Multivariate comparison of trophic networks of grassland ecosystems

2016 ◽  
Vol 27 (1-2) ◽  
pp. 49-71 ◽  
Author(s):  
O. Y. Buzhdygan ◽  
S. S. Rudenko
Keyword(s):  
Indirect Effects ◽  
Network Size ◽  
Total System ◽  
Scale Invariant ◽  
Trophic Networks ◽  
Grassland Ecosystems ◽  
Link Density ◽  
Developmental Capacity ◽  
Network Properties ◽  
Highly Correlated

This article compares 13 network properties of food webs of 31 Ukrainian grasslands. The properties are: network size N, trophic link number L, trophic classes Cl, system connectance C, link density LD, total system throughflow TST, network cycling FCI, ascendency AS, developmental capacity DC, indirect effects dominance IE, system aggradation AI, system synergism SI, and mutualism MI. Our results show these properties are highly correlated and can be aggregated into the three latent factors. The first factor includes N, TST, AS, DC, SI, L, and LD, where network size N appears to be a central defining variable. The second latent factor includes FCI, AI, and Cl, and is driven by indirect effects dominance IE.  The third factor includes mutualism MI and connectance C, the last being the driving variable. Network Synergism SI is negatively correlated with the other network properties, while all others are positively intercorrelated. Network connectance appears to be a scale invariant property, while link density is highly sensitive to network size. Our data also show that network mutualism MI is more tied to the network complexity than simply to system scale or number of feeding links.

scholarly journals Topological complexity of frictional interfaces: friction networks

2012 ◽  
Vol 19 (2) ◽  
pp. 215-225 ◽  
Author(s):  
H. O. Ghaffari ◽  
R. P. Young
Keyword(s):  
Topological Complexity ◽  
Type Ii ◽  
Stored Energy ◽  
Fracture Permeability ◽  
Radiated Energy ◽  
Universal Power Law ◽  
Shear Rupture ◽  
Crack Type ◽  
Network Properties ◽  
Highly Correlated

Abstract. Through research conducted in this study, a network approach to the correlation patterns of void spaces in rough fractures (crack type II) was developed. We characterized friction networks with several networks characteristics. The correlation among network properties with the fracture permeability is the result of friction networks. The revealed hubs in the complex aperture networks confirmed the importance of highly correlated groups to conduct the highlighted features of the dynamical aperture field. We found that there is a universal power law between the nodes' degree and motifs frequency (for triangles it reads T(k) ∝ kβ (β ≈ 2 ± 0.3)). The investigation of localization effects on eigenvectors shows a remarkable difference in parallel and perpendicular aperture patches. Furthermore, we estimate the rate of stored energy in asperities so that we found that the rate of radiated energy is higher in parallel friction networks than it is in transverse directions. The final part of our research highlights 4 point sub-graph distribution and its correlation with fluid flow. For shear rupture, we observed a similar trend in sub-graph distribution, resulting from parallel and transversal aperture profiles (a superfamily phenomenon).

scholarly journals Towards resolving the phosphorus chaos created by food systems

AMBIO ◽  
2019 ◽  
Vol 49 (5) ◽  
pp. 1076-1089 ◽  
Author(s):  
Paul J. A. Withers ◽  
Kirsty G. Forber ◽  
Christopher Lyon ◽  
Shane Rothwell ◽  
Donnacha G. Doody ◽  
...  
Keyword(s):  
Value Chain ◽  
Food Systems ◽  
Regional Governance ◽  
Total System ◽  
P Efficiency ◽  
Sustainable Food Systems ◽  
Sustainable Food ◽  
System P ◽  
Chaotic Distribution ◽  
Highly Correlated

Abstract The chaotic distribution and dispersal of phosphorus (P) used in food systems (defined here as disorderly disruptions to the P cycle) is harming our environment beyond acceptable limits. An analysis of P stores and flows across Europe in 2005 showed that high fertiliser P inputs relative to productive outputs was driving low system P efficiency (38 % overall). Regional P imbalance (P surplus) and system P losses were highly correlated to total system P inputs and animal densities, causing unnecessary P accumulation in soils and rivers. Reducing regional P surpluses to zero increased system P efficiency (+ 16 %) and decreased total P losses by 35 %, but required a reduction in system P inputs of ca. 40 %, largely as fertiliser. We discuss transdisciplinary and transformative solutions that tackle the P chaos by collective stakeholder actions across the entire food value chain. Lowering system P demand and better regional governance of P resources appear necessary for more efficient and sustainable food systems.

scholarly journals Modelling community formation driven by the status of individual in a society

2017 ◽  
Vol 5 (6) ◽  
pp. 817-838 ◽  
Author(s):  
Jan E Snellman ◽  
Gerardo Iñiguez ◽  
Tzipe Govezensky ◽  
R A Barrio ◽  
Kimmo K Kaski
Keyword(s):  
Social Status ◽  
Network Size ◽  
Community Formation ◽  
Human Society ◽  
Agent Based ◽  
The Social ◽  
The Status ◽  
Network Properties ◽  
Willingness To Compete ◽  
New Strategies

Abstract In human societies, people’s willingness to compete and strive for better social status, as well as being envious of those perceived in some way superior, lead to social structures that are intrinsically hierarchical. Here, we propose an agent-based, network model to mimic the ranking behaviour of individuals and its possible repercussions in human society. The main ingredient of the model is the assumption that the relevant feature of social interactions is each individual’s keenness to maximize his or her status relative to others. The social networks produced by the model are homophilous and assortative, as frequently observed in human communities, and most of the network properties seem quite independent of its size. However, we see that for a small number of agents the resulting network consists of disjoint weakly connected communities, while being highly assortative and homophilic. On the other hand, larger networks turn out to be more cohesive with larger communities but less homophilic. We find that the reason for these changes is that larger network size allows agents to use new strategies for maximizing their social status, allowing for more diverse links between them.

scholarly journals Topological Properties of Network of Global Currency Exchange Rates

2020 ◽  
Vol 8 (5) ◽  
pp. 5450-5459
Keyword(s):  
Exchange Rates ◽  
Portfolio Management ◽  
Geographical Location ◽  
Centrality Measures ◽  
Crisis Period ◽  
Currency Exchange ◽  
Rolling Window ◽  
Before And After ◽  
Network Properties ◽  
Highly Correlated

We study time series of exchange rates of 37 global currencies expressed in terms of US dollars. We take US dollar is as the base currency because it is one of dominant currencies, which is used almost in 66 countries as their currency. The average volatility is computed from returns using overlapped rolling window technique. To study the effects of crisis on the structure and dynamics, we consider three sub periods; before crisis, during crisis and after crisis. Different statistical properties and network properties in three sub periods. From analysis of currency network at different thresholds, we find change in the structure of network in the period of crisis. We find the highly correlated and weakly correlated currencies in the calm and crisis period using threshold networks, which can help the investors in portfolio management. The group of most correlated currencies in the crisis period is different from that in before and after crisis period. Different centrality measures can differentiate the currencies according to their geographical location.

Resource availability influences global social network properties in Gunnison’s prairie dogs (Cynomys gunnisoni)

Behaviour ◽  
2021 ◽  
pp. 1-18
Author(s):  
Ferenc Jordán ◽  
Bálint Kovács ◽  
Jennifer L. Verdolin
Keyword(s):  
Social Network ◽  
Group Dynamics ◽  
Resource Availability ◽  
Network Size ◽  
Prairie Dogs ◽  
Word Index ◽  
Cynomys Gunnisoni ◽  
Network Connectedness ◽  
Network Properties ◽  
Gunnison's Prairie Dogs

Abstract Increasingly we are discovering that the interactions between individuals within social groups can be quite complex and flexible. Social network analysis offers a toolkit to describe and quantify social structure, the patterns we observe, and evaluate the social and environmental factors that shape group dynamics. Here, we used 14 Gunnison’s prairie dogs networks to evaluate how resource availability and network size influenced four global properties of the networks (centralization, clustering, average path length, small word index). Our results suggest a positive correlation between overall network cohesion and resource availability, such that networks became less centralized and cliquish as biomass/m2 availability decreased. We also discovered that network size modulates the link between social interactions and resource availability and is consistent with a more ‘decentralized’ group. This study highlights the importance of how individuals modify social cohesions and network connectedness as a way to reduce intragroup competition under different ecological conditions.

scholarly journals Metapopulation stability in branching river networks

2018 ◽  
Vol 115 (26) ◽  
pp. E5963-E5969 ◽  
Author(s):  
Akira Terui ◽  
Nobuo Ishiyama ◽  
Hirokazu Urabe ◽  
Satoru Ono ◽  
Jacques C. Finlay ◽  
...  
Keyword(s):  
Environmental Changes ◽  
Strong Association ◽  
Network Size ◽  
Population Diversity ◽  
River Networks ◽  
Emergent Properties ◽  
2D Systems ◽  
Scale Invariant ◽  
Ecosystem Size ◽  
Theoretical Predictions

Intraspecific population diversity (specifically, spatial asynchrony of population dynamics) is an essential component of metapopulation stability and persistence in nature. In 2D systems, theory predicts that metapopulation stability should increase with ecosystem size (or habitat network size): Larger ecosystems will harbor more diverse subpopulations with more stable aggregate dynamics. However, current theories developed in simplified landscapes may be inadequate to predict emergent properties of branching ecosystems, an overlooked but widespread habitat geometry. Here, we combine theory and analyses of a unique long-term dataset to show that a scale-invariant characteristic of fractal river networks, branching complexity (measured as branching probability), stabilizes watershed metapopulations. In riverine systems, each branch (i.e., tributary) exhibits distinctive ecological dynamics, and confluences serve as “merging” points of those branches. Hence, increased levels of branching complexity should confer a greater likelihood of integrating asynchronous dynamics over the landscape. We theoretically revealed that the stabilizing effect of branching complexity is a consequence of purely probabilistic processes in natural conditions, where within-branch synchrony exceeds among-branch synchrony. Contrary to current theories developed in 2D systems, metapopulation size (a variable closely related to ecosystem size) had vague effects on metapopulation stability. These theoretical predictions were supported by 18-y observations of fish populations across 31 watersheds: Our cross-watershed comparisons revealed consistent stabilizing effects of branching complexity on metapopulations of very different riverine fishes. A strong association between branching complexity and metapopulation stability is likely to be a pervasive feature of branching networks that strongly affects species persistence during rapid environmental changes.

scholarly journals Correlations and path analysis for fruit yield in pepper lines (Capsicum chinense L.)

2018 ◽  
Vol 8 (2) ◽  
pp. 247-255
Author(s):  
Renato Silva Soares ◽  
Hellismar Wakson da Silva ◽  
Willame Dos Santos Candido ◽  
Luís Sérgio Rodrigues Vale
Keyword(s):  
Path Analysis ◽  
Indirect Effects ◽  
Agronomic Traits ◽  
Selection Process ◽  
Selection Index ◽  
High Yield ◽  
Direct Selection ◽  
Direct And Indirect Effects ◽  
Environmental Correlations ◽  
Highly Correlated

Information regarding the correlation between characters are of great importance to simultaneous traits selection in breeding programs. However, quantification and interpretation of the correlations magnitude do not imply in direct and indirect effects. In this context, the path analysis is presented as an alternative and viable tool for the selection process. The objective of this study was to evaluate the phenotypic, genotypic and environmental correlations between eight major agronomic characters in pepper lines (C. chinense L.) and its consequences in direct and indirect effects by path analysis. Eight agronomic traits were assessed under field conditions in 22 C. chinense L lines. According to the results, there is a genetic variability among the evaluated lines, whose yield per plant (PY) and total number of fruits (NF) variables are highly correlated with high direct effect on pepper lines yield. The selection of pepper lines with high yield can be accomplished through direct selection or using a suitable selection index, being advantageous to select lines with other characteristics, such as appropriate scion height and diameter for conducting manual and mechanized harvesting. The use of the constant k is efficient to reduce the variance of path coefficients, providing better estimation of the effects that affects yield.

scholarly journals Influence of Irradiation Temperature on Oxidative and Network Properties of X-Ray Cross-Linked Vitamin E Stabilized UHMWPE for Hip Arthroplasty

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
M. A. Mulliez ◽  
C. Schilling ◽  
T. M. Grupp
Keyword(s):  
Vitamin E ◽  
Room Temperature ◽  
Electron Beam Irradiation ◽  
Elevated Temperatures ◽  
Cross Link ◽  
Oxidation Induction Time ◽  
X Ray ◽  
Link Density ◽  
Network Properties ◽  
Cross Link Density

Previous studies have shown that increased cross-link density, reduced free radicals, and increased antioxidant grafting resulting from electron-beam irradiation at elevated temperatures improved the wear performance and the oxidative stability of vitamin E blended UHMWPE. The current study explores the impact of elevated irradiation temperature on vitamin E blended UHMWPE using X-ray. We hypothesize that the effects of temperature would be similar to those observed after electron-beam irradiation due to the relatively high dose rate of X-rays. Two X-ray doses of 80 and 100 kGy and two irradiation temperatures, that is, room temperature and 100°C were considered. The reference was Vitelene®, a vitamin E stabilized polyethylene cross-linked with 80 kGy by e-beam at 100°C. Oxidation index and oxidation induction time, as well as cross-link density, gel fraction, and trans-vinylene index, were determined, as the oxidative and network properties are decisive for the long-term implant performance. Gel fraction and oxidation induction time were significantly improved subsequently to warm irradiation in comparison with the material irradiated at room temperature. In conclusion, X-ray irradiation at elevated temperatures resulted in an increase of cross-linking and oxidative resistance of vitamin E stabilized polyethylene comparable to those of e-beam irradiated UHMWPE.

The inverted U-shaped relationship between the network profile and the competitive advantage of supply chains

2018 ◽  
Vol 29 (4) ◽  
pp. 1379-1400 ◽  
Author(s):  
Artur Swierczek
Keyword(s):  
Supply Chains ◽  
Competitive Advantage ◽  
Network Size ◽  
Curvilinear Relationship ◽  
Content Type ◽  
Network Profile ◽  
Network Properties ◽  
Multiple Network ◽  
The Relationship ◽  
The Ideal

PurposeThe purpose of this paper is twofold. First, the author aims to explore if there is a curvilinear relationship between the network rent, generated as a combination of the relational performance of two dyads and the network profile of the triadic supply chains. Second, the author seek to recognize the ideal network profile, consisting of the properties at the node and relationship level, that provides the highest network rents, and thus enables to increase the competitive advantage of supply chains.Design/methodology/approachThe paper opted for an exploratory study using a survey of triads forming supply chains. In order to reveal the capability of yielding the network rent in the examined triads, multiple regression analysis with interaction effects was employed. Having confirmed the existence of supernormal profit, the author investigated the relationship between the network rent and the network index. Finally, a cluster analysis was conducted to compare the network profile in the group of triads generating higher network rents with the cluster yielding relatively lower network rents.FindingsThe obtained findings show that a combination of the relational performance of two dyads contributes to generating the network rent, and thus ensures a more favorable competitive position of supply chains. The results of the study also indicate that there is a significant curvilinear, inverted U-shaped relationship between the network profile and the competitive advantage of triadic supply chains. In addition, the following network properties appear to be particularly important for yielding higher network rents: network centrality, betweenness, network density and network size.Originality/valueThe study contributes to the theory by testing if the network rent can be yielded as a combination of the relational performance of two dyads in the triadic supply chains. The research also indicates that there is a curvilinear relationship between the network rent and the network profile of examined supply chains. Moreover, the study also addresses the link between the network profile, consisting of the multiple network properties simultaneously, in relation to the competitive advantage of supply chains.

On Link Density and Network Synchronization in Scale-Free Network

2013 ◽  
Vol 380-384 ◽  
pp. 2276-2279
Author(s):  
Wen Wei Liu ◽  
Dan Wang
Keyword(s):  
Network Size ◽  
Type I ◽  
Type Ii ◽  
Scale Free Network ◽  
Network Synchronization ◽  
Scale Free ◽  
Weighted Networks ◽  
Link Density ◽  
Free Network

The relations between link density and network synchronizability based on scale-free weighted networks is investigated. In this work, it shows that synchronizability of networks Type I decrease along with the increases of link density, when the netwrok size is fixed. While the synchronizability of networks Type II is remarkable decreased by enhancing the link density with different network size.

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