70,509 research outputs found

    Modelling uncertainties for measurements of the H ‚Üí ő≥ő≥ Channel with the ATLAS Detector at the LHC

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    The Higgs boson to diphoton (H ‚Üí ő≥ő≥) branching ratio is only 0.227 %, but this final state has yielded some of the most precise measurements of the particle. As measurements of the Higgs boson become increasingly precise, greater import is placed on the factors that constitute the uncertainty. Reducing the effects of these uncertainties requires an understanding of their causes. The research presented in this thesis aims to illuminate how uncertainties on simulation modelling are determined and proffers novel techniques in deriving them. The upgrade of the FastCaloSim tool is described, used for simulating events in the ATLAS calorimeter at a rate far exceeding the nominal detector simulation, Geant4. The integration of a method that allows the toolbox to emulate the accordion geometry of the liquid argon calorimeters is detailed. This tool allows for the production of larger samples while using significantly fewer computing resources. A measurement of the total Higgs boson production cross-section multiplied by the diphoton branching ratio (ŌÉ √ó Bő≥ő≥) is presented, where this value was determined to be (ŌÉ √ó Bő≥ő≥)obs = 127 ¬Ī 7 (stat.) ¬Ī 7 (syst.) fb, within agreement with the Standard Model prediction. The signal and background shape modelling is described, and the contribution of the background modelling uncertainty to the total uncertainty ranges from 18‚Äď2.4 %, depending on the Higgs boson production mechanism. A method for estimating the number of events in a Monte Carlo background sample required to model the shape is detailed. It was found that the size of the nominal ő≥ő≥ background events sample required a multiplicative increase by a factor of 3.60 to adequately model the background with a confidence level of 68 %, or a factor of 7.20 for a confidence level of 95 %. Based on this estimate, 0.5 billion additional simulated events were produced, substantially reducing the background modelling uncertainty. A technique is detailed for emulating the effects of Monte Carlo event generator differences using multivariate reweighting. The technique is used to estimate the event generator uncertainty on the signal modelling of tHqb events, improving the reliability of estimating the tHqb production cross-section. Then this multivariate reweighting technique is used to estimate the generator modelling uncertainties on background V ő≥ő≥ samples for the first time. The estimated uncertainties were found to be covered by the currently assumed background modelling uncertainty

    Miniaturización de antenas tipo microstrip mediante recubrimientos con materiales ferroeléctricos

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    La limitaci√≥n en el espacio donde se dispone la antena dentro de un dispositivo electr√≥nico ha promovido la investigaci√≥n de alternativas que permitan el desarrollo de antenas miniaturizadas con una amplia capacidad de emisi√≥n y recepci√≥n, siendo los materiales ferroel√©ctricos una de las opciones m√°s acertadas para reducir el tama√Īo de las antenas sin generar cambios significativos en el dise√Īo. Adicionalmente, estos materiales pueden ser obtenidos por diferentes t√©cnicas, dentro de las que sobresale sol-gel por su flexibilidad en deposici√≥n de pel√≠cula. Por ello, el presente trabajo se centra en la evaluaci√≥n del factor de miniaturizaci√≥n de antenas de parche microstrip recubiertas con materiales ferroel√©ctricos tales como titanato de estroncio (STO), titanato de bario-estroncio (BSTO), y titanato de bario (BTO), obtenidos v√≠a sol-gel y depositados mediante spin coating a 3000 rpm (20 s) con tratamiento t√©rmico a 700 ¬įC (1 h, 1 ¬įC/min). Estas antenas fueron dise√Īadas y simuladas dentro de un rango de frecuencia entre 1 y 8.5 GHz; se fabricaron por fotolitograf√≠a usando substratos de al√ļmina de 635 m con metalizaci√≥n en oro (3.0 m) y capa de adherencia de n√≠quel-cromo (0.2 m), para ser caracterizadas con el uso de un analizador vectorial de red (VNA). La ejecuci√≥n de esta investigaci√≥n se verific√≥ mediante difracci√≥n de rayos X, mostrando la presencia de estructuras cristalinas en fase perovskita c√ļbica, con par√°metros de red para STO, BSTO y BTO de 3.9012 ¬Ī 0.0049 √Ö, 3.9631 ¬Ī 0.0055 √Ö, y 4.0268 ¬Ī 0.0119 √Ö, respectivamente. La caracterizaci√≥n microestructural y morfol√≥gica permiti√≥ establecer las condiciones de deposici√≥n y de tratamiento t√©rmico de la pel√≠cula que permitieran uniformidad, homogeneidad y adherencia aceptable de la capa con poca presencia de defectos superficiales. Por su parte, la espectroscop√≠a de rayos X de energ√≠a dispersa cuantific√≥ composiciones elementales para STO de 1.48 ¬Ī 0.13 % wt Sr, y 0.54 ¬Ī 0.07 % wt Ti; BSTO: 0.69 ¬Ī 0.22 % wt Ba, 1.22 ¬Ī 0.12 % wt Sr, 0.63 ¬Ī 0.09 % wt Ti, y 6.05 ¬Ī 0.85 % wt O; y para BTO de 1.28 ¬Ī 0.23 % wt Ba, 0.74 ¬Ī 0.09 % wt Ti, y 7.28 ¬Ī 0.92 % O; todos estos materiales analizados en forma de pel√≠cula cristalizada y depositada sobre Al2O3/Ni-Cr/Au. Los espesores obtenidos para las pel√≠culas de STO, BSTO, y BTO fueron: 2.8130, 4.1070, y 3.9217 m; con constante diel√©ctrica de 92, 136, y 232; tangente de p√©rdida de 0.0112, 0.0104, y 0.0080, con operaci√≥n en 4.116 GHz (-12.6000 dB), 4.0800 GHz (-10.0900 dB), y 4.0200 GHz (-10.0900 dB), respectivamente para STO, BSTO y BTO. Por otro lado, las antenas recubiertas con STO, BSTO y BTO evidenciaron tasas de miniaturizaci√≥n de 4.7 %, 7.0 %, y 15.6 %, con frecuencia de operaci√≥n en 2.5925 GHz, 2.5300 GHz, y 2.2950 GHz, respectivamente. De este modo se comprob√≥ dentro de las instalaciones de la Universidad EAFIT la aplicabilidad de las pel√≠culas ferroel√©ctricas en los procesos de miniaturizaci√≥n de antenas

    The Influence of Frontal and Axial Plane Deformities on Contact Mechanics during Squatting: A Finite Element Study

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    Knee Osteoarthritis (KOA) is a degenerative joint disease and a leading cause of disability worldwide. Lower limb malalignment was a risky factor leading to KOA, altering the load distributions. This study aimed to study the influence of knee deformities on knee contact mechanics and knee kinematics during squatting. A full-leg squat FE model was developed based on general open-source models and validated with in vivo studies to investigate the outputs under frontal malalignment (valgus 8¬į to varus 8¬į) and axial malalignment (miserable malalignment 30¬į). As a result, Varus-aligned and miserable aligned models increased medial tibiofemoral force and lateral patellar contact pressures, while the valgus-aligned model increased lateral tibiofemoral force medial patellar contact pressures with no effects on total contact loads. The Model with a higher medial force ratio (medial force/total force) induced a higher internal tibial rotation. In conclusion, we recommended that patients with knee malalignment be taken care of alignments in both frontal and axial planes

    Constraints on Incremental Assembly of Upper Crustal Igneous Intrusions, Mount Ellen, Henry Mountains, Utah

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    Magma systems within the shallow crust drive volcanic processes at the surface. Studying active magma systems directly poses significant difficulty but details of ancient magma systems can provide insight to modern systems. The ancient intrusions now exposed in the Henry Mountains of southern Utah provide an excellent opportunity to study the emplacement of igneous intrusions within the shallow crust. The five main intrusive centers of the Henry Mountains are Oligocene in age and preserve different stages in the development of an igneous system within the shallow crust. Recent studies worldwide have demonstrated that most substantial (> 0.5 km3) igneous intrusions in the shallow crust are incrementally assembled from multiple magma pulses. In the Henry Mountains, smaller component intrusions (< 0.5 km3) clearly demonstrate incremental assembly but an evaluation of incremental assembly for an entire intrusive center has yet to be performed. The Mount Ellen intrusive complex is the largest intrusive center (~ 100 km3, 15 √Ę‚ā¨‚Äú 20 km diameter) in the Henry Mountains. This thesis research provides constraints on the construction history and emplacement of Mount Ellen using a combination of multiple techniques, including fieldwork, whole-rock major and trace element geochemistry, anisotropy of magnetic susceptibility, and crystal size distribution analysis. Field work and anisotropy of magnetic susceptibility data suggest that Mount Ellen is a laccolith that in cross section is built a network of stacked igneous sheets. In map-view, the laccolith has an elliptical shape built from numerous igneous lobes radiating away from the central portion of the intrusion. Field observations suggest most lobes are texturally homogenous and likely emplaced from a single magma batch. Samples collected throughout Mount Ellen were divided into five groups based on a qualitative evaluation of texture. Possible distinctions between these textural groups were then tested using several different techniques. Geochemistry, anisotropy of magnetic susceptibility, and phenocryst crystal size distribution data are individually not sufficient to distinguish all five textural groups. However, limited datasets for two textures can be consistently distinguished using these techniques. These new results can be integrated with existing constraints to create a comprehensive model for the construction history of Mount Ellen. The intrusive center was constructed in approximately 1 million years at a time-averaged magma injection rate of 0.0004 km3 y-1. The laccolith geometry was built from a radiating network of stacked igneous sheets. The sheets are lobate in map-view (longer than they are wide) and were fed radially outward from a central feeder zone. These component intrusions were emplaced by a minimum of 5 texturally distinct magma pulses, with periods of little or no magmatism between sequential pulses

    Biomedical applications of polymer and ceramic coatings: a review of recent developments

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    Recent literature concerning the use of polymer and ceramic coatings for a variety of biomedical applications is surveyed in this review. Applications have been grouped into six broad categories: orthopaedic materials, cardiovascular stents, antibacterial surfaces, drug delivery, tissue engineering and biosensors. Polymer and ceramic coatings add enhanced corrosion protection, antiwear, antibacterial and biocompatibility properties to various substrates for biomedical applications. Processes favoured for polymer coating formation included dip, electrodeposition, spin (including electrospin) and spray (including electrospray and ultrasonic spray). Ceramic coatings were formed using magnetron sputtering and a combination of 3-D printing and in-situ mineralisation, among others. The review period is from 2017 to the present (mid-2021)

    Increased lifetime of Organic Photovoltaics (OPVs) and the impact of degradation, efficiency and costs in the LCOE of Emerging PVs

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    Emerging photovoltaic (PV) technologies such as organic photovoltaics (OPVs) and perovskites (PVKs) have the potential to disrupt the PV market due to their ease of fabrication (compatible with cheap roll-to-roll processing) and installation, as well as their significant efficiency improvements in recent years. However, rapid degradation is still an issue present in many emerging PVs, which must be addressed to enable their commercialisation. This thesis shows an OPV lifetime enhancing technique by adding the insulating polymer PMMA to the active layer, and a novel model for quantifying the impact of degradation (alongside efficiency and cost) upon levelized cost of energy (LCOE) in real world emerging PV installations. The effect of PMMA morphology on the success of a ternary strategy was investigated, leading to device design guidelines. It was found that either increasing the weight percent (wt%) or molecular weight (MW) of PMMA resulted in an increase in the volume of PMMA-rich islands, which provided the OPV protection against water and oxygen ingress. It was also found that adding PMMA can be effective in enhancing the lifetime of different active material combinations, although not to the same extent, and that processing additives can have a negative impact in the devices lifetime. A novel model was developed taking into account realistic degradation profile sourced from a literature review of state-of-the-art OPV and PVK devices. It was found that optimal strategies to improve LCOE depend on the present characteristics of a device, and that panels with a good balance of efficiency and degradation were better than panels with higher efficiency but higher degradation as well. Further, it was found that low-cost locations were more favoured from reductions in the degradation rate and module cost, whilst high-cost locations were more benefited from improvements in initial efficiency, lower discount rates and reductions in install costs

    Nocturnal survival of isoprene linked to formation of upper tropospheric organic aerosol

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    Seasonal variations in air concentrations of 27 organochlorine pesticides (OCPs) and 25 current-use pesticides (CUPs) across three agricultural areas of South Africa

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    For decades pesticides have been used in agriculture, however, the occurrence of legacy organochlorine pesticides (OCPs) and current-use pesticides (CUPs) is poorly understood in Africa. This study investigates air concentrations of OCPs and CUPs in three South African agricultural areas, their spatial/seasonal variations and mixture profiles. Between 2017 and 2018, 54 polyurethane foam-disks passive air-samplers (PUF-PAS) were positioned in three agricultural areas of the Western Cape, producing mainly apples, table grapes and wheat. Within areas, 25 CUPs were measured at two sites (farm and village), and 27 OCPs at one site (farm). Kruskal-Wallis tests investigated area differences in OCPs concentrations, and linear mixed-effect models studied differences in CUPs concentrations between areas, sites and sampling rounds
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