10,225 research outputs found

    Genetic variation within and among asexual populations of Porphyra umbilicalis Kützing (Bangiales, Rhodophyta) in the Gulf of Maine, USA

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    The intertidal marine red alga Porphyra umbilicalis reproduces asexually in the Northwest Atlantic. We looked for population substructure among typical open-coastal and atypical estuarine habitats in seven asexual populations of P. umbilicalis from Maine to New Hampshire using eight expressed sequence tag-simple sequence repeats (EST-SSR) or microsatellite loci. Six genotypes were identified, four of which may represent recombinant genotypes from a recombination event that took place locally, or that took place prior to introduction to the Northwest Atlantic. Genotypic diversity was lowest in a population from Wiscasset, Maine, which inhabits an atypical habitat high in the intertidal zone of a bridge piling in an estuarine tidal rapid. Genotypic diversity was highest in the southernmost populations from New Hampshire; we identified two genotypes that were unique to the southernmost populations, and probably represent the most derived genotypes. We looked at genetic distances among populations in similar habitats, and found that populations were more closely related to their closest neighboring population than to a population in a similar habitat. We show that genotypic diversity within P. umbilicalis populations in the Gulf of Maine is relatively high and thus fits a model of high steady-state variation within asexual populations

    Transmission electron microscopy of an interplanetary dust particle with links to CI chondrites

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    The majority of hydrated interplanetary dust particles (IDPs) have compositions that resemble CI and CM chondrites, however, their mineralogies are most similar to the fine grained material in certain altered type-3 carbonaceous and ordinary chondrites. During the transmission electron microscope studies of hydrated IDPs, a unique particle was discovered whose mineralogy is very similar to that reported from CI chondrites. W7013F5 is the first IDP whose mineralogy and chemistry approximates that of CI chondrites. The similarity in mineralogy and mineral chemistry suggests that W7013F5 was altered under conditions similar to those that existed on the CI parent bodies

    “If You Are Old Enough to Die for Your Country, You Should Be Able to Get a Pinch of Snuff”: Views of Tobacco 21 Among Appalachian Youth

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    Background: Multiple strategies have been utilized in attempts to decrease the prevalence of youth tobacco use. One strategy, raising the minimum legal sale age (MLSA) of tobacco products to 21, known as Tobacco 21, has recently gained popularity. Tobacco 21 legislation targets youth tobacco use by obstructing two main sources of youth tobacco products: stores and older friends. Although these sources are the most common for youth across the nation, regional differences have not been explored. Further, youth perspectives about raising the tobacco MLSA have not been considered. Youth may help identify potential challenges to implementing tobacco control measures, as well as suggest alternatives for intervention, thus helping to shape successful tobacco control policies. Study Aim: This study aimed to 1) examine youth perspectives on raising the tobacco minimum legal sale age to 21 and 2) identify common sources of tobacco products among middle and high school students living in rural, low-income Appalachian communities. Methods: A cross-sectional survey about perceptions and use of tobacco products was conducted with students in the Appalachian regions of Kentucky and North Carolina (N=426). Questions were asked concerning perspectives on the effect of Tobacco 21 implementation. Descriptive statistics characterized participants by Tobacco 21 perspectives. Participants were given the opportunity to further expand upon their opinions in an open-ended format. Results: The majority (58.7%) of participants responded that the same number of youth would use tobacco if the legal purchase age were raised, followed by responses that fewer would use (28.9%) and more would use (12.4%). Significant differences emerged based on tobacco use status (p\u3c.05), friends’ tobacco use (p\u3c.001), and whether participants identified family members as sources of youth tobacco products (p=.047). When given the opportunity to expand upon their views concerning the implementation of Tobacco 21 laws in their communities, many respondents cited poor enforcement of tobacco MLSAs at stores, continued access to tobacco products from family members and friends, and the overall abundance of tobacco in their communities as potential barriers to the successful implementation. Conclusion: Fewer than one-third of participants believed that Tobacco 21 legislation would succeed in reducing the prevalence of youth tobacco use. Perspectives on the effect of Tobacco 21 legislation were related to personal tobacco use, exposure to tobacco users, and beliefs that family members provide tobacco products to youth. Open-ended responses identify potential obstacles in implementing Tobacco 21 legislation in Appalachia. Future research should attempt to include youth perspectives when designing and implementing tobacco control policies and examine family members as sources of tobacco products for youth

    Ramsar Policy Brief No. 5. Restoring drained peatlands: A necessary step to achieve global climate goals

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    Peatlands cover about 400 million hectares (ha), or 3% of the land surface of our planet. Yet they store more carbon, more effectively and for longer periods, than any other ecosystem on land. Intact peatlands also provide essential ecosystem services such as regulating water cycles, purifying water, and supporting a wealth of biodiversity. Since peat is hidden below ground, it is often unrecognised and can be damaged unknowingly. New, large peatland areas are still being discovered including forest-covered peatlands in the tropics. Around 50 million ha of peatlands globally are currently drained and have been transformed to grazing land, forestry land and cropland, used for peat extraction or impacted by infrastructure. These drained peatlands are responsible for approximately 4% (2 Gt CO2 -eq/year) of all anthropogenic greenhouse gas emissions. Achieving the climate goals of the Paris Agreement requires protection of all remaining intact peatland and rapid restoration of almost all drained peatlands. This will also contribute to delivering the Sustainable Development Goals (SDGs), in particular SDG 6, Target 6.6, on protecting and restoring water related ecosystems and SDG 15, Targets 15.1, on conservation, restoration and sustainable use of terrestrial and inland freshwater ecosystems and their services, as well as 15.5 on reducing degradation of natural habitats. The United Nations Decade on Ecosystem Restoration 2021-2030 provides the opportunity to rapidly scale up efforts

    Melting-freezing cycles in a relatively sheared pair of crystalline monolayers

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    The nonequilibrium dynamical behaviour that arises when two ordered two-dimensional monolayers of particles are sheared over each other is studied in Brownian dynamics simulations. A curious sequence of nonequilibrium states is observed as the driving rate is increased, the most striking of which is a sliding state with irregular alternation between disordered and ordered states. We comment on possible mechanisms underlying these cycles, and experiments that could observe them.Comment: 7 pages, 8 figures, minor changes in text and figures, references adde

    Pathways into services for offenders with intellectual disabilities : childhood experience, diagnostic information and offence variables

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    The patterns and pathways into intellectual disability (ID) offender services were studied through case file review for 477 participants referred in one calendar year to community generic, community forensic, and low, medium, and maximum secure services. Data were gathered on referral source, demographic information, index behavior, prior problem behaviors, diagnostic information, and abuse or deprivation. Community referrers tended to refer to community services and secure service referrers to secure services. Physical and verbal violence were the most frequent index behaviors, whereas contact sexual offenses were more prominent in maximum security. Age at first incident varied with security, with the youngest in maximum secure services. Attention-deficit/hyperactivity disorder or conduct disorder was the most frequently recorded diagnosis, and severe deprivation was the most frequent adverse developmental experience. Fire starting, theft, and road traffic offenses did not feature prominently. Generic community services accepted a number of referrals with forensic-type behavior and had higher proportions of both women and people with moderate or severe ID

    Magnon Orbital Angular Momentum of Ferromagnetic Honeycomb and Zig-Zag Lattices

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    By expanding the gauge λn(k)\lambda_n(k) for magnon band nn in harmonics of momentum k=(k,ϕ){\bf k} =(k,\phi ), we demonstrate that the only observable component of the magnon orbital angular momentum On(k)O_n({\bf k}) is its angular average over all angles ϕ\phi, denoted by Fn(k)F_n(k). For both the FM honeycomb and zig-zag lattices, we show that Fn(k)F_n(k) is nonzero in the presence of a Dzyalloshinzkii-Moriya (DM) interaction. The FM zig-zag lattice model with exchange interactions 0<J1<J20<J_1< J_2 provides a new system where the effects of orbital angular momentum are observable. For the zig-zag model with equal exchange interactions J1xJ_{1x} and J1yJ_{1y} along the xx and yy axis, the magnon bands are degenerate along the boundaries of the Brillouin zone with kxky=±π/ak_x-k_y =\pm \pi/a and the Chern numbers CnC_n are not well defined. However, a revised model with J1yJ1xJ_{1y}\ne J_{1x} lifts those degeneracy and produces well-defined Chern numbers of Cn=±1C_n=\pm 1 for the two magnon bands. When J1y=J1xJ_{1y}=J_{1x}, the thermal conductivity κxy(T)\kappa^{xy}(T) of the FM zig-zag lattice is largest for J2/J1>6J_2/J_1>6 but is still about four times smaller than that of the FM honeycomb lattice at high temperatures. Due to the removal of band degeneracies, κxy(T)\kappa^{xy}(T) is slightly enhanced when J1yJ1xJ_{1y}\ne J_{1x}.Comment: 13 figure
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