The Critical Behaviour of the Spin-3/2 Blume-Capel Model in Two Dimensions

The phase diagram of the spin-3/2 Blume-Capel model in two dimensions is explored by conventional finite-size scaling, conformal invariance and Monte Carlo simulations. The model in its $\tau$-continuum Hamiltonian version is also considered and compared with others spin-3/2 quantum chains. Our results indicate that differently from the standard spin-1 Blume-Capel model there is no multicritical point along the order-disorder transition line. This is in qualitative agreement with mean field prediction but in disagreement with previous approximate renormalization group calculations. We also presented new results for the spin-1 Blume-Capel model.Comment: latex 18 pages, 4 figure

Relations de phases et cristallogenèse de phases de Chevrel séliniées TRMo6Se8\mathsf{TRMo_{6}Se_{8}} (TR = Terre rare) : premiers résultats sur monocristal

An approach to grow single crystals of chosen RE-Mo-Se Chevrel phase materials from a liquid phase was done. To reduce the effects of compositional shifts due to incongruent melting (at 1 650-1 750 $^{\circ}$C), off-stoichiometric selenium-rich compositions were used. Prior to this, a detailed study of phase relations at 1 200 $^{\circ}$C was done and extended to 1 700 $^{\circ}$C. First preliminary magnetic and superconducting measurements were done on crystals containing RE = Gd, Ho, Er and Yb.La cristallogenèse de phases de Chevrel séléniés à base de terres rares (TRMo$_{6}$Se$_{8}$) a été réalisée avec succès pour TR = Gd, Ho, Er et Yb. La technique consiste en la fusion (non congruente) des compositions riches en terres rares et en sélénium, dans des nacelles hermétiques, à 1 650-1 750 $^{\circ}$C. Une étude des relations de phases à 1 200 $^{\circ}$C et son extension à 1 700 $^{\circ}$C ont dû être préalablement effectuées. Les mesures préliminaires de propriétés magnétiques et supraconductrices de ces cristaux ont été effectuées

Characterization of Citrus tristeza virus isolates from grapefruit (Citrus paradisi Macf.) accessions of Citrus Active Germplasm Bank Caracterização de isolados do vírus da tristeza dos citros de acessos de pomelos (Citrus paradisi Macf.) do Banco Ativo de Germoplasma de Citros

Citrus tristeza virus (CTV) isolates from 35 grapefruit accessions belonging to Citrus Active Germplasm Bank of the "Instituto Agronômico de Campinas" located at the "Centro APTA Citros Sylvio Moreira", Cordeirópolis, São Paulo state, Brazil, were characterized and evaluated through symptoms in the trees, biological indexing, immunological diagnosis with different monoclonal antibodies and SSCP analysis (single-strand conformation polymorphism) of the coat protein gene. Symptomatology indicated that, in general, the group of plants with smaller canopy volume and severe stem pitting differed significantly from the group that presented greater vegetative development and mild to moderate stem pitting. However, the isolates from most of the accessions induced mild reaction on Mexican lime. The serological evaluation through the DAS-ELISA using monoclonal antibodies did not reveal any association between virus titer in the plant tissue and symptoms. The reaction with different monoclonal antibodies and the distinct electrophoresis patterns obtained through SSCP showed that there is a high degree of diversity among the isolates that infect these grapefruit accessions. High complexity within the same isolate was also observed in the SSCP profiles. This finding indicates that the CTV isolates from these plants are a complex mixture of CTV haplotypes. Similar SSCP banding patterns were observed among some plants with strong stem pitting symptoms, and among some plants with weak or moderate stem pitting symptoms.<br>Isolados do vírus da tristeza dos citros (CTV) de 35 acessos de pomelos que fazem parte do Banco Ativo de Germoplasma de Citros, localizado no Centro APTA Citros Sylvio Moreira, Cordeirópolis, São Paulo, Brasil, pertencente ao Instituto Agronômico de Campinas (IAC), foram caracterizados através dos sintomas observados nas árvores, indexação biológica, diagnóstico imunológico e análise SSCP (polimorfismo de conformação de fita simples) do gene da proteína do capsídeo. O grupo de plantas que, em geral, apresentou menor volume de copa e severo sintoma de canelura diferenciou-se significativamente do grupo com maior desenvolvimento vegetativo e fraco a moderado sintoma de canelura. No entanto, a maioria dos isolados de CTV das plantas de ambos os grupos induziu fraca reação em limão galego e nenhuma relação entre títulos do vírus nos tecidos e sintomatologia foi observada na avaliação sorológica conduzida por DAS-ELISA. A reação com diferentes anticorpos monoclonais e os distintos padrões eletroforéticos obtidos por SSCP demonstraram que há uma grande diversidade entre os isolados de CTV que infectam os acessos de pomelos. Alta complexidade de bandas dentro de um mesmo isolado foi também observada nos perfis SSCP, demonstrando que cada isolado é constituído por uma mistura de diferentes haplótipos de CTV. Padrões SSCP semelhantes foram observados entre algumas plantas com fortes sintomas de caneluras e entre algumas plantas com sintomas fracos ou moderados de caneluras

Biodegradation of blend films PVA/PVC, PVA/PCL in soil and soil with landfill leachate

This study investigated the biodegradation of blends films of poly(vinyl alcohol)/poly(vinyl chloride) (PVA/PVC) and poly(vinyl alcohol)/poly(caprolactone) (PVA/PCL) blends films prepared with dimethylformamide under a variety of conditions by respirometry, spectrophotometry (FTIR), scanning electron microscopy (SEM), and contact angle. The films were buried in the garden soil and in the soil mixed with the landfill leachate for 120 days at 28ºC. Significant levels of biodegradation were achieved in fairly short incubation times in the soil. The results indicated that PVA was the most biodegradable film in the soil and in the soil with the leachate

Chevrel Phases: Genesis and Developments

International audienceThis chapter summarizes the important role played by Marcel Sergent in the discovery in the Rennes Laboratory of the Chevrel Phases, which stimulated considerable interest in the international solid-state chemistry community, because of their remarkable superconducting properties. After a brief general introduction to this topic, the seminal discoveries associated with these phases between 1970 and 1990 are described. After that their initial synthesis and structural determination was discovered, it was necessary to establish their critical superconducting transition temperature, the critical magnetic field, and the critical current density in wires, single crystals, and thin films. More recently their applications as battery materials, in catalysis, and their thermoelectric properties have been studied and are briefly described. These phases opened up the way not only to a rich solid-state chemistry but also to a rich solution chemistry, which complemented the classical field of transition metal carbonyl clusters. The basic cluster units of the Chevrel Phases continue to be studied in the Rennes Laboratory by the heirs of Marcel Sergent and more widely in the international community