1,420 research outputs found

    Multiwavelength campaign on Mrk 509. I. Variability and spectral energy distribution

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    (Abridged) Active galactic nuclei show a wealth of interesting physical processes, some of which are poorly understood. We want to address a number of open questions, including the location and physics of the outflow from AGN, the nature of the continuum emission, the geometry and physical state of the X-ray broad emission line region, the Fe-K line complex, the metal abundances of the nucleus and finally the interstellar medium of our own Galaxy. We study one of the best targets for these aims, the Seyfert 1 galaxy Mrk 509 with a multiwavelength campaign using five satellites (XMM-Newton, INTEGRAL, Chandra, HST and Swift) and two ground-based facilities (WHT and PAIRITEL). Our observations cover more than five decades in frequency, from 2 um to 200 keV. The combination of high-resolution spectroscopy and time variability allows us to disentangle and study the different components. Our campaign covers 100 days from September to December 2009, and is centred on a simultaneous set of deep XMM-Newton and INTEGRAL observations with regular time intervals, spanning seven weeks. We obtain a continuous light curve in the X-ray and UV band, showing a strong, up to 60% flux increase in the soft X-ray band during the three weeks in the middle of our deepest monitoring campaign, and which is correlated with an enhancement of the UV flux. This allows us to study the time evolution of the continuum and the outflow. By stacking the observations, we have also obtained one of the best X-ray and UV spectra of a Seyfert galaxy ever obtained. In this paper we also study the effects of the spectral energy distribution (SED) that we obtained on the photo-ionisation equilibrium. Thanks to our broad-band coverage, uncertainties on the SED do not strongly affect the determination of this equilibrium.Comment: 10 pages, 5 figures, 2 tables. Accepted for publication in Astronomy & Astrophysic

    Proposal for the determination of nuclear masses by high-precision spectroscopy of Rydberg states

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    The theoretical treatment of Rydberg states in one-electron ions is facilitated by the virtual absence of the nuclear-size correction, and fundamental constants like the Rydberg constant may be in the reach of planned high-precision spectroscopic experiments. The dominant nuclear effect that shifts transition energies among Rydberg states therefore is due to the nuclear mass. As a consequence, spectroscopic measurements of Rydberg transitions can be used in order to precisely deduce nuclear masses. A possible application of this approach to the hydrogen and deuterium, and hydrogen-like lithium and carbon is explored in detail. In order to complete the analysis, numerical and analytic calculations of the quantum electrodynamic (QED) self-energy remainder function for states with principal quantum number n=5,...,8 and with angular momentum L=n-1 and L=n-2 are described (j = L +/- 1/2).Comment: 21 pages; LaTe

    Long Overall Survival After Dendritic Cell Vaccination in Metastatic Uveal Melanoma Patients

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    Purpose: To assess the safety and efficacy of dendritic cell vaccination in metastatic uveal melanoma. Design: Interventional case series. Methods: We analyzed 14 patients with metastatic uveal melanoma treated with dendritic cell vaccination. Patients with metastatic uveal melanoma received at least 3 vaccinations with autologous dendritic cells, professional antigen-presenting cells loaded with melanoma antigens gp100 and tyrosinase. The main outcome measures were safety, immunologic response, and overall survival. Results: Tumor-specific immune responses were induced with dendritic cell vaccination in 4 (29%) of14 patients. Dendritic cell-vaccinated patients showed a median overall survival with metastatic disease of 19.2months, relatively long compared with that reported in the literature. No severe treatment-related toxicities (common toxicity criteria grade 3 or 4) were observed. Conclusions: Dendritic cell vaccination is feasible and safe in metastatic uveal melanoma. Dendritic cell-based immunotherapy is potent to enhance the host's antitumor immunity against uveal melanoma in approximately one third of patients. Compared with other prospective studies with similar inclusion criteria, dendritic cell vaccination may be associated with longer than average overall survival in patients with metastatic uveal melanoma

    Long-term recurrence and complication rates after incisional hernia repair with the open onlay technique

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    <p>Abstract</p> <p>Background</p> <p>Incisional hernia after abdominal surgery is a well-known complication. Controversy still exists with respect to the choice of hernia repair technique. The objective of this study was to evaluate the long-term recurrence rate as well as surgical complications in a consecutive group of patients undergoing open repair using an onlay mesh technique.</p> <p>Methods</p> <p>Consecutive patients undergoing open incisional hernia repair with onlay-technique between 01/05/1995 and 01/09/2007 at a single institution were included in the study. For follow-up patients were contacted by telephone, and answered a questionnaire containing questions related to the primary operation, the hernia and general risk factors. Patients were examined by a consultant surgeon in the outpatient clinic or in the patient's home if there was suspicion of an incisional hernia recurrence.</p> <p>Results</p> <p>The study included 56 patients with 100% follow-up. The median follow-up was 35 months (range 4–151). Recurrent incisional hernia was found in 8 of 56 patients (15%, 95% CI: 6–24). The overall complication rate was 13% (95% CI, 4–22). All complications were minor and needed no hospital admission.</p> <p>Conclusion</p> <p>This study with a long follow-up showed low recurrence and complication rates in patients undergoing incisional hernia repair with the open onlay technique.</p

    Shaping bursting by electrical coupling and noise

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    Gap-junctional coupling is an important way of communication between neurons and other excitable cells. Strong electrical coupling synchronizes activity across cell ensembles. Surprisingly, in the presence of noise synchronous oscillations generated by an electrically coupled network may differ qualitatively from the oscillations produced by uncoupled individual cells forming the network. A prominent example of such behavior is the synchronized bursting in islets of Langerhans formed by pancreatic \beta-cells, which in isolation are known to exhibit irregular spiking. At the heart of this intriguing phenomenon lies denoising, a remarkable ability of electrical coupling to diminish the effects of noise acting on individual cells. In this paper, we derive quantitative estimates characterizing denoising in electrically coupled networks of conductance-based models of square wave bursting cells. Our analysis reveals the interplay of the intrinsic properties of the individual cells and network topology and their respective contributions to this important effect. In particular, we show that networks on graphs with large algebraic connectivity or small total effective resistance are better equipped for implementing denoising. As a by-product of the analysis of denoising, we analytically estimate the rate with which trajectories converge to the synchronization subspace and the stability of the latter to random perturbations. These estimates reveal the role of the network topology in synchronization. The analysis is complemented by numerical simulations of electrically coupled conductance-based networks. Taken together, these results explain the mechanisms underlying synchronization and denoising in an important class of biological models

    Inhibition of Osteoclastogenesis by Mechanically Loaded Osteocytes: Involvement of MEPE

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    In regions of high bone loading, the mechanoresponsive osteocytes inhibit osteoclastic bone resorption by producing signaling molecules. One possible candidate is matrix extracellular phosphoglycoprotein (MEPE) because acidic serine- and aspartate-rich MEPE-associated motif peptides upregulate osteoprotegerin (OPG) gene expression, a negative regulator of osteoclastogenesis. These peptides are cleaved from MEPE when relatively more MEPE than PHEX (phosphate-regulating gene with homology to endopeptidases on the X chromosome) is present. We investigated whether mechanical loading of osteocytes affects osteocyte-stimulated osteoclastogenesis by involvement of MEPE. MLO-Y4 osteocytes were mechanically loaded by 1-h pulsating fluid flow (PFF; 0.7 ± 0.3 Pa, 5 Hz) or kept under static control conditions. Recombinant MEPE (0.05, 0.5, or 5 μg/ml) was added to some static cultures. Mouse bone marrow cells were seeded on top of the osteocytes to determine osteoclastogenesis. Gene expression of MEPE, PHEX, receptor activator of nuclear factor kappa-B ligand (RANKL), and OPG by osteocytes was determined after PFF. Osteocytes supported osteoclast formation under static control conditions. Both PFF and recombinant MEPE inhibited osteocyte-stimulated osteoclastogenesis. PFF upregulated MEPE gene expression by 2.5-fold, but not PHEX expression. PFF decreased the RANKL/OPG ratio at 1-h PFF treatment. Our data suggest that mechanical loading induces changes in gene expression by osteocytes, which likely contributes to the inhibition of osteoclastogenesis after mechanical loading of bone. Because mechanical loading upregulated gene expression of MEPE but not PHEX, possibly resulting in the upregulation of OPG gene expression, we speculate that MEPE is a soluble factor involved in the inhibition of osteoclastogenesis by osteocytes

    Tensor Analyzing Powers for Quasi-Elastic Electron Scattering from Deuterium

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    We report on a first measurement of tensor analyzing powers in quasi-elastic electron-deuteron scattering at an average three-momentum transfer of 1.7 fm1^{-1}. Data sensitive to the spin-dependent nucleon density in the deuteron were obtained for missing momenta up to 150 MeV/cc with a tensor polarized 2^2H target internal to an electron storage ring. The data are well described by a calculation that includes the effects of final-state interaction, meson-exchange and isobar currents, and leading-order relativistic contributions.Comment: 4 pages, 3 figure

    An All-Sky Search for Three Flavors of Neutrinos from Gamma-Ray Bursts with the IceCube Neutrino Observatory

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    We present the results and methodology of a search for neutrinos produced in the decay of charged pions created in interactions between protons and gamma-rays during the prompt emission of 807 gamma-ray bursts (GRBs) over the entire sky. This three-year search is the first in IceCube for shower-like Cherenkov light patterns from electron, muon, and tau neutrinos correlated with GRBs. We detect five low-significance events correlated with five GRBs. These events are consistent with the background expectation from atmospheric muons and neutrinos. The results of this search in combination with those of IceCube's four years of searches for track-like Cherenkov light patterns from muon neutrinos correlated with Northern-Hemisphere GRBs produce limits that tightly constrain current models of neutrino and ultra high energy cosmic ray production in GRB fireballs.Comment: 33 pages, 14 figures; minor changes made to match published version in the Astrophysical Journal, 2016 June 2

    Improved limits on dark matter annihilation in the Sun with the 79-string IceCube detector and implications for supersymmetry

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    We present an improved event-level likelihood formalism for including neutrino telescope data in global fits to new physics. We derive limits on spin-dependent dark matter-proton scattering by employing the new formalism in a re-analysis of data from the 79-string IceCube search for dark matter annihilation in the Sun, including explicit energy information for each event. The new analysis excludes a number of models in the weak-scale minimal supersymmetric standard model (MSSM) for the first time. This work is accompanied by the public release of the 79-string IceCube data, as well as an associated computer code for applying the new likelihood to arbitrary dark matter models.Comment: 24 pages, 8 figs, 1 table. Contact authors: Pat Scott & Matthias Danninger. Likelihood tool available at http://nulike.hepforge.org. v2: small updates to address JCAP referee repor

    All-sky search for time-integrated neutrino emission from astrophysical sources with 7 years of IceCube data

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    Since the recent detection of an astrophysical flux of high energy neutrinos, the question of its origin has not yet fully been answered. Much of what is known about this flux comes from a small event sample of high neutrino purity, good energy resolution, but large angular uncertainties. In searches for point-like sources, on the other hand, the best performance is given by using large statistics and good angular reconstructions. Track-like muon events produced in neutrino interactions satisfy these requirements. We present here the results of searches for point-like sources with neutrinos using data acquired by the IceCube detector over seven years from 2008--2015. The discovery potential of the analysis in the northern sky is now significantly below Eν2dϕ/dEν=1012TeVcm2s1E_\nu^2d\phi/dE_\nu=10^{-12}\:\mathrm{TeV\,cm^{-2}\,s^{-1}}, on average 38%38\% lower than the sensitivity of the previously published analysis of four years exposure. No significant clustering of neutrinos above background expectation was observed, and implications for prominent neutrino source candidates are discussed.Comment: 19 pages, 17 figures, 3 tables; ; submitted to The Astrophysical Journa
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