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31.
Hardness and Young's modulus were measured by nanoindentation on a series of electrodeposited nanocrystalline nickel and nickel–iron alloys. Hardness values showed a transition from regular to inverse Hall–Petch behaviour, consistent with previous studies. There was no significant influence of grain size on the Young's modulus of nanocrystalline nickel and nickel–iron alloys with grain sizes greater than 20?nm. The Young's modulus values for nanocrystalline nickel and nickel–iron alloys for grain sizes less than 20?nm were slightly reduced when compared to their conventional (randomly oriented) polycrystalline counterparts. The observed trend with decreasing grain size was found to be consistent with composite model predictions that consider the influence of intercrystalline defects. However, there was some notable variability of the measured values when compared to the model predictions. Three theoretical relationships were used to characterise the anisotropic elastic behaviour of these materials. As a result, texture was also considered to have an influence on the measured Young's modulus and used to explain some of the observed variability for the entire grain size range (9.8–81?nm). 相似文献
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Rick Schneider Heinz L?ster Wolfram Aust Steffen Craatz Klaus Welt Günther Fitzl 《Monatshefte für Chemie / Chemical Monthly》2005,83(5):1467-1481
We investigated the protective effects of L-carnitine against damage to the heart caused by diabetes-induced alterations and additional ischaemia and reperfusion in diabetic BB/OK rats using histological techniques, morphometry, biochemical parameters of oxidative stress, and SOD expression. The results revealed that diabetes-induced morphological changes were partly improved or nearly prevented by substitution of L-carnitine, which also seemed to improve the reduced tolerance of diabetic myocardium towards ischaemia/reperfusion with respect to morphological parameters. Immunohistochemical and biochemical parameters of oxidative stress such as SOD protein expression as well as SOD and GPx activity indicate increased free oxygen radical level in the ischaemic/reperfused diabetic myocardium, which is clearly decreased by L-carnitine treatment. We suggest that L-carnitine may be an adequate “causal” agent in the protection of myocardial alterations in diabetes with additional ischaemia and reperfusion, as it stabilizes mitochondrial and cellular function and acts through its antioxidative or radical scavenging potential. Further investigations are necessary to determine an approach towards adjuvant treatment of diabetic myocardial complications using L-carnitine. 相似文献
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Metabolites from fungi 15. New isocoumarins from an endophytic fungus isolated from the Canadian thistle Cirsium arvense 总被引:1,自引:0,他引:1
Krohn K Flörke U Rao MS Steingröver K Aust HJ Draeger S Schulz B 《Natural product letters》2001,15(5):353-361
One known (1) and five new polyketide metabolites (2-6) were isolated from the culture extract of an endophytic fungus, Mycelia sterila, from the Canadian thistle Cirsium arvense. Compounds 1-4 are members of the isocoumarin family, whereas metabolite 5 is a dihydrobenzofuran and 6 has an open chain structure. All compounds have an unusual methyl group at the aromatic ring that does not fit into the usual polyketide pattern. 相似文献
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Correlation between the real part of the dielectric constant and the structure of glasses in the system AsxSe1?x and GexSe1?x is reported. The mole polarization is calculated using the Sellmeyer approximation neglecting the Lorentz field. The vibrationally caused part of the permittivity which is obtained by subtraction of the mole refraction reflects ordered states in the investigated series. Besides the known crystalline compounds As2Se3 and As4Se4 the formation of the vitreous AsSe3 and As3Se2 from the liquid state has to be supposed. In the system GexSe1?x the formation of the compounds GeSe2 and Ge2Se3 is completed by GeSe4 which as Ge2Se3 obviously only exists in the non-crystalline state. GeTe4 has been reported as a metastable crystalline phase. The temperature dependence of ?r of vitreous As2Se3 is tentatively interpreted in terms of the dipole orientation caused by conversion of the charge in valence alternation pairs. 相似文献
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Driess M Aust J Merz K van Wüllen C 《Angewandte Chemie (International ed. in English)》1999,38(24):3677-3680
A novel intriguing type of coordination mode in phosphorus chemistry has been established that is of fundamental interest in the understanding of chemical bonding. Besides the synthesis of the first planar phosphonium cation PR(4)(+) 1 by a surprisingly simple metathesis reaction, a potentially general experimental method that reaches the seemingly impossible high-energy region of basic molecular and isoelectronic ER(4) systems (E=B(-), C, N(+), Al(-), Si, P(+)) is provided. 相似文献
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Using absorption-detected magnetic resonance, a new triplet state was observed in reaction centres of Rhodobacter sphaeroides R26 at 7 K. Its zero-field splitting parameters &|;D&|; = 220.5 × 10−4 cm−1 and &;|;E&|; = 65.4 × 10−4 cm−1, its spin polarization and its microwave-induced absorption spectrum indicate that it belongs to one of the accessory monomeric bacteriochlorophyll molecules and that it is populated through the same excitation path as the primary donor triplet 3P870, via the radical pair 3[P870+H−]. 相似文献
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Arunjunai Raj Mahendran Nicolai Aust Günter Wuzella Andreas Kandelbauer 《Macromolecular Symposia》2012,311(1):18-27
Summary: The use of renewable raw materials in the polymer industries is becoming increasingly popular because of environmental concerns and the need to substitute fossil resources. Plant oils with triglyceride backbones can be chemically modified and used to synthesize polymers from renewable resources (biopolymers). In the present study, linseed oil was epoxidized using a chemo-enzymatic method based on Candida Antarctica lipase B (CALB) as a biocatalyst and the modified linseed oil was cured using maleinated linseed oil and a commercial polyamide resin. The amount of epoxidation achieved depended on the amount of lipase used and was determined by infrared (IR) and nuclear magnetic resonance (NMR) spectroscopies. With 20% (weight per weight) catalyst concentration based on the wt % of oil a degree of epoxidation of > 90% was achieved. The cross-linking reaction of epoxidized linseed oil with the maleinated linseed oil and the polyamide resin was studied using differential scanning calorimetry (DSC). DSC traces showed that an increase in epoxidation degree lead to larger values for the exothermic enthalpy integrals of the curing reactions and hence to a higher reactivity of the linseed oil towards the cross-linking agents. 相似文献
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Henning Hopf Peter G. Jones Eva Goclik Pauline Aust Johanna Rdiger 《Acta Crystallographica. Section C, Structural Chemistry》2012,68(8):o317-o319
The structure of the title compound, 7‐methoxy‐2‐methyl‐4,5‐dihydroxyanthracene‐9,10‐dione, C16H12O5, was originally reported by Ulickýet al. [Acta Cryst. (1991). C 47 , 1879–1881] in the space group P212121 [polymorph (Io)]. The new polymorph, (Im), crystallizes in the space group P21/c. The molecular structures are closely similar, with both –OH groups forming intramolecular hydrogen bonds to one of the neighbouring quinone O atoms, thus slightly lengthening this C=O bond; the pattern of C—C bond lengths in the ring system is consistent with some contribution from a resonance form with a negative charge at the hydrogen‐bonded quinone O atom and an aromatic region around its neighbouring C atoms. The packing of (Im) is simpler than the extensively crosslinked pattern of (Io), with molecular tapes connected by classical (but three‐centre) and `weak' hydrogen bonds, parallel to [20]. 相似文献