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1.
Na-montmorillonite hydrates in presence of ethane molecules are studied by means of hybrid Monte Carlo simulations in the NP(zz)T and muP(zz)T ensembles. The NP(zz)T ensemble allows us to study the interlaminar distance as a function of water and ethane content. These data show clear plateaus for lower ethane contents and mainly for water contents consistent with the formation of a single water layer. In addition, from this ensemble the structure for some of these interlaminar compositions were analyzed. For systems containing few ethane molecules and water enough to complete a single layer, it was observed that ethane mainly situates close to the interlayer midplane and adopts a nearly parallel arrangement to the clay surface. On the other hand, the muP(zz)T ensemble allows us to determine the interlaminar distance and water-ethane content for any specific reservoir. Here, some important findings are the following: the partial exchange of water by ethane molecules that enhances for decreasing the water vapor pressure; the obtention of a practically constant interlaminar space distance as a function of the water vapor pressure; the conservation of ion solvation shells; the enhancement of the water-ethane exchange for burial conditions; and finally, the incapability for a dehydrated clay mineral to swell in a dry and rich ethane atmosphere. 相似文献
2.
Helena Odriozola J. M. G. Tijero I. Esquivias L. Borruel A. Martín-Mínguez N. Michel M. Calligaro M. Lecomte O. Parillaud M. Ruiz M. Krakowski 《Optical and Quantum Electronics》2008,40(14-15):1123-1127
Numerical simulations have been used to produce advanced designs of high brightness gain guided tapered lasers emitting at 1,060 nm. The simulations predicted high modulation efficiency in devices with separate contacts and low front facet reflectivity. The devices fabricated following these design guidelines demonstrated high internal quantum efficiency in Broad Area lasers, output power of 3 W with good beam quality in tapered lasers with common contacts, and modulation efficiencies up to 20 W/A in tapered lasers with separate contacts, in good agreement with the simulation predictions. 相似文献
3.
W.Y. Hernández O.H. Laguna M.A. Centeno J.A. Odriozola 《Journal of solid state chemistry》2011,184(11):3014-3020
Ce0.9M0.1O2−δ mixed oxides (M=La, Eu and Gd) were synthesized by coprecipitation. Independent of the dopant cation, the obtained solids maintain the F-type crystalline structure, characteristic of CeO2 (fluorite structure) without phase segregation. The ceria lattice expands depending on the ionic radii of the dopant cation, as indicated by X-ray diffraction studies. This effect also agrees with the observed shift of the F2g Raman vibrational mode. The presence of the dopant cations in the ceria lattice increases the concentration of structural oxygen vacancies and the reducibility of the redox pair Ce4+/Ce3+. All synthesized materials show higher catalytic activity for the CO oxidation reaction than that of bare CeO2, being Eu-doped solid the one with the best catalytic performances despite of its lower surface area. 相似文献
4.
We implemented the replica exchange Monte Carlo technique to produce the equation of state of hard 1:5 aspect-ratio oblate ellipsoids for a wide density range. For this purpose, we considered the analytical approximation of the overlap distance given by Bern and Pechukas and the exact numerical solution given by Perram and Wertheim. For both cases we capture the expected isotropic-nematic transition at low densities and a nematic-crystal transition at larger densities. For the exact case, these transitions occur at the volume fraction 0.341, and in the interval 0.584-0.605, respectively. 相似文献
5.
Classic simulations are used to study interlayer structure, swelling curves, and stability of Ca-montmorillonite hydrates. For this purpose, NP(zz)T and muP(zz)T ensembles are sampled for ground level and given burial conditions. For ground level conditions, a double layer hydrate having 15.0 A of basal spacing is the predominant state for relative vapor pressures (p/p0) ranging 0.6-1.0. A triple hydrate counting on 17.9 A of interlaminar distance was also found stable for p/p0 = 1.0. For low vapor pressures, the system may produce a less hydrated but still double layer state with 13.5 A or even a single layer hydrate with 12.2 A of interlaminar distance. This depends on the established initial conditions. On the other hand, the effect of burial conditions is two sided. It was found that it enhances dehydration for all vapor pressures except for saturation, where swelling is promoted. 相似文献
6.
Alaitz Ruiz de Luzuriaga Irma Perez-Baena Sarah Montes Iraida Loinaz Ibon Odriozola Ignacio García José A. Pomposo 《Macromolecular Symposia》2010,296(1):303-310
A new route to functional polymeric nanoparticles (PNPs) of different chemical nature in the 3 to 20 nm size range is reported by combining both radical addition fragmentation chain transfer (RAFT) polymerization and “click” chemistry (CC) techniques. RAFT polymerization was employed for the synthesis of well-defined statistical copolymers with pending –Cl groups along the macromolecular chain. After transformation of the –Cl groups to –N3 groups by treatment with sodium azide, an appropriate bifunctional cross-linker is employed to obtain PNPs under CC conditions promoting intramolecular cycloaddition (cross-linking). Following this new route, polystyrene, poly(alkyl (meth)acrylate), polymethacrylic acid, poly(sodium styrenesulfonate) and poly(N-isopropyl) NPs have been synthesized and in-deep characterized. 相似文献
7.
Jesús M. García José M. Odriozola Ainara Lecumberri Jesús Razkin Alberto González 《Tetrahedron》2008,64(47):10664-10669
A short and efficient procedure for the preparation of (R)-arundic acid, a therapeutic agent for the treatment of Alzheimer's disease, has been developed. Based on cheap and commercially available (1R)-(+)-camphor as the source of chiral information, (R)-arundic acid is synthesized in a four-step cyclic sequence with 55% overall yield and high optical purity, ≥98% ee. Alkyl halide and acetylene constitute the only consumable carbon sources of this method, which allows obtaining of both enantiomers and recycling of chiral auxiliary. 相似文献
8.
9.
Ibon Odriozola Nerea Ormategui Iraida Loinaz José A. Pomposo Hans J. Grande 《Macromolecular Symposia》2008,266(1):96-100
Summary: Coinage metal salts (e.g. AuIII, AgI and CuII salts) readily react with thiols to give the corresponding metal(I) thiolates. These thiolate species are known to either self-assemble into insoluble polymeric species or to form soluble oligomers, depending on the nature of the thiol ligand. Here we demonstrate that this self-assembling ability can be applied to create supramolecular hydrogels. Glutathione (GSH), a naturally occurring tripeptide, has been used in combination with AuIII, AgI and CuII salts to obtain pH responsive hydrogels that are able to gelate 100 times their weight in water. 相似文献
10.
Guadiana River Chalcolithic middle basin (Badajoz, Spain) pottery was
in many cases decorated with bone, which suffers a hydroxyapatite to β
tri-calcium phosphate transformation while firing. The evolution of physico-chemical
characteristics of bone decorations and experimentally heated fossil bone
as a function of temperature through 1) major XRD planes, and 2) OH librational
mode at 630 cm–1 in the FTIR spectra let
us establish a correlation between the physico-chemical features and firing
temperature, allowing the estimate of firing temperatures for bone decorated
pottery. What is a reliable criterion to differentiate over potters behavior
and skill during the pottery production. 相似文献