1,023 research outputs found
Assessing movements of three buoy line types using DSTmilli Loggers: Implications for entanglements of bottlenose dolphins in the crab pot fishery
A study was conducted in October 2006 in the Charleston, South Carolina area to test the movements of three different buoy line types to determine which produced a preferred profile that could reduce the risk of dolphin entanglement. Tests on diamond-braided nylon commonly used in the crab pot fishery were compared with stiffened line of Esterpro and calf types in both shallow and deep water environments using DSTmilli data loggers. Loggers were placed at intervals along the lines to record depth, and thus movements, over a 24 hour period. Three observers viewed video animations and charts created for each of the six trial days from the collected logger data and provided their opinions on the most desirable line type that fit set criteria. A quantitative analysis (ANCOVA) of the data was conducted taking into consideration daily tidal fluctuations and logger movements. Loggers tracking the tides had an r2 value approaching 1.00 and produced little movement other than with the tides. Conversely, r2 values approaching 0.00 were less affected by tidal movement and influenced by currents that cause more erratic movement. Results from this study showed that stiffened line, in particular the medium lay Esterpro type, produced the more desirable profiles that could reduce risk of dolphin entanglement. Combining the observer’s results with the ANCOVA results, Esterpro was chosen nearly 60% of the time as opposed to the nylon line which was only chosen 10% of the time. ANCOVA results showed that the stiffened lines performed better in both the shallow and deep water environments, while the nylon line only performed better during one trial in a deep water set, most probably due to the increased current velocities experienced that day. (58pp.)(PDF contains 68 pages
Pleural mesothelioma and lung cancer risks in relation to occupational history and asbestos lung burden.
BACKGROUND: We have conducted a population-based study of pleural mesothelioma patients with occupational histories and measured asbestos lung burdens in occupationally exposed workers and in the general population. The relationship between lung burden and risk, particularly at environmental exposure levels, will enable future mesothelioma rates in people born after 1965 who never installed asbestos to be predicted from their asbestos lung burdens. METHODS: Following personal interview asbestos fibres longer than 5 µm were counted by transmission electron microscopy in lung samples obtained from 133 patients with mesothelioma and 262 patients with lung cancer. ORs for mesothelioma were converted to lifetime risks. RESULTS: Lifetime mesothelioma risk is approximately 0.02% per 1000 amphibole fibres per gram of dry lung tissue over a more than 100-fold range, from 1 to 4 in the most heavily exposed building workers to less than 1 in 500 in most of the population. The asbestos fibres counted were amosite (75%), crocidolite (18%), other amphiboles (5%) and chrysotile (2%). CONCLUSIONS: The approximate linearity of the dose-response together with lung burden measurements in younger people will provide reasonably reliable predictions of future mesothelioma rates in those born since 1965 whose risks cannot yet be seen in national rates. Burdens in those born more recently will indicate the continuing occupational and environmental hazards under current asbestos control regulations. Our results confirm the major contribution of amosite to UK mesothelioma incidence and the substantial contribution of non-occupational exposure, particularly in women
Spatial and temporal analysis of bottlenose dolphin strandings in South Carolina, 1992-2005
This CD contains summary data of bottlenose dolphins stranded in South Carolina using a Geographical Information System (GIS) and contains two published manuscripts in .pdf files. The intent of this CD is to provide data on bottlenose dolphin strandings in South Carolina to marine mammal researchers and managers.
This CD is an accumulation of 14 years of stranding data collected through the collaborations of the National Ocean Service, Center for Coastal Environmental Health and Biomolecular Research (CCEHBR), the South Carolina Department of Natural Resources, and numerous volunteers and veterinarians that comprised the South Carolina Marine Mammal Stranding Network.
Spatial and temporal information can be visually represented on maps using GIS. For this CD, maps were created to show relationships of stranding densities with land use, human population density, human interaction with dolphins, high geographical regions of live strandings, and seasonal changes. Point maps were also created to show individual strandings within South Carolina.
In summary, spatial analysis revealed higher densities of bottlenose dolphin strandings in Charleston and Beaufort Counties, which consist of urban land with agricultural input. This trend was positively correlated with higher human population levels in these coastal counties as compared with other coastal counties. However, spatial analysis revealed that certain areas within a county may have low human population levels but high stranding density, suggesting that the level of effort to respond to strandings is not necessarily positively correlated with the density of strandings in South Carolina.
Temporal analysis revealed a significantly higher density of bottlenose dolphin strandings in the northern portion of the State in the fall, mostly due to an increase of neonate strandings. On a finer geographic scale, seasonal stranding densities may fluctuate depending on the region of interest.
Charleston Harbor had the highest density of live bottlenose dolphin strandings compared to the rest of the State. This was due in large part to the number of live dolphin entanglements in the crab pot fishery, the largest source of fishery-related mortality for bottlenose dolphins in South Carolina (Burdett and McFee 2004). Spatial density calculations also revealed that Charleston and Beaufort accounted for the majority of dolphins that were involved with human activities.
A pilot study to determine the movements of buoy line used in the crab pot fishery to assess bottlenose dolphin entanglement
A pilot study on the characteristics of crab pot buoy line movements to assess bottlenose dolphin entanglement was conducted from 19 September to 30 September 2005 in the Charleston Harbor, Charleston, South Carolina. The objectives of this study were to determine: 1) the movements of the buoy line in the water at various tidal stages, current strengths, lengths of line, and water depth, 2) if lead-core rope was a better alternative to nylon rope, 3) and if the manner of deployment of the gear affected the suspension of the line in the water and on the bottom. Diamond braided nylon (#10) rope of varying length (20 ft. – 80 ft.) were used during 31 trials and stiffened (polypropylene lead-core) rope was used in four trials. Observations of the buoy line movements were captured with an Atlantis underwater camera attached to a Digital DPC-1000 video recorder. Results from this study showed that: 1) the method used for deployment was important in keeping the buoy line from arcing or coiling, 2) little to no arcing occurred in water current velocities of >0.20 m/s, 3) rope lengths of ≥50 ft. deployed in <10 ft. of water produced waving in the water column and arcing on the bottom, 4) slack tide was a period of increased risk of entanglement for bottlenose dolphins, and 5) poly lead-core rope was not a good alternative to nylon rope unless in deep water with strong water current velocities. This pilot study produced questions that can be used for future studies on the characteristics of buoy line movements in the crab pot fishery as it relates to bottlenose dolphin entanglements
Superconductivity of metallic boron in MgB_2
Boron in MgB_2 forms layers of honeycomb lattices with magnesium as a space
filler. Band structure calculations indicate that Mg is substantially ionized,
and the bands at the Fermi level derive mainly from B orbitals. Strong bonding
with an ionic component and considerable metallic density of states yield a
sizeable electron-phonon coupling. Using the rigid atomic sphere approximation
and an analogy to Al, we estimate the coupling constant lambda to be of order
1. Together with high phonon frequencies, which we estimate via zone-center
frozen phonon calculations to be between 300 and 700 cm^-1, this produces a
high critical temperature, consistent with recent experiments reporting Tc=39 K
(J. Akimitsu et al., to be published). Thus MgB_2 can be viewed as an analog of
the long sought, but still hypothetical, superconducting metallic hydrogen.Comment: several typos corrected, most importantly, units in the tables fixed
and a missing zero in the expression for the resistivity restore
Mixed valency in cerium oxide crystallographic phases: Determination of valence of the different cerium sites by the bond valence method
We have applied the bond valence method to cerium oxides to determine the
oxidation states of the Ce ion at the various site symmetries of the crystals.
The crystals studied include cerium dioxide and the two sesquioxides along with
some selected intermediate phases which are crystallographically well
characterized. Our results indicate that cerium dioxide has a mixed-valence
ground state with an f-electron population on the Ce site of 0.27 while both
the A- and C-sesquioxides have a nearly pure f^1 configuration. The Ce sites in
most of the intermediate oxides have non-integral valences. Furthermore, many
of these valences are different from the values predicted from a naive
consideration of the stoichiometric valence of the compound
Job Mobility and Sorting: Theory and Evidence
I derive a measure of job mobility that reflects individuals ability to sort into the preferred jobs. Relying on the Survey of Income and Program Participation, I find that educational attainment tends to have a strong positive effect on internal (i.e., within firms) and external (i.e., between firms) job mobility. General experience and occupation-specific human capital have only a limited effect on both internal and external mobility. The impact of being versatile on an individual s external job mobility is substantial and similar in magnitude as the effect of a college degree on a high school dropout s external mobility
The Structure, Dynamics and Electronic Structure of Liquid Ag-Se Alloys Investigated by Ab Initio Simulation
Ab initio molecular-dynamics simulations have been used to investigate the
structure, dynamics and electronic properties of the liquid alloy Ag(1-x)Se(x)
at 1350 K and at the three compositions x=0.33, 0.42 and 0.65. The calculations
are based on density-functional theory in the local density approximation and
on the pseudopotential plane-wave method. The reliability of the simulations is
confirmed by detailed comparisons with very recent neutron diffraction results
for the partial structure factors and radial distribution functions (RDF) of
the stoichiometric liquid Ag2Se. The simulations show a dramatic change of the
Se-Se RDF with increasing Se content. This change is due to the formation of Se
clusters bound by covalent bonds, the Se-Se bond length being almost the same
as in pure c-Se and l-Se. The clusters are predominantly chain-like, but for
higher x a large fraction of 3-fold coordinated Se atoms is also found. It is
shown that the equilibrium fractions of Se present as isolated atoms and in
clusters can be understood on a simple charge-balance model based on an ionic
interpretation. The Ag and Se diffusion coefficients both increase with Se
content, in spite of the Se clustering. An analysis of the Se-Se bond dynamics
reveals surprisingly short bond lifetimes of less than 1 ps. The changes in the
density of states with composition arise directly from the formation of Se-Se
covalent bonds. Results for the electronic conductivity obtained using the
Kubo-Greenwood approximation are in adequate agreement with experiment for
l-Ag2Se, but not for the high Se contents. Possible reasons for this are
discussed.Comment: 14 pages, Revtex, 14 Postscript figures embedded in the tex
Quasiparticle interfacial level alignment of highly hybridized frontier levels: HO on TiO(110)
Knowledge of the frontier levels' alignment prior to photo-irradiation is
necessary to achieve a complete quantitative description of HO
photocatalysis on TiO(110). Although HO on rutile TiO(110) has been
thoroughly studied both experimentally and theoretically, a quantitative value
for the energy of the highest HO occupied levels is still lacking. For
experiment, this is due to the HO levels being obscured by hybridization
with TiO(110) levels in the difference spectra obtained via ultraviolet
photoemission spectroscopy (UPS). For theory, this is due to inherent
difficulties in properly describing many-body effects at the
HO-TiO(110) interface. Using the projected density of states (DOS) from
state-of-the-art quasiparticle (QP) , we disentangle the adsorbate and
surface contributions to the complex UPS spectra of HO on TiO(110). We
perform this separation as a function of HO coverage and dissociation on
stoichiometric and reduced surfaces. Due to hybridization with the TiO(110)
surface, the HO 3a and 1b levels are broadened into several peaks
between 5 and 1 eV below the TiO(110) valence band maximum (VBM). These
peaks have both intermolecular and interfacial bonding and antibonding
character. We find the highest occupied levels of HO adsorbed intact and
dissociated on stoichiometric TiO(110) are 1.1 and 0.9 eV below the VBM. We
also find a similar energy of 1.1 eV for the highest occupied levels of HO
when adsorbed dissociatively on a bridging O vacancy of the reduced surface. In
both cases, these energies are significantly higher (by 0.6 to 2.6 eV) than
those estimated from UPS difference spectra, which are inconclusive in this
energy region. Finally, we apply self-consistent QP (scQP1) to obtain
the ionization potential of the HO-TiO(110) interface.Comment: 12 pages, 12 figures, 1 tabl
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