A simple strategy to generate light-responsive azobenzene-containing epoxy networks

Azobenzene containing epoxy networks are a class of photosensitive materials characterized by high thermal, optical and mechanical stability, promising for reversible optical storage applications. Here, we propose an encouraging two-step method to fabricate crosslinked coatings by simply reacting an amine-functionalized azobenzene and an epoxy resin in bulk for specified times to get soluble products (network precursors). Thin films based on these precursors were prepared, and thermally crosslinked in order to obtain high-T_g materials. The optical response of the materials was determined, both before and after crosslinking. In the case of the samples as prepared, the dynamic time response of the system is fast, as well as the relaxation of the photoinduced birefringence, as expected due to the high mobility of the chromophore. On the other hand, crosslinked systems have a slightly slower response, but higher values of remnant birefringence, providing stability of the photoinduced orientation, what makes them promising materials to use in optical storage applications. Besides, further analysis on the effect of temperature on the induced birefringence of the polymeric networks was also conducted to help optimization of material design. Finally, we had presented some preliminary investigations of surface relief grating recording in the obtained new materials.     

Electricity and telecoms reforms in the EU: Insights from the economics of federalism

The economics of federalism is a broad discipline with more than five decades of experience. It may shed light on how regulatory jurisdiction is allocated in EU electricity and telecommunications markets. The liberalization of these markets has been accompanied by gradual harmonization of national markets to overcome resistance to competitive forces. Less steps than necessary have been undertaken to promote market integration. Positive and normative reasons remain however for the participation of national or even regional/local powers. Vertical cooperation will remain a necessary condition of a sound regulatory framework, but cooperation may sometimes be inhibited by distributive considerations.     

Electrocatalytic properties of diamond in the oxidation of a persistant pollutant

This work is focused on the study of the role of several conductive-diamond characteristics (boron doping, sp³/sp² ratio, diamond-layer thickness) on the performance of the electrolysis of enrofloxacin (as model complex-organic pollutant). Commercial lots provided by an important conductive-diamond manufacturing company have been used. Results show that enrofloxacin electrooxidation is strongly influenced by the conductive-diamond characteristics; particularly the ratio diamond/graphite carbon was found one of the most significant parameters in this process: the higher the content in diamond-carbon the greater the TOC and COD decays in the bulk electrolyses. These results have been interpreted in terms of the oxidation mechanism involved. High graphite content favours direct oxidation of the pollutant on the electrode surface and leads to the formation of many intermediates. On contrary, high diamond content seems to favour the complete oxidation of the organic to carbon dioxide, thanks to the contribution of the oxidants (hydroxyl radicals and electrogenerated reagents) present in a region close to the electrode surface. Likewise, the oxidation rate seems to be improved with increase in the concentration of boron and decrease in the thickness of the substrate layer.     

Swallowing changes in cerebrovascular accidents: incidence, natural history, and repercussions on the nutritional status, morbidity, and mortality

OBJECTIVE: To determine the frequency of dysphagia in CVA, its natural history and value as a risk factor of respiratory infection, malnutrition and death. PATIENTS AND METHODS: A prospective study was made of 187 consecutive patients with cerebrovascular accidents (CVA). A standardized test for dysphagia was done during the first two days of the illness and repeated three days a week. The levels of urea, total proteins and albumin were determined on admission and on discharge. The patients were questioned by phone after 6 months. RESULTS: There was dysphagia of liquids in 36.4% of the patients. The incidence of dysphagia for semisolids was of the same frequency but more severe. Coma was the cause of inability to swallow in 25.7% of the patients. During their stay in hospital one third of the patients with dysphagia died, one third became normal and one third still had dysphagia when they were discharged. After one week, one, three and six months respectively, the cure rate for dysphagia was 29.4%, 4.1%, 55.9% and 55.9%, and survival 83.8%, 67.6%, 61.8% and 60.3%. Thus after 6 months only 3 patients (4.4%) were alive and dysphagic. Half of the 'cures' occurred in the first week, and none occurred after more than 77 days. As compared to the non-dysphagic patients, the dysphagic patients had 10 times more risk of respiratory infection, 18 times higher risk of death, greater loss of albumin and less loss of urea. CONCLUSIONS: There is a high prevalence of dysphagia in CVA and although functional prognosis is not unfavorable, respiratory infections, malnutrition and death are frequent.     

Polypyrrole materials doped with weakly coordinating anions: influence of substituents and the fate of the doping anion during the overoxidation process

The influence of weakly coordinating anions with different shapes and substituents has been studied to get the overoxidation resistance limit of the material, ORL. The anions utilized are derivatives of [Co(C₂B₉H₁₁)₂]⁻, [B₁₂H₁₂]²⁻ and [B₁₂H₁₁NH₃]⁻. The following tendencies have been established (1) boron cluster monoanions are to date the anions that offer the highest stability to overoxidation of PPy doped materials (2) the ORL stability of the material can not be attributed only to the shape of the cluster (3) monoanionic clusters are far superior than dianionic to get an ORL rise (4) cluster charge density reduction results in ORL rise as has been observed in [Co(C₂B₉H₁₁)₂]⁻ after incorporation of electron-withdrawing substituents with no electron back-donation (5) globular, rigid and large monoanions are less suitable for enhanced ORL values than elongated and non-rigid species (6) adequate anion's substitution produce a rise in the ORL of the material, thus polyether side-arms are beneficial with [Co(C₂B₉H₁₁)₂]⁻, whereas, T-shaped methylaryl groups are appealing in [B₁₂H₁₁NH₃]⁻ based materials, respectively, (7) substituents on the anions usually imply higher difficulty in the materials' growth. The high boron contents in these materials has permitted to learn on the fate of the doping anions during the overoxidation process. There is a built-up of the concentration of the doping anion in the electrolyte near surface area, whereas, a depletion is observed in the nearest inner layers.     

Occurrence of α-Eleostearic Acid in Parinarium excelsum and Parinarium macrophyllum Seed Oils

The seeds of Parinarium excelsum and P. macrophyllum (Rosaceae or Chrysobalanaceae) yield about 65-66% of oil. ¹³C NMR and gas chromatographic analyses show that these two oils have a high content in α-eleostearic acid, about 62% for P. excelsum and 33% for P. macrophyllum. These results indicate that α-eleosteatic acid can be used as chemotaxonomic tracer and are in agreement, from a chemical point of view, with authors which consider that Chrysobalanaceae constitute a family different from Rosaceae.     

Contact angle measurements of Sn-Ag and Sn-Cu lead-free solders on copper substrates

In this study, the contact angles of four lead-free solders, namely, Sn-3.5Ag, Sn-3.5Ag-4.8Bi, Sn-3.8Ag-0.7Cu, and Sn-0.7Cu (wt.%), were measured on copper substrates at different temperatures. Measurements were performed using the sessile-drop method. Contact angles ranging from 30° to 40° after wetting under vacuum with no fluxes and between 10° and 30° with rosin mildly activated (RMA) and rosin activated (RA) fluxes were obtained. The Sn-3.5Ag-4.8Bi exhibited the lowest contact angles, indicating improved wettability with the addition of bismuth. For all soldering alloys, lower contact angles were observed using RMA flux. Intermetallics formed at the solder/Cu interface were identified as Cu₆Sn₅ adjacent to the solder and Cu₃Sn adjacent to the copper substrate. The Cu₃Sn intermetallic phase was generally not observed when RMA flux was used. The effect of temperature on contact angle was dependent on the type of flux used.     

Risk assessment of the lead intake by consumption of red deer and wild boar meat in Southern Spain

The presence of heavy metals in big game meat may pose a risk to human health. The main objective of this paper is to carry out a risk assessment study (using a probabilistic and point-estimate approach) of lead intake by consumption of red deer and wild boar meat in Southern Spain based on Spanish data collected in the period 2003-2006. In general, the concentration levels found for wild boar meat (mean?=?1291?μg?kg(-1)) were much higher than those observed in red deer meat (mean?=?326?μg?kg(-1)). The results from a point-estimate risk assessment showed that the estimated average intake of lead among different exposure scenarios varied from 0.1 to 6.5 and from 0.3 to 38?μg?kg(-1)?week(-1) for red deer and wild boar meat, respectively; and from 0.3 to 35?μg?kg(-1)?week(-1) for individuals consuming both red deer and wild boar meat, and that the estimated intake of lead by consumption of big game meat differed significantly between hunters and non-hunters, it being higher for hunters. Besides this, results from the probabilistic risk assessment study corroborated the fact that risk is greater in hunter populations, reaching a maximum in individuals consuming only wild boar and both types of meat, with 0.4% and 0.2% of the population above the provisional tolerable weekly intake (PTWI), respectively. Likewise, the hunter populations consuming wild boar and both types of big game meat (red deer and wild boar meat) were exposed to the maximum lead level (56?μg?kg(-1)?week(-1)), which corresponded approximately to 224% of the PTWI. Further data and studies will be needed to give a complete risk estimation in which it will be crucial to consider the contribution to the lead intake level of other foods in the diet of both population groups.     

Removing interference components in time–frequency representations using morphological operators

Time–frequency representations have been of great interest in the analysis and classification of non-stationary signals. The use of highly selective transformation techniques is a valuable tool for obtaining accurate information for studies of this type. The Wigner-Ville distribution has high time and frequency selectivity in addition to meeting some interesting mathematical properties. However, due to the bi-linearity of the transform, interference terms emerge when the transform is applied over multi-component signals. In this paper, we propose a technique to remove cross-components from the Wigner-Ville transform using image processing algorithms. The proposed method exploits the advantages of non-linear morphological filters, using a spectrogram to obtain an adequate marker for the morphological processing of the Wigner-Ville transform. Unlike traditional smoothing techniques, this algorithm provides cross-term attenuations while preserving time–frequency resolutions. Moreover, it could also be applied to distributions with different interference geometries. The method has been applied to a set of different time–frequency transforms, with promising results.