The ratio between cerebral blood flow and Tmax predicts the quality of collaterals in acute ischemic stroke

Background In acute ischemic stroke the status of collateral circulation is a critical factor in determining outcome. We propose a less invasive alternative to digital subtraction angiography for evaluating collaterals based on dynamic-susceptibility contrast magnetic resonance imaging. Methods Perfusion maps of Tmax and cerebral blood flow (CBF) were created for 35 patients with baseline occlusion of a major cerebral artery. Volumes of hypoperfusion were defined as having a Tmax delay of > 4 seconds (Tmax4s) and > 6 seconds (Tmax6s) and a CBF drop below 80% of healthy, contralateral tissue. For each patient a ratio between the volume of the CBF and the Tmax based perfusion deficit was calculated. Associations with collateral status and radiological outcome were assessed with the Mann-Whitney-U test, uni- and multivariable logistic regression analyses as well as area under the receiver-operator- characteristic (ROC) curve. Results The CBF/Tmax volume ratios were significantly associated with bad collateral status in crude logistic regression analysis as well as with adjustment for NIHSS at admission and baseline infarct volume (OR = 2.5 95% CI[1.2–5.4] p = 0.020 for CBF/Tmax 4s volume ratio and OR = 1.6 95% CI[1.0–2.6] p = 0.031 for CBF/Tmax6s volume ratio). Moreover, the ratios were significantly correlated to final infarct size (Spearman’s rho = 0.711 and 0.619, respectively for the CBF/Tmax4s volume ratio and CBF/Tmax6s volume ration, all p<0.001). The ratios also had a high area under the ROC curve of 0.93 95%CI[0.86–1.00]) and 0.90 95%CI[0.80–1.00]respectively for predicting poor radiological outcome. Conclusions In the setting of acute ischemic stroke the CBF/Tmax volume ratio can be used to differentiate between good and insufficient collateral circulation without the need for invasive procedures like conventional angiography

Effect of saccharides on the hydration of ordinary Portland cement

Recently, the use of natural fibres as a sustainable alternative for reinforcements in cement-based materials has increased significantly. However, these lignocellulose fibres containing saccharides can have important retarding effects on cement hydration. The objective of this study is to characterise the effect of different organic compounds present in lignocellulose fibres on the cement hydration reactions. For a better understanding of this process, sugars such as fructose, glucose and sucrose, lignin and cellulose have been added to a cement paste as well as leachates of fibres. Experimental results show that glucose, mannose and xylose in fibre leachates had a significant impact on the cement hydration, slowing down the hydration for up to 2 days

Effect of saccharides on the hydration of ordinary Portland cement

\u3cp\u3eRecently, the use of natural fibres as a sustainable alternative for reinforcements in cement-based materials has increased significantly. However, these lignocellulose fibres containing saccharides can have important retarding effects on cement hydration. The objective of this study is to characterise the effect of different organic compounds present in lignocellulose fibres on the cement hydration reactions. For a better understanding of this process, sugars such as fructose, glucose and sucrose, lignin and cellulose have been added to a cement paste as well as leachates of fibres. Experimental results show that glucose, mannose and xylose in fibre leachates had a significant impact on the cement hydration, slowing down the hydration for up to 2 days.\u3c/p\u3

Investigation of local degradation in wood stands and its effect on cement wood composites

Wood-wool cement boards (WWCB) are a type of cement/fibre composite using wood strands as reinforcement. When lignocellulosic materials such as wood are mixed with cement, polysaccharides can leach out and negatively affect the cement hydration. Thus, the WWCB industry has to face those problems, which can cause significant problems during the manufacturing process. This study aims to identify the parameters that can influence the quality of wood and thus the WWCB. The investigation focuses on the potential differences between these two wood samples, by analysing the cement/wood compatibility, the mechanical properties of the wood strands, the microstructure and the chemical composition of the leachates. Two similar spruce wood samples, which have been grown and harvested under the same conditions are compared to each other. When mixed with cement, one sample performed up to expectation in WWCB whereas the second one shows chemical and mechanical problems, resulting in weak WWCBs that cannot fulfil the standards. A comparison two wood samples shows not only different properties of WWCB. Cement-fibre compatibility for one of the sample is below the limit to be used in composite and tensile strength shows a similar behaviour

Comparison of two patients both imaged 1 hour after symptom onset with a proximal occlusion of the middle cerebral artery and a Higashida score of 2 on source DSC MRI.

<p>Patient A had a left-sided stroke with NIHSS at admission of 12, an initial infarct volume of 3.8ml, perfusion deficit of 200ml on Tmax4s and 108ml on CBF with a CBF/Tmax4s volume ratio of 0.54. The final infarct size was 15.5ml. Patient B had a right-sided stroke with NIHSS at admission of 19, an initial infarct volume of 5.8ml, perfusion deficit of 87ml on Tmax4s and 84ml on CBF with a CBF/Tmax4s volume ratio of 0.96. The final infarct size was 208ml.</p