458 research outputs found

    The New World of News

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    Louis D. Boccardi was the President and Chief Executive Officer of the Associated Press from 1985 to 2003. This is a lightly-edited version of a talk presented at Sacred Heart University on December 1, 2003, as part of the College of Arts and Sciences Lecture Series on Media and Society

    Synthesis of monodispersed Ag-doped bioactive glass nanoparticles via surface modification

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    © 2016 by the authors.Monodispersed spherical Ag-doped bioactive glass nanoparticles (Ag-BGNs) were synthesized by a modified Stöber method combined with surface modification. The surface modification was carried out at 25, 60, and 80 °C, respectively, to investigate the influence of processing temperature on particle properties. Energy-dispersive X-ray spectroscopy (EDS) results indicated that higher temperatures facilitate the incorporation of Ag. Hydroxyapatite (HA) formation on Ag-BGNs was detected upon immersion of the particles in simulated body fluid for 7 days, which indicated that Ag-BGNs maintained high bioactivity after surface modification. The conducted antibacterial assay confirmed that Ag-BGNs had an antibacterial effect on E. coli. The above results thereby suggest that surface modification is an effective way to incorporate Ag into BGNs and that the modified BGNs can remain monodispersed as well as exhibit bioactivity and antibacterial capability for biomedical applications

    Radio morphology-accretion mode link in FRII low-excitation radio galaxies

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    Fanaroff-Riley II low-excitation radio galaxies (FRII-LERGs) are characterized by weak nuclear excitation on pc-scales and by properties typical of powerful FRIIs (defined as high-excitation, hereafter HERGs/BLRGs) on kp-scales. Since a link between the accretion properties and the power of the produced jets is expected both from theory and observations, their nature is still debated. In this work we investigate the X-ray properties of a complete sample of 19 FRII-LERGs belonging to the 3CR catalog, exploiting Chandra and XMM-Newton archival data. We also analyze 32 FRII-HERGs/BLRGs with Chandra data as a control sample. We compared FRII-LERG and FRII-HERG/BLRG X-ray properties and optical data available in literature to obtain a wide outlook of their behavior. The low accretion rate estimates for FRII-LERGs, from both X-ray and optical bands, allow us to firmly reject the hypothesis for that they are the highly obscured counterpart of powerful FRII-HERGs/BLRGs. Therefore, at least two hypothesis can be invoked to explain the FRII-LERGs nature: (i) they are evolving from classical FRIIs because of the depletion of accreting cold gas in the nuclear region, while the extended radio emission is the heritage of a past efficiently accreting activity; (ii) they are an intrinsically distinct class of objects with respect to classical FRIs/FRIIs. Surprisingly, in this direction a correlation between accretion rates and environmental richness is found in our sample. The richer the environment, the more inefficient is the accretion. In this framework, the FRII-LERGs are intermediate between FRIs and FRII-HERGs/BLRGs both in terms of accretion rate and environment.Comment: 13 pages, 7 figures, Accepted for publication in MNRA

    The magnetic field structure in CTA 102 from high-resolution mm-VLBI observations during the flaring state in 2016-2017

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    CONTEXT: Investigating the magnetic field structure in the innermost regions of relativistic jets is fundamental to understanding the crucial physical processes giving rise to jet formation, as well as to their extraordinary radiation output up to γ-ray energies. AIMS: We study the magnetic field structure of the quasar CTA 102 with 3 and 7 mm VLBI polarimetric observations, reaching an unprecedented resolution (∼50 μas). We also investigate the variability and physical processes occurring in the source during the observing period, which coincides with a very active state of the source over the entire electromagnetic spectrum. METHODS: We perform the Faraday rotation analysis using 3 and 7 mm data and we compare the obtained rotation measure (RM) map with the polarization evolution in 7 mm VLBA images. We study the kinematics and variability at 7 mm and infer the physical parameters associated with variability. From the analysis of γ-ray and X-ray data, we compute a minimum Doppler factor value required to explain the observed high-energy emission. RESULTS: Faraday rotation analysis shows a gradient in RM with a maximum value of ∼6 × 104⁴ rad m⁻² and intrinsic electric vector position angles (EVPAs) oriented around the centroid of the core, suggesting the presence of large-scale helical magnetic fields. Such a magnetic field structure is also visible in 7 mm images when a new superluminal component is crossing the core region. The 7 mm EVPA orientation is different when the component is exiting the core or crossing a stationary feature at ∼0.1 mas. The interaction between the superluminal component and a recollimation shock at ∼0.1 mas could have triggered the multi-wavelength flares. The variability Doppler factor associated with such an interaction is large enough to explain the high-energy emission and the remarkable optical flare occurred very close in time.Accepted manuscrip

    Reference standard space hippocampus labels according to the EADC-ADNI harmonized protocol: Utility in automated volumetry

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    BACKGROUND: A harmonized protocol (HarP) for manual hippocampal segmentation on magnetic resonance imaging (MRI) has recently been developed by an international European Alzheimer's Disease Consortium–Alzheimer's Disease Neuroimaging Initiative project. We aimed at providing consensual certified HarP hippocampal labels in Montreal Neurological Institute (MNI) standard space to serve as reference in automated image analyses. METHODS: Manual HarP tracings on the high-resolution MNI152 standard space template of four expert certified HarP tracers were combined to obtain consensual bilateral hippocampus labels. Utility of these reference labels is demonstrated in a simple atlas-based morphometry approach for automated calculation of HarP-compliant hippocampal volumes within SPM software. RESULTS: Individual tracings showed very high agreement among the five expert tracers (pairwise Jaccard indices 0.82–0.87). Automatically calculated hippocampal volumes were highly correlated (rL/R = 0.89/0.91) with gold standard volumes in the HarP benchmark data set (N = 135 MRIs), with a mean volume difference of 9% (standard deviation 7%). CONCLUSION: The consensual HarP hippocampus labels in the MNI152 template can serve as a reference standard for automated image analyses involving MNI standard space normalization

    Security challenges of small cell as a service in virtualized mobile edge computing environments

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    Research on next-generation 5G wireless networks is currently attracting a lot of attention in both academia and industry. While 5G development and standardization activities are still at their early stage, it is widely acknowledged that 5G systems are going to extensively rely on dense small cell deployments, which would exploit infrastructure and network functions virtualization (NFV), and push the network intelligence towards network edges by embracing the concept of mobile edge computing (MEC). As security will be a fundamental enabling factor of small cell as a service (SCaaS) in 5G networks, we present the most prominent threats and vulnerabilities against a broad range of targets. As far as the related work is concerned, to the best of our knowledge, this paper is the first to investigate security challenges at the intersection of SCaaS, NFV, and MEC. It is also the first paper that proposes a set of criteria to facilitate a clear and effective taxonomy of security challenges of main elements of 5G networks. Our analysis can serve as a staring point towards the development of appropriate 5G security solutions. These will have crucial effect on legal and regulatory frameworks as well as on decisions of businesses, governments, and end-users

    MRI analysis for Hippocampus segmentation on a distributed infrastructure

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    Medical image computing raises new challenges due to the scale and the complexity of the required analyses. Medical image databases are currently available to supply clinical diagnosis. For instance, it is possible to provide diagnostic information based on an imaging biomarker comparing a single case to the reference group (controls or patients with disease). At the same time many sophisticated and computationally intensive algorithms have been implemented to extract useful information from medical images. Many applications would take great advantage by using scientific workflow technology due to its design, rapid implementation and reuse. However this technology requires a distributed computing infrastructure (such as Grid or Cloud) to be executed efficiently. One of the most used workflow manager for medical image processing is the LONI pipeline (LP), a graphical workbench developed by the Laboratory of Neuro Imaging (http://pipeline.loni.usc.edu). In this article we present a general approach to submit and monitor workflows on distributed infrastructures using LONI Pipeline, including European Grid Infrastructure (EGI) and Torque-based batch farm. In this paper we implemented a complete segmentation pipeline in brain magnetic resonance imaging (MRI). It requires time-consuming and data-intensive processing and for which reducing the computing time is crucial to meet clinical practice constraints. The developed approach is based on web services and can be used for any medical imaging application
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