Anisotropic superconducting properties of aligned MgB2 crystallites

Samples of aligned MgB2 crystallites have been prepared, allowing for the first time the direct identification of an upper critical field anisotropy Hc2^{ab}/Hc2^{c}= xi_{ab}/xi_{c} ~ 1.73; with xi_{o,ab} ~ 70 A, xi_{o,c} ~ 40 A, and a mass anisotropy ratio m_{ab}/m_{c} ~ 0.3. A ferromagnetic background signal was identified, possibly related to the raw materials purity.Comment: 4 pages, 4 figures; Revised version to appear in Phys. Rev. Let

Magnetic reconfiguration of MnAs/GaAs(001) observed by Magnetic Force Microscopy and Resonant Soft X-ray Scattering

We investigated the thermal evolution of the magnetic properties of MnAs epitaxial films grown on GaAs(001) during the coexistence of hexagonal/orthorhombic phases using polarized resonant (magnetic) soft X-ray scattering and magnetic force microscopy. The results of the diffuse satellite X-ray peaks were compared to those obtained by magnetic force microscopy and suggest a reorientation of ferromagnetic terraces as temperature rises. By measuring hysteresis loops at these peaks we show that this reorientation is common to all ferromagnetic terraces. The reorientation is explained by a simple model based on the shape anisotropy energy. Demagnetizing factors were calculated for different configurations suggested by the magnetic images. We noted that the magnetic moments flip from an in-plane mono-domain orientation at lower temperatures to a three-domain out-of-plane configuration at higher temperatures. The transition was observed when the ferromagnetic stripe width L is equal to 2.9 times the film thickness d. This is in good agreement with the expected theoretical value of L = 2.6d.Comment: 16 pages in PD

(1S,2R,6R,7aS)-1,2,6-Trihy­droxy­hexa­hydro-1H-pyrrolizin-3-one

In the title compound, C7H11NO4, prepared via a Morita–Baylis–Hillman adduct, the five-membered ring bearing three O atoms approximates to a twisted conformation, whereas the other ring is close to an envelope, with a C atom in the flap position. The dihedral angle between their mean planes (all atoms) is 23.11 (9)°. The new stereocenters are created in a trans-diaxial configuration. In the crystal, O—H⋯O and O—H⋯(O,O) hydrogen bonds link the mol­ecules, generating a three-dimensional network. A weak C—H⋯O inter­action also occurs

(1S,2S,6R,7aR)-2-Benzyl-1,6-dihy­droxy­hexa­hydro­pyrrolizin-3-one

In the title compound, C14H17NO3, the dihedral angles show that the H atoms at two stereocenters are in a trans-diaxial configuration. In the crystal, the molecules are linked by O—H⋯O hydrogen bonds. The absolute configuration of the molecule has been established on the basis of refinement of the Hooft and Flack parameters

Levantamento pedológico semidetalhado (1:25.000) da microbacia da Água Três Unidos, Município de Vera Cruz (SP).

Este trabalho é um relato dos solos identificados no levantamento pedológico semidetalhado da microbacia da Água Três Unidos. Abrangendo aproximadamente 1.624 hectares, a microbacia situa-se no município de Vera Cruz, localizada a oeste do Estado de São Paulo, entre as coordenadas geográficas 22º13? e 22º17? de latitude sul e 49º49? e 49º52? de longitude oeste. Está inserida no compartimento geomorfológico do Planalto Ocidental Paulista e, geologicamente, é caracterizada pelos arenitos cretácicos do Grupo Bauru, Formações Marília e Adamantina. O relevo varia de plano, nos topos e planícies aluviais, a montanhoso e escarpado, nas escarpas areníticas, predominando os relevos suave ondulado sob domínio dos solos latossolizados e ondulado nas áreas de ocorrência dos Podzólicos abruptos. O tipo climático predominante é Cwa, segundo a classificação de Köppen, com temperatura média anual de 21,4 ºC e pluviosidade média anual próxima a 1.500 mm. A cultura do café está entre as de maior importância nos relevos plano e suave ondulado sob domínio dos solos latossolizados, enquanto as pastagens estendem-se em grandes áreas dominadas com os Podzólicos abruptos eutróficos e álicos. Foram identificadas e cartografadas 9 unidades de solos na microbacia da Água Três Unidos, as quais apresentam uma estreita relação com o relevo. Assim, duas toposseqüências são predominantes na região. A primeira, caracteriza-se pela presença dos Latossolos Vermelho-Amarelos ou Vermelho-Escuros álicos ou distróficos nos topos aplainados, transicionando-se para os Podzólicos abruptos e Podzólicos latossólicos com o aumento da declividade, nas posições de ombro e terço superior das vertentes. Enquanto os abruptos podem ser álicos, distróficos e, predominantemente eutróficos, os Podzólicos latossólicos são essencialmente álicos ou distróficos, de textura binária arenosa/média, mais friáveis e de menor gradiente textural em relação aos Podzólicos abruptos. Sucedendo aos solos com B textural na toposseqüência, são encontrados solos poucos desenvolvidos (Solos Litólicos, Regossolos e Podzólicos abruptos rasos) nas proximidades das escarpas areníticas em relevo, predominantemente, ondulado e forte ondulado. Abaixo da escarpa, os Podzólicos abruptos são dominantes, predominantemente eutróficos, de textura binária arenosa/média e com características semelhantes àqueles localizados a montante da mesma, enquanto nas planícies aluviais predominam os solos hidromórficos (Gleissolos) e os aluviais em menores proporções. A segunda toposseqüência difere da anterior pela predominância dos Podzólicos Vermelho-Amarelos latossólicos nos topos, geralmente, mais estreitos e declivosos em relação aos locais de ocorrência de Latossolos.bitstream/CNPS/11839/1/bp12002lvtomicrobacia.pd

Gene identification for the cblD defect of vitamin B12 metabolism

Background Vitamin B12 (cobalamin) is an essential cofactor in several metabolic pathways. Intracellular conversion of cobalamin to its two coenzymes, adenosylcobalamin in mitochondria and methylcobalamin in the cytoplasm, is necessary for the homeostasis of methylmalonic acid and homocysteine. Nine defects of intracellular cobalamin metabolism have been defined by means of somatic complementation analysis. One of these defects, the cblD defect, can cause isolated methylmalonic aciduria, isolated homocystinuria, or both. Affected persons present with multisystem clinical abnormalities, including developmental, hematologic, neurologic, and metabolic findings. The gene responsible for the cblD defect has not been identified. Methods We studied seven patients with the cblD defect, and skin fibroblasts from each were investigated in cell culture. Microcell-mediated chromosome transfer and refined genetic mapping were used to localize the responsible gene. This gene was transfected into cblD fibroblasts to test for the rescue of adenosylcobalamin and methylcobalamin synthesis. Results The cblD gene was localized to human chromosome 2q23.2, and a candidate gene, designated MMADHC (methylmalonic aciduria, cblD type, and homocystinuria), was identified in this region. Transfection of wild-type MMADHC rescued the cellular phenotype, and the functional importance of mutant alleles was shown by means of transfection with mutant constructs. The predicted MMADHC protein has sequence homology with a bacterial ATP-binding cassette transporter and contains a putative cobalamin binding motif and a putative mitochondrial targeting sequence. Conclusions Mutations in a gene we designated MMADHC are responsible for the cblD defect in vitamin B12 metabolism. Various mutations are associated with each of the three biochemical phenotypes of the disorder