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Reproducción en cámara climática de las formas de alteración más frecuentes detectadas en materiales graníticos, en clima de tendencia continental
This present work tries to reproduce, through test of controlled conditions in accelerate aging, reproducing the most frequent ambients in places affected by a clime of continental tendency, the more common forms of deterioration in historical interesting buildings, constructed with granitic rocks in those places. We…
Congresos, Seminarios y Cursos
Expansion of scalar validation criteria to three dimensions: theRtensor
Assessment of quality in crystal structure determination entails analysis of global statistics. In data reduction, quality is assessed using R(merge) and mean I/sigma(I). Progress in structure solution and refinement is checked by the goodness of fit, variants of the R index, R(cryst), and its cross-validation counter…
Review article: silicon carbide. Structure, properties and processing
In view of considerable interest in the development of liquid phase sintered structural and high-temperature ceramics on the base of silicon carbide, a comprehensive review of the data on structure, properties and the known methods of processing of silicon carbide seems timely. The most striking feature of silicon car…
First-principles computation of the vibrational entropy of ordered and disorderedPd3V
Experimental as well as theoretical work indicates that the relative stability of the ordered and the disordered states of a compound may be significantly affected by their difference in vibrational entropy. The origin of this difference is usually attributed to the fact that disordering reduces the number of stiff bo…
Effect of Thermal History on the Rheological Behavior of Thermoplastic Polyurethanes
The effect of thermal history on the rheological behavior of ester- and ether-based commercial thermoplastic polyurethanes (TPUs) was investigated. 1 H and 13 C nuclear magnetic resonance (NMR) spectroscopy indicated that the ester-based TPU consisted of 4,4‘-diphenylmethane diisocyanate (MDI) and butanediol (BDO) as…
Effects of Pores on Mechanical Properties of Plasma‐Sprayed Ceramic Coatings
The effects of pore sizes, shapes, and orientations on the mechanical properties of thermally sprayed ceramic coatings are investigated. The analysis is conducted using detailed finite‐element models with geometries similar to those of actual ceramic coatings containing many embedded pores. These microstructural model…
Inhibition of Pitting Corrosion on Aluminum Alloy 2024-T3: Effect of Soluble Chromate Additions vs Chromate Conversion Coating
Pitting potentials (Epit) of aluminum alloy (AA) 2024-T3 (UNS A92024) were improved with additions of 0.01 M sodium chromate (Na2CrO4, pH 8) and 0.0062 M Na2CrO4 + 0.0038 M chromic acid (H2CrO4, pH 6) additions to 0.1 M sodium sulfate (Na2SO4) + 0.005 M sodium chloride (NaCl, pH 6) after 2-h periods at open-circuit po…
Hybrid Biomaterials for Tissue Engineering: A Preparative Method for PLA or PLGA-Collagen Hybrid Sponges
A novel hybrid biomaterial for tissue engineeringhas been developed by forming collagen microsponges in the pores of poly(alpha ester) sponge. Poly(alpha ester) sponge provides the skeleton with a high degree of mechanical strength, while the collagen provides cell compatibility. The Figure shows mouse fibroblast cell…
Synthesis of thiophene/phenylene co‐oligomers. II [1]. Block and alternating co‐oligomers
Abstract We report the synthesis of block and alternating thiophene/phenylene co‐oligomers that is based either on the Suzuki coupling reaction or on the Grignard reaction. These reaction schemes enable us to obtain the target compounds at reasonably high yields. The resulting materials have been fully characterized t…
Hopping transport in the presence of site-energy disorder: Temperature and concentration scaling of conductivity spectra
Recent measurements on ion-conducting glasses have revealed that conductivity spectra for various temperatures T and ionic concentrations n can be superimposed onto a common master curve by an appropriate rescaling of the conductivity and frequency. In order to understand the origin of the observed scaling behavior, w…
Molecular Dynamics Simulations of Dynamic Force Microscopy: Applications to the Si(111)-7x7 Surface
Molecular dynamics simulations have been performed to understand true atomic resolution, which has been observed on the Si(111)-7$\times$7 surface by dynamic force microscopy in ultra high vacuum(UHV). Stable atomic-scale contrast is reproduced in simulations at constant mean height above a critical tip-sample separat…
Relative energetics and structural properties of zirconia using a self-consistent tight-binding model
We describe an empirical, self-consistent, orthogonal tight-binding model for zirconia, which allows for the polarizability of the anions at dipole and quadrupole levels and for crystal field splitting of the cation d orbitals. This is achieved by mixing the orbitals of different symmetry on a site with coupling coeff…
Synthesis of Polycarbonate-Layered Silicate Nanocomposites via Cyclic Oligomers
A partially exfoliated bisphenol A polycarbonate nanocomposite has been prepared by using carbonate cyclic oligomers and ditallow dimethyl exchanged montmorillonite (B34). Wide-angle X-ray diffraction (WAXD) indicated that exfoliation of this organically modified layered silicate (OLS) occurs after mixing with the cyc…
Validation of protein crystal structures
Since the process of building and refining a model of a biomacromolecule based on crystallographic data is subjective, quality-control techniques are required to assess the validity of such models. During the 1990s, much experience was gained; the methods used and some of the lessons learned are reviewed here. In addi…
Tight-Binding Linear Scaling Method Applications to Silicon Surfaces
The past years have witnessed impressive advances in electronic structure calculation, especially in the complexity and size of the systems studied, as well as in computation time. Linear scaling methods based on empirical tight-binding Hamiltonians which can describe chemical bonding, and have a computational time pr…
Surface-Enhanced Infrared Spectroscopy: A Comparison of Metal Island Films with Discrete and Nondiscrete Surface Plasmons
A study of the surface-enhanced infrared absorption (SEIRA) spectroscopy of para-nitrobenzoic acid (PNBA) adsorbed on thermally evaporated silver films has been conducted to determine the effect of film architecture on the magnitude of the SEIRA enhancement. Ordered arrays of uniformly sized silver nanoparticles, term…
Selective Functionalization of Mesoporous Silica
Selective functionalization of the internal and external surfaces of MCM-41 silica has been achieved using a topochemical molecular engineering approach. Functionalization is carried out in a stepwise process, the groups becoming selectively attached via silane coupling reactions and through use of a template to produ…
Size and confinement effects on the glass transition behavior of polystyrene/o-terphenyl polymer solutions
Polystyrene $(\mathrm{PS})/o\ensuremath{-}\mathrm{terphenyl} (o\mathrm{TP})$ solutions confined to nanometer scale pores were studied by differential scanning calorimetry to investigate size and confinement effects on the glass transition. We observed two glass transitions ${T}_{g}$ in all thermograms for materials co…