49,316 research outputs found
Probing Neutral Majorana Fermion Edge Modes with Charge Transport
We propose two experiments to probe the Majorana fermion edge states that
occur at a junction between a superconductor and a magnet deposited on the
surface of a topological insulator. Combining two Majorana fermions into a
single Dirac fermion on a magnetic domain wall allows the neutral Majorana
fermions to be probed with charge transport. We will discuss a novel
interferometer for Majorana fermions, which probes their Z_2 phase. This setup
also allows the transmission of neutral Majorana fermions through a point
contact to be measured. We introduce a point contact formed by a
superconducting junction and show that its transmission can be controlled by
the phase difference across the junction. We discuss the feasibility of these
experiments using the recently discovered topological insulator Bi_2 Se_3.Comment: 4 page
Electricity from photovoltaic solar cells: Flat-Plate Solar Array Project final report. Volume VII: Module encapsulation
The Flat-Plate Solar Array (FSA) Project, funded by the U.S. Government and managed by the Jet Propulsion Laboratory, was formed in 1975 to develop the module/array technology needed to attain widespread terrestrial use of photovoltaics by 1985. To accomplish this, the FSA Project established and managed an Industry, University, and Federal Government Team to perform the needed research and development.
The objective of the Encapsulation Task was to develop, demonstrate, and qualify photovoltaic (PV) module encapsulation systems that would provide 20-year (later increased to 30-year) life expectancies in terrestrial environments, and which would be compatible with the cost and performance goals of the FSA Project. The scope of the Encapsulation Task included the identification, development, and evaluation of material systems and configurations required to support and protect the optically and electrically active solar cell circuit components in the PV module operating environment. Encapsulation material technologies summarized in this report include the development of low-cost ultraviolet protection techniques, stable low-cost pottants, soiling resistant coatings, electrical isolation criteria, processes for optimum interface bonding, and analytical and experimental tools for evaluating the long-term durability and structural adequacy of encapsulated modules. Field testing, accelerated stress testing, and design studies have demonstrated that encapsulation materials, processes, and configurations are available that will meet the FSA cost and performance goals. Thirty-year module life expectancies are anticipated based on accelerated stress testing results and on extrapolation of real-time field exposures in excess of 9 years
Arbitrary Dimensional Schwarzschild-FRW Black Holes
The metric of arbitrary dimensional Schwarzschild black hole in the
background of Friedman-Robertson-Walker universe is presented in the cosmic
coordinates system. In particular, the arbitrary dimensional Schwarzschild-de
Sitter metric is rewritten in the Schwarzschild coordinates system and basing
on which the even more generalized higher dimensional Schwarzschild-de Sitter
metric with another extra dimensions is found. The generalized solution shows
that the cosmological constant may roots in the extra dimensions of space.Comment: 10 page
SIRIS: a high resolution scanning infrared camera for examining paintings
The new SIRIS (Scanning InfraRed Imaging System) camera developed at the National Gallery in London allows highresolution images of paintings to be made in the near infrared region (900–1700 nm). Images of 5000 × 5000 pixels are made by moving a 320 × 256 pixel InGaAs array across the focal plane of the camera using two orthogonal translation stages. The great advantages of this camera over scanning infrared devices are its relative portability and that image acquisition is comparatively rapid – a full 5000 × 5000 pixel image can be made in around 20 minutes. The paper describes the development of the mechanical, optical and electronic components of the camera, including the design of a new lens. The software routines used to control image capture and to assemble the individual 320 × 256 pixel frames into a seamless mosaic image are also mentioned. The optics of the SIRIS camera have been designed so that the camera can operate at a range of resolutions; from around 2.5 pixels per millimetre on large paintings of up to 2000 × 2000 mm to 10 pixels per millimetre on smaller paintings or details of paintings measuring 500 × 500 mm. The camera is primarily designed to examine underdrawings in paintings; preliminary results from test targets and paintings are presented and the quality of the images compared with those from other cameras currently used in this field
A Cosmology-Independent Calibration of Gamma-Ray Burst Luminosity Relations and the Hubble Diagram
An important concern in the application of gamma-ray bursts (GRBs) to
cosmology is that the calibration of GRB luminosity/energy relations depends on
the cosmological model, due to the lack of a sufficient low-redshift GRB
sample. In this paper, we present a new method to calibrate GRB relations in a
cosmology-independent way. Since objects at the same redshift should have the
same luminosity distance and since the distance moduli of Type Ia supernovae
(SNe Ia) obtained directly from observations are completely cosmology
independent, we obtain the distance modulus of a GRB at a given redshift by
interpolating from the Hubble diagram of SNe Ia. Then we calibrate seven GRB
relations without assuming a particular cosmological model and construct a GRB
Hubble diagram to constrain cosmological parameters. From the 42 GRBs at
, we obtain ,
for the flat CDM model, and
for the dark energy model with a constant equation of state
, which is consistent with the concordance model in
a 1- confidence region.Comment: 7 pages, 3 figures, 1 table, now matches the editorially revised
version; accepted for publication in ApJ (vol 685)
Multiphoton entanglement through a Bell multiport beam splitter
Multiphoton entanglement is an important resource for linear optics quantum
computing. Here we show that a wide range of highly entangled multiphoton
states, including W-states, can be prepared by interfering single photons
inside a Bell multiport beam splitter and using postselection. A successful
state preparation is indicated by the collection of one photon per output port.
An advantage of the Bell multiport beam splitter is that it redirects the
photons without changing their inner degrees of freedom. The described setup
can therefore be used to generate polarisation, time-bin and frequency
multiphoton entanglement, even when using only a single photon source.Comment: 8 pages, 2 figures, carefully revised version, references adde
Multiwavelength Observations of GX 339-4 in 1996. II. Rapid X-ray Variability
As part of our multiwavelength campaign of GX 339-4 observations in 1996 we
present the rapid X-ray variability observed July 26 using the RXTE when the
source was in a hard state (= soft X-ray low state). We found that the source
was extremely variable, with many bright flares. The flares have relatively
symmetric time profiles. There are a few time intervals where the flux rises
steadily and then drops suddenly, sometimes to a level lower than the average
before the increase. Hardness ratios showed that the source was slightly softer
when the flux was brighter. The power density spectra (PDS) were also
complicated and we found that broken power laws do not provide adequate fits to
any of them. Instead a pair of zero-centered Lorentzians gives a good general
description of the shape of the PDS. We found several quasi-periodic
oscillations (QPO), including some that are harmonically spaced with the most
stable frequency at 0.35 Hz. While the overall rms variability of the source
was close to being constant throughout the observation (29% integrating between
0.01 and 50 Hz), there is a small but significant change in the PDS shape with
time. More importantly, we show that the soft 2-5 keV band is more variable
than the harder 5-10 and 10-40 keV bands, which is unusual for this source and
for other black hole candidates. Cross correlation functions (CCF) between
these bands show that the light curve for the 10-40 keV band lags that of the
2-5 keV band by 5 msec.Comment: Submitted to Astrophysical Journal. 20 pages. 8 figure
Photovoltaic module encapsulation design and materials selection, volume 1
Encapsulation material system requirements, material selection criteria, and the status and properties of encapsulation materials and processes available are presented. Technical and economic goals established for photovoltaic modules and encapsulation systems and their status are described. Available encapsulation technology and data are presented to facilitate design and material selection for silicon flat plate photovoltaic modules, using the best materials available and processes optimized for specific power applications and geographic sites. The operational and environmental loads that encapsulation system functional requirements and candidate design concepts and materials that are identified to have the best potential to meet the cost and performance goals for the flat plate solar array project are described. Available data on encapsulant material properties, fabrication processing, and module life and durability characteristics are presented
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