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901.
Theory predicts that consumers may stabilise or destabilise plant production depending on model assumptions, and tests in aquatic food webs suggest that trophic interactions are stabilising. We quantified the effects of trophic interactions on temporal variability (standard deviation) and temporal stability (mean/standard deviation) of grassland biomass production and the plant diversity–stability relationship by experimentally removing heterotrophs (large vertebrates, arthropods, foliar and soil fungi) from naturally and experimentally assembled grasslands of varying diversity. In both grassland types, trophic interactions proportionately decreased plant community biomass mean and variability over the course of 6 years, leading to no net change in temporal stability or the plant diversity–stability relationship. Heterotrophs also mediated plant coexistence; their removal reduced diversity in naturally assembled grasslands. Thus, herbivores and fungi reduce biomass production, concurrently reducing the temporal variability of energy and material fluxes. Because of this coupling, grassland stability is robust to large food web perturbations. 相似文献
902.
Eric Jacquelin Denis Brizard Raphael Dumas 《Computer methods in biomechanics and biomedical engineering》2019,22(10):925-935
The study presents a screening method used to identify the influential parameters of a lower limb model including ligaments, at low numerical cost. Concerning multibody kinematics optimisation, the ligament parameters (isometric length) were found the most influential ones in a previous study. The screening method tested if they remain influential with minimised length variations. The most important parameters for tibiofemoral kinematics were the skin markers, segment lengths and joint parameters, including two ligaments. This was confirmed by a quantitative sensitivity analysis. The screening method has the potential to be used as a stand-alone procedure for a sensitivity analysis. 相似文献
903.
Roshan Dsouza Darold R. Spillman Ronit Barkalifa Guillermo L. Monroy Eric J. Chaney Karen C. White Stephen A. Boppart 《Journal of biophotonics》2019,12(5)
The formation of biofilms in the endotracheal tubes (ETTs) of intubated patients on mechanical ventilation is associated with a greater risk of ventilator‐associated pneumonia and death. New technologies are needed to detect and monitor ETTs in vivo for the presence of these biofilms. Longitudinal OCT imaging was performed in mechanically ventilated subjects at 24‐hour intervals until extubation to detect the formation and temporal changes of in vivo ETT biofilms. OCT‐derived attenuation coefficient images were used to differentiate between mucus and biofilm. Extubated ETTs were examined with optical and electron microscopy, and all imaging results were correlated with standard‐of‐care clinical test reports. OCT and attenuation coefficient images from four subjects were positive for ETT biofilms and were negative for two subjects. The processed and stained extubated ETTs and clinical reports confirmed the presence/absence of biofilms in all subjects. Our findings confirm that OCT can detect and differentiate between biofilm‐positive and biofilm‐negative groups (P < 10?5). OCT image‐based features may serve as biomarkers for direct in vivo detection of ETT biofilms and help drive investigation of new management strategies to reduce the incidence of VAP. 相似文献
904.
905.
Lasha Gogokhia Kate Buhrke Rickesha Bell Brenden Hoffman D. Garrett Brown Christin Hanke-Gogokhia Nadim J. Ajami Matthew C. Wong Arevik Ghazaryan John F. Valentine Nathan Porter Eric Martens Ryan O’Connell Vinita Jacob Ellen Scherl Carl Crawford W. Zac Stephens Sherwood R. Casjens June L. Round 《Cell host & microbe》2019,25(2):285-299.e8
906.
Eric E. Abrahamson Elizabeth Head Ira T. Lott Benjamin L. Handen Elliott J. Mufson Bradley T. Christian William E. Klunk Milos D. Ikonomovic 《Developmental neurobiology》2019,79(7):750-766
Down syndrome (DS) results in an overproduction of amyloid‐β (Aβ) peptide associated with early onset of Alzheimer's disease (AD). DS cases have Aβ deposits detectable histologically as young as 12–30 years of age, primarily in the form of diffuse plaques, the type of early amyloid pathology also seen at pre‐clinical (i.e., pathological aging) and prodromal stages of sporadic late onset AD. In DS subjects aged >40 years, levels of cortical Aβ deposition are similar to those observed in late onset AD and in addition to diffuse plaques involve cored plaques associated with dystrophic neurites (neuritic plaques), which are of neuropathological diagnostic significance in AD. The purpose of this review is to summarize and discuss findings from amyloid PET imaging studies of DS in reference to postmortem amyloid‐based neuropathology. PET neuroimaging applied to subjects with DS has the potential to (a) track the natural progression of brain pathology, including the earliest stages of amyloid accumulation, and (b) determine whether amyloid PET biomarkers predict the onset of dementia. In addition, the question that is still incompletely understood and relevant to both applications is the ability of amyloid PET to detect Aβ deposits in their earliest form. 相似文献
907.
Ronan James O'Sullivan Tutku Aykanat Susan E. Johnston Adam Kane Russell Poole Ger Rogan Paulo A. Prodhl Craig R. Primmer Philip McGinnity Thomas Eric Reed 《Ecology and evolution》2019,9(12):7096-7111
Comparing observed versus theoretically expected evolutionary responses is important for our understanding of the evolutionary process, and for assessing how species may cope with anthropogenic change. Here, we document directional selection for larger female size in Atlantic salmon, using pedigree‐derived estimates of lifetime reproductive success as a fitness measure. We show the trait is heritable and, thus, capable of responding to selection. The Breeder's Equation, which predicts microevolution as the product of phenotypic selection and heritability, predicted evolution of larger size. This was at odds, however, with the observed lack of either phenotypic or genetic temporal trends in body size, a so‐called “paradox of stasis.” To investigate this paradox, we estimated the additive genetic covariance between trait and fitness, which provides a prediction of evolutionary change according to Robertson's secondary theorem of selection (STS) that is unbiased by missing variables. The STS prediction was consistent with the observed stasis. Decomposition of phenotypic selection gradients into genetic and environmental components revealed a potential upward bias, implying unmeasured factors that covary with trait and fitness. These results showcase the power of pedigreed, wild population studies—which have largely been limited to birds and mammals—to study evolutionary processes on contemporary timescales. 相似文献
908.
Christine B. Rohal Chad Cranney Eric L. G. Hazelton Karin M. Kettenring 《Ecology and evolution》2019,9(24):13835-13849
The outcomes of invasive plant removal efforts are influenced by management decisions, but are also contingent on the uncontrolled spatial and temporal context of management areas. Phragmites australis is an aggressive invader that is intensively managed in wetlands across North America. Treatment options have been understudied, and the ecological contingencies of management outcomes are poorly understood. We implemented a 5‐year, multi‐site experiment to evaluate six Phragmites management treatments that varied timing (summer or fall) and types of herbicide (glyphosate or imazapyr) along with mowing, plus a nonherbicide solarization treatment. We evaluated treatments for their influence on Phragmites and native plant cover and Phragmites inflorescence production. We assessed plant community trajectories and outcomes in the context of environmental factors. The summer mow, fall glyphosate spray treatment resulted in low Phragmites cover, high inflorescence reduction, and provided the best conditions for native plant recruitment. However, returning plant communities did not resemble reference sites, which were dominated by ecologically important perennial graminoids. Native plant recovery following initial Phragmites treatments was likely limited by the dense litter that resulted from mowing. After 5 years, Phragmites mortality and native plant recovery were highly variable across sites as driven by hydrology. Plots with higher soil moisture had greater reduction in Phragmites cover and more robust recruitment of natives compared with low moisture plots. This moisture effect may limit management options in semiarid regions vulnerable to water scarcity. We demonstrate the importance of replicating invasive species management experiments across sites so the contingencies of successes and failures can be better understood. 相似文献
909.