3,615 research outputs found
Effects of vertical distribution of soil inorganic nitrogen on root growth and subsequent nitrogen uptake by field vegetable crops
Information is needed about root growth and N uptake of crops under different soil conditions to increase nitrogen use efficiency in horticultural production. The purpose of this study was to investigate if differences in vertical distribution of soil nitrogen (Ninorg) affected root growth and N uptake of a variety of horticultural crops. Two field experiments were performed each over 2 years with shallow or deep placement of soil Ninorg obtained by management of cover crops. Vegetable crops of leek, potato, Chinese cabbage, beetroot, summer squash and white cabbage reached root depths of 0.5, 0.7, 1.3, 1.9, 1.9 and more than 2.4 m, respectively, at harvest, and showed rates of root depth penetration from 0.2 to 1.5 mm day)1 C)1. Shallow placement of soil Ninorg resulted in greater N uptake in the shallow-rooted leek and potato. Deep placement of soil Ninorg resulted in greater rates of root depth penetration in the deep-rooted Chinese cabbage, summer squash and white cabbage, which increased their depth by 0.2–0.4 m. The root frequency was decreased in shallow soil layers (white cabbage) and increased in deep soil layers (Chinese cabbage, summer squash and white cabbage). The influence of vertical distribution of soil Ninorg on root distribution and capacity for depletion of soil Ninorg was much less than the effect of inherent differences between species. Thus, knowledge about differences in root growth between species should be used when designing crop rotations with high N use efficiency
Controlled traffic farming increases root growth, crop and soil nitrogen in vegetable cropping systems
Results from field trials on sandy and sandy loam of controlled traffic farmin
Influence of Pure Dephasing on Emission Spectra from Single Photon Sources
We investigate the light-matter interaction of a quantum dot with the
electromagnetic field in a lossy microcavity and calculate emission spectra for
non-zero detuning and dephasing. It is found that dephasing shifts the
intensity of the emission peaks for non-zero detuning. We investigate the
characteristics of this intensity shifting effect and offer it as an
explanation for the non-vanishing emission peaks at the cavity frequency found
in recent experimental work.Comment: Published version, minor change
Major differences in rates of occupational accidents between different nationalities of seafarers
Objectives. Earlier studies and statistics have shown that merchant seafarers from the South
East Asia had considerable lower accident rates when compared with seafarers from
Western Europe. The purposes of the study were to investigate whether the earlier observations were sustained if further sources on occurrence of accidents were used and
to identify specific causes of excess accident rates among certain nationalities.
Methods. Occupational accidents aboard Danish merchant ships during one year were
identified from four different sources. These included accidents reported to the maritime
authorities, accidents reported to a mutual insurance company, files on medical costs
reimbursed by the government and finally, accidents in which there has been contact to
the radio medical service. Time at risk aboard was obtained from a register on all
employment periods aboard merchant ships.
Results. A total of 943 accidents causing personal injury to a seafarer directly caused by
work aboard were identified. Among these accidents, 499 had taken place aboard cargo
ships in international trade. Only these were used in the detailed analysis. The accident
rate for all identified accidents aboard cargo ships were 84 accidents per 1,000 years
aboard. The crude incidence rate ratio (IRR) for East European seafarers was 0.88 and
for South East Asians 0.38 using West European seafarers as reference. In a Poisson
regression analysis, the IRR for South East Asians was 0.29 (0.22-0.38). In an analysis
including only more serious accidents, IRR for South East Asians rose to 0.36 (0.26-
0.48).
Discussion. This study indicates that seafarers from South East Asia, mainly the Philippines,
may have a genuine lower risk of occupational accidents in comparison with seafarers
from Western and Eastern Europe. Differences in approach to safety and risk taking
between South East Asian and European seafarers should be identified and positives
attitudes included in accident preventing programmes.
Main messages. Seafarers from South East Asia, mainly the Philippines, seem to have a genuine
lower risk of occupational accidents in comparison with seafarers from Western and
Eastern Europe.
Policy implications. Differences in approach to safety and risk taking between South East Asian and
European seafarers should be identified and positives attitudes included in accident
preventing programmes
An extremely high velocity molecular jet surrounded by an ionized cavity in the protostellar source Serpens SMM1
We report ALMA observations of a one-sided, high-velocity (80 km
s) CO() jet powered by the intermediate-mass
protostellar source Serpens SMM1-a. The highly collimated molecular jet is
flanked at the base by a wide-angle cavity; the walls of the cavity can be seen
in both 4 cm free-free emission detected by the VLA and 1.3 mm thermal dust
emission detected by ALMA. This is the first time that ionization of an outflow
cavity has been directly detected via free-free emission in a very young,
embedded Class 0 protostellar source that is still powering a molecular jet.
The cavity walls are ionized either by UV photons escaping from the accreting
protostellar source, or by the precessing molecular jet impacting the walls.
These observations suggest that ionized outflow cavities may be common in Class
0 protostellar sources, shedding further light on the radiation, outflow, and
jet environments in the youngest, most embedded forming stars.Comment: 6 pages, 4 figures, accepted for publication in the Astrophysical
Journal Letter
CTMC calculations of electron capture and ionization in collisions of multiply charged ions with elliptical Rydberg atoms
We have performed classical trajectory Monte Carlo (CTMC) studies of electron
capture and ionization in multiply charged (Q=8) ion-Rydberg atom collisions at
intermediate impact velocities. Impact parallel to the minor and to the major
axis, respectively, of the initial Kepler electron ellipse has been
investigated. The important role of the initial electron momentum distribution
found for singly charged ion impact is strongly disminished for higher
projectile charge, while the initial spatial distribution remains important for
all values of Q studied.Comment: 3 pages, 5 figure
Imaging Oxygen Distribution in Marine Sediments. The Importance of Bioturbation and Sediment Heterogeneity
The influence of sediment oxygen heterogeneity, due to bioturbation, on diffusive oxygen flux was investigated. Laboratory experiments were carried out with 3 macrobenthic species presenting different bioturbation behaviour patterns:the polychaetes Nereis diversicolor and Nereis virens, both constructing ventilated galleries in the sediment column, and the gastropod Cyclope neritea, a burrowing species which does not build any structure. Oxygen two-dimensional distribution in sediments was quantified by means of the optical planar optode technique. Diffusive oxygen fluxes (mean and integrated) and a variability index were calculated on the captured oxygen images. All species increased sediment oxygen heterogeneity compared to the controls without animals. This was particularly noticeable with the polychaetes because of the construction of more or less complex burrows. Integrated diffusive oxygen flux increased with oxygen heterogeneity due to the production of interface available for solute exchanges between overlying water and sediments. This work shows that sediment heterogeneity is an important feature of the control of oxygen exchanges at the sediment–water interface
Decreased plasma concentration of nitric oxide metabolites in dogs with untreated mitral regurgitation
Water and methanol in low-mass protostellar outflows: gas-phase synthesis, ice sputtering and destruction
Water in outflows from protostars originates either as a result of gas-phase synthesis from atomic oxygen at T ≳ 200 K, or from sputtered ice mantles containing water ice. We aim to quantify the contribution of the two mechanisms that lead to water in outflows, by comparing observations of gas-phase water to methanol (a grain surface product) towards three low-mass protostars in NGC 1333. In doing so, we also quantify the amount of methanol destroyed in outflows. To do this, we make use of James Clerk Maxwell Telescope and Herschel-Heterodyne Instrument for the Far-Infrared data of H2O, CH3OH and CO emission lines and compare them to RADEX non-local thermodynamic equilibrium excitation simulations. We find up to one order of magnitude decrease in the column density ratio of CH3OH over H2O as the velocity increases in the line wings up to ∼15 km s−1. An independent decrease in X(CH3OH) with respect to CO of up to one order of magnitude is also found in these objects. We conclude that gas-phase formation of H2O must be active at high velocities (above 10 km s−1 relative to the source velocity) to re-form the water destroyed during sputtering. In addition, the transition from sputtered water at low velocities to form water at high velocities must be gradual. We place an upper limit of two orders of magnitude on the destruction of methanol by sputtering effects
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