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1.
Q. Gong R. N tzel P.J. van Veldhoven T.J. Eijkemans J.H. Wolter 《Journal of Crystal Growth》2005,280(3-4):413-418
We report on the shape transition from InAs quantum dashes to quantum dots (QDs) on lattice-matched GaInAsP on InP(3 1 1)A substrates. InAs quantum dashes develop during chemical-beam epitaxy of 3.2 monolayers InAs, which transform into round InAs QDs by introducing a growth interruption without arsenic flux after InAs deposition. The shape transition is solely attributed to surface properties, i.e., increase of the surface energy and symmetry under arsenic deficient conditions. The round QD shape is maintained during subsequent GaInAsP overgrowth because the reversed shape transition from dot to dash is kinetically hindered by the decreased ad-atom diffusion under arsenic flux. 相似文献
2.
Three fixtures for conducting laboratory fretting fatigue tests are described and their respective testing methods and the
results of the analysis are compared. Each of these fixtures has been used to investigate the effects of various parameters
of interest in fretting fatigue. These fixtures include a unique apparatus in which all load applied to the specimen is transferred
to the fretting pads, an apparatus similar to many found in the literature where partial load transfer occurs across the pads,
and a simplified dovetail fixture in which the clamping load, P, and the shear load, Q, are varied in phase. Select test conditions from prior experiments performed on identical material and resulting in similar
lives ranging from one to ten million cycles from these fixtures are identified. The various testing conditions were used
to compute the unique stress field for each case. The resulting contact stresses were used to calculate crack initiation based
criteria, and to calculate stress intensity factors. The three fixtures were shown to be able to accommodate a range of loads,
fretting pad contours, and specimen geometries that produced a variety of stress fields. A crack-initiation-based criterion
was shown to predict the failure lives of thinner specimens accurately. The stress intensity factor calculations showed the
possibility of a crack arresting for a stress field that decays rapidly and the possibility of a local minimum for K as a function of depth. The fixtures are shown to be complementary in generating data for development of robust fretting
fatigue models that use these criteria. 相似文献
3.
4.
An electrochemical method for the simultaneous determinations of HgII concentration and total AsIII and AsV concentration has been developed. The method does not require the additional preliminary step of the chemical reduction of AsV to AsIII, or oxidation of AsIII to AsV before stripping analysis takes place. Also, the method for the simultaneous determination of HgII concentration and AsIII concentration is described. Measurements were performed in 0.1 M HCl using a gold-plated graphite electrode as sensor. Detection limits for both methods are below 0.4 ppb. Relative standard deviation did not exceed 15%. The possible interference by other trace metals was investigated. Analyses of natural water and industrial solutions were made using proposed methods and AAS. The t-test demonstrates that there was no significant difference between the results obtained with these methods. Proposed methods decrease the time of analysis because concentrations of the HgII and arsenic ions were measured simultaneously. Also, the removal of the additional step of chemical reduction of AsV to AsIII or oxidation of AsIII to AsV decreases analysis time, and also reduces the chance of contamination due to the use of additional reagents. 相似文献
5.
Posudievskii O. Yu. Kurys' Ya. I. Biskulova S. A. Malinovskii Yu. K. Pokhodenko V. D. 《Theoretical and Experimental Chemistry》2002,38(5):278-282
The possibility of the production of nanocomposites based on V2O5 and conducting polymers by direct intercalation of macromolecules of secondary doped polyaniline into the interlayer galleries of nanoparticles of aqueous V2O5 sol was demonstrated for the first time. The driving force of the intercalation process is substitution of the protons present in the galleries of the V2O5 by a polyaniline chain carrying a positive charge. 相似文献
6.
The rate of electron transfer from organic sulfides to [CrV(ehba)2]− (ehba-2-ethyl-2-hydroxy butyric acid) decreases with a decrease in the polarity of the medium. The anionic surfactant, SDS and the cationic surfactant, CTAB have different effects on the kinetics of this reaction. The micellar inhibition observed in the presence of SDS is probably due to the decrease in the polarity and the electrostatic repulsion faced by the anionic oxidant from the anionic micelle and the partition of the hydrophobic substrate between the aqueous and micellar phases. The micellar catalysis in the presence of CTAB is attributed to the increase in the concentration of both reactants in the micellar phase. This micellar catalysis is observed to offset the retarding effects of the less polar micellar medium and the unfavorable charge-charge interaction between the + charge developed on S center in the transition state and the cationic micelle. This catalysis is contrary to the enormous micellar inhibition observed with IO4−, HSO5− and HCO4− oxidation of organic sulfides. 相似文献
7.
Changes of the rheological properties of hyaluronic acid (sodium-magnesium salt) solutions after exposure to UV radiation
indicate a vigorous decrease in their viscosity, but its still strong shear rate dependence. Whereas the presence of the singlet
oxygen sensitizer (anthracene-1-sulphonic acid) brings about a loss of shear dependence; the studied solutions show newtonian
behavior. 相似文献
8.
K. Ajiki D. Shimada T. Kido N. Miyakawa N. Tsuda 《Applied Physics A: Materials Science & Processing》1991,52(1):1-6
fine structure was observed in the conductance curve of a tunneling junction composed of a single crystalline Bi2212 and an evaporated SnO2 film. It is similar to those of Bi2212-GaAs mechanical junctions and there is a certain correspondence between the structure and the phonon density of states. Thus the previous conclusion that the structure is due to phonons has been complemented by this work. The energy gap 2 was 57 meV at 13 K and T
c was 78 K. 2(0)/k
B
T
c is then 8.3. (T) showed the BCS-like temperature dependence. 相似文献
9.
Secretory group V phospholipase A2 (PLA2-V) is known to be involved in inflammatory processes in cellular studies, nevertheless, the biochemical and the enzymatic characteristics of this important enzyme have been unclear yet. We reported, as a first step towards understanding the biochemical properties, catalytic characteristics, antimicrobial and cytotoxic effects of this PLA2, the production of PLA2-V from dromedary. The obtained DrPLA2-V has an absolute requirement for Ca2+ and NaTDC for enzymatic activity with an optimum pH of 9 and temperature of 45 °C with phosphatidylethanolamine as a substrate. Kinetic parameters showed that Kcat/Kmapp is 2.6 ± 0.02 mM−1 s−1. The enzyme was found to display potent Gram-positive bactericidal activity (with IC50 values of about 5 µg/mL) and antifungal activity (with IC50 values of about 25 µg/mL)in vitro. However, the purified enzyme did not display a cytotoxic effect against cancer cells. 相似文献
10.