Supercritical phase inversion of starch-poly(e-caprolactone) for tissue engineering applications

In this work, a starch-based polymer, namely a blend of starch-poly(ε-caprolactone) was processed by supercritical assisted phase inversion process. This processing technique has been proposed for the development of 3D structures with potential applications in tissue engineering applications, as scaffolds. The use of carbon dioxide as non-solvent in the phase inversion process leads to the formation of a porous and interconnected structure, dry and free of any residual solvent. Different processing conditions such as pressure (from 80 up to 150 bar) and temperature (45 and 55°C) were studied and the effect on the morphological features of the scaffolds was evaluated by scanning electron microscopy and micro-computed tomography. The mechanical properties of the SPCL scaffolds prepared were also studied. Additionally, in this work, the in vitro biological performance of the scaffolds was studied. Cell adhesion and morphology, viability and proliferation was assessed and the results suggest that the materials prepared are allow cell attachment and promote cell proliferation having thus potential to be used in some for biomedical applications.Ana Rita C. Duarte is grateful for financial support from Fundacao para a Ciencia e Tecnologia through the grant SFRH/BPD/34994/2007

Limiting radial pedal forces greatly reduces maximal power output and efficiency in sprint cycling: an optimal control study

A cyclist's performance depends critically on the generated average mechanical power output (AMPO). The instantaneous mechanical power output equals the product of crank angular velocity, crank length, and the tangential pedal force. Radial pedal forces do not contribute to mechanical power. It has been suggested that radial pedal forces arise from suboptimal pedaling technique and that limiting these would increase AMPO and efficiency. Here, we presented an optimal control musculoskeletal model of a cyclist (consisting of five segments driven by nine Hill-type muscle-tendon units) to predict maximal AMPO during sprint cycling at different levels of allowed radial pedal forces. Our findings showed that limiting radial pedal forces has a detrimental effect on maximal AMPO; it dropped from 1,115 W without a limit on radial forces to 528 W when no radial forces were allowed (both at 110 rpm). We explained that avoiding radial pedal forces causes ineffective use of muscles: muscles deliver less positive power and have a higher muscle power dissipation ratio (average mechanical power dissipated per unit of average positive power delivered). We concluded that radial pedal forces are an unavoidable by-product when optimizing for maximal AMPO and that limiting these leads to a performance decrease.NEW & NOTEWORTHY In the literature, but also in the "cycling field" [e.g., trainers, coaches, and (professional) cyclists], it is often suggested that trying to limit/avoid radial pedal forces enhances cycling technique and with that maximal average power output and efficiency. In this paper, we introduce an optimal control model of a human cyclists (consisting of five segments and driven by nine Hill-type muscle-tendon complex models). With that we not only show, but also explain why limiting radial forces is a bad idea: it will decrease maximal attainable AMPO and will decrease efficiency

Time to delivery after the first course of antenatal corticosteroids: a cohort study

The optimal time interval between administration of antenatal corticosteroids and delivery is 1 to 7 days. This study evaluates the timing of the first course of antenatal corticosteroids in clinical practice. We performed a retrospective cohort study of consecutive women who had received antenatal corticosteroids and/or delivered between 24 and 34 weeks of gestation. Time between administration of corticosteroids and delivery was compared between women with different causes of anticipated preterm deliveries: symptomatic preterm labor with intact membranes; preterm premature rupture of the membranes; (pre)eclampsia; hemolysis, elevated liver enzymes, and low platelet count; intrauterine growth restriction; vaginal blood loss; and suspected fetal distress. We included 439 women of whom 348 (79%) completed the course of corticosteroids. In women with a complete course, 143 (41%) delivered within 7 days. The median interval between the course and delivery was 11 days and varied between 41 days in women with vaginal blood loss, 25 days in women with spontaneous preterm labor with intact membranes, and 8 days in women with preeclampsia (p < 0.001). In women with spontaneous preterm labor with intact membranes and in women with vaginal blood loss, we can benefit substantially from a more accurate discrimination of women who need corticosteroids immediately and women who do not.Jolande Y. Vis, Femke F. Wilms, Rosanna A. Kuin, Janine M. Reuvers, Monique C. Stam, Desiree A.P.M. Pattinaja, Ben Willem J. Mo