1,524 research outputs found
The Evolution of Hetergeneous "Clumpy Jets": A Parameter Study
We investigate the role discrete clumps embedded in an astrophysical jet play
on the jet's morphology and line emission characteristics. By varying clumps'
size, density, position, and velocity, we cover a range of parameter space
motivated by observations of objects such as the Herbig Haro object HH~34. We
here extend the results presented in Yirak et al. 2009, including how analysis
of individual observations may lead to spurious sinusoidal variation whose
parameters vary widely over time, owing chiefly to interacts between clumps.
The goodness of the fits, while poor in all simulations, are best when
clump-clump collisions are minimal. Our results indicate that a large velocity
dispersion leads to a clump-clump collision-dominated flow which disrupts the
jet beam. Finally, we present synthetic emission images of H- and [SII]
and note an excess of [SII] emission along the jet length as compared to
observations. This suggests that observed beams undergo earlier processing, if
they are present at all.Comment: 18 pages, 7 figures. Submitted to the Astrophysical Journa
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Evaluation of simulated O-3 production efficiency during the KORUS-AQ campaign: Implications for anthropogenic NOx emissions in Korea
We examine O3 production and its sensitivity to precursor gases and boundary layer mixing in Korea by using a 3-D global chemistry transport model and extensive observations during the KORea-US cooperative Air Quality field study in Korea, which occurred in MayâJune 2016. During the campaign, observed aromatic species onboard the NASA DC-8 aircraft, especially toluene, showed high mixing ratios of up to 10 ppbv, emphasizing the importance of aromatic chemistry in O3 production. To examine the role of VOCs and NOx in O3 chemistry, we first implement a detailed aromatic chemistry scheme in the model, which reduces the normalized mean bias of simulated O3 mixing ratios from â26% to â13%. Aromatic chemistry also increases the average net O3 production in Korea by 37%. Corrections of daytime PBL heights, which are overestimated in the model compared to lidar observations, increase the net O3 production rate by ~10%. In addition, increasing NOx emissions by 50% in the model shows best performance in reproducing O3 production characteristics, which implies that NOx emissions are underestimated in the current emissions inventory. Sensitivity tests show that a 30% decrease in anthropogenic NOx emissions in Korea increases the O3 production efficiency throughout the country, making rural regions ~2 times more efficient in producing O3 per NOx consumed. Simulated O3 levels overall decrease in the peninsula except for urban and other industrial areas, with the largest increase (~6 ppbv) in the Seoul Metropolitan Area (SMA). However, with simultaneous reductions in both NOx and VOCs emissions by 30%, O3 decreases in most of the country, including the SMA. This implies the importance of concurrent emission reductions for both NOx and VOCs in order to effectively reduce O3 levels in Korea
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A Little Blue Bird Told Me: Sentiment Change on Orphanage Tourism
This study examined Twitter conversations to understand the changes in the sentiments related to orphanage tourism between 2009 and 2019. Past research on orphanage tourism mostly took a qualitative approach, which provided profound knowledge but was limited to a single time and those directly involved. This study fills the gap by analyzing the tweets posted by different parties, including the individuals that have participated or are willing to participate in orphanage tourism, institutions that have campaigned against the phenomenon, and organizations that have promoted orphanage volunteering. Analysis of 109,723 tweets using lexicons and supervised learningâSupport Vector Machine, Random Forest, Naive Bayes, and Logistic regressionârevealed that the year 2014 marked a turning point for orphanage tourism conversations as the number of posts dropped significantly, and the messages against orphanage tourism received attention. However, the positive sentiment still prevailed throughout the decade when all tweets were considered
Pediatric surgical extracorporeal membrane oxygenation - a case series
Objective. To review demographic and procedural factors and their association with weaning rate and survival from extracorporeal membrane oxygenation (ECMO) in pediatric patients undergoing repair of cardiac malformations.
Methods. The hospital records of children requiring ECMO during cardiac operation due to failure to wean from cardio-pulmonary by pass (CPB) were retrospectively reviewed, and an analysis of variables affecting survival was performed.
Results. Thirty-five pediatric patients between January 1, 2000 and December 31, 2006 required ECMO for cardiopulmonary support during cardiac operations. ECMO survival was 54.3% and was comparable across all age groups. The lowest pH during ECMO treatment was the only predictor of mortality (P = 0.006). No other patient, surgical or anesthetic, factor was associated with either weaning from ECMO or hospital survival.
Conclusions. No clear risk factor could be identified for survival from ECMO in our pediatric patients who underwent cardiac surgery and failed weaning from cardiopulmonary bypass
A mixed methods study of the factors that influence whether intervention research has policy and practice impacts: perceptions of Australian researchers
Objectives: To investigate researchersâ perceptions about the factors that influenced the policy and practice impacts (or lack of impact) of one of their own funded intervention research studies.
Design: Mixed method, cross-sectional study.
Setting: Intervention research conducted in Australia and funded by Australiaâs National Health and Medical Research Council between 2003 and 2007.
Participants: The chief investigators from 50 funded intervention research studies were interviewed to determine if their study had achieved policy and practice impacts, how and why these impacts had (or had not) occurred and the approach to dissemination they had employed.
Results: We found that statistically significant intervention effects and publication of results influenced whether there were policy and practice impacts, along with factors related to the nature of the intervention itself, the researchersâ experience and connections, their dissemination and translation efforts, and the postresearch context.
Conclusions: This study indicates that sophisticated approaches to intervention development, dissemination actions and translational efforts are actually widespread among experienced researches, and can achieve policy and practice impacts. However, it was the links between the intervention results, further dissemination actions by researchers and a variety of postresearch contextual factors that ultimately determined whether a study had policy and practice impacts. Given the complicated interplay between the various factors, there appears to be no simple formula for determining which intervention studies should be funded in order to achieve optimal policy and practice impacts
Tracking funded health intervention research
Objective: To describe the research publication outputs from intervention research funded by Australiaâs National Health and Medical Research Council (NHMRC).
Design and setting: Analysis of descriptive data and data on publication outputs collected between 23 July 2012 and 10 December 2013 relating to health intervention research project grants funded between 1 January 2003 and 31 December 2007.
Main outcome measures: Stages of development of intervention studies (efficacy, effectiveness, replication, adaptation or dissemination of intervention); types of interventions studied; publication output per NHMRC grant; and whether interventions produced statistically significant changes in primary outcome variables.
Results: Most of the identified studies tested intervention efficacy or effectiveness in clinical or community settings, with few testing the later stages of intervention development, such as replication, adaptation or dissemination. Studies focused largely on chronic disease treatment and management, and encompassed various medical and allied health disciplines. Equal numbers of studies had interventions that produced statistically significant results on primary outcomes, (27) and those that did not (27). The mean number of total published articles per grant was 3.3, with 2.0 articles per grant focusing on results, and the remainder covering descriptive, exploratory or methodological aspects of intervention research.
Conclusions: Our study provides a benchmark for the publication outputs of NHMRC-funded health intervention research in Australia. Research productivity is particularly important for intervention research, where findings are likely to have more immediate and direct applicability to health policy and practice. Tracking research outputs in this way provides information on whether current research investment patterns match the need for evidence about health care interventions
Change management: The case of the elite sport performance team
The effective and efficient implementation of change is often required for both successful performance and management survival across a host of contemporary domains. However, although of major theoretical and practical significance, research to date has overlooked the application of change management (hereafter CM) knowledge to the elite sport performance team environment. Considering that the success of âoff-fieldâ sports businesses are largely dependent on the performances of their âon-fieldâ team, this article explores the application of current CM theorizing to this specific setting and the challenges facing its utility. Accordingly, we identify the need and importance of developing theory specific to this area, with practical application in both sport and business, through examination of current knowledge and identification of the domain's unique, dynamic and contested properties. Markers of successful change are then suggested to guide initial enquiry before the article concludes with proposed lines of research which may act to provide a valid and comprehensive theoretical account of CM to optimize the research and practice of those working in the field
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Observation-based modeling of ozone chemistry in the Seoul metropolitan area during the Korea-United States Air Quality Study (KORUS-AQ)
The Seoul Metropolitan Area (SMA) has a population of 24 million and frequently experiences unhealthy levels of ozone (O3). In this work, measurements taken during the Korea-United States Air Quality Study (KORUS-AQ, 2016) are used to explore regional gradients in O3 and its chemical precursors, and an observationally-constrained 0-D photochemical box model is used to quantify key aspects of O3 production including its sensitivity to precursor gases. Box model performance was evaluated by comparing modeled concentrations of select secondary species to airborne measurements. These comparisons indicate that the steady state assumption used in 0-D box models cannot describe select intermediate species, highlighting the importance of having a broad suite of trace gases as model constraints. When fully constrained, aggregated statistics of modeled O3 production rates agreed with observed changes in O3, indicating that the box model was able to represent the majority of O3 chemistry.
Comparison of airborne observations between urban Seoul and a downwind receptor site reveal a positive gradient in O3 coinciding with a negative gradient in NOx, no gradient in CH2O, and a slight positive gradient in modeled rates of O3 production. Together, these observations indicate a radical-limited (VOC-limited) O3 production environment in the SMA. Zero-out simulations identified C7+ aromatics as the dominant VOC contributors to O3 production, with isoprene and anthropogenic alkenes making smaller but appreciable contributions. Simulations of model sensitivity to decreases in NOx produced results that were not spatially uniform, with large increases in O3 production predicted for urban Seoul and decreases in O3 production predicted for far-outlying areas. The policy implications of this work are clear: Effective O3 mitigation strategies in the SMA must focus on reducing local emissions of C7+ aromatics, while reductions in NOx emissions may increase O3 in some areas but generally decrease the regional extent of O3 exposure
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