49 research outputs found

    Simulations of extensional flow in microrheometric devices

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    We present a detailed numerical study of the flow of a Newtonian fluid through microrheometric devices featuring a sudden contraction–expansion. This flow configuration is typically used to generate extensional deformations and high strain rates. The excess pressure drop resulting from the converging and diverging flow is an important dynamic measure to quantify if the device is intended to be used as a microfluidic extensional rheometer. To explore this idea, we examine the effect of the contraction length, aspect ratio and Reynolds number on the flow kinematics and resulting pressure field. Analysis of the computed velocity and pressure fields show that, for typical experimental conditions used in microfluidic devices, the steady flow is highly three-dimensional with open spiraling vortical structures in the stagnant corner regions. The numerical simulations of the local kinematics and global pressure drop are in good agreement with experimental results. The device aspect ratio is shown to have a strong impact on the flow and consequently on the excess pressure drop, which is quantified in terms of the dimensionless Couette and Bagley correction factors. We suggest an approach for calculating the Bagley correction which may be especially appropriate for planar microchannels

    Association of Osteocalcin and Abdominal Aortic Calcification in Older Women: The Study of Osteoporotic Fractures

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    Osteocalcin (OC) is produced by osteoblasts and vascular smooth muscle cells. In animal models, serum OC levels are strongly correlated with vascular calcium content, however, the association of OC with vascular calcification in humans is uncertain. The Study of Osteoporotic Fractures (SOF) enrolled community-living women, age ≥65 years. The present study included a subsample of 363 randomly selected SOF participants. Serum total OC was measured by ELISA, and abdominal aortic calcification (AAC) was evaluated on lateral lumbar radiographs. We examined the cross-sectional association between serum OC and AAC. The mean serum OC level was 24 ± 11 ng/ml and AAC was present in 188 subjects (52%). We observed no association of OC and AAC in either unadjusted or adjusted analyses. For example, each standard deviation higher OC level was associated with an odds ratio (OR) for AAC prevalence (AAC score >0) near unity (OR = 1.06; 95% CI, 0.82–1.36) in models adjusted for CVD risk factors. Further adjustment for intact parathyroid hormone, bone-specific alkaline phosphatase, 25-hydroxyvitamin D, and hip and spine bone mineral density did not materially change the results (OR = 1.22; 95% CI, 0.86–1.75). Similarly, higher OC levels were not associated with severity of AAC (P = 0.87). In conclusion, among community-living older women, serum OC is not associated with AAC. These findings suggest that serum OC levels may more closely reflect bone formation than vascular calcification in humans

    The Rotterdam Study: 2016 objectives and design update

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    Knowledge and Attitudes of Pharmacists in a Midwestern State Regarding Natural Products

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    Objectives. The purpose of this descriptive investigation was to determine the perceived knowledge of and attitudes toward natural products by pharmacists in Missouri. Methods. A questionnaire was mailed to 2921 licensed pharmacists. Assessments were conducted regarding the venues and specific resources these pharmacists utilized in order to gain knowledge in the area of natural products. Results. Over half (56.9%) of those surveyed indicated that they received natural product questions on a weekly basis, but only a minority (2.4%) felt they could “always answer natural product questions.” The most commonly used means for education was printed continuing education (70.2%). Only 12.5% of pharmacists indicated that they had gained knowledge about natural products from their didactic pharmacy education. Conclusions. These results confirm the need to provide pharmacists with additional education on natural products. Ideas for integrating education on natural products into pharmacy school curricula are presented. Read More: https://www.ajpe.org/doi/full/10.5688/aj67024
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