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排序方式: 共有466条查询结果,搜索用时 15 毫秒
1.
2.
R. Schilling 《Journal of statistical physics》1988,53(5-6):1227-1235
A one-dimensional kinetic Ising model with Glauber dynamics subjected to a slow continuous quench to zero temperature is studied. For a rather general class of cooling schemes, described by a time-dependent temperatureT(t), the mean domain sizeL(t) is calculated along with the residual energye
res
(r) as a function of the cooling rater. If the attempt frequency =0 exp(–/kT), entering into the transition rates, is temperature dependent (i.e., the barrier is non-zero), the asymptotic growth ofL(t) is given byL()–L(t)~exp[–/kT(t)]. For this case the residual energy exhibits a power-law behaviore
res(r) ~r
/2(1 + ) forr small, where =4J/ andJ is the nearest neighbor coupling constant. For =0 and for certain cooling schemes the residual energy is zero andL(t)~t1/2, independent ofr. 相似文献
3.
Simultaneous analysis of oxidized and reduced glutathione in cell extracts by capillary zone electrophoresis 总被引:1,自引:0,他引:1
Yang Q Krautmacher C Schilling D Pittelkow MR Naylor S 《Biomedical chromatography : BMC》2002,16(3):224-228
Glutathione (GSH) and glutathione disulfide (GSSG) levels in cells constitute a thiol redox system. They can be used as an indicator of oxidative stress of the cell. In this study, a capillary zone electrophoresis (CZE) method is described that enables quantitation of GSH and GSSG from cellular extracts. The CZE buffer used was 20 mM ammonium acetate containing 5% (v/v) acetic acid at pH 3.1 in conjunction with a polybrene coated capillary operated in reverse polarity mode. Effects of different acids used to prepare cell samples were investigated on CZE performance. The acids include meta phosphoric acid (MPA), trichloroacetic acid (TCA), phosphoric acid (PA) and sulfosalicylic acid (SSA) and are used to stabilize GSH and GSSG before performing CZE analysis. The method features a limit of detection of 4 microM and a limit of quantitation of 12 microM for both GSSG and GSH and recoveries of 94% for GSH and 100% for GSSG. Quantitative analysis of GSSG and GSH in HaCaT cell extracts (5% SSA, w/v) was performed with this method and changes in the ratio of GSH to GSSG in N-ethylmaleimide treated cell sample was observed by comparing with control cell samples. 相似文献
4.
R. J. Schilling 《纯数学与应用数学通讯》1987,40(4):455-522
The following observation, due to E. Trubowitz, illustrates an intimate relationship between spectral theory and Hamiltonian mechanics in the presence of constraints. Let q(s) be a real periodic function such that the Hill operator, has only a finite number gR of simple eigenvalues. There exist gR + 1 periodic eigenfunctions x1,…, x and corresponding eigenvalues a1,…, a of L such that where yr = dxr/ds. The equations Lxr = arxr, r = 1,…,gR+1, make up the classical Neumann system, a system of harmonic oscillators constrained to the unit sphere. H. Flaschka obtained similar results about the Neumann system from a more general point of view. His assumption, that there exists an operator of odd order that commutes with L, leads to algebraic curve theory by the method of Krichever and from there to the Neumann formulas above. The familiar Lax pairs, the constants of motion and the quadrics of the Neumann system emerge as consequences of the Riemann-Roch theoreni. The existence of isospectral deformations of L, the Korteweg de-Vries hierarchy of the soliton equations, underlies the complete integrability of the Neumann system. This paper extends Flaschka's techniques, replacing L by an operator of order n 2 2. Higher Neumann systems are defined in a way that leads naturally to interesting symplectic manifolds, Lax pairs and integrals of motion. C. Tomei, using scattering theory, obtained some of our n = 3 formulas. 相似文献
5.
Gas-phase derivatization of [C3H5]+ ions using tandem mass spectrometry methods A13C labelling study
Nguyen Kieu My Marita Schilling Helmut Schwarz 《Journal of mass spectrometry : JMS》1987,22(5):254-258
The study of specifically 13C-labelled precursors sheds further light on the gas-phase chemistry of allyl and 2-propenyl cations. It is demonstrated that both species are formed from allyl and 2-propenyl bromide upon 70 eV electron impact ionization without skeletal reorganization. Gas-phase derivatization of the [C3 H5]+ ions with benzene facilitates, as suggested and observed earlier, the distinction of the two isomers using collision-induced dissociation of the Wheland complexes (or isomers thereof). The 13C labelling data clearly demonstrate that 64% of allyl cations survive the derivatization while 36% isomerize to 2-phenylpropyl cations; the latter are also formed via the reaction of 2-propenyl cation with benzene, protonation of α-methylstyrene and water loss from protonated 2-phenyl-2-propanol, respectively. Unimolecular loss of C2H4 from protonated allylbenzene proceeds via two competing reaction channels: one involves heterolysis of 1-phenylpropyl cations (~30%); the major pathway (~70%), however, involves decomposition via propylene benzenium ions. 相似文献
6.
R. G?tz P. Enge P. Friesel K. Roch B. Schilling B. Hartmann H. Wunsch 《Fresenius' Journal of Analytical Chemistry》1994,348(10):694-695
Sampling and determination of dissolved and particlebound PCBs and HCB in the river Elbe are described. A new filtration/adsorption unit for sampling of dissolved lipophilic contaminants was developed. The detection limit for dissolved PCBs and HCB was 5 pg/l. The data show that more than 98% of the PCBs and of HCB in the water of the river Elbe are particle-bound. 相似文献
7.
We investigate the influence of long range interactions on the relaxation behaviour of a lattice model with an on-site potential of
4-type and infinite range harmonic interactions. For finite number of particlesN, it is shown that the autocorrelation functions <E
n(t)E
n
> of the fluctuations of the one-particle energiesE
n(t) decays exponentially. The corresponding relaxation time is proportional toN and is given by (T, N) =N0(T). The temperature dependent time scale 0 can explicitly be related to the dynamics of a one-particle correlator of the noninteracting system. The results are derived using Mori-Zwanzig projection formalism. The corresponding memory kernel is calculated within a mode coupling approximation and by a perturbative approach. Both results agree in leading order in 1/N. It is speculated that any interaction of range generates a timescale . 相似文献
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