AdS/Ricci-flat correspondence

We present a comprehensive analysis of the AdS/Ricci-flat correspondence, a map between a class of asymptotically locally AdS spacetimes and a class of Ricci-flat spacetimes. We provide a detailed derivation of the map, discuss a number of extensions and apply it to a number of important examples, such as AdS on a torus, AdS black branes and fluids/gravity metrics. In particular, the correspondence links the hydrodynamic regime of asymptotically flat black $p$-branes or the Rindler fluid with that of AdS. It implies that this class of Ricci-flat spacetimes inherits from AdS a generalized conformal symmetry and has a holographic structure. We initiate the discussion of holography by analyzing how the map acts on boundary conditions and holographic 2-point functions.Comment: v3: Minor edits, references added, matches published versio

Hands-free Electric Skateboard

An electric skateboard functions as a skateboard propelled by electric motors. It is usually controlled with a handheld controller. This project describes an electric skateboard controlled via weight distribution. To accelerate, the rider leans forward, and to decelerate, the rider leans backward. It can travel 17 miles per hour and has regenerative braking to recharge the battery

Contribution à l'évaluation écotoxicologique du Tébuthiuron - un herbicide de la classe des urées substituées

Une étude écotoxicologique a été menée à l'égard du Tébuthiuron (TB), un phytocide homologué inhibant la croissance de végétation nuisible, afin de mieux cerner son impact sur le milieu aquatique susceptible d'être affecté par des épandages terrestres. La toxicité du TB a été évaluée en réalisant des bioessais à trois paliers écologiques, soit avec la truite arc-en-ciel (Salmo gairdneri), avec l'algue Selenaslrum capricornutum et avec la bactérie (Photobacterium phosphoreum) du système Microtox®. Parmi ces trois indicateurs, les algues se sont montrées les plus sensibles (C150 = 0,08 mg • L-1), suivies des truites (CL50 = 115 mg • L-1) et enfin, des bactéries du système Microtoxe (C150 - 328 mg • L-1). Des résidus maximaux variant de 0,091 à 0,18 mg • L-1 rapportés pour le TB en milieu aquatique, suite à des applications expérimentales, laissent donc croire que seules les algues pourraient étre victimes d'une agression marquée. D'autre part, les essais réalisés avec le SOS Chromotest ont démontré que le TB était faiblement génotoxique sans activation métabolique. En revanche, des algues exposées à 1 mg • L-1 de TB durant 4 heures n'ont pu ni (dés)actlver ni bioaccumuier l'herbicide. En général, notre enquéte corrobore certaines données générées pour fins d'homologation de ce produit, lesquelles concluaient en faveur de son innocuité relative à l'égard de l'environnement aquatique. Les effets chroniques que pourrait avoir une longue exposition de faibles concentrations de TB sur certains paliers écologiques devraient cependant faire l'objet d'lnvestigations futures.A wide array of chemical products are commonly used to inhibit the growth of a diversity of undesirable vegetation types for numerous purposes. In forestry applications, herbicides can improve ranges, contribute to sylviculture and facilitate rights-of-way management, for example. Among congeners of the substituted urea class herbicides, Tebuthiuron (TB) has proven efficient for such activities. Since its commercial appearance in 1974, this broad-spectrum weed killer was employed to control a variety of herbaceous and woody plants. When applied on soil before or during the onset of plant emergence, TB irreversibly affects photosynthesis after being absorbed by roots and translocated to its target sites. Prior to its registration as a herbicide, TB had undergone extensive (eco)toxicological testing which had generally indicated low potential for environmental concern, with regards to terrestrial and avian fauna. Although TB is generally purported to be unproblematic towards fish, the overall impact of substituted urea class herbicides is still not fully documented, as far as various members of the aquatic community are concerned. The experimental results presented herein - specifically on TB - contribute both confirmatory as well as some new information in this respect.In our study, TB toxicity was investigated at three ecological levels by undertaking acute bioassays with rainbow trout (Salmo gairdeneri), algae (Selenastrum capricornutum) and bacteria (Photobacterium phosphoreum). Among these bio-indicators, algae proved to be the most sensitive (EC50 = 0.08 mg • L-1), followed by rainbow trout (LC50 = 115 mg • L-1) and bacteria (EC50 = 328 mg • L-1). Since maximum TB residues lying between 0.091 and 0.18 mg • L-1 have been reported for aquatic systems following experimental terrestrial applications, our toxicity results suggest that only algae could be adversely affected following acute exposure to the herbicide.Additional tests performed with the SOS Chromotest, a bacterial colorimetric assay for detecting DNA-damaging agents, first showed that TB is weakly genotoxic without metabolic activation. Since recent genotoxicity studios have revealed that vegetal systems can either detoxify, activate or uptake specific chemicals, we then explored this possibility by exposing S. capricornutum (106 cells • mL-1) to 1 mg • L-1 of TB for 4 h. Results of this acute exposure indicated an absence of positive (detoxication) or negative (activation, accumulation) phytoplanktonic interactions. Indeed, the genotoxic characteristics of TB, before and after algal exposure, were unaltered, as demonstrated by SOS Chromotest assays. In this same experiment, a similar assay on TB-exposed algal cells (i.e. SOS Chromotest on an algal cell solvent extract) detected no genotoxic activity.In conclusion, our study corroborates existing data generated for TB registration purposes and essentially supports the notion that this chemical is relatively harmless towards the aquatic environment under normal use conditions. Nevertheless, an important caveat remains concerning chronic affects on specific organisms, which could result from long term exposure to low concentrations of TB. Since such potential effects have not yet been adequately addressed, further studios are warranted in this area

Optimized Drug Distribution for Pharmacies of the National Order of Pharmacists in DR Congo using a Multi-Agent Engineering Approach

This paper focuses on a Multi-Agent Oriented Engineering for the problem of registration of pharmacists in the National Order of Pharmacists NOP and the regulation of the sale of pharmaceutical products in a distributed environment The behavior of a pharmacist in the practice of pharmacy is characterized by interactions with the Provincial Council of the Order of Pharmacists PCOP of his jurisdiction where he obtains an authorization to practice pharmacy This authorization is accompanied by the ethical rules to be observed in order to expose medicines on the market The activities of each pharmacist are continuously subject to quality control and pharmaceutical vigilance to protect the health of the population In this paper we focus on the design of a Multi-Agent System MAS in order to help the PCOP to control the pharmaceutical activity on the one hand and the pharmacists to sell their drugs safely on the other han

Influence of Plasmopara viticola on gas exchange parameters on field-grown Vitis vinifera 'Merlot'

The impact of downy mildew (Plasmopara viticola) epidemic on main and lateral leaf assimilation capacity of Vitis vinifera 'Merlot' has been quantified, under field conditions during the ripening phase, by means of leaf gas exchange measurements. The aim was to describe the impact of different disease severity levels on the gas exchange rate of symptomless portions of main and lateral leaves and of the sporulating parts in comparison with healthy leaves. The measurements were carried out on plants normally treated and on plants where only the clusters were treated with a contact fungicide to prevent quantity yield losses. A drastic reduction in the photosynthetic rate was observed on the sporulating area of main and lateral leaf tissues. Stomatal and mesophyll conductance decreased and stomatal resistance increased, indicating the difficulty of CO2 diffusing through the stomata into the mesophyll to the site of carboxylation. Downy mildew affected more negatively the gas exchange parameters on the symptomless parts of a diseased lateral leaf than of a main leaf, indicating a greater susceptibility of lateral leaves. A decrease of stomatal conductance and, consequently, of the photosynthetic rate, transpiration and water use efficiency was observed already at low severity level with increments of the disease severity on the leaf. At the same time an increase of stomatal resistance on the symptomless area of a lateral leaf was measured. Visual assessment of the diseased leaf area didn’t reflect the actual part colonized by the pathogen and at least a portion of the leaf area determined as healthy has in fact a latent lesion. Therefore, the visual estimation of downy mildew infection may not give a good indication of the effect of the pathogen on host physiology. The results also emphasized the important role of downy mildew as a stress element for the plant during ripening phase, a source element for carbohydrate production.

Quantification of the influence of the downy mildew (Plasmopara viticola) epidemics on the compensatory capacities of Vitis vinifera 'Merlot' to limit the qualitative yield damage

A preview study on the analysis of the impact of downy mildew (Plasmopara viticola) epidemics on the plant growth and yield quality has shown no correlation between disease severity progress on the canopy and sugar accumulation in the berries from veraison until harvest, indicating the capacity of the vine to compensate a stress situation induced by the downy mildew damage on leaf canopy. In this study the compensation capacity of the plant was analysed during three years under field conditions comparing three different downy mildew control strategies: A = “Untreated canopy” (to prevent quantity losses, the clusters were treated once with a contact fungicide at the discovery of the first downy mildew sporulation); B = “Reduced fungicide schedule” (based on a first treatment at the appearance of the first symptoms, to avoid yield quantity losses followed by one or two additional fungicide applications during the early epidemic phase with the aim of delaying the epidemic). C = “Standard schedule” (schedule normally applied in the vineyard). The experimental plot was moved each year to avoid stress influence due to a repetition of the trials on the same place. The grapevine compensated for the carbohydrate requirements of the cluster by mobilizing the starch reserves stored in the woody parts. Roots were the most important site of carbohydrate accumulation used from the grapevine and the mobilisation was higher in treatment A followed by treatment B. This compensation did not completely exhaust the reserves of each woody part and lets suppose a hierarchical pattern of the mobilisation; first a mobilisation of the reserves stored in the roots, and secondly those from the trunk, cane and shoot. The downy mildew could be considered as a stress factor for the grapevine.

Quantitative effect of leaf damage caused by downy mildew (Plasmopara viticola) on growth and yield quality of grapevine 'Merlot' (Vitis vinifera)

The impact of downy mildew (Plasmopara viticola) epidemics on the plant growth and yield quality was analysed during three years under field conditions in order to show a relationship between disease severity on leaves and yield quality losses. Three different treatments were compared: A = “Untreated canopy” (to prevent quantity losses, the clusters were treated once with a contact fungicide at the discovery of the first downy mildew sporulation); B = “Reduced fungicide schedule” (based on a first treatment at the appearance of the first symptoms, to avoid yield quantity losses followed by one or two additional fungicide applications during the early epidemic phase with the aim of delaying the epidemic). C = “Standard schedule” (schedule normally applied in the vineyard). The experimental plot was moved each year to avoid stress influence due to a repetition of the trials on the same place. The epidemic progress in the treatment A has shown the same tendency during the three years with an increase starting from the beginning of the ripening phase. The disease severity was more important on the lateral than on the main leaves. During the three years of the study, the disease did not influence the amount of total healthy leaf area per plant until veraison. From this phenological stage until harvest, the healthy leaf area per plant decreased rapidly at the same time as the epidemic increased. The yield quantity was not affected indicating that a single fungicide application at the finding of the first sporulation was enough to preserve the crop production. Among the yield quality parameters, the sugar content has been negatively influenced by the downy mildew leaf damage. The difference was particularly evident between the treatments A and C with differences from 1.4 to 2.04 °Brix. Generally, treatment B didn’t differ from C. Sugar uptake in the berries begun to show a different dynamic between 7 and 14 days after the onset of ripening. No correlation between disease severity progress on the canopy and sugar accumulation in the berries from veraison until harvest was found, indicating the capacity of the vine to compensate a stress situation induced by the downy mildew damage on leaf canopy.

Response of 'Merlot' (Vitis vinifera) grapevine to defoliation caused by downy mildew (Plasmopara viticola) during the following growing season

The downy mildew (Plasmopara viticola) epidemics on leaf canopy during the ripening phase causes a stress situation for the grapevine. The plant compensates the carbohydrate request of the berries mobilising the carbohydrate reserves stored in the woody parts. In this fourth study the impact of the reserves reduction on the growth and fertility and the recovering capacity of the plant were analysed during two consecutive periods of two years (first year = stress; second year = recovering). Two treatments were compared: “Untreated canopy” (to prevent quantity losses, the clusters were treated once with a contact fungicide at the discovery of the first downy mildew sporulation) and “Standard schedule” (schedule normally applied in the vineyard). The impact of decreased reserve contents in the following growth season has negatively influenced only the shoot elongation and the potential crop yield quantity of the “Untreated canopy” treatment. Nevertheless, a single recovery year was enough to rebuild the reserve pool particularly in the roots, confirming the acclimation potential of the grapevine.

AdS/Ricci-flat correspondence and the Gregory-Laflamme instability

We show that for every asymptotically anti–de Sitter (AdS) solution compactified on a torus there is a corresponding Ricci-flat solution obtained by replacing the torus by a sphere, performing a Weyl rescaling of the metric and appropriately analytically continuing the dimension of the torus/sphere (as in generalized dimensional reduction). In particular, it maps Minkowski spacetime to AdS on a torus, the holographic stress energy tensor of AdS to the stress energy tensor due to a brane localized in the interior of spacetime and AdS black branes to (asymptotically flat) Schwarzschild black branes. Applying it to the known solutions describing the hydrodynamic regime in AdS/CFT, we derive the hydrodynamic stress tensor of asymptotically flat black branes to second order, which is constrained by the parent conformal symmetry. We compute the dispersion relation of the Gregory-Laflamme unstable modes through cubic order in the wave number, finding remarkable agreement with numerical data. In the case of no transverse sphere, AdS black branes are mapped to Rindler spacetime and the second-order transport coefficients of the fluid dual to Rindler spacetime are recovered