5,459 research outputs found
Millimeter radiation from a 3D model of the solar atmosphere II. Chromospheric magnetic field
We use state-of-the-art, three-dimensional non-local thermodynamic
equilibrium (non-LTE) radiative magnetohydrodynamic simulations of the quiet
solar atmosphere to carry out detailed tests of chromospheric magnetic field
diagnostics from free-free radiation at millimeter and submillimeter
wavelengths (mm/submm). The vertical component of the magnetic field was
deduced from the mm/submm brightness spectra and the degree of circular
polarization synthesized at millimeter frequencies. We used the frequency bands
observed by the Atacama Large Millimeter/Submillimeter Array (ALMA) as a
convenient reference. The magnetic field maps obtained describe the
longitudinal magnetic field at the effective formation heights of the relevant
wavelengths in the solar chromosphere. The comparison of the deduced and model
chromospheric magnetic fields at the spatial resolution of both the model and
current observations demonstrates a good correlation, but has a tendency to
underestimate the model field. The systematic discrepancy of about 10 percent
is probably due to averaging of the restored field over the heights
contributing to the radiation, weighted by the strength of the contribution. On
the whole, the method of probing the longitudinal component of the magnetic
field with free-free emission at mm/submm wavelengths is found to be applicable
to measurements of the weak quiet-Sun magnetic fields. However, successful
exploitation of this technique requires very accurate measurements of the
polarization properties (primary beam and receiver polarization response) of
the antennas, which will be the principal factor that determines the level to
which chromospheric magnetic fields can be measured. Consequently,
high-resolution and high-precision observations of circularly polarized
radiation at millimeter wavelengths can be a powerful tool for producing
chromospheric longitudinal magnetograms.Comment: 12 pages, 13 figures, accepted for publication in A&
Using Spin Correlations to Distinguish Zh from ZA at the International Linear Collider
We investigate how to exploit the spin information imparted to the Z boson in
associated Higgs production at a future linear collider as an aid in
distinguishing between CP-even and CP-odd Higgs bosons. We apply a generalized
spin-basis analysis which allowsus to study the possibilities offered by
non-traditional choices of spin projection axis. In particular, we find that
the Z bosons produced in association with a CP-even Higgs via polarized
collisions are in a single transverse spin-state (>90% purity) when we use the
Zh-transverse basis, provided that the Z~bosons are not ultra-relativistic
(speed <0.9c). This same basis applied to the associated production of a CP-odd
Higgs yields Z's that are an approximately equal mixture of longitudinal and
transverse polarizations. We present a decay angular distribution which could
be used to distinguish between the CP-even and CP-odd cases. Finally, we make a
few brief remarks about how this distribution would be affected if the Higgs
boson turns out to not be a CP-eigenstate.Comment: 48 pages, 18 figures, revtex
Orion Ground Test Article Water Impact Tests: Photogrammetric Evaluation of Impact Conditions
The Ground Test Article (GTA) is an early production version of the Orion Crew Module (CM). The structural design of the Orion CM is being developed based on LS-DYNA water landing simulations. As part of the process of confirming the accuracy of LS-DYNA water landing simulations, the GTA water impact test series was conducted at NASA Langley Research Center (LaRC) to gather data for comparison with simulations. The simulation of the GTA water impact tests requires the accurate determination of the impact conditions. To accomplish this, the GTA was outfitted with an array of photogrammetry targets. The photogrammetry system utilizes images from two cameras with a specialized tracking software to determine time histories for the 3-D coordinates of each target. The impact conditions can then be determined from the target location data
Elevated temperature treatment as a novel method for decreasing p57 on the cell surface of Renibacterium salmoninarum
Renibacterium salmoninarum is a Gram-positive diplo-bacillus and the causative agent of bacterial kidney disease, a prevalent disease of salmonid fish. Virulent isolates of R. salmoninarum have a hydrophobic cell surface and express the 57-58 kDa protein (p57). Here we have investigated parameters which effect cell hydrophobicity and p57 degradation. Incubation of R, salmoninarum cells at 37 degrees C for \u3e4 h decreased cell surface hydrophobicity as measured by the salt aggregation assay, and decreased the amount of cell associated p57. Incubation of cells at lower temperatures (22, 17, 4 or -20 degrees C) for up to 16 h did not reduce hydrophobicity or the amount of cell associated p57. Both the loss of cell surface hydrophobicity and the degradation of p57 were inhibited by pre-incubation with the serine protease inhibitor phenylmethylsulfonyl fluoride (PMSF). Cell surface hydrophobicity was specifically reconstituted by incubation with extracellular protein (ECP) concentrated from culture supernatant and was correlated with the reassociation of p57 onto the bacterial cell surface as determined by western blot and total protein stain analyses. The ability of p57 to reassociate suggests that the bacterial cell surface is not irreversibly modified by the 37 degrees C treatment and that p57 contributes to the hydrophobic nature of R. salmoninarum. In summary, we describe parameters effecting the removal of the p57 virulence factor and suggest the utility of this modification for generating a whole cell vaccine against bacterial kidney disease
Progress towards omnidirectional transformation optics with lenses
We study, theoretically, omni-directional Euclidean transformation-optics (TO) devices comprising planar, light-ray-direction changing, imaging, interfaces. We initially studied such devices in the case when the interfaces are homogeneous, showing that very general transformations between physical and electromagnetic space are possible. We are now studying the case of inhomogeneous interfaces. This case is more complex to analyse, but the inhomogeneous interfaces include ideal thin lenses, which gives rise to the hope that it might be possible to construct practical omni-directional TO devices from lenses alone. Here we report on our progress in this direction
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