The organization of soil disposal by ants

Colonies of Pheidole ambigua ants excavate soil and drop it outside the nest entrance. The deposition of thousands of loads leads to the formation of regular ring-shaped piles. How is this pattern generated? This study investigated soil pile formation on level and sloping surfaces, both empirically and using an agent-based model. We found that ants drop soil preferentially in the direction in which the slope is least steeply uphill from the nest entrance, both when adding to an existing pile and when starting a new pile. Ants respond to cues from local slope to choose downhill directions. Ants walking on a slope increase the frequency and magnitude of changes in direction, and more of these changes of direction take them downhill than uphill. Also, ants carrying soil on a slope wait longer before dropping their soil compared to ants on a level plane. These mechanisms combine to focus soil dropping in the downhill direction, without the necessity of a direct relationship between slope and probability of dropping soil. These empirically determined rules were used to simulate soil disposal. The slight preference for turning downhill measured empirically was shown in the model to be sufficient to generate biologically realistic patterns of soil dumping when combined with memory of the direction of previous trips. From simple rules governing individual behaviour an overall pattern emerges, which is appropriate to the environment and allows a rapid response to changes

Introducing spatial information into predictive NF-kappa B modelling - an agent-based approach

Nature is governed by local interactions among lower-level sub-units, whether at the cell, organ, organism, or colony level. Adaptive system behaviour emerges via these interactions, which integrate the activity of the sub-units. To understand the system level it is necessary to understand the underlying local interactions. Successful models of local interactions at different levels of biological organisation, including epithelial tissue and ant colonies, have demonstrated the benefits of such 'agent-based' modelling [1-4]. Here we present an agent-based approach to modelling a crucial biological system the intracellular NF-kappa B signalling pathway. The pathway is vital to immune response regulation, and is fundamental to basic survival in a range of species [5-7]. Alterations in pathway regulation underlie a variety of diseases, including atherosclerosis and arthritis. Our modelling of individual molecules, receptors and genes provides a more comprehensive outline of regulatory network mechanisms than previously possible with equation-based approaches [8]. The method also permits consideration of structural parameters in pathway regulation; here we predict that inhibition of NF-kappa B is directly affected by actin filaments of the cytoskeleton sequestering excess inhibitors, therefore regulating steady-state and feedback behaviour

Examining the Effects of a High School Healthcare Summer Immersion Program

The purpose of the current study was to assess the effectiveness of the DREAMWork (Diversity Recruitment and Education to Advance Minorities in the nursing Workforce) summer high school program within the context of the substantial current and anticipated nursing shortage in the United States (Buerhaus, 2002). Previous research has shown that creating positive perceptions of nursing through programs like DREAMWork can lead to an increase in student desire to pursue a career in nursing (Cohen, Palumbo, Rambur, & Mongeon, 2004; Tomey, Schwier, Marticke, & May, 1996). More specifically, this study was interested in significant student changes (desire to pursue a career in nursing, knowledge of nursing, etc.) as a result of program participation and stakeholder perceptions of the program including student impact. A mixed method, within subjects design was used to collect multiple quantitative and qualitative measures from program participants as well as the major stakeholders of the DREAMWork summer high school program. Descriptive analyses and paired samples t tests were used to assess the data. Results indicate that students experienced significant improvements in knowledge of academic content related to nursing and realistic perceptions of nursing as a career. Overall perceptions of the program by all stakeholder groups were overwhelmingly positive; students enjoyed learning new things and participating in new experiences; other stakeholders highly rated the importance of the DREAMWork program goals and the impact of the program on the student participants. Implications of the findings will be discussed along with potential reasons for results that were not significant. Potential changes for future DREAMWork summer program cohorts will also be explored. For future study, a longitudinal design is recommended as well as the incorporation of more consistent measures across all stakeholder groups

Checking experiments for stream X-machines

This article is a post-print version of the published article which may be accessed at the link below. Copyright © 2010 Elsevier B.V. All rights reserved.Stream X-machines are a state based formalism that has associated with it a particular development process in which a system is built from trusted components. Testing thus essentially checks that these components have been combined in a correct manner and that the orders in which they can occur are consistent with the specification. Importantly, there are test generation methods that return a checking experiment: a test that is guaranteed to determine correctness as long as the implementation under test (IUT) is functionally equivalent to an unknown element of a given fault domain Ψ. Previous work has show how three methods for generating checking experiments from a finite state machine (FSM) can be adapted to testing from a stream X-machine. However, there are many other methods for generating checking experiments from an FSM and these have a variety of benefits that correspond to different testing scenarios. This paper shows how any method for generating a checking experiment from an FSM can be adapted to generate a checking experiment for testing an implementation against a stream X-machine. This is the case whether we are testing to check that the IUT is functionally equivalent to a specification or we are testing to check that every trace (input/output sequence) of the IUT is also a trace of a nondeterministic specification. Interestingly, this holds even if the fault domain Ψ used is not that traditionally associated with testing from a stream X-machine. The results also apply for both deterministic and nondeterministic implementations

Reducing complexity in an agent based reaction model-Benefits and limitations of simplifications in relation to run time and system level output.

Agent based modelling is a methodology for simulating a variety of systems across a broad spectrum of fields. However, due to the complexity of the systems it is often impossible or impractical to model them at a one to one scale. In this paper we use a simple reaction rate model implemented using the FLAME framework to test the impact of common methods for reducing model complexity such as reducing scale, increasing iteration duration and reducing message overheads. We demonstrate that such approaches can have significant impact on simulation runtime albeit with increasing risk of aberrant system behaviour and errors, as the complexity of the model is reduced

What makes testing work: Nine case studies of software development teams

Recently there has been a focus on test first and test driven development; several empirical studies have tried to assess the advantage that these methods give over testing after development. The results have been mixed. In this paper we investigate nine teams who tested during coding to examine the effect it had on the external quality of their code. Of the top three performing teams two used a documented testing strategy and the other an ad-hoc approach to testing. We conclude that their success appears to be related to a testing culture where the teams proactively test rather than carry out only what is required in a mechanical fashion. © 2009 IEEE

Inclusive leadership : realizing positive outcomes through belongingness and being valued for uniqueness

We introduce a theoretically-grounded conceptualization of inclusive leadership and present a framework for understanding factors that contribute to and follow from inclusive leadership within work groups. We conceptualize inclusive leadership as a set of positive leader behaviors that facilitate group members perceiving belongingness in the work group while maintaining their uniqueness within the group as they fully contribute to group processes and outcomes. We propose that leader pro-diversity beliefs, humility, and cognitive complexity increase the propensity of inclusive leader behaviors. We identify five categories of inclusive leadership behaviors that facilitate group members' perceptions of inclusion, which in turn lead to member work group identification, psychological empowerment, and behavioral outcomes (creativity, job performance, and reduced turnover) in the pursuit of group goals. This framework provides theoretical grounding for the construct of inclusive leadership while advancing our understanding of how leaders can increase diverse work group effectiveness

The Epitheliome: agent-based modelling of the social behaviour of cells

We have developed a new computational modelling paradigm for predicting the emergent behaviour resulting from the interaction of cells in epithelial tissue. As proof-of-concept, an agent-based model, in which there is a one-to-one correspondence between biological cells and software agents, has been coupled to a simple physical model. Behaviour of the computational model is compared with the growth characteristics of epithelial cells in monolayer culture, using growth media with low and physiological calcium concentrations. Results show a qualitative fit between the growth characteristics produced by the simulation and the in vitro cell models

Tenzing and the importance of tool development for research efficiency

The way science is done is changing. While some tools are facilitating this change, others lag behind. The resulting mismatch between tools and researchers' workflows can be inefficient and delay the progress of research. As an example, information about the people associated with a published journal article was traditionally handled manually and unsystematically. However, as large-scale collaboration, sometimes referred to as “team science,” is now common, a more structured and easy-to-automate approach to managing meta-data is required. In this paper we describe how the latest version of tenzing (A.O. Holcombe et al., Documenting contributions to scholarly articles using CRediT and tenzing, PLOS One 15(12) (2020)) helps researchers collect and structure contributor information efficiently and without frustration. Using tenzing as an example, we discuss the importance of efficient tools in reforming science and our experience with tool development as researchers.</p