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排序方式: 共有195条查询结果,搜索用时 15 毫秒
101.
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
102.
103.
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
104.
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
105.
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
106.
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
107.
This work presents a theoretical study of the energy spectrum of GaAs/AlGaAs concentric double quantum rings, under an applied magnetic field directed perpendicular to the ring plane. The Schrödinger equation for this system is solved in a realistic model consisting of rings with finite barrier potentials. Numerical results show that increasing the magnetic field intensity leads to oscillations in the ground state energy which, in contrast to the usual Aharonov-Bohm oscillations, do not have a well defined period, due to the coupling between inner and outer ring states. However, when one considers an elliptical geometry for the rings, the energy spectra of the inner and outer ring states are decoupled and the periodicity of the oscillations is recovered. 相似文献
108.
Farias Jan-Michel C. Stainier Laurent Fancello Eduardo Alberto 《Continuum Mechanics and Thermodynamics》2020,32(4):1037-1055
Continuum Mechanics and Thermodynamics - In this paper, a viscoelastic model able to capture important mechanical features of a wide class of glassy polymers is presented. Among them, the ability... 相似文献
109.
110.
A. Steimacher M.J. Barboza A.M. Farias O.A. Sakai J.H. Rohling A.C. Bento M.L. Baesso A.N. Medina C.M. Lepienski 《Journal of Non》2008,354(42-44):4749-4754
The calcium aluminosilicate glass (CAS) is an important class of optical materials due to the many applications envisaged, including its use as active media for glass lasers. In order to study how Nd2O3 doping affects the mechanical and the thermo-optical properties of CAS glass, two series of CAS glass, doped with Nd2O3 up to 5 wt%, were prepared in a vacuum atmosphere. The rare earth changes the physical properties, and this influence of doping ion content is discussed for both the series of samples in terms of mechanical, thermal, and thermo-optical properties. The study analyzed hardness and elastic moduli, glass transition temperature, crystallization temperature, thermal diffusivity, specific heat, density, thermal conductivity, refractive index, and thermo-optical properties, like temperature coefficient of the optical path length (dS/dT). The results presented provide information about the sample’s structure, and show that for Nd2O3 concentration up to 5 wt% there were no significant changes in the glass host material. 相似文献