4,956 research outputs found
Topologically protected charge transfer along the edge of a chiral -wave superconductor
The Majorana fermions propagating along the edge of a topological
superconductor with pairing deliver a shot noise power of
per eV of voltage bias. We calculate the full
counting statistics of the transferred charge and find that it becomes
trinomial in the low-temperature limit, distinct from the binomial statistics
of charge- transfer in a single-mode nanowire or charge- transfer
through a normal-superconductor interface. All even-order correlators of
current fluctuations have a universal quantized value, insensitive to disorder
and decoherence. These electrical signatures are experimentally accessible,
because they persist for temperatures and voltages large compared to the
Thouless energy.Comment: 5 pages, 4 figures. v3 [post-publication]: added an appendix on the
effect of a tunnel barrier at the normal-superconductor contac
Inertial electrostatic confinement as a power source for electric propulsion
The potential use of an INERTIAL ELECTROSTATIC CONFINEMENT (IEC) power source for space propulsion has previously been suggested by the authors and others. In the past, these discussions have generally followed the charged-particle electric-discharge engine (QED) concept proposed by Bussard, in which the IEC is used to generate an electron beam which vaporizes liquid hydrogen for use as a propellant. However, an alternate approach is considered, using the IEC to drive a 'conventional' electric thruster unit. This has the advantage of building on the rapidly developing technology for such thrusters, which operate at higher specific impulse. Key issues related to this approach include the continued successful development of the physics and engineering of the IEC unit, as well as the development of efficient step-down dc voltage transformers. The IEC operates by radial injection of energetic ions into a spherical vessel. A very high ion density is created in a small core region at the center of the vessel, resulting in extremely high fusion power density in the core. Experiments at the U. of Illinois in small IEC devices (is less than 60 cm. dia.) demonstrated much of the basic physics underlying this concept, e.g. producing 10(exp 6) D-D neutrons/sec steady-state with deuterium gas flow injection. The ultimate goal is to increase the power densities by several orders of magnitude and to convert to D-He-3 injection. If successful, such an experiment would represent a milestone proof-of-principle device for eventual space power use. Further discussion of IEC physics and status are presented with a description of the overall propulsion system and estimated performance
Response of selected plant and insect species to simulated solid rocket exhaust mixtures and to exhaust components from solid rocket fuels
The effects of solid rocket fuel (SRF) exhaust on selected plant and and insect species in the Merritt Island, Florida area was investigated in order to determine if the exhaust clouds generated by shuttle launches would adversely affect the native, plants of the Merritt Island Wildlife Refuge, the citrus production, or the beekeeping industry of the island. Conditions were simulated in greenhouse exposure chambers and field chambers constructed to model the ideal continuous stirred tank reactor. A plant exposure system was developed for dispensing and monitoring the two major chemicals in SRF exhaust, HCl and Al203, and for dispensing and monitoring SRF exhaust (controlled fuel burns). Plants native to Merritt Island, Florida were grown and used as test species. Dose-response relationships were determined for short term exposure of selected plant species to HCl, Al203, and mixtures of the two to SRF exhaust
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SEM-EDS analyses of small craters in stardust aluminium foils: implications for the Wild-2 dust distribution
Implications for the Wild-2 dust distribution of the statistical results obtained by SEM-EDS from nearly 300 impact craters on aluminium foils of the Stardust sample tray assembly
Charm Production in DPMJET
In this work, charm production in the {\sc dpmjet} hadronic jet simulation is
compared to experimental data. Since the major application of {\sc dpmjet} is
the simulation of cosmic ray-induced air showers, the version of the code
integrated in the CORSIKA simulation package has been used for the comparison.
Wherever necessary, adjustments have been made to improve agreement between
simulation and data. With the availability of new muon/neutrino detectors that
combine a large fiducial volume with large amounts of shielding, investigation
of prompt muons and neutrinos from cosmic ray interactions will be feasible for
the first time. Furthermore, above TeV charmed particle decay
becomes the dominant background for diffuse extraterrestrial neutrino flux
searches. A reliable method to simulate charm production in high-energy
proton-nucleon interactions is therefore required.Comment: 10 pages, to be published in JCA
Heliophysics Event Knowledgebase for the Solar Dynamics Observatory and Beyond
The immense volume of data generated by the suite of instruments on SDO
requires new tools for efficient identifying and accessing data that is most
relevant to research investigations. We have developed the Heliophysics Events
Knowledgebase (HEK) to fill this need. The HEK system combines automated data
mining using feature-detection methods and high-performance visualization
systems for data markup. In addition, web services and clients are provided for
searching the resulting metadata, reviewing results, and efficiently accessing
the data. We review these components and present examples of their use with SDO
data.Comment: 17 pages, 4 figure
Root cortex development is fine-tuned by the interplay of MIGs, SCL3 and DELLAs during arbuscular mycorrhizal symbiosis
Root development is a crucial process that determines the ability of plants to acquire nutrients, adapt to the substrate and withstand changing environmental conditions. Root plasticity is controlled by a plethora of transcriptional regulators that allow, in contrast to tissue development in animals, post-embryonic changes that give rise to new tissue and specialized cells.
One of these changes is the accommodation in the cortex of hyperbranched hyphae of symbiotic arbuscular mycorrhizal (AM) fungi, called arbuscules. Arbuscule-containing cells undergo massive reprogramming to coordinate developmental changes with transport processes.
Here we describe a novel negative regulator of arbuscule development, MIG3. MIG3 induces and interacts with SCL3, both of which modulate the activity of the central regulator DELLA, restraining cortical cell growth. As in a tug-of-war, MIG3-SCL3 antagonizes the function of the complex MIG1-DELLA, which promotes the cell expansion required for arbuscule development, adjusting cell size during the dynamic processes of the arbuscule life cycle.
Our results in the legume plant Medicago truncatula advance the knowledge of root development in dicot plants, showing the existence of additional regulatory elements not present in Arabidopsis that fine-tune the activity of conserved central modules
Utilização de caldas orgânicas fermentadas no controle do Mal-do-Panamá da bananeira.
A banana é uma das culturas mais importantes no cenário agrícola nacional, tendo cerca de 520 mil hectares de área plantada. Dentre as doenças que ocorre na cultura da bananeira, o mal-do-Panamá, causado pelo fungo Fusariumoxysporum f. sp. cubense (Foc) é considerada a mais destrutiva
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