111 research outputs found
Anthropogenic impacts on tidal creek sedimentation since 1900
Land cover and use around the margins of estuaries has shifted since 1950 at many sites in North America due to development pressures from higher population densities. Small coastal watersheds are ubiquitous along estuarine margins and most of this coastal land-cover change occurred in these tidal creek watersheds. A change in land cover could modify the contribution of sediments from tidal creek watersheds to downstream areas and affect estuarine habitats that rely on sediments to persist or are adversely impacted by sediment loading. The resilience of wetlands to accelerating relative sea-level rise depends, in part, on the supply of lithogenic sediment to support accretion and maintain elevation; however, subtidal habitats such as oyster reefs and seagrass beds are stressed under conditions of high turbidity and sedimentation. Here we compare sediment accumulation rates before and after 1950 using 210Pb in 12 tidal creeks across two distinct regions in North Carolina, one region of low relief tidal-creek watersheds where land cover change since 1959 was dominated by fluctuations in forest, silviculture, and agriculture, and another region of relatively high relief tidal-creek watersheds where land-use change was dominated by increasing suburban development. At eight of the creeks, mass accumulation rates (g cm-2 y-1) measured at the outlet of the creeks increased contemporaneously with the largest shift in land cover, within the resolution of the land-cover data set (~5-years). All but two creek sites experienced a doubling or more in sediment accumulation rates (cm yr-1) after 1950 and most sites experienced sediment accumulation rates that exceeded the rate of local relative sea-level rise, suggesting that there is an excess of sediment being delivered to these tidal creeks and that they may slowly be infilling. After 1950, land cover within one creek watershed changed little, as did mass accumulation rates at the coring location, and another creek coring site did not record an increase in mass accumulation rates at the creek outlet despite a massive increase in development in the watershed that included the construction of retention ponds. These abundant tidal-creek watersheds have little relief, area, and flow, but they are impacted by changes in land cover more, in terms of percent area, than their larger riverine counterparts, and down-stream areas are highly connected to their associated watersheds. This work expands the scientific understanding of connectivity between lower coastal plain watersheds and estuaries and provides important information for coastal zone managers seeking to balance development pressures and environmental protections
062 BONE-MARROW STIMULATION BY DRILLING VERSUS MICROFRACTURE LEADS TO BETTER CARTILAGE REPAIR IN RABBITS
Origin and Evolution of Saturn's Ring System
The origin and long-term evolution of Saturn's rings is still an unsolved
problem in modern planetary science. In this chapter we review the current
state of our knowledge on this long-standing question for the main rings (A,
Cassini Division, B, C), the F Ring, and the diffuse rings (E and G). During
the Voyager era, models of evolutionary processes affecting the rings on long
time scales (erosion, viscous spreading, accretion, ballistic transport, etc.)
had suggested that Saturn's rings are not older than 100 My. In addition,
Saturn's large system of diffuse rings has been thought to be the result of
material loss from one or more of Saturn's satellites. In the Cassini era, high
spatial and spectral resolution data have allowed progress to be made on some
of these questions. Discoveries such as the ''propellers'' in the A ring, the
shape of ring-embedded moonlets, the clumps in the F Ring, and Enceladus' plume
provide new constraints on evolutionary processes in Saturn's rings. At the
same time, advances in numerical simulations over the last 20 years have opened
the way to realistic models of the rings's fine scale structure, and progress
in our understanding of the formation of the Solar System provides a
better-defined historical context in which to understand ring formation. All
these elements have important implications for the origin and long-term
evolution of Saturn's rings. They strengthen the idea that Saturn's rings are
very dynamical and rapidly evolving, while new arguments suggest that the rings
could be older than previously believed, provided that they are regularly
renewed. Key evolutionary processes, timescales and possible scenarios for the
rings's origin are reviewed in the light of tComment: Chapter 17 of the book ''Saturn After Cassini-Huygens'' Saturn from
Cassini-Huygens, Dougherty, M.K.; Esposito, L.W.; Krimigis, S.M. (Ed.) (2009)
537-57
The UltraLight Project: The Network as an Integrated and Managed Resource for Data-Intensive Science
Cluster Density and the IMF
Observed variations in the IMF are reviewed with an emphasis on environmental
density. The remote field IMF studied in the LMC by several authors is clearly
steeper than most cluster IMFs, which have slopes close to the Salpeter value.
Local field regions of star formation, like Taurus, may have relatively steep
IMFs too. Very dense and massive clusters, like super star clusters, could have
flatter IMFs, or inner-truncated IMFs. We propose that these variations are the
result of three distinct processes during star formation that affect the mass
function in different ways depending on mass range. At solar to intermediate
stellar masses, gas processes involving thermal pressure and supersonic
turbulence determine the basic scale for stellar mass, starting with the
observed pre-stellar condensations, and they define the mass function from
several tenths to several solar masses. Brown dwarfs require extraordinarily
high pressures for fragmentation from the gas, and presumably form inside the
pre-stellar condensations during mutual collisions, secondary fragmentations,
or in disks. High mass stars form in excess of the numbers expected from pure
turbulent fragmentation as pre-stellar condensations coalesce and accrete with
an enhanced gravitational cross section. Variations in the interaction rate,
interaction strength, and accretion rate among the primary fragments formed by
turbulence lead to variations in the relative proportions of brown dwarfs,
solar to intermediate mass stars, and high mass stars.Comment: 14 pages, 3 figures, to be published in ``IMF@50: A Fest-Colloquium
in honor of Edwin E. Salpeter,'' held at Abbazia di Spineto, Siena, Italy,
May 16-20, 2004. Kluwer Academic Publishers; edited by E. Corbelli, F. Palla,
and H. Zinnecke
The burden of unintentional drowning: Global, regional and national estimates of mortality from the Global Burden of Disease 2017 Study
__Background:__ Drowning is a leading cause of injury-related mortality globally. Unintentional drowning (International Classification of Diseases (ICD) 10 codes W65-74 and ICD9 E910) is one of the 30 mutually exclusive and collectively exhaustive causes of injury-related mortality in the Global Burden of Disease (GBD) study. This study's objective is to describe unintentional drowning using GBD estimates from 1990 to 2017.
__Methods:__ Unintentional drowning from GBD 2017 was estimated for cause-specific mortality and years of life lost (YLLs), age, sex, country, region, Socio-demographic Index (SDI) quintile, and trends from 1990 to 2017. GBD 2017 used standard GBD methods for estimating mortality from drowning.
__Results:__ Globally, unintentional drowning mortality decreased by 44.5% between 1990 and 2017, from 531 956 (uncertainty interval (UI): 484 107 to 572 854) to 295 210 (284 493 to 306 187) deaths. Global age-standardised mortality rates decreased 57.4%, from 9.3 (8.5 to 10.0) in 1990 to 4.0 (3.8 to 4.1) per 100 000 per annum in 2017. Unintentional drowning-associated mortality was generally higher in children, males and in low-SDI to middle-SDI countries. China, India, Pakistan and Bangladesh accounted for 51.2% of all drowning deaths in 2017. Oceania was the region with the highest rate of age-standardised YLLs in 2017, with 45 434 (40 850 to 50 539) YLLs per 100 000 across both sexes.
__Conclusions:__ There has been a decline in global drowning rates. This study shows that the decline was not consistent across countries. The results reinforce the need for continued and improved policy, prevention and research efforts, with a focus on low-and middle-income countries
Design and construction of the MicroBooNE detector
This paper describes the design and construction of the MicroBooNE liquid
argon time projection chamber and associated systems. MicroBooNE is the first
phase of the Short Baseline Neutrino program, located at Fermilab, and will
utilize the capabilities of liquid argon detectors to examine a rich assortment
of physics topics. In this document details of design specifications, assembly
procedures, and acceptance tests are reported
Global, regional, and national comparative risk assessment of 79 behavioural, environmental and occupational, and metabolic risks or clusters of risks, 1990-2015: A systematic analysis for the Global Burden of Disease Study 2015
Background: The Global Burden of Diseases, Injuries, and Risk Factors Study 2015 provides an up-to-date synthesis of the evidence for risk factor exposure and the attributable burden of disease. By providing national and subnational assessments spanning the past 25 years, this study can inform debates on the importance of addressing risks in context.
Methods: We used the comparative risk assessment framework developed for previous iterations of the Global Burden of Disease Study to estimate attributable deaths, disability-adjusted life-years (DALYs), and trends in exposure by age group, sex, year, and geography for 79 behavioural, environmental and occupational, and metabolic risks or clusters of risks from 1990 to 2015. This study included 388 risk-outcome pairs that met World Cancer Research Fund-defined criteria for convincing or probable evidence. We extracted relative risk and exposure estimates from randomised controlled trials, cohorts, pooled cohorts, household surveys, census data, satellite data, and other sources. We used statistical models to pool data, adjust for bias, and incorporate covariates. We developed a metric that allows comparisons of exposure across risk factors—the summary exposure value. Using the counterfactual scenario of theoretical minimum risk level, we estimated the portion of deaths and DALYs that could be attributed to a given risk. We decomposed trends in attributable burden into contributions from population growth, population age structure, risk exposure, and risk-deleted cause-specific DALY rates. We characterised risk exposure in relation to a Socio-demographic Index (SDI).
Findings: Between 1990 and 2015, global exposure to unsafe sanitation, household air pollution, childhood underweight, childhood stunting, and smoking each decreased by more than 25%. Global exposure for several occupational risks, high body-mass index (BMI), and drug use increased by more than 25% over the same period. All risks jointly evaluated in 2015 accounted for 57·8% (95% CI 56·6–58·8) of global deaths and 41·2% (39·8–42·8) of DALYs. In 2015, the ten largest contributors to global DALYs among Level 3 risks were high systolic blood pressure (211·8 million [192·7 million to 231·1 million] global DALYs), smoking (148·6 million [134·2 million to 163·1 million]), high fasting plasma glucose (143·1 million [125·1 million to 163·5 million]), high BMI (120·1 million [83·8 million to 158·4 million]), childhood undernutrition (113·3 million [103·9 million to 123·4 million]), ambient particulate matter (103·1 million [90·8 million to 115·1 million]), high total cholesterol (88·7 million [74·6 million to 105·7 million]), household air pollution (85·6 million [66·7 million to 106·1 million]), alcohol use (85·0 million [77·2 million to 93·0 million]), and diets high in sodium (83·0 million [49·3 million to 127·5 million]). From 1990 to 2015, attributable DALYs declined for micronutrient deficiencies, childhood undernutrition, unsafe sanitation and water, and household air pollution; reductions in risk-deleted DALY rates rather than reductions in exposure drove these declines. Rising exposure contributed to notable increases in attributable DALYs from high BMI, high fasting plasma glucose, occupational carcinogens, and drug use. Environmental risks and childhood undernutrition declined steadily with SDI; low physical activity, high BMI, and high fasting plasma glucose increased with SDI. In 119 countries, metabolic risks, such as high BMI and fasting plasma glucose, contributed the most attributable DALYs in 2015. Regionally, smoking still ranked among the leading five risk factors for attributable DALYs in 109 countries; childhood underweight and unsafe sex remained primary drivers of early death and disability in much of sub-Saharan Africa.
Interpretation: Declines in some key environmental risks have contributed to declines in critical infectious diseases. Some risks appear to be invariant to SDI. Increasing risks, including high BMI, high fasting plasma glucose, drug use, and some occupational exposures, contribute to rising burden from some conditions, but also provide opportunities for intervention. Some highly preventable risks, such as smoking, remain major causes of attributable DALYs, even as exposure is declining. Public policy makers need to pay attention to the risks that are increasingly major contributors to global burden.
Funding: Bill & Melinda Gates Foundation
The Physics of Star Cluster Formation and Evolution
© 2020 Springer-Verlag. The final publication is available at Springer via https://doi.org/10.1007/s11214-020-00689-4.Star clusters form in dense, hierarchically collapsing gas clouds. Bulk kinetic energy is transformed to turbulence with stars forming from cores fed by filaments. In the most compact regions, stellar feedback is least effective in removing the gas and stars may form very efficiently. These are also the regions where, in high-mass clusters, ejecta from some kind of high-mass stars are effectively captured during the formation phase of some of the low mass stars and effectively channeled into the latter to form multiple populations. Star formation epochs in star clusters are generally set by gas flows that determine the abundance of gas in the cluster. We argue that there is likely only one star formation epoch after which clusters remain essentially clear of gas by cluster winds. Collisional dynamics is important in this phase leading to core collapse, expansion and eventual dispersion of every cluster. We review recent developments in the field with a focus on theoretical work.Peer reviewe
Measurement of event-shape observables in Z→ℓ+ℓ− events in pp collisions at √ s=7 TeV with the ATLAS detector at the LHC
Event-shape observables measured using charged particles in inclusive
-boson events are presented, using the electron and muon decay modes of the
bosons. The measurements are based on an integrated luminosity of of proton--proton collisions recorded by the ATLAS detector at the
LHC at a centre-of-mass energy TeV. Charged-particle
distributions, excluding the lepton--antilepton pair from the -boson decay,
are measured in different ranges of transverse momentum of the boson.
Distributions include multiplicity, scalar sum of transverse momenta, beam
thrust, transverse thrust, spherocity, and -parameter, which are
in particular sensitive to properties of the underlying event at small values
of the -boson transverse momentum. The Sherpa event generator shows larger
deviations from the measured observables than Pythia8 and Herwig7. Typically,
all three Monte Carlo generators provide predictions that are in better
agreement with the data at high -boson transverse momenta than at low
-boson transverse momenta and for the observables that are less sensitive to
the number of charged particles in the event.Comment: 36 pages plus author list + cover page (54 pages total), 14 figures,
4 tables, submitted to EPJC, All figures including auxiliary figures are
available at
http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2014-0
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