119,803 research outputs found

    Modelling uncertainties for measurements of the H → γγ Channel with the ATLAS Detector at the LHC

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    The Higgs boson to diphoton (H → γγ) 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 (σ × Bγγ) is presented, where this value was determined to be (σ × Bγγ)obs = 127 ± 7 (stat.) ± 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 18–2.4 %, 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 γγ 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 γγ samples for the first time. The estimated uncertainties were found to be covered by the currently assumed background modelling uncertainty

    Prospective life cycle assessment of hydrogen production by waste photoreforming

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    Identifying sustainable energy vectors is perhaps one of the most critical issues that needs addressing to achieve a climate-neutral society by 2050. In this context, the hydrogen economy has been proposed as a solution to mitigate our current fossil-based energy system while the concept of the circular economy aims to boost the efficient use of resources. Photoreforming offers a promising opportunity for recycling and transforming widely available biomass-derived wastes (e.g., crude glycerol from biodiesel) into clean hydrogen fuel. This processing technology may be a versatile method that can be performed not only under UV light but also under visible light. However, this approach is currently at the lab-scale and some inherent challenges must be overcome, not least the relatively modest hydrogen production rates for the lamps? substantial energy consumption. This study aims to assess the main environmental impacts, identifying the hotspots and possible trade-off in which this technology could operate feasibly. We introduce an assessment of the windows of opportunity using seven categories of environmental impact with either artificial light or sunlight as the source of photocatalytic conversion. We compared the environmental indicators from this study with those of the benchmark water electrolysis and steam?methane reforming (SMR) technologies, which are currently operating at a commercial scale. The results obtained in this study situate biowaste photoreforming within the portfolio of sustainable H2 production technologies of interest for future development in terms of target H2 production rates and lifetimes of sustainable operation.Financial support from projects RTI2018-099407-B-I00 and RTI2018-099407-B-I00 funded by MCIN/AEI/10.13039/501100011033/FEDER and by “ERDF A way of making Europe” by the “European Union” is gratefully acknowledged. We would like also to thank MICIN for providing Marta Rumayor with a Juan de la Cierva postdoctoral contract IJCI-2017-32621

    CO2 electroreduction: sustainability analysis of the renewable synthetic natural gas

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    Capture and utilization of industrial CO2 emissions into low-carbon fuels is a promising alternative to store renewable electricity into chemical vectors while decarbonizing the economy. This work evaluates the viability pathways of producing synthetic natural gas (SNG) by direct CO2 electroreduction (ER) in Power-To-Synthetic Natural Gas electrolyzers (PtSNG). We perform an ex-ante techno-economic (TEA) and life cycle analysis (LCA) for a 2030 framework in Europe. ER performance is varied in defined scenarios and assessed using a built-in process model of the PtSNG system, revealing uncharted limitations and benchmarks to achieve. Results show that substitution of fossil natural gas with renewable SNG could avoid more than 1 kg CO2e/kg SNG under moderate ER conditions when using low-carbon electricity (< 60 kg CO2e/MWh). SNG profitability for 2030 would rely on: i) higher CH4 current densities (800–1000 mA/cm2), ii) improvements in energy efficiency (higher than 60%), and iii) valorization of the anodic product or additional carbon incentives. Our study proves that if market and technology evolve appropriately in the coming years, the SNG by CO2 ER may be a mid-term climate change mitigation technology, among others.The authors thank the Spanish Ministry of Economy and Competitiveness for the financial support through the project PID2020–114,787-RB-I00. Javier Fernández-González and Marta Rumayor would also like to thank the financial support of the Spanish Ministry of Science and Innovation for the concession of a FPU grant (FPU19/05483) and a Juan de la Cierva postdoctoral contract (IJCI-2017-32621), respectively

    Hybrid Perovskite Thin Film

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    Hybrid perovskite thin film offers diverse advantages like low cost deposition techniques, less material consumption and superior optoelectronic properties. These merits including high voltage and high efficiency performance in a wide range of high light intensity are sufficient to distinguish perovskite thin films/devices from their contenders as a thin film technology with greater potential for industrial applications. Perovskite thin film technology demonstrates potency in a variety of applications in optoelectronic devices especially photovoltaic applications. The National Renewable Energy Laboratory (NREL) of the USA categorizes a number of thin films technologies including perovskite thin film, as emerging photovoltaics with the bulk of them yet to be commercially applied but are still in the research or developmental stage. In this chapter, various processing methods and material combinations as well as current trends in this technology are subjects of discussion

    The Cerebral Plasticity Prospect of Stingless Bee Honey-Polyphenols Supplementation in Rehabilitation of Post-Stroke Vascular Cognitive Impairment

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    The neuroprotective potential of stingless bee honey (SBH) is still to be documented from numerous studies including that of its effect on cerebrovascular event. This review should guide stroke rehabilitation specialties to a high understanding of the overall circuit changes post-stroke, the clinical relevance of this change in stroke to cognitive impairment and dementia, and SBH as a supplementation in modern stroke rehabilitation in progresses. However, the potential of SBH as a supplementation therapy and highlights treatment to induced plasticity for post-stroke vascular cognitive impairment (PSVCI) remains largely unexplored. This Chapter attempts to deliberate on recent evidence that highlight the therapeutic properties of honey and SBH, the features of PSVCI, and proposing the plausible mechanism of action for SBH as a supplementation during stroke rehabilitation that could halt the progression of PSVCI. It is hoped that such an approach could complement the existing evidence-based stroke care, and which will help in the development of future direction of brain plasticity to delay the progression of cognitive impairment post-stroke

    Macrophage: A Key Player of Teleost Immune System

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    Fish, the free-living organisms, residing in aquatic environment, are earliest vertebrates with fully developed innate and adaptive immunity. Immune organs homologous to those of mammalian immune system are found in fish. Macrophages are best known for their role in immunity, basic function of which being cytokine production and phagocytosis. Due to environmental adaptation and whole genome duplication, macrophages in teleost are differently modulated (pro-inflammatory, M1-type, and anti-inflammatory/regulatory, M2-type) and perform a variety of different functions as compared with those of mammals. Phagocytosis is a major mechanism for removing pathogens and/or foreign particles in immune system and therefore is a critical component of the innate and adaptive immune system. One of the most competent phagocytes in teleost is found to be macrophages/monocytes. Increasing experimental evidence demonstrates that teleost phagocytic cells can recognize and destroy antigens to elicit adaptive immune responses that involve multiple cytokines. A detail understanding of teleost macrophages and phagocytosis would not only help in understanding the immune mechanism but will also help in disease prevention in teleost

    Probing the Intergalactic medium properties using X-ray absorption from multiple tracers

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    Based on the Lambda Cold Dark Matter concordance cosmological model (ΛCDM), the majority of baryons exist in the Intergalactic medium (IGM). It is extremely challenging to observationally trace the IGM, especially at higher temperatures and low densities. Post reionisation, the vast majority of hydrogen and helium is ionized in the IGM and therefore, the observation of metals is essential for parametrising the IGM properties. My hypothesis is that there is significant absorption in the diffuse highly ionisied IGM and that this IGM column density increases with redshift. I use X-ray absorption in multiple tracers which yields information on the total absorbing column density of the matter between the observer and the source. Clear IGM detections require tracer sources that are bright, distant, and common enough to provide a good statistical sample of IGM lines of sight (LOS). To more accurately isolate any IGM contribution to spectral absorption, I examine each tracer host type to realistically model it, in addition to using appropriate intrinsic continuum curvature models. I test the robustness of the result from a number of perspectives. I examine the impact of the key underlying assumptions that affect the column density calculations including metallicity, ionisation and location of absorption. I look for any evidence of evolution in the parameters. In Chapters 2, 3, 4 and 5, I use gamma-ray bursts (GRBs), blazars and quasars (QSOs) to estimate IGM baryon column densities, metallicity, temperature, ionisation parameters and redshift distributions. My results for each tracer are presented in each of the respective chapters and collectively in Chapter 5 which includes comparative analysis. In conclusion, through the work in this thesis I demonstrate a consistent case for strong X-ray absorption in the IGM on the LOS to three different tracer types and that it is related to redshift. The results are consistent with the ΛCDM model for density, temperature and metallicity. Given these results, I would recommend that studies of distant objects should not follow the convention of assuming all X-ray absorption in excess of our Galaxy is attributed to the host galaxy, that the host is neutral and has solar metallicity. Instead, particularly at higher redshift, absorption in the IGM should be accounted for to give more accurate results for the tracer host properties

    Analysis of the kinematic boundaries of the quasielastic neutrino-nucleus cross section in the superscaling model with a relativistic effective mass

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    This work has been partially supported by the former Spanish Ministerio de Economia y Competitividad and ERDF (European Regional Development Fund) under Contract No. FIS2017-85053-C2-1P, by the Junta de Andalucía Grant No. FQM225, by Contract No. PID2020– 114767 GB-I00 funded by MCIN/ AEI /10.13039/ 501100011033, and by the Russian Science Foundation Grant No. 18-12-00271.In this work we obtain the analytical expressions for the boundaries of the charged current quasielastic (CCQE) double differential cross section in terms of dimensionless energy and momentum transfers, for the Relativistic Fermi Gas (RFG) and the Superscaling approach with relativistic effective mass (SuSAM∗) models, within the scaling formalism. In addition, we show that this double differential cross section in the scaling formalism has very good properties to be implemented in the Monte Carlo (MC) neutrino event generators, particularly because its peak is almost flat with the (anti)neutrino energy. This makes it especially well suited for the event generation by the acceptance-rejection method usually used in the neutrino generators. Finally, we analyze the total CCQE cross section σ(Eν) for both models and attribute the enhancement observed in the SuSAM∗ total cross section to the high-momentum components which are present, in a phenomenological way, in its scaling function, while these are absent in the RFG model.Spanish Ministerio de Economia y CompetitividadEuropean Regional Development FundJunta de AndalucíaRussian Science Foundatio
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