Design and Implementation of a Detector for High Flux Mixed Radiation Fields

The main purpose of the LHC Beam Loss Monitoring (BLM) system is the active protection of the LHC accelerators' elements against the quench of superconducting magnets and the damage of equipment caused by the loss of circulating protons. The lost protons initiate a shower of secondary particles, which deposit their energy in the equipment and partly in a radiation detector. If thresholds in the BLM system are exceeded, the circulating LHC beam is directed towards a dump to stop the energy deposition in the fragile equipment. The LHC BLM system will use ionization chambers as standard detectors, and in the areas with very high dose rates Secondary Emission Monitor (SEM) chambers will be employed to increase the dynamic range. The SEM is characterized by a high linearity and accuracy, low sensitivity, fast response and a good radiation tolerance. The emission of electrons from the surface layer of metals by the passage of charged particles is only measurable in a vacuum environment. This requirement leads together with the foreseen operation of 20 years to an ultra high vacuum preparation of the components and even to an additional active pumping realized by a getter pump (NEG). The signal and bias electrodes are made of Ti to make use of its Secondary Emission Yield (SEY) stability and favorable vacuum properties. The sensitivity of the SEM was modeled in GEANT4 via the Photo-Absorption Ionization module together with a custom parameterization for the very low energy secondary electron production using the modified Sternglass formula. The simulations were validated by comparative measurements of several prototypes with proton beams of the CERN PS Booster dump line, the SPS transfer line, the PSI Optis line and by a muon beam in the COMPASS beam line. Tests of the complete acquisition chain were performed in the LHC test collimation area of the SPS and compared to the combined Fluka and GEANT4 simulations. The linearity and long term stability was also tested in the high energy beam dump area of the SPS. A dedicated fixed target experiment was designed in the CERN H4 secondary beam line for testing all the 400 detectors produced in IHEP Protvino. The simulations were also used for the prediction of the signal levels expected in the LHC and for an absolute dose calibration. The comparison of simulations and measurements and of SEM and ionisation chamber measurements resulted in the relative difference range between 8 and 43% for different setups and radiation fields

Optical concentrators for Čerenkov light detector

RICH1 (Ring Imaging Cherenkov) detector is an important part of COMPASS particle physics experiment in CERN. Its central area photon detection part is being upgraded from wire chambers with CsI layers to very fast UV extended Hamamatsu MAPMTs (Multi Anode Photo Multiplier Tubes) array. MAPMTs have approx. 3 times smaller active area than the covered region, thus optical concentrators transforming image from old system focal plane to the new photocathode were needed. System was expected to be efficient from 200 to 600nm with best performance at 300nm and with angular acceptance including all interesting physics processes. Several design types (including i.e. a hollow waveguide) were investigated and the “telescopic” two lens aspherical design concept was selected for its proven functionality in HERA-B experiment. Chosen material was UV grade fused silica. System consists of a field lens placed in the focal plane of the RICH mirrors and a condenser lens downstream. Designing procedure started with a high optical quality fully aspherical system and continued by a gradual decrease in imaging performance to match the budget but still satisfy the physics requirements. Particle simulations showed a necessity of the system tilt but mounting constraints didn’t fully allow it, so the field lens was made prismatic with one flat side and the condenser lens off centered and tilted. Performance of the designs was tested by Monte Carlo method allowing a better optimization. Testing by rays from complex detector simulation implied a necessity of tilt in another plane. Design ready for production satisfies all performance, dimensional, mounting and cost expectations

Development of high-precision snow mapping tools for Arctic environments

Le manteau neigeux varie grandement dans le temps et l’espace, il faut donc de nombreux points d’observation pour le décrire précisément et ponctuellement, ce qui permet de valider et d’améliorer la modélisation de la neige et les applications en télédétection. L’analyse traditionnelle par des coupes de neige dévoile des détails pointus sur l’état de la neige à un endroit et un moment précis, mais est une méthode chronophage à laquelle la distribution dans le temps et l’espace font défaut. À l’opposé sur la fourchette de la précision, on retrouve les solutions orbitales qui couvrent la surface de la Terre à intervalles réguliers, mais à plus faible résolution. Dans l’optique de recueillir efficacement des données spatiales sur la neige durant les campagnes de terrain, nous avons développé sur mesure un système d’aéronef télépiloté (RPAS) qui fournit des cartes d’épaisseur de neige pour quelques centaines de mètres carrés, selon la méthode Structure from motion (SfM). Notre RPAS peut voler dans des températures extrêmement froides, au contraire des autres systèmes sur le marché. Il atteint une résolution horizontale de 6 cm et un écart-type d’épaisseur de neige de 39 % sans végétation (48,5 % avec végétation). Comme la méthode SfM ne permet pas de distinguer les différentes couches de neige, j’ai développé un algorithme pour un radar à onde continue à modulation de fréquence (FM-CW) qui permet de distinguer les deux couches principales de neige que l’on retrouve régulièrement en Arctique : le givre de profondeur et la plaque à vent. Les distinguer est crucial puisque les caractéristiques différentes des couches de neige font varier la quantité d’eau disponible pour l’écosystème lors de la fonte. Selon les conditions sur place, le radar arrive à estimer l’épaisseur de neige selon un écart-type entre 13 et 39 %. vii Finalement, j’ai équipé le radar d’un système de géolocalisation à haute précision. Ainsi équipé, le radar a une marge d’erreur de géolocalisation d’en moyenne <5 cm. À partir de la mesure radar, on peut déduire la distance entre le haut et le bas du manteau neigeux. En plus de l’épaisseur de neige, on obtient également des points de données qui permettent d’interpoler un modèle d’élévation de la surface solide sous-jacente. J’ai utilisé la méthode de structure triangulaire (TIN) pour toutes les interpolations. Le système offre beaucoup de flexibilité puisqu’il peut être installé sur un RPAS ou une motoneige. Ces outils épaulent la modélisation du couvert neigeux en fournissant des données sur un secteur, plutôt que sur un seul point. Les données peuvent servir à entraîner et à valider les modèles. Ainsi améliorés, ils peuvent, par exemple, permettre de prédire la taille, le niveau de santé et les déplacements de populations d’ongulés, dont la survie dépend de la qualité de la neige. (Langlois et coll., 2017.) Au même titre que la validation de modèles de neige, les outils présentés permettent de comparer et de valider d’autres données de télédétection (par ex. satellites) et d’élargir notre champ de compréhension. Finalement, les cartes ainsi créées peuvent aider les écologistes à évaluer l’état d’un écosystème en leur donnant accès à une plus grande quantité d’information sur le manteau neigeux qu’avec les coupes de neige traditionnelles.Abstract: Snow is highly variable in time and space and thus many observation points are needed to describe the present state of the snowpack accurately. This description of the state of the snowpack is necessary to validate and improve snow modeling efforts and remote sensing applications. The traditional snowpit analysis delivers a highly detailed picture of the present state of the snow in a particular location but lacks the distribution in space and time as it is a time-consuming method. On the opposite end of the spatial scale are orbital solutions covering the surface of the Earth in regular intervals, but at the cost of a much lower resolution. To improve the ability to collect spatial snow data efficiently during a field campaign, we developed a custom-made, remotely piloted aircraft system (RPAS) to deliver snow depth maps over a few hundred square meters by using Structure-from-Motion (SfM). The RPAS is capable of flying in extremely low temperatures where no commercial solutions are available. The system achieves a horizontal resolution of 6 cm with snow depth RMSE of 39% without vegetation (48.5% with vegetation) As the SfM method does not distinguish between different snow layers, I developed an algorithm for a frequency modulated continuous wave (FMCW) radar that distinguishes between the two main snow layers that are found regularly in the Arctic: “Depth Hoar” and “Wind Slab”. The distinction is important as these characteristics allow to determine the amount of water stored in the snow that will be available for the ecosystem during the melt season. Depending on site conditions, the radar estimates the snow depth with an RMSE between 13% and 39%. v Finally, I equipped the radar with a high precision geolocation system. With this setup, the geolocation uncertainty of the radar on average < 5 cm. From the radar measurement, the distance to the top and the bottom of the snowpack can be extracted. In addition to snow depth, it also delivers data points to interpolate an elevation model of the underlying solid surface. I used the Triangular Irregular Network (TIN) method for any interpolation. The system can be mounted on RPAS and snowmobiles and thus delivers a lot of flexibility. These tools will assist snow modeling as they provide data from an area instead of a single point. The data can be used to force or validate the models. Improved models will help to predict the size, health, and movements of ungulate populations, as their survival depends on it (Langlois et al., 2017). Similar to the validation of snow models, the presented tools allow a comparison and validation of other remote sensing data (e.g. satellite) and improve the understanding limitations. Finally, the resulting maps can be used by ecologist to better asses the state of the ecosystem as they have a more complete picture of the snow cover on a larger scale that it could be achieved with traditional snowpits

Serum Glucose Levels and Hospital Outcomes in the Setting of Acute Myocardial Infarction in Patients Not Known to Have Diabetes: A Community-Wide Perspective

Background: Elevated serum glucose levels during hospital admission for acute myocardial infarction (AMI) have been associated with an increased risk of adverse short-term outcomes in diabetic patients (Capes, 2000; Oswald, 1986; Wahab, 2002). Although diabetics, compared with non-diabetics, have a worse prognosis after AMI (Mak, 1997; Herlitz, 1986; Miettinen, 1998), recent studies have suggested that hyperglycemia is also associated with an increased risk of various clinical complications and death in non-diabetic patients (Capes, 2000; Wahab, 2002; Sewardsen, 1989). While the pathophysiologic substrates responsible for these associations remain poorly understood, it appears that neither a catecholamine-induced stress response nor underlying impaired glucose tolerance are the only mechanisms involved (Wong, 2004; Marfella, 2003; Ceriello, 2005). While several recent studies have demonstrated the prognostic importance of elevated glucose levels in non-diabetic patients hospitalized with AMI (Norhammar, 1999; Tenerz, 2003; Timmer 2004), few investigations have examined the characteristics and hospital management practices of patients with varying levels of serum glucose and the relation of elevated glucose levels to hospital outcomes. None of these studies have assessed changes in these endpoints over time. In addition to the use of different glucose cutpoints in prior investigations, previous studies have examined relatively few strata of patients with varying glucose levels, making interpretation of the role of serum glucose in the pathogenesis of AMI difficult. Moreover, few of these investigations have been carried out from the more generalizable perspective of a community-wide investigation. Objectives: The purpose of this population-based study is to examine the overall, and potentially changing, relation between levels of serum glucose at the time of hospital admission for AMI, occurrence of AMI associated complications, and the risk of dying during hospitalization in patients hospitalized with AMI without previously diagnosed diabetes. A secondary objective of this study is to examine the demographic and clinical characteristics of patients who present with different serum glucose levels as well as the overall, and potentially changing, hospital management of patients with AMI according to admission serum glucose levels. Patients hospitalized with AMI at all greater Worcester (MA) hospitals in 5 biennial periods between 1995 and 2003, and not known to have previously diagnosed diabetes, comprised the population of interest. Methods: The Worcester Heart Attack Study is an ongoing population-based investigation examining changes over time in the hospital incidence and case-fatality rates of AMI in residents of the Worcester metropolitan area. The medical records of all greater Worcester residents hospitalized for possible AMI at all area medical centers were individually reviewed and validated by trained study physicians and nurses according to predefined diagnostic criteria. These criteria take into account clinical presentation, increases in serum enzyme levels, and serial electrocardiographic findings. Demographic and clinical data including age, sex, comorbidities (e.g., history of angina, heart failure, hypertension, or stroke), order of the AMI (initial vs prior event) and type (Q-wave vs non–Q-wave AMI), use of cardiac medications and coronary revascularization procedures during hospitalization, and hospital discharge status were abstracted from hospital medical records by trained nurse and physician reviewers. The 3,601 patients without a history of previously diagnosed diabetes, based on the review of information contained in hospital medical records, included in the present analysis were hospitalized in 5 biennial periods between 1995 and 2003. Data analysis: Patients with independently validated AMI and without a history of diabetes were stratified into quintiles based on the initial serum glucose level recorded at the time of hospital admission. These quintiles consisted of the following: quintile 1: \u3c120\u3emg/dl; quintile 2: 120 to 139 mg/dl; quintile 3: 140-159 mg/dl; quintile 4: 160 to 179 mg/dl; and quintile 5: \u3e180 mg/dl. We also categorized patients’ serum glucose levels into 2 additional strata at the extremes of this distribution (\u3c100 and\u3e200 mg/dl) for purposes of further characterizing the distribution of serum glucose levels in the study sample. Logistic regression analysis was used to assess the independence of the association between serum glucose levels and the development of heart failure, cardiogenic shock, and death during hospitalization while controlling for several potentially confounding prognostic variables. Our initial regression model controlled for the effects of age and sex only. A second regression model controlled for medical history, AMI associated characteristics, and time (cohort year) in addition to age and sex. A third model controlled for these variables in addition to hospital use of effective cardiac medications (angiotensin converting enzyme (ACE) inhibitors, aspirin, beta blockers, lipid lowering agents, and thrombolytics) and hospital use of coronary angioplasty. Multivariable adjusted odds ratios and accompanying 95% confidence intervals were calculated in a standard manner. Results: Approximately one-third of patients presented with glucose levels \u3c120\u3emg/dl while one-quarter had serum glucose levels \u3e160 mg/dl. Patients in the uppermost quintiles of serum glucose were significantly more likely to develop heart failure, cardiogenic shock, and die during hospitalization than patients with lower serum glucose levels. Patients with the highest glucose levels were less aggressively treated with effective cardiac medications and coronary interventions. The results of this population-based investigation provide insights to the magnitude and impact of hyperglycemia in patients not known to have diabetes hospitalized with AMI. Increased surveillance and more aggressive treatment strategies remain needed to improve the outlook of patients with elevated glucose levels. Discussion: Numerous studies have demonstrated that patients with elevated serum glucose levels in the setting of AMI, irrespective of diabetes status, are more likely to experience adverse hospital outcomes. A limited number of studies have suggested that this risk may be exaggerated in non-diabetic patients in comparison to those with established diabetes (Wahab, 2002; Sewardsen, 1989). While early studies hypothesized that the presence of hyperglycemia in the setting of AMI in patients without previously diagnosed diabetes may represent a combination of underlying impaired glucose tolerance and a catecholamine-induced stress response to myocardial damage (Oswald, 1986; Wahab, 2002; Sewardsen, 1989), current research suggests a more complex pathophysiologic mosaic (Ceriello, 2005). Evidence that strict glycemic control with insulin significantly decreases mortality in diabetic patients with AMI further suggests that hyperglycemia in the setting of AMI is not purely an epiphenomenon of the stress response (Malmberg, 1997; Malmberg, 1999, Fath-Ordoubadi, 1997). Our data supports previous findings that an elevated serum glucose upon admission for AMI is a significant risk factor for heart failure, cardiogenic shock, and dying during the acute hospitalization. Increased attention to serum glucose levels should assist in the risk stratification of patients with AMI, especially in non-diabetics where serum glucose levels may go largely ignored. Further risk stratification regarding patients’ underlying glycometabolic status, and need for short as well as long-term risk factor modification, is also warranted. Although the mechanisms remain unclear, tight glycemic control with glucose-insulin infusions during the first 24 hours of an AMI has been shown to improve both short and long-term outcomes in patients with diabetes (Malmberg, 1997; Malmberg, 1999, Fath-Ordoubadi, 1997). The survival benefit has been found to be greatest in those not already receiving insulin treatment (Malmberg, 1995). These findings, coupled with the universally adverse outcomes experienced by non-diabetic patients who present with both hyperglycemia and AMI in our study and others, suggest that tight glycemic control in the acute care setting may play an important role in improving the clinical outcomes of non-diabetic patients hospitalized with AMI. Study Strengths and Limitations: The strengths of the present study include the large number of patients with independently validated AMI from several relatively recent periods of investigation and inclusion of patients from a representative Northeast metropolitan area whose socioeconomic characteristics reflect those of the U.S. population as a whole, reinforcing the generalizability of the present findings. A primary limitation of this observational study is that admission serum glucose levels in the setting of AMI can fluctuate widely, due to factors such as time and content of last meal, and due to acute myocardial damage. While one recent study showed fasting glucose to be superior to admission glucose in the assessment of short-term mortality risk among patients admitted with AMI (Suleiman, 2005), there is significant support for the efficacy of aggressive glucose management on the basis of admission blood glucose levels (Malmberg, 1995). Neither HbA1c levels, systematically collected fasting blood sugars, nor glucose tolerance test results were available to further assess chronic glycometabolic status and to assess the true prevalence of impaired glucose tolerance or frank diabetes in our study population. Conclusion: The results of the present investigation confirm that, even among non-diabetic patients, the prevalence of elevated serum glucose levels upon admission for AMI is high. Furthermore, these patients are consistently less likely to receive optimal treatment for AMI, while experiencing significantly higher rates of clinical complications, including in-hospital mortality, in comparison to patients with lower serum glucose levels. These and other data suggest the need for a randomized controlled trial of tight glycemic control in non-diabetic patients with AMI presenting with hyperglycemia on admission for purposes of assessing the optimal treatment of these high-risk patients

Dust and gas emission from cometary nuclei: the case of comet 67P/Churyumov-Gerasimenko

Comets display with decreasing solar distance an increased emission of gas and dust particles, leading to the formation of the coma and tail. Spacecraft missions provide insight in the temporal and spatial variations of the dust and gas sources located on the cometary nucleus. For the case of comet 67P/Churyumov-Gerasimenko (67P/C-G), the long-term observations from the Rosetta mission point to a homogeneous dust emission across the entire illuminated surface. Despite the homogeneous initial distribution, a collimation in jet-like structures becomes visible. We propose that this observation is linked directly to the complex shape of the nucleus and projects concave topographical features into the dust coma. To test this hypothesis, we put forward a gas-dust description of 67P/C-G, where gravitational and gas forces are accurately determined from the surface mesh and the rotation of the nucleus is fully incorporated. The emerging jet-like structures persist for a wide range of gas-dust interactions and show a dust velocity dependent bending.Comment: 17 pages, with 7 figures. To appear in Advances in Physics X (2018

Improving Pneumococcal Vaccination Rates in Jefferson Hospital Ambulatory Practice Patients

AIM: To improve the pneumococcal vaccination initiation rates in patients 65 years and older in Jefferson Hospital Ambulatory Practice (JHAP) to the institutional quality measure goal of 80% over a 4 month period from January to May of 2017.https://jdc.jefferson.edu/patientsafetyposters/1031/thumbnail.jp

Linking turbulent waves and bubble diffusion in self-aerated open-channel flows: Two-state air concentration

High Froude-number flows become self-aerated when the destabilizing effect of turbulence overcomes gravity and surface tension forces. Traditionally, the resulting air concentration profile has been explained using single-layer approaches that invoke solutions of the advection-diffusion equation for air in water, i.e., bubbles' dispersion. Based on a wide range of experimental evidences, we argue that the complete air concentration profile shall be explained through the weak interaction of different canonical turbulent flows, namely a Turbulent Boundary Layer (TBL) and a Turbulent Wavy Layer (TWL). Motivated by a decomposition of the streamwise velocity into a pure wall flow and a free-stream flow [Krug et al., J. Fluid Mech. (2017), vol. 811, pp. 421--435], we present a physically consistent two-state formulation of the structure of a self-aerated flow. The air concentration is mathematically built upon a modified Rouse profile and a Gaussian error function, resembling vertical mass transport in the TBL and the TWL. We apply our air concentration theory to over 500 profiles from different data sets, featuring excellent agreement. Finally, we show that the turbulent Schmidt number, characterizing the momentum-mass transfer, ranges between 0.2 to 1, which is consistent with previous mass-transfer experiments in TBLs. Altogether, the proposed flow conceptualization sets the scene for more physically-based numerical modelling of turbulent mass diffusion in self-aerated flows.Comment: 47 pages, 7 figures, includes supplemental material, accepted for publication in Journal of Fluid Mechanic