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91.
Experimental Techniques - In experimental studies the need of having replicates of specimens is crucial. This requirement becomes even more critical when performing statistical analysis in... 相似文献
92.
L.M. da Silva M.C. de Melo A.N. Medina F.G. Gandra 《Physica B: Condensed Matter》2009,404(19):3018-3020
We report on results of X-ray powder diffraction, magnetization and specific heat measurements of the pseudo-ternary (Ce1−xLax)PdIn2 system with x=0; 0.2; 0.4 and 0.6. The results show a linear increase of the unit cell volume and a reduction of the ferromagnetic transition as La content increases. The Debye temperature, Sommerfeld coefficient and crystal field parameters were estimated from specific heat data, and are found to be weakly dependent of the Ce concentration. Also, the variation of magnetic entropy at TC is only weakly dependent on x (ΔS≅0.92Rln2) indicating that TK/TC is approximately constant along the series. The TC and TK behaviors are explained by the variation of the exchange parameter due to the volume change when Ce is replaced by La. Our results indicate that the chemical pressure is the dominant effect rather than the chemical disorder for determining the physical proprieties of the (Ce1−xLax)PdIn2 system. 相似文献
93.
Iliana Medina-Ramirez Sajid Bashir Zhiping Luo Jingbo Louise Liu 《Colloids and surfaces. B, Biointerfaces》2009,73(2):185-191
Silver nanoparticles (Ag-NPs) were synthesized using a facile green chemistry synthetic route. The reaction occurred at ambient temperature with four reducing agents introduced to obtain nanoscale Ag-NPs. The variables of the green synthetic route, such as acidity, concentration of starting materials, and molar ratio of reactants were optimized. Dispersing agents were employed to prevent Ag-NPs from aggregating. Advanced instrumentation techniques, such as X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible spectroscopy (UV–vis), and phase analysis light scattering technique (ZetaPALS) were applied to characterize the morphology, particle size distribution, elemental composition, and electrokinetic behavior of the Ag-NPs. UV–vis spectra detected the characteristic plasmon at approximately 395–410 nm; and XRD results were indicative of face-centered cubic phase structure of Ag. These particles were found to be monodispersed and highly crystalline, displaying near-spherical appearance, with average particle size of 10.2 nm using citrate or 13.7 nm using ascorbic acid as reductants from particle size analysis by ZetaPALS, respectively. The rapid electrokinetic behavior of the Ag was evaluated using zetapotential (from −40 to −42 mV), which was highly dependant on nanoparticle acidity and particle size. The current research opens a new avenue for the green fabrication of nanomaterials (including variables optimization and aggregation prevention), and functionalization in the field of nanocatalysis, disinfection, and electronics. 相似文献
94.
Eutimio G. Fernández Rodolfo Valdés Yenisley Medina José A. Montero Alejandro Figueroa Williams Ferro Yarysel Guevara Tatiana Álvarez Andrés Tamayo Regla M. Somoza Leonardo Canaán-Haden Jorge L. López 《Chromatographia》2009,70(7-8):1179-1183
Sepharose CL-4B and Sepharose CL-2B with immobilized CB.Hep-1 monoclonal antibody were compared for studying the matrix efficiency in the immunopurification of the recombinant hepatitis B surface antigen (rHBsAg). The elution capacities of both matrices were similar over eight chromatographic cycles, significant differences were only observed in the first purification cycles. A high percentage of the adsorbed rHBsAg was not eluted from both matrices. The rHBsAg purity was not affected by matrix characteristics (pore size and percentage of agarose) and differences between Sepharose CL-4B and Sepharose CL-2B do not provoke differences in the antibody released from the matrices under defined experimental conditions. 相似文献
95.
96.
A new two-dimensional framework germanate, Ge3O5(OH)4[C2N2H10] (denoted ICMM-8), with a 3:9 Ge:O ratio has been synthesized, using a mixture of pyridine, water, and ethanol as the solvent and 1,4-diazabicyclo[2.2.2]octane and ethylenediamine as the structure-directing agents, under solvothermal conditions. The structure was determined by single-crystal X-ray diffraction. In this new compound, the GeO2 natrolite-type infinite four and eight R-containing layers appears for the first time in a pure GeO2 framework. The total 2D structure is built up from SBU-6, four tetrahedra, and two octahedra. The hydroxyl groups occupy four positions of each octahedral germanium atom. The compound is characterized by IR spectra and TGA-DTA. Crystal data: Ge3O5(OH)4[C2N2H10], monoclinic space group P2(1)/c; a = 11.3570(9) Angstroms, b = 8.8819(7) Angstroms, c = 9.9200(8) Angstroms, beta = 90.710(1), V = 1000.6(1) Angstroms(3), Z = 4, R(1) = 0.044 (I > 2(I)), and wR(2) = 0.1051 (all data). 相似文献
97.
Annia?GalanoEmail author Juan?Raúl?Alvarez-IdaboyEmail author Misaela?Francisco-Márquez Manuel?E.?Medina 《Theoretical chemistry accounts》2012,131(3):1173
The free radical scavenging activity of hydroxytyrosol (HTyr) and tyrosol (Tyr) has been studied in aqueous and lipid solutions,
using the density functional theory. Four mechanisms of reaction have been considered: single electron transfer (SET), sequential
electron proton transfer (SEPT), hydrogen transfer (HT), and radical adduct formation. It was found that while SET and SEPT
do not contribute to the overall reactivity of HTyr and Tyr toward ·OOH and ·OCH3 radicals, they can be important for their reactions with ·OH, ·OCCl3, and ·OOCCl3. The ·OOH-scavenging activity of HTyr and Tyr was found to take place exclusively by HT, and it is also predicted to be the main
mechanism for their reactions with ·OCH3. HT is proposed as the main mechanism for the scavenging activity of HTyr and Tyr when reacting with other ·OR and ·OOR radicals, provided that R is an alkyl or an alkenyl group. The major products of reaction are predicted to be the phenoxyl
radicals. In addition, Tyr was found to be less efficient than HTyr as free radical scavenger. Moreover, while HTyr is predicted
to be a good peroxyl scavenger, Tyr is predicted to be only moderately for that purpose. 相似文献
98.
Lucas BS Fisher B McGee LR Olson SH Medina JC Cheung E 《Journal of the American Chemical Society》2012,134(30):12855-12860
The development of the structurally complex MDM2/p53 inhibitor AM-8553 was impeded by the low yield of the initial synthesis. A second generation synthesis is described that features a Noyori dynamic kinetic resolution, a highly diastereoselective allylation, and a novel oxazoline-assisted piperidinone forming reaction to provide AM-8553 in 35.6% yield and 11 steps. 相似文献
99.
We use equilibrium molecular dynamics methods to compute the shear and bulk viscosities of the pairwise additive and rigid SPC/E, TIP4P, and TIP4P/2005 water models. For the latter model it was found in a recent study (J. Chem. Phys. 2009, 131, 246101) an excellent agreement with experiment in the prediction of the shear viscosity over a range of different thermodynamic conditions. Here, we examine, for a wide range of temperatures, whether this remarkable accuracy of the TIP4P/2005 model remains in the prediction of the bulk viscosity. Moreover, we examine whether equilibrium molecular dynamics methods provide reasonable accuracy in the calculation of the bulk viscosity, as it was previously found for the shear viscosity (J. Chem. Phys. 2010, 132, 096101). We concluded that, by performing the appropriate data analysis, accurate estimates of the bulk viscosity can be obtained, while, compared to the other simple rigid/pairwise additive water models, the predictions of the TIP4P/2005 model for the bulk viscosity are significantly closer to the experiment. 相似文献
100.
Fabio Furini Enrico Malaguti Rosa Medina Durán Alfredo Persiani Paolo Toth 《European Journal of Operational Research》2012,218(1):251-260
We consider a two-dimensional cutting stock problem where stock of different sizes is available, and a set of rectangular items has to be obtained through two-staged guillotine cuts. We propose a heuristic algorithm, based on column generation, which requires as its subproblem the solution of a two-dimensional knapsack problem with two-staged guillotines cuts. A further contribution of the paper consists in the definition of a mixed integer linear programming model for the solution of this knapsack problem, as well as a heuristic procedure based on dynamic programming. Computational experiments show the effectiveness of the proposed approach, which obtains very small optimality gaps and outperforms the heuristic algorithm proposed by Cintra et al. [3]. 相似文献