En este trabajo se reportan las medidas de susceptibilidad magnetica c en funcion de la temperatura en el rango de 2-300 K de muestras policristalinas del sistema de aleaciones semiconductor magnetico Cu 2 Cd 1 − z Mn z SnSe 4 . La constante de Curie C aumenta linealmente con la concentracion z. La temperatura de Curie-Weiss q y la temperatura de Neel T N aumentan linealmente con la concentracion z, debido a un cambio de orden parcial a desorden total de los atomos de Mn 2+ en el sistema. En una primera aproximacion, se puede considerar que el sistema de aleaciones tiene un comportamiento tipico de vidrio de espin, lo que implica que los iones de Mn 2+ se encuentran de alguna manera desordenados en la red cationica del material. Measurements of magnetic susceptibility c as a function of temperature in the range 2-300 K on polycrystalline samples of Cu 2 Cd 1 − z Mn z SnSe 4 magnetic semiconductor alloy system are reported. The Curie constant C increase linearly with z. The Curie-Weiss temperature θ and Neel temperature T N increase linearly with z due to a partial order change to total disorder of the Mn +2 ions in the system. In a first approximation, it can be considered that this system has typical spin glass behavior (spin glass system), which means that ions Mn +2 are somewhat disorderly way cationic network of material.

X-ray powder diffraction and differential thermal analysis (DTA) measurements were made on polycrystalline samples of the Cu2Zn1-zFezGeSe4 alloy system. The diffraction patterns were used to show the equilibrium conditions and to estimate crystalline parameter values. It was found that, at room temperature, a single phase solid solution with the tetragonal stannite alpha structure (1 (4) over bar 2m) occurs across the whole composition range. The DTA thermograms were used to construct the phase diagram of the Cu2Zn1-zFezGeSe4 alloy system. It was confirmed that the Cu2ZnGeSe4 compound melts incongruently. It was observed that undercooling effects occur for samples with z > 0.9. (C) 2007 Elsevier B.V. All rights reserved.

In order to resolve the crystal structure and the corresponding space group of the tetrahedrally coordinated II–III2–V I4 defective semiconductor ZnGa2Se4, a study of the magnetic susceptibility of the alloy system Zn1−zMnzGa2Se4 is performed. The analysis of the Curie–Weiss temperature confirms, consistently with the phase diagram previously reported, that the room temperature crystal structure of the alloy system Zn1−zMnzGa2Se4 in all the composition ranges (0≤z≤1) is of defect chalcopyrite type with space group I4̄ while samples obtained at temperatures higher than about 500°C, which are rapidly cooled to room temperature, crystallizes in the partially disordered stannite-type structure I4̄2m. Hence, a careful process of crystal growth of this system, including a study of the phase diagram, annealing at adequate temperature, and slow cooling of the samples is necessary in order to obtain specimens in the ordered phase.

X-ray powder diffraction measurements, at room temperature, and magnetic susceptibility χ measurements, in the temperature range from 2 to 300K, were made on polycrystalline samples of Mn2GeTe4, Fe2GeTe4 and Fe2SnSe4 compounds, which would be useful for spintronic device production. Magnetization M measurements at various temperatures were carried out on the Fe-compounds. From the analysis of the X-ray diffraction patterns, it was found that the Mn2GeTe4, Fe2GeTe4 and Fe2SnSe4 have orthorhombic structure, possibly an olivine structure-type (SG: Pnma No. 62, z=4). It was found that Mn2GeTe4 has a Néel temperature of 30K, shows mainly antiferromagnetic behavior with a weak superimposed ferromagnetic component which is attributed to spin canting. The resulting susceptibility χ versus T curves for Fe2GeTe4 and Fe2SnSe4 were found to have, in each case, a form which is typical of a ferromagnetic material with Curie temperatures TC of 149.9 and 301K, respectively. The critical exponent β for the Fe-compounds were found to be very similar and close to the expected value for a ferromagnetic material, in the range 0.33–0.39. The values of the coercive field BC and the remanent magnetization Mr were found to vary nonlinearly with the temperature T.

Measurements of magnetic susceptibility χ, in the temperature range from 2 to 300K, and of magnetization M vs. applied magnetic field B, up to 5T, at various temperatures were made on polycrystalline samples of the Mn2GeTe4 compound. It was found that Mn2GeTe4 has a Néel temperature TN of about 135K, shows mainly antiferromagnetic behavior with a very weak superimposed ferromagnetic component that is attributed to spin canting. Also, the magnetic results suggest that a possible spin-glass transition takes place at Tf≈45K. The spin-glass order parameter q(T), determined from the susceptibility data, was found to be in agreement with the prediction of conventional spin-glass theory. The M vs. B results indicated that bound magnetic polarons (BMPs) occur in the compound, and that the effects from BMPs disappear at approximately 80K. The M vs. B curves were well fitted by a Langevin type of equation, and the variation of the fitting parameters determined as a function of temperature. Using a simple spherical model, the radius of the BMP in the material was found to be about 27Å; this value is similar to the effective Bohr radius for an acceptor in the II–IV–V2 and I–III–VI2 ternary semiconductor compounds.

X-ray powder diffraction measurements, at room temperature, and magnetic susceptibility Χ measurements, in the temperature range from 2 to 300 K, were made on polycrystalline samples of Mn 2 GeTe 4 and Fe 2 GeTe 4 compounds, which would be useful for spintronic device production. Magnetization measurements at various temperatures were carried out on these compounds. From the analysis of the x-ray diffraction lines, it was found that both Mn 2 GeTe 4 and Fe 2 GeTe 4 have an orthorhombic olivine structure-type (SG: Pnma No. 62, z=4). It was found that Mn 2 GeTe 4 has a Neel temperature of 30 K and shows mainly antiferromagnetic behaviour with a weak superimposed ferromagnetic component which is attributed to spin canting. The resulting 1/Χ versus T curve for Fe 2 GeTe 4 was found to have a form which is typical of a ferromagnetic material with a Curie temperature T c of 149.9 K.

Measurements of magnetic susceptibility as a function of temperature T were made on polycrystalline samples of the Zn 1-z Mn z Ga 2 Se 4 alloy system. From the 1/Χ vs T curves, values of the critical Neel temperature T N and the Curie-Weiss 0 were determined for z > 0.7. An analysis was carried out in terms of a simple mean-field theory. Using the exchange interaction relation of Geertsma et al., values of exchange interaction parameters were determined from the T N and θ. Hence, the value for any J i , i.e. for any i-th set of neighbors, can be estimated.

X-ray powder diffraction measurements and differential thermal analysis (DTA) were made on polycrystalline samples of the Cu2Cd1−zMnzGeSe4 and Cu2Cd1−zFezGeSe4 alloy systems. The diffraction patterns were used to show the equilibrium conditions and to derive lattice parameter values. The effect of the annealing temperature and cooling rate to room temperature are discussed. For the Cu2Cd1−zFezGeSe4 system, only two single solid phase fields, the tetragonal stannite α and the wurtz-stannite δ structures were found to occur in the diagram. For the Cu2Cd1−zMnzGeSe4 system, in addition to the tetragonal stannite α and the wurtz-stannite δ phases, MnSe was found to exist in the diagram. The DTA experiments showed that the cooling curves for both systems exhibited effects of undercooling.

Measurements of low field static magnetic susceptibility and of magnetization with pulsed magnetic fields up to 32T have been made as a function of temperature on polycrystalline samples of the compound MnGa2Se4 which has a tetragonal structure. The resulting data have been used to give information on the magnetic spin-flop and magnetic saturation transitions. It has been found that MnGa2Se4 has a zero-field Néel temperature TN of 8.1K and shows a triple point at (7.8K, 2.2T). Details of the magnetic B-T phase diagrams were determined for the phases and the results compared with the predictions of theoretical uniaxial models. The susceptibility χ(T) curves for B=3 and 5T show magnetothermal effects below 4.5K.

tempi di esecuzione (circa una settimana).

LiPA Mycobacteria (Innogenetics) per l'identificazione dei MOTT.

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We report our experience of leprosy surgery in terms of feasibility and efficacy in a small hospital of bush in Madagascar during the period of September 1989 to January 1993. Operations of neurolysis, corrections of claw hands by the techniques of Lasso-Zancolli or Van Droogenbroeck, arthrodesis, resections and amputations have been performed. Our results suggest that at least a part of these surgical procedures may be performed by a non specialized medical team, taught on the premises. Thus, the cost of treatment will be low and accessible to more leprosy patients.

47 cases (14 men and 33 women) of cholelithiasis were described in a southern district of Madagascar. Ultrasonography was used for diagnosis. In most cases, calculi were numerous. In this study, risk factors correlated with cholelithiasis were not found.

Nous rapportons l'observation de 47 sujets (14 hommes et 33 femmes) porteurs de lithiase biliaire, dans une region du Sud de Madagascar. Le diagnostic a ete effectue grâce a l'echographie qui a permis de mettre en evidence le plus souvent des calculs multiples. Il sujets ont subi une intervention chirurgicale. Dans cette etude n'ont pas ete releves des facteurs de risque significatifs correles avec la pathologie lithiasique

"38 observations of reperfusion of ascitic fluid ". In this study, the authors report their experiences of paracentesis associated with the perfusion or the reperfusion of the sick's own ascitic fluid in the treatment of tense ascite determined mostly by Schistosomiasis mansoni.