Gause's exclusion principle revisited: artificial modified species and competition

Gause's principle of competition between two species is studied when one of them is sterile. We study the condition for total extinction in the niche, namely, when the sterile population exterminates the native one by an optimal use of resources. A mathematical Lotka-Volterra non linear model of interaction between a native and sterile species is proposed. The condition for total extinction is related to the initial number $M_{o}$ of sterile individuals released in the niche. In fact, the existence of a critical sterile-population value $M_{c}$ is conjectured from numerical analysis and an analytical estimation is found. When spatial diffusion (migration) is considered a critical size territory is found and, for small territory, total extinction exist in any case. This work is motived by the extermination agriculture problem of fruit flies in our region.Comment: 11 pages. Published in Jour.Phys.A Math.Gen. 33, 4877 (2000

Amplitude dependent frequency, desynchronization, and stabilization in noisy metapopulation dynamics

The enigmatic stability of population oscillations within ecological systems is analyzed. The underlying mechanism is presented in the framework of two interacting species free to migrate between two spatial patches. It is shown that that the combined effects of migration and noise cannot account for the stabilization. The missing ingredient is the dependence of the oscillations' frequency upon their amplitude; with that, noise-induced differences between patches are amplified due to the frequency gradient. Migration among desynchronized regions then stabilizes a "soft" limit cycle in the vicinity of the homogenous manifold. A simple model of diffusively coupled oscillators allows the derivation of quantitative results, like the functional dependence of the desynchronization upon diffusion strength and frequency differences. The oscillations' amplitude is shown to be (almost) noise independent. The results are compared with a numerical integration of the marginally stable Lotka-Volterra equations. An unstable system is extinction-prone for small noise, but stabilizes at larger noise intensity

Field Selection of American Sweetgum Transformed for Herbicide Resistance

One American sweetgum clone from an open-pollinated parent was transformed with Agrobacterium tumefaciens containing the gene for acetolactate synthase (ALS), and regenerated through organogenesis. Seventy independently transformed lines were selected in vitro in the presence of an ALS-targeting herbicide. Containerized ramets of the 70 lines were established at an irrigated fiber farm in South Carolina, in May, 2002. Over 1,000 trees were planted in a completely randomized design with up to 15 ramets per transline. Establishment survival in June was near 100 percent. Two months after planting, the actively growing trees received one over-the-top application of a tank mix of two ALS-targeting herbicides to evaluate resistance in each transformed line. Thirty days following application, over 85 percent of the planted ramets from three lines displayed no damage symptoms. Sixteen additional lines had a mean damage rating less than �slight�. Twelve of these nineteen lines had first-year heights that were not significantly different from the non-sprayed control line. One transformed line was significantly taller than the control clone (103 cm vs 91 cm mean height, respectively). At the end of the year, only 11 of 1,027 individual trees (1 ramet from each of 9 lines and 2 ramets of another line) died due to herbicide damage. Although the test was terminated after only one growing season, at least four lines were sufficiently resistant to be considered for further plantation development.Papers and abstracts from the 27th Southern Forest Tree Improvement Conference held at Oklahoma State University in Stillwater, Oklahoma on June 24-27, 2003

Globally coupled chaotic maps and demographic stochasticity

The affect of demographic stochasticity of a system of globally coupled chaotic maps is considered. A two-step model is studied, where the intra-patch chaotic dynamics is followed by a migration step that coupled all patches; the equilibrium number of agents on each site, $N$, controls the strength of the discreteness-induced fluctuations. For small $N$ (large fluctuations) a period-doubling cascade appears as the coupling (migration) increases. As $N$ grows an extremely slow dynamic emerges, leading to a flow along a one-dimensional family of almost period 2 solutions. This manifold become a true solutions in the deterministic limit. The degeneracy between different attractors that characterizes the clustering phase of the deterministic system is thus the $N \to \infty$ limit of the slow dynamics manifold

Dapagliflozin reduces albuminuria in patients with diabetes and hypertension receiving renin-angiotensin blockers

AIMS: To characterize the effect of dapagliflozin on albuminuria and estimated glomerular filtration rate (eGFR) and to determine whether effects on albuminuria were mediated through changes in glycated haemoblogin (HbA1c), systolic blood pressure (SBP), body weight or eGFR. METHODS: We conducted a post hoc analysis of data pooled from two phase III clinical trials in hypertensive patients with type 2 diabetes (T2DM) on stable angiotensin‐converting enzyme inhibitor or angiotensin receptor blocker therapy, randomly assigned to dapagliflozin 10 mg/day or matched placebo. This analysis included only patients with microalbuminuria or macroalbuminuria at baseline. RESULTS: Patients were randomized to receive dapagliflozin 10 mg (n = 167) or placebo (n = 189). Dapagliflozin resulted in greater 12‐week reductions in albuminuria compared with placebo: −33.2% [95% confidence interval (CI) −45.4, −18.2]. The reduction in albuminuria was also present after adjusting for age, sex and changes in HbA1c, SBP, body weight and eGFR: −23.5% (95% CI −37.6, −6.3). There was a decrease in eGFR with dapagliflozin versus placebo that was readily reversed 1 week after last dose. No serious renal‐related adverse events were observed in any group. CONCLUSIONS: Dapagliflozin was effective in lowering albuminuria in patients with T2DM and hypertension using renin‐angiotensin system blockade therapy. Reductions in albuminuria were still present after adjusting for changes in HbA1c, SBP, body weight and eGFR. Dapagliflozin‐induced improvements in glycaemic control and reductions in SBP, coupled with other potentially beneficial renal effects, may lead to a reduced long‐term renal and cardiovascular risk

A Systemic Approach to Multi-Party Relationship Modeling

Socio-economic systems exist in a wide variety of activity domains and are composed of multiple stakeholder groups. These groups pursue objectives which are often entirely motivated from within their local context. Domain specificities in the form of institutional design, for example the deregulation of Public Utility systems, can further fragment this context. Nevertheless, for these systems to be viable, a management subsystem that maintains a holistic view of the system is required. From a Systems perspective, this highlights the need to invest in methods that capture the interactions between the different stakeholders of the system. It is the understanding of the individual interactions that can help piece together a holistic view of the system thereby enabling system level discourse. In this paper we present a modeling technique that models industry interactions as a multi-party value realization process and takes a Systems approach in analyzing them. Every interaction is analyzed both from outside – system as a black box and from within – system as a white box. The design patterns that emerge from this whole/composite view of value realization provide the necessary foundation to analyze the working of multi-stakeholder systems. An explicit specification of these concepts is presented as Regulation Enabling Ontology, REGENT. As an example, we instantiate REGENT for the urban residential electricity market and demonstrate its effectiveness in identifying the requirements for time-based electricity supply systems

Statistical mechanics of ecological systems: Neutral theory and beyond

The simplest theories often have much merit and many limitations, and, in this vein, the value of neutral theory (NT) of biodiversity has been the subject of much debate over the past 15 years. NT was proposed at the turn of the century by Stephen Hubbell to explain several patterns observed in the organization of ecosystems. Among ecologists, it had a polarizing effect: There were a few ecologists who were enthusiastic, and there were a larger number who firmly opposed it. Physicists and mathematicians, instead, welcomed the theory with excitement. Indeed, NT spawned several theoretical studies that attempted to explain empirical data and predicted trends of quantities that had not yet been studied. While there are a few reviews of NT oriented toward ecologists, the goal here is to review the quantitative aspects of NT and its extensions for physicists who are interested in learning what NT is, what its successes are, and what important problems remain unresolved. Furthermore, this review could also be of interest to theoretical ecologists because many potentially interesting results are buried in the vast NT literature. It is proposed to make these more accessible by extracting them and presenting them in a logical fashion. The focus of this review is broader than NT: new, more recent approaches for studying ecological systems and how one might introduce realistic non-neutral models are also discussed

Re-branding Abu Dhabi: From oil giant to energy titan

This article presents a case study of Abu Dhabi\u27s \u27energy re-branding\u27 since 2005 when it declared its intention to transform itself from an oil exporter to a total energy giant that also embraces alternative (renewable and nuclear) energy. The first part of the article identifies the benefits of this policy for Abu Dhabi\u27s external diplomacy but argues that the real driver is the emirate\u27s domestic gas shortage and its effects on economic diversification and political legitimacy. The second part of the article discusses the motivations and interactions of local and foreign agents by focusing on the implementation of alternative energy platforms. It therefore provides a rare glimpse of the policy-making process in Abu Dhabi. The final part of the article examines the extent to which energy re-branding may be linked to a process by the government to reiterate, reinterpret and repudiate Emirati identity in order to enhance regime legitimacy in the twenty-first century. © 2012 Macmillan Publishers Ltd

The Coiled Coils of Cohesin Are Conserved in Animals, but Not In Yeast

The SMC proteins are involved in DNA repair, chromosome condensation, and sister chromatid cohesion throughout Eukaryota. Long, anti-parallel coiled coils are a prominent feature of SMC proteins, and are thought to serve as spacer rods to provide an elongated structure and to separate domains. We reported recently that the coiled coils of mammalian condensin (SMC2/4) showed moderate sequence divergence (approximately 10-15%) consistent with their functioning as spacer rods. The coiled coils of mammalian cohesins (SMC1/3), however, were very highly constrained, with amino acid sequence divergence typically <0.5%. These coiled coils are among the most highly conserved mammalian proteins, suggesting that they make extensive contacts over their entire surface.Here, we broaden our initial analysis of condensin and cohesin to include additional vertebrate and invertebrate organisms and multiple species of yeast. We found that the coiled coils of SMC1/3 are highly constrained in Drosophila and other insects, and more generally across all animal species. However, in yeast they are no more constrained than the coils of SMC2/4 and Ndc80/Nuf2p, suggesting that they are serving primarily as spacer rods.SMC1/3 functions for sister chromatid cohesion in all species. Since its coiled coils apparently serve only as spacer rods in yeast, it is likely that this is sufficient for sister chromatid cohesion in all species. This suggests an additional function in animals that constrains the sequence of the coiled coils. Several recent studies have demonstrated that cohesin has a role in gene expression in post-mitotic neurons of Drosophila, and other animal cells. Some variants of human Cornelia de Lange Syndrome involve mutations in human SMC1/3. We suggest that the role of cohesin in gene expression may involve intimate contact of the coiled coils of SMC1/3, and impose the constraint on sequence divergence