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排序方式: 共有134条查询结果,搜索用时 31 毫秒
21.
álvaro?Reyes-Carmona Ramón?Moreno-Tost Josefa?Mérida-Robles José?Santamaría-González Pedro?J.?Maireles-Torres Antonio?Jiménez-López Elisa?Moretti Maurizio?Lenarda Enrique?Rodríguez-CastellónEmail author 《Adsorption》2011,17(3):527-538
This work presents some applications of ZrO2 supported over SBA-15 silica as promoter of sulfated zirconia and as support from CuO/CeO2 catalytic system for preferential oxidation of CO to CO2 in hydrogen rich streams, used as feed for proton exchange membrane fuel cells (PEMFC). Different amounts of ZrO2, from 10 to 30 wt.% were incorporated. These prepared materials were characterized by powder XRD, adsorption-desorption of
N2 at 77 K, transmission and scanning electron microscopy (TEM and SEM) and X-rays photoelectron spectroscopy (XPS). The acidity
was studied by thermo-programmed desorption of ammonia (NH3-TPD). These materials were tested, after treatment with H2SO4, by 2-propanol dehydration and 1-butene isomerization catalytic tests. The samples were found quite good catalyst with strong
acid sites, the sample with 20 wt.% of ZrO2 being the better performing sample. Finally this material was successfully used as support for a CuO/CeO2 system, with 6 wt.% of Cu and 20 wt.% of Ce. The resulting catalyst was tested in the preferential oxidation of CO (CO-PROX)
attaining conversions close to 100% and high selectivity to CO2. 相似文献
22.
Lithium aluminates Li[Al(O-2,6-Me(2)C(6)H(3))R'(3)] (R' = Et, Ph) react with the μ(3)-alkylidyne oxoderivative ligands [{Ti(η(5)-C(5)Me(5))(μ-O)}(3)(μ(3)-CR)] [R = H (1), Me (2)] to afford the aluminum-lithium-titanium cubane complexes [{R'(3)Al(μ-O-2,6-Me(2)C(6)H(3))Li}(μ(3)-O)(3){Ti(η(5)-C(5)Me(5))}(3)(μ(3)-CR)] [R = H, R' = Et (5), Ph (7); R = Me, R' = Et (6), Ph (8)]. Complex 7 evolves with the formation of a lithium dicubane species and a Li{Al(μ-O-2,6-Me(2)C(6)H(3))Ph(3)}(2)] unit. 相似文献
23.
Francisco Gmez Robert Quintana Antxon Martez De Ilarduya Elisabet Rud Sebastin Muoz‐Guerra 《Journal of polymer science. Part A, Polymer chemistry》2005,43(1):92-100
A series of poly(butylene terephthalate) copolyesters containing 5‐tert‐butyl isophthalate units up to 50 mol %, as well as the homopolyester entirely made of these units, were prepared by polycondensation from a melt. The microstructure of the copolymers was determined by NMR to be random for the whole range of compositions. The effect exerted by the 5‐tert‐butyl isophthalate units on thermal, tensile, and gas transport properties was evaluated. Both the melting temperature (Tm) and crystallinity were found to decrease steadily with copolymerization, whereas the glass‐transition temperature (Tg) increased and the polyesters became more brittle. Permeability and solubility slightly increased with the content in substituted isophthalic units, whereas the diffusion coefficient remained practically constant. For the homopolyester poly(5‐tert‐butyl isophthalate), all these properties were found to deviate significantly from the general trend displayed by copolyesters, suggesting that a different structure in the solid state is likely adopted in this case. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 92–100, 2005 相似文献
24.
Darwin P. R. Kint Antxon Martínez de Ilarduya Abdelilah Alla Sebastin Muoz‐Guerra 《Journal of polymer science. Part A, Polymer chemistry》2003,41(1):124-134
Poly(ethylene terephthalate‐co‐isophthalate‐co‐5‐tert‐butylisophthalate) (PETItBI) terpolymers were investigated with reference to poly(ethylene terephthalate) (PET) homopolymer and poly(ethylene terephthalate‐co‐isophthalate) (PETI) copolymers. Three series of PETItBI terpolyesters, characterized by terephthalate contents of 90, 80, and 60 mol %, respectively, with different isophthalate/5‐tert‐butylisophthalate molar ratios, were prepared from ethylene glycol and mixtures of dimethyl terephthalate, dimethyl isophthalate, and 5‐tert‐butylisophthalic acid. The composition of the terpolymers and the composition of the feed agreed. All terpolymers had a random microstructure and number‐average molecular weights ranging from 10,000 to 20,000. The PETItBI terpolyesters displayed a higher glass‐transition temperature and a lower melting temperature than the PETI copolymers having the same content of terephthalic units. Thermal stability appeared essentially unchanged upon the incorporation of the 5‐tert‐butylisophthalic units. The PETItBIs were crystalline for terephthalate contents higher than 80 mol %, and they crystallized at lower rates than PETI. The crystal structure of the crystalline terpolymers was the same as that of PET with the 1,3‐phenylene units being excluded from the crystalline phase. Incorporation of isophthalate comonomers barely affected the tensile modulus and strength of PET, but the brittleness of the terpolymers decreased for higher contents in 5‐tert‐butylisophthalic units. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 124–134, 2003 相似文献
25.
Modelling the Recurrence of Bladder Cancer 总被引:1,自引:0,他引:1
The risk of a new tumor recurrence after transurethral resection (surgical operation) in patients with primary superficial
bladder carcinoma is evaluated. As the exact time of the event is not known, it is suggested to consider interval-censored
survival data methodology. We use the model of Farrington to perform a prognostic model for predicting a new recurrence and
to determine the clinicopathologic factors associated within interval-censored data framework. The implementation of this
method is easy using standard statistical packages. Anyway, we use diagnostic methods for the validation of the model developed
by the same author for interval-censored data. The obtained model is easily interpretable and let us to individualize the
course of follow-up and treatment of each patient in order to improve the patient’s quality of life.
相似文献
26.
Marqués M Flórez M Recio JM Santamaría D Vegas A García Baonza V 《The journal of physical chemistry. B》2006,110(37):18609-18618
This paper reports a theoretical investigation of the structure, stability, and electron charge density of cubic, rhombohedral, hexagonal, and monoclinic Al lattices. The equations of state and the elastic constants are computed from total energy calculations at different volumes and unit cell strains using the density functional theory approximation. The topology of the electron density is analyzed within the crystalline implementation of the atoms in molecules formalism. The results are discussed in light of the so-called anions in metallic matrices model, which permits the interpretation of the chemical bonding and the explanation of the existence of particular symmetries of inorganic crystals. First, the Al sublattices are identified as the reference building blocks of AlX(3) (X = F, Cl, OH) compounds. The calculations reveal that the equilibrium zero-pressure Al-Al shortest distance is around 2.75 A in all of the Al matrixes, similar to the value observed in the stable face centered cubic structure of Al at room conditions. Second, at their zero-pressure equilibrium geometries, the Al sublattices are found to fulfill the mechanical stability criteria or, alternatively, to show mechanical instabilities that are compatible with the distortions observed for the structures in AlX(3) crystals. However, at the equilibrium volumes of the AlX(3) crystals, all of the Al matrices violate the spinodal condition, and the cohesion and stabilization are provided by the nonmetallic X atoms. Third, the structural anisotropy of the Al sublattices seems to be the main factor to discriminate metallic matrices able to host nonmetallic elements. The inhomogeneities of the electron charge density, which favor the arrival of nonmetallic elements and the crystal formation, are notably enhanced in passing from the fcc structure of pure Al to the less isotropic Al matrices observed in AlX(3) compounds. 相似文献
27.
J. López-Solano P. Rodríguez-Hernández A. Muñoz D. Santamaría-Pérez F. J. Manjón S. Ray 《高压研究》2013,33(1):58-63
HgWO4 at ambient pressure is characterized using a combination of ab initio calculations, X-ray diffraction and Raman scattering measurements. The effect of low pressure and temperature on the structural stability is analysed. Extending our ab initio study to the range of higher pressures, a sequence of stable phases up to 30 GPa is proposed. 相似文献
28.
Prof. Antonio Molinaro Prof. Otto Holst Dr. Flaviana Di Lorenzo Dr. Maire Callaghan Dr. Alessandra Nurisso Dr. Gerardino D'Errico Dr. Alla Zamyatina Prof. Francesco Peri Dr. Rita Berisio Prof. Roman Jerala Prof. Jesús Jiménez‐Barbero Dr. Alba Silipo Prof. Sonsoles Martín‐Santamaría 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(2):500-519
In many Gram‐negative bacteria, lipopolysaccharide (LPS) and its lipid A moiety are pivotal for bacterial survival. Depending on its structure, lipid A carries the toxic properties of the LPS and acts as a potent elicitor of the host innate immune system via the Toll‐like receptor 4/myeloid differentiation factor 2 (TLR4/MD‐2) receptor complex. It often causes a wide variety of biological effects ranging from a remarkable enhancement of the resistance to the infection to an uncontrolled and massive immune response resulting in sepsis and septic shock. Since the bioactivity of lipid A is strongly influenced by its primary structure, a broad range of chemical syntheses of lipid A derivatives have made an enormous contribution to the characterization of lipid A bioactivity, providing novel pharmacological targets for the development of new biomedical therapies. Here, we describe and discuss the chemical aspects regarding lipid A and its role in innate immunity, from the (bio)synthesis, isolation and characterization to the molecular recognition at the atomic level. 相似文献
29.
Leandro F. Gil‐Silva Raquel Santamaría‐Fernández Prof. Dr. Armando Navarro‐Vázquez Prof. Roberto R. Gil 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(2):472-476
A new DMSO‐compatible aligning gel based on cross‐linked poly(2‐hydroxylethyl methacrylate) (poly‐HEMA) has been developed. Due to a significant difference in bulk magnetic susceptibility between the DMSO inside and outside the gel, it is possible to simultaneously collect isotropic and anisotropic NMR data, such as residual dipolar couplings (RDC), in the same NMR tube. RDC‐assisted structural analysis of menthol and the alkaloid retrorsine is reported as proof of concept. 相似文献
30.
S. Zalamea M. P. Pina A. Villellas M. Menéndez J. Santamaría 《Reaction Kinetics and Catalysis Letters》1999,67(1):13-19
Catalytic membranes operating in a mixed permeation regime (i.e., with significant Knudsen and laminar contributions) have been developed. The membranes prepared had wide pores and presented
a low pressure drop. After the addition of γ-Al2O3 and Pt, the resulting catalytic membranes were active for the combustion of VOCs. Their performance was compared with that
of similar catalytic membranes operating under the Knudsen diffusion regime. 相似文献