Search results for "Stability."
showing 10 items of 3015 documents
Resistant Microbial Cooccurrence Patterns Inferred by Network Topology
2015
ABSTRACT Although complex cooccurrence patterns have been described for microbes in natural communities, these patterns have scarcely been interpreted in the context of ecosystem functioning and stability. Here we constructed networks from species cooccurrences between pairs of microorganisms which were extracted from five individual aquatic time series, including a dystrophic and a eutrophic lake as well as an open ocean site. The resulting networks exhibited higher clustering coefficients, shorter path lengths, and higher average node degrees and levels of betweenness than those of random networks. Moreover, simulations demonstrated that taxa with a large number of cooccurrences and place…
Revisiting the role of top-down and bottom-up controls in stabilisation of nutrient-rich plankton communities
2019
Understanding the conditions for successful control of phytoplankton by zooplankton in eutrophic ecosystems is a highly important research area with a wide implementation of mathematical modelling. Theoretical models generally predict destabilisation of food webs in eutrophic environments with large-amplitude oscillations of population densities which would eventually result in species extinction. On the other hand, these theoretical predic- tions are often at odds with ecological observations demonstrating stable dynamics even for a high nutrient load. This apparent discrepancy is known in the literature as Rosen- zweig’s “paradox of enrichment”. Recent theoretical works emphasize a crucia…
Genomic signatures of recent adaptation in a wild bumblebee
2021
AbstractBehavioral experiments and analyses of observation records have shown that environmental changes threaten insect pollinators, creating risks for agriculture and ecosystem stability. Despite their importance, we know little about how wild insects or other animals can adapt in response to environmental pressures. To understand the genomic bases of adaptation in an ecologically important pollinator, we analyzed genomes ofBombus terrestrisbumblebees collected across Great Britain. We reveal extensive genetic diversity within this population, and strong signatures of recent adaptation throughout the genome. More specifically, we find that selection recently affected key processes underpi…
Re-Emerging Vaccine-Preventable Diseases in War-Affected Peoples of the Eastern Mediterranean Region—An Update
2017
For the past few decades, the Eastern Mediterranean Region has been one area of the world profoundly shaped by war and political instability. On-going conflict and destruction have left the region struggling with innumerable health concerns that have claimed the lives of many. Wars, and the chaos they leave behind, often provide the optimal conditions for the growth and re-emergence of communicable diseases. In this article, we will highlight three of the major re-emerging vaccine preventable diseases cholera, measles, and polio, in four countries of the Eastern Mediterranean Region that are currently affected by war leading to a migration crisis: Iraq, South Sudan, Syria, and Yemen. The re…
An Ecology and Economy Coupling Model. A global stationary state model for a sustainable economy in the Hamiltonian formalism
2020
Abstract The severity of the two deeply correlated crises, the environmental and the economic ones, needs to be faced also in theoretical terms; thus, the authors propose a model yielding a global “stationary state”, following the idea of a “steady-state economics” by Georgescu-Rogen and Herman Daly, by constructing only one dynamical system of ecological and economic coupled variables. This is possible resorting to the generalized Volterra model, that, translated in the Hamiltonian formalism and its Hamilton equations, makes possible to “conjugate” every pair of variables, one economic, the other one ecological, in describing the behavior in time of a unique dynamical system. Applying the …
Asset price dynamics in a “bull and bear market”
2021
Abstract We generalize an existing asset market model with heterogenous agents. In particular, we consider the case in which no-trade and low-trade intervals of chartists and fundamentalists respectively are not congruent. Thus we model chartist and fundamentalists who respond to asset prices in agent-specific neighborhoods around the fundamental value with different trade intensities. The resulting asset price dynamics is generated by a one-dimensional 5-piece linear map with discontinuities. Our analysis of this map focusses on coexisting price equilibria. Conditions for their existence and stability are determined analytically. By visualizing the results we allow for a basic bifurcation …
Bank fragility and contagion: Evidence from the bank CDS market
2016
Understanding how contagion works among financial institutions is a top priority for regulators and policy makers who aim to foster financial stability and to prevent financial crises. Using bank credit default swap (CDS) data, we provide a framework for the evaluation of contagion among banks in different countries and regions during a period of prolonged financial distress. We measure contagion in terms of return spillovers, following a Generalized VAR (GVAR) approach. In addition, we propose an innovative framework to distinguish between two types of contagion: systematic (linked to global factors), and idiosyncratic (linked to bank specific factors). We find evidence of both types of co…
Investment–productivity dynamics and distribution dynamics in a multisector economy: some theory and an application to Italian regions
2003
Abstract In this paper, we study the investment–productivity dynamics in the Framework Space, presented by Bohm and Punzo [Cycles, Growth and Structural Change, Routledge, London (2001) 47], as the distribution dynamics of the production sectors of an economy. We apply such theoretical framework to data from Italian regions to identify differences in sectoral behaviors both within and across regions. Our main findings are: sectors within a region generally follow different regime dynamics; Southern Italian regions are generally characterized by higher degrees of heterogeneity in sectoral growth behaviors and of regime instability. Also, we find support to the hypothesis of a positive relati…
Spillovers through banking centers: a panel data analysis of bank flows
2003
Abstract This paper presents evidence that spillovers through bank lending contributed to the transmission of currency crises during the recent episodes of financial instability in emerging markets. The innovation of the paper is that it looks beyond aggregated measures of contagion into the structure of bank flows, disaggregating by banking centers. The main findings are that spillovers caused by banks’ exposures to a crisis country help predict flows in third countries after the Mexican and Asian crises, but not after the Russian crisis. In the latter, there is evidence of a generalized outflow from emerging markets. The importance of spillovers through banking centers suggests that count…
The Role of Capital and Liquidity in Bank Lending: Are Banks Safer?
2020
The aim of this paper is to examine whether and to what extent bank capital requirements and liquidity standards influence the level of bank stability. Our approach is that both capital and liquidity affect lending growth, which in turn affects bank stability. We construct a panel dataset on a sample of 2,054 commercial banks from 117 developed and developing countries during the 2000–16 period. By applying a two-stage least squares (2SLS) empirical methodology, our findings show that capital and liquidity have a negative direct impact on the level of bank stability. However, this influence is counteracted by an indirect positive effect through the increased level of credit. Our results are…