357 research outputs found
Duckweed production on diluted chicken manure
The aim of this study was to test chicken manure as duckweed (Lemna minor) fertiliser. Duckweed was grown using three different concentrations (low, medium and high; dilution factors 1:16, 1:12 and 1:8, respectively) of previously solubilised chicken manure. Subsequently, duckweed was evaluated for its fresh and dry biomass production, protein content and protein production capacity. Ammonium-nitrogen (NH4-N) concentrations increased in all substrates during an experimental week, with the increase being steeper in the treatments with higher chicken manure concentrations. However, duckweed populations were unable to fully utilise all the provided nitrogen. As the concentration of chicken manure increased, growth and protein production decreased. Adding the highest concentration of chicken manure (1:8 dilution) led to nearly complete die-off of the duckweed population. The low concentrated (1:16 dilution) chicken manure fertilisation resulted in acceptable growth (1.85 g dry matter (DM) per m2 and day) and high crude protein content (42.8% DM). The medium concentration (1:12 dilution) of chicken manure still stimulated growth, although it was significantly lower compared to duckweed grown on the low concentrated poultry manure and declined towards the end of the experiment (0.88 g DM per m2 and day). The biomass from this treatment also contained slightly lower protein content (40.6% DM). Duckweed cultivated using low and medium chicken manure concentrations produced an average of 0.79 and 0.36 g protein per m2 and day, respectively. Although solubilised chicken manure can serve as a potential fertiliser for duckweed, balancing the amount of chicken manure necessary to obtain a target NH4-N concentration when compared to cow or pig slurries is challenging
Technical design and commissioning of the KATRIN large-volume air coil system
The KATRIN experiment is a next-generation direct neutrino mass experiment
with a sensitivity of 0.2 eV (90% C.L.) to the effective mass of the electron
neutrino. It measures the tritium -decay spectrum close to its endpoint
with a spectrometer based on the MAC-E filter technique. The -decay
electrons are guided by a magnetic field that operates in the mT range in the
central spectrometer volume; it is fine-tuned by a large-volume air coil system
surrounding the spectrometer vessel. The purpose of the system is to provide
optimal transmission properties for signal electrons and to achieve efficient
magnetic shielding against background. In this paper we describe the technical
design of the air coil system, including its mechanical and electrical
properties. We outline the importance of its versatile operation modes in
background investigation and suppression techniques. We compare magnetic field
measurements in the inner spectrometer volume during system commissioning with
corresponding simulations, which allows to verify the system's functionality in
fine-tuning the magnetic field configuration. This is of major importance for a
successful neutrino mass measurement at KATRIN.Comment: 32 pages, 16 figure
Background due to stored electrons following nuclear decays in the KATRIN spectrometers and its impact on the neutrino mass sensitivity
The KATRIN experiment is designed to measure the absolute neutrino mass scale
with a sensitivity of 200 meV at 90% C.L. by high resolution tritium
beta-spectroscopy. A low background level of 10 mHz at the beta-decay endpoint
is required in order to achieve the design sensitivity. In this paper we
discuss a novel background source arising from magnetically trapped keV
electrons in electrostatic retarding spectrometers. The main sources of these
electrons are alpha-decays of the radon isotopes (219,220)Rn as well as
beta-decays of tritium in the volume of the spectrometers. We characterize the
expected background signal by extensive MC simulations and investigate the
impact on the KATRIN neutrino mass sensitivity. From these results we refine
design parameters for the spectrometer vacuum system and propose active
background reduction methods to meet the stringent design limits for the
overall background rate
Utilization of duckweed as fish meal replacement in common carp (Cyprinus carpio)
Duckweed, the family Lemnaceae, comprises a group of around 40 different aquatic flowering plant species. They can grow very fast, producing higher biomasses compared to terrestrial plants (up to 79 t DM ha-1 a-1, Leng et al. 1995). Furthermore, they are very efficient in uptake of nitrogen and phosphorous and are producing protein of high quality (Stadtlander et al. 2019). Protein contents usually range between 25 to 35% of DM (dry matter) but have been reported to be as high as 45% of DM. Duckweed (Spirodela polyrhiza) has been successfully grown on diluted cow slurry and been fed to rainbow trout fry (Stadtlander et al. 2019). Common carp (Cyprinus carpio) is among the most important cultured fish species in the world, with a production of 4.13 mio t in 2017, and cyprinids (carp-like fish) in general contribute around 50% of global aquaculture fish production. In this study, we tested two different duckweed (S. polyrhiza) meals, one dried (DWD) and one fermented (DWF), in three different concentrations in the diet of carp fry and compared results to a duckweed free control (C)
Stochastic Heating by ECR as a Novel Means of Background Reduction in the KATRIN Spectrometers
The primary objective of the KATRIN experiment is to probe the absolute
neutrino mass scale with a sensitivity of 200 meV (90% C.L.) by precision
spectroscopy of tritium beta-decay. To achieve this, a low background of the
order of 10^(-2) cps in the region of the tritium beta-decay endpoint is
required. Measurements with an electrostatic retarding spectrometer have
revealed that electrons, arising from nuclear decays in the volume of the
spectrometer, are stored over long time periods and thereby act as a major
source of background exceeding this limit. In this paper we present a novel
active background reduction method based on stochastic heating of stored
electrons by the well-known process of electron cyclotron resonance (ECR). A
successful proof-of-principle of the ECR technique was demonstrated in test
measurements at the KATRIN pre-spectrometer, yielding a large reduction of the
background rate. In addition, we have carried out extensive Monte Carlo
simulations to reveal the potential of the ECR technique to remove all trapped
electrons within negligible loss of measurement time in the main spectrometer.
This would allow the KATRIN experiment attaining its full physics potential
Feasibility studies of the time-like proton electromagnetic form factor measurements with PANDA at FAIR
The possibility of measuring the proton electromagnetic form factors in the
time-like region at FAIR with the \PANDA detector is discussed. Detailed
simulations on signal efficiency for the annihilation of into a
lepton pair as well as for the most important background channels have been
performed. It is shown that precision measurements of the differential cross
section of the reaction can be obtained in a wide
angular and kinematical range. The individual determination of the moduli of
the electric and magnetic proton form factors will be possible up to a value of
momentum transfer squared of (GeV/c). The total cross section will be measured up to (GeV/c).
The results obtained from simulated events are compared to the existing data.
Sensitivity to the two photons exchange mechanism is also investigated.Comment: 12 pages, 4 tables, 8 figures Revised, added details on simulations,
4 tables, 9 figure
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