Foraging as an evidence accumulation process

A canonical foraging task is the patch-leaving problem, in which a forager must decide to leave a current resource in search for another. Theoretical work has derived optimal strategies for when to leave a patch, and experiments have tested for conditions where animals do or do not follow an optimal strategy. Nevertheless, models of patch-leaving decisions do not consider the imperfect and noisy sampling process through which an animal gathers information, and how this process is constrained by neurobiological mechanisms. In this theoretical study, we formulate an evidence accumulation model of patch-leaving decisions where the animal averages over noisy measurements to estimate the state of the current patch and the overall environment. Evidence accumulation models belong to the class of drift diffusion processes and have been used to model decision making in different contexts. We solve the model for conditions where foraging decisions are optimal and equivalent to the marginal value theorem, and perform simulations to analyze deviations from optimal when these conditions are not met. By adjusting the drift rate and decision threshold, the model can represent different strategies, for example an increment-decrement or counting strategy. These strategies yield identical decisions in the limiting case but differ in how patch residence times adapt when the foraging environment is uncertain. To account for sub-optimal decisions, we introduce an energy-dependent utility function that predicts longer than optimal patch residence times when food is plentiful. Our model provides a quantitative connection between ecological models of foraging behavior and evidence accumulation models of decision making. Moreover, it provides a theoretical framework for potential experiments which seek to identify neural circuits underlying patch leaving decisions

Boundary layer charge dynamics in ionic liquid-ionic polymer transducers

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98705/1/JApplPhys_109_014909.pd

Nonlinear capacitance and electrochemical response of ionic liquid-ionic polymers

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98712/1/JApplPhys_109_084901.pd

Multiscale modeling and simulation of crosslinked polymers

The combination of physics-based modeling and coarse-grained molecular dynamics simulations is a powerful tool to understand how molecular properties and processes affect the mechanical properties of crosslinked polymers. In this dissertation polymer network structure and chain behavior are analyzed in order to connect these microscopic characteristics and deformation mechanisms to the macroscopic material properties of nonlinear elasticity and the shape memory effect. A new physics-based model of rubber elasticity is constructed which can capture the strain softening, strain hardening, and deformation-state dependent response of rubber materials undergoing finite deformations. This model is unique in its ability to capture large-stretch mechanical behavior with only three parameters that are each connected to the polymer chemistry and the important characteristics of the macroscopic stress-stretch response. Coarse-grained molecular dynamics simulations are used to analyze chain behavior during deformation. This work is the first to track primitive path length changes in a deformed polymer network. The primitive path of a polymer chain is defined as the shortest path from one end of the chain to the other which preserves the topological state of the network (i.e. retaining all inter-chain entanglements). Through a comparison of simulated networks with different structures, it is demonstrated that changes in average primitive path length are always nonaffine, even for long, entangled chain networks. A visualization of time-dependent chain conformations and the restraining “tube” in deformed networks demonstrates the viability of using primitive path analysis to quantify micro-macro deformation in crosslinked polymers. The shape memory effect in crosslinked polymers is the ability of a material to hold a deformed shape, then subsequently recover the initial shape when heated above the glass transition temperature. This work is the first to construct a suitable coarse-grained model for examining shape memory polymer behavior via molecular dynamics simulation. It is found that simply including monomer-monomer attraction in the simulation model is sufficient to reproduce the nonlinear thermomechanical trends seen experimentally. Because of the simplicity of the simulation model, these results give important information as to how to model and understand these systems.PhDAerospace EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/107284/1/jddavid_1.pd

Behavioral variation across the days and lives of honey bees

In honey bee colonies, workers generally change tasks with age (from brood care, to nest work, to foraging). While these trends are well established, our understanding of how individuals distribute tasks during a day, and how individuals differ in their lifetime behavioral trajectories, is limited. Here, we use automated tracking to obtain long-term data on 4,100+ bees tracked continuously at 3 Hz, across an entire summer, and use behavioral metrics to compare behavior at different timescales. Considering single days, we describe how bees differ in space use, detection, and movement. Analyzing the behavior exhibited across their entire lives, we find consistent inter-individual differences in the movement characteristics of individuals. Bees also differ in how quickly they transition through behavioral space to ultimately become foragers, with fast-transitioning bees living the shortest lives. Our analysis framework provides a quantitative approach to describe individual behavioral variation within a colony from single days to entire lifetimes

How honeybees respond to heat stress from the individual to colony level

A honey bee colony functions as an integrated collective, with individuals coordinating their behaviour to adapt and respond to unexpected disturbances. Nest homeostasis is critical for colony function; when ambient temperatures increase, individuals switch to thermoregulatory roles to cool the nest, such as fanning and water collection. While prior work has focused on bees engaged in specific behaviours, less is known about how responses are coordinated at the colony level, and how previous tasks predict behavioural changes during a heat stress. Using BeesBook automated tracking, we follow thousands of individuals during an experimentally induced heat stress, and analyse their behavioural changes from the individual to colony level. We show that heat stress causes an overall increase in activity levels and a spatial reorganization of bees away from the brood area. Using a generalized framework to analyse individual behaviour, we find that individuals differ in their response to heat stress, which depends on their prior behaviour and correlates with age. Examining the correlation of behavioural metrics over time suggests that heat stress perturbation does not have a long-lasting effect on an individual’s future behaviour. These results demonstrate how thousands of individuals within a colony change their behaviour to achieve a coordinated response to an environmental disturbance

Sheep Updates 2005 - Part 3

This session covers seven papers from different authors: CUSTOMER 1. Benefits VIAscanR to producers and WAMMCO, Rob Davidson, Supply Development Manager, David Pethick, School of Veterinary and Biomedical Studies, Murdock University. 2. Healthy fats in lamb: how WA lambs compare with others, C. F. Engelke Animal Biology, University of Western Australia, bCSIRO Livestock Industries, Western Australia B.D. Siebert, Department of Animal Science, University of Adelaide, South Australia, K. Gregg, Centre for High-Throughput Agricultural Genetic Analysis, Murdoch University, Western Australia. A-D.G. Wright CSIRO Livestock Industries, Western Australia, P.E Vercoe Animal Biology, University of Western Australia 3. Shelf life of fresh lamb meat: lamb age & electrical stimulation, Dr Robin Jacob, Department of Agriculture, Western Australia 4. Pastures from space - An evaluation of adoption of by Australian woolgrowers, Russell Barnett, Australian Venture Consultants, Joanne Sneddon, University of Western Australia 5. Your clients can learn from ASHEEP\u27s example, Sandra Brown Department of Agriculture Western Australia 6. Lifetime Wool - Farmers attitudes affect their adoption of recommended ewe management, G. Rose Department of Agriculture Western Australia, C. Kabore, Kazresearch, Lower Templestowe Vic, J. Dart, Clear Horizons, Hastings Vic 7. Sustainable certification of Australian Merino, what will customers be looking for? Stuart Adams, i-merino / iZWool International Pty Lt

Enhancing the genome editing toolbox: genome wide CRISPR arrayed libraries.

CRISPR-Cas9 technology has accelerated biological research becoming routine for many laboratories. It is rapidly replacing conventional gene editing techniques and has high utility for both genome-wide and gene-focussed applications. Here we present the first individually cloned CRISPR-Cas9 genome wide arrayed sgRNA libraries covering 17,166 human and 20,430 mouse genes at a complexity of 34,332 sgRNAs for human and 40,860 sgRNAs for the mouse genome. For flexibility in generating stable cell lines the sgRNAs have been cloned in a lentivirus backbone containing PiggyBac transposase recognition elements together with fluorescent and drug selection markers. Over 95% of tested sgRNA induced specific DNA cleavage as measured by CEL-1 assays. Furthermore, sgRNA targeting GPI anchor protein pathway genes induced loss of function mutations in human and mouse cell lines measured by FLAER labelling. These arrayed libraries offer the prospect for performing screens on individual genes, combinations as well as larger gene sets. They also facilitate rapid deconvolution of signals from genome-wide screens. This set of vectors provide an organized comprehensive gene editing toolbox of considerable scientific value

Postdoctoral researchers' perspectives on working conditions and equal opportunities in German academia

Postdoctoral researchers (postdocs) are an essential component of the scientific workforce in German universities and research institutions and play a vital role in advancing knowledge and innovation. However, the experiences of postdocs and other early career researchers (ECRs) indicate that working conditions pose a significant challenge to the pursuit of a long-term research career in Germany—particularly for international scientists and those from marginalized groups. We examine how unstable working conditions as well as insufficient structural support for equal opportunities and diversity are significant obstacles for the career development of ECRs in German academia. We discuss these issues with the aid of an extensive survey recently conducted and published by PostdocNet, a target-group network representing the interests of postdocs across Germany's Max Planck Society. The survey drew responses from 659 postdoctoral researchers working at the Max Planck Society and represents one of the few datasets of postdoctoral researchers' perspectives in Germany. Building on these findings, we suggest actions at governmental, institutional, and individual levels to improve the working conditions of postdoctoral researchers in Germany

The Impact of a SIG on Assessment Literacy

A major aim of professional associations is to provide opportunities for professionals to interact with others, share ideas and develop in their chosen profession. Professional associations exist to provide specialized networking and development opportunities to a specific profession, group of individuals or field of study. To promote and support specialized research and communication, smaller subgroups within an association are often chartered or developed. These subgroups are typically known as Special Interest Groups. According to Jacob et al. (2013), association members join SIGs because they want to go deeper into a specialized content area and they enjoy networking with others who ‘speak the same language.’ The TESOL Arabia Testing, Assessment and Evaluation SIG (TAE SIG) has focused their professional development activities on an important trend in the field, that of language assessment literacy (LAL). Language assessment literacy has been a critical topic in English language teaching since the late 1990s. Unfortunately, this is mainly due to the fact that so many English language teachers are not assessment literate. In other words, many English language teachers lack the knowledge and skills to write effective language tests, evaluate the effectiveness of their tests, and use their test results in meaningful ways. The purpose of this chapter is to critically examine the status of LAL in the Middle East and North Africa (MENA) region and report on activities that the TAE SIG has implemented to increase LAL