Exchange bias and interface electronic structure in Ni/Co3O4(011)

A detailed study of the exchange bias effect and the interfacial electronic structure in Ni/Co3O4(011) is reported. Large exchange anisotropies are observed at low temperatures, and the exchange bias effect persists to temperatures well above the Neel temperature of bulk Co3O4, of about 40 K: to ~80 K for Ni films deposited on well ordered oxide surfaces, and ~150 K for Ni films deposited on rougher Co3O4 surfaces. Photoelectron spectroscopy measurements as a function of Ni thickness show that Co reduction and Ni oxidation occur over an extended interfacial region. We conclude that the exchange bias observed in Ni/Co3O4, and in similar ferromagnetic metallic/Co3O4 systems, is not intrinsic to Co3O4 but rather due to the formation of CoO at the interface.Comment: 8 pages, 6 figures. Accepted for publication in Physical Review B

Autonomy as a Central Category in the Concept of Health Promotion

Objectives: To describe the central concepts of health promotion in primary care in Brazil, through a review of case studies

Building blocks of a black hole

What is the nature of the energy spectrum of a black hole ? The algebraic approach to black hole quantization requires the horizon area eigenvalues to be equally spaced. As stressed long ago by by Mukhanov, such eigenvalues must be exponentially degenerate with respect to the area quantum number if one is to understand black hole entropy as reflecting degeneracy of the observable states. Here we construct the black hole states by means of a pair of "creation operators" subject to a particular simple algebra, a slight generalization of that for the harmonic oscillator. We then prove rigorously that the n-th area eigenvalue is exactly 2 raised to the n-fold degenerate. Thus black hole entropy qua logarithm of the number of states for fixed horizon area comes out proportional to that area.Comment: PhysRevTeX, 14 page

Embrapa Instrumentação Agropecuária - 21 anos de contribuições para o agronegócio.

bitstream/CNPDIA/10485/1/DOC20_2005_Livro.pd

The early days of pandemic (H1N1) 2009 virus infection in the central region of Portugal

BACKGROUND: The first case of pandemic (H1N1) 2009 virus infection was diagnosed in the central region of Portugal on June 16, 2009, in a woman infected in Canada. METHODS: The aim of our study was, first to characterize the clinical and epidemiologic aspects of all the patients with clinical manifestations included in the definition of case for investigation with samples submitted to diagnosis of the pandemic (H1N1) 2009 virus infection, in the central region of Portugal; second to assess the precision of the case definition of case for investigation considered in the study according to the presence or the absence of fever at the moment of clinical observation. We reviewed the medical records of all the patients presenting with Influenza like-illness classified as case for investigation and the first cases of patients infected with the new pandemic (H1N1) 2009 virus, diagnosed in the central region of Portugal during the pandemic period between June and August, 2009, were analyzed. Real-time reverse-transcriptase polymerase-chain-reaction (RT-PCR) testing was used to confirm the pandemic (H1N1) 2009 virus infection. Data collection was performed on a standardized paper format in agreement with the General Health Directorate. Results and discussion: Pandemic (H1N1) 2009 virus infection was confirmed in 255 patients. Overall, median age was 23 years and 42.7 % were included in the category of 20 to 29 years. Confirmed infection in patients with less than 2 years or greater than 50 years was a rare event. The first cases were imported from Europe, namely France, Spain and England. On a second phase, pandemic (H1N1) 2009 virus infection was acquired in the south of Portugal (Algarve), before de diagnosis of the first domestic case. The incidence rate for pandemic (H1N1) 2009 virus infection was 10.7 per 100,000 persons and was different according to the district. It was higher in the district of Coimbra and Guarda were the main roads connecting to Europe are. The median calculated incubation period for the for pandemic (H1N1) 2009 virus infection was 2 days. The length of the clinical manifestations until the patients look for medical observation had a median time of 2 days. All the cases were of mild to moderate severity. No deaths were observed. CONCLUSIONS: The early days of pandemic (H1N1) 2009 virus infection was mild in our region. Most affected patients were young adults, with the extreme categories ages of life being spared. Early detection and diagnosis, combined with stringent isolation and treatment procedures could have slowed the spread of the infection in our region

Electronic phase separation at LaAlO3/SrTiO3 interfaces tunable by oxygen deficiency

Electronic phase separation is crucial for the fascinating macroscopic properties of the LaAlO3/SrTiO3 (LAO/STO) paradigm oxide interface, including the coexistence of superconductivity and ferromagnetism. We investigate this phenomenon using angle-resolved photoelectron spectroscopy (ARPES) in the soft-X-ray energy range, where the enhanced probing depth combined with resonant photoexcitation allow access to fundamental electronic structure characteristics (momentum-resolved spectral function, dispersions and ordering of energy bands, Fermi surface) of buried interfaces. Our experiment uses X-ray irradiation of the LAO/STO interface to tune its oxygen deficiency, building up a dichotomic system where mobile weakly correlated Ti t2g-electrons co-exist with localized strongly correlated Ti eg-ones. The ARPES spectra dynamics under X-ray irradiation shows a gradual intensity increase under constant Luttinger count of the Fermi surface. This fact identifies electronic phase separation (EPS) where the mobile electrons accumulate in conducting puddles with fixed electronic structure embedded in an insulating host phase, and allows us to estimate the lateral fraction of these puddles. We discuss the physics of EPS invoking a theoretical picture of oxygen-vacancy clustering, promoted by the magnetism of the localized Ti eg-electrons, and repelling of the mobile t2g-electrons from these clusters. Our results on the irradiation-tuned EPS elucidate the intrinsic one taking place at the stoichiometric LAO/STO interfaces.Comment: In review with Phys. Rev. Material

Dynamics of thermophilic campylobacter colonization in broiler flocks reared on reused litter.

Projeto/Plano de Ação: 03.08.06.004

Frequency of thermophilic Campylobacter in commercial broiler farms in southern Brazil using different culturing techniques and selective media.

Projeto/Plano de Ação: 03.08.06.004