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101.
Yevhen Zelenyuk 《Topology and its Applications》2007,154(2):339-357
A topological space X is called almost maximal if it is without isolated points and for every x∈X, there are only finitely many ultrafilters on X converging to x. We associate with every countable regular homogeneous almost maximal space X a finite semigroup Ult(X) so that if X and Y are homeomorphic, Ult(X) and Ult(Y) are isomorphic. Semigroups Ult(X) are projectives in the category F of finite semigroups. These are bands decomposing into a certain chain of rectangular components. Under MA, for each projective S in F, there is a countable almost maximal topological group G with Ult(G) isomorphic to S. The existence of a countable almost maximal topological group cannot be established in ZFC. However, there are in ZFC countable regular homogeneous almost maximal spaces X with Ult(X) being a chain of idempotents. 相似文献
102.
Data in social and behavioral sciences are often hierarchically organized. Multilevel statistical methodology was developed to analyze such data. Most of the procedures for analyzing multilevel data are derived from maximum likelihood based on the normal distribution assumption. Standard errors for parameter estimates in these procedures are obtained from the corresponding information matrix. Because practical data typically contain heterogeneous marginal skewnesses and kurtoses, this paper studies how nonnormally distributed data affect the standard errors of parameter estimates in a two-level structural equation model. Specifically, we study how skewness and kurtosis in one level affect standard errors of parameter estimates within its level and outside its level. We also show that, parallel to asymptotic robustness theory in conventional factor analysis, conditions exist for asymptotic robustness of standard errors in a multilevel factor analysis model. 相似文献
103.
Hiromichi Hashimoto 《Journal of Differential Equations》2007,237(2):491-525
We consider a hyperbolic-parabolic singular perturbation problem for a quasilinear equation of Kirchhoff type, and obtain parameter-dependent time decay estimates of the difference between the solutions of a quasilinear dissipative hyperbolic equation of Kirchhoff type and the corresponding quasilinear parabolic equation. For this purpose we show time decay estimates for hyperbolic-parabolic singular perturbation problem for linear equations with a time-dependent coefficient. 相似文献
104.
Ryuichi Tanaka 《Topology and its Applications》2007,154(15):2849-2855
We describe a finite complex B as I-trivial if there does not exist a Z2-map from Si−1 to S(α) for any vector bundle α over B and any integer i with i>dimα. We prove that the m-fold suspension of projective plane FP2 is I-trivial if and only if m≠0,2,4 for F=C, m≠0,4 for F=H. In the case where F is the Cayley algebra, the m-fold suspension is shown to be I-trivial for every m>0. 相似文献
105.
We study the large-time behavior and rate of convergence to the invariant measures of the processes dX
(t)=b(X)
(t)) dt + (X
(t)) dB(t). A crucial constant appears naturally in our study. Heuristically, when the time is of the order exp( – )/2 , the transition density has a good lower bound and when the process has run for about exp( – )/2, it is very close to the invariant measure. LetL
=(2/2) – U · be a second-order differential operator on d. Under suitable conditions,L
z has the discrete spectrum
- \lambda _2^\varepsilon ...and lim \varepsilon ^2 log \lambda _2^\varepsilon = - \Lambda \hfill \\ \varepsilon \to 0 \hfill \\ \end{gathered} $$
" align="middle" vspace="20%" border="0"> 相似文献
106.
János Komlós 《Order》1990,7(2):107-113
Using Ramsey theory, we establish the following pigeon-hole type principle: From a large number of random variables (functions, vectors, etc.) one can always select two, X and Y, such that P(X < Y) 1/2. We apply the principle for a poset problem. 相似文献
107.
Summary A new and highly sensitive HPLC method for the simultaneous determination of pirarubicine (THP-doxorubicin) and its metabolites, adriamycin and adriamycinol, in human plasma, is described. Samples were treated by liquid-liquid extraction, the organic phase removed and the residue dissolved in methanol. Separation was on a Lichrocart Supersher RP 8 column, (250×4 mm) 4 m, with a mobile phase of acetonitrile/methanol/formate-buffer. 相似文献
108.
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Analysis of caffeine and its metabolites is of interest with respect to caffeine exposure, for kinetic and metabolism studies and for opportunistic in vivo estimation of drug metabolizing enzyme activity in humans and animals. For the latter, analysis is usually done by high-performance liquid chromatography (HPLC) with UV detection. However, this method is close to the detection limit for certain of the metabolites and requires very long chromatography, 30-60 min. We have developed a fast method for the quantification of caffeine and its metabolites 1-methylxanthine, 1-methyluric acid, 1,7-dimethyluric acid, 5-acetylamino-6-amino-3-methyluracil (AAMU) and 5-acetylamino-6-formylamino-3-methyluracil (AFMU) by HPLC tandem mass spectrometry (MS/MS) in urine that requires only its dilution with buffer and centrifugation before injection into the HPLC/MS/MS system. The chromatography lasts 7 min and is followed by 4.5 min for re-equilibration of the HPLC column, giving a total analysis time of 11.5 min. The method provides a great sensitivity improvement with detection limits for all analytes
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