16,798 research outputs found
Three-Body Elastic and Inelastic Scattering at Intermediate Energies
The Faddeev equation for three-body scattering at arbitrary energies is
formulated in momentum space and directly solved in terms of momentum vectors
without employing a partial wave decomposition. For identical bosons this
results in a three-dimensional integral equation in five variables, magnitudes
of relative momenta and angles. The cross sections for both elastic and breakup
processes in the intermediate energy range up to about 1 GeV are calculated
based on a Malfliet-Tjon type potential, and the convergence of the multiple
scattering series is investigated.Comment: Talk at the 18th International IUPAP Conference on Few-Body Problems
in Physics, Aug. 21-26, 2006, Santos, Brazi
A Possible Detection of Occultation by a Proto-planetary Clump in GM Cephei
GM Cep in the young (~ 4 Myr) open cluster Trumpler 37 has been known to be an abrupt variable and to have a circumstellar disk with very active accretion. Our monitoring observations in 2009–2011 revealed the star to show sporadic ?are events, each with brightening of . 0.5 mag lasting for days. These brightening events, associated with a color change toward the blue, should originate from an increased accretion activity. Moreover, the star also underwent a brightness drop of ~ 1 mag lasting for about a month, during which the star became bluer when fainter. Such brightness drops seem to have a recurrence time scale of a year, as evidenced in our data and the photometric behavior of GM Cep over a century. Between consecutive drops, the star brightened gradually by about 1 mag and became blue at peak luminosity. We propose that the drop is caused by obscuration of the central star by an orbiting dust concentration. The UX Orionis type of activity in GM Cep therefore exemplifies the disk inhomogeneity process in transition between grain coagulation and planetesimal formation in a young circumstellar disk
Simultaneous current-, force- and work function measurement with atomic resolution
The local work function of a surface determines the spatial decay of the
charge density at the Fermi level normal to the surface. Here, we present a
method that enables simultaneous measurements of local work function and
tip-sample forces. A combined dynamic scanning tunneling microscope and atomic
force microscope is used to measure the tunneling current between an
oscillating tip and the sample in real time as a function of the cantilever's
deflection. Atomically resolved work function measurements on a silicon
(111)-() surface are presented and related to concurrently recorded
tunneling current- and force- measurements.Comment: 8 pages, 4 figures, submitted to Applied Physics Letter
Hooge's Constant of Carbon Nanotube Field Effect Transistors
The 1/f noise in individual semiconducting carbon nanotubes (s-CNT) in a
field effect transistor configuration has been measured in ultra-high vacuum
and following exposure to air. The amplitude of the normalized current spectral
noise density is independent of source-drain current, indicating the noise is
due to mobility rather than number fluctuations. Hooge's constant for s-CNT is
found to be 9.3 plus minus 0.4x10^-3. The magnitude of the 1/f noise is
substantially degreased by exposing the devices to air
Absorbate-Induced Piezochromism in a Porous Molecular Crystal
Atmospherically stable porous frameworks
and materials are interesting
for heterogeneous solid–gas applications. One motivation is
the direct and selective uptake of pollutant/hazardous gases, where
the material produces a measurable response in the presence of the
analyte. In this report, we present a combined experimental and theoretical
rationalization for the piezochromic response of a robust and porous
molecular crystal built from an extensively fluorinated trispyrazole.
The electronic response of the material is directly determined by
analyte uptake, which provokes a subtle lattice contraction and an
observable bathochromic shift in the optical absorption onset. Selectivity
for fluorinated absorbates is demonstrated, and toluene is also found
to crystallize within the pore. Furthermore, we demonstrate the application
of electronic structure calculations to predict a physicochemical
response, providing the foundations for the design of electronically
tunable porous solids with the chemical properties required for development
of novel gas-uptake media
Evolutionary game of coalition building under external pressure
We study the fragmentation-coagulation (or merging and splitting)
evolutionary control model as introduced recently by one of the authors, where
small players can form coalitions to resist to the pressure exerted by the
principal. It is a Markov chain in continuous time and the players have a
common reward to optimize. We study the behavior as grows and show that the
problem converges to a (one player) deterministic optimization problem in
continuous time, in the infinite dimensional state space
Sliding charge density wave in manganites
The so-called stripe phase of the manganites is an important example of the
complex behaviour of metal oxides, and has long been interpreted as the
localisation of charge at atomic sites. Here, we demonstrate via resistance
measurements on La_{0.50}Ca_{0.50}MnO_3 that this state is in fact a
prototypical charge density wave (CDW) which undergoes collective transport.
Dramatic resistance hysteresis effects and broadband noise properties are
observed, both of which are typical of sliding CDW systems. Moreover, the high
levels of disorder typical of manganites result in behaviour similar to that of
well-known disordered CDW materials. Our discovery that the manganite
superstructure is a CDW shows that unusual transport and structural properties
do not require exotic physics, but can emerge when a well-understood phase (the
CDW) coexists with disorder.Comment: 13 pages; 4 figure
EOG-Based Eye Movement Classification and Application on HCI Baseball Game
© 2013 IEEE. Electrooculography (EOG) is considered as the most stable physiological signal in the development of human-computer interface (HCI) for detecting eye-movement variations. EOG signal classification has gained more traction in recent years to overcome physical inconvenience in paralyzed patients. In this paper, a robust classification technique, such as eight directional movements is investigated by introducing a concept of buffer along with a variation of the slope to avoid misclassification effects in EOG signals. Blinking detection becomes complicated when the magnitude of the signals are considered. Hence, a correction technique is introduced to avoid misclassification for oblique eye movements. Meanwhile, a case study has been considered to apply these correction techniques to HCI baseball game to learn eye-movements
A Monte Carlo Study of the Dynamical-Flucautation Property of the Hadronic System Inside Jets
A study of the dynamical fluctuation property of jets is carried out using
Monte Carlo method. The results suggest that, unlike the average properties of
the hadronic system inside jets, the anisotropy of dynamical fluctuations in
these systems changes abruptly with the variation of the cut parameter \yct.
A transition point exists, where the dynamical fluctuations in the hadronic
system inside jet behave like those in soft hadronic collisions, i.e. being
circular in the transverse plan with repect to dynamical fluctuations. This
finding obtained from Jetset and Herwig Monte Carlo is encouraged to be checked
by experiments.Comment: 8 pages, 3 figure
Theory of Chiral Modulations and Fluctuations in Smectic-A Liquid Crystals Under an Electric Field
Chiral liquid crystals often exhibit periodic modulations in the molecular
director; in particular, thin films of the smectic-C* phase show a chiral
striped texture. Here, we investigate whether similar chiral modulations can
occur in the induced molecular tilt of the smectic-A phase under an applied
electric field. Using both continuum elastic theory and lattice simulations, we
find that the state of uniform induced tilt can become unstable when the system
approaches the smectic-A--smectic-C* transition, or when a high electric field
is applied. Beyond that instability point, the system develops chiral stripes
in the tilt, which induce corresponding ripples in the smectic layers. The
modulation persists up to an upper critical electric field and then disappears.
Furthermore, even in the uniform state, the system shows chiral fluctuations,
including both incipient chiral stripes and localized chiral vortices. We
compare these predictions with observed chiral modulations and fluctuations in
smectic-A liquid crystals.Comment: 11 pages, including 9 postscript figures, uses REVTeX 3.0 and
epsf.st
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