11,649 research outputs found

    Nuclear Bar, Star Formation and Gas Fueling in the Active Galaxy NGC 4303

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    A combination of Hubble Space Telescope (HST) WFPC2 and NICMOS images are used to investigate the gas/dust and stellar structure inside the central 300 pc of the nearby active galaxy NGC 4303. The NICMOS H-band (F160W) image reveals a bright core and a nuclear elongated bar-like structure of 250 pc in diameter. The bar is centered on the bright core, and its major axis is oriented in proyection along the spin axis of the nuclear gaseous rotating disk recently detected (Colina & Arribas 1999). The V-H (F606W - F160W) image reveals a complex gas/dust distribution with a two-arm spiral structure of about 225 pc in radius. The southwestern arm is traced by young star-forming knots while the northeastern arm is detected by the presence of dust lanes. These spirals do not have a smooth structure but rather they are made of smaller flocculent spirals or filament-like structures. The magnitudes and colors of the star-forming knots are typical of clusters of young stars with masses of 0.5 to 1 x 105Msolar,andagesof5to25millionyears.Theoverallstructureofthenuclearspiralsaswellasthesize,numberandmassesofthestarformingknotsareexplainedinthecontextofamassivegaseousnucleardisksubjecttoselfgravitationalinstabilitiesandtothegravitationalfieldcreatedbythenuclearbar.Accordingtothemodel,thegaseousdiskhasamassofabout5x107Msolarinsidearadiusof400pc,thebarhasaradiusof150pcandapatternspeedofabout0.5Myr1,andtheaveragemassaccretionrateintothecore(R<8pc)isabout0.01Msolar10^5 M_{solar}, and ages of 5 to 25 million years. The overall structure of the nuclear spirals as well as the size, number and masses of the star-forming knots are explained in the context of a massive gaseous nuclear disk subject to self-gravitational instabilities and to the gravitational field created by the nuclear bar. According to the model, the gaseous disk has a mass of about 5 x 10^7 M_{solar} inside a radius of 400 pc, the bar has a radius of 150 pc and a pattern speed of about 0.5 Myr^{-1}, and the average mass accretion rate into the core (R < 8 pc) is about 0.01 M_{solar} yr^{-1} for about 80 Myr.Comment: ApJ, in press (February 1, 2000

    Non-equilibrium hydrodynamics of a rotating filament

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    The nonlinear dynamics of an elastic filament that is forced to rotate at its base is studied by hydrodynamic simulation techniques; coupling between stretch, bend, twist elasticity and thermal fluctuations is included. The twirling-overwhirling transition is located and found to be strongly discontinuous. For finite bend and twist persistence length, thermal fluctuations lower the threshold rotational frequency, for infinite persistence length the threshold agrees with previous analytical predictions

    Partly melted DNA conformations obtained with a probability peak finding method

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    Peaks in the probabilities of loops or bubbles, helical segments, and unzipping ends in melting DNA are found in this article using a peak finding method that maps the hierarchical structure of certain energy landscapes. The peaks indicate the alternative conformations that coexist in equilibrium and the range of their fluctuations. This yields a representation of the conformational ensemble at a given temperature, which is illustrated in a single diagram called a stitch profile. This article describes the methodology and discusses stitch profiles vs. the ordinary probability profiles using the phage lambda genome as an example.Comment: 11 pages, 9 figures; v3: major changes; v4: applications sectio

    International Stock Market Efficiency: A Non-Bayesian Time-Varying Model Approach

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    This paper develops a non-Bayesian methodology to analyze the time-varying structure of international linkages and market efficiency in G7 countries. We consider a non-Bayesian time-varying vector autoregressive (TV-VAR) model, and apply it to estimate the joint degree of market efficiency in the sense of Fama (1970, 1991). Our empirical results provide a new perspective that the international linkages and market efficiency change over time and that their behaviors correspond well to historical events of the international financial system.Comment: 21 pages, 2 tables, 6 figure

    Derivation of the Quantum Probability Rule without the Frequency Operator

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    We present an alternative frequencists' proof of the quantum probability rule which does not make use of the frequency operator, with expectation that this can circumvent the recent criticism against the previous proofs which use it. We also argue that avoiding the frequency operator is not only for technical merits for doing so but is closely related to what quantum mechanics is all about from the viewpoint of many-world interpretation.Comment: 12 page

    Focusing of upward fluid migration beneath volcanic arcs : effect of mineral grain size variation in the mantle wedge

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    Author Posting. © American Geophysical Union, 2015. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 16 (2015): 3905–3923, doi:10.1002/2015GC005950.We use numerical models to investigate the effects of mineral grain size variation on fluid migration in the mantle wedge at subduction zones and on the location of the volcanic arc. Previous coupled thermal-grain size evolution (T-GSE) models predict small grain size (<1 mm) in the corner flow of the mantle wedge, a downdip grain size increase by ∼2 orders of magnitude along the base of the mantle wedge, and finer grain size in the mantle wedge for colder-slab subduction zones. We integrate these T-GSE modeling results with a fluid migration model, in which permeability depends on grain size, and fluid flow through a moving mantle matrix is driven by fluid buoyancy and dynamic pressure gradients induced by mantle flow. Our modeling results indicate that fluids introduced along the base of the mantle wedge beneath the fore arc are initially dragged downdip by corner flow due to the small grain size and low permeability immediately above the slab. As grain size increases with depth, permeability increases, resulting in upward fluid migration. Fluids released beneath the arc and the back arc are also initially dragged downdip, but typically are not transported as far laterally before they begin to travel upward. As the fluids rise through the back-arc mantle wedge, they become deflected toward the trench due to the effect of mantle inflow. The combination of downdip migration in the fore arc and trench-ward migration in the back arc results in pathways that focus fluids beneath the arc.International Research Institute of Disaster Science, Tohoku University; NSF; MARGINS Postdoctoral Fellowship . Grant Number: NSF OCE-08408002016-05-1

    Экспресс-методы диагностики психофизического состояния на занятиях по физическому воспитанию студентов высшего учебного заведения

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    Розглянуті прості, доступні та інформативні методи діагностування студентів в умовах учбового процесу: кольоровий тест М. Люшеру та тейпинг тест. Особливість тестування зумовле на хронічними порушеннями здоров’я студентів, які тестуються. Виокремленні та сформовані групи з різних хронічних захворювань. Тестування проводилось до заняття та після заняття. Аналіз результатів проводився з врахуванням пропозиції щодо фізичного навантаження. В ході проведеного дослідження доведено, що випробувані методи є дієвими та доступними в умовах учбового заняття. А також, допомагають коригувати об’єм та інтенсивність фізичного навантаження; cвоєчасно та професійно проводити реабілітаційні вправи та рекреаційні заходи. Таким інформативним показником може слугувати реакція втоми відбита коричневим кольором в тестуванні М. Люшера. Також доведено, що рівень лабільності нервових процесів не однаковий в групах різних нозологій і різних учбових курсів за результатами тейпинг – тесту.The simple, accessible and informational methods of the diagnostic of the students in the conditions of study process: the color test of M. Lucher and taping test are considered. The features of the testing related chronic health problem of testing students. The group of different chronic illness are separated and formed. The testing made before and after lesson. The analysis of the results made account proposition of the physical strain. During this experiment its proved that testing methods are effective and accessible in the studying conditions. Also they help to correct the volume and intensity physical strain, in time and professionally make rehabilitees exercise and recreational action. Such informational indicator may serve the brown reaction of the tiredness in the test of M. Lusher. According the taping test its also proved that the level of the labiality of the nervous process is different in the group of the different nozology and different studying course

    The Mass Inflow Rate in the Barred Galaxy NGC 1530

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    Mass inflow in barred galaxies has been invoked to account for a wide variety of phenomena, but until now direct evidence for inflow has been lacking. We present Fabry-Perot H-alpha observations of the barred spiral galaxy NGC 1530 from which we determine velocities of the ionized gas for the entire region swept by the bar. We compare the velocity field to models of gas flow in barred spirals and show that it is well reproduced by ideal gas hydrodynamic models. Inspection of the models and observations reveals that gas entering the bar dust lanes streams directly down the dust lanes toward the 2 kpc radius nuclear ring. The models predict that approximately 20% of the gas flowing down the dust lane enters the nuclear ring; the remaining gas sprays around the ring to the other bar dust lane. The fraction of the gas entering the ring is relatively insensitive to the shape or size of the bar. Our observations of the velocity field and dust optical depth yield a mass inflow rate into the nuclear ring of 1 solar mass per year.Comment: 13 pages, 3 figures, aastex 4.0, accepted for publication in Ap J Letter
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