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101.
Wohnrath K Constantino CJ Antunes PA dos Santos PM Batista AA Aroca RF Oliveira ON 《The journal of physical chemistry. B》2005,109(11):4959-4964
Langmuir-Blodgett (LB) films from a ruthenium complex mer-[RuCl3 (dppb)(4-Mepy)] (dppb = PPh2 (CH2)4PPh2; 4-Mepy = 4-methylpyridine), termed Ru-Pic, display a distinct color, which is different from the coloration exhibited by cast films or chloroform solutions. The solution and cast films are red, while the LB films are green-bluish. The manifestation of the blue color in the LB film finds its explanation in a unique absorption band at 690 nm, which is associated with the oxidation of the phosphine moieties. Fluorescence emission and absorption-reflection infrared spectroscopy measurements revealed the molecular organization in the LB films. In contrast, cast films showed a random distribution of complexes. Surface-enhanced Raman scattering was also used in an attempt to identify the main interactions in Ru-Pic. 相似文献
102.
Jo o Batista Lopes Martins Elson Longo Octavio D. Rodr guez Salmon Vicente A.A. Espinoza Carlton A. Taft 《Chemical physics letters》2004,400(4-6):481-486
We have used the Oniom method with three layers in order to study the interaction of CO, H2, H2O, NH3 and CO2 molecules with the ZnO surfaces using a (ZnO)348 cluster model. The layers are divided into the high layer at the CCSD level, the medium layer at the RHF level and the low level layer using the UFF force field method. The orbital and binding energies of the adsorbed molecules, Mulliken and ChelpG charges as well as geometrical parameters were analyzed and compared with the available experimental and theoretical data. 相似文献
103.
Stowers MA van Wuijckhuijse AL Marijnissen JC Scarlett B van Baar BL Kientz CE 《Rapid communications in mass spectrometry : RCM》2000,14(10):829-833
Matrix-assisted laser desorption/ionization (MALDI) mass spectra were obtained from single biological aerosol particles using an aerosol time-of-flight mass spectrometer (ATOFMS). The inlet to the ATOFMS was coupled with an evaporation/condensation flow cell that allowed the aerosol to be coated with matrix material as the sampled stream entered the spectrometer. Mass spectra were generated from aerosol composed either of gramicidin-S or erythromycin, two small biological molecules, or from aerosolised spores of Bacillus subtilis var niger. Three different matrices were used: 3-nitrobenzyl alcohol, picolinic acid and sinapinic acid. A spectrum of gramicidin-S was generated from approximately 250 attomoles of material using a molar ratio of 3-nitrobenzyl alcohol to analyte of approximately 20:1. A single peak, located at 1224 Da, was obtained from the bacterial spores. The washing liquid and extract solution from the spores were analyzed using electrospray mass spectrometry and subsequent MS/MS product ion experiments. This independent analysis suggests that the measured species represents part of the B. subtilis peptidoglycan. The on-line addition of matrix allows quasi-real-time chemical analysis of individual, aerodynamically sized particles, with an overall system residence time of less than 5 seconds. These results suggest that a MALDI-ATOFMS can provide nearly real-time identification of biological aerosols. Copyright 2000 John Wiley & Sons, Ltd. 相似文献
104.
Alda K.M. Holanda Francisco O.N. da Silva Idalina M.M. Carvalho Alzir A. Batista Javier Ellena Eduardo E. Castellano Ícaro S. Moreira Luiz G.F. Lopes 《Polyhedron》2007
The trans-[Fe(cyclam)(NO)Cl]Cl2 complex was synthesized by the reaction of cis-[Fe(cyclam)Cl2]Cl with NO gas. The X-ray structure of the complex showed that the [Fe–NO] moiety is linear, consistent with the NO+ character of the nitric oxide ligand. This suggestion was reinforced by the IR data, which showed the νNO at 1888 cm−1. The cyclic voltammogram of the trans-[Fe(cyclam)(NO)Cl]2+ complex presented three electrochemical processes at −0.70, 0.08 and 0.40 V versus Ag/AgCl. The first and last redox processes are centered at the NO ligand, whereas the second is characteristic of the generated aqua species, trans-[Fe(cyclam)Cl(H2O)]2+. Upon irradiation at 330 nm, pH 3.4, the title complex releases the NO moiety with the concomitant generation of the trans-[Fe(cyclam)(H2O)Cl]+ complex as suggested by electronic and IR spectroscopy as well as by cyclic voltammetry technique. 相似文献
105.
Alves Lourdes A. Vitolo Michele Felipe Maria das Graças A. de Almeida e Silva João Batista 《Applied biochemistry and biotechnology》2002,98(1-9):403-413
The sugarcane bagasse hydrolysate, which is rich in xylose, can be used as culture medium for Candida guilliermondii in xylitol production. However, the hydrolysate obtained from bagasse by acid hydrolysis at 120°C for 20 min has by-products
(acetic acid and furfural, among others), which are toxic to the yeast over certain concentrations. So, the hydrolysate must
be pretreated before using in fermentation. The pretreatment variables considered were: adsorption time (15,37.5, and 60 min),
type of acid used (H2So4 and H3Po4), hydrolysate concentration (original, twofold, and fourfold. concentrated), and active
charcoal (0.5, 1.75 and 3.0%). The suitability of the pretreatment was followed by measuring the xylose reductase (XR) and
xylitol dehydrogenase (XD) activity of yeast grown in each treated hydrolysate. The response surface methodology (24 full factorial design with a centered face) indicated that the hydrolysate might be concentrated fourfold and the pH adjusted
to 7.0 with CaO, followed by reduction to 5.5 with H3PO4. After that it was treated with active charcoal (3.0%) by 60 min. This pretreated hydrolysate attained the high XR/XD ratio
of 4.5. 相似文献
106.
We introduce a new technique to solve period problems on minimal surfaces called “limit-method”. If a family of surfaces has Weierstraß data converging to the data of a known example, and this presents a transversal solution of periods, then the original family contains a sub-family with closed periods. 相似文献
107.
Sílvio L.T. de Souza Iberê L. Caldas Ricardo L. Viana Antnio M. Batista Tomasz Kapitaniak 《Chaos, solitons, and fractals》2005,26(5):1523-1531
We investigate some dynamical effects of adding a certain amount of noise in a theoretical model for rattling in single-stage gearbox systems with a backlash, consisting of two wheels with a sinusoidal driving. The parameter intervals we are dealing with show an extremely involved attraction basin structure in phase space. One of the observable effects of noise is basin hopping, or the switching between basins of different attractors. We characterize this effect and its relation to the presence of chaotic transients. 相似文献
108.
A. C. S. da Costa I. G. de Souza Junior M. A. Batista D. A. Lopes K. L. da Silva J. V. Bellini A. Paesano Jr. 《Hyperfine Interactions》2007,176(1-3):107-111
In the present study, zinc-substituted magnetites of the Fe3???X Zn X O4 type were prepared by co-precipitation in the range 0 ≤?X?≤ 1 and, further, annealed in free atmosphere, at 800° for 3 h. The samples were characterized by X-ray diffraction and Mössbauer spectroscopy. The results showed that the annealed samples were oxidized and converted into Fe2O3 and ZnFe2O4, in relative amounts that varied with X. 相似文献
109.
A. C. S. da Costa I. G. de Souza Jr. M. A. Batista K. L. da Silva J. V. Bellini A. Paesano Jr. 《Hyperfine Interactions》2007,175(1-3):103-111
Nanosized Fe3???x Zn x O4 powders were synthesized by co-precipitation and characterized by total chemical analysis, X-ray diffraction, magnetic susceptibility and Mössbauer spectroscopy. The results showed that, for x?≤?0.15, the as-prepared samples are mostly zinc-substituted magnetites but have maghemite as a minor phase. For x?≥?0.30, only the Fe3???x Zn x O4 solid solution is found. Increasing the zinc content from the end concentration x?=?0, increases the lattice parameter but smaller become the mean crystalline diameter and the magnetic susceptibility. In addition, the magnetic hyperfine fields of the iron sites in the spinel structure, A and B, decrease up to collapse at x?≤?0.90. 相似文献
110.
The intrinsic bistable terahertz response of intersubband plasmons in wide n-type delta-doped quantum wells is predicted to be enhanced by a resonant Fabry-Perot cavity. With a simple low-Q resonator, the threshold for bistability is decreased by a factor of 2-3 compared with that for bare multiple quantum wells. 相似文献