Large critical current density improvement in Bi-2212 wires through groove-rolling process

Recently the interest about Bi-2212 round wire superconductor for high magnetic field use has been enhancing despite the fact that an increase of the critical current is still needed to boost its successful use in such applications. Recent studies have demonstrated that the main obstacle to current flow, especially in long wires, is the residual porosity inside these Powder-In-Tube processed conductors which develops in bubbles-agglomeration when the Bi-2212 melts. Through this work we tried to overcome this issue acting on the wire densification by changing the deformation process. Here we show the effects of groove-rolling versus drawing process on the critical current density JC and on the microstructure. In particular, groove-rolled multifilamentary wires show a JC increased by a factor of about 3 with respect to drawn wires prepared with the same Bi-2212 powder and architecture. We think that this approach in the deformation process is able to produce the required improvements both because the superconducting properties are enhanced and because it makes the fabrication process faster and cheaper

The influence of twin boundaries on the Flux Line Lattice structure in YBaCuO: a study by Small Angle Neutron Scattering

The influence of Twin Boundaries (TB) on the Flux Line Lattice(FLL) structure was investigated by Small Angle Neutron Scattering (SANS). YBaCuO single crystals possessing different TB densities were studied. The SANS experiments show that the TB strongly modify the structure of the FLL. The flux lines meander as soon as the magnetic field makes an angle with the TB direction. According to the value of this angle but also to the ratio of the flux lines density over the TB density, one observes that the FLL exhibits two different unit cells in the plane perpendicular to the magnetic field. One is the classical hexagonal and anisotropic cell while the other is affected by an additional deformation induced by the TB. We discuss a possible relation between this deformation and the increase of the critical current usually observed in heavily twinned samples.Comment: accepted for publication in Phys Rev

Analysis of Mortality in Africanized Honey Bee Colonies with High Levels of Infestation by Varroa destructor

The mite Varroa destructor (Anderson & Treuman 2000) is one of the world’s most important plagues of apiculture. In Brazil this mite does not encounter good conditions for parasitism because weather conditions are not ideal for its maintenance, and some strains of Africanized honey bees are resistant to the parasite. This status is reflected in the low number of dead colonies caused by varroatosis and also the stability of infestation levels. The aim of this study was to evaluate the damage caused by mite infestations in hives with higher levels of infestation than the ones considered normal for Brazilian apiaries. The level of infestation in each colony was determined and the mortality rates of parasitized bees during development were periodically recorded. The G Test of Independence and a Test of Proportions were used to compare the data. The rates of mortality of pupae and larvae were mostly proportional to the level of infestation in each colony. All colonies showed mortality rates significantly higher than the control one. In Africanized honeybee colonies with high rates of infestation by Varroa destructor mortality rates varied from 19.27% to 23.28% in pupae ( X = 21.27%) and from 15.71% to 16.15% in larvae ( X = 15.93%), against 3.85% and 3.74% in the control colony, respectively. In the parasitized colonies the average rates of mortality caused by the hurtful effects of the mite were, respectively, 5.52 and 4.26 times greater in those two developmental stages. Thus it can be concluded that even in tropical regions, like Brazil, it is necessary to give special attention to the levels of mite infestation (IR), particularly where the IR tends to be higher

Magnetic order in the pseudogap phase of high-TCT_C superconductors

One of the leading issues in high-$T_C$ superconductors is the origin of the pseudogap phase in underdoped cuprates. Using polarized elastic neutron diffraction, we identify a novel magnetic order in the YBa$_2$Cu$_3$O$_{6+x}$ system. The observed magnetic order preserves translational symmetry as proposed for orbital moments in the circulating current theory of the pseudogap state. To date, it is the first direct evidence of an hidden order parameter characterizing the pseudogap phase in high-$T_C$ cuprates.Comment: 3 figure

Dietas para perda de peso anunciadas na imprensa leiga

Weight-loss diets advertised in mainstream non-scientific publications and targeting the adult female public were evaluated in relation to total energy value, macronutrients, calcium, iron, vitamins A and E, and cholesterol content, as well as the presence of information regarding the duration of diets, fluid intake, physical activity, and maintenance diets. Two publications were selected, considering periodicity, circulation, readership, and years in publication. The Virtual Nutri software was used to evaluate the nutrients of 112 diets. Micronutrient content was compared to the Dietary Reference Intakes. All diets were inadequate in at least one of the evaluated items. Less than 25.0% of the diets presented adequate macronutrient distribution. Calcium, iron, and vitamin E were also predominantly inadequate (85.7, 97.3, and 91.9%, respectively). Non-scientific publications should not be allowed to advertise weight-loss diets. In addition, their chemical composition is inadequate and they are not accompanied by important instructions for such therapy.Diversas dietas para redução de peso, anunciadas em periódicos não-científicos de grande circulação, foram avaliadas em relação ao teor energético e de macronutrientes, cálcio, ferro, vitaminas A e E, colesterol e presença de informações sobre a duração da dieta, ingestão de fluidos, atividade física e dieta de manutenção. Duas publicações foram selecionadas em função da periodicidade, tiragem, número de leitores e anos de publicação. Foi utilizado o programa Virtual Nutri para medir os nutrientes de 112 dietas. Os teores de micronutrientes foram comparados com as Dietary Reference Intakes. Todas as dietas eram inadequadas em relação a uma ou mais substâncias avaliadas. Menos de 25,0% das dietas apresentaram distribuição adequada de macronutrientes. Predominavam os níveis inadequados de cálcio, ferro e vitamina E (85,7, 97,3, e 91,9%, respectivamente). Não deveria ser permitido que publicações não-científicas anunciassem dietas para perda de peso que não apresentassem também uma composição química adequada.Universidade Federal de São Paulo (UNIFESP) Escola Paulista de MedicinaUNIFESP, EPMSciEL

Pulsed-field magnetization of drilled bulk high-temperature superconductors: flux front propagation in the volume and on the surface

We present a method for characterizing the propagation of the magnetic flux in an artificially drilled bulk high-temperature superconductor (HTS) during a pulsed-field magnetization. As the magnetic pulse penetrates the cylindrical sample, the magnetic flux density is measured simultaneously in 16 holes by means of microcoils that are placed across the median plane, i.e. at an equal distance from the top and bottom surfaces, and close to the surface of the sample. We discuss the time evolution of the magnetic flux density in the holes during a pulse and measure the time taken by the external magnetic flux to reach each hole. Our data show that the flux front moves faster in the median plane than on the surface when penetrating the sample edge; it then proceeds faster along the surface than in the bulk as it penetrates the sample further. Once the pulse is over, the trapped flux density inside the central hole is found to be about twice as large in the median plane than on the surface. This ratio is confirmed by modelling

La dieta y el déficit alimenticio en periodos de lactancia

ARTÍCULO DE DIVULGACIÓN PUBLICADO EN SITIO EXTERNO. VERSIÓN FINAL DEL AUTOR. Un equipo de investigación de Mendoza propone la aproximación Una de las investigaciones llevadas a cabo en conjunto por integrantes de la Universidad Maza (Mendoza) y el Banco de Leche Humana (BLH) del Hospital Lagomaggiore de dicha provincia descubrió que muchas mujeres presentan excesos y déficit en la ingesta de micro y macronutrientes, lo que afecta a la calidad de la leche que reciben los bebés. El artículo fue publicado por el portal Argentina Investiga: http://argentinainvestiga.edu.ar/noticia.php?titulo=la_dieta_y__el_deficit_alimenticio_en_periodos_de_lactancia&id=281

Secretos del añejamiento

ARTÍCULO DE DIVULGACIÓN PUBLICADO EN SITIO EXTERNO. VERSIÓN FINAL DEL AUTOR. Una investigación analizó cómo varía la influencia del oxígeno en la etapa de crianza del vino según el tipo de recipiente utilizado. El artículo fue publicado por el portal Argentina Investiga: http://argentinainvestiga.edu.ar/noticia.php?titulo=secretos_del_anejamiento&id=338