Search Results

You are looking at 31 - 40 of 183 items for

  • Author or Editor: X. Wang x
  • All content x
Clear All Modify Search

Abstract  

2,2-dinitropropyl acrylate (DNPA), 2,2-dinitrobutyl acrylate (DNBA) and 2,2-dinitrobutyl methacrylate (DNBMA) were synthesized and the kinetics of their free-radical polymerization in the presence of 2,2′-azobisisobutyronitrile (AIBN) were investigated by DSC in the non-isothermal mode. The kinetics of the free-radical polymerization as estimated by the Kissinger and Ozawa methods showed that the reaction is disfavoured by increasing steric hindrance around the acrylyl double bond. The rate constants calculated from the activation parameters showed the structural dependency. The polymerization kinetics revealed that the polymerizability of three monomers decreased due to the presence of substituent methyl groups on the acrylyl double bond and 2,2-dinitrobutyl on ester group. Thus, the polymerization tendency increased in the order DNPA>DNBA>DNBMA.

Restricted access

Abstract  

Combustion experiments of three typical seaweeds (Gracilaria cacalia, Enteromorpha clathrata and Laminaria japonica) have been studied using a DTA-60H Thermal Analyzer and the combustion processes and characteristics are studied. Thermogravimetric experiments are carried out on the samples with 0.18 mm particle size at the heating rate of 20°C min−1. The results indicate that the ignition mode of seaweed is homogeneous and the combustion process is composed of dehydration, the pyrolysis and combustion of volatile, transition stage, the combustion of char as well as the reaction at high temperature. And the combustion characteristic parameters are obtained such as ignition temperature, maximum rate of combustion, burnout temperature etc. The combustion models of these seaweeds are also analyzed. The combustion characteristics and model differences between the seaweed and woody biomass are caused by the differences of volatile components. The combustibility indexes of seaweeds calculated are better than that of woody biomass, and the index of Gracilaria cacalia is the best. At last, activation energies are determined using Arrhenius model that is solved by binary linear regression method.

Restricted access

Abstract  

The thermal decomposition of strontium acetate hemihydrate has been studied by TG-DTA/DSC and TG coupled with Fourier transform infrared spectroscopy (FTIR) under non-isothermal conditions in nitrogen gas from ambient temperature to 600°C. The TG-DTA/DSC experiments indicate the decomposition goes mainly through two steps: the dehydration and the subsequent decomposition of anhydrous strontium acetate into strontium carbonate. TG-FTIR analysis of the evolved products from the non-oxidative thermal degradation indicates mainly the release of water, acetone and carbon dioxide. The model-free isoconversional methods are employed to calculate the E a of both steps at different conversion α from 0.1 to 0.9 with increment of 0.05. The relative constant apparent E a values during dehydration (0.5<α<0.9) of strontium acetate hemihydrate and decomposition of anhydrous strontium acetate (0.5<α<0.9) suggest that the simplex reactions involved in the corresponding thermal events. The most probable kinetic models during dehydration and decomposition have been estimated by means of the master plots method.

Restricted access

Two new y-type HMW-GSs in Ae. tauschii , 1Dy12.1* t and 1Dy12.2 t with the mobility order of 1Dy12.2 t > 1Dy12.1* t > 1Dy12.1 t >1Dy12, were identified by both SDS-PAGE and MALDI-TOF-MS. Molecular cloning and sequencing showed that the genes encoding subunits 1Dy12.1* t and 1Dy12.2 t had identical nucleotide acid sequences with 1,947 bp encoding a mature protein of 627 residues. Their deduced molecular weights were 67,347.6 Da, satisfactorily corresponding to that of 1Dy12.2 t subunit determined by MALDI-TOF-MS (67,015.7 Da), but was significantly smaller than that of the the 1Dy12.1* t subunit (68,577.1 Da). Both subunits showed high similarities to 1Dy10, suggesting that they could have a positive effect on bread-making quality. Interestingly, the expressed protein of the cloned ORF from accessions TD87 and TD130 in E. coli co-migrated with subunit 1Dy12.2 t , but moved slightly faster than 1Dy12.1* t on SDS-PAGE. The expressed protein in transgenic tobacco seeds, however, had the same mobility as the 1Dy12.1* t subunit, as confirmed by both SDS-PAGE and Western blotting. Although direct evidence of phosphoprotein could not be obtained by specific staining method, certain types of post-translational modifications (PTMs) of the 1Dy12.1* t subunit could not be excluded. We believe PTMs might be responsible for the molecular weight difference between the subunits 1Dy12.1* t and 1Dy12.2 t .

Restricted access

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.

Restricted access

Abstract  

A radioactive multitracer solution was prepared from the reaction of selenium with 25 MeV/nucleon40Ar ions. Using off-line -ray spectrometry, the solution containing 47 radioactive isotopes of 24 elements was obtained. The nucleide with the longest half-life was22Na, and the shortest-lived one was81Rb8.

Restricted access

The hypothesis of niche differentiation with respect to resources is considered to be one of the most influential explanations for the maintenance of species diversity. The hypothesis has been examined extensively by testing its prediction of species-habitat association, which posits that the spatial distribution of species is highly correlated with environmental variables. However, we argue that widespread evidence of the species-habitat association lacks adequate rigor to justify the niche differentiation hypothesis. In this study, we tested whether and to what extent the observed species-habitat association could be caused by ecological processes other than niche differentiation, in a 20-ha subtropical forest plot. The niche differentiation hypothesis was evaluated by testing the species-habitat association and performing a cross-evaluation of the habitat-diversity expectation, which posits that a strong positive correlation exists between species diversity and habitat complexity. Failure to support the habitat-diversity expectation would at a minimum indicate that the niche differentiation hypothesis might not be the main underlying process of species distribution, despite prevalence of the species-habitat association in the same plot. Our analysis revealed that distributions of most species (86.11%) in the plot were significantly associated with at least one of eight topographical and soil nutrient variables. However, there was almost no significant positive correlation between species diversity and habitat complexity at various spatial scales in the same plot. The results indicate that additional caution is warranted when interpreting the species-habitat association from the niche differentiation perspective. A significant species-habitat association indicates only a species’ habitat preference. The association may reveal nothing about interspecific differences in habitat preference, which is a requirement of the niche differentiation hypothesis.

Restricted access

Summary

To control the quality of Euonymus fortunei (Turcz.) Hand.-Mazz., a simple and reliable method of high-performance liquid chromatography (HPLC) coupled with photodiode array detector (PAD) was developed for both fingerprint analysis and quantitative determination. Four representative flavonoids, namely, kaempferol-3-O-β-D-glucopyranosyl-(1→4)-α-L-rhamnopyranosyl-7-O-β-D-glucopyranosyl-(1→4)-α-L-rhamnopyranoside (I), kaempferol-3,7-O-α-dirhamnopyranoside (II), apigenin-7-O-β-D-glucopyranoside (III), and kaempferol-3-(4″-O-acetyl)-O-α-L-rhamnopyranoside-7-O-α-L-r hamnopyranoside (IV) isolated from E. fortunei, were used as reference compounds and simultaneously determined by the validated HPLC method. The unique properties of the chromatographic fingerprint were validated by analyzing 11 batches of E. fortunei, E. japonicus, E. laxiflorus, E. myrianthus, and E. hamiltonianus samples. Our results revealed that the chromatographic fingerprint combined with similarity measurement could efficiently identify and distinguish E. fortunei from the other investigated Euonymus species.

Restricted access

A two-year field experiment with a split-split plot design was conducted to investigate the effects of soil N(0, 120 and 240 kg N·ha−1) and foliar Zn applications at different growth stages (jointing, flowering, early grain filling, and late grain filling) on Zn translocation and utilization efficiency in winter wheat grown on potentially Zn-deficient soil. Our results showed that foliar Zn application at the early grain filling stage significantly increased the Zn concentration in the grain (by 82.9% compared to control) and the Zn utilization efficiency (by 49% compared to jointing). The Zn concentration in the straw consistently increased with the timing of the foliar Zn application and was highest at late grain filling. However, the timing of the Zn application had little effect on Zn uptake in the grain and straw. A high N supply significantly increased the Zn concentration in and uptake by grain and straw, but it had little effect on the efficiency of Zn utilization. Consequently, a foliar Zn application at early grain filling causes Zn to re-translocate into grain from vegetative tissues, resulting in highly nutritional wheat grain. Finally, these practices improved the efficiency of Zn utilization in winter wheat and led to Zn-enriched straw, which may contribute to Zn recycling if it is returned to the field. The results also indicated that N nutrition is a critical factor in both the concentration and translocation of Zn in wheat.

Restricted access

To comprehensively understand the genetic basis of plant height (PH), quantitative trait locus (QTL) analysis for internode lengths, internode component indices and plant height component index (PHCI) were firstly conducted in the present study. Two related F8:9 recombinant inbred line (RIL) populations comprising 485 and 229 lines were used. Two hundred and nine putative additive QTL for the eight traits were identified, 35 of which showed significance in at least three trials. Of these, at least 11 pairwise QTL were common to the two populations. PH components at the QTL level had different effects on PH, confirming our previous multivariate conditional analysis (Cui et al. 2011). Eleven major QTL that showed consistency in expression across environments should be of great value in the genetic improvement of PH in wheat. The results above will enhance the understanding of the genetic basis of PH in wheat.

Restricted access