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Introduction: Age and systolic blood pressure (SBP) are important predictors of Acute Cerebrovascular Syndrome (ACVS). Yet, the effect of SBP is confounded by age, making its independent contribution to ACVS risk difficult to quantify. Here we use logistic regression to explore the role of SBP in younger and older ED patients. Methods: Data comprised 1019 ED patients (ACVS 70%, 30% non-ACVS) enrolled during a 28-month period of an ongoing prospective, observational, multi-site stroke biomarker study (SpecTRA). We used logistic regression to examine the effects of age, sex, and the age:SBP interaction as predictive markers of the diagnosis of ACVS. Results: Participants (53% male) ranged in age from 18 to 97 years (Q1=58, median=70, Q3=80). SBP ranged from 84 to 248 mmHg (Q1=137, median=154, Q3=174). In our initial regression model, age, sex, SBP and the age:SBP interaction were all significant (p<0.01). Using cubic regression splines for age, sbp and their interaction yields the same conclusion (p<0.01). To better understand the role of SBP in younger vs. older patients, we stratified the sample at the median age (70 years of age). In the younger group (n=510), participants were 55% male, 60% ACVS, and had SBP ranging from 91 to 236 mmHg (Q1=133, median=148, Q3=165). In the older group (n=509), participants were 51% male, 82% ACVS and had SBP ranging from 84 to 248 mmHg (Q1=143, median=159, Q3=179), a shift of approximately 10 mmHg between the groups. The logistic regression model was then fit separately to each group without the age:SBP interaction term. In the younger group, we found SBP to be highly significant (p<0.001), with an odds-ratio (OR) of 1.18 per 10 mmHg (95% CI: 1.10-1.29). In the older group, we found that SBP was not significant (p=0.91), with an OR of 1.00 per 10 mmHg (95% CI: 0.91-1.08). Age and sex were also significant risk factors in the younger group (each p<0.01), though not in the older group (both p>0.07). Conclusion: Our findings suggest that for ED patients suspected of ACVS, SBP is a clinically relevant predictor for younger patients, with higher SBP associated with an increased risk of ACVS, regardless of patient age and sex. SBP does not appear to be a strong predictor for patients over 70. ED physicians can leverage this finding by attributing greater importance to elevated SBP in younger patients than older patients when working toward a clinical suspicion of ACVS.
Introduction: The risk of recurrent stroke following a transient ischemic attack (TIA) has been estimated to be as much as 5 percent in the first 48 hours and ten percent in the first week following initial TIA symptoms, but can be modified as a result of intensive risk factor management. Care pathways for these patients vary between different regions within Alberta with Edmonton admitting more TIA patients and Calgary using computed tomography angiography (CTA) based triage. To examine regional differences in the quality of care, the rate of admission for stroke within 90 days of an index ED visit for TIA/minor stroke was investigated. Methods: Data analysts from the Data Integration, Measurement and Reporting (DIMR) branch of Alberta Health Services (AHS) used the National Ambulatory Care Reporting System (NACRS) to identify patients in Alberta who were admitted for stroke within 90-days of an index emergency department (ED) visit for TIA/minor stroke from April 2010 to March 2016. Information extracted included patient demographics, region of residence (Edmonton, Calgary or non-major urban [NMU]), return diagnosis and timing of return ED visit. Analysis included descriptive summaries and proportions were compared using a χ2 test. Results: During the study period, there were 26,232 index visits to Alberta EDs for TIA/minor stroke. 5426 (26.1%) of patients were admitted on their index visit. Calgary (22.5%) had lower rates of admission on index visit followed by Edmonton (31.4%) and the NMU (46%). 20,806 (79.3%) were discharged home following their index visit. Of the patients discharged on their index visit 729 (3.5%) had an admission for stroke within 90-days of their index ED visit with rates in Edmonton (3.8%) and the NMU regions (3.8%) being significantly higher than Calgary (2.8%, p<0.01). Conclusion: Our study demonstrates significantly lower rates of admission for stroke within 90-days of ED visit for minor stroke/TIA in Calgary compared to Edmonton and the NMU. Further work should focus on validating this result and consideration of standardized care pathways that promote effective resource utilization and quality of care.
Background: Stroke is often preceded by transient symptoms. Although global stroke rates have been shown to be declining, previous studies have reported inconsistent temporal trends of transient ischemic attacks (TIA). The objective of the current study is to report the temporal trends of TIA admissions and outcomes in Canada over the last 11 years. Methods: We conducted a complete population cohort study using a national administrative database to study the temporal trend of age- and sex-adjusted TIA admission rates in Canada from 2003 to 2013. We also determined the rates of TIA and stroke diagnoses in the emergency department in the province of Ontario during the same period. We used multivariable analyses to study discharge location after acute hospitalization as well as 90-day stroke and/or TIA readmission rates. Results: Of 425,799 admissions to an acute care hospital for all stroke and TIA, 71,443 (16.8%) were TIA. The age- and sex-standardized rates of TIA admission decreased significantly during the study period from 30.0 to 20.6 per 100,000 (p<0.0001). In Ontario, decreasing TIA admissions is mirrored by decreasing rates of TIA directly discharged from the emergency department (55.1 to 46.8 per 100,000, p = 0.002). The odds of 90-day readmission rates for stroke or TIA are also decreasing (adjusted odds ratio, 0.97; 95% confidence interval, 0.96-0.99). Conclusions: We show that TIA admission rates have declined in the past 11 years in Canada, reflecting improved vascular risk reduction and stroke care. Future studies to confirm our findings on improved stroke or TIA recurrence rates are necessary.
Introduction: National guidelines (NICE, AHA) for management of Acute Cerebrovascular Syndrome (ACVS) in the Emergency Department (ED) recommend the use of ABCD2 score to risk stratify patients despite its poor specificity and low diagnostic accuracy. The SpecTRA project previously developed a clinical classifier for ACVS vs. Mimic derived from historical clinical data collected during a 5-year period at an outpatient stroke clinic (Victoria, BC). Here we present a prospective evaluation of the performance of our clinical classifier on prospectively collected ED patient data compared to the industry-standard ABCD2. Methods: The prospective cohort consisted of ED patients (N=555, Male=54%, Mean (SD) Age=68.7(15.5), ACVS=70%) enrolled between Jan 2014 and May 2015 at Victoria General Hospital (BC) and Foothills Medical Centre (Calgary, AB). ABCD2 and clinical classifier scores were calculated from clinical data from the ED. We compared the performance of the two classifiers using DeLong’s test of Dependent Receiver Operating Curves (ROC). In keeping with national guidelines, we used a score of 4 or more to assess sensitivity, specificity and accuracy (sens/spec and acc) of the ABCD2; for our clinical classifier, we used the cut point previously determined to maximize agreement between predictions and true class labels in the historical data. Results: Our new clinical classifier significantly outperformed the ABCD2 (z=2.44, p=0.015) with an AUC of 0.72, (95% CI: 0.68, 0.77) vs. 0.66 (0.61, 0.71). In terms of sens/spec and acc, our classifier achieved 0.78/0.55 with acc 71% compared to 0.75/0.46 with acc 66% for the ABCD2 (using the previously specified cut points). Conclusion: Our ACVS clinical classifier showed better performance than the ABCD2 score on a prospective sample of ED patients. The improved specificity of the clinical classifier relative to existing prognostic tools would reduce the number of non-ACVS patients referred for early treatment as well as conserve medical resources. Our ongoing multi-site study will evaluate the utility of the ACVS classifier embedded in a logic-enabled e-fillable form. This form will also provide risk-based thresholds guiding timely ordering of CTA as well as links to clinical treatment guidelines. Longer-term, the e-form and classifiers will be further enhanced to include plasma-based protein biomarker data.
transient ischemic attack (tIA) and minor stroke have a high risk of early neurological deterioration, and patients who experience early improvement are at risk of deterioration. We generated a score for quantifying the worst reported motor and speech deficits and assessed whether this predicted outcome.
510 tIA or minor stroke (NIHSS>4) patients were included. the Historical Stroke Severity Score (HSSS) prospectively quantified the patient's description of the worst motor or speech deficits. the HSSS was rated at the time of first assessment with more severe deficits scoring higher. Motor HSSS included assessments of arm and leg motor power (score total 0-5). Speech HSSS assessed severity of dysarthria and aphasia (total 0-3). the association between motor and speech HSSS and symptom progression was assessed during the 90-day follow-up period.
the proportion of patients in each category of the motor HSSS was 0: 43% (216/510), 1: 22%(110/510), 2: 17% (89/510), 3: 7% (37/510), 4: 5% (28/510) and 5: 6% (30/510). Motor HSSS was associated with symptom progression (p=0.004) but not recurrent stroke. Speech HSSS was not associated with either progression or recurrent stroke. Motor HSSS predicted disability (p=0.002) and intracranial occlusion (p=0.012). Disability increased with increasing motor HSSS.
taking a detailed history about the severity of motor deficits, but not speech, predicted outcome in tIA and minor stroke patients. A score based on the patient's description of the severity of motor symptoms predicted symptom progression, intracranial occlusion and functional outcome, but not recurrent stroke in a tIA and minor stroke population.
The risk of stroke after transient ischemic attack (TIA) is elevated in the days to weeks after TIA. A variety of prediction rules to predict stroke risk have been suggested. In Alberta a triage algorithm to facilitate urgent access based on risk level was agreed upon for the province. Patients with ABCD2 score ≥ 4, or motor or speech symptoms lasting greater than five minutes, or with atrial fibrillation were considered high risk (the ASPIRE approach). We assessed the ability of the ASPIRE approach to identify patients at risk for stroke.
We retrospectively reviewed charts from 573 consecutive patients diagnosed with TIA in Foothills Hospital emergency room from 2002 through 2005. We recorded clinical and event details and identified the risk of stroke at three months.
Among 573 patients the 90-day risk of stroke was 4.7% (95% CI 3.0%, 6.4%). 78% of the patients were identified as high risk using this approach. In patients defined as high risk on the ASPIRE approach there was a 6.3% (95% CI 4.2%, 8.9%) risk of stroke. In patients defined as low risk using the ASPIRE approach there were no recurrent strokes (100% negative predictive value). In contrast, two patients with low ABCD2 scores (ABCD2 score < 4) suffered recurrent strokes.
The ASPIRE approach has a perfect negative predictive value in the population in predicting stroke. However, this high sensitivity comes at a cost of identifying most patients as high risk.
We have shown that variation in the real part of the dielectric permittivity of typical transparent conducting oxide (TCO) films can have a profound effect on the optical properties of the material. This has been demonstrated by adding small amounts of Zr to an ITO ceramic sputtering target and analyzing the resulting ITO and ITO:Zr (ITZO) films. Comparative electrical and optical analyses of the films show that, although the carrier concentration and mobility do not change appreciably by adding 1 wt.% ZrO2 to the ITO sputtering target, the plasma wavelength increases significantly for the ITZO film. We believe that the underlying physics of these results can be exploited in designing future TCO films for photovoltaic (PV) applications—especially those that embody industrial advantages but remain limited by low mobility.
Cu(In,Ga)Se2 (CIGS) photovoltaic cells require a highly conducting and transparent top electrode for optimum device performance. ZnO thin films doped with 2 wt.% Al (ZnO:Al) are commonly used to ensure sufficient conductivity while providing acceptable transparency to the active absorber layers. Deposition of transparent conducting oxide (TCO) films on CIGS cells often is performed at room temperature in the manufacturing process because of production advantages. However, material properties and reproducibility may be poorer at room temperature than at higher temperatures. Maximum mobilities of 2 wt.%-doped ZnO:Al grown at room temperature in pure Ar are typically ∼20-25 cm2V-1s-1. Relatively high carrier concentration is therefore required to achieve the desired conductivity. This high carrier concentration produces low infrared transmittance due to increased free-carrier absorption.
World-record CIGS cells produced at the National Renewable Energy Laboratory (NREL) are known to tolerate photolithographic processing temperatures of ∼100Â°C, though significant changes in device performance occur beyond 200Â°C. In this study, we investigate whether ZnO:Al films with superior material properties can be produced at the elevated temperatures consistent with CIGS processing parameters. We examine undoped ZnO and ZnO:Al with doping levels of 0.5, 1, and 2 wt.% Al2O3 for growth at substrate temperatures from 25Â° to 360Â°C using radio-frequency magnetron sputtering. For films grown in a 100% Ar ambient, optimal electrical and optical properties are achieved at ∼150Â°-200Â°C. Controlled incorporation of H2 in the Ar sputtering ambient at 200Â°C increases mobility to 48 cm2V-1s-1 for undoped ZnO and 36 cm2V-1s-1 for 0.5 wt.%-doped ZnO:Al. Both values are considerably higher than the 25 cm2V-1s-1 of 2 wt.%-doped ZnO:Al deposited at 200Â°C in 100% Ar. We have explored whether these higher-mobility films can be exploited in the design of high-quality CIGS devices produced at NREL. Preliminary results show similar open-circuit voltage and only slightly lower short-circuit current compared to devices utilizing the standard 2 wt.%-doped ZnO:Al deposited at room temperature. This suggests that higher-performance devices may result once the TCO thickness is optimized for the higher mobility.
Trials at Tulloch, Aberdeen (sandy loam soil, 820 mm rainfall) and Woodside, Elgin (light sandy loam, 730 mm) compared organically managed crop rotations containing different proportions of spring oats, swedes, potatoes and grass/clover leys (0·50 and 0·67 of the rotation at Tulloch; 0·38 and 0·50 at Woodside). The trials simulated farm conditions through the use of grazing animals and the recycling of farmyard manure. The rotations at each site gave similar financial outputs. Yields of oats were higher where these were grown after the main ley phase of the rotation than where they were grown later in the rotation (more ears/m2 and grains/ear), but were not significantly higher after a 4-year ley than after a 3-year ley at Tulloch. It was concluded that all of the rotations were agronomically and financially sustainable. Cereal yields showed large year-to-year variations but little indication of a progressive decline. There were only small changes in soil organic matter, soil P and soil K. Increased early summer weed cover in the arable crops was not matched by increases in weed invasion in the grass/clover leys and did not appear to be affecting yields.
Accuracy of intracranial magnetic resonance angiography (MRA) and reliability of interpretation are not well established compared to conventional selective catheter angiography. The purpose of this study was to determine the accuracy of MRA in evaluation of intracranial vessels in acute stroke and transient ischemic attack (TIA) patients.
Twenty-nine patients (seven females, 22 males; median age 53) with acute stroke or TIA were enrolled into the study. All patients underwent both MRA using a 3 T clinical magnet and conventional angiography within 48 hours. Median time between MRA and angiography was 263 minutes. Conventional angiography preceded MRA in 15 cases. Fourteen patients received thrombolysis during MRA or angiography. National Institutes of Health Stroke Scale scores were obtained prior to the MR exam. One neuroradiologist rated all conventional angiograms, which were used as gold standard. Five observers, blinded to conventional angiography results and all clinical information except symptom side, rated the MR angiograms. Kappa statistics were used to assess reliability; contingency tables were used to assess accuracy of non-enhanced and enhanced MRA.
Two hundred and fifty two intracranial vessels were assessed. Agreement between raters was good for both non-enhanced (k=0.50) and gadolinium-enhanced (k=0.46) images. There were a total of 26 vessels occluded by DSA. Overall, the non-enhanced MRA showed sensitivity of 84.2% (95% CI 60.4-96.6) and specificity of 84.6% (95% CI 78.6-89.4). The enhanced MRA showed sensitivity of 69.2 (95% CI 38.6-90.9) and specificity of 73.6 (95% CI 65.5-80.7).
Magnetic resonance angiography is a good non-invasive screening tool for assessing intracranial vessel status in acute ischemic stroke. Angiography remains the gold standard for definitive assessment of the intracranial circulation.
Phase equilibria and dielectric properties were analyzed for selected compositions in both LaCa0.5Zr0.5O3–CaTiO3 (LCZ-CT) and LaCa0.5Zr0.5O3–SrTiO3 (LCZ–ST) systems using x-ray powder diffraction and transmission electron microscopy. The end-member LaCa0.5Zr0.5O3 does not occur as a single phase but rather as a mixture of a perovskite-type phase with approximate composition La0.94Ca0.53Zr0.53O3 plus a minor amount of La2O3. This perovskite phase exhibited a combination of 1:1 ordering of Ca and Zr on the B-sites and octahedral tilting. In the (1 – x)LCZ– xCT system, the compositions x = 1/3 and x = 1/2 yielded single phases with perovskite-like structures featuring similar 1:1 B-site ordering superimposed onto octahedral tilting. The x = 1/2 composition in the LCZ–ST system resides in a two-phase field and contains a major perovskite phase and La2O3; the B-cations in the perovskite phase remain disordered at all temperatures. The approximate boundaries of perovskite-like phase fields in the La2O3–ATiO3–CaZrO3 (A = Ca, Sr) systems were outlined, as well as a schematic diagram for perovskite B-cation ordering transitions in the LCZ–CT system. The dielectric properties of the compositions investigated were measured at microwave frequencies and were correlated with the observed structural behavior.
This paper reports the properties of undoped CdO films and CdO films doped with the group VII element F and the group IV element Sn. The CdO films are made by low-pressure chemical-vapor deposition. We observe that undoped CdO films can achieve a carrier concentration of 1021 cm−3, apparently by controlling the intrinsic defect. However, the electron mobility of these films is only around 2 cm2 V−1 s−1. With fluorine doping, an electron mobility of ∼260 cm2 V−1 s−1 has been achieved. However, low carrier concentration results because of the low solubility of F in CdO film. CdO films doped with both Sn and F demonstrate carrier concentrations of 1021 cm−3 and reasonable electron mobilities of around 20 cm2 V−1 s−1. Due to the small effective electron mass of CdO, a large Burstein-Moss shift is observed for films with high carrier concentration. The shift enables the fundamental absorption edges of undoped CdO films to reach 3.0 eV and 3.3 eV for films doped with both Sn and F.
Two experiments were carried out with Sitka spruce and European larch grown under intermittent wind in tunnels. In the first, both species were grown to determine whether there are any specific effects of wind on root growth, as opposed to effects on growth in general. In the second experiment, larch seedlings had their tap root removed 20 mm below the soil surface to mimic the formation of a shallow root plate, such as develops when larch is planted on seasonally waterlogged peat in much of the United Kingdom. In both experiments, lateral roots were counted and their orientation relative to the tap root recorded. In the wind-stressed trees in both experiments there was an increase of almost 60% in the number of large roots on the windward side of the trees and of 45% on the leeward side of larch trees compared with the number of roots growing at right angles to the direction of wind. In the first experiment, the sum of the cross-sectional area (Σ CSA) of lateral root bases was greater on the windward side of the tree compared with the other sides in both species. In the second experiment, Σ CSA of lateral root bases of wind-stressed larches was greatest on the leeward side whereas the control plants had a larger Σ CSA in the regions perpendicular to the wind direction. It appears that wind action stimulates the diameter growth of those roots most important for anchorage, but has a smaller effect on root development than other factors such as uneven nutrient supply.
Winds over topography and inside forests produce mechanical reactions in trees, and eventually failure in stems and roots when stressed by storms. The mechanics of these reactions and the physiological responses to wind in leaves, stems and root systems, and the important ecological consequences of wind-throw are described in this book. Management techniques of forests in windy climates are detailed, including the use of models predicting risk of wind damage. It is clear that the whole field of wind effects on trees has benefited from recent multi-disciplinary research, and significant advances in knowledge of most parts of the subject have been made in the last decade. This book brings the up-to-date theories, methodologies and results together, and gives the reader a sense of coherence in this complex but fascinating field.
The effects of tree improvement on factors likely to influence tree stability were investigated using clonal Sitka spruce trees that had been grown for 11 years on an unploughed nursery site. The distribution of biomass between root and shoot, and within the root systems of trees from five improved clones, was examined and compared with control trees grown from unimproved cuttings and transplants. The direction (azimuth) of growth and dimensions of the main woody roots were also measured. Differences between clones were found in allocation of biomass between root and shoot, and in root system architecture. Large differences were found between clones in proportions of below-ground biomass allocated to stumps and woody roots (which function for anchorage). These results indicate that root: shoot ratio can be a poor indicator of tree stability when the stump is included as part of the root biomass. The distribution of root origins around the stump showed no significant clumping but the allocation of biomass between roots was found to differ between tree types. On average, the improved clones had allocated biomass to fewer roots than the controls. The amount of branching in the proximal 45 cm of the root system also differed between clones. Distribution of root cross-sectional area around the tree was significantly asymmetric in two of the clones. Overall, root biomass was allocated more to the lee side of the prevailing wind direction. The substantial differences found in allocation between root and shoot, and within the root system, may have implications for the wind stability of trees and could present opportunities for improving stability by clonal selection.
Damage by windthrow causes important economic losses to forestry in northern Europe.
Wind not only causes extensive damage to trees in many parts of the world, it also has more subtle effects on their growth, form and ecology. This, the first symposium volume on the topic, contains a selection from the papers presented at a conference, Wind and Wind-Related Damage to Trees, held at Heriot-Watt University, Edinburgh, in July 1993. The conference, which was initiated by Chris Quine, was held under the auspices of the International Union of Forestry Research Organisations, and brought together about a hundred people from seventeen countries.
Wind damage to trees has historically been the province of the silviculturist, but increasing recognition of the importance and complexity of the subject has more recently involved people from many other discplines, and this has resulted in a greatly increased understanding of the main processes involved. The conference served to bring together the new approaches and methodologies; it enabled discussion between physicists, aerodynamicists, foresters, engineers, physiologists, ecologists, pathologists and modellers, and led to a remarkable cross-fertilisation of ideas between scientists who would not normally meet.
For convenience the papers have been gathered into five parts, each beginning with a review. The parts are: Airflow over topography and in forests; Mechanics of trees under wind loading; Tree physiological responses; Impacts of wind on forests and ecology; Risk assessment and management response. The coverage of different aspects of the subject is decidedly uneven. For example, tree root development and the way in which roots and soil anchor the tree have received less attention than what is going on above ground, and the contents of this book reflect such disparities.