On the long-term correlation between the flux in the Ca II H & K and Halpha lines for FGK stars

The re-emission in the cores of the Ca II H & K and H$\alpha$ lines, are well known proxies of stellar activity. However, these activity indices probe different activity phenomena, the first being more sensitive to plage variation, while the other one being more sensitive to filaments. In this paper we study the long-term correlation between $\log R'_{HK}$ and $\log I_{H\alpha}$, two indices based on the Ca II H & K and H$\alpha$ lines respectively, for a sample of 271 FGK stars using measurements obtained over a $\sim$9 year time span. Because stellar activity is one of the main obstacles to the detection of low-mass and long-period planets, understanding further this activity index correlation can give us some hints about the optimal target to focus on, and ways to correct for these activity effects. We found a great variety of long-term correlations between $\log R'_{HK}$ and $\log I_{H\alpha}$. Around 20% of our sample has strong positive correlation between the indices while about 3% show strong negative correlation. These fractions are compatible with those found for the case of early-M dwarfs. Stars exhibiting a positive correlation have a tendency to be more active when compared to the median of the sample, while stars showing a negative correlation are more present among higher metallicity stars. There is also a tendency for the positively correlated stars to be more present among the coolest stars, a result which is probably due to the activity level effect on the correlation. Activity level and metallicity seem therefore to be playing a role on the correlation between $\log R'_{HK}$ and $\log I_{H\alpha}$. Possible explanations based on the influence of filaments for the diversity in the correlations between these indices are discussed in this paper.Comment: 18 pages, 13 figures, 4 tables, accepted for publication in Astronomy and Astrophysic

Circuitos de comercialização e valorização dos produtos locais: caso estudo do pêssego na Beira Interior

Só está disponível o resumo.A valorização dos produtos locais passa, inevitavelmente, pela implementação de estratégias de comercialização que valorizem a sua qualidade intrínseca e promovam a sua identidade junto aos consumidores. O acesso ao mercado a um preço compensador é um fator de sustentabilidade económica das explorações agrícolas e um dos vetores do desenvolvimento rural. O paradigma dos circuitos de comercialização longos, alicerçados na grande distribuição parece estar a ser substituído por um sistema misto em que, a par dos circuitos longos tradicionais, coexistem circuitos curtos adaptados a um público alvo que valoriza a proximidade, a frescura e a autenticidade dos produtos. Na Beira Interior a cultura do pessegueiro desempenha um importante papel na economia regional: de acordo com os dados do Instituto Nacional de Estatística, 2015, a área de pessegueiro é de 1.630 ha e a produção ascende às 20.206 t, sendo a principal região produtora de pêssego a nível nacional. A comercialização do pêssego apresenta algumas dificuldades que estão relacionadas com o preço de venda, variedades comercializadas e respetivo calibre, venda a granel ou em embalagem e existência ou não de marca comercial. Nesta comunicação iremos caracterizar os principais circuitos de comercialização do pêssego na Beira Interior e referir as estratégias de comercialização adotadas pelos produtores no sentido de valorizar a sua produção.info:eu-repo/semantics/publishedVersio

Meio seletivo para isolamento de Armillaria sp.

Resumo

Evolução e controle da armilariose em pínus no Sul do Brasil.

O gênero Pinus tem ocupado a segunda maior área com florestas plantadas de espécies exóticas para produção de madeira no Brasil. As espécies comercialmente plantadas são consideradas bem adaptadas às condições de clima e solos brasileiros e dentre os fatores adversos ao seu cultivo encontram-se as doenças. A armilariose causada pelo fungo Armillaria sp. é a principal doença em pínus no Brasil e provoca o apodrecimento das raízes e do colo da árvore, resultando na morte do hospedeiro. A rizomorfas que disseminam-se de árvores doentes ou mortas ou de madeira colonizada pelo fungo através do solo são o principal veículo de disseminação desta doença. Este trabalho apresenta as informações mais atuais da armilariose em pínus na região Sul do Brasil, enfocando a etiologia, distribuição geográfica e o controle biológico.1 CD-ROM. Palestra (Doenças florestais). Co-promoção: Embrapa Florestas

Correlations and Omori law in Spamming

The most costly and annoying characteristic of the e-mail communication system is the large number of unsolicited commercial e-mails, known as spams, that are continuously received. Via the investigation of the statistical properties of the spam delivering intertimes, we show that spams delivered to a given recipient are time correlated: if the intertime between two consecutive spams is small (large), then the next spam will most probably arrive after a small (large) intertime. Spam temporal correlations are reproduced by a numerical model based on the random superposition of spam sequences, each one described by the Omori law. This and other experimental findings suggest that statistical approaches may be used to infer how spammers operate.Comment: Europhysics Letters, to appea

Baseline information on prokaryotic and microeukaryotic plankton communities inside and outside of Indonesian marine lakes

Marine lakes represent a unique and globally rare aquatic environment characterised by lower salinities and pH and higher temperatures than the surrounding open water environment. Here we provide baseline data on planktonic communities of Archaea, Bacteria and microeukaryotes inside and outside (open water habitat) of three marine lakes (Kakaban, Haji Buang and Tanah Bamban) in the Berau region of Indonesia. Compositional variation was highly congruent with the major axis of variation separating open water from marine lake samples for all three domains. Planktonic Archaea mainly consisted of OTUs assigned to Euryarchaeota that were closely related to organisms in Genbank previously obtained from seawater samples. The majority of archaeal OTUs were most abundant in open water habitat with a few OTUs abundant in all habitats. Most bacterial sequences were assigned to Proteobacteria, Cyanobacteria and Bacteroidetes with the percentage of Cyanobacteria highest in two of the marine lakes and lowest in the remaining lake (Tanah Bamban). In contrast to Archaea, there were a number of bacterial OTUs that were markedly more abundant in marine lake habitat. Most microeukaryote sequences were assigned to the Alveolata, Stramenopiles, Opisthokonta, Archaeplastida and Hacrobia. As was the case with Bacteria, a number of abundant microeukaryote OTUs were more abundant in marine lake habitat. Our results thus indicate similar compositional responses to the environmental conditions in marine lake habitat across the major domains of life and point to marine lakes harbouring distinct microbial communities.publishe

Eigenvalue estimates for a class of elliptic differential operators in divergence form on Riemannian manifolds isometrically immersed in Euclidean space

In this paper, we obtain eigenvalue estimates for a larger class of elliptic differential operators in divergence form on a bounded domain in a complete Riemannian manifold isometrically immersed in Euclidean space. As an application, we give eigenvalue estimates in the Gaussian shrinking soliton, and we find a domain that makes the behavior of these estimates similar to the estimates for the case of the Laplacian. Moreover, we also give an answer to the generalized conjecture of P\'olya.Comment: 17 page