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131.
Jairo Quiroga Mario Alvarado Braulio Insuasty Rodolfo Moreno Enrique Ravia Isabel Estevez Regina H. De Almeida S. 《Journal of heterocyclic chemistry》1999,36(5):1311-1316
This paper describes the synthesis of a new series of 6-amino-4-aryl-5-cyanopyrazolo[3,4-b]pyridines 4 and 4-aryl-5-cyano-6H-pyrazolo[3,4-b]pyridin-6-ones 5 from the reaction of 5-amino-3-methyl-1-phenylpyrazole 1 with arylidene derivatives of malonodinitrile 2 and ethyl cyanoacetate 3 . The structure of the final compounds was determined on the basis of nmr measurements, especially by 1H, 1H-, 1H, 13C-COSY, DEPT and X-ray diffraction. 相似文献
132.
Regina Janciene Ausra Vektariene Zita Stumbreviciute Lidija Kosychova Algirdas Klimavicius Benedikta D. Puodziunaite 《Heteroatom Chemistry》2004,15(5):363-368
The novel 4H‐thiazolo[3,2‐d][1,5]benzodiazepinium salts have been synthesized in a single step by the reaction of the variously substituted 2,3,4,5‐tetrahydro‐1,5‐benzodiazepine‐2(1H)‐thiones and bromoacetaldehyde diethyl acetal. Cyclization is obviously influenced by the nature of the substituents in the benzodiazepine system. Theoretical modeling and B3LYP DFT computational studies are presented. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:363–368, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20026 相似文献
133.
Cristiane N. Lopes Regina F. P. M. Moreira Ricardo A. F. Machado Pedro H. H. Araújo 《Macromolecular Symposia》2005,229(1):72-80
Summary: The incorporation of graphite into polystyrene (PS) particles produced by suspension polymerization was studied using a monofunctional and a bifunctional initiator, benzoyl peroxide (BPO) and 2,5-dimethyl-2,5-bis(2-ethyl hexanoyl peroxide) hexane (L256), respectively. The results showed that the polymerization rate was affected by graphite concentration when BPO was used as the initiator while no such effect was observed for L256. Results also showed that the incorporation of graphite in the PS particles was higher when using BPO than when using L256. Molecular weight distribution showed that during the reaction with BPO and graphite oligomers were formed indicating that the free radicals generated by the decomposition of BPO presented a very high reactivity with the functional groups present at the graphite surface while no significant effect was observed for the reaction with L256. 相似文献
134.
TiCl4 reacts quantitatively with Cl2Si(NHSiMe3)2 in n‐pentane under evolution of Me3SiCl yielding [μ‐ClTiCl2N(SiMe3)‐SiCl2NH2]2 ( 1 ), which is obtained as a yellow, crystalline solid forming small intergrown needles, that rapidly hydrolyse. The product 1 shows a thermal stability up to 80?C. The molecular structure of 1 has been solved by X‐ray powder diffraction methods and it could be confirmed by single‐crystal X‐ray structure determination at ‐70 ?C. Accordingly, in the solid 1 is a dimer ([μ‐ClTiCl2N(SiMe3)SiCl2NH2]2, P21/n (no. 14), Z = 2, a = 1504.89(6), b = 1296.33(6), c = 710.90(4) pm, and β = 91.276(2)?). 相似文献
135.
Aniketa Shinde Juexian Cao Wenjie Ouyang Ruqian Wu Regina Ragan 《Physics letters. A》2009,373(38):3459-3463
The adsorption patterns of rare earth atoms on Si(001) were investigated using scanning tunneling microscopy measurements and density functional calculations. Stable configurations were systematically determined via calculation of binding energies of various adatom coverage and adsorption geometry. Competition between inter-adatom hybridization and Coulomb repulsion is the mechanism contributing to binding energy minima associated with commonly observed rare earth adsorption geometries. Comparison of stable configurations with experimental scanning tunneling microscopy images demonstrated accuracy of the theoretical models. This paves a way for the understanding of self-assembly of rare earth disilicide nanowires on vicinal Si(001) substrates. 相似文献
136.
Wagner José Barreto Sonia Regina Giancoli Barreto Waleria Pickina Silva 《Transition Metal Chemistry》2009,34(6):677-681
The reaction between Fe(III) and dopamine in aqueous solution in the presence of Na2S2O3 was followed through UV–Vis spectroscopy, pH and oxy-reduction potential (Eh) measurements. The formation and quick disappearing
of the complex [Fe(III)HL1−]2+, HL1− = monoprotonated dopamine was observed with or without S2O3
2− at pH 3. An unexpected reaction occurs in presence of thiosulfate forming the stable anion complex [Fe(III)(L2−)2]1−, L2− = dopacatecholate (λ = 580 nm) and the auto-increasing of the pH, from 3 to 7. It was proposed that H+ and molecular oxygen are consumed by free radical thiosulfate formed during the reaction. 相似文献
137.
Schiave LA Pedroso RS Candido RC Roberts DW Braga GU 《Photochemistry and photobiology》2009,85(1):205-213
Solar radiation is one of the major factors responsible for the control of fungus populations in the environment. Inactivation by UVA and UVB radiation is especially important for the control of fungi that disperse infective units through the air, including fungi such as Cryptococcus spp. that infect their vertebrate hosts by inhalation. Cryptococcus neoformans produces melanin in the presence of certain exogenous substrates such as l-3,4 dihydroxyphenylalanine and melanization may protect the fungus against biotic and abiotic environmental factors. In the present study, we investigated the effect of exposure to an UVB irradiance of 1000 mW m(-2) (biologically effective weighted irradiance) on the survival of melanized and nonmelanized cells of four strains of C. neoformans and four strains of C. laurentii. The relative survival (survival of cells exposed to radiation in relation to cells not exposed) of cells grown 2, 4, 6 or 8 days on medium with or without L-dopa was determined after exposure to UVB doses of 1.8 and 3.6 kJ m(-2). Both the irradiance spectrum and the intensities of those doses are environmentally realistic, and, in fact, occur routinely during summer months in temperate regions. Differences in tolerance to UVB radiation were observed between the C. neoformans and C. laurentii strains. The C. neoformans strains were more susceptible to UVB radiation than the C. laurentii strains. In C. neoformans, differences in tolerance to radiation were observed during development of both melanized and nonmelanized cells. For most treatments (strain, time of growth and UVB dose), there were virtually no differences in tolerances between melanized and nonmelanized cells, but when differences occurred they were smaller than those previously observed with UVC. In tests with two strains of C. laurentii, there was no difference in tolerance to UVB radiation between melanized and nonmelanized cells during 8 days of culture; and in tests with four strains for less culture time (4 days) there were no significant differences in tolerance between melanized and nonmelanized cells of any strain of this species. 相似文献
138.
139.
Fleroxacin is a third generation fluoroquinolone with broad spectrum antibacterial activity. In this work an LC-DAD method
for the analysis of fleroxacin was developed and validated using UV detection at 286 nm. The method was validated for linearity,
precision, robustness, LOD, LOQ, specificity and accuracy at concentrations of 0.2–20.0 μg mL−1 and r
2 = 1. The LOD and LOQ were 0.059 and 0.197 μg, respectively, the recoveries were 99.92–102.0% and the CV was less than 2.0%.
The LC-DAD validated method provided analytical sensitivity, specificity and reproducibility suitable for quality control
analysis. 相似文献
140.
Vera L. P. Soares Regina S. V. Nascimento Sandra R. Albinante 《Journal of Thermal Analysis and Calorimetry》2009,97(2):621-626
Biodiesel from soybean oil transesterified with methanol (TSO) becomes viscous and gelifies at low storage temperatures which makes it difficult to pump. To inhibit this behaviour bulky esters were added to reduce the crystallization temperature of TSO and to modify the rate of conversion of crystallized mass. This rate was found to follow a JMAK kinetic model. The Avrami’s parameter n was constant for TSO, while two n values were found for TSO-additive solutions, meaning that the additives first slowed down the rate of nucleation and, later on as enough nuclei had been formed, crystal growth rate dominated and the previous crystallization rate was recovered. 相似文献