We report measurements to 500°C of resistivity and Hall mobility in Sn-doped, n-type GaP grown by liquid phase epitaxy. Samples
with room-temperature carrier densities between 1 × 1016 and 1 × 1018cm−3 were studied. Mobilities were in the range 100–180 cm2/V-sec at room temperature and in the range 27–35 cm2/V-sec at 400°C. Carrier densities increased by only about a factor of two with increasing temperature. Theoretical fits to
the mobility data were made by considering contributions from intervalley, polar-optic, acoustic-deformation-potential, and
ionlzed-impurity scattering mechanisms. Our results confirm the utility of GaP for high-temperature device applications and
provide important information on electrical parameters needed for device modeling and design. 相似文献
Three different industrial wastewaters from the production of stilbene-based fluorescent whitening agents were investigated with regard to the applicability of advanced oxidation processes combined with biodegradation. Oxidation processes included the application of ozone, hydrogen peroxide, UV-radiation and Fenton's reagent (Fe(2+)/H(2)O(2)). Characterization of the combined chemical-biological treatment was done by sum parameters and HPLC analysis. In addition, toxicity was determined using the luminescence inhibition test. Results showed that processes producing OH-radicals without the need of UV-irradiation proved to be suited for the oxidation of all three wastewaters. H(2)O(2)/UV processes were ineffective due to the high inner filter effect of the effluents. Comparing the combined oxidative-biological process with biological treatment, the applied pre-oxidation steps did not always lead to a significant improvement of the biological degradation. In one case, an inverted treatment starting with biodegradation followed by oxidation turned out to be the preferable procedure. After oxidation with ozone or ozone combined with UV-irradiation, an increase in toxicity was partly observed indicating the formation of toxic intermediate products. In some cases samples had to be diluted before the biodegradation step to achieve a better biodegradability. 相似文献
A prerequisite of the efficient recycling of demolition waste and its evaluation in terms of the material specific recycling rates is information on the composition of the building material stock (as the source of future demolition waste). A practical method is presented that characterizes the material composition of buildings prior to their demolition. The characterization method is based on the analysis of available construction documents and different approaches of on-site investigation. The method is tested in different buildings and the results from four case studies indicate that the documents are useful to quantify bulk materials (e.g. bricks, concrete, sand/gravel, iron/steel and timber). However, on-site investigations are necessary to locate and determine the trace materials such as metals (e.g. copper and aluminium), or different types of plastics. The overall material intensity of the investigated buildings ranges from 270 to 470?kg/m³ gross volume. With ongoing surveys about the composition of different buildings, the collected data will be used to establish a building-specific database about the amount of materials contained in Vienna's building stock. 相似文献
To optimize strategies and measurement parameters for quantification of small fat and water fractions (<10%) in mixtures of
both components by 4-point in-phase and opposed-phase gradient-echo imaging and to compare theoretical results with in-vitro
experiments using emulsions. 相似文献
To provide a basis for the selection of suitable emulsifiers in oil-in-water emulsions used as tissue analogs for MRI experiments. Three different emulsifiers were investigated with regard to their ability to stabilize tissue-like oil-in-water emulsions. Furthermore, MR signal properties of the emulsifiers themselves and influences on relaxation times and ADC values of the aqueous phase were investigated.
Materials and methods
Polysorbate 60, sodium dodecyl sulfate (SDS) and soy lecithin were used as emulsifiers. MR characteristics of emulsifiers were assessed in aqueous solutions and their function as a stabilizer was examined in oil-in-water emulsions of varying fat content (10, 20, 30, 40, 50%). Stability and homogeneity of the oil-in-water emulsions were evaluated with a delay of 3 h and 9 h after preparation using T1 mapping and visual control. Signal properties of the emulsifiers were investigated by 1H-MRS in aqueous emulsifier solutions. Relaxometry and diffusion weighted MRI (DWI) were performed to investigate the effect of various emulsifier concentrations on relaxation times (T1 and T2) and ADC values of aqueous solutions.
Results
Emulsions stabilized by polysorbate 60 or soy lecithin were stable and homogeneous across all tested fat fractions. In contrast, emulsions with SDS showed a significantly lower stability and homogeneity. Recorded T1 maps revealed marked creaming of oil droplets in almost all of the emulsions with SDS. The spectral analysis showed several additional signals for polysorbate and SDS. However, lecithin remained invisible in 1H-MRS. Relaxometry and DWI revealed different influences of the emulsifiers on water: Polysorbate and SDS showed only minor effects on relaxation times and ADC values of aqueous solutions, whereas lecithin showed a strong decrease in both relaxation times (r1,lecithin = 0.11 wt.%−1 s−1, r2,lecithin = 0.57 wt.%−1 s−1) and ADC value (Δ(ADC)lecithin = − 0.18 × 10–3 mm2/s⋅wt.%) with increasing concentration.
Conclusion
Lecithin is suggested as the preferred emulsifier of oil-in-water emulsions in MRI as it shows a high stabilizing ability and remains invisible in MRI experiments. In addition, lecithin is suitable as an alternative means of adjusting relaxation times and ADC values of water.
Molding of micro structures by injection molding leads to special requirements for the molds e.g. regarding wear resistance
and low release forces of the molded components. At the same time it is not allowed to affect the replication precision. Physical
vapor deposition (PVD) is one of the promising technologies for applying coatings with adapted properties like high hardness,
low roughness, low Young’s modulus and less adhesion to the melt of polymers. Physical vapor deposition technology allows
the deposition of thin films on micro structures. Therefore, the influence of these PVD layers on the contour accuracy of
the replicated micro structures has to be investigated. For this purpose injection mold inserts were laser structured with
micro structures of different sizes and afterwards coated with two different coatings, which were deposited by a magnetron
sputter ion plating PVD technology. After deposition, the coatings were analyzed by techniques regarding hardness, Young’s
modulus and morphology. The geometries of the micro structures were analyzed by scanning electron microscopy before and after
coating. Afterwards, the coated mold inserts were used for injection molding experiments. During the injection molding process,
a conventional and a variothermal temperature control of the molds were used. The molded parts were analyzed regarding roughness,
structure height and structure width by means of laser microscopy. 相似文献
The authors apply an embodied account to mere exposure, arguing that through the repeated exposure of a particular stimulus, motor responses specifically associated to that stimulus are repeatedly simulated, thus trained, and become increasingly fluent. This increased fluency drives preferences for repeated stimuli. This hypothesis was tested by blocking stimulus-specific motor simulations during repeated exposure. In Experiment 1, chewing gum while evaluating stimuli destroyed mere exposure effects (MEEs) for words but not for visual characters. However, concurrently kneading a ball left both MEEs unaffected. In Experiment 2, concurrently whispering an unrelated word destroyed MEEs for words but not for characters, even when implemented either exclusively during the initial presentation or during the test phase and when the first presentation involved an evaluation or a mere study of the stimuli. In Experiment 3, a double dissociation between 2 classes of stimuli was demonstrated, namely, words (oral) and tunes (vocal). A concurrent oral task (tongue movements) destroyed MEEs for words but not for tone sequences. A concurrent vocal task (humming “mm-hm”) destroyed MEEs for tone sequences but not for words. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
Mineral growth in nacre and other CaCO3-containing biominerals is controlled by biopolymers. Water-soluble proteins were extracted from nacre of the sea snail Haliotis laevigata by dissolving the mineral phase with 6% acetic acid. The influence of this protein mixture on CaCO3 precipitation rates was investigated at different concentrations. A well-established assay for measuring the pH-value during CaCO3 precipitation with and without protein additives was extended by calculating maximum precipitation rates from the pH-values. It could be shown that precipitation rates are greatly influenced by the mixtures of water-soluble nacre proteins. At very low protein concentrations (0.02 μg/ml) a rate enhancement in comparison to the pure supersaturated calcium carbonate solution by a factor of 1.4 was observed. At higher protein concentrations, a strong inhibitory effect occurred, with total inhibition at concentrations of 1.0 μg/ml and higher. Two unspecific proteins (bovine serum albumin and lysozyme) showed little or no modification of precipitation rates. In vivo, the function of the strong inhibition of CaCO3 precipitation by nacre proteins at higher concentrations is presumably to prevent uncontrolled crystallization in the extrapallial fluid. The rate-enhancing capability of proteins at low concentrations may be explained by the presence of acidic and/or hydrophilic moieties. 相似文献