The Structure of the Spring Thermal Bar in Lake Superior,II

The thermal bar was studied during May and June of 1974 and 1975 near the Keweenaw Peninsula along the south shore of Lake Superior. Temperature distributions and the distributions of naturally fluorescent material were measured in order to determine the nature of the energy and mass transport in the thermal bar zone. Transects were located perpendicular to the thermal bar, and temperature was measured at 5 m intervals to a depth of 45 m using a thermistor probe with a 3 sec time constant interfaced with a signal conditioner and digital voltmeter. Accuracy in the range of 4°C was ± 0.01°C. Water samples were collected, and the natural fluorescence arising from land runoff was measured. Station locations were determined by triangulation. Data for both temperature and fluorescence were plotted by a computer mapping program (SYMAP).The computer plotted temperature distributions provide the most detailed picture of the thermal bar thus far obtained. The complexity suggests considerable turbulence. A strong correlation between natural fluorescence and temperature supports the concept that little mixing occurs between inshore and offshore waters and that a significant portion of inshore water arises from runoff. The bottom slope seems to have a strong influence on the flow near the thermal bar and on the rate of movement offshore.     

Short-term memory scan in normal individuals and individuals with aphasia

Ten matched pairs of normal adults and adults with aphasia participated in a short-term memory, visual recognition paradigm wherein each determined whether or not a probe digit appeared in a subset of digits previously presented. Reaction times, measured in milliseconds from onset of probe digits until completion of visual-motor responses, were analyzed as a function of increasing subset size (two, four, and six digits) and the positive versus the negative response condition. Reaction times were significantly slower for the subjects with aphasia. Both groups of subjects demonstrated linear increases in reaction time across levels of subset size. For both groups, increases in reaction time were similar in the positive vs the negative-response conditions. Resulting parallel slopes suggested that both groups of subjects used a serial exhaustive scan of short-time memory. Results from this study did not support results obtained by others in previous studies which may have been confounded by group differences in visual retention spans.     

Gas chromatography of the fat-soluble vitamins: A review

The application of gas liquid chromatography (GLC) as an analytical tool for the determination of the fat-soluble vitamins A, D, E and K has yet to be utilized to its full potential. A review of the published work of many researchers in this field is presented. GLC methods to measure the vitamin A isomers have not been developed to any appreciable practical extent. Liquid liquid chromatography might well be the technique of choice. In the field of vitamin D there are indications that a practical GLC analysis is feasible for pharmaceutical preparations. The GLC applications for vitamin E are diverse, well defined and generally widely accepted in research laboratory situations and for regulatory and quality control usage. Vitamins K₁ and K₂ have been measured with limited success in a few research laboratories, but the GLC methods have not developed on a practical basis. However GLC is used for measuring vitamin K₃ (menadione and menadione sodium bisulfite) on a fairly routine basis in quality control laboratories.     

Disease induced dynamics in host–parasitoid systems: chaos and coexistence

All animals and plants are, to some extent, susceptible to disease caused by varying combinations of parasites, viruses and bacteria. In this paper, we present a mathematical model of interactions between a host, two parasitoids and a pathogen which shows that the presence of an infection can preserve and promote diversity in such multi-species systems. Initially, we use a system of ordinary differential equations to investigate interactions between two species of parasitoids, a host and a host infection. We show that the presence of all four species is necessary for the system as a whole to persist, and that in particular, the presence of the pathogen is necessary for the coexistence of the two parasitoid species. The inclusion of infection induces a wide range of dynamics, including chaos, and these dynamics are robust for a wide range of parameter values. We then extend the model to include spatial effects by introducing random motility (diffusion) of all three species and examine the subsequent spatio-temporal dynamics, including travelling waves and other more complicated heterogeneous behaviour. The computational simulation results of the model suggest that infection in the hosts can blunt the effects of competition between parasitoids, allowing the weaker competitor to survive. Regardless of the nature of the stability of the coexistent steady state of the system, there is an initial period of transient dynamics, the length of which can be extended by an appropriate choice of initial conditions. The existence of these transient dynamics suggests that systems subject to regular restoration to a starting state, such as agro-ecosystems, may be kept in a continual state of dynamic transience, and this has implications for the use of natural enemies to control insect pests, the preservation of biodiversity in farmland habitats and the more general dynamics of disease processes.     

Constitutive model of tendon responses to multiple cyclic demands (I)

The work reported here is an extensive study of tendon response to multiple cyclic tests including 3% constant peak strain level test (A-type test), 3% constant peak strain level test with two rest periods (B-type test), and 3–4% different peak strain level test (C-type test). A sufficient number of speciments were tested at each type of the test to statistically evaluate many changes in response during testing and differences in response between each type of the test. In cyclic tests, there were decreses (relaxations) in the peak stresses and hysteresis, increases in the slack strains, and during lower peak strain level (3%) cyclic block after higher peak strain level (4%) cyclic block in the C-type tests. Considering the results of this study and those of the other study of multiple cyclic tests with rest periods by Hubbard and Chun, 1985,recovery phenomena during the rest periods occurred predominantly at the beginning of the rest periods. Consistently in both studies, the effects of rest periods were small and transient compared to the effects of the cyclic extensions. The recovery with cycles at lower peak strain level (3%) after higher peak strain level (4%) in the C-type test has not been previously documented. This recovery seems to be a natural phenomena in tissue behavior so that collagenous structures recover during periods of decreased demand.     

Continued Corrosion After Removal of Corrosive Drywall

Copper coupons in sealed glass jars were exposed to corrosive drywall (CDW) and a moisture source while experiencing temperature variation from room temperature to about 120 °F (49 °C). After several weeks of exposure, the CDW source was removed and coupons were replaced into sealed glass jars with a moisture source for extended periods of time under similar temperature cycling. These coupons continued to corrode at a faster rate than coupons that had only been exposed to moisture in the absence of CDW. Analytical scanning electron microscopy (SEM) was used to augment weight change measurements. The results demonstrate that once corrosion is initiated by exposure to CDW, simple removal/replacement of the drywall will not mitigate the corrosion process.     

The ‘sub-trigger’ crisis: An economic analysis of flexible stock policies

This paper investigates the value of international cooperation during an oil supply disruption. The International Energy Agency provides the aegis for energy cooperation among the industrialized countries, but only an enormous disruption would ‘trigger’ the Agency's emergency mechanism. Smaller (‘sub-trigger’) disruptions have occurred three times in the past decade, and twice, in 1973–1974, and again in 1979, the result was havoc in the international oil markets and substantial economic damage. General consensus credits oil inventory accumulation with exacerbating these shocks and decumulation with averting similar problems during the 1980 disruption. The paper employs a small short-run econometric model of the oil market to examine inventory behaviour and to test coordinated government stockpile drawdowns (termed ‘flexible stock policies’) which have been proposed to address these issues. Impacts on GNP are obtained by solving the oil market model simultaneously with an econometric model of the US macro-economy.     

A standardized model for the evaluation of machining coolant/lubricant costs

Compliance with environmental regulations is becoming more and more costly for manufacturers as government scrutiny and global trade agreements become more stringent. Metal-cutting fluid use and disposal is a major concern as these environmental issues become more prominent. Gaining a clear understanding of the costs associated with machining coolant/lubricant use can be difficult. Many factors impact this cost, such as the original purchase price, maintenance costs, disposal management and fees, and performance factors related to the particular fluid. This paper develops a detailed cost and performance-based methodology for machining coolant/lubricant selection. A model by which to evaluate the relative impacts of coolant/lubricant decisions on the unit workpiece cost of production is described. At present, a widely accepted methodology is not available for this purpose. The model presented here will assist manufacturing companies of all types in making this critical decision.     

In-roads to the spread of antibiotic resistance: regional patterns of microbial transmission in northern coastal Ecuador

The evolution of antibiotic resistance (AR) increases treatment cost and probability of failure, threatening human health worldwide. The relative importance of individual antibiotic use, environmental transmission and rates of introduction of resistant bacteria in explaining community AR patterns is poorly understood. Evaluating their relative importance requires studying a region where they vary. The construction of a new road in a previously roadless area of northern coastal Ecuador provides a valuable natural experiment to study how changes in the social and natural environment affect the epidemiology of resistant Escherichia coli. We conducted seven bi-annual 15 day surveys of AR between 2003 and 2008 in 21 villages. Resistance to both ampicillin and sulphamethoxazole was the most frequently observed profile, based on antibiogram tests of seven antibiotics from 2210 samples. The prevalence of enteric bacteria with this resistance pair in the less remote communities was 80 per cent higher than in more remote communities (OR = 1.8 [1.3, 2.3]). This pattern could not be explained with data on individual antibiotic use. We used a transmission model to help explain this observed discrepancy. The model analysis suggests that both transmission and the rate of introduction of resistant bacteria into communities may contribute to the observed regional scale AR patterns, and that village-level antibiotic use rate determines which of these two factors predominate. While usually conceived as a main effect on individual risk, antibiotic use rate is revealed in this analysis as an effect modifier with regard to community-level risk of resistance.