193 research outputs found

    CuWO4 as a Photoanode for Solar-Driven Water Oxidation toward Sustainable Hydrogen Production

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    Honors (Bachelor's)BiochemistryUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/107750/1/joskurtz.pd

    Evaluation of Operation IceBridge quick-look snow depth estimates on sea ice

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    We evaluate Operation IceBridge (OIB) ‘quick-look’ (QL) snow depth on sea ice retrievals using in situ measurements taken over immobile first-year ice (FYI) and multi-year ice (MYI) during March of 2014. Good agreement was found over undeformed FYI (-4.5 cm mean bias) with reduced agreement over deformed FYI (-6.6 cm mean bias). Over MYI, the mean bias was -5.7 cm but 54% of retrievals were discarded by the OIB retrieval process as compared to only 10% over FYI. Footprint scale analysis revealed a root mean square error (RMSE) of 6.2 cm over undeformed FYI with RMSE of 10.5 cm and 17.5 cm in the more complex deformed FYI and MYI environments. Correlation analysis was used to demonstrate contrasting retrieval uncertainty associated with spatial aggregation and ice surface roughness

    Fluctuation Domains in Adaptive Evolution

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    We derive an expression for the variation between parallel trajectories in phenotypic evolution, extending the well known result that predicts the mean evolutionary path in adaptive dynamics or quantitative genetics. We show how this expression gives rise to the notion of fluctuation domains - parts of the fitness landscape where the rate of evolution is very predictable (due to fluctuation dissipation) and parts where it is highly variable (due to fluctuation enhancement). These fluctuation domains are determined by the curvature of the fitness landscape. Regions of the fitness landscape with positive curvature, such as adaptive valleys or branching points, experience enhancement. Regions with negative curvature, such as adaptive peaks, experience dissipation. We explore these dynamics in the ecological scenarios of implicit and explicit competition for a limiting resource

    Intercomparison of snow depth retrievals over Arctic sea ice from radar data acquired by Operation IceBridge

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    Since 2009, the ultra-wideband snow radar on Operation IceBridge (OIB; a NASA airborne mission to survey the polar ice covers) has acquired data in annual campaigns conducted during the Arctic and Antarctic springs. Progressive improvements in radar hardware and data processing methodologies have led to improved data quality for subsequent retrieval of snow depth. Existing retrieval algorithms differ in the way the air–snow (a–s) and snow–ice (s–i) interfaces are detected and localized in the radar returns and in how the system limitations are addressed (e.g., noise, resolution). In 2014, the Snow Thickness On Sea Ice Working Group (STOSIWG) was formed and tasked with investigating how radar data quality affects snow depth retrievals and how retrievals from the various algorithms differ. The goal is to understand the limitations of the estimates and to produce a well-documented, long-term record that can be used for understanding broader changes in the Arctic climate system. Here, we assess five retrieval algorithms by comparisons with field measurements from two ground-based campaigns, including the BRomine, Ozone, and Mercury EXperiment (BROMEX) at Barrow, Alaska; a field program by Environment and Climate Change Canada at Eureka, Nunavut; and available climatology and snowfall from ERA-Interim reanalysis. The aim is to examine available algorithms and to use the assessment results to inform the development of future approaches. We present results from these assessments and highlight key considerations for the production of a long-term, calibrated geophysical record of springtime snow thickness over Arctic sea ice

    The BLAST View of the Star Forming Region in Aquila (ell=45deg,b=0deg)

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    We have carried out the first general submillimeter analysis of the field towards GRSMC 45.46+0.05, a massive star forming region in Aquila. The deconvolved 6 deg^2 (3\degree X 2\degree) maps provided by BLAST in 2005 at 250, 350, and 500 micron were used to perform a preliminary characterization of the clump population previously investigated in the infrared, radio, and molecular maps. Interferometric CORNISH data at 4.8 GHz have also been used to characterize the Ultracompact HII regions (UCHIIRs) within the main clumps. By means of the BLAST maps we have produced an initial census of the submillimeter structures that will be observed by Herschel, several of which are known Infrared Dark Clouds (IRDCs). Our spectral energy distributions of the main clumps in the field, located at ~7 kpc, reveal an active population with temperatures of T~35-40 K and masses of ~10^3 Msun for a dust emissivity index beta=1.5. The clump evolutionary stages range from evolved sources, with extended HII regions and prominent IR stellar population, to massive young stellar objects, prior to the formation of an UCHIIR.The CORNISH data have revealed the details of the stellar content and structure of the UCHIIRs. In most cases, the ionizing stars corresponding to the brightest radio detections are capable of accounting for the clump bolometric luminosity, in most cases powered by embedded OB stellar clusters

    The Balloon-Borne Large Aperture Submillimeter Telescope (BLAST) 2005: A 10 deg^2 Survey of Star Formation in Cygnus X

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    We present Cygnus X in a new multi-wavelength perspective based on an unbiased BLAST survey at 250, 350, and 500 micron, combined with rich datasets for this well-studied region. Our primary goal is to investigate the early stages of high mass star formation. We have detected 184 compact sources in various stages of evolution across all three BLAST bands. From their well-constrained spectral energy distributions, we obtain the physical properties mass, surface density, bolometric luminosity, and dust temperature. Some of the bright sources reaching 40 K contain well-known compact H II regions. We relate these to other sources at earlier stages of evolution via the energetics as deduced from their position in the luminosity-mass (L-M) diagram. The BLAST spectral coverage, near the peak of the spectral energy distribution of the dust, reveals fainter sources too cool (~ 10 K) to be seen by earlier shorter-wavelength surveys like IRAS. We detect thermal emission from infrared dark clouds and investigate the phenomenon of cold ``starless cores" more generally. Spitzer images of these cold sources often show stellar nurseries, but these potential sites for massive star formation are ``starless" in the sense that to date there is no massive protostar in a vigorous accretion phase. We discuss evolution in the context of the L-M diagram. Theory raises some interesting possibilities: some cold massive compact sources might never form a cluster containing massive stars; and clusters with massive stars might not have an identifiable compact cold massive precursor.Comment: 42 pages, 31 Figures, 6 table

    Globalisation, the practice of devotional songs and poems and the linguistic repertoires of young British Muslims

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    This article provides empirical data from transnational religious contexts which highlight the complexity, fluidity and indexicality of language and religious practices in globalising settings. Through an examination of the role of devotional song and poetry in the Islamic world, and in particular, among young multilingual and multivarietal British Muslims, an attempt is made to show how globalising processes of the present age contribute to, on the one hand, novel forms of language resources and innovative religious practices and, on the other, co-existing traditional approaches to faith and language practices. It also shows how young people deploy their linguistic repertoires and language resources in order to re-construct their religious and linguistic identities. A conclusion is presented that such practices, whilst drawing on old and traditional roots, become transformed when enacted in these newer settings, both linguistically and religiously
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