233 research outputs found
Energy transfer dynamics and thermalization of two oscillators interacting via chaos
We consider the classical dynamics of two particles moving in harmonic
potential wells and interacting with the same external environment (HE),
consisting of N non-interacting chaotic systems. The parameters are set so that
when either particle is separately placed in contact with the environment, a
dissipative behavior is observed. When both particles are simultaneously in
contact with HE an indirect coupling between them is observed only if the
particles are in near resonance. We study the equilibrium properties of the
system considering ensemble averages for the case N=1 and single trajectory
dynamics for N large. In both cases, the particles and the environment reach an
equilibrium configuration at long times, but only for large N a temperature can
be assigned to the system.Comment: 8 pages, 6 figure
A new protein curbs the hypertrophic effect of myostatin inhibition, adding remarkable endurance to motor performance in mice
Current efforts to improve muscle performance are focused on muscle trophism via inhibition of the myostatin pathway: however they have been unsuccessful in the clinic to date. In this study, a novel protein has been created by combining the soluble activin receptor, a strong myostatin inhibitor, to the C-terminal agrin nLG3 domain (ActR-Fc-nLG3) involved in the development and maintenance of neuromuscular junctions. Both domains are connected via the constant region of an Igg1 monoclonal antibody. Surprisingly, young male mice treated with ActR-Fc-nLG3 showed a remarkably increased endurance in the rotarod test, significantly longer than the single domain compounds ActR-Fc and Fc-nLG3 treated animals. This increase in endurance was accompanied by only a moderate increase in body weights and wet muscle weights of ActR-Fc-nLG3 treated animals and were lower than expected. The myostatin inhibitor ActR-Fc induced, as expected, a highly significant increase in body and muscle weights compared to control animals and ActR-Fc-nLG3 treated animals. Moreover, the prolonged endurance effect was not observed when ActR-Fc and Fc-nLG3 were dosed simultaneously as a mixture and the body and muscle weights of these animals were very similar to ActR-Fc treated animals, indicating that both domains need to be on one molecule. Muscle morphology induced by ActR-Fc-nLG3 did not appear to be changed however, close examination of the neuromuscular junction showed significantly increased acetylcholine receptor surface area for ActR-Fc-nLG3 treated animals compared to controls. This result is consistent with published observations that endurance training in rats increased acetylcholine receptor quantity at neuromuscular junctions and provide evidence that improving nerve-muscle interaction could be an important factor for sustaining long term muscle activity
Hippocampal and Amygdalar Volumes Changes in Drug Addicts: A Preliminary Study
Oral comunication for American Society of Neuroradiology 45th Annual Meeting. Chicago, June 9-14 200
Regular and chaotic interactions of two BPS dyons at low energy
We identify and analyze quasiperiodic and chaotic motion patterns in the time
evolution of a classical, non-Abelian Bogomol'nyi-Prasad-Sommerfield (BPS) dyon
pair at low energies. This system is amenable to the geodesic approximation
which restricts the underlying SU(2) Yang-Mills-Higgs dynamics to an
eight-dimensional phase space. We numerically calculate a representative set of
long-time solutions to the corresponding Hamilton equations and analyze
quasiperiodic and chaotic phase space regions by means of Poincare surfaces of
section, high-resolution power spectra and Lyapunov exponents. Our results
provide clear evidence for both quasiperiodic and chaotic behavior and
characterize it quantitatively. Indications for intermittency are also
discussed.Comment: 22 pages, 6 figures (v2 contains a few additional references, a new
paragraph on intermittency and minor stylistic corrections to agree with the
published version
Chaotic thermalization in Yang-Mills-Higgs theory on a spacial lattice
We analyze the Hamiltonian time evolution of classical SU(2) Yang-Mills-Higgs
theory with a fundamental Higgs doublet on a spacial lattice. In particular, we
study energy transfer and equilibration processes among the gauge and Higgs
sectors, calculate the maximal Lyapunov exponents under randomized initial
conditions in the weak-coupling regime, where one expects them to be related to
the high-temperature plasmon damping rate, and investigate their energy and
coupling dependence. We further examine finite-time and finite-size errors,
study the impact of the Higgs fields on the instability of constant non-Abelian
magnetic fields, and comment on the implications of our results for the
thermalization properties of hot gauge fields in the presence of matter.Comment: 33 pages, 16 figures (vs2 contains, as the published version, an
additional section on potential implications of chaotic thermalization for
nonequilibrium processes in the early Universe and in the aftermath of
ultrarelativistic nuclear collisions.
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A Cultural Quest: A Study of Organizational Use of New Cultural Resources in Strategy Formation.
Our study was motivated by the growing influence in cultural sociology and organizational research of the view of culture as a “toolkit”, from which individuals draw resources flexibly to develop strategies of action that address different circumstances. To investigate if and how organizations can also use new and diverse cultural resources, we undertook a historical case study of the incorporation of new cultural resources in an organization’s cultural repertoire. In-depth analysis of four rounds of incorporation of new cultural resources led to the development of a robust theoretical model that identifies cultural repertoire enrichment and organizational identity redefinition as two core mechanisms that facilitate the use of new cultural resources for the development of unconventional strategies and strategic versatility. Our model contributes to organizational research novel theoretical understanding regarding the use of cultural resources in strategy formation and change
Scans for signatures of selection in Russian cattle breed genomes reveal new candidate genes for environmental adaptation and acclimation
Domestication and selective breeding has resulted in over 1000 extant cattle breeds. Many of these breeds do not excel in important traits but are adapted to local environments. These adaptations are a valuable source of genetic material for efforts to improve commercial breeds. As a step toward this goal we identified candidate regions to be under selection in genomes of nine Russian native cattle breeds adapted to survive in harsh climates. After comparing our data to other breeds of European and Asian origins we found known and novel candidate genes that could potentially be related to domestication, economically important traits and environmental adaptations in cattle. The Russian cattle breed genomes contained regions under putative selection with genes that may be related to adaptations to harsh environments (e.g., AQP5, RAD50, and RETREG1). We found genomic signatures of selective sweeps near key genes related to economically important traits, such as the milk production (e.g., DGAT1, ABCG2), growth (e.g., XKR4), and reproduction (e.g., CSF2). Our data point to candidate genes which should be included in future studies attempting to identify genes to improve the extant breeds and facilitate generation of commercial breeds that fit better into the environments of Russia and other countries with similar climates
Leukocytospermia and sperm preparation - a flow cytometric study
Reprod Biol Endocrinol. 2009 Nov 19;7:12
Genetic diversity and signatures of selection in various goat breeds revealed by genome-wide SNP markers
Enhanced tonic GABAA inhibition in typical absence epilepsy
The cellular mechanisms underlying typical absence seizures, which characterize various idiopathic generalized epilepsies, are not fully understood, but impaired GABAergic inhibition remains an attractive hypothesis. In contrast, we show here that extrasynaptic GABAA receptor–dependent ‘tonic’ inhibition is increased in thalamocortical neurons from diverse genetic and pharmacological models of absence seizures. Increased tonic inhibition is due to compromised GABA uptake by the GABA transporter GAT–1 in the genetic models tested, and GAT–1 is critical in governing seizure genesis. Extrasynaptic GABAA receptors are a requirement for seizures in two of the best characterized models of absence epilepsy, and the selective activation of thalamic extrasynaptic GABAA receptors is sufficient to elicit both electrographic and behavioural correlates of seizures in normal animals. These results identify an apparently common cellular pathology in typical absence seizures that may have epileptogenic significance, and highlight novel therapeutic targets for the treatment of absence epilepsy.peer-reviewe
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