Accretion onto the first stellar mass black holes (open access)

Accretion onto the first stellar mass black holes

The first stars, forming at redshifts z > 15 in minihalos with M {approx} 10{sup 5-6} M{sub {circle_dot}} may leave behind remnant black holes, which could conceivably have been the 'seeds' for the supermassive black holes observed at z {approx}< 7. We study remnant black hole growth through accretion, including for the first time the radiation emitted due to accretion, with adaptive mesh refinement cosmological radiation-hydrodynamical simulations. The effects of photo-ionization and heating dramatically affect the large-scale inflow, resulting in negligible mass growth. We compare cases with accretion luminosity included and neglected to show that accretion radiation drastically changes the environment within 100 pc of the black hole, increasing gas temperatures by an order of magnitude. Gas densities are reduced and further star formation in the same minihalo is prevented for the two hundred million years we followed. Without radiative feedback included most seed black holes do not gain mass as efficiently as has been hoped for in previous theories, implying that black hole remnants of Pop III stars in minihalos are not likely to be miniquasars. Most importantly, however, our calculations demonstrate that if these black holes are indeed accreting close to the Bondi-Hoyle rate with ten percent radiative …
Date: August 5, 2009
Creator: Alvarez, Marcelo A.; Wise, John H. & Abel, Tom
Object Type: Article
System: The UNT Digital Library
Albeni Falls Wildlife Mitigation Project, 2008 Annual Report. (open access)

Albeni Falls Wildlife Mitigation Project, 2008 Annual Report.

The Albeni Falls Interagency Work Group (AFIWG) was actively involved in implementing wildlife mitigation activities in late 2007, but due to internal conflicts, the AFIWG members has fractionated into a smaller group. Implementation of the monitoring and evaluation program continued across protected lands. As of 2008, The Albeni Falls Interagency Work Group (Work Group) is a coalition comprised of wildlife managers from three tribal entities (Kalispel Tribe, Kootenai Tribe, Coeur d Alene Tribe) and the US Army Corps of Engineers. The Work Group directs where wildlife mitigation implementation occurs in the Kootenai, Pend Oreille and Coeur d Alene subbasins. The Work Group is unique in the Columbia Basin. The Columbia Basin Fish and Wildlife Authority (CBFWA) wildlife managers in 1995, approved what was one of the first two project proposals to implement mitigation on a programmatic basis. The maintenance of this kind of approach through time has allowed the Work Group to implement an effective and responsive habitat protection program by reducing administrative costs associated with site-specific project proposals. The core mitigation entities maintain approximately 9,335 acres of wetland/riparian habitats in 2008.
Date: August 5, 2009
Creator: Soults, Scott
Object Type: Report
System: The UNT Digital Library
Faculty and Student Teams and National Laboratories: Expanding the Reach of Research Opportunities and Workforce Development (open access)

Faculty and Student Teams and National Laboratories: Expanding the Reach of Research Opportunities and Workforce Development

The Faculty and Student Teams (FaST) Program, a cooperative effort between the US Department of Energy (DOE) Office of Science and the National Science Foundation (NSF), brings together collaborative research teams composed of a researcher at Brookhaven National Laboratory, and a faculty member with two or three undergraduate students from a college or university. Begun by the Department of Energy in 2000 with the primary goal of building research capacity at a faculty member's home institution, the FaST Program focuses its recruiting efforts on faculty from colleges and universities with limited research facilities and those institutions that serve populations under-represented in the fields of science, engineering and technology, particularly women and minorities. Once assembled, a FaST team spends a summer engaged in hands-on research working alongside a laboratory scientist. This intensely collaborative environment fosters sustainable relationships between the faulty members and BNL that allow faculty members and their BNL colleagues to submit joint proposals to federal agencies, publish papers in peer-reviewed journals, reform local curriculum, and develop new or expand existing research labs at their home institutions.
Date: August 5, 2009
Creator: Blackburn,N.; White, K. & Stegman, M.
Object Type: Report
System: The UNT Digital Library
Nature Collections: Energy - Supplement and Websit Focussing on Scientific and Social Aspects of Energy Research (open access)

Nature Collections: Energy - Supplement and Websit Focussing on Scientific and Social Aspects of Energy Research

Journal article submitted as a final report - publication date August 2007
Date: August 5, 2009
Creator: Nature Publishing Group
Object Type: Report
System: The UNT Digital Library

Striving for a Standard Protocol for Preconditioning or Stabilization of Polycrystalline Thin Film Photovoltaic Modules

Stabilization/preconditioning promise stable performance. CV-derived depletion width changes & hysteresis appear linked to stability; dark exposure in forward bias emulates light exposure at 1-sun.
Date: August 5, 2009
Creator: del Cueto, J. A.; Deline, C. A.; Albin, D. S.; Rummel, S. R. & Anderberg, A.
Object Type: Presentation
System: The UNT Digital Library
Viscosity of aqueous and cyanate ester suspensions containing alumina nanoparticles (open access)

Viscosity of aqueous and cyanate ester suspensions containing alumina nanoparticles

The viscosities of both aqueous and cyanate ester monomer (BECy) based suspensions of alumina nanoparticle were studied. The applications for these suspensions are different: aqueous suspensions of alumina nanoparticles are used in the production of technical ceramics made by slip casting or tape casting, and the BECy based suspensions are being developed for use in an injection-type composite repair resin. In the case of aqueous suspensions, it is advantageous to achieve a high solids content with low viscosity in order to produce a high quality product. The addition of a dispersant is useful so that higher solids content suspensions can be used with lower viscosities. For BECy suspensions, the addition of nanoparticles to the BECy resin is expected to enhance the mechanical properties of the cured composite. The addition of saccharides to aqueous suspensions leads to viscosity reduction. Through DSC measurements it was found that the saccharide molecules formed a solution with water and this resulted in lowering the melting temperature of the free water according to classic freezing point depression. Saccharides also lowered the melting temperature of the bound water, but this followed a different rule. The shear thinning and melting behaviors of the suspensions were used to develop …
Date: August 5, 2009
Creator: Lawler, Katherine
Object Type: Thesis or Dissertation
System: The UNT Digital Library