Final report on interrelationships between chemical, physical and biological conditions of the waters of Las Vegas Bay of Lake Mead

This program was a status study of the interaction between Las Vegas Wash, an enriched stream, and Las Vegas Bay, a wedge shaped arm of one of the world\u27s deeper reservoirs. The program centered primarily on identification and counting of planktonic algae from several points in Las Vegas Bay. Additional work on nutrient enrichment of water samples was conducted to aid in interpretation of algal distribution related to nutrient input. Examination of a variety of physical, chemical, and biological parameters, both at many surface points in the bay, as well as in vertical profile, was also accomplished and further aided interpretation of nutrient cycling, sources of nutrient input and other limnological events commonly associated with the process of eutrophication. One copy of data is provided as an appendix to this report. Other copies are available on request. An intensive sampling program has been the core of the project. Fifteen stations were located to provide an early warning network for detection of directed movement of water bodies or strata in the bay, reliability in evaluation of surface plankton distributions, and reference points for exploitation of unanticipated opportunities. These stations were visited approximately weekly during the contract period for plankton samples to evaluate biologically-induced or biologically - responsive changes as cumulative indices of the chemical status of the system. Evaluation of results was aided by determinations of depth profiles of the standard limnological parameters: temperature, a measure of the degree of stratification or mixing of a lake, oxygen, pH and oxidation-reduction potential. Conductivity, to identify isothermal yet saline discontinuities and especially the location of the flow from Las Vegas Wash, was also measured. Colonies or unicellular plankton were counted to determine distribution versus time over the bay surface. Distribution and density, rather than productivity, was of primary interest; although evidence for growth or accumulation at given points was also obtained. Chemical analyses for principal anions and cations (such as sulfate, chloride, sodium and potassium) and major nutrients (such as phosphate) were performed in cooperation with Desert Research Institute and Environmental Protection Agency. Counts of total and coliform bacteria were made on samples from vertical profiles at various times to establish the reason for the pattern of oxygen depletion found

Evaluation of Unmanned Radar Installations

Several unmanned radar devices were installed on I75 in northern Kentucky in an attempt to reduce speeds. It was assumed that drivers use radar detectors to exceed the speed limit with a resulting variance between their speeds and others in the traffic stream. Therefore, a reduction in overall speeds and variance was expected to reduce the probability of accidents. Historical data indicated an unusually high accident rate for the study area. Emphasis was placed on collection and analysis of speed-related data. In addition, a survey of radar detector usage was made and accident patterns were documented. Speed measures analyzed included mean speed, standard deviation in speed, numbers of vehicles exceeding specified speed levels, and 85th percentile speed. Results indicate that unmanned radar was an effective means of reducing the number of vehicles traveling at excessive speeds. The differences in mean speeds were small and the impact of unmanned radar was less obvious than it was for the percentage of vehicles exceeding speed levels of 65, 70, 75, and 80 mph. The speeds of vehicles with radar detectors decreased significantly as a result of unmanned radar while the speeds of vehicles without detectors were not affected. Radar detector usage was found to be 42 percent in trucks and 11 percent in cars. When comparing accident data three years before and one year after truck diversion and unmanned radar installations, there was a reduction in truck-related and speed-related accidents

Modelling activities at a neurological rehabilitation unit

A queuing model of a specialist neurological rehabilitation unit is studied. The application is to the Neurological Rehabilitation Centre at Rookwood Hospital (Cardiff, UK), the national rehabilitation unit for Wales. Due to high demand this 21-bed inpatient facility is nearly always at maximum occupancy, and with a significant bed-cost per day this makes it a prime candidate for mathematical modelling. Central to this study is the concept that treatment intensity has an effect on patient length of stay. The model is constructed in four stages. First, appropriate patient groups are determined based on a number of patient-related attributes. Second, a purpose-built scheduling program is used to deduce typical levels of treatment to patients of each group. These are then used to estimate the mean length of stay for each patient group. Finally, the queuing model is constructed. This consists of a number of disconnected homogeneous server queuing systems; one for each patient group. A Coxian phase-type distribution is fitted to the length of time from admission until discharge readiness and an exponential distribution models the remainder of time until discharge. Some hypothetical scenarios suggested by senior management are then considered and compared on the grounds of a number of performance measures and cost implications

Phytoplankton successions and lake dynamics in Las Vegas Bay, Lake Mead, Nevada

Phytoplankton successions, applications of the general growth equation, and physical measurements have been employed to investigate events occurring at the interface between industrial and sewage effluent contained in Las Vegas Wash and the waters of Lake Mead, Nevada. The data indicate that the entering waters tend to form a density current interrupted at intervals by dynamic effects generated in the lake. The dynamic relationships described here for the spring months suggest that a much more thorough understanding of physical, chemical and biological interactions is necessary to permit solution of the numerous problems of Las Vegas Bay discussed or alluded to by Hoffman et al

Ages for the Middle Stone Age of Southern Africa: Implications for Human behavior and Dispersal

The expansion of modern human populations in Africa 80,000 to 60,000 years ago and their initial exodus out of Africa have been tentatively linked to two phases of technological and behavioral innovation within the Middle Stone Age of southern Africa - the Still Bay and Howieson's Poort industries - that are associated with early evidence for symbols and personal ornaments. Establishing the correct sequence of events, however, has been hampered by inadequate chronologies. We report ages for nine sites from varied climatic and ecological zones across southern Africa that show that both industries were short-lived (5000 years or less), separated by about 7000 years, and coeval with genetic estimates of population expansion and exit times. Comparison with climatic records shows that these bursts of innovative behavior cannot be explained by environmental factors alone

Distribution of stream pollution in lake water

Wastewater effluent-laden waters from Las Vegas Wash (LVW) form a density current that may be detected in Boulder Basin of Lake Mead at considerable distances from the wash estuary. This led to the suspicion that water from the inflowing stream [40 mgd (1.5 X 105 cu m/day)] might not be rapidly diluted in the enormous volume of the lake [19 mil acre-ft (2.3 X 1010 cu m)], but might persist as a recognizable entity to the vicinity of the intake of a major water source for populous Clark County, Nev. Because of the detection sensitivity implicit in the use of bacteria as tracers, the signal amplification factor inherent in their growth on media, and precedent in work on streams and air, it was decided to investigate the possibility that they might be used to study the practical problem under consideration. Ideally, certain thermophilic spore-forming bacteria may be deliberately added as tracers. The next best choice would be a rnesophilic spore former (such as Bacillus subtilis var. niger), and a third alternative would be naturally occurring populations of bacteria indigenous to LVW. The last alternative was adopted because of the health hazards (though slight) inherent in adding large numbers of spores to the envirqnrnent under investigation

Valine Pyrrolidide Preserves Intact Glucose-Dependent Insulinotropic Peptide and Improves Abnormal Glucose Tolerance in Minipigs With Reduced β-Cell Mass

The incretin hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are important in blood glucose regulation.However, both incretin hormones are rapidly degraded by the enzyme dipeptidyl peptidase IV (DPPIV). The concept of DPPIV inhibition as a treatment for type 2 diabetes was evaluated in a new large animal model of insulin-deficient diabetes and reduced β-cell mass, the nicotinamide (NIA) (67 mg/kg) and streptozotocin (STZ) (125 mg/kg)–treated minipig, using the DPPIV inhibitor, valine pyrrolidide (VP) (50 mg/kg).VP did not significantly affect levels of intact GLP-1 but increased levels of intact GIP (from 4543 ± 1880 to 9208 ± 3267 pM × min; P<.01), thus improving glucose tolerance (area under the curve [AUC] for glucose reduced from 1904 ± 480 to 1582 ± 353 mM × min;P = .05).VP did not increase insulin levels during the oral glucose tolerance test (OGTT) but increased the insulinogenic index in normal animals (from 83 ± 42 to 192 ± 108; P < .05), but not after NIA + STZ, possibly because of less residual insulin secretory capacity in these animals. GIP seems to contribute to the antihyperglycemic effect of VP in this model; however, additional mechanisms for the effect of DPPIV inhibition cannot be excluded. The authors conclude that DPPIV inhibitors may be useful to treat type 2 diabetes, even when this is due to reduced β-cell mass