607 research outputs found
Long sandwich modules for photon veto detectors
Long lead-scintillator sandwich modules developed for the BNL experiment
KOPIO are described. The individual 4 m long module consists of 15 layers of 7
mm thick extruded scintillator and 15 layers of 1 mm lead absorber. Readout is
implemented via WLS fibers glued into grooves in a scintillator with 7 mm
spacing and viewed from both ends by the phototubes. Time resolution of 300 ps
for cosmic MIPs was obtained. Light output stability monitored for 2 years
shows no degradation beyond the measurement errors. A 4 m long C-bent sandwich
module was also manufactured and tested.Comment: 14 pages, 13 figures, 1 tabl
A panchromatic analysis of starburst galaxy M82: Probing the dust properties
(Abridged) We combine NUV, optical and IR imaging of the nearby starburst
galaxy M82 to explore the properties of the dust both in the interstellar
medium of the galaxy and the dust entrained in the superwind. The three NUV
filters of Swift/UVOT enable us to probe in detail the properties of the
extinction curve in the region around the 2175A bump. The NUV colour-colour
diagram strongly rules out a Calzetti-type law, which can either reflect
intrinsic changes in the dust properties or in the star formation history
compared to starbursts well represented by such an attenuation law. We
emphasize that it is mainly in the NUV region where a standard Milky-Way-type
law is preferred over a Calzetti law. The age and dust distribution of the
stellar populations is consistent with the scenario of an encounter with M81 in
the recent 400 Myr. The radial gradients of the NUV and optical colours in the
superwind region support the hypothesis that the emission in the wind cone is
driven by scattering from dust grains entrained in the ejecta. The observed
wavelength dependence reveals either a grain size distribution , where is the size of the grain, or a flatter distribution with a
maximum size cutoff, suggesting that only small grains are entrained in the
supernovae-driven wind.Comment: 12 pages, 12 figures, 3 tables, MNRAS, in pres
USAGE OF INTERVAL CAUSE-EFFECT RELATIONSHIP COEFFICIENTS IN THE QUANTITATIVE MODEL OF STRATEGIC PERFORMANCE
This paper proposes the method to obtain values of the coefficients of cause-effect relationships between strategic objectives in the form of intervals and use them in solving the problem of the optimal allocation of organization’s resources. We suggest taking advantage of the interval analytical hierarchy process for obtaining the ntervals. The quantitative model of strategic performance developed by M. Hell, S. Vidučić and Ž. Garača is employed for finding the optimal resource allocation. The uncertainty originated in the optimization problem as a result of interval character of the cause-effect relationship coefficients is eliminated through the application of maximax and maximin criteria. It is shown that the problem of finding the optimal maximin, maximax, and compromise resource allocation can be represented as a mixed 0-1 linear programming problem. Finally, numerical example and directions for further research are given
ДЕНЕЖНО-КРЕДИТНАЯ ПОЛИТИКА: ОСТАЕТСЯ НЕМАЛО ВОПРОСОВ
The ruble economy must be shaped by a correct monetary policy; therefore, ruble assets must be estimated more realistically (which means they should cost more). „When they try to convince us that the weak ruble is better for us it seems absurd and akin to the saying that the more lightweighted is the salary we receive or are the rubles placed with our bank accounts or in the purse and the less we can buy for them it is advantageous for us. We are setting up the ruble-, not the dollar-based economy, and the more expensive will be ruble assets owned by the households and business, the richer they will be. Of course, mechanisms are needed to protect the domestic market and promote exports. But who said that they are all confined to the exchange rate? After all, its impact has often opposite venues, and the devaluation stimulates primarily the export of raw materials increasing the dependence of our economy on the world market…” (from an interview with „Bankovsky Ryad”).Правильная денежно-кредитная политика должна формировать рублевую экономику, для этого необходимо, чтобы рублевые активы оценивались более реально (а это означает - они должны стоить дороже). «Когда нам пытаются доказать, что при слабом рубле нам же лучше, - это абсурдно и равносильно утверждению, что та зарплата, которую мы получаем, и те рубли, которые лежат у нас на вкладах или в кошельке, чем они легковеснее и чем на них меньше можно купить, тем нам же выгоднее. Мы формируем рублевую, а не долларовую экономику, и чем дороже будут рублевые активы у населения и бизнеса, тем они богаче… Конечно, нужно использовать рычаги защиты внутреннего рынка и стимулирования экспорта. Но кто сказал, что все они сводятся только к валютному курсу? Ведь его воздействие часто носит разнонаправленный характер, а девальвация лишь стимулирует сырьевой экспорт, увеличивая зависимость нашей экономики от мировой конъюнктуры…» (из интервью журналу «Банковский ряд»)
The use and calibration of read-out streaks to increase the dynamic range of the Swift Ultraviolet/Optical Telescope
The dynamic range of photon counting micro-channel-plate (MCP) intensified
charged-coupled device (CCD) instruments such as the Swift Ultraviolet/Optical
Telescope (UVOT) and the XMM-Newton Optical Monitor (XMM-OM) is limited at the
bright end by coincidence loss, the superposition of multiple photons in the
individual frames recorded by the CCD. Photons which arrive during the brief
period in which the image frame is transferred for read out of the CCD are
displaced in the transfer direction in the recorded images. For sufficiently
bright sources, these displaced counts form read-out streaks. Using UVOT
observations of Tycho-2 stars, we investigate the use of these read-out streaks
to obtain photometry for sources which are too bright (and hence have too much
coincidence loss) for normal aperture photometry to be reliable. For
read-out-streak photometry, the bright-source limiting factor is coincidence
loss within the MCPs rather than the CCD. We find that photometric measurements
can be obtained for stars up to 2.4 magnitudes brighter than the usual
full-frame coincidence-loss limit by using the read-out streaks. The resulting
bright-limit Vega magnitudes in the UVOT passbands are UVW2=8.80, UVM2=8.27,
UVW1=8.86, u=9.76, b=10.53, v=9.31 and White=11.71; these limits are
independent of the windowing mode of the camera. We find that a photometric
precision of 0.1 mag can be achieved through read-out streak measurements. A
suitable method for the measurement of read-out streaks is described and all
necessary calibration factors are given.Comment: 11 pages, accepted for publication in MNRAS. Code available from the
calibration link at http://www.mssl.ucl.ac.uk/www_astro/uvo
Constraints on the dust extinction law of the Galaxy with Swift/UVOT, Gaia, and 2MASS
We explore variations of the dust extinction law of the Milky Way by selecting stars from the Swift/UVOT Serendipitous Source Catalogue, cross-matched with Gaia DR2 and 2MASS to produce a sample of 10 452 stars out to ∼4 kpc with photometry covering a wide spectral window. The near ultraviolet passbands optimally encompass the 2175 Å bump, so that we can simultaneously fit the net extinction, quoted in the V band (A_{V}), the steepness of the wavelength dependence (δ), and the bump strength (E_{b}). The methodology compares the observed magnitudes with theoretical stellar atmospheres from the models of Coelho. Significant correlations are found between these parameters, related to variations in dust composition that are complementary to similar scaling relations found in the more complex dust attenuation law of galaxies – that also depend on the distribution of dust among the stellar populations within the galaxy. We recover the strong anticorrelation between AV and Galactic latitude, as well as a weaker bump strength at higher extinction. δ is also found to correlate with latitude, with steeper laws towards the Galactic plane. Our results suggest that variations in the attenuation law of galaxies cannot be fully explained by dust geometry
The Swift-UVOT ultraviolet and visible grism calibration
We present the calibration of the Swift UVOT grisms, of which there are two,
providing low-resolution field spectroscopy in the ultraviolet and optical
bands respectively. The UV grism covers the range 1700-5000 Angstrom with a
spectral resolution of 75 at 2600 Angstrom for source magnitudes of u=10-16
mag, while the visible grism covers the range 2850-6600 Angstrom with a
spectral resolution of 100 at 4000 Angstrom for source magnitudes of b=12-17
mag. This calibration extends over all detector positions, for all modes used
during operations. The wavelength accuracy (1-sigma) is 9 Angstrom in the UV
grism clocked mode, 17 Angstrom in the UV grism nominal mode and 22 Angstrom in
the visible grism. The range below 2740 Angstrom in the UV grism and 5200
Angstrom in the visible grism never suffers from overlapping by higher spectral
orders. The flux calibration of the grisms includes a correction we developed
for coincidence loss in the detector. The error in the coincidence loss
correction is less than 20%. The position of the spectrum on the detector only
affects the effective area (sensitivity) by a few percent in the nominal modes,
but varies substantially in the clocked modes. The error in the effective area
is from 9% in the UV grism clocked mode to 15% in the visible grism clocked
mode .Comment: 27 pages, 31 figures; MNRAS accepted 23 February 201
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