Computer models of crystal growth

Dynamic models of crystal surfaces have provided new insights into the crystal growth process. The effects of surface roughening, dislocations, and impurities have been assessed. Certain impurities have been found to cause a larger increase in the growth rate than screw dislocations.     

Direction-specific interactions control crystal growth by oriented attachment

The oriented attachment of molecular clusters and nanoparticles in solution is now recognized as an important mechanism of crystal growth in many materials, yet the alignment process and attachment mechanism have not been established. We performed high-resolution transmission electron microscopy using a fluid cell to directly observe oriented attachment of iron oxyhydroxide nanoparticles. The particles undergo continuous rotation and interaction until they find a perfect lattice match. A sudden jump to contact then occurs over less than 1 nanometer, followed by lateral atom-by-atom addition initiated at the contact point. Interface elimination proceeds at a rate consistent with the curvature dependence of the Gibbs free energy. Measured translational and rotational accelerations show that strong, highly direction-specific interactions drive crystal growth via oriented attachment.     

Colloidal hard-sphere crystal growth frustrated by large spherical impurities

Impurities affect the nucleation, growth, and structure of crystals. Here we report the effect of large, spherical, polymethylmethacrylate impurities on the crystal growth of monodisperse, hard, polymethylmethacrylate colloids in a density- and optically matching apolar solvent mixture. Crystal growth, initiated at the bottom of the sample, was studied by imaging sequences of two-dimensional xy slices in the plane of the impurity's center with a laser scanning confocal microscope. Impurities form the center of grain boundaries, and a single fluid particle layer around the impurity persists in all cases. The growth rate sensitively depends on the impurity's size. Crystal growth is inhibited to a greater extent near smaller impurities, pointing to local crystal frustration induced by the curvature of the impurity.     

Materials: marangoni convection in space microgravity environments

Thermally induced surface-driven convection (thermal Marangoni convection) was investigated in the Spacelab 1 microgravity environment. The configuration studied is related to the floating-zone technique used for crystal growth.     

Filamentary crystal growth associated with impact craters from hypervelocity microparticles

A filamentary crystal growth is associated with impacts of hypervelocity microparticles upon copper foil. They are copper whiskers formed by the condensation of the target material vaporzied by the impact.     

Protein content of seed: increase improves growth and yield

Oat seeds with a higher protein content as a result of chemical applications in 1967 yielded 21 to 42 percent more grain in 1968. Wheat seed, whether from Michigan, Illinois, or Mexico, that contained more protein as a result of field applications of chemicals or nitrogen developed into larger seedlings. The content of protein in the seed correlated with subsequent growth and yield, indicating that the amount of endogenous protein or of a proteinaceous moiety, which can be controlled, may be an important factor in subsequent yield of major agronomic crops.     

Control of calcium carbonate nucleation and crystal growth by soluble matrx of oyster shell

A calcium-binding soluble protein extracted from oyster shell suppresses calcium carbonate nucleation and decreases the rate of crystal growth in vitro. These findings suggest that soluble matrix may regulate shell growth.     

苏云金杆菌菌株YJ-2000生长和伴孢晶体形成的适宜培养条件

苏云金杆菌菌株YJ-2000是本所选育的一个对家蚕蚁蚕无毒性,而对多种其他鳞翅目害虫表现强毒性的新菌株[3,4].本文通过研究培养基初始pH、碳源、氮源和金属离子对苏云金杆菌菌株YJ-2000生物量和伴孢晶体产量的影响,以确定该菌生长和伴孢晶体形成的适宜培养条件.结果表明:既满足该菌生长,又能获得最高伴孢晶体产量的该菌的适宜培养条件是,培养基初始pH为 6.5,碳源为麦芽糖,氮源为蛋白胨与(NH4)2SO4的混合物(比例为1∶1),培养基中Mg2+和Cu2+的浓度各为1×10-3和0.008×10-3mol/L.     

全自动凯氏定氮仪测定蛋白饮料中蛋白质的不确定度分析

[目的]减少试验过程中带来的误差,确保蛋白质含量的数据准确性。[方法]采用GB 5009.5—2016第一法,凯氏定氮法测定蛋白饮料中蛋白质含量,其测量不确定度来源于样品称量、消化、蒸馏及滴定等过程。通过对各个不确定度分量的计算合成,找出影响测量不确定度的因素,并对各个不确定度分量进行评估,最终分析出样品核桃花生奶中蛋白质的标准不确定度及扩展不确定度,并描述影响核桃花生奶蛋白质测定结果各分量对其不确定度的相对贡献。[结果]最终通过合成和扩展得出了核桃花生奶中蛋白质含量测定的扩展不确定度为(1.30±0.03)%。[结论]不确定度主要由全自动凯氏定氮仪的仪器滴定体积的不确定度引入,说明仪器的先进性能够有效减少试验过程中的误差。     

Tuhualite crystal structure

As judged by crystal structure analysis, the crystallochemical formula of tuhualite is (Na,K)(2)(VI) (Fe(+3))(2)(VI) (Fe(+2))(2)(VI) Si(12)O(30) . H(2)O, with four such formulas in the unit cell. The structure is characterized by six-repeat double chains of silicon tetrahedrons and chains of edge-sharing, alternating iron tetrahedrons and octahedrons. Chains of each kind are connected by corner sharing to four chains of the other type. The iron cations appear to be anomalously ordered with Fe(+2) in tetrahedral and Fe(+3) in octahedral sites.     

大豆蛋白饮料中大豆蛋白定量方法研究

[目的]建立基于竞争酶联免疫分析(ELISA)的大豆蛋白饮料中大豆蛋白定量方法.[方法]以变性的大豆球蛋白和β-伴球蛋白为抗原,分别制备抗这2种蛋白的多克隆抗体,构建竞争ELISA方法.分析了9个品系的大豆球蛋白、β-伴球蛋白、可溶蛋白的含量.基于大豆球蛋白与伴球蛋白含量之和与可溶蛋白的比例关系,得出了植物蛋白饮料中大豆蛋白含量的计算方法.[结果]该方法的线性范围均为2.0 ～ 80 μg/ml(R2=0.99),样品前处理使用含有0.1％二硫苏糖醇(DTT)的7 mol/L尿素作为提取液.大豆球蛋白与伴球蛋白含量之和除以系数0.682可换算得到蛋白饮料中大豆蛋白含量,方法的相对标准偏差＜12％.[结论]研究可为其他热加工食品的蛋白特异性定量提供参考.     

啤酒中浑浊活性蛋白与泡沫蛋白及其相关性研究

以啤酒中的蛋白质为研究对象,综述了啤酒中浑浊活性蛋白、泡沫蛋白的生化性质、结构特点,并初步分析了浑浊活性蛋白与泡沫蛋白之间的相关性,为提高啤酒的品质和营养价值提供理论依据与技术参考.     

大豆蛋白在早期断奶仔猪蛋白质营养中的有效利用

大豆蛋白是应用最广泛的植物饲料蛋白质资源,由于其蛋白质含量高,富含蛋氨酸,其他氨基酸也较平衡,以及其价格较为便宜而愈来愈普遍地使用于早期断奶仔猪饲粮中。由于大豆中存在一些抗营养因子(如抗胰蛋白酶因子、抗原蛋白和低聚糖),从而限制了其在早期断奶仔猪日粮中的用量。断奶后的仔猪常出现食欲差、消化不良、下痢、生长缓慢、饲料利用率低、抗病力下降、精神状态不佳等现象,这些现象被称为早期断奶仔猪的应激反应,而且在断奶的前2周这种应激尤其明显。Funderburke等(1990)的研究表明,这些应激主要来源于营养方面。畜牧业发达的国家采…     

不同饲料蛋白来源对犊牛能量及蛋白代谢的影响

选择品种来源一致、发育良好、体重(143.17±8.89)kg的4月龄中国荷斯坦早期断奶公犊9头,随机分为3组,分别饲喂以豆粕、1/2豆粕+1/2玉米蛋白粉、玉米蛋白粉为蛋白质主要来源的犊牛料,采用消化、代谢试验探索不同蛋白来源对犊牛能量和蛋白代谢的影响。结果显示,以豆粕、1/2豆粕+1/2玉米蛋白粉、玉米蛋白粉分别作为蛋白质主要来源的3种犊牛料,蛋白质的表观消化率、沉积量和BV差异不显著,平均分别为(65.89±1.86)%、(203.31±14.13)g/d、(45.25±1.54)%;总能消化率、消化能转化为代谢能效率、代谢能用于沉积的效率相近,平均相应为(72.16±1.36)%、(88.34±0.18)%、(68.14±0.30)%。本试验结果表明玉米蛋白粉作为犊牛料的蛋白质饲料来源,对犊牛蛋白质和能量的消化代谢及有效利用可达到与蛋白质比价相对较高的豆粕相似的效果,可作为犊牛料理想的蛋白质饲料来源。     

同源异型域-亮氨酸拉链蛋白研究进展

同源异型域-亮氨酸拉链蛋白(HD-Zip)是高等植物所特有的一种转录因子,根据氨基酸同源序列的不同分为4大类。虽然各个HD-Zip蛋白的基因具有序列相似性,但它们在植物生长发育过程中发挥的作用是多种多样的。以拟南芥HD-Zip转录因子研究现状为主线,辅以其他植物中HD-Zip转录因子基因的研究,主要对HD-Zip蛋白的种类、生物学功能、影响其基因表达的因素及它们的表达规律4个方面进行了综述。     

激光辐射与模拟微重力对大豆种子萌发的影响

对He—Ne激光辐射和模拟微重力对大豆种子发芽率和幼苗长势的影响进行了研究,He—Ne激光辐照的连续输出功率为1．5mW。结果表明,辐照时间以15min为最适时间,超过这一时间将产生对大豆幼苗生长的抑制作用;模拟微重力处理后的大豆种子发芽率提高,其中以处理24h的种子发芽率最高,但是大豆幼苗矮化程度随着处理时间增加而加剧,以处理48h的幼苗矮化程度最明显。     

发酵鸭肌肉蛋白质的降解

发酵鸭加工过程中肌肉蛋白质降解和小肽的变化对其特殊风味的形成具有重要意义.该研究以发酵鸭的腿肌为参试对象,在鸭坯中添加植物乳杆菌、戊糖乳杆菌、变异微球菌与汉逊德巴利氏酵母菌.通过SDSPAGE电泳、HPLC分析,探讨了加工过程中肌肉蛋白质降解和小肽的变化规律.结果表明:与对照组相比,发酵剂促进了肌肉蛋白质的降解,且在后熟的过程中蛋白质分解量增多,小肽总量增加.