Spreading of a Herschel-Bulkley fluid using lubrication approximation

In this work the flow of 1.5% Carbopol-940 solution was studied as it was transported through a wedge-like system at different angles, entrance heights, exit heights, and velocities. The high-speed video recordings of the flow were processed by tracking air bubbles entrapped in the solution. This data was used to find the velocity field of the solution beneath the wedge. Also, the force imposed by the solution on the inclined top plate of the wedge was measured. The theoretical description in the framework of the lubrication approximation for Newtonian fluids was used for comparison to the experimental results. It was found that Herschel-Bulkley fluids exhibit qualitatively similar behavior to the Newtonian fluid, such as the reverse flow near the top of the wedge. Overall, this work proves that the lubrication approximation can be effectively used to characterize the flow field of non-Newtonian Herschel-Bulkley fluids at the wedge angles at least up to 20 degrees

Effects of phlebotomy-induced reduction of body iron stores on metabolic syndrome: results from a randomized clinical trial

<p>Abstract</p> <p>Background</p> <p>Metabolic syndrome (METS) is an increasingly prevalent but poorly understood clinical condition characterized by insulin resistance, glucose intolerance, dyslipidemia, hypertension, and obesity. Increased oxidative stress catalyzed by accumulation of iron in excess of physiologic requirements has been implicated in the pathogenesis of METS, but the relationships between cause and effect remain uncertain. We tested the hypothesis that phlebotomy-induced reduction of body iron stores would alter the clinical presentation of METS, using a randomized trial.</p> <p>Methods</p> <p>In a randomized, controlled, single-blind clinical trial, 64 patients with METS were randomly assigned to iron reduction by phlebotomy (n = 33) or to a control group (n = 31), which was offered phlebotomy at the end of the study (waiting-list design). The iron-reduction patients had 300 ml of blood removed at entry and between 250 and 500 ml removed after 4 weeks, depending on ferritin levels at study entry. Primary outcomes were change in systolic blood pressure (SBP) and insulin sensitivity as measured by Homeostatic Model Assessment (HOMA) index after 6 weeks. Secondary outcomes included HbA1c, plasma glucose, blood lipids, and heart rate (HR).</p> <p>Results</p> <p>SBP decreased from 148.5 ± 12.3 mmHg to 130.5 ± 11.8 mmHg in the phlebotomy group, and from 144.7 ± 14.4 mmHg to 143.8 ± 11.9 mmHg in the control group (difference -16.6 mmHg; 95% CI -20.7 to -12.5; <it>P </it>< 0.001). No significant effect on HOMA index was seen. With regard to secondary outcomes, blood glucose, HbA1c, low-density lipoprotein/high-density lipoprotein ratio, and HR were significantly decreased by phlebotomy. Changes in BP and HOMA index correlated with ferritin reduction.</p> <p>Conclusions</p> <p>In patients with METS, phlebotomy, with consecutive reduction of body iron stores, lowered BP and resulted in improvements in markers of cardiovascular risk and glycemic control. Blood donation may have beneficial effects for blood donors with METS.</p> <p>Trial registration</p> <p>ClinicalTrials.gov: <a href="http://www.clinicaltrials.gov/ct2/show/NCT01328210">NCT01328210</a></p> <p>Please see related article: <url>http://www.biomedcentral.com/1741-7015/10/53</url></p

Mechanics and Rheological Characterization of Construction Materials

This work deals with mechanical behavior and rheological characterization of construction materials. In particular, it describes self-healing fibers, characterization techniques, and two apparatuses, all of which serve to improve on already developed construction materials. Self-healing core-shell nanofibers are created using emulsion electrospinning, coelectrospinning, and emulsion solution blowing. Fiber crush test and interlayer pull out test are conducted to verify the expulsion of the core material under stress. The mechanical properties of foams with different surfactant concentrations, air contents, and the addition of PEO are measured using free drainage in a gravity settler. It was found that an increase in concentration and the addition of PEO both reduce drainage rates of the foam, making it more stable, and the air content only effects the total liquid volume in the foam. Constant volume squeeze flow of soft solids, modeled under the assumption that normal stresses are dominant, relates the axisymmetrical spreading rate to the force applied divided by the viscosity of the fluid. Also, the material’s yield stress is calculated. Then, an experimental apparatus was constructed in concert with the theory and the known rheological parameters of bentonite and Carbopol were used to validate the squeezing apparatus. Furthermore, the squeezing apparatus can measure the rheological properties of abrasive joint compounds and correlates component variation to changes in viscosity and yield stress. The same squeezing apparatus was modified in order to vary the applied force in time and identifies a transition of bentonite dispersions when squeezed from liquid-like (flowing) to solid-like (cracking) behavior. The stress required for bentonite dispersions to crack was investigated for concentrations of 11 wt% to 13 wt% and an aging time of 0 hours to 72 hours. The spreading of thick dispersions by a knife or trowel was simulated by spreading Carbopol solution with seeding particles to reveal an experimental velocity profile under a wedge at three angles and two heights using a moving plate pulled at two velocities. The experimental velocity profile is compared to the one-dimensional analytical result for a Newtonian fluid in the lubrication approximation and with the Bingham fluid model

Spreading of a Herschel-Bulkley fluid using lubrication approximation

In this work the flow of 1.5% Carbopol-940 solution was studied as it was transported through a wedge-like system at different angles, entrance heights, exit heights, and velocities. The high-speed video recordings of the flow were processed by tracking air bubbles entrapped in the solution. This data was used to find the velocity field of the solution beneath the wedge. Also, the force imposed by the solution on the inclined top plate of the wedge was measured. The theoretical description in the framework of the lubrication approximation for Newtonian fluids was used for comparison to the experimental results. It was found that Herschel-Bulkley fluids exhibit qualitatively similar behavior to the Newtonian fluid, such as the reverse flow near the top of the wedge. Overall, this work proves that the lubrication approximation can be effectively used to characterize the flow field of non-Newtonian Herschel-Bulkley fluids at the wedge angles at least up to 20 degrees.</jats:p

THE CONTROL OF REPRODUCTION IN THE NURSING COW WITH A PROGESTAGEN SHORT-TERM TREATMENT

International audienc

SYNCHRONIZATION OF OESTRUS IN HEIFERS AND CYCLIC COWS WITH PROGESTAGENS AND PROSTAGLANDINS ANALOGUES ALONE OR IN COMBINATION

International audienc

SYNCHRONIZATION OF OESTRUS IN HEIFERS AND CYCLIC COWS WITH PROGESTAGENS AND PROSTAGLANDINS ANALOGUES ALONE OR IN COMBINATION

International audienc