Effect of Sr substitution on superconductivity in Hg2(Ba1-ySry)2YCu2O8-d (part2): bond valence sum approach of the hole distribution

The effects of Sr substitution on superconductivity, and more particulary the changes induced in the hole doping mechanism, were investigated in Hg2(Ba1-ySry)2YCu2O8-d by a "bond valence sum" analysis with Sr content from y = 0.0 to y = 1.0. A comparison with CuBa2YCu2O7-d and Cu2Ba2YCu2O8 systems suggests a possible explanation of the Tc enhancement from 0 K for y = 0.0 to 42 K for y = 1.0. The charge distribution among atoms of the unit cell was determined from the refined structure, for y = 0.0 to 1.0. It shows a charge transfer to the superconducting CuO2 plane via two doping channels pi(1) and pi(2), i.e. through O2(apical)-Cu and Ba/Sr-O1 bonds respectively.Comment: 13 pages, 5 figures, accepted for publication in Journal of Physics: Condensed Matte

Absence of a structural transition up to 40 Gpa in MgB2 and the relevance of magnesium non-stoichiometry

We report measurements on MgB2 up to ~40GPa. Increasing pressure yields a monotonous decrease of the lattice parameters and of the c/a ratio, but no structural transition down to parameters smaller than those of AlB2. The transition superconducting temperature also decreases with temperature in a sample dependent way. The results are explained by an increase of the filling of the 2D pxy bands with pressure, the Mg stoichiometry determining the starting position of the Fermi level. Our measurements indicate that these hole bands are the relevant ones for superconductivity.Comment: submitted March 9th 2001, PRB accepte

ARPES Study of the Metal-Insulator Transition in Bismuth Cobaltates

We present an angle-resolved photoemission spectroscopy (ARPES) study of a Mott-Hubbard-type bismuth cobaltate system across a metal-insulator transition. By varying the amount of Pb substitution, and by doping with Sr or Ba cation, a range of insulating to metallic properties is obtained. We observe a systematic change in the spectral weight of the coherent and incoherent parts, accompanied by an energy shift of the incoherent part. The band dispersion also shows the emergence of a weakly dispersing state at the Fermi energy with increasing conductivity. These changes correspond with the changes in the temperature-dependent resistivity behavior. We address the nature of the coherent-incoherent parts in relation to the peak-dip-hump feature seen in cuprates superconductors

Expression analyses of candidate resistance genes in the Rpp4 Asian Soybean Rust resistance locus.

Asian Soybean Rust (ASR), caused Phakopsora pachyrhizi, is considered the most severe soybean disease around the world. Infection of susceptible genotypes leads to early defoliation, incomplete seed development, and yield losses as high as 80%. Five ASR resistance genes have been identified in soybean: Rpp1, Rpp2, Rpp3, Rpp4 and Rpp5. Of particular interest is Rpp4, which has remained stable and confers resistance against P. pachyrhizi isolates from around the world. Rpp4 was mapped to soybean linkage group G (chromosome 18), 1.9 cM from simple sequence repeat (SSR) marker Satt288. Sequencing of this region in the susceptible genotype Williams 82 identified a cluster of three CC-NBS-LRR resistance genes. Virus Induced Gene Silencing was used to demonstrate that orthologous genes were responsible for resistance. We have now sequenced a >460 kb region of the Rpp4 locus in the resistant mapping parent PI459025B. Eight CC-NBS-LRR resistance genes have been identified in this region. In order to obtain more information about Rpp4 function, we are using real time quantitative PCR (qRT-PCR) to analyze the expression of all eight genes in different plant tissues, in different stages of development and after inoculation with P. pachyrhizi. We have developed a single pair of primers from the NBD domain that monitors the expression of all eight genes. Direct sequencing of the RT-PCR product differentiates between the eight genes. Detailed sequence analyses of the Rpp4 locus suggest that intra- and intergenic duplications and recombination have played an important role in creating genetic diversity. Alternative splicing of intragenic duplications may create additional sequence diversity at an RNA level. We are developing primers that will allow us to monitor alternative splicing events. Sequencing of the RT-PCR products will determine if alternative splicing plays a role in generating additional sequence diversity at the Rpp4 locus.Edição de Poster da 11. Annual National Outreach Scholarship Conference, Raleigh

Central factorials under the Kontorovich-Lebedev transform of polynomials

We show that slight modifications of the Kontorovich-Lebedev transform lead to an automorphism of the vector space of polynomials. This circumstance along with the Mellin transformation property of the modified Bessel functions perform the passage of monomials to central factorial polynomials. A special attention is driven to the polynomial sequences whose KL-transform is the canonical sequence, which will be fully characterized. Finally, new identities between the central factorials and the Euler polynomials are found.Comment: also available at http://cmup.fc.up.pt/cmup/ since the 2nd August 201

Cultivares melhoradas de feijão (Phaseolus vulgaris L.) avaliadas a nível de propriedades agrícolas.

Como etapa inicial no processo de adocao de uma cultivar pelos agricultores, ha necessidade de que ela mantenha nas propriedades agricola o seu bom desempenho obtido nas estacoes experimentais. Visando a comprovar esse fato, varias cultivares foram avaliadas simultaneamente na estacao experimental do Centro Nacional de Pesquisa de Milho e Sorgo e em algumas propriedades do estado de Minas Gerais. Ao todo foram conduzidos 13 ensaios na safra "outubro-inverno", dos anos agricolas de 1988 e 1990 e na "seca" do ano de 1990. Constatou-se que as cultivares apresentaram diferencas em produtividade e que o comportamento dessas cultivares nao foi coincidente nos diferentes locais. Esse ultimo fato contribuiu para que a correlacao classificatoria de Spearman fosse de pequena magnitude. Isso evidencia que ha necessidade das cultivares serem avaliadas nas propriedades agricolas antes de sua recomendacao aos agricultores. Verificou-se, tambem, que algumas cultivares apresentaram, na media de todos os experimentos, produtividade superior a da cultivar Carioca, entre elas a 'Jalo', ESAL 506'. 'Rio Vermelho' e 'ESAL -512'

The Portuguese Severe Asthma Registry: Development, Features, and Data Sharing Policies

The Portuguese Severe Asthma Registry (Registo de Asma Grave Portugal, RAG) was developed by an open collaborative network of asthma specialists. RAG collects data from adults and pediatric severe asthma patients that despite treatment optimization and adequate management of comorbidities require step 4/5 treatment according to GINA recommendations. In this paper, we describe the development and implementation of RAG, its features, and data sharing policies. The contents and structure of RAG were defined in a multistep consensus process. A pilot version was pretested and iteratively improved. The selection of data elements for RAG considered other severe asthma registries, aiming at characterizing the patient's clinical status whilst avoiding overloading the standard workflow of the clinical appointment. Features of RAG include automatic assessment of eligibility, easy data input, and exportable data in natural language that can be pasted directly in patients' electronic health record and security features to enable data sharing (among researchers and with other international databases) without compromising patients' confidentiality. RAG is a national web-based disease registry of severe asthma patients, available at asmagrave.pt. It allows prospective clinical data collection, promotes standardized care and collaborative clinical research, and may contribute to inform evidence-based healthcare policies for severe asthma.info:eu-repo/semantics/publishedVersio