scholarly journals Metacommunity stability and persistence for predation turnoff in selective patches

2021 ◽  
Author(s):  
Dweepabiswa Bagchi ◽  
Ramesh Arumugam ◽  
V K Chandrasekar ◽  
D V Senthilkumar
Keyword(s):  
Large Scale ◽  
Ecological Communities ◽  
Number Of Clusters ◽  
Complete Extinction ◽  
Local Loss ◽  
Oscillatory State ◽  
Spatially Distributed ◽  
The Stability ◽  
Source Sink ◽  
The Impact

Predation as an important trophic interaction of ecological communities controls the large-scale patterns of species distribution, population abundance and community structure. Numerous studies address that predation can mediate diversity and regulate the ecological community and food web stability through changes in the behaviour, morphology, development, and abundance of prey. Since predation has large effects on persistence and diversity, the local loss or removal of predation in a community can trigger a cascade of extinctions. In ecological theory, the effect of predation removal has been well studied in foodwebs, but it remains unclear in the case of a spatially distributed community connected by dispersal. In this study, the interaction between local and spatial processes is taken into account, we present how a predation turnoff in selective patches affects the stability and persistence of a metacommunity. Using a simple predator-prey metacommunity with a diffusive dispersal, we show the impact of predation on synchronized, asynchronized and source-sink dynamics. Our results reveal that predation turnoff in very few patches alters a perfectly synchronized oscillatory state into multicluster states consisting of various patterns. In a source-sink behaviour, predation turnoff in a source patch reduces the number of sink patches and changes the clusters. In general, predation turnoff in a finite number of patches increases the number of clusters through asynchronized (inhomogeneous) states, whereas predation turnoff in a larger number of patches can lead to the complete extinction of predators. Typically, there exists a critical number of patches below which the predation turnoff results in asynchronized states and above that predation turnoff leads to a synchronized state in prey population with complete extinction of predators. Further, our results identify the network configurations that exhibit a unique number of clusters. Moreover, prey density from the patches where predation is absent goes to a saturating state near the carrying capacity. Thus, this study stresses that predation turnoff in selective patches acts as a stabilizing mechanism that can promote metacommunity persistence.

scholarly journals Imposed dynamic irradiation to intensify photocatalytic reactions

2021 ◽  
Author(s):  
Fabian Guba ◽  
Florian Gaulhofer ◽  
Dirk Ziegenbalg
Keyword(s):  
Large Scale ◽  
Reaction Rate ◽  
Photochemical Reactions ◽  
Test Reaction ◽  
Light Emitting ◽  
Photochemical Processes ◽  
Spatially Distributed ◽  
Photocatalytic Reactions ◽  
The Impact ◽  
Photonic Efficiency

AbstractDynamic irradiation is a potent option to influence the interaction between photochemical reactions and mass transport to design high performant and efficient photochemical processes. To systematically investigate the impact of this parameter, the photocatalytic reduction of nitrobenzene was conducted as a test reaction. Dynamic irradiation was realized through provoked secondary flow patterns, multiple spatially distributed light emitting diodes (LEDs) and electrical pulsation of LEDs. A combined experimental and theoretical approach revealed significant potential to enhance photochemical processes. The reaction rate was accelerated by more than 70% and even more important the photonic efficiency was increased by more than a factor of 4. This renders imposed dynamic irradiation an innovative and powerful tool to intensify photoreactions on the avenue to large scale sustainable photochemical processes.

scholarly journals Australian agricultural scale and corporate agroholdings: environmental and climatic impacts

2017 ◽  
Vol 20 (2) ◽  
pp. 187-190 ◽  
Author(s):  
Bradley Plunkett ◽  
Andrew Duff ◽  
Ross Kingwell ◽  
David Feldman
Keyword(s):  
Large Scale ◽  
Climatic Variability ◽  
Institutional Setting ◽  
Corporate Ownership ◽  
Family Structures ◽  
Climatic Impacts ◽  
The Stability ◽  
Average Size ◽  
The Impact ◽  
Concentrate Production

The average size of Australian farms in scale and revenue are the globe’s largest. This scale is a result, in part, of low average rural population densities; development patterns in broadacre production; low levels of effective public policy transfers; a stable and suitable institutional setting suitable for corporate and other large scale investment; and low yields. It is also a factor of the natural variability of the country’s climatic systems which have contributed to the scale of extensive northern cattle production; this variability has implications for the pattern of ownership of broadacre and extensive production. Corporate ownership, tends to concentrate production aggregations at sufficient scale to offset its additional overheads in areas of relative climatic stability and to replicate these agroholding aggregations spatially to protect the stability of revenue flows. Family structures are more dominant in areas of greater climatic variability. Of interest is the impact that any increasing climatic variability (versus rapid changes in technology) may have upon this pattern.

A Predictive Energy Landscape Model of Metamorphic Protein Conformational Specificity

2021 ◽  
Author(s):  
James O. Wrabl ◽  
Keila Voortman-Sheetz ◽  
Vincent J. Hilser
Keyword(s):  
Amino Acid ◽  
Structure Prediction ◽  
Large Scale ◽  
Energy Landscape ◽  
Thermodynamic Approach ◽  
High Identity ◽  
Denatured State ◽  
Metamorphic Protein ◽  
The Stability ◽  
The Impact

'Metamorphic' proteins challenge state-of-the-art structure prediction methods reliant on amino acid similarity. Unfortunately, this obviates a more effective thermodynamic approach necessary to properly evaluate the impact of amino acid changes on the stability of two different folds. A vital capability of such a thermodynamic approach would be the quantification of the free energy differences between 1) the energy landscape minima of each native fold, and 2) each fold and the denatured state. Here we develop an energetic framework for conformational specificity, based on an ensemble description of protein thermodynamics. This energetic framework was able to successfully recapitulate the structures of high-identity engineered sequences experimentally shown to adopt either Streptococcus protein GA or GB folds, demonstrating that this approach indeed reflected the energetic determinants of fold. Residue-level decomposition of the conformational specificity suggested several testable hypotheses, notably among them that fold-switching could be affected by local de-stabilization of the populated fold at positions sensitive to equilibrium perturbation. Since this ensemble-based compatibility framework is applicable to any structure and any sequence, it may be practically useful for the future targeted design, or large-scale proteomic detection, of novel metamorphic proteins.

Method of Image Matching for Seabed Sonar Images Based on Regions of Interest

2014 ◽  
Vol 532 ◽  
pp. 126-129
Author(s):  
Zhi Gang Zhang ◽  
Hong Yu Bian ◽  
Hui Xu ◽  
Zi Qi Song
Keyword(s):  
Target Detection ◽  
Image Matching ◽  
Large Scale ◽  
Regions Of Interest ◽  
Matching Method ◽  
Aspect Angle ◽  
Sonar Images ◽  
The Stability ◽  
Imaging Sonar ◽  
The Impact

One of the most effective instruments for target detection in turbid waters is imaging sonar. However, the aspect angle of imaging sonar is usually small and that is a sacrifice for high detection precision. To make imaging sonar practical in large scale target detection with wide aspect angle, investigating image matching methods for continuous sonar frames is of great importance. A novel image matching method using local features of SIFT is described in this paper, which mainly focuses on the problem of weak echo signals and the following sonar images mismatch. The correspondence between objects and cast shadow regions is employed to extract regions of interest. Besides, status parameters of underwater vehicle are used to approximate the image transformation. Image segmentation methods are involved to decrease the size of the feature extracting regions and reduce the impact of non-target seabed areas, which improves the stability of this sonar image matching method significantly.

scholarly journals Shared ancestry influences community stability by altering competitive interactions: evidence from a laboratory microcosm experiment using freshwater green algae

2013 ◽  
Vol 280 (1768) ◽  
pp. 20131548 ◽  
Author(s):  
Patrick A. Venail ◽  
Markos A. Alexandrou ◽  
Todd H. Oakley ◽  
Bradley J. Cardinale
Keyword(s):  
Related Species ◽  
Temporal Stability ◽  
Biodiversity Loss ◽  
Competitive Interactions ◽  
Ecological Communities ◽  
Freshwater Microalgae ◽  
Community Biomass ◽  
Shared Ancestry ◽  
The Stability ◽  
The Impact

The impact of biodiversity on the stability of ecological communities has been debated among biologists for more than a century. Recently summarized empirical evidence suggests that biodiversity tends to enhance the temporal stability of community-level properties such as biomass; however, the underlying mechanisms driving this relationship remain poorly understood. Here, we report the results of a microcosm study in which we used simplified systems of freshwater microalgae to explore how the phylogenetic relatedness of species influences the temporal stability of community biomass by altering the nature of their competitive interactions. We show that combinations of two species that are more evolutionarily divergent tend to have lower temporal stability of biomass. In part, this is due to negative ‘selection effects’ in which bicultures composed of distantly related species are more likely to contain strong competitors that achieve low biomass. In addition, bicultures of distantly related species had on average weaker competitive interactions, which reduced compensatory dynamics and decreased the stability of community biomass. Our results demonstrate that evolutionary history plays a key role in controlling the mechanisms, which give rise to diversity–stability relationships. As such, patterns of shared ancestry may help us predict the ecosystem-level consequences of biodiversity loss.

scholarly journals Effect of Localization on the Stability of Mutualistic Ecological Networks

2015 ◽  
Author(s):  
Samir Suweis ◽  
Jacopo Grilli ◽  
Jayanth Banavar ◽  
Stefano Allesina ◽  
Amos Maritan
Keyword(s):  
Species Abundance ◽  
Interaction Network ◽  
Species Interaction ◽  
Interaction Networks ◽  
Ecological Communities ◽  
Weighted Degree ◽  
Perturbation Propagation ◽  
The Stability ◽  
The Impact ◽  
The Relationship

The relationships between the core-periphery architecture of the species interaction network and the mechanisms ensuring the stability in mutualistic ecological communities are still unclear. In particular, most studies have focused their attention on asymptotic resilience or persistence, neglecting how perturbations propagate through the system. Here we develop a theoretical framework to evaluate the relationship between architecture of the interaction networks and the impact of perturbations by studying localization, a measure describing the ability of the perturbation to propagate through the network. We show that mutualistic ecological communities are localized, and localization reduces perturbation propagation and attenuates its impact on species abundance. Localization depends on the topology of the interaction networks, and it positively correlates with the variance of the weighted degree distribution, a signature of the network topological hetereogenity. Our results provide a different perspective on the interplay between the architecture of interaction networks in mutualistic communities and their stability.

scholarly journals Investigating the impact of atmospheric stability on thunderstorm outflow winds and turbulence

2018 ◽  
Vol 3 (1) ◽  
pp. 203-219 ◽  
Author(s):  
Patrick Hawbecker ◽  
Sukanta Basu ◽  
Lance Manuel
Keyword(s):  
Large Scale ◽  
Atmospheric Stability ◽  
Temperature Inversion ◽  
Ring Vortex ◽  
Large Eddy Simulation Model ◽  
Eddy Simulation ◽  
Large Scale Flow ◽  
The Stability ◽  
Thunderstorm Outflow ◽  
The Impact

Abstract. Downburst events initialized at various hours during the evening transition (ET) period are simulated to determine the effects of ambient stability on the outflow of downburst winds. The simulations are performed using a pseudo-spectral large eddy simulation model at high resolution to capture both the large-scale flow and turbulence characteristics of downburst winds. First, a simulation of the ET is performed to generate realistic initial and boundary conditions for the subsequent downburst simulations. At each hour in the ET, an ensemble of downburst simulations is initialized separately from the ET simulation in which an elevated cooling source within the model domain generates negatively buoyant air to mimic downburst formation. The simulations show that while the stability regime changes, the ensemble mean of the peak wind speed remains fairly constant (between 35 and 38 m s−1) and occurs at the lowest model level for each simulation. However, there is a slight increase in intensity and decrease in the spread of the maximum outflow winds as stability increases as well as an increase in the duration over which these strongest winds persist. This appears to be due to the enhanced maintenance of the ring vortex that results from the low-level temperature inversion, increased ambient shear, and a lack of turbulence within the stable cases. Coherent turbulent kinetic energy and wavelet spectral analysis generally show increased energy in the convective cases and that energy increases across all scales as the downburst passes.

scholarly journals From giant clumps to clouds – I. The impact of gas fraction evolution on the stability of galactic discs

2021 ◽  
Vol 508 (1) ◽  
pp. 352-370
Author(s):  
Florent Renaud ◽  
Alessandro B Romeo ◽  
Oscar Agertz
Keyword(s):  
Large Scale ◽  
Molecular Gas ◽  
Stellar Component ◽  
Main Driver ◽  
Spiral Structures ◽  
The Stability ◽  
Stability Regime ◽  
The Impact ◽  
Gas Fractions ◽  
Disc Galaxies

ABSTRACT The morphology of gas-rich disc galaxies at redshift $\sim 1\!-\!3$ is dominated by a few massive clumps. The process of formation or assembly of these clumps and their relation to molecular clouds in contemporary spiral galaxies are still unknown. Using simulations of isolated disc galaxies, we study how the structure of the interstellar medium and the stability regime of the discs change when varying the gas fraction. In all galaxies, the stellar component is the main driver of instabilities. However, the molecular gas plays a non-negligible role in the interclump medium of gas-rich cases, and thus in the assembly of the massive clumps. At scales smaller than a few 100 pc, the Toomre-like disc instabilities are replaced by another regime, especially in the gas-rich galaxies. We find that galaxies at low gas fraction (10 per cent) stand apart from discs with more gas, which all share similar properties in virtually all aspects we explore. For gas fractions below $\approx 20{{\ \rm per\ cent}}$, the clump-scale regime of instabilities disappears, leaving only the large-scale disc-driven regime. Associating the change of gas fraction to the cosmic evolution of galaxies, this transition marks the end of the clumpy phase of disc galaxies, and allows for the onset of spiral structures, as commonly found in the local Universe.

scholarly journals Transmission Dynamics of Resistant Bacteria in a Predator-Prey System

2015 ◽  
Vol 2015 ◽  
pp. 1-12
Author(s):  
Xubin Gao ◽  
Qiuhui Pan ◽  
Mingfeng He
Keyword(s):  
Human Health ◽  
Large Scale ◽  
Equilibrium Points ◽  
Predation Rate ◽  
Resistant Bacteria ◽  
Mathematical Methods ◽  
Predator Prey ◽  
Prey System ◽  
The Stability ◽  
The Impact

This paper discusses the impact on human health caused by the addition of antibiotics in the feed of food animals. We use the established transmission rule of resistant bacteria and combine it with a predator-prey system to determine a differential equations model. The equations have three steady equilibrium points corresponding to three population dynamics states under the influence of resistant bacteria. In order to quantitatively analyze the stability of the equilibrium points, we focused on the basic reproduction numbers. Then, both the local and global stability of the equilibrium points were quantitatively analyzed by using essential mathematical methods. Numerical results are provided to relate our model properties to some interesting biological cases. Finally, we discuss the effect of the two main parameters of the model, the proportion of antibiotics added to feed and the predation rate, and estimate the human health impacts related to the amount of feed antibiotics used. We further propose an approach for the prevention of the large-scale spread of resistant bacteria and illustrate the necessity of controlling the amount of in-feed antibiotics used.

scholarly journals Land Tenure and Green Production Behavior: Empirical Analysis Based on Fertilizer Use by Cotton Farmers in China

2021 ◽  
Vol 18 (9) ◽  
pp. 4677
Author(s):  
Hui Mao ◽  
Yujia Chai ◽  
Shaojian Chen
Keyword(s):  
Land Tenure ◽  
Large Scale ◽  
Land Rights ◽  
Chinese Government ◽  
Fertilizer Use ◽  
Green Production ◽  
Production Behavior ◽  
Cotton Farmers ◽  
The Stability ◽  
The Impact

Stable land rights can increase farmers’ expectations regarding the future and encourage their adoption of green production methods, which is an important guarantee for promoting the development of green agriculture development. This paper takes the fertilizer use as an example and systematically investigated the impact of land tenure stability on the green production behavior of heterogeneous farmers based on a field survey data of 349 cotton-planting farmers from Xinjiang, China. Furthermore, this research aims to assess the differential impact of land tenure stability on different risk preferences, organizational forms and ethnic groups. This study is a continuation of previous studies on factors influencing green production behavior. The results show that land transfers have an inhibiting effect on farmers’ green production behavior and this effect is more significant among risk-averse farmers, local farmers and minority nationalities farmers. The land tenure period can promote the green production of farmers and alleviate the restraining effect of land transfers on farmers’ green production behavior. Additionally, farmers of Xinjiang Production and Construction Corps (XPCC) and large-scale households are more inclined to green production. The Chinese Government needs to further promote land transfer to large-scale households, improve the stability of land rights and adopt differentiated policies for heterogeneous farmers to encourage their green production.

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