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排序方式: 共有143条查询结果,搜索用时 15 毫秒
101.
Marcelo M Cavalcanti Valéria N Domingos Cavalcanti 《Journal of Differential Equations》2004,203(1):119-158
The wave equation with a source term is considered
102.
103.
Erisandro S. Silva Marta M. Conceição Eduardo H. S. Cavalcanti Valter J. Fernandes Jr. Ana C. D. Medeiros Antonio G. Souza 《Journal of Thermal Analysis and Calorimetry》2013,113(2):437-442
The oxidation of oils and biodiesels occurs due to several factors: the quantity of double bonds and the presence of allylic and bis-allylic hydrogens. Esters (biodiesel) that have large amounts of unsaturated fatty acids are more susceptible to oxidation than saturated. The aim of this work was to analyze the thermal and oxidative stability of ethyl biodiesel from Jatropha curcas L. and beef tallow by thermogravimetric, pressure differential scanning calorimetry, and PetroOxy methods. The samples of biodiesel from beef tallow present higher oxidation stability compared to biodiesel from J. curcas. In relation to calorimetric curves of biodiesel from J. curcas and beef tallow stored by 60 days without and with antioxidant, there was verified displacement of peak temperature of the transition to higher temperatures, respectively. Just a sample of biodiesel from beef tallow stored for 60 days with 3,000 ppm of antioxidant t-butyl-hydroxyquinone was within the standard established by Brazilian National Agency of Petroleum, Natural Gas, and Biofuels (ANP). The biodiesel from beef tallow was more stable in terms of thermal and oxidative stability than biodiesel from J. curcas. The thermal and oxidative stability of biodiesel depends on its chemical structure; this corroborates the fact that the oils with a predominance of saturated fatty acids are more stable than the unsaturated. 相似文献
104.
Marcelo M. Cavalcanti Valéria N. Domingos Cavalcanti Irena Lasiecka 《Journal of Differential Equations》2007,236(2):407-459
We establish, subject to some natural additional assumptions imposed on the relation between the source and the damping, both well-posedness and effective optimal decay rates for the solutions of a semilinear model of the wave equation. The theory presented allows to consider both superlinear and sublinear behaviours of the dissipation in the presence of unstructured sources. 相似文献
105.
G. H. Cavalcanti F. O. Borges A. J. Mania R. V. Orloski A. G. Trigueiros 《Journal of Quantitative Spectroscopy & Radiative Transfer》2005,90(3-4):291-308
The weighted oscillator strengths (gf) and the lifetimes for Si II presented in this work were carried out in a multiconfiguration Hartree–Fock relativistic (HFR) approach. In this calculation, the electrostatic parameters were optimized by a least-squares procedure, in order to improve the adjustment to experimental energy levels. This method produces gf-values that are in better agreement with intensity observations and lifetime values that are closer to the experimental ones. In this work we presented all the experimentally known electric dipole Si II spectral lines. 相似文献
106.
Berrin Ozcelik Javed Sheikh Ilkay E. Orhan Harjeet Juneja Brahim Bennani Abdelali Kerbal S. M. T. Cavalcanti Ana C. L. Leite Taibi Ben Hadda 《Research on Chemical Intermediates》2013,39(7):2955-2962
Conformational restriction constitutes a useful strategy of molecular modification for the design of new potential drug candidates. Herein we present the planning, antimicrobial evaluation, and establishment of structure–activity relationship (SAR) data for some isoxazole (3a–k, 8a–c, and 9a–c) and pyrazole (5a–h) derivatives. These derivatives were structurally designed by conformational restriction followed by bioisosteric exchange of previously described antimicrobial isoquinolines (1a–c). Some of these more conformationally restricted derivatives present improved properties as new antibacterial drug candidates. 相似文献
107.
108.
Kowarik S Gerlach A Sellner S Schreiber F Pflaum J Cavalcanti L Konovalov O 《Physical chemistry chemical physics : PCCP》2006,8(15):1834-1836
We study the growth and structure of thin films of the organic semiconductor rubrene during organic molecular beam deposition (OMBD) on silicon oxide in situ and in real time using X-ray scattering. Using in situ grazing incidence diffraction (GID) we find a small degree of local order but an otherwise largely disordered structure, consistent with out of plane scans. Monitoring the surface morphology in real time during growth, we find relatively smooth films (surface roughness sigma below approximately 15 A for thicknesses up to at least 600 A) and a significant delay before the onset of roughening. This anomalous roughening in the beginning and crossover to normal roughening later during growth may be related to conformational changes of rubrene in the early stages of growth. 相似文献
109.
Brayner FA Araújo HR Cavalcanti MG Alves LC Peixoto CA 《Micron (Oxford, England : 1993)》2005,36(4):359-367
Six hemocytes cell types from Culex quinquefasciatus were identified by light and transmission electron microscopy: They are prohemocytes (9.3%), spherulocytes (1.6%), adipohemocytes (0.8%), oenocytoids (4.6%), plasmatocytes (43.4%) and granulocytes (40.3%). The prohemocytes were the smallest hemocytes encountered in the hemolymph, displaying a large and centrally located nucleus, almost filling the whole cell. The spherulocytes, which were small hemocytes, presented small and numerous spherules with a lamellar pattern and an electron-dense core. Rare adipohemocytes were observed in the C. quinquefasciatus hemolymph, presenting large nucleus with an evident nucleolus, cytoplasm containing rough endoplasmic reticulum (RER), mitochondriae and lipid inclusions. C. quinquefasciatus oenocytoids showed homogeneous cytoplasm with several granules, completely or partially filled with amorphous material. These cells showed abundant smooth endoplasmic reticulum (SER) and dense mitochondriae. By light microscopy analysis we identified two morphological types of plasmatocytes, granular and agranular. However, ultrastructural investigation revealed that the granular cells contained lipid inclusion between RER membranes, instead of membrane-bounded granules. The granulocytes presented a fusiform or circular profile and displayed a unique and very complex process of granules formation, including organization of polysomes inside vesicles that protrude from the Golgi system, synthesis of a proteinaceous material, condensation of the granule matrix and recycling of endoplasmic membranes. Intense endocytic pathways were also observed in the granulocytes. 相似文献
110.
F. O.?BorgesEmail author F.?Bredice G. H.?Cavalcanti M.?Gallardo M.?Raineri J. G.?Reyna Almandos A. G.?Trigueiros 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2005,36(1):23-27
The current status of the determination of corrections to the hyperfine
splitting of the ground state in hydrogen is considered. Improved calculations
are provided taking into account the most recent value for
the proton charge radius. Comparing experimental data with predictions for
the hyperfine splitting, the Zemach radius of the proton is deduced to be
1.045(16) fm.
Employing exponential parametrizations for the electromagnetic form
factors we determine the magnetic radius of the proton to be
0.778(29) fm.
Both values are compared with the corresponding ones derived from the data
obtained in electron-proton scattering experiments and the data extracted
from a rescaled difference between the hyperfine splittings in hydrogen and
muonium. 相似文献