2,759 research outputs found

    As Low Birth Weight Babies Grow, Can 'Good' Parents Buffer this Adverse Factor? A Research Note.

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    This research note combines two national Taiwanese datasets to investigate the relationship between low birth weight (LBW) babies, their family background and their future academic outcomes. We find that LBW is negatively correlated with the probability of such children attending university at the age of 18; however, when both parents are college or senior high school graduates, such negative effects may be partially offset. We also show that discrimination against daughters does occur, but only in those cases where the daughters were LBW babies. Moreover, high parental education (HPE) can only buffer the LBW shock among moderately-LBW children (as compared to very-LBW children) and full term-LBW children (as compared to preterm-LBW children).

    Unsteady Aerodynamic Interaction Between Rotor and Ground Obstacle

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    The mutual aerodynamic interaction between rotor wake and surrounding obstacles is complex, and generates high compensatory workload for pilots, degradation of the handling qualities and performance, and unsteady force on the structure of the obstacles. The interaction also affects the minimum distance between rotorcrafts and obstacles to operate safely. A vortex-based approach is then employed to investigate the complex aerodynamic interaction between rotors and ground obstacle, and identify the distance where the interaction ends, and this is also the objective of the GARTEUR AG22 working group activities. In this approach, the aerodynamic loads of the rotor blades are described through a panel method, and the unsteady behaviour of the rotor wake is modelled using a vortex particle method. The effects of the ground plane and obstacle are accounted for via a viscous boundary model. The method is then applied to a “Large” and a “Wee” rotor near the ground and obstacle, and compared with the earlier experiments carried out at the University of Glasgow. The results show that the predicted rotor induced inflow and flow field compare reasonably well with the experiments. Furthermore, at certain conditions the tip vortices are pushed up and re-injected into the rotor wake due to the effect of the obstacle resulting in a recirculation. Moreover, contrary to without the obstacle case, the peak and thickness of the radial outwash near the obstacle is smaller due to the barrier effect of the obstacle, and an up-wash is observed. Additionally, as the rotor closes to the obstacle, the rotor slipstreams impinge directly on the obstacle, and the up-wash near the obstacle is faster, indicating a stronger interaction between the rotor wake and the obstacle. Also, contrary to the case without the obstacle, the fluctuations of the rotor thrust, rolling and pitching moments are obviously strengthened. When the distance between the rotor and the obstacle is larger than 3R, the effect of the obstacle is small

    Rootstock and seasonal variations affect anthocyanin accumulation and quality traits of ‘Kyoho’ grape berries in subtropical double cropping system

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    The double cropping system has been commercially adopted in subtropical viticulture regions. However, very limited information about rootstock and seasonal effects on berry quality traits are available for this unique production system. Developing ‘Kyoho’ berries from own-rooted vines and from vines on 5C and 1202C rootstocks were periodically sampled from veraison until harvest in two consecutive cropping cycles to document the potential seasonal influence on rootstock effects. Anthocyanin concentration in berry skin, total soluble solids content (TSS), and titratable acidity (TA) were analyzed. In both cropping cycles, own-rooted vines produced berries with the highest anthocyanin concentration while vines on 1202C produced berries with the lowest anthocyanin concentration among the three scion/rootstocks. Anthocyanin concentrations were not differentiated by the differential climate pattern between the summer and the winter cropping cycles. Berries of own-rooted ‘Kyoho’ and ‘Kyoho’/5C vines accumulated satisfactory and equal amount of TSS in both cropping cycles. 1202C rootstocks did not affect berry TSS in the summer cropping cycle but reduced TSS in the winter cropping cycle. Significant rootstock and seasonal effects on berry TA were detected. Own-rooted vines produced berries with the lowest TA while vines on 1202C produced berries with the highest TA among the three scion/rootstock combinations. TA of berries from the winter cropping cycle was significantly higher than that from the summer cropping cycle especially in ‘Kyoho’/1202C. Relationships between anthocyanins and TSS of developing berries after veraison properly fitted into a sigmoidal function regardless of rootstocks and cropping cycles. However, the duration of the initial lag phase, the onset and the trend of both quality triats in the increasing phase, and the presence and degree of the final lag phase in the relationship were all modulated by rootstocks and by seasonal variations.

    Experimental analysis of submerged flapping foils; implications for autonomous surface vehicles (ASVs)

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    Autonomous surface vehicles (ASVs) have proven effective as ocean observing platforms for maritime operations. In most cases it is advantageous to operate ASVs for extensive missions in order to maximize their cost effectiveness. Such long endurance missions require ASVs to be capable of scavenging ambient energy from the surrounding ocean environment. Submerged flapping foils are currently utilized as an effective mechanism to convert ocean wave energy directly into propulsion.The authors propose a novel setup whereby these foils can heave relative to the surface vehicle and, through the application of a power take off (PTO) system, can recover a proportion of the incoming wave energy.Experiments were performed to investigate the coupled response between a surface vehicle and submerged flapping foils within the context of generating power and propulsion from incoming waves onboard ASVs. Results show that the response of a surface vehicle with submerged flapping foils is particularly sensitive to design parameters such as the longitudinal location of the foils and the seakeeping characteristics of the surface vehicle.Through optimising the PTO system, this setup could recover a useful proportion of wave energy for ASV platforms

    Vortex approach for downwash and outwash of tandem rotors in ground effect

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    A vortex-based approach is employed to predict the downwash and outwash of a tandem rotor in ground effect and provide an understanding of its wake. The aerodynamic loads of the blades are represented through a panel method, and the behavior of the wake is captured by a viscous vortex particle method. The viscous effects of the ground are accounted for by a viscous boundary model satisfying the no-slip and nonpenetration boundary conditions. The method is first validated for an isolated full-scale Lynx tail rotor and a 172-mm-diameter-scale rotor in ground effect. The results show that the predicted trajectories of the tip vortices and the radial velocity profiles compare favorably with experiments and published computational fluid dynamics results. The results for model CH-47D are then compared with experiments for the downwash and outwash of the tandem rotor. As opposed to the isolated single rotor, a radial outward expansion in the overlapping area is observed, and the peak and the corresponding vertical distance of the velocity maximum of the radial outwash flow for the tandem rotor are larger. Moreover, the rotational direction of the tandem rotor leads to a wake with several vortical interactions resulting in different outwashes on the port and starboard sides

    Free surface flow and wave impact at complex solid structures

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    Hydrodynamic wave loading at structures is a complex phenomenon to quantify. The design of structures to resist wave loading has been historically and predominantly achieved through empirical and experimental observations. This is due to the challenging understanding and quantification of wave impact energy transfer processes with air entrainment at solid structures. This paper investigates wave loading on such structures with effects of air entrapment. Specifically, it focuses on predicting the multi-modal oscillatory wave impact pressure signals which result from transient waves impinging upon a solid wall. A large dataset of compressible (and incompressible) numerical modelling scenarios have been generated to investigate these processes. The modelling simulation data are verified through a grid scaling analysis and validated against previous studies. Air bubble entrapment oscillatory pressure response trends are observed in the compressible simulation during wave impact. A frequency domain analysis of the impact pressure response is undertaken. The numerical modelling results are found in good agreement with theoretical and experimental observation data. These findings provide good confidence on the robustness of our numerical model foundations particularly for investigating the air bubbles formation, their mechanics and adjusted resonance frequency modes at impact with solid wall

    Aerosolized amphotericin B as prophylaxis for invasive pulmonary aspergillosis: a meta-analysis

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    SummaryObjectivesInvasive pulmonary aspergillosis (IPA) is associated with high mortality in high-risk (immunosuppressed) patients. Many studies have investigated whether prophylactic inhalation of amphotericin B (AMB) reduces the incidence of IPA, but no definitive conclusions have been reached. The present meta-analysis was performed to evaluate the efficacy of prophylactic inhalation of AMB for the prevention of IPA.MethodsMEDLINE and other databases were searched for relevant articles published until December 2013. Randomized controlled trials that compared aerosolized AMB with placebo were included. Two reviewers independently assessed and extracted the data of all trials.ResultsSix animal studies and two clinical trials involving 768 high-risk patients were eligible. The animal studies showed lower overall mortality rate among animals that underwent aerosolized AMB prophylaxis (odds ratio (OR) 0.13, 95% confidence interval (CI) 0.08–0.21). Similarly, the clinical trials showed a lower incidence of IPA among patients who underwent aerosolized AMB prophylaxis (OR 0.42, 95% CI 0.22–0.79).ConclusionsThis analysis provides evidence supporting the notion that the prophylactic use of aerosolized AMB effectively reduces the incidence of IPA among high-risk patients
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