68 research outputs found
Presettlement Vegetation of the Nemadji River Basin
Features of presettlement vegetation of the Nemadji River watershed were determined from surveying records covering three counties in two states. Data from 3,346 trees indicated major distributional differences in portions of the watershed. White pine (Pinus strobus L.) was the predominant species of the Glacial Lake Duluth Basin, while Tamarack (Larix laricina (Du Roi, K. Koch) characterized the surrounding area of glacial till. In addition, forests occupying ravines were, in general, composed of larger individuals and exhibited less evidence of reproduction than trees in adjacent uplands, which might suggest less erosional disturbance than is evident today
Non-liftable Calabi-Yau spaces
We construct many new non-liftable three-dimensional Calabi-Yau spaces in
positive characteristic. The technique relies on lifting a nodal model to a
smooth rigid Calabi-Yau space over some number field as introduced by the first
author and D. van Straten.Comment: 16 pages, 5 tables; v2: minor corrections and addition
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Evaluation of transboundary environmental issues in Central Europe
Central Europe has experienced environmental degradation for hundreds of years. The proximity of countries, their shared resources, and transboundary movement of environmental pollution, create the potential for regional environmental strife. The goal of this project was to identify the sources and sinks of environmental pollution in Central Europe and evaluate the possible impact of transboundary movement of pollution on the countries of Central Europe. In meeting the objectives of identifying sources of contaminants, determining transboundary movement of contaminants, and assessing socio-economic implications, large quantities of disparate data were examined. To facilitate use of the data, the authors refined mapping procedures that enable processing information from virtually any map or spreadsheet data that can be geo-referenced. Because the procedure is freed from a priori constraints of scale that confound most Geographical Information Systems, they have the capacity to generate new projections and apply sophisticated statistical analyses to the data. The analysis indicates substantial environmental problems. While transboundary pollution issues may spawn conflict among the Central European countries and their neighbors, it appears that common environmental problems facing the entire region have had the effect of bringing the countries together, even though opportunities for deteriorating relationships may still arise
The Shaqadud Archaeological Project (Sudan): exploring prehistoric cultural adaptations in the Sahelian hinterlands
The authors present preliminary results from a new research project based in Jebel Shaqadud, Sudan. Their findings highlight the potential for this region's archaeological record to expand our understanding of the adaptation strategies used by human groups in arid north-east African environments away from rivers and lakes during the Holocene. Furthermore, they present exceptionally early radiocarbon dates that push postglacial human occupation in the eastern Sahel back to the twelfth millennium BP
Depurated fish as an alternative reference for field-based biomarker monitoring
The whole of the Swan-Canning Estuary, in the south-west of Australia, is impacted by human activity, and the selection of a local reference site to assess the impact of environmental contamination on the health of biota is not possible. To determine whether fish depurated under laboratory conditions could be used as an alternative to a reference site; adult black bream (Acanthopagrus butcheri) were collected from the estuary and maintained in clean water (S24) for 3 months. A suite of biomarkers of fish health were assessed, and the results were compared with field-captured black bream from three sites within the estuary (Ascot, Claisebrook, and Riverton). Comparisons of a subset of biomarkers were also made between hatchery-bred juvenile fish and the depurated fish. Biomarker levels were up to 3.8 times higher in field captured fish compared with depurated fish, while DNA integrity was lower. EROD activity was comparable in the hatchery-bred black bream to the depurated fish while s-SDH levels were two times higher in the hatchery fish. From the results obtained, field-captured black bream depurated for 3 months are suitable to determine reference/baseline levels for biomarker of health studies in estuarine environments
Trapping in irradiated p-on-n silicon sensors at fluences anticipated at the HL-LHC outer tracker
The degradation of signal in silicon sensors is studied under conditions expected at the CERN High-Luminosity LHC. 200 m thick n-type silicon sensors are irradiated with protons of different energies to fluences of up to neq/cm. Pulsed red laser light with a wavelength of 672 nm is used to generate electron-hole pairs in the sensors. The induced signals are used to determine the charge collection efficiencies separately for electrons and holes drifting through the sensor. The effective trapping rates are extracted by comparing the results to simulation. The electric field is simulated using Synopsys device simulation assuming two effective defects. The generation and drift of charge carriers are simulated in an independent simulation based on PixelAV. The effective trapping rates are determined from the measured charge collection efficiencies and the simulated and measured time-resolved current pulses are compared. The effective trapping rates determined for both electrons and holes are about 50% smaller than those obtained using standard extrapolations of studies at low fluences and suggests an improved tracker performance over initial expectations
Spatially Explicit Analysis of Metal Transfer to Biota: Influence of Soil Contamination and Landscape
Concepts and developments for a new field in ecotoxicology, referred to as âlandscape ecotoxicology,â were proposed in the 1990s; however, to date, few studies have been developed in this emergent field. In fact, there is a strong interest in developing this area, both for renewing the concepts and tools used in ecotoxicology as well as for responding to practical issues, such as risk assessment. The aim of this study was to investigate the spatial heterogeneity of metal bioaccumulation in animals in order to identify the role of spatially explicit factors, such as landscape as well as total and extractable metal concentrations in soils. Over a smelter-impacted area, we studied the accumulation of trace metals (TMs: Cd, Pb and Zn) in invertebrates (the grove snail Cepaea sp and the glass snail Oxychilus draparnaudi) and vertebrates (the bank vole Myodes glareolus and the greater white-toothed shrew Crocidura russula). Total and CaCl2-extractable concentrations of TMs were measured in soils from woody patches where the animals were captured. TM concentrations in animals exhibited a high spatial heterogeneity. They increased with soil pollution and were better explained by total rather than CaCl2-extractable TM concentrations, except in Cepaea sp. TM levels in animals and their variations along the pollution gradient were modulated by the landscape, and this influence was species and metal specific. Median soil metal concentrations (predicted by universal kriging) were calculated in buffers of increasing size and were related to bioaccumulation. The spatial scale at which TM concentrations in animals and soils showed the strongest correlations varied between metals, species and landscapes. The potential underlying mechanisms of landscape influence (community functioning, behaviour, etc.) are discussed. Present results highlight the need for the further development of landscape ecotoxicology and multi-scale approaches, which would enhance our understanding of pollutant transfer and effects in ecosystems
Description and performance of track and primary-vertex reconstruction with the CMS tracker
A description is provided of the software algorithms developed for the CMS tracker both for reconstructing charged-particle trajectories in proton-proton interactions and for using the resulting tracks to estimate the positions of the LHC luminous region and individual primary-interaction vertices. Despite the very hostile environment at the LHC, the performance obtained with these algorithms is found to be excellent. For tbar t events under typical 2011 pileup conditions, the average track-reconstruction efficiency for promptly-produced charged particles with transverse momenta of pT > 0.9GeV is 94% for pseudorapidities of |Ρ| < 0.9 and 85% for 0.9 < |Ρ| < 2.5. The inefficiency is caused mainly by hadrons that undergo nuclear interactions in the tracker material. For isolated muons, the corresponding efficiencies are essentially 100%. For isolated muons of pT = 100GeV emitted at |Ρ| < 1.4, the resolutions are approximately 2.8% in pT, and respectively, 10Îźm and 30Îźm in the transverse and longitudinal impact parameters. The position resolution achieved for reconstructed primary vertices that correspond to interesting pp collisions is 10â12Îźm in each of the three spatial dimensions. The tracking and vertexing software is fast and flexible, and easily adaptable to other functions, such as fast tracking for the trigger, or dedicated tracking for electrons that takes into account bremsstrahlung
Alignment of the CMS tracker with LHC and cosmic ray data
Š CERN 2014 for the benefit of the CMS collaboration, published under the terms of the Creative Commons Attribution 3.0 License by IOP Publishing Ltd and Sissa Medialab srl. Any further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation and DOI.The central component of the CMS detector is the largest silicon tracker ever built. The precise alignment of this complex device is a formidable challenge, and only achievable with a significant extension of the technologies routinely used for tracking detectors in the past. This article describes the full-scale alignment procedure as it is used during LHC operations. Among the specific features of the method are the simultaneous determination of up to 200 000 alignment parameters with tracks, the measurement of individual sensor curvature parameters, the control of systematic misalignment effects, and the implementation of the whole procedure in a multi-processor environment for high execution speed. Overall, the achieved statistical accuracy on the module alignment is found to be significantly better than 10Οm
LAKE SUPERIOR SHORELINE VEGETATION AND EROSION: AN ECOLOGICAL SURVEY
Shoreline erosion along the Great Lakes continues to be a major economic and environmental concern. Of the nearly 5900 km. of shore- line, approximately 60% is erodible glacial clays, sands, or gravels. Fifty percent of these erodible shores have been developed as residential or commercial-industrial sites (Quisenberry, 1976}. The Wisconsin shorelines of Lake Superior and Lake Michigan have extensive zones of highly erodible materials. Sydor (1976) estimated 2.3 x 106 metric tons of soil is eroded from the glacial-lacustrine red clay shore line of Douglas County, Wisconsin alone. Hess (1973) estimated 8 x 106 metric tons are lost annually from the Wisconsin shores of Lake Superior. The chief monetary loss (reaching $15 million in Wisconsin in 19721 occurs from the irretrievable loss of land and the devaluation of real estate with the encroachment of the waterfront.Wisconsin Sea Gran
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