Use of a hot-box facility to evaluate hybrid reflective insulation assemblies

The determination of the thermal performance of hybrid insulation assemblies that include an enclosed reflective airspace and a separate layer of insulation is being done using a hot-box test facility operated in accordance with ASTM C1224, the Standard Specification for Reflective Insulation. The thermal resistance determination of the insulated region requires a hot-box test with known thermal insulation to determine heat flow through the framing. Factors that affect the result for the hybrid insulation assembly will be discussed along with results obtained using the ASTM C1224 protocol. The thermal resistance obtained using the hot-box apparatus will be compared with calculated values obtained from published correlations. The uncertainty in the hybrid insulation assembly and the enclosed reflective airspace due to uncertainty in the thermal resistance of the calibration material are of particular interest.

Influence of calibration method and material on the accuracy of stress distribution measurement systems

Biomechanical analyses of the stress distribution and the force transfer in the human knee are essential to better understand the aetiology of joint diseases. Accuracy studies of commonly used capacitive or resistive-based stress distribution measurement systems have led to severe problems caused by an inaccurate experimental setup. For instance, in one study, overestimations of the measured forces in the sensor’s centre were reported. Therefore, the primary aim of this study was to investigate the ability of capacitive and resistive-based sensors to measure forces in a homogenous pressure environment and the secondary goal was to analyse the influence of different calibration materials on the measurement accuracy. A Novel pressure vessel and metal indenters covered with different rubber materials were used in combination with a material testing machine to load the sensors. Four different linearly increasing nominal forces (925–3670 N) were applied and the deviations between the nominal and the measured forces were calculated. The capacitive measurement system showed errors between 1% and 7% in the homogenous pressure environment, whereas the errors of the resistive system were found to vary between 4% and 17%. The influence of the calibration material was observed to be greater for the resistive sensors (1–179%) than for the capacitive sensors (0.5–25%). In conclusion, it can be stated that – for the pressure measurement systems compared in this article – the capacitive one is less sensitive to the calibration method and the calibration material than the resistive system.

The Measure of Plasma Concentrations Is Crucial in Managing Dabigatran Treatment in Non-Valvular Atrial Fibrillation

One of the most popular features utilized to promote direct oral anticoagulants diffusion in stroke prevention in non-valvular atrial fibrillation is that these drugs do not require monitoring of their anticoagulant activity or plasma level measurements. We believe that there are clinical scenarios in which monitoring can help guide clinical management. Here we describe a clinical case in which close monitoring of thrombin inhibitor dabigatran peak plasma levels helped in maintaining the patient drug administration schedule, despite the interference of mirabegron, a beta-3 adrenergic agonist, utilized for the symptomatic treatment overactive bladder (OAB) syndrome, and of amiodarone, an effective and commonly prescribed antiarrhythmic drug. These P-glycoprotein (P-gp) inhibitors drugs may increase the blood levels and effects of dabigatran. Combining these medications may increase the risk of bleeding complications and anemia, especially when associated to mild to moderate renal insufficiency. Dabigatran etexilate is a pro-drug that has a low (3%-7%) bioavailability. Once dabigatran etexilate is absorbed, the pro-drug is hydrolyzed to the active drug, dabigatran, by carboxylesterases in the bloodstream. Dabigatran etexilate is a substrate of the efflux transporter P-gp, but dabigatran, the active drug, is not. P-gp is present on the luminal side of absorptive cells in the small intestine and takes drug molecules from the cell cytoplasm and transports them back into the intestinal lumen for excretion. An inhibitor of P-gp, as mirabegron or amiodarone, will increase bioavailability of a P-gp substrate by reducing drug efflux. Our patients suffers from persistent non-valvular atrial fibrillation, complicated by ischemic stroke. He has been assigned a dabigatran 150 mg b.i.d. treatment in may 2014. His creatinine clearance was 75 mL/min. One month later, due to OAB syndrome, he started mirabegron, a drug which might potentially increase the risk of bleeding and which generally causes to stop dabigatran administration. We decided instead to set up a monitoring plan, utilizing plasma-diluted thrombin time to measure dabigatran concentrations. Calibration material consisted of pooled normal plasma with known quantities of dabigatran. By using this calibration material, we constructed a dose-response curve ranging from 0 to 500 ng/mL of dabigatran. An examination of the published literature of the pharmacology of dabigatran indicated that the expected peak steady-state concentration of dabigatran in patients with atrial fibrillation (150 mg, 2 times daily) was approximately 180 ng/mL with a trough of approximately 90 ng/mL (12 hours after last dose). After 4 weeks of mirabegron administration, dabigatran plasma trough level of our patient was 126.4 ng/mL. We therefore decided not to modify the 150 mg b.i.d. treatment. Three weeks later, patient suffered from acute cardiac failure associated to a creatinine clearance reduction to 41 mL/min. As a consequence, mirabegron treatment was stopped. At this point, dabigatran plasma trough level was 148.6 ng/mL. Again, we decided not to modify the 150 mg b.i.d. treatment. Six weeks later, due to an elevated cardiac rate (140/min) a treatment with 300 mg o.d. of amiodarone was started. A week later dabigatran plasma trough level was 219.6 ng/mL, with a creatinine clearance of 58mL/min. We decided then to reduce the administration of dabigatran to 110 mg twice daily. After two weeks, dabigatran plasma trough level lowered to 120.2 ng/mL. Our patient is still on dabigatran treatment which has so far never been stopped. At this time, studies addressing the correlation of dabigatran concentration with risk of bleeding (overdose) or breakthrough thrombosis (underdosing) are unavailable. The lack of such studies currently limits the predictive power of the plasma-diluted thrombin time to determine hemorrhage/thrombosis risk. However, we believe that in situations like our patient’s the adoption of this assay would be a valuable tool to aid adjusting dabigatran treatment. With access to appropriate pharmacodynamic and pharmacokinetic data and relevant calibration material, the plasma–diluted thrombin time assay can easily be applied for use in the monitoring dabigatran etexilate. Disclosures No relevant conflicts of interest to declare.

Single Particle Soot Photometer intercomparison at the AIDA chamber

Soot particles, consisting of black carbon (BC), organic carbon (OC), inorganic salts, and trace elements, are emitted into the atmosphere during incomplete combustion. Accurate measurements of atmospheric BC are important as BC particles cause adverse health effects and impact the climate. Unfortunately, the accurate measurement of the properties and mass concentrations of BC particles remains difficult. The Single Particle Soot Photometer (SP2) can contribute to improving this situation by measuring the mass of refractory BC in individual particles as well as its mixing state. Here, the results of the first detailed SP2 intercomparison, involving 6 SP2s from 6 different research groups, are presented, including the most evolved data products that can presently be calculated from SP2 measurements. It was shown that a detection efficiency of almost 100% down to 1 fg BC per particle can readily be achieved, and that this limit can be pushed down to ∼0.2 fg BC with optimal SP2 setup. Number and mass size distributions of BC cores agreed within ±5% and ±10%, respectively, in between the SP2s, with larger deviations in the range below 1 fg BC. The accuracy of the SP2's mass concentration measurement depends on the calibration material chosen. The SP2 has previously been shown to be equally sensitive to fullerene soot and ambient BC from sources where fossil fuel was dominant and less sensitive to fullerene soot than to Aquadag. Fullerene soot was therefore chosen as the standard calibration material by the SP2 user community; however, many data sets rely solely on Aquadag calibration measurements. The difference in SP2 sensitivity was found to be almost equal (fullerene soot to Aquadag response ratio of ∼0.75 at 8.9 fg BC) for all SP2s. This allows the calculation of a fullerene soot equivalent calibration curve from a measured Aquadag calibration, when no fullerene soot calibration is available. It could be shown that this approach works well for all SP2s over the mass range of 1–10 fg. This range is suitable for typical BC mass size distributions in the ambient air far from sources. The number size distribution of purely scattering particles optically measured by the 6 SP2s also agreed within 15%. Measurements of the thickness of non-refractory coatings (i.e. product from α-pinene ozonolysis) on the BC particles, relying on BC mass optical size and on an additional particle position measurement, also compared well (within ±17%). The estimated coating thickness values were consistent with thermo-optical analysis of OC and elemental carbon (EC) content, though absolutely accurate values cannot be expected given all the assumptions that have to be made regarding refractive index, particle morphology, etc. This study showed that the SP2 provides accurate and reproducible data, but also that high data quality is only achieved if the SP2 is carefully tuned and calibrated. It has to be noted that the agreement observed here does not account for additional variability in output data that could result from the differences in the potentially subjective assumptions made by different SP2 users in the data processing.

Single Particle Soot Photometer intercomparison at the AIDA chamber

Soot particles, consisting of black carbon (BC), organic carbon (OC), inorganic salts, and trace elements, are emitted into the atmosphere during incomplete combustion. Accurate measurements of atmospheric BC are important as BC particles cause adverse health effects and impact the climate. Unfortunately, the accurate measurement of the properties and mass concentrations of BC particles remains difficult. The Single Particle Soot Photometer (SP2) can contribute to improving this situation by measuring the mass of refractory BC in individual particles as well as its mixing state. Here, the results of the first detailed SP2 intercomparison, involving 6 SP2s from 6 different research groups, are presented, including the most evolved data products that can presently be calculated from SP2 measurements. It was shown that a detection efficiency of almost 100% down to 1 fg BC per particle can readily be achieved, and that this limit can be pushed down to ~0.3 fg BC with optimal SP2 setup. Number and mass size distributions of BC cores agreed within ±5% and ±10%, respectively, in between the SP2s, with larger deviations in the range below 1 fg BC. The accuracy of the SP2's mass concentration measurement depends on the calibration material chosen. The SP2 has previously been shown to be equally sensitive to fullerene soot and ambient BC from sources where fossil fuel were dominant and less sensitive to fullerene soot than to Aquadag. Fullerene soot was therefore chosen as the standard calibration material by the SP2 user community, however many datasets rely solely on Aquadag calibration measurements. The difference in SP2 sensitivity was found to be almost equal (fullerene soot to Aquadag response ratio of ~0.75 at 8.9 fg BC) for all SP2s. This allows the calculation of a fullerene soot equivalent calibration curve from a measured Aquadag calibration, when no fullerene soot calibration is available. It could be shown that this approach works well for all SP2s over the mass range of 1–10 fg. This range is suitable for typical BC mass distributions in the ambient air far from sources. The number size distribution of purely scattering particles optically measured by the 6 SP2s also agreed within 15%. Measurements of the thickness of non-refractory coatings (i.e. product from α-pinene ozonolysis) on the BC particles, relying on BC mass, optical size and on an additional particle position measurement, compared also well (within ±17%). The estimated coating thickness values were consistent with thermo-optical analysis of OC and EC content, though absolutely accurate values cannot be expected given all the assumptions that have to be made regarding refractive index, particle morphology etc. This study showed that the SP2 provides accurate and reproducible data but also that high data quality is only achieved if the SP2 is carefully tuned and calibrated.