scholarly journals Complex eco-evolutionary dynamics induced by the coevolution of predator-prey movement strategies

2020 ◽  
Author(s):  
Christoph Netz ◽  
Hanno Hildenbrandt ◽  
Franz J Weissing
Keyword(s):  
Degrees Of Freedom ◽  
Evolutionary Dynamics ◽  
Theoretical Research ◽  
Discrete Variation ◽  
Strategy Space ◽  
Individual Level ◽  
Fine Grained ◽  
Movement Strategies ◽  
Ecological Patterns ◽  
Individual Based Simulation

The coevolution of predators and prey has been the subject of much empirical and theoretical research, which has produced intriguing insights into the intricacies of eco-evolutionary dynamics. Mechanistically detailed models are rare, however, because the simultaneous consideration of individual-level behaviour (on which natural selection is acting) and the resulting ecological patterns is challenging and typically prevents mathematical analysis. Here we present an individual-based simulation model for the coevolution of predators and prey on a fine-grained resource landscape. Throughout their lifetime, predators and prey make repeated movement decisions on the basis of heritable and evolvable movement strategies. We show that these strategies evolve rapidly, inducing diverse ecological patterns like spiral waves and static spots. Transitions between these patterns occur frequently, induced by coevolution rather than by external events. Regularly, evolution leads to the emergence and stable coexistence of qualitatively different movement strategies. Although the strategy space considered is continuous, we often observe discrete variation. Accordingly, our model includes features of both population genetic and quantitative genetic approaches to coevolution. The model demonstrates that the inclusion of a richer ecological structure and higher number of evolutionary degrees of freedom results in even richer eco-evolutionary dynamics than anticipated previously.

scholarly journals Complex eco-evolutionary dynamics induced by the coevolution of predator–prey movement strategies

2021 ◽  
Author(s):  
Christoph Netz ◽  
Hanno Hildenbrandt ◽  
Franz J. Weissing
Keyword(s):  
Degrees Of Freedom ◽  
Evolutionary Dynamics ◽  
Rapid Evolution ◽  
Population Level ◽  
Coarse Grained ◽  
Theoretical Research ◽  
Strategy Space ◽  
Predator Prey ◽  
Individual Level ◽  
Movement Strategies

AbstractThe coevolution of predators and prey has been the subject of much empirical and theoretical research that produced intriguing insights into the interplay of ecology and evolution. To allow for mathematical analysis, models of predator–prey coevolution are often coarse-grained, focussing on population-level processes and largely neglecting individual-level behaviour. As selection is acting on individual-level properties, we here present a more mechanistic approach: an individual-based simulation model for the coevolution of predators and prey on a fine-grained resource landscape, where features relevant for ecology (like changes in local densities) and evolution (like differences in survival and reproduction) emerge naturally from interactions between individuals. Our focus is on predator–prey movement behaviour, and we present a new method for implementing evolving movement strategies in an efficient and intuitively appealing manner. Throughout their lifetime, predators and prey make repeated movement decisions on the basis of their movement strategies. Over the generations, the movement strategies evolve, as individuals that successfully survive and reproduce leave their strategy to more descendants. We show that the movement strategies in our model evolve rapidly, thereby inducing characteristic spatial patterns like spiral waves and static spots. Transitions between these patterns occur frequently, induced by antagonistic coevolution rather than by external events. Regularly, evolution leads to the emergence and stable coexistence of qualitatively different movement strategies within the same population. Although the strategy space of our model is continuous, we often observe the evolution of discrete movement types. We argue that rapid evolution, coexistent movement types, and phase shifts between different ecological regimes are not a peculiarity of our model but a result of more realistic assumptions on eco-evolutionary feedbacks and the number of evolutionary degrees of freedom.

scholarly journals A Multi-level Review of Engineering Ethics Education: Towards a Socio-technical Orientation of Engineering Education for Ethics

2021 ◽  
Vol 27 (5) ◽  
Author(s):  
Diana Adela Martin ◽  
Eddie Conlon ◽  
Brian Bowe
Keyword(s):  
Engineering Education ◽  
Ethics Education ◽  
Engineering Ethics ◽  
Theoretical Research ◽  
Policy And Practice ◽  
Individual Level ◽  
Multi Level ◽  
Engineering Ethics Education ◽  
Four Levels ◽  
The Individual

AbstractThis paper aims to review the empirical and theoretical research on engineering ethics education, by focusing on the challenges reported in the literature. The analysis is conducted at four levels of the engineering education system. First, the individual level is dedicated to findings about teaching practices reported by instructors. Second, the institutional level brings together findings about the implementation and presence of ethics within engineering programmes. Third, the level of policy situates findings about engineering ethics education in the context of accreditation. Finally, there is the level of the culture of engineering education. The multi-level analysis allows us to address some of the limitations of higher education research which tends to focus on individual actors such as instructors or remains focused on the levels of policy and practice without examining the deeper levels of paradigm and purpose guiding them. Our approach links some of the challenges of engineering ethics education with wider debates about its guiding paradigms. The main contribution of the paper is to situate the analysis of the theoretical and empirical findings reported in the literature on engineering ethics education in the context of broader discussions about the purpose of engineering education and the aims of reform programmes. We conclude by putting forward a series of recommendations for a socio-technical oriented reform of engineering education for ethics.

scholarly journals Asymmetry in Three-Dimensional Sprinting with and without Running-Specific Prostheses

Symmetry ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 580
Author(s):  
Anna Lena Emonds ◽  
Katja Mombaur
Keyword(s):  
Degrees Of Freedom ◽  
Body Position ◽  
Three Dimensional ◽  
Problem Formulation ◽  
Contact Phase ◽  
Individual Level ◽  
Lower Trunk ◽  
Floating Base ◽  
The Asymmetry ◽  
Limb Asymmetry

As a whole, human sprinting seems to be a completely periodic and symmetrical motion. This view is changed when a person runs with a running-specific prosthesis after a unilateral amputation. The aim of our study is to investigate differences and similarities between unilateral below-knee amputee and non-amputee sprinters—especially with regard to whether asymmetry is a distracting factor for sprint performance. We established three-dimensional rigid multibody models of one unilateral transtibial amputee athlete and for reference purposes of three non-amputee athletes. They consist of 16 bodies (head, ipper, middle and lower trunk, upper and lower arms, hands, thighs, shanks and feet/running specific prosthesis) with 30 or 31 degrees of freedom (DOFs) for the amputee and the non-amputee athletes, respectively. Six DOFs are associated with the floating base, the remaining ones are rotational DOFs. The internal joints are equipped with torque actuators except for the prosthetic ankle joint. To model the spring-like properties of the prosthesis, the actuator is replaced by a linear spring-damper system. We consider a pair of steps which is modeled as a multiphase problem with each step consisting of a flight, touchdown and single-leg contact phase. Each phase is described by its own set of differential equations. By combining motion capture recordings with a least squares optimal control problem formulation including constraints, we reconstructed the dynamics of one sprinting trial for each athlete. The results show that even the non-amputee athletes showed less symmetrical sprinting than expected when examined on an individual level. Nevertheless, the asymmetry is much more pronounced in the amputee athlete. The amputee athlete applies larger torques in the arm and trunk joints to compensate the asymmetry and experiences a destabilizing influence of the trunk movement. Hence, the inter-limb asymmetry of the amputee has a significant effect on the control of the sprint movement and the maintenance of an upright body position.

scholarly journals Effective Degrees of Freedom of the Pearson’s Correlation Coefficient under Autocorrelation

2018 ◽  
Author(s):  
Soroosh Afyouni ◽  
Stephen M. Smith ◽  
Thomas E. Nichols
Keyword(s):  
Time Series ◽  
Correlation Coefficient ◽  
Degrees Of Freedom ◽  
Brain Regions ◽  
Resting State Functional Connectivity ◽  
Pearson’S Correlation ◽  
Individual Level ◽  
Human Connectome Project ◽  
Pearson's Correlation ◽  
The Impact

AbstractThe dependence between pairs of time series is commonly quantified by Pearson’s correlation. However, if the time series are themselves dependent (i.e. exhibit temporal autocorrelation), the effective degrees of freedom (EDF) are reduced, the standard error of the sample correlation coefficient is biased, and Fisher’s transformation fails to stabilise the variance. Since fMRI time series are notoriously autocorrelated, the issue of biased standard errors – before or after Fisher’s transformation – becomes vital in individual-level analysis of resting-state functional connectivity (rsFC) and must be addressed anytime a standardized Z-score is computed. We find that the severity of autocorrelation is highly dependent on spatial characteristics of brain regions, such as the size of regions of interest and the spatial location of those regions. We further show that the available EDF estimators make restrictive assumptions that are not supported by the data, resulting in biased rsFC inferences that lead to distorted topological descriptions of the connectome on the individual level. We propose a practical “xDF” method that accounts not only for distinct autocorrelation in each time series, but instantaneous and lagged cross-correlation. We find the xDF correction varies substantially over node pairs, indicating the limitations of global EDF corrections used previously. In addition to extensive synthetic and real data validations, we investigate the impact of this correction on rsFC measures in data from the Young Adult Human Connectome Project, showing that accounting for autocorrelation dramatically changes fundamental graph theoretical measures relative to no correction.

Lingering neighbourhood effects: A framework to account for residential histories and temporal dynamics

Urban Studies ◽  
2016 ◽  
Vol 55 (1) ◽  
pp. 151-174 ◽  
Author(s):  
Emily M Miltenburg ◽  
Tom WG van der Meer
Keyword(s):  
Temporal Dynamics ◽  
Single Point ◽  
Population Data ◽  
Blind Spot ◽  
Neighbourhood Effects ◽  
Temporal Dimension ◽  
Individual Level ◽  
Fine Grained ◽  
Conventional Models ◽  
Total Body

The large and growing body of neighbourhood effect studies has almost exclusively neglected individuals’ particular residential histories. Yet, former residential neighbourhoods are likely to have lingering effects beyond those of the current one and are dependent on exposure times and number of moves. This paper tests to what extent this blind spot induced a misestimation of neighbourhood effects for individuals with differential residential histories. Ultimately, we develop a methodological framework for studying the temporal dynamics of neighbourhood effects, capable of dealing with residential histories (moving behaviour, the passage of time and temporal exposure to different neighbourhoods). We apply cross-classified multi-level models (residents nested in current and former neighbourhoods) to analyse longitudinal individual-level population data from Dutch Statistics, covering fine-grained measures of residential histories. Our systematic comparison to conventional models reveals the necessity of including a temporal dimension: our models reveal an overestimation of the effect of the current neighbourhood by 16–30%, and an underestimation of the total body of neighbourhood effects by at least 13–24%. Our results show that neighbourhood effects are lingering, long-lasting and structural and also cannot be confined to a single point in time.

scholarly journals Hypothesized, Directly-Coded Curve Shapes in Growth Curve Analysis: An Example

2013 ◽  
Vol 3 (2) ◽  
pp. 13 ◽  
Author(s):  
Patricia M. Herman ◽  
Lee Sechrest
Keyword(s):  
Hierarchical Linear Modeling ◽  
Growth Curve ◽  
Degrees Of Freedom ◽  
Growth Curves ◽  
Curve Analysis ◽  
Small Samples ◽  
Growth Curve Analysis ◽  
Linear Modeling ◽  
Individual Level ◽  
The Individual

Growth curve analysis provides important informational benefits regarding intervention outcomes over time. Rarely, however, should outcome trajectories be assumed to be linear. Instead, both the shape and the slope of the growth curve can be estimated. Non-linear growth curves are usually modeled by including either higher-order time variables or orthogonal polynomial contrast codes. Each has limitations (multicollinearity with the first, a lack of coefficient interpretability with the second, and a loss of degrees of freedom with both) and neither encourages direct testing of alternative hypothesized curve shapes. Especially in studies with relatively small samples it is likely to be useful to preserve as much information as possible at the individual level. This article presents a step-by-step example of the use and testing of hypothesized curve shapes in the estimation of growth curves using hierarchical linear modeling for a small intervention study. DOI:10.2458/azu_jmmss_v3i2_herman

scholarly journals Host age modulates within-host parasite competition

2015 ◽  
Vol 11 (5) ◽  
pp. 20150131 ◽  
Author(s):  
Rony Izhar ◽  
Jarkko Routtu ◽  
Frida Ben-Ami
Keyword(s):  
Evolutionary Dynamics ◽  
Parasite Prevalence ◽  
Host Age ◽  
Individual Level ◽  
Pasteuria Ramosa ◽  
Age Dependent ◽  
The Individual ◽  
Host Parasite ◽  
Parasite Exposure ◽  
Age At Exposure

In many host populations, one of the most striking differences among hosts is their age. While parasite prevalence differences in relation to host age are well known, little is known on how host age impacts ecological and evolutionary dynamics of diseases. Using two clones of the water flea Daphnia magna and two clones of its bacterial parasite Pasteuria ramosa , we examined how host age at exposure influences within-host parasite competition and virulence. We found that multiply-exposed hosts were more susceptible to infection and suffered higher mortality than singly-exposed hosts. Hosts oldest at exposure were least often infected and vice versa. Furthermore, we found that in young multiply-exposed hosts competition was weak, allowing coexistence and transmission of both parasite clones, whereas in older multiply-exposed hosts competitive exclusion was observed. Thus, age-dependent parasite exposure and host demography (age structure) could together play an important role in mediating parasite evolution. At the individual level, our results demonstrate a previously unnoticed interaction of the host's immune system with host age, suggesting that the specificity of immune function changes as hosts mature. Therefore, evolutionary models of parasite virulence might benefit from incorporating age-dependent epidemiological parameters.

scholarly journals Clinical Validation of Kinematic Assessments of Post-Stroke Upper Limb Movements with a Multi-Joint Arm Exoskeleton

2020 ◽  
Author(s):  
Florian Grimm ◽  
Jelena Kraugmann ◽  
Georgios Naros ◽  
Alireza Gharabaghi
Keyword(s):  
Clinical Outcome ◽  
Upper Limb ◽  
Convergent Validity ◽  
Degrees Of Freedom ◽  
Clinical Status ◽  
Multiple Regression Model ◽  
Fine Grained ◽  
Starting Position ◽  
Upper Limb Function ◽  
Upper Limb Movements

Abstract Background: Robotic and gravity-balancing exoskeletons, originally designed for the rehabilitation training of neurological patients, are now being increasingly applied in objective and fine-grained sensor-based assessments of upper limb function. However, gravity compensation, inertia and damping properties of the exoskeleton interfere with the natural sensorimotor interaction, proprioceptive and visual feedback during movement execution. This may endanger the validity of the kinematic assessments in relation to the clinical outcome measures that they were supposed to reflect. Here, we appliedMethods: In a proof of concept study involving nineteen severely impaired chronic stroke patients, we assessed sensor-based kinematic data acquired with a multi-joint arm exoskeleton and compared it to the clinical outcome measure Upper Extremity Fugl-Meyer Assessment (UE-FMA) scale. During this assessment, real-time movement feedback of the system’s seven degrees of freedom was provided with a biomorphic 3D virtual representation of the upper limb, including the proximal component of the arm. To align posture and to minimize the exoskeleton-patient interaction, the same position (neutral zero) with a distance of 90 degrees between forearm and upper arm was taken as the starting position for all assessments. Within self-contained tasks, we assessed separately and subsequently the range of motion/spatial posture of four single joints (i.e., joint angles of wrist, elbow, arm, and shoulder movement) and the closing and opening of the hand with a pressure sensor placed in the handle.Results: A strong correlation was observed between wrist and elbow movements within the kinematic parameters (r > 0.7, p<0.003; Bonferroni corrected). A multiple regression model predicted the UE-FMA significantly (F (5, 13) = 12.22, p < 0.0005, adj. R2 = 0.83). Both shoulder rotation and grip pressure added significantly (p < 0.05) to the prediction with the standardized coefficients β of 0.55 and 0.38, respectively.Conclusions: Exoskeleton-based evaluation of single-joint movements and grip force facilitates the assessment of upper limb kinematics after stroke with high structural and convergent validity. Proximal and distal measures may contribute independently to the prediction of the clinical status.

scholarly journals Doing Well by Doing Good, Uniquely: Materiality and the Market Value of Unique CSR Strategies

2021 ◽  
Author(s):  
Leandro Nardi ◽  
Todd Zenger ◽  
Sérgio Giovanetti Lazzarini ◽  
Sandro Cabral
Keyword(s):  
Degrees Of Freedom ◽  
Strong Support ◽  
Market Value ◽  
Strategic Decision ◽  
Market Returns ◽  
Individual Level ◽  
Csr Strategies ◽  
Key Stakeholders ◽  
Corporate Social

Corporate social responsibility (CSR) has become a strategic decision for organizations. The capacity to invest in several distinct CSR categories at varying levels (e.g., environmental innovation, diversity, community) leaves firms with a multitude of patterns from which to choose. However, the question of whether market returns to CSR are defined by individual-level positioning choices or by industry-level conditions––particularly the materiality of distinct categories of CSR––remains unresolved. Drawing on the literature arguing that stakeholders are crucial enablers of value creation and capture, we theorize that unique CSR strategies more effectively promote stakeholder engagement by helping firms develop differentiated and unrivaled positions with key stakeholders. Thus, we argue that CSR uniqueness is positively associated with market value. Yet we also argue that uniqueness can be constrained by materiality: in industries in which a higher number of CSR categories are considered material, firms have fewer degrees of freedom to successfully differentiate from competitors; hence, the market returns to unique CSR positioning are negatively associated with the number of CSR categories deemed material to the industry. Using a novel measure of uniqueness of CSR strategies and a database containing environmental, social, and financial information of 2,093 firms between 2002 and 2017, we find strong support for our hypotheses. To shed further light on the mechanisms driving the role of materiality, we examine the 2010 BP Deepwater Horizon oil spill.

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