In powder mixtures of ZnO and TiO2 the compounds Zn2TiO4, ZnTiO3 and Zn2Ti3O8 can be formed as a result of solid state reactions. The mechanism of the double oxide formation is essentially determined by the microstructure of the powder mixture. Furthermore, the kind of the double oxide depends on the TiO2-modification. There exist structural similarities between Zn2TiO4 (spinel) and TiO2 (anatase) on the one hand and ZnTiO3 and TiO2 (rutile) on the other hand. The compound Zn2Ti3O8 is formed only on the basis of the Zn2TiO4-phase. The crystal structure of Zn2Ti3O8 was derived as a defect spinel. The unoccupied sites of cations are not arranged statistically, but they are ordered in the structure. This order leads to the decrease of the space group symmetry from Fd-3 m to P4332. 相似文献
A simple method for the simultaneous quantification of meropenem and the recently approved β-lactamase inhibitor, vaborbactam, in human plasma and renal replacement therapy effluent (RRTE) was developed and validated. This antibiotic combination protects a primary β-lactam, meropenem, with a new β-lactamase inhibitor, and expands the limited options for treatment of multidrug-resistant Gram-negative infections. Meropenem, vaborbactam, and the internal standards [2H6]-meropenem and sulbactam in plasma and RRTE were processed using acetonitrile followed by a chromatographic separation on a Poroshell HPH-C18 column with a gradient elution of the mobile phases and monitored using mass spectrometry detection. The calibration range was 0.05 to 100 μg mL−1 for both meropenem and vaborbactam. The intra-day and inter-day precision and accuracy were less than 15% for both meropenem and vaborbactam and the recovery from plasma was 96% for both meropenem and vaborbactam and the recovery from RRTE was 93% and 103% for meropenem and vaborbactam, respectively. This methodology was successfully applied to an ex vivo characterisation study of the effects of renal replacement therapy modalities on the pharmacokinetics of meropenem and vaborbactam (Antimicrob Agents Chemother 62(10), 2018).
Synthesis of a novel 1′,2′-oxetane-uridine bearing a 2′-C-methyl substituent, [1-(1′,3′-O-anhydro-3′-C-methyl-β-d-psicofuranosyl)uracil], is described. Key to its construction was the use of 6-O-(p-toluoyl)-1,2:3,4-di-O-isopropylidene-3-C-methyl-d-psicofuranose as a nucleosidation substrate, which itself was derived from d-fructose. Anti-HCV activity was examined for the corresponding triphosphate which was not found to be an inhibitor of HCV NS5B 1b wild type polymerase in vitro. The 1′,2′-oxetane uridine triphosphate without 2′-C-methyl substitution was similarly inactive, however, the guanosine analog displayed modest inhibition (IC50 = 10 μM). 相似文献
High-pressure photoluminescence (PL) experiments (at 9 K) are reported for GaAs1−xNx/GaAs quantum wells having N compositions (x=0.0025, 0.004) in the dilute regime where the GaAs1−xNx alloy conduction band (CB) evolves rapidly by incorporation of N-pair states. Under increasing pressure, the PL spectra exhibit several new N-pair features that derive from CB-resonant states at 1 atm. Two of these features appear strongly at sub-band-gap energies for P29 kbar in the x=0.0025 sample, but are absent for all pressures in the x=0.004 sample. Several competing PL assignments due to bound-exciton recombination at NNi pairs (i=1–4 is the anion separation) are considered in light of prior findings for N-doped (1017 cm−3) GaAs. The absence of certain PL features in the x=0.004 sample shows that N-pair states mix into the CB-continuum via a selective process, and this selectivity offers an important test for band-structure calculations in dilute GaAs1−xNx alloys. 相似文献
A theoretical investigation of surface magnetoplasmons in n-type InSb has been carried out with the effect of damping taken into account. Part of the investigation included surface magnetoplasmons interacting with surface optical phonons. The calculated dispersion curves show backbending, in contrast to the situation were damping is neglected. In addition, there are gaps in the dispersion curves for certain frequency ranges. 相似文献
The influence of a thermal boundary resistance (TBR) on temperature distribution in ungated AlGaN/GaN field-effect devices was investigated using 3-D micro-Raman thermography. The temperature distribution in operating AlGaN/GaN devices on SiC, sapphire, and Si substrates was used to determine values for the TBR by comparing experimental results to finite-difference thermal simulations. While the measured TBR of about 3.3 x 10-8 W-1 ldr m2 ldr K for devices on SiC and Si substrates has a sizeable effect on the self-heating in devices, the TBR of up to 1.2 x 10-8 W-1 ldr m2 ldr K plays an insignificant role in devices on sapphire substrates due to the low thermal conductivity of the substrate. The determined effective TBR was found to increase with temperature at the GaN/SiC interface from 3.3 x 10-8 W-1 ldr m2 ldr K at 150degC to 6.5 x 3.3 x 10-8 W-1 ldr m2 ldr K at 275degC, respectively. The contribution of a low-thermal-conductivity GaN layer at the GaN/substrate interface toward the effective TBR in devices and its temperature dependence are also discussed. 相似文献
The dispersoon curves for surface plasma waves (SPW) in Ag have been determined from calculated reflectivity minima as exhibited by attenuated total reflection (ATR spectra) for the prism-metal-air (PMA) configuration and from the direct calculation of the dispersion relation for the same configuration. Comparison is made with published results. The dispersion curves for Au and Cu have been determined for the same configuration from calculated ATR spectra and verified experimentally. Comparison is made with the direct calculation of the dispersion relation. The direct calculation yields two types of modes; namely the surface or Brewster mode and the virtual mode. Both modes are discussed. The marked effect of small electronic damping as exhibited by Ag and moderate electronic damping as exhibited by Au and Cu upon the PMA dispersion curves from ATR spectra is examined. Finally the direct calculation of the dielectric shift (perturbing effect of the prism-metal surface upon the active metal-air surface dispersion curve) is presented for the three metals as a function of film thickness and photon energy. 相似文献
Inspired by ethnopharmacological knowledge, we conducted a bioassay-guided fractionation of the leaves of Tristaniopsis laurina which led to the discovery of a new anti-inflammatory compound, tristaenone A (1). The structure was elucidated by detailed spectroscopic data analysis, and the absolute configuration was established using X-ray crystallography analysis. Tristaenone A (1) suppressed LPS and IFN-γ-induced NO, TNF-α and IL-6 production in RAW 264.7 cells with IC50 values of 37.58 ± 2.45 μM, 80.6 ± 5.82 μM and 125.65 ± 0.34 μM, respectively. It also inhibited NF-κB nuclear translocation by 52.93 ± 14.14% at a concentration of 31.85 μM. 相似文献