665 research outputs found
Control of nonenzymatic browning in intermediate-moisture foods
Series of compounds called humectants were found to decrease rate of browning when added to intermediate-moisture foods. Twenty percent level of humectant can increase shelf life of foods by factor of 5 or 6
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Applications of fiber optics in physical protection
The purpose of this NUREG is to provide technical information useful for the development of fiber-optic communications and intrusion detection subsystems relevant to physical protection. There are major sections on fiber-optic technology and applications. Other topics include fiber-optic system components and systems engineering. This document also contains a glossary, a list of standards and specifications, and a list of fiber-optic equipment vendors
JHK Observations of Faint Standard Stars in the Mauna Kea Near-Infrared Photometric System
JHK photometry in the Mauna Kea Observatory (MKO) near-IR system is presented
for 115 stars. Of these, 79 are UKIRT standards and 42 are LCO standards. The
average brightness is 11.5 mag, with a range of 10 to 15. The average number of
nights each star was observed is 4, and the average of the internal error of
the final results is 0.011 mag. These JHK data agree with those reported by
other groups to 0.02 mag. The measurements are used to derive transformations
between the MKO JHK photometric system and the UKIRT, LCO and 2MASS systems.
The 2MASS-MKO data scatter by 0.05 mag for redder stars: 2MASS-J includes H2O
features in dwarfs and MKO-K includes CO features in giants. Transformations
derived for stars whose spectra contain only weak features cannot give accurate
transformations for objects with strong absorption features within a filter
bandpasses. We find evidence of systematic effects at the 0.02 mag level in the
photometry of stars with J<11 and H,K<10.5. This is due to an underestimate of
the linearity correction for stars observed with the shortest exposure times;
very accurate photometry of stars approaching the saturation limits of infrared
detectors which are operated in double-read mode is difficult to obtain. Four
stars in the sample, GSPC S705-D, FS 116 (B216-b7), FS 144 (Ser-EC84) and FS 32
(Feige 108), may be variable. 84 stars in the sample have 11< J< 15 and
10.5<H,K<15, are not suspected to be variable, and have magnitudes with an
estimated error <0.027 mag; 79 of these have an error of <0.020 mag. These
represent the first published high-accuracy JHK stellar photometry in the MKO
photometric system; we recommend these objects be employed as primary standards
for that system [abridged].Comment: Accepted for publication in MNRAS, 14 pages, 5 Figure
Band anticrossing in GaNxSb1–x
Fourier transform infrared absorption measurements are presented from the dilute nitride semiconductor GaNSb with nitrogen incorporations between 0.2% and 1.0%. The divergence of transitions from the valence band to E– and E+ can be seen with increasing nitrogen incorporation, consistent with theoretical predictions. The GaNSb band structure has been modeled using a five-band k·p Hamiltonian and a band anticrossing fitting has been obtained using a nitrogen level of 0.78 eV above the valence band maximum and a coupling parameter of 2.6 eV
A Surface-Gated InSb Quantum Well Single Electron Transistor
Single electron charging effects in a surface-gated InSb/AlInSb QW structure
are reported. This material, due to its large g-factor and light effective
mass, offers considerable advantages over more commonly used materials, such as
GaAs, for quantum information processing devices. However, differences in
material and device technology result in significant processing challenges.
Simple Coulomb blockade and quantised confinement models are considered to
explain the observation of conductance oscillations in these structures. The
charging energy is found to be comparable with the energy spectrum for single
particle states
The JCMT 12CO(3-2) Survey of the Cygnus X Region: I. A Pathfinder
Cygnus X is one of the most complex areas in the sky. This complicates
interpretation, but also creates the opportunity to investigate accretion into
molecular clouds and many subsequent stages of star formation, all within one
small field of view. Understanding large complexes like Cygnus X is the key to
understanding the dominant role that massive star complexes play in galaxies
across the Universe.
The main goal of this study is to establish feasibility of a high-resolution
CO survey of the entire Cygnus X region by observing part of it as a
Pathfinder, and to evaluate the survey as a tool for investigating the
star-formation process.
A 2x4 degree area of the Cygnus X region has been mapped in the 12CO(3-2)
line at an angular resolution of 15" and a velocity resolution of ~0.4km/s
using HARP-B and ACSIS on the James Clerk Maxwell Telescope. The star formation
process is heavily connected to the life-cycle of the molecular material in the
interstellar medium. The high critical density of the 12CO(3-2) transition
reveals clouds in key stages of molecule formation, and shows processes that
turn a molecular cloud into a star.
We observed ~15% of Cygnus X, and demonstrated that a full survey would be
feasible and rewarding. We detected three distinct layers of 12CO(3-2)
emission, related to the Cygnus Rift (500-800 pc), to W75N (1-1.8 kpc), and to
DR21 (1.5-2.5 kpc). Within the Cygnus Rift, HI self-absorption features are
tightly correlated with faint diffuse CO emission, while HISA features in the
DR21 layer are mostly unrelated to any CO emission. 47 molecular outflows were
detected in the Pathfinder, 27 of them previously unknown. Sequentially
triggered star formation is a widespread phenomenon.Comment: 18 pages, 13 figures, accepted for publication in Astronomy &
Astrophysic
The JCMT Gould Belt survey: Dense core clusters in Orion B
The James Clerk Maxwell Telescope Gould Belt Legacy Survey obtained SCUBA-2 observations of dense cores within three sub-regions of OrionB: LDN1622, NGC2023/2024, and NGC2068/2071, all of which contain clusters of cores. We present an analysis of the clustering properties of these cores, including the two-point correlation function and Cartwright’s Q parameter. We identify individual clusters of dense cores across all three regions using a minimal spanning tree technique, and find that in each cluster, the most massive cores tend to be centrally located. We also apply the independent M–Σ technique and find a strong correlation between core mass and the local surface density of cores. These two lines of evidence jointly suggest that some amount of mass segregation in clusters has happened already at the dense core stage
The JCMT Gould Belt Survey: a quantitative comparison between SCUBA-2 data reduction methods
Performing ground-based submillimetre observations is a difficult task as the measurements are subject to absorption and emission from water vapour in the Earth's atmosphere and time variation in weather and instrument stability. Removing these features and other artefacts from the data is a vital process which affects the characteristics of the recovered astronomical structure we seek to study. In this paper, we explore two data reduction methods for data taken with the Submillimetre Common-User Bolometer Array-2 (SCUBA-2) at the James Clerk Maxwell Telescope (JCMT). The JCMT Legacy Reduction 1 (JCMT LR1) and The Gould Belt Legacy Survey Legacy Release 1 (GBS LR1) reduction both use the same software (starlink) but differ in their choice of data reduction parameters. We find that the JCMT LR1 reduction is suitable for determining whether or not compact emission is present in a given region and the GBS LR1 reduction is tuned in a robust way to uncover more extended emission, which better serves more in-depth physical analyses of star-forming regions. Using the GBS LR1 method, we find that compact sources are recovered well, even at a peak brightness of only three times the noise, whereas the reconstruction of larger objects requires much care when drawing boundaries around the expected astronomical signal in the data reduction process. Incorrect boundaries can lead to false structure identification or it can cause structure to be missed. In the JCMT LR1 reduction, the extent of the true structure of objects larger than a point source is never fully recovered
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