Brood sex ratio in the Yellow-bellied Prinia(Prinia flaviventris)

Background:The adjustment of sex ratios in birds can occur at the egg and nestling stages. Previous studies showed that the sex ratio was affected by environmental factors and parental condition; it may result in seasonal and ecosystem differences.Methods:In this study, the brood sex ratio of the Yellow-bellied Prinia(Prinia flaviventris) in the Nonggang area, Guangxi, southwestern China, was investigated during the breeding season from May to June in 2013 using PCR amplification from whole-genome DNA extracted from blood samples. A total of 31 nests of Yellow-bellied Prinia, including 132 brood fledglings and 31 pairs, were sampled.Results:The results showed that the brood sex ratio of the Yellow-bellied Prinia was 1:1, and sex ratios of different nests were evenly distributed within the study area. No significant relationship was found between parental quality and nest characteristics with the brood sex ratio.Conclusions:The present study indicated that no brood sex ratio bias in the Yellow-bellied Prinia highlighted the complexity of sex ratio adjustment in birds. In spite of our negative results, the lack of an association between brood sex ratio and parental quality and environmental factors in the Yellow-bellied Prinia provides valuable information on the adjustment of sex ratios in birds.

Minimum MSE Weighted Estimator to Make Inferences for a Common Risk Ratio across Sparse Meta-Analysis Data

The paper aims to discuss three interesting issues of statistical inferences for a common risk ratio (RR) in sparse meta-analysis data. Firstly, the conventional log-risk ratio estimator encounters a number of problems when the number of events in the experimental or control group is zero in sparse data of a 2 × 2 table. The adjusted log-risk ratio estimator with the continuity correction points based upon the minimum Bayes risk with respect to the uniform prior density over (0, 1) and the Euclidean loss function is proposed. Secondly, the interest is to find the optimal weights of the pooled estimate that minimize the mean square error (MSE) of subject to the constraint on where , , . Finally, the performance of this minimum MSE weighted estimator adjusted with various values of points is investigated to compare with other popular estimators, such as the Mantel-Haenszel (MH) estimator and the weighted least squares (WLS) estimator (also equivalently known as the inverse-variance weighted estimator) in senses of point estimation and hypothesis testing via simulation studies. The results of estimation illustrate that regardless of the true values of RR, the MH estimator achieves the best performance with the smallest MSE when the study size is rather large and the sample sizes within each study are small. The MSE of WLS estimator and the proposed-weight estimator adjusted by , or , or are close together and they are the best when the sample sizes are moderate to large (and) while the study size is rather small.

液氧煤油发动机混合比调整技术研究

The LM-5B carrier rocket’s first stage is equipped with eight 120 t.thrust high-pressure staged combustion LOX/kerosene engines(YF-100).The YF-100 engine features a throttle valve in the main fuel path,which allows the adjustment of the throttle area,thereby controlling the engine’s mixture ratio.Engine parameters for the throttle valve were determined based on design conditions(mixture ratio of 2.6),and the engine was then tested for ignition.After testing,if the mixture ratio was found not to meet the overall requirements of the rocket,the throttle area could be adjusted prior to subsequent ignition or installation in the whole system,enabling a secondary adjustment of the mixture ratio.This paper outlines the methodology for static parameter calculations of the engine and the analysis of internal and external interference factors,and presents a scheme for the secondary adjustment of the engine’s mixture ratio and examines the precision of this secondary adjustment.The mixture ratio adjustment technology can notably reduce the dispersion range of mixture ratios for YF-100 engines.Moreover,the influence of mixture ratio adjustment on engine performance parameters was obtained.The approach of mixture ratio adjustment proposed in this paper lays the technical foundation for the precise adjustment of mixture ratio for future heavy-lift rocket engines.

Pollinating fig wasp Ceratosolen solmsi adjusts the offspring sex ratio to other foundresses

Local mate competition theory predicts that offspring sex ratio in pollinating fig wasps is female-biased when there is only one foundress, and increased foundress density results in increased offspring sex ratio. Information of other foundresses and clutch size have been suggested to be the main proximate explanations for sex ratio adjustment under local mate competition. Our focus was to show the mechanism of sex ratio adjustment in a pollinating fig wasp, Ceratosolen solmsi Mayr, an obligate pollinator of the functionally dioecious fig, Ficus hispida Linn., with controlled experiments in the field. First, we obtained offspring from one pollinator and offspring at different oviposition sequences, and found that offspring sex ratio decreased with clutch size, and pollinators produced most of their male offspring at the start of bouts, followed by mostly females. Second, we found that offspring sex ratio increased with foundress density, and pollinators did adjust their offspring sex ratio to other females in the oviposition patches. We suggest that when oviposition sites are not limited, pollinators will mainly adjust their offspring sex ratio to other foundresses independent of clutch size changes, whereas adjusting clutch size may be used to adjust sex ratio when oviposition sites are limited.

Investigations of entrainment characteristics and shear-layer vortices evolution in an axisymmetric rear variable area bypass injector

In this study,firstly,for the axisymmetric RVABI,the change-rule of adverse pressure gradient caused by radial velocity during the transition of internal flow mode in variable geometry is summarized,and a Bypass Ratio(BR) iterative algorithm based on the empirical correlation of non-equilibrium pressure is proposed.The algorithm can estimate the nonlinear relationship between area ratio and BR,with an error range falling below 6.5%.Then,we discuss the favorable effect of uniform mixing on the thrust augmentation of mixed exhaust under variable BR conditions.From this point of view,the characteristics of vortices evolution in different shear strength jets are compared,to clarify the effect of variable cycle parameters on jet mixing.As the results suggest,when ■ is as low as 0.22,the K-H disturbance is of high-frequency wavelet property,and it is difficult to induce large-scale spanwise vortices.The macro migrations of fluid elements in span wise vortices and the diffusion effect caused by edge tearing is weak,which is not conducive to the energy exchange between the two streams.However,the low ■ jet will also correspondingly weaken the viscous dissipation effect of vortices.It is concluded that the dissipation level is proportional to the 2.31 power of the ■.