559 research outputs found

    Line and Continuum Variability in Active Galaxies

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    We compared optical spectroscopic and photometric data for 18 AGN galaxies over 2 to 3 epochs, with time intervals of typically 5 to 10 years. We used the Multi-Object Double Spectrograph (MODS) at the Large Binocular Telescope (LBT) and compared the spectra to data taken from the SDSS database and the literature. We find variations in the forbidden oxygen lines as well as in the hydrogen recombination lines of these sources. For 4 of the sources we find that, within the calibration uncertainties, the variations in continuum and line spectra of the sources are very small. We argue that it is mainly the difference in black hole mass between the samples that is responsible for the different degree of continuum variability. In addition we find that for an otherwise constant accretion rate the total line variability (dominated by the narrow line contributions) reverberates the continuum variability with a dependency ΔLline∝(ΔLcont.)32\Delta L_{line} \propto (\Delta L_{cont.})^{\frac{3}{2}}. Since this dependency is prominently expressed in the narrow line emission it implies that the luminosity dominating part of the narrow line region must be very compact with a size of the order of at least 10 light years. A comparison to literature data shows that these findings describe the variability characteristics of a total of 61 broad and narrow line sources.Comment: 30 pages including the appendix, 18 figures including the appendix. Accepted 2015 September 3. Received 2015 August 24; in original form 2015 July 3 in Monthly Notices of the Royal Astronomical Societ

    Cultural heritage and Tourism: Luxor of Egypt? Las Vegas?

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    Abstract: Luxor (Thebes for the ancient Greeks); the treasure of world-renowned monuments is one of the major nodes on the Egyptian map of tourism. The form and fabric of Luxor is a story of 5000 years of history and development. This longstanding historical development, accompanied with continuous physical, social and political change, has made it's the conservation of Luxor a rather difficult task. The burgeoning populations combined with the hordes of tourists visiting each year have caused more havoc in the past few decades than thousands of years of erosion. Appeals are made for the safe-guarding of Luxor, studies and planes have been undertaken, but unfortunately, reality has always been frustrating. On the other hand, a mock-up of Luxor heritage was presented in Luxor Mega hotel project of Las Vegas (1989); the symbol of the American Dream. The Hotel was built as a 30-story pyramid in an Egyptian style, rising from the desert with 4,400 rooms and 120,000 square feet of casino space. Prefabricated "Egyptian" attractions and structures are scattered across the vast floor of the Luxor-replicas of tombs, statues of kings and queens. The business of using replicas to promote "heritage" as a vehicle for tourism is remarkable. Ironically, for many the name "Luxor" today means "Luxor, Las Vegas" rather than the real Luxor of Egypt!! The purpose of this paper is two-fold: first, to make a comparative study between both the original and the replica in terms of tourism management and heritage conservation, and second, to discuss the notion of heritage reproduction in terms of its copy-right status, and the implications for such right. Specifically, the paper discusses the following arguments: ‱ Tourism industry has different meanings and dimensions in Luxor Egypt as opposite to Luxor Las Vegas ‱ Real culture tourism could include recreation tourism, while recreational tourism utilizes culture tourism. ‱ Tourism management is the art of how to import people from place to another with political, social, economical and technical aspects. ‱ In the time of globalization, discussions should be given to the issue of copyrights and cultural property (an analogous to "intellectual property") between Luxor Egypt (the original) and its reproduction, Luxor Las Vegas (the replica)

    Experimental Indicators of Accretion Processes in Active Galactic Nuclei

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    Bright Active Galactic Nuclei are powered by accretion of mass onto the super massive black holes at the centers of the host galaxies. For fainter objects star formation may significantly contribute to the luminosity. We summarize experimental indicators of the accretion processes in Active Galactic Nuclei (AGN), i.e., observable activity indicators that allow us to conclude on the nature of accretion. The Galactic Center is the closest galactic nucleus that can be studied with unprecedented angular resolution and sensitivity. Therefore, here we also include the presentation of recent observational results on Sagittarius A* and the conditions for star formation in the central stellar cluster. We cover results across the electromagnetic spectrum and find that the Sagittarius A* (SgrA*) system is well ordered with respect to its geometrical orientation and its emission processes of which we assume to reflect the accretion process onto the super massive black hole.Comment: 16 pages, 4 figures, conference proceeding: Accretion Processes in Cosmic Sources - APCS2016 - 5-10 September 2016, Saint Petersburg, Russi

    GAPPS (Grading and Assessment of Pharmacokinetic-Pharmacodynamic Studies) a critical appraisal system for antimicrobial PKPD studies - development and application in pediatric antibiotic studies

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    Introduction: There are limited data on optimal dosing of antibiotics in different age groups for neonates and children. Clinicians usually consult pediatric formularies or online databases for dose selection, but these have variable recommendations, are usually based on expert opinion and are not graded based on the existing pharmacokinetic-pharmacodynamic (PKPD) studies. We describe here a potential new tool that could be used to grade the strength of evidence emanating from PKPD studies. Areas covered: A scoring system was developed (GAPPS tool) to quantify the strength of each PK assessment and rate the studies quality in already published articles. GAPPS was evaluated by applying it to pediatric PKPD studies of antibiotics from the 2019 Essential Medicines List for children (EMLC), identified through a search of PubMed. Expert opinion: Evidence for most antibiotic dose selection decisions was generally weak, coming from individual PK studies and lacked PKPD modeling and simulations. However, the quality of evidence appears to have improved over the last two decades. Incorporating a formal grading system, such as GAPPS, into formulary development will provide a transparent tool to support decision-making in clinical practice and guideline development, and guide PKPD authors on study designs most likely to influence guidelines

    Modelling and control of a multi-stage interleaved DC-DC converter with coupled inductors for super-capacitor energy storage system

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    Interleaved converters with coupled inductors are widely used to share load current in high power applications. It offers high equivalent switching frequency and reduced output current ripples using small size magnetic components. Due to smaller common-mode inductance, control system can be designed to achieve fast dynamic response. This paper proposes 8 channel interleaved DC/DC converter for interfacing super-capacitor energy storage system to a 400V DC voltage bus. Multi-stage interleaving magnetic circuit with two-phase coupling inductor as a building block is proposed. A methodology is developed to construct the model of the multi-stage magnetic circuit from the basic two-phase coupled inductor model. The derived model is successfully used to evaluate the system power losses and to design the magnetic circuit parameters and its current controller to fulfil the DC/DC converter steady state and dynamic performance specifications. A 20kW/four stage/8 channel DC/DC converter laboratory prototype has been built to connect a super-capacitor stack to 400V DC voltage bus. Experimental investigation validates the modeling, the system losses calculations and the design specifications of the system

    Methionine Adenosyltransferase I/III Deficiency in Portugal: High Frequency of a Dominantly Inherited Form in a Small Area of Douro High Lands

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    Methionine adenosyltransferase deficienc(MAT I/III deficiency) is an inborn error of metabolism resulting in isolated hypermethioninemia, and usually inherited as an autosomal recessive trait, although a dominant form has been reported in several families. During the last 6 years, approximately 520,000 newborns were screened in the Portuguese Newborn Screening Laboratory by MS/MS, and 21 cases of persistent hypermethioninemia were found. One case was confirmed to be a deficiency of cystathionine b-synthase and 20 cases were confirmed by MAT1A gene analysis to have an elevation of methionine due to MAT I/III deficiency, which indicates an incidence for this condition of 1/26,000. Twelve of the MAT I/III deficient newborns, belonging to 11 families, were identified in the northern region of Portugal and sent to the same treatment center, where they are under follow-up. Clinical, biochemical, and genetic characteristics of individuals from these 11 families are presented. Plasma methionine and homocysteine concentrations were found to be moderately increased in all newborns, and molecular analysis revealed that they all were heterozygous for R264H mutation. Normal growth,development, and neurological examination were observed in all cases, and cerebral MRI performed in six cases revealed myelination abnormalities in one case. Plasma methionine concentration for all 12 cases was always below 300 mM, and they are all on a normal diet for their age
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