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1.
A method for construction of the characteristic polynomial (CP) coefficients of the three classes of reciprocal graphs, viz., Ln + n(p), Cn + n(p), and K1,n?1 + n(p), has been developed that requires only the value of n. The working formulas have been expressed in matrix product form, computer programs for which can easily be developed. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005  相似文献   

2.
The spread s(G) of a graph G is defined as s(G) = max i,j i − λ j |, where the maximum is taken over all pairs of eigenvalues of G. Let U(n,k) denote the set of all unicyclic graphs on n vertices with a maximum matching of cardinality k, and U *(n,k) the set of triangle-free graphs in U(n,k). In this paper, we determine the graphs with the largest and second largest spectral radius in U *(n,k), and the graph with the largest spread in U(n,k).   相似文献   

3.
4.
Maleopimar adducts of tall colophony esters with alcohols-telomers 1H,1H,5H-perfluoropentane-1-ol, 1H,1H,7H-perfluoroheptane-1-ol, and 1H,1H,9H-perfluorononane-1-ol were synthesized in conditions of Diels-Alder reaction.  相似文献   

5.
N-o-, -m-, and -p-carboxyphenyl-D-glucosylamines and N-o-, -m-, and -p-hydroxyphenyl-D-glucosylamines were synthesized by reaction of D-glucose with o-, m-, and p-aminobenzoic acids and o-, m-, and p-aminophenols. It was demonstrated that both - and -anomers were formed by N-glycosylation of o-, m-, and p-aminobenzoic acids; only -anomers, by N-glycosylation of o-, m-, and p-aminophenols.  相似文献   

6.
The fracture energy G of an adhesive bond appears to be a product of two terms: G = GO [1 + f(R, T)], where GO is the intrinsic (chemical) strength of the interface and f(R, T), usually much larger than unity, reflects energy dissipated within the adherends at a crack speed R and temperature T. Values of GO have been determined for interlinked sheets of an SBR elastomer by measuring the peel strength at low rates and high temperatures, and in the swollen state, to minimize internal losses. Both the density ΔN and molecular length L of interlinking molecules were varied. GO was found to increase in proportion to (ΔN)L3/2, in accord with the molecular theory of Lake and Thomas. As the peel rate was raised and the test temperature lowered, G was considerably increased by internal dissipative processes, becoming as much as 1000 × GO near the glass transition. The loss function f(R, T) was found to depend somewhat upon the strand length L, being about twice as large at intermediate peel rates when L was increased by 40%. It also depended on the density ΔN of interlinking molecules, being about twice as large at high peel rates when the density of interlinks was reduced by a factor of six. Thus, the loss function f(R, T) is greater when the interlinking molecules are few and long, and it is lower when they are many and short. However, it is mainly governed by two parameters: peel rate R and temperature difference (TTg), in accord with a viscoelastic loss mechanism. © 1996 John Wiley & Sons, Inc.  相似文献   

7.
The standard (p o=0.1 MPa) molar enthalpies of combustion atT=298.15 K were measured by static bomb combustion calorimetry for liquidN,N-diethylaniline,N,N-dimethyl-m-toluidine,N,N-dimethyl-p-toluidine, andN-ethyl-m-toluidine. Vaporization enthalpies forN,N-dimethyl-m-toluidine andN-ethyl-m-toluidine were determined by correlation gas chromatography. Derived standard molar values of f H m o (g) at 298.15 K forN,N-diethylaniline (62.1±7.6);N,N-dimethyl-m-toluidine (72.6±7.3),N,N-dimentyl-p-toluidine (68.9±7.4),N-ethyl-m-toluidine (30.5±3.8 kJ· mol–1) were obtained.  相似文献   

8.
9.
The replacement of theN-acetyl group by anN-benzoyl group inN-acyldehydrodipeptides results, first, in an increase in the asymmetric induction in their hydrogenation in the case ofN-Bz-Phe-(S)-Glu.N-Bz-(S)-Phe-(S)-Glu is obtained with a diastereomeric excess (de) of 52 %. Second, no poisoning of the Pd-catalyst by sulfur inN-Bz-Phe-(S)-Met occurs, andN-Bz-(R)-Phe(S)-Met is obtained with ade of 26 %. The formation of complexes ofN-Bz-Phe-AA with Ca2+ and Mg2+ ions does not, as a rule, affect the diastereoselectivity of the hydrogenation. The structure of the dehydrodipeptides has been determined on the basis of1H NMR spectra, potentiometric titration, and molecular mechanics calculations.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 884–887, May, 1994.This work was carried out with the financial support of the Russian Foundation for Basic Research (Project 93-03-4646).  相似文献   

10.
By Heck reaction of isoalantolactone with aryl bromides or aryl iodides (3aR,4aS, 8aR,9aR,E)-3-arylmethylidene-8a-methyl-5-methylidenedecahydronaphtho[2,3-b]furan-2(3H)-ones and (4aS,8aR,9aS)-3-arylmethyl-8a-methyl-5-methylidene-4a,5,6,7,8,8a,9,9a-octahydronaphtho[2,3-b]furan-2(4H)-ones, products of the double bond shift, were synthesized. The yields of the arylation products depend on the nature of the catalytic system and on the structure of the aryl halide. The structures of (3aR,4aS,8aR,9aR,E)-3-(3,4-dimethoxybenzylidene)-8amethyl-5-methylidenedecahydronaphtho[2,3-b]furan-2(3H)-one and (4aS,8aR,9aS)-3-(2-methylsulfanylbenzyl)-8amethyl-5-methylidene-4a,5,6,7,8,8a,9,9a-octahydronaphtho[2,3-b]furan-2(4H)-one were proved by XRD analysis.  相似文献   

11.
Monolinuron, chlortoluron, diuron, isoproturon, linuron, diflubenzuron, dimefuron, teflubenzuron, and lufenuron have been chromatographed on an RP-HPLC column and on RP-HPTLC plates with methanol–water in different volume proportions as mobile phases. The retention values log k, and RM were extrapolated to zero methanol content. Chromatographic lipophilicities (log kw, RMw, o(HPLC), and o (TLC)) were compared with measured (log Pexp) partition coefficients and with values (A log Ps, IA log P, C log P, log PKowin, and x log P) calculated by use of five different software products. The most significant correlations were found between the chromatographic lipophilicities and C log P values. Satisfactory linear correlation was also obtained between lipophilicity (log kw, RMw) and the valence Gutman index (M).  相似文献   

12.
The diffusion limited cluster-cluster aggregation (DLCA) model is modified by including cluster deformations during aggregation, with a tuning flexibility parameter F. A three-dimensional computer simulation is presented, which starts from a collection of f-functional monomers randomly distributed in a cubic box with a volumic fraction c (concentration) and which uses the highly efficient bond fluctuation algorithm to describe the cluster deformations. It is shown that, for F 0, there exists a well defined threshold value of the volumic fraction below which the realization of all intra-aggregate bonding possibilities prevents the formation of a gelling network. For c > c g , a true sol-gel transition occurs at a characteristic time t g , after which an infinite cluster (which is self connected via the boundary conditions) appears. In contrast to DLCA, t g does not increase as the box size increases. The transition at c g is characterized by a divergence of the final clusters size for c<c g and a divergence of the gel time for c>c g . Several other numerical results are reported.  相似文献   

13.
Summary The [h]phenylene C6h H2h+4 isomers are enumerated up toh=12. The numbers are compared with old and new data for C n H5 isomers of benzenoids, fluoranthenoids and biphenylenoids.
Anzahl möglicher Isomerer von Phenylenen
Zusammenfassung Die Anzahl der [h]Phenylen-Isomeren C6h H2h+4 wurde bish=12 ausgewertet. Die Zahlen wurden mit alten und neuen Daten für C n H s -Isomere von Benzenoiden, Fluoranthenoiden und Biphenyloiden verglichen.
  相似文献   

14.
The kinetic study of the gas-phase thermal elimination reactions of N-ethyl-3,5 dimethyl-pyrazole (I), N-ethyl-pyrazole (II), N-sec-butyl-pyrazole (III), and N-tert-butyl-pyrazole (IV) using a flow system is reported. After obtaining activation parameters for I we carried out competitive reactions with II, III and IV using I as internal standard to obtain their Ea. The values of Δ(ΔH) calculated for II, III and IV agree with the little differences in Ea experimentally found.  相似文献   

15.
Seed oils of 12 Salvia species collected from different regions in Turkey (S. Albimaculata Hedge & Hub.-Mor., S. Candidisima Vahl., S. Cedronella Boiss., S. Cryptantha Montbret & Aucher ex Bentham, S. Forskahlei L., S. Fruticosa Miller (Sin. S. Triloba L. Fil), S. Halophila Hedge, S. Hypargeia Fisch. & Mey., S. Sclarea L., S. Tomentosa Miller, S. Tchihatcheffii (Fisch. & Mey.) Boiss., S. Virgata Jacq.) were obtained by Soxhlet apparatus using hexane. The oil yields were found to be between 2.0% and 20.9%. Fatty acids in the oils were converted to methyl esters and determined by GC/MS in methyl ester form. The main fatty acid components of S. halophila, S. Hypargeia, and S. Sclarea are unsaturated oleic, linoleic, and linolenic acids. In others except S. Candidissima, the dominant acids are oleic, linoleic and palmitic acids.  相似文献   

16.
The large N expansion of the restricted Hartree–Fock (RHF) exchange energy per atom E(N) of the Pariser–Parr–Pople (PPP) model of cyclic polyenes (annulenes) CNHN is derived in detail. We explicitly derive the coefficients E0 and E1 of the asymptotic expansion: E(N)=E0+E1 ln N/N2+O(N−2), N→∞, in the very simple case of half-filling and no bond alternation. The exchange energy per atom in the infinite chain can be written as Eex=(2/π2)∑j=1{[γ(2j−1)]/[(2j−1)2]}, where γ is the two-electron repulsion integral in the infinite chain. On the other hand, the second coefficient E1 giving a finite-size correction is found to be 1/2b, where b is the bond length. This value of E1 differs slightly from that of a linear chain with periodic boundary conditions because the distance between sites depends upon the radius of the ring, i.e., upon N. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 66 : 397–407, 1998  相似文献   

17.
A new generalized perturbed thermodynamic nonlinear isotherm regularity (GPTNLIR) equation of state (EoS) has been proposed for the fluids over the entire density range from gas to liquid. The GPTNLIR has been derived on the basis of an effective nearest neighbor pair interaction of an extended average effective pair potential (AEPP) in the framework of the thermodynamic perturbation theory (TPT). The selected AEPP is an extended Lennard-Jones (12, 6, 3) type which considers the repulsive, dispersion, dipole-dipole and longer-range interactions between pair molecules, respectively. Based on the EoS, a non-linear relationship exists between (ZZCS)v2 and ρ for each isotherm of fluid, where Zis the compression factor, v=1/ρis the molar volume, ZCS is Carnahan–Starling (CS) expression for the compression factor of the reference fluid with the temperature-dependent effective hard-core diameter (σeff). The validity of EoS against the experimental pvTdata were tested for a variety of fluids, including polar, non-polar, hydrogen bonded and quantum fluids. This EoS provides the estimation of σeff at T>Tc, T=Tc and T<Tc, in which Tc is critical temperature, for each real fluid using its experimental pvT data and the extension of TPT theory as well.  相似文献   

18.
Summary: Biodegradation of film specimens from polyhydroxyalkanoates (PHAs) of two types – poly-3-hydroxybutyrate (PHB) and poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) – was analysed in different environments: tropical sea waters of the South China Sea (Nha Trang, Vietnam) and soils in the environs of Hanoi (Vietnam), Nha Trang (Vietnam) and Krasnoyarsk (Siberia, Russia). In seawater, the mass loss of the specimens of both types was almost equal. However, in tropical soils, PHB degraded quicker than PHBV. In the Siberian soil, the degradation rate of the PHBV was generally higher than that of PHBV. Analysis of molecular mass of PHA specimens showed its decreasing during biodegradation. In the tropical sea conditions, PHA degrading microorganisms were represented by bacteria of Enterobacter, Bacillus and Gracilibacillus genera. Among PHA degrading bacteria, Burkholderia, Alcaligenes, Bacillus, Mycobacterium and Streptomyces genera were identified in Vietnamese soils, and Variovorax, Stenotrophomonas, Acinetobacter, Pseudomonas, Bacillus and Xanthomonas genera in Siberian soils. Micromycetes of Gongronella, Paecilomyces, Penicillium and Trichoderma genera exhibited PHA degrading activity in Vietnamese soils, and Paecilomyces, Penicillium, Acremonium, Verticillium and Zygosporium genera – in Siberian soils.  相似文献   

19.
A new series of iron(III) complexes with different fourth generation of quinolone drugs of the type [Fe(L)n(Cl)x]?yH2O (( 1 ) L: nalidixic acid, n = 3, x = 3, y = 3; ( 2 ) L: oxolonic acid, n = 3, x = 3, y = 0; ( 3 ) L: pipemidic acid, n = 3, x = 3, y = 2; ( 4 ) L: lomefloxacin, n = 3, x = 3, y = 0; ( 5 ) L: pefloxacin mesylate, n = 3, x = 3, y = 2; ( 6 ) L: levofloxacin, n = 3, x = 3, y = 6) were synthesized and identified using microanalysis, Fourier transform infrared spectroscopy, conductance data, effective magnetic moments and electronic UV–visible spectra. In these six complexes, the quinolone drug chelates act in a unidentate manner via nitrogen atom of pyridone/piperazyl moiety. Electronic spectroscopic data are in agreement with an octahedral geometrical structure. Thermal degradation analyses in nitrogen gas were used to investigate the number and location of water molecules. The thermal decomposition process is completed in 3?5 steps, the first step being responsible for loss of uncoordinated water molecules and the steady state of all complexes occurs at around 500 °C with oxide forms as residual products. The stabilities of iron(III) complexes 1 – 6 were studied in terms of activation energy E*, entropy ΔS*, enthalpy ΔH* and Gibbs free energy ΔG* that were estimated using Coats–Redfern and Horowitz–Metzger non‐isothermal methods. Molecular docking was used to predict the binding between some of the quinolone drugs and the receptor of prostate cancer 2q7k hormone.  相似文献   

20.
Two trans stereoisomers of 3‐methylcyclopentadecanol (=muscol), (1R,3R)‐ 2 and (1S,3S)‐ 2 , were efficiently synthesized from (3RS)‐3‐methylcyclopentadecanone (=muscone; (3RS)‐ 1 ) by a highly stereoselective reduction (Scheme). L‐Selectride® (=lithium tri(sec‐butyl)borohydride) was used, followed by the enantiomer resolution by lipase QLG (Alcaligenes sp.). The cis stereoisomers of muscol, (1S,3R)‐ 2 and (1R,3S)‐ 2 , were obtained by the Mitsunobu inversion of (1R,3R)‐ 2 and (1S,3S)‐ 2 , respectively (Scheme). The absolute configuration of (1R,3R)‐ 2 was determined by X‐ray crystal‐structure analysis of its 3‐nitrophthalic acid monoester, 2‐[(1R,3R)‐3‐methylcyclopentadecyl hydrogen benzene‐1,2‐dicarboxylate ((1R,3R)‐ 3b ), and by oxidation of (1R,3R)‐ 2 to (3R)‐muscone.  相似文献   

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