Environmental regulation of growth in black brant

Thesis (Ph.D.) University of Alaska Fairbanks, 2002Body size is an important determinant of life history traits such as survival and fecundity. There is a positive correlation between growth during the first summer and final body size in goose populations. I examined how environmental factors influence growth in Black Brant (Branta bernicla; hereafter brant) goslings. Growth declined seasonally and varied among brood-rearing areas. However, the pattern was not consistent among years. Models containing only environment and maternal effects explained 75% of variation in gosling mass, indicating that little of the observed variation in size is directly of genetic origin. Heritability did not differ from zero for both mother-daughter and father-daughter regressions. I also conducted an experiment to study the effect of gosling density on food abundance, feeding behavior, and development of brant goslings, in two habitat types important to brant: (1) Carex subspathacea grazing lawns and (2) slough levees which contain Triglochin palustris. Variation in grazing pressure was experimentally manipulated. Biomass and offtake of C. subspathacea was higher in lightly grazed plots than in heavily grazed plots even though goslings within heavily grazed plots spent more time feeding. Within slough levee habitat there were no differences between heavily and lightly grazed plots in either biomass or offtake of T. palustris. Peck rates were lower in slough levee habitat than in grazing lawns. Change in mass over an eight hour trial was positively correlated with the amount of forage biomass in the plot at the start of the trial. I found no variation in internal morphometrics or body composition among goslings. I also examined the relationship between forage available within a brood-rearing area, the number of birds using the area, and gosling growth. Annual variation in use of brood-rearing areas was correlated with forage availability. Gosling mass was negatively correlated with brood numbers when examined across all areas, however, within each brood-rearing area, the relationship between mass and numbers of birds was positive. I did not see a relationship between estimates of food availability (per m²) and brood numbers. Spatial variation in growth among habitats may result from habitats varying in quality and quantity of forage

METABOLIC EFFECTS OF DIET INDUCED OBESITY

INTRODUCTION Obesity is generally defined as a condition where excess body fat has accumulated to a point where it can cause detrimental health effects [1]. Obesity in children and teenagers is becoming more common, with worldwide rates increasing by 50% in the last 30 years [2]. The purpose of this project was to investigate how inducing obesity through a high-fat/high-sugar (HFHS) diet affects a variety of metabolic, physical, and behavioral factors when utilizing a rat model to study dietary-induced obesity. To our knowledge, an in depth analysis of metabolic parameters using this model has not been conducted based on the current literature. Expected observations included an increased caloric intake for the obese animals and no change in caloric expenditure between groups, accompanied by a decrease in activity for the obese animals once the animals began to show signs of increased fat mass.  METHODS Twenty male Sprague Dawley rats were randomly divided into two groups of ten at three weeks of age (post-weaning). The control group was fed regular rat chow and the experimental group was fed a custom HFHS diet in order to induce obesity.  Both groups were provided with food ad libitum. From weaning until 16 weeks of age, each rat spent one period of at least 24 hours in a metabolic chamber per week.  The metabolic chambers were set up to monitor a variety of parameters. These included gas exchange (caloric expenditure), food consumption, and activity levels.  Data collection is ongoing, therefore statistics have been run based on the latest time point at which data has been collected for all animals. RESULTS Shown in Figure 1, the experimental group of rats which were fed the HFHS diet consumed significantly more calories than the control group for each week after the first two. Interestingly, there was no statistical significance between the mass of food consumed by each group. There was also no statistical significance between the mass of the two groups over the time period we tested. In addition to this, we also found that at 10 weeks of age the experimental group expended over 25% more calories (p<0.001) when compared to the controls, and the caloric expenditure was significantly higher for the experimental group for all but the first week. The experimental group was significantly more active (p<0.05) for weeks five through eight.DISCUSSION AND CONCLUSIONS The experimental animals did not become heavier than the controls to the extent that was expected. Despite this, there was still increased caloric intake relative to the controls. The experimental group also had significantly higher energy expenditure compared to the controls, potentially as a result of higher activity levels, which was unexpected and may help explain the minimal weight gain. Testing will continue until 16 weeks of age, at which point we expect to see statistical significance for body mass based on the way the data is trending

Heterogeneity in vaccination coverage explains the size and occurrence of measles epidemics in German surveillance data

The objective of this study was to characterize empirically the association between vaccination coverage and the size and occurrence of measles epidemics in Germany. In order to achieve this we analysed data routinely collected by the Robert Koch Institute, which comprise the weekly number of reported measles cases at all ages as well as estimates of vaccination coverage at the average age of entry into the school system. Coverage levels within each federal state of Germany are incorporated into a multivariate time-series model for infectious disease counts, which captures occasional outbreaks by means of an autoregressive component. The observed incidence pattern of measles for all ages is best described by using the log proportion of unvaccinated school starters in the autoregressive component of the mode

Heavy flavor diffusion in weakly coupled N=4 Super Yang-Mills theory

We use perturbation theory to compute the diffusion coefficient of a heavy quark or scalar moving in N=4 SU(N_c) Super Yang-Mills plasma to leading order in the coupling and the ratio T/M<<1. The result is compared both to recent strong coupling calculations in the same theory and to the corresponding weak coupling result in QCD. Finally, we present a compact and simple formulation of the Lagrangian of our theory, N=4 SYM coupled to a massive fundamental N=2 hypermultiplet, which is well-suited for weak coupling expansions.Comment: 22 pages, 4 figures; v3: error corrected in calculations, figures and discussion modified accordingl

Hard thermal loops and the entropy of supersymmetric Yang-Mills theories

We apply the previously proposed scheme of approximately self-consistent hard-thermal-loop resummations in the entropy of high-temperature QCD to N=4 supersymmetric Yang-Mills (SYM) theories and compare with a (uniquely determined) R[4,4] Pad\'e approximant that interpolates accurately between the known perturbative result and the next-to-leading order strong-coupling result obtained from AdS/CFT correspondence. We find good agreement up to couplings where the entropy has dropped to about 85% of the Stefan-Boltzmann value. This is precisely the regime which in purely gluonic QCD corresponds to temperatures above 2.5 times the deconfinement temperature and for which this method of hard-thermal-loop resummation has given similar good agreement with lattice QCD results. This suggests that in this regime the entropy of both QCD and N=4 SYM is dominated by effectively weakly coupled hard-thermal-loop quasiparticle degrees of freedom. In N=4 SYM, strong-coupling contributions to the thermodynamic potential take over when the entropy drops below 85% of the Stefan-Boltzmann value.Comment: 14 pages, 2 figures, JHEP3. v2: revised and expanded, with unchanged HTL results but corrected NLO strong-coupling result from AdS/CFT (which is incorrectly reproduced in almost all previous papers comparing weak and strong coupling results of N=4 SYM) and novel (unique) Pade approximant interpolating between weak and strong coupling result

Comment on "Loss-error compensation in quantum-state measurements"

In the two papers [T. Kiss, U. Herzog, and U. Leonhardt, Phys. Rev. A 52, 2433 (1995); U. Herzog, Phys. Rev. A 53, 1245 (1996)] with titles similar to the one given above, the authors assert that in some cases it is possible to compensate a quantum efficiency $\eta\leq 1/2$ in quantum-state measurements, violating the lower bound 1/2 proved in a preceding paper [G. M. D'Ariano, U. Leonhardt and H. Paul, Phys. Rev. A 52, R1801 (1995)]. Here we re-establish the bound as unsurpassable for homodyning any quantum state, and show how the proposed loss-compensation method would always fail in a real measurement outside the allowed $\eta >1/2$ region.Comment: 3 pages, RevTeX, 2 figures included, to appear on Phys. Rev. A (April 1998