Nuevos datos sobre los acridoidea (Insecta: Orthoptera) del Pirineo y Prepirineo catalano-aragones

Hom presenta els resultats de les campanyes de recol•lecció realitzades el juliol de 1985 i 1986 a les zones pirenenca i pre-pirenenca de Girona, Osca i Lleida, que constitueixen la primera aportació al coneixement de l'acridofauna de la zona. Hom cita per segona vegada Omocestus antigai i 0. navasi.New data on the distribution of Acridoidea in Pyrenean and prepyrenean zones of Gerona, Huesca and Lerida provinces are presented. The material has been collected along july 1985 and july 1986. This paper is the first summarized work on acridological faune for the studied area. The presence of Omocestus antigai and 0. navasi is confirmed.Se presentan los resultados de las campanas acridológicas realizadas en julio de 1985 y 1986 en las zonas pirenaica y prepirenaica de las provincias de Gerona, Huesca y Lerida. Estos resultados constituyen la primera aportación de conjunto para el conocimiento de la acridofauna de la zona considerada. Se dan las segundas citas conocidas de las especies Omocestus antigai y 0. navasi

A workflow management system for early feeding of the European hake

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Comment on “Nature and entropy content of the ordering transitions in RCo₂”

In their analysis of our perturbed angular correlation (PAC) study of the magnetic phase transitions of RCo₂ [Phys. Rev. B 68, 014409 (2003)], Herrero-Albillos [Phys. Rev. B 73, 134410 (2006)] come to the conclusion that it is very difficult for PAC spectroscopy to distinguish a first-order from a second-order phase transition. The statement is incorrect and does not resolve the conflict between the conclusion drawn from the PAC data and the differential scanning calorimetry data of Herrero- Albillos on the order of the magnetic phase transitions of PrCo₂ and NdCo₂. In this Comment we show that measurements of hyperfine interactions by PAC and other microscopic techniques are a very powerful tool for the investigation of phase transitions which may provide details on the transition not accessible to macroscopic methods. We explain why the PAC data leave no alternative to the conclusion that the spontaneous magnetization of PrCo₂ and NdCo₂ undergoes a discontinuous, first-order phase transition at T_(C)

Perturbed angular correlation study of the magnetic phase transitions in the rare-earth cobalt Laves phases RCo₂

The order and other properties of the magnetic phase transitions in the rare-earth (R)-cobalt Laves phases RCo2 have been studied for R=Gd, Tb, Dy, Ho, Er, Sm, Nd, and Pr by measuring the temperature dependence of the magnetic hyperfine interaction of the nuclear probe ^111Cdon the cubic R sites using the perturbed angular correlation technique. Both for heavy and light R constituents the transitions change from second order (Gd, Tb, Sm) to first order (Dy, Ho, Er, Nd, Pr) at order temperatures of 150-200 K. For heavy R constituents, the order deduced from the hyperfine interaction is in agreement with previous investigations. The observation of first order transitions in NdCo₂ and PrCo₂, however, is unexpected. In earlier studies the transitions in these compounds are usually classified as second order transitions. Both in the heavy and the light RCo₂ the discontinuous jump of the hyperfine interaction at the first order transitions increases with decreasing order temperature. This trend implies that the Co magnetization at the transition increases with decreasing T_C which can be related to the temperature dependence of the coefficient of the M^(4) term of the free energy in the Wohlfarth-Rhodes-Shimizu theory of itinerant electron magnetism. All compounds investigated presented a spread of the order temperature of similar to1-2 K which results in a coexistence of the paramagnetic and the magnetically ordered phase near the transition and causes a critical increase of the relative linewidth of the hyperfine frequency diverging as δ ∞ [(1-T/T_(C)]^ε with ε =-1.0(1)

Ligand exchange in gold-coated FePt nanoparticles

In this work we present the magnetic properties of gold coated FePt nanoparticles and the study of stable aqueous dispersions of FePt@Au and FePt synthesized after ligand exchange with mercaptoundecanoic acid. The particle size determined from TEM micrographs goes from 4 nm for the uncoated nanoparticles to a maximum of 10 nm for the gold coated ones indicating that the thickness of the shell ranges from 1 to 3 nm. The magnetic characterization consists in hysteresis cycles at 10 and 300 K. The results show that, at low field and room temperature, the magnetic behavior of uncoated and coated nanoparticles are surprisingly quite similar. Since the gold coated nanoparticles keep the magnetic properties of FePt and the presence of gold improves the functionalization of nanoparticles, the system is suitable for biological application. Mercaptoundecanoic ligand transfer was used to render water stable nanoparticles in a wide pH range. Transmission electron microscopy and dynamic light scattering results show the nanoparticles slightly agglomerate after ligand exchange. Fourier transform infrared spectroscopy results suggest that thiol bind to the gold atoms of the surface.Comment: Intermag 2008, conference pape

Genetic population structure and connectivity of Azorean limpets

Ocean Science Meeting. Hawaii Convention Center, Honolulu, Hawaii, USA, 23-28 de Fevereiro.There is growing consensus that anthropogenic activities significantly rarefy the structure and functioning of marine ecosystems. Oceanic islands such as the Azores (NE Atlantic) constitute unique habitats with fragile communities, which are highly susceptible to degradation and ecosystem disruption. . Patellid limpets have traditionally been collected as a food resource and in 1988 the limpet fishery in São Miguel Island collapsed, and after a one-year ban throughout the archipelago, the stocks were allowed to recover, avoiding catastrophic overexploitation effects. In 1993, legislation was passed to protect this resource, i.e. limpet no-take areas were created, seasonal harvesting restrictions were applied and minimum legal catch sizes were established. However, a recent survey has shown that limpet populations still show clear signs of overexploitation and some populations are virtually extinct in some islands. Here we have developed new multiplexed and described microsatellite markers for the species Patella aspera and P. candei and have examined their genetic diversity, gene flow and population connectivity in the Azores Archipelago. Overall, such information is a fundamental asset to inform conservation strategies and to promote the sustainable exploitation of macaronesian limpets.FC

Spectrum of magnetic hyperfine fields at ^111 C probe nuclei in the pseudobinary rare-earth Laves-phase compounds R_(1-x)Y_xCo₂

The spectrum of the magnetic hyperfine fields at the closed-shell probe nucleus ^111 Cd on the rare earth (R) site of the pseudobinary Laves-phase compounds R_81-x)Y_xCo₂ has been investigated by perturbed angular correlation (PAC) spectroscopy at 10 K for the rare earth R=Tb and Ho at various Y concentrations x ≤ 0.8 and for R=Gd, Dy, Er at the concentration x=0.3. Up to four components with different magnetic interaction frequencies ν^(i) _(M) could be resolved from the PAC spectra. The relative intensities of these components are in fair agreement with those of a binomial distribution of Y atoms on the four nearest neighbor (NN) R sites of the probe nucleus. For all R constituents, one finds a strictly linear relation between the number n_(R) of NN R atoms and the magnetic hyperfine frequencies: ν^(i) _(M) =ν_(M)(4Y)+∆ ν(M) Xn_(R).The frequency ν_(M)(4Y)=35(2) MHz is independent of the R constituent and of the Y concentration up to x ≤ 0.6. These properties identify ν_(M)(4Y) as the contribution of the Co 3d moments to the hyperfine interaction at the ^111 Cdsite. The frequency steps ∆ ν_(M)[≤ 0.1 ν_(M)(4Y)] reflect the spin polarization directly induced by the 4f spins at the probe nucleus. From Gd to Er, the spin polarization decreases much stronger than expected from the linear variation of the 4f spin in the heavy R series. An indirect 4f contribution caused by a dependence of the Co 3d moment on the number of R neighbors can be excluded. The relation ν_(M)^(i) = ν_(M)(4Y) + ∆ν_(M) X n_(R) then implies that the contributions of the 3d and 4f spins to the magnetic hyperfine field in RCo₂ have the same relative sign