Factors determining plant–neighbour interactions on different spatial scales in young species-rich grassland communities

In naturally colonised species-rich grassland communities, we examined the properties of a plant’s aboveground neighbourhood that affect its performance (aboveground biomass). To this end a range of neighbourhood parameters were measured: number, biomass and species richness of the neighbours, number and biomass of the conspecific neighbours, and light availability at the base of the target plant. We also determined at which neighbourhood size the strongest target plant–neighbour interactions occurred, and whether conspecific neighbours affected competitively stronger or weaker target species differently. Target plant performance varied with target identity, and was significantly affected by light availability and the number of neighbouring plants (neighbourhood density). Depending on the target species, there was also an effect of total neighbour biomass on plant performance. The target plants were most strongly affected by their neighbours within a 3-cm distance, which could account for 78% of the variance in target biomass. Number or biomass of the conspecific neighbours did not contribute to the explanation of target performance in any of the target species. Whereas in an 8-cm neighbourhood the amount of light penetration was the strongest predictor of target performance, the number of neighbours was more important in a 3-cm neighbourhood. These experimental results might be useful to extend existing neighbourhood competition models for one or two species to multi-species competition models.     

中性大气稳定度条件下林冠湍流特征模拟

基于欧拉二阶闭合模型,利用2003年长白山阔叶红松林微气象资料,计算并分析了长白山阔叶红松林林冠内/上的湍流特征.结果表明:模拟得到的平均风速廓线与实测值吻合;雷诺应力在林内衰减较大,而近地面处几乎没有动量传输贡献;湍流强度、速度方差和速度偏度在林冠与大气交界面处达到最大,同时剪切也达到最强;速度偏度越大,则湍流间歇性越强,并且向下的湍涡越难穿透林冠内部;林内深处的大部分湍流能量不是由局地产生,而来自于林上.     

Agitation induced cell injury in microcarrier cultures. Protective effect of viscosity is agitation intensity dependent: Experiments and modeling

The effect of medium viscosity on the specific death rate of bovine embryonic kidney (BEK) cells cultured in spinner flask microcarrier cultures has been examined for various impeller speeds. Two types of media were used, a serum-containing growth medium and a serum-free maintenance medium. The latter does not support cell growth. We found that increasing medium viscosity suppresses cell death rates in both growth and maintenance medium cultures in an agitation-intensity-dependent fashion; the beneficial effect of medium viscosity in reducing the specific death rate is amplified as the agitation rate is increased. Furthermore, increasing medium viscosity has no effect on the specific death rate of the cells when the agitation rate is below a critical level. A model based on the turbulent energy content of eddies in the dissipation spectrum of turbulence of length scales on the order of magnitude of the microcarrier diameter and lower has been developed to account for cell death due to both bead-to-bead and bead-to-eddy interactions. The model constitutes a significant departure from previous efforts first because both types of interactions are accounted for simultaneously and second because the properties of a spectrum of eddies instead of the Kolmogorov-scale eddy size alone are used in the model. The model explains the functional dependence of the specific death rates on the medium viscosity at varying agitation intensities.     

A Desktop Apparatus for Studying Interactions Between Microorganisms and Small-Scale Fluid Motion

Low levels of kinetic energy dissipation were successfully generated in a reactor using two submersible speakers. A software programme controlled the amplitude and frequency of the signal fed to each speaker and achieved good repeatability of flow conditions. The flow reactor had a near isotropic flow regime with a low mean flow, values were calculated from particle image velocimetry measurements. The flow characteristics compared well with grid turbulence reactors, though as no moving parts are present in this reactor design the strain rates were lower compared to oscillating grid set-ups. The low range of Reynolds numbers based on Taylor microscales (Re_λ~0.5–5.9) covered both turbulent and non-turbulent flow regimes. The small-scale fluid motion produced over the entire volume of this reactor makes it suitable for experiments examining the physiological responses of fluid motion on microorganisms.     

脑出血患者急性期窦性心率震荡结果分析

目的:观察首次脑出血(intracerebral hemorrhage,ICH)患者急性期窦性心率震荡(heart rate turbulence,HRT)的变化特点.方法:从44例脑出血患者选择20例符合HRT分析条件的患者为脑出血组,选择无心脑器质性疾病且符合HRT分析条件的20例患者作为对照组.所有患者发病5天内行24小时动态心电图监测,计算并分析HRT指标震荡初始(turbulence onset,TO)、震荡斜率(turbulence slope,TS),同时收集患者临床资料.结果:与对照组TO、TS比较,脑出血组TO值升高有统计学意义(P＜0.05),TS值降低无显著性意义(P＞0.05).不同部位脑出血患者TO及TS差异无统计学意义(渐进显著性＞0.01).结论:脑出血组患者急性期的HRT减弱,自主神经功能受到损害,推测脑出血患者急性期心脏意外发生可能性大.左右半球、蛛网膜下腔出血时自主神经损害程度是否存在差异仍待探讨.     

Evidence from hunter-gatherer and subsistence agricultural populations for the universality of contagion sensitivity

The phenomenon of magical contagion – the unobserved passage of properties between entities that come into physical contact – was described by anthropologists over a century ago, yet questions remain about its origin, function, and universality. Contagion sensitivity, along with the emotion of disgust, has been proposed to be part of a biologically-evolved system designed to reduce exposure to pathogens by increasing the avoidance of “contaminated” objects. Yet this phenomenon has not been studied using systematic psychological comparison outside of industrialized populations. Here we document contagion sensitivity in two culturally, geographically, and economically distinct populations with little exposure to Western biomedicine and formal education: the Hadza hunter-gatherers of Tanzania and Tannese subsistence-agriculturalists of Vanuatu. In both populations, a majority of individuals rejected familiar and palatable foods when contaminating items touched the food but were subsequently removed. The Tannese children in our study showed a similar response, consistent with previous research with Western children. Our data support the proposal that contagion sensitivity is universal in human populations.     

Comparative behaviour of two species of Lepadogaster (Pisces: Gobiesocidae) living at different depths

The two clingfish species studied occupied similar habitats but occurred at different depths. When compared with the subtidal species Lepadogaster candollei , the intertidal species Lepadogaster l. purpurea was less active, spent more time in shelters, visited fewer shelters, showed more site fidelity, and spent less time swimming. Feeding, swimming, and agonistic behaviours were performed mainly in close contact with the substrate in this species. It is hypothesized that these contrasts in behaviour may have evolved under different levels of turbulence.     

Integrating small-scale landscape elements into land use/cover: The impact on landscape metrics’ values

Over the last 30 years the use and misuse of landscape metrics has been widely studied. However, there has been less attention on incorporating small-scale landscape elements into landscape analysis. Data type used in the analysis can be either vector or raster, while the raster format is more widely used. However, using large-scale topographical vector databases has several advantages – they cover whole countries with very detailed and accurate topographical data. Despite the high level of detail, their amount in Mb is small, which allows simultaneously to analyse large areas. The peculiarity of vector data is that small-scale landscape elements are mapped as point elements or lines. For calculating landscape metrics, the integration of these features and LULC (land use/cover) polygons is needed. In the current study we investigated how integration of point and linear elements into polygon layers affects the values of landscape metrics. Adding line buffers influenced metrics’ values more than adding point elements. The ensemble of point and linear objects is similar to linear objects. Our study revealed that integrating small-scale landscape elements into land use/cover layers by using buffers gives more realistic values if the buffer size is in compliance with the size of the phenomena in the real world and suitable landscape metrics are chosen. However, the metrics that responded to adding small-scale landscape elements in correspondence with their real world impact on landscape metric values might not always be the best ecological indicators in terms of small-scale landscape elements. Another issue is that values of landscape metrics depend directly on the number of classes determined in the data specification, and on the data model. If the number of mappable point and linear objects changes, or the data model of the linear objects changes, the values of landscape metrics differ.     

Determination of the γ-secretase inhibitor MK-0752 in human plasma by online extraction and electrospray tandem mass spectrometry (HTLC–ESI-MS/MS)

A sensitive and rapid HTLC–ESI-MS/MS method with an advanced online sample preparation was developed for determination of the γ-secretase inhibitor MK-0752 in human plasma using an internal standard. Plasma samples (100 μL) were diluted and injected directly onto an online extraction column (Cohesive Cyclone MAX 0.5 mm × 50 mm, >30 μm), the sample matrix was washed out with an aqueous solution, and retained analytes were eluted out and transferred directly to the analytical column (Phenomenex Gemini 3μ C18 110A, 50 mm × 2.0 mm at 50 °C) for separation using a gradient mobile phase. The eluted analytes were then detected on an API-3000 LC–MS/MS System with ESI and a negative multiple reaction monitoring mode. The monitored ion transitions were m/z 441 → 175 for MK-0752 and 496 → 175 for the internal standard. Online extraction recoveries were 81%. The method was validated and was linear in the range of 0.05–50 μg/mL. Within-day and between-day precisions were < 8.6%, and accuracies were 0.7 and 7.1%. This method was applied to the measurement of plasma MK-0752 levels in a Phase I study of pediatric patients with recurrent or refractory brain tumors.     

Velocity gradients and turbulence around macrophyte stands in streams

1. Submerged macrophytes strongly modify water flow in small lowland streams. The present study investigated turbulence and vertical velocity gradients using small hot-wire anemometers in the vicinity and within the canopies of four macrophyte species with the objective of evaluating: (a) how plant canopies influence velocity gradients and shear force on the surfaces of the plants and the stream bed; and (b) how the presence and morphology of plants influence the intensity of turbulence. 2. Water velocity was often relatively constant with water depth both outside and inside the plant canopies, but the velocity declined steeply immediately above the unvegetated stream bed. Steep vertical velocity profiles were also observed in the transition to the surface of the macrophyte canopy of three of the plant species forming a dense shielding structure of high biomass. Less steep vertical profiles were observed at the open canopy surface of the fourth plant species, growing from a basal meristem and having the biomass more homogeneously distributed with depth. The complex distribution of hydraulic roughness between the stream bed, the banks and the plants resulted in velocity profiles which often fitted better to a linear than to a logarithmic function of distance above the sediment and canopy surfaces. 3. Turbulence increased in proportion to the mean flow velocity, but the slope of the relationships differed in a predictable manner among positions outside and inside the canopies of the different species, suggesting that their morphology and movements influenced the intensity of turbulence. Turbulence was maintained in the attenuated flow inside the plant canopies, despite estimates of low Reynolds numbers, demonstrating that reliable evaluation of flow patterns requires direct measurements. The mean velocity inside plant canopies mostly exceeded 2 cm s^??1 and turbulence intensity remained above 0.2 cm s^??1, which should be sufficient to prevent carbon limitation of photosynthesis in CO₂-rich streams, while plant growth may benefit from the reduced physical disturbance and the retention of nutrient-rich sediment particles. 4. Flow patterns were highly reproducible within canopies of the individual species despite differences in stand size and location among streams. We propose that individual plant stands are suitable functional units for analysing the influence of submerged macrophytes on flow patterns, retention of particles and biological communities in lowland streams.