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The field of composites materials has evolved from the use of traditional fillers (e.g. carbon and glass fibers) to nanoscale fillers that add unique and often multifunctional properties to the neat polymer. Because nanoparticles have extremely high surface to volume ratios, that alter the mobility of polymer chains near their interfaces, even a small addition of nanoparticles. These components have the potential to drastically transform the properties of the host polymers. While the last decade has observed several advances in the field of nanocomposites, some recent reviews have made it clear that definitive structure-property relationships are insufficient in the literature. The influence of inorganic TiO2 nanoparticles on the dynamic mechanical properties and microstructure of copolymer based on Butyl acrylate - Methyl methacrylate - Acrylic Acid has been investigated. The mechanical relaxations of the reinforced copolymer/TiO2 composites were studied under tension mode. Addition of TiO2 nanoparticles to acrylic copolymer produced a decrease in the glass transition temperature. Dynamic mechanical analysis (DMA) showed that the local motions associated with the alpha-transition (40°C) are enhanced as the frequency of oscillation increases, i.e. the tan d maximum increases at higher frequencies. The addition of TiO2 nanoparticles reduces significantly the strength of the alpha-transition. Thus, the cooperative molecular motions involving segments of the molecular chains associated with the alpha-transition were compromised by the presence of TiO2 nanoparticles resulting in a decrement of the storage modulus.
Based on the nature of the links and interactions existing at the hybrid interface, hybrid materials can be broadly classified in two main designations: a) Hybrid compounds Class I, that include all systems with electrostatic forces, hydrogen bonding or Van der Waals interactions and b) Hybrid compounds Class II, showing that the inorganic and organic components are linked through strong covalent or ionic-covalent bonds. The physico–chemical properties of nanostructured copolymer acrylates based on butyl acrylate (BA), methyl methacrylate (MMA) and acrylic acid (AA) has been investigated employing un-modified SiO2 (Class I) and modified SiO2 particles (Class II) using 3-(trimethoxysilyl) propyl methacrylate (MPS) as compatibilizing agent. The synthesis was carried out using seeded batch emulsion polymerization system. Metastable nanostructured emulsions containing 1 wt% nanoparticles were obtained. Films casted from the in-situ nanostructured latex exhibited excellent optical transparency suggesting good nanoparticles dispersion. However, the mechanical properties showed by SiO2-MPS nanocomposite, are better than the Class I hybrid compounds. Therefore, SiO2-MPS surface treatment prior to polymerization enhances the physical properties of copolymer BA-MMA-AA film. The mass loss derivative traces for the polyacrylic nanocomposites and the neat polymer obtained by thermogravimetric analysis showed that the onset temperature for thermal decomposition was shifted towards a higher temperature than the neat polyacrylic, indicating the enhancement of thermal stability of the un-modified SiO2 nanocomposite. However, there is a decrease of 40°C in the decomposition temperature for the modified polyacrylic nanocomposite. The results obtained so far have shown that weak Van der Waals and H-bonding interactions may be sufficient to enable improvement of the physical properties of the acrylate nanocomposites.
Earth based multichannel photometry of integral sunlight has been obtained at Izaña (Tenerife) during 1984–1986. Power spectra of the solar luminosity variations of individual days show power in the 5 minute interval above noise at a level comparable to SMM datad). When combining contigous days of data the signature of p mode solar oscillations spectrum appears* although individual peak identification is difficult.
The European Union Network ANTENA started to work in October 1993. During these last three years, several collaborative projects have been undertaken. ANTENA has offered a very good opportunity for most of the European people doing asteroseismology to work together. The asteroseismological networks STEPHI and STACC have run within the framework of the project, obtaining fairly good results. New instrumentation has also been developed, such as the Four-Channel Stellar Photometer.
In this work we propose a preliminary seismic investigation of δ Scuti stars in the Pleiades cluster, focusing on potential diagnostics of convection and core-overshooting. Taking into account the effect of fast rotation in the modelling, we compare observed frequencies for 4 δ Scuti stars with radial linear instability predictions. A satisfying agreement is reached between the predicted ranges of unstable modes and those derived from observations for “low-mass” stars (∼ 1.55M⊙). However, a strong disagreement is found for “high-mass” stars (∼ 1.77M⊙), whatever the mixing length (α) value. These results are compared with previous ones obtained for Praesepe.
The δ Scuti stars are pulsating variables located in the lower part of the Cepheid instability strip with spectral types from A2 to F0 on the main sequence, and from A3 to F5 at luminosity class III. These variables show short periods (< 0.3day) and luminosity amplitudes ranging from a few thousandths of a magnitude to several tenths. Over the last few years, significant progress has been made in the detection of pulsating modes in the framework of the multisite campaigns, e.g. STACC (Frandsen et al. 1996), DSN (Breger et al. 1998), STEPHI (Michel et al. 2000). For the 1998 STEPHI IX photometry campaign, the δ Scuti star V534 Tau of the Pleiades cluster (see Table 1) was monitored during a three week, three continent run. Preliminary results are reported here.
On the 1992 STEPHI IV campaign, the multi-periodic δ Scuti stars BN Cnc and BU Cnc of the Praesepe cluster were monitored during a three-week, three-continental run (Belmonte et al. 1994). Five and six frequency peaks, respectively, were recorded as a result of the campaign. In a subsequent paper (Pérez Hernández et al. 1995, hereafter Paper I), an attempt to identify these frequency peaks as pulsation modes was done. An important point is that both stars belong to the same cluster and, hence, more severe constraints than for isolated stars can be imposed. Recently, Breger et al. (1994) have reported results on EP Cnc, another δ Scuti in Praesepe. This star is also multi-periodic, showing three frequency peaks above the noise level. In the present work we extend our analysis to this star.
Some results of the photometry multi-site observations of two δ Scuti stars, V624 Tau and HD 23194, are presented. The observations were carried out in the framework of a STEPHI network in 1999. We collected 343 hours of useful data and detected seven frequencies in V624 Tau and two frequencies in HD 23194.
Influenza vaccination has been shown to be the most effective preventive strategy to reduce influenza-related morbidity and mortality in high-risk groups. Despite healthcare personnel (HCP) being considered part of such high-risk groups, their vaccination coverage is low in Europe. In January 2012, we distributed an 18-question survey regarding influenza vaccination to HCP at Gregorio Marañon Paediatric Hospital, in Madrid, Spain. After we documented that only ~30% of HCP were vaccinated an educational programme was implemented in October 2012 before the next influenza season. In January 2013, the same survey delivered again to all HCP documented a significant increase in vaccination rates (from 30% to 40%, P = 0·007) mainly among physicians and for patients' protection. In summary we found that a simple and inexpensive educational programme significantly improved the uptake of influenza vaccination in HCP in our centre. Nevertheless, vaccination rates remained low, and broader and updated campaigns are needed to overcome perception barriers.
We present a technique to detect Ultra-Faint Dwarf Galaxies (UFDs) in the Galactic Halo, using sky and proper motion information.The method uses wavelet transforms to detect peaks in the sky and proper motion planes, and to evaluate the probability of these being stochastic fluctuations. We aim to map thoroughly the detection limits of this technique. For this, we have produced a library of 15,000 synthetic UFDs, embedded in the Gaia Universe Model Snapshot (GUMS) background (Robin et al. 2012), each at a different distance, different luminosity, half-light radius, velocity dispersion and center-of-mass velocity, varying in ranges that extend well beyond those spanned by known classical and ultra-faint dSphs. We use these synthetic UFDs as a benchmark to characterize the completeness and detection limits of our technique, and present our results as a function of different physical and observable parameters of the UFDs (see full poster for more details at https://gaia.ub.edu/Twiki/pub/GREATITNFC/ProgramFinalconference/Poster_UFGX_Bcn_C_Mateu.pdf).
We have carried out photometry and spectroscopy on a sample of 10 cD galaxies. The photometry shows, in general, fairly flat and red profile colours, implying an envelope with the same stellar population as the central galaxy. This may indicate a possible primordial origin for both structures, consistent with ideas of downsizing. Preliminary spectroscopic results are generally in agreement with the photometry, with for example younger populations at large radii for A2199, but A2589 has only younger populations.
Wolf-Rayet HII galaxies are local metal-poor star-forming galaxies, observed when the most massive stars are evolving from O stars to WR stars, making them template systems to study distant starbursts. We have been performing a program to investigate the interplay between massive stars and gas in WR HII galaxies using IFS. Here, we highlight some results from the first 3D spectroscopic study of Mrk 178, the closest metal-poor WR HII galaxy, focusing on the origin of the nebular HeII emission and the aperture effects on the detection of WR features.
Collagen-covered prostheses can be used as a non-circumferential segmental tracheal replacement. However, the applicability of these implants in young subjects has not yet been reported.
In this experimental, longitudinal study, dogs aged 29–32 days underwent limited segmental tracheal replacement with a polyester prosthesis or were allocated to a control, untreated group. The dogs were evaluated clinically, endoscopically and tomographically for up to one year.
Although there was evidence of tracheal growth in the experimental group, tomographic measurements were significantly smaller in this group than in the control group throughout the observation period. At the end of the study, there was no evidence of implant rejection, stenosis or collapse. Normal respiratory epithelium had grown across the implanted membrane in the experimental group.
The homologous collagen mersylene membrane allowed for limited structural tracheal growth and was functionally integrated into the segmented tracheal wall in growing dogs.
Networks of protected areas are one of the main strategies used to address the biodiversity crisis. These should encompass as many species and ecosystems as possible, particularly in territories with high biological diversity, such as the Spanish arid zones. We produce a priority ranking of the arid zones of south-east Spain according to the rarity and richness of their characteristic flora and the level of endangerment. The resulting hierarchy shows that optimal zones for the preservation of the flora are located outside the network of protected areas. In particular, it is important to extend the network and encourage the creation of microreserves in the depression of the River Guadiana Menor (Granada), where there is least protection. This river valley is a particularly important arid site because of its unique flora and fauna, and palaeontological and archaeological findings.
Introduction. México is one
of the most important producers and exporters of blackberries in
the world. During postharvest handling, blackberry fruits are exposed
to the attack of phytopathogenic fungi. Materials and methods.
To obtain Rhizopus stolonifer isolates, samples
of leaves and rhizospheric soils were placed on Petri plates containing
Potato Dextrose Agar (PDA). In addition, fruits were also placed
in humidity chambers at 25 °C. To describe the infection process
on blackberry fruits by Rhizopus stolonifer, samples
were taken at different intervals for a period of 72 h. All fungal
isolates obtained were maintained on PDA. The bacterial colonies
were isolated and purified by streaking on PDA. The antagonistic
activity of the bacteria was assessed against R. stolonifer by
dual culture technique on PDA. To detect the production of siderophores,
the chrome azurol S assay was carried out. Results.
The infection process of R. stolonifer on blackberry
fruits was described for the first time in this work. Eighty-six
bacterial isolates from different parts of the plant and rhizospheric
soil were obtained. Bacterial isolates with antagonistic activity
were identified and the production of siderophores was measured.
Four isolates showed antagonistic activity against R. stolonifer.
Bacillus subtilis obtained from soil was the most
effective isolate. Conclusion. In this study we isolated
and identified antagonistic bacteria with potential for biocontrol
on Rhizopus stolonifer obtained from blackberry fruits.
To our knowledge this is the first report regarding this topic.
The synthesis of mullite from kaolin clay and two precursors of aluminum: α-Al2O3 and Al(NO3)3 was investigated. In order to study the temperature effect, the system kaolin-α-Al2O3 was calcined in air in a range of 1200 to 1500°C, for 2 h. For the system kaolin-Al(NO3)3, the combustion method was employed, using urea as fuel, and calcined in air at 1500°C for 2 h. The products were characterized by X-ray diffraction, scanning electronic microscopy (SEM), energy dispersive spectroscopy and particle size analysis in order to analyze and compare their morphology and structure. The crystallographic study revealed an incomplete reaction between the kaolin and the α-Al2O3. Nevertheless, in the system kaolin-Al(NO3)3, it was obtained mullite with high purity and trace amounts of cristobalite.
Silicon nanoparticles of 100 nm obtained by high-energy ball milling were characterized by X-ray diffraction (XRD) and transmission electronic microscopy (TEM). Results show dark areas due to a staking of defects. On the other hand, brighter areas exhibit a combination of small crystalline and amorphous zones. To fulfill and cover the micro-cracking and micro-pores generated during the welding process of 304 stainless steels joined by brazing, these nanoparticles were deposited directly in the fracture. The amorphous silicon drove the Transient Liquid Phase (TLP) at 1000°C for 20 min. This amorphous silicon decreases the energies of reaction between the substrate and melting filler. TLP increases the wettability and capillary forces between micro-cracking and micro-pores; due to that, the eutectic phase contained by the melting filler forms a liquid. Moreover, the weld beads were characterized by Scanning Electron Microscopy (SEM) to analyze the effect of silicon nanoparticles on the weld beads. These results showed that the interaction of the Si nanoparticles with metallic filler in the melting zone decreases the size and change the morphology of the present phases as well as the zone of isothermic growth.