1,122 research outputs found

    Nanostructured exchange coupled hard / soft composites: from the local magnetization profile to an extended 3D simple model

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    In nanocomposite magnetic materials the exchange coupling between phases plays a central role in the determination of the extrinsic magnetic properties of the material: coercive field, remanence magnetization. Exchange coupling is therefore of crucial importance in composite systems made of magnetically hard and soft grains or in partially crystallized media including nanosized crystallites in a soft matrix. It has been shown also to be a key point in the control of stratified hard / soft media coercive field in the research for optimized recording media. A signature of the exchange coupling due to the nanostructure is generally obtained on the magnetization curve M(H)M(H) with a plateau characteristic of the domain wall compression at the hard/soft interface ending at the depinning of the wall inside the hard phase. This compression / depinning behavior is clearly evidenced through one dimensional description of the interface, which is rigorously possible only in stratified media. Starting from a local description of the hard/soft interface in a model for nanocomposite system we show that one can extend this kind of behavior for system of hard crystallites embedded in a soft matrix.Comment: 18 pages, 8 figures. To be published in the Journal of Magnetism and Magnetic Materials. (To be found at http://www.sciencedirect.com/science/journal/03048853

    Preliminary notes on invasion and proliferation of foodborne Listeria monocytogenes strains

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    In this study, virulence properties of L. monocytogenes strains isolated from food and food environments were evaluated. In particular, adhesion and invasion efficiencies were tested in a cell culture model (HeLa). Half of the isolates (9/18) exhibited a high invasion index. In particular, the strain isolated from smoked salmon had the highest invasion index. The remaining isolates showed an intermediate invasion index. All environmental isolates belonged to this group. Finally, no isolates revealed a low invasion index. Regarding intracellular growth, all tested isolates had a replication time between 2 and 6 hours. For this reason, they can be considered virulent. In spite of its capability to invade HeLa cells with a medium/high invasion index, a non-haemolytic rabbit isolate did not show any intracellular growth. In conclusion, differences in invasion efficiency and intracellular growth did not seem strictly related to the origin of the strains. Moreover, invasiveness of an organism is not the only requirement for establishing an infection. Virulence of L. monocytogenes also depends on ability to grow intracellularly and to spread from cell to cell. For these reasons, PCR detection of known virulence genes has the potential to gain additional insight into their pathogenic potential. A comprehensive comparative virulence characterization of different L. monocytogenes strains in studies that include tissue culture models and PCR detection of virulence genes will be necessary to investigate differences in human-pathogenic potentials among the subtypes of this bacterium

    Desarrollo de un chip de DNA para la detección de dianas génicas bacterianas de interés en el campo de la acuicultura

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    La adquisición bacteriana de multiresistencias frente a antimicrobianos es un fenómeno cada vez más preocupante, con gran repercusión para la salud pública, pero también con impacto en sectores de la producción animal, como es el caso particular de la acuicultura. Entre los años 2010-2012, como objetivo de un Proyecto de Investigación Italiano (Progetti d’interesse Nazionale, PRIN), se realizaron diferentes campañas de muestreo a lo largo de la costa del mar Adriático, en centros dedicados a la acuicultura y áreas costeras, estudiando la incidencia de bacterias multiresistentes, así como de los elementos genéticos móviles responsables de su adquisición, desarrollando además una herramienta biotecnológica que agiliza este tipo de estudios permitiendo detectar 164 dianas génicas en un único soporte. Se obtuvo una colección de 1274 aislados bacterianos, a partir de muestras de agua, sedimento y biofilm, resistentes a las distintas combinaciones de antibióticos utilizados según la legislación italiana. Del total, 105 (8,25%) aislados resultaron ser multiresistentes, detectándose en el 13,59% el integrón de clase I, en el 14,56% el plásmido pAb5s9, en el 5,82% el elemento SXT/R391, y en el 15,52% diferentes combinaciones de estos elementos genéticos. Basándonos en estos resultados, se ha desarrollado y validado un chip de DNA que permite detectar en un mismo soporte, genes que codifican para determinantes de resistencia a antimicrobianos, elementos genéticos móviles (MGE), genes para la detección de especies bacterianas patógenas con repercusión en acuicultura y para la salud del hombre, e indicadores de contaminación fecal.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

    Magnetoelectric CoFe2O4/polyvinylidene fluoride electrospun nanofibres.

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    Magnetoelectric 0-1 composites comprising CoFe2O4 (CFO) nanoparticles in a polyvinylidene fluoride (PVDF) polymer-fibre matrix have been prepared by electrospinning. The average diameter of the electrospun composite fibres is ∼325 nm, independent of the nanoparticle content, and the amount of the crystalline polar β phase is strongly enhanced when compared to pure PVDF polymer fibres. The piezoelectric response of these electroactive nanofibres is modified by an applied magnetic field, thus evidencing the magnetoelectric character of the CFO/PVDF 0-1 composites.This work was supported by FEDER through the COMPETE Program and by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Project PEST C/FIS/UI607/2014 and PTDC/CTM NAN/112574/2009. R. G., P. M., V. S., G. B. and S. L. M. acknowledge support from “Matepro – Optimizing Materials and Processes” (ref. NORTE-07-0124-FEDER-000037), co funded by “Programa Operacional Regional do Norte” (ON.2 – O Novo Norte, QREN, FEDER). P. M. and R. Gonçalves acknowledges also support from FCT (SFRH/BPD/96227/2013 and SFRH/BD/88397/2012 grants respectively). X. M. acknowledges support from the Ramón y Cajal (RYC) Programme (Spanish MEC) and the Royal Society.This is the accepted manuscript. The final version is available at http://pubs.rsc.org/en/Content/ArticleLanding/2015/NR/c5nr00453e#!divAbstract

    Pentacene thin films on ferromagnetic oxide: Growth mechanism and spintronic devices

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    [EN] Cation-exchange membranes made exclusively from ceramic materials have been synthesized by means of the impregnation of microporous ceramic supports with zirconium phosphate. Changes in the pore size distribution and total pore volume of the supports were provoked by the addition of starch as pore former in the fabrication procedure. This allowed the production of supports with increased effective electrical conductivities and with larger pores available for the zirconium phosphate deposition. An improved functionality for the exchange of cations was given to the ceramic membranes by means of their impregnation with the active particles of zirconium phosphate. The ion-exchange properties of the membranes were increased with further impregnation cycles and the resulting current–voltage curves showed a similar shape to that typical of commercial polymeric ion-exchange membranes. The production of ionexchange membranes with increased chemical and radiation stability will broaden their applicability for the treatment of specific industrial waste waters, which are very aggressive for the current commercial ion-exchange membranes.The authors acknowledge the technical help from Federico Bona at CNR-ISMN in Bologna and the extensive use of the scanning probe microscopes at "Centro Interfacolta Misure" of the University of Parma. Financial support from the FP7 Projects NMP-2010-SMALL-4-263104 (HINTS), NMP3-SL-2010-246073 (GRENADA), and NMP3-LA-2010-246102 (IFOX) is acknowledged.Graziosi, P.; Riminucci, A.; Prezioso, M.; Newby, C.; Brunel, D.; Bergenti, I.; Pullini, D.... (2014). Pentacene thin films on ferromagnetic oxide: Growth mechanism and spintronic devices. Applied Physics Letters. 105(2):1-5. https://doi.org/10.1063/1.4890328S15105

    Influenza delle condizioni di conservazione sulla qualità e sulla stabilità nel tempo di filetti di alici sott’olio.

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    The overall quality of semi-preserved anchovy fillets in oil is strongly dependent on the quality of the catch as well as on the manufacturing processes adopted by the fishing industry. The enzymatic processes underlying the fish ripening tend to remain also during the storage, especially if holding temperatures and packaging materials are inappropriate, thus being potentially responsible for the rapid loss of the sensorial properties of the fish product. In the present work the modification over time of different qualitative parameters of samples of anchovy fillets in oil stored in different packaging materials (glass and plastic) and at different temperatures (18 and 28°C) was instrumentally evaluated. The exposure to high temperature determined a rapid and widespread deterioration of the anchovy fillets, while no significant packaging-dependent modification of the organoleptic quality of the fish were identified

    Assessment of the antibiotic resistance profile, genetic heterogeneity and biofilm production of methicillin-resistant staphylococcus aureus (MRSA) isolated from the italian swine production chain

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    The main aim of the present study was to evaluate the level of antibiotic resistance, prevalence and virulence features of methicillin-resistant Staphylococcus aureus (MRSA) isolated from heavy swine at abattoir level and farming environments in Lombardy (Northern Italy). With this scope, 88 different heavy swine farms were surveyed, obtaining a total of n = 440 animal swabs and n = 150 environmental swabs. A total of n = 87 MRSA isolates were obtained, with an overall MRSA incidence of 17.50% (n = 77) among animal samples and a 6.67% (n = 10) among environmental. Molecular characterisation using multilocus sequence typing (MLST) plus spa-typing showed that sequence type ST398/t899 and ST398/t011 were the most commonly isolated genotypes, although other relevant sequence types such as ST1 or ST97 were also found. A lack of susceptibility to penicillins, tetracycline and ceftiofur was detected in >91.95, 85.05 and 48.28% of the isolates, respectively. Resistance to doxycycline (32.18%), enrofloxacin (27.59%) and gentamicin (25.29%) was also observed. Additionally, a remarkable level of antibiotic multiresistance (AMR) was observed representing a 77.01% (n = 67) of the obtained isolates. Genetic analysis revealed that 97.70% and 77.01% of the isolates harboured at least one antibiotic resistance or enterotoxin gene, respectively, pointing out a high isolate virulence potential. Lastly, 55.17% (n = 48) were able to produce measurable amounts of biofilm after 24 h. In spite of the current programmes for antibiotic reduction in intensively farming, a still on-going high level of AMR and virulence potential in MRSA was demonstrated, making this pathogen a serious risk in swine production chain, highlighting once more the need to develop efficient, pathogen-specific control strategies

    Backward pion-nucleon scattering

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    A global analysis of the world data on differential cross sections and polarization asymmetries of backward pion-nucleon scattering for invariant collision energies above 3 GeV is performed in a Regge model. Including the NαN_\alpha, NγN_\gamma, Δδ\Delta_\delta and Δβ\Delta_\beta trajectories, we reproduce both angular distributions and polarization data for small values of the Mandelstam variable uu, in contrast to previous analyses. The model amplitude is used to obtain evidence for baryon resonances with mass below 3 GeV. Our analysis suggests a G39G_{39} resonance with a mass of 2.83 GeV as member of the Δβ\Delta_{\beta} trajectory from the corresponding Chew-Frautschi plot.Comment: 12 pages, 16 figure
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