Gamma-Ray Spectral Characteristics of Thermal and Non-Thermal Emission from Three Black Holes

Cygnus X-1 and the gamma-ray transients GROJ0422+32 and GROJ1719-24 displayed similar spectral properties when they underwent transitions between the high and low gamma-ray (30 keV to few MeV) intensity states. When these sources were in the high gamma-ray intensity state (gamma-2, for Cygnus X-1), their spectra featured two components: a Comptonized shape below 200-300 keV with a soft power-law tail (photon index >3) that extended to ~1 MeV or beyond. When the sources were in the low-intensity state (gamma-0, for Cygnus X-1), the Comptonized spectral shape below 200 keV typically vanished and the entire spectrum from 30 keV to ~1 MeV can be characterized by a single power law with a relatively harder photon index ~2-2.7. Consequently the high- and low-intensity gamma-ray spectra intersect, generally in the ~400 keV - 1 MeV range, in contrast to the spectral pivoting seen previously at lower (~10 keV) energies. The presence of the power-law component in both the high- and low-intensity gamma-ray spectra strongly suggests that the non-thermal process is likely to be at work in both the high and the low-intensity situations. We have suggested a possible scenario (Ling & Wheaton, 2003), by combining the ADAF model of Esin et al. (1998) with a separate jet region that produces the non-thermal gamma-ray emission, and which explains the state transitions. Such a scenario will be discussed in the context of the observational evidence, summarized above, from the database produced by EBOP, JPL's BATSE earth occultation analysis system.Comment: 6 pages, 3 figures, accepted for publication in Proceedings of 2004 Microquasar Conference, Beijing, China, Chinese Journal of Astronomy and Astrophysics, minor corrections per refere

An investor loss function for earnings forecasts with an empirical application / BEBR No 694

Includes bibliographical references (p. 20-21)

Chaos For the Halibut?

A generalized method for analyzing stability potential in discrete time renewable resource models subject to market-driven harvest is discussed. Two means by which harvest activity can influence dynamical properties of renewable resource models are identified: the "growth factor" and the "market response effect". The growth factor is a systematic influence on stability tied to changes in the position of the bioeconomic equilibrium point along a given open access supply locus. The market response effect involves variation in harvest in response to stock level changes. The analysis is applied to a model of the Pacific Halibut Fishery: a modified discrete-time version of the traditional Schaefer model. In order to investigate potential instability, we vary certain parameters of the model and study the resulting effects on stability. We find that enhancing harvest response by changing the slope of the demand schedule can thrust the model into instability, chaos, and extinction, without changing the bioeconomic equilibrium point for the Pacific Halibut Fishery Model. We also show that enhancing harvest response via slope preserving increases in market demand can push the model into instability, chaos, and even extinction. Finally, we show that similar adjustments in market demand may be capable of eliminating instability and chaos rooted in powerful intrinsic growth of the stockStability Analysis, Chaos, Open-Access Fisheries, Renewable Resource Models., Environmental Economics and Policy, Production Economics,

ASSET FIXITY, ASSET SPECIFICITY AND REGIONAL ECONOMIC CHANGE: HYPOTHESIS AND IMPLICATIONS

That asset specificity and asset fixity are impediments to economic adjustment is well understood in the literatures of industrial organization and agricultural economics. In this paper, we show that spatial factors can plausible be expected to be arguments in functions that define asset fixity and specificity and, hence, asset fixity may be systematically related to space. The implications with regard to differences across space in rates of adjustment to market signals suggest that the short run is longer in remote than in less remote places, which may prove useful in explaining the behavior of a spatial economic system during times of rapid technological change.Industrial Organization,

LANDSAT-4 and LANDSAT-5 Multispectral Scanner Coherent Noise Characterization and Removal

A technique is described for characterizing the coherent noise found in LANDSAT-4 and LANDSAT-5 MSS data and a companion technique for filtering out the coherent noise. The techniques are demonstrated on LANDSAT-4 and LANDSAT-5 MSS data sets, and explanations of the noise pattern are suggested in Appendix C. A cookbook procedure for characterizing and filtering the coherent noise using special NASA/Goddard IDIMS functions is included. Also presented are analysis results from the retrofitted LANDSAT-5 MSS sensor, which shows that the coherent noise has been substantially reduced

Effect of location of aft-mounted nacelles on the longitudinal aerodynamic characteristics of a high-wing transport airplane

As part of a propulsion/airframe integration program at Langley Research Center, tests were conducted in the Langley 16-Foot Transonic Tunnel to determine the effects of locating flow-through mixed flow engine nacelles in several aft underwing positions on the longitudinal aerodynamics of a high wing transport airplane. D-shaped inlet nacelles were used in the test. Some configurations with antishock bodies and with nacelle toe-in were also tested. Data were obtained for a free stream Mach number range of 0.70 to 0.85 and a model angle-of-attack range from -2.5 to 4.0 degrees

A survey of elementary school banking in New England

Thesis (Ed.M.)--Boston Universit

Ethnicity, Obesity, and Type 2 Diabetes of Adults in Urban Populations of Central America

The purpose of this meta-analysis was to examine the impact of ethnicity and obesity as it relates to Type-2 Diabetes (T2D) in specific Central American countries. A meta-analysis was conducted to determine the association of ethnicity, obesity, and T2D. Four studies that qualified for inclusion were identified by searching MEDLINE and PubMed databases. The studies on the association of ethnicity and T2D had a combined population resulted in 265,858 study participants. Two studies on the association of obesity and T2D had 197,899 participants. An analysis of the data was conducted utilizing the relative risk ration, odds ratio, and forest plots. The comparison of the relative risk of T2D across ethnic categories by studies range for Blacks was 1.59 to 2.74, Asians was 1.43 to 2.08, and Hispanics .92 to 2.91. The ethnic difference in the prevalence of diabetes was almost two-fold higher in all ethnic groups than among the Caucasians with a significance level of 95%. A comparison of relative risk of T2D across weight categories was significantly higher among those with a diagnosed of diabetes in all reported areas. The odds ratio was very close to the risk ratio in both ethnicity and obesity to the development of T2D.The meta-analysis findings documented that an association does exist between ethnicity and obesity to the development of type 2 diabetes