2,353 research outputs found

    Optical radiation from the interaction of energetic atoms, ions, electrons, and photons with surfaces

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    Heavy particle, electron, and UV photon bombardment of solid surfaces has been recently observed to result in the emission of infrared, visible, and ultraviolet radiation. This effect occurs over a wide range of incident projectile energies. Line radiation arising from transitions between discrete atomic or molecular levels may be attributed to the decay of excited particles which have been sputtered or electronically/chemically desorbed from the surface. Broadband continuum radiation, which is also observed, is believed to arise either from fluorescence of the near surface bulk or from the radiative decay of desorbed excited clusters. Spacecraft, in the ambient near Earth environment, are subject to such bombardment. The dynamics of energetic particle and photon beam interactions with surfaces which lead to surface erosion and glow phenomena will be treated. In addition, projected experimental and theoretical studies of oxygen and nitrogen beam surface interactions on materials characteristic of spacecraft surfaces will be discussed

    Improving exciton dissociation and charge transport in organic photovoltaic cells

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    I have divided this dissertation into three chapters: introduction to organic solar cells, thermo-chemical lithography of a conjugated polymer, and triplet emitters in organic solar cells (OSCs). The first chapter introduces OSCs giving the background necessary to understand the problem of simultaneous optimisation of exciton dissociation and charge transport. The second chapter deals with scanning thermo-chemical lithography (SThL) of PPV on indium-tin oxide (ITO) by means of a thermal AFM, i.e. an AFM that has a hot probe scanning across the surface, to ultimately pattern the active layer of an OSC. I investigate the influence of the thermal conductivity of the substrate on the lithography by combining finite element simulations of the heat transfer and experimental results. The model explains the rather substrate-independent feature size observed during experiments and it is found that for the highest resolution features, there exists a small gap of unconverted polymer near the substrate, which is why SThL is possible on high thermal conductivity substrates such as gold. In the third chapter I report experimental findings regarding the inclusion of triplet emitters in organic photovoltaic cells. The idea is to increase the exciton diffusion length (L) of the primary photoexcitations by converting them into triplet excitons, which are known to have longer lifetimes and hence offer the potential of increased exciton diffusion lengths. Several host systems were chosen, among them P3HT:PC61BM, MDMO-PPV:PC61BM and PBTTT:bis-PC61BM. As phosphorescent molecules I used Cu-complexes and different Ir-complexes. Results on MDMO-PPV:PC61BM blends and bilayer devices showed a promising increase in the short-circuit current density (Jsc) partly supported by an increase in the incident photon to current efficiency peak in the polymer absorption wavelength range. The overall achievability of the idea is critically discussed and a 1D random walk model used to estimate possible improvements of Jsc upon increases in L

    Combining Green Metrics and Digital Twins for Sustainability Planning and Governance of Smart Buildings and Cities

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    Creating a more sustainable world will require a coordinated effort to address the rise of social, economic, and environmental concerns resulting from the continuous growth of cities. Supporting planners with tools to address them is pivotal, and sustainability is one of the main objectives. Modeling and simulation augmenting digital twins can play an important role to implement these tools. Although various green best practices have been utilized over time and there are related attempts at measuring green success, works in the published literature tend to focus on addressing a single problem (e.g., energy efficiency), and a comprehensive approach that takes the multiple facets of sustainable urban planning into consideration has not yet been identified. This paper begins with a review of recent research efforts in green metrics and digital twins. This leads to developing an approach that evaluates organizational green best practices to derive metrics, which are used for computational decision support by digital twins. Furthermore, it leverages these research results and proposes a metric-driven framework for sustainability planning that understands a city as a sociotechnical complex system. Such a framework allows the practitioner to take advantage of recent developments and provides computational decision support for the complex challenge of sustainability planning at the various levels of urban planning and governance

    Outcome Expectations of Total Knee Arthroplasty Patients: The Influence of Demographic Factors, Pain, Personality Traits, Physical and Psychological Status

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    Unfulfilled preoperative expectations have a strong influence on the outcome after total knee arthroplasty (TKA). More insight into determinants of the level of expectations is useful in identifying patients at risk for having expectations of the treatment result that are too high or too low. This information can be used in optimizing preoperative expectation management. The aim of the current study was to analyze to what extent preoperative outcome expectations of TKA patients are affected by psychological factors, demographic factors, pain, physical function, and general health status. We performed a cross-sectional analysis of 204 patients with symptomatic and radiographic knee osteoarthritis (OA), scheduled for primary TKA. Outcome expectations were measured using the hospital for special surgery knee replacement expectations survey. Independent variables included were age, sex, body mass index, and patient-reported outcome measures for pain, physical function, quality of life, anxiety, depression, catastrophizing, optimism, and pessimism. Multiple linear regression analyses were used to evaluate associations between these variables and preoperative outcome expectations. Female sex, higher age, higher depression score, and duration of complaints > 50 months showed to be significant predictors of lower expectations for the treatment outcome after TKA. Baseline pain and function scores were not related to the level of preoperative expectations. The present study aids in identifying patients at risk for having either too high or too low expectations. This knowledge can be utilized in individualized expectation management interventions

    Effect of tranexamic acid on intraoperative blood loss in pediatric osteotomies around the hip:Study protocol for a double-blind randomized placebo-controlled trial

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    Background: Proximal femoral and/or pelvic osteotomies (PFPOs) can be indicated for a multitude of hip pathologies in (often asymptomatic) children, to prevent future hip problems. These procedures can result in significant blood loss. Tranexamic acid (TXA) is an antifibrinolytic agent routinely administered in adult trauma and joint reconstruction surgery to reduce blood loss. TXA is also registered for use in children and reported safe and beneficial for pediatric trauma, cardiac, and spinal surgery. However, for pediatric orthopedics, particularly for PFPOs, the available evidence is limited. Therefore, the current trial will investigate the potential reducing effect of preoperative TXA on intraoperative blood loss in pediatric PFPOs. Methods: In this single-center, double-blind, randomized placebo-controlled trial, we aim to include 180 participants aged from 1 to 18 years undergoing PFPOs for any indication at our institution. Participants will be randomized to receive either TXA or placebo (saline) during anesthetic induction. The primary outcome is intraoperative estimated blood loss (mL/kg), which is determined gravimetrically. Secondary outcomes include the percentage of patients with excessive blood loss (&gt;20 mL/kg), procedure time and hospital stay, and postoperative hemoglobin level changes. Discussion: This will be the first prospective study investigating the effect of preoperative TXA on intraoperative blood loss in pediatric PFPOs. Its results will help to determine whether it would be advisable to adopt preoperative TXA as a standard medication to minimize blood loss and prevent complications in this vulnerable population. Trial registration: EudraCT: 2022-002384-30. Prospectively registered on September 26, 2022.</p

    Testing of a Water Loss Distribution Model for Moving Sprinkler Systems

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    Field water balance measurements using monolithic lysimeters were used in validating the Cupid-DPE model for predicting water loss partitioning during sprinkler irrigation from a moving lateral system fitted with impact sprinklers and spray nozzles. The model combines equations governing water droplet evaporation and droplet ballistics with a comprehensive plant-environment energy balance model. Comparisons indicate good agreement between measured and modeled transpiration, and the measured and modeled soil evaporation during the day of irrigation. Total predicted evapotranspiration during the day of irrigation was greater than measured totals using the monolithic lysimeters. However, part of this difference was because the lysimeters could not measure water use during irrigation. Total measured and predicted evapo-transpiration agreed well for the day following irrigation. Predicted soil evaporation rates matched well for the period immediately following irrigation, and cumulative soil evaporation was nearly identical to the measured total through the end of the next day. During irrigation, the main water loss was shifted from transpiration to evaporation of the wetted-canopy. For equal application volumes, the duration of this effect was greater using impact sprinklers due to the greater wetted diameter and lower average application rate compared to spray nozzles. Predicted water flux rates during irrigation were up to 50% greater for canopy evaporation than for transpiration rates predicted immediately prior to the start of irrigation. Canopy evaporation amounted to 69% and 63% of the total predicted water use during impact and spray irrigation, respectively. It also was 0.69 and 0.28 mm greater, respectively, than the predicted transpiration total during this same time span assuming no irrigation had been applied. About 13 and 5% of the water applied by overhead sprinkling was evaporated or transpired during impact and spray irrigation, respectively. However, the net increase in predicted water loss during irrigation was only 5.8% and 2.4% of the irrigated water depth applied for the impact and spray cases, respectively, because transpiration and soil evaporation would have occurred even without irrigation. Although droplet evaporation represented less than 1% of the total water loss for the day using either type of sprinkler, irrigation water did influence the energy transfer between the plant-environment and water droplets during flight, on the canopy, and the soil

    MtDNA Haplogroups in the Populations of Croatian Adriatic Islands

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    The number of previous anthropological studies pointed to very complex ethnohistorical processes that shaped the current genetic structure of Croatian island isolates. The scope of this study was limited to the general insight into their founding populations and the overall level of genetic diversity based on the study mtDNA variation. A total of 444 randomly chosen adult individuals from 32 rural communities of the islands of Krk, Brač, Hvar and Korčula were sampled. MtDNA HVS-I region together with RFLP sites diagnostic for main Eurasian and African mtDNA haplogroups were analysed in order to determine the haplogroup structure. The most frequent haplogroups were »H« (27.8–60.2%), »U« (10.2–24.1%), »J« (6.1–9.0%) and »T« (5.1–13.9%), which is similar to the other European and Near Eastern populations. The genetic drift could have been important aspect in history, as there were examples of excess frequencies of certain haplogroups (11.3% of »I« and 7.5% of »W« in Krk, 10.5% of »HV« in Brač, 13.9% of »J« in Hvar and 60.2% of »H« in Korčula). As the settlements on the islands were formed trough several immigratory episodes of genetically distant populations, this analysis (performed at the level of entire islands) showed greater genetic diversity (0.940–0.972) than expected at the level of particular settlements

    Improved performance of the LHCb Outer Tracker in LHC Run 2

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    The LHCb Outer Tracker is a gaseous detector covering an area of 5×6m25\times 6 m^2 with 12 double layers of straw tubes. The performance of the detector is presented based on data of the LHC Run 2 running period from 2015 and 2016. Occupancies and operational experience for data collected in ppp p, pPb and PbPb collisions are described. An updated study of the ageing effects is presented showing no signs of gain deterioration or other radiation damage effects. In addition several improvements with respect to LHC Run 1 data taking are introduced. A novel real-time calibration of the time-alignment of the detector and the alignment of the single monolayers composing detector modules are presented, improving the drift-time and position resolution of the detector by 20\%. Finally, a potential use of the improved resolution for the timing of charged tracks is described, showing the possibility to identify low-momentum hadrons with their time-of-flight.Comment: 29 pages, 20 figures, minor changes to match the published versio

    Measurement of the CP-violating phase phi(s) from B-s(0) -&gt; J/psi pi(+)pi(-) decays in 13 TeV pp collisions

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    Decays of B-s(0) and (B) over bar (0)(s) mesons into J/psi pi(+)pi(-) final states are studied in a data sample corresponding to 1.9 fb(-1) of integrated luminosity collected with the LHCb detector in 13 TeV pp collisions. A time-dependent amplitude analysis is used to determine the final-state resonance contributions, the CP-violating phase phi(s) = -0.057 +/- 0.060 +/- 0.011 rad, the decay-width difference between the heavier mass B-s(0) eigenstate and the B-0 meson of -0.050 +/- 0.004 +/- 0.004 ps(-1), and the CP-violating parameter vertical bar lambda vertical bar = 1.01(-0.06)(+0.08) +/- 0.03, where the first uncertainty is statistical and the second systematic. These results are combined with previous LHCb measurements in the same decay channel using 7 TeV and 8 TeV pp collisions obtaining phi(s) = 0.002 +/- 0.044 +/- 0.012 rad, and vertical bar lambda vertical bar = 0.949 +/- 0.036 +/- 0.019. (C) 2019 The Author. Published by Elsevier B.V
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