5,735 research outputs found
How to Track Protists in Three Dimensions
We present an apparatus optimized for tracking swimming microorganisms in the
size range 10-1000 microns, in three dimensions (3D), far from surfaces, and
with negligible background convective fluid motion. CCD cameras attached to two
long working distance microscopes synchronously image the sample from two
perpendicular directions, with narrowband dark-field or bright-field
illumination chosen to avoid triggering a phototactic response. The images from
the two cameras can be combined to yield 3D tracks of the organism. Using
additional, highly directional broad-spectrum illumination with millisecond
timing control the phototactic trajectories in 3D of organisms ranging from
Chlamydomonas to Volvox can be studied in detail. Surface-mediated hydrodynamic
interactions can also be investigated without convective interference. Minimal
modifications to the apparatus allow for studies of chemotaxis and other taxes.Comment: 8 pages, 7 figure
Localized matter-waves patterns with attractive interaction in rotating potentials
We consider a two-dimensional (2D) model of a rotating attractive
Bose-Einstein condensate (BEC), trapped in an external potential. First, an
harmonic potential with the critical strength is considered, which generates
quasi-solitons at the lowest Landau level (LLL). We describe a family of the
LLL quasi-solitons using both numerical method and a variational approximation
(VA), which are in good agreement with each other. We demonstrate that kicking
the LLL mode or applying a ramp potential sets it in the Larmor (cyclotron)
motion, that can also be accurately modeled by the VA.Comment: 13 pages, 11 figure
Model for hypernucleus production in heavy ion collisions
We estimate the production cross sections of hypernuclei in projectile like
fragment (PLF) in heavy ion collisions. The discussed scenario for the
formation cross section of hypernucleus is: (a) Lambda particles are produced
in the participant region but have a considerable rapidity spread and (b)
Lambda with rapidity close to that of the PLF and total momentum (in the rest
system of PLF) up to Fermi motion can then be trapped and produce hypernuclei.
The process (a) is considered here within Heavy Ion Jet Interacting Generator
HIJING-BBbar model and the process (b) in the canonical thermodynamic model
(CTM). We estimate the production cross-sections for light hypernuclei for C +
C at 3.7 GeV total nucleon-nucleon center of mass energy and for Ne+Ne and
Ar+Ar collisions at 5.0 GeV. By taking into account explicitly the impact
parameter dependence of the colliding systems, it is found that the cross
section is different from that predicted by the coalescence model and large
discrepancy is obtained for 6_He and 9_Be hypernuclei.Comment: 9 pages, 4 figures, 3 tables, revtex4, added reference
Systematic study of high- hadron and photon production with the PHENIX experiment
The suppression of hadrons with large transverse momentum () in
central Au+Au collisions at = 200 GeV compared to a binary
scaled p+p reference is one of the major discoveries at RHIC. To understand the
nature of this suppression PHENIX has performed detailed studies of the energy
and system-size dependence of the suppression pattern, including the first RHIC
measurement near SPS energies. An additional source of information is provided
by direct photons. Since they escape the medium basically unaffected they can
provide a high baseline for hard-scattering processes.
An overview of hadron production at high in different colliding
systems and at energies from GeV will be
given. In addition, the latest direct photon measurements by the PHENIX
experiment shall be discussed.Comment: 6 pages, 3 figures, Proceeding for the Conference Strangeness in
Quark Matter, Levoca, Slovakia, June 24-29, 200
Fluctuation Dissipation Relation for a Langevin Model with Multiplicative Noise
A random multiplicative process with additive noise is described by a
Langevin equation. We show that the fluctuation-dissipation relation is
satisfied in the Langevin model, if the noise strength is not so strong.Comment: 11 pages, 6 figures, other comment
The interfirm contracting value of management accounting information
We examine how firms’ management accounting information influences interfirm contract design. We theorize that comprehensive accounting information enables firms to design more complete contracts with suppliers, as indicated by increased issue inclusiveness and clause specificity. Survey data of Japanese manufacturing firms about the management of supplier relationships support the expectation that comprehensive management accounting information enables the development of more inclusive and specific contracts with suppliers. These contracts are also less subject to additional informal agreements between exchange partners. These results are consistent with the idea that better accounting information enables more complete contracting
Bleaching of sol-gel glass film with embedded gold nanoparticles by thermal poling
Gold clusters embedded in glass are expected to be hard to dissolve in the form of ions since gold is essentially a nonreactive metal. In spite of that, bleaching of Au-doped nanocomposite sol-gel glass film on a soda-lime glass substrate is demonstrated in which electric-field thermal poling is employed to effectively dissolve randomly distributed gold nanoparticles (15 nm in diameter) embedded in a low conductivity sol-gel glass film with a volume filling factor as small as 2.3%. The surface plasmon absorption band at 520 nm is suppressed in the region covered by the anodic electrode. The phenomenon is explained by the ionization of the gold nanoparticles and the redistribution of gold ions in the glass matrix due to the action of the extremely high electrostatic field locally developed during poling
Gap solitons in quasiperiodic optical lattices
Families of solitons in one- and two-dimensional (1D and 2D) Gross-Pitaevskii
equations with the repulsive nonlinearity and a potential of the
quasicrystallic type are constructed (in the 2D case, the potential corresponds
to a five-fold optical lattice). Stable 1D solitons in the weak potential are
explicitly found in three bandgaps. These solitons are mobile, and they collide
elastically. Many species of tightly bound 1D solitons are found in the strong
potential, both stable and unstable (unstable ones transform themselves into
asymmetric breathers). In the 2D model, families of both fundamental and
vortical solitons are found and are shown to be stable.Comment: 8 pages, 11 figure
Holes in the valence band of superconducting boron-doped diamond film studied by soft X-ray absorption and emission spectroscopy
Carbon- and boron-2 states of superconducting and non-superconducting
boron-doped diamond samples are measured using soft X-ray emission and
absorption spectroscopy. For the superconducting sample, a large density of
hole states is observed in the valence band in addition to the states in the
impurity band. The hole states in the valence band is located at about 1.3 eV
below the valence band maximum regardless of the doping level, which cannot be
interpreted within a simple rigid band model. Present experimental results,
combined with the first principles calculations, suggest that superconductivity
is to be attributed to the holes in the valence band.Comment: 4 pages, 4 figure
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