Biology and potential biogeochemical impacts of novel predatory flavobacteria

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 2010Predatory bacteria are ubiquitous in aquatic environments and may be important players in the ecology and biogeochemistry of microbial communities. Three novel strains belonging to two genera of marine flavobacteria, Olleya and Tenacibaculum, were cultured from coastal sediments and found to be predatory on other bacteria on surfaces. Two published species of the genus Tenacibaculum were also observed to grow by lysis of prey bacteria, raising the possibility that predation may be a widespread lifestyle amongst marine flavobacteria, which are diverse and abundant in a variety of marine environments. The marine flavobacterial clade is known to include species capable of photoheterotrophy, scavenging of polymeric organic substances, pathogenesis on animals, the degradation and lysis of phytoplankton blooms and, now, predation on bacterial communities. Strains from the two genera were found to exhibit divergent prey specificities and growth yields when growing predatorily. Olleya sp. predatory cells accumulated to an order of magnitude greater cell densities than Tenacibaculum sp. cells on equivalent prey cell densities. Experiments were conducted to constrain the potential of the novel isolates to affect prey communities under more environmentally relevant conditions. An investigation of the minimum number of predatory cells needed to generate clearings of prey cells found that the inoculation of individual predatory flavobacteria cells can ultimately result in dense lytic swarms. In some cases, the susceptibility of particular prey species to lysis by a flavobacterial predator was found to vary based on the growth state of the prey cells or the presence of their spent growth media. A novel methodology for the experimental study of biofilms was used to assess the impact of exposure to predatory marine flavobacteria on the release of macronutrients from prey biofilms. The Olleya sp. predator had a stimulative effect on macronutrient release while the Tenacibaculum sp. did not, further suggesting the two groups of predators are adapted to different ecological niches.Support by the National Science Foundation (NSF) Division of Molecular and Cellular Biosciences Grant (MCB- 0348425), the MIT Student Assistance Fund, the Woods Hole Oceanographic Institution (WHOI) Academic Programs Office, WHOI Coastal Ocean Institute (COI) and WHOI Ocean Venture Fund grant, COI and the WHOI Ocean Life Institute

High-risk pooling for mitigating risk selection incentives in health insurance markets with sophisticated risk equalization:an application based on health survey information

Background: Despite sophisticated risk equalization, insurers in regulated health insurance markets still face incentives to attract healthy people and avoid the chronically ill because of predictable differences in profitability between these groups. The traditional approach to mitigate such incentives for risk selection is to improve the risk-equalization model by adding or refining risk adjusters. However, not all potential risk adjusters are appropriate. One example are risk adjusters based on health survey information. Despite its predictiveness of future healthcare spending, such information is generally considered inappropriate for risk equalization, due to feasibility challenges and a potential lack of representativeness. Methods: We study the effects of high-risk pooling (HRP) as a strategy for mitigating risk selection incentives in the presence of sophisticated– though imperfect– risk equalization. We simulate a HRP modality in which insurers can ex-ante assign predictably unprofitable individuals to a ‘high risk pool’ using information from a health survey. We evaluate the effect of five alternative pool sizes based on predicted residual spending post risk equalization on insurers’ incentives for risk selection and cost control, and compare this to the situation without HRP. Results: The results show that HRP based on health survey information can substantially reduce risk selection incentives. For example, eliminating the undercompensation for the top-1% with the highest predicted residual spending reduces selection incentives against the total group with a chronic disease (60% of the population) by approximately 25%. Overall, the selection incentives gradually decrease with a larger pool size. The largest marginal reduction is found moving from no high-risk pool to HRP for the top 1% individuals with the highest predicted residual spending. Conclusion: Our main conclusion is that HRP has the potential to considerably reduce remaining risk selection incentives at the expense of a relatively small reduction of incentives for cost control. The extent to which this can be achieved, however, depends on the design of the high-risk pool.</p

Attractive Stepping Stones Landscapes:Preference for Stone Height Variation Appears to Be Age Independent

An earlier study on the attractiveness of stepping stones configurations revealed that children like variation in stone height better than variation in stone size or gap width. In the present study, we conducted two experiments to examine whether this preference is found also in young and older adults. In Experiment 1, participants stepped freely in a standardized configuration, and three configurations with either height, size or gap width variation. Most interestingly, adults judged playgrounds with variation in stone height as most fun and beautiful, suggesting that the preference for variation in height is indeed age independent. In Experiment 2, we compared the configuration with only height variation with three configurations in which variation in height was combined with variation in stone size or gap width, or both. Although we found no significant differences among the configurations in the older adults, young adults judged the combination of height with size and gap width variation as more fun and esthetically appealing than the configuration with only height variation. The implications of our findings for playground research and designers are discussed.</p

Attractive Stepping Stones Landscapes:Preference for Stone Height Variation Appears to Be Age Independent

An earlier study on the attractiveness of stepping stones configurations revealed that children like variation in stone height better than variation in stone size or gap width. In the present study, we conducted two experiments to examine whether this preference is found also in young and older adults. In Experiment 1, participants stepped freely in a standardized configuration, and three configurations with either height, size or gap width variation. Most interestingly, adults judged playgrounds with variation in stone height as most fun and beautiful, suggesting that the preference for variation in height is indeed age independent. In Experiment 2, we compared the configuration with only height variation with three configurations in which variation in height was combined with variation in stone size or gap width, or both. Although we found no significant differences among the configurations in the older adults, young adults judged the combination of height with size and gap width variation as more fun and esthetically appealing than the configuration with only height variation. The implications of our findings for playground research and designers are discussed.</p

Attractive Stepping Stones Landscapes:Preference for Stone Height Variation Appears to Be Age Independent

An earlier study on the attractiveness of stepping stones configurations revealed that children like variation in stone height better than variation in stone size or gap width. In the present study, we conducted two experiments to examine whether this preference is found also in young and older adults. In Experiment 1, participants stepped freely in a standardized configuration, and three configurations with either height, size or gap width variation. Most interestingly, adults judged playgrounds with variation in stone height as most fun and beautiful, suggesting that the preference for variation in height is indeed age independent. In Experiment 2, we compared the configuration with only height variation with three configurations in which variation in height was combined with variation in stone size or gap width, or both. Although we found no significant differences among the configurations in the older adults, young adults judged the combination of height with size and gap width variation as more fun and esthetically appealing than the configuration with only height variation. The implications of our findings for playground research and designers are discussed.</p

Aldo van Eyck's Playgrounds:Aesthetics, Affordances, and Creativity

After World War II, the Dutch architect Aldo van Eyck developed hundreds of playgrounds in the city of Amsterdam. These public playgrounds were located in parks, squares, and derelict sites, and consisted of minimalistic aesthetic play equipment that was supposed to stimulate the creativity of children. Over the last decades, these playgrounds have been studied by sociologists, theorists of art and architecture, and psychologists. Adopting an ecological approach to the human environment, it is argued that the abstract forms of van Eyck’s play sculptures indeed stimulate the creativity of the child. Whereas a slide or a swing almost dictates what a child is supposed to do, van Eyck’s play equipment invites the child to actively explore the numerous affordances (action possibilities) it provided. However, it is argued that the standardization (e.g., equal distances between blocks or bars) that tends to characterize van Eyck’ play equipment has negative effects on the playability. This standardization, which was arguably the result of the aesthetic motives of the designer, might be appealing to children when simply looking at the equipment, but it is not of overriding importance to them when playing in it. Indeed, a recent study indicates that the affordances provided by messy structures appear to have a greater appeal to playing children

Height, Size, and/or Gap Width Variation in Jumping Stone Configurations:Which Form of Variation Attracts Children the Most?

Earlier studies revealed that children prefer nonstandardized jumping stone configurations to standardized ones. In the present study, we examined whether children playing on jumping stones prefer variation in stone height, stone size, and/or gap width. In Experiment 1, children could play freely on one standardized configuration and three configurations in which one of the aforementioned factors was varied. It was found that children judged the variation in height as most fun. Yet, the configuration with gap width variation appeared to be most challenging for the children-most overground steps were made in this configuration. In Experiment 2, we examined whether the attractiveness of the configurations increased when height variation was combined with the other forms of variation. Adding size and/or gap width variation to the variation in height did not contribute to the attractiveness of the configuration. In line with experiment 1, it was found that the configurations with gap width variation were judged as the most challenging for children. The implications of these results are discussed in the context of the literature on play.</p

Inciting protocols

This paper studies patenting decisions by firms in relation to the negotiation and signing of the Helsinki and Oslo protocol as part of the Convention on Long-Range Transboundary Air Pollution. We use a uniquely constructed patent data set on SO 2 abatement technologies filed in 15 signatory and non-signatory countries in the period 1970-1997. The data distinguish between so-called 'mother' patents, or original inventions, and 'family' patents, which represent the same invention but are patents filed in foreign countries. Our analysis suggests that not only local environmental regulations matter for patenting decisions. International environmental agreements provide incentives for additional inventive activity in and the diffusion of knowledge towards signatory countries by reducing investment uncertainty for inventing firms

'The End of Sitting':An Empirical Study on Working in an Office of the Future

Background Inspired by recent findings that prolonged sitting has detrimental health effects, Rietveld Architecture Art Affordances (RAAAF) and visual artist Barbara Visser designed a working environment without chairs and desks. This environment, which they called The End of Sitting, is a sculpture whose surfaces afford working in several non-sitting postures (e.g. lying, standing, leaning). Objective In the present study, it was tested how people use and experience The End of Sitting. Eighteen participants were to work in this environment and in a conventional office with chairs and desks, and the participants' activities, postures, and locations in each working environment were monitored. In addition, participants' experiences with working in the offices were measured with a questionnaire. Results It was found that 83 % of participants worked in more than one non-sitting posture in The End of Sitting. All these participants also changed location in this working environment. On the other hand, in the conventional office all but one participant sat on a chair at a desk during the entire work session. On average, participants reported that The End of Sitting supported their well-being more than the conventional office. Participants also felt more energetic after working in The End of Sitting. No differences between the working environments were found in reported concentration levels and satisfaction with the created product. Conclusion The End of Sitting is a potential alternative working environment that deserves to be examined in more detail

The degree to which traditional play equipment, Parkour play elements, and Aldo van Eyck's play sculptures have an open function

The concept of open functions was introduced to capture an intended feature of van Eyck's seminal play sculptures - they do not suggest a specific action. In a recent study, Van der Schaaf, A. L., S. R. Caljouw, and R. Withagen. (2020. "Are Children Attracted to Play Elements with an Open Function?" Ecological Psychology 32: 79-94) aimed to determine the degree of openness of Parkour play elements by asking participants what behavior children will mainly perform on them. In the present study, we used this method to determine the degree of openness of traditional play elements (e.g. a slide), van Eyck's play sculptures, and Parkour play elements. In addition, we measured the time participants needed to answer the question of what action children will mainly perform on the different elements. We found that generally the Parkour elements have the highest degree of openness. Interestingly, van Eyck's play elements appeared not to be that open. Moreover, the reaction time proved to be an alternative measure for the degree of openness