8,861 research outputs found
Life cycle assessment of Swiss organic farming systems
The impacts of organic and integrated farming systems in Switzerland on the environment have been assessed in a comprehensive study by the life cycle assessment method. This paper reports a comparison of the treatments of the DOC experiment. Organic farming showed clear ecological advantages particularly for eco- and human toxicity, resource use and biodiversity. These ecological advantages only partly apply to nutrient losses and are not always found for single products. Per kg of organic product, higher impacts were often found for global warming potential, ozone formation, eutrophication and acidification compared to integrated production. In the same crop rotation with the same amount of organic fertilisers there were no systematic differences in soil quality of organic compared with integrated production. Further improvement of the environmental performance of organic farming should focus on achieving higher yields of good quality – especially in potatoes and cereals - by using inputs more efficiently and minimising nitrogen losses
Alien Registration- Dubois, Joseph O. (Sanford, York County)
https://digitalmaine.com/alien_docs/2688/thumbnail.jp
Exact time dependent Hopf solitons in 3+1 dimensions
We construct an infinite number of exact time dependent soliton solutions,
carrying non-trivial Hopf topological charges, in a 3+1 dimensional Lorentz
invariant theory with target space S^2. The construction is based on an ansatz
which explores the invariance of the model under the conformal group SO(4,2)
and the infinite dimensional group of area preserving diffeomorphisms of S^2.
The model is a rare example of an integrable theory in four dimensions, and the
solitons may play a role in the low energy limit of gauge theories.Comment: 4 pages revtex, 2 eps figures, replaced with one reference adde
Relationship between clustering and algorithmic phase transitions in the random k-XORSAT model and its NP-complete extensions
We study the performances of stochastic heuristic search algorithms on
Uniquely Extendible Constraint Satisfaction Problems with random inputs. We
show that, for any heuristic preserving the Poissonian nature of the underlying
instance, the (heuristic-dependent) largest ratio of constraints per
variables for which a search algorithm is likely to find solutions is smaller
than the critical ratio above which solutions are clustered and
highly correlated. In addition we show that the clustering ratio can be reached
when the number k of variables per constraints goes to infinity by the
so-called Generalized Unit Clause heuristic.Comment: 15 pages, 4 figures, Proceedings of the International Workshop on
Statistical-Mechanical Informatics, September 16-19, 2007, Kyoto, Japan; some
imprecisions in the previous version have been correcte
Characterising QT interval prolongation in early clinical development: a case study with methadone
Recently, we have shown how pharmacokinetic-pharmacodynamic (PKPD) modelling can be used to assess the probability of QTc interval prolongation both in dogs and humans. A correlation between species has been identified for a drug-specific parameter, making it possible to prospectively evaluate non-clinical signals. Here, we illustrate how nonclinical data on methadone can be used to support the evaluation of prodromic drug effects in humans. ECG and drug concentration data from safety pharmacology study in dogs were analysed using nonlinear mixed effects modelling. The slope of the PKPD model describing the probability of QT interval prolongation was extrapolated from dogs to humans and subsequently combined with methadone pharmacokinetic data as input for clinical trial simulations. Concentration vs. time profiles were simulated for doses between 5 and 500 mg. Predicted peak concentrations in humans were then used as reference value to assess the probability of an increase in QTc interval of ≥ 5 and ≥10 ms. Point estimates for the slope in dogs suggested low probability of ≥10 ms prolongation in humans. However, an effect of approximately 5 ms increase is predicted when accounting for the 90% credible intervals the drug-specific parameter in dogs. In addition, our analysis show that understanding of interspecies differences in drug disposition is required to accurately predict the QT prolonging effects in humans. Extrapolation of the effects of parent compound may not be sufficient to describe the increase in QT interval observed after administration of methadone in humans. Assessment of the contribution of enantioselective metabolism and active metabolites is critical
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Multispectral Image Processing for Navigation Using Low Performance Computing
Space debris represents a growing threat for both current spacecraft and future launches. This is exceptionally alarming in the case of low Earth orbits, where chain impacts of existing debris generate even more fragments, increasing the probability of further collisions. The now defunct satellite Envisat represents one of the largest objects classified as space debris. The e.Deorbit mission will demonstrate active debris removal (ADR) technology to successfully decommission Envisat and other non-functional target spacecraft in orbit. Relative navigation solutions shall be achieved using image processing algorithms, which implies the detection and matching of two-dimensional regions of interest. In this work, multiple pattern recognition techniques are investigated for the detection and description of these features. This analysis of feature perception is achieved for the first time in the context of space non-cooperative rendezvous (NCRV) across two different modalities: the visible (0.39-0.70 µm) and the thermal infrared (8-14 µm). The assessed algorithms are implemented in a dedicated, space-appropriate hardware processor to benchmark their real-time capabilities
Yang-Mills gauge anomalies in the presence of gravity with torsion
The BRST transformations for the Yang-Mills gauge fields in the presence of
gravity with torsion are discussed by using the so-called Maurer-Cartan
horizontality conditions. With the help of an operator \d which allows to
decompose the exterior spacetime derivative as a BRST commutator we solve the
Wess-Zumino consistency condition corresponding to invariant Chern-Simons terms
and gauge anomalies.Comment: 24 pages, report REF. TUW 94-1
AMBER on the VLTI: data processing and calibration issues
We present here the current performances of the AMBER / VLTI instrument for
standard use and compare these with the offered modes of the instrument. We
show that the instrument is able to reach its specified precision only for
medium and high spectral resolution modes, differential observables and bright
objects. For absolute observables, the current achievable accuracy is strongly
limited by the vibrations of the Unit Telescopes, and also by the observing
procedure which does not take into account the night-long transfer function
monitoring. For low-resolution mode, the current limitation is more in the data
reduction side, since several effects negligible at medium spectral resolution
are not taken into account in the current pipeline. Finally, for faint objects
(SNR around 1 per spectral channel), electromagnetic interferences in the VLTI
interferometric laboratory with the detector electronics prevents currently to
get unbiased measurements. Ideas are under study to correct in the data
processing side this effect, but a hardware fix should be investigated
seriously since it limits seriously the effective limiting magnitude of the
instrument.Comment: 10 page
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