Quantificação e isolamento de bactérias diazotróficas associadas a coqueiro (Cocos nucifera L.).

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Seleção de rizóbios nativos para guandu, caupi e feijão-de-porco nos tabuleiros costeiros de Sergipe.

A inoculação de estirpes de rizóbios em sementes de feijão-de-porco (Canavalia ensiformis), caupi (Vigna unguiculata) e guandu (Cajanus cajan), recomendadas para outras regiões do País, não tem resultado em incrementos nas taxas de fixação biológica de N2 nem no crescimento dessas leguminosas em solos dos tabuleiros costeiros de Sergipe. Os objetivos deste trabalho foram avaliar a eficiência simbiótica de rizóbios nativos dos tabuleiros costeiros associados a essas leguminosas e a tolerância deles a estresses. Das 17 estirpes de rizóbios isoladas e analisadas em casa de vegetação, quatro foram selecionadas para o guandu, sete para o caupi e três para o feijão-de-porco. O número e a massa de nódulos secos por planta correlacionaram-se com a massa da parte aérea seca, a área foliar e o N total acumulado nas folhas das três leguminosas. Os mesmos rizóbios foram eficientes para o caupi e para o guandu. Três estirpes do guandu (R35, R43 e R45) e duas do caupi (R10 e R17) foram caracterizadas in vitro e todas apresentaram tolerância às concentrações elevadas de ácido nalidíxico, cloranfenicol e tetraciclina, porém, foram sensíveis à estreptomicina e à kanamicina. Todas as estirpes cresceram a 35ºC e, exceto a R17, toleraram o alumínio (10 mg L-1)

Caracterização genética de rizóbios nativos dos tabuleiros costeiros eficientes em culturas do guandu e caupi.

O objetivo deste trabalho foi caracterizar geneticamente sete estirpes de rizóbios nativos dos tabuleiros costeiros de Sergipe com alta eficiência de fixação biológica do N2 em associação com guandu (Cajanus cajan) e caupi (Vigna unguiculata). A amplificação do DNA pela técnica de PCR (polymerase chain reaction) com o oligonucleotídeo específico BOX indicou um grau elevado de diversidade genética, uma vez que todas as estirpes apresentaram perfis únicos de DNA. A análise por BOX-PCR revelou, ainda, que essa metodologia é eficiente para diferenciar estirpes, mas não para a diferenciação de espécies de rizóbio. Pela técnica do RFLP (restriction fragment length polymorphism) da região do DNA que codifica o gene 16S rRNA e da região intergênica entre os genes 16S e 23S rRNA, com cinco enzimas de restrição, bem como pelo seqüenciamento parcial da região do 16S rRNA, foi possível classificar as estirpes nos gêneros Bradyrhizobium e Rhizobium. Houve coerência entre as análises envolvendo a região do 16S rRNA, mas o agrupamento com uma das estirpes diferiu pela análise do espaço intergênico. Os resultados obtidos com a estirpe R11 indicam variabilidade genética elevada em relação às espécies de rizóbios descritas, inclusive diferindo em diversas bases da região do 16S rRNA, e podem indicar uma nova espécie

Interplay between superconductivity and itinerant magnetism in underdoped Ba1−x_{1-x}Kx_xFe2_2As2_2 (x=x= 0.2) probed by the response to controlled point-like disorder

The response of superconductors to controlled introduction of point-like disorder is an important tool to probe their microscopic electronic collective behavior. In the case of iron-based superconductors (IBS), magnetic fluctuations presumably play an important role in inducing high temperature superconductivity. In some cases, these two seemingly incompatible orders coexist microscopically. Therefore, understanding how this unique coexistence state is affected by disorder can provide important information about the microscopic mechanisms involved. In one of the most studied pnictide family, hole-doped Ba$_{1-x}$K$_x$Fe$_2$As$_2$ (BaK122), this coexistence occurs over a wide range of doping levels, 0.16~$\lesssim x \lesssim$~0.25. We used relativistic 2.5 MeV electrons to induce vacancy-interstitial (Frenkel) pairs that act as efficient point-like scattering centers. Upon increasing dose of irradiation, the superconducting transition temperature $T_c$ decreases dramatically. In the absence of nodes in the order parameter this provides a strong support for a sign-changing $s_{\pm}$ pairing. Simultaneously, in the normal state, there is a strong violation of the Matthiessen's rule and a decrease (surprisingly, at the same rate as $T_c$) of the magnetic transition temperature $T_{sm}$, which indicates the itinerant nature of the long-range magnetic order. Comparison of the hole-doped BaK122 with electron-doped Ba(Fe$_x$Co$_{1-x}$)$_2$As$_2$ (FeCo122) with similar $T_{sm}\sim$110~K, $x=$0.02, reveals significant differences in the normal states, with no apparent Matthiessen's rule violation above $T_{sm}$ on the electron-doped side. We interpret these results in terms of the distinct impact of impurity scattering on the competing itinerant antiferromagnetic and $s_{\pm}$ superconducting orders

Two-band superconductivity in doped SrTiO3_{3} films and interfaces

We investigate the possibility of multi-band superconductivity in SrTiO$_{3}$ films and interfaces using a two-dimensional two-band model. In the undoped compound, one of the bands is occupied whereas the other is empty. As the chemical potential shifts due to doping by negative charge carriers or application of an electric field, the second band becomes occupied, giving rise to a strong enhancement of the transition temperature and a sharp feature in the gap functions, which is manifested in the local density of states spectrum. By comparing our results with tunneling experiments in Nb-doped SrTiO$_{3}$, we find that intra-band pairing dominates over inter-band pairing, unlike other known multi-band superconductors. Given the similarities with the value of the transition temperature and with the band structure of LaAlO$_{3}$/SrTiO$_{3}$ heterostructures, we speculate that the superconductivity observed in SrTiO$_{3}$ interfaces may be similar in nature to that of bulk SrTiO$_{3}$, involving multiple bands with distinct electronic occupations.Comment: revised expanded versio

Possible unconventional superconductivity in substituted BaFe2_{2}As2_{2} revealed by magnetic pair-breaking studies

The possible existence of a sign-changing gap symmetry in BaFe$_{2}$As$_{2}$-derived superconductors (SC) has been an exciting topic of research in the last few years. To further investigate this subject we combine Electron Spin Resonance (ESR) and pressure-dependent transport measurements to investigate magnetic pair-breaking effects on BaFe$_{1.9}M_{0.1}$As$_{2}$ ($M=$ Mn, Co, Cu, and Ni) single crystals. An ESR signal, indicative of the presence of localized magnetic moments, is observed only for $M=$ Cu and Mn compounds, which display very low SC transition temperature ($T_{c}$) and no SC, respectively. From the ESR analysis assuming the absence of bottleneck effects, the microscopic parameters are extracted to show that this reduction of $T_{c}$ cannot be accounted by the Abrikosov-Gorkov pair-breaking expression for a sign-preserving gap function. Our results reveal an unconventional spin- and pressure-dependent pair-breaking effect and impose strong constraints on the pairing symmetry of these materials

On the nature of the near-UV extended light in Seyfert galaxies

We study the nature of the extended near-UV emission in the inner kiloparsec of a sample of 15 Seyfert galaxies which have both near-UV (F330W) and narrow band [OIII] high resolution Hubble images. For the majority of the objects we find a very similar morphology in both bands. From the [OIII] images we construct synthetic images of the nebular continuum plus the emission line contribution expected through the F330W filter, which can be subtracted from the F330W images. We find that the emission of the ionised gas dominates the near-UV extended emission in half of the objects. A further broad band photometric study, in the bands F330W (U), F547M (V) and F160W (H), shows that the remaining emission is dominated by the underlying galactic bulge contribution. We also find a blue component whose nature is not clear in 4 out of 15 objects. This component may be attributed to scattered light from the AGN, to a young stellar population in unresolved star clusters, or to early-disrupted clusters. Star forming regions and/or bright off-nuclear star clusters are observed in 4/15 galaxies of the sample.Comment: 23 pages, 6 figures, 3 tables; accepted for publication in MNRA

Prescribed Fire Plus Grazing Horses: A Sustainable Model to Decrease Fire Hazard in a Mountain Landscape

The mountain landscapes of northern Portugal have been modified through rural depopulation and the absence of rangeland management. As such, increased above-ground biomass and higher fire hazard resulted, as well as decreased ecosystem biodiversity. The objectives of the OpentoPreserve Interreg SUDOE project are to evaluate the effects of the combined use of prescribed fire with grazing horses, and also to develop strategies of socio-economic valorization of this model. Concerning the evaluation of prescribed fire and grazing effects, the experimental design consisted of three plots in the Natura 2000 Alvão/Marão Site, respectively Control, Fire x Grazing, and Fire. The Fire plots were burned in early spring and vegetation percent cover and height were measured in all plots in late spring. We have implemented four transects in the three different plots, used the line intercept method and subsequently estimated vegetation volume. This methodology is also applied on Forestation of Agricultural Land with More Silviculture, Silvopasture, Innovation and Value project. Concerning socio-economic valorization, the stakeholders related to the native horse breed, were interviewed and a focus-group was held. The study intends to identify both the benefits resulting from the adoption of a management system that includes the native horse breed, named Garrano, and the main weaknesses related to environmental, economic and social sustainability. Initial results for total vegetation in each plot show a high reduction in vegetation percent cover and its volume in the burned plots (33.5% and 268.3 m3 ha-1) in comparison to the control plot (183.7% and 12862.5 m3 ha-1). Furthermore, a fast recovery was observed in July, mainly of the Pterospartum tridentatum shrub species. Interviews and focus-group results shows the important role of these grazing animals in vegetation control as well as in other ecosystems services, involving an environmental and a socio-economic dimension. A strategy to value contribution to the economy of agricultural holdings has been proposed