947 research outputs found
Impact of slurry application method on phosphorus loss in runoff from grassland soils during periods of high soil moisture content
peer-reviewedPrevious studies have reported that the trailing shoe application technique reduces phosphorus (P) in the runoff postslurry application when compared to the traditional splash-plate application technique. However, the effectiveness of the trailing-shoe technique as a means of reducing P losses has not been evaluated when slurry is applied during periods of high soil moisture levels and lower herbage covers. To address this issue, three treatments were examined in a 3 × 4 factorial design split-plot experiment, with treatments comprising three slurry treatments: control (no slurry), splashplate and trailing-shoe, and four slurry application dates: 7 December, 18 January, 1 March and 10 April. Dairy cow slurry was applied at a rate of 20 m3/ha, while simulated runoff was generated 2, 9 and 16 days later and analysed for a range of P fractions. Dissolved reactive P concentrations in runoff at day two was 41% lower when slurry was applied using the trailing-shoe technique, compared to the splash-plate technique (P < 0.05). In addition, P concentrations in runoff were higher (P < 0.05) from slurry applied in December and March compared to slurry applied in January or April, coinciding with periods of higher soil moisture contents. While the latter highlights that ‘calendar’-based non-spreading periods might not always achieve the desired consequences, the study demonstrated that further field-scale investigations into the trailing shoe as a mitigation measure to reduced P loss from agricultural soils is warranted
Sedimentology and kinematics of a large, retrogressive growth-fault system in Upper Carboniferous deltaic sediments, western Ireland
Growth faulting is a common feature of many deltaic environments and is vital in determining local sediment dispersal and accumulation, and hence in controlling the resultant sedimentary facies distribution and architecture. Growth faults occur on a range of scales, from a few centimetres to hundreds of metres, with the largest growth faults frequently being under-represented in outcrops that are often smaller than the scale of feature under investigation. This paper presents data from the exceptionally large outcrops of the Cliffs of Moher, western Ireland, where a growth-fault complex affects strata up to 60 m in thickness and extends laterally for 3 km. Study of this Namurian (Upper Carboniferous) growth-fault system enables the relationship between growth faulting and sedimentation to be detailed and permits reconstruction of the kinematic history of faulting. Growth faulting was initiated with the onset of sandstone deposition on a succession of silty mudstones that overlie a thin, marine shale. The decollement horizon developed at the top of the marine shale contact for the first nine faults, by which time aggradation in the hangingwall exceeded 60 m in thickness. After this time, failure planes developed at higher stratigraphic levels and were associated with smaller scale faults. The fault complex shows a dominantly landward retrogressive movement, in which only one fault was largely active at any one time. There is no evidence of compressional features at the base of the growth faults, thus suggesting open-ended slides, and the faults display both disintegrative and non-disintegrative structure. Thin-bedded, distal mouth bar facies dominate the hangingwall stratigraphy and, in the final stages of growth-fault movement, erosion of the crests of rollover structures resulted in the highest strata being restricted to the proximity of the fault. These upper erosion surfaces on the fault scarp developed erosive chutes that were cut parallel to flow and are downlapped by the distal hangingwall strata of younger growth faults
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Validation of NCSSHP for highly enriched uranium systems containing beryllium
This document describes the validation of KENO V.a using the 27-group ENDF/B-IV cross section library for highly enriched uranium and beryllium neutronic systems, and is in accordance with ANSI/ANS-8.1-1983(R1988) requirements for calculational methods. The validation has been performed on a Hewlett Packard 9000/Series 700 Workstation at the Oak Ridge Y-12 Plant Nuclear Criticality Safety Department using the Oak Ridge Y-12 Plant Nuclear Criticality Safety Software code package. Critical experiments from LA-2203, UCRL-4975, ORNL-2201, and ORNL/ENG-2 have been identified as having the constituents desired for this validation as well as sufficient experimental detail to allow accurate construction of KENO V.a calculational models. The results of these calculations establish the safety criteria to be employed in future calculational studies of these types of systems
Ab initio study of Cu diffusion in alpha-cristobalite
We have studied the geometries, formation energies, migration barriers and diffusion of a copper interstitial with different charge states with and without an external electric field in the α-cristobalite crystalline form of SiO2 using ab initio computer simulation. The most stable state almost throughout the band gap is charge q = + 1. The height of the migration barrier depends slightly on the charge state and varies between 0.11 and 0.18 eV. However, the charge has a strong influence on the shape of the barrier, as metastable states exist in the middle of the diffusion path for Cu with q = + 1. The heights and shapes of barriers also depend on the density of SiO2, because volume expansion has a similar effect to increase the positive charge on Cu. Furthermore, diffusion coefficients have been deduced from our calculations according to transition-state theory and these calculations confirm the experimental result that oxidation of Cu is a necessary condition for diffusion. Our molecular dynamics simulations show a similar ion diffusion, and dependence on charge state. These simulations also confirm the fact that diffusion of ions can be directly simulated using ab initio molecular dynamics.Peer reviewe
Arrival time and magnitude of airborne fission products from the Fukushima, Japan, reactor incident as measured in Seattle, WA, USA
We report results of air monitoring started due to the recent natural
catastrophe on 11 March 2011 in Japan and the severe ensuing damage to the
Fukushima Dai-ichi nuclear reactor complex. On 17-18 March 2011, we registered
the first arrival of the airborne fission products 131-I, 132-I, 132-Te,
134-Cs, and 137-Cs in Seattle, WA, USA, by identifying their characteristic
gamma rays using a germanium detector. We measured the evolution of the
activities over a period of 23 days at the end of which the activities had
mostly fallen below our detection limit. The highest detected activity amounted
to 4.4 +/- 1.3 mBq/m^3 of 131-I on 19-20 March.Comment: 7 pages, 5 figures, published in Journal of Environmental
Radioactivit
Staphylococcus aureus nasal colonization in HIV-seropositive and HIV-seronegative drug users
Nasal colonization plays an important role in the pathogenesis of Staphylococcus aureus infections. To identify characteristics associated with colonization, we studied a cross-section of a well-described cohort of HIV-seropositive and -seronegative active and former drug users considered at risk for staphylococcal infections. Sixty percent of the 217 subjects were Hispanic, 36% were women, 25% actively used injection drugs, 23% actively used inhalational drugs, 23% received antibiotics, and 35% were HIV-seropositive. Forty-one percent of subjects had positive nasal cultures for S. aureus. The antibiotic susceptibility patterns were similar to the local hospital's outpatient isolates and no dominant strain was identified by arbitrarily primed polymerase chain reaction (AB-PCR). Variables significantly and independently associated with colonization included antibiotic use (odds ratio [OR] = 0.37; confidence interval [CI] = 0.18-0.77), active inhalational drug use within the HIV-seropositive population (OR = 2.36; CI = 1.10-5.10) and female gender (OR = 1.97; CI = 1.09-3.57). Characteristics not independently associated included injection drug use, HIV status, and CD4 count. The association with active inhalational drug use, a novel finding, may reflect alterations in the integrity of the nasal mucosa. The lack of association between HIV infection and S. aureus colonization, which is contrary to most previous studies, could be explained by our rigorous control for confounding variables or by a limited statistical power due to the sample sizes
Charged Higgs boson in the next-to-minimal supersymmetric standard model with explicit CP violation
The phenomenology of the explicit CP violation in the Higgs sector of the
next-to-minimal supersymmetric standard model (NMSSM) is investigated, with
emphasis on the charged Higgs boson. The radiative corrections due to both
quarks and scalar-quarks of the third generation are taken into account, and
the negative result of the search for the Higgs bosons at CERN LEP2, with the
discovery limit of 0.1 pb, is imposed as a constraint. It is found that there
are parameter regions of the NMSSM where the lightest neutral Higgs boson may
even be massless, without being detected at LEP2. This implies that the LEP2
data do not contradict the existence of a massless neutral Higgs boson in the
NMSSM. For the charged Higgs boson, the radiative corrections to its mass may
be negative in some parameter regions of the NMSSM. The phenomenological lower
bound on the radiatively corrected mass of the charged Higgs boson is increased
as the CP violation becomes maximal, i.e., as the CP violating phase becomes
. At the maximal CP violation, its lower bound is about 110 GeV for 5
40. The vacuum expectation value (VEV) of the
neutral Higgs singlet is shown to be no smaller than 16 GeV for any parameter
values of the NMSSM with explicit CP violation. This value of the lower limit
is found to increase up to about 45 GeV as the ratio () of the VEVs
of the two Higgs doublets decreases to smaller values ( 2). The discovery
limit of the Higgs boson search at LEP2 is found to cover about a half of the
kinematically allowed part of the whole parameter space of the NMSSM, and the
portion is roughly stable against the CP violating phase.Comment: Latex, 24 pages, 6 figure
Higgs Scalars in the Minimal Non-minimal Supersymmetric Standard Model
We consider the simplest and most economic version among the proposed
non-minimal supersymmetric models, in which the -parameter is promoted to
a singlet superfield, whose all self-couplings are absent from the
renormalizable superpotential. Such a particularly simple form of the
renormalizable superpotential may be enforced by discrete -symmetries which
are extended to the gravity-induced non-renormalizable operators as well. We
show explicitly that within the supergravity-mediated supersymmetry-breaking
scenario, the potentially dangerous divergent tadpoles associated with the
presence of the gauge singlet first appear at loop levels higher than 5 and
therefore do not destabilize the gauge hierarchy. The model provides a natural
explanation for the origin of the -term, without suffering from the
visible axion or the cosmological domain-wall problem. Focusing on the Higgs
sector of this minimal non-minimal supersymmetric standard model, we calculate
its effective Higgs potential by integrating out the dominant quantum effects
due to stop squarks. We then discuss the phenomenological implications of the
Higgs scalars predicted by the theory for the present and future high-energy
colliders. In particular, we find that our new minimal non-minimal
supersymmetric model can naturally accommodate a relatively light charged Higgs
boson, with a mass close to the present experimental lower bound.Comment: 63 pages (12 figures), extended versio
Tourism income and economic growth in Greece: Empirical evidence from their cyclical components
This paper examines the relationship between the cyclical
components of Greek GDP and international tourism income for
Greece for the period 1976–2004. Using spectral analysis the authors
find that cyclical fluctuations of GDP have a length of about nine
years and that international tourism income has a cycle of about
seven years. The volatility of tourism income is more than eight
times the volatility of the Greek GDP cycle. VAR analysis shows that
the cyclical component of tourism income is significantly influencing
the cyclical component of GDP in Greece. The findings support the
tourism-led economic growth hypothesis and are of particular
interest and importance to policy makers, financial analysts and
investors dealing with the Greek tourism industry
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