4,776 research outputs found

    The Effects of Inhomogeneities on Evaluating the Deceleration Parameter q0_0

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    Analytic expressions for distance-redshift relations which have been corrected for the effects of some inhomogeneities in the Friedmann-Robertson-Walker (FRW) mass density are used to illustrate the significance of inhomogeneities on a determination of q0q_0 made by using Type Ia supernovae. The value of q0q_0 inferred from a given set of observations depends on the fractional amount of matter in inhomogeneities and is up to 50 percent larger than that obtained by using the standard Mattig mm-zz result for pure dust FRW models.Comment: 16 pages, 7 figures in separate uuencoded fil

    Managing the Regulatory State: The Experience of the Bush Administration

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    This Article traces the history of Presidential management of the regulatory state up to the administration of President George W. Bush. It focuses on the latter\u27s implementation of smarter regulation, an approach to regulation based on unfunded mandates on the private sector implemented through the Office of Management and Budget, an organization within the Executive Office of the President. It finds cost-benefit analysis an essential, yet often neglected, tool for implementing efficient and effective regulations. It concludes the policies promoted under President Bush\u27s OMB have effectively cut costs by streamlining the rule-making process and discouraging adopting new federal rules, but cautions there is still a sea of overlapping regulations and conflict over turf among agencies causing the administrative state to steadily rise in cost

    Access to Higher Education for Black Men: A Narrative Perspective

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    A college degree is important because it provides opportunities for graduates to become educated in a field of study that they can start a career in. There is a large underrepresentation of Black male students in higher education. This lack of representation reflects the lack of professional Black men in our society and limits the number of Black role models these men have can look up tot. The purpose of the qualitative study is to identify what influences Black men to attend college and what challenges they may face getting admitted to college. It also examined how these men transition to a predominantly White institution and adjust to their new environments. Results from the study presents influences, challenges, and identifies how the transition to college is experienced by Black men providing a better understanding of they perceived their college admission journey. These results are guides to help professionals within education guide Black men to college

    Determination of the Hubble Constant Using a Two-Parameter Luminosity Correction for Type Ia Supernovae

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    In this paper, we make a comprehensive determination of the Hubble constant H0H_0 by using two parameters - the B-V color and the rate of decline Δm15\Delta m_{15} - to simultaneously standardize the luminosities of all nearby Cepheid-calibrated type Ia supernovae (SNe Ia) and those of a larger, more distant sample of 29 SNe Ia. Each group is treated in as similar a manner as possible in order to avoid systematic effects. A simultaneous χ2\chi ^2 minimization yields a standardized absolute luminosity of the Cepheid-calibrated supernovae as well as the Hubble constant obtained from the more distant sample. We find H0=62km/sMpc1H_0 = 62 km/s Mpc^{-1} and a standardized absolute magnitude of -19.46. The sensitivity of H0H_0 to a metallicity dependence of the Cepheid-determined distances is investigated. The total uncertainty δH0\delta H_0, dominated by uncertainties in the primary Cepheid distance indicator, is estimated to be 5 km/s Mpc^{-1}.Comment: To appear in Ap

    A new adder (Bitis; Viperidae) from the Western Cape Province, South Africa

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    A new species of small, terrestrial Bitis is described from the Western Cape Province, South Africa. It occurs in sympatry with Bitis comuta and Bifis atropos on the upper slopes and summit of the Cedarberg, and with the latter on the Swartberg. Features of scalation, colour and body form distinguish the new species from all other southern African Bitis. Its range extends in an arc from the northern Cape Fold Mountains, southwards into the western regions of the Little Karoo, with a possibly isolated population on the Roggeveldberg and Komsberg of the inland escarpment.S. Afr. J. ZooI. 1997,32(2

    Computer programs for reduction of microphotometer data

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    Five computer programs for analyzing magnetic tape recordings of digital data from microphotomete

    The Probable Detection of SN 1923A: The Oldest Radio Supernova?

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    Based upon the results of VLA observations, we report the detection of two unresolved radio sources that are coincident with the reported optical position of SN 1923A in M83. For the source closest to the SN position, the flux density was determined to be 0.30 +/- 0.05 mJy at 20 cm and 0.093 +/- 0.028 mJy at 6 cm. The flux density of the second nearby source was determined to be 0.29 +/- 0.05 at 20 cm and 0.13 +/- 0.028 at 6 cm. Both sources are non-thermal with spectral indices of alpha = -1.0 +/- 0.30 and -0.69 +/- 0.24, respectively. SN 1923A has been designated as a Type II-P. No Type II-P (other than SN 1987A) has been detected previously in the radio. The radio emission from both sources appears to be fading with time. At an age of approximately 68 years when we observed it, this would be the oldest radio supernova (of known age) yet detected

    Hydrogen in Type Ic Supernovae?

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    By definition, a Type Ic supernova (SN Ic) does not have conspicuous lines of hydrogen or helium in its optical spectrum. SNe Ic usually are modelled in terms of the gravitational collapse of bare carbon-oxygen cores. We consider the possibility that the spectra of ordinary (SN 1994I-like) SNe Ic have been misinterpreted, and that SNe Ic eject hydrogen. An absorption feature usually attributed to a blend of Si II 6355 and C II 6580 may be produced by H-alpha. If SN 1994I-like SNe Ic eject hydrogen, the possibility that hypernova (SN 1998bw-like) SNe Ic, some of which are associated with gamma-ray bursts, also eject hydrogen should be considered. The implications of hydrogen for SN Ic progenitors and explosion models are briefly discussed.Comment: Accepted by PASP. Several significant changes including one additional figur

    Strategic Review of Tropical Fisheries Management

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    This project addresses the constraints to tropical fisheries development with sustainable exploitation through a strategic assessment of tropical fisheries management with the following purposes: (1) To evaluate relevant research methods for the development of assessment models appropriate to the circumstances of tropical coastal fisheries; and (2) To evaluate the utility of existing strategies for the implementation of management advice. The report consists of three substantive chapters. Chapter 2 contains a detailed socio-economic assessment of various instruments and implementation strategies applicable to tropical capture fisheries. In Chapter 3, a detailed assessment of the fisheries for tropical large marine ecosystems has been conducted using a technique developed by FAO (Granger & Garcia 1996). The data used were the FAO statistics published regularly by FAO. This analysis has been conducted for each of the tropical large marine ecosystems and indicates that there is the potential for increased fishing in a number of these ecosystems. One of the clear requirements identified in Chapter 2 and implicit in Chapter 3, is that there is a significant need for simple and robust fisheries assessment methods which can estimate the potential of a particular resource, its capacity in terms of the level of fishing effort and its current status ie whether it is currently exploited sustainably or not. In Chapter 4, these problems are addressed directly and, using two approaches, significant simplification of fishery methods is developed. In the first approach, simple empirical relationships between the life history parameters of a species are used to develop models of potential yield which can be determined by a simple assessment of fish growth. In the second approach, optimal life history theory is applied to the key demographic parameters of exploited fish populations and using estimates of the Beverton & Holt invariants a significant simplifying of the basic stock assessment equations is developed
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