1,184 research outputs found
Small-Angle CMB Temperature Anisotropies Induced by Cosmic Strings
We use Nambu-Goto numerical simulations to compute the cosmic microwave
background (CMB) temperature anisotropies induced at arcminute angular scales
by a network of cosmic strings in a Friedmann-Lemaitre-Robertson-Walker (FLRW)
expanding universe. We generate 84 statistically independent maps on a 7.2
degree field of view, which we use to derive basic statistical estimators such
as the one-point distribution and two-point correlation functions. At high
multipoles, the mean angular power spectrum of string-induced CMB temperature
anisotropies can be described by a power law slowly decaying as \ell^{-p}, with
p=0.889 (+0.001,-0.090) (including only systematic errors). Such a behavior
suggests that a nonvanishing string contribution to the overall CMB
anisotropies may become the dominant source of fluctuations at small angular
scales. We therefore discuss how well the temperature gradient magnitude
operator can trace strings in the context of a typical arcminute
diffraction-limited experiment. Including both the thermal and nonlinear
kinetic Sunyaev-Zel'dovich effects, the Ostriker-Vishniac effect, and the
currently favored adiabatic primary anisotropies, we find that, on such a map,
strings should be ``eye visible,'' with at least of order ten distinctive
string features observable on a 7.2 degree gradient map, for tensions U down to
GU \simeq 2 x 10^{-7} (in Planck units). This suggests that, with upcoming
experiments such as the Atacama Cosmology Telescope (ACT), optimal
non-Gaussian, string-devoted statistical estimators applied to small-angle CMB
temperature or gradient maps may put stringent constraints on a possible cosmic
string contribution to the CMB anisotropies.Comment: 17 pages, 9 figures. v2: matches published version, minor
clarifications added, typo in Eq. (8) fixed, results unchange
Machine vision based system for flower counting in strawberry plants
Background: For strawberry production, accurate yield prediction is very important to help growers increase their profit by efficiently managing their harvesting operation and setting their contracts with buyers. Strawberry plants produce flowers and fruits simultaneously throughout the season. Strawberry flowers are white in color with a yellow pollen at the center, which later becomes a fruit. Strawberry yield can be estimated by counting the number of flowers in a field in advance of harvesting. The objective of this project is to count the number of flowers using image processing techniques, create a map of flower counts using gee-tagging and provide farmers with an estimate of the yield in a given area.
Methods: Strawberry flowers could be at different stages of maturation during imaging. We pre-process images using edge-preserving smoothing filter to remove noise without removing fine features. The next stage involves segmentation of flowers from the background. Since flowers are brighter than most other components of plants, simple thresholding with segmentation algorithm will produce candidate pixels. Then flower detection will be conducted using traditional feature engineering along with a classifier such as Histogram of Oriented Gradients, Wavelet Transform, Local Binary Patterns, and the Deep Learning based techniques.
Results: Once flowers are detected, the number of flowers is counted to provide farmers with an estimate of yield and variability at different locations in the field.
Discussions: One of the biggest challenges with outdoor imaging is the variable lighting conditions. We propose a camera mounted autonomous system to go over rows of strawberry plants to capture images with geo-tags. Cameras are positioned to capture images from different angles to capture occluded flowers.
Conclusion: A novel image processing method for accurate strawberry yield prediction is proposed by counting the number of flowers from images for efficient crop management
Hereditary sensory and autonomic neuropathy type IV and orthopaedic complications
SummaryHereditary sensory and autonomic neuropathy type IV (HSAN-IV) is a very rare autosomal recessive disorder characterized by recurrent episodes of unexplained fever, extensive anhidrosis, total insensitivity to pain, hypotonia, and mental retardation. The most frequent complications of this disease are corneal scarring, multiple fractures, joint deformities, osteomyelitis, and disabling self-mutilations. We reported the case of a 12-year-old boy. The goal was to discuss our decision-making and compare this case with cases described in the literature
Acceleration of small astrophysical grains due to charge fluctuations
We discuss a novel mechanism of dust acceleration which may dominate for
particles smaller than m. The acceleration is caused by their
direct electrostatic interactions arising from fluctuations of grain charges.
The energy source for the acceleration are the irreversible plasma processes
occurring on the grain surfaces. We show that this mechanism of
charge-fluctuation-induced acceleration likely affects the rate of grain
coagulation and shattering of the population of small grains.Comment: 8 pages, 2 figures, revised version, submitted to Astrophysical
Journa
CMBPol Mission Concept Study: Prospects for polarized foreground removal
In this report we discuss the impact of polarized foregrounds on a future
CMBPol satellite mission. We review our current knowledge of Galactic polarized
emission at microwave frequencies, including synchrotron and thermal dust
emission. We use existing data and our understanding of the physical behavior
of the sources of foreground emission to generate sky templates, and start to
assess how well primordial gravitational wave signals can be separated from
foreground contaminants for a CMBPol mission. At the estimated foreground
minimum of ~100 GHz, the polarized foregrounds are expected to be lower than a
primordial polarization signal with tensor-to-scalar ratio r=0.01, in a small
patch (~1%) of the sky known to have low Galactic emission. Over 75% of the sky
we expect the foreground amplitude to exceed the primordial signal by about a
factor of eight at the foreground minimum and on scales of two degrees. Only on
the largest scales does the polarized foreground amplitude exceed the
primordial signal by a larger factor of about 20. The prospects for detecting
an r=0.01 signal including degree-scale measurements appear promising, with 5
sigma_r ~0.003 forecast from multiple methods. A mission that observes a range
of scales offers better prospects from the foregrounds perspective than one
targeting only the lowest few multipoles. We begin to explore how optimizing
the composition of frequency channels in the focal plane can maximize our
ability to perform component separation, with a range of typically 40 < nu <
300 GHz preferred for ten channels. Foreground cleaning methods are already in
place to tackle a CMBPol mission data set, and further investigation of the
optimization and detectability of the primordial signal will be useful for
mission design.Comment: 42 pages, 14 figures, Foreground Removal Working Group contribution
to the CMBPol Mission Concept Study, v2, matches AIP versio
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