Patterns in the spatial distribution of organisms provide important information about mechanisms that regulate the diversity of life and the complexity of ecosystems. Although microorganisms may ...comprise much of the Earth's biodiversity and have critical roles in biogeochemistry and ecosystem functioning, little is known about their spatial diversification. Here we present quantitative estimates of microbial community turnover at local and regional scales using the largest spatially explicit microbial diversity data set available (> 106 sample pairs). Turnover rates were small across large geographical distances, of similar magnitude when measured within distinct habitats, and did not increase going from one vegetation type to another. The taxa-area relationship of these terrestrial microbial eukaryotes was relatively flat (slope z = 0.074) and consistent with those reported in aquatic habitats. This suggests that despite high local diversity, microorganisms may have only moderate regional diversity. We show how turnover patterns can be used to project taxa-area relationships up to whole continents. Taxa dissimilarities across continents and between them would strengthen these projections. Such data do not yet exist, but would be feasible to collect.
Background
Searching the World Wide Web using search engines and websites can be conducted to identify studies for systematic reviews. When searching to support systematic reviews, the searcher faces ...challenges in using the basic search interfaces of most search engines and websites.
Objectives
To describe and evaluate current practice of web searching in a cross‐sectional sample of Cochrane Reviews. The study also describes the stated aims of web searching, i.e. the identification of published or unpublished studies or both.
Methods
A six‐month cross‐sectional sample of Cochrane Reviews was identified via the Cochrane Library. Reviews were inspected for detail about web searching. Findings were described and evaluated using a framework of key principles for web searching.
Results
423 Cochrane Reviews published August 2016–January 2017 were identified of which 61 (14%) reported web searching. Web searches were typically simplified versions of the bibliographic database search. Advanced and iterative approaches were not widely used. Google Search and Google Scholar were the most popular search engines. Most reports stated identification of grey literature as their aim.
Conclusion
Basic web search interfaces necessitate simple searches. However, there is scope to use more diverse search features and techniques and a greater variety of search engines.
Netrin-1 is a neuronal guidance cue that regulates cellular activation, migration, and cytoskeleton rearrangement in multiple cell types. It is a chemotropic protein that is expressed within tissues ...and elicits both attractive and repulsive migratory responses. Netrin-1 has recently been found to modulate the immune response via the inhibition of neutrophil and macrophage migration. However, the ability of Netrin-1 to interact with lymphocytes and its in-depth effects on leukocyte migration are poorly understood. In this study, we profiled the mRNA and protein expression of known Netrin-1 receptors on human CD4(+) T cells. Neogenin, uncoordinated-5 (UNC5)A, and UNC5B were expressed at low levels in unstimulated cells, but they increased following mitogen-dependent activation. By immunofluorescence, we observed a cytoplasmic staining pattern of neogenin and UNC5A/B that also increased following activation. Using a novel microfluidic assay, we found that Netrin-1 stimulated bidirectional migration and enhanced the size of migratory subpopulations of mitogen-activated CD4(+) T cells, but it had no demonstrable effects on the migration of purified CD4(+)CD25(+)CD127(dim) T regulatory cells. Furthermore, using a short hairpin RNA knockdown approach, we observed that the promigratory effects of Netrin-1 on T effectors is dependent on its interactions with neogenin. In the humanized SCID mouse, local injection of Netrin-1 into skin enhanced inflammation and the number of neogenin-expressing CD3(+) T cell infiltrates. Neogenin was also observed on CD3(+) T cell infiltrates within human cardiac allograft biopsies with evidence of rejection. Collectively, our findings demonstrate that Netrin-1/neogenin interactions augment CD4(+) T cell chemokinesis and promote cellular infiltration in association with acute inflammation in vivo.
The ocean is a dynamic environment inhabited by a diverse array of highly migratory species, many of which are under direct exploitation in targeted fisheries. The time-scales of variability in the ...marine realm coupled with the extreme mobility of ocean-wandering species such as tuna and billfish complicates fisheries management. Developing eco-informatics solutions that allow for near real-time prediction of the distributions of highly mobile marine species is an important step towards the maturation of dynamic ocean management and eco-logical forecasting. Using 25 yr (1990–2014) of NOAA fisheries' observer data from the California drift gillnet fishery, we model relative probability of occurrence (presence–absence) and catchability (total catch per gillnet set) of broadbill swordfish Xiphias gladius in the California Current System. Using freely available environmental data sets and open source software, we explore the physical drivers of regional swordfish distribution. Comparing models built upon remotely sensed data sets with those built upon a data-assimilative configuration of the Regional Ocean Modelling System (ROMS), we explore trade-offs in model construction, and address how physical data can affect predictive performance and operational capacity. Swordfish catchability was found to be highest in deeper waters (>1,500 m) with surface temperatures in the 14–20°C range, isothermal layer depth (ILD) of 20–40 m, positive sea surface height (SSH) anomalies, and during the new moon (<20% lunar illumination). We observed a greater influence of mesoscale variability (SSH, wind speed, isothermal layer depth, eddy kinetic energy) in driving swordfish catchability (total catch) than was evident in predicting the relative probability of presence (presence–absence), confirming the utility of generating spatiotemporally dynamic predictions. Data-assimilative ROMS circumvent the limitations of satellite remote sensing in providing physical data fields for species distribution models (e.g., cloud cover, variable resolution, subsurface data), and facilitate broad-scale prediction of dynamic species distributions in near real time.
Species distribution models (SDMs) have become key tools for describing and predicting species habitats. In the marine domain, environmental data used in modelling species distributions are often ...remotely sensed, and as such have limited capacity for interpreting the vertical structure of the water column, or are sampled in situ, offering minimal spatial and temporal coverage. Advances in ocean models have improved our capacity to explore subsurface ocean features, yet there has been limited integration of such features in SDMs. Using output from a data-assimilative configuration of the Regional Ocean Modeling System, we examine the effect of including dynamic subsurface variables in SDMs to describe the habitats of four pelagic predators in the California Current System (swordfish Xiphias gladius, blue sharks Prionace glauca, common thresher sharks Alopias vulpinus, and shortfin mako sharks Isurus oxyrinchus). Species data were obtained from the California Drift Gillnet observer program (1997-2017). We used boosted regression trees to explore the incremental improvement enabled by dynamic subsurface variables that quantify the structure and stability of the water column: isothermal layer depth and bulk buoyancy frequency. The inclusion of these dynamic subsurface variables significantly improved model explanatory power for most species. Model predictive performance also significantly improved, but only for species that had strong affiliations with dynamic variables (swordfish and shortfin mako sharks) rather than static variables (blue sharks and common thresher sharks). Geospatial predictions for all species showed the integration of isothermal layer depth and bulk buoyancy frequency contributed value at the mesoscale level (<100 km) and varied spatially throughout the study domain. These results highlight the utility of including dynamic subsurface variables in SDM development and support the continuing ecological use of biophysical output from ocean circulation models.
How morphogen gradients govern the pattern of gene expression in developing tissues is not well understood. Here, we describe a statistical thermodynamic model of gene regulation that combines the ...activity of a morphogen with the transcriptional network it controls. Using Sonic hedgehog (Shh) patterning of the ventral neural tube as an example, we show that the framework can be used together with the principled parameter selection technique of approximate Bayesian computation to obtain a dynamical model that accurately predicts tissue patterning. The analysis indicates that, for each target gene regulated by Gli, which is the transcriptional effector of Shh signalling, there is a neutral point in the gradient, either side of which altering the Gli binding affinity has opposite effects on gene expression. This explains recent counterintuitive experimental observations. The approach is broadly applicable and provides a unifying framework to explain the temporospatial pattern of morphogen-regulated gene expression.
Display omitted
Whilst bottlebrush polymers have been studied in aqueous media for their conjectured role in biolubrication, surface forces and friction mediated by bottlebrush polymers in non-polar ...media have not been previously reported. Here, small-angle neutron scattering (SANS) showed that a diblock bottlebrush copolymer (oligoethyleneglycol acrylate/ethylhexyl acrylate; OEGA/EHA) formed spherical core–shell aggregates in n-dodecane (a model oil) in the polymer concentration range 0.1–2.0 wt%, with a radius of gyration Rg ∼ 7 nm, comprising 40–65 polymer molecules per aggregate. The surface force apparatus (SFA) measurements revealed purely repulsive forces between surfaces bearing inhomogeneous polymer layers of thickness L ∼ 13–23 nm, attributed to adsorption of a mixture of polymer chains and surface-deformed micelles. Despite the surface inhomogeneity, the polymer layers could mediate effective lubrication, demonstrating superlubricity with the friction coefficient as low as µ ∼ 0.003. The analysis of velocity-dependence of friction using the Eyring model shed light on the mechanism of the frictional process. That is, the friction mediation was consistent with the presence of nanoscopic surface aggregates, with possible contributions from a gel-like network formed by the polymer chains on the surface. These unprecedented results, correlating self-assembled polymer micelle structure with the surface forces and friction the polymer layers mediate, highlight the potential of polymers with the diblock bottlebrush architecture widespread in biological living systems, in tailoring desired surface interactions in non-polar media.
As an editorial to the special issue “new avenues in international careers research” this article discusses the roots of the international careers research stream, which sits at the intersection ...between career studies, HRM and international management. In order to support future studies in this emerging area of enquiry, we attempt to lay down the foundations of a research agenda based around what we see as the three core areas of interest: contextualised careers research, comparative careers research and careers research in internationally operating organisations. After providing some suggestions for the kinds of theoretical and methodological tools that will be required to build on these foundations, we introduce the five empirical papers that comprise this special issue.
PDF
