Optimal adult growth of Daphnia in a seasonal environment

1. The cladoceran Daphnia serves as an example of an iteroparous organism, with overlapping generations, that is capable of substantial adult growth. The life history of Daphnia was modelled as the consequence of a series of decisions about allocation of energetic resources to growth and reproduction. 2. We used numerical methods to find resource allocation patterns that maximized fitness of Daphnia in a temporally variable environment. Temporal variation was modelled as alternating active and dormant seasons; length of the active season was uniformly distributed. Fitness was measured by the geometric mean of resting eggs produced at the end of the active season. We examined effects of mean and range of the active season on the optimal life history; we also examined effects of increasing (invertebrate predation), constant (non-selective) and decreasing (fish) size-specific survival rates. For comparison, we found resource allocation patterns that maximized fitness in a constant environment, where fitness was measured by the intrinsic rate of increase r. 3. Life histories optimized for seasonal environments generally showed earlier maturity and greater adult growth than those optimized for constant environments. Adult growth occurred with non-selective predation, and even with fish predation, conditions under which it does not occur in the optimal life histories for constant environments. 4. Greatest size at maturity and adult growth occurred in life histories optimized to invertebrate predation in seasonal environments. Smallest size at maturity and least adult growth occurred in life histories optimized to fish predation. 5. In the optimal life histories, size at maturity generally increased with mean length of the active season. Adult growth reached a maximum for mean seasons of length equal to about one-half to one life span of Daphnia. 6. Increasing the variation in season length decreased adult growth in the optimal life history, but had little effect on size at maturity. 7. We expect that life histories are adapted to the long-term average of season length and its variation. If the animals can detect the type of predator, selection could favour phenotypic variation in resource allocation

Evaluation of critical nuclear power plant electrical cable response to severe thermal fire conditions

The failure of electrical cables exposed to severe thermal fire conditions are a safety concern for operating commercial nuclear power plants (NPPs). The Nuclear Regulatory Commission (NRC) has promoted the use of risk-informed and performance-based methods for fire protection which resulted in a need to develop realistic methods to quantify the risk of fire to NPP safety. Recent electrical cable testing has been conducted to provide empirical data on the failure modes and likelihood of fire-induced damage. This thesis evaluated numerous aspects of the data. Circuit characteristics affecting fire-induced electrical cable failure modes have been evaluated. In addition, thermal failure temperatures corresponding to cable functional failures have been evaluated to develop realistic single point thermal failure thresholds and probability distributions for specific cable insulation types. Finally, the data was used to evaluate the prediction capabilities of a one-dimension conductive heat transfer model used to predict cable failure

Living Together: The Economics of Cohabitation

Analyzes trends among unmarried couples ages 30 to 44 living together by education. Compares median household income, poverty rate, composition of household income, and number of children with those of married couples and those without partners

Senior Recital, Gabriel Taylor, guitar

The presentation of this senior recital will fulfill in part the requirements for the Bachelor of Music degree in Performance. Gabriel Taylor studies guitar with David Toussaint

Imidazole aldoximes effective in assisting butyrylcholinesterase catalysis of organophosphate detoxification.

Intoxication by organophosphate (OP) nerve agents and pesticides should be addressed by efficient, quickly deployable countermeasures such as antidotes reactivating acetylcholinesterase or scavenging the parent OP. We present here synthesis and initial in vitro characterization of 14 imidazole aldoximes and their structural refinement into three efficient reactivators of human butyrylcholinesterase (hBChE) inhibited covalently by nerve agent OPs, sarin, cyclosarin, VX, and the OP pesticide metabolite, paraoxon. Rapid reactivation of OP-hBChE conjugates by uncharged and nonprotonated tertiary imidazole aldoximes allows the design of a new OP countermeasure by conversion of hBChE from a stoichiometric to catalytic OP bioscavenger with the prospect of oral bioavailability and central nervous system penetration. The enhanced in vitro reactivation efficacy determined for tertiary imidazole aldoximes compared to that of their quaternary N-methyl imidazolium analogues is attributed to ion pairing of the cationic imidazolium with Asp 70, altering a reactive alignment of the aldoxime with the phosphorus in the OP-hBChE conjugate