198 research outputs found
The late quaternary evolution of a twin barrier-island complex, Cape Charles, Virginia (stratigraphy, sedimentology, Wisconsinan, sea-level highstand)
A total of 68 vibra-cores and 14-box cores in conjunction with high-resolution seismic records are used to describe the late Quaternary development of a twin-barrier island complex. Based on the stratigraphy, radiocarbon dates, and microfossils, a transgressive outer Holocene and inner Pleistocene barrier island complex are recognized. The two subaerial sub-parallel barriers are a result of separate marine transgressions that occurred before and after late Wisconsin glaciation. Pollen assemblages and ten radiocarbon dates from the lagoonal sediments below the older island concur on a date of approximately 30,000 years B.P., hence a probable mid-Wisconsinan age for the overriding barrier island. The uncertainty surrounding a sea level near today\u27s position 30,000 years ago is not unnoticed; neotectonics may be an important consideration in this apparent rise in sea-level. Holocene sediments deposited in the backbarrier environment show a general shallowing and fining upward sequence. The Holocene stratigraphic sequence indicates a narrowing of the backbarrier region, a decrease in the tidal prism, and an increase in marsh and tidal flat infilling associated with calmer water conditions. Most backbarrier sediments are introduced through tidal inlets. Despite Holocene, backbarrier deposits greater than 8 meters thick, only 2 meters may be preserved below 75-100 cm thick nearshore sands in some areas. Inlet fill deposits will not be preserved. However inner barrier sands and lower Holocene backbarrier sands and muds have a strong preservational potential. The stacking of transgressive barrier deposits, albeit those from different transgressions, may provide a stratigraphic oil trap
Late Pleistocene barrier-island sequence along the southern Delmarva Peninsula: Implications for middle Wisconsin sea levels
Evidence for a middle Wisconsin sea-level high at or above modern limits along the east coast of the United States has long been controversial. Most reports have been dismissed as poorly dated or lacking unequivocal documentation of a marine transgression. We describe here a 14C-dated, middle Wisconsin transgressive sequence with an extant subaerial barrier facies along the southern Delmarva Peninsula. This sequence indicates that sea levels were near their present position between ca. 23 and 34 ka; it may correlate with other inferred similar-age littoral deposits of the area, and it suggests that the evidence for glacioeustatic fluctuations during the Wisconsin Glaciation should be reconsidered
SAMS Acceleration Measurements on MIR
During NASA Increment 3 (September 1996 to January 1997), about 5 gigabytes of acceleration data were collected by the Space Acceleration Measurement System (SAMS) onboard the Russian Space Station, Mir. The data were recorded on 11 optical disks and were returned to Earth on STS-81. During this time, SAMS data were collected in the Priroda module to support the following experiments: the Mir Structural Dynamics Experiment (MiSDE) and Binary Colloidal Alloy Tests (BCAT). This report points out some of the salient features of the microgravity environment to which these experiments were exposed. Also documented are mission events of interest such as the docked phase of STS-81 operations, a Progress engine burn, attitude control thruster operation, and crew exercise. Also included are a description of the Mir module orientations, and the panel notations within the modules. This report presents an overview of the SAMS acceleration measurements recorded by 10 Hz and 100 Hz sensor heads. Variations in the acceleration environment caused by unique activities such as crew exercise and life-support fans are presented. The analyses included herein complement those presented in previous mission summary reports published by the Principal Investigator Microgravity Services (PIMS) group
Breaking the Curve with CANDELS: A Bayesian Approach to Reveal the Non-Universality of the Dust-Attenuation Law at High Redshift
Dust attenuation affects nearly all observational aspects of galaxy
evolution, yet very little is known about the form of the dust-attenuation law
in the distant Universe. Here, we model the spectral energy distributions
(SEDs) of galaxies at z = 1.5--3 from CANDELS with rest-frame UV to near-IR
imaging under different assumptions about the dust law, and compare the amount
of inferred attenuated light with the observed infrared (IR) luminosities. Some
individual galaxies show strong Bayesian evidence in preference of one dust law
over another, and this preference agrees with their observed location on the
plane of infrared excess (IRX, ) and UV slope
(). We generalize the shape of the dust law with an empirical model,
where
is the dust law of Calzetti et al. (2000), and show that there
exists a correlation between the color excess and tilt with
+ . Galaxies with high
color excess have a shallower, starburst-like law, and those with low color
excess have a steeper, SMC-like law. Surprisingly, the galaxies in our sample
show no correlation between the shape of the dust law and stellar mass,
star-formation rate, or . The change in the dust law with color excess
is consistent with a model where attenuation is caused by by scattering, a
mixed star-dust geometry, and/or trends with stellar population age,
metallicity, and dust grain size. This rest-frame UV-to-near-IR method shows
potential to constrain the dust law at even higher () redshifts.Comment: 20 pages, 18 figures, resubmitted to Ap
Selection on moral hazard in health insurance
We use employee-level panel data from a single rm to explore the possibility that
individuals may select insurance coverage in part based on their anticipated behavioral
( moral hazard ) response to insurance, a phenomenon we label selection on moral
hazard. Using a model of plan choice and medical utilization, we present evidence of
heterogeneous moral hazard as well as selection on it, and explore some of its implica-
tions. For example, we show that, at least in our context, abstracting from selection
on moral hazard could lead to over-estimates of the spending reduction associated with
introducing a high-deductible health insurance option.National Institute on Aging (NIA (R01 AG032449))National Cancer Institute (U.S.) (Grant SES-0643037)United States. Social Security Administration (grant #5 RRC08098400-03-00)Aluminum Company of AmericaAlfred P. Sloan FoundationJohn D. and Catherine T. MacArthur Foundation (Network on Socioeconomic Status and Health
Photocathode Behavior During High Current Running in the Cornell ERL Photoinjector
The Cornell University Energy Recovery Linac (ERL) photoinjector has recently
demonstrated operation at 20 mA for approximately 8 hours, utilizing a
multialkali photocathode deposited on a Si substrate. We describe the recipe
for photocathode deposition, and will detail the parameters of the run.
Post-run analysis of the photocathode indicates the presence of significant
damage to the substrate, perhaps due to ion back-bombardment from the residual
beamline gas. While the exact cause of the substrate damage remains unknown, we
describe multiple surface characterization techniques (X-ray fluorescence
spectroscopy, X-ray diffraction, atomic force and scanning electron microscopy)
used to study the interesting morphological and crystallographic features of
the photocathode surface after its use for high current beam production.
Finally, we present a simple model of crystal damage due to ion
back-bombardment, which agrees qualitatively with the distribution of damage on
the substrate surface.Comment: 20 pages, 15 figure
A Cohort Study of Traffic-Related Air Pollution and Mortality in Toronto, Ontario, Canada
BackgroundChronic exposure to traffic-related air pollution (TRAP) may contribute to premature mortality, but few studies to date have addressed this topic.ObjectivesIn this study we assessed the association between TRAP and mortality in Toronto, Ontario, Canada.MethodsWe collected nitrogen dioxide samples over two seasons using duplicate two-sided Ogawa passive diffusion samplers at 143 locations across Toronto. We calibrated land use regressions to predict NO2 exposure on a fine scale within Toronto. We used interpolations to predict levels of particulate matter with aerodynamic diameter < or = 2.5 microm (PM(2.5)) and ozone levels. We assigned predicted pollution exposures to 2,360 subjects from a respiratory clinic, and abstracted health data on these subjects from medical billings, lung function tests, and diagnoses by pulmonologists. We tracked mortality between 1992 and 2002. We used standard and multilevel Cox proportional hazard models to test associations between air pollution and mortality.ResultsAfter controlling for age, sex, lung function, obesity, smoking, and neighborhood deprivation, we observed a 17% increase in all-cause mortality and a 40% increase in circulatory mortality from an exposure contrast across the interquartile range of 4 ppb NO2. We observed no significant associations with other pollutants.ConclusionsExposure to TRAP was significantly associated with increased all-cause and circulatory mortality in this cohort. A high prevalence of cardiopulmonary disease in the cohort probably limits inference of the findings to populations with a substantial proportion of susceptible individuals
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