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Etude du mecanisme de sensibilisation par des allergenes chimiques dans les reactions d'hypersensibilite immediate, de contact et retardee chez le cobaye. Etudes de transfert

The high-temperature superconductor (${\mathrm{La}}_{2\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Sr}}_{\mathrm{x}}$)${\mathrm{CuO}}_{4}$ has the ${\mathrm{K}}_{2}$${\mathrm{NiF}}_{4}$ structure, as does ${\mathrm{Sr}}_{2}$${\mathrm{TiO}}_{4}$. In order to understand better the phonon spectra obtained from ceramic (${\mathrm{La}}_{2\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Sr}}_{\mathrm{x}}$)${\mathrm{CuO}}_{4}$, we have performed Raman and infrared measurements on ceramic, insulating ${\mathrm{Sr}}_{2}$${\mathrm{TiO}}_{4}$. All four Raman-allowed phonons are observed and found to be quite sharp, because in this centrosymmetric structure the Raman-mode frequencies are isotropic. The infrared reflectivity spectra are more difficult to interpret because reststrahlen bands are measured, which extend from the transverse-optic (TO) frequency to the longitudinal-optic (LO) frequency. Symmetry forbids overlap of the 3${A}_{2u}$ bands as well as the 4${E}_{u}$ bands. The interpretation, nevertheless, is difficult because the ${A}_{2u}$ and ${E}_{u}$ bands can overlap one another. By comparison with single-crystal results in fluorides and chlorides having the same structure, we have been able to identify many of the infrared modes in our spectra. This knowledge permits a determination of most of the infrared active modes in (${\mathrm{La}}_{2\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Sr}}_{\mathrm{x}}$)${\mathrm{CuO}}_{4}$. In the superconductor, two other effects aid our understanding of the spectra. (a) The effective charges are smaller than in ${\mathrm{Sr}}_{2}$${\mathrm{TiO}}_{4}$, reducing the TO-LO splitting, and thus the overlap of the reflectivity bands. (b) The electron plasma is confined to the xy plane, and consequently it interacts strongly only with the ${E}_{u}$ phonons, and leaves the ${A}_{2u}$ phonons largely unaffected.

We report a study of the magnetic susceptibility, Hall effect, resistivity and specific heat of pure and Sr-doped La 2 CuO 4 . Undoped La 2 CuO 4 exhibits antiferromagnetic order and traces of superconductivity, sensitivity dependent on stoichiometry. The data provide evidence for strong electron-electron correlations in the Sr-doped superconductors, and a scaling of T c with the electron deficiency, supporting an all-electronic model for the oxide superconductivity.

We measure the reflectivity of pure and doped polycrystalline La/sub 2-//sub x/Sr/sub x/CuO/sub 4/ in the gap region and up to 40,000 cm/sup -1/(approx. =5 eV). For the doped sample we analyze the reflectivity in terms of a superposition of a metallic a-b plane component and a nearly insulating c-axis component with ordinary phonons. This approach removes several unphysical results obtained assuming a homogeneous surface and allows agreement between the measured infrared and dc properties, which has not been previously obtained. This approach further indicates that our infrared gap signature is dominated by the c-axis contribution and insensitive to the gap in the a-b plane. We estimate the c-axis gap to be 2..delta..approx. =2k/sub B/T/sub c/, which is small compared to both the isotropic BCS prediction and tunnelling measurements.

Macro-defect-free cements, based mostly on Secar-71 and using polyvinyl acetate as a plasticizer, have been prepared. Dielectric constant and loss factor at 1 MHz and d.c. resistivity of these cements have been measured as a function of their composition, processing conditions and humidity. For some of the samples, flexural strengths have been measured in order to correlate with their electrical properties. Results of efforts to inhibit the effects of higher humidities on the electrical properties are also reported.

Circulating antibodies were detected before treatment in the serum of 18 of 40 patients with newly acquired tuberculosis and of eight of 12 patients with reactivated tuberculosis by microimmunodiffusion tests with unheated mycobacterial culture filtrate, arabinogalactan, arabinomannan, and a specific culture filtrate fraction. Some patients responded to a single antigen, while others responded to two and at times four or more. Some of these antibodies reacted with polysaccharides, but many reacted with protein. Antibiotic treatment increased the percentage of responders from 46% to 60%0 in new cases and from 66% to 75% in relapse cases and increased the concentration of antibodies. In evaluation of serologic tests in tuberculosis, the effect of prior chemotherapy must be weighed. These microimmunodiffusion tests appear to be specific for Mycobacterium tuberculosis. The significance of antibodies to mycobacteria in human tuberculosis (TB) has long been debated. In this report we present a study of the initial development of antibody in human TB and of changes in the antibody response throughout the course of antibiotic treatment. Fifty-two patients with mycobacterial infection were followed; TB was found in 50, while in two others, organisms falling within the Mycobacterium avium-Mycobacterium intracellulare-Mycobacterium scrofulaceum complex were isolated. Antibody was detected by a modified Ouchterlony technique of double diffusion, using patients' sera and native culture filtrate from Mycobacterium tuberculosis strain H37Rv, special subfractions, and certain purified carbohydrates. In another paper we describe the specific antigens that induce antibody in these patients [1]. Historically, antibodies to mycobacteria have been detected by various techniques. Tuberculocarbohydrates (from undiluted tuberculin) were found to bind to sheep erythrocytes, which could be agglutinated by serum from some tuberculous individuals. In the presence of antibody these same cells could be lysed on addition of complement [2]. Boyden [3, 4] and Boyden and Andersen [5] used tanned red blood cells to bind protein antigens and extended the number of detectable antibodies. Other techniques include using latex particles coated with culture filtrate of the avirulent strain H37Ra or acid-precipitable proteins prepared from the filtrate [6, 7], using bentonite particles sensitized directly with old tuberculin or with chromatographed fractions of whole

The crystallization mechanism of high-cordierite (2MgO·2Al2O3·5SiO2) from a bulkglass containing B2O3 and P2O5 as nucleating agents was studied using X-ray diffraction, differential thermal analysis and a polarizing microscope. Thin glass specimens, with a mirror surface, were heated rapidly in an electric furnace in the temperature range 888 to 1363° C for a desired time and then rapidly quenched to room temperature. The normal rate of growth of precipitated cordierite crystals was measured and their morphological change was observed photographically. The growth rate increased with temperature, and the maximum rate occurred at about 1250° C. The crystal morphology was hexagonalprismatic, elongated along thec-axis. Faceted interface morphology was observed when the range of undercooling was from 7 to 174° C. Judging from the relationship between the reduced growth rate and the degree of undercooling, the crystallization mechanism in the range of lower undercooling was governed by a layer growth depending on the surface nucleation mechanism. In the range of higher undercooling, continuous growth was seen and at intermediate undercooling a transition range from a layer growth to a continuous growth was evident.

Sixteen genera and 27 species of Recent brachiopods are reported from the far southern Pacific Ocean and adjacent parts of the South Atlantic and southern Indian Ocean. These specimens extend the known geographic ranges of at least 10 species and the known bathymetric ranges of at least seven species. The new material gives greater support to the idea that many Recent brachiopod species have a wide geographic range and calls into question the very limited geographic ranges of many species known only from the fossil record. Puncta density appears to be a useful character for distinguishing Neothyris compressa and N. lenticularis. At least nine different types of geographic distribution are represented among the species studied for this paper. Areas of moderate depth on seamounts, particularly along oceanic ridges and on oceanic rises, may form important geographic areas of distribution, avenues of dispersal, and barriers to brachiopods. Four examples of polytypic species are cited. The new specimens lend additional support to the notion that one polytypic species of Liothyrella extends, with clinal morphological changes, from southernmost South America to Antarctica. Students of modern brachiopods are urged to consider large-scale geographic variation within species and not to hide it with finely delimited taxa. This approach has the potential to lead, in both modern and ancient brachiopods, to a taxonomy with fewer and more meaningful species and genera. Progenetic changes seem to be a common adaptive strategy in brachiopods on largely soft substrates and in deep water. The progenesis may be short term within a single species or long term involving evolution of new species and genera.