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Particle loading as a design parameter for composite radiation shielding
Baumann N.,Diaz K. Marquez,Simmons-Potter K.,Potter B.G.,Bucay J. 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.10
An evaluation of the radiation shielding performance of high-Z-particle-loaded polylactic acid (PLA) composite materials was pursued. Specimens were produced via fused deposition modeling (FDM) using copper-PLA, steel-PLA, and BaSO4-PLA composite filaments containing 82.7, 75.2, and 44.6 wt% particulate phase contents, respectively, and were tested under broad-band flash x-ray conditions at the Sandia National Laboratories HERMES III facility. The experimental results for the mass attenuation coefficients of the composites were found to be in good agreement with GEANT4 simulations carried out using the same exposure conditions and an atomistic mixture as a model for the composite materials. Further simulation studies, focusing on the Cu-PLA composite system, were used to explore a shield design parameter space (in this case, defined by Cu-particle loading and shield areal density) to assess performance under both high-energy photon and electron fluxes over an incident energy range of 0.5 e15 MeV. Based on these results, a method is proposed that can assist in the visualization and isolation of shield parameter coordinate sets that optimize performance under targeted radiation characteristics (type, energy). For electron flux shielding, an empirical relationship was found between areal density (AD), electron energy (E), composition and performance. In cases where E AD 2 MeVcmg1 , a shield composed of >85 wt% Cu results in optimal performance. In contrast, a shield composed of <10 wt% Cu is anticipated to perform best against electron irradiation when E AD <2 MeVcmg1 .
Sushanth Rao Aroor,Kaiz S. Asif,Jennifer Potter-Vig,Arun Sharma,Bijoy K. Menon,Violiza Inoa,Cynthia B. Zevallos,Jose G. Romano,Santiago Ortega-Gutierrez,Larry B. Goldstein,Dileep R. Yavagal 대한뇌졸중학회 2022 Journal of stroke Vol.24 No.1
Mechanical thrombectomy (MT) is the most effective treatment for selected patients with an acute ischemic stroke due to emergent large vessel occlusions (LVOs). There is an urgent need to identify and address challenges in access to MT to maximize the numbers of patients who can benefit from this treatment. Barriers in access to MT include delays in evaluation and accurate diagnosis of LVO leading to inappropriate triage, logistical delays related to availability of facilities and trained interventionalists, and financial hurdles that affect treatment reimbursement. Collection of regional data related to these barriers is critical to better understand current access gaps and a measurable access score to thrombectomy could be useful to plan local public health intervention.
A 6-Point TACS Score Predicts In-Hospital Mortality Following Total Anterior Circulation Stroke
Adrian D Wood,Nicholas D Gollop,Joao H Bettencourt-Silva,Allan B Clark,Anthony K Metcalf,Kristian M Bowles,Marcus D Flather,John F Potter,Phyo Kyaw Myinta 대한신경과학회 2016 Journal of Clinical Neurology Vol.12 No.4
Background and Purpose Little is known about the factors associated with in-hospital mortality following total anterior circulation stroke (TACS). We examined the characteristics and comorbidity data for TACS patients in relation to in-hospital mortality with the aim of developing a simple clinical rule for predicting the acute mortality outcome in TACS. Methods A routine data registry of one regional hospital in the UK was analyzed. The sub¬jects were 2,971 stroke patients with TACS (82% ischemic; median age=81 years, interquar¬tile age range=74–86 years) admitted between 1996 and 2012. Uni- and multivariate regres¬sion models were used to estimate in-hospital mortality odds ratios for the study covariates. A 6-point TACS scoring system was developed from regression analyses to predict in-hospi¬tal mortality as the outcome. Results Factors associated with in-hospital mortality of TACS were male sex [adjusted odds ratio (AOR)=1.19], age (AOR=4.96 for ≥85 years vs. <65 years), hemorrhagic subtype (AOR=1.70), nonlateralization (AOR=1.75), prestroke disability (AOR=1.73 for moderate disability vs. no symptoms), and congestive heart failure (CHF) (AOR=1.61). Risk stratifica¬tion using the 6-point TACS Score [T=type (hemorrhage=1 point) and territory (nonlateral¬ization=1 point), A=age (65–84 years=1 point, ≥85 years=2 points), C=CHF (if present=1 point), S=status before stroke (prestroke modified Rankin Scale score of 4 or 5=1 point)] reli-ably predicted a mortality outcome: score=0, 29.4% mortality; score=1, 46.2% mortality [negative predictive value (NPV)=70.6%, positive predictive value (PPV)=46.2%]; score=2, 64.1% mortality (NPV=70.6, PPV=64.1%); score=3, 73.7% mortality (NPV=70.6%, PPV=73.7%); and score=4 or 5, 81.2% mortality (NPV=70.6%, PPV=81.2%). Conclusions We have identified the key determinants of in-hospital mortality following TACS and derived a 6-point TACS Score that can be used to predict the prognosis of particular patients.
Emma J. Foster,Raphae S. Barlas,Adrian D Wood,Joao H. Bettencourt-Silva,Allan B Clark,Anthony K Metcalf,Kristian M Bowles,John F Potter,Phyo K. Myint 대한신경과학회 2017 Journal of Clinical Neurology Vol.13 No.4
Background and Purpose The risks of falls and fractures increase after stroke. Little is known about the prognostic significance of previous falls and fractures after stroke. This study examined whether having a history of either event is associated with poststroke mortality. Methods We analyzed stroke register data collected prospectively between 2003 and 2015. Eight sex-specific models were analyzed, to which the following variables were incrementally added to examine their potential confounding effects: age, type of stroke, Oxfordshire Community Stroke Project classification, previous comorbidities, frailty as indicated by the prestroke modified Rankin Scale score, and acute illness parameters. Logistic regression was applied to investigate in-hospital and 30-day mortality, and Cox proportional-hazards models were applied to investigate longer-term outcomes of mortality. Results In total, 10,477 patients with stroke (86.1% ischemic) were included in the analysis. They were aged 77.7±11.9 years (mean±SD), and 52.2% were women. A history of falls was present in 8.6% of the men (n=430) and 20.2% of the women (n=1,105), while 3.8% (n=189) of the men and 12.9% of the women (n=706) had a history of both falls and fractures. Of the outcomes examined, a history of falls alone was associated with increased in-hospital mortality [odds ratio (OR)=1.33, 95% confidence interval (CI)=1.03–1.71] and 30-day mortality (OR=1.34, 95% CI=1.03–1.73) in women in the fully adjusted models. The Cox proportional-hazards models for longer-term outcomes and the history of falls and fractures combined showed no significant results. Conclusions The history of falls is an important factor for acute stroke mortality in women. A previous history of falls may therefore be an important factor to consider in the short-term stroke prognosis, particularly in women.