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121.
Matloob R 《Physical review letters》2005,94(5):050404
The effect of a uniformly moving medium on the decay rate of an excited atom is calculated. When the local field effects are neglected, the free space decay rate is modified by a factor which is a complicated function of refractive index, permeability, and velocity of the medium. It is shown that the decay rate vanishes if the velocity of the medium exceeds the phase velocity of light in the stationary medium. 相似文献
122.
Self-similar space-filling bearings have been proposed some time ago as models for the motion of tectonic plates and appearance of seismic gaps. These models have two features which, however, seem unrealistic, namely, high symmetry in the arrangement of the particles, and lack of a lower cutoff in the size of the particles. In this work, an algorithm for generating random bearings in both two and three dimensions is presented. Introducing a lower cutoff for the sizes of the particles, the instabilities of the bearing under an external force such as gravity, are studied. 相似文献
123.
Simultaneous microwave and ultrasound irradiation is shown as a new technique for digestion of solid and liquid samples suitable for chemical and food analysis. Its application in analytical chemistry has been shown by decreases in digestion time: determination of copper in edible oils and total Kjeldahl nitrogen. 相似文献
124.
Mohamadzadeh M Mohamadzadeh H Brammer M Sestak K Luftig RB 《Journal of immune based therapies and vaccines》2004,2(1):8
Dendritic cells (DC) are known to present exogenous protein Ag effectively to T cells. In this study we sought to identify
the proteases that DC employ during antigen processing. The murine epidermal-derived DC line Xs52, when pulsed with PPD, optimally
activated the PPD-reactive Th1 clone LNC.2F1 as well as the Th2 clone LNC.4k1, and this activation was completely blocked
by chloroquine pretreatment. These results validate the capacity of XS52 DC to digest PPD into immunogenic peptides inducing
antigen specific T cell immune responses. XS52 DC, as well as splenic DC and DCs derived from bone marrow degraded standard
substrates for cathepsins B, C, D/E, H, J, and L, tryptase, and chymases, indicating that DC express a variety of protease
activities. Treatment of XS52 DC with pepstatin A, an inhibitor of aspartic acid proteases, completely abrogated their capacity
to present native PPD, but not trypsin-digested PPD fragments to Th1 and Th2 cell clones. Pepstatin A also inhibited cathepsin
D/E activity selectively among the XS52 DC-associated protease activities. On the other hand, inhibitors of serine proteases
(dichloroisocoumarin, DCI) or of cystein proteases (E-64) did not impair XS52 DC presentation of PPD, nor did they inhibit
cathepsin D/E activity. Finally, all tested DC populations (XS52 DC, splenic DC, and bone marrow-derived DC) constitutively
expressed cathepsin D mRNA. These results suggest that DC primarily employ cathepsin D (and perhaps E) to digest PPD into
antigenic peptides. 相似文献
125.
A novel approach to reconstructing both the absorption and the scattering properties of a turbid medium simultaneously from steady-state broadband spectral measurements is presented that utilizes second-differential fitting to the water spectrum to estimate the optical path length in tissue. Theoretical and experimental evidence is provided to demonstrate the robust accuracy of the spectroscopy approach and reconstructed absorption images. The steady-state broadband CCD system has the potential to provide accurate chromophore imaging without the technological complexity of time- or frequency-domain systems. 相似文献
126.
Gary Chartrand Lisa Hansen Reza Rashidi Naveed Sherwani 《Czechoslovak Mathematical Journal》2000,50(1):35-46
A graph G is stratified if its vertex set is partitioned into classes, called strata. If there are k strata, then G is k-stratified. These graphs were introduced to study problems in VLSI design. The strata in a stratified graph are also referred to as color classes. For a color X in a stratified graph G, the X-eccentricity e
X(v) of a vertex v of G is the distance between v and an X-colored vertex furthest from v. The minimum X-eccentricity among the vertices of G is the X-radius radX
G of G and the maximum X-eccentricity is the X-diameter diamX
G. It is shown that for every three positive integers a, b and k with ab, there exist a k-stratified graph G with radX
G = a and diamX
G = b. The number s
X denotes the minimum X-eccetricity among the X-colored vertices of G. It is shown that for every integer t with radX
G t diamX
G, there exist at least one vertex v with e
X(v) = t; while if radX
G t s
X, then there are at least two such vertices. The X-center C
X(G) is the subgraph induced by those vertices v with e
X(v) = radX
G and the X-periphery P
X (G) is the subgraph induced by those vertices v with e
X(G) = diamX
G. It is shown that for k-stratified graphs H
1, H
2,..., H
k with colors X
1, X
2,..., X
k and a positive integer n, there exists a k-stratified graph G such that C
X
i(G) H
i (1 ; i
; k1) and
for i j. Those k-stratified graphs that are peripheries of k-stratified graphs are characterized. Other distance-related topics in stratified graphs are also discussed. 相似文献
127.
Ali Reza Ashrafi 《Algebra Colloquium》2000,7(2):139-146
For a finite group G, let Cent(G) denote the set of centralizers of single elements of G and #Cent(G) = |Cent(G)|. G is called an n-centralizer group if #Cent(G) = n, and a primitive n-centralizer group if #Cent(G) = #Cent(G/Z(G)) = n. In this paper, we compute #Cent(G) for some finite groups G and prove that, for any positive integer n 2, 3, there exists a finite group G with #Cent(G) = n, which is a question raised by Belcastro and Sherman [2]. We investigate the structure of finite groups G with #Cent(G) = 6 and prove that, if G is a primitive 6-centralizer group, then G/Z(G) A4, the alternating group on four letters. Also, we prove that, if G/Z(G) A4, then #Cent(G) = 6 or 8, and construct a group G with G/Z(G) A4 and #Cent(G) = 8.This research was in part supported by a grant from IPM.2000 Mathematics Subject Classification: 20D99, 20E07 相似文献
128.
This paper explains some drawbacks on previous approaches for detecting influential observations in deterministic nonparametric data envelopment analysis models as developed by Yang et al. (Annals of Operations Research 173:89–103, 2010). For example efficiency scores and relative entropies obtained in this model are unimportant to outlier detection and the empirical distribution of all estimated relative entropies is not a Monte-Carlo approximation. In this paper we developed a new method to detect whether a specific DMU is truly influential and a statistical test has been applied to determine the significance level. An application for measuring efficiency of hospitals is used to show the superiority of this method that leads to significant advancements in outlier detection. 相似文献
129.
The effect of the counterpoise correction on the geometries, stabilization energies, and vibrational harmonic frequencies of some hydrogen- and halogen-bonded systems (B?=?CH3CN,?HCN,?NH3,?N2,?CO,?H2O,?H2S,?PH3;?HX?=?HF,?HCl,?HBr,?HCN,?HCF3; XY?=?Br2,?BrCl,?BrF,?Cl2,?ClF,?F2) has been analysed at the MP2 level of theory using the popular 6-311++G(d,p) basis set. The optimized B?···?H and B?···?X bond lengths increase with counterpoise (CP) correction. In some cases standard values and in other cases CP-corrected values are close to experimental data. The absolute values of complexation energies of CP-corrected structures are higher than standard by inclusion of BSSE correction. The effect of CP correction on intermolecular bond lengths and complexation energies of B?···?XY series are usually higher than B?···?HX. Also, this effect is higher for H2S and PH3 groups. The CP correction changes the vibrational harmonic frequencies by 0–100%. The changes are frequently lower than 20% for frequencies higher than 300?cm?1. 相似文献
130.
Mahboob Nemati Mir Ali Farajzadeh Ali Mohebbi Fariba Khodadadeian Mohammad Reza Afshar Mogaddam 《Journal of separation science》2020,43(6):1119-1127
A stir bar sorptive extraction method coupled with deep eutectic solvent based solidification of floating organic droplets–dispersive liquid–liquid microextraction has been used for the simultaneous derivatization and extraction of some acidic pesticides in tomato samples. In this method, initially the analytes are adsorbed on a coated stir bar from tomato juice filled in a narrow tube. After extraction, the stir bar is removed and a water–miscible deep eutectic solvent is used to elute the analytes. Afterward, a derivatization agent and a water–immiscible deep eutectic solvent (as an extraction solvent) with melting point near to room temperature are added to the obtained eluant at µL–levels and the obtained mixture is rapidly injected into deionized water. Under the optimum conditions, the introduced method indicated high enhancement (1543–3353) and enrichment (2530–2999) factors, low limits of detection (7–14 ng/L) and quantification (23–47 ng/L), good linearity (r2 ≥ 0.9982), and satisfactory repeatabilities (relative standard deviation ≤12% for intra– and inter–day precisions at a concentration of 100 ng/L of each analyte). Finally, the proposed method was applied in analysis of the analytes in tomato samples. 相似文献