An epoxy adhesive system, commonly used in wind turbine blade manufacturing, is experimentally investigated with respect to its chemical shrinkage behavior to show the shrinkage evolution within ...rotor blade production related process conditions. Therefore, a new test configuration is set up to record the resulting chemical shrinkage of the adhesive at cross-linking temperatures ranging from 20°C to 90°C. The respective conversion evolution is simulated under several temperature conditions through a curing kinetics model. This is generated with state of the art formulations, implementing test results from a differential scanning calorimeter (DSC). Moreover, the transformation of the curing degree to the corresponding glass transition temperature (Tg) is performed through an experimentally based Di-Benedetto curve-fitting. By the combination of curing kinetics and chemical shrinkage test data, a model for the temperature and conversion dependant chemical shrinkage evolution during cure is developed. This is applied to a realistic curing cycle for adhesive materials in rotor blade production.
ABSTRACT
At eight different dates during the 2000 growing season, δ13C and δ18O were determined in the phloem of adult beech trees growing in natural beech stands in south‐west Germany differing in ...stand density and local climate. In addition, stand transpiration, precipitation, photosynthetic active radiation, relative air humidity, water pressure deficit of the air, air and soil temperature, soil water potential, and sugar concentration of the phloem sap were determined directly and evaporation and canopy stomatal conductance were modelled. All parameters were related to δ13C. The study aimed to identify the time integral within which the δ13C of organic compounds transported in the phloem is an indicative measure of these environmental influences. δ13C of soluble carbon transported in the phloem was well correlated with mean stomatal conductance in a two‐day integral prior to phloem sampling but did not depend on either light intensity or soil water availability. A strong positive relationship between δ13C and δ18O pointed to observed variation in δ13C of phloem sap being a result of variation in stomatal conductance. Bulk leaf δ13C was a poor indicator of changes in environmental conditions during the growing season. From these results we conclude that the analysis of δ13C in soluble carbon transported in the phloem is a reliable indicator of short‐term changes in Ci/Ca. In contrast, the δ13C of structural carbon in beech foliage represents an integration of a range of factors that mask short‐term influences responsible for Ci/Ca.
High latitude wetlands play an important role for the surface-atmosphere exchange of carbon dioxide (CO2) and methane (CH4), but fluxes of biogenic volatile organic compounds (BVOC) in these ...ecosystems have to date not been extensively studied. This is despite BVOC representing a measurable proportion of the total gaseous C fluxes at northern locations and in the face of the high temperature sensitivity of these systems that requires a much improved process understanding to interpret and project possible changes in response to climate warming. We measured emission of isoprene and photosynthetic gas exchange over two growing seasons (2005–2006) in a subarctic wetland in northern Sweden with the objective to identify the physiological and environmental controls of these fluxes on the leaf scale. The sedge species Eriophorum angustifolium and Carex rostrata were both emitters of isoprene. Springtime emissions were first detected after an accumulated diurnal mean temperature above 0°C of about 100 degree days. Maximum measured growing season standardized (basal) emission rates (20°C, 1000 μmol m−2 s−1) were 1075 (2005) and 1118 (2006) μg C m−2 (leaf area) h−1 in E. angustifolium, and 489 (2005) and 396 (2006) μg C m−2 h−1 in C. rostrata. Over the growing season, basal isoprene emission varied in response to the temperature history of the last 48 h. Seasonal basal isoprene emission rates decreased with leaf nitrogen (N), which may be explained by the typical growth and resource allocation pattern of clonal sedges as the leaves age. The observations were used to model emissions over the growing season, accounting for effects of temperature history, links to leaf assimilation rate and the light and temperature dependencies of the cold-adapted sedges.
While emissions of many biogenic volatile organic compounds (BVOCs), such as terpenoids, have been studied quite intensively in North American and Scandinavian boreal forests, the vast Siberian ...boreal forests have remained largely unexplored by experimental emission studies. In this study the shoot-scale terpenoid emission rates from two mature Larix cajanderi trees growing in their natural habitat in eastern Siberia were measured at the Spasskaya Pad flux measurement site (62°15´18.4" N, 129°37´07.9" E) located on the western bank of the Lena river. The measurements were conducted during three campaigns: 3–24 June, 8–26 July, and 14–30 August, in the summer of 2009. A dynamic flow-through enclosure technique was applied for adsorbent sampling, and the samples were analysed offline with a gas chromatograph. Between 29 and 45 samples were taken from each shoot during all three campaigns. Seven different monoterpenes, six different sesquiterpenes, linalool isoprene, and 2-methyl-3-buten-2-ol (MBO) were identified. The monthly median value of the total terpenoid emissions varied between 0.006 and 10.6 μg gdw−1 h−1. The emissions were dominated by monoterpenes, which constituted between 61 and 92% of the total emissions. About half of the monoterpene emissions were comprised of Δ 3-carene; α- and β-pinene had significant emissions as well. Linalool emissions were also substantial, comprising 3–37% of the total emissions, especially in June. Sesquiterpenes accounted for less than 3% and isoprene less than 1% of the total emissions. Based on the measured emission rates, the relative atmospheric concentration of each compound was estimated. Monoterpenes were the species with the highest relative concentration, while linalool and sesquiterpenes had a notably smaller contribution to the estimated atmospheric concentration than to the emission rates. A temperature-dependent pool algorithm with a constant β (0.09 °C−1 for monoterpenes and 0.143 °C−1 for sesquiterpenes) was used to normalize the measured emission data. For monoterpenes the emission potential varied between 0.5 and 18.5 μg gdw−1 h−1 and for sesquiterpenes between 0.02 and 0.4 μg gdw−1 h−1.
Low energy X-ray imaging (E < 25 keV) is herein demonstrated to be a rapid, effective and non-destructive tool for the quantitative determination of the platinum loading and distribution over the ...entire geometric area of gas diffusion electrodes for polymer electrolyte membrane fuel cells. A linear correlation was found in order for the average image grayscale intensity to be calibrated to the platinum loading, while the platinum distribution was mapped across the electrode geometric area. The resolution was found to be sufficient in identifying flaws and inhomogeneities in the catalyst layer of electrodes fabricated using an industrial spraying process. This technique proves to be an attractive option for the electrode performance study, the process optimization and quality control of electrode fabrication on an industrial scale.
•Low energy X-ray imaging evaluated as a tool for non-destructive characterization of electrodes.•Linear correlation between image grayscale and platinum loading observed.•Platinum distribution mapping across electrode area implemented.•Resolution sufficient to identify flaw and inhomogeneity of industrial electrode fabrication.
The first documented case of COVID-19 in the United States occurred on January 30th, 2020. Soon after, a global pandemic was declared in March 2020 with each state issuing stay at home orders based ...on population, risk for community transmission and current number of positive cases. A priority for each region was to develop efficient systems for testing large patient volumes in a safe manner to reduce the risk of community transmission. A community based United States health care system in the upper mid-west implemented a drive through testing site in an attempt to divert suspected cases of COVID-19 away from larger patient areas while protecting staff and patients. This commentary outlines the planning, work flow and challenges of implementing this drive through testing site in a rural community setting.
The efficacy of i. v. thrombolysis in acute stroke with high clot burden is limited. Successful recanalization is very unlikely if the thrombus length exceeds 7 mm. Thus this retrospective controlled ...study evaluated the efficacy and safety of neurothrombectomy in the treatment of acute embolic stroke in patients selected by a thrombus length of ≥ 8 mm using the stent retriever Trevo(®) device.
40 patients with acute occlusion of the anterior intracranial arteries with a thrombus length of ≥ 8 mm were treated with neurothrombectomy. We compared the outcome with a historical cohort of 42 patients with a thrombus length of ≥ 8 mm that received i. v. thrombolysis only. Clinical outcome was assessed by modified Rankin scale in both groups at discharge and on day 90.
Patients did not differ in age, mRS on admission, thrombus length or time from symptom onset to i. v. thrombolysis, but the thrombectomy group had higher NIHSS on admission. Successful recanalization was achieved in 33/40 patients (83 %) with neurothrombectomy. 15 patients received i. v. thrombolysis prior to neurothrombectomy. Median mRS at discharge was 3.5 (1.25 - 5) vs. 5 (4 - 6; p < 0.01) and on day 90 3 (1 - 4) vs. 5 (4 - 6; p < 0.01). Symptomatic hemorrhage occurred in 3 vs. 7 patients. 3 vs. 17 patients died within 90 days (thrombectomy vs. control each). There were only a few intervention-related complications.
Thrombectomy in acute stroke with high clot burden using the Trevo(®) device has a low risk and improved clinical outcome compared to i. v. thrombolysis alone. Treatment selection by a clot length of ≥ 8 mm might be a powerful approach to improve the outcome of mechanical thrombectomy.
• Clot length of ≥ 8 mm might be a valuable criterion for indicating neurothrombectomy. • Thrombolysis only in high clot burden is associated with poor clinical outcome. • Thrombectomy using the Trevo(®) stent retriever is safe and effective.
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