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51.
Edgar Ocando-mavarez Merlin Rosales Ninoska Silva 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1)
Abstract Addition of four equivalents of tButyldiallylphosphine to a solution of one equivalent of [(COE)2Cl]2 in CHCl3 at low temperature produced two isomers of the metallated complex 2, formed by C-H activation. 2 evolve at 40°C to 3, by a hydride transfer from iridium to the cyclooctene (COE) ligand. 相似文献
52.
Merlín Rosales Regina Vallejo Luis Jhonatan Bastidas Beatriz González Angel González 《Reaction Kinetics and Catalysis Letters》2007,92(1):99-104
The systems prepared in situ by addition of two equivalents of diphosphine [1,2-bis(diphenylphosphino)ethane (dppe), 1,3-bis(diphenylphosphino)propane
(dppp) and 1,4-bis(diphenylphosphino)butane (dppb)] to M2Cl2(COE)4 (M = Rh, Ir; COE = cyclooctene) showed to be efficient and regioselective precatalysts for the hydrogenation of quinoline,
isoquinoline, 5,6- and 7,8-benzoquinoline and acridine, under mild reaction conditions (130°C and 4 atm H2). The Rh systems showed to be more active than the corresponding Ir ones, except for the case of acridine, where an inversed
tendency was observed (Ir > Rh). 相似文献
53.
J. J. LaBrecque P. A. Rosales P. R. Cordoves 《Journal of Radioanalytical and Nuclear Chemistry》2001,247(3):563-566
The activity of 137 Cs in surface soils (2-5 cm) was determined at twenty-one sampling sites along the northwestern and eastern coast of the Paraguana peninsula (Venezuela), as well as, at nine locations, between 95 and 535 m.a.s.l. on Cerro Santa Ana. The measurements were performed by high-resolution gamma-ray spectroscopy employing a compatible IBM computer. Most of the values were much higher than those found along the coastline of the mainland; four sites were found to be anomalously high, with 137 Cs values greater than 10 Bq/kg. It is difficult to explain these anomalous 137 Cs values by geographical or climatological factors since there is little rainfall here and the clouds and fog are rarely if never present along the coast of the peninsula. Possibly, some mechanism of the mist that is blown ashore could explain these anomalies. The values of the 137 Cs versus altitude on the Cerro Santa Ana show an increase of two or three times at 500 m.a.s.l. level, thus we have concluded that the base of the clouds was at this height when the fallout was directly deposited by condensation in this cloud forest. These results in the Cerro Santa Ana cloud forest are similar to those of other cloud forests along the Venezuelan coast, but the altitude (m.a.s.l.) of the base of the clouds here are much lower. 相似文献
54.
Robles-Pérez Aureliano M. Rosales José Carlos 《Annali di Matematica Pura ed Applicata》2015,194(1):275-287
Annali di Matematica Pura ed Applicata (1923 -) - The common behavior of several families of numerical semigroups led up to defining the Frobenius varieties. However, some interesting families were... 相似文献
55.
Johan Urdaneta Yaneth Bermúdez Federico Arrieta Merlin Rosales Néstor Cubillán Javier Hernández Olga Castellano Humberto Soscún 《Theoretical chemistry accounts》2010,126(1-2):27-37
The linear (α), and nonlinear (β, γ) optical NLO properties of ortho-, meta- and para-nitrophenol (ONP, MNP and PNP) isomers have been calculated in gas phase by using ab initio (HF, MP2 and MP4) and density functional theory (DFT) (B3LYP, CAM-B3LYP) methods, with the 6-31+G(d,p) and 6-311+G(3d,3p) standard and the Sadlej specialized basis sets. These properties were evaluated both at static and at dynamic regime within the finite field FF numerical techniques and the time-dependent-Hartree–Fock approach at 1,910 nm, respectively. Additional calculations were performed for the β static hyperpolarizability of these isomers in presence of p-dioxane solvent with the Onsager Model and the SCRF-PCM approach, using B3LYP/6-31+G(d,p) and MP2/6-31+G(d,p) levels of theory. Additionally, CCSD/6-31+G(d,p) calculations were performed for the α, β and γ properties of PNP isomer. The B3LYP and MP2 α ave results of the nitrophenol isomers are comparable to the experimental α ave reports; while the tendency for the β v calculated values (β v PNP > β v MNP > β v ONP), that can be explained in terms of the O x atomic charge of the –NO2 group, does not follow exactly the experimental ones. The B3LYP γ ave results are in correspondence to the experimental measurements, the correlation of which is r 2 = 0.99. The use of FF methodology in conjunction with the B3LYP and MP2 methods and the 6-31+G(d,p) basis set show to be appropriate approaches to predict qualitative optical properties of Push–Pull like organic molecules, provided are considered the solvent effects or frequency dependence. However, to have a clear picture of the NLO properties of an isolated molecule, higher order correlation effects combined with specialized basis sets, frequency and solvent effects should be employed. We have demonstrated that MP4/Sadlej level of theory is able to reproduce NLO properties that can be considered equivalent to those from more sophisticated approaches, such as CCSD together with extended basis sets. 相似文献
56.
Fontana A Viale M Guernelli S Gasbarri C Rizzato E Maccagno M Petrillo G Aiello C Ferrini S Spinelli D 《Organic & biomolecular chemistry》2010,8(24):5674-5681
Different nitronaphthylbutadienes have been previously proved to have antitumour activity. The main drawback of these derivatives is their low water solubility. With the aim of facilitating the administration of these new drugs we have synthesized the hexyl (2Z,4E)-2-methylsulfanyl-5-(1-naphthyl)-4-nitro-2,4-pentadienoate analogue (1-Naph-NHCB) which is demonstrated to be easily included into cyclodextrins and/or entrapped into liposomes. Its antitumour activity was revealed to be almost comparable with that of the previously studied methyl analogue ester (1-Naph-NMCB). On the other hand, in vitro studies with different cancer cell lines showed that the cytotoxic activity of both 1-Naph-NMCB and 1-Naph-NHCB were fully preserved and in some cases also enhanced when entrapped into liposomal carriers. 相似文献
57.
L. Chumakova F. E. Menzaque P. A. Milewski R. R. Rosales E. G. Tabak C. V. Turner 《Studies in Applied Mathematics》2009,122(2):123-137
Two and three-layer models of stratified flows in hydrostatic balance are studied. For the former, nonlinear transformations are found that map [ baroclinic ] two-layer flows with either rigid top and bottom lids or vertical periodicity, into [ barotropic ] single-layer, shallow water free-surface flows. We have previously shown that two-layer flows with Richardson number greater than one are nonlinearly stable, in the following sense: when the system is well-posed at a given time, it remains well-posed through the nonlinear evolution. Here, we give a general necessary condition for the nonlinear stability of systems of mixed type. For three-layer flows with vertical periodicity, the domains of local stability are determined and the system is shown not to satisfy the necessary condition for nonlinear stability. This means that there are wave-motions that evolve into shear unstable flows. 相似文献
58.
The acid-base properties of bisbiacetylmonoxime-o-phenylenediimine were studied spectrophotometrically. The ionization constants of the acid-base equilibria involved were calculated from the A = f(pH) dependence for the aqueous ethanolic solutions (2% ethanol, I = 0.1, room temperature). The pKa values were evaluated by means of a variety of methods. Results obtained were compared with values reported in the literature for other dioximes derivatives. 相似文献
59.
The autoprotolysis constants of several water-N,N-dimethylformamide mixtures were determined. The acid dissociation constants of formic, acetic, propionic, n-butyric, isobutyric, n-valeric, isovaleric, 2-methylbutyric and trimethylacetic acids were evaluated in the same media by potentiometric titration. Empirical equations for the calculation of autoprotolysis constants and acid dissociation constants at 25° C in the mixed solvents are proposed. Approximate solvation numbers were obtained by multiple linear regression analyses of pKa values. 相似文献
60.
A novel ring C aromatic diterpene (4) has been prepared in three steps from natural (+)-manool (1). The structure and anticancer activity data for 4 has been investigated. This key intermediate (4) was easily transformed into 7-deoxo nimbidiol dimethyl ether (8). The present work represents the first formal synthesis of (+)-nimbidiol (10). 相似文献