Materials Literature
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Abstract Resistivity and dielectric constant of polyethylene/carbon black compounds were measured from room temperature to 140°C. Within the polyethylene melting region a PTC/NTC (positive followed by negative temperature coefficients) phenomenon is observed, whose intensity depends on the type of carbon black, its co…
1. Considerations of Friction and Wear. 2. Methods of Impact Stress Analysis. 3. Impact Response of Engineering Surfaces. 4. Erosion by Solid Particles: Ductile and Brittle Theories. 5. General Aspects of Solid Particle Erosion. 6. Experimental Background of Percussive Impact Wear. 7. The Zero Impact Wear Model. 8. Me…
A beta bulge is a region between two consecutive beta-type hydrogen bonds which includes two residues (positions 1 and 2) on one strand opposite a single residue (position x) on the other strand. Compared to regular beta structure, a beta bulge puts the usual alternation of side-chain direction out of register on one…
The Young’s modulus E of metallic glasses increases by ∼7% while the density ρ increases by only ∼0.5% upon annealing near the glass transition temperature. ρ and E of an ’’ideal’’ glass are calculated to approach the crystalline values within 0.5 and 10%, respectively. The large decrease in E of ∼30% observed upon vi…
In this paper Onsager's theory of the orientational order in a three-dimensional system of hard rods is reanalyzed as a nonlinear eigenvalue problem. Bifurcation is found and the equation of state is calculated from the orientational distribution function for a nematic phase. We also investigate the corresponding twod…
In this review we have attempted to highlight each of the major areas of interest in liposome-cell interactions: the purely physical chemical, the cell biological, and the medical. Liposomes can be generated in a number of ways and are classified as small unilamellar, large unilamellar, and multilamellar vesicles. Alt…
Las sales y la humedad son los dos factores que condicionan las alteraciones de los materiales de construcción. Los citados materiales, bien de por sí —piedras y ladrillos—, bien una vez endurecidos —morteros y hormigones—, están estructurados por partículas sólidas granulares, separadas por un sistema poroso, que con…
Los materiales conglomerados que se presentan en la naturaleza deben su génesis estructural a la acomodación geométrica de unos y otros componentes. Tras un proceso de "cimentación", este acomodo, según sea la disposición particular, conlleva por parte del material una respuesta resistente frente a las acciones exteri…
A partir de la lectura del artículo original reseñado en la llamada (1), en el Departamento de Materiales de Construcción del I.E.T.c.c, se han comprobado algunos ajustes granuiométricos de áridos obtenidos por otros métodos clásicos con los resultados que se obtienen aplicando el presente método. La buena corresponde…
La determinación de elementos minoritarios en la industria del cemento adquiere cada día mayor importancia, debido a la investigación de los efectos producidos por éstos. En particular es sabido que los cloruros intervienen en varias fases del proceso de fabricación del clínker, llegando a afectar posteriormente a las…
Los ensayos de la resistencia a la compresión de un hormigón, tienen, generalmente, la mayor significación para proyectistas y constructores, por ello estimamos muy interesantes las experiencias que J. D. Pateman publicó en la revista "Concrete" (febrero 1977). Según Pateman la influencia del curado sobre las propieda…
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Abstract The electrical conductivity of crystalline polyacetylene films having various cis‐trans compositions was measured. The resistivity and the energy gap of a 92,5% trans polymer were 1,01·10 4 Ω·cm and 0,56 eV, respectively, whereas the values of a 20,0% trans polymer were 2,35·10 8 Ω·cm and 0,93 eV, respectivel…
Progressive heating of seawater to 350 degrees C causes it to become increasingly acid and depleted in Ca, Mg, and SO4, because anhydrite and a previously undescribed magnesium oxysulfate are precipitated. Observed composition changes and calculation of activities of dissolved species reveal a progressive increase of…
The temperature dependence of the magnetic susceptibility and the electron paramagnetic resonance spectra of the thiazole complexes dichloro- and dibromobis(thiazole)copper(II) are reported, along with a complete three-dimensional X-ray structure analysis of the dichloro complex based on counter data. The dichloro com…
To mineralogists and earth scientists the zeolites and clay minerals have been of great interest for a very long time. Chemists and engineers became interested primarily in the years following the Second War, and their attention has for the most part been concentrated upon the zeolits. So great has been the effort exp…
Abstract Optical luminescence of amorphous bright poly(ethylene terephthalate) (PET) films and the changes in luminescence due to certain morphological changes have been studies at 77 K to identify the luminescent centres in this polymer. The emission spectrum consists of both fluorescence and phosphorescence with dis…
Abstract The crosslinking of atactic and isotactic polypropylene initiated by organic peroxides in presence of diallyl maleate or pentaerythrityl tetramethacrylate was studied. The influence of concentration of the components of the crosslinking system as well as the effect of temperature and reaction time was followe…