14,630 research outputs found
From Grain to Feed
Horse beans are used as an example of grain, which have potentials to substitute fish meal in fish feed. After several grinding and fractionation steps it was possible to obtain a protein-rich horse bean fraction with a yield of 19 %. This fraction contained 55.9 % protein. The high protein content together with the amino acid profile makes the fraction very suitable as a substitute to fish meal in fish feed. The protein-rich fraction was used as a successful additive in extruded fish pellets
Mortality rates of the Alpine Chamois : the influence of snow-meteorological factors
Especially for animals inhabiting alpine areas, winter environmental conditions can be limiting. Cold temperatures, hampered food availability and natural perils are just three of many potential threats that mountain ungulates face in winter. Understanding their sensitivity to climate variability is essential for game management. Here we focus on analyzing the influence of snow and weather conditions on the mortality pattern of Alpine chamois. Our mortality data are derived from a systematic assessment of 6,500 chamois that died of natural causes over the course of 13 years. We use population- and habitat-specific data on snow, climate and avalanche danger to identify the key environmental factors that essentially determine the spatio-temporal variations in chamois mortality. Initially, we show that most fatalities occurred in winter, with a peak around March, when typically snow depths were highest. Death causes related to poor general conditions were the major component of seasonal variations. As for the interannual variations in mortality, snow depth and avalanche risk best explained the occurrence of winters with increased numbers of fatalities. Finally, analyzing differences in mortality rates between populations, we identified sun-exposed winter habitats with little snow accumulation as favourable for alpine chamois
Many-body localization in a disordered quantum Ising chain
Many-body localization occurs in isolated quantum systems when Anderson
localization persists in the presence of finite interactions. Despite strong
evidence for the existence of a many-body localization transition a reliable
extraction of the critical disorder strength is difficult due to a large drift
with system size in the studied quantities. In this work we explore two
entanglement properties that are promising for the study of the manybody
localization transition: the variance of the half-chain entanglement entropy of
exact eigenstates and the long time change in entanglement after a local quench
from an exact eigenstate. We investigate these quantities in a disordered
quantum Ising chain and use them to estimate the critical disorder strength and
its energy dependence. In addition, we analyze a spin-glass transition at large
disorder strength and provide evidence for it being a separate transition. We
thereby give numerical support for a recently proposed phase diagram of
many-body localization with localization protected quantum order [Huse et al.
Phys. Rev. B 88, 014206 (2013)].Comment: 4+ pages + 1.5 pages appendix, 5 figure
Dicke-type phase transition in a multimode optomechanical system
We consider the "membrane in the middle" optomechanical model consisting of a
laser pumped cavity which is divided in two by a flexible membrane that is
partially transmissive to light and subject to radiation pressure. Steady state
solutions at the mean-field level reveal that there is a critical strength of
the light-membrane coupling above which there is a symmetry breaking
bifurcation where the membrane spontaneously acquires a displacement either to
the left or the right. This bifurcation bears many of the signatures of a
second order phase transition and we compare and contrast it with that found in
the Dicke model. In particular, by studying limiting cases and deriving
dynamical critical exponents using the fidelity susceptibility method, we argue
that the two models share very similar critical behaviour. For example, the
obtained critical exponents indicate that they fall within the same
universality class. Away from the critical regime we identify, however, some
discrepancies between the two models. Our results are discussed in terms of
experimentally relevant parameters and we evaluate the prospects for realizing
Dicke-type physics in these systems.Comment: 14 pages, 6 figure
Impurity in a bosonic Josephson junction: swallowtail loops, chaos, self-trapping and the poor man's Dicke model
We study a model describing identical bosonic atoms trapped in a
double-well potential together with a single impurity atom, comparing and
contrasting it throughout with the Dicke model. As the boson-impurity coupling
strength is varied, there is a symmetry-breaking pitchfork bifurcation which is
analogous to the quantum phase transition occurring in the Dicke model. Through
stability analysis around the bifurcation point, we show that the critical
value of the coupling strength has the same dependence on the parameters as the
critical coupling value in the Dicke model. We also show that, like the Dicke
model, the mean-field dynamics go from being regular to chaotic above the
bifurcation and macroscopic excitations of the bosons are observed. Overall,
the boson-impurity system behaves like a poor man's version of the Dicke model.Comment: 17 pages, 16 figure
Tailoring laser-generated plasmas for efficient nuclear excitation by electron capture
The optimal parameters for nuclear excitation by electron capture in plasma
environments generated by the interaction of ultra-strong optical lasers with
solid matter are investigated theoretically. As a case study we consider a 4.85
keV nuclear transition starting from the long-lived Mo isomer
that can lead to the release of the stored 2.4 MeV excitation energy. We find
that due to the complex plasma dynamics, the nuclear excitation rate and the
actual number of excited nuclei do not reach their maximum at the same laser
parameters. The nuclear excitation achievable with a high-power optical laser
is up to twelve and up to six orders of magnitude larger than the values
predicted for direct resonant and secondary plasma-mediated excitation at the
x-ray free electron laser, respectively. Our results show that the experimental
observation of the nuclear excitation of Mo and the subsequent
release of stored energy should be possible at laser facilities available
today.Comment: 6 pages, 3 figures, 1 table; minor modifications made; accepted for
publication in Physical Review Letter
Nuclear excitation by electron capture in optical-laser-generated plasmas
The process of nuclear excitation by electron capture in plasma environments
generated by the interaction of ultra-strong optical lasers with solid-state
samples is investigated theoretically. With the help of a plasma model we
perform a comprehensive study of the optimal parameters for most efficient
nuclear excitation and determine the corresponding laser setup requirements. We
discern between the low-density plasma regime, modeled by scaling laws, and the
high-density regime, for which we perform particle-in-cell calculations. As
nuclear transition case study we consider the 4.85 keV nuclear excitation
starting from the long-lived Mo isomer. Our results show that
the optimal plasma and laser parameters are sensitive to the chosen observable
and that measurable rates of nuclear excitation and isomer depletion of
Mo should be already achievable at laser facilities existing
today.Comment: 19 pages, 16 figures; minor modifications made; accepted for
publication in Physical Review
- …