Study of Growth Mechanism of Lysozyme Crystal by Batch Crystallization Method

The lysozyme crystals were made by batch crystallization method and the distribution of aggregate in solution were measured by dynamic light scattering. The results showed that the dimension of aggregate increased with the increase of the concentration of lysozyme and NaCl, lysozyme molecules aggregated gradually in solution and finally arrived at balance each other. The higher the concentrations of lysozyme and NaCl were, the faster the growth rate of （110） face was. The growth rates of lysozyme crystal were obtained by a Zeiss microscope, and the effective surface energy （a） of growing steps were calculated about 4.01×10^-8s J·cm^-2 according to the model of multiple two-dimensional nucleation mechanism.

Growth mechanism of reinforcements in in-situ synthesized (TiB+TiC)/Ti composites

The growth mechanism of reinforcement in in situ synthesized (TiB+TiC)/Ti composites was investigated. The results show that reinforcements nucleate and grow in a way of dissolution precipitation. The morphologies of reinforcements are closely related to the solidification paths and crystal structure of reinforcements. TiB, as a reinforcement, is liable to grow along [010] direction and forms in short fibre shape due to its B27 structure, whereas primary TiC is liable to form composition undercooling and grow in dendritic shape. TiC phases precipitated in binary eutectic and ternary eutectic reactions grow in equiaxial shape. The addition of aluminum element refines TiB and TiC particles, and makes TiC reinforcements grow into the equiaxial particles easily. The addition of graphite adjusts the solidification paths and forms more TiC with dendritic shape. [

Template growth mechanism of spherical Ni(OH)_2

The microstructures and growth process characteristics of spherical Ni(OH)2 particles synthesized by the aqueous precipitation-crystallization method were investigated by SEM, TEM and XRD, and their growth mechanism was discussed. With the reaction beginning and continuing, amorphous Ni(OH)2 nano-crystallites grow up to spherical micron-particles with radially arranged crystallites. The nucleation, crystallization and re-crystallization led by Ostwald ripening simultaneously take place through the whole growth processes. With the course from reversible aggregation to irreversible agglomeration, the Ni(OH)2 particles tend to grow according to the template growth model: the growth on the crystallite templates stretching in the radius directions is free and quick, while the growth rate for crystallites in other directions is confined due to lower monomers concentration and tends to dissolve. So it is only the radially arranged crystallites that predominate in the particle and lead to characteristic microstructures.

Synthesis and Controllable Growth Dynamics of Third Order Nonlinear Optical Material of 2-Amino-4-Methylpyridinium 2-Chloro 4-Nitro Benzoate Electro-Mechanical Investigation and Device Fabrication

An organic nonlinear optical material 2-Amino-4-methylpyridinium 2-chloro 4-nitro benzoate (AMPCNB) was synthesized and large size single crystals were grown by slow evaporation solution growth method. Single crystal X-ray diffraction study showed that the title compound belongs to monoclinic crystal system with P21/n space group. A powder XRD study was performed to ascertain its phase. The UV–VIS-NIR study was performed to investigate the transparency window and lower cutoff wavelength of the compound, no absorption has been observed between 318 and 1100 nm. The third harmonic efficiency of the title compound has been studied using the Z-scan technique using continuous-wave Nd:YAG laser to confirm its saturable absorption and self-defocusing effect. The photo conducting and charge transport properties are analyzed using photoconductivity and dielectric measurements. Theoretical calculation of molecular polarizability, which is helpful in device fabrication, was carried out from Penn gap, Clausius-Mosotti equations and the obtained results were compared. Mechanical properties of the grown crystal were investigated by Vicker’s microhardness study.

Growth Mechanism of Different Morphologies of ZnO Crystals Prepared by Hydrothermal Method

Different morphologies of zinc oxide（ZnO）,including microrods,hexagonal pyramid-like rods and flower-like rod aggregates,had been synthesized,respectively,on glass substrates by controlling the reaction conditions（such as precursor concentration,reaction time and pH value） of hydrothermal method.The morphologies of the as-obtained ZnO were observed with scanning electron microscopy and transmission electron microscopy.Also,the crystalline natures of different ZnO crystals were analyzed with X-ray diffraction.The possible growth mechanism of ZnO crystals with different morphologies was discussed.

Crystal formation and growth mechanism of inorganic nanomaterials in sonochemical syntheses

A clear understanding of the nucleation, growth, coarsening, and aggregation processes of nanomaterials is necessary to enable the preparation of highly controlled nanostructures. Among wet chemical synthetic methods, ultrasound-assisted preparation has become an important tool in material science. The formation and crystal growth mechanism under ultrasound is special compared with other wet chemical synthetic routes. In this review, we discussed the chemical and physical effect of ultrasound and summarized the ultrasonic effect on crystallization. The sonolysis of water and the cavitation-induced microjet impact and shockwave are the two key factors in the sonochemical formation of inorganic nanomaterials. The ultrasonic-assisted Ostwald ripening and oriented attachment processes have been reviewed for the possible crystal growth mechanisms in the fabrication of inorganic nanostructures.

Inhibition mechanism of aspartic acid on crystal growth of hydroxyapatite

The effects of aspartic acid on the crystal growth, morphology of hydroxyapatite(HAP) crystal were investigated, and the inhibition mechanism of aspartic acid on the crystal growth of hydroxyapatite was studied. The results show that the crystal growth rate of HAP decreases with the increase of the aspartic acid concentration, and the HAP crystal is thinner significantly compared with that without amino acid, which is mainly due to the (1 010) surface of HAP crystal being inhibited by the aspartic acids. The calculation analysis indicates that the crystal growth mechanism of HAP, following surface diffusion controlled mechanism, is not changed due to the presence of aspartic acid. AFM result shows that the front of terrace on vicinal growth hillocks is pinned, which suggests that the aspartic acid is adsorbed onto the (1 010) surface of HAP and interacts with the Ca2+ ions of HAP surface, so as to block the growth active sites and result in retarding of the growth of HAP crystal.

Growth Habit of Polar Crystal ZnO by Solid-vapor Method

Crystals of semiconductor ZnO were fabricated by means of solid-vapor growth method-carbon thermal reduction. Powder X-ray diffraction and field emission scanning electron microscope were used to characterize the phase and morphology of the samples. The results showed that the samples were wurtzite ZnO crystals and anisotropy of crystal growth relied on reaction temperature in solid-vapor process. The crystals synthesized at different temperatures were of short column-like shape, flat top hexagon pyramidal-like shape and polyhedron shape. The growth mechanisms of the above three kinds of crystal were consistent with the theory of growth basic structural unit of negative ion coordination polyhedron. At first, Zn2＋ and four O2- form [Zn-O4]6- coordination tetrahedron at any temperature. Then, tetrahedrons stack in different ways into different morphology crystal at different temperatures.

The growth mechanism of the basic magnesium chloride whisker

Based on the theoretical model of anion coordination polyhedron growth units, the growth mechanism of the basic magnesium chloride whisker was discussed in this paper.It was found that the basic magnesium chloride whisker habits were related to the different environments in which anion coordination polyhedra grew. The growth units of basic magnesium chloride whiskers are [Mg - (OH) 4]2 -and [Mg - Cl 4]2 -. The growth process is the incorporation process of growth units. Growth units will have different incorporations and orientations caused by different system characters or heating. Furthermore, the formation mechanism of basic magnesium chloride whiskers was also interpreted using anion coordination polyhedron growth units.

SOLUTION CRYSTALLIZATION OF METALLOCENE SHORT CHAIN BRANCHED POLYETHYLENE:MORPHOLOGY AND MECHANISM

Solution crystallization of metallocene short chain branched polyethylene (SCBPE) was carried out and very nice single crystals were obtained. Compared with single crystals grown from linear polyethylene, SCBPE single crystals are dirty due to intermolecular heterogeneity The crystal morphology changes with crystallization temperatures. Lozenge, truncated lozenge, hexagonal, rounded and elongated crystal morphologies have been found at much lower crystallization temperature than in linear polyethylene. The electron diffraction shows there is a possibility that the single crystals may have hexagonal packing in a crystallization temperature range. The lateral habits of single crystal are discussed based on roughening theories.

Synthesization and crystallization mechanism of nano-scale γ-AlOOH with various morphologies

Nano-scale γ-AIOOH with various morphologies, such as whisker, bar, ball, and sheet, was synthesized successfully and control- lably through a facile hydrothermal method just by adjusting the pH value of the solvent. Based on the analysis of the experimental data, the growth mechanism of nano-scale γ-AlOOH in the hydrothermal process was established. It is proposed that the growth unit and the growth direction are determined by the pH value of the solution and the growth unit, respectively. One-dimensional γ-AlOOH, such as whisker and bar, is formed in lower pH ranges, while two-dimensional γ-AlOOH sueli as sheet is formed only in high pH environment following the plane expansion crystallization mechanism.

基于明考斯基最优距离的不完美排错SRGM决策机制

针对软件可靠性增长模型(software reliability growth model,SRGM)决策机制欠缺的问题,提出了基于明考斯基最优距离的不完美排错SRGM决策方法。首先,对真实软件测试过程与可靠性模型进行分析,建立分类视角下的SRGM归类集合;其次,从矩阵分析的角度形式化描述SRGM的评价与选择问题,建立基于明考斯基距离的双最优化排序方法;最后,对模型的性能进行综合评价,给出SRGM间的性能偏序关系。在4个实际计算机应用系统测试过程中记录并公开发表的失效数据集上进行实验,验证和阐释模型性能之间的排序机制效用,并进行参数敏感性分析,为模型决策提供定量化的参考。

虾壳源多肽酶解条件的优化及其抗冻活性和作用机制的探究

目的优化从虾壳中提取多肽的酶解条件,并探究虾壳多肽的抗冻活性及作用机制。方法以小龙虾虾壳为原料,使用复合酶酶解提取多肽。在单因素实验的基础上,通过正交实验得到虾壳最佳酶解条件。以面包酵母菌为抗冻测试对象测试其抗冻能力。采用液相色谱-串联质谱法(liquid chromatography-mass spectrometry,LC-MS/MS)对虾壳多肽的组成进行鉴定,基于多肽的理化性质和序列,结合抗冻预测平台筛选抗冻肽(antifreeze peptides,AFPs)。使用分子动力学模拟探究了AFPs的作用机制。结果在酶解温度40℃,底物质量浓度20mg/mL,加酶量12000U,酶比0.33的最佳酶解条件下,多肽提取率达到了70%以上。虾壳多肽中含有1004种肽段,能明显提升酵母菌存活率。从具有抗冻活性且置信度靠前的20条多肽中进一步筛选出了潜在的抗冻肽AFP1、AFP2。AFP2和冰面之间形成的氢键数量为14,部分水分子同时与2个氨基酸残基形成氢键,充当水桥稳定多肽的构象,AFP2与冰之间的结合能为-105.08 kcal/mol,冰结合模拟效果理想。结论AFPs与冰结合并抑制冰晶生长可能归因于带电荷的亲水性氨基酸残基与水分子形成的氢键、范德华力等分子间作用力,可开发为有益的冷冻保护剂,用于冷冻食品加工,具备良好的应用前景。

CsPbBr_(3)晶体生长及变温霍尔效应研究

以定向凝固法提纯的CsPbBr_(3)多晶为原料,采用垂直布里奇曼法生长出尺寸为∅30 mm×70 mm的CsPbBr_(3)单晶。采用ICP-OES对提纯后的多晶测试表明,提纯后的CsPbBr_(3)多晶中杂质含量减少了28.7%。经XRD和EDS对切割得到的晶片分析发现,晶片的晶面方向属{210}晶面族,晶体中Cs、Pb、Br_(3)种元素分布均匀,原子百分含量符合化学计量比。采用傅里叶红外光谱仪和紫外-可见分光光度计对晶体的透过率测试显示,生长晶体在500~4000 cm^(-1)波数范围内的红外透过率超过75%,紫外短波截止边为552 nm,拟合计算出对应的禁带宽度为2.246 eV。选取7个不同温度点对CsPbBr_(3)单晶进行变温霍尔效应测试发现,生长晶体为P型导电,在250~300 K和300~350 K之间晶体中主要的载流子散射机制分别为声学波散射和电离杂质散射,在150~250 K温度范围内,更符合多种散射机构共同作用的散射机制。进一步拟合载流子浓度p与1/T的关系,计算获得晶体中杂质电离能ΔE_(A)=0.3042 eV。

Morphology and crystalline property of an AlN single crystal grown on AlN seed

AlN single crystal grown by physical vapor transport (PVT) using homogeneous seed is considered as the most promising approach to obtain high-quality AlN boule.In this work,the morphology of AlN single crystals grown under different modes (3D islands and single spiral center) were investigated.It is proved that,within an optimized thermal distribution chamber system,the surface temperature of AlN seed plays an important role in crystal growth,revealing a direct relationship between growth mode and growth condition.Notably,a high-quality AlN crystal,with (002) and (102) reflection peaks of 65and 36 arcsec at full width at half maximum (FWHM),was obtained grown under a single spiral center mode.And on which,a high-quality Al_x Ga_(1–x) N epitaxial layer with high Al content (x=0.54) was also obtained.The FWHMs of (002) and (102) reflection of Al_x Ga_(1–x) N were 202 and 496 arcsec,respectively,which shows superiority over their counterpart grown on SiC or a sapphire substrate.

STUDIES ON PRIMARY CRYSTALLIZATION OF RAPIDLY QUENCHED Al-Ni-Cu-Nd METALLIC GLASS BY USING HIGH RESOLUTION TRASMISSION ELECTRON MICROSCOPY

Rapidly solidified Al87Ni7Cu3Nd3 metallic glasses, prepared by using melt spinning, were treated under both isothermal and non-isothermal regime. The amorphous ribbon and the annealed samples were closely examined by means of differential scanning calorimetric, conventional X-ray diffraction and high resolution transmission electron microscopy with selected-area electron diffraction, with special interest in primary crystallization into α-Al nanocrystalline particles, in order to understand structural characteristics of Al-based amorphous/nanocrystalline alloys, and nucleation and grain growth mechanism on the nanometer scale during primary crystallization. The results show that, the as-prepared ribbons are fully amorphous and homogeneous in the micron scale, but contain high density of quenched-in clusters or crystallite embryos. Primary crystallization mainly leads to formation of two-phase mixture of a-Al crystal and residual amorphous phase. The annealed ribbons exposed isother-mally at HOP C for 5, 130 minutes and heated continuously up to less than 310℃ at 40℃ C/min consist of large amount of α-Al fcc crystal nanoparticles dispersed uniformly in an amorphous matrix. However, a very little amount of finer orthorhombic Al3Ni intermetalics particles exist in the annealed ribbons heated up to 310℃. During primary crystallization, the leading kinetic mechanics to impede growth of the α-Al crystal is soft impingement, instead of geometric impingement.

低温碳化法制备高分散性纳米碳酸钙的研究

以石灰石为原料,采用低温碳化法制备了高分散性纳米碳酸钙。通过XRD、SEM、TEM等对纳米碳酸钙样品进行表征,考察了浆料比、碳化温度、CO_(2)通气速率、陈化时间、晶型控制剂对纳米碳酸钙粒径和分散程度的影响。研究结果表明,制备纳米碳酸钙的最佳工艺条件为:浆料比为5%,碳化温度为15℃,CO_(2)通气速率为200 mL/min,陈化时间2 h,并选用ZnCl_(2)为添加剂。在此条件下,制得晶粒尺寸为25~35 nm、分布均匀的立方体状纳米碳酸钙。结合Materials Studio对纳米碳酸钙的生长机理进行了分析,结果表明:碳酸钙的(104)和(116)2个晶面具有热力学稳定性,最终会成为顽强显露的晶面,促使生成立方体型纳米碳酸钙。

Electrochemical Quartz Crystal Microbalance(EQCM) Characterization of Electrodeposition and Catalytic Activity of Pd-based Electrocatalysts for Ethanol Oxidation

Pd was electrochemically deposited on gold-coated quartz crystals at nanogram-level. The coulombic efficiency and initial nucleation and growth mechanism of potentiostatic Pd deposition were investigated via in situ electrochemical quartz crystal microbalance（EQCM）. The coulombic efficieneies are 84%, 93% and 95% for Pd deposition at 0.3, 0.2 and 0.1 V（vs. SCE）, respectively. The results of chronoamperometric measurements show that the Pd deposition proceeded by an instantaneous nucleation（at 0.3 V） or progressive nucleation（at 0.2 and 0.1 V） in a three-dimensional（3D） growth mode. The catalytic activity of Pd-based electrocatalyst for ethanol oxidation was characterized in an alkaline solution. It was found that the highest mass activity for ethanol oxidation on Pd-based electrocatalyst is 1.8× 10^4 A/（g Pd） deposited at 0.3 V for 5 s.

面向2035年上海经济稳增长动力机制和对策研究

上海经济稳增长对全国经济稳增长的实现具有重要意义。本文从投资、消费、技术进步、产业聚集、贸易开放、债务、突发性公共卫生事件等方面对上海经济增长动力源泉与稳定性影响因素进行理论回顾。通过数据对比分析,明确上海经济稳增长动力的阶段性特征。从投资效率、科技创新、产业环境、人力资本几方面构建上海经济稳增长的动力机制,提出基于新发展理念“创新、协调、绿色、开放、共享”的五大战略对策。

Growth, structure and upconversion mechanisms of Ba_2ErCl_7 crystal

The methods to grow a novel upconversion crystal Ba2ErCI7 are reported in this note. Ba2ErCI7 material was synthesized with Er2O3, BaCI2-2H2O and NH4CI by using a so-called "direct synthesis method". High quality Ba2ErCI7 single crystals with size up to 4 mm×8 mm×15 mm were grown by using the Czochralski and the Bridgman methods. Intense yellow-green luminescence was detected when the crystal was pumped by an 803 laser diode (LD). Transmittance spectrum was measured by using HITACH U-3500 spectrophotometer at room temperature for the first time, in which one can see that the transmittance is high in the range from 350 to 1 600 nm and the cut-off wavelength of the crystal was 230 nm. The upconversion mechanisms were discussed.