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53.
Barbero G Freire FC Scalerandi M Alexe-Ionescu AL 《The journal of physical chemistry. B》2006,110(36):17889-17897
We analyze the influence of the adsorption of ions at the interfaces on the transient phenomena occurring in an electrolytic cell submitted to a steplike external voltage. In the limit of small amplitude of the applied voltage, where the equation of the problem can be linearized, we obtain an analytical solution for the bulk and surface densities of ions and for the electrical potential. We also obtain, in this limit, the relaxation time for the transient phenomena. 相似文献
54.
Freire RO da Costa NB Rocha GB Simas AM 《The journal of physical chemistry. A》2006,110(17):5897-5900
The sparkle/AM1 model for the quantum chemical prediction of coordination polyhedron crystallographic geometries from isolated lanthanide complex ion calculations, defined recently for Eu(III), Gd(III), and Tb(III) (Inorg. Chem. 2005, 44, 3299) is now extended to La(III) and Lu(III). Thus, for each of the metal ions we chose a training set of 15 complexes that possess various representative ligands of high crystallographic quality (R factor < 0.05 Angstroms) and oxygen and/or nitrogen as coordinating atoms. In the validation procedure we used a set of 60 more La(III) coordination compound structures, as well as 15 more Lu(III) coordination compound structures, all of high crystallographic quality. For both the 75 La(III) compounds and the 30 Lu(III) compounds, the Sparkle/AM1 unsigned mean error, for all interatomic distances between the metal ions and the ligand atoms of the first sphere of coordination, is 0.08 Angstroms, thus comparable to the accuracy normally achievable by present day ab initio/ECP calculations, while being hundreds of times faster. 相似文献
55.
The absolute configuration of 1,2,3-prim,sec,sec-triols can be assigned by comparison of the 1H NMR spectra of the tris-(R)- and the tris-(S)-MPA ester derivatives. An experimental demonstration of this correlation with 24 triols of known absolute configuration and a protocol using two parameters-Deltadelta(RS)(H3) and the difference between Deltadelta RS (H2) and Deltadelta RS (H3) = absolute value (Delta(Deltadelta RS))-for its application to the determination of the absolute configuration of other triols are presented. 相似文献
56.
Exposure risk assessment of uranium intake of the milk products from the region of Pernambuco,Brazil
dos Santos Amaral Romilton dos Santos Júnior José Araújo da Silva Aquino Fabiana de Albuquerque Amaral Bruno Fernández Zahily Herrero Bezerra Mariana Brayner Cavalcanti Freire da Silva Arykerne Nascimento Casado dos Santos Djalma Cordeiro do Nascimento Santos Josineide Marques da Silva Alberto Antônio de Barros Correia Filipe Lopes 《Journal of Radioanalytical and Nuclear Chemistry》2019,319(3):927-935
Journal of Radioanalytical and Nuclear Chemistry - Haloperidol (HP) is a dopamine blocking agent. HP was radiolabeled with 125I using direct electrophilic substitution. Different HP formulations... 相似文献
57.
de Melo JV Vasconcelos RH Furtado AF Peixoto CA Silva-Filha MH 《Micron (Oxford, England : 1993)》2008,39(8):1342-1350
The larvicidal action of the entomopathogen Bacillus sphaericus towards Culex quinquefasciatus is due to the binary (Bin) toxin present in crystals, which are produced during bacterial sporulation. The Bin toxin needs to recognize and bind specifically to a single class of receptors, named Cqm1, which are 60-kDa α-glucosidases attached to the apical membrane of midgut cells by a glycosylphosphatidylinositol anchor. C. quinquefasciatus resistance to B. sphaericus has been often associated with the absence of the α-glucosidase Cqm1 in larvae midgut microvilli. In this work, we aimed to investigate, at the ultrastructural level, the midgut cells from C. quinquefasciatus larvae whose resistance relies on the lack of the Cqm1 receptor. The morphological analysis showed that midgut columnar cells from the resistant larvae are characterized by a pronounced production of lipid inclusions, throughout the 4th instar. At the end of this stage, resistant larvae had an increased size and number of these inclusions in the midgut cells, while only a small number were observed in the cells from susceptible larvae. The morphological differences in the midgut cells of resistant larvae found in this work suggested that the lack of the Cqm1 receptor, which also has a physiological role as being an α-glucosidase, can be related to changes in the cell metabolism. The ultrastructural effects of Bin toxin on midgut epithelial cells from susceptible and resistant larvae were also investigated. The cytopathological alterations observed in susceptible larvae treated with a lethal concentration of toxin included breakdown of the endoplasmic reticulum, mitochondrial swelling, microvillar disruption and vacuolization. Some effects were observed in cells from resistant larvae, although those alterations did not lead to larval death, indicating that the receptor Cqm1 is essential to mediate the larvicidal action of the toxin.This is the first ultrastructural study to show differences in the cell morphology of resistant larvae and further investigation is needed to understand the impact of the lack of expression of midgut enzymes on the physiology of resistant insects. 相似文献
58.
The origin of paramagnetic centers in graphite-like amorphous carbon is investigated. The films were deposited by the ion beam assisted deposition (IBAD) and have a concentration of sp2 sites of about 90% and zero energy band gap. The density of the film and the electrical resistivity are close to these of crystalline graphite. However, the hardness and stress of the films are similar to those of diamond-like carbon. Electron spin resonance (ESR) performed at the X-band (9.4 GHz) revealed an unexpected low density of paramagnetic centers, ascribed to conduction electrons with a g-value of about 2.003. 相似文献
59.
Vibrational properties of Cs4W11O35 and Rb4W11O35 systems: high pressure and polarized Raman spectra
K. Pereira da Silva W. Paraguassu M. Maczka A. G. Souza Filho P. T. C. Freire J. Mendes Filho J. Hanuza 《Journal of Raman spectroscopy : JRS》2011,42(3):474-481
Cs4 W11O35 (CW) and Rb4 W11O35 (RW) belong to the class of hexagonal bronzes whose structure originates from the KxWO3 superconductor hexatungstate. Charge‐imbalanced tungsten bronzes are dielectric materials with rich polymorphism, ferroelectric properties and second‐harmonic generation. In this work, we report the polarized Raman spectra results for both CW and RW, as well as results of high‐pressure Raman scattering experiments (0.0–11.0 GPa) for the Cs4 W11O35 system, in which we have observed two structural phase transitions at ∼4 and 7.5 GPa. We discuss these transformations and polarized Raman spectra on the basis of lattice dynamics calculation in the related system KNbW2O9. Polarized Raman spectra provide strong indication that the highest wavenumber modes observed in these systems originate from tungsten or oxygen vacancies. The observation of a soft‐like mode indicates that the observed phase transitions exhibit a displacive‐type behavior, thus further indicating that these transformations are likely related to reorientations of the octahedral units. The soft mode nature is discussed as well. PACS: 77.80.Bh; 78.30.Hv; 78.30.‐j. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
60.
C. Luz Lima G. D. Saraiva P. T. C. Freire M. Maczka W. Paraguassu F. F. de Sousa J. Mendes Filho 《Journal of Raman spectroscopy : JRS》2011,42(4):799-802
Temperature‐dependent Raman studies on Na2WO4and Na2MoO4 crystals were performed in order to obtain information on structural changes induced by temperature evolution. The stability of the cubic phase of Na2WO4and Na2MoO4crystals was assessed and our results indicate that this phase is stable in the 8–823 K and 15–773 K ranges for Na2WO4 and Na2MoO4, respectively. The crystal of Na2WO4 shows a phase transition occurring at 833 K. Na2MoO4undergoes a sequence of three phase transitions, which were observed at 783–803, 823–913 and 943–950 K. In both crystals, a strong first‐order phase transition occurs as indicated by the behavior of the Raman modes: the Raman bands split and new bands appear below 100 cm−1. These transitions are connected with tilting and/or rotations of the WO4and MoO4 tetrahedra, which leads to a disorder at the WO4and MoO4 sites. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献