102 research outputs found
CEG 2350: OS Concepts and Usage
Provides introduction to Linux and Windows operating systems and system administration. Covers files and directories, ownership and sharing, programs and processes, system calls, libraries, dynamic linking, command line shells, scripting, regular expressions and secure network protocols
Patch-based gaussian mixture model for scene motion detection in the presence of atmospheric optical turbulence
In long-range imaging regimes, atmospheric turbulence degrades image quality. In addition to blurring, the turbulence causes geometric distortion effects that introduce apparent motion in acquired video. This is problematic for image processing tasks, including image enhancement and restoration (e.g., superresolution) and aided target recognition (e.g., vehicle trackers). To mitigate these warping effects from turbulence, it is necessary to distinguish between actual in-scene motion and apparent motion caused by atmospheric turbulence. Previously, the current authors generated a synthetic video by injecting moving objects into a static scene and then applying a well-validated anisoplanatic atmospheric optical turbulence simulator. With known per-pixel truth of all moving objects, a per-pixel Gaussian mixture model (GMM) was developed as a baseline technique. In this paper, the baseline technique has been modified to improve performance while decreasing computational complexity. Additionally, the technique is extended to patches such that spatial correlations are captured, which results in further performance improvement
Application of tilt correlation statistics to anisoplanatic optical turbulence modeling and mitigation
Atmospheric optical turbulence can be a significant source of image degradation, particularly in long range imaging applications. Many turbulence mitigation algorithms rely on an optical transfer function (OTF) model that includes the Fried parameter. We present anisoplanatic tilt statistics for spherical wave propagation. We transform these into 2D autocorrelation functions that can inform turbulence modeling and mitigation algorithms. Using these, we construct an OTF model that accounts for image registration. We also propose a spectral ratio Fried parameter estimation algorithm that is robust to camera motion and requires no specialized scene content or sources. We employ the Fried parameter estimation and OTF model for turbulence mitigation. A numerical wave-propagation turbulence simulator is used to generate data to quantitatively validate the proposed methods. Results with real camera data are also presented
Deep learning for anisoplanatic optical turbulence mitigation in long-range imaging
We present a deep learning approach for restoring images degraded by atmospheric optical turbulence. We consider the case of terrestrial imaging over long ranges with a wide field-of-view. This produces an anisoplanatic imaging scenario where turbulence warping and blurring vary spatially across the image. The proposed turbulence mitigation (TM) method assumes that a sequence of short-exposure images is acquired. A block matching (BM) registration algorithm is applied to the observed frames for dewarping, and the resulting images are averaged. A convolutional neural network (CNN) is then employed to perform spatially adaptive restoration. We refer to the proposed TM algorithm as the block matching and CNN (BM-CNN) method. Training the CNN is accomplished using simulated data from a fast turbulence simulation tool capable of producing a large amount of degraded imagery from declared truth images rapidly. Testing is done using independent data simulated with a different well-validated numerical wave-propagation simulator. Our proposed BM-CNN TM method is evaluated in a number of experiments using quantitative metrics. The quantitative analysis is made possible by virtue of having truth imagery from the simulations. A number of restored images are provided for subjective evaluation. We demonstrate that the BM-CNN TM method outperforms the benchmark methods in the scenarios tested
The Fading Optical Counterpart of GRB~970228, Six Months and One Year Later
We report on observations of the fading optical counterpart of the gamma-ray
burst GRB 970228, made with the Hubble Space Telescope STIS CCD approximately
six months after outburst and with the HST/NICMOS and Keck/NIRC approximately
one year after outburst. The unresolved counterpart is detected by STIS at
V=28.0 +/- 0.25, consistent with a continued power-law decline with exponent
-1.14 +/- 0.05. The counterpart is located within, but near the edge of, a
faint extended source with diameter ~0."8 and integrated magnitude V=25.8 +/-
0.25. A reanalysis of HST and NTT observations performed shortly after the
burst shows no evidence of proper motion of the point source or fading of the
extended emission. Only the extended source is visible in the NICMOS images
with a magnitude of H=23.3 +/- 0.1. The Keck observations find K = 22.8 +/-
0.3. Several distinct and independent means of deriving the foreground
extinction in the direction of GRB 970228 all agree with A_V = 0.75 +/- 0.2.
After adjusting for Galactic extinction, we find that the size of the observed
extended emission is consistent with that of galaxies of comparable magnitude
found in the Hubble Deep Field (HDF) and other deep HST images. Only 2% of the
sky is covered by galaxies of similar or greater surface brightness; therefore
the extended source is almost certainly the host galaxy. Additionally, we find
that the extinction-corrected V - H and V - K colors of the host are as blue as
any galaxy of comparable or brighter magnitude in the HDF. Taken in concert
with recent observations of GRB 970508, GRB 971214, and GRB 980703 our work
suggests that all four GRBs with spectroscopic identification or deep
multicolor broad-band imaging of the host lie in rapidly star-forming galaxies.Comment: 24 pages, Latex, 4 PostScript figures, to appear in the May 10 issue
of The Astrophysical Journal (Note: displayed abstract is abridged
The Hubble Deep Field: Observations, Data Reduction, and Galaxy Photometry
The Hubble Deep Field (HDF) is a Director's Discretionary program on HST in
Cycle 5 to image an undistinguished field at high Galactic latitude in four
passbands as deeply as reasonably possible. These images provide the most
detailed view to date of distant field galaxies and are likely to be important
for a wide range of studies in galaxy evolution and cosmology. In order to
optimize observing in the time available, a field in the northern continuous
viewing zone was selected and images were taken for ten consecutive days, or
approximately 150 orbits. Shorter 1-2 orbit images were obtained of the fields
immediately adjacent to the primary HDF in order to facilitate spectroscopic
follow-up by ground-based telescopes. The observations were made from 18 to 30
December 1995, and both raw and reduced data have been put in the public domain
as a community service.
We present a summary of the criteria for selecting the field, the rationale
behind the filter selection and observing times in each band, and the
strategies for planning the observations to maximize the exposure time while
avoiding earth-scattered light. Data reduction procedures are outlined, and
images of the combined frames in each band are presented. Objects detected in
these images are listed in a catalog with their basic photometric parameters.Comment: 37 pages, XX PostScript figures, uses aaspp4.sty astrobib.sty.
(Astrobib is available from http://www.stsci.edu/software/TeX.html .) To
appear the Astronomical Journal. More info on the Hubble deep field can be
found at http://www.stsci.edu/../ftp/observer/hdf/hdf.html . More figures
(images) can be found at
http://www.stsci.edu/../ftp/observer/hdf/references/williams/ and the full
source catalog is available at
http://www.stsci.edu/../ftp/observer/hdf/archive/v2catalog
First-Year Spectroscopy for the SDSS-II Supernova Survey
This paper presents spectroscopy of supernovae discovered in the first season
of the Sloan Digital Sky Survey-II Supernova Survey. This program searches for
and measures multi-band light curves of supernovae in the redshift range z =
0.05 - 0.4, complementing existing surveys at lower and higher redshifts. Our
goal is to better characterize the supernova population, with a particular
focus on SNe Ia, improving their utility as cosmological distance indicators
and as probes of dark energy. Our supernova spectroscopy program features
rapid-response observations using telescopes of a range of apertures, and
provides confirmation of the supernova and host-galaxy types as well as precise
redshifts. We describe here the target identification and prioritization, data
reduction, redshift measurement, and classification of 129 SNe Ia, 16
spectroscopically probable SNe Ia, 7 SNe Ib/c, and 11 SNe II from the first
season. We also describe our efforts to measure and remove the substantial host
galaxy contamination existing in the majority of our SN spectra.Comment: Accepted for publication in The Astronomical Journal(47pages, 9
figures
Gemini GMOS and WHT SAURON integral-field spectrograph observations of the AGN driven outflow in NGC 1266
We use the SAURON and GMOS integral field spectrographs to observe the active
galactic nucleus (AGN) powered outflow in NGC 1266. This unusual galaxy is
relatively nearby (D=30 Mpc), allowing us to investigate the process of AGN
feedback in action. We present maps of the kinematics and line strengths of the
ionised gas emission lines Halpha, Hbeta, [OIII], [OI], [NII] and [SII], and
report on the detection of Sodium D absorption. We use these tracers to explore
the structure of the source, derive the ionised and atomic gas kinematics and
investigate the gas excitation and physical conditions. NGC 1266 contains two
ionised gas components along most lines of sight, tracing the ongoing outflow
and a component closer to the galaxy systemic, the origin of which is unclear.
This gas appears to be disturbed by a nascent AGN jet. We confirm that the
outflow in NGC 1266 is truly multiphase, containing radio plasma, atomic,
molecular and ionised gas and X-ray emitting plasma. The outflow has velocities
up to \pm900 km/s away from the systemic velocity, and is very likely to be
removing significant amounts of cold gas from the galaxy. The LINER-like
line-emission in NGC 1266 is extended, and likely arises from fast shocks
caused by the interaction of the radio jet with the ISM. These shocks have
velocities of up to 800 km/s, which match well with the observed velocity of
the outflow. Sodium D equivalent width profiles are used to set constraints on
the size and orientation of the outflow. The ionised gas morphology correlates
with the nascent radio jets observed in 1.4 GHz and 5 GHz continuum emission,
supporting the suggestion that an AGN jet is providing the energy required to
drive the outflow.Comment: Contains 18 figures. Accepted to MNRA
The impact of the initial COVID-19 outbreak on young adults’ mental health: a longitudinal study of risk and resilience factors
Few studies assessing the effects of COVID-19 on mental health include prospective markers of risk and resilience necessary to understand and mitigate the combined impacts of the pandemic, lockdowns, and other societal responses. This population-based study of young adults includes individuals from the Neuroscience in Psychiatry Network (n = 2403) recruited from English primary care services and schools in 2012–2013 when aged 14–24. Participants were followed up three times thereafter, most recently during the initial outbreak of the COVID-19 outbreak when they were aged between 19 and 34. Repeated measures of psychological distress (K6) and mental wellbeing (SWEMWBS) were supplemented at the latest assessment by clinical measures of depression (PHQ-9) and anxiety (GAD-7). A total of 1000 participants, 42% of the original cohort, returned to take part in the COVID-19 follow-up; 737 completed all four assessments [mean age (SD), 25.6 (3.2) years; 65.4% female; 79.1% White]. Our findings show that the pandemic led to pronounced deviations from existing mental health-related trajectories compared to expected levels over approximately seven years. About three-in-ten young adults reported clinically significant depression (28.8%) or anxiety (27.6%) under current NHS guidelines; two-in-ten met clinical cut-offs for both. About 9% reported levels of psychological distress likely to be associated with serious functional impairments that substantially interfere with major life activities; an increase by 3% compared to pre-pandemic levels. Deviations from personal trajectories were not necessarily restricted to conventional risk factors; however, individuals with pre-existing health conditions suffered disproportionately during the initial outbreak of the COVID-19 pandemic. Resilience factors known to support mental health, particularly in response to adverse events, were at best mildly protective of individual psychological responses to the pandemic. Our findings underline the importance of monitoring the long-term effects of the ongoing pandemic on young adults’ mental health, an age group at particular risk for the emergence of psychopathologies. Our findings further suggest that maintaining access to mental health care services during future waves, or potential new pandemics, is particularly crucial for those with pre-existing health conditions. Even though resilience factors known to support mental health were only mildly protective during the initial outbreak of the COVID-19 pandemic, it remains to be seen whether these factors facilitate mental health in the long term
Psychosocial impact of undergoing prostate cancer screening for men with BRCA1 or BRCA2 mutations.
OBJECTIVES: To report the baseline results of a longitudinal psychosocial study that forms part of the IMPACT study, a multi-national investigation of targeted prostate cancer (PCa) screening among men with a known pathogenic germline mutation in the BRCA1 or BRCA2 genes. PARTICPANTS AND METHODS: Men enrolled in the IMPACT study were invited to complete a questionnaire at collaborating sites prior to each annual screening visit. The questionnaire included sociodemographic characteristics and the following measures: the Hospital Anxiety and Depression Scale (HADS), Impact of Event Scale (IES), 36-item short-form health survey (SF-36), Memorial Anxiety Scale for Prostate Cancer, Cancer Worry Scale-Revised, risk perception and knowledge. The results of the baseline questionnaire are presented. RESULTS: A total of 432 men completed questionnaires: 98 and 160 had mutations in BRCA1 and BRCA2 genes, respectively, and 174 were controls (familial mutation negative). Participants' perception of PCa risk was influenced by genetic status. Knowledge levels were high and unrelated to genetic status. Mean scores for the HADS and SF-36 were within reported general population norms and mean IES scores were within normal range. IES mean intrusion and avoidance scores were significantly higher in BRCA1/BRCA2 carriers than in controls and were higher in men with increased PCa risk perception. At the multivariate level, risk perception contributed more significantly to variance in IES scores than genetic status. CONCLUSION: This is the first study to report the psychosocial profile of men with BRCA1/BRCA2 mutations undergoing PCa screening. No clinically concerning levels of general or cancer-specific distress or poor quality of life were detected in the cohort as a whole. A small subset of participants reported higher levels of distress, suggesting the need for healthcare professionals offering PCa screening to identify these risk factors and offer additional information and support to men seeking PCa screening
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