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41.
CM Thaker S Rayaprol Krushna Mavani DS Rana MS Sahasrabudhe SI Patil DG Kuberkar 《Pramana》2002,58(5-6):1035-1039
The effect of simultaneous substitution of a fluctuating cation and a divalent cation in LaMnO3 perovskite modifies the properties of the material to exhibit large valence colossal magnetoresistance (CMR) effect. A good
example of these properties is (La1−2x
Pr
x
Ca
x
)MnO3 (LPCMO) type CMR material. In this communication it is reported that, with the increase in x (for x=0.1, 0.15, 0.2), the T
c varies between 100 and 120 K with improvisation in metal-insulator transition. Interestingly, resistance increases with x from few hundred ohms to few kilo ohms with corresponding decrease in the unit cell volume. The results of the studies using
X-ray diffraction (XRD), electrical resistivity, magnetoresistance and ac susceptibility measurements on LPCMO samples for
understanding the structural, transport and magnetic properties are discussed in detail. 相似文献
42.
Michael H. Abraham Asadollah Nasehzadeh Joaquim J. Moura Ramos 《Tetrahedron letters》1981,22(20):1929-1932
From standard Gibbs energies of transfer, corrected for cavity or nonelectrostatic effects, it is concluded that the solvolysis of methyl perchlorate takes place through a looser-than-usual SN2 transition state with a charge separation of about 0.52 units. 相似文献
43.
D.C. Cabral-de-Mello R.C. Moura R. Carvalho M.J. Souza 《Micron (Oxford, England : 1993)》2010,41(2):112-117
Male mitotic and meiotic chromosomes of two species of the genus Deltochilum (Scarabaeidae) were analyzed through conventional staining, C-banding, base-specific fluorochromes, silver nitrate staining (AgNO3) and FISH (45S rDNA). The two species possessed karyotypes with 2n = 14, neo-XY and meta-submetacentric chromosomes. The analysis of constitutive heterochromatin (CH) revealed mainly diphasic chromosomes in the two species, showing heterochromatic long arms. Silver nitrate staining labeled the blocks corresponding to CH in D. (Deltohyboma) aff morbillosum while in D. (Deltohyboma) calcaratum, AgNO3 staining revealed only the CH blocks of the diphasic autosomes. The fluorochrome staining revealed in D. (D.) calcaratum the diphasic autosomes and the sex chromosomes with CMA3+ blocks, and in D. (D.) aff morbillosum, the GC-rich sequences were restricted to the terminal regions of the long arms of the pairs 1 and 2 and the X. The FISH revealed 45S rDNA sites in two autosomic pairs and in the X chromosome. The analyses performed allowed for the identification of cytogenetic markers and the discussion of possible chromosome rearrangements that have been involved in the karyotypic differentiation of these species mainly related to the repetitive genome. 相似文献
44.
We analyze the transfer of angular spectrum and fourth-order image formation in two-photon states generated by spontaneous parametric down-conversion in both type I and type II phase matchings. We show how the image transfer from the pump beam to the two-photon field is affected by the anisotropy of the nonlinear crystal and by the coupling between frequency and wave vector. We also show how the distortion produced by the anisotropy can be compensated by the frequency bandwidth in type II phase matching. 相似文献
45.
Moura Ramos JJ Correia NT Diogo HP Descamps M 《The journal of physical chemistry. B》2006,110(16):8268-8273
Molecular mobility in crystalline anhydrous caffeine was studied by the dielectric technique of thermally stimulated depolarization currents (TSDC). Two relaxational processes were found, one appearing at approximately -10 degrees C that is ascribed to a reorientational glass transition, and a higher temperature one that probably arises from local molecular motions that are precursors of diffusion and sublimation. The experimental results suggest that both crystalline phases II and I of caffeine, that have distinct crystal structures, are solid rotator phases. Furthermore, this dynamic reorientational disorder shows a reorientational glass transition at the same temperature in phase II and in metastable phase I. 相似文献
46.
We investigate a single-qubit state transfer protocol along a channel featuring diagonal diluted disorder. In the regime where the source and destination sites are weakly coupled to the channel, we report the possibility of transmitting quantum states with high fidelity as well as establishing end-to-end entanglement in that sort of configuration. We further discuss how the performance of the protocol depends upon the availability of extended states within the disordered channel. 相似文献
47.
P. A. S. Moura D. P. Bezerra E. Vilarrasa-Garcia M. Bastos-Neto D. C. S. Azevedo 《Adsorption》2016,22(1):71-80
Ion-exchange with different cations (Na+, NH4 +, Li+, Ba2+ and Fe3+) was performed in binderless 13X zeolite pellets. Original and cation-exchanged samples were characterized by thermogravimetric analysis coupled with mass spectrometry (inert atmosphere), X-ray powder diffraction and N2 adsorption/desorption isotherms at 77 K. Despite the presence of other cations than Na (as revealed in TG-MS), crystalline structure and textural properties were not significantly altered upon ion-exchange. Single component equilibrium adsorption isotherms of carbon dioxide (CO2) and methane (CH4) were measured for all samples up to 10 bar at 298 and 348 K using a magnetic suspension balance. All of these isotherms are type Ia and maximum adsorption capacities decrease in the order Li > Na > NH4–Ba > Fe for CO2 and NH4–Na > Li > Ba for CH4. In addition to that, equilibrium adsorption data were measured for CO2/CH4 mixtures for representative compositions of biogas (50 % each gas, in vol.) and natural gas (30 %/70 %, in vol.) in order to assess CO2 selectivity in such scenarios. The application of the Extended Sips Model for samples BaX and NaX led to an overall better agreement with experimental data of binary gas adsorption as compared to the Extended Langmuir Model. Fresh sample LiX show promise to be a better adsorption than NaX for pressure swing separation (CO2/CH4), due to its higher working capacity, selectivity and lower adsorption enthalpy. Nevertheless, cation stability for both this samples and NH4X should be further investigated. 相似文献
48.
G. L. Dotto R. Ocampo-Pérez J. M. Moura T. R. S. CadavalJr. L. A. A. Pinto 《Adsorption》2016,22(7):973-983
The overall adsorption rate of Reactive Black 5 dye (RB5) on chitosan based materials was elucidated using diffusional models. Fundamental aspects, such as, geometry of the adsorbents and swelling effects were considered. Chitosan based materials (powder and film) were prepared from shrimp wastes and characterized regarding to the fundamental features for adsorption. Experimental decay curves were obtained under different conditions of stirring rate and initial dye concentration. The data were modeled according to the external mass transfer and diffusional models. The kL (external mass transfer coefficient), Dep (effective pore diffusion coefficient) and Ds (surface diffusion coefficient) values were estimated. For both adsorbents, it was found that the surface diffusion was the intraparticle diffusion mechanism governing the adsorption rate of RB5, since its contribution was higher than 92 % regardless the position and time. The Ds values ranged from 2.85 × 10?11 to 5.78 × 10?11 for chitosan powder and from 4.15 × 10?11 to 12.12 × 10?11 cm2 s?1 for chitosan films. The RB5 adsorption was faster when chitosan powder was used, mainly at higher stirring rates and initial dye concentrations. The swelling effect was most pronounced for the chitosan films, where, provided an increase of about 65 times in the Ds value. 相似文献
49.
Roger Peres de Moura 《Journal of Mathematical Analysis and Applications》2007,326(2):1254-1267
We establish local well-posedness for small initial data in the usual Sobolev spaces Hs(R), s?1, and global well-posedness in H1(R), for the Cauchy problem associated to the nonlocal nonlinear Schrödinger equation
50.
Carreira RJ Cordeiro FM Moro AJ Rivas MG Rial-Otero R Gaspar EM Moura I Capelo JL 《Journal of chromatography. A》2007,1153(1-2):291-299
New findings in sample treatment based on high-intensity focused ultrasound (HIFU) for protein digestion after polyacrylamide gel electrophoresis separation are presented. The following variables were studied: (i) sample volume; (ii) sonotrode diameter; (iii) previous protein denaturation; (iv) cooling; (v) enzyme concentration; and (vi) protein concentration. Results showed that positive protein identification could be done after protein separation by gel electrophoresis through peptide mass fingerprint (PMF) in a volume as low as 25 microL. The time needed was less than 2 min and no cooling was necessary. The importance of the sonotrode diameter was negligible. On the other hand, protein denaturation before sonication was a trade-off for the success of procedure here described. The protein coverage was raised from 5 to 30%, and the number of peptides matching the proteins was also increased in a percentage ranging 10-100% when the classical overnight treatment is compared with the proposed HIFU procedure. The minimum amount of protein that can be identified using the HIFU sample treatment by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) was 0.06 microg. The lower concentration of trypsin successfully used to obtain an adequate protein digestion was 3.6 microg/mL. 相似文献