Species composition, distribution, and relative abundance of fishes in the coastal habitat off the southeastern United States

Ichthyofauna of the coastal «10 m depth) habitat of the South Atlantic Bight were investigated between Cape Fear, North Carolina, and the St. John's River, Florida. Trawl collections from four nonconsecutive seasons in the period July 1980 to December 1982 indicated that the fish community is dominated by the family Sciaenidae, particularly juvenile forms. Spot (Leiostomus xanthurus) and Atlantic croaker (Micropogonias undulatus) were the two most abundant species and dominated catches during all seasons. Atlantic menhaden (Brevoortin tyrannus) was also very abundant, but only seasonally (winter and spring) dominant in the catches. Elasmobranch fIShes, especially rajiforms and carcharinids, contributed to much of the biomass of fishes collected. Total fish abundance was greatest in winter and lowest in summer and was influenced by the seasonality of Atlantic menhaden and Atlantic croaker in the catches. Biomass was highest in spring and lowest in summer, and was influenced by biomass of spot. Fish density ranged from 321 individuals and 12.2 kg per hectare to 746 individuals and 25.2 kg per hectare. Most species ranged widely throughout the bight, and showed some evidence of seasonal migration. Species assemblages were dominated by ubiquitous year-round residents of the coastal waters of the bight. Diversity (H') was highest in summer, and appeared influenced by the evenness of distribution of individuals among species. (PDF file contains 56 pages.

Retirement Security: Improved Guidance Could Help Account Owners Understand the Risks of Investing in Unconventional Assets

[Excerpt] Federal law places few restrictions on the types of investments allowable in tax-favored retirement accounts, such as IRAs or employer-sponsored 401(k) plans. Recent federal and state investigations and litigation have raised questions as to whether investing in unconventional assets may jeopardize the accounts’ tax-favored status, placing account owners’ retirement security at risk. GAO was asked to examine issues related to the potential risks and responsibilities associated with investments in unconventional assets. GAO examined: (1) what is known about the prevalence of accounts that invest in unconventional assets; (2) how these accounts are managed; and (3) what challenges are associated with administering these retirement accounts. GAO reviewed relevant federal laws, regulations, and guidance; analyzed data collected from the retirement industry; analyzed available industry documents; and reviewed 334 related consumer complaints collected from three federal agencies and two independent entities

Superhumps in Low-Mass X-Ray Binaries

We propose a mechanism for the superhump modulations observed in optical photometry of at least two black hole X-ray transients (SXTs). As in extreme mass-ratio cataclysmic variables (CVs), superhumps are assumed to result from the presence of the 3:1 orbital resonance in the accretion disc. This causes the disc to become non-axisymmetric and precess. However the mechanism for superhump luminosity variations in low mass X-ray binaries (LMXBs) must differ from that in CVs, where it is attributed to a tidally-driven modulation of the disc's viscous dissipation, varying on the beat between the orbital and disc precession period. By contrast in LMXBs, tidal dissipation in the outer accretion disc is negligible: the optical emission is overwhelming dominated by reprocessing of intercepted central X-rays. Thus a different origin for the superhump modulation is required. Recent observations and numerical simulations indicate that in an extreme mass-ratio system the disc area changes on the superhump period. We deduce that the superhumps observed in SXTs arise from a modulation of the reprocessed flux by the changing area. Therefore, unlike the situation in CVs, where the superhump amplitude is inclination-independent, superhumps should be best seen in low-inclination LMXBs, whereas an orbital modulation from the heated face of the secondary star should be more prominent at high inclinations. Modulation at the disc precession period (10s of days) may indicate disc asymmetries such as warping. We comment on the orbital period determinations of LMXBs, and the possibility and significance of possible permanent superhump LMXBs.Comment: 6 pages, 1 encapsulated figure. MNRAS in press; replaced to correct typographical error

Spectroscopic Identification of the Infrared Counterpart to GX5-1

Using CGS4 on UKIRT, we have obtained a 1.95-2.45 micron infrared spectrum of the primary candidate counterpart to the bright Z LMXB GX5-1. IR photometry by Naylor, Charles, & Longmore (1992) and the astrometry of Jonker et al. (2000) had previously identified this star as the most likely counterpart to GX5-1. The spectrum presented here clearly shows Brackett gamma and He lines in emission, for the first time confirming the identity of the counterpart. Similar to our previous spectroscopy of the Z source LMXBs Sco X-1 and Sco X-2 (Bandyopadhyay et al. 1999), the K-band spectrum of GX5-1 shows emission lines only. We briefly discuss the implications of this spectrum for the nature of the Z sources.Comment: accepted for publication as a Letter in MNRA

Separator development for a heat sterilizable battery Quarterly report, 1 Oct. - 31 Dec. 1966

Composite separator production for heat sterilizable silver-zinc batterie