3,418 research outputs found

    Foliations and Chern-Heinz inequalities

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    We extend the Chern-Heinz inequalities about mean curvature and scalar curvature of graphs of C2C^{2}-functions to leaves of transversally oriented codimension one C2C^{2}-foliations of Riemannian manifolds. That extends partially Salavessa's work on mean curvature of graphs and generalize results of Barbosa-Kenmotsu-Oshikiri \cite{barbosa-kenmotsu-Oshikiri} and Barbosa-Gomes-Silveira \cite{barbosa-gomes-silveira} about foliations of 3-dimensional Riemannian manifolds by constant mean curvature surfaces. These Chern-Heinz inequalities for foliations can be applied to prove Haymann-Makai-Osserman inequality (lower bounds of the fundamental tones of bounded open subsets Ω⊂R2\Omega \subset \mathbb{R}^{2} in terms of its inradius) for embedded tubular neighborhoods of simple curves of Rn\mathbb{R}^{n}.Comment: This paper is an improvment of an earlier paper titled On Chern-Heinz Inequalities. 8 Pages, Late

    Gipsy 3D: Analysis, Visualization and Vo-Tools

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    The scientific goals of the AMIGA project are based on the analysis of a significant amount of spectroscopic 3D data. In order to perform this work we present an initiative to develop a new VO compliant package, including present core applications and tasks offered by the Groningen Image Processing System (GIPSY), and new ones based on use cases elaborated in collaboration with ad- vanced users. One of the main goals is to provide local interoperability between GIPSY (visualization and data analysis) and other VO software. The connectivity with the Virtual Observatory environment will provide general access to 3D data VO archives and services, maximizing the potential for scientific discovery.Comment: 2 pages, 1 figure, to appear in the proceedings of the "Multi-wavelength Astronomy and Virtual Observatory" Workshop held at ESAC 1-3 Dec 200

    Monitoring biofilm formation by using cyclic voltametry: effect of the experimental conditions on biofilm removal and activity

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    The effect of experimental conditions on cyclic voltammetry experiments on platinum electrodes covered with biofilms formed by Pseudomonas fluorescens for 2 hours was investigated. Results show that recycling the potencial stabilizes the shape of the cyclic voltammogram after 130 cycles, but the observation of this electrode by epifluorescence microscopy showed that cells are still adhered to the platinum surface. Some experimental conditions were changed during the electrochemical measurements – sweep rate, pH of the buffer and applied potential range. Some of these parameters had a strong impact on the bacteria that are adhered to the surface, increasing the death and removal in some circumstances.Fundação para a Ciência e a Tecnologia (FCT

    Medical Termination of Delayed Miscarriage: Four-Year Experience with an Outpatient Protocol

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    Purpose: To evaluate the efficacy of an outpatient protocol with vaginal misoprostol to treat delayed miscarriage. Methods: Retrospective analysis of prospectively collected data on women medically treated for missed abortion with an outpatient protocol. The inclusion criteria were: ultrasound-based diagnosis of missed abortion with less than 10 weeks; no heavy bleeding, infection, inflammatory bowel disease or misoprostol allergy; no more than 2 previous spontaneous abortions; the preference of the patient regarding the medical management. The protocol consisted of: 1) a single dose of 800 µg of misoprostol administered intravaginally at the emergency department, after which the patients were discharged home; 2) clinical and ultrasonographic evaluation 48 hours later – if the intrauterine gestational sac was still present, the application of 800 µg of vaginal misoprostol was repeated, and the patients were discharged home; 3) clinical and ultrasonography evaluation 7 days after the initiation of the protocol – if the intrauterine gestational sac was still present, surgical management was proposed. The protocol was introduced in January 2012. Every woman received oral analgesia and written general recommendations. We also gave them a paper form to be presented and filled out at each evaluation. Results: Complete miscarriage with misoprostol occurred in 340 women (90.2%). Surgery was performed in 37 (9.8%) patients, representing the global failure rate of the protocol. Miscarriage was completed after the first misoprostol administration in 208 (55.2%) women, with a success rate after the second administration of 78.1% (132/169). The average age of the women with complete resolution using misoprostol was superior to the average age of those who required surgery (33.99 years versus 31.74 years; p = 0.031). Based on the ultrasonographic findings in the first evaluation, the women diagnosed with fetal loss achieved greater success rates compared with those diagnosed with empty sac (p = 0.049). Conclusions: We conclude this is an effective and safe option in the majority of delayed miscarriage cases during the first trimester, reducing surgical procedures and their consequences

    Fingerprinting the magnetic behavior of antiferromagnetic nanostructures using remanent magnetization curves

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    Antiferromagnetic (AF) nanostructures from Co3O4, CoO and Cr2O3 were prepared by the nanocasting method and were characterized magnetometrically. The field and temperature dependent magnetization data suggests that the nanostructures consist of a core-shell structure. The core behaves as a regular antiferromagnet and the shell as a two-dimensional diluted antiferromagnet in a field (2d DAFF) as previously shown on Co3O4 nanowires [Benitez et al., Phys. Rev. Lett. 101, 097206 (2008)]. Here we present a more general picture on three different material systems, i.e. Co3O4, CoO and Cr2O3. In particular we consider the thermoremanent (TRM) and the isothermoremanent (IRM) magnetization curves as "fingerprints" in order to identify the irreversible magnetization contribution originating from the shells. The TRM/IRM fingerprints are compared to those of superparamagnetic systems, superspin glasses and 3d DAFFs. We demonstrate that TRM/IRM vs. H plots are generally useful fingerprints to identify irreversible magnetization contributions encountered in particular in nanomagnets.Comment: submitted to PR

    Efectos espaciales en la formación de precios en mercados minoristas de Gas Natural Vehicular

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    El mecanismo de fijación de precio de venta de gas natural vehicular (GNV) en las Estaciones de Servicio (EDS´s) en Colombia se asemeja al de un modelo teórico oligopolístico tipo Bertrand, en el cual se identifica una empresa líder en el mercado y otras seguidoras, precio-aceptantes con un alto mark up de beneficios. La ubicación geográfica de las EDS´S, genera estrategias que influyen en la formación del precio. En esta investigación se diseña una matriz de contigüidad espacial, que recoge características socio-económicas y de distancia relacionadas con la ubicación geográfica de las EDS´s y se utiliza un modelo de panel espacial del tipo Durbin, que además incluye variables fundamentales para explicar la formación del precio del GNV.The gas distribution system for natural gas vehicles (NGV) in the Service Stations (EDS) in Colombia is highly concentrated, which gives the retail distributors market power. The pricing mechanism appears to approximate a Bertrand type of oligopolistic model, with a dominant firm setting the prices. The geographical location of the EDS generates strategies that influence price formation. In this research, a spatial contiguity matrix is designed, which includes socio-economic and distance characteristics, related to the EDS geographic location. We use a spatial panel model of Durbin type, which includes fundamental variables to explain the GNV price formation

    Effects of the environment on galaxies in the Catalogue of Isolated Galaxies: physical satellites and large scale structure

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    We aim to identify and quantify the effects of the satellite distribution around a sample of galaxies in the Catalogue of Isolated Galaxies (CIG), as well as the effects of the Large Scale Structure (LSS) using the SDSS-DR9. To recover the physically bound galaxies we focus on the satellites which are within the escape speed of each CIG galaxy. We also propose a more conservative method using the stacked Gaussian distribution of the velocity difference of the neighbours. The tidal strengths affecting the primary galaxy are estimated to quantify the effects of the local and LSS environments. We also define the projected number density parameter at the 5th^{\rm th} nearest neighbour to characterise the LSS around the CIG galaxies. Out of the 386 CIG galaxies considered in this study, at least 340 (88\% of the sample) have no physically linked satellite. Out of the 386 CIG galaxies, 327 (85\% of the sample) have no physical companion within a projected distance of 0.3 Mpc. The CIG galaxies are distributed following the LSS of the local Universe, although presenting a large heterogeneity in their degree of connection with it. A clear segregation appears between early-type CIG galaxies with companions and isolated late-type CIG galaxies. Isolated galaxies are in general bluer, with likely younger stellar populations and rather high star formation with respect to older, redder CIG galaxies with companions. Reciprocally, the satellites are redder and with an older stellar populations around massive early-type CIG galaxies, while they have a younger stellar content around massive late-type CIG galaxies. This suggests that the CIG is composed of a heterogeneous population of galaxies, sampling from old to more recent, dynamical systems of galaxies.Comment: 19 pages, 10 figures, 1 table, accepted for publication in Astronomy & Astrophysic
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