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1.
H. Frahm C. Rödenbeck 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(3):409-414
We study the phase diagram of coupled spin-1/2 chains with bilinear and (chiral) three-spin exchange interactions in a magnetic
field. The model is soluble on a one-parametric line in the space of coupling constants connecting the limiting cases of a
single and two decoupled Heisenberg chains with nearest neighbour exchange only. We give a complete classification of the
low-energy properties of the integrable system and introduce a numerical method which allows to study the possible phases
of spin ladder systems away from the soluble line in a magnetic field.
Received 17 November 1998 and Received in final form 22
January 1999 相似文献
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H.-K. Kim E. Tuite B. Nordén B.W. Ninham 《The European physical journal. E, Soft matter》2001,4(4):411-417
The source of the activation energy that allows cutting of DNA by restriction enzymes is unclear. A systematic study of the
cutting efficiency of the type-II restriction endonuclease EcoRI, with varying background electrolyte ion pair and buffer reported here, shows only a modest dependence of efficiency on
cation type. Surprisingly, efficiency does depend strongly on the presumed indifferent anion of the background salt. What
emerges is that competition between the background salt anion and the buffer anion for the enzyme and DNA surfaces is crucial.
The results are unexpected and counterintuitive from the point of view of conventional electrolyte theory. However, taken
together with recent developments in surface chemistry, the results do fall into place and could also suggest a novel mechanism
for enzyme activity as an alternative to metal-activated hydrolysis: microscopic cavitation in a hydrophobic pocket might
be the source of activation energy.
Received 19 June 2000 and Received in final form 17 October 2000 相似文献
4.
Protocatechualdehyde (PCA) is one of the effective ingredients extracted from Danshen (Radix Salviae Miltiorrhizae) and was employed to modify the silk fibroin (SF) by graft polymerization and surface adsorption. The surface composition of modified SF was characterized by attenuated total reflectance Fourier-transform infrared (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and UV spectrophotometer. The anticoagulant activity of modified SF was assessed by in vitro coagulation test and platelet adhesion measurement. The endothelial cell affinity was evaluated by a parallel plate flow chamber. The test results indicated that with the introduction of PCA into SF, the anticoagulant activity has been improved obviously. And the SF surface composition altered by PCA, but did not disturb its β-sheet conformation. Moreover, the adsorbed PCA on SF surface can enhance the endothelial cell affinity. 相似文献
5.
Alexander E.S. Van Driessche Jose A. GaviraLuis D. Patiño Lopez Fermin Otalora 《Journal of Crystal Growth》2009,311(13):3479-3484
We describe a method for precisely measuring the solubility of proteins in aqueous solution using laser confocal differential interference contrast microscopy. The method is based on the in situ observation of single steps on a protein crystal surface which allows a fast and precise determination of solubility as a function of temperature. To demonstrate the effectiveness of this novel approach the solubility dependence on temperature of glucose isomerase and hen egg white lysozyme was determined with a precision of ±0.5 °C or smaller. It was found that a small amount of impurities did not significantly change the obtained solubility data. Numerical values for enthalpies and entropies of crystallization were calculated and they compare well to previously reported values but the experimental errors were significantly reduced. 相似文献
6.
The magnetoelectric properties of a rhombohedrally distorted perovskite BiFe0.7Mn0.3O3 are reported. An anomaly in the dielectric constant, related to enhanced thermal fluctuations around the antiferromagnetic transition, was induced near room temperature by the substitution of Mn for Fe in BiFeO3. This substitution also brings about non-trivial magnetocapacitance effects at room temperature. 相似文献
7.
A. El-Korashy 《Solid State Communications》2005,135(5):298-303
Single crystals [N(CH3)4]2MnCl4 and [N(CH3)4]2CoCl4 were grown by the slow evaporation technique from the super-saturated solutions. The samples obtained were undergone the X-ray and spectroscopic studies. Absorption spectra in the paraelectric phase at T=303 K have been recorded using the Shimadzu 160A double beam automatic scanning spectrophotometers. On the basis of the exchange charge model and Racah theory the crystal field parameters and Racah parameters have been calculated; all absorption bands for both crystals were given an assignment. 相似文献
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Magnetic susceptibility, heat capacity and electrical resistivity measurements have been carried out on a new ruthenate, La2RuO5 (monoclinic, space group P21/c) which reveal that this compound is a magnetic semiconductor with a high magnetic ordering temperature of 170 K. The entropy associated with the magnetic transition is 8.3 J/mol K close to that expected for the low spin (S=1) state of Ru4+ ions. The low temperatures specific heat coefficient γ is found to be nearly zero consistent with the semiconducting nature of the compound. The magnetic ordering temperature of La2RuO5 is comparable to the highest known Curie temperature of another ruthenate, namely, metallic SrRuO3, and in both these compounds the nominal charge state of Ru is 4+. 相似文献
9.
First-principles molecular dynamics simulation has been performed so as to investigate the optical and energy-loss spectra of ZnS. Features such as dielectric function, density of states, reflectivity, refractive index and energy-loss function have been studied. Furthermore, the influence of temperature on the optical properties of interest is reported and discussed. 相似文献
10.
With the help of group theory analysis of absorption spectra of the transition 3H6 → 3F3 of Tm3+ ion in TmAl3(BO3)4 crystal, measured at several temperatures from 1.8 till 293 K, it has been shown, that the local symmetry of the Tm3+ environment is C3 and it decreases to C1 at a low temperature. Effective selection rules and polarizations of lines at high enough temperatures (when the line-width is larger than the splitting in C3 symmetry) have been obtained. 相似文献