Synthesis and study of binuclear vanadyl complexes with acyldihydrazones of salicylaldehyde and dicarboxylic acids

The binuclear vanadyl(ii) complexes [(VO)₂·2Py·2EtOH]·mH₂O with acyldihydrazones of salicylaldehyde (H₄L) and dicarboxylic acids were synthesized and studied. In these complexes, two chelate vanadyl(ii) complexes with the tridentate bicyclic ligands are linked to each other by the polymethylene bridges —(CH₂) _n — of different lengths varying from one to four units. The ESR spectra of solutions of these complexes, unlike those of analogous copper(ii) complexes, have an isotropic signal with an eight-line hyperfine structure (g = 1.972, a _V = 93·10^–4 cm^–1) typical of monomeric vanadyl complexes, which indicates that no exchange interactions occur between the paramagnetic centers through the polymethylene chain.     

Solubility Behavior in Ternary Water-Salt Systems under Sub- and Supercritical Conditions

Summary.  Two main types of binary systems with distinctive solubility behavior under sub- and supercritical conditions were used to subdivide ternary water-salt systems into three classes. Characteristic features of solubility behavior and phase equilibria in ternary water-salt systems of each class at temperatures above 200°C are discussed on the basis of available experimental data and some conclusions obtained as a result of theoretical derivation of fluid and complete phase diagrams. Corresponding author. E-mail: Valyashko@IGIC.RAS.RU Received September 25, 2002; accepted (revised) November 28, 2002 Published online April 24, 2003 RID="a" ID="a" Dedicated to Prof. Dr. H. Gamsjaeger on the occasion of his 70^th birthday anniversary     

Intramolecular cyclization of ketene containing both acyl andN-alkylimidoyl substituents. Synthesis and crystal and molecular structure of 3-benzoyl-5-phenyl-2H,4H-furo[3,2-c] isoquinolin-2-one

Thermal decarbonylation of 1-benzyl-4,5-dibenzoyl-2,3-dihydropyrrole-2,3-dione yields benzoyl[N-benzyl(phenylglyoxalimidoyl)]ketene. The latter undergoes intramolecular cyclization to 3-benzoyl-5-phenyl-2,3,4,5-tetrahydrofuro[3,2-c]isoquinolin-2-one. Which is oxidized to 3-benzoyl-5-phenyl-2H,4H-furo[3,2-c]isoquinolin-2-one under the reaction conditions. The crystal and molecular structure of the title compound was studied by X-ray structural analysis. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 563–565, March, 1997.     

Influence of quaternary onium salts,crown ethers and cryptands on olefin epoxidations promoted by HOCl/ClO− in the Presence of Mn(III)-tetrakis(2,6-dichlorophenyl)porphyrin chloride

Reaction rates of alkene epoxidations, promoted by aqueous NaOCl and catalyzed by Mn(III)-tetrakis(2,6-dichlorophenyl)porphyrin chloride1 (P) in the presence of a lipophilic axial ligand (L) (e.g.N-hexylimidazole) and carried out under H₂O/CH₂Cl₂ two phase conditions at 0°C, are strongly enhanced by lowering the pH of the aqueous phase from 12.7 to 9.5. Under these conditions, a further relevant increase in the reaction rates can be achieved by adding phase-transfer catalysts (PT), e.g. quaternary ammonium salt 3, lipophilic crown ether4 or cryptand5, provided that the amount of L is very small (L/P=1 for very reactive alkenes, e.g. cyclooctene, and 10 for poorly reactive ones, e.g. 1-dodecene). In the case of cyclooctene epoxidation, the use of 0.006–0.03 mol. equiv. of PT completes the reaction in 1–10 min., the initial rates being up to 600 turnovers/min. with (2.2.2,C₁₀) cryptand. In the absence of the axial ligand, the quaternary ammonium salt3 and cryptand5 show an inhibitory effect. Such an effect is due to the formation of the poorly reactive Mn(P)CI species, by Cl– extraction to the organic phase. However, dibenzo crown ether 4 does not show this effect. In the presence of 4, and with L/P =1, the 1-dodecene epoxidation reaches 94% in 1 min. The unique behavior of crown ethers can be explained by their ineffectiveness in extracting alkali chlorides, providing a very low concentration of Cl– in the organic phase and thus avoiding the Mn(III)-porphyrin deactivation.This paper is dedicated to the memory of the late Dr C. J. Pedersen.     

GC–MS analysis of phenolic compounds in fuels after conversion to trifluoroacetate esters

The GC–MS characteristics of trifluoroacetate esters of phenolic compounds are discussed. Linear temperature programmed retention indices and total ion current MS response factors of over 120 phenolic esters are reported. The main GC advantages from analysis of trifluoroacetate esters as compared to plain phenols are enhanced volatility and improved resolution. For example, the elution temperature of a given phenol is typically 50 °C greater than that of the corresponding trifluoroacetate ester. Also, while retention of compounds with two trifluoroacetate groups is only moderately greater than mono esters, underivatized dihydroxy compounds are very difficult to elute from any GC column. Complete resolution of isomeric C₀-, C₁- and C₂-alkylphenol esters is readily achieved on conventional fused silica GC columns; resolution of the corresponding underivatized compounds requires specialized GC columns with low temperature limits. In general, mass spectra of trifluoroacetate esters are more characteristic of a given structure than those of the corresponding phenols and may be more rigorously interpreted towards structural elucidation. A table in the report summarizes some of the more important spectral features used in compound identification. Example applications in analysis of coal-, shale- and petroleum-derived materials are presented. Selected ion monitoring is used to determine individual phenolic components in whole distillates; reconstructed ion chromatograms are used to illustrate distributions of selected species as a function of fuel storage and thermal stress.     

Time-dependent mixing and demixing processes in binary lipid monolayers studied by mixed and separate spreading using film pressure and film potential measurements

Using both spreading techniques — mixed spreading and separate spreading- and, simultaneously, film pressure and film potential measurements, the mixing behavior of the following five binary systems was investigated and compared: 1) system 1,2-dilauroyl-phosphatidylethanolamine/cholesterol; 2) system 1,2-dimyristoyl-phosphatidylethanolamine/cholesterol; 3) system 1,2-dipalmitoyl-phosphatidylethanolamine/cholesterol; 4) system Na-eicosyl sulphate/hexadecanol; 5) system phosphatidic acid/1,2-dimyristoyl-phosphatidylethanolamine.Analyzing the time and concentration dependence of the /a isotherms and v/a isotherms (^s = film pressure, v ^s potential,a=average area per molecule in mixed films in the monolayers) of the binary monolayers it can be concluded that the components of the binary systems 1–4 are complete miscible in the monolayers. On the other hand the components of the system 5 are probably partially miscible only.     

Comparative analysis of affine scaling algorithms based on simplifying assumptions

We analyze several affine potential reduction algorithms for linear programming based on simplifying assumptions. We show that, under a strong probabilistic assumption regarding the distribution of the data in an iteration, the decrease in the primal potential function will be with high probability, compared to the guaranteed(1). ( 2n is a parameter in the potential function andn is the number of variables.) Under the same assumption, we further show that the objective reduction rate of Dikin's affine scaling algorithm is with high probability, compared to no guaranteed convergence rate.Research supported in part by NSF Grant DDM-8922636.     

An efficient fault-tolerant decentralized commit protocol for single site failure

To maintain consistency on a distributed database system, a commit protocol is often employed to ensure that either all the sub-transactions of a transaction commit or all abort. Special care needs to be taken to ensure the correct functioning of a commit protocol in the face of node failures during the execution of the protocol. A protocol is said to be fault-tolerant if it properly commits or aborts, even if nodes fail.In this paper, we present a fault tolerant decentralized commit protocol which is message optimal in the absence of failures. Furthermore, the protocol (FTDCP) ensures that all sites can achieve a consistent final decision by at most 4 extra messages in the single site failure situation.     

Optimal convergence properties of kernel density estimators without differentiability conditions

Let X ₁, X ₂, ..., X _n be independent observations from an (unknown) absolutely continuous univariate distribution with density f and let % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXafv3ySLgzGmvETj2BSbqefm0B1jxALjhiov2D% aebbfv3ySLgzGueE0jxyaibaiiYdd9qrFfea0dXdf9vqai-hEir8Ve% ea0de9qq-hbrpepeea0db9q8as0-LqLs-Jirpepeea0-as0Fb9pgea% 0lrP0xe9Fve9Fve9qapdbaqaaeGacaGaaiaabeqaamaabaabcaGcba% GabmOzayaajaGaaiikaiaadIhacaGGPaGaeyypa0Jaaiikaiaad6ga% caWGObGaaiykamaaCaaaleqabaGaeyOeI0IaaGymaaaakmaaqadaba% Gaam4saiaacUfadaWcgaqaaiaacIcacaWG4bGaeyOeI0Iaamiwamaa% BaaaleaacaWGPbaabeaakiaacMcaaeaacaWGObGaaiyxaaaaaSqaai% aadMgacqGH9aqpcaaIXaaabaGaamOBaaqdcqGHris5aaaa!5356!\[\hat f(x) = (nh)^{ - 1} \sum\nolimits_{i = 1}^n {K[{{(x - X_i )} \mathord{\left/ {\vphantom {{(x - X_i )} {h]}}} \right. \kern-\nulldelimiterspace} {h]}}} \] be a kernel estimator of f(x) at the point x, \s-<x<, with h=h _n (h _n O and nh _n , as n) the bandwidth and K a kernel function of order r. Optimal rates of convergence to zero for the bias and mean square error of such estimators have been studied and established by several authors under varying conditions on K and f. These conditions, however, have invariably included the assumption of existence of the r-th order derivative for f at the point x. It is shown in this paper that these rates of convergence remain valid without any differentiability assumptions on f at x. Instead some simple regularity conditions are imposed on the density f at the point of interest. Our methods are based on certain results in the theory of semi-groups of linear operators and the notions and relations of calculus of finite differences.This research was supported in part by grants from the Natural Sciences and Engineering Research Council of Canada and the University of Alberta Central Research Fund.     

Repleteness and regular lattice measures

Let X be an abstract set and L a lattice of subsets of X. To each lattice regular measure µ, we associate two induced measures and on suitable lattices of the Wallman space IR(L) and another measure µ on the spaceIR(L). We will investigate the reflection of smoothness properties of p onto , and µ; and try to set some new criterion for repleteness and measure repleteness.