The surface reactions of uranium metal with carbon monoxide at 25 and 200 °C have been studied by X-ray photoelectron spectroscopy (XPS); respectively. Adsorption of carbon monoxide on the surface layer of uranium metal leads to partial reduction of surface oxide and results in U4f photoelectron peak shifting to the lower binding energy. The content of oxygen in the surface oxide is decreased and O1s/O4f ratio decreases with increasing the exposure of carbon monoxide. The investigation indicates the surface layer of uranium metal has resistance to further oxidation in the atmosphere of carbon monoxide.
A new thermokinetic reduced extent method for the product inhibition of single substrate enzyme-catalyzed reactions is proposed
and compared with the traditional initial rate method in this paper. The arginase-catalyzed hydrolysis of L-arginine to L-ornithine and urea was studied at 37C in 40 mM sodium barbiturate-HCl buffer solution (pH=9.4). Michaelis constant (Km) for arginine and maximum velocity (Vm) of the reaction were determined by initial method and thermokinetic method. The activation of exogenous manganese to this
reaction was also studied. The product inhibition constant (KP), which cannot be obtained directly from the initial rate method, was determined by thermokinetic without adding L-ornithine
to the reaction system. When the concentration of Mn2+ in cell is 0.1 mM, the enzyme gets its full activity. Incubation arginase with appropriate concentration of Mn2+resulted in increased Vmax and a higher sensitivity of the enzyme to product with no change in the Km for arginine. We suggest that the exogenous manganese ions in solution have just recovered the activity of arginase, which
was lost in dissolving and dilution, but no effect on the mechanism of the reaction.
The surface structure of triuranium octaoxide (U3O8) and the effect of CO on surface behaviour have been studied by X-ray photoelectron spectroscopy (XPS). An intensity analysis of the composite U4f photoelectron spectrum of U3O8 shows that this compound should be written as U2VIUIVOg. After exposure to 7.2·106 L CO (1 L=1.33·10–4 Pa·s), the oxygen content in the surface is decreased and the O1s/U4f ratio decreases about 10%. The investigation indicated that the surface layer of triuranium octaoxide was partially reduced in the atmosphere of carbon monoxide.
Authors:Y. Chen, H. Wang, X. Meng, X. Zeng, and J. Xie
A novel thermokinetic research method for determination of the rate constant of a reaction taking place in a batch conduction
calorimeter under isothermal conditions is proposed: the double-thermoanalytical curve method. The method needs only the characteristic
time parameter tm, the peak height Δm at time tm and the peak area a*m after time tm for two thermoanalytical curves measured with different initial concentrations of the reactants: it conveniently calculates
the rate constants. The thermokinetics of four reaction systems were studied with this method, and its validity was verified
by the experimental results.
Ultrahigh molecular mass polyethylene (UHMMPE) is filled with carbon nano-tubes (CNTs) by solution in the presence of maleic
anhydride grafted styrene-(ethylene-co-butylene)-styrene copolymer (MA-SEBS) as a compatibilizer. The UHMMPE/CNT composites
crystallized from melt were prepared at a cooling rate of 20C min-1. The melting and crystallization behaviors of UHMMPE/ CNT composites were investigated by differential scanning calorimetry.
The results showed that onset melting temperature (Tm) and degree of crystallinity (Xc) of UHMMPE/CNT composites crystallized from solution are higher than those from melt due to the larger crystalline lamellar
thickness. The onset crystallization temperature (Tc) of UHMMPE/CNT composites tends to shift to higher temperature region with increasing CNT content in the composites. Tm and
Tc of UHMMPE phase in UHMMPE/CNT composites decrease with the addition of MA-SEBS. Moreover, the crystallization rate of UHMMPE
phase in UHMMPE/CNT composite is increased due to the introduction of CNTs. MA-SEBS acts as compatilizer, enhances the dispersion
of CNTs in the UHMMPE matrix. Thereby, the crystallization rate of UHMMPE phase in UHMMPE/CNT composite is further increased
with the addition of MA-SEBS.
Two methods, e.g. initial rate method and thermokinetic reduced extent method were presented for studies on non-competitive
inhibition. Arginase-catalyzed the hydrolysis of L-arginine toL-ornithine and urea and the inhibition of this reaction by sodium fluoride were studied in the absence and presence of exogenous
of Mn2+at 37C in 40 mM sodium barbiturate-hydrochloric acid buffer solution (pH 7.4). Both methods were successively used to determine
the values of K1. The advances and disadvantages of each method were compared in this paper. Exogenous Mn2+ could result in more sensitivity of arginase to F-1. Since the inhibition of arginase by F-1 depends on the pH values of the reaction system and behave as a non-competitive inhibition, it probably due to its small
volume and high electronic density allow it access to the activity site of the enzyme and replaces of -OH2 (or -OH) as the bridge ligand with Mn(II, II) cluster. However, further studies are necessary to determine the modes of
interaction of F-1 with bovine liver arginase.
Authors:J. Ying, S. Liu, F. Guo, X. Zhou, and X. Xie
Polypropylene (PP) /ethylene-octene copolymer (POE) blends with different content of POE were prepared by mixing chamber of
a Haake torque rheometer. The crystallization behaviors and crystal structure of PP/POE blends were systematically investigated
by differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD) and polarized optical microscopy (POM). The
results showed that PP spherulites became defective and the crystallization behavior was influenced intensely with the introduction
of POE. At the low content of POE, the addition of POE decreases the apparent incubation period (Δti) and the apparent total crystallization period (Δtc) of PP in blends due to the heterogeneous nucleation of POE, and small amount of β-form PP crystals form because of the existence
of POE. However, at high content of POE, the addition of POE decreases the mobility of PP segments due to their strong intermolecular
interaction and chain entanglements, resulting in retarding the crystallization of PP, decreasing in the amount of β-form
PP crystals, and increasing in Δti and Δtc of PP in blends.
Lanzou Alkaline Stretched Noodles (LASN) was a traditional staple food in northwest China for nearly 90 years. LASN specialty wheat breeding has become an important target since 1990s. In order to discover the LASN specialty wheat quality requirement for allelic variations at
of northwest China spring wheats. Two northwest China spring wheat cultivars and 39 elite F6 breeding lines were adopted to determine the low-molecular-weight glutenin subunits (LMW-GS) composition by one step one-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) basing on the protocol of Singh et al. (1991). The results showed that
were correlated to high protein content, high volume of SDS-sediment and super dough strength (W). While
was bad to dry gluten content and SDS-sediment as well as dough properties such as dough strength (W) and dough tenacity (P). Moreover,
has not significant influence on flour quality, but it has the negative effect on dough strength (W) and dough extensibility (L). As for LASN quality,
were beneficial alleles and
was unbeneficial alleles for LASN quality.
Authors:X. Wang, X. Li, H. Yan, Y. Qu, G. Sun, X. Xie, and Y. Zhang
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.