Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

Simple scoring system to predict in-hospital mortality after surgery for infective endocarditis

BACKGROUND: Aspecific scoring systems are used to predict the risk of death postsurgery in patients with infective endocarditis (IE). The purpose of the present study was both to analyze the risk factors for in-hospital death, which complicates surgery for IE, and to create a mortality risk score based on the results of this analysis. METHODS AND RESULTS: Outcomes of 361 consecutive patients (mean age, 59.1\ub115.4 years) who had undergone surgery for IE in 8 European centers of cardiac surgery were recorded prospectively, and a risk factor analysis (multivariable logistic regression) for in-hospital death was performed. The discriminatory power of a new predictive scoring system was assessed with the receiver operating characteristic curve analysis. Score validation procedures were carried out. Fifty-six (15.5%) patients died postsurgery. BMI >27 kg/m2 (odds ratio [OR], 1.79; P=0.049), estimated glomerular filtration rate 55 mm Hg (OR, 1.78; P=0.032), and critical state (OR, 2.37; P=0.017) were independent predictors of in-hospital death. A scoring system was devised to predict in-hospital death postsurgery for IE (area under the receiver operating characteristic curve, 0.780; 95% CI, 0.734-0.822). The score performed better than 5 of 6 scoring systems for in-hospital death after cardiac surgery that were considered. CONCLUSIONS: A simple scoring system based on risk factors for in-hospital death was specifically created to predict mortality risk postsurgery in patients with IE

ATLAS Run 1 searches for direct pair production of third-generation squarks at the Large Hadron Collider

This paper reviews and extends searches for the direct pair production of the scalar supersymmetric partners of the top and bottom quarks in proton-proton collisions collected by the ATLAS collaboration during the LHC Run 1. Most of the analyses use 20 fb$^{-1}$ of collisions at a centre-of-mass energy of $\sqrt{s}$ = 8 TeV, although in some case an additional 4.7 fb$^{-1}$ of collision data at $\sqrt{s}$ = 7 TeV are used. New analyses are introduced to improve the sensitivity to specific regions of the model parameter space. Since no evidence of third-generation squarks is found, exclusion limits are derived by combining several analyses and are presented in both a simplified model framework, assuming simple decay chains, as well as within the context of more elaborate phenomenological supersymmetric models

3D electrical resistivity tomography to locate DNAPL contamination around a housing estate

International audienceA 3D electrical resistivity survey is carried out downstream of a former coal refinery plant in France to determine the spatial extent of a DNAPL contaminant plume and to optimize the implantation of further boreholes. The site, which is located in the north of France, is the subject of an extensive conventional site investigation including the characterization of the contaminant source and natural attenuation monitoring of the plume. Previous geochemical and geophysical studies including 2D electrical resistivity profiles have shown a possible migration of the contaminant plume toward a housing estate, where no geochemical boreholes have been drilled. The purpose of this study was to achieve a real 3D imaging of the subsoil to locate the extent of the contaminant plume above the housing estate and determine the location of new boreholes. As geophysical measurements are difficult to perform in such an urban environment, a new electrical campaign was realized with innovative acquisition geometries and arrangement of surface electrodes in an L-shape, disposing electrodes in lines around the housing estate. Data were inverted in 3D with ERTLab software from Multi-Phase Technologies and Geostudi Astier. Results show a conductive plume emanating from old tar ponds and a slag heap that spreads through the housing estate. Based on these results, new boreholes were drilled in the housing estate, which confirm the extent of the contaminant plume estimated from the 3D electrical resistivity survey

Influence of Ageing of Polluted Soils on Bioavailability of Phenanthrene

Polycyclic aromatic hydrocarbons (PAH) are aromatic compounds persistent in the environment because of their hydrophobic nature, low water solubility and high adsorption onto soils and sediments. Bacteria can degrade phenanthrene dissolved in water but not when adsorbed onto soil particles. The bioavailability of phenanthrene for bacteria used for pollutant degradation was evaluated as a function of ageing of a soil polluted by phenanthrene. Ageing and biodegradation were studied in batches containing a sterile contaminated soil (soil H) and kaolinite coated with heavy fuel oil (KF2), both spiked with 14C-labelled phenanthrene. The solid matrix was kept in contact with the pollutant for 2, 48 h, 1 week, and 1, 2 and 4 months for soil H, and 2, 48 h and 2 months for KF2. After each contact time, a bacterial culture able to degrade phenanthrene and the nutrient medium was added. For 25 days, 14CO2 produced and 14C-residual activity in the liquid phase were monitored using liquid scintillation. The metabolites formed during biodegradation were determined by HPLC/UV. Adsorption of phenanthrene on soil H or KF2 was shown by comparing assay without ageing and those with different ageing times. For Soil H, 8%, 40% and 55% of the phenanthrene had been adsorbed after 2, 48h and 4 months of ageing, respectively. After the addition of degrading bacteria, 25% of phenanthrene had been mineralized in non-aged soil H and only 8% after a 4-month ageing time. This indicates that the amount of substrate available is a limiting factor for bacterial activity. For KF2, phenanthrene adsorption onto the solid was more rapid than that observed with the soil H since 55% of the pollutant had been adsorbed after only 2 h of ageing. This is due to the different nature of the organic matter in KF2 (only one type of organic matter and numerous available adsorption sites) and in the soil H (heterogeneous organic matter and adsorption sites). For both soil H and KF2, 60% of phenanthrene had been adsorbed after 2 months of ageing. With KF2, the percentage of phenanthrene mineralized reached 20% after 2 and 48 h of ageing and decreased to 6% after 2 months of ageing. These experiments show that the availability of the pollutant for bacteria decreased with soil ageing

Estimation of the residual stress field of laminated aeronautical parts to prevent distortion after machining

The estimation of post-machining distortion of monolithic aeronautical parts induced by the redistribution of the bulk residual stresses (RS) during machining is one of the major challenges of aeronautical parts manufacturing. Since it is the main cause of thick parts post-machining distortion, it is essential to know the state of the initial RS so that the machining strategy can be modified to minimize distortion of each part. The problem is even more complex because the RS field is not identical from one part to another. Considering an average stress field provides satisfactory results only for parts with simple geometries and a highly repeatable manufacturing process, which is rarely the case in an industrial setting. By simulating the steps of the production of the laminated blank, the variability of RS field will be established. This variability can be used to determine the distribution of the RS field of each part during machining

3D electrical resistivity tomography to locate DNAPL contamination around a housing estate

A 3D electrical resistivity survey is carried out downstream of a former coal refinery plant in France to determine the spatial extent of a DNAPL contaminant plume and to optimize the implantation of further boreholes. The site, which is located in the north of France, is the subject of an extensive conventional site investigation including the characterization of the contaminant source and natural attenuation monitoring of the plume. Previous geochemical and geophysical studies including 2D electrical resistivity profiles have shown a possible migration of the contaminant plume toward a housing estate, where no geochemical boreholes have been drilled. The purpose of this study was to achieve a real 3D imaging of the subsoil to locate the extent of the contaminant plume above the housing estate and determine the location of new boreholes. As geophysical measurements are difficult to perform in such an urban environment, a new electrical campaign was realized with innovative acquisition geometries and arrangement of surface electrodes in an L-shape, disposing electrodes in lines around the housing estate. Data were inverted in 3D with ERTLab software from Multi-Phase Technologies and Geostudi Astier. Results show a conductive plume emanating from old tar ponds and a slag heap that spreads through the housing estate. Based on these results, new boreholes were drilled in the housing estate, which confirm the extent of the contaminant plume estimated from the 3D electrical resistivity survey