Deuterated hen egg-white lysozyme crystals: Optimization of the growth conditions and morphology

Deuterated and protonated tetragonal lysozyme crystals are grown using the hanging-drop vapor-diffusion method. The size of the lysozyme crystals grown is determined as a function of the concentration of sodium chloride used as a precipitant. It is found that crystallization leads to the formation of lysozyme crystals with three different habits. Morphological and X-ray diffraction analyses of the deuterated and protonated lysozyme crystals demonstrate that, despite the different habits, all the crystals grown belong to the tetragonal crystal system. The simple forms of lysozyme crystals are revealed. It is shown that the habits of the lysozyme crystals are determined by the specific combinations of simple forms. The mechanisms responsible for the formation of lysozyme crystals with different habits are discussed.     

Influence of gel inclusions on the mechanical behaviour of Gypsum

In a single test tube system, gypsum crystals grown in alcoholic gel comprise of interpenetration twinned crystals at the interface towards the gel, whereas untwinned tabular crystals are observed at greater depths inside the gel. By indentation of the crystals with a microhardness tool and recording the indentation impressions by means of a scanning electron microscope (SEM) and a transmission electron microscope (TEM) it is found that the hardness of the tabular crystals is of the same order of magnitude as those of natural crystals of gypsum, whereas interpenetration twinned crystals show a remarkable increase in hardness. On studying the morphology of cleavage faces and on carrying out energy dispersive X-ray analysis (EDXA), it is concluded that the increase in hardness of interpenetration twinned crystals with respect to tabular and natural crystals may be due to the role of the inclusion of gel particles during the growth. The implications are discussed.     

Water-soluble ferroelectric crystals with inhomogeneous impurity distribution

Stabilization of the unipolar state via the formation of inhomogeneous impurity distribution in crystal bulk is considered. Possible growth of crystals with stable characteristics is demonstrated on triglycine sulfate (TGS) crystals with a regular inhomogeneous impurity distribution. The properties of TGS crystals with an inhomogeneous distribution of chromium ions grown above and below the Curie temperature T_C are studied. Inhomogeneous TGS crystals of three types are obtained: type-I crystals with a smooth variation of the concentration gradient along the growth direction, type-II crystals with a periodic layer variation of the impurity concentration, and type-III crystals with a sawtooth-like variation of the impurity concentration along the sample length. The TGS crystals with the regular inhomogeneous impurity distribution in the ferroelectric phase are characterized by higher values of the internal bias field E _b , unipolarity coefficient k, and pyroelectric coefficient γ than the inhomogeneous crystals in the paraelectric phase and the crystals with the statistic impurity distribution grown by the conventional method.     

溶液法五氯硝基苯单晶生长的研究

测定PCNB在丙酮溶剂中的溶解度,采用恒温溶剂蒸发法首次在丙酮中成功生长出PCNB单晶.结果显示:302 K以下温区具有较小的温度系数,适用于恒温蒸发法生长单晶;生长出了厘米尺寸的PCNB晶体;红外和拉曼光谱的测量结果说明所生长的晶体中未包裹溶剂;X射线衍射分析表明,所生长出晶体结构为六方晶系,单晶质量较好.     

Melting temperatures of NaClO3-NaBrO3 mixed crystals

The melting points of mixed crystals of sodium chlorate and sodium bromate have been determined. The variation of melting point with composition is non-linear with negative deviations from linearity. This negative deviation from linearity is attributed to a possible increase in the vacancy concentration in mixed crystals as compared to the pure end crystals.     

Induced growth of Pb0.97La0.02(Zr0.66Sn0.27Ti0.07)O3 antiferroelectric single crystals with a platinum wire

Relaxor antiferroelectric (Pb,La)(Zr,Sn,Ti)O₃ (PLZST) with the composition near the morphotropic phase boundary shows excellent electrical properties. However, the crystal growth of PLZST is limited by the incongruent melting of the materials. Crystal growth of PLZST was induced by a platinum wire in the flux solution with 50 wt% PbO‐PbF₂‐B₂O₃ as a solvent. The obtained PLZST single crystals are optical transparent with light yellow color. The size of the crystals in regular rectangular shape varies from 0.5 mm to 1 mm. The PLZST single crystals exhibit tetragonal phase structure. The element contents of the crystals were measured by inductively coupled plasma atomic emission spectrometry. The results show that the composition of as‐grown crystals is a little bit deviated from the starting composition. The single crystals show two dielectric peaks at 115 °C and 182 °C, corresponding to antiferroelectric‐ferroelectric and ferroelectric‐paraelectric phase transitions. The dielectric data of as‐grown crystals indicate there is typical relaxor behavior near 182 °C. The value of relaxor factor n is 1.49642.     

Radiation hardening studies in KBr-KI mixed crystals

Radiation hardening studies have been made in KBr, KI and in different compositions of KBr-KI mixed crystals, grown from melt by Kyropoulos technique. The irradiation hardness in mixed crystals is found to vary non-linearly with composition, attaining a minimum value at intermediate compositions. Dislocation density measurements have shown a high concentration of dislocations and grain boundaries in mixed crystals as compared to end crystals. The results obtained on radiation hardening of mixed crystals were explained in terms of dislocations present in them.     

Morphology of PbI2 Crystals Grown by Gel Method

The single crystals of Lead Iodide have been grown by gel method. X‐ray diffraction studies on these crystals shows that the lattice parameters of grown crystals are almost matching with reported values. The results of detailed studies made on the microstructures of Lead Iodide crystals, have been described. The observations of the faces of these crystals revealed that they have grown by layer as well as spiral mechanisms. The probable role of these parameters is explained along with the surface microstructures on these various shaped crystals.     

Disorder in GeSe2 small crystals and medium-range structure in amorphous GeSe2

The Raman scattering spectra of various forms of GeSe₂, such as amorphous films, single crystals, and small crystals prepared by a gas-evaporation deposition technique, are investigated with an excitation photon energy ranging from 2.1 to 2.8 eV. In the spectra of the crystals, there are two Raman bands, originating from two types of breathing vibrations of the GeSe_4/2 tetrahedra: one is spread over the corner-sharing tetrahedra and the other is quasi-localized on the edge-sharing tetrahedra. In addition to the resonant Raman scattering related to the edge-sharing tetrahedra through the exciton transition observed with 2.71 eV excitation in the single crystals, a new resonant spectrum is found only in the small crystals with 2.54 eV excitation. With increasing disorder in the crystals, the intensity ratio between the two breathing vibration bands increases in the off-resonant excitation region. The Raman spectra in the amorphous states are ascribed to the breathing vibrations of GeSe_4/2 tetrahedra which form a medium-range structure topologically similar to that of crystalline fragments.     

不同Yb掺质浓度的Yb:Y3Al5O12晶体激光性能的比较

采用提拉法生长了Yb3+掺质浓度为5;原子分数、 50;原子分数和100;原子分数的Yb:Y3Al5O12(Yb: YAG)晶体,系统地分析了不同Yb3+掺质浓度晶体的吸收光谱和荧光光谱.从吸收峰和吸收系数可以看出采用940nm LD泵浦三种不同浓度的Yb:YAG晶体都比较合适.随着Yb3+离子掺质浓度的增高,晶体中出现的自吸收现象越为明显.通过对三种不同Yb掺质浓度晶体激光性能参数的计算,得出高掺质浓度Yb:YAG和YbAG晶体是有前景的激光增益介质.     

Adhesion of protein crystals: Measurement of the detachment force

The degree of adhesion of protein crystals, heterogeneously nucleated and grown on different supports (e.g. glass plates and plates coated with poly‐L‐lysine, hexamethyl‐disilazane and silicon) is measured directly with a purposely‐developed technique. The sticking force crystal/support is determined by means of a flexible glass fibre, which bending is calibrated by means of series of weights. In this way an elastic constant, specific for each glass fiber is determined individually. Appropriate glass fibres with relative bending less than 10% (Hook's law) are used. The force which is necessary to be exerted, by means of a micro‐manipulator, in order to detach the crystal from the support is taken as a quantitative measure for the adhesion strength. Forces between 10 N cm^‐2 and 1 N cm^‐2 for differently oriented tetragonal hen‐egg‐white lysozyme and cubic ferritin crystals, and 0.1 N cm^‐2 for rhombohedral (porcine) insulin and orthorhombic trypsin crystals are measured. The tetragonal HEWL and rhombohedral insulin crystals show anisotropy of the adhesion strength. In contrast, the cubic ferritin crystals are isotropic also in this respect. For comparison purposes adhesion measurements are performed with NaCl and sugar crystals. An attempt is made to evaluate also the adhesion energy of the protein crystals. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Compositional variation in Si-rich SiGe single crystals grown by multi-component zone melting method using Si seed and source crystals

The effect of the supply of depleted Si solute elements on the compositional variation in the Si-rich SiGe bulk crystals was studied using the method which was used to grow Ge-rich SiGe single crystals with a uniform composition. By selecting the proper pulling rate, we can obtain Si-rich Si_1−xGe_x bulk crystals with uniform composition of x=0.1 without using the supply mechanism of depleted Si solute elements. When the supply mechanism of Si solute elements was used, the initial composition in Si-rich SiGe crystals can be much more easily determined by controlling the growth temperature than that in Ge-rich crystals because the Si seed crystal is not melted down. The supply of Si solute elements is very effective to change the compositional variation even for Si-rich SiGe crystals.     

Number of optical axes in absorbing triclinic crystals

The possible numbers of optical axes in absorbing triclinic crystals have been considered. Most of these crystals possess four circular optical axes; however, there may be crystals having one isotropic optical axis, two or three circular optical axes, or simultaneously one isotropic and one or two circular optical axes. It is shown that particular cases significantly differ from the general case of crystal with four circular axes. The dependence of the form of the complex permittivity tensor on the number of optical axes is presented. The ellipticities of eigenwaves and the transmitted-light ellipticity in the case of normal incidence of a wave with a right- or left-hand circular polarization are calculated for these crystals.     

A survey of research on KTP and its analogue crystals

This paper reviews the growth and properties of KTiOPOP₄ (KTP) and its analogue crystals including its isomorphous crystals and doped crystals. Based on the calculation of the refractive indices and phase matching of KTP crystals, it is shown that non-critical phase matching can be achieved theoretically. In a 4%Nb-doped KTP crystal, non-critical phase matching was obtained with a pulsed Nd:YAG laser in an efficiency of ca. 4%. Most of the isomorphous and doped KTP crystals possess similar physical, optical and nonlinear optical properties as those of KTP.RbTiOPO₄, KTiOASO₄ and RbTiOASO₄ crystals have better electrooptical figure of merit and RbTiOPO₄ crystals have a fast ion conductor character. Some doped KTP crystals have shown high second harmonic generation efficiencies and damage thresholds. But the homogeneity of KTP analogue crystals is poorer than that of KTP. On the base of damage threshold tests using a CW Argon laser, it is concluded that the best second harmonic generation crystal among all the KTP analogue crystals is still KTP itself. Special care must be taken to eliminate impurity centers to avoid the formation of gray track and photorefractive centers.     

Dielectric properties of rapidly grown KDP crystals

The dielectric properties of rapidly grown potassium dihydrogen phosphate KH₂PO₄ (KDP) crystals have been studied over a wide temperature range and compared with the properties of traditionally grown KDP crystals. It was found that the contribution of domains to permittivity in rapidly grown crystals is considerably less than in conventionally grown ones. The dielectric properties in various growth sectors of KDP crystals are determined.     

Zur Züchtung von β-Kupferphthalocyanin-Einkristallen aus der Gasphase

An apparatus useful for many kinds of vapour phase growth used in order to clarify reasons for bad reproducibility and constancy of growth conditions by an growing method known since 1936 and reasons for cavity growth. The characteristics of growth are described dependent on different growing methods and on various kinds of nucleation and crystal growth. The introduction of new growing methods allows the production of larger crystals. The growth of the needle-like crystals is governed by diffusion. The shape of the crystals does not differ qualitatively from their equilibrium shape. The crystals grow with smooth surfaces. Only the front surfaces show morphological imperfections, if the crystals exceed a critical size.     

Experimental Solution of the Local Field Problem in Uniaxial Liquid Crystals†

A method of experimental determination of the Lorentz-factor tensor in uniaxial liquid crystals is suggested. The specific features of the local field tensor of the light wave in a nematic liquid crystal with low optical anisotropy have been investigated experimentally. Anisotropy of the local field and Lorentz-factor tensors has been found to decrease with the decreasing optical and molecular-optical anisotropies. These results appear to contradict the existing polarization theories of liquid crystals. The local field problem in cholesteric liquid crystals has been considered. A new approach to the local field problem in uniaxial liquid crystals with arbitrary optical anisotropy is developed and the experimental results are explained.     

Some properties of the solvent in monoclinic lysozyme crystals

Study by the luminescent-probe (Eu³⁺) method has demonstrated that water in monoclinic lysozyme crystals is readily exchanged with water from the environment. Molecules of certain organic molecules about 2 nm in size equally readily penetrate into crystals. The state of water directly surrounding protein molecules both in the protein solution and crystals differs from the state of other water molecules. The percentage of water molecules of the former type is higher in crystals than in solution. Water was found to be removed in two steps during crystal drying. The weight loss of samples upon storage at a constant temperature of ～30°C under nitrogen for 3 h is about 24%. Heating of crystals, which were dried under the above-mentioned conditions, led to the additional loss of 2.1 wt % of water. Therefore, the total water content in crystals is ～26 wt %.     

近化学计量比Tb:Fe:LiNbO3晶体的光谱特性及组分测定

按化学计量比,用提拉法成功生长了不同掺量的Tb:Fe:LiNbO3晶体,分别测量了掺杂LiNbO3晶体在紫外(313nm)曝光前后的吸收光谱,曝光后吸收谱线整体上移,找到了吸收谱线上移最大的掺量比.并用差热分析仪DTA测量了居里温度Tc, 从而计算出Li/Nb的比例.分析表明,Tb:Fe:LiNbO3晶体的存储性能与掺量、定比有密切的联系,是一种优良的大容量体全息记录材料.     

Growth of dl-malic acid-doped ammonium dihydrogen phosphate crystal and its characterization

Single crystals of dl-malic acid-doped ammonium dihydrogen phosphate have been grown using slow evaporation method and also by Sankaranarayanan–Ramasamy (SR) method with the vision to improve the properties of the ADP crystals. The characterization of grown crystals was made by single-crystal X-ray diffraction, powder X-ray diffraction, UV–vis. spectroscopy, Fourier transform infrared spectroscopy (FTIR), differential thermal analysis (DTA), Vicker's microhardness, dielectric measurements, high-resolution X-ray diffraction (HRXRD) and second-harmonic studies. Structural difference between pure and doped crystal has been studied by XRD analysis. Functional groups were identified by FTIR spectroscopy. The grown crystals were found to be transparent in the entire visible region. Decomposition temperatures of the grown crystals were measured by DTA. Vicker's hardness study carried out on (0 0 1) face at room temperature shows increased hardness of the doped crystals and SR-method-grown crystals. Dielectric measurements reveal that SR-method-grown DLM-doped ADP crystals have low dielectric loss. Crystalline perfection of the grown crystals is analyzed using HRXRD. Preliminary measurements indicate that the second harmonic generation efficiency of the doped crystals at a fundamental wavelength of 1064 nm is roughly 1.5 times greater than that of pure ADP.