5,561 research outputs found
The role of bacteria in pine wilt disease: insights from microbiome analysis.
Pine Wilt Disease (PWD) has a significant impact on Eurasia pine forests. The microbiome of the nematode (the primary cause of the disease), its insect vector, and the host tree may be relevant for the disease mechanism. The aim of this study was to characterize these microbiomes, from three PWD-affected areas in Portugal, using Denaturing Gradient Gel Electrophoresis, 16S rRNA gene pyrosequencing, and a functional inference-based approach (PICRUSt). The bacterial community structure of the nematode was significantly different from the infected trees but closely related to the insect vector, supporting the hypothesis that the nematode microbiome might be in part inherited from the insect. Sampling location influenced mostly the tree microbiome (P < 0.05). Genes related both with plant growth promotion and phytopathogenicity were predicted for the tree microbiome. Xenobiotic degradation functions were predicted in the nematode and insect microbiomes. Phytotoxin biosynthesis was also predicted for the nematode microbiome, supporting the theory of a direct contribution of the microbiome to tree-wilting. This is the first study that simultaneously characterized the nematode, tree and insect-vector microbiomes from the same affected areas, and overall the results support the hypothesis that the PWD microbiome plays an important role in the disease's development
Stable Umbral Chromospheric Structures
Aims. To understand the morphology of the chromosphere in sunspot umbra. We
investigate if the horizontal structures observed in the spectral core of the
Ca II H line are ephemeral visuals caused by the shock dynamics of more stable
structures, and examine their relationship with observables in the H-alpha
line. Methods. Filtergrams in the core of the Ca II H and H-alpha lines as
observed with the Swedish 1-m Solar Telescope are employed. We utilise a
technique that creates composite images and tracks the flash propagation
horizontally. Results. We find 0"15 wide horizontal structures, in all of the
three target sunspots, for every flash where the seeing was moderate to good.
Discrete dark structures are identified that are stable for at least two umbral
flashes, as well as systems of structures that live for up to 24 minutes. We
find cases of extremely extended structures with similar stability, with one
such structure showing an extent of 5". Some of these structures have a
correspondence in H-alpha but we were unable to find a one to one
correspondence for every occurrence. If the dark streaks are formed at the same
heights as umbral flashes then there are systems of structures with strong
departures from the vertical for all three analysed sunspots. Conclusions.
Long-lived Ca II H filamentary horizontal structures are a common and likely
ever-present feature in the umbra of sunspots. If the magnetic field in the
chromosphere of the umbra is indeed aligned with the structures, then the
present theoretical understanding of the typical umbra needs to be revisited.Comment: Accepted to Astronomy and Astrophysics. Online material (Fig3.mov and
Fig4.mov) will be available at A&
O sistema dois-hÃbridos de Saccharomyces cerevisiae.
Variações e potencial para a análise funcional e montagem de redes de interações proteÃna-proteÃna
The influence of tin on the activity and selectivity of Sn-Pd/HY zeolites, in the hydrocracking and hydroisomerization of n-heptane
Al-containing MCM-41 type materials prepared by different synthesis methods: hydrothermal stability and catalytic properties
Al-containing MCM-41 type materials were prepared by three different synthesis methods
(aluminum grafting on the calcined MCM-41, pH adjustment during the crystallization period
and crystallization in the presence of zeolite seeds). The samples were characterized by
powder XRD, nitrogen adsorption, 27Al MAS NMR and FTIR with pyridine as probe
molecule. All the samples exhibit a high hydrothermal stability at high temperature just with a
minor structural degradation. N2 adsorption data obtained for the sample prepared from a gel
containing zeolite seeds suggest a higher structural resistance to the hydrothermal treatment in
comparison with the samples prepared by other methods. A different type of pyridine
adsorbed, probably interacting simultaneously with a Brönsted and a Lewis acid site, is
observed upon pyridine adsorption. This type of adsorption is stronger for the sample
prepared in the presence of zeolite seeds and is not observed on Al-grafted MCM-41.
2
The catalytic activity towards the isomerization of α-pinene depends mainly on the number of
Brönsted acid sites. The data obtained in this study strongly indicate that for this type of
materials, the Lewis acid sites do not influence the selectivity for the isomerization products
Sharp lines in the absorption edge of EuTe and PbEuTe in high magnetic fields
The optical absorption spectra in the region of the \fd transition energies
of epitaxial layers of of EuTe and \PbEuTe, grown by molecular beam epitaxy,
were studied using circularly polarized light, in the Faraday configuration.
Under \sigmam polarization a sharp symmetric absorption line (full width at
half-maximum 0.041 eV) emerges at the low energy side of the band-edge
absorption, for magnetic fields intensities greater than 6 T. The absorption
line shows a huge red shift (35 meV/T) with increasing magnetic fields. The
peak position of the absorption line as a function of magnetic field is
dominated by the {\em d-f} exchange interaction of the excited electron and the
\Euion spins in the lattice. The {\em d-f} exchange interaction energy was
estimated to be eV. In \PbEuTe the same absorption line
is detected, but it is broader, due to alloy disorder, indicating that the
excitation is localized within a finite radius. From a comparison of the
absorption spectra in EuTe and \PbEuTe the characteristic radius of the
excitation is estimated to be \AA.Comment: Journal of Physics: Condensed Matter (2004, at press
Measurement of miniband parameters of a doped superlattice by photoluminescence in high magnetic fields
We have studied a 50/50\AA superlattice of GaAs/AlGaAs
composition, modulation-doped with Si, to produce
cm electrons per superlattice period. The modulation-doping was tailored
to avoid the formation of Tamm states, and photoluminescence due to interband
transitions from extended superlattice states was detected. By studying the
effects of a quantizing magnetic field on the superlattice photoluminescence,
the miniband energy width, the reduced effective mass of the electron-hole
pair, and the band gap renormalization could be deduced.Comment: minor typing errors (minus sign in eq. (5)
Análise Económica - Financeira das 3 Grandes Sociedades Desportivas (Sporting, Benfica e Porto)
O futebol é um desporto, considerado como um fenómeno a nÃvel mundial, porque molda culturas, atrai multidões e quebra barreiras culturais e sociais. Contudo, nos últimos anos, aumentou a importância a nÃvel económico e, por isso, a Union of European Football Associations (UEFA) foi forçada a implementar mudanças desportivas, em geral, com exigências ao nÃvel do Fair Play Financeiro (FFP), em particular, tendo como foco os aspetos económicos e financeiros.
Face ao referido justifica-se que o projeto aplicado tenha como objetivo a análise económica e financeira das três Sociedades Anónimas Desportivas que detêm em Portugal mais tÃtulos desportivos, isto é: Sporting Clube de Portugal – Futebol, SAD, Sport Lisboa e Benfica – Futebol SAD e o Futebol Clube do Porto – Futebol, SAD Metodologicamente, a primeira parte do projeto aplicado centrou-se numa revisão da literatura sobre o futebol e as Sociedades Anónimas Desportiva (SAD), bem como a análise de leis e normas que regem estas sociedades e, ainda, a prestação de contas das mesmas. Na segunda parte do projeto aplicado desenvolve-se uma análise empÃrica que permitiu realizar uma avaliação individual longitudinal com uma comparação das três SAD, justificadas num perÃodo de estudo de oito épocas desportivas que compreende a época de 2007/2008 a 2014/2015.
Os resultados do projeto aplicado permitiram concluir que cada Sociedade Anónima Desportiva representa e interpreta a sua própria prestação de contas, de uma maneira relevante e face aos resultados desportivos alcançados. Assim, com base na classificação desportiva dos clubes na UEFA, foi elaborado um indicador para comparar os resultados desportivos e económicos e o modo como uns podem influenciar os outros. Paralelamente, foram realizadas análises económicas e financeiras das três sociedades obtendo assim uma perspetiva da posição financeira e da sua performance no perÃodo em estudo de cada uma das SAD, de modo a identificar o equilÃbrio e a sua sustentabilidade
- …