Significant enhancement of irreversibility field in clean-limit bulk MgB2

Low resistivity ("clean") MgB2 bulk samples annealed in Mg vapor show an increase in upper critical field Hc2(T) and irreversibility field Hirr(T) by a factor of 2 in both transport and magnetic measurements. The best sample displayed Hirr above 14 T at 4.2 K and 6 T at 20 K. These changes were accompanied by an increase of the 40 K resistivity from 1.0 to 18 microohm-cm and a lowering of the resistivity ratio from 15 to 3, while the critical temperature Tc decreased by only 1-2 K. These results point the way to make prepare MgB2 attractive for magnet applications.Comment: 3 pages, 4 figures, submitted to Applied Physics Letter

Six freshwater microturbellarian species (Platyhelminthes) in permanent wetlands of the Coastal plain of southern Brazil: new records, abundance, and distribution

Microturbellarians occur in a wide range of ecosystems, but their diversity and distribution are largely unknown. In this work, we report on the morphology, abundance, and distribution of 6 species of microturbellarians, namely Baicalellia evelinae, Catenula evelinae, C. leuca, C. turgida, Gieysztoria chiqchi, and Stenostomum hemisphericum. We provide photographs and schematic drawings of the specimens in vivo. Three of them were known only for their type localities. Most species showed low to moderate abundance and were found in a single wetland in this study. Gieysztoria chiqchi is reported from Brazil for the first time. All records extend the ranges of the species at least 800 km to the southeast.Facultad de Ciencias Naturales y Muse

Highly effective and isotropic pinning in epitaxial Fe(Se,Te) thin films grown on CaF2 substrates

We report on the isotropic pinning obtained in epitaxial Fe(Se,Te) thin films grown on CaF2 (001) substrate. High critical current density values larger than 1 MA/cm2 in self field in liquid helium are reached together with a very weak dependence on the magnetic field and a complete isotropy. Analysis through Transmission Electron Microscopy evidences the presence of defects looking like lattice disorder at a very small scale, between 5 and 20 nm, which are thought to be responsible for such isotropic behavior in contrast to what observed on SrTiO3, where defects parallel to the c-axis enhance pinning in that directio

The cytotoxic activity of diiron bis-cyclopentadienyl complexes with bridging c3-ligands

Diiron bis-cyclopentadienyl bis-carbonyl cationic complexes with a bridging vinylim-inium ligand, [Fe2Cp2 (CO)(µ-CO){µ-η1:η3-C3 (R′)C2HC1NMe(R′′)}]CF3SO3 (R = Xyl = 2,6-C6H3Me2, R′ = Ph, R′′ = H, 2a; R = Xyl, R′ = R′′ = Me, 2b; R = R′ = Me, R′′ = H, 2c; R = Me, R′ = 2-naphthyl, R′′ = H, 2d; R = Me, R′ = R′′ = Ph, 2e), are easily available from commercial chemicals, robust in aqueous media and exert a variable in vitro cytotoxicity against cancer cell lines depending on the nature of the substituents on the vinyliminium ligand. The anticancer activity is, at least in part, associated to fragmentation reactions, leading to iron oxidation and active neutral and well-defined monoiron species. We report an innovative synthetic procedure for the preparation of 2a,c,d, and a facile method to access the monoiron derivative of 2a, i.e., [FeCp(CO){C1 (NMeXyl)C2HC3 (Ph)C(O)}] (3a). According to IC50 analyses at different times of incubation of the complexes, 3a is significantly faster in inhibiting cell viability compared to its diiron precursor 2a. The neutral complexes [Fe2Cp2 (CO)(µ-CO){µ-k1N:k1C:k1C-C3 (R′)C2 (Se)C1 (NMe2)C4 (CO2Y)C5 (CO2Y)}] (R′ = Y = Me, 4a; R′ = Pr, Y =tBu, 4b; R′ = Y = Et, 4c) are obtained via the two-step modification of the vinyliminium moiety and comprise a bridging selenophene-decorated alkylidene ligand. The antiproliferative activity exhibited by 4a-c is moderate but comparable on the ovarian cancer cell line A2780 and the corresponding cisplatin resistant cell line, A2780cisR. Complexes 4a-c in aqueous solutions undergo progressive release of the alkylidene ligand as a functionalized selenophene, this process being slower in cell culture medium. Since the released selenophenes SeC1 {C(O)R′ }C2 (NMe2)C3 (CO2Y)C4 (CO2Y) (R′ = Y = Me, 5a; R′ = Pr, Y =tBu, 5b) are substantially not cytotoxic, it is presumable that the activity of 4a-c is largely ascribable to the {Fe2Cp2 (CO)2 } scaffold

Magnetic field dependence of vortex activation energy: a comparison between MgB2, NbSe2 and Bi2Sr2Ca2Cu3O10 superconductors

The dissipative mechanism at low current density is compared in three different classes of superconductors. This is achieved by measurement of resistance as a function of temperature and magnetic field in clean polycrystalline samples of NbSe2, MgB2 and Bi2Sr2Ca2Cu3O10 superconductors. Thermally activated flux flow behavior is clearly identified in bulk MgB2. While the activation energy at low fields for MgB2 is comparable to Bi2Sr2Ca2Cu3O10, its field dependence follows a parabolic behavior unlike a power law dependence seen in Bi2Sr2Ca2Cu3O10. We analyze our results based on the Kramer's scaling for grain boundary pinning in MgB2and NbSe2

Genomic predictions for economically important traits in Brazilian Braford and Hereford beef cattle using true and imputed genotypes.

Genomic selection (GS) has played an important role in cattle breeding programs. However, genotyping prices are still a challenge for implementation of GS in beef cattle and there is still a lack of information about the use of low-density Single Nucleotide Polymorphisms (SNP) chip panels for genomic predictions in breeds such as Brazilian Braford and Hereford. Therefore, this study investigated the effect of using imputed genotypes in the accuracy of genomic predictions for twenty economically important traits in Brazilian Braford and Hereford beef cattle. Various scenarios composed by different percentages of animals with imputed genotypes and different sizes of the training population were compared.Article 2

Qualidade de sementes de quatro cultivares se soja, colhidas em dois locais no Estado do Mato Grosso do Sul

O trabalho foi realizado com objetivo de avaliar a qualidade das sementes de quatro cultivares de soja (BRS 133, BRS 206, BRS 239 e CD 202), colhidas em quatro épocas (Estádio R7 e 7, 14 e 21 dias após a primeira época) e produzidas em dois locais do Estado do Mato Grosso do Sul (Sidrolândia e Dourados), nos anos agrícolas de 2004/05 e 2005/06. O delineamento experimental utilizado foi em blocos casualizados com três repetições e tratamentos arranjados no esquema de parcelas subdivididas. As parcelas foram constituídas pelas cultivares de soja e as subparcelas pelas épocas de colheita. A germinação foi avaliada pelo teste de germinação; teste de envelhecimento acelerado e o vigor pelo teste de frio sem solo, teste de emergência das plântulas em substrato de areia e teste de sanidade. Os dados coletados nos diferentes locais foram submetidos à análise de variância conjunta de parcelas subdivididas e, na presença de interação significativa, foram realizados os desdobramentos necessários para os dois anos agrícolas, separadamente. No ano agrícola 2004/05, as cultivares BRS 239 e CD 202 apresentaram-se com elevada porcentagem de germinação para a produção de sementes na região de Dourados. No ano agrícola 2005/06, a cultivar BRS 239 foi a que apresentou melhor germinação e vigor. A cultivar BRS 239 apresenta menor índice de infecção de microrganismos em relação a cultivar BRS 206. Melhor qualidade de sementes é obtida das sementes colhidas aos sete dias após o estádio R7. Em relação à qualidade sanitária das sementes, à medida que se retarda a época de colheita, a porcentagem total de microrganismos aumenta linearmente para todas as cultivares.Disponivel em:.Acesso em : 11 nov. 2010