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201.
Zvi?AradEmail author Ya’akov?Erez Mikhail?Muzychuk 《Israel Journal of Mathematics》2004,142(1):285-314
The paper studies standard integral table algebras containing an element of width two. It is shown that the table subalgebra
generated by such an element is exactly isomorphic to one of the table algebras described in Main Theorems 1.1. and 1.2.
The contribution of this author is a part of his Ph.D. thesis at Bar-Ilan University under the supervision of Z. Arad and
M. Muzychuk.
This author was partially supported by the Israeli Ministry of Absorption. 相似文献
202.
Condensation of organic isothiocyanates with active methylene compounds gave nine thioamides RNHCSCHYY′ or their isomeric thioenols RNHC(SH) = CYY′ for substrates in which Y and Y′ are electron‐withdrawing groups (EWG). These included derivatives of Meldrum's acid (MA) which showed 100% thioenol in all solvents. For other compounds the percentages of thioenol in CDCl3 when R = Ph are 100% when Y = CN and Y′ = CO2Me or Y′ = CO2CH2CCl3, 6% when Y = Y′ = CO2CH2CF3, and 0% when Y = Y′ = CO2Me. The chemical shift of SH (highest values 12.0–16.0 ppm) served as a probe for the thioenol structures and also for the extent of hydrogen bonding to the SH group. In contrast to simple ketones and thioketones in which thioenolization is favored over enolization by factors as large as 106, for intramolecular competition KThioenol/KEnol ratios are much lower than for systems not substituted by β‐EWGs. X‐ray crystallography of the 5‐anilido‐MA derivative shows a hydrogen‐bonded thioenol structure. δ(OH), δ(NH), KEnol, and crystallographic data for analogous thioenol and enol systems are compared. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
203.
The design of horizontal boiler-tube arrays, for both fluidized bed combustors and conventional power plants, is today constrained by the uncertainty in the circumferential wall temperature profile prevailing in the tubes. High circumferential anisothermality at elevated temperatures can lead to high thermal stress and threaten both the load carrying and operating life of steam-generating boiler tubes.A critical review of the available results and a detailed analysis of two-phase flow regimes in boiler tubes appear to indicate that a reduced circumferential temperature difference is associated with transition from intermittent to annular flow, rather than the termination of stratified flow. The two-phase flow regime analysis is, furthermore, shown to successfully predict the axial variation and flow rate dependence of circumferential anisothermality. 相似文献
204.
Chiral 1-[9'-(2'-methoxyanthryl)]-2,2-dimesitylethenol (2), 1-[9'-(2'-fluoroanthryl)]-2,2-dimesitylethenol (3), and 1-[9'-(2'-fluoroanthryl)]-2,2- dimesitylvinyl acetate (4) were synthesized and their DNMR behavior in C6D5NO2 was studied. 3 and 4 were resolved on an amylose tris(3,5-dimethylphenylcarbamate) HPLC column to their enantiomers. Acetate 4 racemizes slowly in solution with DeltaG(e)(++), DeltaH(e)(++), and DeltaS(e)(++) values of 26.2, 27.6 kcal mol(-)(1), and 4.3 eu, respectively, as expected for a rotational betabeta'-2-ring flip process in a vinyl propeller and the racemization is unaffected by added TFA, Et3N, and EtOD. Although 3 racemizes almost 350 times faster, the racemization is catalyzed by TFA and shows bell-shape catalysis by Et3N and a KIE in a partially deuteriated solvent. From this and the DNMR data, it is concluded that 3 does not racemize via a rotational betabeta'-2-ring flip. Five nonflip routes are discussed for the racemization of 3, and it is concluded that only the one initiated by protonation at C1 does not contradict the experimental data. By analogy with the E/Z isomerization of the structurally related 2-(m-methoxymesityl)-1,2-dimesitylethenol 17, it is suggested that in the absence of added catalyst one or more enol molecule(s) catalyze the enantiomerization of another one. Only partial resolution was achieved for 2 and from the similarity of its behavior with that of 3, it is suggested that it racemizes by the same mechanism. 相似文献
205.
As the intermittent (slug) flow pattern was recently shown to be, along with the stratified flow regime, responsible for circumferential anisothermality of horizontal steam generating tubes operating at moderate steam qualities, the ability to estimate the local liquid levels in such tubes and to compare them with the position of the circumferentially maximum value of the externally applied heat loading appears to be of great practical importance for boiler designers. While the procedure of the estimation of minimum liquid heights (hL) in horizontal stratified flows was suggested in previous papers, this study presents an analytical approach for engineering evaluations of hL in the horizontal, diabatic slug flow pattern. It is, importantly, shown that the use of the stratified flow-based approach to evaluate hL in slug flows results in the overestimation of actual liquid heights which may be detrimental for boiler tubes, especially under circumferentially nonuniform heat loading. 相似文献
206.
207.
A Probabilistic Minimax Location Problem on the Plane 总被引:1,自引:0,他引:1
Oded Berman Jiamin Wang Zvi Drezner George O. Wesolowsky 《Annals of Operations Research》2003,122(1-4):59-70
In this paper we consider the weighted minimax (1-center) location problem in the plane when the weights are not given but rather drawn from independent uniform distributions. The problem is formulated and analyzed. For certain parameters of the uniform distributions the objective function is proven to be convex and thus can be easily solved by standard software such as the Solver in Excel. Computational experience is reported. 相似文献
208.
A sensitive on-chip acetylcholinesterase (AChE) assay that serves as a basis for the development of a fully integrated on-chip AChE-inhibitor detection assay is presented. The sequential steps required for the on-chip analysis process were integrated into a microchip. Transport and mixing of the reagents occurred by a combination of electroosmosis and electrophoresis using computer-controlled electrokinetic transport. AChE-catalyzed hydrolysis of acetylthiocholine to thiocholine was determined by on-chip reaction of thiocholine with eosinmaleimide, and the resulting thioether was electrophoretically separated and detected by laser-induced fluorescence (LIF). Enzyme-substrate mixing and reaction by confluent flow of reagents was compared with electrophoretically mediated microanalysis (EMMA), based on injection of an enzyme plug, and the utilization of differences in electrophoretic mobility as a driving force for efficient mixing and reaction. Both methods yielded similar results, however the EMMA-plug technique is preferable. The EMMA-plug technique was optimized for length and pushing time of enzyme plug, length of dyes mixture plug, acetylthiocholine concentration, and detector location. Detection of O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothiolate (VX) and paraoxon, two AChE inhibitors, was demonstrated by off-chip mixing of the inhibitor and AChE, followed by the on-chip AChE assay. Limit of detection of VX for 5.5 min incubation and of paraoxon for 8 min incubation was 4 × 10−10 and 4 × 10−7 M, respectively. Utilization of the AChE microchip assay for inhibition kinetics was demonstrated also by evaluation of the inhibitor-enzyme bimolecular reaction constant (ki). The evaluated ki values for VX and paraoxon for AChE from the electric eel were 3.5 × 107 and 1.7 × 105 M−1 min−1, respectively, conforming well to reported values obtained by bulk methods. 相似文献
209.
Zvi Drezner 《The Journal of the Operational Research Society》1987,38(6):509-514
In this paper, the p-median and p-centre problems are generalized by considering the possibility that one or more of the facilities may become inactive. The unreliable p-median problem is defined by introducing the probability that a facility becomes inactive. The (p, q)-centre problem is defined when p facilities need to be located but up to q of them may become unavailable at the same time. An heuristic procedure is presented for each problem. A rigorous procedure is discussed for the (p, q)-centre problem. Computational results are presented. 相似文献
210.
Zvi Drezner 《The Journal of the Operational Research Society》1984,35(8):741-748
The p-centre problem, or minimax location-allocation problem in location theory terminology, is the following: given n demand points on the plane and a weight associated with each demand point, find p new facilities on the plane that minimize the maximum weighted Euclidean distance between each demand point and its closest new facility. We present two heuristics and an optimal algorithm that solves the problem for a given p in time polynomial in n. Computational results are presented. 相似文献