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31.
The integral enthalpies of dilution of sodium dextran sulphate and sodium alginate have been measured at 15, 25 and 40°. The results are compared with the predictions of the line charge theory. The experimental values show a much greater decrease with temperature than the calculated values and this difference is attributed to a contribution from solute/solvent interactions. 相似文献
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Raman spectroscopy complimented with supplementary infrared spectroscopy has been used to characterise a synthetic nickel substituted aurichalcite a zinc/nickel hydroxy carbonate, (Zn2+, Cu2+, Ni2+)5(CO3)2(OH)6. XRD patterns show high orientation and indicate the presence of some minor impurities. The diffraction patterns for the Ni-aurichalcite are well correlated with the standard reference patterns. EDAX analyses indicate variations in chemical composition of Zn/Ni ratios of ∼20:1. The symmetry of the carbonate anion in aurichalcite is Cs and is composition dependent. This symmetry reduction results in multiple bands in both the symmetric stretching and bending regions. The intense band for the Ni-aurichalcite at 1070 cm−1 is assigned to the ν1(CO3)2− symmetric stretching mode. Three Raman bands assigned to the ν3(CO3)2− antisymmetric stretching modes are observed for Ni-aurichalcite at 1372, 1480 and 1543 cm−1. Multiple Raman bands are observed in the regions from 800 to 850 cm−1 and 720 to 750 cm−1, and are attributed to ν2 and ν4 bending modes confirming the reduction of the carbonate anion symmetry in the aurichalcite structure. This research proves that nickel containing aurichalcites can be synthesised in the laboratory thus mimicing the natural nickel containing aurichalcites. 相似文献
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We study the quantum transport through entropic barriers induced by hardwall constrictions of hyperboloidal shape in two and three spatial dimensions. Using the separability of the Schrödinger equation and the classical equations of motion for these geometries, we study in detail the quantum transmission probabilities and the associated quantum resonances, and relate them to the classical phase structures which govern the transport through the constrictions. These classical phase structures are compared to the analogous structures which, as has been shown only recently, govern reaction type dynamics in smooth systems. Although the systems studied in this paper are special due their separability they can be taken as a guide to study entropic barriers resulting from constriction geometries that lead to non-separable dynamics. 相似文献
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Define the directed genus, Γ(G), of an Eulerian digraph G to be the minimum value of p for which G has a 2-cell embedding in the orientable surface of genus p so that every face of the embedding is bounded by a directed circuit in G. The directed genus of the de Bruijn graph Dn is shown to be 相似文献
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We used an LC-MS/MS metabolomics approach to investigate one-carbon metabolism in the plasma of flaxseed-fed White Leghorn laying hens (aged 3.5 years). In our study, dietary flaxseed (via the activity of a vitamin B6 antagonist known as “1-amino d-proline”) induced at least 15-fold elevated plasma cystathionine. Surprisingly, plasma homocysteine (Hcy) was stable in flaxseed-fed hens despite such highly elevated cystathionine. To explain stable Hcy, our data suggest accelerated Hcy remethylation via BHMT and MS-B12. Also supporting accelerated Hcy remethylation, we observed elevated S-adenosylmethionine (SAM), an elevated SAM:SAH ratio, and elevated methylthioadenosine (MTA), in flaxseed-fed hens. These results suggest that flaxseed increases SAM biosynthesis and possibly increases polyamine biosynthesis. The following endpoint phenotypes were observed in hens consuming flaxseed: decreased physiological aging, increased empirical lifespan, 9–14% reduced body mass, and improved liver function. Overall, we suggest that flaxseed can protect women from ovarian tumor metastasis by decreasing omental adiposity. We also propose that flaxseed protects cancer patients from cancer-associated cachexia by enhancing liver function. 相似文献
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Matthew C. Hales Ray L. Frost Wayde N. Martens 《Journal of Raman spectroscopy : JRS》2008,39(9):1141-1149
Pure nesquehonite (MgCO3·3H2O)/Mg(HCO3)(OH)·2H2O was synthesised and characterised by a combination of thermo‐Raman spectroscopy and thermogravimetry with evolved gas analysis. Thermo‐Raman spectroscopy shows an intense band at 1098 cm−1, which shifts to 1105 cm−1 at 450 °C, assigned to the ν1CO32− symmetric stretching mode. Two bands at 1419 and 1509 cm−1 assigned to the ν3 antisymmetric stretching mode shift to 1434 and 1504 cm−1 at 175 °C. Two new peaks at 1385 and 1405 cm−1 observed at temperatures higher than 175 °C are assigned to the antisymmetric stretching modes of the (HCO3)− units. Throughout all the thermo‐Raman spectra, a band at 3550 cm−1 is attributed to the stretching vibration of OH units. Raman bands at 3124, 3295 and 3423 cm−1 are assigned to water stretching vibrations. The intensity of these bands is lost by 175 °C. The Raman spectra were in harmony with the thermal analysis data. This research has defined the thermal stability of one of the hydrous carbonates, namely nesquehonite. Thermo‐Raman spectroscopy enables the thermal stability of the mineral nesquehonite to be defined, and, further, the changes in the formula of nesquehonite with temperature change can be defined. Indeed, Raman spectroscopy enables the formula of nesquehonite to be better defined as Mg(OH)(HCO3)·2H2O. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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