scholarly journals Spatial patterns emerging from a stochastic process near criticality

2019 ◽  
Author(s):  
Fabio Peruzzo ◽  
Mauro Mobilia ◽  
Sandro Azaele
Keyword(s):  
Spatial Scales ◽  
Detailed Balance ◽  
Spatial Effects ◽  
Tropical Rain Forests ◽  
Regular Lattice ◽  
Model Framework ◽  
Physical Systems ◽  
Analytical Formulae ◽  
Living Organisms ◽  
Number Of Individuals

There is mounting empirical evidence that many communities of living organisms display key features which closely resemble those of physical systems at criticality. We here introduce a minimal model framework for the dynamics of a community of individuals which undergoes local birth-death, immigration and local jumps on a regular lattice. We study its properties when the system is close to its critical point. Even if this model violates detailed balance, within a physically relevant regime dominated by fluctuations, it is possible to calculate analytically the probability density function of the number of individuals living in a given volume, which captures the close-to-critical behavior of the community across spatial scales. We find that the resulting distribution satisfies an equation where spatial effects are encoded in appropriate functions of space, which we calculate explicitly. The validity of the analytical formulæ is confirmed by simulations in the expected regimes. We finally discuss how this model in the critical-like regime is in agreement with several biodiversity patterns observed in tropical rain forests.

scholarly journals Self-replication of a quantum artificial organism driven by single-photon pulses

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Daniel Valente
Keyword(s):  
Self Assembly ◽  
Artificial Life ◽  
Single Photon ◽  
Self Organization ◽  
Physical Systems ◽  
Self Organized ◽  
Living Organisms ◽  
A Chain ◽  
Thermodynamic Mechanism ◽  
Self Replication

AbstractImitating the transition from inanimate to living matter is a longstanding challenge. Artificial life has achieved computer programs that self-replicate, mutate, compete and evolve, but lacks self-organized hardwares akin to the self-assembly of the first living cells. Nonequilibrium thermodynamics has achieved lifelike self-organization in diverse physical systems, but has not yet met the open-ended evolution of living organisms. Here, I look for the emergence of an artificial-life code in a nonequilibrium physical system undergoing self-organization. I devise a toy model where the onset of self-replication of a quantum artificial organism (a chain of lambda systems) is owing to single-photon pulses added to a zero-temperature environment. I find that spontaneous mutations during self-replication are unavoidable in this model, due to rare but finite absorption of off-resonant photons. I also show that the replication probability is proportional to the absorbed work from the photon, thereby fulfilling a dissipative adaptation (a thermodynamic mechanism underlying lifelike self-organization). These results hint at self-replication as the scenario where dissipative adaptation (pointing towards convergence) coexists with open-ended evolution (pointing towards divergence).

scholarly journals Enabling Cyber Physical Systems with Wireless Sensor Networking Technologies, Multiagent System Paradigm, and Natural Ecosystems

2015 ◽  
Vol 2015 ◽  
pp. 1-15 ◽  
Author(s):  
Nafaâ Jabeur ◽  
Nabil Sahli ◽  
Sherali Zeadally
Keyword(s):  
Cyber Physical Systems ◽  
Wireless Sensor ◽  
Natural Ecosystems ◽  
Distributed Sensors ◽  
Physical Systems ◽  
Structure Topology ◽  
Spatially Distributed ◽  
Engineered Systems ◽  
Networking Technologies ◽  
Living Organisms

Wireless sensor networks (WSNs) are key components in the emergent cyber physical systems (CPSs). They may include hundreds of spatially distributed sensors which interact to solve complex tasks going beyond their individual capabilities. Due to the limited capabilities of sensors, sensor actions cannot meet CPS requirements while controlling and coordinating the operations of physical and engineered systems. To overcome these constraints, we explore the ecosystem metaphor for WSNs with the aim of taking advantage of the efficient adaptation behavior and communication mechanisms of living organisms. By mapping these organisms onto sensors and ecosystems onto WSNs, we highlight shortcomings that prevent WSNs from delivering the capabilities of ecosystems at several levels, including structure, topology, goals, communications, and functions. We then propose an agent-based architecture that migrates complex processing tasks outside the physical sensor network while incorporating missing characteristics of autonomy, intelligence, and context awareness to the WSN. Unlike existing works, we use software agents to map WSNs to natural ecosystems and enhance WSN capabilities to take advantage of bioinspired algorithms. We extend our architecture and propose a new intelligent CPS framework where several control levels are embedded in the physical system, thereby allowing agents to support WSNs technologies in enabling CPSs.

Bird research in the ACWERN lab at the Faculty of Forestry and Environmental Management, University of New Brunswick

2008 ◽  
Vol 84 (4) ◽  
pp. 548-552 ◽  
Author(s):  
Antony W Diamond
Keyword(s):  
New Brunswick ◽  
Forest Cover ◽  
Spatial Scales ◽  
Breeding Habitat ◽  
Research Network ◽  
Spatial Effects ◽  
Winter Habitat ◽  
Forested Landscapes ◽  
Carry Over ◽  
Species Specific

Research on forest bird ecology in the ACWERN (Atlantic Cooperative Wildlife Ecology Research Network) lab at the University of New Brunswick, Fredericton, since 1995 has focused on assessing the relative contributions of habitat quality at large (“landscape”) and small (“local” or “stand”) spatial scales. To do so we had to develop methods for assessing key demographic components of fitness (productivity and survival) at large spatial scales. The large extent of forest cover in the Maritimes contrasts with regions where such work has traditionally been carried out, in which forest is clearly fragmented by agriculture or residential development. Our main findings are that spatial effects in highly forested landscapes can often be detected only by using species-specific habitat models, rather than broader categories such as “mature” or “softwood”, that Blackburnian Warblers (Dendroica fusca) are effective indicators of mixedwood forest but define it differently than forest managers do, and that cavity nesters (e.g., woodpeckers) may require different habitat components for nesting and feeding and so cannot be managed for solely on the basis of providing snags for nesting. Our focus has shifted recently to intensive studies on a species at risk, Bicknell's Thrush (Catharus bicknelli), which in New Brunswick breeds in man-made regenerating softwood forest stands, and assessing its response both to precommercial thinning of the breeding habitat and to effects carrying over from the winter habitat in the Caribbean. Key words: landscape effects, thresholds, survival, productivity, fitness, carry-over, habitat, fragmentation

When and why do sit-and-wait social spiders disperse?

2019 ◽  
Vol 66 (1-2) ◽  
pp. 15-25
Author(s):  
Bharat Parthasarathy ◽  
Hema Somanathan
Keyword(s):  
Information Transfer ◽  
Spatial Scales ◽  
Structured Populations ◽  
Social Spiders ◽  
Intrinsic Factors ◽  
Area Of Interest ◽  
Evolution Of Sociality ◽  
Dispersal Distances ◽  
Complex Relationships ◽  
Living Organisms

Abstract Dispersal is inherent to all living organisms. Sit-and-wait predators such as social spiders, with their sedentary lifestyles, present an intriguing and underexplored case to examine the proximate and ultimate reasons for dispersal. Though a reduction in dispersal tendencies must accompany the evolution of sociality in spiders, a fraction of the colony may disperse in groups or individually in many species. Such group or solitary dispersal by female social spiders in specific life stages, can lead to colony fission or colony foundation. Males move between colonies, however, there are no direct estimations of male dispersal distances for any species. The structured populations and high inbreeding within colonies suggest that dispersal events occur over limited spatial scales and may be mediated by extrinsic and intrinsic factors. Future studies exploring complex relationships between environmental variables, phenotypes of individuals, colony state and dispersal are advocated. Another area of interest is probing the dispersal process itself to understand the mechanisms of information transfer between individuals at the onset of dispersal. This involves designing studies to examine how break-away groups reach a consensus on when to disperse and where to go.

How Can High Animal Diversity Be Supported in Low-Productivity Deserts?: The Role of Macrodetritivory and Habitat Physiognomy

2005 ◽  
Author(s):  
Gary A. Polis ◽  
Yael Lubin
Keyword(s):  
High Temperatures ◽  
Primary Productivity ◽  
Salt Marshes ◽  
Spatial Scales ◽  
General Pattern ◽  
Trophic Levels ◽  
High Productivity ◽  
Number Of Species ◽  
Mechanics Model ◽  
Number Of Individuals

On large spatial scales, species diversity is typically correlated positively with productivity or energy supply (Wright et al. 1993, Huston 1994, Waide et al. 1999). In line with this general pattern, deserts are assumed to have relatively few species for two main reasons. First, relatively few plants and animals have acquired the physiological capabilities to withstand the stresses exerted by the high temperatures and shortage of water found in deserts (reviewed by Noy-Meir 1974, Evenari 1985, Shmida et al. 1986). A second, more ecological mechanism is resource limitation. In deserts, the low and highly variable precipitation levels, high temperatures and high evapotranspiration ratios limit both plant abundance and productivity to very low levels (Noy-Meir 1973, 1985, Polis 1991d). This lack of material at the primary producer level should exacerbate the harsh abiotic conditions and reduce the abundance of animals at higher trophic levels by limiting the types of resources and their availability. Animal abundance should be even further reduced because primary productivity is not only low, but also tends to be sporadic in time and space (MacMahon 1981, Crawford 1981, Ludwig 1986). Herbivores should have difficulties tracking these variations (e.g., Ayal 1994) and efficiently using the available food resources. Hence, herbivore populations in deserts have low densities relative to other biomes (Wisdom 1991) and most of the primary productivity remains unused (Crawford 1981, Noy-Meir 1985). This low abundance of herbivores should propagate through the food web and result as well in lower abundance of higher trophic levels. The number of individuals and the number of species are not always positively correlated; in particular, some examples of low diversity at high productivity with high densities are well documented (e.g., salt marshes, reviewed by Waide et al. 1999). However, several distinct mechanisms have led to the expectation that when productivity and the number of individuals are low, the number of species is also likely to be low. First, within trophic levels, the “statistical mechanics” model of Wright et al. (1993) may operate. In this model, the amount of energy present determines the probability distribution of population sizes for the members of the species pool in a region.

Preservation Paradigms and Tropical Rain Forests

Last Stand ◽  
1997 ◽  
Author(s):  
Randall A. Kramer ◽  
Carel P. van Schaik
Keyword(s):  
Protected Areas ◽  
Rain Forest ◽  
Past Century ◽  
Strict Sense ◽  
Tropical Rain Forests ◽  
Rain Forests ◽  
The Past ◽  
Living Organisms ◽  
The Developed Countries ◽  
Definition Of

Tropical rain forests are disappearing rapidly as a result of increasing human encroachment. During the past century, tropical rain forests have been reduced to about half of their original area. And the rate of deforestation is accelerating, fueled by population growth in developing countries and resource demands in the developed countries. The remaining forests are subject to increasingly intensive human use. Deforestation, fragmentation, and exploitation cause a plethora of problems, including soil erosion; siltation of rivers, lakes, and estuaries; increased flooding and droughts; release of carbon dioxide and other greenhouse gases into the atmosphere; and loss of species. In recent years, these problems have become the subject of international concern. This book focuses on the loss of biodiversity in tropical rain forests and on the role of protected areas in stemming the loss. This chapter examines the meaning of biodiversity and the history of the park movement in the tropics. What began as protection of habitat through the exclusion of people has transformed into sustainable use of biological resources. This new emphasis provides local control of important resources and greater income, but does it conserve habitat and species? We will argue that a renewed focus on protected areas as the primary storehouse of biodiversity is needed. We will also make the case for a focus on the tropical rain forest biome and will conclude with an overview of the rest of the book. In its strict sense, biodiversity refers to the “variety and variability among living organisms and the ecological complexes in which they occur” (Office of Technology Assessment, U.S. Congress, 1987:3). This definition can be extended both downward to cover genetic variability within a species and upward to include habitat and ecosystem diversity. practical terms, however, biodiversity is most profitably expressed as species diversity (weighted for rarity, endemism, and taxonomic distinctiveness, if necessary) at the landscape level (see chapter 6). We adopt this definition of biodiversity. During the past few years, attempts to link rain forest protection with sustainable development have led to a noticeable expansion of the meaning of the phrase “biodiversity conservation.”

scholarly journals Regional-scale analysis of high-mountain multi-hazard and risk indicators in the Pamir (Tajikistan) with GRASS GIS

2013 ◽  
Vol 13 (11) ◽  
pp. 2779-2796 ◽  
Author(s):  
F. E. Gruber ◽  
M. Mergili
Keyword(s):  
Spatial Scales ◽  
Regional Scale ◽  
Risk Indicators ◽  
High Mountain ◽  
Scale Analysis ◽  
Model Framework ◽  
Rock Face ◽  
Grass Gis ◽  
Hazard And Risk ◽  
The Impact

Abstract. We present a model framework for the regional-scale analysis of high-mountain multi-hazard and -risk indicators, implemented with the open-source software package GRASS GIS. This framework is applied to a 98 300 km2 study area centred in the Pamir (Tajikistan). It includes (i) rock slides, (ii) ice avalanches, (iii) periglacial debris flows and (iv) lake outburst floods. First, a hazard indicator is assigned to each relevant object (steep rock face, glacier or periglacial slope, lake). This indicator depends on the susceptibility and on the possible event magnitude. Second, the possible travel distances, impact areas and, consequently, impact hazard indicators for all types of processes are computed using empirical relationships. The impact hazard indicators are finally superimposed with an exposure indicator derived from the type of land use, resulting in a raster map of risk indicators finally discretized at the community level. The analysis results are presented and discussed at different spatial scales. The major outcome of the study, a set of comprehensive regional-scale hazard and risk indication maps, shall represent an objective basis for the prioritization of target communities for further research and risk mitigation measures.

scholarly journals Influence of Geographical Effects in Hedonic Pricing Models for Grass-Fed Cattle in Uruguay

Agriculture ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 299
Author(s):  
Paul Harris ◽  
Bruno Lanfranco ◽  
Binbin Lu ◽  
Alexis Comber
Keyword(s):  
Spatial Information ◽  
Production Systems ◽  
Spatial Scales ◽  
Health And Safety ◽  
Ecological Factors ◽  
Hedonic Pricing ◽  
Hedonic Model ◽  
Soil Productivity ◽  
Spatial Effects ◽  
Water Characteristics

A series of non-spatial and spatial hedonic models of feeding and replacement cattle prices at video auctions in Uruguay (2002 to 2009) were specified with predictors measuring marketing conditions (e.g., steer price), cattle characteristics (e.g., breed) and agro-ecological factors (e.g., soil productivity, water characteristics, pasture condition, season). Results indicated that cattle prices produced under extensive production systems were influenced by all of predictor categories, confirming that found previously. Although many of the agro-ecological predictors were inherently spatial in nature, the incorporation of spatial effects into the estimation of the hedonic model itself, through either a spatially-autocorrelated error term or allowing the regression coefficients to vary spatially and at different scales, was able to provide greater insight into the cattle price process. Through the latter extension, using a multiscale geographically weighted regression, which was the most informative and most accurate model, relationships between cattle price and predictors operated at a mixture of global, regional, local and highly local spatial scales. This result is considered a key advance, where uncovering, interpreting, and utilizing such rich spatial information can help improve the geographical provenance of Uruguayan beef and is critically important for maintaining Uruguay’s status as a key exporter of beef with respect to the health and safety benefits of natural, open-sky, grass-fed production systems.

scholarly journals An ego-centred approach for the evaluation of spatial effects on health in urban areas based on parametric semi-variogram models: concept and validation

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Odile Sauzet ◽  
Janne H. Breiding ◽  
Kim A. Zolitschka ◽  
Jürgen Breckenkamp ◽  
Oliver Razum
Keyword(s):  
Urban Areas ◽  
Spatial Scales ◽  
Complex Structure ◽  
Exponential Model ◽  
Small Sample ◽  
Spatial Effects ◽  
Sample Sizes ◽  
Quantitative Analyses ◽  
Small Sample Sizes ◽  
Two Parameters

Abstract Background Neighbourhood is a complex structure but of high relevance for health. Its operationalisation remains however a challenge.The aim of this work is to present a new application of the use of semi-variograms as an approach for the evaluation of spatial effects on health. For this, we propose to estimate two parameters providing a measure of an average neighbourhood or spatial effect at city level without having to predefine any notion of physical neighbourhood. Methods We present the statistical method to estimate the parameters of this correlation neighbourhood by fitting an exponential model to the empirical semi-variogram at short distances. With a simulation study, we show for which sample size and sampling density the method performs well and illustrate how to use the method with data from a birth cohort using the outcome birthweight. Results For small sample sizes (500) the method provides reliable estimates if the density of observations is high. For larger sample sizes other parameters influencing the quality of estimates are the maximal distance at which the semi-variograms are estimated. Conclusions Given the complexity of spatial scales relative to neighbourhood spatial processes, our approach offers the possibility to incorporate existing approaches to the operationalisation of neighbourhood in quantitative analyses while providing a measure of the part of health inequalities which could be possibly due to unmeasured spatial exposure as well as a measure of their spatial scale.

scholarly journals Regional-scale analysis of high-mountain multi-hazard and risk in the Pamir (Tajikistan) with GRASS GIS

2013 ◽  
Vol 1 (2) ◽  
pp. 1689-1747
Author(s):  
F. E. Gruber ◽  
M. Mergili
Keyword(s):  
Risk Mitigation ◽  
Spatial Scales ◽  
Regional Scale ◽  
Mitigation Measures ◽  
High Mountain ◽  
Scale Analysis ◽  
Model Framework ◽  
Rock Face ◽  
Grass Gis ◽  
Hazard And Risk

Abstract. We present a model framework for the regional-scale analysis of high-mountain multi-hazard and -risk, implemented with the Open Source software package GRASS GIS. This framework is applied to a 98 300 km2 study area centred in the Pamir (Tajikistan). It includes (i) rock slides, (ii) ice avalanches, (iii) periglacial debris flows, and (iv) lake outburst floods. First, a hazard indication score is assigned to each relevant object (steep rock face, glacier or periglacial slope, lake). This score depends on the susceptibility and on the expected event magnitude. Second, the possible travel distances, impact areas and, consequently, impact hazard indication scores for all types of processes are computed using empirical relationships. These scores are finally superimposed with an exposure score derived from the type of land use, resulting in a raster map of risk indication scores finally discretized at the community level. The analysis results are presented and discussed at different spatial scales. The major outcome of the study, a set of comprehensive regional-scale hazard and risk indication maps, shall represent an objective basis for the prioritization of target communities for further research and risk mitigation measures.

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