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A structural investigation of self-consolidating concrete (SCC) in AASHTO Type I precast, prestressed girders was performed. Six test girders were subjected to transfer length and flexural testing. Three separate concrete mixtures, two girders per mixture, were used to construct these specimens. A moderate-strength, conventional-slump concrete mixture, similar to the concrete used in typical ALDOT girders was evaluated versus moderate-strength SCC and high-strength SCC. No significant difference in transfer bond behavior was found between the full-scale SCC girders and the conventional concrete girders. High-strength SCC girders had shorter transfer lengths than moderate-strength (SCC and conventional) girders. After normalization to account for the difference in prestress magnitude and concrete strength, there was no discernible difference in the magnitude of the transfer lengths between the concrete types. After a composite, cast-in-place concrete deck was added to each girder, flexural testing was performed near each girder end, resulting in two flexural tests per girder. Embedment lengths were varied for each test in order to bracket the AASHTO strand development length. Results indicated that the use of SCC had no adverse effects on the overall flexural performance, and the flexural bond lengths were conservatively predicted by the relevant ACI and AASHTO expressions. Similarly, the SCC girders exhibited comparable service-level performance to the conventional girders. Based on the work performed in this study SCC should perform well in prestressed concrete girder applications.
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Dr Heckman is correct in his assertion that our study was not designed to assess the accuracy of the clinical diagnosis of venous thrombosis according to the degree of certainty of the clinical diagnosis made by the referring physician. This problem was well studied by Haeger,1who demonstrated that the clinical diagnosis of "suspected" and "classic" deep-vein thrombosis was correct in 34% and 55%, respectively, as confirmed by immediate contrast phlebography. The overall clinical accuracy in Haeger's study was 45%. The patients reported in our study had sufficient clinical signs of deepvein thrombosis to warrant anticoagulant therapy until the diagnosis was established by objective techniques. Indeed, prior to the establishment of our laboratory, these patients generally received a full course of anticoagulant therapy. It has been only since the availability of simple noninvasive diagnostic techniques, such as Doppler ultrasound, that we have come to appreciate the fallibility
Introduction: Hemorrhagic transformation is a common complication of mechanical thrombectomy (MT), often as a result of reperfusion injury. We investigated the correlation between automated CT perfusion (CTP) parameters and Hemorrhagic transformation after MT in acute ischemic stroke. Method: We conducted a retrospective cohort analysis of patients consecutively admitted to the Providence Health System between January 2018 and February 2022 with acute ischemic stroke who underwent MT and had a CTP on admission. We also addressed each CTP parameter’s predictive power through bivariate logistic regression and ROC/AUC analysis. We compared the median and IQR ranges of volumes of automated CTP parameters between patients with and without ICH. Any degree of hemorrhagic transformation in the ECASS II classification system was considered ICH. Symptomatic intracranial hemorrhage (sICH) was defined by The Heidelberg Bleeding Classification. (4 point increase in NIHSS, or 2 in one NIHSS subcategory, major medical/surgical intervention involved) Results: We included 513 patients with a ischemic stroke who had an MT. Median age was 75(63, 85) years old. Higher blood sugar (p=0.003) and chronic kidney disease (p=0.001) were significantly associated with sICH Table1. Cerebral blood flow( CBF)<30%, cerebral blood volume (CBV)<38%, CBV<42%, mismatch ratio, and CBV index were associated to sICH as shown in Table 2. ROC analysis for CBV index showed an AUC of 0.64 in the bivariate analysis. Other CTP parameter logistic regression and an ROC/AUC analysis are shown in Table 3. Conclusion: Higher CBF<30%, CBV<38%, and CBV<42% volumes were associated with an increased frequency of ICH and sICH. Higher mismatch ratios correlated with a lower frequency of ICH and sICH. Lower hypoperfusion index; and, elevated Tmax volumes >10s and >8s, were associated to a higher frequency of ICH. However, these parameters were insufficiently powered to show a significant association with sICH. CBV index outperformed the other CTP parameters in the ROC analysis. Larger studies are needed to clarify these associations.
