212 research outputs found
Wigner function negativity and contextuality in quantum computation on rebits
We describe a universal scheme of quantum computation by state injection on
rebits (states with real density matrices). For this scheme, we establish
contextuality and Wigner function negativity as computational resources,
extending results of [M. Howard et al., Nature 510, 351--355 (2014)] to
two-level systems. For this purpose, we define a Wigner function suited to
systems of rebits, and prove a corresponding discrete Hudson's theorem. We
introduce contextuality witnesses for rebit states, and discuss the
compatibility of our result with state-independent contextuality.Comment: 18 + 4 page
Rouille brune du blé, un modèle pour évaluer les risques
peer reviewedL’article présente un outil de prévision de la rouille brune au G.-D. de Luxembourg. De 2000 à 2003, cette maladie apparaissait à la fin de l’épiaison, mais depuis 2003, elle apparaît de plus en plus tôt (GS45 stade gonflement). Cette apparition précoce est probablement liée à des températures printanières supérieures par rapport à la normale 1971-2000. Une analyse des données météorologiques nocturnes et des données d’observation de la maladie sur quatre sites expérimentaux (Everlange, Christnach, Burmerange et Reuler) entre 2000 et 2003 a révélé une forte corrélation positive entre la prédiction de la maladie basée sur le critère d’au moins 12 heures consécutives avec une température comprise entre 8 et 16°C et une humidité supérieure à 60% et la maladie observée sur la F1 (R = 0.93 ; P < 0.05) et sur la F2 (R = 0.87 ; P < 0.05). Les sorties de ce modèle qui a été développé sur base d’une approche stochastique ont été utilisées dans les bulletins d’avertissements diffusés conjointement par le Centre de Recherche Public – Gabriel Lippmann et l’Université de Liège-Campus d’Arlon à partir de 2004. La mise en application de ce modèle a montré un taux de réussite oscillant entre 80 et 85% pour la simulation de la rouille brune au G.-D. de Luxembourg.
L’effort se poursuit pour spatialiser les sorties du modèle sur tout le territoire luxembourgeois et faciliter son utilisation par tous les vulgarisateurs agricoles
Electronic nose Technology for reactor state and biogas quality assessment in anaerobic digestion
ECOBIOGA
First results from the Canada-France High-z Quasar Survey: Constraints on the z=6 quasar luminosity function and the quasar contribution to reionization
We present preliminary results of a new quasar survey being undertaken with
multi-colour optical imaging from the Canada-France-Hawaii Telescope. The
current data consists of 3.83 sq. deg. of imaging in the i' and z' filters to a
10 sigma limit of z'<23.35. Near-infrared photometry of 24 candidate 5.7<z<6.4
quasars confirms them all to be low mass stars including two T dwarfs and four
or five L dwarfs. Photometric estimates of the spectral type of the two T
dwarfs are T3 and T6. We use the lack of high-redshift quasars in this survey
volume to constrain the z=6 quasar luminosity function. For reasonable values
of the break absolute magnitude M*_1450 and faint-end slope alpha, we determine
that the bright-end slope beta>-3.2 at 95% confidence. We find that the
comoving space-density of quasars brighter than M_1450=-23.5 declines by a
factor >25 from z=2 to z=6, mirroring the decline observed for high-luminosity
quasars. We consider the contribution of the quasar population to the ionizing
photon density at z=6 and the implications for reionization. We show that the
current constraints on the quasar population give an ionizing photon density
<<30% that of the star-forming galaxy population. We conclude that active
galactic nuclei make a negligible contribution to the reionization of hydrogen
at z~6.Comment: 9 pages, 6 figures, ApJ, in pres
Modeling the Main Fungal Diseases of Winter Wheat: Constraints and Possible Solutions
The first step in the formulation of disease management strategy for any cropping system is to identify the most important risk factors. This is facilitated by basic epidemiological studies of pathogen life cycles, and an understanding of the way in which weather and cropping factors affect the quantity of initial inoculum and the rate at which the epidemic develops. Weather conditions are important factors in the development of fungal diseases in winter wheat, and constitute the main inputs of the decision support systems used to forecast disease and thus determine the timing for efficacious fungicide application. Crop protection often relies on preventive fungicide applications. Considering the slim cost−revenue ratio for winter wheat and the negative environmental impacts of fungicide overuse, necessity for applying only sprays that are critical for disease control becomes paramount for a sustainable and environmentally friendly crop production. Thus, fungicides should only be applied at critical stages for disease development, and only after the pathogen has been correctly identified. This chapter provides an overview of different weather-based disease models developed for assessing the real-time risk of epidemic development of the major fungal diseases (Septoria leaf blotch, leaf rusts and Fusarium head blight) of winter wheat in Luxembourg
Gas sensor array applied to the monitoring of biogas process
There is a lack of simple online monitoring system to control the performances of biogas reactors. The electronic nose technology appears to be an adapted device to deliver fast information about process disturbances in anaerobic reactors as it is adequate for online monitoring. In this study, twelve anaerobic mini-reactors were supervised with a home-made e-nose to observe process reaction in relation to organic overloads events. Usually, to avoid overload situations, on farms reactors are not fed at maximum load capacity, resulting in non optimized biogas production. The objective of the experiment was to determine if the gas sensors array feature can be related to the process state and if an indirect state variable, giving early warning of process faults, can be derived from the e-nose response.
The results demonstrated that focusing on gas phase of anaerobic reactors with a simple device composed of an array of non-specific gas sensors helped in the warning of disorders of the anaerobic digestion process. Mahalanobis distance from a cautious feeding group (group of observations indicating a good process) can be used as an indirect variable to evaluate the intensity of the state disorder. Euclidean distance has been also calculated but it was less informative than the Mahalanobis distance.Optibioga
Assessing the Interplay between Weather and Septoria Leaf Blotch Severity on Lower Leaves on the Disease Risk on Upper Leaves in Winter Wheat
peer reviewedSeptoria leaf blotch (SLB) is among the most damaging foliar diseases of wheat worldwide. In this study, data for seven cropping seasons (2003–2009) at four representative wheat-growing sites in the Grand-Duchy of Luxembourg (GDL) were used to assess SLB risk on the three upper leaves (L3 to L1, L1 being the flag leaf) based on the combination of conducive weather conditions, simulated potential daily infection events by Zymoseptoria tritici, and SLB severity on lower leaves between stem elongation and mid-flowering. Results indicated that the variability in SLB severity on L3 to L1 at soft dough was significantly (p < 0.05) influenced by the disease severity on the lower leaf L5 at L3 emergence and the sum of daily mean air temperature between stem elongation and mid-flowering. Moreover, analyzing the predictive power of these variables through multiple linear regression indicated that the disease severity on L5 at L3 emergence and mild weather conditions between stem elongation and mid-flowering critically influenced the progress of SLB later in the season. Such results can help fine tune weather-based SLB risk models to guide optimal timing of fungicide application in winter wheat fields and ensure economic and ecological benefits
Spatial heterogeneity of leaf wetness duration in winter wheat canopy and its influence on plant disease epidemiology
peer reviewedLeaf wetness duration (LWD) is an important factor influencing the occurrence of plant disease
epidemiology. Despite considerable efforts to determine LWD, little attention has been given to
study its variability within the canopy. The objective of this study was to evaluate its
spatiotemporal variability in wheat fields in a heterogeneous landscape. The spatiotemporal
variability of LWD was evaluated in a site close to Arlon (Belgium) during the period May to July
2006 and 2007. LWD measurements were made using a set of flat plate sensors deployed at
five different distances from a 18 m high hedge (5, 10, 20, 50, 100 m). Each set of two
sensors was placed horizontally close the flag leaf. In addition, we collected the amount of
dew water that deposited on rigid epoxy plates placed next to each sensors. Experimental
results showed that LWD measurements revealed substantial heterogeneity among sensor
positions. LWD is longer for sensors closer to the hedge mainly because of its shadowing
effect. 3 to 4 hours of difference was observed between sensors located at 5 m and those
located at 100 m, and besides, a significant quantitative difference (p < 0.0001) of dew
deposit was observed between area beside hedge and those placed at 100 m. In summary, this
study provides new information on how wetness is distributed on wheat leaves according to
the distance from a hedge. This leads to local microclimate conditions that will contribute to
the disease spatial heterogeneity
- …