Efeito de extractos de raízes eliciadas de Castanea sativa no crescimento do fungo ectomicorrízico Pisolithus tinctorius

O castanheiro (Castanea sativa Mill.) estabelece associação com numerosas espécies de fungos ectomicorrízicos, estando descritos os efeitos benéficos para a planta após micorrização com Pisolithus tinctorius. Neste processo é essencial que ocorra a troca de sinais entre os simbiontes, para que seja reconhecida a sua compatibilidade e para que ocorra a formação dos órgãos ectomicorrízicos. Neste trabalho são fornecidas evidências que sugerem a capacidade de extractos de raízes de castanheiro, nos estádios iniciais de contacto com P. tinctorius regularem o crescimento do fungo micorrízico

Electrodeposition of WO3 Nanoparticles for Sensing Applications

The motivation of using metal oxides is mainly due to its charge storage capabilities, and electrocatalytic, electrochromic and photoelectrochemical properties. But comparing with bulk, nanostructured materials present several advantages related with the spatial confinement, large fraction of surface atoms, high surface energy, strong surface adsorption and increased surface to volume ratio, which greatly improves the performances of these materials. The deposition of this materials can be accomplished by a variety of physical and chemical techniques but nowadays, electrodeposited metal oxides are generally used in both laboratories and industries due to the flexibility to control structure and morphology of the oxide electrodes combined with a reduced cost. Tungsten oxide (WO3) is a well-studied semiconductor and is used for several applications as chromogenic material, sensor and catalyst. The major important features is its low cost and availability, improved stability, easy morphologic and structural control of the nanostructures, reversible change of conductivity, high sensitivity, selectivity and biocompatibility. For the electrodeposition of WO3, more than one method can be adopted: electrodeposition from a precursor solution, anodic oxidation, and electrodeposition of already produced nanoparticles; however, in this case the mechanism of the electrodeposition is not fully understood. In this chapter, a review of the latest published work of electrodeposited nanostructured metal oxides is provided to the reader, with a more detailed explanation of WO3 material applied in sensing devices

Astrometry of the main satellites of Uranus: 18 years of observations

We determine accurate positions of the main satellites of Uranus: Miranda, Ariel, Umbriel, Titania, and Oberon. Positions of Uranus, as derived from those of these satellites, are also determined. The observational period spans from 1992 to 2011. All runs were made at the Pico dos Dias Observatory, Brazil. We used the software called Platform for Reduction of Astronomical Images Automatically (PRAIA) to minimise (digital coronography) the influence of the scattered light of Uranus on the astrometric measurements and to determine accurate positions of the main satellites. The positions of Uranus were then indirectly determined by computing the mean differences between the observed and ephemeris positions of these satellites. A series of numerical filters was applied to filter out spurious data. These filters are mostly based on the comparison between the positions of Oberon with those of the other satellites and on the offsets as given by the differences between the observed and ephemeris positions of all satellites. We have, for the overall offsets of the five satellites, -29 (+/-63) mas in right ascension and -27 (+/-46) mas in declination. For the overall difference between the offsets of Oberon and those of the other satellites, we have +3 (+/-30) mas in right ascension and -2 (+/-28) mas in declination. Ephemeris positions for the satellites were determined from DE432+ura111. Comparisons using other modern ephemerides for the solar system -INPOP13c- and for the motion of the satellites -NOE-7-2013- were also made. They confirm that the largest contribution to the offsets we find comes from the motion of the barycenter of the Uranus system around the barycenter of the solar system, as given by the planetary ephemerides. Catalogues with the observed positions are provided.Comment: 13 pages, 21 figure

Caracterização do sistema antioxidativo no estabelecimento da associação micorrízica Castanea sativa Mill. / Amanita muscaria

Poster apresentado no 5º Congresso Florestal Nacional, Viseu, Portugal, 16 Maio - 19 Maio 2005.As micorrizas são associações mutualistas que se estabelecem entre fungos, pertencentes sobretudo às divisões Basidiomycota, Ascomycota e Zigomycota, e raízes de plantas vasculares. Com o estabelecimento da associação micorrízica, ocorrem várias alterações morfológicas, fisiológicas e ecológicas em ambos os intervenientes, que têm sido objecto de estudo por diversos autores. Contudo, os mecanismos que controlam o processo de colonização e como este processo se inicia é completamente desconhecido. Os poucos trabalhos desenvolvidos nesta área, utilizando micorrizas arbusculares, sugerem que, durante as primeiras horas de invasão do fungo, ocorre uma indução de resposta de defesa por parte da planta hospedeira, semelhante à observada na interacção planta-patogénio. O presente trabalho pretende averiguar o efeito da inoculação de plantas de Castanea sativa Mill. com o fungo ectomicorrízico Amanita muscaria, na indução de resposta de defesa da planta hospedeira. O trabalho experimental decorreu num sistema in vitro estabelecido entre plantas de C. sativa e o fungo A. muscaria. Durante as primeiras horas de contacto (0 às 48 horas) procedeu-se à recolha de amostras de raízes, caules e folhas da planta hospedeira e de micélio de fungo que esteve em contacto com a raiz. Nestas amostras analisaram-se os níveis de peróxido de hidrogénio (H2O2), a actividade da catalase (CAT) (EC 1.11.1.6) e da superóxido dismutase (SOD) (EC 1.15.1.1). Os resultados obtidos evidenciam três picos de produção de H2O2, sugerindo o seu possível envolvimento no estabelecimento de micorrizas, nas primeiras horas de contacto planta-fungo. As variações observadas na actividade da SOD e da CAT, indiciam o seu envolvimento no controlo dos níveis de H2O2 em raízes, permitindo que esta molécula possa actuar como molécula sinalizadora, mas evitando que os níveis se tornem nocivos para o sistema. Estes resultados, apesar de preliminares, reflectem uma condição de stresse oxidativo semelhante àquela observada em interacções planta-patogénio.Fundação para a Ciência e a Tecnologia (FCT) - Programa Operacional “Ciência, Tecnologia, Inovação” (POCTI) - POCTI/BSE/38059/2001 - Study of the mechanisms regulating the interactions between ectomycorrhizal fungi and roots of Castanea sativa Mill. (European chestnut)

Stripes and spin-incommensurabilities are favored by lattice anisotropies

Structural distortions in cuprate materials give a natural origin for anisotropies in electron properties. We study a modified one-band t-J model in which we allow for different hoppings and antiferromagnetic couplings in the two spatial directions ($t_x \ne t_y$ and $J_x \ne J_y$). Incommensurate peaks in the spin structure factor show up only in the presence of a lattice anisotropy, whereas charge correlations, indicating enhanced fluctuations at incommensurate wave vectors, are almost unaffected with respect to the isotropic case.Comment: accepted for publication on Physical Review Letters, one color figur

On the Stability of the Satellites of Asteroid 87 Sylvia

he triple asteroidal system (87) Sylvia is composed of a 280-km primary and two small moonlets named Romulus and Remus (Marchis et al 2005). Sylvia is located in the main asteroid belt. The satellites are in nearly equatorial circular orbits around the primary. In the present work we study the stability of the satellites Romulus and Remus, in order to identify the effects and the contribution of each perturber. The results from the 3-body problem, Sylvia-Romulus-Remus, show no significant variation of their orbital elements. However, the inclinations of the satellites present a long period evolution, when the Sun is included in the system. Such amplitude is amplified when Jupiter is included. An analysis of these results show that Romulus and Remus are librating in a secular resonance and their longitude of the nodes are locked to each other. The satellites get caught in an evection resonance with Jupiter. However, the orbital evolutions of the satellites became completely stable when the oblateness of Sylvia is included in the simulations.Comment: 11 pages, 8 figures and 1 tabl