3,774 research outputs found
Jet coherence in QCD media: the antenna radiation spectrum
We study the radiation of a highly energetic partonic antenna in a colored
state traversing a dense QCD medium. Resumming multiple scatterings of all
involved constituents with the medium we derive the general gluon spectrum
which encompasses both longitudinal color coherence between scattering centers
in the medium, responsible for the well known Landau-Pomeranchuk-Migdal (LPM)
effect, and transverse color coherence between partons inside a jet, leading,
in vacuum, to angular ordering of the parton shower. We discuss shortly the
onset of transverse decoherence which is reached in opaque media. In this
regime, the spectrum consists of independent radiation off the antenna
constituents.Comment: 15 pages, 2 figures, paper shortened and partly rewritten, references
added, results unchange
Jet quenching and broadening: the transport coefficient in an anisotropic plasma
The jet quenching parameter is analyzed for a quark jet propagating
in an anisotropic plasma. The momentum anisotropy is calculated at high
temperature of the underlying quark-gluon plasma. is explicitly
estimated in leading-logarithmic approximation by the broadening of the
massless quark interacting via gluon exchange. A plasma instability is present.
Strong indications are found that is increasing with increasing
anisotropy. Possible implications for the saturation scale in
collisions are pointed out.Comment: 1
Improved Nonrelativistic QCD for Heavy Quark Physics
We construct an improved version of nonrelativistic QCD for use in lattice
simulations of heavy quark physics, with the goal of reducing systematic errors
from all sources to below 10\%. We develop power counting rules to assess the
importance of the various operators in the action and compute all leading order
corrections required by relativity and finite lattice spacing. We discuss
radiative corrections to tree level coupling constants, presenting a procedure
that effectively resums the largest such corrections to all orders in
perturbation theory. Finally, we comment on the size of nonperturbative
contributions to the coupling constants.Comment: 40 pages, 2 figures (not included), in LaTe
Monitoring drought response and chlorophyll content in Quercus by consumer-grade, near-infrared (NIR) camera: a comparison with reflectance spectroscopy
Septin assemblies form by diffusion-driven annealing on membranes
Author Posting. © The Author(s), 2013. This is the author's version of the work. It is posted here by permission of National Academy of Sciences for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences of the United States of America 111 (2014): 2146-2151, doi:10.1073/pnas.1314138111.Septins assemble into filaments and higher-order structures that act as scaffolds for diverse cell functions including cytokinesis, cell polarity, and membrane remodeling. Despite their conserved role in cell organization, little is known about how septin filaments elongate and are knit together into higher-order assemblies. Using fluorescence correlation spectroscopy (FCS), we determined that cytosolic septins are in small complexes suggesting that septin filaments are not formed in the cytosol. When the plasma membrane of live cells is monitored by total internal reflection fluorescence (TIRF) microscopy, we see that septin complexes of variable size diffuse in two dimensions. Diffusing septin complexes collide and make end-on associations to form elongated filaments and higher-order structures, an assembly process we call annealing. Septin assembly by annealing can be reconstituted in vitro on supported lipid bilayers with purified septin complexes. Using the reconstitution assay, we show that septin filaments are highly flexible, grow only from free filament ends and do not exchange subunits in the middle of filaments. This work shows for the first time that annealing is an intrinsic property of septins in the presence of membranes and demonstrates that cells exploit this mechanism to build large septin assemblies.This project was supported with funding from by NSF (MCB-507511, ASG) and NIH (GM100160, TT and ASG), and Colwin, Lemann and Spiegel summer fellowships and The Nikon Award for summer investigation at MBL in Woods Hole, MA (ASG) and instrument support from Micro Video Instruments (MVI).2014-07-2
Dynamics of Polymeric Protein Assemblies in Live Cells Revealed by Fluorescence Polarization Imaging of Single Molecules
Integration of Action and Language Knowledge: A Roadmap for Developmental Robotics
âThis material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder." âCopyright IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.âThis position paper proposes that the study of embodied cognitive agents, such as humanoid robots, can advance our understanding of the cognitive development of complex sensorimotor, linguistic, and social learning skills. This in turn will benefit the design of cognitive robots capable of learning to handle and manipulate objects and tools autonomously, to cooperate and communicate with other robots and humans, and to adapt their abilities to changing internal, environmental, and social conditions. Four key areas of research challenges are discussed, specifically for the issues related to the understanding of: 1) how agents learn and represent compositional actions; 2) how agents learn and represent compositional lexica; 3) the dynamics of social interaction and learning; and 4) how compositional action and language representations are integrated to bootstrap the cognitive system. The review of specific issues and progress in these areas is then translated into a practical roadmap based on a series of milestones. These milestones provide a possible set of cognitive robotics goals and test scenarios, thus acting as a research roadmap for future work on cognitive developmental robotics.Peer reviewe
Autonomous Robust Skill Generation Using Reinforcement Learning with Plant Variation
This paper discusses an autonomous space robot for a truss structure assembly using some reinforcement learning. It is difficult for a space robot to complete contact tasks within a real environment, for example, a peg-in-hole task, because of error between the real environment and the controller model. In order to solve problems, we propose an autonomous space robot able to obtain proficient and robust skills by overcoming error to complete a task. The proposed approach develops skills by reinforcement learning that considers plant variation, that is, modeling error. Numerical simulations and experiments show the proposed method is useful in real environments
Spectroscopy of Heavy Mesons Expanded in 1/m_Q
Operating just once with the naive Foldy-Wouthuysen-Tani transformation on
the relativistic Fermi-Yang equation for bound states described by
the semi-relativistic Hamiltonian which includes Coulomb-like as well as
confining scalar potentials, we have calculated heavy meson mass spectra of D
and B together with higher spin states. Based on the formulation recently
proposed, their masses and wave functions are expanded up to the second order
in with a heavy quark mass and the lowest order equation is
examined carefully to obtain a complete set of eigenfunctions for the
Schr\"odinger equation. Heavy quark effective theory parameters, ,
, and , are also determined at the first and second order
in .Comment: 49 pages, 5 epsf figure
L'impianto, la gestione e la valorizzazione multifunzionale dei boschi periurbani
I boschi periurbani, come tutti gli spazi verdi prossimi agli agglomerati urbani, migliorano le condizioni ambientali e la qualit\ue0 dell'aria, contribuiscono alla conservazione della biodiversit\ue0, possono favorire l'aggregazione sociale.
I boschi prossimi ai centri urbani rivestono inoltre un ruolo importante dal punto di vista paesaggistico e turistico e contribuiscono a contrastare i cambiamenti climatici.
Questa pubblicazione, redatta con il supporto tecnico-scientifico dell'Accademia italiana di scienze forestali di Firenze, si propone di fornire linee guida per la progettazione, la realizzazione e la gestione dei boschi periurbani e delle fasce verdi nelle aree prossime agli agglomerati urbani ed agli insediamenti industriali
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