Habitable Zone Lifetime of Exoplanets around Main Sequence Stars

Funding: Dean's Scholarship at the University of East Anglia.The potential habitability of newly discovered exoplanets is initially assessed by determining whether their orbits fall within the circumstellar habitable zone of their star. However, the habitable zone (HZ) is not static in time or space, and its boundaries migrate outward at a rate proportional to the increase in luminosity of a star undergoing stellar evolution, possibly including or excluding planets over the course of the star’s main sequence lifetime. We describe the time that a planet spends within the HZ as its ‘‘habitable zone lifetime.’’ The HZ lifetime of a planet has strong astrobiological implications and is especially important when considering the evolution of complex life, which is likely to require a longer residence time within the HZ. Here, we present results from a simple model built to investigate the evolution of the ‘‘classic’’ HZ over time, while also providing estimates for the evolution of stellar luminosity over time in order to develop a ‘‘hybrid’’ HZ model. These models return estimates for the HZ lifetimes of Earth and 7 confirmed HZ exoplanets and 27 unconfirmed Kepler candidates. The HZ lifetime for Earth ranges between 6.29 and 7.79 · 109 years (Gyr). The 7 exoplanets fall in a range between ∼1 and 54.72 Gyr, while the 27 Kepler candidate planets’ HZ lifetimes range between 0.43 and 18.8 Gyr. Our results show that exoplanet HD 85512b is no longer within the HZ, assuming it has an Earth analog atmosphere. The HZ lifetime should be considered in future models of planetary habitability as setting an upper limit on the lifetime of any potential exoplanetary biosphere, and also for identifying planets of high astrobiological potential for continued observational or modeling campaigns.Publisher PDFPeer reviewe

Scottish overseas trade, 1597-1645

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Understanding radionuclide migration from the D1225 Shaft, Dounreay, Caithness, UK

A 65 m vertical shaft was sunk at Dounreay in the 1950s to build a tunnel for the offshore discharge of radioactive effluent from the various nuclear facilities then under construction. In 1959, the Shaft was licensed as a disposal facility for radioactive wastes and was routinely used for the disposal of ILW until 1970. Despite the operation of a hydraulic containment scheme, some radioactivity is known to have leaked into the surrounding rocks. Detailed logging, together with mineralogical and radiochemical analysis of drillcore has revealed four distinct bedding-parallel zones of contamination. The data show that Sr-90 dominates the bulk beta/gamma contamination signal, whereas Cs-137 and Pu-248/249 are found only to be weakly mobile, leading to very low activities and distinct clustering around the Shaft. The data also suggest that all uranium seen in the geosphere is natural in origin. At the smaller scale, contamination adjacent to fracture surfaces is present within a zone of enhanced porosity created by the dissolution of carbonate cements from the Caithness flagstones during long-term rockwater interactions. Quantitative modelling of radionuclide migration, using the multiphysics computer code QPAC shows the importance of different sorption mechanisms and different mineralogical substrates in the Caithnesss flagstones in controlling radionuclide migration

Single Nucleotide Polymorphism Analysis of European Archaeological M. leprae DNA

Background: Leprosy was common in Europe eight to twelve centuries ago but molecular confirmation of this has been lacking. We have extracted M. leprae ancient DNA (aDNA) from medieval bones and single nucleotide polymorphism (SNP) typed the DNA, this provides insight into the pattern of leprosy transmission in Europe and may assist in the understanding of M. leprae evolution. Methods and Findings: Skeletons have been exhumed from 3 European countries (the United Kingdom, Denmark and Croatia) and are dated around the medieval period (476 to 1350 A.D.). we tested for the presence of 3 previously identified single nucleotide polymorphisms (SNPs) in 10 aDNA extractions. M. leprae aDNA was extracted from 6 of the 10 bone samples. SNP analysis of these 6 extractions were compared to previously analysed European SNP data using the same PCR assays and were found to be the same. Testing for the presence of SNPs in M. leprae DNA extracted from ancient bone samples is a novel approach to analysing European M. leprae DNA and the findings concur with the previously published data that European M. leprae strains fall in to one group (SNP group 3). Conclusions: These findings support the suggestion that the M. leprae genome is extremely stable and show that archaeological M. leprae DNA can be analysed to gain detailed information about the genotypic make-up of European leprosy, which may assist in the understanding of leprosy transmission worldwide

Exploring the Context of Canadian Graduate Student Teaching Certificates in University Teaching

A growing number of Canadian universities offer graduate student certificate programs in university teaching. This paper examines such programs at 13 Canadian universities and presents a discussion of program structures and practices. The findings suggest that most programs were offered over one to two years, and upon successful completion, participants were issued a centre-approved certificate paired with a more formalized method of recognition, such as a transcript notation. The core focus of certificate programs appears to be divided between those that emphasize practical skill development (46%) and those that offer practical skill development along with a focus on the scholarship of teaching and learning (54%). Most certificates included active and authentic assessment methods, such as dossiers (69%), and practice teaching sessions (62%). These findings help to inform the continued evolution of graduate student teaching certificate programs

Solar absorption chiller

In developing nations access to electricity is inconsistent at best, and food spoilage is a prevalent issue. The solar powered absorption chiller is a refrigeration system designed to provide refrigeration to these developing areas. This year, our team has worked to develop a system where the sun\u27s rays are collected as heat to power an absorption refrigerator. The goal of this project was to take an existing solar tracker system and use its collected heat to power a refrigerator. Our team designed and built heat exchangers to extract heat from the concentrated solar system; assembled components for a fluid circulation loop; and retrofitted an absorption chiller refrigerator to be powered by our heated fluid. Additionally, we redesigned an existing solar tracking system to improve function and decrease power consumption. By the end of this year we assembled the entire system and performed months of solar testing as well as proof-ofconcept testing that the refrigerator could receive necessary heat through a heated fluid. By the end of the school year, we concluded that the heated fluid would need to reach 150°C to begin the refrigeration cycle (with current heat exchanger design), which was 25° higher than our solar testing had achieved. With further improvements, the refrigerator could be designed to run with lower heat inputs and the tracker system could be designed to attain heat at higher temperatures. With these changes, a working refrigeration system could have dramatic impacts on farming communities in developing countries; reducing food spoilage, increasing family income, and preventing food-borne illnesses

Embedding research into practice through innovation and creativity : a case study from social services

This paper explores ways in which IRISS (Institute for Research and Innovation in Social Services) promotes the delivery of cost effective social services in Scotland that support the achievement of positive outcomes. The approach to evidence-informed practice is characterised as four pillars of activity. The first focuses on improving awareness and access to evidence. The second refers to strengthening the evidence base and is discussed in the context of work on self-directed support. Improving skills and confidence to use evidence forms the third pillar. The final pillar is embedding evidence in organisations, through coproduction, creating spaces to test and challenge evidence, and through the development of evidence-based products

Signalling C-Type lectin receptors, microbial recognition and immunity

This work was supported in part by the Wellcome Trust, Medical Research Council (UK) and the University of Cape Town. J.C. Hoving is a Carnegie Corporation postdoctoral researcher at the University of Cape Town. We apologize of all our colleagues whose important contributions we could not cite due to space constraints.Peer reviewedPublisher PD

Knockdown of piRNA pathway proteins results in enhanced Semliki forest virus production in mosquito cells

The exogenous siRNA pathway is important in restricting arbovirus infection in mosquitoes. Less is known about the role of the PIWI-interacting RNA pathway, or piRNA pathway, in antiviral responses. Viral piRNA-like molecules have recently been described following infection of mosquitoes and derived cell lines with several arboviruses. The piRNA pathway has thus been suggested to function as an additional small RNA-mediated antiviral response to the known infection-induced siRNA response. Here we show that piRNA-like molecules are produced following infection with the naturally mosquito-borne Semliki Forest virus in mosquito cell lines. We show that knockdown of piRNA pathway proteins enhances the replication of this arbovirus and defines the contribution of piRNA pathway effectors, thus characterizing the antiviral properties of the piRNA pathway. In conclusion, arbovirus infection can trigger the piRNA pathway in mosquito cells, and knockdown of piRNA proteins enhances virus production