Carboxylated Organic Matter Influences Magnesium Uptake in Three Low-Temperature Dolomite Models

Numerous geochemical models explain the formation of dolomite at low temperature, a controversial mineral due to its abundance in geological deposits but paucity in modern environments. Several of these models are based on environments where dolomite either forms in the modern or is hypothesized to have formed in the past– mixing zones, sabkhas, and alkaline lakes. In the last twenty years, results of field and laboratory studies have found that microorganisms can promote the precipitation of dolomite at low temperature, either through active metabolism or by providing a reactive surface for mineral nucleation. The work summarized here utilizes bench-scale laboratory batch experiments to study simplified geochemical environments associated with low temperature dolomite formation both containing and excluding synthetic carboxylated organic matter in the form of functionalized polystyrene microspheres. These environments were characterized by their pH, alkalinity, and salinity to form geochemical end members. In effect, this combines longstanding geochemical models of dolomite formation with a mechanism known to overcome kinetic barriers to dolomite formation at low temperature. Experiments did not demonstrate formation of significant amounts of dolomite, however, data suggest that while bulk precipitation products reflect the specific geochemical environments, the presence of carboxylated organic matter promotes the incorporation of magnesium into the precipitate across geochemical environments. The amount of magnesium in the precipitate on the microsphere surface appears to be a function of the Mg/Ca ratio of the bulk solution. Magnesium is observed both in precipitates forming on the microsphere surface and is more broadly distributed in the bulk precipitate when microspheres are present. These results suggest that carboxylated organic matter can sequester magnesium into precipitates, which could have implications for magnesium availability during diagenesis. Results from experiments studying the impact of carboxylated organic matter on dolomitization of calcium carbonate sediments in mixing, sabkha, and artificial fluids are inconclusive. These negative results potentially arise from short experimental time scales and scaling issues during analysis. Future low temperature dolomitization experiments should include advection in the experimental design to provide the mass transfer presumably necessary for significant dolomitization

Diet Choices of Blue Jays (Cyanocitta cristata) as a Function of Time Spent Foraging

Optimal diet theory predicts choices among prey types. With sequential prey encounters, less profitable prey types may be rejected immediately because rejecting the prey item at hand increases the probability of encountering more profitable types. However, Lucas (1985) argued that at the end of a foraging bout, all encountered prey types should be accepted because the opportunity to encounter more profitable types is limited. We tested Lucas’s prediction in a simulation, allowing blue jays to hunt for two moth types differing in profitability. During the last min of both 10- and 20-min foraging bouts, the less profitable type was attacked more often than during the middle of the bouts; this is an end-of-the-bout effect. The less profitable type was also attacked more often at the beginning of the bouts; this is probably a sampling effect. Jays appear to integrate information about time spent foraging with information about relative prey profitability

Diet Choices of Blue Jays (Cyanocitta cristata) as a Function of Time Spent Foraging

Optimal diet theory predicts choices among prey types. With sequential prey encounters, less profitable prey types may be rejected immediately because rejecting the prey item at hand increases the probability of encountering more profitable types. However, Lucas (1985) argued that at the end of a foraging bout, all encountered prey types should be accepted because the opportunity to encounter more profitable types is limited. We tested Lucas’s prediction in a simulation, allowing blue jays to hunt for two moth types differing in profitability. During the last min of both 10- and 20-min foraging bouts, the less profitable type was attacked more often than during the middle of the bouts; this is an end-of-the-bout effect. The less profitable type was also attacked more often at the beginning of the bouts; this is probably a sampling effect. Jays appear to integrate information about time spent foraging with information about relative prey profitability

Sex Differences in Psychosocial Quality of Life of Long-Term Melanoma Survivors

This research was supported by the Undergraduate Research Opportunities Program (UROP)

Isotopic Composition of the Ogallala-high Plains Aquifer Andvadose Zone

AbstractThe Ogallala-High Plains aquifer is an important resource for irrigated agriculture in a semi-arid region of the United States. Steep declines in groundwater levels are putting increasing strain on the viability of the aquifer for irrigation, necessitating improved estimates of recharge rates and sources to the aquifer. This study uses a combined approach to obtain high resolution geochemical and isotopic composition of the vadose zone and aquifer pore fluids to better understand recharge dynamics to the aquifer. Significant differences between the shallow, intermediate and deep vadose zone and shallow and deep aquifer indicate modern precipitation is not providing a significant source of recharge to the aquifer across a large area (diffuse recharge). Rather, recharge to the aquifer is a result of either focused recharge or long-term, delayed drainage from the portion of the vadose zone which was saturated before irrigation development

The effects of prey depletion on the patch choice of foraging blue jays (\u3ci\u3eCyanocitta cristata\u3c/i\u3e)

Blue jays (Cyanocitta cristata) were trained to hunt for non-cryptic moths presented in projected images. On each trial, the jays chose one of two patches to hunt in: (1) a uniform, “non-depleting” patch with constant prey density of 0.25; or (2) a “depleting” patch in which prey density changed during the foraging bout. In the depleting patch, the initial prey density was 0.50, declining to zero in a single step part-way through each foraging bout (session). The patch choices of the jays were greatly affected by these conditions. The jays chose the depleting patch early in the session, and then switched to the uniform patch. They obtained nearly all of the prey available. Analysis of the events preceding switches between patches suggested that the jays used different rules to switch out of each of the two patches

Response strategies in the radial arm maze: Running around in circles

The effects of the size of the central arena on the use of response strategies by rats on an eight~arm elevated maze were examined. The size of the central arena had no effect on accuracy, but the use of adjacent arms increased significantly with a larger central arena, regardless of the size of arena to which rats were first exposed. These results are interpreted in terms of foraging efficiency

Integrating Cognitive Ethology with Cognitive Psychology

Cognitive ethology has been defined by Griffin (1978,1981, 1984) as the study of mental experiences in animals, restricting the domain of the field to phenomena thought to reveal intentionality, awareness, and conscious thinking. We argue that attempts to study these processes, while revealing impressive behavioral complexity, have proven unsuccessful in establishing the importance of mental experiences in determining animal behavior primarily because of the intractability of the problem. We suggest a different approach that draws upon the rich theory and sophisticated methodology of human and animal cognitive psychology while retaining an ecological and evolutionary perspective. Brief accounts of the conceptual underpinnings of cognitive psychology are presented as well as examples of empirical work, including the analysis of imagery in human and nonhuman animals. We hope our broad redefinition of cognitive ethology provides a rigorous framework within which to examine the role of cognition in ecologically relevant behavior