Association between allergic conditions and prostate cancer risk has been investigated for many years. However, the results from available evidence for the association are inconsistent. We conducted a meta-analysis to evaluate the relationship between allergic conditions (asthma, atopy, hay fever and “any allergy”) and risk of prostate cancer. The PubMed and Embase databases were searched to screen observational studies meeting our meta-analysis criteria. Study selection and data extraction from included studies were independently performed by two authors. Twenty studies were considered eligible involving 5 case-control studies and 15 cohort studies. The summary relative risk (RR) for developing prostate cancer risk was 1.04 (95%CI: 0.92–1.17) for asthma, and 1.25 (95%CI: 0.74–2.10) for atopy, 1.04 (95%CI: 0.99–1.09) for hay fever, 0.96 (95%CI: 0.86–1.06) for any allergy. In the Subgroup and sensitivity analysis, similar results were produced. Little evidence of publication bias was observed. The present meta-analysis of observational studies indicates that no indication of an association between allergic conditions and risk of prostate cancer was found, and the meta-analysis does not support neither the original hypothesis of an overall cancer protective effect of allergic conditions, nor that of an opposite effect in the development of prostate cancer.

To deepen our understanding of the aerodynamics by which hummingbirds use flexible wings to hover efficiently during flapping flight, a three-dimensional wing model with dynamic morphing was developed according to the morphological and kinematic data of a hovering hummingbird’s wing. Navier-Stokes equations were solved on a dynamically deforming grid to study wing aerodynamics. In numerical simulations, boundary-based smoothing and overset methodologies were used in combination to update the interior nodes of cells in the computational domain, allowing those nodes to accommodate the motion of the flexible wall. This study showed that the leading edge vortex (LEV) attached to the wing was stable during the downstroke but extremely unstable and shed continuously during the upstroke. In the results of the downward stroke, the different vortices separated from the surface and formed a vortex ring. The difference is that the leading edge vortex induced a vortex ring near the root and a smaller and weaker vortex ring near the wingtip during the upstroke. A significant enhancement in aerodynamic forces was found during the downstroke, along with a large number of power consumptions. We found that the asymmetry in the time-averaged vertical force between the two half strokes was 3.5, and the value was higher than that reported earlier. Aerodynamic force coefficients and efficiency matched well with those of another hummingbird wing (the ruby-throated hummingbird). It is worth noting that hummingbirds can maintain a similar wingtip speed by flapping their wings, but different strategies are adapted to hover efficiently due to the differences in size and body weight. The results of this study help to better understand the aerodynamics of the hovering hummingbird.

With the purpose to improve the performance of the flexible membrane flapping wing, a kind of flapping wing with an attached airfoil to the root is designed and tested in a wind tunnel. In order to study, the actual performance improvement of the flapping wing, the flight performance is calculated and compared instead of the aerodynamic performance. A method to establish a semi-empirical cycle-averaged mathematical model for the flapping wing with high precision based on the wind tunnel experiment is proposed to calculate the flight performance. The established continuous mathematical model can solve the problem of how to obtain the trimmed state by using discrete experimental data. By attaching the airfoil EPPLER 378 with a thickness of 4.07% chord length to the root, the cruise velocity envelope is expanded, especially with a small cruise velocity. Although the attached airfoil to the root can cause a slight decrease in endurance and range of the flapping wing, it will greatly enhance the climbing performance and effectively reduce the demand for the takeoff sites. Besides, the flapping wing with an attached airfoil to the root will result in a significant reduction in the radius of steady turning and will improve the maneuverability. In addition, the airfoil EJ 85, which is similar to the airfoil EPPLER 378 in shape and camber but has a larger thickness of 6.5% chord length, is attached to the root of the original flapping wing. The same experiment and modeling procedure are performed on the airfoil EJ 85 to analyze the difference in performance of the flapping wing with different airfoil thickness.

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Due to the complexity of tailoring the wing flexibility and selecting favorable kinematics, the design of flapping wings is a considerably challenging problem. Therefore, there is an urgent need to investigate methods that can be used to design wings with high energy efficiency. In this study, an optimization model was developed to improve energy efficiency by optimizing wing geometric and kinematic parameters. Then, surrogate optimization was used to solve the design optimization model. Finally, the optimal design parameters and the associated sensitivity were provided. The optimized flapping wing, inspired by hummingbirds, features large geometrical parameters, a moderate amplitude of the flapping angle, and low frequency. With the spanwise twisting deformation considered in the parameterization model, the optimization solver gave an optimized wing with a pitching amplitude of approximately 39 deg at the root and 76 deg at the tip. According to the sensitivity analysis, the length of the wing, flapping frequency, and flapping amplitude are the three critical parameters that determine both force generation and power consumption. The amplitude of the pitching motion at the wing root contributes to lowering power consumption. These results provide some guidance for the optimal design of flapping wings.