Hand force of men and women over 65 years of age as measured by maximum pinch and grip force

This cross-sectional study aimed to assess the impact of age and gender on 4 measures of grip and pinch force of well elderly community dwellers and to provide normative values. The hypotheses were that age and gender affect pinch and grip force and that these 2 factors might interact. Hand strength of 224 seniors 65-92 years old was tested. Grip and pinch force decreased in successively older age groups past 65 years. Men's grip force exceeded that of women in all age groups. Men's hand-force decline was steeper than that of women over successive age groups, suggesting that gender differences in force decreased with age. Trends were the same for all 4 types of grip- and pinch-force measurement but were most clearly visible in grip and key-pinch force. Norms were provided for seniors age 65-85+ years in 5-yr increments.     

Irregularly observed time series – some asymptotics and the block bootstrap

We consider time series being observed at random time points. In addition to Parzen's classical modelling by amplitude modulating sequences, we state another modelling using an integer-valued sequence as the observation times. Limiting results are presented for the sample mean and are generalized to the class of functions of smooth means. Motivated by the complicated limiting behaviour, (moving) block bootstrap possibilities are investigated. Conditional on the used modelling for the irregular spacings, one is lead to different interpretations for the block length and hence bootstrap approaches. The block length either can be interpreted as the time (resulting in an observation string of fixed length containing a random number of observations) or as the number of observations (resulting in an observation string of variable length containing a fixed number of values). Both bootstrap approaches are shown to be asymptotically valid for the sample mean. Numerical examples and an application to real-world ozone data conclude the study.     

Urbanization homogenizes the interactions of plant-frugivore bird networks

Urban Ecosystems - Anthropogenic activities are the main cause of habitat loss and fragmentation, which directly affects biodiversity. Disruption in landscape connectivity among populations may...     

Specification testing in nonparametric AR‐ARCH models

In this paper, an autoregressive time series model with conditional heteroscedasticity is considered, where both conditional mean and conditional variance function are modeled nonparametrically. Tests for the model assumption of independence of innovations from past time series values are suggested. Tests based on weighted L²‐distances of empirical characteristic functions are considered as well as a Cramér–von Mises‐type test. The asymptotic distributions under the null hypothesis of independence are derived, and the consistency against fixed alternatives is shown. A smooth autoregressive residual bootstrap procedure is suggested, and its performance is shown in a simulation study.