888 research outputs found
First Record of \u3ci\u3eHarpalus Ochropus\u3c/i\u3e Kirby (Coleoptera: Carabidae) From Minnesota and the Conterminous United States
(excerpt)
The epigeal ground beetle Harpalus ochropus Kirby (Coleoptera: Carabidae) has been reported from Alaska and across Canada from British Columbia into Quebec (Bousquet and Larochelle 1993). It is local and rarely collected. Gandhi et al. (2005) surveyed for carabids extensively for several years along the Gunflint Trail and adjacent Boundary Waters Canoe Area in northeastern Minnesota
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The effects of landscape modifications on the long-term persistence of animal populations
Background: The effects of landscape modifications on the long-term persistence of wild animal populations is of crucial
importance to wildlife managers and conservation biologists, but obtaining experimental evidence using real landscapes is
usually impossible. To circumvent this problem we used individual-based models (IBMs) of interacting animals in
experimental modifications of a real Danish landscape. The models incorporate as much as possible of the behaviour and
ecology of four species with contrasting life-history characteristics: skylark (Alauda arvensis), vole (Microtus agrestis), a
ground beetle (Bembidion lampros) and a linyphiid spider (Erigone atra). This allows us to quantify the population
implications of experimental modifications of landscape configuration and composition.
Methodology/Principal Findings: Starting with a real agricultural landscape, we progressively reduced landscape
complexity by (i) homogenizing habitat patch shapes, (ii) randomizing the locations of the patches, and (iii) randomizing the
size of the patches. The first two steps increased landscape fragmentation. We assessed the effects of these manipulations
on the long-term persistence of animal populations by measuring equilibrium population sizes and time to recovery after
disturbance. Patch rearrangement and the presence of corridors had a large effect on the population dynamics of species
whose local success depends on the surrounding terrain. Landscape modifications that reduced population sizes increased
recovery times in the short-dispersing species, making small populations vulnerable to increasing disturbance. The species
that were most strongly affected by large disturbances fluctuated little in population sizes in years when no perturbations
took place.
Significance: Traditional approaches to the management and conservation of populations use either classical methods of
population analysis, which fail to adequately account for the spatial configurations of landscapes, or landscape ecology,
which accounts for landscape structure but has difficulty predicting the dynamics of populations living in them. Here we
show how realistic and replicable individual-based models can bridge the gap between non-spatial population theory and
non-dynamic landscape ecology. A major strength of the approach is its ability to identify population vulnerabilities not
detected by standard population viability analyses
Joint Effects of Population Density and Toxicant Exposure on Population Dynamics of \u3ci\u3eCapitella\u3c/i\u3e Sp. I
Very few studies have analyzed the dependence of population growth rate on population density, and even fewer have considered interaction effects of density and other stresses, such as exposure to toxic chemicals. Yet without such studies we cannot know whether chemicals harmful at low density have effects on carrying capacity or, conversely, whether chemicals reducing carrying capacity are also harmful at low density, impeding a population’s capacity to recover from disturbance. This study examines the combined effects of population density and a toxicant (fluoranthene) on population growth rate (pgr) and carrying capacity using the deposit-feeding polychaete Capitella sp. I as a test organism. Populations were initiated with a stable age distribution, and population density and age/size distribution were followed during a period of 28 wk. Fluoranthene (FLU), population density, and their interaction influenced population growth rate. Population growth rate declined linearly with the logarithm of population biomass, but the slope of the relationship was steeper for the control populations than for populations exposed to 50 μg FLU/(g sediment dry mass). Populations exposed to 150 μg FLU/(g sediment dry mass) went extinct after 8 wk of exposure. Despite concerns that toxicant effects would be exacerbated at high density, we found the reverse to be the case, and effects of fluoranthene on population growth rate were much reduced in the region of carrying capacity. Fluoranthene did reduce carrying capacity by 46%, and this could have important implications for interacting species and/or sediment biogeochemical processes
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Understanding global model systematic shortwave radiation errors in subtropical marine boundary layer cloud regimes
Global numerical weather prediction and climate models are subject to long‐standing systematic shortwave radiation errors due to deficiencies in the representation of boundary layer clouds over the ocean. In the subtropics, clouds are typically too reflective in the cumulus regime and not reflective enough in the stratocumulus regime. Potential sources of error include cloud cover, liquid water path, effective radius, and subgrid heterogeneity, but diagnosing the absolute contributions of each to the radiation bias is hampered by uncertainties and sometimes contradictory information from different observational products. This paper draws on a set of ship‐based observations of boundary layer clouds obtained during the ARM MAGIC campaign along a northeast Pacific Ocean transect, crossing both stratocumulus and shallow cumulus cloud regimes. The surface‐based observations of cloud properties are compared with various satellite products, taking account of the diurnal cycle, to provide an improved quantitative assessment of the deficiencies in the European Centre for Medium‐Range Weather Forecasts global numerical weather prediction model. A series of off‐line radiation calculations are then performed to assess the impact on the shortwave radiation bias of correcting each of the model's deficiencies in cloud characteristics along the transect. A reduction in the bias is achieved by improving the agreement between modeled and observed in‐cloud liquid water path frequency distributions. In the cumulus regime, this is accomplished primarily by reducing the all‐sky water path, while for the stratocumulus regime, an underestimate of cloud cover and liquid water and an overestimate in effective radius and subgrid heterogeneity all contribute to a lack of reflected shortwave radiation
Restoring observed classical behavior of the carbon nanotube field emission enhancement factor from the electronic structure
Experimental Fowler-Nordheim plots taken from orthodoxly behaving carbon
nanotube (CNT) field electron emitters are known to be linear. This shows that,
for such emitters, there exists a characteristic field enhancement factor (FEF)
that is constant for a range of applied voltages and applied macroscopic fields
. A constant FEF of this kind can be evaluated for classical CNT
emitter models by finite-element and other methods, but (apparently contrary to
experiment) several past quantum-mechanical (QM) CNT calculations find
FEF-values that vary with . A common feature of most such
calculations is that they focus only on deriving the CNT real-charge
distributions. Here we report on calculations that use density functional
theory (DFT) to derive real-charge distributions, and then use these to
generate the related induced-charge distributions and related fields and FEFs.
We have analysed three carbon nanostructures involving CNT-like nanoprotrusions
of various lengths, and have also simulated geometrically equivalent classical
emitter models, using finite-element methods. We find that when the
DFT-generated local induced FEFs (LIFEFs) are used, the resulting values are
effectively independent of macroscopic field, and behave in the same
qualitative manner as the classical FEF-values. Further, there is fair to good
quantitative agreement between a characteristic FEF determined classically and
the equivalent characteristic LIFEF generated via DFT approaches. Although many
issues of detail remain to be explored, this appears to be a significant step
forwards in linking classical and QM theories of CNT electrostatics. It also
shows clearly that, for ideal CNTs, the known experimental constancy of the FEF
value for a range of macroscopic fields can also be found in appropriately
developed QM theory.Comment: A slightly revised version has been published - citation below -
under a title different from that originally used. The new title is:
"Restoring observed classical behavior of the carbon nanotube field emission
enhancement factor from the electronic structure
Dating and Digging Stratified Archaeology in Circumpolar North America : A View from Nunalleq, Southwestern Alaska
The results presented in this paper were funded by a NERC Radiocarbon Facility grant (NRCF 1917.0415), while the wider project is funded by the Arts and Humanities Research Council (AH/K006029/1). The authors wish to thank all the members of the excavation crew from the 2014 field season for their hard work in the challenging weather conditions of southwest Alaska – without their attention to detail this study would not have been possible. Additional thanks are also due to Qanirtuuq Incorporated for logistical support and warm hospitality in Quinhagak. We also wish to thank Kevin Edwards and Kate Britton, who read an earlier draft of this paper, and three anonymous reviewers for highly constructive criticism that helped us to improve the final manuscript.Peer reviewedPublisher PD
Implementation of the orthodoxy test as a validity check on experimental field emission data
In field electron emission (FE) studies, it is important to check and analyse
the quality and validity of experimental current-voltage data, which is usually
plotted in one of a small number of standard forms. These include the so-called
Fowler-Nordheim (FN), Millikan-Lauritsen (ML) and Murphy-Good (MG) plots. The
Field Emission Orthodoxy Test is a simple quantitative test that aims to check
for the reasonableness of the values of the parameter "scaled field" that can
be extracted from these plots. This is done in order to establish whether
characterization parameters extracted from the plot will be reliable or,
alternative, likely to be spurious. This paper summarises the theory behind the
orthodoxy test, for each of the plot forms, and confirms that it is easy to
apply it to the newly developed MG plot. A simple web tool has been developed
that extracts scaled-field values from any of these three plot forms, and tests
for lack of field emission orthodoxy.Comment: 14 typescript pages, 2 figure
Raising awareness of research evidence among health professionals delivering dementia care: Are knowledge translation workshops useful?
Providing information about the latest research via educational sessions to health professionals caring for people with dementia may be insufficient to drive change. This project explored self-reported impacts on practice change of adding information about knowledge translation (KT) to a national dementia education program. Six national workshop days were held. Each provided the option of participating in a Principles of KT and innovation implementation seminar in addition to a clinical topic update (sexualities and dementia, or managing behavioral and psychological symptoms of dementia). Six months postworkshop, 321 participants were invited to complete a research utilization survey. Seventy-five responded. KT seminar participants were more likely to report instrumental outcomes (e.g. changed policies, procedures) than those who did not participate in the KT seminar. Including KT information in educational sessions for health professionals may increase the likelihood of practice change in the field of dementia care and warrants further research
Simple good approximations for the special elliptic functions in standard Fowler-Nordheim tunneling theory for a Schottky-Nordheim barrier
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