185 research outputs found
A scaling law for the dust cloud in radio frequency discharge under microgravity conditions
We employ the approximation of overlapped scattering potentials of charged
dust particles exposed to streaming ions to deduce the "equation of state" for
a stationary dust cloud in the radio frequency discharge apart from the void
dust boundary. The obtained equation defines the potential of a dust particle
as a function of the ion number density, the mass of a carrier gas atom, and
the electron temperature. A scaling law that relates the particle number
density to the particle radius and electron temperature in different systems is
formulated. Based on the proposed approach the radius of a cavity around a
large particle in the bulk of a cloud is estimated. The results of calculation
are in a reasonable agreement with the experimental data available in
literature.Comment: 10 pages, 7 figures, and 1 tabl
Minimalist design of a robust real-time quantum random number generator
We present a simple and robust construction of a real-time quantum random
number generator (QRNG). Our minimalist approach ensures stable operation of
the device as well as its simple and straightforward hardware implementation as
a stand-alone module. As a source of randomness the device uses measurements of
time intervals between clicks of a single-photon detector. The obtained raw
sequence is then filtered and processed by a deterministic randomness
extractor, which is realized as a look-up table. This enables high speed
on-the-fly processing without the need of extensive computations. The overall
performance of the device is around 1 random bit per detector click, resulting
in 1.2 Mbit/s generation rate in our implementation
Measurement of the speed of sound by observation of the Mach cones in a complex plasma under microgravity conditions
We report the first observation of the Mach cones excited by a larger
microparticle (projectile) moving through a cloud of smaller microparticles
(dust) in a complex plasma with neon as a buffer gas under microgravity
conditions. A collective motion of the dust particles occurs as propagation of
the contact discontinuity. The corresponding speed of sound was measured by a
special method of the Mach cone visualization. The measurement results are
incompatible with the theory of ion acoustic waves. The estimate for the
pressure in a strongly coupled Coulomb system and a scaling law for the complex
plasma make it possible to derive an evaluation for the speed of sound, which
is in a reasonable agreement with the experiments in complex plasmas.Comment: 5 pages, 2 figures, 1 tabl
Phenomena in Complex (Dusty) Plasma Studied under Microgravity Conditions
Complex (dusty) plasmas are composed of weakly ionized gas and charged microparticles and represent the plasma state of soft matter. The investigations which are not available on ground have been per-formed onboard the International Space Station (ISS) with the help of the “Plasma Crystal-3 Plus” (PK-3 Plus) laboratory. A number of interesting phenomena has been observed. The phase transition from iso-tropic plasma into electrorheological plasma was initiated. The crystal-liquid phase transition was ob-tained in large 3D isotropic dusty plasma. The slow compression of the dust particle subsystem has been investigated
Diffuse Neuroendocrine System: Structural and Functional Effects of Radiation Injury to Amine Precursor Uptake and Decarboxylation (APUD) Cells
The paper presents a review of the results obtained by the authors on the study of external (gamma) and internal (I-131) radiation effects on the functional morphology and linkage of the diffuse neuroendocrine system (DNES) and amine precursor uptake and decarboxylation (APUD) cells of the stomach and duodenum. The investigations performed enabled us to determine that the morphological changes noted in APUD cells had a dose and time dependency. The present study supports the point of view that the radiation initiates serotonin release from APUD cells, which appears to initiate the mechanism of early postirradiation dysfunctions of the gastrointestinal tract and the subsequent adaptive response of DNES. Analysis of our results, together with a review of the literature, indicates that APUD cells actively participate both in pathogenesis of radiation injury and development of organ and tissue radiosensitivity
Superembedding methods for 4d N=1 SCFTs
We extend SO(4,2) covariant lightcone embedding methods of four-dimensional
CFTs to N=1 superconformal field theory (SCFT). Manifest superconformal
SU(2,2|1) invariance is achieved by realizing 4D superconformal space as a
surface embedded in the projective superspace spanned by certain complex chiral
supermatrices. Because SU(2,2|1) acts linearly on the ambient space, the
constraints on correlators implied by superconformal Ward identities are
automatically solved in this formalism. Applications include new, compact
expressions for correlation functions containing one anti-chiral superfield and
arbitrary chiral superfield insertions, and manifestly invariant expressions
for the superconformal cross-ratios that parametrize the four-point function of
two chiral and two anti-chiral fields. Superconformal expressions for the
leading singularities in the OPE of chiral and anti-chiral operators are also
given. Because of covariance, our expressions are valid in any superconformally
flat background, e.g., AdS_4 or R times S^3.Comment: 33 pages, clarification of constraints, version to appear in PR
Freezing and melting of 3D complex plasma structures under microgravity conditions driven by neutral gas pressure manipulation
Freezing and melting of large three-dimensional complex plasmas under
microgravity conditions is investigated. The neutral gas pressure is used as a
control parameter to trigger the phase changes: Complex plasma freezes (melts)
by decreasing (increasing) the pressure. Evolution of complex plasma structural
properties upon pressure variation is studied. Theoretical estimates allow us
to identify main factors responsible for the observed behavior.Comment: Phys. Rev. Lett. (in press); 4 pages, 4 figure
- …