Gamma-ray Burst Positions from the ASM on RXTE

The RXTE/ASM has detected and positioned 14 confirmed GRB bursts (at this writing, Jan. 1999) including six whose positions were comunicated to the community 2 to 32 hours after the burst. Two of these latter bursts led to measurements of optical red shifts but one, despite an easily detected x-ray afterglow, produced no detectable optical or radio afterglow.Comment: 2 pages, 1 Figure, A&A format, accepted to appear in the proceedings of the conference "Gamma-Ray Bursts in the Afterglow Era", Rome, 3-6 Nov, 199

X-ray Transients Monitored by the All-Sky Monitor on RXTE: A Tabulation

We present a tabulation of 46 transient x-ray sources monitored with the All-Sky Monitor (ASM) on the Rossi X-ray Timing Explorer (RXTE). They fall into four broad categories: short (~d), intermediate, and long (>500 d) duration of outbursts, and long period binary systems that flare up at periastron (e.g., Be systems). The mixture of outburst/quiescent cycles and low-level persistent emission in a few systems could indicate conditions are near the limit for stable mass flow in the accretion disk. The two short-time-scale systems, CI Cam and V4641 Sgr, are within 1 kpc of the sun, and hence many more such systems may await discovery.Comment: 18 pages, 2 figures, Submitted for publication in "X-ray Astronomy '99; Stellar Endpoints, AGN and the Diffuse Background", Ed: G.Malaguti, G.Palumbo, and N.White, pub. Gordon and Breach (v.2: Additional references added, erroneous figure replaced

An Economic Evaluation of Selected Treatments for Avian Botulism in Waterfowl on Utah Marshes, 1953-54

Purpose and scope Each year thousands of western waterfowl succumb to disease, predators, mechanical injury and other decimating factors . Based on a review of records it is conservatively estimated that an average of 25,000 ducks have succumbed to botulism on western marsh areas annually. In a recent study, the United States Fish and Wildlife Service valued each duck and goose at $8.00 (McLeod, 1950). Applying this value to the estimated annual numerical loss, a total of$200,000 has been lost each season in mortality of western waterfowl from botulism. Control of this malady would reduce annual waterfowl and monetary losses. Prevention and cure are the only means of controlling botulism in wild ducks. At present, no economical preventative measure exists and control is based on curing stricken birds. The purpose of this study was to evaluate the cost of treatment and rate of recovery of birds stricken with botulism when treated by selected methods . The 4 treatments selected for evaluation were: (1) hospital inoculation, (2) fresh water, (3) field inoculation, and (4) no treatment or control . Research included a comprehensive evaluation of factors such as age, sex, species, body condition, degree of affliction, reaction to various amounts of antitoxin, and reaction t o selected treatment methods, thought to be pertinent in botulism control. This study was conducted during botulism outbreaks of 1953 and 1954, and was confined to state-owned marshlands of Utah. Study areas Three major areas provided sick birds used in this research: (1) Ogden Bay Refuge, (2) Farmington Bay Refuge, and (3) the Public Shooting Grounds . These man-made marsh areas are located on the saline flat lands adjacent to Great Salt Lake. The majority, 1,979 or 89.3 percent, of sick birds were taken from Ogden Bay Refuge on the Weber River Delta. This state-owned waterfowl refuge contains approximately 13,700 acres of diversified habitat . Excellent conditions for the production and existence of Clostridium botulinum, type c, the causative agent of botulism, were apparently present throughout the area. Farmington Bay Refuge, approximately 20 miles south of Ogden Bay Refuge in Davis County, Utah, was dried for improvements in 1953, but was traversed regularly during the 1954 season. In preparation for the hunting season, water was diverted into the north lake of Farmington Bay on October 1, 1953. A two-man crew picked up and disposed of approximately 2,000 dead ducks from approximately 20 acres of the reflooded marsh on October 6, 1953. This was the most serious outbreak of the study and indicated the rapidity with which sickness advanced. Few sick birds were noted, which indicated that the crisis had passed. Farmington Bay Refuge provided 121 of the 2,214 ducks treated during 1953 and 1954. Not more than 12 sick or dead birds were seen on the Public Shooting Grounds, 8 miles west of Corinne, Utah, in 1953. During the 1953 season, 3 sick birds were transported from the area to Ogden Bay Refuge for treatment. In 1954 this state-owned shooting area supplied lll sick birds for treatment. Other areas were observed during the study but did not provide sick birds for treatment. These areas consisted of : (1) State -owned lands beyond Bear River Migratory Bird Refuge, and (2) Smith and Utah Lakes west of Provo, Utah

Mammals of the Mixedwood Plains Ecozone

Ontario and Quebec were totally covered with ice during the last glaciation. Deglaciation was followed by gradual post-glacial repopulation of these two provinces (and others) by mammals from source areas in the United States. Thus most range expansions were from south to north east of the Great Lakes. The mammalian fauna of the Mixedwood Plains Ecozone has been steadily changing since deglaciation about 10 000 years ago. During this period a succession of species assemblages has moved through this ecozone as the climate warmed. Several of the larger mammal species known from this area became extinct during this period of change. These included giant beavers, woolly mammoths, mastodons and species of deer and bison (Harington, 1989). Throughout this period there have been steady, gradual changes in the biodiversity of the Mixedwood Plains Ecozone, but the most rapid changes have occurred over the last 300 years. The best sources of information on the ranges of the mammals of the Ontario and Quebec parts of this ecozone are Peterson (1966) for both parts; Dobbyn (1994) and Peterson (1957) for Ontario; and Prescott and Richard (1982) for Quebec. Currently in the Mixedwood Plains Ecozone there are about 59 species of mammals in 44 genera and 16 families. This does not include four species recorded in this ecozone, but not established as part of its mammal fauna. An Evening Bat (Nycticeius humeralis) accidently occurred in the Lake Erie Lowland Ecoregion once. Black Rats (Rattus rattus), Coypus (Myocaster coypus), and Domestic Ferrets (Mustela putorius) have all been introduced but have not persisted. Although the species richness of mammals has increased since European settlement, biodiversity has decreased in the Mixedwood Plains Ecozone through the reduction in population size of many ecologically important species and the complete disappearance of others. Wolverines, Cougars and Wapiti have all been extirpated from this ecozone. Many species of mammals have been extirpated from much of their former ranges in this ecozone because of destruction of forest habitat, over-harvesting of pelts by fur trappers, over-hunting, and persecution of predators. Southwestern Ontario is an area of special concern because of the permanent conversion of most forests to agricultural land; this has resulted in a dramatic decrease in mammalian biodiversity. The loss of some native species has been coupled with increases in several new species through range expansion or direct introduction from other ecozones. The new species are typically generalists that have adapted to living in disturbed habitats. Our knowledge of the status of mammal populations in the Mixedwood Plains Ecozone is nowhere near complete. The status and complete distribution are known for only a few species monitored today because of their economic importance. The status of a few other species has been examined by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC); its status designations will be mentioned later in the species accounts. Monitoring programs should be established to determine the status of ecologically important species for proper biodiversity assessments of this ecozone. Many small mammals such as shrews, moles, bats, squirrels, mice, and voles could easily be monitored with existing techniques. Larger mammals would be more difficult to monitor but there are effective methods available. Large mammalian predator populations should be monitored as indicators of ecosystem health. Historically in the Mixedwood Plains Ecozone predator populations have declined most dramatically because of human disturbances

Metal Distributions, Efficient n-Type Doping, and Evidence for in-Gap States in TiNiM_<i>y</i>Sn (M = Co, Ni, Cu) half-Heusler Nanocomposites

XNi1+ySn nanocomposites consisting of a XNiSn half-Heusler (HH) matrix with segregated XNi2Sn Full Heusler (FH) inclusions promise improvements in thermoelectric efficiencies. We extend recent research by reporting on TiNiMySn (0 ≤ y ≤ 1) nanocomposites with M = Co (3d9), Ni (3d10) and Cu (3d104s1). Neutron powder diffraction reveals that the Ni and Cu series produce a matrix of TiNiSn with nanosegregated TiNi2Sn and TiNi1+dCu1–dSn, respectively. For the Co series, the Co inserts into both phases to obtain a TiNi1–yCoySn matrix with nanosegregated TiNi2–yCoySn. Systematic changes in Seebeck coefficient (S) and electrical resistivity (ρ) are observed in all three series. For M = Ni, changes in S and ρ are attributed to in-gap states arising from the nanosegregation. The M = Co composites show a complex interplay between the hole doped TiNi1–yCoySn matrix and similar in-gap states, where the p- to n-type transition temperature increases but the maximum S remains unchanged at +30 μV K–1. The 4s1 electron for M = Cu is delocalized in the HH matrix, leading to metal-like ρ(T) and up to 100% improved thermoelectric power factors compared to TiNiSn (S2/ρ = 2 mW m–1 K–2 at 600–700 K for y = 0.025). These results broaden the range of segregated FH phases that could be used to enhance HH thermoelectric performance

Photolytically generated aerosols in the mesosphere and thermosphere of Titan

Analysis of the Cassini Ultraviolet Imaging Spectrometer (UVIS) stellar and solar occultations at Titan to date include 12 species: N$_{2}$ (nitrogen), CH$_{4}$ (methane), C$_{2}$H$_{2}$ (acetylene), C$_{2}$H$_{4}$ (ethylene), C$_{2}$H$_{6}$ (ethane), C$_{4}$H$_{2}$ (diacetylene), C$_{6}$H$_{6}$ (benzene), C$_{6}$N$_{2}$ (dicyanodiacetylene), C$_{2}$N$_{2}$ (cyanogen), HCN (hydrogen cyanide), HC$_{3}$N (cyanoacetylene), and aerosols distinguished by a structureless continuum extinction (absorption plus scattering) of photons in the EUV. The introduction of aerosol particles, retaining the same refractive index properties as tholin with radius $\sim$125 \AA and using Mie theory, provides a satisfactory fit to the spectra. The derived vertical profile of aerosol density shows distinct structure, implying a reactive generation process reaching altitudes more than 1000 km above the surface. A photochemical model presented here provides a reference basis for examining the chemical and physical processes leading to the distinctive atmospheric opacity at Titan. We find that dicyanodiacetylene is condensable at $\sim$650 km, where the atmospheric temperature minimum is located. This species is the simplest molecule identified to be condensable. Observations are needed to confirm the existence and production rates of dicyanodiacetylene.Comment: A typo in Table 1 was made in the previous version. The corrected tholin abundance is 4.6x10^11. ApJL in press. Will be published on June 1st, or May 21 onlin