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101.
Six adducts of general formula MCl2·4L (M = Cu and Co; L = ethyleneurea, eu; ethylenethiourea, etu; and propyleneurea, pu) were prepared and characterized by elemental analysis, i.r. spectroscopy and by thermogravimetry (t.g.). Using the non-isothermal Coats–Redfern method, the kinetic parameters for the non-isothermal degradation of the adducts were calculated using thermogravimetric data. The i.r. results show that, for eu and pu adducts, coordination occurs through oxygen, whereas for etu nitrogen is the donor atom. All the adducts exhibited a single mass loss step in the t.g. curve, related to the release of ligand molecules. For eu, etu and pu adducts, the associated activation energies for the degradation process are: 36.4; 68.07 and 103.07 kJ mol–1; 67.15; 80.86 and 121.06 kJ mol–1 for copper and cobalt adducts, respectively. 相似文献
102.
L. J. Borrero-González I. A. A. Terra L. A. O. Nunes A. M. Farias M. J. Barboza J. H. Rohling A. N. Medina M. L. Baesso 《Applied physics. B, Lasers and optics》2012,107(2):415-420
We have studied the influence of SiO2 content on the spectroscopic properties and laser emission efficiency of Yb3+-Er3+ co-doped calcium aluminosilicate glasses. An increase in SiO2 content resulted in higher phonon energy, which reduced the up-conversion emission, enhanced the energy transfer efficiency up to 70 % from Yb3+ to Er3+, and enhanced the optical quality. All these results led to an increase from 20 to 30 % in the laser emission efficiency. 相似文献
103.
V.J.da C. Farias B.R.P. da Rocha M.P.da C. da Rocha H.R. Tavares 《Applied Mathematical Modelling》2013
Several researchers demonstrated that spectral parameters in induced polarization can be applied to discriminate different IP sources. In this paper it was applied an inversion procedure using the Gauss–Newton method to recover the spectral parameters of fractal model to complex resistivity. The finite element method was applied to carry out the forward modeling. The procedure was applied in synthetic data and simulations were carried out in five different frequencies. The inversion of the data were carried out in each frequency, further the inversion was applied also to each cell of the finite element mesh to recover the fractal parameter in order to analyze the possibility of using the fractal model parameters in the interpretation of the induced polarization response to this geological geometry. The results showed that the anomalies are well detected by the image of the fractal model parameters. 相似文献
104.
Ana T.A. Lima R.N. Costa Filho G.A. Farias N.S. Almeida 《Solid State Communications》2010,150(17-18):812-815
We obtain the magnetic susceptibility of systems constituted of two coupled magnetic layers. We consider that the coupling of the films is well described by a Heisenberg like interaction to write the equation of motion for the magnetization of each part of the system. The dynamical response of each constituent material is calculated taking into account the presence of an interacting magnetic media (a magnetic layer) in its border. The susceptibility obtained incorporates the effects of a different magnetic film in the neighborhood (via the interfilm interaction), as well as the properties of the interface. We use a procedure similar to the effective medium approach developed for superlattices to obtain an effective magnetic permeability for the whole system. We show that the knowledge of this property allows one to have information on the interface of the magnetic bilayer through the analysis of its optical properties. We illustrate this point by calculating the dispersion relation of magnetic polaritons propagating in a system consisting of an antiferromagnetic (MnF2) layer grown in direct contact with a ferromagnetic film (Fe). We also simulate numerically an optical experiment where ATR (Attenuated Total Reflection) spectra are obtained. 相似文献
105.
Daniele Farias Rafael R. de Andrade Francisco Maugeri-Filho 《Applied biochemistry and biotechnology》2014,172(1):361-379
This work focuses on the kinetics of ethanol production by Scheffersomyces stipitis on xylose with the development of a mathematical model considering the effect of substrate and product concentrations on growth rate. Experiments were carried out in batch and continuous modes, with substrate concentration varying from 7.2 to 145 g L?1. Inhibitory effects on cell growth, substrate uptake, and ethanol production rates were found to be considerable. Kinetic parameters were obtained through linear and non-linear regression methods. Experiments in continuous mode were performed at different dilution rates to evaluate the inhibitory effect of ethanol. A mixed mathematical model which combined Andrews and Levenspiel's models, combining substrate and product inhibition, was used. A quasi-Newton routine was applied to obtain a more accurate fitting of kinetic parameters. The parameters such as cell to product factor (Y P/X) and limiting cell yield (Y X) were shown to be dependent on substrate concentration. The kinetic model fitted satisfactorily the experimental data. 相似文献
106.
107.
Hankin JA Farias SE Barkley RM Heidenreich K Frey LC Hamazaki K Kim HY Murphy RC 《Journal of the American Society for Mass Spectrometry》2011,22(6):1014-1021
Matrix-assisted laser desorption ionization/ionization imaging mass spectrometry (MALDI IMS) with a time-of-flight analyzer
was used to characterize the distribution of lipid molecular species in the brain of rats in two injury models. Ischemia/reperfusion
injury of the rat brain after bilateral occlusion of the carotid artery altered appearance of the phospholipids present in
the hippocampal region, specifically the CA1 region. These brain regions also had a large increase in the ion abundance at
m/z 548.5 and collisional activation supported identification of this ion as arising from ceramide (d18:1/18:0), a lipid known
to be associated with cellular apoptosis. Traumatic brain injury model in the rat was examined by MALDI IMS and the area of
damage also showed an increase in ceramide (d18:1/18:0) and a remarkable loss of signal for the potassium adduct of the most
abundant phosphocholine molecular species 16:0/18:1 (PC) with a corresponding increase in the sodium adduct ion. This change
in PC alkali attachment ion was suggested to be a result of edema and influx of extracellular fluid likely through a loss
of Na/K-ATPase caused by the injury. These studies reveal the value of MALDI IMS to examine tissues for changes in lipid biochemistry
and will provide data needed to eventually understand the biochemical mechanisms relevant to tissue injury. 相似文献
108.
Anne G. D. Santos Vinícius P. S. Caldeira Mirna F. Farias Antonio S. Araújo Luiz D. Souza Allan K. Barros 《Journal of Thermal Analysis and Calorimetry》2011,106(3):747-751
In this study, the physico-chemistry characterization and kinetic study of the thermal decomposition of sunflower oil and
its biodiesel were carried out. Sunflower biodiesel was synthesized by the methanol route and basic homogeneous catalysis.
The physicochemical characterization of the sunflower oil and biodiesel were performed according to standards set out in the
ANP resolution, and both are in accordance to the specifications. The chromatographic analysis was obtained by GC-FID. The
yield of conversion of 97.4 wt% of sunflower oil in methyl esters confirms the efficiency of the conversion of the fatty acids
into esters. The thermal analysis was performed on a thermobalance, using heating rates of 5, 10, and 20 °C min−1. In these three rates, we observed a single well-defined step of mass loss that describes the volatilization and decomposition
of the sunflower oil and the biodiesel. The kinetic study was performed using equations of approximation and integration methods
such as Coats–Redfern, Van Krevelen, and Horowitz–Metzger. The kinetic parameters reaction order (n) and apparent activation energy (E
a), obtained by applying these method were correlated. 相似文献
109.
Pieroni LG de Rezende FM Ximenes VF Dokkedal AL 《Molecules (Basel, Switzerland)》2011,16(11):9439-9450
Miconia is one of the largest genus of the Melastomataceae, with approximately 1,000 species. Studies aiming to describe the diverse biological activities of the Miconia species have shown promising results, such as analgesic, antimicrobial and trypanocidal properties. M. albicans leaves were dried, powdered and extracted to afford chloroformic and methanolic extracts. Total phenolic contents in the methanolic extract were determined according to modified Folin-Ciocalteu method. The antioxidant activity was measured using AAPH and DPPH radical assays. Chemical analysis was performed with the n-butanol fraction of the methanolic extract and the chloroformic extract, using different chromatographic techniques (CC, HPLC). The structural elucidation of compounds was performed using 500 MHz NMR and HPLC methods. The methanolic extract showed a high level of total phenolic contents; the results with antioxidant assays showed that the methanolic extract, the n-butanolic fraction and the isolated flavonoids from M. albicans had a significant scavenging capacity against AAPH and DPPH. Quercetin, quercetin-3-O-glucoside, rutin, 3-(E)-p-coumaroyl-α-amyrin was isolated from the n-butanolic fraction and α-amyrin, epi-betulinic acid, ursolic acid, epi-ursolic acid from the chloroformic extract. The results presented in this study demonstrate that M. albicans is a promising species in the search for biologically active compounds. 相似文献
110.
Delatorre P Rocha BA Simões RC Pereira-Júnior FN Silva HC Bezerra EH Bezerra MJ Marinho ES Gadelha CA Santi-Gadelha T Farias DL Assreuy AM Marques-Domingos GF Nagano CS Cavada BS 《Applied biochemistry and biotechnology》2011,164(6):741-754
The lectin from seeds of Dioclea virgata (DvirL) was purified in a single step affinity chromatography, sequenced by tandem mass spectrometry and submitted to crystallization and biological experiments. DvirL has a molecular mass of 25,412?±?2 Da and the chains β and γ has 12,817 Da?±?2 and 12,612 Da?±?2, respectively. Primary sequence determination was assigned by tandem mass spectrometry and revealed a protein with 237 amino acids and 87% of identify with ConA. The protein crystals were obtained native and complexed with X-Man using vapor-diffusion method at a constant temperature of 293 K. A complete X-ray dataset was collected at 1.8 ? resolution. DvirL crystals were found to be orthorhombic, belonging to the space group I222, with a unit cell parameters a?=?647.5 ?, b?=?86.6 ?, c?=?90.2 ?. Molecular replacement search found a solution with a correlation coefficient of 77.1% and an R(factor) of 44.6%. The present study also demonstrated that D. virgata lectin presents edematogenic and antinociceptive activities in rodents electing this protein as a candidate to structure/function analysis. 相似文献