The exposure of the hybrid detector of the Pierre Auger Observatory

The Pierre Auger Observatory is a detector for ultra-high energy cosmic rays. It consists of a surface array to measure secondary particles at ground level and a fluorescence detector to measure the development of air showers in the atmosphere above the array. The "hybrid" detection mode combines the information from the two subsystems. We describe the determination of the hybrid exposure for events observed by the fluorescence telescopes in coincidence with at least one water-Cherenkov detector of the surface array. A detailed knowledge of the time dependence of the detection operations is crucial for an accurate evaluation of the exposure. We discuss the relevance of monitoring data collected during operations, such as the status of the fluorescence detector, background light and atmospheric conditions, that are used in both simulation and reconstruction.Comment: Paper accepted by Astroparticle Physic

Description of Atmospheric Conditions at the Pierre Auger Observatory using the Global Data Assimilation System (GDAS)

Atmospheric conditions at the site of a cosmic ray observatory must be known for reconstructing observed extensive air showers. The Global Data Assimilation System (GDAS) is a global atmospheric model predicated on meteorological measurements and numerical weather predictions. GDAS provides altitude-dependent profiles of the main state variables of the atmosphere like temperature, pressure, and humidity. The original data and their application to the air shower reconstruction of the Pierre Auger Observatory are described. By comparisons with radiosonde and weather station measurements obtained on-site in Malarg\"ue and averaged monthly models, the utility of the GDAS data is shown

Ultrahigh energy neutrinos at the pierre auger observatory

The observation of ultrahigh energy neutrinos (UHEs) has become a priority in experimental astroparticle physics. UHEs can be detected with a variety of techniques. In particular, neutrinos can interact in the atmosphere (downward-going ) or in the Earth crust (Earth-skimming ), producing air showers that can be observed with arrays of detectors at the ground. With the surface detector array of the Pierre Auger Observatory we can detect these types of cascades. The distinguishing signature for neutrino events is the presence of very inclined showers produced close to the ground (i.e., after having traversed a large amount of atmosphere). In this work we review the procedure and criteria established to search for UHEs in the data collected with the ground array of the Pierre Auger Observatory.This includes Earth-skimming as well as downward-going neutrinos. No neutrino candidates have been found, which allows us to place competitive limits to the diffuse flux of UHEs in the EeV range and above

Risk profiles and one-year outcomes of patients with newly diagnosed atrial fibrillation in India: Insights from the GARFIELD-AF Registry.

BACKGROUND: The Global Anticoagulant Registry in the FIELD-Atrial Fibrillation (GARFIELD-AF) is an ongoing prospective noninterventional registry, which is providing important information on the baseline characteristics, treatment patterns, and 1-year outcomes in patients with newly diagnosed non-valvular atrial fibrillation (NVAF). This report describes data from Indian patients recruited in this registry. METHODS AND RESULTS: A total of 52,014 patients with newly diagnosed AF were enrolled globally; of these, 1388 patients were recruited from 26 sites within India (2012-2016). In India, the mean age was 65.8 years at diagnosis of NVAF. Hypertension was the most prevalent risk factor for AF, present in 68.5% of patients from India and in 76.3% of patients globally (P < 0.001). Diabetes and coronary artery disease (CAD) were prevalent in 36.2% and 28.1% of patients as compared with global prevalence of 22.2% and 21.6%, respectively (P < 0.001 for both). Antiplatelet therapy was the most common antithrombotic treatment in India. With increasing stroke risk, however, patients were more likely to receive oral anticoagulant therapy [mainly vitamin K antagonist (VKA)], but average international normalized ratio (INR) was lower among Indian patients [median INR value 1.6 (interquartile range {IQR}: 1.3-2.3) versus 2.3 (IQR 1.8-2.8) (P < 0.001)]. Compared with other countries, patients from India had markedly higher rates of all-cause mortality [7.68 per 100 person-years (95% confidence interval 6.32-9.35) vs 4.34 (4.16-4.53), P < 0.0001], while rates of stroke/systemic embolism and major bleeding were lower after 1 year of follow-up. CONCLUSION: Compared to previously published registries from India, the GARFIELD-AF registry describes clinical profiles and outcomes in Indian patients with AF of a different etiology. The registry data show that compared to the rest of the world, Indian AF patients are younger in age and have more diabetes and CAD. Patients with a higher stroke risk are more likely to receive anticoagulation therapy with VKA but are underdosed compared with the global average in the GARFIELD-AF. CLINICAL TRIAL REGISTRATION-URL: http://www.clinicaltrials.gov. Unique identifier: NCT01090362

Rolling contact fatigue in bearings:Phenomenology and modelling techniques

Current understanding of rolling contact fatigue is reviewed. The stress developed in the subsurface as a function of loading conditions, along with the resulting microstructural changes are described. Focusing on the dissolution of hardening phases and the occurrence of recovery and recrystallization, the relationship between load and microstructure evolution is analysed in terms of component life. The role played by inclusions and intermetallic particles, as well as primary precipitates, is outlined. The complexity of rolling contact fatigue is explained in terms of the many factors influencing it, which makes difficult to generalise its fundamentals. The importance of the choice and suitability of computational techniques employed to simulate it is highlighted, along with the available characterisation techniques. A variety of modelling techniques is presented. Empirical models have been an aid in predicting rolling contact fatigue, especially when combined with statistical approaches, but fail in addressing the fundamentals of the phenomenon, particularly at submicron scales. Micromechanics modelling is useful in understanding the spatial distribution of stresses and the evolution of damage, but fails in finding strategies for controlling it. The need for models able to relate rolling contact fatigue with microstructural evolution is described, available computational tools and mathematical models are reviewed, and a new irreversible thermodynamics approach linking the phenomena across the scales is proposed

Formation of oxide under rolling contact fatigue

Rolling contact fatigue (RCF) of a variety of bearing steels was studied with a ball-on-rod configuration rig. Systematic sectioning of the specimens across the spalls revealed the presence of oxide near the cracks. Further characterisation of this phase using electron microscopy revealed that it was formed during testing, after crack initiation. It is highlighted that the discovered oxide could, in some cases, be mistaken for a non-metallic inclusion. The authors suggest that attributing RCF failure initiation to non-metallic inclusions should not only rely on optical microscopy but also on EDX measurements, as this reveals a composition inconsistent with non-metallic inclusions. A mechanism for the in situ formation of the oxide is suggested and its possible role on failure is discussed

Dislocation annihilation in plastic deformation:I. Multiscale irreversible thermodynamics

Irreversible thermodynamics is employed as a framework to describe plastic deformation in pure metals and alloys. Expressions to describe saturation stress in single crystals and nanocrystals are employed over wide ranges of temperature, strain rate and grain size. The importance of the roles played by vacancy self-diffusion in dislocation climb and in plasticity is shown. Equations to describe the stress-strain response of single crystals and ultrafine-grained metals are derived. The activation energy for dislocation annihilation plays a central role in the mechanical response of the systems. Succinct formulations for predicting hot deformation behaviour and relaxation of industrial alloys are presented; the influence of composition in the activation energy for dislocation annihilation is shown. All formulations describing stress-strain relationships can be reduced to Kocks-Mecking classical formulation, but incorporating grain size and compositional effects. The importance of the recovery term in such formulation is established, as well as the need to obtain it employing more fundamental approaches

Nanoprecipitation in bearing steels

θ-phase is the main hardening species in bearing steels and appears in both martensitically and bainitically hardened microstructures. This work presents a survey of the microstrucural features accompanying nanoprecipitation in bearing steels. Nanoprecipitate structures formed in 1C-1.5Cr wt.% with additions of Cr, Mn, Mo, Si and Ni are studied. The work is combined with thermodynamic calculations and neural networks to predict the expected matrix composition, and whether this will transform martensitically or bainitically. Martensite tetragonality, composition and the amount of retained austenite are related to hardness and the type of nanoprecipitate structures in martensitic grades. The θ-phase volume fraction, the duration of the bainite to austenite transformation and the amount of retained austenite are related to hardness and a detailed quantitative description of the precipitate nanostructures. Such description includes compositional studies using energy-dispersive spectroscopy, which shows that nanoprecipitate formation takes place under paraequilibrium. Special attention is devoted to a novel two-step bainite tempering process which shows maximum hardness; we prove that this is the most effective process for incorporating solute into the precipitates, which are finer than those resulting from one-step banitic transformation processes

Unveiling the nature of hydrogen embrittlement in bearing steels employing a new technique

Hydrogen-charged and non-charged 1C-1.5Cr steel has been subjected to mechanical testing. Rolling contact fatigue life is dramatically reduced in the presence of hydrogen, while hardness and impact toughness remain nearly unchanged. The controlled formation of cracks in hydrogen-rich samples is demonstrated to continuously release hydrogen, supporting the view that hydrogen-enhanced localized plasticity is the principal hydrogen embrittlement mechanism in bearing steels. A new technique to determine the nature of the hydrogen embrittlement process is proposed

A criterion for the formation of high entropy alloys based on lattice distortion

Lattice distortion in high entropy alloys (HEAs) is one of their main crystallographic features. Its description is possible by means of unit cell parameter and bulk modulus variations of their constituent elements. The balance of forces acting on the lattice atoms under such distortion is related to the formation of a solid solution of a given crystal structure. This leads to the definition of a novel criterion for selecting HEA compositions. The main existing families of HEAs have been classified under this approach, in addition to an extensive list of multicomponent alloys including intermetallics and bulk metallic glasses. Criteria reported in the literature have been revised with the multicomponent alloy database used in this work which, together with the proposed approach, can be used to improve our understanding of HEAs formation