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41.
Jiří Bednář Ladislav Svoboda Pavel Mančík Richard Dvorský 《Materials Science & Technology》2019,35(7):775-781
Zinc sulphide (ZnS) nanoparticles were prepared by an aerosol method from zinc acetate and sodium sulphide (Na2S) aqueous solutions. Aqueous solution of zinc acetate was dispersed into the form of microdroplets, which were introduced by airflow to vigorously stirred aqueous solution of Na2S, which was in excess. Microdroplets served as microreactors, so the reaction took place only in limited volume. Particle size distribution was studied by transmission electron microscopy and by dynamic light scattering measurements. In this work, the equation that allows us to predict the final size distribution of ZnS nanoparticles using exact concentration of zinc acetate was derived and ZnS nanoparticles with predicted mean particle diameter around 50 and 70?nm were successfully synthetised. 相似文献
42.
J. Novák J. Šoltýs P. Eliáš S. Hasenöhrl I. Vávra 《Materials Science in Semiconductor Processing》2010,13(3):167-172
The growth of InMnAs quantum dots by low pressure MOVPE technique on patterned (1 0 0) GaAs substrates was studied. The patterning in the form of ridges with sidewalls having (2 1 1) and (3 1 1) facets was prepared by wet chemical etching via a GaAs/AlAs sacrificial etching mask structure. AFM studies showed that the dots formation and distribution were very similar for both types of facets under study. InMnAs dot density on the (3 1 1) plane is about 5–7 times lower in comparison to that on the (1 0 0) planar substrate. The dots on sidewalls are larger in comparison to average dots formatted on planar GaAs (1 0 0) substrate. The lateral dimensions of these dots are in the interval 100–180 nm. In addition, dot distribution along the sidewall (from top to bottom) is not uniform. A higher dot concentration was observed close to the intersection of (3 1 1) facets with concave bottom part of the valleys between ridges. Finally, no dots were grown on the (1 0 0) plane created by self-faceting on the top of the triangular ridges. This is probably a consequence of the high quality of the (1 0 0) facet formed by lateral overgrowth. 相似文献
43.
The analysis of expression of pheromone-carrying major urinary proteins (MUPs) from two subspecies of house mice (Mus m. musculus, Mus m. domesticus) was studied. It has been previously shown that commensal populations of the two subspecies can discriminate on the basis
of urinary signals. MUPs are predominant urinary proteins that protect pheromones from rapid degradation in a hydrophilic
environment, and individuals of M. m. musculus tend to rely on these urinary cues in the process of subspecies discrimination more than M. m. domesticus individuals. Although it is not precisely known what triggers phenotypic and epigenetic changes of MUP expression, our results
show that in the subspecies M. m. musculus, sex is a significant factor influencing variations in the regulation of selected MUPs in the liver. Furthermore, male M. m. musculus individuals expressed all the studied MUPs’ mRNA significantly more than females or individuals of either sex in M. m. domesticus. Correspondingly, the pattern of mRNA abundance was corroborated with the level of total MUP concentration in the urine,
such that the level of sexual dimorphism was also significant and species-specific. Our finding introduces a hypothesis that
quantitative variation of these proteins may be an essential part of a subspecies recognition system that maintains homospecific
mixing. 相似文献
44.
High-dose gamma irradiation of electrodes provided with an active film consisting of 5 mol. % RuO2 and 95 mol. % TiO2 may produce electrodes whose chlorine overvoltage at 60°C in a solution containing 300 g NaCl per dm3 conforms to the relation for A 60Co source and doses about 4.9.105 C kg?1 (1.9 GR) were used. The gamma radiation has a positive effect of short duration in that it decreases the chlorine overvoltage, especially at higher cds. In the course of time the chlorine overvoltage of irradiated electrodes will increase beyond the values obtained with untreated electrodes. 相似文献
45.
Effective interfacial areas for gas absorption were measured at various irrigation rates for Raschig rings made of a ceramic (industrial porcelain) and of various plastics. The plastics used were polyethylene and polypropylene having very low wettabilities with water. The surface of some of the plastic packings was covered with a hydrophilic layer. The absorption of pure oxygen by a sodium sulphite solution containing cobalt catalyst was used for the measurement of effective interfacial area. It has been found that the effective interfacial area of plastic packings was about 40 per cent of that of geometrically similar ceramic packings. The effective interfacial area of the plastic packings was increased about 2·5 times by application of the hydrophilic layer. Thus, the wetted surface areas of plastic packings with hydrophilic surface and of ceramic packings are practically the same. 相似文献
46.
47.
Summary It has been found that the three-phase heterogeneous reaction of propane sultone with hydrolyzed macroporous glycidylmethacrylate copolymers in an aqueous alkaline medium proceeds to a higher degree in presence of phase transfer catalyst. The best results were obtained using tetra(n-butyl)ammonium hydroxide. An important finding is the increase in the degree of transformation of the reaction in flow arrangement compared with the batch procedure. The influence of phase transfer catalyst is also more effective. The reaction is discussed with respect to the properties of the products, i.e. of the overall and surface contents of groups introduced into the reaction, of the specific surface area and specific pore volume of sulfopropylated copolymers. 相似文献
48.
The reactions between resorcinol and formaldehyde were led in aluminium pans of a d.s.c. Perkin Elmer calorimeter. The products were separated by means of high performance liquid chromatography and identified by 1H and 13C n.m.r. Depending on the catalyst concentration and molar ratio the mixtures reacted at two different temperature ranges, 317–332K and 332–366K. The heat of the reaction in the first temperature range was between 16.8 and 45.0 kJ mol?1 for molar ratios 1:1 and 1:3 respectively. By 1H and 13C n.m.r. spectroscopy five addition products were determined. The reaction heat in the second temperature range was 73.5 kJ mol?1 and was attributed to condensation reactions. The activation energies were 95.0 and 120.0 kJ mol?1 for addition and condensation reactions respectively. For addition, order two and for condensation, order one of reaction was established. On the basis of these foundings tentative reaction schemes were prepared. 相似文献
49.
Colour constancy of prints with vat dyes on cotton fabrics was investigated by computing the CMCCON02 colour inconstancy index with the key element CAT02 for chromatic adaptation transform. The results show that the highest changes in colour appearance can be expected when the average daylight is replaced with fluorescent light. If D65 daylight is replaced with some other type of daylight, such as D50 or D55, only minor colour deviations occur which do not substantially change the colour appearance of the prints. The analysis of the influence of the lightness and chromaticity of prints shows that the chromaticity of the samples significantly affects their colour constancy. The change of appearance of the prints with lower chroma because of changed illumination conditions is less probable. The influence of a dye blend composition was also investigated. On average, multi‐coloured dye blends have proved to be more colour constant. 相似文献
50.
Biljana Škrbić Jelena Cvejanov Nataša Đurišić-Mladenović 《Polycyclic Aromatic Compounds》2013,33(4-5):348-361
The levels of 16 EPA polycyclic aromatic hydrocarbons (PAHs) were investigated in samples of sugar beets and their products representative for a beet sugar factory located in the central part of Vojvodina, the main agricultural region in Serbia. The sum of the detected PAHs ranged from 51 pg g ?1 ww for molasses to 391 pg g ?1 ww for dried sugar beet pulp. The concentration of benzo(a)pyrene (BaP) for all sample types was about or less than 100 pg g ?1 ww, which is far less than the existing Serbian and EU tolerances set for some foodstuffs. The Serbian intake of BaP via total sugar consumption that ranged from 70–85 g per capita day ?1 , was assessed to be from 0.029 to 0.035 ng kg ?1 b.w. day ?1 . Furthermore, the toxic equivalency factor (TEF) approach was used to estimate the carcinogenicity of PAH mixture found in analyzed samples. 相似文献