Age-Related Microaggressions: Their Frequency, Emotional Impact, and Relationship to Negative Affect.

Age-related microaggressions are forms of ageist discrimination that occur in day-to-day interactions. This study aimed to validate the findings of a previous study, to identify common age-related microaggressions, and determine how affect influences emotional reactions to microaggressions. Using an online survey, participants (n = 200) were asked about their experience with age-related microaggressions, their affect, and their physical health. Participants were familiar with these microaggressions 53% of the time and had negative reactions to 43% of these microaggressions. The frequency of negative reactions to microaggressions was significantly correlated with scores of negative affect (r = .34, P < .001) and with ratings of perceived physical health (r = -.32, P = .002). The results of the study provide further insight into the topography of, and how older adults experience microaggressions. This information should be used as an educational tool to reduce the prevalence of ageism.

Digital image analysis for biothreat detection via rapid centrifugal microfluidic orthogonal flow immunocapture.

We report clear proof-of-principle for centrifugally-driven, multiplexed, paper-based orthogonal flow sandwich-style immunocapture (cOFI) and colorimetric detection of Zaire Ebola virus-like particles. Capture antibodies are immobilized onto nanoporous nitrocellulose membranes that are then laminated into polymeric microfluidic discs to yield ready-to-use analytical devices. Fluid flow is controlled solely by rotational speed, obviating the need for complex pneumatic pumping systems, and providing more precise flow control than with the capillary-driven flow used in traditional lateral flow immunoassays (LFIs). Samples containing the antigen of interest and gold nanoparticle-labeled detection antibodies are pumped centrifugally through the embedded, prefunctionalized membrane where they are subsequently captured to generate a positive, colorimetric signal. When compared to the equivalent LFI counterparts, this cOFI approach generated immunochromatographic colorimetric responses that are objectively darker (saturation), more intense (grayscale), and less variable regarding total area of the color response. We also describe an image analysis approach that enables access to rich color data and area statistics without the need for a commercial 'strip reader' or custom-written image analysis algorithms. Instead, our analytical method exploits inexpensive equipment (e.g., smart phone, flatbed scanner, etc.) and freely available software (Fiji distribution of ImageJ) to permit characterization of immunochromatographic responses that includes multiple color metrics, offering insights beyond typical grayscale analysis. The findings reported here stand as clear proof-of-principle for the feasibility of disc-based, centrifugally driven orthogonal flow through a membrane with immunocapture (cOFI) and colorimetric readout of a sandwich-type immunoassay in less than 15 minutes. Once fully developed, this cOFI platform could render a faster, more accurate diagnosis, while processing multiple samples simul-taneously.

Characterization of a Centrifugal Microfluidic Orthogonal Flow Platform.

To bring to bear the power of centrifugal microfluidics on vertical flow immunoassays, control of flow orthogonally through nanoporous membranes is essential. The on-disc approach described here leverages the rapid print-cut-laminate (PCL) disc fabrication and prototyping method to create a permanent seal between disc materials and embedded nanoporous membranes. Rotational forces drive fluid flow, replacing capillary action, and complex pneumatic pumping systems. Adjacent microfluidic features form a flow path that directs fluid orthogonally (vertically) through these embedded membranes during assay execution. This method for membrane incorporation circumvents the need for solvents (e.g., acetone) to create the membrane-disc bond and sidesteps issues related to undesirable bypass flow. In other recently published work, we described an orthogonal flow (OF) platform that exploited embedded membranes for automation of enzyme-linked immunosorbent assays (ELISAs). Here, we more fully characterize flow patterns and cellulosic membrane behavior within the centrifugal orthogonal flow (cOF) format. Specifically, high-speed videography studies demonstrate that sample volume, membrane pore size, and ionic composition of the sample matrix significantly impact membrane behavior, and consequently fluid drainage profiles, especially when cellulosic membranes are used. Finally, prototype discs are used to demonstrate proof-of-principle for sandwich-type antigen capture and immunodetection within the cOF system.

Closable Valves and Channels for Polymeric Microfluidic Devices.

This study explores three unique approaches for closing valves and channels within microfluidic systems, specifically multilayer, centrifugally driven polymeric devices. Precise control over the cessation of liquid movement is achieved through either the introduction of expanding polyurethane foam, the application of direct contact heating, or the redeposition of xerographic toner via chloroform solvation and evaporation. Each of these techniques modifies the substrate of the microdevice in a different way. All three are effective at closing a previously open fluidic pathway after a desired unit operation has taken place, i.e., sample metering, chemical reaction, or analytical measurement. Closing previously open valves and channels imparts stringent fluidic control-preventing backflow, maintaining pressurized chambers within the microdevice, and facilitating sample fractionation without cross-contamination. As such, a variety of microfluidic bioanalytical systems would benefit from the integration of these valving approaches.

Optically-controlled closable microvalves for polymeric centrifugal microfluidic devices.

Microvalving is a pivotal component in many microfluidic lab-on-a-chip platforms and micro-total analysis systems (µTAS). Effective valving is essential for the integration of multiple unit operations, such as, liquid transport, mixing, aliquoting, metering, washing, and fractionation. The ideal microfluidic system integrates numerous, sequential unit operations, provides precise spaciotemporal reagent release and flow control, and is amenable to rapid, low-cost fabrication and prototyping. Centrifugal microfluidics is an attractive approach that minimizes the need for supporting peripheral hardware. However, many of the microfluidic valving methods described in the literature suffer from operational limitations and fail when high rotational frequencies or pressure heads are required early in the analytical process. Current approaches to valve closure add unnecessary complexity to the microfluidic architecture, require the incorporation of additional materials such as wax, and entail extra fabrication steps or processes. Herein we report the characterization and optimization of a laser-actuated, closable valve method for polymeric microfluidic devices that ameliorates these shortcomings. Under typical operational conditions (rcf ≤605 ×g) a success rate >99% was observed, i.e. successful valve closures remained leak free through 605 ×g. Implementation of the laser-actuated closable valving system is demonstrated on an automated, centrifugally driven dynamic solid phase extraction (dSPE) device. Compatibility of this laser-actuated valve closure approach with commercially available polymerase chain reaction (PCR) assays is established by the generation of full 18-plex STR profiles from DNA purified via on-disc dSPE. This novel approach promises to simplify microscale valving, improve functionality by increasing the number of integrated unit operations, and allow for the automation of progressively complex biochemical assays.

High mobility explains demand sharing and enforced cooperation in egalitarian hunter-gatherers.

'Simple' hunter-gatherer populations adopt the social norm of 'demand sharing', an example of human hyper-cooperation whereby food brought into camps is claimed and divided by group members. Explaining how demand sharing evolved without punishment to free riders, who rarely hunt but receive resources from active hunters, has been a long-standing problem. Here we show through a simulation model that demand-sharing families that continuously move between camps in response to their energy income are able to survive in unpredictable environments typical of hunter-gatherers, while non-sharing families and sedentary families perish. Our model also predicts that non-producers (free riders, pre-adults and post-productive adults) can be sustained in relatively high numbers. As most of hominin pre-history evolved in hunter-gatherer settings, demand sharing may be an ancestral manifestation of hyper-cooperation and inequality aversion, allowing exploration of high-quality, hard-to-acquire resources, the evolution of fluid co-residence patterns and egalitarian resource distribution in the absence of punishment or warfare.

Transmission fidelity is the key to the build-up of cumulative culture.

Many animals have socially transmitted behavioural traditions, but human culture appears unique in that it is cumulative, i.e. human cultural traits increase in diversity and complexity over time. It is often suggested that high-fidelity cultural transmission is necessary for cumulative culture to occur through refinement, a process known as 'ratcheting', but this hypothesis has never been formally evaluated. We discuss processes of information transmission and loss of traits from a cognitive viewpoint alongside other cultural processes of novel invention (generation of entirely new traits), modification (refinement of existing traits) and combination (bringing together two established traits to generate a new trait). We develop a simple cultural transmission model that does not assume major evolutionary changes (e.g. in brain architecture) and show that small changes in the fidelity with which information is passed between individuals can lead to cumulative culture. In comparison, modification and combination have a lesser influence on, and novel invention appears unimportant to, the ratcheting process. Our findings support the idea that high-fidelity transmission is the key driver of human cumulative culture, and that progress in cumulative culture depends more on trait combination than novel invention or trait modification.

Ecological networks--beyond food webs.

1. A fundamental goal of ecological network research is to understand how the complexity observed in nature can persist and how this affects ecosystem functioning. This is essential for us to be able to predict, and eventually mitigate, the consequences of increasing environmental perturbations such as habitat loss, climate change, and invasions of exotic species. 2. Ecological networks can be subdivided into three broad types: 'traditional' food webs, mutualistic networks and host-parasitoid networks. There is a recent trend towards cross-comparisons among network types and also to take a more mechanistic, as opposed to phenomenological, perspective. For example, analysis of network configurations, such as compartments, allows us to explore the role of co-evolution in structuring mutualistic networks and host-parasitoid networks, and of body size in food webs. 3. Research into ecological networks has recently undergone a renaissance, leading to the production of a new catalogue of evermore complete, taxonomically resolved, and quantitative data. Novel topological patterns have been unearthed and it is increasingly evident that it is the distribution of interaction strengths and the configuration of complexity, rather than just its magnitude, that governs network stability and structure. 4. Another significant advance is the growing recognition of the importance of individual traits and behaviour: interactions, after all, occur between individuals. The new generation of high-quality networks is now enabling us to move away from describing networks based on species-averaged data and to start exploring patterns based on individuals. Such refinements will enable us to address more general ecological questions relating to foraging theory and the recent metabolic theory of ecology. 5. We conclude by suggesting a number of 'dead ends' and 'fruitful avenues' for future research into ecological networks.

Abundance-body size relationships: the roles of metabolism and population dynamics.

1. Species' abundance scales approximately as an inverse power of body mass. This property has been explained on the basis of metabolic rates of organisms of different sizes. 2. This paper considers the additional effect of population dynamics on the abundance-body size relationship, on the grounds that mass flow through food webs also depends on interactions between predators and their prey. To do this, an analysis of simple dynamical food-chain models was carried out, using rate parameters which scaled with body mass according to empirically based rules. 3. The analysis shows that a function for the abundance-body size relationship derived from metabolic theory is a good first approximation to a function derived for food chains at dynamic equilibrium, although the mechanistic interpretation of terms in the functions is not the same. 4. The results are sensitive to assumptions about the scaling of the self-limitation of basal species with respect to body size. Depending on the assumption made, the abundance-body size relationship may have a power parameter -1 at all trophic levels, or be described by different functions at different trophic levels.

Effects of dynamics on ecological networks.

Ecological food webs define the feeding patterns of interacting species. The architecture of such networks may be affected by dynamical processes operating within them, ultimately influencing the capacity of the networks to persist. As yet relatively little is known about these effects. We compared the architecture of ecological networks with a fixed number of species, constructed in four contrasting ways: (I) topological networks, which required only that species had prey to eat; (II) persistent networks, in which species had also to persist under a simple model of population dynamics; (III) assembled networks, built up by sequential addition of species with dynamical persistence at each step in the sequence; (IV) evolved networks where, in addition to dynamical persistence, body size of species was determined by a simple mutation-selection process. Dynamics had fundamental effects on architecture, the networks of classes II, III and IV being restricted to a small number of trophic levels, in contrast to the non-dynamic, topological class I networks. Class III assembled networks tended to have fewer trophic levels and a more pyramidal biomass distribution than networks of classes II and IV. In evolved class IV networks, the smallest consumers converged to similar body sizes, whereas larger consumers evolved more slowly and did not show such convergence. The results indicate that dynamics affect the architecture of food webs, and that assumptions about simultaneous arrival, sequential arrival and evolution lead to different outcomes. Sequential assembly was shown to have a special property of finding rare sets of persistent species in a small number of steps, suggesting that the rarity of stable communities is not a serious problem in the development of complex communities.