The catalytic core of DEMETER guides active DNA demethylation in Arabidopsis.

The Arabidopsis DEMETER (DME) DNA glycosylase demethylates the maternal genome in the central cell prior to fertilization and is essential for seed viability. DME preferentially targets small transposons that flank coding genes, influencing their expression and initiating plant gene imprinting. DME also targets intergenic and heterochromatic regions, but how it is recruited to these differing chromatin landscapes is unknown. The C-terminal half of DME consists of 3 conserved regions required for catalysis in vitro. We show that this catalytic core guides active demethylation at endogenous targets, rescuing dme developmental and genomic hypermethylation phenotypes. However, without the N terminus, heterochromatin demethylation is significantly impeded, and abundant CG-methylated genic sequences are ectopically demethylated. Comparative analysis revealed that the conserved DME N-terminal domains are present only in flowering plants, whereas the domain architecture of DME-like proteins in nonvascular plants mainly resembles the catalytic core, suggesting that it might represent the ancestral form of the 5mC DNA glycosylase found in plant lineages. We propose a bipartite model for DME protein action and suggest that the DME N terminus was acquired late during land plant evolution to improve specificity and facilitate demethylation at heterochromatin targets

Mapping rational rotation-minimizing frames from polynomial curves on to rational curves

Given a polynomial space curve r(ξ) that has a rational rotation–minimizing frame (an RRMF curve), a methodology is developed to construct families of rational space curves r˜(ξ) with the same rotation–minimizing frame as r(ξ) at corresponding points. The construction employs the dual form of a rational space curve, interpreted as the edge of regression of the envelope of a family of osculating planes, having normals in the direction u(ξ)=r′(ξ)×r″(ξ) and distances from the origin specified in terms of a rational function f(ξ) as f(ξ)/‖u(ξ)‖. An explicit characterization of the rational curves r˜(ξ) generated by a given RRMF curve r(ξ) in this manner is developed, and the problem of matching initial and final points and frames is shown to impose only linear conditions on the coefficients of f(ξ), obviating the non–linear equations (and existence questions) that arise in addressing this problem with the RRMF curve r(ξ). Criteria for identifying low–degree instances of the curves r˜(ξ) are identified, by a cancellation of factors common to their numerators and denominators, and the methodology is illustrated by a number of computed examples

Operating Risk Assessment of Modern Power System in Presence of Flywheel Energy Storage

Stochastic perturbations in supply and demand during power system operations have always been a concern for power system operators and/or planners. These concerns have been aggravated in the past decade with large-scale integration of renewable energy sources (RES) such as wind and photovoltaics. The impacts of load fluctuations and/or random outages of major system components during the operation, such as loss of generating unit(s) and transmission line(s) are further aggravated due to increasing addition of intermittent RES in the system. Energy storage systems (ESS) can act as a buffer to maintain the supply-demand balance, and are therefore, gaining considerable attention in modern power system planning. It is important to have the ability to make quantitative assessment of associated risks in the system operation and to explore the potential of suitable resources such as ESS in mitigating these risks. A reliability model of flywheel energy storage system (FESS) suitable for power system operational risk evaluation was developed in the research work presented in this thesis. Appropriate reliability assessment frameworks for different hierarchical levels of power system reliability evaluation were also introduced. The proposed frameworks and models were applied to the IEEE reliability test system and a modified Roy Billinton test system through several case studies. This thesis presents a novel approach to quantify the impact of growing wind penetration on power system operational reliability and quantify the implications of implementing flywheel energy storage systems in mitigating these concerns. The work presented in this thesis provides methodology and indicators that will be valuable in developing operating policies for sustainable wind energy for the future

Incremental learning with social media data to predict near real-time events

International audienceIn this paper, we focus on the problem of predicting some particular user activities in social media. Our challenge is to consider real events such as message posting to friends or forwarding received ones, connecting to new friends, and provide near real-time prediction of new events. Our approach is based on latent factor models which can exploit simultaneously the timestamped interaction information among users and their posted content information. We propose a simple strategy to learn incrementally the latent factors at each time step. Our method takes only recent data to update latent factor models and thus can reduce computational cost. Experiments on a real dataset collected from Twitter show that our method can achieve performances that are comparable with other state-of-the-art non-incremental techniques

Extended Producer Responsibility in East Asia: Approaches and lessons learnt from the management of waste electrical and electronic equipment

Environmental protection has become high in the policy agenda of East Asian countries by the end of the last century due to both internal and external stimuli. One of the main environmental issues is the management of solid waste. The concept of circular economy which encourages reduce, reuse, and recycling, i.e. 3Rs, together with the principle of Extended Producer Responsibility (EPR) has been promoted principally in the region by the Japanese government and the Organisation for Economic Co-operation and Development (OECD), respectively. This paper reviews approaches to pursue EPR and analyses factors behind policy development and environmental effectiveness of the respective programmes in China, Japan, South Korea, and Taiwan from the 1990s onward. The management of waste electrical and electronic equipment (WEEE, or e(lectronic)-waste) is selected as an object of the study. A two-step theory-based evaluation (TBE) is employed to evaluate the effectiveness of WEEE programmes. This paper concludes that internal factors such as limits in waste disposal capacity are more powerful in explaining the speed of policy development and the exact design of WEEE programmes though the role of epistemic communities helps in understanding the policy discourse. The adoption of the restriction of the use of hazardous substances (RoHS) in East Asia, on the other hand, was driven mainly by international trade harmonisation. TBE shows that the impacts of existing WEEE programmes on design improvements varied and the main explanation was the degree of producers’ involvement in the end-of-life management, which was highest in Japan and lowest in Taiwan. It also shows that programmes in Japan, South Korea, and Taiwan, succeeded to an extent in promoting WEEE recycling although the actual achievements in the area of waste collection were not completely in line with the EPR intervention and implementation theories. In addition, this paper questions the role of exports of used products to less developed countries because this form of “reuse” can compromise environmental protection goals where the imported countries do not have a proper system to ensure environmentally sound management of WEEE when these products reach their ultimate end-of-life stage