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1.
N Z Med J ; 136(1580): 12-25, 2023 Aug 04.
Article in English | MEDLINE | ID: mdl-37536308

ABSTRACT

AIM: To describe atrial fibrillation (AF) patient characteristics and anticoagulation patterns in stroke patients in Aotearoa. METHODS: Reducing Ethnic and Geographic Inequities to Optimise New Zealand Stroke (REGIONS) Care study is a prospective, nation-wide observational study of consecutive adult stroke patients admitted to hospital between 1 May and 31 October 2018. AF and anticoagulation prescribing, intracerebral haemorrhage (ICH) and differences by Maori ethnicity and hospital location are described. RESULTS: Of 2,379 patients, 807 (34.3%) had a diagnosis of AF. AF patients were older than non-AF patients (mean 79.9 [SD 11] versus 72.5 [14.2], p<0.0001). AF was diagnosed before stroke in 666 patients (82.5%), of whom 442 (66.4%) were taking an anticoagulant. The most common documented reasons for non-anticoagulation were prior bleeding (20.5%), patient preference (18.1%), frailty, comorbidities/side effects (13.2%) and falls (6.8%). The ICH rate was similar for AF patients on versus not on an anticoagulant (adjusted odds ratio [aOR] 0.99, 95% confidence interval [CI] 0.55-1.80). Rates and reasons for oral anticoagulant non-prescribing were similar for Maori, non-Maori, urban and non-urban populations. CONCLUSIONS: Although anticoagulation prescribing in AF has improved, one third of stroke patients with known AF were not taking an anticoagulant prior to admission and the majority did not appear to have an absolute contraindication offering a multidisciplinary opportunity for improvement. There were no significant differences for Maori and non-urban populations in anticoagulant prescribing.


Subject(s)
Atrial Fibrillation , Stroke , Adult , Humans , Atrial Fibrillation/complications , Atrial Fibrillation/drug therapy , Atrial Fibrillation/epidemiology , Prospective Studies , New Zealand/epidemiology , Risk Factors , Stroke/drug therapy , Stroke/epidemiology , Anticoagulants/therapeutic use , Administration, Oral
2.
Neurorehabil Neural Repair ; 37(7): 475-487, 2023 Jul.
Article in English | MEDLINE | ID: mdl-37191349

ABSTRACT

BACKGROUND: Atlas-based voxel features have the potential to aid motor outcome prognostication after stroke, but are seldom used in clinically feasible prediction models. This could be because neuroimaging feature development is a non-standardized, complex, multistep process. This is a barrier to entry for researchers and poses issues for reproducibility and validation in a field of research where sample sizes are typically small. OBJECTIVES: The primary aim of this review is to describe the methodologies currently used in motor outcome prediction studies using atlas-based voxel neuroimaging features. Another aim is to identify neuroanatomical regions commonly used for motor outcome prediction. METHODS: A Preferred Reporting Items for Systematic Reviews and Meta-Analyses protocol was constructed and OVID Medline and Scopus databases were searched for relevant studies. The studies were then screened and details about imaging modality, image acquisition, image normalization, lesion segmentation, region of interest determination, and imaging measures were extracted. RESULTS: Seventeen studies were included and examined. Common limitations were a lack of detailed reporting on image acquisition and the specific brain templates used for normalization and a lack of clear reasoning behind the atlas or imaging measure selection. A wide variety of sensorimotor regions relate to motor outcomes and there is no consensus use of one single sensorimotor atlas for motor outcome prediction. CONCLUSION: There is an ongoing need to validate imaging predictors and further improve methodological techniques and reporting standards in neuroimaging feature development for motor outcome prediction post-stroke.


Subject(s)
Stroke , Humans , Reproducibility of Results , Stroke/diagnostic imaging , Stroke/pathology , Brain/diagnostic imaging , Brain/pathology , Prognosis , Neuroimaging
4.
Eur Stroke J ; 8(1): 191-198, 2023 03.
Article in English | MEDLINE | ID: mdl-37021178

ABSTRACT

Introduction: The very elderly (⩾80 years) are under-represented in randomised endovascular thrombectomy (EVT) clinical trials for acute ischaemic stroke. Rates of independent outcome in this group are generally lower than the less-old patients but the comparisons may be biased by an imbalance of non-age related baseline characteristics, treatment related metrics and medical risk factors. Patients and methods: We compared outcomes between very elderly (⩾80) and the less-old (<80 years) using retrospective data from consecutive patients receiving EVT from four comprehensive stroke centres in New Zealand and Australia. We used propensity score matching or multivariable logistic regression to account for confounders. Results: We included 600 patients (300 in each age cohort) after propensity score matching from an initial group of 1270 patients. The median baseline National Institutes of Health Stroke Scale was 16 (11-21), with 455 (75.8%) having symptom free pre-stroke independent function, and 268 (44.7%) receiving intravenous thrombolysis. Good functional outcome (90-day modified Rankin Scale 0-2) was achieved in 282 (46.8%), with very elderly patients having less proportion of good outcome compared to the less-old (118 (39.3%) vs 163 (54.3%), p < 0.01). There was no difference between the very elderly and the less-old in the proportion of patients who returned to baseline function at 90 days (56 (18.7%) vs 62 (20.7%), p = 0.54). All-cause 90-day mortality was higher in the very elderly (75 (25%) vs 49 (16.3%), p < 0.01), without a difference in symptomatic haemorrhage (very elderly 11 (3.7%) vs 6 (2.0%), p = 0.33). In the multivariable logistic regression models, the very elderly were significantly associated with reduced odds of good 90-day outcome (OR 0.49, 95% CI 0.34-0.69, p < 0.01) but not with return to baseline function (OR 0.85, 90% CI 0.54-1.29, p = 0.45) after adjusting for confounders. Conclusion: Endovascular thrombectomy can be successfully and safely performed in the very elderly. Despite an increase in all-cause 90-day mortality, selected very elderly patients are as likely as younger patients with similar baseline characteristics to return to baseline function following EVT.


Subject(s)
Brain Ischemia , Endovascular Procedures , Ischemic Stroke , Stroke , Humans , Aged , Stroke/surgery , Brain Ischemia/surgery , Retrospective Studies , Propensity Score , Treatment Outcome , Endovascular Procedures/adverse effects , Thrombectomy/adverse effects , Ischemic Stroke/surgery
6.
Eur J Neurol ; 30(3): 671-677, 2023 03.
Article in English | MEDLINE | ID: mdl-36463490

ABSTRACT

BACKGROUND AND PURPOSE: Limited data guide the selection of patients with large vessel occlusion ischaemic stroke who may benefit from referral to a distant tertiary centre for mechanical thrombectomy (MT). We aimed to characterize this population, describe clinical outcomes and develop a screening system to identify patients most likely to benfit from delayed mechanical thrombectomy (MT). METHODS: We undertook a retrospective cohort analysis enrolling patients transferred from regional sites to one of two MT comprehensive stroke units with a time from non-contrast computed tomography (NCCT) of the brain to reperfusion of 4 h or more. We describe Alberta Stroke Programme Early Computed Tomography Score (ASPECTS), National Institute of Health Stroke Scale (NIHSS) and modified Rankin Scale (mRS) in our patients and compare these patients to those in extended-time-window trials. Lastly, we developed and validated a scoring model to help clinicians identify appropriate patients based on variables associated with poor outcomes. RESULTS: We included 563 patients, 46% of whom received thrombolysis; the median (interquartile range [IQR]) ASPECTS was 8 (7-10) and the median (IQR) NIHSS score was 16 (11-20). The median (IQR) symptom to mechanical reperfusion time was 390 (300-580) min. Eight patients (1%) had a symptomatic haemorrhage. We achieved good clinical outcome (defined as mRS score ≤2) in 299 patients (54%). Age, diabetes, NIHSS score and ASPECTS were used to create a weighted scoring system with a validated area under the curve of 0.83 (95% confidence interval 0.74-0.92). CONCLUSION: Our study shows, in highly selected patients, that delayed MT many hours after baseline NCCT is associated with good clinical outcomes. However, older patients with diabetes, high NIHSS score and low ASPECTS may not benefit from transfer to a hub centre many hours away for MT in this model of care.


Subject(s)
Brain Ischemia , Ischemic Stroke , Stroke , Humans , Stroke/diagnostic imaging , Stroke/surgery , Brain Ischemia/diagnostic imaging , Brain Ischemia/surgery , Retrospective Studies , Thrombectomy/methods , Treatment Outcome , Ischemic Stroke/etiology
7.
Aust J Rural Health ; 31(2): 274-284, 2023 Apr.
Article in English | MEDLINE | ID: mdl-36382851

ABSTRACT

OBJECTIVES: To compare processes of care and clinical outcomes of community-based management of TIAs and minor strokes (TIAMS) between rural and metropolitan Australia. DESIGN: Inception cohort study between 2012 and 2016 with 12-month follow-up after index event (sub-study of INSIST). SETTING: Hunter and Manning valley regions of New South Wales, within the referral territory of the John Hunter Hospital Acute Neurovascular Clinic (JHHANC). PARTICIPANTS: Consecutive patients of 16 participating general practices, presenting with possible TIAMS to either primary or secondary care. MAIN OUTCOME MEASURES: Processes of care (referrals, key management processes, time-based metrics) and clinical outcomes. RESULTS: Of 613 participants with possible TIAMS who completed the baseline interview, 298 were adjudicated as having TIAMS (119 from rural, 179 from metropolitan). Mean age was 72.3 years (SD, 10.7) and 127 (43%) were women. Rural participants were more likely to be managed solely by a general practitioner (GP) than metropolitan participants (34% v 20%) and less likely to be referred to a JHHANC specialist (13% v 38%) or have brain magnetic resonance imaging (MRI) [24% v 51%]. Those rural participants who were referred, also waited longer (both p < 0.001). Recurrent stroke, myocardial infarction and death at 12 months were not significantly different between rural and metropolitan participants. CONCLUSIONS: Although TIAMS prognosis in rural settings where solely GP care is common is very good, the processes of care in such areas are inferior to metropolitan. This suggests there is further scope to support rural GPs to optimise care of TIAMS patients.


Subject(s)
Delivery of Health Care , General Practice , Ischemic Attack, Transient , Rural Health Services , Stroke , Aged , Female , Humans , Male , Australia , Cohort Studies , Ischemic Attack, Transient/therapy , Stroke/therapy , Patient Reported Outcome Measures , Community Health Services
8.
JMIR Res Protoc ; 10(1): e25374, 2021 Jan 12.
Article in English | MEDLINE | ID: mdl-33433396

ABSTRACT

BACKGROUND: Stroke systems of care differ between larger urban and smaller rural settings and it is unclear to what extent this may impact on patient outcomes. Ethnicity influences stroke risk factors and care delivery as well as patient outcomes in nonstroke settings. Little is known about the impact of ethnicity on poststroke care, especially in Maori and Pacific populations. OBJECTIVE: Our goal is to describe the protocol for the Reducing Ethnic and Geographic Inequities to Optimise New Zealand Stroke Care (REGIONS Care) study. METHODS: This large, nationwide observational study assesses the impact of rurality and ethnicity on best practice stroke care access and outcomes involving all 28 New Zealand hospitals caring for stroke patients, by capturing every stroke patient admitted to hospital during the 2017-2018 study period. In addition, it explores current access barriers through consumer focus groups and consumer, carer, clinician, manager, and policy-maker surveys. It also assesses the economic impact of care provided at different types of hospitals and to patients of different ethnicities and explores the cost-efficacy of individual interventions and care bundles. Finally, it compares manual data collection to routine health administrative data and explores the feasibility of developing outcome models using only administrative data and the cost-efficacy of using additional manually collected registry data. Regarding sample size estimates, in Part 1, Study A, 2400 participants are needed to identify a 10% difference between up to four geographic subgroups at 90% power with an α value of .05 and 10% to 20% loss to follow-up. In Part 1, Study B, a sample of 7645 participants was expected to include an estimated 850 Maori and 419 Pacific patients and to provide over 90% and over 80% power, respectively. Regarding Part 2, 50% of the patient or carer surveys, 40 provider surveys, and 10 focus groups were needed to achieve saturation of themes. The main outcome is the modified Rankin Scale (mRS) score at 3 months. Secondary outcomes include mRS scores; EQ-5D-3L (5-dimension, 3-level EuroQol questionnaire) scores; stroke recurrence; vascular events; death; readmission at 3, 6, and 12 months; cost of care; and themes around access barriers. RESULTS: The study is underway, with national and institutional ethics approvals in place. A total of 2379 patients have been recruited for Part 1, Study A; 6837 patients have been recruited for Part 1, Study B; 10 focus groups have been conducted and 70 surveys have been completed in Part 2. Data collection has essentially been completed, including follow-up assessment; however, primary and secondary analyses, data linkage, data validation, and health economics analysis are still underway. CONCLUSIONS: The methods of this study may provide the basis for future epidemiological studies that will guide care improvements in other countries and populations. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/25374.

9.
J Stroke Cerebrovasc Dis ; 29(3): 104589, 2020 Mar.
Article in English | MEDLINE | ID: mdl-31879136

ABSTRACT

INTRODUCTION: Community knowledge and stroke awareness is crucial for primary prevention of stroke and timely access to stroke treatments including acute reperfusion therapies. We conducted a national telephone survey to quantify the level of community stroke awareness. METHODS: A random sample of 400 adults in New Zealand (NZ), stratified by the 4 main ethnic groups, was surveyed. Eligible participants answered stroke awareness questions using both unprompted (open-ended) and prompted questions (using a list). Proportional odds logistic regression models were used to identify factors associated with stroke awareness. RESULTS: Only 1.5% of participants named stroke as a major cause of death. The stroke signs and symptoms most frequently identified from a list were sudden speech difficulty (94%) and sudden 1-sided weakness (92%). Without prompting, 78% of participants correctly identified at least 1 risk factor, 62% identified at least 2, and 35% identified 3 or more. When prompted with the list, scores increased 10-fold compared with unprompted responses. Ethnic disparities were observed, with Pacific peoples having the lowest level of awareness among the 4 ethnic groups. Higher education level, higher income, and personal experience of stroke were predictive of greater awareness (P ≤ .05). CONCLUSIONS: Stroke was not recognized as a major cause of death. Although identification of stroke risk factors was high with prompting, awareness was low without prompting, particularly among those with lower education and income. Nationwide, culturally tailored public awareness campaigns are necessary to improve knowledge of stroke risk factors, recognition of stroke in the community and appropriate actions to take in cases of suspected stroke.


Subject(s)
Awareness , Health Knowledge, Attitudes, Practice/ethnology , Native Hawaiian or Other Pacific Islander/psychology , Stroke/ethnology , Adult , Cause of Death , Cultural Characteristics , Culturally Competent Care/ethnology , Female , Health Promotion , Humans , Male , Middle Aged , New Zealand/epidemiology , Prognosis , Risk Assessment , Risk Factors , Stroke/diagnosis , Stroke/mortality , Stroke/therapy
10.
N Z Med J ; 129(1438): 44-9, 2016 Jul 15.
Article in English | MEDLINE | ID: mdl-27447135

ABSTRACT

The New Zealand National Stroke Network introduced a National Stroke Thrombolysis Register on the first of January 2015 to assist with quality assurance and continuous service improvement. In the first 6 months, there were 179 [75 women, mean (SD) age 69.9 (14) years] treated with stroke thrombolysis out of a total of 2,796 ischaemic stroke patients, giving a national thrombolysis rate of 6.4%. The median [Inter-quartile range (IQR)] onset-to-treatment time was 154 (125-190) minutes, and the median (IQR) door-to-needle time was 74.5 (55.7-105.0) minutes. The rate of symptomatic intracranial haemorrhage following thrombolysis was 4.4%. These results are similar to other international centres, and indicate an approximate doubling of the proportion of stroke patients treated with stroke thrombolysis since a 2009 national audit. However, there is need for on-going efforts to improve treatment rates and process efficiency, particularly door-toneedle times.


Subject(s)
Fibrinolytic Agents/administration & dosage , Stroke/drug therapy , Thrombolytic Therapy/statistics & numerical data , Time-to-Treatment/statistics & numerical data , Tissue Plasminogen Activator/administration & dosage , Aged , Aged, 80 and over , Cerebral Hemorrhage/epidemiology , Female , Hospitals/statistics & numerical data , Humans , Male , New Zealand/epidemiology , Prospective Studies , Registries
11.
N Z Med J ; 128(1423): 57-62, 2015 Oct 16.
Article in English | MEDLINE | ID: mdl-26645756

ABSTRACT

AIMS: In acute ischaemic stroke, endovascular therapy with the Solitaire FR stent retriever has been shown to double recanalisation rates and the numbers of patients who recover to be functionally independent, when compared to standard therapy. We present the Auckland City Hospital experience of clot retrieval. METHODS: Previously independent ischaemic stroke patients with contraindications to, or no response following, i.v. alteplase, were treated with clot retrieval. All patients had proximal large artery occlusions on CT angiography and many also had CT perfusion scans showing salvageable ischaemic tissue. RESULTS: Clot retrieval was performed in 33 patients (10 women, mean (SD) age of 54 (17) years) since 2011. Twenty-two (67%) patients were first treated with alteplase. Patients fell into three groups: 17 (52%) had anterior circulation occlusion, similar to those in recent clot retrieval studies; 10 (30%) had posterior circulation occlusion; and six (18%) had 'Rescue' clot retrieval, usually with stroke that followed a procedure. Patients with anterior circulation occlusion had a median time from symptom onset to groin puncture of 225 (range 95-450) minutes, full recanalisation occurred in 76%, and by day 90, all 17 were alive and living at home, with 63% functionally independent (modified Rankin Scale (mRS) 0-2). At day 90, eight of 10 posterior circulation occlusion group patients were alive and living at home, four with a mRS of 0-2. In contrast, four of six 'Rescue' patients had died, and another was functionally dependent with a mRS of 4. CONCLUSIONS: Endovascular clot retrieval can be safely and effectively performed in a New Zealand setting with similar results to recent trials in anterior circulation occlusion patients. We suggest that District Health Boards develop clot retrieval services as part of regional hyperacute stroke treatment pathways.


Subject(s)
Intracranial Thrombosis/therapy , Stroke/etiology , Thrombectomy/methods , Adolescent , Adult , Aged , Aged, 80 and over , Arterial Occlusive Diseases/etiology , Arterial Occlusive Diseases/therapy , Female , Fibrinolytic Agents/therapeutic use , Humans , Intensive Care Units , Intracranial Thrombosis/complications , Male , Middle Aged , New Zealand , Stents , Stroke/therapy , Thrombectomy/instrumentation , Tissue Plasminogen Activator/therapeutic use , Young Adult
12.
J Stroke Cerebrovasc Dis ; 24(6): 1153-62, 2015 Jun.
Article in English | MEDLINE | ID: mdl-25847304

ABSTRACT

BACKGROUND: Stroke is the third most common cause of death and a major cause of chronic disability in New Zealand. Linked to risk factors that develop across the life-course, stroke is considered to be largely preventable. This study assessed the awareness of stroke risk, symptoms, detection, and prevention behaviors in an urban New Zealand population. METHODS: Demographics, stroke risk factors awareness, symptoms, responsiveness, and prevention behaviors were evaluated using a structured oral questionnaire. Binomial logistic regression analyses were used to identify predictors of stroke literacy. RESULTS: Although personal experience of stroke increased awareness of symptoms and their likeliness to indicate the need for urgent medical attention, only 42.7% of the respondents (n = 850) identified stroke as involving both blood and the brain. Educational attainment at or above a trade certificate, apprenticeship, or diploma increased the awareness of stroke symptoms compared with those with no formal educational attainment. Pacific Island respondents were less likely than New Zealand Europeans to identify a number of stroke risk factors. Maori, Pacific Island, and Asian respondents were less likely to identify symptoms of stroke and indicate the need for urgent medical attention. CONCLUSIONS: The variability in stroke awareness and knowledge may suggest the need to enhance stroke-related health literacy that facilitates understanding of risk and of factors that reduce morbidity and mortality after stroke in people of Maori and Pacific Island descent and in those with lower educational attainment or socioeconomic status. It is therefore important that stroke awareness campaigns include tailored components for target audiences.


Subject(s)
Health Knowledge, Attitudes, Practice , Health Literacy , Stroke , Adolescent , Adult , Aged , Female , Humans , Male , Middle Aged , New Zealand , Risk Factors , Urban Population , Young Adult
15.
Stroke ; 45(1): 205-10, 2014 Jan.
Article in English | MEDLINE | ID: mdl-24178916

ABSTRACT

BACKGROUND AND PURPOSE: The ability to live independently after stroke depends on the recovery of upper limb function. We hypothesized that bilateral priming with active-passive movements before upper limb physiotherapy would promote rebalancing of corticomotor excitability and would accelerate upper limb recovery at the subacute stage. METHODS: A single-center randomized controlled trial of bilateral priming was conducted with 57 patients randomized at the subacute stage after first-ever ischemic stroke. The PRIMED group made device-assisted mirror symmetrical bimanual movements before upper limb physiotherapy, every weekday for 4 weeks. The CONTROL group was given intermittent cutaneous electric stimulation of the paretic forearm before physiotherapy. Assessments were made at baseline, 6, 12, and 26 weeks. The primary end point was the proportion of patients who reached their plateau for upper limb function at 12 weeks, measured with the Action Research Arm Test. RESULTS: Odds ratios indicated that PRIMED participants were 3× more likely than controls to reach their recovery plateau by 12 weeks. Intention-to-treat and per-protocol analyses showed a greater proportion of PRIMED participants achieved their plateau by 12 weeks (intention to treat, χ2=4.25; P=0.039 and per protocol, χ2=3.99; P=0.046). ANOVA of per-protocol data showed PRIMED participants had greater rebalancing of corticomotor excitability than controls at 12 and 26 weeks and interhemispheric inhibition at 26 weeks (all P<0.05). CONCLUSIONS: Bilateral priming accelerated recovery of upper limb function in the initial weeks after stroke. CLINICAL TRIAL REGISTRATION: URL: http://www.anzctr.org.au. Unique identifier: ANZCTR1260900046822.


Subject(s)
Physical Therapy Modalities , Stroke Rehabilitation , Upper Extremity/physiology , Adult , Aged , Aged, 80 and over , Analysis of Variance , Arm/physiology , Brain Ischemia/rehabilitation , Disability Evaluation , Electric Stimulation , Electromyography , Endpoint Determination , Female , Functional Laterality/physiology , Hand/physiology , Humans , Male , Middle Aged , Motor Skills/physiology , Neurologic Examination , Quality of Life , Recovery of Function , Transcranial Magnetic Stimulation , Treatment Outcome
16.
Stroke ; 44(8): 2327-9, 2013 Aug.
Article in English | MEDLINE | ID: mdl-23696547

ABSTRACT

BACKGROUND AND PURPOSE: There is a temporal relationship between cannabis use and stroke in case series and population-based studies. METHODS: Consecutive stroke patients, aged 18 to 55 years, who had urine screens for cannabis were compared with a cohort of control patients admitted to hospital without cardiovascular or neurological diagnoses. RESULTS: One hundred sixty of 218 (73%) ischemic stroke/transient ischemic attack patients had urine drug screens (100 men; mean [SD] age, 44.8 [8.7] years). Twenty-five (15.6%) patients had positive cannabis drug screens. These patients were more likely to be men (84% versus 59%; χ2: P=0.016) and tobacco smokers (88% versus 28%; χ2: P<0.001). Control urine samples were obtained from 160 patients matched for age, sex, and ethnicity. Thirteen (8.1%) control participants tested positive for cannabis. In a logistic regression analysis adjusted for age, sex, and ethnicity, cannabis use was associated with increased risk of ischemic stroke/transient ischemic attack (odds ratio, 2.30; 95% confidence interval, 1.08-5.08). However after adjusting for tobacco use, an association independent of tobacco could not be confirmed (odds ratio, 1.59; 95% confidence interval, 0.71-3.70). CONCLUSIONS: This study provides evidence of an association between a cannabis lifestyle that includes tobacco and ischemic stroke. Further research is required to clarify whether there is an association between cannabis and stroke independent of tobacco. CLINICAL TRIAL REGISTRATION URL: http://www.anzctr.org.au. Unique identifier: ACTRN12610000198022.


Subject(s)
Brain Ischemia/epidemiology , Cannabis/adverse effects , Stroke/epidemiology , Substance-Related Disorders/epidemiology , Adolescent , Adult , Brain Ischemia/urine , Case-Control Studies , Cohort Studies , Comorbidity , Female , Humans , Ischemic Attack, Transient/epidemiology , Ischemic Attack, Transient/urine , Male , Middle Aged , New Zealand/epidemiology , Stroke/urine , Substance-Related Disorders/urine , Nicotiana/adverse effects , Young Adult
17.
ACS Appl Mater Interfaces ; 2(9): 2553-9, 2010 Sep.
Article in English | MEDLINE | ID: mdl-20804129

ABSTRACT

We report the preparation of new polymer composite dielectric materials for energy storage applications. New layered 1:1 mixed A+2/Ti4+ metal phenylphosphonates, ATi(O3PC6H5)3, A=Mg, Ca, Sr, Ba, and Pb, have been prepared via a melt route, in which mixed metal oxides, ATiO3, were reacted with molten phenyl phosphonic acid. The mixed-metal phosphonates were combined with polystyrene (PS) via a solution route and cast as thin films for dielectric permittivity measurements. The ATi(O3PC6H5)3-PS composites exhibit a substantial enhancement in the dielectric permittivity as a function of weight loading relative to the parent ATiO3-PS composites. For both ATiO3-PS and ATi(O3PC6H5)3-PS, the composites' dielectric permittivity increases with A cation polarizability. Unusually large increases for 40 wt% ATi(O3PC6H5)3-PS composites (A=Sr, Ba, and Pb) indicate permittivity enhancement that goes beyond the effect of varying filler composition.


Subject(s)
Electric Capacitance , Electric Power Supplies , Metals/chemistry , Organophosphonates/chemistry , Polymers/chemistry , Energy Transfer , Equipment Design , Equipment Failure Analysis
20.
J Air Waste Manag Assoc ; 54(6): 711-26, 2004 Jun.
Article in English | MEDLINE | ID: mdl-15242151

ABSTRACT

During the spring and summer of 2000, 2001, and 2002, gaseous and particulate matter (PM) fuel-based emission factors for approximately 150,000 low-tailpipe, individual vehicles in the Las Vegas, NV, area were measured via on-road remote sensing. For the gaseous pollutants (carbon monoxide, hydrocarbons, and nitrogen oxide), a commercial vehicle emissions remote sensing system (VERSS) was used. The PM emissions were determined using a Lidar-based VERSS. Emission distributions and their shapes were analyzed and compared with previous studies. The large skewness of the distributions is evident for both gaseous pollutants and PM and has important implications for emission reduction policies, because the majority of emissions are attributed to a small fraction of vehicles. Results of this Las Vegas study and studies at other geographical locations were compared. The gaseous pollutants were found to be close to those measured by VERSS in other U.S. cities. The PM emission factors for spark ignition and diesel vehicles are in the range of previous tunnel and dynamometer studies.


Subject(s)
Air Pollutants/analysis , Air Pollution/analysis , Nevada , Vehicle Emissions/analysis
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