The oil from the 2010 Deepwater Horizon spill in the Gulf of Mexico was documented by shoreline assessment teams as stranding on 1,773 km of shoreline. Beaches comprised 50.8%, marshes 44.9%, and ...other shoreline types 4.3% of the oiled shoreline. Shoreline cleanup activities were authorized on 660 km, or 73.3% of oiled beaches and up to 71 km, or 8.9% of oiled marshes and associated habitats. One year after the spill began, oil remained on 847 km; two years later, oil remained on 687 km, though at much lesser degrees of oiling. For example, shorelines characterized as heavily oiled went from a maximum of 360 km, to 22.4 km one year later, and to 6.4 km two years later. Shoreline cleanup has been conducted to meet habitat-specific cleanup endpoints and will continue until all oiled shoreline segments meet endpoints. The entire shoreline cleanup program has been managed under the Shoreline Cleanup Assessment Technique (SCAT) Program, which is a systematic, objective, and inclusive process to collect data on shoreline oiling conditions and support decision making on appropriate cleanup methods and endpoints. It was a particularly valuable and effective process during such a complex spill.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The quark and gluon structure of the proton has been under intense experimental and theoretical investigation for five decades. Even for the distributions of the well-studied valence quarks, ...challenges such as the value of the down quark to up quark ratio at high fractional momenta remain. Much of the sea of quark-antiquark pairs emerges from the splitting of gluons and is well described by perturbative evolution in quantum chromodynamics. However, experiments confirm that there is a non-perturbative component to the sea that is not well understood and hitherto has been difficult to calculate with ab initio non-perturbative methods. This non-perturbative structure shows up, perhaps most directly, in the flavor dependence of the sea antiquark distributions. While some of the general trends can be reproduced by models, there are features of the data that do not seem to be well described. This article discusses the experimental situation, the status of calculations and models, and the directions where these studies will progress in the near future.
In two experiments, we systematically investigated the reasons why people retained certain autobiographical events in their memory, as well as the properties of those events and their predicted ...memorability. The first experiment used three methods (word-cued, free-recalled, and "memorable, interesting, and/or important") to retrieve event memories, and examined memories from three different time-frames: very recent (within past 7 days), recent (past 2 weeks and 6 months), and older events (at least one year). In addition, data were also collected for an important transitional event recently experienced by all participants ("starting university"). The results revealed that people had access to three types of event memories: memories for life transitions, memories for older distinctive events, and memories for recent mundane events. Participants reported remembering events that were distinctive, first-time experiences, emotionally impactful, or simply because they were recent. They also predicted that older events would be more resistant to forgetting than very recent and recent events. The second experiment examined participants' memorable and forgettable events, and found that memorable events tended to be older, while forgettable events were more likely to be recent. These findings suggested that many retrievable memorable autobiographical memories were neither important nor transitional in nature. The studies contribute to our understanding of people's metamnemonic knowledge about their autobiographical memories.
Radiocarbon (
C), as a consequence of its production in the atmosphere and subsequent dispersal through the carbon cycle, is a key tracer for studying the Earth system. Knowledge of past
C levels ...improves our understanding of climate processes, the Sun, the geodynamo, and the carbon cycle. Recently updated radiocarbon calibration curves (IntCal20, SHCal20, and Marine20) provide unprecedented accuracy in our estimates of
C levels back to the limit of the
C technique (~55,000 years ago). Such improved detail creates new opportunities to probe the Earth and climate system more reliably and at finer scale. We summarize the advances that have underpinned this revised set of radiocarbon calibration curves, survey the broad scientific landscape where additional detail on past
C provides insight, and identify open challenges for the future.
The IntCal04 and Marine04 radiocarbon calibration curves have been updated from 12 cal kBP (cal kBP is here defined as thousands of calibrated years before AD 1950), and extended to 50 cal kBP, ...utilizing newly available data sets that meet the IntCal Working Group criteria for pristine corals and other carbonates and for quantification of uncertainty in both the 14C and calendar timescales as established in 2002. No change was made to the curves from 0–12 cal kBP. The curves were constructed using a Markov chain Monte Carlo (MCMC) implementation of the random walk model used for IntCal04 and Marine04. The new curves were ratified at the 20th International Radiocarbon Conference in June 2009 and are available in the Supplemental Material at www.radiocarbon.org.
We report a precision measurement of the parity-violating asymmetry APV in the elastic scattering of longitudinally polarized electrons from 208Pb. We measure APV= 550 ± 16 (stat) ±8 (syst) parts per ...billion, leading to an extraction of the neutral weak form factor FW(Q2= 0.00616 GeV2) = 0.368 ± 0.013. Combined with our previous measurement, the extracted neutron skin thickness is Rn-Rp= 0.283 ± 0.071 fm. The result also yields the first significant direct measurement of the interior weak density of 208Pb: ρ$^0_W$ = -0.0796 ± 0.0036(exp) ± 0.0013(theo) fm-3 leading to the interior baryon density ρ$^0_b$ = 0.1480 ± 0.0036(exp) ± 0.0013(theo) fm-3. Finally, the measurement accurately constrains the density dependence of the symmetry energy of nuclear matter near saturation density, with implications for the size and composition of neutron stars.
Recent measurements on dendrochronologically-dated wood from the Southern Hemisphere have shown that there are differences between the structural form of the radiocarbon calibration curves from each ...hemisphere. Thus, it is desirable, when possible, to use calibration data obtained from secure dendrochronologically-dated wood from the corresponding hemisphere. In this paper, we outline the recent work and point the reader to the internationally recommended data set that should be used for future calibration of Southern Hemisphere 14C dates.
Agricultural best management practices (BMPs), or conservation practices, can help reduce nonpoint source pollution from agricultural lands, as well as provide valuable wildlife habitat. There is a ...large literature exploring factors that lead to a producer’s voluntary adoption of BMPs, but there have been inconsistent findings. Generally, this literature has not examined specific attributes of BMPs that may affect acceptability to farmers and ultimately adoption. To address these limitations, a qualitative analysis of in-depth interviews with farmers was conducted to determine which characteristics make four common BMPs more or less acceptable to agricultural producers. Interviews were conducted with forty-five producers in two watersheds in Indiana, USA. The producers were asked about their use of these conservation practices and the reasons behind their decisions. This study outlines the perceived characteristics of each conservation practice that are most important in either facilitating or impeding adoption of those practices. Results indicate that perceived high levels of relative advantage (e.g., reduced inputs, time-savings, and on-farm and environmental benefits), compatibility (with farm system and needs of producer), and observability (observing practice’s advantages) are most important in increasing adoption of conservation practices. Low levels of perceived relative advantage and incompatibility of practices were found to be most important in non-adoption of conservation practices. Perceived risk and complexity associated with specific practices were only found to limit adoption for a few practices, though it was an important barrier for conservation tillage. In order to increase adoption, conservation promoters should focus on raising awareness of the on-farm and financial benefits, the environmental benefits, and compatibility of conservation practices with current farm operations.
The proton is one of the main building blocks of all visible matter in the Universe
. Among its intrinsic properties are its electric charge, mass and spin
. These properties emerge from the complex ...dynamics of its fundamental constituents-quarks and gluons-described by the theory of quantum chromodynamics
. The electric charge and spin of protons, which are shared among the quarks, have been investigated previously using electron scattering
. An example is the highly precise measurement of the electric charge radius of the proton
. By contrast, little is known about the inner mass density of the proton, which is dominated by the energy carried by gluons. Gluons are hard to access using electron scattering because they do not carry an electromagnetic charge. Here we investigated the gravitational density of gluons using a small colour dipole, through the threshold photoproduction of the J/ψ particle. We determined the gluonic gravitational form factors of the proton
from our measurement. We used a variety of models
and determined, in all cases, a mass radius that is notably smaller than the electric charge radius. In some, but not all cases, depending on the model, the determined radius agrees well with first-principle predictions from lattice quantum chromodynamics
. This work paves the way for a deeper understanding of the salient role of gluons in providing gravitational mass to visible matter.
Calibration is essential for interpretation of radiocarbon dates, especially when the 14C dates are compared to historical or climatic records with a different chronological basis. 14C ages of ...samples from the marine environment, such as shells or fish bones, or samples with a marine component, such as human bone in coastal regions, require an additional consideration because of the reservoir age of the ocean. While the pre-industrial global mean reservoir correction, R(t), is about 400 years, local variations (ΔR) can be several hundred years or more. ΔR compilations on a global scale have been undertaken previously (Stuiver et al. 1986; Stuiver and Braziunas 1993), but have not been updated recently. Here we describe an on-line reservoir correction database accessed via mapping software. Rather than publishing a static ΔR compilation, new data will be incorporated when it becomes available. The on-line marine reservoir correction database can be accessed at the website http://www.calib.org/.
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