Meteoroid Engineering Model (MEM): A Meteoroid Model For The Inner Solar System

In an attempt to overcome some of the deficiencies of existing meteoroid models, NASA’s Space Environments and Effects (SEE) Program sponsored a 3 year research effort at the University of Western Ontario. The resulting understanding of the sporadic meteoroid environment – particularly the nature and distribution of the sporadic sources – were then incorporated into a new Meteoroid Engineering Model (MEM) by members of the Space Environments Team at NASA’s Marshall Space Flight Center. This paper discusses some of the revolutionary aspects of MEM which include (a) identification of the sporadic radiants with real sources of meteoroids, such as comets, (b) a physics-based approach which yields accurate fluxes and directionality for interplanetary spacecraft anywhere from 0.2 to 2.0 astronomical units (AU), and (c) velocity distributions obtained from theory and validated against observation. Use of the model, which gives penetrating fluxes and average impact speeds on the surfaces of a cube-like structure, is also described along with its current limitations and plans for future improvements.     

Antibiotic resistance in coliform and faecal coliform bacteria from natural waters and effluents

Coliform and faecal coliform bacteria isolated from potable water supplies (springs and wells), streams, seawater, and effluents were examined for the incidence of antibiotic resistance. More than 40% of the coliform and faecal coliform bacteria isolated from drinking water supplies were resistant to one or more antibiotics. In stream and seawater samples, the incidence was increased to more than 60%, and to more than 70% among faecal coliforms isolated from effluents. Approximately 40% of the isolates resistant to streptomycin or tetra‐cycline were able to transfer their resistance determinants to an antibiotic‐sensitive strain of Escherichia coli within 2 h.

Although the widespread use of antibiotics is perhaps the major selective force favouring the increased incidence of antibiotic‐resistant bacteria, antibiotic‐resistant faecal coliforms may also have a selective advantage in natural waters.     

Nitrate loss and transformation in 2 vegetated headwater streams

The processes of nitrate removal from the stream waters of 2 headwater catchments were studied. In study stretches where the stream channels were vegetated with thick mats of grass (Gly‐ceria fluitans), nitrate removal processes were particularly active. In such grassed stream channels, c. 75% of the nitrate removal was attributable to plant uptake and the remainder to denitrifica‐tion. Both of these nitrate removal processes were linearly dependent on nitrate concentration, resulting in an exponential decline of nitrate level from the springs along the stream's length. Regeneration of nitrogen, by plant decay within the stream channel, results in export of dissolved organic nitrogen and paniculate nitrogen from the catchments. The overall impact of vegetated stream channels in modifying nitrogen exports from catchments is discussed.     

Water quality of the Waiohewa Stream,Rotorua

The chemical quality of the Waiohewa stream, Rotorua, was assessed from the results of 2 longitudinal surveys in summer 1978–79. In particular, changes in nitrogen concentration were examined. The quantity of ammonia increased downstream from unmonitored geothermal inputs, but, after dilution and neutralisation by a larger inflow of freshwater, considerable proportions of ammonia were converted to nitrate. In the first survey ammonia concentrations decreased from 4.48 to 2.47 g m^‐3 and nitrate concentrations increased from 0.59 to 1.13 g ^‐3 in a 3‐km stretch of the stream. Mass flow calculations show that nitrification could account for at least 55% of the ammonia decrease, the rest probably being lost through assimilation or denitrification. Laboratory incubation experiments showed that nitrification occurred in the stream bed. The geothermal waters contained low concentrations of boron (1.1–4.0 g m^‐3), filterable mercury (0.1–0.8 mg m^‐3) and arsenic (10–14 mg m^‐3).     

Taphonomy at two contiguous coastal rockshelters in Panama: Preliminary observations focusing on fishing and curing fish

The scarcity of animal products negatively influences nutrition in tropical inland areas, which lack large rivers. Consuming cured marine fish mitigates this deficiency. In Panama, trading cured fish from coastal to inland sites is documented ethnohistorically and can be inferred from the current archaeozoological record. Very large numbers of marine fish remains have been recovered at pre-Columbian sites located on and around Parita Bay, a mangrove-fringed estuary on the central Pacific coast. At Sitio Sierra, a farming village 12 km inland from the active marine shore, more than 70% of fish remains deposited between ca. 1800 and 1500 uncalibrated radiocarbon years BP proved to be of marine origin. Two small rock-shelters located downriver from Sitio Sierra and now 2.6 km from the marine shore (Vampiros-1 and Vampiros-2) show evidence for having been used intensively for fishing and preparing fish between ca. 2200 and 1900 BP. A prior model based on air photograph interpretation and sedimentological analyses of marine and terrigenous sediments suggest that these shelters would have been on or very near the active marine shore at this time. A much earlier occupation at Vampiros-1 dating to ca. 11,500–7700 BP corresponds to pre-agricultural (Paleoindian) and early agricultural (Early Preceramic) people who camped occasionally in this shelter when the transgressing ocean was in the process of flooding Parita Bay. No shell or bone was recovered in this earlier cultural component. In the more recent (2200–1900 BP), component abundant remains of marine mollusks and crustaceans and vertebrate bones (mostly fish) are in excellent condition. A synopsis of the geological and cultural history of the Vampiros shelters is followed by preliminary observations on the relationship between pre-Columbian human activities and these sites’ formation processes, soil chemistry, bone integrity and animal species. Evidence is accruing for human impacts on fish skeletons resulting from the in situ preparation of fish (i.e., gutting, cutting and smoking) providing the opportunity to compare our archaeofaunal data with the results of Irit Zohar's ethno-archeological research, which identified how preparing fish for salting and sun-drying at present-day Panamanian fishing villages around Parita Bay affects the fish skeleton physically and proportionally. There is a strong possibility that the Vampiros shelters were used to provision inland sites like Sitio Sierra with inshore marine fish although we cannot yet ascertain the means by which coastal foodstuffs may have arrived at the latter site.     

Apparent calcite supersaturation at the ocean surface: Why the present solubility product of pure calcite in seawater does not predict the correct solubility of the salt in nature

It is generally accepted that seawaters near the ocean surface are supersaturated with calcite and that increasing atmospheric CO₂ will not overcome this condition until late in the 21st century. These expectations are based on comparisons of the ion activity products (IAPs) of various seawaters to the solubility product (K) of seawater saturated with pure calcite at 1 atm and a given temperature. It has been shown in recent papers, however, that calcites in contact with natural seawater in the surface oceans are not pure, but are magnesian calcite compositions. As a result, the presently accepted values of the solubility product of calcite in seawater cannot be used to obtain a correct, or even a reasonable estimate of the saturation state of sea water relative to either pure or magnesian calcite. Data are presented demonstrating that use of the currently accepted solubility product of calcite in seawater to determine seawater's relative calcite saturation leads to gross overestimates of its extent.     

The Migration of Partnered Gays and Lesbians between 1995 and 2000

This research investigates the interregional migration of partnered gays and lesbians between 1995 and 2000 as the first attempt at understanding the determinants of gay and lesbian migration using data from the Public Use Microdata Sample of the 2000 U.S. Census. Briefly, the findings are as follows. Both partnered gays and lesbians are regionally distributed throughout the United States consistent with the geographical distribution of the entire U.S. population. However, the shifting location of the partnered gay and lesbian population between 1995 and 2000 demonstrates significant variability. The general conclusion to be reached from models of the net migration of the partnered gay and lesbian population in that period is as follows: Partnered gay migration is directed toward moderate‐sized urban regions rich in natural amenities without regard for tolerance toward gay lifestyles or the absolute or relative size of the partnered gay community. Partnered lesbian migration is focused on less‐populous regions with a large, existing, partnered lesbian population. The role of natural amenities, the tolerance for lesbian lifestyles, and population density are not significant in determining partnered lesbian migration. The only trait partnered gay and lesbian migrations have in common is in their move toward less populous regions.