Population Synthesis of Isolated Neutron Stars with magneto-rotational evolution II: from radio-pulsars to magnetars

Population synthesis studies constitute a powerful method to reconstruct the birth distribution of periods and magnetic fields of the pulsar population. When this method is applied to populations in different wavelengths, it can break the degeneracy in the inferred properties of initial distributions that arises from single-band studies. In this context, we extend previous works to include $X$-ray thermal emitting pulsars within the same evolutionary model as radio-pulsars. We find that the cumulative distribution of the number of X-ray pulsars can be well reproduced by several models that, simultaneously, reproduce the characteristics of the radio-pulsar distribution. However, even considering the most favourable magneto-thermal evolution models with fast field decay, log-normal distributions of the initial magnetic field over-predict the number of visible sources with periods longer than 12 s. We then show that the problem can be solved with different distributions of magnetic field, such as a truncated log-normal distribution, or a binormal distribution with two distinct populations. We use the observational lack of isolated NSs with spin periods P>12 s to establish an upper limit to the fraction of magnetars born with B > 10^{15} G (less than 1\%). As future detections keep increasing the magnetar and high-B pulsar statistics, our approach can be used to establish a severe constraint on the maximum magnetic field at birth of NSs.Comment: 12 pages, 11 figures, 5 table

Shape-Dependent Electrocatalysis: Oxygen Reduction on Carbon-Supported Gold Nanoparticles

Cubic, octahedral and quasi-spherical (two different particle sizes) Au nanoparticles are synthesised and dispersed in a carbon-black powder. The size and morphology of the Au nanocatalysts is confirmed by transmission electron microscopy and X-ray diffraction. Au nanospheres are approximately 5 and 30 nm in diameter, whereas the size of Au octahedra and nanocubes is approximately 40–45 nm. The electrocatalytic activity of these carbon-supported particles towards the oxygen reduction reaction (ORR) is studied in 0.5 M H2SO4 and 0.1 M KOH solutions by using the rotating-disk-electrode method. The specific activity (SA) for O2 reduction is measured, and the highest SA is observed for Au nanocubes supported on carbon. The highest mass activities are found for the smallest Au nanoparticles. Tafel analysis suggests that the mechanism of the ORR on shape-controlled Au/C catalysts is the same as on bulk Au.This research was financially supported by institutional research funding (IUT 20–16) of the Estonian Ministry of Education and Research and by the Estonian Research Council (Grant No. 8380), by Archimedes Foundation (Project No. 3.2.0501.10–0015), by the MCINN-FEDER (Spain) (project CTQ 2010–16271) and by the Generalitat Valenciana (project PROMETEO/2009/045)

PdPt alloy nanocubes as electrocatalysts for oxygen reduction reaction in acid media

In this work, PdPt alloy nanocubes with different metal ratios were synthesised in the presence of polyvinylpyrrolidone (PVP). The surface morphology of the PdPt samples was characterised by transmission electron microscopy (TEM). TEM images showed that PdPt nanoparticles were cubic-shaped and the average size of the cubes was about 8–10 nm. Their electrocatalytic activity towards the oxygen reduction reaction (ORR) was studied in 0.5 M H2SO4 using the rotating disc electrode method. All the alloyed catalysts showed enhanced electrocatalytic activity for ORR as compared to the monometallic cubic Pd nanoparticles. Half-wave potential values for PdPt catalysts were comparable with that of Pt nanocubes. From the alloyed catalysts Pd36Pt64 exhibited the highest specific activity, which was only slightly lower than that of cubic Pt nanoparticles. The Koutecky–Levich analysis revealed that the reduction of oxygen proceeded via 4-electron pathway on all the electrocatalysts studied.This research was financially supported by institutional research funding (IUT20-16) of the Estonian Ministry of Education and Research and by the Estonian Research Council (Grant No. 9323) and by Archimedes Foundation (Project No. 3.2.0501.10-0015). KJ thanks the Archimedes Foundation for scholarship. JMF acknowledges financial support from MINECO (Spain), project CTQ2013-44083-P

Structure and morphology of shape-controlled Pd nanocrystals

Pd nanocrystals were produced with uniform truncated-cube shape and a narrow size distribution, yielding controlled surface area fractions from low Miller index ({100}, {110}, {111}) crystalline facets. Details on the structure and morphology of the nanocrystals were obtained by combining X-ray powder diffraction line profile analysis, high-resolution transmission electron microscopy and surface electrochemistry based on Cu underpotential deposition.ML acknowledges support from the Italian government (Ministero dell’Istruzione, dell’Università e della Ricerca) through the project FIRB Futuro in Ricerca RBFR10CWDA. JMF acknowledges financial support from the MINECO (Spain) project CTQ2013-44083-P and Generalitat Valenciana project PROMETEOII/2014/013

Seaweeds as promising resource of bioactive compounds: Overview of novel extraction strategies and design of tailored meat products

peer-reviewedBackground Meat and meat products have been recently perceived by consumers as unhealthy foods. To avoid this drawback, the reformulation is a feasible approach that allows obtaining custom meat-based products that incorporate compounds with certain beneficial properties for health and remove other attributes considered negative. In this framework, the edible seaweeds have been proposed to offer interesting possibilities in the meat sector to develop functional foods as they are an excellent natural source of nutrients and biocompounds with myriad functionalities. Scope and approach This review collects aspects related to the recent technologies employed to obtain and isolate biocompounds from seaweeds. The use of whole seaweeds and their bioactive extracts to develop meat foods that confer them health properties while simultaneously reducing components considered unhealthy in meat are reviewed. Furthermore, the prevention of oxidation events was also described. Key findings and conclusions Several studies have demonstrated that the incorporation of whole seaweeds and their bioactives to reformulate meat products is an excellent approach to improve certain nutritional aspects considered “bad”. However, there are still some challenges regarding the organoleptic and sensory properties of the resulting products that affect the consumer acceptability. In conclusion, more research is necessary to overcome these gaps allowing put in the market seaweeds -based meat products.Axencia Galega de Innovació

On the behavior of CO oxidation on shape-controlled Pt nanoparticles in alkaline medium

In this work, the behavior of the CO electro-oxidation reaction on shape-controlled Pt nanoparticles in alkaline medium was examined in order to understand the effect of the surface structure on this reaction. A series of experiments using Pt nanoparticles of different surface structures/shapes was used and the results obtained were compared with the previous knowledge gained from stepped platinum single crystal electrodes. Independently of the preferential orientation of the nanoparticles, the CO oxidation voltammetry exhibits two main peaks: one at ca. 0.56–0.59 V and the second one at 0.66–0.67 V, being the intensity of the peaks dependent on the shape of the nanoparticle. These two peaks have been assigned to the oxidation of CO on the (1 1 1) terraces and on the rest of the sites, respectively. The appearance of two differentiated peaks reveals that these (1 1 1) terraces and the rest of the sites on the nanoparticle surface behave independently of the presence of the other type of sites, that is, they are not connected. The results are discussed considering the effects of the surface mobility of CO and of the OH adsorption properties on the different sites in the oxidation peaks.Farias, M.J.S. would like to thanks CNPq, Brazil, for financial support for his postdoctoral stay at Universidad de Alicante. This work has been financially supported by the MICINN (Spain) (project CTQ2010-16271) and Generalitat Valenciana (project PROMETEO/2009/045, FEDER)