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排序方式: 共有243条查询结果,搜索用时 31 毫秒
1.
In this paper, we introduce a new concept of semi-preemptive scheduling and we show how it can be used to derive a maximum-flow-based lower bound for the P|rj|Lmax which dominates the well-known preemptive lower bound. We show that, in some cases, the proposed bound strictly dominates the preemptive one while having the same complexity. 相似文献
2.
Summary Dielectric measurements on Na2B4O7(99.5%)−V2O5(0.5%) glass system, in the frequency range 10−3 to 104 Hz and temperature range 300 to 500 K, have been carried out. The normalized plots of complex capacitance have shown a single
mechanism responsible for conduction for both volume and surface measurements with their close values of activation energies
(0.67±0.03) eV and (0.64±0.03) eV, respectively. The low-frequency dispersion (LFD) behaviour has been observed to be perturbed
by the presence of more than one competing process. The impedance plots have shown a parallel combination of a capacitor (C) and a resistor (R), with some contribution of a dispersive element due to charge accumulation in the vicinity of the electrodes. The values
ofR andC were found to be of the same order of magnitude, for both surface and volume measurements. The observedR has shown a decrease with an increase in temperature due to an increase in mobility of Na+ ions, whereasC remains practicaly constant. The complex capacitance surface behaviour is dominated by volume, due to hygroscopy of this
glass system. 相似文献
3.
Eldefrawi ME Azer NL Nath N Anis NA Bangalore MS O'Connell KP Schwartz RP Wright J 《Applied biochemistry and biotechnology》2000,87(1):25-35
An automated flow fluorometer designed for kinetic binding analysis was adapted to develop a solid-phase competitive fluoroimmunoassay
for urinalysis of opiates. The solid phase consisted of polymer beads coated with commercial monoclonal antibodies (MAbs)
raised against morphine. Fluorescein-conjugated morphine (FL-MOR) was used as the fluorescein-labeled hapten. The dissociation
equilibrium constant (K
D
) for the binding of FL-MOR to the anti-MOR MAb was 0.23 nM. The binding of FL-MOR to the anti-MOR MAb reached steady state within minutes and was displaced effectively by morphine
and other opiates. Morphine-3-glucuronide (M3G), the major urinary metabolite of heroin and morphine, competed effectively
with FL-MOR in a concentration-dependent manner for binding to the antimorphine MAb and was therefore used to construct the
calibration curve. The sensitivity of the assay was 0.2 ng/mL for M3G. The assay was effective at concentrations of M3G from
0.2 to 50 ng/mL, with an IC50 of 2 ng/mL. Other opiates and heroin metabolites that showed >50% crossreactivity when present at 1 μg/mL included codeine,
morphine-6-glucuronide, and oxycodone. Methadone showed very low crossreactivity (<5%), which is a benefit for testing in
patients being treated for opiate addictions. The high sensitivity of the assay and the relatively high cutoff value for positive
opiate tests allows very small sample volumes (e.g., in saliva or sweat) to be analyzed. A double-blind comparison using 205
clinical urine samples showed good agreement between this single-step competitive assay and a commercially performed enzyme
multiplied immunoassay technique for the detection of opiates and benzoylecgonine (a metabolite of cocaine). 相似文献
4.
Messaoud T Duplâtre G Waton G Michels B 《Physical chemistry chemical physics : PCCP》2005,7(22):3839-3844
The new method based on positron annihilation lifetime spectroscopy (PALS) to determine both the mean core radius, R(core), and aggregation number, N(ag), of micelles is applied to the study of aqueous solutions of the triblock Pluronic P84 copolymer as a function of temperature (T), beyond the gelification point (334 K). Two long-lived components appear in the PALS spectra, ascribed to triplet positronium in the water bulk (o-Ps(aq)) and in the organic core of the micelles (o-Ps(org)). Of the various fitting parameters, only the lifetime of the latter species, tau4, and the micellar parameters, R(core) and N(ag), disclose the occurrence of gelification by first increasing up to 334 K, then decreasing. By contrast to what is known in case of phase transition, none of the parameters shows any abrupt change at 334 K, whereas the macroscopic viscosity of the solutions suffers a drastic increase. This is attributed to the fact that positronium is sensitive to the microviscosity of the solutions. At the transition point, the properties of the polyoxipropylene aggregates forming the organic core of the P84 micelles are not greatly affected. Furthermore, the fact that the experimental N(ag) values coincide with those calculated for spheres, from the R(core) values, indicates that the shape of the P84 cores does not change significantly after gelification. The onset of gelification results from a decrease in the hydrogen bonding interactions in the solution with an ensuing relative increase in the interactions between the polyoxipropylene (PPO) groups, initially forming the corona of the P84 micelles, in an intermicellar mode. This increased solicitation of the PPO groups outside their initial location would result in depletion in the number of surfactant molecules forming the micelles, viz. a decrease in both R(core) and N(ag) above 334 K. From the data, additional information can be gained regarding the local viscosity and surface tension in the micellar cores. 相似文献
5.
Mehmood A Malik A Anis I Khan PM Riaz M Makhmoor T Choudhary MI 《Natural product letters》2002,16(6):371-376
Two new oleanane triterpenes; 2alpha,3alpha,24-trihydroxyolean-12-ene-28,30-dioic acid ([structure: see text]) and 2alpha,3alpha,24,28-tetrahydroxyolean-12-ene ([structure: see text]) have been isolated from the roots of Atropa acuminata. Anti-oxidant p-hydroxyphenethyl trans-ferulate ([structure: see text]), beta-sitosterol-3-O-beta-D-glucopyranoside ([structure: see text]) and oleanolic acid ([structure: see text]) have also been reported for the first time from this species. The structures were determined by spectroscopic studies including 2D-NMR. 相似文献
6.
7.
Xanthates were easily prepared by adsorption of alcohol on KF-Al2O3 followed by treatment of carbon disulfide and iodomethane at room temperature. Pyrolysis of benzyl xanthate affords to a complex mixture of products. A radical process was proposed to explain the nature of products obtained. 相似文献
8.
Solvent-Free Condensation of Methyl Pyridinium and Quinolinium Salts with Aldehydes Catalyzed by DBU
Methylpyridinium and methylquinolinium salts were condensed under solvent-free conditions with aromatic aldehydes in the presence of 1,8-diazabicyclo[5.4.]undec-7-ene (DBU) as catalyst, by grinding at room temperature. The products are dyes or useful intermediates. The DBU can be easily recycled and reused. 相似文献
9.
I. N. Klochkova A. A. Anis’kov M. P. Shchekina S. V. Chuvaikina K. A. Andreev 《Russian Journal of Organic Chemistry》2013,49(9):1344-1347
Carbocyclization of unsymmetrical 1,5-diarylpenta-1,4-dien-3-ones with thiobarbituric acid afforded previously unknown 7,11-diaryl-3-thioxo-2,4-diazaspiro[5.5]undecane-1,5,9-triones with high regio- and stereoselectivity. The same spiro compounds were also synthesized by three-component condensation of thiobarbituric acid with the corresponding aromatic aldehydes and 4-arylbut-3-en-2-ones. 相似文献
10.