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Congresos, Seminarios y Cursos

New advances in the carbonation of aluminous cement. Alkaline hydrolisis

The carbonation process of aluminous cement in presence of high alkali content is studied. In this work, the formation of a compound which formula is close to K4Al6(CO3)11-x(OH)2x(H2O)y is shown for the studies samples. The aluminous cement carbonation in alkali presence take place, at least, in two stages. In a first…

Decay of granite monuments due to salt crystallization in a non-polluted urban environment

The effect of salt crystallization on granite (s.l) rocks used as building material in an urban environment with low atmospheric pollution was studied. The manners of salt crystallization and the subsequent deterioration caused were analyzed in unweathered granite and other fades which had undergone strong transformat…

Measurement of color in different construction materials. The restoration in sandstone buildings

The use of construction materials and their subsequent repair purposes include a search of knowledge and preservation of their original appearance. For this reason, the main aim of this study is to determine a color range which does not change with the possible actions on a building, both when restoration works which…

El coeficiente de eficacia del humo de sílice

Silica fume is a pozzolanic addition specially used to get high resistance concrete. Present Spanish standards on additives dictate that silica fumes have to comply with specific requirements when used as concrete addition. Once it has been proved they comply with those requirements, microsilicas of different characte…

Near-Band-Edge Luminescence Studies of Diamond Doped during CVD Growth or by Ion Implantation

Near-band-edge cathodoluminescence of doped diamonds was studied at low temperatures. The doped diamonds were prepared either during the CVD growth of the diamond films by adding boron, phosphorus, or lithium sources to the reaction gases, or alternatively by ion implantation of boron, phosphorus, sodium, or arsenic.…

Effects of the second harmonic on the secondary Bjerknes force

The time-averaged interaction force exerted by an acoustic field between two gas bubbles, known as the secondary Bjerknes force, is derived with an accuracy up to a component induced by the second harmonic of bubble oscillations. The surrounding medium is assumed to be an incompressible viscous liquid and the distance…

Electrode Characteristics of Nanostructured Mg2Ni ‐ Type Alloys Prepared by Mechanical Alloying

A mechanical alloying process is introduced to produce nanocrystalline metal hydride. The mechanical alloying process has recently emerged as a novel technique for producing alloy powders whose structures are nanocrystalline. alloys were prepared using planetary ball mill starting from mixtures of elemental powders. N…

Crystal structures and reference powder patterns of BaR2ZnO5 (R = La, Nd, Sm, Eu, Gd, Dy, Ho, Y, Er, and Tm)

Reference x-ray powder patterns and the crystal structures of the lanthanide compounds, BaR2ZnO5, in which R = La, Nd, Sm, Eu, Gd, Dy, Ho, Y, Er, or Tm, were determined by the x-ray Rietveld refinement technique. A structural trend was confirmed for this series of compounds. The compounds with smaller ionic radii (R =…

The Culture of Mammalian Cells on Nanostructured Silicon

For biologically interfaced sensing applications, nanostructured porous silicon (PSi) is a very promising candidate, since mammalian cells can be cultured directly onto it. The development of cell culture systems for a PSi–cell interface is described, together with the development of a more “nature-identical” simulate…

Microphase separation versus the vapor-liquid transition in systems of spherical particles

The conditions, i.e., the interparticle potentials, for which vapor–liquid coexistence is supplanted by microphase separation are examined. The liquid phase is found for potentials with a steeply repulsive core and an attraction of not-too-short a range. To this potential we add a repulsion of longer range than the at…

Silicon Oxycarbide Ceramic Foams from a Preceramic Polymer

Open‐cell ceramic foams were obtained from the pyrolysis, at 1000° to 1200°C under nitrogen, of a preceramic polymer (a silicone resin) and blown polyurethanes. The morphology of the expanded polyurethane was reproduced in the final architecture of the ceramic foam. The foams produced in this way consisted of an amorp…

Electric field dependent structural and vibrational properties of the Si(100)-H(2 \times 1) surface and its implications for STM induced hydrogen desorption

We report a first principles study of the structure and the vibrational properties of the Si(100)-H(2 \times 1) surface in an electric field. The calculated vibrational parameters are used to model the vibrational modes in the presence of the electric field corresponding to a realistic STM tip-surface geometry. We fin…

Universal dynamics of phase-field models for dendritic growth

We compare time-dependent solutions of different phase-field models for dendritic solidification in two dimensions, including a thermodynamically consistent model and several ad hoc models. The results are identical when the phase-field equations are operating in their appropriate sharp interface limit. The long time…

Many-spin interactions and spin excitations inMn12

In this work, the many-spin interactions taking place in ${\mathrm{Mn}}_{12}$ large-spin clusters are extensively studied using the 8-spin model Hamiltonian, for which we determine the possible parameters based on experimental data. Account of the many-spin excitations satisfactorily explains positions of the neutron…

Hydrothermal Synthesis of Nanocrystalline Cerium(IV) Oxide Powders

Nanocrystalline cerium(IV) oxide (CeO 2 ) powders were prepared by heating solutions of cerium(IV) salts in the presence of urea under hydrothermal conditions at 120° to 180°C. The effects of the concentration of urea and hydrothermal treatment temperature on the morphology and crystallite size of the synthesized part…

Use of an air brush to spray dry samples for X-ray powder diffraction

Abstract The construction and operation of a spray drier is described where the spray is produced using an air brush, essentially a miniature spray gun. The spray-dried products consist of spheres 50–60 µm in diameter and typical product recoveries are 80%, a marked improvement over simple two-nozzle systems. The spra…

Electron Shuttling Across the Interface of CdSe Nanoparticles Monitored by Femtosecond Laser Spectroscopy

The formation and decay of the optical hole (bleach) for 4 nm CdSe nanoparticles (NPs) with adsorbed electron acceptors (1,4-benzoquinone and 1,2-naphthoquinone) and the rise and decay of the reduced electron acceptors formed after interfacial electron transfer from the CdSe NPs were investigated by femtosecond laser…

Influence of Spectral Diffusion on the Line Shapes of Single CdSe Nanocrystallite Quantum Dots

We study the emission line shapes of single CdSe nanocrystallite quantum dots. Single dot line shapes are found to result from rapid spectral shifting of the emission spectrum rather than the intrinsic physics of the quantum dot. A strong dependence of single dot line widths on excitation intensity, wavelength, temper…

Unusual Kinetic Stability of a Ground-State Singlet Oxomanganese(V) Porphyrin. Evidence for a Spin State Crossing Effect

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTUnusual Kinetic Stability of a Ground-State Singlet Oxomanganese(V) Porphyrin. Evidence for a Spin State Crossing EffectNing Jin and John T. GrovesView Author Information Department of Chemistry, Princeton University Princeton, New Jersey 08544 Cite this: J. Am. Chem.…