Protección del hormigón en las aguas agresivas. Principios y procedimientos
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Materials Literature
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Las colas para el hormigón
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Determinación del título calcimétrico en los crudos de cemento en función del valor del módulo hidráulico
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Thermal Conductivity of Pure and Impure Silicon, Silicon Carbide, and Diamond
Thermal conductivity measurements on high-purity SiC and impure Si and SiC have been made over the temperature range from 3° to 300°K. These results show that the thermal conductivity K, of the highest purity SiC is intermediate between those of pure Si and pure diamond, and at 300°K is greater than that of copper. Th…
Synthesis and Fluorescence of Some Trivalent Lanthanide Complexes
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis and Fluorescence of Some Trivalent Lanthanide ComplexesL. R. Melby, N. J. Rose, E. Abramson, and J. C. CarisCite this: J. Am. Chem. Soc. 1964, 86, 23, 5117–5125Publication Date (Print):December 1, 1964Publication History Published online1 May 2002Published inissue…
Rare-Earth Ions in the Alkali Halides. I. Emission Spectra ofSm2+-Vacancy Complex
Measurements have been made of the crystal-field splitting of the $^{7}F_{J}$ energy levels of the $4{f}^{6}$ configuration of the ${\mathrm{Sm}}^{2+}$ ion which is dissolved in a number of alkali-halide lattices. Crystal-field term assignments were made from the results of polarized-emission measurements. Observed cr…
Low-Temperature Recombination Luminescence in Alkali Halide Crystals
Luminescence observed upon low-temperature x-ray excitation of alkali-halide crystals has been identified as due to radiative electron-hole recombination in the perfect lattice. In KCl the emission spectrum is a single band, while in KBr, KI, and NaCl there are two bands. In crystals containing self-trapped holes, opt…
Kramers-Kronig Analysis of Reflectance Data for Diamond
The use of the Kramers-Kronig relation in the analysis of reflectance data is discussed briefly. The recent results of Walker and Osantowski for diamond are reanalyzed and found to be in some error. New data are presented which appear more consistent with the expected optical behavior of diamond.
High-Pressure B-Type Polymorphs of Some Rare-Earth Sesquioxides
New high pressure forms of the sesquioxides of holminum, erbium, thulium, ytterbium, lutetium, and yttrium have been obtained by exposure of the C-type sesquioxides to pressures between 25 and 40 kilobars and temperatures between 900 degrees and 1020 degrees C. X-ray diffraction analysis shows that these new high-pres…
The brittle fracture of solids by liquid impact, by solid impact, and by shock
Abstract The type of stress pulse produced when a liquid mass strikes a solid at high velocity is first examined. Compressible behaviour, giving rise to a sharp peak of pressure, is found to occur in the initial stages of the impact. The duration of this peak depends on the dimensions and impact velocity of the liquid…
Adhesiveness of Spider Silk
Moths, by virtue of the loose scales that cover their wings and bodies, are admirably adapted to elude capture by orb-weaving spiders. Rather than sticking to the web, they may simply lose some of their scales to the viscid threads, and then fly on. Other insects, covered with detachable hairs or waxy powder, are simi…
Scattering of Phonons by Electrons in Germanium-Silicon Alloys
The theory developed by Ziman for the scattering of phonons by electrons is extended to high temperatures using the formalism of Klemens and Callaway. The theory is applied to the experimental results recently published by Dismukes et al. on the effect of doping on the thermal conductivity of Ge-Si alloys. After subtr…
Photoemission Studies of Copper and Silver: Experiment
Experimental photoemission data from copper and silver are presented and interpreted in detail in terms of the calculated band structures over a photon energy range from 1.5 to 11.5 eV. It is shown that nondirect optical transitions are stronger than direct ones in both metals. In fact, the only direct optical transit…
Electron Paramagnetic Resonance of Re4+ in Single Crystals of K2PtCl6
The electron paramagnetic resonance of Re4+ in single cubic crystals of K2PtCl6 at wavelengths of 3 cm, 1 cm, and 8 mm is reported. The experimental results were analyzed assuming the Re4+ ground state is a spin quartet with S=32 and I=52. The cubic spin Hamiltonian is given by H=gβH·S+AI·S+uβ{HxSx3+HySy3+HzSz3−15(H·S…
Absorption and Fluorescence of Europium(III) in Aqueous Solutions
Absorption, fluorescence, and excitation spectra of aqueous solutions of europium(III) perchlorate, chloride, nitrate, ethylenediaminetetra-acetate, and diethylenetriaminepenta-acetate were investigated. The latter three anions readily form complexes and were examined over a range of concentrations. The organic anions…
Energy of Excimer Luminescence. I. A Reconsideration of Excimer Processes
The interpretation of the energies of excimer luminescence of some polyacenes is considered and it is shown that neither simple molecular exciton attitudes nor charge resonance attitudes can provide satisfactory agreement with experiment. The D2k excimer formed from D2h aromatics is investigated and it is shown that t…
Kinetics of Diffusion-Controlled Whisker Growth
The problem of surface diffusion-controlled whisker growth is considered in a moving frame of reference. In addition, diffusive exchange with the substrate, a problem not treated heretofore, is considered. The results are compared with experiment and with prior treatments of whisker growth. The possibility of occurren…
Spectra and Energy Levels of Eu3+ in Y2O3
The absorption and fluorescence spectra of Eu3+ in single crystals of Y2O3 have been observed and analyzed. The intermediate-coupling free-ion energy levels for Eu3+, including the effects of the 46 singlet states of the 4f6 configuration, are presented for all levels appearing below 41 000 cm—1. The results obtained…
Dendrites
I have touched upon the great variety of crystal forms and dendritic forms in nature, have discussed the essential physics involved in the generation of these forms during either constrained or unconstrained crystal growth, and have shown how this knowledge helps in the classification of this seemingly infinite variet…
On the high-pressure form of FeVO4
Abstract : Evidence is presented that the atomic arrangement of high-pressure FeVO4 is similar to that of ambientpressure FeNbO4. Evidence is presented in the form of comparing the indexing of high-pressure FeVO4 and the disordered wolframite FeNbO4, which indicates that FeVO4 crystallizes in the disordered wolframite…