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101.
E. A. Oliveira E. N. Silva A. R. Paschoal S. M. Dantas I. Guedes J. Mendes‐Filho G. Polla A. P. Ayala 《Journal of Raman spectroscopy : JRS》2011,42(7):1567-1573
Raman spectroscopy, polarized microscopy and thermal measurements were used to investigate the sequence of phase transition in the lead oxide salts Pb8O5(XO4)2 (where X = As and V). For Pb8O5(AsO4)2, a second‐order phase transition is observed at 500 K. For Pb8O5(VO4)2, a second‐order and a first‐order structural phase transitions are observed at 425 and 525 K, respectively. The ferroelastic character of Pb8O5(VO4)2 is also discussed. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
102.
Sofia Guedes Rui Vitorino Maria R. M. Domingues Francisco Amado Pedro Domingues 《Analytical and bioanalytical chemistry》2010,397(5):1985-1995
At the present, the term “glycoxidation” is recognized as the synergistic interaction between glycation and oxidative processes
which, with the help of redox-active metals, consequently leads to the production of deleterious tissue modifications. The
association between glycation and oxidation events is considered one of the major factors in the accumulation of non-functional
damaged proteins, enhancing the oxidative damage at the cellular level. Because of the central role of insulin in the biology
of diabetes, we investigated the site-specific oxidation of native and glycated insulin (mono, di, and tri-glycated forms),
through metal-catalyzed oxidation, with a combination of liquid chromatography and mass spectrometry. With this approach we
were able to identify the residues that were mainly oxidized, and peptide sequences resulting from oxidative cleavage of insulin.
Tyrosine, phenylalanine, and cysteine were the main affected residues. Time-course analysis (0–48 h) of the oxidative damage
enabled to detect more pronounced and earlier oxidative modifications in the case of glycated insulin. We also observed more
severe oxidative damage as the number of glycation sites increased in insulin. These oxidative modifications included other
oxidized residues, namely proline, histidine, valine, leucine, and glycine, which were shown to be carbonylated. In addition,
we identified new sites of peptide cleavage with the formation of new fragments, derived mainly from chain B, which were both
glycated and oxidatively modified. Peptide fragmentation occurred mainly between the residues phenylalanine, glycine, leucine,
and tyrosine. Moreover, for diglycated and triglycated forms we observed further oxidative cleavage occurring in both chains,
with oxidation and fragmentation of residues occurring near cysteine bridges, especially in chain A. 相似文献
103.
Effects of localized elliptical (circular being a special case) cylindrical surface flaws in laminated composite plates are investigated by using C°-type triangular composite plate elements, formulated on the assumptions of transverse inextensibility and layer-wise constant shear-angle theory (LCST). Numerical results for a cross-ply laminate compromised by the presence of an external part-through elliptical/circular cylindrical slot indicate the existence of severe cross-sectional warping in the vicinity of the surface flaw and plate boundaries. Furthermore, three-dimensional nature of the stress concentration factor in the neighborhood of the elliptical or circular cylinder shaped surface flaw boundary is clearly exhibited. Besides, very high stress concentration factors are found in the layer weakened by the surface flaw. Most importantly, the effects of stress singularity in the neighborhood of the circumferential re-entrant corner lines of the elliptical/circular cylindrical surface flaws, weakening laminated composite plates, are numerically assessed, because of their role in crack initiation. Finally, the interaction of this singularity with free edge stress singularity at the plate boundary, and the implication of such interactions (i.e., violation of St. Venant’s principle) in regards to testing of laminated composite specimens are thoroughly investigated. 相似文献
104.
R Pazzetto SB Ferreira EJ Santos C Moriwaki TA Guedes G Matioli 《Molecules (Basel, Switzerland)》2012,17(8):9476-9488
The preservation of Bacillus firmus strain 37 cells by lyophilization was evaluated and response surface methodology (RSM) was used to optimize the β-cyclodextrin (β-CD) production by cells immobilized on loofa sponge. Interactions were studied with the variables temperature, pH and dextrin concentration using a central composite design (CCD). Immobilization time influence on β-CD production was also investigated. B. firmus strain 37 cells remained viable after one year of storage, showing that the lyophilization is a suitable method for preservation of the microorganism. From the three-dimensional diagrams and contour plots, the best conditions for β-CD production were determined: temperature 60 °C, pH 8, and 18% dextrin. Considering that the amount of dextrin was high, a new assay was carried out, in which dextrin concentrations of 10, 15, and 18% were tested and the temperature of 60 °C and pH 8 were maintained. The results achieved showed very small differences and therefore, for economic reasons, the use of 10% dextrin is suggested. Increasing the immobilization time of cells immobilized on synthetic sponge the β-CD production decreased and did not change for cells immobilized on loofa sponge. The results of this research are important for microorganism preservation and essential in the optimization of the biosynthesis of CD. 相似文献
105.
Alexander M. Kirillov M. Fátima C. Guedes da Silva João J.R. Fraústo da Silva 《Journal of organometallic chemistry》2006,691(19):4153-4158
A new dinitrogen rhenium(I) complex with a picolinate ligand has been prepared and fully characterized, providing the first example of a genuine NN complex bearing a carboxylate or a N,O-coligand. The Lever electrochemical EL ligand parameter was estimated for the first time for the picolinate ligand and shows that its carboxylate arm has a net electron-donor character similar to that of chloride, thus stabilizing the trans Re-N2 bond. 相似文献
106.
107.
J V Guedes de Avellar A Z Milioni T N Rabello 《The Journal of the Operational Research Society》2007,58(9):1246-1251
In this paper, a Data Envelopment Analysis (DEA) model in which a fixed input needs to be assigned to a group of Decision-Making Units (DMUs) is presented. This is performed by assuming the existence of a geometric place represented by a sphere that characterizes the DEA frontier. It is shown that, under this assumption, it becomes relatively easy to find a way to distribute the fixed input to all DMUs, by considering that the individual assignments will be fair through the requirement that all DMUs be efficient or, in other words, be located on the spherically shaped efficiency frontier. A model is presented and results are compared to those obtained by using two different methods proposed in the literature within the same context. 相似文献
108.
S. Guedes J.C. Hadler N P.J. Iunes K.M.G. Oliveira P.A.F.P. Moreira C.A. Tello S 《Radiation measurements》2005,40(2-6):517-521
A model for the annealing kinetics of fission tracks is proposed based on a simplified track. The principal hypothesis is that the atoms displaced during the passage of the fission fragment have to transmit through a potential barrier to occupy the vacant sites left. The resulting model equation is applied to zircon data both from laboratory and geological sources. The model succeeded in fitting the data and the addition of the geological data during the fitting procedure improved the extrapolation of the model to the timescale of millions of years, which is the timescale of interest in geology applications. 相似文献
109.
R. Cordovil K. Fukuda A. Guedes de Oliveira 《Discrete and Computational Geometry》2000,24(2-3):257-266
In this paper we consider the cocircuit graph G
M
of an oriented matroid M , the 1 -skeleton of the cell complex W formed by the span of the cocircuits of M . In general, W is not determined by G
M
. However, we show that if the vertex set (resp. edge set) of G
M
is properly labeled by the hyperplanes (resp. colines) of M , G
M
determines W . Also we prove that, when M is uniform, the cocircuit graph together with all antipodal pairs of vertices being marked determines W . These results can be considered as variations of Blind—Mani's theorem that says the 1-skeleton of a simple convex polytope
determines its face lattice.
Received August 14, 1998, and in revised form March 2, 1999. 相似文献
110.
C.A. Tello Saenz J.C. Hadler Neto P.J. Iunes S. Guedes P.C. Hackspacher L.F.B. Ribeiro S.R. Paulo A.M. Osorio A 《Radiation measurements》2005,39(6):635-640
The fission-track method (FTM) in apatite was applied to 45 samples collected in the Serra da Mantiqueira (Mantiqueira mountain range), the Serra do Mar (Mar mountain range), regions next to these mountain ranges and the coastal region between Ubatuba and Santos in the State of São Paulo, Brazil, to study the thermochronology of the South American Platform in southeast Brazil and its influence on Santos and Campos basins. The data presented in this work complement the previously presented data on the same region (Tello Saenz et al., 2003. J. S. Am. Earth Sci. 15, 765–774) with 31 new samples analyzed. The weighted mean of the corrected ages from high Mantiqueira (around 1000 m), , coincides with the South Atlantic opening. The fact that its thermal history starts at a relatively low temperature suggests that the age of would be the formation age of Serra da Mantiqueira due to a rapid pulse, in which tracks had no time to be retained at the closure temperature, that is . The Serra do Mar presents a more complicated thermal history, with several reactivations indicated by the changes in the slope of its cooling curve. The thermal histories obtained in the regions next to these mountain ranges are compatible with the results mentioned above. The Santos Basin has unconformities that agree with changes in the slope thermal histories of the studied region. 相似文献