scholarly journals The Minimum Environmental Perturbation Principle: A New Perspective on Niche Theory

2019 ◽  
Author(s):  
Robert Marsland ◽  
Wenping Cui ◽  
Pankaj Mehta

Contemporary niche theory is a powerful conceptual framework for understanding how organisms interact with each other and with their shared environment. Here we show that a large segment of niche theory is equivalent to a Minimum Environmental Perturbation Principle (MEPP): ecosystems self-organize into a state that minimizes the impact of organisms on their environment. Different choices of environmental dynamics naturally give rise to distinct dissimilarity measures for quantifying environmental impact. The MEPP allows for the analysis of ecosystems with large numbers of species and environmental factors and provides a new avenue for analyzing ecological invasions. The MEPP also rigorously connects ecological bistability with the existence of multiple minima in a statistical-physics inspired landscapes. We show that the presence of environmental feedbacks where organisms can produce new resources in addition to depleting them violates the global MEPP. However, even in the presence of such feedbacks, a weaker, local version of the MEPP still applies in a limited region of resource space.

2020 ◽  
Vol 196 (3) ◽  
pp. 291-305
Author(s):  
Robert Marsland ◽  
Wenping Cui ◽  
Pankaj Mehta

2015 ◽  
Vol 12 (3) ◽  
pp. 181-192 ◽  
Author(s):  
Pinar Yazgan ◽  
Deniz Eroglu Utku ◽  
Ibrahim Sirkeci

With the growing insurrections in Syria in 2011, an exodus in large numbers have emerged. The turmoil and violence have caused mass migration to destinations both within the region and beyond. The current "refugee crisis" has escalated sharply and its impact is widening from neighbouring countries toward Europe. Today, the Syrian crisis is the major cause for an increase in displacement and the resultant dire humanitarian situation in the region. Since the conflict shows no signs of abating in the near future, there is a constant increase in the number of Syrians fleeing their homes. However, questions on the future impact of the Syrian crisis on the scope and scale of this human mobility are still to be answered. As the impact of the Syrian crisis on host countries increases, so does the demand for the analyses of the needs for development and protection in these countries. In this special issue, we aim to bring together a number of studies examining and discussing human mobility in relation to the Syrian crisis.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Brian J. Johnson ◽  
Amy Robbins ◽  
Narayan Gyawali ◽  
Oselyne Ong ◽  
Joanne Loader ◽  
...  

AbstractKoala populations in many areas of Australia have declined sharply in response to habitat loss, disease and the effects of climate change. Koalas may face further morbidity from endemic mosquito-borne viruses, but the impact of such viruses is currently unknown. Few seroprevalence studies in the wild exist and little is known of the determinants of exposure. Here, we exploited a large, spatially and temporally explicit koala survey to define the intensity of Ross River Virus (RRV) exposure in koalas residing in urban coastal environments in southeast Queensland, Australia. We demonstrate that RRV exposure in koalas is much higher (> 80%) than reported in other sero-surveys and that exposure is uniform across the urban coastal landscape. Uniformity in exposure is related to the presence of the major RRV mosquito vector, Culex annulirostris, and similarities in animal movement, tree use, and age-dependent increases in exposure risk. Elevated exposure ultimately appears to result from the confinement of remaining coastal koala habitat to the edges of permanent wetlands unsuitable for urban development and which produce large numbers of competent mosquito vectors. The results further illustrate that koalas and other RRV-susceptible vertebrates may serve as useful sentinels of human urban exposure in endemic areas.


2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Andoni Garitano-Trojaola ◽  
Ana Sancho ◽  
Ralph Götz ◽  
Patrick Eiring ◽  
Susanne Walz ◽  
...  

AbstractThe presence of FMS-like tyrosine kinase 3-internal tandem duplication (FLT3-ITD) is one of the most frequent mutations in acute myeloid leukemia (AML) and is associated with an unfavorable prognosis. FLT3 inhibitors, such as midostaurin, are used clinically but fail to entirely eradicate FLT3-ITD + AML. This study introduces a new perspective and highlights the impact of RAC1-dependent actin cytoskeleton remodeling on resistance to midostaurin in AML. RAC1 hyperactivation leads resistance via hyperphosphorylation of the positive regulator of actin polymerization N-WASP and antiapoptotic BCL-2. RAC1/N-WASP, through ARP2/3 complex activation, increases the number of actin filaments, cell stiffness and adhesion forces to mesenchymal stromal cells (MSCs) being identified as a biomarker of resistance. Midostaurin resistance can be overcome by a combination of midostaruin, the BCL-2 inhibitor venetoclax and the RAC1 inhibitor Eht1864 in midostaurin-resistant AML cell lines and primary samples, providing the first evidence of a potential new treatment approach to eradicate FLT3-ITD + AML.


2014 ◽  
Vol 3 (2) ◽  
pp. 186-196 ◽  
Author(s):  
Rosa Caiazza ◽  
David Audretsch ◽  
Tiziana Volpe ◽  
Julie Debra Singer

Purpose – Existing work documents the role that institutional setting plays in the process of spin-off creation. However, despite decades of studies, scholars have not clearly explained why some regions are more involved in spin-off activity than others. Drawing from institutional theory, the purpose of this paper is to compare different institutional settings identifying factors affecting the general environment capability to support spin-off activity of a specific region. Design/methodology/approach – The authors utilize a cross-national analysis of American, Asian, and European areas identifying factors affecting their different rate of spin-off activity. This study contributes to the policy debate concerning entrepreneurship and how best to spur spin-off activities. Findings – In this paper, the authors identify the general and specific factors that explain the cross-national diversity in spin-off creation. The authors then perform an analysis of the impact of these factors in various regions of the USA, Asia, and Europe, providing evidence for the necessity of specific combinations of these factors. Originality/value – The paper offers a new perspective on the causes of spin-offs through a cross-national analysis of many areas around the world.


Economica ◽  
2017 ◽  
Vol 85 (337) ◽  
pp. 92-123 ◽  
Author(s):  
Vivien Burrows

2018 ◽  
Vol 120 (3) ◽  
pp. 1-40
Author(s):  
Pascale Benoliel ◽  
Anit Somech

Background/Context Increasingly, educational leadership research has stressed that leadership is not solely embedded in formal roles but often emerges from relationships between individuals. Senior management teams (SMTs) are an important expression of a formal management structure based on the principle of distributed leadership. Such structures may require a reconceptualization of school leadership and the role of the principal in such a way as to better meet new challenges and enable principals to manage SMTs more effectively. Accordingly, it is proposed that to improve effectiveness, principals engage in boundary activities, the principals’ internal activities directed toward the SMT aimed at dealing with internal team matters and the principals’ external activities directed toward external agents in the team's focal environment to acquire resources and protect the team. Purpose/Objective The present study attempts to advance a theoretical model of principals’ internal and external activities toward their SMTs. This study's purpose is twofold: First, the study tries to determine which of the internal and external activities principals engage in more frequently and less frequently and to what extent. Second, the study attempts to determine how these activities are related to the SMT effectiveness outcomes: in-role performance and innovation. Taking on a distributive perspective to school leadership, our goal is to extend our knowledge about the activities that might facilitate SMT effectiveness, by highlighting the principal boundary activities as fundamental. Research Design Quantitative study. Data Collection and Analysis Data were collected from two sources to minimize problems associated with same source bias: 92 SMTs and their principals from 92 public schools in Israel. Principals evaluated the SMTs’ effectiveness through validated surveys of team in-role performance and team innovation, and SMT members evaluated the internal and external activities of the principal. Findings/Results ANOVA analyses indicate significant mean differences between the principal's internal and external activities. Results from Structural Equation Model indicate that internal activities were related to SMT performance, whereas external activities were related to SMT innovation. Conclusions/Recommendations Principals who manage both the internal SMT dynamic by promoting SMT identity and building team trust, while also promoting a common mission, serve the role of coordinator between SMT members and constituencies external to the SMT, enhancing SMT effectiveness. It may be, then, that studying new models of school leadership and management, including the relationship of the principal and the SMT, may deepen our understanding of the increasingly complex role of principals today.


2009 ◽  
Vol 8 (1) ◽  
Author(s):  
Chris Roseveare ◽  

Milestones are often seen as opportunities for reflection and reminiscence. As this edition of the journal coincides with the 10th anniversary of my consultant appointment I hope readers will forgive a couple of paragraphs of self-indulgence. The phrase: ‘Where did all that time go?’ will probably be familiar to physicians at a more advanced stage of their career. With medical students now returning as specialist registrars, and former house officers appearing as consultant colleagues, the passage of time is increasingly apparent. I recently realised that our current third year students were born in the year I clerked my first patient: surprisingly I still remember his name, age and diagnosis, unlike many of those (and all of the students!) who I have seen since. On a more positive note, there have clearly been a lot of changes over these ten years: at the time of my appointment in June 1999 there was just a small handful of ‘acute physicians’ in the UK. SAM meetings attracted barely 100 delegates, despite providing free admission, and most of us had planned our escape route in case the acute medicine concept went ‘belly-up’ before our retirement. Now, with several hundred acute medicine consultants, similar numbers of trainees, and ‘full speciality’ status rapidly approaching, job security should no longer be a major concern. Indeed, the last 12 months has seen a further considerable expansion of the speciality; all of the first cohort of acute medicine trainees in Wessex have secured consultant positions, and I am told that SAM now has close to 700 full members. What the next ten years will bring remains to be seen, but with an ageing population and year-round pressures from rising emergency admissions, acute medicine will surely continue to strengthen. As I indicated last time, an increasing number of research-based submissions will be trickling into the journal over the next few editions. The impact of alcohol on the Health Service is a subject which has been at the top of the political agenda in recent months. So it is timely to include an article highlighting its impact on the Acute Medical intake in a busy Teaching hospital in this edition of the journal. The finding that one-in-five patients admitted to the AMU were considered ‘hazardous’ drinkers will probably come as no surprise to acute physicians working elsewhere in the UK. In fact this figure may have been an under-estimate given that the number of units consumer per week was not documented in 30% of clerking records. The demographic shift away from the stereotype ‘middle-aged male’ drinker is also apparent with large numbers of females aged 40-59 falling into this category. Recent editions of this journal would not seem complete without mention of training in practical procedures. In this issue the SAM trainee representatives have summarised the recent trainee survey in this area, providing some recommendations which will hopefully be incorporated into the new curriculum. Readers who are becoming tired of this subject can be reassured that this should be the final article relating to this for the time being! I hope this edition provides interesting reading and please keep the submissions coming – although the review articles are usually solicited by the editorial team, we will continue to consider any submitted article for publication, provided there is a clear teaching message for those working in the field of Acute Medicine. Any feedback on the articles included in this or previous editions would also be welcome, and may be included in a future ‘viewpoint’ or ‘letters to the editor’ section.


2018 ◽  
Vol 10 (10) ◽  
pp. 3458
Author(s):  
Jingli Li ◽  
Min Zhao ◽  
Guanjun Xia ◽  
Chao Liu

Since no specialized work has researched the relationship between team members’ hometown diversity (team hometown diversity) and team creativity, we investigated their underlying relationship by conducting a two-wave survey from 304 employees in 54 teams and 54 team leaders from 17 companies. The results proved that team hometown diversity was negatively related to both team information exchange and team creativity, while team information exchange was significantly positively associated with team creativity and the mediation effect of team information exchange between team hometown diversity and team creativity was verified. The moderation role of team identification in the relationship between team hometown diversity and team information exchange as well as the moderation function of team conformity on the relationship between team information exchange and team creativity were both verified. This work made at least four contributions. Firstly, it was among the first to research the impact of team hometown diversity on team creativity, which supplemented the gap and provided a new perspective for exploration of team creativity in future. Secondly, we adopted a two-wave design to check the dynamic impact of earlier team information exchange and team conformity on team creativity afterwards, which can be replicated for future studies. Thirdly, by using supervisor and subordinate ratings together and conducting electronic and paper surveys together, the results were more persuasive. Finally, we included a large dataset from a broad range of companies, which maximized the variables and generated our results. The implications and limitations were also illustrated.


Sign in / Sign up

Export Citation Format

Share Document