Rubisco evolution in C4 eudicots: an analysis of Amaranthaceae sensu lato

BACKGROUND Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase) catalyses the key reaction in the photosynthetic assimilation of CO₂. In C₄ plants CO₂ is supplied to Rubisco by an auxiliary CO₂-concentrating pathway that helps to maximize the carboxylase activity of the enzyme while suppressing its oxygenase activity. As a consequence, C₄ Rubisco exhibits a higher maximum velocity but lower substrate specificity compared with the C₃ enzyme. Specific amino-acids in Rubisco are associated with C₄ photosynthesis in monocots, but it is not known whether selection has acted on Rubisco in a similar way in eudicots. METHODOLOGY/PRINCIPAL FINDINGS We investigated Rubisco evolution in Amaranthaceae sensu lato (including Chenopodiaceae), the third-largest family of C₄ plants, using phylogeny-based maximum likelihood and Bayesian methods to detect Darwinian selection on the chloroplast rbcL gene in a sample of 179 species. Two Rubisco residues, 281 and 309, were found to be under positive selection in C₄ Amaranthaceae with multiple parallel replacements of alanine by serine at position 281 and methionine by isoleucine at position 309. Remarkably, both amino-acids have been detected in other C₄ plant groups, such as C₄ monocots, illustrating a striking parallelism in molecular evolution. CONCLUSIONS/SIGNIFICANCE Our findings illustrate how simple genetic changes can contribute to the evolution of photosynthesis and strengthen the hypothesis that parallel amino-acid replacements are associated with adaptive changes in Rubisco.This research was funded by NERC (http://www.nerc.ac.uk/; grant number NE/H007741/1)

Observable effects caused by vacuum pair creation in the field of high-power optical lasers

We consider the possibility of an experimental proof of vacuum e+e- pair creation in the focus of two counter-propagating optical laser beams with an intensity of the order of 10^20 - 10^22 W/cm^2. Our approach is based on the collisionless kinetic equation for the distribution function of the e+e- pairs with the source term for particle production. As a possible experimental signal of vacuum pair production we consider the refraction of a high-frequency probe laser beam by the produced e+e- plasma to be observed by an interference filter. The generation of higher harmonics of the laser frequency in the self-consistent electric field is also investigated.Comment: 7 pages, 7 figures; typos corrected, Eq.(16) corrected, reference adde

The Models of Strategic Interaction between Network and Generating Companies at Electricity Transmission Market

The paper considers the strategic interaction between network and generating companies at electricity transmission market within the simplest electric power system with two nodes. The four possible variants of the market organization are investigated: guaranteed regulated and non-regulated network monopoly, network monopoly facing potential competition from the independent network company or generating company. The possible consequences and by-effects of vertical unbundling, in particular, influence of such a regulation on the prices and network transfer capabilities, are analyzed. It is shown that the elimination of monopolistic preferences on electric power transmission with the possibility of network objects building and operation by the generating companies is an effective mechanism for electricity price reduction.oligopoly, monopoly, strategic interaction, potential competition, Nash equilibrium, electricity transmission market

Flywheel energy storage system with homopolar electrodynamic magnetic bearing

The goal of this research was to evaluate the potential of homopolar electrodynamic magnetic bearings for flywheel energy storage systems (FESSs). The primary target was a FESS for Low Earth Orbit (LEO) satellites; however, the design can also be easily adapted for Earth-based applications. The main advantage of Homopolar Electrodynamic Bearings compared to more conventional Active Magnetic Bearings (AMB) is simplicity and very low power rating of its electronics, resulting in higher system reliability - a critical factor for space applications. For commercial applications this technologies may also be found very attractive due to a potentially lower cost compared to AMB.Center for Electromechanic

Venture community: democratisation of entrepreneurship in developing economies

The motivation of this paper is to assist SMEs (mainly micro and informal enterprises) in developing economies to find the required resources to establish, or develop, their business. We introduce the concept of 'Venture Communities' to provide direct peer-to-peer connections between individuals and SMEs in all parts of the global market. We draw on the well-established concepts of networking, crowdfunding, living labs and value co-creation. The contribution we make lies in the introduction of a novel ecosystem, constructed by multiple actors, through dynamic and interconnected networks, accumulating resources for the benefit of all stakeholders of this community. Our model presents a challenge to the conventional conceptualizations of dyadic relationships between developed economies and emerging economies. Alternatively, we suggest anti-essentialist communities that are temporary constellation of social elements from all parts of the global market to create "hybridized and nomadic" (Laclau and Mouffe 1995) market arrangements