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

EXAMINING QUALITY INDICATOR RATES FOR OLDER HOME CARE CLIENTS WITH DUAL SENSORY IMPAIRMENT (DSI) AND EXPLORING THE HETEROGENEITY WITHIN DSI.

Older adults with impairments in both hearing and vision, called dual sensory impairment (DSI), are at an increased risk of negative health outcomes such as impaired communication and difficulties with mobility. It is unknown whether DSI is associated with potential quality of care issues. This study used a set of home care quality indicators (HCQIs) to examine potential quality issues in older clients (65+) with DSI. Further, it looked to explore how HCQI rates differed based on the geographic region of care and whether the client’s level of hearing and vision impairment was related to certain HCQIs. The HCQIs were generated from data collected using the Resident Assessment Instrument for Home Care and capture undesirable outcomes (e.g., falls, cognitive decline). Higher rates indicate a greater frequency of experiencing the issue. In this sample (n=352,656), the average age was 82.8 years (sd=7.9), the majority were female (63.2%), and 20.5% experienced DSI. Compared to those without DSI, clients with DSI had higher rates across 20 of the 22 HCQIs. The HCQI rates differed by geographic region, with specific regions consistently performing worse than others. Finally, the level of hearing and vision impairment was related to certain HCQIs more than others, for example hearing impairment appeared to be more related to the quality indicator measuring communication difficulty. Overall, the hope is that this information can help to identify some of the potential issues around quality and in turn, assist in continually improving the services being provided to these clients

Effect of Different Methods and Timing of Nitrogen (N) Application on Sorghum (Sorghum bicolor L) Grain Yield

Sorghum (Sorghum bicolor) is rapidly becoming a needed crop due to its drought tolerance. High production levels of this crop could assist in fulfilling the intense growing food demands. This study was conducted to determine the effect of different methods and timing of nitrogen (N) application on sorghum grain yield. Data was collected in 2018 at two locations in Oklahoma. Urea was used as the N source where three different rates (0, 30, 60 kg N ha-1) were applied either as a pre-plant application, a side-dress application, or both. Three different N application methods (broadcast, dribble surface band, and the OSU hand planter) were used in this study to see if they had an effect on grain yields. Normalized difference vegetation index (NDVI) readings were taken biweekly throughout the growing season. When no N or low rates were applied with the seed, a loss in yields were recorded. This loss could have different causes, from soil fertility issues to the abnormal amount of rainfall, or other environmental issues beyond human control. When comparing applied N with the seed to a surface pre-plant and midseason application, a distinct advantage was present for applying N in split applications. This work showed that as much as 30 kg N ha-1 can be applied in-furrow with the sorghum seed without significant yield reductions

Comparative Deregulation of Far Eastern Telecommunications Markets: Economic Incentives and International Competitive Strategies

The deregulation of telecommunications has taken a major step with the WTO agreements in February of this year. Namely, each of the major Far Eastern countries has agreed to open their market in some form of planned entry. These markets will allow for the introduction of competition of local and international services now currently restricted to the local PTT as well as allowing the entry of new services in what are generally closed markets. This paper analyzes the implications of changes in several key Far Eastern countries and discusses how this will impact the U.S. economy and the overall policy implications that this will focus on

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

Towards a Realistic Model for Cavity-Enhanced Atomic Frequency Comb Quantum Memories

Atomic frequency comb (AFC) quantum memory is a favorable protocol in long distance quantum communication. Putting the AFC inside an asymmetric optical cavity enhances the storage efficiency but makes the measurement of the comb properties challenging. We develop a theoretical model for cavity-enhanced AFC quantum memory that includes the effects of dispersion, and show a close alignment of the model with our own experimental results. Providing semi quantitative agreement for estimating the efficiency and a good description of how the efficiency changes as a function of detuning, it also captures certain qualitative features of the experimental reflectivity. For comparison, we show that a theoretical model without dispersion fails dramatically to predict the correct efficiencies. Our model is a step forward to accurately estimating the created comb properties, such as the optical depth inside the cavity, and so being able to make precise predictions of the performance of the prepared cavity-enhanced AFC quantum memory.Comment: 7 figures, 10 page

Group A Streptococcal Septic Hip Arthritis in a Child With Spastic Triplegic Cerebral Palsy

Reports of septic hip arthritis in children with cerebral palsy are exceedingly rare. This case report describes a 10-year-old boy with spastic triplegic cerebral palsy (Gross Motor Functional Classification System), who presented with fever and irritability. This case highlights the difficulties in diagnosing septic joint arthritis in patients with cerebral palsy who are nonverbal and have limited mobility. A high index of suspicion is necessary in this population when presented with fever and new limitations in mobility