252 research outputs found
An evolutionary computation approach for optimizing connectivity in disaster response scenarios
Digital Simulation for Automobile Maneuvers
A new all-digital simulation of automobile handling allows severe maneuvers involving braking or accel eration and cornering. A novel feature is the in corporation of closed-loop control based on a mathematical model of the human driver. The program is modular and well-documented. The model includes provisions for nonlinear tire and suspension forces and moments; it also allows the user to switch off the nonlinearities and to include an antilock brake system.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68886/2/10.1177_003754978103700304.pd
Low-Luminosity Accretion in Black Hole X-ray Binaries and Active Galactic Nuclei
At luminosities below a few percent of Eddington, accreting black holes
switch to a hard spectral state which is very different from the soft
blackbody-like spectral state that is found at higher luminosities. The hard
state is well-described by a two-temperature, optically thin, geometrically
thick, advection-dominated accretion flow (ADAF) in which the ions are
extremely hot (up to K near the black hole), the electrons are also
hot ( K), and thermal Comptonization dominates the X-ray
emission. The radiative efficiency of an ADAF decreases rapidly with decreasing
mass accretion rate, becoming extremely low when a source reaches quiescence.
ADAFs are expected to have strong outflows, which may explain why relativistic
jets are often inferred from the radio emission of these sources. It has been
suggested that most of the X-ray emission also comes from a jet, but this is
less well established.Comment: To appear in "From X-ray Binaries to Quasars: Black Hole Accretion on
All Mass Scales" edited by T. Maccarone, R. Fender, L. Ho, to be published as
a special edition of "Astrophysics and Space Science" by Kluwe
Annihilation-Type Charmless Radiative Decays of B Meson in Non-universal Z^\prime Model
We study charmless pure annihilation type radiative B decays within the QCD
factorization approach. After adding the vertex corrections to the naive
factorization approach, we find that the branching ratios of
, and
within the standard model are at the order of
, and ,
respectively. The smallness of these decays in the standard model makes them
sensitive probes of flavor physics beyond the standard model. To explore their
physics potential, we have estimated the contribution of boson in
the decays. Within the allowed parameter space, the branching ratios of these
decay modes can be enhanced remarkably in the non-universal model:
The branching ratios can reach to for and for the , which are large enough for LHC-b and/or Super B-factories to detect
those channels in near future. Moreover, we also predict large CP asymmetries
in suitable parameter space. The observation of these modes could in turn help
us to constrain the mass within the model.Comment: 13 pages, 8 figure
Search for B -> h(*) nu nubar Decays at Belle
We present a search for the rare decays B -> h(*) nu nubar, where h(*) stands
for a light meson. A data sample of 535 million BBbar pairs collected with the
Belle detector at the KEKB e+e- collider is used. Signal candidates are
required to have an accompanying B meson fully reconstructed in a hadronic mode
and signal-side particles consistent with a single h(*) meson. No significant
signal is observed and we set upper limits on the branching fractions at 90%
confidence level. The limits on B0 -> K*0 nu nubar and B+ -> K+ nu nubar decays
are more stringent than the previous constraints, while the first searches for
B0 -> K0 nu nubar, pi0 nu nubar, rho0 nu nubar, phi nu nubar and B+ -> K*+ nu
nubar, rho+ nu nubar are reported.Comment: 6 pages, 2 figures, submit to PR
Modelling spectral and timing properties of accreting black holes: the hybrid hot flow paradigm
The general picture that emerged by the end of 1990s from a large set of
optical and X-ray, spectral and timing data was that the X-rays are produced in
the innermost hot part of the accretion flow, while the optical/infrared (OIR)
emission is mainly produced by the irradiated outer thin accretion disc. Recent
multiwavelength observations of Galactic black hole transients show that the
situation is not so simple. Fast variability in the OIR band, OIR excesses
above the thermal emission and a complicated interplay between the X-ray and
the OIR light curves imply that the OIR emitting region is much more compact.
One of the popular hypotheses is that the jet contributes to the OIR emission
and even is responsible for the bulk of the X-rays. However, this scenario is
largely ad hoc and is in contradiction with many previously established facts.
Alternatively, the hot accretion flow, known to be consistent with the X-ray
spectral and timing data, is also a viable candidate to produce the OIR
radiation. The hot-flow scenario naturally explains the power-law like OIR
spectra, fast OIR variability and its complex relation to the X-rays if the hot
flow contains non-thermal electrons (even in energetically negligible
quantities), which are required by the presence of the MeV tail in Cyg X-1. The
presence of non-thermal electrons also lowers the equilibrium electron
temperature in the hot flow model to <100 keV, making it more consistent with
observations. Here we argue that any viable model should simultaneously explain
a large set of spectral and timing data and show that the hybrid
(thermal/non-thermal) hot flow model satisfies most of the constraints.Comment: 26 pages, 13 figures. To be published in the Space Science Reviews
and as hard cover in the Space Sciences Series of ISSI - The Physics of
Accretion on to Black Holes (Springer Publisher
Further search for the decay in the momentum region P < 195 MeV/c
We report the results of a search for the decay
in the kinematic region with momentum MeV/c using the
data collected by the E787 experiment at BNL. No events were observed. When
combined with our previous search in this region, one candidate event with an
expected background of events results in a 90% C.L. upper limit
of on the branching ratio of .
We also report improved limits on the rates of and where are hypothetical, massless, long-lived
neutral particles.Comment: 5 pages, 3 figures, Accepted for publication in Phys. Rev.
Internal representations of smell in the Drosophila brain
Recent advances in sensory neuroscience using Drosophila olfaction as a model system have revealed brain maps representing the external world. Once we understand how the brain's built-in capability generates the internal olfactory maps, we can then elaborate how the brain computes and makes decision to elicit complex behaviors. Here, we review current progress in mapping Drosophila olfactory circuits and discuss their relationships with innate olfactory behaviors
Phosphorothioate antisense oligonucleotides induce the formation of nuclear bodies
Antisense oligonucleotides are powerful tools for the in vivo regulation of gene expression. We have characterized the intracellular distribution of fluorescently tagged phosphorothioate oligodeoxynucleotides (PS-ONs) at high resolution under conditions in which PS-ONs have the potential to display antisense activity. Under these conditions PS-ONs predominantly localized to the cell nucleus where they accumulated in 20-30 bright spherical foci designated phosphorothioate bodies (PS bodies), which were set against a diffuse nucleoplasmic population excluding nucleoli. PS bodies are nuclear structures that formed in cells after PS-ON delivery by transfection agents or microinjection but were observed irrespectively of antisense activity or sequence. Ultrastructurally, PS bodies corresponded to electron-dense structures of 150-300 nm diameter and resembled nuclear bodies that were found with lower frequency in cells lacking PS-ONs. The environment of a living cell was required for the de novo formation of PS bodies, which occurred within minutes after the introduction of PS-ONs. PS bodies were stable entities that underwent noticeable reorganization only during mitosis. Upon exit from mitosis, PS bodies were assembled de novo from diffuse PS-ON pools in the daughter nuclei. In situ fractionation demonstrated an association of PS-ONs with the nuclear matrix. Taken together, our data provide evidence for the formation of a nuclear body in cells after introduction of phosphorothioate oligodeoxynucleotides
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