结晶时使用粒度小的晶种可得到粒度分布较均匀的晶体．     

常压盐溶液法转化脱硫石膏制备α-半水石膏的相变机理

采用常压复合盐溶液水热法对钙基湿法烟气脱硫(FGD)工艺的副产品FGD石膏进行转化,以制备α-半水石膏。利用DSC/TG综合热分析、SEM和化学分析对转化后的石膏样品进行研究。结果表明,FGD石膏转化为α-半水石膏的过程遵循溶解-重结晶机理。在重结晶诱导期内,FGD石膏首先在热盐溶液中溶解,形成硫酸钙过饱和溶液,在一定的过饱和度区域内,α-半水石膏雏晶直接从溶液中析出,发生石膏晶体亚微观结构上的改变。随后石膏雏晶继续生长,形成了均匀粗大的棱柱状α-半水石膏晶体,实现结晶物质在各个晶体上的重新分布。     

Mg2+影响方解石晶体生长机制的分子动力学研究

采用分子动力学(MD)方法模拟计算了方解石(110)、(104)晶面分别与Mg2+、Ca2+的相互作用.结果表明,在相同的外界条件下,方解石两个晶面与Mg2+的结合能均大于它们与Ca2+的结合能,说明这两个晶面易对Mg2+形成优先吸附.(110)晶面上的结合能远大于(104)面上的结合能,说明前者比后者更活跃.由于Mg2+的优先吸附占据了原本属于Ca2+的晶格点,因此引起方解石晶体发生形变进而达到了阻止方解石晶体生长的结果.通过对体系的对关联函数g(r)的分析,证明方解石晶面与Mg2+和Ca2+均形成了化学键,但前者更强一些,进一步说明了Mg2+的阻垢作用.     

Ca~(2+)对水稻幼苗生长的影响

对水稻幼苗进行不同水平Ca2 + 处理 ,结果表明 :缺钙和加 0 75～ 10 5mmol/LCa2 + 处理对水稻幼苗的株高无明显影响 ;缺Ca2 + 会降低水稻幼苗的根系活力、叶绿素含量和光合强度 ;加Ca2 + 能增加水稻幼苗根冠比和根系活力 ;加低浓度 ( 0 75～ 1 5mmol/L)Ca2 + 可增加水稻幼苗的干物重、叶绿素含量和光合强度 ,促进水稻幼苗生长 ;加高浓度 ( 5 5～ 10 5mmol/L)Ca2 + 则降低叶绿素含量和光合强度 ,对水稻幼苗生长产生抑制作用     

Effects of collagen types II and X on the kinetics of crystallization of calcium phosphate in biomineralization

The effects of the components of cartilages matrix on the process of endochondral ossification and the kinetics of crystal growth of calcium phosphate have been studied in the presence of type II or X collagen. During the experiments, type I collagen was added as the seed material. FT-IR analysis shows that calcium phosphate crystallized on the surface of type I collagen was mainly hydroxyapatite. Both type II and X collagens could reduce the growth rate of calcium phosphate crystals, and the effect of type X collagen is more obvious. The reaction was in the fourth order in the presence of type II collagen. The results showed that type II or X collagen had the ability to make Ca2+ accumulate in the process of endochondral ossification, but has little effect on crystal growth and the product of biomineralization.     

Growth factor-like action of phosphatidic acid

Phosphatidic acid (PA), an intriguing phospholipid that is rapidly produced during receptor-stimulated breakdown of phosphoinositides, has often been proposed to function as a Ca2+ ionophore in activated cells. The PA-ionophore hypothesis is supported by the fact that exogenously applied PA stimulates Ca2+ uptake in various cells and can evoke Ca2+-mediated physiological responses, but it is not known whether PA accumulation affects cytoplasmic free Ca2+ concentration ([Ca2+]i). Here we report that PA elicits a transient rise in [Ca2+]i in cultured cells, not by stimulating Ca2+ influx, but, surprisingly, by releasing Ca2+ from intracellular stores. We further show that PA evokes growth factor-like effects in that it raises cytoplasmic pH, induces expression of the c-fos and c-myc proto-oncogenes and stimulates DNA synthesis. Our results indicate that, unlike an ionophore, PA acts by triggering the hydrolysis of phosphoinositides, with consequent formation of second messengers such as inositol trisphosphate signalling Cai2+ release. Furthermore, our data strengthen the notion that any Ca2+-mobilizing stimulus acting through phospholipase C may ultimately function as a growth factor.     

纳米磷灰石微晶对牙釉质脱矿的影响

目的：研究纳米磷灰石微晶对牙釉质脱矿的影响。方法：采用pH循环法模拟口腔环境进行脱矿，测定酸液中的钙离子浓度，对样本进行微光共聚焦（Laser Scanning Confocal Microscopy,LSCM)扫描，并进行图象分析，结果在纳米钇磷灰石（纳米钇HA）的酸液中钙离子含量与对照组有明显的差异，且高于纳米羟磷灰石（纳米HA）和普通羟磷灰石（HA）；而纳米HA和HA与对照组无差异。LSCM图象分析显示，纳米钇HA牙釉质脱矿程度大于对照组，而纳米HA和HA脱矿程度小于对照组，其大小依次为：纳米钇HA，纳米HA和HA。结论：纳米HA和普通HA有明显的防龋效果，而用纳米钇HA处理牙表面后，能大大地增加其表面活性，使牙体的耐酸性降低，钙磷易从牙体表面析出而脱矿。     

Built-up Effect of Core Material for Microencapsulated Flame Retardant Containing Dimethyl Methyl Phosphate

The flame retardants containing organophosphorus compounds have extensively been used inthe flame retarding of polymer materials.Among others,dimethyl methyl phosphate (DMMP) was applied in flame retarding of polyurethane owmg to its so much merit.However,the water-soluble property of DMMP restricted its application in textile fabric.The flame retardtag systemcontainirm DMMP will be microencapsulated to form a novel flame retardant that could be used in textiles.We have studied the builtup effect of DMMP with some inorganic compounds to improve the afterflame and afterglow suppression in the flame retarding system.The experimeatal data indicated that inorganic compounds containing various non-metal elements P,N,B and metal ions Mg2 ,Al3 ,Ca2 ,Zn2 ,Cu2 ,Mn4 could be applied in flame retarding systems as additives to effectively suppress afterflame or afterglow.     

NMDA-receptor activation increases cytoplasmic calcium concentration in cultured spinal cord neurones

Excitatory amino acids act via receptor subtypes in the mammalian central nervous system (CNS). The receptor selectively activated by N-methyl-D-aspartic acid (NMDA) has been best characterized using voltage-clamp and single-channel recording; the results suggest that NMDA receptors gate channels that are permeable to Na+, K+ and other monovalent cations. Various experiments suggest that Ca2+ flux is also associated with the activation of excitatory amino-acid receptors on vertebrate neurones. Whether Ca2+ enters through voltage-dependent Ca2+ channels or through excitatory amino-acid-activated channels of one or more subtype is unclear. Mg2+ can be used to distinguish NMDA-receptor-activated channels from voltage-dependent Ca2+ channels, because at micromolar concentrations Mg2+ has little effect on voltage-dependent Ca2+ channels while it enters and blocks NMDA receptor channels. Marked differences in the potency of other divalent cations acting as Ca2+ channel blockers compared with their action as NMDA antagonists also distinguish the NMDA channel from voltage-sensitive Ca2+ channels. However, we now directly demonstrate that excitatory amino acids acting at NMDA receptors on spinal cord neurones increase the intracellular Ca2+ activity, measured using the indicator dye arsenazo III, and that this is the result of Ca2+ influx through NMDA receptor channels. Kainic acid (KA), which acts at another subtype of excitatory amino-acid receptor, was much less effective in triggering increases in intracellular free Ca2+.     

草酸钙结石结构中“菱形”晶体的性质——用弗氏台测定草酸钙结晶的光学常数

偏光显微镜下草酸钙晶体被描述为哑呤状、颗粒状、信封状或菱形状晶体,并把菱形结晶一直认为是二水草酸钙。有关其分类问题仍有争论。本文用弗氏台测定了结石中草酸钙的各种晶体形态的光学特征性常数和光率体成分(晶面夹角、晶棱与光学主轴之间关系,2V)。证实二水草酸钙属于中级晶族,四方晶系,晶体的形态是扁平四方双锥(信封状),一水草酸钙是低级晶族,单斜晶系,形态是斜方柱。本研究发现菱形晶属于一水和二水草酸钙的中问晶体,菱形晶有两种晶体形式,单锥和双锥的结晶形式,菱形晶不是二水草酸钙。     

Calcium signalling in the guidance of nerve growth by netrin-1

Pathfinding by growing axons in the developing nervous system is guided by diffusible or bound factors that attract or repel the axonal growth cone. The cytoplasmic signalling mechanisms that trigger the responses of the growth cone to guidance factors are mostly unknown. Previous studies have shown that the level and temporal patterns of cytoplasmic Ca2+ can regulate the rate of growth-cone extension in vitro and in vivo. Here we report that Ca2+ also mediates the turning behaviour of the growth cones of cultured Xenopus neurons that are induced by an extracellular gradient of netrin-1, an established diffusible guidance factor in vivo. The netrin-1-induced turning response depends on Ca2+ influx through plasma membrane Ca2+ channels, as well as Ca2+-induced Ca2+ release from cytoplasmic stores. Reduction of Ca2+ signals by blocking either of these two Ca2+ sources converted the netrin-1-induced response from attraction to repulsion. Activation of Ca2+-induced Ca2+ release from internal stores with a gradient of ryanodine in the absence of netrin-1 was sufficient to trigger either attractive or repulsive responses, depending on the ryanodine concentration used. These results support the model that cytoplasmic Ca2+ signals mediate growth-cone guidance by netrin-1, and different patterns of Ca2+ elevation trigger attractive and repulsive turning responses.