4,689 research outputs found

    GALEX measurements of the Big Blue Bump as a tool to study bolometric corrections in AGNs

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    Active Galactic Nuclei emit over the entire electromagnetic spectrum with the peak of the accretion disk emission in the far-UV, a wavelength range historically difficult to investigate. We use here the GALEX (Galaxy Evolution Explorer) Near-UV and Far-UV measurements (complemented with optical data from Sloan Digital Sky Survey (SDSS) and XMM-Newton X-ray spectra) of a sample of 83 X-ray selected type 1 AGN extracted from the XMM-Newton Bright Serendipitous Survey to study their spectral energy distribution (SED) in the optical, Near and Far-UV and X-ray energy bands. We have constrained the luminosity of the accretion disk emission component and calculated the hard X-ray bolometric corrections for a significant sample of AGN spanning a large range in properties (z, L(x)).Comment: 2 pages, 2 figures, To appear in refereed Proceedings of "X-ray Astronomy 2009: Present Status, Multi-Wavelength Approach and Future Perspectives", Bologna, Italy, September 7-11, 2009, AIP, eds. A. Comastri, M. Cappi, and L. Angelin

    Black-hole masses of type 1 AGN in the XMM-Newton bright serendipitous survey

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    We derive masses of the central super-massive black hole (SMBH) and accretion rates for 154 type1 AGN belonging to a well-defined X-ray-selected sample, the XMM-Newton Serendipitous Sample (XBS). To this end, we use the most recent "single-epoch" relations, based on Hbeta and MgII2798A emission lines, to derive the SMBH masses. We then use the bolometric luminosities, computed on the basis of an SED-fitting procedure, to calculate the accretion rates, both absolute and normalized to the Eddington luminosity (Eddington ratio). The selected AGNs cover a range of masses from 10^7 to 10^10 Msun with a peak around 8x10^8 Msun and a range of accretion rates from 0.01 to ~50 Msun/year (assuming an efficiency of 0.1), with a peak at ~1 Msun/year. The values of Eddington ratio range from 0.001 to ~0.5 and peak at 0.1.Comment: 14 pages, 11 figures. Accepted for publication in Astronomy & Astrophysic

    Botulinum toxin therapy: functional silencing of salivary disorders.

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    Botulinum toxin (BTX) is a neurotoxic protein produced by Clostridium botulinum, an anaerobic bacterium. BTX therapy is a safe and effective treatment when used for functional silencing of the salivary glands in disorders such as sialoceles and salivary fistulas that may have a post-traumatic or post-operative origin. BTX injections can be considered in sialoceles and salivary fistulas after the failure of or together with conservative treatments (e.g. antibiotics, pressure dressings, or serial aspirations). BTX treatment has a promising role in chronic sialadenitis. BTX therapy is highly successful in the treatment of gustatory sweating (Frey\u2019s syndrome), and could be considered the gold standard treatment for this neurological disorder

    Determinants associated with obesity and physical activity in the public and private schools of the city of palermo

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    Introduction: Obesity is a medical condition associated with premature death and it is a risk factor for many chronic diseases. In this context, performing a regular physical activity promotes a healthy lifestyle, with significant health benefits. The aim of the study was to investigate behaviors that increase the risk of obesity and the determinants that encourage physical activity among adolescents. Materials and methods: The HBSC (Health Behavior in School-aged Children) questionnaire was administered to students in Palermo's private and public schools. For the sampling of public schools the protocol of the HBSC Surveillance System was followed; for the private ones it was opportunistic. Results: Private school students are more likely to exercise more than 3 days per week (OR 1.58) and are more likely to exercise more than 2 times a week (OR 2.08). Obese students in private schools in Palermo are more likely to perform physical activity for less than 3 days a week (OR 3.52) and a higher risk of not having breakfast (OR 10.11) and a snack between main meals (OR 3.82) every day. For all the schools examined, it emerged that obese subjects are more likely not to consume fruit (OR 3.13), to stay more than 6 hours a day in front of PCs and video games (OR 3.24) and more than 2 hours a day in front of TV (OR 3.79). Male students are more likely to perform physical activity for more than 3 days per week (OR 1.48) and intense physical activity at least 2 times per week (OR 1.76) Conclusions: It is necessary to intervene early with training on school and family in order to promote correct and responsible food choices and increase the level of physical activity among students. Therefore prevention interventions must be an integral part of coherent strategies based on tests of agreed effectiveness in order to minimize the risk linked to the development of diseases

    A critical analysis of the hydrino model

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    Recently, spectroscopic and calorimetric observations of hydrogen plasmas and chemical reactions with them have been interpreted as evidence for the existence of electronic states of the hydrogen atom with a binding energy of more than 13.6 eV. The theoretical basis for such states, that have been dubbed hydrinos, is investigated. We discuss both, the novel deterministic model of the hydrogen atom, in which the existence of hydrinos was predicted, and standard quantum mechanics. Severe inconsistencies in the deterministic model are pointed out and the incompatibility of hydrino states with quantum mechanics is reviewed.Comment: 9 page

    Low value of detection of KRAS2 mutations in circulating DNA to differentiate chronic pancreatitis to pancreatic cancer

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    We read with great interest the article by Maire et al (2002), who evaluate the K-Ras mutations in circulating DNA to differentiate pancreatic cancer from chronic pancreatitis. Based on this, we also analysed KRAS2 mutations in the serum of 30 patients with pancreatic cancer and 40 patients with chronic pancreatitis. Pancreatic cancer patients were staged by means of dynamic computed tomography, magnetic resonance imaging, and angiography and/or endoscopic ultrasonography. Diagnosis was histologically confirmed for the patients who underwent surgery. The diagnosis of chronic pancreatitis was based on the radiologic data obtained by means of either endoscopic retrograde cholangiopancreatography or computed tomography. DNA was extracted from 20 ml of the serum by using the QIAmp Blood Kit (Qiagen) and the mutations in codon 12 of the K-ras gene were searched as described previously (Jiang et al, 1989). As positive controls, we used DNA from neoplastic tissues of 10 patients with pancreatic carcinoma by using the DNeasy Tissue Kit (Qiagen). For molecular analysis, DNA was amplified in the codon 12 region introducing a restriction site (GACCT) for digestion with BstNl restriction enzyme (PCR-RFLP). DNA from peripheral blood resulted not mutated in the 40 patients with chronic pancreatitis and in the 30 with pancreatic carcinoma, while DNA from pancreatic neoplastic tissue resulted mutated in 70% of the samples. To verify our results, all the samples were analysed by direct sequencing using Big Dye terminator v 1.1 cycle sequencing Kit and performing runs on ABI Prism 310 genetic analyzer (Applied Biosystem) Despite what was mentioned in Maire's article, we failed to find any mutations in all patients analysed, as well as we failed to correlate K-ras mutations with the levels of tumour markers such as Ca 19.9, CA242, CA50, CEA. The results of the present investigation lead us to these conclusions: (1) the eventual presence of cancer cells in peripheral blood may be a rare event, even if numerous reports support the detection of K-ras abnormalities in the serum, (2) neoplastic cells are supposed to circulate in clusters, and consequently their cognition could be hampered by a single blood sample extraction. (3) Large amounts of nonmutated DNA, coming from leucocytes held in the buffy coat layer, might also mask some vestiges of the mutant type of K-ras gene
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