Modela-r as a Froude and Strouhal dimensionless numbers combination for dynamic similarity in running

The aim of this study was to test the hypothesis that running at fixed fractions of Froude (Nfr) and Strouhal (Str) dimensionless numbers combinations induce dynamic similarity between humans of different sizes. Nineteen subjects ran in three experimental conditions, (i) constant speed, (ii) similar speed (Nfr) and (iii) similar speed and similar step frequency (Nfr and Str combination). In addition to anthropometric data, temporal, kinematic and kinetic parameters were assessed at each stage to measure dynamic similarity informed by dimensional scale factors and by the decrease of dimensionless mechanical parameter variability. Over a total of 54 dynamic parameters, dynamic similarity from scale factors was met for 16 (mean r=0.51), 32 (mean r=0.49) and 52 (mean r=0.60) parameters in the first, the second and the third experimental conditions, respectively. The variability of the dimensionless preceding parameters was lower in the third condition than in the others. This study shows that the combination of Nfr and Str, computed from the dimensionless energy ratio at the center of gravity (Modela-r) ensures dynamic similarity between different-sized subjects. The relevance of using similar experimental conditions to compare mechanical dimensionless parameters is also proved and will highlight the study of running techniques, or equipment, and will allow the identification of abnormal and pathogenic running patterns. Modela-r may be adapted to study other abilities requiring bounces in human or animal locomotion or to conduct investigations in comparative biomechanics.     

Economic values and dominant providers of key ecosystem services of wetlands in Beijing,China

This study estimates the economic values of and the dominant contributors to five key ecosystem services of wetlands in Beijing, by using the wetland inventory data in 2014 and economic valuation methods. Results indicate that the 51,434 ha of wetlands in Beijing annually provide 2.07 billion m³ of flood regulation, 944.01 million m³ of water provision, 42,154 tons of chemical oxygen demand (COD) purification, 3.03 PJ of heat absorption, and 9587 ha of habitat. Their economic values are estimated to be 15.89 billion RMB, 1.19 billion RMB, 169 million RMB, 421 million RMB, and 1.08 billion RMB in 2014 (RMB: Chinese currency, US$1 = RMB 6.14), respectively. The total values of five key wetland ecosystem services reach 18.76 billion RMB. In addition, the reservoir and river wetlands in Miyun, Yanqing, Fangshan, Huairou, and Mentougou Districts contribute 78% of key ecosystem services, whereas the urban wetlands in Xicheng, Dongcheng, Haidian, Chaoyang, and Tongzhou Districts more conveniently serve densely local people, hence they should be given particular attentions. In this paper, we develop the valuation methods of wetland ecosystem services, and recommend diversified strategies, regulations, and programs to protect the remaining wetlands in Beijing. This work can also provide a reference for the valuating of wetland ecosystem services for other urban-rural areas.     

Direct observation of toxic effects of cyanobacterial extracellular products on Daphnia

The filtrate from a suspension of the cyanobacterium Anabaena minutissima var. attenuata depressed thoracic limb beat frequency of Daphnia carinata by 38–45% in a food-free medium. Repeated exposure to the filtrate produced a similar depression of activity with full or neary full recovery. Response time to the filtrate was 5–8 min and recovery time was 8–12 min. The dose effect on limb beat frequency was continuous, linear, correlated with increased concentration and with no threshold. There was no relationship between body length and limb beat frequency.The interaction between toxicity and food concentration was tested using the diatom Cyclotella suspended in Anabaena filtrate. Daphnia limb beat frequency was depressed by 62%.     

The fate of balanced,phenotypic polymorphisms in fragmented metapopulations

In large populations, genetically distinct phenotypic morphs can be maintained in equilibrium (at a 1 : 1 ratio in the simplest case) by frequency‐dependent selection, as shown by Sewall Wright. The consequences of population fragmentation on this equilibrium are not widely appreciated. Here, I use a simple computational model to emphasize that severe fragmentation biases the morph ratio towards the homozygous recessive genotype through drift in very small populations favouring the more common recessive allele. This model generalizes those developed elsewhere for heterostylous plants and major histocompatibility complex alleles, emphasizes one particular outcome and avoids the restricting assumptions of more analytical models. There are important implications for both fundamental evolutionary biology and conservation genetics. I illustrate this with a range of examples but refer particularly to shell polymorphism in snails. These examples show how habitat fragmentation could have a direct and often unappreciated effect on species at the level of their population genetics.     

Effects of local density and flower colour polymorphism on pollination and reproduction in the rewardless orchid Dactylorhiza sambucina (L.) Soò

The rewardless orchid Dactylorhiza sambucina shows a stable flower colour polymorphism, with both yellow- and red-flowered morphs growing sympatrically. Pollination biology and breeding system were investigated to examine the effects of density of plants, colour polymorphism, inflorescence dimension, and flower position within inflorescence on male and female reproductive success in three natural populations of D. sambucina. There were significant differences among sites in the number of pollinia removed and in fruit set per inflorescence. Number of removed pollinia and capsule production in D. sambucina were independent from flower and inflorescence size or flower position. As a whole, the red morphs showed the highest number of capsules produced, while the yellow morphs had the greatest male success. The relative male and female reproductive success were independent from plant density but were significantly correlated with the yellow morph frequency at the population level. Overall, our findings show that the contribution to the total reproductive success deriving from the two colour morphs does not conform with the predictions of negative frequency-dependent selection.     

图形视网膜电图的空间和时间调谐特性——FFT分析

用快速傅里叶转换(FFT)技术分析了图形视网膜电图(PERG)的空间和时间调谐特性。PERG 的二次谐波在较高的空间频率(>0.46周/度)逐渐下降,与 PERG振幅的变化相似,但显示明显的低空间频率衰减。空间和时间调谐特性存在一定的相关。引起最大二次谐波振幅的最佳时间频率,在低空间频率时(<0.23周/度)由低频(≤3.91Hz)移至 7.81Hz。     

Optimal stimulation frequency for vibrational optical coherence elastography

Vibrational optical coherence elastography (OCE) is a promising tool for extracting the mechanical property of soft tissue. Purpose of this study is focusing on settling the optimal frequency range for vibrational OCE with evenly distributed stress filed. A finite element model of 2% agar phantom was built by ANSYS with a vibration stimulation frequency range from 200 to 3000 Hz. Practical experiments were carried out for cross‐validation with the same frequencies and sample. Lateral and horizontal stress filed distributions under different frequencies were mathematically evaluated by coefficient of variance and degree of linearity. Results from simulation and practical experiment cross‐validated each other and 1000 Hz was set as the maximum ideal frequency for vibrational OCE, while the minimum frequency is set by theoretical calculation with a result of 250 Hz. An ex vivo biological sample was utilised to testify performance of vibrational OCE with excitation frequencies in and out of concluded optimal range, which showed that stiffness was better mapped out in optimal frequency range.     

Rates of small-scale species mobility in alvar limestone grassland

Abstract. Small-scale species frequency and cumulative species frequency were studied in four plots in limestone grassland of the Veronica spicata-Avenula pratensis association on Stora Alvaret on the Baltic island of Öland, Sweden. Species mobility was expressed as increase in cumulative species frequency in 20 subplots of 100 cm². Observed cumulative frequencies from 1985–1989 in all four plots, and from 1985–1995 in one plot were compared with values following from two null models, a ‘minimal mobility’ model and a random mobility model. In ca. 50 % of the cases the observed cumulative frequency was not significantly different from the random expectation. However, in many such cases the mean annual frequency was either very high or very low. Three ways of calculating the mobility rate are presented though only one is used: (observed cumulative frequency -lowest annual frequency) / expected cumulative frequency. Values × 100 range from 0 to 100. There were slight differences between the four plots which were interpreted in terms of differences in grazing intensity and soil depth. It is stressed that the idea of the Carousel model has never been meant to suggest that all species would show random mobility, which we now quantify, but that species differ in their mobility rate and that the mean rate is much higher than generally realized.