PROPERTIES OF METAKAOLIN CONCRETE – A REVIEW

The use of cement supplementary materials in structural concrete is widely accepted by the construction industry for technical, economical and environmental reasons. Metakaolin (MK), produced by calcining kaolinite at high temperature is suitable for concrete production due to its pozzolanic property. This paper reviews the some of the research published on effects of using MK on engineering properties of structural concrete as a cement replacement material. The review shows that the use of relatively finer MK to partially replace cement reduces the consistency of concrete and enhanced the strengths, deformational and durability properties of concrete. MK is most effective in enhancing compressive strength (particularly at early ages) compared to other strengths and modulus of elasticity was least improved. Drying shrinkage and creep of MK concretes are lower than those for the control concrete. The high pozzolanic reactivity of MK with calcium hydroxide contributes to both porosity reduction and pore-structure refinement in the pastes and concrete. As the consequence, the durability of concrete is improved through increased resistance to chloride penetration and controlled expansion, due to alkali-silica reaction and sodium sulphate attack

Blood pressure in frail older adults: associations with cardiovascular outcomes and all-cause mortality

Background: Blood pressure (BP) management in frail older people is challenging. An randomised controlled trial of largely non-frail older people found cardiovascular and mortality benefit with systolic (S) BP target <120 mmHg. However, all-cause mortality by attained BP in routine care in frail adults aged above 75 is unclear. Objectives: To estimate observational associations between baseline BP and mortality/cardiovascular outcomes in a primary-care population aged above 75, stratified by frailty. Methods: Prospective observational analysis using electronic health records (clinical practice research datalink, n = 415,980). We tested BP associations with cardiovascular events and mortality using competing and Cox proportional-hazards models respectively (follow-up ≤10 years), stratified by baseline electronic frailty index (eFI: fit (non-frail), mild, moderate, severe frailty), with sensitivity analyses on co-morbidity, cardiovascular risk and BP trajectory. Results: Risks of cardiovascular outcomes increased with SBPs >150 mmHg. Associations with mortality varied between non-frail <85 and frail 75-84-year-olds and all above 85 years. SBPs above the 130-139-mmHg reference were associated with lower mortality risk, particularly in moderate to severe frailty or above 85 years (e.g. 75-84 years: 150-159 mmHg Hazard Ratio (HR) mortality compared to 130-139: non-frail HR = 0.94, 0.92-0.97; moderate/severe frailty HR = 0.84, 0.77-0.92). SBP <130 mmHg and Diastolic(D)BP <80 mmHg were consistently associated with excess mortality, independent of BP trajectory toward the end of life. Conclusions: In representative primary-care patients aged ≥75, BP <130/80 was associated with excess mortality. Hypertension was not associated with increased mortality at ages above 85 or at ages 75-84 with moderate/severe frailty, perhaps due to complexities of co-existing morbidities. The priority given to aggressive BP reduction in frail older people requires further evaluation.This article is freely available via Open Access. Click on the Publisher URL to access it via the publisher's site.J.M. is funded by a National Institute for Health Research (NIHR), Doctoral Research Fellowship DRF-2014-07-177 for this research project. This paper presents independent research funded by the National Institute for Health Research (NIHR). The views expressed are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health and Social Care.published version, accepted version (12 month embargo), submitted versio

Low blood pressure and adverse outcomes in acute stroke HeadPoST study explanations

Objective: As uncertainties exist over underlying causes, we aimed to define the characteristics and prognostic significance of low blood pressure (BP) early after the onset of acute stroke. Methods: Post hoc analyzes of the international Head Positioning in acute Stroke Trial (HeadPoST), a pragmatic cluster-crossover randomized trial of lying flat versus sitting up in stroke patients from nine countries during 2015–2016. Associations of baseline BP and death or dependency [modified Rankin scale (mRS) scores 3–6] and serious adverse events (SAEs) at 90 days were assessed in generalized linear mixed models with adjustment for multiple confounders. SBP and DBP was analysed as continuous measures fitted with a cubic spline, and as categorical measures with low (<10th percentile) and high (≥140 and ≥90 mmHg, respectively) levels compared with a normal range (≥10th percentile; 120–139 and 70–89 mmHg, respectively). Results: Among 11 083 patients (mean age 68 years, 39.9% women) with baseline BP values, 7.2 and 11.7% had low SBP (<120 mmHg) and DBP (<70 mmHg), respectively. Patients with low SBP were more likely to have preexisting cardiac and ischemic stroke and functional impairment, and to present earlier with more severe neurological impairment than other patients. Nonlinear ‘J-shaped’ relationships of BP and poor outcome were apparent: compared with normal SBP, those with low SBP had worse functional outcome (adjusted odds ratio 1.27, 95% confidence interval 1.02–1.58) and more SAEs, particularly cardiac events, with adjustment for potential confounders to minimize reverse causation. The findings were consistent for DBP and were stronger for ischemic rather than hemorrhagic stroke. Conclusion: The prognostic significance of low BP on poor outcomes in acute stroke was not explained by reverse causality from preexisting cardiovascular disease, and propensity towards greater neurological deficits and cardiac events. These findings provide support for the hypothesis that low BP exacerbates cardiac and cerebral ischemia in acute ischemic stroke

Role of frailty assessment in patients undergoing cardiac interventions.

Average life expectancy is increasing in the western world resulting in a growing number of frail individuals with coronary heart disease, often associated with comorbidities. Decisions to proceed to invasive interventions in elderly frail patients is challenging because they may gain benefit, but are also at risk of procedure-related complications. Current risk scores designed to predict mortality in cardiac procedures are mainly based on clinical and angiographic factors, with limitations in the elderly because they are mainly derived from a middle-aged population, do not account for frailty and do not predict the impact of the procedure on quality of life which often matters more to elderly patients than mortality. Frailty assessment has emerged as a measure of biological age that correlates well with quality of life, hospital admissions and mortality. Potentially, the incorporation of frailty into current risk assessment models will cause a shift towards more appropriate care. The need for a more accurate method of risk stratification incorporating frailty, particularly for elderly patients is pressing. This article reviews the association between frailty and cardiovascular disease, the impact of frailty on outcomes of cardiac interventions and suggests ways in which frailty assessment could be incorporated into cardiology clinical practice

Measurement of bitumen viscosity in the room-temperature drop experiment: student education, public outreach and modern science in one

Slow flow of the viscous liquid is a thought-provoking experiment that challenges students, academics and public to think about some fundamental questions in modern science. In the Queensland demonstration, the world-longest running experiment earning the Ig Nobel prize, one drop of pitch takes about 10 years to fall, leading to problems of actually observing the drops. Here, we describe our recent demonstration of slowly-flowing bitumen where appreciable flow is observed on the time scale of months. The experiment is free from dissipative heating effects and has the potential to improve the accuracy of measurement. Bitumen viscosity was calculated by undergraduate students during the summer project. The worldwide access to the running experiment is provided by webcams uploading the images to a dedicated website, enhancing student education experience and promotion of science. This demonstration serves as an attractive student education exercise and stimulates the discussion of fundamental concepts and hotly debated ideas in modern physics research: difference between solids and liquids, the nature of liquid-glass transition, emergence of long time scales in a physical process, and the conflict between human intuition and physical reality

Biomarkers associated with mortality in aortic stenosis: A systematic review and meta-analysis

The optimal timing of aortic valve replacement (AVR) remains controversial. Several biomarkers reflect the underlying pathophysiological processes in aortic stenosis (AS) and may be of use as mortality predictors. The aim of this systematic review and meta-analysis is to evaluate the blood biomarkers utilised in AS and assess whether they associate with mortality. PubMed and Embase were searched for studies reporting baseline biomarker level and mortality outcomes in patients with AS. A total of 83 studies met the inclusion criteria and were systematically reviewed. Of these, 21 reporting brain natriuretic peptide (BNP), N-terminal pro B-type natriuretic peptide (NT-proBNP), Troponin and Galectin-3 were meta-analysed. Pooled analysis demonstrated that all-cause mortality was significantly associated with elevated baseline levels of BNP (HR 2.59; 95% CI 1.95–3.44; p < 0.00001), NT-proBNP (HR 1.73; 95% CI 1.45–2.06; p = 0.00001), Troponin (HR 1.65; 95% CI 1.31–2.07; p < 0.0001) and Galectin-3 (HR 1.82; 95% CI 1.27–2.61; p < 0.001) compared to lower baseline biomarker levels. Elevated levels of baseline BNP, NT-proBNP, Troponin and Galectin-3 were associated with increased all-cause mortality in a population of patients with AS. Therefore, a change in biomarker level could be considered to refine optimal timing of intervention. The results of this meta-analysis highlight the importance of biomarkers in risk stratification of AS, regardless of symptom status