Increased mantle convection during the mid-Cretaceous: A comparative study of mantle potential temperature

Mantle convection patterns of the past are not well known, yet an understanding of changing mantle convection characteristics is fundamental to understanding the evolution of plate tectonics. There are very few ways to examine mantle characteristics of the past. Changes in spreading rate and volcanic activity with time have been used to draw conclusions about historic changes in mantle activity. Mantle temperature has been found to be related to crustal thickness. With this relationship, crustal thicknesses may now yield new conclusions about historic changes in mantle characteristics. We have inferred changes in mantle convection patterns throughout the last 180 m.y. by examining variations in assumed crustal thickness within the Pacific basin. Crustal thicknesses were calculated from residual depth anomalies by assuming that residual depth anomalies are the result of isostatic compensation of variations in crustal thickness. Crustal thickness is determined at the time of crustal formation and is dependent upon the temperature of the mantle source material. Intraplate hot spot volcanism effects on crustal thickness were not ignored. Examination of variations in crustal thickness of crust of different ages can reveal information about changing temperatures of the mantle at the ridge through time. We have learned that mantle temperatures at the ridge during the mid-Cretaceous were more variable than those temperatures at the ridge after the mid-Cretaceous. Furthermore, we have inferred from the data that mantle temperatures at hot spots were higher during the mid-Cretaceous than those at hot spots existing after the mid-Cretaceous. We suggest that mantle convection at the ridge was more rapid during the mid-Cretaceous causing a higher variability of temperatures at the ridge. We also note that this period of increased mantle convection is concurrent with the increased mantle temperatures at hot spots within the Pacific basin

Trade-offs and coexistence: A lottery model applied to fig wasp communities

Ecological communities in which organisms complete their life cycles on discrete ephemeral patches are common and often support an unusually large number of species. Explaining this diversity is challenging for communities of ecologically similar species undergoing preemptive competition, where classic coexistence mechanisms may not readily apply. We use nonpollinating fig wasps as a model community characterized by high diversity and preemptive competition to show how subadditive population growth and a trade-off between competitor fecundity and dispersal ability can lead to coexistence. Because nonpollinator species are often closely related, have similar life histories, and compete for the same discrete resources, understanding their coexistence is challenging given competitive exclusion is expected. Empirical observations suggest that nonpollinating fig wasp species may face a trade-off between egg loads and dispersal abilities. We model a lottery in which a species’ competitive ability is determined by a trade-off between fecundity and dispersal ability. Variation in interpatch distance between figs generates temporal variability in the relative benefit of fecundity versus dispersal. We show that the temporal storage effect leads to coexistence for a range of biologically realistic parameter values. We further use individual-based modeling to show that when species’ traits evolve, coexistence is less likely but trait divergence can result. We discuss the implications of this coexistence mechanism for ephemeral patch systems wherein competition is strongly preemptive

Aberrant Disgust Responses and Immune Reactivity in Cocaine-Dependent Men

Background: Infectious diseases are the most common and cost-intensive health complications associated with drug addiction. There is wide belief that drug-dependent individuals expose themselves more regularly to disease-related pathogens through risky behaviors such as sharing pipes and needles, thereby increasing their risk for contracting an infectious disease. However, evidence is emerging indicating that not only lifestyle but also the immunomodulatory effects of addictive drugs, such as cocaine, may account for their high infection risk. As feelings of disgust are thought to be an important psychological mechanism in avoiding the exposure to pathogens, we sought to investigate behavioral, physiological, and immune responses to disgust-evoking cues in both cocaine-dependent and healthy men. Methods: All participants (N = 61) were exposed to neutral and disgust-evoking photographs depicting food and nonfood images while response accuracy, latency, and skin conductivity were recorded. Saliva samples were collected before and after exposure to neutral and disgusting images, respectively. Attitudes toward disgust and hygiene behaviors were assessed using questionnaire measures. Results: Response times to disgust-evoking photographs were prolonged in all participants, and specifically in cocaine-dependent individuals. While viewing the disgusting images, cocaine-dependent individuals exhibited aberrant skin conductivity and increased the secretion of the salivary cytokine interleukin-6 relative to control participants. Conclusion: Our data provide evidence of a hypersensitivity to disgusting stimuli in cocaine-dependent individuals, possibly reflecting conditioned responses to noningestive sources of infection. Coupled with a lack of interoception of bodily signals, aberrant disgust responses might lead to increased infection susceptibility in affected individuals

Repositioning Rangeland Education for a Changing World

Rangelands in North America and abroad are important ecosystems because of the vast areas they cover and the essential products and ecological services they provide. A strong workforce of well-trained professionals is needed to manage these ecosystems; however, undergraduate rangeland education faces several major challenges pertaining to curriculum content and resources, teaching approaches and faculty preparedness, and student awareness and recruitment. A collaborative project, developed in 2010 by members of the Range Science Education Council (RSEC) and funded by a USDA Higher Education Challenge Grant, addresses these challenges. The initial step is a needs assessment using focus groups with rangeland stakeholders and surveys with recent range student graduates to identify current and future issues and associated knowledge and skills on which to build a forward-looking rangeland education program. Assessment outcomes will provide a starting point for modernizing Society for Range Management accreditation and Office of Personnel Management hiring standards. Next, is the development of an interstate pool of curriculum resources that embrace new technology and a variety of instructional formats. An online clearinghouse of educational materials will include a catalog of online, intensive workshop-style, and traveling field courses, and open-source instructional materials, including Virtual Exploration of Rangeland Ecosystems modules developed by RSEC members. Ecosystem modules contain written and narrative instruction, video footage, GigaPan panoramic images, and management scenarios, which include interviews with progressive land managers. During 2011-2013, professional development workshops, webinars, symposia, and a mentorship program will provide opportunities to advance faculty teaching skills. Lastly, market research will be used to identify factors that influence educational choices of students and parents from traditional, non-traditional, and underrepresented groups. Market research will be coupled with the needs assessment to develop targeted recruitment and career materials. Project activities and products will be posted online (www.rangelandswest.org) and also disseminated through professional and popular publications and newsletters of universities, agencies, agricultural associations, professional organizations and NGOs