The enthalpies of combustion of more than 200 organic compounds were analyzed. Group contributions to Δc H o were calculated and used to estimate the enthalpies of combustion of a wide range of organic substances of various classes.
相似文献The contents of zinc, copper, lead and cadmium were measured in the dominant species (plants:Scripus triquetor andPhrgrmites australis, macrobenthos:Ilyoplax deschampsin, Helice tridens tientsinensis, Bullacta exarata and Corbicula fluminea, and migrating waders: Calidris ruficollis and C. alpina) of the ecosystem of Yangtze Estuary, China, from 1995–1998. Results show that:
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(1)
Since the heavy metals stored in plants during growth seasons will be released into the environment in winter, plants are temporary stocks for metals. For the aboveground parts of reeds, about 156.6 kg·ha-1·a-1 of zinc, 369.9 kg·ha-1·a-10 of copper, 32.9 kg·ha-·a-1 of lead and 6.5 kg·ha-1·a-1 of cadmium were released.
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(2)
The mollusca, especially C.fluminea, are the key species storing and transporting heavy metals on the food chain.
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(3)
The temporal change in the highest trophic level was studied and found that it was significantly related with metabolic rates. The contents of heavy metals in Dunlin reach the peaks in January and October, which are wintering season and migratory season, respectively, of the bird.
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(4)
Organisms often show regulation/accumulation mechanisms to different elements of heavy metals. The elements that are widely required, such as zinc and copper, are accumulated at the metabolically active parts. It is quite another thing for the other two elements. Lead was regulated well and scarcely accumulated in the bodies of macrobenthos, but cadmium was absolutely accumulated in the animals.
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(5)
Heavy metals were found accumulated in some parts of the bodies of these organisms, such as shells and skeletons of macrobenthos and lives and muscles of waders.
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(6)
All these four elements were accumulated higher in the bodies of waders than in the plants and macrobenthos, which showed a bio-magnification function of the food chain. Overall, besides the physical and chemical processes, biological processes of heavy metal elements in Yangtze Estuarine ecosystem play a very important role in self-purification function of the ecosystem. Measurement of heavy metal contents in plants and animals in the estuarine ecosystem is an efficient technology for monitoring the environmental quality of the estuary.
Plant polyphenols are naturally occurring secondary plant metabolites, synthesized in response to environmental stress factors. As anti-oxidants and free-radical scavengers they serve as essential components of the human diet. Among polyphenols well studied representatives are the trans-resveratrol and trans-piceid molecules, the latter being the glycoside of trans-resveratrol. trans-Resveratrol is known to have anti-inflammatory, anti-tumor, cardio- and vasoprotective effects which help in the prevention of chronic cardiovascular and tumorous diseases.
In the present study, 42 Hungarian wines were analyzed using LC-DAD detection. The wines were from Villány and Eger wine regions representing three wineries from 2003 to 2007 vintage years. The trans-resveratrol amount in the processed wines ranged from 0.75 to 10.4 mg mL−1 and for trans-piceid from 0.1 to 3.7 mg mL−1.
相似文献Mit 1 Abbildung
2. Mitt.:J. Graefe, G. Haufe undM. Mühlstädt, Z. Chem.16 180 (1976).
Aus der Dissertation zur PromotionA. G. Haufe, Universität Leipzig, 1975. 相似文献
In this study, trans-resveratrol levels were determined in 147 Iranian grape cultivars using a modified extraction and gradient HPLC procedure with photodiode array detection. It was found that 41 out of 147 cultivars contained significant levels of trans-resveratrol. The detected amounts ranged from 0.98 to 6.25 mg kg−1 fresh weight with a mean value of 3.59 (white grapes) and 3.08 mg kg−1 (red grapes), respectively.
相似文献Densities and viscosities of binary mixtures of dimethyl sulfoxide (DMSO) with tert-butyl alcohol, butyl acetate, butanone, and butyl amine were determined over the entire range of mole fractions at temperatures of 298.15, 308.15, and 318.15 K. At each temperature, the excess molar volume (V E), viscosity deviations (Δη), and Gibbs excess free energy of activation for viscous flow (ΔG *E) have been investigated from these measured density (ρ) and viscosity (η) values. The experimental viscosity data were correlated by means of the equations of Grunberg-Nissan, Tamura and Kurata, and Hind et al. The deviations have been fitted to a Redlich-Kister equation, and the results are discussed in terms of molecular interactions and structural effects.
相似文献Zusammenfassung Die Wellenfunktionen und verschiedene Zerlegungen der Energie werden für eine Reihe kleiner Moleküle untersucht (H2, H3, H4, HeH, HeH2, He2, LiH und BH), um die Faktoren zu finden, die für die Bindungsbildung ausschlaggebend sind. Die natürliche Zerlegung der Energie läßt die Folgerung zu, daß der bestimmende Faktor der Austauschanteil T x(oder nichtklassische Anteil) der kinetischen Energie ist. Die Änderung von T xbeim Zusammenführen der Atome ist der dominierende Term für die Bindungsenergie; er ist negativ, wenn das resultierende Molekül stabil ist, und positiv, falls es instabil ist. Es wird gezeigt, daß T x im Zusammenhang zum Wechselwirkungsanteil der kinetischen Energie nach Ruedenberg steht.
Partially supported by a grant (GP-15423) from the National Science Foundation. This paper is based on a portion of the PhD thesis (California Institute of Technology, 1970) by CWW.
National Science Foundation Predoctoral Trainee.
Alfred P. Sloan Foundation Research Fellow.
Contribution No. 3917. 相似文献
The aminophosphine ligand was synthesized by the reaction of N-ethylaniline with chlorodiphenylphosphine in the presence of triethylamine at low temperature. Oxidation of the ligand with elemental sulfur or selenium afforded the corresponding aminophosphine sulfide and selenide. The compounds were characterized by elemental analyses, IR, 1H and 31P NMR. N-diphenylphosphino-N-ethylaniline and its chalcogen derivatives were used as ligands in solvent extraction of metal picrates such as Cd2+ and Ni2+ from the aqueous to the organic phase. Influences of parameters such as pH of the aqueous phase, solvent, extraction time, and extradant concentration were investigated to determine the extraction ability of ligands for metal ions. Results of the experiments showed that an extractability of 95.5 and 97.8%, respectively for Ni2+, and Cd2+ at pH 2 could be achieved.
相似文献Xanthine oxidase, a complex molybdoflavoprotein, catalyzes the hydroxylation of xanthine to uric acid, which has emerged as an important target for gout and hyperuricemia. In this work, a combination of molecular modeling methods was performed on a series of febuxostat analogues as xanthine oxidase inhibitors to establish molecular models for new drug design, including three-dimensional quantitative structure–activity relationship, topomer comparative molecular field analysis (CoMFA), molecular docking and molecular dynamic simulations. The optimal CoMFA model yielded a leave-one-out correlation coefficient (q2) of 0.841 and a non-validated correlation coefficient (r2) of 0.985. The respective q2 and r2 of the best comparative molecular similarity indices analysis (CoMSIA) model were 0.794 and 0.972, respectively. The Topomer CoMFA model provided a q2 of 0.915 and an r2 of 0.977. 3D contour maps generated from CoMFA and CoMSIA have identified several key features responsible for the inhibition activity. Molecular modeling was taken to further elucidate the proposed binding conformations of the inhibitors to the protein. The obtained results can be served as a useful guideline for designing novel febuxostat derivatives with improved activity against xanthine oxidase.
相似文献The through-diffusion method and batch sorption experiments were used to explore the influence of pH on the diffusion behavior of 75Se(IV) in matrix Beishan granite (BsG). In the pH range of 2.0–8.5, the De values of 75Se(IV) in BsG decreased first and then increased with pH increasing, while the changing trend of Kd was nearly opposite. It was speculated that the influence of pH on the diffusion of 75Se(IV) in BsG was due to the joint effects of different species distribution of Se, change in surface charge of BsG and change in ionic strength at various pH values.
相似文献The first and second constant of dissociation of tartaric acid, and the constants of dissociation of the complex ionsLnH2 T +,Ln 2H2 T 4+,Ln(H2 T)2- andLnHT were determined, making use of pH-measurements.
Zugl. 30. Mitt. der Reihe: Koordinationsverbindungen mit organischen Hydroxysäuren.
Ln 3+=La3+, Ce3+.
H4 T=C4H6O6. 相似文献
Four types of undisturbed soils around the Es-Salam reactor (Algeria) were used to evaluate the sorption behavior of strontium. The batch study was carried out under different experimental conditions. The kinetics were well fited by pseudosecond order model. Soils’s activation energies were 12.37, 14.76, 15.5 and 16.17 kJ mol−1, corresponding to ion-exchange-type sorption. Sorption was exothermic (ΔH° < 0), spontaneous (ΔG° < 0) and favorable at low temperature. Competing cations, particularly Ca2+ reduce the Sr adsorption. Desorption reaction showed a higher value of Sr in the easily extractible phase indicating a relative availability of the element.
相似文献A sensitive and selective method for determination of (S,R)-penehyclidine in rat plasma by liquid chromatography-tandem mass spectrometry is described. The procedure employed the use of an internal standard (I.S.) and a simple protein precipitation step. The method developed was linear from 0.1 to 100 ng mL−1, with a sensitivity of 0.1 ng mL−1 as the lower limit of quantification. The intra- and inter-day assay accuracy (relative error) was within 8.27% and precision (RSD) was below 6.7%. It was successfully applied to pharmacokinetic studies of (S,R)-penehyclidine in rat plasma.
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