Physics of Polymorphic Transitions in CeRuSn

We report a detailed study of the polymorphic transitions in ternary stannide CeRuSn on high quality single crystals through a combination of X-ray diffraction experiments conducted at 300, 275 and 120 K, and measurements of the thermal expansion, magnetization, and resistivity, along main crystallographic axes. In addition, the transition was followed as a function of pressure up to 0.8 GPa. The present X-ray diffraction data show that the room temperature polymorph consists of the lattice doubled along the c axis with respect to the CeCoAl-type structure consistent with previous reports. Upon cooling, the compound undergoes two successive transitions, first to a quintuple (290 K) and than to a triple CeCoAl superstructure at 225 K. The transitions are accompanied by a tremendous volume change due to a strong shrinking of the lattice along the c axis, which is clearly observed in thermal expansion. We advance arguments that the volume collapse originates from an increasing number of crystallographically inequivalent Ce sites and the change of ratio between the short and long Ce-Ru bonds. The observed properties of the polymorphic transition in CeRuSn are reminiscent of the transition in elementary Cerium, suggesting that similar physics, i.e., a Kondo influenced transition and strong lattice vibrations might be the driving forces

Specific heat measurements and structural investigation of CeCu6 - xSnx compounds

International audienceThe evolution of the crystal structure and some magnetic properties of the heavy-fermion material CeCu6 - xSnx (x = 0, 0.25, 0.65, 0.75, 0.85 and 1.0) has been studied by powder neutron diffraction and by specific heat measurements. The substitution of Cu by Sn suppresses the temperature induced orthorhombic to monoclinic transition, known to occur in the pure CeCu6 phase. No structural phase transition has been observed in these samples as a function of x but the cell volume increases considerably in an anisotropic way. Sn occupies preferentially the special Cu crystallographic site which is next to each of the four Ce atoms in the unit cell. The transition to antiferromagnetic order, characterizing the samples with higher x, is sensitive to both x and magnetic field. The results are discussed in the context of the competition between Kondo and RKKY interactions in disordered or not heavy-fermion systems and reveal an interesting interplay between composition, structure and magnetism in CeCu6 - xSnx

Fibrinogen Birmingham: A Heterozygous Dysfibrinogenemia (Aα 16 Arg → His) Containing Heterodimeric Molecules

Fibrinogen was isolated from the plasma of a 25-year-old female with a history of mild bleeding and several recent moderate to severe hemorrhagic episodes. Coagulability with thrombin approached 100% and varied directly with the time of incubation with the enzyme. High- performance liquid chromatography analysis of thrombin-induced fibrinopeptide release demonstrated retarded fibrinopeptide A (FPA) and fibrinopeptide B (FPB) release and the presence of an abnormal A peptide (FPA) amounting to 50% of the total. The same biochemical abnormalities were found in her asymptomatic father. Amino acid analysis and carboxypeptidase digestion of FPA demonstrated the substitution of His for Arg at A alpha 16. In contrast to the thrombin- and reptilase-sensitive Arg-Gly bond in the normal A alpha chain, the abnormal A alpha chain (A alpha) sequence is resistant to reptilase attack but is slowly cleaved by thrombin. To evaluate whether Birmingham A alpha and A alpha chains had been assembled nonselectively into heterodimeric (ie, 50% A alpha, A alpha) and homodimeric (ie, 25% A alpha, A alpha; 25% A alpha, A alpha) species, the clot and the clot liquor resulting from reptilase treatment of normal or Birmingham fibrinogen were separated, and each was then further incubated with thrombin to release remaining fibrinopeptides. Assuming that fibrinogen Birmingham contained heterodimeric molecules and that these and the normal molecules were completely incorporated into a reptilase clot, the expected coagulability would be 75%. In addition, subsequent thrombin treatment of the reptilase clot would release 50% of the total FPA and 75% of the total FPB present in the original sample. On the other hand, if only homodimeric fibrinogen species (50% A alpha, A alpha; 50% A alpha, A alpha) existed, the maximum reptilase coagulability would be 50%, and after thrombin treatment, 50% of the total FPB and no FPA would be recovered from the reptilase clot. We found the propositus\u27s fibrinogen to be 68% coagulable, and we recovered 45% of the FPA and 70% of the FPB from the reptilase clot. Essentially the same coagulability and distribution of fibrinopeptides was found in the reptilase clot from her father\u27s fibrinogen. We therefore conclude that fibrinogen Birmingham contains heterodimeric species (A alpha, A alpha) amounting to approximately 50% of the circulating fibrinogen molecules. The existence of heterodimers is consistent with a nonselective intracellular process of constituent chain assembly of dimeric plasma fibrinogen molecules

MODELO EXPERIMENTAL DE GLOMERULONEFRITIS MEMBRANOSA INDUCIDA CON ALBUMINA BOVINA

El objetivo del presente trabajo fue diseñar un modelo experimental de Glomerulonefritis Membranosa (GM) en ratas Wistar, inducida con Seroalbúmina Bovina (BSA), y validarlo mediante la determinación de parámetros bioquímicos, histológicos, ultraestructurales y detección de inmunocomplejos por inmunofluorescencia (IF). Los animales del grupo experimental fueron inmunizados por vía subcutánea, con dosis de 3 mg c/u de BSA/PBS con adyuvante de Freund. Se efectuaron diferentes esquemas de inmunización. Cuando el título de anticuerpos fue ≥1/2, comenzó la administración diaria de 2 mg, por vía endovenosa de BSA/PBS, durante 15 días. Se evaluó la funcionalidad renal por la proteinuria; después de la 5° semana, desde su aparición, se determinó: depuración (clearance) de creatinina, uremia, proteinemia y perfil lipídico. Los dos riñones se usaron para estudios histológicos, ultraestructurales y detección de inmunocomplejos por IF. Los resultados mostraron que la inmunización fue efectiva con 5 R E S U M E N inoculaciones c/15 días. En los animales nefróticos la proteinuria, depuración (clearance) de creatinina, proteinemia , uremia y el perfil lipídico presentaron alteraciones significativas (p<0.0001). Al microscopio óptico se observó hipercelularidad, engrosamiento difuso de las membranas basales de los capilares glomerulares y diferentes grados de atrofia, esclerosis e hialinización de los glomérulos. Por IF se detectó inmunocomplejos IgG en el 100 % de los glomérulos. Ultraestructuralmente, se observaron depósitos subepiteliales electrodensos en la membrana basal engrosada, compatibles con inmunocomplejos . Se encontraron alteraciones en la estructura de los podocitos. En conclusión, los estudios bioquímicos, estructurales y ultraestructurales permitieron inferir la inducción de un síndrome nefrótico experimental. Concluimos que el protocolo utilizado tiene validez para la inducción de una glomerulonefritis membranosa en ratas Wistar

Pressure-induced huge increase of Curie temperature of the van der Waals ferromagnet VI3

Evolution of magnetism in single crystals of the van der Waals compound VI3 in external pressure up to 7.3 GPa studied by measuring magnetization and ac magnetic susceptibility is reported. Four magnetic phase transitions, at T1 = 54.5 K, T2 = 53 K, TC = 49.5 K, and TFM = 26 K, respectively have been observed at ambient pressure. The first two have been attributed to the onset of ferromagnetism in specific crystal-surface layers. The bulk ferromagnetism is characterized by the magnetic ordering transition at Curie temperature TC and the transition between two different ferromagnetic phases TFM, accompanied by a structure transition from monoclinic to triclinic symmetry upon cooling. The pressure effects on magnetic parameters were studied with three independent techniques. TC was found to be almost unaffected by pressures up to 0.6 GPa whereas TFM increases rapidly with increasing pressure and reaches TC at a triple point at ~ 0.85 GPa. At higher pressures, only one magnetic phase transition is observed moving to higher temperatures with increasing pressure to reach 99 K at 7.3 GPa. In contrast, the low-temperature bulk magnetization is dramatically reduced by applying pressure (by more than 50% at 2.5 GPa) suggesting a possible pressure-induced reduction of vanadium magnetic moment. We discussed these results in light of recent theoretical studies to analyze exchange interactions and provide how to increase the Curie temperature of VI3.Comment: 20 pages, 16 figure

Multiple functional regression with both discrete and continuous covariates

International audienceIn this paper we present a nonparametric method for extending functional regression methodology to the situation where more than one functional covariate is used to predict a functional response. Borrowing the idea from Kadri et al. (2010a), the method, which support mixed discrete and continuous explanatory variables, is based on estimating a function-valued function in reproducing kernel Hilbert spaces by virtue of positive operator-valued kernels

Association of G6PD 202A,376G with lower haemoglobin concentration but not increased haemolysis in patients with sickle cell anaemia

The genetic bases of the highly variable degrees of anaemia and haemolysis in persons with Hb SS are not fully known, but several studies have indicated that G6PD deficiency is not a factor. The G6PD 202A and G6PD 376G alleles and α-thalassaemia were determined by molecular genetic testing in 261 children and adolescents with Hb SS in a multicentre study. G6PD 202A,376G (G6PD A−) was defined as hemizygosity for both alleles in males and homozygosity in females. Among the participants 41% were receiving hydroxycarbamide. The prevalence of G6PD 202A,376G was 13·6% in males and 3·3% in females with an overall prevalence of 8·7%. G6PD 202A,376G was associated with a 10 g/l decrease in haemoglobin concentration ( P  = 0·008) but not with increased haemolysis as measured by lactate dehydrogenase, bilirubin, aspartate-aminotransferase, reticulocyte count or a haemolytic component derived from these markers ( P  > 0·09). Similar results were found within a sub-group of children who were not receiving hydroxycarbamide. By comparison, single and double α-globin deletions were associated with progressively higher haemoglobin concentrations ( P  = 0·005 for trend), progressively lower values for haemolytic component ( P  = 0·007), and increased severe pain episodes ( P  < 0·001). In conclusion, G6PD 202A,376G may be associated with lower haemoglobin concentration in sickle cell anaemia by a mechanism other than increased haemolysis.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/79250/1/j.1365-2141.2010.08215.x.pd