oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Search Results: 1 - 10 of 3856 matches for " Joe Wolf "
All listed articles are free for downloading (OA Articles)
Page 1 /3856
Display every page Item
Testing galaxy formation scenarios with a new mass estimator
Joe Wolf
Physics , 2009, DOI: 10.1063/1.3458536
Abstract: We present the recently derived Wolf et al. (2009) mass estimator, which is applicable for spherical pressure-supported stellar systems spanning over ten orders of magnitude in luminosity, as a tool to test galaxy formation theories. We show that all of the Milky Way dwarf spheroidal galaxies (MW dSphs) are consistent with having formed within a halo of mass approximately 3 x 10^9 Msun in LCDM cosmology. The faintest MW dSphs seem to have formed in dark matter halos that are at least as massive as those of the brightest MW dSphs, despite the almost five orders of magnitude spread in luminosity. We expand our analysis to the full range of observed pressure-supported stellar systems and examine their half-light I-band mass-to-light ratios. The M/L vs. half-light mass M_1/2 relation for pressure-supported galaxies follows a U-shape, with a broad minimum near M/L ~ 3 that spans dwarf elliptical galaxies to normal ellipticals, a steep rise to M/L ~ 3,200 for ultra-faint dSphs, and a more shallow rise to M/L ~ 800 for galaxy cluster spheroids.
Modeling mass independent of anisotropy
Joe Wolf
Physics , 2010, DOI: 10.1017/S1743921311017510
Abstract: By manipulating the spherical Jeans equation, Wolf et al. (2010) show that the mass enclosed within the 3D deprojected half-light radius r_1/2 can be determined with only mild assumptions about the spatial variation of the stellar velocity dispersion anisotropy as long as the projected velocity dispersion profile is fairly flat near the half-light radius, as is typically observed. They find M_1/2 = 3 \sigma_los^2 r_1/2 / G ~ 4 \sigma_los^2 R_eff / G, where \sigma_los^2 is the luminosity-weighted square of the line-of-sight velocity dispersion and R_eff is the 2D projected half-light radius. This finding can be used to show that all of the Milky Way dwarf spheroidal galaxies (MW dSphs) are consistent with having formed within a halo of mass approximately 3 x 10^9 M_sun assuming a LCDM cosmology. In addition, the dynamical I-band mass-to-light ratio (M/L) vs. M_1/2 relation for dispersion-supported galaxies follows a U-shape, with a broad minimum near M/L ~ 3 that spans dwarf elliptical galaxies to normal ellipticals, a steep rise to M/L ~ 3,200 for ultra-faint dSphs, and a more shallow rise to M/L ~ 800 for galaxy cluster spheroids.
Local Group Dwarf Spheroidals: Correlated Deviations from the Baryonic Tully-Fisher Relation
Stacy S. McGaugh,Joe Wolf
Physics , 2010, DOI: 10.1088/0004-637X/722/1/248
Abstract: Local Group dwarf spheroidal satellite galaxies are the faintest extragalactic stellar systems known. We examine recent data for these objects in the plane of the Baryonic Tully-Fisher Relation (BTFR). While some dwarf spheroidals adhere to the BTFR, others deviate substantially. We examine the residuals from the BTFR and find that they are not random. The residuals correlate with luminosity, size, metallicity, ellipticity, and susceptibility of the dwarfs to tidal disruption in the sense that fainter, more elliptical, and tidally more susceptible dwarfs deviate farther from the BTFR. These correlations disfavor stochastic processes and suggest a role for tidal effects. We identify a test to distinguish between the {\Lambda}CDM and MOND based on the orbits of the dwarf satellites of the Milky Way and how stars are lost from them.
Dark matter concentrations and a search for cores in Milky Way dwarf satellites
Joe Wolf,James S. Bullock
Physics , 2012,
Abstract: We investigate the mass distributions within eight classical Milky Way dwarf spheroidal galaxies (MW dSphs) using an equilibrium Jeans analysis and we compare our results to the mass distributions predicted for subhalos in dissipationless \Lambda CDM simulations. In order to match the dark matter density concentrations predicted, the stars in these galaxies must have a fairly significant tangential velocity dispersion anisotropy (\beta ~-1.5). For the limiting case of an isotropic velocity dispersion (\beta =0), the classical MW dSphs predominantly prefer to live in halos that are less concentrated than \Lambda CDM predictions. We also investigate whether the dSphs prefer to live in halos with constant density cores in the limit of isotropic velocity dispersion. Interestingly, even in this limit, not all of the dSphs prefer large constant-density cores: the Sculptor dSph prefers a cusp while Carina, Draco and Leo I prefer cores. The other four dSphs do not show a statistically significant preference for either cuspy or cored profiles. Finally, we re-examine the hypothesis that the density profiles of these eight MW dSphs can be quantified by a common dark matter halo.
A Quality-of-Service Mechanism for Interconnection Networks in System-on-Chips
Wolf-Dietrich Weber,Joe Chou,Ian Swarbrick,Drew Wingard
Computer Science , 2007,
Abstract: As Moore's Law continues to fuel the ability to build ever increasingly complex system-on-chips (SoCs), achieving performance goals is rising as a critical challenge to completing designs. In particular, the system interconnect must efficiently service a diverse set of data flows with widely ranging quality-of-service (QoS) requirements. However, the known solutions for off-chip interconnects such as large-scale networks are not necessarily applicable to the on-chip environment. Latency and memory constraints for on-chip interconnects are quite different from larger-scale interconnects. This paper introduces a novel on-chip interconnect arbitration scheme. We show how this scheme can be distributed across a chip for high-speed implementation. We compare the performance of the arbitration scheme with other known interconnect arbitration schemes. Existing schemes typically focus heavily on either low latency of service for some initiators, or alternatively on guaranteed bandwidth delivery for other initiators. Our scheme allows service latency on some initiators to be traded off smoothly against jitter bounds on other initiators, while still delivering bandwidth guarantees. This scheme is a subset of the QoS controls that are available in the SonicsMX? (SMX) product.
Are the ASISA Standards with Respect to Unit Trust Classification Representative of Homogeneous Risk Classes?  [PDF]
Joe Kainja
Journal of Financial Risk Management (JFRM) , 2016, DOI: 10.4236/jfrm.2016.52008
Abstract: We examine the information content of South African (SA) equity unit trusts to investigate whether risk is heterogeneous between investment objective groups and homogeneous within groups because those characteristics are vital to proper investment decision making. We find risk differences within SA equity groups especially in the Equity-General and Equity-Growth. However, in the other categories, the systematic risk differences depended on the choice of benchmark. Those risk differences may have significant implications for investors. Examination of between-group risk revealed that not all the equity categories were heterogeneous. We also find that the choice of benchmark is critical when measuring and comparing performance characteristics of funds.
Stealth Galaxies in the Halo of the Milky Way
James S. Bullock,Kyle R. Stewart,Manoj Kaplinghat,Erik J. Tollerud,Joe Wolf
Physics , 2009, DOI: 10.1088/0004-637X/717/2/1043
Abstract: We predict that there is a population of low-luminosity dwarf galaxies orbiting within the halo of the Milky Way that have surface brightnesses low enough to have escaped detection in star-count surveys. The overall count of stealth galaxies is sensitive to the presence (or lack) of a low-mass threshold in galaxy formation. These systems have luminosities and stellar velocity dispersions that are similar to those of known ultrafaint dwarf galaxies but they have more extended stellar distributions (half light radii greater than about 100 pc) because they inhabit dark subhalos that are slightly less massive than their higher surface brightness counterparts. As a result, the typical peak surface brightness is fainter than 30 mag per square arcsec. One implication is that the inferred common mass scale for Milky Way dwarfs may be an artifact of selection bias. If there is no sharp threshold in galaxy formation at low halo mass, then ultrafaint galaxies like Segue 1 represent the high-mass, early forming tail of a much larger population of objects that could number in the hundreds and have typical peak circular velocities of about 8 km/s and masses within 300 pc of about 5 million solar masses. Alternatively, if we impose a low-mass threshold in galaxy formation in order to explain the unexpectedly high densities of the ultrafaint dwarfs, then we expect only a handful of stealth galaxies in the halo of the Milky Way. A complete census of these objects will require deeper sky surveys, 30m-class follow-up telescopes, and more refined methods to identify extended, self-bound groupings of stars in the halo.
From Galaxy Clusters to Ultra-Faint Dwarf Spheroidals: A Fundamental Curve Connecting Dispersion-supported Galaxies to Their Dark Matter Halos
Erik J. Tollerud,James S. Bullock,Genevieve J. Graves,Joe Wolf
Physics , 2010, DOI: 10.1088/0004-637X/726/2/108
Abstract: We examine scaling relations of dispersion-supported galaxies over more than eight orders of magnitude in luminosity by transforming standard fundamental plane parameters into a space of mass (M1/2), radius (r1/2), and luminosity (L1/2). We find that from ultra-faint dwarf spheroidals to giant cluster spheroids, dispersion-supported galaxies scatter about a one-dimensional "fundamental curve" through this MRL space. The weakness of the M1/2-L1/2 slope on the faint end may imply that potential well depth limits galaxy formation in small galaxies, while the stronger dependence on L1/2 on the bright end suggests that baryonic physics limits galaxy formation in massive galaxies. The mass-radius projection of this curve can be compared to median dark matter halo mass profiles of LCDM halos in order to construct a virial mass-luminosity relationship (Mvir-L) for galaxies that spans seven orders of magnitude in Mvir. Independent of any global abundance or clustering information, we find that (spheroidal) galaxy formation needs to be most efficient in halos of Mvir ~ 10^12 Msun and to become inefficient above and below this scale. Moreover, this profile matching technique is most accurate at the high and low luminosity extremes (where dark matter fractions are highest) and is therefore quite complementary to statistical approaches that rely on having a well-sampled luminosity function. We also consider the significance and utility of the scatter about this relation, and find that in the dSph regime observational errors are almost at the point where we can explore the intrinsic scatter in the luminosity-virial mass relation. Finally, we note that purely stellar systems like Globular Clusters and Ultra Compact Dwarfs do not follow the fundamental curve relation. This allows them to be easily distinguished from dark-matter dominated dSph galaxies in MRL space. (abridged)
Phytoestrogene
Wolf AS
Journal für Menopause , 1998,
Abstract: Mit dem Thema Phytoestrogene wird derzeit ein Neuland in der angewandten klinischen Medizin betreten, welches in der Pr vention und Gesundheitsf rderungsBeratung einen bedeutsamen Platz einnehmen kann. Es existieren bislang zwar zahlreiche Untersuchungen insbesondere zur Karzinom-Pr vention für Kolon-, Rektum-, Magen-, Prostata- und Mamma-Karzinom, jedoch ist die überwiegende Zahl der Studien mangelhaft aufgrund des statistischen Designs und der geringen Zahl an untersuchten Anwenderinnen. Prospektiv randomisierte Untersuchungen bestehen nicht. Experimentelle Studien zum Wirkmechanismus und zur biologischen Wirkung der Phytoestrogene deuten jedoch auf die Potenz und das immense Wirkpotential dieser Pflanzenestrogene hin. Eine m glichst frühzeitig begonnene, langzeitig phytoestrogenhaltige, ballaststoffreiche Kost kann anscheinend das Risiko für Wechseljahrsbeschwerden, Osteoporose und darüber hinaus für Mamma-Karzinom, Kolon- und Endometrium-Karzinom sowie kardiovaskul re Erkrankungen deutlich reduzieren. Aus diesem Grunde kann man bereits heute bei Frauen nach MammaCa, bei Vorliegen besonderer famili rer oder pers nlicher Risiken für die Entwicklung eines Mamma-Ca oder bei erh htem kardiovaskul rem Risiko zur "Sojaeinnahme" in Form von 30 g Sojamehl oder Sojadrinks pro Tag raten. Zahleiche Rezeptbücher und Anleitungen vermitteln dafür schmackhafte Zubereitungen und Kochvorschl ge. Weltweit sind alle Endokrinologen aufgefordert, sich in Zukunft über das tats chliche Wirkpotential der Phytoestrogene zu bemühen, um pr zise Daten für alternative Behandlungsm glichkeiten und Lebensstilberatung allgemein sowie nach Malignomerkrankungen zur Verfügung zu haben.
Should gait speed be included in the clinical evaluation of Parkinson’s disease?  [PDF]
Joe Nocera, Chris Hass
Advances in Parkinson's Disease (APD) , 2012, DOI: 10.4236/apd.2012.11001
Abstract: Background: The Unified Parkinson’s Disease Rating Scale is the most commonly used scale in the clinical study of Parkinson’s disease. However, it may fail to capture the essence of physical impairment in patients with Parkinson’s disease and thus limit responsiveness of care-givers, patients, and/or clinicians as to increasing physical disability. This study sought to compare subjective measures of physical disability in Parkinson’s disease to an objective, accurate, and proven measure of physical function-gait speed. Methods: Eighty-eight individuals with early to moderate stage Parkinson’s disease were evaluated on the Unified Parkinson’s Disease Rating Scale, the Parkinson’s disease Questionnaire 39 and during five 8 meter walking trials. Spearman correlations coefficients were used to determine the association among all variables of interest. Results: The findings demonstrate that only a fair to moderate relationship between objectively measured gait speed and physical function as measured subjectively by the clinical rating scale and as evaluated by the patients during self report. Conclusions: The results of this study suggest that commonly utilized measures of physical function in Parkinson’s disease are not highly correlated with gait speed. Because gait speed is demonstrated as a dependable proxy for physical function, the results of this study may provide a rational for the use of gait speed to provide a more accurate picture of physical function in patients with Parkinson’s disease.
Page 1 /3856
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.