4,117 research outputs found
Super-Alfv\'enic propagation of reconnection signatures and Poynting flux during substorms
The propagation of reconnection signatures and their associated energy are
examined using kinetic particle-in-cell simulations and Cluster satellite
observations. It is found that the quadrupolar out-of-plane magnetic field near
the separatrices is associated with a kinetic Alfv\'en wave. For magnetotail
parameters, the parallel propagation of this wave is super-Alfv\'enic
(V_parallel ~ 1500 - 5500 km/s) and generates substantial Poynting flux (S ~
10^-5 - 10^-4 W/m^2) consistent with Cluster observations of magnetic
reconnection. This Poynting flux substantially exceeds that due to frozen-in
ion bulk outflows and is sufficient to generate white light aurora in the
Earth's ionosphere.Comment: Submitted to PRL on 11/1/2010. Resubmitted on 4/5/201
Temperature dependence of the bandgap of Eu doped {ZnCdO/ZnO}30 multilayer structures
In situ Eu-doped {ZnCdO/ZnO}30 multilayer systems were grown on p-type
Si-substrates and on quartz substrates by plasma-assisted molecular beam
epitaxy. Various Eu concentrations in the samples were achieved by controlling
temperature of the europium effusion cell. The properties of as-grown and
annealed {ZnCdO/ZnO}30:Eu multilayers were investigated using secondary ion
mass spectrometry (SIMS) and X-ray diffraction methods. SIMS measurements
showed that annealing at 700{\deg}C and 900{\deg}C practically did not change
the Eu concentration and the rare earth depth profiles are uniform. It was
found that the band gap depends on the concentration of Eu and it was changed
by rapid thermal annealing. Varshni and Bose-Einstein equations were used to
describe the temperature dependence of the band gap of {ZnCdO/ZnO}30:Eu
multilayer structures and Debye and Einstein temperatures were obtained.Comment: 16 pages, 8 figures, 3 table
Catastrophic chromosomal restructuring during genome elimination in plants.
Genome instability is associated with mitotic errors and cancer. This phenomenon can lead to deleterious rearrangements, but also genetic novelty, and many questions regarding its genesis, fate and evolutionary role remain unanswered. Here, we describe extreme chromosomal restructuring during genome elimination, a process resulting from hybridization of Arabidopsis plants expressing different centromere histones H3. Shattered chromosomes are formed from the genome of the haploid inducer, consistent with genomic catastrophes affecting a single, laggard chromosome compartmentalized within a micronucleus. Analysis of breakpoint junctions implicates breaks followed by repair through non-homologous end joining (NHEJ) or stalled fork repair. Furthermore, mutation of required NHEJ factor DNA Ligase 4 results in enhanced haploid recovery. Lastly, heritability and stability of a rearranged chromosome suggest a potential for enduring genomic novelty. These findings provide a tractable, natural system towards investigating the causes and mechanisms of complex genomic rearrangements similar to those associated with several human disorders
Effect of rapid thermal annealing on short period {CdO/ZnO}m SLs grown on m-Al2O3
Here, we report on the characterization of {CdO/ZnO}m superlattice structures
(SLs) grown by plasma assisted molecular beam epitaxy. The properties of
as-grown and annealed SLs deposited on m-oriented sapphire were investigated by
secondary ion mass spectrometry (SIMS) and scanning electron microscopy (SEM)
in cathodoluminescence (CL) and energy dispersive X-ray modes. The deformation
of the crystallographic structure of SLs was observed after rapid thermal
annealing at 900{\deg}C in oxygen flow due to migration and segregation of Cd
atoms. SIMS measurements revealed that the distributions of cadmium in the
annealed samples depend on the thicknesses of the CdO and ZnO sublayers in the
as grown superlattice structures. Depth-resolved CL measurements showed that
shifting of the near band edge emission peaks is closely related to the Cd
profiles measured with SIMS.Comment: 14 pages, 6 figure
The oblique firehose instability in a bi-kappa magnetized plasma
In this work, we derive a dispersion equation that describes the excitation
of the oblique (or Alfv\'en) firehose instability in a plasma that contains
both electron and ion species modelled by bi-kappa velocity distribution
functions. The equation is obtained with the assumptions of low-frequency waves
and moderate to large values of the parallel (respective to the ambient
magnetic field) plasma beta parameter, but it is valid for any direction of
propagation and for any value of the particle gyroradius (or Larmor radius).
Considering values for the physical parameters typical to those found in the
solar wind, some solutions of the dispersion equation, corresponding to the
unstable mode, are presented. In order to implement the dispersion solver,
several new mathematical properties of the special functions occurring in a
kappa plasma are derived and included. The results presented here suggest that
the superthermal characteristic of the distribution functions leads to
reductions to both the maximum growth rate of the instability and of the
spectral range of its occurrence
Data production models for the CDF experiment
The data production for the CDF experiment is conducted on a large Linux PC
farm designed to meet the needs of data collection at a maximum rate of 40
MByte/sec. We present two data production models that exploits advances in
computing and communication technology. The first production farm is a
centralized system that has achieved a stable data processing rate of
approximately 2 TByte per day. The recently upgraded farm is migrated to the
SAM (Sequential Access to data via Metadata) data handling system. The software
and hardware of the CDF production farms has been successful in providing large
computing and data throughput capacity to the experiment.Comment: 8 pages, 9 figures; presented at HPC Asia2005, Beijing, China, Nov 30
- Dec 3, 200
Markers of early diagnostics of cardiorenal syndrome in practice of therapeutic
Actuality. Cardiorenal syndrome (CRS) is a pathophysiological disorder of the heart and kidneys, in which the dysfunction of one of these organs leads to the dysfunction of the other. Timely diagnosed (cattle) allows you to start the necessary therapy on time, prevent the development of complications and reduce lethality. Clinical symptoms appear only in the late stages of cattle, so the use and development of early diagnosis can detect damage at the cellular level
Data processing model for the CDF experiment
The data processing model for the CDF experiment is described. Data
processing reconstructs events from parallel data streams taken with different
combinations of physics event triggers and further splits the events into
datasets of specialized physics datasets. The design of the processing control
system faces strict requirements on bookkeeping records, which trace the status
of data files and event contents during processing and storage. The computing
architecture was updated to meet the mass data flow of the Run II data
collection, recently upgraded to a maximum rate of 40 MByte/sec. The data
processing facility consists of a large cluster of Linux computers with data
movement managed by the CDF data handling system to a multi-petaByte Enstore
tape library. The latest processing cycle has achieved a stable speed of 35
MByte/sec (3 TByte/day). It can be readily scaled by increasing CPU and
data-handling capacity as required.Comment: 12 pages, 10 figures, submitted to IEEE-TN
Effect of temperature anisotropy on various modes and instabilities for a magnetized non-relativistic bi-Maxwellian plasma
Using kinetic theory for homogeneous collisionless magnetized plasmas, we
present an extended review of the plasma waves and instabilities and discuss
the anisotropic response of generalized relativistic dielectric tensor and
Onsager symmetry properties for arbitrary distribution functions. In general,
we observe that for such plasmas only those electromagnetic modes whose
magnetic field perturbations are perpendicular to the ambient magneticeld,
i.e.,B1 \perp B0, are effected by the anisotropy. However, in oblique
propagation all modes do show such anisotropic effects. Considering the
non-relativistic bi-Maxwellian distribution and studying the relevant
components of the general dielectric tensor under appropriate conditions, we
derive the dispersion relations for various modes and instabilities. We show
that only the electromagnetic R- and L- waves, those derived from them and the
O-mode are affected by thermal anisotropies, since they satisfy the required
condition B1\perpB0. By contrast, the perpendicularly propagating X-mode and
the modes derived from it (the pure transverse X-mode and Bernstein mode) show
no such effect. In general, we note that the thermal anisotropy modifies the
parallel propagating modes via the parallel acoustic effect, while it modifies
the perpendicular propagating modes via the Larmor-radius effect. In oblique
propagation for kinetic Alfven waves, the thermal anisotropy affects the
kinetic regime more than it affects the inertial regime. The generalized fast
mode exhibits two distinct acoustic effects, one in the direction parallel to
the ambient magnetic field and the other in the direction perpendicular to it.
In the fast-mode instability, the magneto-sonic wave causes suppression of the
firehose instability. We discuss all these propagation characteristics and
present graphic illustrations
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