scholarly journals Interaction strength and extinction risk in a metacommunity

2005 ◽  
Vol 272 (1572) ◽  
pp. 1571-1576 ◽  
Author(s):  
Frédéric Guichard
Keyword(s):  
Species Interactions ◽  
Large Scale ◽  
Extinction Risk ◽  
Interaction Strength ◽  
Community Stability ◽  
Scale Invariant ◽  
Regional Stability ◽  
Regional Community ◽  
The Stability

Species interactions and connectivity are both central to explaining the stability of ecological communities and the problem of species extinction. Yet, the role of species interactions for the stability of spatially subdivided communities still eludes ecologists. Ecological models currently address the problem of stability by exploring the role of interaction strength in well mixed habitats, or of connectivity in subdivided communities. Here I propose a unification of interaction strength and connectivity as mechanisms explaining regional community stability. I introduce a metacommunity model based on succession dynamics in coastal ecosystems, incorporating limited dispersal and facilitative interactions. I report a sharp transition in regional stability and extinction probability at intermediate interaction strength, shown to correspond to a phase transition that generates scale-invariant distribution and high regional stability. In contrast with previous studies, stability results from intermediate interaction strength only in subdivided communities, and is associated with large-scale (scale-invariant) synchrony. These results can be generalized to other systems exhibiting phase transitions to show how local interaction strength can be used to resolve the link between regional community stability and pattern formation.

scholarly journals Feasibility and coexistence of large ecological communities

2017 ◽  
Vol 8 (1) ◽  
Author(s):  
Jacopo Grilli ◽  
Matteo Adorisio ◽  
Samir Suweis ◽  
György Barabás ◽  
Jayanth R. Banavar ◽  
...  
Keyword(s):  
Asymptotic Stability ◽  
Species Interactions ◽  
Ecological Communities ◽  
Ecological Network ◽  
Small Perturbations ◽  
Local Asymptotic Stability ◽  
Species Abundances ◽  
The Stability ◽  
Empirical Networks

Abstract The role of species interactions in controlling the interplay between the stability of ecosystems and their biodiversity is still not well understood. The ability of ecological communities to recover after small perturbations of the species abundances (local asymptotic stability) has been well studied, whereas the likelihood of a community to persist when the conditions change (structural stability) has received much less attention. Our goal is to understand the effects of diversity, interaction strengths and ecological network structure on the volume of parameter space leading to feasible equilibria. We develop a geometrical framework to study the range of conditions necessary for feasible coexistence. We show that feasibility is determined by few quantities describing the interactions, yielding a nontrivial complexity–feasibility relationship. Analysing more than 100 empirical networks, we show that the range of coexistence conditions in mutualistic systems can be analytically predicted. Finally, we characterize the geometric shape of the feasibility domain, thereby identifying the direction of perturbations that are more likely to cause extinctions.

scholarly journals Exploring the role of lexis and grammar for the stable identification of register in an unrestricted corpus of web documents

2021 ◽  
Author(s):  
Veronika Laippala ◽  
Jesse Egbert ◽  
Douglas Biber ◽  
Aki-Juhani Kyröläinen
Keyword(s):  
Large Scale ◽  
Classification Performance ◽  
News Article ◽  
Automatic Identification ◽  
Linguistic Features ◽  
Online Data ◽  
Web Documents ◽  
Essential Information ◽  
The Stability

AbstractThe Internet offers great possibilities for many scientific disciplines that utilize text data. However, the potential of online data can be limited by the lack of information on the genre or register of the documents, as register—whether a text is, e.g., a news article or a recipe—is arguably the most important predictor of linguistic variation (see Biber in Corpus Linguist Linguist Theory 8:9–37, 2012). Despite having received significant attention in recent years, the modeling of online registers has faced a number of challenges, and previous studies have presented contradictory results. In particular, these have concerned (1) the extent to which registers can be automatically identified in a large, unrestricted corpus of web documents and (2) the stability of the models, specifically the kinds of linguistic features that achieve the best performance while reflecting the registers instead of corpus idiosyncrasies. Furthermore, although the linguistic properties of registers vary importantly in a number of ways that may affect their modeling, this variation is often bypassed. In this article, we tackle these issues. We model online registers in the largest available corpus of online registers, the Corpus of Online Registers of English (CORE). Additionally, we evaluate the stability of the models towards corpus idiosyncrasies, analyze the role of different linguistic features in them, and examine how individual registers differ in these two aspects. We show that (1) competitive classification performance on a large-scale, unrestricted corpus can be achieved through a combination of lexico-grammatical features, (2) the inclusion of grammatical information improves the stability of the model, whereas many of the previously best-performing feature sets are less stable, and that (3) registers can be placed in a continuum based on the discriminative importance of lexis and grammar. These register-specific characteristics can explain the variation observed in previous studies concerning the automatic identification of online registers and the importance of different linguistic features for them. Thus, our results offer explanations for the jungle-likeness of online data and provide essential information on online registers for all studies using online data.

Community Dynamics and Stability

2013 ◽  
Author(s):  
Eric Post
Keyword(s):  
Community Composition ◽  
Species Interactions ◽  
Community Dynamics ◽  
Species Coexistence ◽  
Environmental Variability ◽  
Climatic Variability ◽  
Self Regulation ◽  
Community Stability ◽  
Biological Communities ◽  
The Stability

This chapter explores the implications of climate change for community composition, dynamics, and stability. It also looks at further examples in which climatic variability mediates interactions among species, in some cases degrading community stability and in other cases promoting it. Ecological theory offers contrasting predictions regarding the consequences for species coexistence and community stability of environmental variability. For instance, short-term instabilities in community composition owing to, for example, high-frequency environmental disturbance may promote the long-term coexistence of species by preventing competitive exclusion of one species by another. Other work suggests, however, that the stability of biological communities in stochastic environments is only possible if there is sufficiently strong self-regulation at one or more trophic levels, or if self-regulation is strong while species interactions are weak, because environmental erosion of population stability at one trophic level may contribute to instability of the community as a whole.

scholarly journals Metabolic analysis of a bacterial synthetic community from maize roots provides new mechanistic insights into microbiome stability

2021 ◽  
Author(s):  
Jenna Krumbach ◽  
Patrizia Kroll ◽  
Vera Wewer ◽  
Sabine Metzger ◽  
Till Ischebeck ◽  
...  
Keyword(s):  
Community Diversity ◽  
Individual Member ◽  
Community Stability ◽  
Maize Roots ◽  
Carbon Substrates ◽  
Poor Understanding ◽  
The Stability ◽  
The Individual ◽  
B Vitamin

Stability is a desirable property for agricultural microbiomes, but there is a poor understanding of the mechanisms that mediate microbial community stability. Recently, a representative bacterial synthetic community from maize roots has been proposed as a model system to study microbiome stability (Niu 2017, PNAS, 114:E2450). This SynCom assembles stably when all seven members are present, but community diversity collapses without the keystone E. cloacae strain. The aim of this study was to assess the role of metabolites for the stability of this SynCom, by defining the metabolic niches occupied by each strain, as well as their cross-feeding phenotypes and B-vitamin dependencies. We show that the individual member strains occupy complementary metabolic niches, measured by the depletion of distinct metabolites in exometabolomic experiments, as well as contrasting growth phenotypes on diverse carbon substrates. Minimal medium experiments show that the established seven-member community comprises a mixture of prototrophic and auxotrophic strains. Correspondingly, experimental cross-feeding phenotypes showed that spent media harvested from the prototrophic strains can sustain growth of two auxotrophs. We suggest that the metabolic mechanisms exhibited by this SynCom could serve as design principles to inform the rational assembly of stable plant-associated microbial communities.

scholarly journals Role of India in Rohingya Crisis: Humanitarian Role and Geopolitical Interest

2021 ◽  
Vol 9 (2) ◽  
pp. 59-66
Author(s):  
Farzana Al Ferdous
Keyword(s):  
Large Scale ◽  
Minority Groups ◽  
Humanitarian Crisis ◽  
Regional Stability ◽  
Peace And Conflict ◽  
Neighbor Country ◽  
The Government ◽  
Military Posts ◽  
Peace And Conflict Resolution

Globally considered one of the most persecuted minority groups, the Rohingyas are a predominantly Muslim ethnic group in northern Rakhine who have fled Myanmar in a large-scale exodus since August 2017. More than 700,000 refugees fled to Bangladesh after a military crackdown on Rohingyas last August, following the Arakan Rohingya Salvation Army’s attack on Myanmar’s military posts. This massive refugee outflow of Rohingya Muslims from Myanmar into Bangladesh has created a humanitarian crisis that carries implications on regional stability and security and also outrage among the international community. As a neighbor country, Bangladesh expects India’s respond promptly to support the government. This paper briefly examines India’s approach towards the Roh-ingya crisis and explores ways for India through its role in humanitarian and geopolitical including diplomatic, domestic political compulsions, security and economic interest. It also analyses India’s response to the Rohingya crisis focusing on India-Myanmar relations and also India’s need to counter China’s growing influence in its neighborhood. The paper also argues that as a neighbor friend and partner of Bangladesh, the role of India in Rohingya crisis has become a global expectation for peace and conflict resolution.

scholarly journals Wavelength-encoded laser particles for massively-multiplexed cell tagging

2018 ◽  
Author(s):  
Nicola Martino ◽  
Sheldon J.J. Kwok ◽  
Andreas C. Liapis ◽  
Sarah Forward ◽  
Hoon Jang ◽  
...  
Keyword(s):  
Single Cell ◽  
Large Scale ◽  
Tumor Model ◽  
Single Mode ◽  
Cellular Heterogeneity ◽  
Imaging Probes ◽  
Cell Groups ◽  
The Stability

Large-scale single-cell analyses have become increasingly important given the role of cellular heterogeneity in complex biological systems. However, no current techniques enable optical imaging of uniquely-tagged individual cells. Fluorescence-based approaches can only distinguish a handful of distinct cells or cell groups at a time because of spectral crosstalk between conventional fluorophores. Here we show a novel class of imaging probes emitting coherent laser light, called laser particles. Made of silica-coated semiconductor microcavities, these laser particles have single-mode emission over a broad range from 1170 to 1580 nm with sub-nm linewidths, enabling massive spectral multiplexing. We demonstrate the stability and biocompatibility of these probes in vitro and their utility for wavelength-multiplexed cell tagging and imaging. We demonstrate real-time tracking of thousands of individual cells in a 3D tumor model for several days showing different behavioral phenotypes. We expect laser particles will enable new approaches for single-cell analyses.

The Role of Sense of Direction and Other Factors During Navigation in a Large-Scale, Unconstrained Environment

2013 ◽  
Author(s):  
Elisabeth J. Ploran ◽  
Ericka Rovira ◽  
James C. Thompson ◽  
Raja Parasuraman
Keyword(s):  
Large Scale ◽  
Sense Of Direction

A Statistical Study of Process Variables to Optimize a High Speed Curtain Coater: Part I

TAPPI Journal ◽  
2009 ◽  
Vol 8 (1) ◽  
pp. 20-26 ◽  
Author(s):  
PEEYUSH TRIPATHI ◽  
MARGARET JOYCE ◽  
PAUL D. FLEMING ◽  
MASAHIRO SUGIHARA
Keyword(s):  
Boundary Layer ◽  
Experimental Design ◽  
High Speed ◽  
Statistical Study ◽  
Process Variables ◽  
High Speeds ◽  
The Stability ◽  
Air Removal ◽  
Removal System

Using an experimental design approach, researchers altered process parameters and material prop-erties to stabilize the curtain of a pilot curtain coater at high speeds. Part I of this paper identifies the four significant variables that influence curtain stability. The boundary layer air removal system was critical to the stability of the curtain and base sheet roughness was found to be very important. A shear thinning coating rheology and higher curtain heights improved the curtain stability at high speeds. The sizing of the base sheet affected coverage and cur-tain stability because of its effect on base sheet wettability. The role of surfactant was inconclusive. Part II of this paper will report on further optimization of curtain stability with these four variables using a D-optimal partial-facto-rial design.

Magnetic Properties of xCeO2•(50 − x) PbO•50B2O3 Glasses and Glass Ceramics

2017 ◽  
Vol 13 (1) ◽  
pp. 4486-4494 ◽  
Author(s):  
G.El Damrawi ◽  
F. Gharghar
Keyword(s):  
Magnetic Properties ◽  
Large Scale ◽  
Glass Ceramics ◽  
Magnetic Behavior ◽  
Crystal Formation ◽  
Dual Roles ◽  
Effective Agent ◽  
Ordered Structures ◽  
Essential Change

Cerium oxide in borate glasses of composition xCeO2·(50 − x)PbO·50B2O3 plays an important role in changing both microstructure and magnetic behaviors of the system. The structural role of CeO2 as an effective agent for cluster and crystal formation in borate network is clearly evidenced by XRD technique. Both structure and size of well-formed cerium separated clusters have an effective influence on the structural properties. The cluster aggregations are documented to be found in different range ordered structures, intermediate and long range orders are the most structures in which cerium phases are involved. The nano-sized crystallized cerium species in lead borate phase are evidenced to have magnetic behavior.  The criteria of building new specific borate phase enriched with cerium as ferrimagnetism has been found to keep the magnetization in large scale even at extremely high temperature. Treating the glass thermally or exposing it to an effective dose of ionized radiation is evidenced to have an essential change in magnetic properties. Thermal heat treatment for some of investigated materials is observed to play dual roles in the glass matrix. It can not only enhance alignment processes of the magnetic moment but also increases the capacity of the crystallite species in the magnetic phases. On the other hand, reverse processes are remarked under the effect of irradiation. The magnetization was found to be lowered, since several types of the trap centers which are regarded as defective states can be produced by effect of ionized radiation. 

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