The last glacial cycle: transient simulations with an AOGCM

A number of transient climate runs simulating the last 120kyr have been carried out using FAMOUS, a fast atmosphere-ocean general circulation model (AOGCM). This is the first time such experiments have been done with a full AOGCM, providing a three-dimensional simulation of both atmosphere and ocean over this period. Our simulation thus includes internally generated temporal variability over periods from days to millennia, and physical, detailed representations of important processes such as clouds and precipitation. Although the model is fast, computational restrictions mean that the rate of change of the forcings has been increased by a factor of 10, making each experiment 12kyr long. Atmospheric greenhouse gases (GHGs), northern hemisphere ice sheets and variations in solar radiation arising from changes in the Earth's orbit are treated as forcing factors, and are applied either separately or combined in different experiments. The long-term temperature changes on Antarctica match well with reconstructions derived from ice-core data, as does variability on timescales longer than 10 kyr. Last Glacial Maximum (LGM) cooling on Greenland is reasonably well simulated, although our simulations, which lack ice-sheet meltwater forcing, do not reproduce the abrupt, millennial scale climate shifts seen in northern hemisphere climate proxies or their slower southern hemisphere counterparts. The spatial pattern of sea surface cooling at the LGM matches proxy reconstructions reasonably well. There is significant anti-correlated variability in the strengths of the Atlantic Meridional Overturning Circulation (AMOC) and the Antarctic Circumpolar Current (ACC) on timescales greater than 10kyr in our experiments. We find that GHG forcing weakens the AMOC and strengthens the ACC, whilst the presence of northern hemisphere ice-sheets strengthens the AMOC and weakens the ACC. The structure of the AMOC at the LGM is found to be sensitive to the details of the ice-sheet reconstruction used. The precessional component of the orbital forcing induces ~20kyr oscillations in the AMOC and ACC, whose amplitude is mediated by changes in the eccentricity of the Earth's orbit. These forcing influences combine, to first order, in a linear fashion to produce the mean climate and ocean variability seen in the run with all forcings

Ventilation Loss in the NASA Space Shuttle Crew Protective Garments: Potential for Heat Stress

The potential of the National Aeronautics and Space Administration (NASA) S1035 Launch/Entry suit (LES) for producing heat stress in a simulated Space Shuttle cabin environment has been studied. The testing was designed to determine if the NASA S1035 poses a greater threat of inducing heat stress than the NASA S1032. Conditions were designed to simulate an extreme prelaunch situation, with chamber temperatures maintained at dry bulb temperature 27.2 +/- 0.1 C, globe temperature - 27.3 +/- 0.1 C, and wet bulb temperature 21.1 +/- 0.3 C. Four males, aged 28-48, were employed in this study, with three subjects having exposures in all four conditions and the fourth subject exposed to 3 conditions. Test durations in the ventilated (V) and unventilated (UV) conditions were designed for 480 minutes, which all subjects achieved. No significant differences related to experimental conditions were noted in rectal temperatures, heart rates or sweat rates. The results indicate that the S1032 and S1035 garments, in either the V or UV state, poses no danger of inducing unacceptable heat stress under the conditions expected within the Shuttle cabin during launch or re-entry

Gallai-Ramsey Number of An 8-Cycle

Given a graph G and a positive integer k, define the Gallai-Ramsey number to be the minimum number of vertices n such that any k-edge-coloring of Kn contains either a rainbow (all different colored) triangle or a monochromatic copy of G. In this work, we establish the Gallai-Ramsey number of an 8-cycle for all positive integers

Nutritional aspects of sexual dimorphism in the American mink mustela vison (schreber)

Nutritional aspects of size-related sex differences in the diets of free-living mink were investigated in laboratory-based feeding trials with adult farm-bred mink maintained on 'natural' diets. As preliminary studies had shown that carcase utility was virtually complete, the rations presented comprised the minced whole carcasses of wild rabbit Oryctolagus cunniculus, eel Anquilla anguilla, laboratory rats and mice, and domestic fowl. Determinations of gross composition revealed significant differences between these diets; the smaller prey types, including rodents, birds and fish, were found to have a higher ratio of Apparent Digestible Energy to Nitrogen than larger items such as rabbits, although comparisons with data presented by other workers demonstrated that the variations between species within these prey groups are as great as, or greater than, those between the diets themselves. From the results of the feeding trials, it was also apparent that such diets do not differ significantly, either in digestibility or biological value and attempts to classify particular prey items in terms of their nutritional value are, therefore, of limited application in analyses of the feeding ecology of a generalist predator. Nutrient intake was related to diet composition and varied widely between trials, although the mass-specific requirements of females were higher than those of males. Comparisons of gut morphology indicated that, in females, hypertrophy of the alimentary tract may develop in response to increased energy demands. A similar adaptation was evident in both males and females from wild populations, suggesting that the natural diets of free-living mink are generally of a lower quality than the rations fed to commercially raised animals. Feeding trials were also carried out on growing kits from 56 to 105 days post partum. Sex differences in nutrient metabolism were not significant but the growth rates of males were higher than those of females. In both sexes the growth rates of kits feeding on 'natural' diets were lower than those of animals raised on commercial rations. This effect was most pronounced in males, a finding which supports the hypothesis that the degree of sexual dimorphism in this species is dependent on the extent to which the growth potential of males is constrained by dietary regime during the early phases of development