Growth of rhombohedral insulin crystals and in vitro modeling of their dissolution in the blood stream

Insulin is the only protein that is secreted in a crystalline form in a human healthy body. To mimic the secretion process we used NaCl salting‐out to growing tiny rhombohedral Zn‐insulin crystals. The dissolution of the insulin crystals is of special interest for the therapeutical praxis, because the human body is supplied with the physiologically active monomers of the insulin through dissolution of the crystalline granules secreted in the pancreatic β‐cells. Sets of tiny rhombohedral Zn‐insulin crystals, which resembled the granules secreted in the β‐cells, were subjected to dissolution in blood plasma and model solutions. The impacts of the solution composition, flow rate, pH and ionic strength on the insulin crystal dissolution were investigated. The effect of the blood plasma was determinant because it dissolved the rhombohedral Zn‐insulin crystals almost instantly, while the effects of solution's physicochemical characteristics were of minor importance. In addition, we found that the presence of abundant zinc ions suppressed the dissolution of the insulin crystals. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Capture centres in yttrium-aluminium borate crystals

The present work is a pioneer study of the capture centres of charge carriers in yttriumaluminium borate crystals. An evaluation was made for the activation energies of the trapping centres and their frequency factors. The highest thermally stable trapping centres were shown to be characterized not so much by relatively high activation energy values, but rather high frequency factors exceeding the values of the natural frequencies of atom oscillations. On the basis of experimental results, models were suggested for some electron capture centres to reveal donor elements.     

Influence of impurities,irradiation and temperature on the mechanical and electrical properties of LiF crystals

On the basis of study of the temperature dependence of mechanical and electrical properties of LiF crystals with different impurities an evident interaction between radiation defects and impurities is revealed. As a result of trapping of radiation defects (F- and H-aggregate colour centres) by impurity centres the reconstruction of impurity centres takes place, causing a change of mechanical and electrical properties.     

Low-temperature Thermoluminescence Glow Curves in NaCl Crystals Doped with Yttrium

Thermoluminescence glow curves were recorded in undoped and yttrium-doped NaCl crystals X-irradiated at liquid nitrogen temperature (LNT). An attempt is made to assign the glow peaks observed to different centres such as V_k-centres and yttrium related centres etc.     

Dye centres in magnesium doped corundum monocrystal

Results of absorption spectra studies in Mg doped Al₂O₃ monocrystals are described. It is shown that due to Mg doping dye centres appear together with the associated additional absorption bands with maxima at 585, 475 and 260 nm. Kinetics of the formation (destruction) of these centres) of these centres in the process of thermal treatment is considered. An assumption on the nature of dye centres and the related absorption bands is proposed together with an evaluation of oscillator strength. Dependences of diffusion coefficients of the subject centres on thermal treatment temperatures are derived.     

The influence of controlled electron-seeking addition agents of the melt on stilbene single crystal structure and radioluminescence properties

The study of certain radioluminescence characteristics of stilbene single crystals is performed. Doping the stilbene melt with electron-seeking (ES) addition agents of benzol and benzophenone halogen derivatives allowed to control the structure perfection of the crystal grown. The root-mean-square random orientation of single crystal mosaic structure, and concentration of the deep traps of charge carriers and excitons were minimum for the single crystals grown from the melt containing 0.1 mol% ES addition agent. Doping the melt with ES addition agents did not cause the appearance of additional luminescence impurity centres or quench luminescence centres in the single crystals grown.     

Photo-EPR of deformation-produced defects in GaAs

Deformation-produced paramagnetic centres have been studied in GaAs crystals uniaxially compressed at 400° using EPR technique (X band). The effect of light with photon energies from 0.4 to 1.5 eV on the populations of the centres has been investigated. On the basis of the experimental results a model is proposed which locates the energy levels of two of the centres at E_c − 1.05 eV and E_v + 0.75 eV.     

EPR of Mo5+ in amorphous MoO3 thin films

Mo⁵⁺ centres in amorphous thin films of MoO₃ have been studied as a function of optical density using EPR techniques. Measurements were made for over an order of magnitude change in optical density and down to helium temperatures. A direct correlation between the optical density and the number of Mo⁵⁺ centres is found for low optical densities but further colouration does not continue to increase the number of Mo⁵⁺ centres. A model is proposed to explain the results.     

Structure and photoluminescence of the a-GexSe1−x system

GeGe like-bonds are formed in as-deposited films at x < 0.33 i.e. they are both chemically and structurally disordered. Photoluminescence (PL) intensity along with the fatigue of PL is presumably controlled by the positions of the demarcation levels which are displaced by changing the concentrations and cross sections of the recombination centres. The increase of Se content in these binary alloys leads to an increase of the concentration of non-radiative recombination centres. During fatigue both new centres are created and the cross sections of the pre-existing ones are changed.     

Oxidation kinetics of BaF2 single crystals

Oxidation of BaF₂ single-crystals as a result of annealing in air in the temperature range 600° to 900 °C leads to mechanical strengthening. The process kinetics was investigated. It is shown that oxidation takes place in the bulk of crystals owing to oxygen diffusion by formation and growth of oxidation centres. These centres are precipitates of a BaO phase which were revealed by chemical etching.     

UV‐visible emission of (O2‐ ‐ F+) centres in KBr

Single crystals of KBr containing the (O^2‐ ‐ F⁺) color centres and elaborated in atmospheric air by the Czochralski method are studied. The measure of the UV‐visible emission spectra at 78 K present several emission bands situated between 340 and 800 nm. The photoluminescence excitation shows that these emissions are attributed to O^‐₂ and (O^2‐ ‐ F⁺) centres. This study show the new emission bands of (O^2‐ ‐ F⁺) centres which are situated in the UV‐visible spectral domain. The comparison between the emission spectra before and after the thermal treatment of samples shows clearly the transformation of O^‐₂ centers at high temperature to (O^2‐ ‐ F⁺) centres. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Initial stages of SiC crystal growth by PVT method

Initial stages of SiC crystal growth by Physical Vapor Transport method were investigated. The following features were observed: (a) many nucleation crystallization centres appeared on the seed surface during the initial stage of the growth, (b) at the same places many separate flat faces generated on the crystallization front, (c) the number of facets was dependent on the shape of the crystallization front and decreased during growth, (d) appearance of many facets lead to decrease of structural quality of crystals due to degradation of regions where crystallization steps from independent centres met. The results revealed that the optimal crystallization front should be slightly convex, which permits the growth of crystals with single nucleation centre and evolution of single facet on the crystallization front. The subjects of study were the shape and the morphology of growth interface. Defects in the crystallization fronts and wafers cut from the crystals were studied by optical microscopy, atomic force microscopy (AFM) combined with KOH etching and X‐ray diffraction. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Dehydration of Selenite Cleavage Faces

Initial dehydration of selenite cleavage surfaces start at temperature 86 °C. The dislocations are revealed by distilled water. Dislocations are mobile at dehydration temperature. Impurity centres may act as obstacles for dislocation movement. Dehydration figures are in probability formed at impurity centres.     

Investigation of the interaction of quartz with H2 under supply of mechanical energy (I)

The gas molecules absorbed during mechanical activation of quartz in a H₂ atmosphere are situated as well as the formed E′ centres in the amorphous ranges. The concentrations of the E′ centres are about one order of magnitude less after activation in H₂ than after an activation in Ar. Hence and because of the existence of a proton doublet (splitting of about 73 G) in the EPR spectra a chemical interaction of a part of the absorbed H₂ molecules with quartz is concluded.     

Reaktivität von mechanisch aktiviertem Quarz

By grinding of quartz arises a strong disorder. In this amorphous range the centres of defectelectrons or the E'centres are concentrated. The amorphous range shows a changed reactivity.     

ESR study and model of paramagnetic defects in GeS glasses

The ESR spectra of very pure GeS glasses were studied. Based on structural considerations, the models of intrinsic defect centres were proposed, ESR spectra simulated, and spin Hamiltonian parameters calculated. The computed spectra are in good agreement with the measured spectra.     

Long-lifetime photoconductivity in Cz n- and p-Si

Long-lifetime photoconductivity is observed in Czochralski-grown oxygen-rich heattreated n- and p-type silicon crystals. It appears due to a slow electron (in Cz n-Si) and hole (in Cz p-Si) recombination via two kinds of oxygen-induced recombination centres. Dependences of the long-lifetime photoconductivity on the oxygen content, excitation intensity and temperature are presented. Possible models to explain an appearance of the long-lifetime photoconductivity in Cz n- and p-Si are discussed. The data presented are important for understanding the long-time photoeffects in semiconductors and for elucidating the origin and structure of oxygen-induced recombination centres in silicon.     

CdS薄膜中"白斑"的研究

本论文对CdS薄膜中的"白斑"进行了研究.化学水浴沉积法(CBD)制备CdS薄膜所需要的化学反应物包括硫脲、氨水、镉盐和铵盐等.文中采用两种镉盐和铵盐来沉积CdS薄膜:氯化镉和氯化铵,乙酸镉和乙酸铵.所沉积的CdS薄膜的表观形貌由SEM表征,成分由EDX表征.当镉盐和铵盐分别采用氯化镉和氯化铵时,生成的薄膜中存在大量的"白斑".这些"白斑"的成分不是CdS,而是(CdCl)2S.增加氨水的浓度可以大大减少这些"白斑",但是不能彻底消除这些"白斑".当镉盐和铵盐分别采用乙酸镉和乙酸铵时,生成的薄膜均匀、平整,薄膜中根本就不存在所谓的"白斑".因此,沉积CdS薄膜时,镉盐和铵盐不宜采用氯化镉和氯化铵,应该采用乙酸镉和乙酸铵.     

Initial Growth Stages of Man-made Quartz Crystals and Growth Mechanism of their (0001) Face

In a series of short term runs it has been shown that in the course of the non-stationary part of the hydrothermal process the quartz seed plate is subject to: 1. fast and deep dissolution; 2. very slow dissolution-and-growth; 3. a shallow complementary etching; 4. mass formation of crystallization centres; 5. tangential and normal growth of these centres accompanied by their aggregation into larger growth units. Every one of theses processes produces a specific structure on the actively growing (0001)-face. The last process which continues also when the temperatures are stationary, creates the well known “cobble structure”. As the growth continues the prolonged aggregation increases perceptibly the growth rate and makes the cobble structure coarser and coarser.     

基于铈钆共掺杂YAG单晶荧光片的高光效白光LED

为了满足高功率白光发光二极管(Light-Emitting Diode,LED)对荧光体的高性能要求,对白光LED用Cex Gd:YAG单晶荧光材料的制备和光学、电学、热学特性进行了研究.采用提拉法生长了CexGd:YAG(x=0.02,0.04,0.06,0.08)单晶,并借助于X射线衍射(XRD)、吸收光谱、发射光谱等对晶体的光谱特性进行了表征,同时也测试分析了相对荧光强度随温度的变化关系、基于不同Ce3+浓度Cex Gd:YAG单晶的白光LED性能参数.结果表明Cex Gd:YAG单晶在450 nm的蓝光激发下,产生一个500～650 nm的宽峰发射,在100℃高温下,其荧光光强比商用荧光体粉末高出10;.当Ce3+浓度为6;时,采用Cex Gd:YAG单晶荧光片的白光LED光效高达153 lm/W,是Ce:YAG和树脂荧光材料白光LED的两倍多.Cex Gd:YAG单晶荧光片,具有更高更稳定的荧光光强,制作的白光LED光效有明显提升,有望成为新型的商用荧光体.