1,779 research outputs found
Plant biomass nitrogen and effects on the risk of nitrate leaching of intercrops under organic farming in Eastern Austria
Data on the potential of intercrops to reduce soil nitrate contents, on their N accumulation and biological nitrogen fixation (BNF) are lacking for organic farming in the dry, pannonic region of Eastern Austria. The effect of legumes, non-legumes, and legumes + non-legumes used as intercrops on inorganic soil nitrogen, crop yield and biomass N, and BNF were tested in comparison to bare fallow. Non-legumes and legumes + non-legumes were more efficient than legumes in reducing inorganic soil N contents in autumn and nitrate contents in soil solution from the subsoil in winter. This reduction in inorganic soil N did not last until March of the following year due to an N mineralisation from the mulch. The legume + non-legume mixture contained a larger amount of crop N than both legumes and non-legumes. This was due to the combined effect of soil-N uptake by the non-legumes and BNF by the legumes in the mixture
Auswirkungen acker- und pflanzenbaulicher Massnahmen auf die arbuskuläre Mykorrhiza im Ökologischen Landbau
Der oekologische Landbau laesst aufgrund der systemeigenen spezifischen Fruchtfolgen, Duengemassnahmen und Bodenbearbeitung positive Auswirkungen auf die Entwicklung d arbuskulaeren Mykorrhiza und die Kolonisierung der Kulturpflanzen erwarten. Diese positiven Auswirkungen wurden in vergleichenden Untersuchungen ueber die Auswirkungen einzelner Kulturmassnahmen auf die arbuskulaere Mykorrhiza in konventionell und nachhaltig bewirtschafteten Standorten nachgewiesen. Wenn in der Zukunft eine Verringerung des Eintrages an Agrochemikalien in die Kulturlandschaften angestrebt wird, muss der Bedeutung der arbuskulaeren Mykorrhiza eine hoehere Aufmerksamkeit gewidmet werden. Um die positiven Auswirkungen der arbuskulaeren Mykorrhiza in landwirtschaftlichen Produktionssystemen optimal zu nutzen, ist die Verwendung von geeigneten Duengemitteln in adaequater Menge, ein groesstmoeglicher Verzicht auf einen Pestizideinsatz und eine entsprechende Fruchtfolgegestaltung mit einem Minimum an Bodenbearbeitung und der Vermeidung von Schwarzbrache sicherzustellen. Ziel dieses Projektes ist die Optimierung der Lebensbedingungen und Leistungen der arbuskulaeren Mykorrhiza im oekologischen Landbau zur Optimierung des Pflanzenwachstums und der Sicherung der Ertraege. Dabei wird im Rahmen von Feldversuchen der Einfluss von acker- und pflanzenbaulichen Massnahmen (Fruchtfolge, Duengung, Bodenbearbeitung) sowie der Dauer der oekologischen Bewirtschaftung auf die arbuskulaere Mykorrhiza untersucht
Evaluation of a Liquid Amine System for Spacecraft Carbon Dioxide Control
The analytical and experimental studies are described which were directed toward the acquisition of basic information on utilizing a liquid amine sorbent for in use in a CO2 removal system for manned spacecraft. Liquid amine systems are successfully used on submarines for control of CO2 generated by the crew, but liquid amines were not previously considered for spacecraft applications due to lack of development of satisfactory rotary phase separators. Developments in this area now make consideration of liquid amines practical for spacecraft system CO2 removal. The following major tasks were performed to evaluate liquid amine systems for spacecraft: (1) characterization, through testing, of the basic physical and thermodynamic properties of the amine solution; (2) determination of the dynamic characteristics of a cocurrent flow absorber; and (3) evaluation, synthesis, and selection of a liquid amine system concept oriented toward low power requirements. A low weight, low power system concept was developed. Numerical and graphical data are accompanied by pertinent observations
Fermi edge singularity in a non-equilibrium system
We report exact results for the Fermi Edge Singularity in the absorption
spectrum of an out-of-equilibrium tunnel junction. We consider two metals with
chemical potential difference V separated by a tunneling barrier containing a
defect, which exists in one of two states. When it is in its excited state,
tunneling through the otherwise impermeable barrier is possible. We find that
the lineshape not only depends on the total scattering phase shift as in the
equilibrium case but also on the difference in the phase of the reflection
amplitudes on the two sides of the barrier. The out-of-equilibrium spectrum
extends below the original threshold as energy can be provided by the power
source driving current across the barrier. Our results have a surprisingly
simple interpretation in terms of known results for the equilibrium case but
with (in general complex-valued) combinations of elements of the scattering
matrix replacing the equilibrium phase shifts.Comment: 4 page
Imaging density disturbances in water with 41.3 attosecond time resolution
We show that the momentum flexibility of inelastic x-ray scattering may be
exploited to invert its loss function, alowing real time imaging of density
disturbances in a medium. We show the disturbance arising from a point source
in liquid water, with a resolution of 41.3 attoseconds (
sec) and 1.27 ( cm). This result is used to
determine the structure of the electron cloud around a photoexcited molecule in
solution, as well as the wake generated in water by a 9 MeV gold ion. We draw
an analogy with pump-probe techniques and suggest that energy-loss scattering
may be applied more generally to the study of attosecond phenomena.Comment: 4 pages, 4 color figure
Density of States in the Magnetic Ground State of the Friedel-Anderson Impurity
By applying a magnetic field whose Zeeman energy exceeds the Kondo energy by
an order of magnitude the ground state of the Friedel-Anderson impurity is a
magnetic state. In recent years the author introduced the Friedel Artificially
Inserted Resonance (FAIR) method to investigate impurity properties. Within
this FAIR approach the magnetic ground state is derived. Its full excitation
spectrum and the composition of the excitations is calculated and numerically
evaluated. From the excitation spectrum the electron density of states is
calculated. Majority and minority d-resonances are obtained. The width of the
resonances is about twice as wide as the mean field theory predicts. This
broadening is due to the fact that any change of the occupation of the d-state
in one spin band changes the eigenstates in the opposite spin band and causes
transitions in both spin bands. This broadening reduces the height of the
resonance curve and therefore the density of states by a factor of two. This
yields an intuitive understanding for a previous result of the FAIR approach
that the critical value of the Coulomb interaction for the formation of a
magnetic moment is twice as large as the mean field theory predicts
Technological quality of organic wheat in Europe
The demand for high quality organic bread wheat is increasing. The quality level of organic wheat harvested in EU is mainly dependant on variety, environmental conditions and agronomic practices. In some countries, protein content and composition, influencing technological value, are equivalent to those produced under conventional practices. Beside agronomical techniques, technological processes can help to maintain a good quality. Pre-treatments before milling such as debranning were found to be efficient in reducing DON contamination. The project highlighted the necessity to redefine the methods to assess the quality of organic wheat
Disclinations, dislocations and continuous defects: a reappraisal
Disclinations, first observed in mesomorphic phases, are relevant to a number
of ill-ordered condensed matter media, with continuous symmetries or frustrated
order. They also appear in polycrystals at the edges of grain boundaries. They
are of limited interest in solid single crystals, where, owing to their large
elastic stresses, they mostly appear in close pairs of opposite signs. The
relaxation mechanisms associated with a disclination in its creation, motion,
change of shape, involve an interplay with continuous or quantized dislocations
and/or continuous disclinations. These are attached to the disclinations or are
akin to Nye's dislocation densities, well suited here. The notion of 'extended
Volterra process' takes these relaxation processes into account and covers
different situations where this interplay takes place. These concepts are
illustrated by applications in amorphous solids, mesomorphic phases and
frustrated media in their curved habit space. The powerful topological theory
of line defects only considers defects stable against relaxation processes
compatible with the structure considered. It can be seen as a simplified case
of the approach considered here, well suited for media of high plasticity
or/and complex structures. Topological stability cannot guarantee energetic
stability and sometimes cannot distinguish finer details of structure of
defects.Comment: 72 pages, 36 figure
Cusp energetic ions: A bow shock source
Recent interpretations of cusp energetic ions observed by the POLAR spacecraft have suggested a new energization process in the cusp [Chen et al., 1997; 1998]. Simultaneous enhancement of H+, He+2, and O\u3e+2 fluxes indicates that they are of solar wind origin. In the present study, we examine H+ and He+2 energy spectra from 20 eV to several 100 keV measured by the Hydra, Toroidal Imaging Mass-Angle Spectrograph (TIMAS), and Charge and Mass Magnetospheric Ion Composition Experiment (CAMMICE) on POLAR. The combined spectrum for each species is shown to be continuous with a thermal distribution below 10 keV/e and an energetic component above 20 keV/e. Energetic ions with comparable fluxes and a similar spectral shape are commonly observed downstream from the Earth\u27s quasi-parallel (Q∥) bow shock. In addition to the similarity in the ion spectra, electric and magnetic field noise and turbulence detected in the cusp by the Plasma Wave Instrument (PWI) and Magnetic Field Experiment (MFE) onboard POLAR are similar to the previously reported observations at the bow shock. The waves appear to be coincidental to the cusp energetic ions rather than causal. We suggest that these ions are not accelerated locally in the cusp. Rather, they are accelerated at the Q∥ bow shock and enter the cusp along open magnetic field lines connecting both regions
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