1,610 research outputs found
Germination of microconidia from selected Neurospora strains
Germination of microconidia from selected Neurospora strain
New Limits on the Polarized Anisotropy of the Cosmic Microwave Background at Subdegree Angular Scales
We update the limit from the 90 GHz PIQUE ground-based polarimeter on the
magnitude of any polarized anisotropy of the cosmic microwave radiation. With a
second year of data, we have now limited both Q and U on a ring of 1 degree
radius. The window functions are broad: for E-mode polarization, the effective
l is = 191 +143 -132. We find that the E-mode signal can be no greater than
8.4 microK (95% CL), assuming no B-mode polarization. Limits on a possible
B-mode signal are also presented.Comment: 4 pages, 3 figures, submitted to Astrophysical Journal Letter
New Insights into Variations in Enceladus Plume Particle Launch Velocities from Cassini-VIMS spectral data
Enceladus' plume consists mainly of a mixture of water vapor and solid ice
particles that may originate from a subsurface ocean. The physical processes
underlying Enceladus' plume particle dynamics are still being debated, and
quantifying the particles' size distribution and launch velocities can help
constrain these processes. Cassini's Visual and Infrared Mapping Spectrometer
(VIMS) observed the Enceladus plume over a wavelength range of 0.9 micron to
5.0 microns for a significant fraction of Enceladus' orbital period on three
dates in the summer of 2017. We find that the relative brightness of the plume
on these different dates varies with wavelength, implying that the particle
size distribution in the plume changes over time. These observations also
enable us to study how the particles' launch velocities vary with time and
observed wavelength. We find that the typical launch velocity of particles
remains between 140 m/s and 148 m/s at wavelengths between 1.2 microns and 3.7
microns. This may not be consistent with prior models where particles are only
accelerated by interactions with the vent walls and gas, and could imply that
mutual particle collisions close to the vent are more important than previously
recognized.Comment: 13 pages, 8 figures, accepted for publication in PS
The population of propellers in Saturn's A Ring
We present an extensive data set of ~150 localized features from Cassini
images of Saturn's Ring A, a third of which are demonstrated to be persistent
by their appearance in multiple images, and half of which are resolved well
enough to reveal a characteristic "propeller" shape. We interpret these
features as the signatures of small moonlets embedded within the ring, with
diameters between 40 and 500 meters. The lack of significant brightening at
high phase angle indicates that they are likely composed primarily of
macroscopic particles, rather than dust. With the exception of two features
found exterior to the Encke Gap, these objects are concentrated entirely within
three narrow (~1000 km) bands in the mid-A Ring that happen to be free from
local disturbances from strong density waves. However, other nearby regions are
similarly free of major disturbances but contain no propellers. It is unclear
whether these bands are due to specific events in which a parent body or bodies
broke up into the current moonlets, or whether a larger initial moonlet
population has been sculpted into bands by other ring processes.Comment: 31 pages, 10 figures; Accepted at A
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