Maquinaria y recambios
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El nuevo Pliego general de Condiciones para la recepción de conglomerantes hidráulicos en las obras de carácter oficial
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Bibliography
Aspecto económico financiero del momento actual en relación con la industria del cemento
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Problemas que plantea un horno Lepol sencillo para convertirlo en doble
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Mechanism of Solid‐state Reaction Between Magnesium Oxide and Aluminum Oxide and Between Magnesium Oxide and Ferric Oxide
Inert marker experiments have shown that the solid‐state reactions forming MgAl 2 O 4 and MgFe 2 O 4 occur by counterdiffusion of the Mg 2+ , Fe 3+ , and A1 3+ ions through the relatively rigid oxygen lattice of the spinel or ferrite. It is suggested that earlier claims that ZnAl 2 O 4 forms by diffusion of Zn 2+ and…
Synthesis of the Cubic Form of Boron Nitride
A study of the formation of cubic boron nitride shows that the alkali and alkaline earth metals and their nitrides are effective catalysts for converting hexagonal boron nitride into cubic. The pressure and temperature required varies with the catalyst, and a minimum of about 45 000 atm and 1500°C has been found to be…
Eine einfache Theorie der dielektrischen Eigenschaften homogen orientierter kristallinflüssiger Phasen des nematischen Typs
Die ONSAGERsche Theorie der „statischen” dielektrischen Polarisation einer Dipolflüssigkeit wird auf die nematische Phase einer kristallinflüssigen Substanz übertragen, wobei die Anisotropie der molekularen Polarisierbarkeit, die Orientierung des permanenten Dipolmoments im Molekül und die nematische Fernordnung berüc…
Deformation twinning in face-centred cubic metals
The principal features of the experimental results of Blewitt et al. (1957) and of Suzuki and Barrett (1958) on deformation twinning in face-centred cubic metals are explained in terms of an extension of the ‘prismatic’ source mechanism of Cottrell and Bilby (1951). Suitable prismatic dislocation sources are thought t…
Intramolecular Energy Transfer in Rare Earth Chelates. Role of the Triplet State
Results of luminescence studies on chelates of La3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+, Tm3+, Yb3+, and Lu3+ are reported. It is shown that the intramolecular energy transfer efficiency is a sensitive function of the relative positions of the resonance energy levels of the ions and the metastable triplet states of the comp…
Nucleation and growth of twins in dislocation-free zinc crystals
Abstract Zinc whiskers and platelets with their largest faces in the basal plane and thin enough (~½μ) to be transparent to 100 kV electrons were strained in tension inside the electron microscope and the nucleation and growth of twins observed by the transmission technique. These observations were then related to the…
Effect of Electron Exchange on the Dispersion Relation of Plasmons
A calculation of the influence of electron exchange on the dispersion relation of a high-density electron gas at 0\ifmmode^\circ\else\textdegree\fi{}K is described. The result is compared with those obtained by various authors using different methods.
Surface Structures and Properties of Diamond-Structure Semiconductors
Low-energy electron-diffraction and secondary electron-emission measurements have been made on (111) and ($11\overline{1}$) surfaces of GaSb and (100) surfaces of InSb. To account for the diffraction patterns observed both for these materials and previously for Ge and Si, a general model for (111) surfaces of diamond-…
Chloritized Weathering Products of a New England Glacial Till
Abstract The clay mineralogy of a soil profile developed in a New England glacial till has been studied to a depth of 55 in. Degraded soil micas, probably produced by weathering, have been chloritized by both iron and aluminum hydroxide complexes. Aluminum and iron determinations and X-ray analyses indicate that iron…
High‐Temperature Energy Relations in the Alkali Borates: Binary Alkali Borate Compounds and Their Glasses
The energy relations existing between the congruently melting compounds Li 2 O ‐2B 2 O 3 , Na 2 O–2B 2 O 3 , Na 2 O‐4B 2 O 3 , and K 2 O‐4B 2 O 3 and their glasses have been determined for the temperature range 25° to 1100°C. High‐temperature heat‐content, entropy, and heat of solution data are given for both the glas…
Twisting of bundles of bacterial cellulose microfibrils
Abstract The majority of, but not all, bundles of bacterial cellulose microfibrils show a characteristic left‐handed twist which has a pitch of about 1 μ. The remainder show no apparent coiling. The twist must reflect an internal strain in the component microfibrils which may be due to a slight progressive molecular a…
Part 1—Electrochemical Studies of Tin, Iron-Tin Alloy, and Steel in Air-Free Acid Media: Corrosion Resistance of Electrolytic Tin Plate
Several types of failure observed in tin plate containers are described in terms of tin-steel potential and current relationships. The effect of Sn++ on potentials and polarization of tin and steel electrodes in deaerated 1N HCl and 0.1M citrate buffer is shown to be important to proper design of electrochemical test…
Origin of the Green Bands in the Boron-Oxygen System
A study has been made of the effect of oxygen on the intensity of absorption in the green or ``fluctuation'' bands by the gas phase in equilibrium with B2O3(l). The reaction which forms the substance responsible for the bands from B2O3(l) in the presence of oxygen was found to be 70 kcal/mole endothermic, in the range…
Thermionic and Photoelectric Emission from Magnesium Oxide
Measurements of the thermionic emission as a function of temperature and the photoelectric yield as a function of the photon energy in the range from 2.5 ev to 11.5 ev have been made on magnesium oxide in the form of thin films, powders, and single crystals. The thermionic emission measurements indicate that the posit…
Some Theoretical Considerations of Cellulose Cross-Linking
Much available chemical evidence supports the hypothesis that covalent cross-linking is the best way to improve the resilience of cellulosic fabrics. This paper reviews the theories relating physical properties to cross-linking in rubbery polymers and shows that they apply in some qualitative aspects to cellulose. Par…