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41.
Long multi-branched gold nanoparticles have been synthesized in a very high yield through a facile synthesis combining two different capping agents. The stability of these materials with the time has been tested and their characterization have been performed by diverse advanced electron microscopy techniques, paying special attention to aberration corrected transmission electron microscopy in order to unambiguously analyze the surface structure of the branches and provide insights for the formation of stellated gold nanoparticles. 相似文献
42.
Eleonora Freire Sergio Baggio Ricardo Baggio Alvaro Mombrú 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(1):14-17
The structures of [Mn(S2O3)2(C12H8N2)(H2O)2] and [Mn(S4O6)(C10H8N2)2] are presented. The former consists of pairs of polymeric chains formed by manganese polyhedra bridged by bidentate thiosulfate anions, which are in turn related to each other by a pseudo-twofold screw axis. The latter has crystallographic twofold symmetry and consists of monomers in which manganese displays its typical octahedral coordination provided by the bidentate bites of two bipyridine bases and a tetrathionate anion, which is, to our knowledge, the first chelating tetrathionate to be reported in the literature. 相似文献
43.
Sergio A. Moya Juana Gajardo Juan C. Araya Jaime J. Cornejo Véronique Guerchais Hubert Le Bozec J. Carles Bayón Alvaro J. Pardey Pedro Aguirre 《应用有机金属化学》2008,22(8):471-478
Novel ruthenium (II) complexes were prepared containing 2‐phenyl‐1,8‐naphthyridine derivatives. The coordination modes of these ligands were modified by addition of coordinating solvents such as water into the ethanolic reaction media. Under these conditions 1,8‐naphthyridine (napy) moieties act as monodentade ligands forming unusual [Ru(CO)2Cl2(η1‐2‐phenyl‐1,8‐naphthyridine‐ kN )(η1‐2‐phenyl‐1,8‐naphthyridine‐kN′)] complexes. The reaction was reproducible when different 2‐phenyl‐1,8‐naphthyridine derivatives were used. On the other hand, when dry ethanol was used as the solvent we obtained complexes with napy moieties acting as a chelating ligand. The structures proposed for these complexes were supported by NMR spectra, and the presence of two ligands in the [Ru(CO)2Cl2(η1‐2‐phenyl‐1,8‐naphthyridine‐ kN )(η1‐2‐phenyl‐1,8‐naphthyridine‐kN′)] type complexes was confirmed using elemental analysis. All complexes were tested as catalysts in the hydroformylation of styrene showing moderate activity in N,N′‐dimethylformamide. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
44.
In this paper,a new approach is devoted to find novel analytical and approximate solutions to the damped quadratic nonlinear Helmholtz equation(HE)in terms of the Weiersrtrass elliptic function.The exact solution for undamped HE(integrable case)and approximate/semi-analytical solution to the damped HE(non-integrable case)are given for any arbitrary initial conditions.As a special case,the necessary and sufficient condition for the integrability of the damped HE using an elementary approach is reported.In general,a new ansatz is suggested to find a semi-analytical solution to the non-integrable case in the form of Weierstrass elliptic function.In addition,the relation between the Weierstrass and Jacobian elliptic functions solutions to the integrable case will be derived in details.Also,we will make a comparison between the semi-analytical solution and the approximate numerical solutions via using Runge-Kutta fourth-order method,finite difference method,and homotopy perturbation method for the first-two approximations.Furthermore,the maximum distance errors between the approximate/semi-analytical solution and the approximate numerical solutions will be estimated.As real applications,the obtained solutions will be devoted to describe the characteristics behavior of the oscillations in RLC series circuits and in various plasma models such as electronegative complex plasma model. 相似文献
45.
Van Zyla RL Seatlholof ST Van Vuuren SF Viljoen A 《Natural product communications》2010,5(9):1381-1386
Complex interactions between numerous components of essential oils often contribute to the pharmacological effect and therapeutic outcome. To further elucidate these interactions, several essential oil constituents (EOCs) were combined in different ratios and their inhibitory effects on the growth of bacteria and yeast determined using the minimum inhibitory concentration (MIC) microplate assay. When combined and tested against Candida albicans, (+)-beta-pinene interacted antagonistically with (-)-menthone (sigmaFIC(T) = 9.80), but synergistically with 1,8-cineole (sigmaFIC(T) = 0.35). Against Escherichia coli, the combination of E- and Z-(+/-)-nerolidol and geranyl acetate displayed an additive interaction (sigmaFIC(T) = 1.04); while a variable interaction was observed between E- and Z-(+/-)-nerolidol and eugenol with antagonism and synergy being observed at different ratios of each EOC. The combination of either carvacrol or eugenol with an antimicrobial agent (ciprofloxacin or amphotericin B) resulted in synergistic interactions against all microorganisms tested. These favourable results further support the use of essential oil constituents as adjuvants in the development of a new generation of phytopharmaceuticals that can be used in combination with synthetic drugs against drug-resistant microorganisms. 相似文献
46.
San Martin A Rovirosa J Carrasco A Orejarena S Soto-Delgado J Contreras R Chamy MC 《Natural product communications》2010,5(12):1859-1864
The sesquiterpene pacifenol is one of the main constituents of the red alga Laurencia claviformis. Earlier work on the semisynthetic derivatives of pacifenol afforded a series of halogenated sesquiterpenes. The aim of the present work was to obtain new hydroxylated derivatives of halogenated sesquiterpenes by means of microbial transformation using Aspergillus niger, Gibberella fujikuroi and Mucor plumbeus. The best results were obtained with M. plumbeus. The microbiological transformation by M. plumbeus of pacifenol, and two semisynthetic derivatives, is described. The structures of the new compounds obtained were determined by spectroscopic means. 相似文献
47.
Paul T. Allen Lars Andersson Alvaro Restuccia 《Communications in Mathematical Physics》2011,301(2):383-410
In this paper we consider the classical initial value problem for the bosonic membrane in light cone gauge. A Hamiltonian
reduction gives a system with one constraint, the area preserving constraint. The Hamiltonian evolution equations corresponding
to this system, however, fail to be hyperbolic. Making use of the area preserving constraint, an equivalent system of evolution
equations is found, which is hyperbolic and has a well-posed initial value problem. We are thus able to solve the initial
value problem for the Hamiltonian evolution equations by means of this equivalent system. We furthermore obtain a blowup criterion
for the membrane evolution equations, and show, making use of the constraint, that one may achieve improved regularity estimates. 相似文献
48.
Cecilia E. Silvana Alvaro Alicia D. Ayala Norma S. Nudelman 《Journal of Physical Organic Chemistry》2011,24(2):101-109
The kinetics of the reactions of 2,4‐dinitrofluorobenzene (DNFB) and 2,4‐dinitrochlorobenzene (DNClB) with 2‐guanidinobenzimidazole (2‐GB) at 40 ± 0.2 °C in dimethylsulphoxide (DMSO), toluene, and in toluene–DMSO mixtures, and with 1‐(2‐aminoethyl)piperidine (2‐AEPip) and N‐(3‐aminopropyl)morpholine (3‐APMo) in toluene at 25 ± 0.2 °C were studied under pseudo first‐order conditions. For the reactions of 2‐GB carried out in pure DMSO, the second‐order rate coefficients were independent of the amine concentration. In contrast, the reactions of 2‐GB with DNFB in toluene, showed a kinetic behaviour consistent with a base‐catalysed decomposition of the zwitterionic intermediate. These results suggest an intramolecular H‐bonding of 2‐GB in toluene, which is not present in DMSO. To confirm this interpretation the reactions were studied in DMSO–toluene mixtures. Small amounts of DMSO produce significant increase in rate that is not expected on the basis of the classical effect of a dipolar aprotic medium; the effect is consistent with the formation of a nucleophile/co‐solvent mixed aggregate. For the reactions of 3‐APMo with both substrates in toluene, the second‐order rate coefficients, kA, show a linear dependence on the [amine]. 3‐APMo is able to form a six‐membered ring by an intramolecular H‐bond which prevents the formation of self‐aggregates. In contrast, a third order was observed in the reactions with 2‐AEPip: these results can be interpreted as a H‐bonded homo‐aggregate of the amine acting as a better nucleophile than the monomer. Most of these results can be well explained within the frame of the ‘dimer nucleophile’ mechanism. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
49.
50.
Alvaro S. de Sousa Zanele Hlam Manuel A. Fernandes Helder M. Marques 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(4):o229-o232
The crystal structure of the title compound, C8H17NO2, consists of (R,R) and (S,S) enantiomeric pairs packed in adjacent double layers which are characterized by centrosymmetric hydrogen‐bonded dimers, generated via N—H...O and O—H...O interactions, respectively. Intermolecular interactions, related to acceptor and donor molecule chirality, link the achiral double layers into tubular columns, which consist of a staggered hydrophilic inner core surrounded by a hydrophobic cycloalkyl outer surface and extend in the [011] direction. 相似文献