Determinación del contenido de compuestos de cromo en el cemento portland por espectrofotometría de absorción atómica. Segunda parte
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Estudio sobre el contenido óptimo de yeso en los cementos, su influencio en las resistencias iniciales
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Nuevo método gravimétrico, esencialmente modificado, para la determinación de sílice en silicatos atacables por ácido, basado en los nuevos conocimientos descubiertos en el estudio del comportamiento de los geles de sílice deshidratados en soluciones ácid
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Calculations of mean free paths and stopping powers of low energy electrons (⩽ 10 keV) in solids using a statistical model
A statistical model is described and employed to calculate inverse mean free paths and stopping powers for electrons of energies from a few eV to 10 keV above the Fermi level in Al, Si, Ni, Cu, Ag, and Au. Brief tables of mean free paths and stopping powers for these solids are presented. In some cases graphical displ…
Contribución al estudio de los reacciones de hidratación del cemento portland por espectroscopia infrarroja. IV Hidratación del cemento con distintas proporciones de yeso y cloruro cálcico hasta 28 días
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Further studies on the mechanical properties of mollusc shell material
Values of tensile strength, compressive strength, bending strength, hardness and modulus of elasticity are reported for the shell material of various species of bivalve, gastropod and cephalopod mollusc. Nacre is the strongest structural type, but crossed lamellar structure is the hardest. Possible selective reasons f…
Influence of Electron Noise on Three-dimensional Image Reconstruction
Abstract A three-dimensional reconstruction requires the same integral dose as a conventional two-dimensional micrograph provided that the level of significance and the resolution are identical. The necessary dose D for one of the K projections in a reconstruction series is, therefore, the integral dose divided by K.
Synthesis and interconversion of the isomeric .alpha.- and .beta.-molybdate (Mo8O264-) ions
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis and interconversion of the isomeric .alpha.- and .beta.-molybdate (Mo8O264-) ionsW. G. Klemperer and W. ShumCite this: J. Am. Chem. Soc. 1976, 98, 25, 8291–8293Publication Date (Print):December 1, 1976Publication History Published online1 May 2002Published inissue…
Line Shift Method for Phosphor Temperature Measurements
Two possible approaches to spectroscopic measurements of the internal temperature of Y 2 O 2 S: Eu are discussed. Methods based on relative Eu 3+ fluorescence line intensities are found either to be insufficiently sensitive or to suffer from unavoidable experimental difficulties. The method which is adopted exploits t…
Studies on chitin, 2. Effect of deacetylation on solubility
Abstract A reproducible method for obtaining water‐soluble chitin and a relationship between solubility and degree of deacetylation of chitin were studied. It was found that the regenerated chitin isolated at low temperature from an alkali chitin solution left at 25°C for 48 to 77h showed very good solubility in water…
Physical properties of thin-film field emission cathodes with molybdenum cones
Field emission cathodes fabricated using thin-film techniques and electron beam microlithography are described, together with effects obtained by varying the fabrication parameters. The emission originates from the tip of molybdenum cones that are about 1.5 μm tall with a tip radius around 500 Å. Such cathodes have be…
Longitudinal Optical Vibrations in Glasses: GeO2and SiO2
We show that longitudinal optical (LO) vibrational modes account for several previously unexplained peaks in the Raman spectra of vitreous Ge${\mathrm{O}}_{2}$ and Si${\mathrm{O}}_{2}$. Identification of LO modes in these and other glasses reduces the complexity of the spectra that must be explained by simple structur…
Valence-Alternation Model for Localized Gap States in Lone-Pair Semiconductors
A model is presented for the structure and properties of active centers in lone-pair semiconductors, based on the possibility of unique bonding configurations which can arise from the presence of nonbonding orbitals. It is shown that the lowest-energy neutral center is unstable towards the creation of different positi…
Raman Spectroscopy of Soft Modes at the Charge-Density-Wave Phase Transition in2H−NbSe2
The Raman spectra of the layer-structure compounds $2H\ensuremath{-}\mathrm{Nb}{\mathrm{Se}}_{2}$ and $2H\ensuremath{-}\mathrm{Ta}{\mathrm{Se}}_{2}$ have been measured between 2 and 300 K. A low-energy peak in the Raman spectrum is found to soften at the charge-density-wave phase transition. This peak is attributed to…
Thermodynamics of rubber elasticity
Abstract The process of vulcanization, which links the polymer molecules into a three dimensional network, enables reversible thermodynamic measurements to be made on elastomeric materials from which the entropy and energy contributions to the free energy of deformation can be determined. The molecular processes respo…
Investigation of deep centres of chlorine-doped zinc sulfide crystals
Deep centres of the ZnS: Cl single crystals are investigated by the method of impurity electroabsorption (IEA) and photoconductivity (PhC). In accordance with estimations fulfilled a number of the levels obtained are ascribed to V″Zn; (VZnClS)′ and V′Zn and also to (VZnGaZn)′, whose energy levels are obtained in a pre…
Phase transitions and semiconductor-metal transition in V1−xGaxO2 Single Crystals
The electrical, thermoelectric, magnetic, and crystallographic properties of Ga-doped VO2 single crystals V1−xGaxO2 (0 ≦ x ≦ 0.013) are investigated. By Ga-doping the transition temperature of the semiconductor-metal transition of VO2 is elevated and the resistivity discontinuity is little increased. The T–x-phase dia…
The anisotropic behavior of Poisson's ratio, Young's modulus, and shear modulus in hexagonal materials
A method of calculating the anisotropy of Poisson's ratio is applied to trigonal and tetragonal crystals in the literature. The method of calculation is extended to hexagonal crystals. The results are illustrated by reference to Tl and Cd.
Yttrium carbonate hydroxide
YOHCO3, or thorhombic, P212~2~; a = 4.809 (1), b=6 .957 (l), c=8 .466 (1) A; Z = 4 , de= 3.89 g c m -a. The final R for 737 reflections was 0.0518. The carbonate-group distances and angles are C-O(1) 1.288 (9), C-O(2) 1.279 (9), C-O(3) 1-287 (8) A, O(1)-C-O(2) 122.8 (7), O(1)-C-O(3) 118-7 (6), and O(2)-C-O(3) 1183 (7)…