Ground State and Resonances in the Standard Model of Non-relativistic QED

We prove existence of a ground state and resonances in the standard model of the non-relativistic quantum electro-dynamics (QED). To this end we introduce a new canonical transformation of QED Hamiltonians and use the spectral renormalization group technique with a new choice of Banach spaces.Comment: 50 pages change

Tissue-specific analysis of chromatin state identifies temporal signatures of enhancer activity during embryonic development

Chromatin modifications are associated with many aspects of gene expression, yet their role in cellular transitions during development remains elusive. Here, we use a new approach to obtain cell type-specific information on chromatin state and RNA polymerase II (Pol II) occupancy within the multicellular Drosophila melanogaster embryo. We directly assessed the relationship between chromatin modifications and the spatio-temporal activity of enhancers. Rather than having a unique chromatin state, active developmental enhancers show heterogeneous histone modifications and Pol II occupancy. Despite this complexity, combined chromatin signatures and Pol II presence are sufficient to predict enhancer activity de novo. Pol II recruitment is highly predictive of the timing of enhancer activity and seems dependent on the timing and location of transcription factor binding. Chromatin modifications typically demarcate large regulatory regions encompassing multiple enhancers, whereas local changes in nucleosome positioning and Pol II occupancy delineate single active enhancers. This cell type-specific view identifies dynamic enhancer usage, an essential step in deciphering developmental networks

A Triangular Formation Strategy for Collective Behaviors of Robot Swarm

International Conference on Computational Science and Its Applications, ICCSA 2009, Seoul, 29 July-2 August 2001This paper presents, a novel decentralized control strategy, named Triangular Formation Algorithm (TFA), for a swarm of simple robots. The TFA is a local interaction strategy which basically makes three neighboring robots to form a regular triangular lattice. This strategy requires minimal conditions for robots and it can be easily realized with real robots. The TFA is executed by every member of the swarm asynchronously. For swarm obstacle avoidance, a simplified artificial physical model is introduced to work with the TFA. Simulation results showed that the global behaviors of swarm such as aggregation, flocking and obstacle avoidance in an unknown environment can be achieved using the TFA and obstacle avoidance mechanism.Department of Electrical Engineerin