[en] Polycrystalline samples of Cd/sub 2x/(AgIn)/sub y/Mn/sub 2z/Te₂ (x + y + z = 1) alloys are prepared by a melt and anneal technique. Debye-Scherrer X-ray powder photographs are used to determine equilibrium conditions and lattice parameter values. It is found that in addition to the zincblende and chalcopyrite structures, a partially ordered structure is obtained, plus a two-phase field at higher z-values. Room temperature measurements of optical absorption are made to give values of the optical energy gap E/sub g/ for all single phase samples. It is found that the variation of a is practically linear with composition. However, while E/sub g/ varied linearly with composition inside a phase field, the resulting lines have different aiming points at z = 1, the values being 2.83 eV for zinc blende, 1.90 eV for the ordered phase, and 1.36 eV for the chalcopyrite phase. Thus the values of E/sub g/ give a very good indication of the phase boundaries. (author)

[en] The objective of this study was to undertake an interlaboratory comparison of a liquid phase blocking ELISA for detection of antibodies to FMD virus. For that purpose sera from 120 vaccinated, 120 infected and 120 FMD negative cattle were tested. All sera were tested in a screening assay at a dilution of 1/32. Positive sera were tested in a titration assay (1/10, 1/50, 1/250, 1/1250). For serotype O₁ Cruzeiro 108 sera from the FMD-free group were classified as negatives giving a specificity of 90%. For the same serotype the group of infected/vaccinated cattle gave 114/115 positive results showing a sensitivity of 95% respectively 96%. For serotype A₂₄ Cruzeiro from the FMD-free group 85 sera were classified as negatives giving a specificity 71%. For the same serotype the group of infected/vaccinated cattle gave 90/99 positive results showing a sensitivity of 75% respectively 82%. The predictive value of the assay was good as results expected for the different serum categories were mainly confirmed in the test. Nevertheless a high number of plates were rejected due to 'outside limits' and further adjustments are necessary to obtain more reliable results. (author)

[en] The Moessbauer measurements at variable temperature (from liquid helium to room temperature) on the layered compound CuFeTe₂ have been able to determine the existence of a magnetically ordered state below T_N= 254 ± 15 K. The general shape of the spectra and the magnitudes of the hyperfine fields let us to propose a Spin Density Wave (SDW) behavior for this compound

[en] Colombia has FMDV type O and type A in some regions with endemic characteristics. At present, the country is involved in the hemispheric plan for eradication of FMDV. To attain this objective, it is necessary to use modern techniques with high sensitivity and specificity as opposed to traditional serological tests. The use of liquid ELISA is of great benefit in places where prevention, control and eradication programmes for FMD are running. This technique gives more security because it is very sensitive and specific and the results are obtained on the same day. In addition, it does not need any cell culture nor a CO₂ environment. The test is based on specific blocking of the liquid phase of FMDV antigen by antibodies in the test sample. After the test serum has been allowed to react with the plate coated with FMDV serotype specific trapping antibodies. The presence of antibodies to FMDV in the serum sample will result in the formation of immune complexes and, consequently, reduce the amount of free antigen trapped by the immobilized rabbit antisera. In turn, fewer guinea pig anti-FMDV detecting antibodies will react in the next incubation step. After the addition of enzyme labelled horseradish peroxidase, anti-guinea-pig Ig and substrate/chromogen solution, a reduction in colour development will be observed when compared to controls containing free antigens only

[en] Polycrystalline samples of Zn_2x(AgIn)_1-xTe₂ alloys are prepared by the melt and anneal technique. Differential thermal analysis measurements are carried out on the alloys and the T(x) diagram is determined. Guinier X-ray powder photographs are used to show the equilibrium conditions and to give lattice parameter values. Two single solid phase fields are observed in the diagram, which is shown not to be pseudobinary. Room temperature optical energy gap values are determined as a function of composition. (author)

[en] The T vs. composition phase diagram of the alloy system Cd_2x(AgIn)_yMn_2zTe₂ was investigated in the range 0 ≤ z ≤ 0.7 by differential thermal analysis and x-ray diffraction measurements. Samples were prepared for various lines of constant x/y ratio, and T vs. z diagram was determined for each line. Values of lattice parameters were determined for all samples and the limits of single-phase solid solution estimated. In addition to liquidus and solidus curves, the zinc blende-chalcopyrite and Mn-disordered-Mn ordered transition lines were determined, these phase fields being the ones of interest for measurements of energy gap and magnetic properties

[en] Polycrystalline samples of the semimagnetic semicondutor alloys (AgIn)_1-zMn_2zTe₂ and (CuIn)_1-zMn_2zTe₂ are used in lattice parameter, optical energy gap E₀, and differential thermal analysis (DTA) measurements. The results indicate that in both, the zinc blende and chalcopyrite ranges of composition, ordering of the manganese can occur at lower temperatures, and a combination of the results is used to delineate the composition and temperature ranges in which disordered α and ordered α' chalcopyrite and disordered β and ordered β' zinc blende is the equilibrium structure. It is shown that while the manganese ordering has little effect on the lattice parameter, it has appreciable effect on the values of E₀. This is demonstrated by the different aiming points at z = 1.0 for the E₀ vs. z lines in the different fields, the values being 2.8 eV for β, 1.95 eV for β', and 1.35 eV for α'. (author)

[en] Polycrystalline samples of Hg_2x(AgIn)_1-xTe₂ alloys are prepared by the melt and anneal technique. Differential thermal analysis (DTA) measurements are carried out on the alloys and the T(x) diagram determined. Guinier X-ray powder photographs are used to show the equilibrium conditions and to give lattice parameter values. Only two single phase solid fields, the zinc blende and chalcopyrite fields are found to exist in the diagram. The form of the solidus curve bounding a wide two-phase liquid plus solid field shows that the section is not pseudobinary. Microscopic and DTA data show the presence of the dissociated phase in the grain boundaries of the zinc blende phase at temperatures below 400 ⁰C. (author)

[en] In this paper, the radial distributions of emissivity of the species present in the helium-nitrogen, helium-oxygen and helium-argon plasmas sustained by the axial injection torch at atmospheric pressure are studied by optical emission spectroscopy using the Abel inversion procedure. The spectrum was scanned for atomic and ionic lines together with rotational bands of neutral and ionic molecules of such species. The variation of the emissivity with different mixture composition was also studied. No emission from oxygen molecular species (O₂, O₂⁺) was found in the discharge or from the atomic ions N⁺ or O⁺. The interaction processes between helium and the introduced species are discussed. A decrease in helium emissivity when compared with the pure helium plasma was found for every plasma gas mixture composition

[en] Polycrystalline samples of (CuIn)_x(AgIn)_yMn_2zTe₂ alloys are used in lattice parameter, optical energy gap E₀, and differential thermal analysis (DTA) measurements and for various sections of constant x/y ratio, T(z) diagrams are determined. The results indicate that for both the zincblende and chalcopyrite phases, ordering of the manganese occurs in the lower temperature range. In contradiction of previous data, it is shown that at temperatures of 200 ⁰C and below, the ordered chalcopyrite α' is the equilibrium condition over the complete range of solid solubility in the adamantine structures. It is shown that the manganese ordering has negligible effect on the lattice parameter but that appreciable lattice parameter differences can occur with different annealing temperatures, these differences being attributed to changes in non-stoichiometry. However, the value of E₀ is appreciably affected by the manganese ordering and it is shown that E₀ gives a very convenient indication of the particular phase present in a single phase sample. (author)