Search Results
You are looking at 1 - 10 of 11 items for
- Author or Editor: H. Qu x
- Refine by Access: All Content x
Abstract
We show that a monotonically normal space X is paracompact if and only if for every increasing open cover {U α : α < κ} of X, there is a closed cover {F nα : n < ω, α < κ} of X such that F nα ⊂ U α for n < ω, α < κ and F nα ⊂ F nβ if α ≦ β.
Abstract
The determination of isotopic thorium by alpha spectrometric methods is a routine practice for bioassay and environmental measurement programs. Alpha-spectrometry has excellent detection limits (by mass) for all isotopes of thorium except 232Th due to its extremely long half-life. This paper discusses improvements in the detection limit and sensitivity over previously reported methods of pre-concentration neutron activation analysis (PCNAA) for the recovery corrected, isotopic determination of thorium in various matrices. Following irradiation, the samples weredissolved, 231Pa added as a tracer, and Pa isolated by two different methods and compared (extraction chromatography and anion exchange chromatography) followed by alpha spectrometry for recovery correction. Ion exchange chromatography was found to be superior for this application at this time, principally for reliability. The detection limit for 232Th of 3.5 · 10-7 Bq is almost three orders of magnitude lower than foralpha spectrometry using the PCRNAA method and one order of magnitude below previously reported PCNAA methods.
This work describes the induction, purification and partial biochemical characterizations of an antimicrobial protein from the housefly larvae induced by ultrasonic wave. It has been purified to apparent homogeneity by ammonium sulfate precipitation followed by Sephadex G-75, Bio-gel P6 gel filtration, and CM-Sepharose Fast Flow cation exchange chromatography. The protein is a cationic protein with an apparent molecular weight of 16315 Da determined by no-denaturing electrophoresis and SDS-PAGE, respectively. Biochemical profile assays show that this protein has good thermal stability, and repeatedly frozen and defrosted durability. The optimum pH for antimicrobial activity is around pH5. The antimicrobial range of the protein includes Gram-positive, Gram-negative bacteria and some fungi. Results of the membrane permeability assays suggest that the probable mode of action of this protein is membrane-disrupting mechanism.
Abstract
A method for the preconcentration of Am and Pu from human tissue solutions (liver, lung, bone etc) using the Actinide-CU Resin (ElChroM Industries) has been developed for their alpha-spectrometric determination. With near 100% recoveries were obtained by preconcentration, subsequent decomposition methods for eluent were developed. Good agreement for Pu and Am determination with the USTUR anion-exchange/solvent extraction method was demonstrated using previously analyzed human tissue solutions and NIST SRMs. The advantages of the preconcentration method applied to human tissue analysis are simplicity of operation, shorter analysis time compared to anion exchange/solvent extraction methods, and capacity to analyze large tissue samples (up to 15 g bone ash per analysis and 500 g soft tissue).
Abstract
The energy of combustion of crystalline 3,4,5-trimethoxybenzoic acid in oxygen at T=298.15 K was determined to be -4795.91.3 kJ mol-1 using combustion calorimetry. The derived standard molar enthalpies of formation of 3,4,5-trimethoxybenzoic acid in crystalline and gaseous states at T=298.15 K, ΔfHm Θ (cr) and ΔfHm Θ (g), were -852.91.9 and -721.72.0 kJ mol-1, respectively. The reliability of the results obtained was commented upon and compared with literature values.
Abstract
The kinetic characteristic of thermal decomposition of the Emulsion Explosive Base Containing Fe and Mn elements (EEBCFM) which was used to prepare nano-MnFe2O4 particles via detonation method was investigated by means of non-isothermal DSC and TG methods at various heating rates of 2.5, 5 and 7.5°C min−1respectively under the atmosphere of dynamic air from room temperature to 400°C. The results indicated that the EEBCFM was sensitive to temperature, especially to heating rate and could decompose at the temperature up to 60°C. The maximum speed of decomposition (dα/dT)m at the heating rate of 5 and 7.5°C min−1 was more than 10 times of that at 2.5°C min−1 and nearly 10 times of that of the second-category coal mine permitted commercial emulsion explosive (SCPCEE). The plenty of metal ions could seriously reduce the thermal stability of emulsion explosive, and the decomposition reaction in the conversion degree range of 0.0∼0.6 was most probably controlled by nucleation and growth mechanism and the mechanism function could be described with Avrami-Erofeev equation with n=2. When the fractional extent of reaction α>0.6, the combustion of oil phase primarily controlled the decomposition reaction.
This research was aimed to study the cell wall degradation and the dynamic changes of Ca2+ and related enzymes in developing aerenchyma of wheat root under waterlogging. An examination of morphological development by light and electron microscope revealed that the structure of cell wall in middle cortical cells remained intact after 12 h of waterlogging and turned thinner after waterlogging for 24 h. At 48 h, the aerenchyma has been formed. The cellulase activity gradually increased in middle cortical cells within 24 h of waterlogging, and decreased with the formation of aerenchyma. Fluorescence detection and subcellular localization of Ca2+ showed the dynamic changing of Ca2+ at the cellular and subcellular levels during the development of aerenchyma. The activity of Ca2+-ATPase enhanced markedly in intercellular space, plasma membrane and tonoplast of some middle cortical cells after 8 h of waterlogging and remained high after 24 h, but it decreased after 48 h of waterlogging. All these suggests that cellulase, Ca2+ and Ca2+-ATPase show a dynamic distribution during the aerenchyma development which associated with the cell wall degradation of middle cortical cells. Moreover, there is a feedback regulation between Ca2+ and Ca2+-ATPase.
Chitosan was obtained from cuticles of the housefly (Musca domestica) larvae. Antibacterial activities of different Mw chitosans were examined against six bacteria. Antibacterial mechanisms of chitosan were investigated by measuring permeability of bacterial cell membranes and observing integrity of bacterial cells. Results show that the antibacterial activity of chitosan decreased with increase in Mw. Chitosan showed higher antibacterial activity at low pH. Ca 2+ and Mg 2+ could markedly reduce the antibacterial activity of chitosan. The minimum inhibitory concentrations of chitosans ranged from 0.03% ∼ 0.25% and varied with the type of bacteria and Mw of chitosan. Chitosan could cause leakage of cell contents of the bacteria and disrupt the cell wall.
Abstract
In this paper, the thermogenesis and differential scanning calorimetry (DSC) curves of energy release of the mitochondria isolated from variant strains of cytoplasmic male sterile lines of rices have been determined by using an LKB2277 Bioactivity Monitor and a DuPont 910 differential scanning calorimeter. The regularity and characteristics of the energy release of the mitochondria at constant and changing temperature were investigated, the differences in shape of the curves and the thermodynamic and kinetic characteristics of the thermogenesis of the mitochondria were compared, the thermodynamic and kinetic parameters of energy release of the mitochondria in the thermogenesis increasing stage were calculated, and the experimental thermokinetic equations describing the different thermogenesis processes were established.
