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  • Author or Editor: D. Zhou x
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Abstract  

We introduce a new class of sequences called NBVS to generalize GBVS, essentially extending monotonicity from “one sided” to “two sided”, while some important classical results keep true.

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Summary By employing a novel idea and simple techniques, we substantially generalize the Turán type inequality for rational functions with real zeros and prescribed poles established by Min [5] to include L p spaces for 1≤ p ≤ ∞ while loosing the restriction ρ > 2 at the same time.

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Abstract  

A new method for the analysis of thermal desorption spectra is presented, based on the experimental peak maximum functions for temperatureT m(β) and pressureP m(β) and a rigorous mathematical treatment. The resonant heating rate βr is determined, satisfyingT mr)=T r, whereT r is the resonant temperature defined byA exp(−E d/(RT r))=1. Desorption energyE d and frequency factorA can be determined simultaneously with relatively high robustness towards statistical experimental errors as demonstrated by computer-simulated thermal desorption spectra.

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Abstract  

A new compound cyclohexyl-t-butyldimethylammonium tetraphenylborate, [C6H11N(CH3)2(C(CH3)3)]BPh4 has been prepared, and its decomposition mechanism was studied by TG. The IR spectra of the products of thermal decomposition were examined at every stage. Kinetic analysis for the first stage of thermal decomposition process was obtained by TG and DTG curves, and kinetic parameters were obtained from the analysis of the TG-DTG curves with integral and differential equations. The most probable kinetic function was suggested by comparison of kinetic parameters.

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The study site is the Honghe National Nature Reserve, a Ramsar designated site on the Sanjiang Plain in Northeast China. We present results regarding the spatial pattern and structure of plant communities in these most important natural but continually diminishing freshwater wetlands of China to help promote both protection and restoration. By investigating three ecological levels (landscape, ecosystem and community), this paper quantifies the characteristics of spatial pattern with the aim to identify specific ecological correlations with different hydrogeomorphic features. Specifically, the research involves hierarchical mapping of vegetation types by use of remote sensed data, and the coupling of landscape indices with fluvial topographic zones that have been deduced by GIS from DEM. Statistics from historical survey data are also used to measure the degradation of marshes as well as the historical change of the hydrological regime. We found that dominant is the Calamagrostis angustifolia — Carex spp. community type, a wet meadow and marsh complex within the prevailing landscape mosaic of shrubland and meadow. The results suggest that the sites’ hydro-geomorphic character has decisive influence on plant community structure and composition. There is only limited direct human interference in the sites and, as a consequence, the spatial pattern of vegetation distribution is natural. However, changes to the hydrological regime as the result of extensive irrigation activity in the surrounding area has led to rapid degradation of marsh wetlands within the sites, which threatens the ecological status in this storehouse of “Natural Genes” in the reserve.

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Karst rocky desertification (KRD) is a process of soil desertification, which leads to the decline of soil quality and biomass. We conducted a plant community survey in KRD areas in Chongqing, China. Our aims were to determine key soil properties that shape plant communities and to identify essential leaf functional traits (LFTs) in responding to the progression of KRD. The vegetation survey was carried in a total of twenty study sites (five replicates for four stages of KRD) in the Wushan County in Chongqing, China. Leaves were collected from all the species in every site and measured/calculated for five LFTs, namely, specific leaf area, leaf area, leaf thickness, leaf tissue density, and leaf dry matter content. Soil samples were collected in triplicates in each site to measure soil properties. We found that the overall richness and diversity of community decreased along with the progression of KRD. Phanerophytes predominated in all the KRD areas. Soil pH was the main determinant of vegetation structure. Leaves with lower area yet higher density had the optimal adaptability in KRD regions, which can be planted as pioneer vegetation to restore land in KRD regions.

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Summary

A new HPLC method has been established for determination of 3-monoiodotyrosine (MIT), 3,5-diiodotyrosine (DIT), 3,5-diiodothyronine (T2), 3,3′,5-triiodothyronine (T3), 3,3′,5′-triiodothyronine (rT3), and thyroxine (T4) produced by hydrolysis of iodinated casein with barium hydroxide. The hydrolytic stability of each analyte was evaluated. Iodinated casein was hydrolyzed with saturated barium hydroxide solution for 16 h at 110°C and the barium ions were then removed as barium sulfate. Reversed-phase HPLC was performed on a 2.1 mm × 150 mm, 5 μm particle, C18 column with a mixture of acetonitrile and 0.1% (v/v) formic acid as mobile phase at a flow rate of 0.2 mL min–1. Acetonitrile was maintained at 5% (v/v) for 5 min and then increased linearly to 50% (v/v) within 35 min. All analytes were quantified by measuring the absorbance at 280 nm. Validation data indicated the method was linear, with regression coefficients (R 2) > 0.998, in the concentration ranges investigated. Sensitivity was adequate—limits of detection (LOD) were 0.04–0.38 μg mL–1 and limits of quantification (LOQ) were 0.05–0.38 μg mL–1. Accuracy and precision were acceptable — for all the analytes recovery was 82.0–93.0% and repeatability, as relative standard deviation, was 1.0–3.0%. Hydrolytic stability tests indicated MIT and DIT are much more stable than the other analytes. rT3 was not released directly from iodinated casein but was formed by deiodination of T4 during hydrolysis. The method could be used to identify iodinated casein, to evaluate its activity and quality, and for supervision and regulation of feed additives.

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Abstract  

The paper presents the results of determination of extractable organohalogens (EOX) by instrumental neutron activation analysis (INAA), and polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) by gas chromatography (GC), in atmospheric precipitation in Shanghai, China, from January to August 2005. The results showed that EOCI was the major component of organohalogens in precipitation. A significant correlation between the concentrations of EOBr and EOI was observed (r 2 = 0.75), which suggested that EOBr and EOI in precipitation might mainly come from the same sources. There were no clear seasonal trends for the concentrations of EOX. The concentrations of ΣPCBs ranged from 0.2–2.8 ng/l, with the dominant PCBs containing 3 to 5 chlorine atoms. HCH was the predominant pesticide in precipitation, accounting for over 80% of total OCPs, in which β-HCH took 28%–72% of total HCH. Also, there may be an evidence for significantly historical usage of DDT.

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Summary

Dithiocarbamates fungicides (DTCs) are worldwidely used fungicides. Residue analytical methods on DTCs are usually based on headspace gas chromatography, which are not much stable and precise. In this study, a specific, simple and reliable method for determining DTCs fungicides residues was optimized and validated. The DTCs in foods and soils were extracted with an alkaline solution of EDTA and l-cysteine, followed by pH adjusting and methyl derivatization in methyl iodine solution. The organic layer of the reactants was separated, concentrated under vacuum and reconstructed in acetonitrile. DTCs residues were eluted on a C18 column and detected by HPLC-DAD at 272 nm. The S-alkyl derivatives of thiram, mancozeb and propineb were separated at different retention times. At fortified levels of 0.05 mg/kg to 2 mg/kg (residue expressed as CS2, in mg/kg, the same below), it is found that recoveries for DTCs spiked in apple, cucumber, tomato, rice and soil samples ranged from 70.8% to 105.3%, with relative standard deviations (RSD) from 0.6% to 13.7%. Limits of detection (LODs) and quantification (LOQs) ranged from 0.003 to 0.026 mg/kg and from 0.011 to 0.105 mg/kg for various foods and soils. This method was also applied to real sample tests.

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