44 research outputs found
Pilot Study: HPV Infection Knowledge & HPV Vaccine Acceptance among Women Residing in Ciudad Juárez, México
The human papillomavirus (HPV) is one of the most common sexually transmitted infections (STI) in the world and it is associated with cervical cancer. The development of a prophylactic HPV vaccine has proven effective in clinical trials and it is now available to the public. The HPV vaccine represents a viable prevention strategy against cervical cancer. However, parental preferences, perceptions, and willingness to use the HPV vaccine are crucial, and if not assessed accurately, may threaten the successful implementation of a broad HPV vaccination program. This pilot study explored the views of 60 adult, Mexican women, all of who were mothers of female children between the ages of ten to 14 years old on the following four areas of interest: HPV knowledge; HPV vaccine knowledge and attitudes; barriers to HPV vaccine use; and potential uses and side effects of the HPV vaccine. Only 7% of respondents knew that HPV was a virus or STI. Eighty-six percent had not heard of the HPV vaccine, but 62% felt that the HPV vaccine would prevent HPV infection. However, 38% said the church would not approve of the HPV vaccine use for 10-14-year-old girls. Twenty-seven percent thought that promiscuous behavior would increase following HPV vaccination. Overall, respondents had very little knowledge of the HPV vaccine, were willing to be vaccinated themselves (83%), but were lesser willing to vaccinate their daughters (63%). Ultimately, understanding the beliefs about and identifying the barriers of HPV vaccine use will influence the effectiveness of the vaccine and its potential impact in reducing cervical cancer incidence rates worldwide
Tropical understory herbaceous community responds more strongly to hurricane disturbance than to experimental warming
Ecology and Evolution published by John Wiley & Sons Ltd. The effects of climate change on tropical forests may have global consequences due to the forests’ high biodiversity and major role in the global carbon cycle. In this study, we document the effects of experimental warming on the abundance and composition of a tropical forest floor herbaceous plant community in the Luquillo Experimental Forest, Puerto Rico. This study was conducted within Tropical Responses to Altered Climate Experiment (TRACE) plots, which use infrared heaters under free-air, open-field conditions, to warm understory vegetation and soils + 4°C above nearby control plots. Hurricanes Irma and María damaged the heating infrastructure in the second year of warming, therefore, the study included one pretreatment year, one year of warming, and one year of hurricane response with no warming. We measured percent leaf cover of individual herbaceous species, fern population dynamics, and species richness and diversity within three warmed and three control plots. Results showed that one year of experimental warming did not significantly affect the cover of individual herbaceous species, fern population dynamics, species richness, or species diversity. In contrast, herbaceous cover increased from 20% to 70%, bare ground decreased from 70% to 6%, and species composition shifted pre to posthurricane. The negligible effects of warming may have been due to the short duration of the warming treatment or an understory that is somewhat resistant to higher temperatures. Our results suggest that climate extremes that are predicted to increase with climate change, such as hurricanes and droughts, may cause more abrupt changes in tropical forest understories than longer-term sustained warming
A New High Contrast Imaging Program at Palomar Observatory
We describe a new instrument that forms the core of a long-term high contrast
imaging program at the 200-inch Hale Telescope at Palomar Observatory. The
primary scientific thrust is to obtain images and low-resolution spectroscopy
of brown dwarfs and young Jovian mass exoplanets in the vicinity of stars
within 50 parsecs of the Sun. The instrument is a microlens-based integral
field spectrograph integrated with a diffraction limited, apodized-pupil Lyot
coronagraph, mounted behind the Palomar adaptive optics system. The
spectrograph obtains imaging in 23 channels across the J and H bands (1.06 -
1.78 microns). In addition to obtaining spectra, this wavelength resolution
allows suppression of the chromatically dependent speckle noise, which we
describe. We have recently installed a novel internal wave front calibration
system that will provide continuous updates to the AO system every 0.5 - 1.0
minutes by sensing the wave front within the coronagraph. The Palomar AO system
is undergoing an upgrade to a much higher-order AO system ("PALM-3000"): a
3388-actuator tweeter deformable mirror working together with the existing
241-actuator mirror. This system will allow correction with subapertures as
small as 8cm at the telescope pupil using natural guide stars. The coronagraph
alone has achieved an initial dynamic range in the H-band of 2 X 10^-4 at 1
arcsecond, without speckle noise suppression. We demonstrate that spectral
speckle suppression is providing a factor of 10-20 improvement over this
bringing our current contrast at an arcsecond to ~2 X 10^-5. This system is the
first of a new generation of apodized pupil coronagraphs combined with
high-order adaptive optics and integral field spectrographs (e.g. GPI, SPHERE,
HiCIAO), and we anticipate this instrument will make a lasting contribution to
high contrast imaging in the Northern Hemisphere for years.Comment: Accepted to PASP: 12 pages, 12 figure
Spectral Typing of Late Type Stellar Companions to Young Stars from Low Dispersion Near-Infrared Integral Field Unit Data
We used the Project 1640 near-infrared coronagraph and integral field
spectrograph to observe 19 young solar type stars. Five of these stars are
known binary stars and we detected the late-type secondaries and were able to
measure their JH spectra with a resolution of R\sim30. The reduced, extracted,
and calibrated spectra were compared to template spectra from the IRTF spectral
library. With this comparison we test the accuracy and consistency of spectral
type determination with the low-resolution near-infrared spectra from P1640.
Additionally, we determine effective temperature and surface gravity of the
companions by fitting synthetic spectra calculated with the PHOENIX model
atmosphere code. We also present several new epochs of astrometry of each of
the systems. Together these data increase our knowledge and understanding of
the stellar make up of these systems. In addition to the astronomical results,
the analysis presented helps validate the Project 1640 data reduction and
spectral extraction processes and the utility of low-resolution, near-infrared
spectra for characterizing late-type companions in multiple systems.Comment: Accepted to Astronomical Journal, 25 pages, 8 figure
Parallactic Motion for Companion Discovery: An M-Dwarf Orbiting Alcor
The A5V star Alcor has an M3-M4 dwarf companion, as evidenced by a novel astrometric technique. Imaging spectroscopy combined with adaptive optics coronagraphy allowed for the detection and spectrophotometric characterization of the point source at a contrast of ~6 J- and H-band magnitudes and separation of 1'' from the primary star. The use of an astrometric pupil plane grid allowed us to determine the projected separations between the companion and the coronagraphically occulted primary star to ≤3 mas precision at two observation epochs. Our measurements demonstrate common parallactic and proper motion over the course of 103 days, significantly shorter than the period of time needed for most companion confirmations through proper motion measurements alone. This common parallax method is potentially more rigorous than common proper motion, ensuring that the neighboring bodies lie at the same distance, rather than relying on the statistical improbability that two objects in close proximity to each other on the sky move in the same direction. The discovery of a low-mass (~0.25 M_☉) companion around a bright (V = 4.0 mag), nearby (d= 25 pc) star highlights a region of binary star parameter space that to date has not been fully probed
Speckle Suppression with the Project 1640 Integral Field Spectrograph
Project 1640 is a high-contrast imaging instrument recently commissioned at
Palomar observatory. A combination of a coronagraph with an integral field
spectrograph (IFS), Project 1640 is designed to detect and characterize
extrasolar planets, brown dwarfs, and circumstellar material orbiting nearby
stars. In this paper, we present our data processing techniques for improving
upon instrument raw sensitivity via the removal of quasi-static speckles. Our
approach utilizes the chromatic image diversity provided by the IFS in
combination with the locally-optimized combination of images (LOCI) algorithm
to suppress the intensity of residual contaminating light in close angular
proximity to target stars. We describe the Project 1640 speckle suppression
pipeline (PSSP) and demonstrate the ability to detect companions with
brightness comparable to and below that of initial speckle intensities using
on-sky commissioning data. Our preliminary results indicate that suppression
factors of at least one order of magnitude are consistently possible, reaching
contrast levels of at 1\arcsec in the H-band in
20 minutes of on-source integration time when non-common-path errors are
reasonably well-calibrated. These results suggest that near-infrared contrast
levels of order at subarcsecond separations will soon be
possible for Project 1640 and similarly designed instruments that receive a
diffraction-limited beam corrected by adaptive optics (AO) systems employing
deformable mirrors with high actuator-density.Comment: accepted to Ap
Establishing Alpha Oph as a Prototype Rotator: Improved Astrometric Orbit
The nearby star Alpha Oph (Ras Alhague) is a rapidly rotating A5IV star
spinning at ~89% of its breakup velocity. This system has been imaged
extensively by interferometric techniques, giving a precise geometric model of
the star's oblateness and the resulting temperature variation on the stellar
surface. Fortuitously, Alpha Oph has a previously known stellar companion, and
characterization of the orbit provides an independent, dynamically-based check
of both the host star and the companion mass. Such measurements are crucial to
constrain models of such rapidly rotating stars. In this study, we combine
eight years of Adaptive Optics imaging data from the Palomar, AEOS, and CFHT
telescopes to derive an improved, astrometric characterization of the companion
orbit. We also use photometry from these observations to derive a model-based
estimate of the companion mass. A fit was performed on the photocenter motion
of this system to extract a component mass ratio. We find masses of
2.40^{0.23}_{0.37} solar masses and 0.85^{0.06}_{0.04} solar masses for Alpha
Oph A and Alpha Oph B, respectively. Previous orbital studies of this system
found a mass too high for this system, inconsistent with stellar evolutionary
calculations. Our measurements of the host star mass are more consistent with
these evolutionary calculations, but with slightly higher uncertainties. In
addition to the dynamically-derived masses, we use IJHK photometry to derive a
model-based mass for Alpha Oph B, of 0.77 +/- 0.05 solar masses marginally
consistent with the dynamical masses derived from our orbit. Our model fits
predict a periastron passage on 2012 April 19, with the two components having a
~50 milliarcsec separation from March to May 2012. A modest amount of
interferometric and radial velocity data during this period could provide a
mass determination of this star at the few percent level.Comment: Accepted to ApJ, 6 pages, 4 figure
Discovery and Characterization of a Faint Stellar Companion to the A3V Star Zeta Virginis
Through the combination of high-order Adaptive Optics and coronagraphy, we
report the discovery of a faint stellar companion to the A3V star zeta
Virginis. This companion is ~7 magnitudes fainter than its host star in the
H-band, and infrared imaging spanning 4.75 years over five epochs indicates
this companion has common proper motion with its host star. Using evolutionary
models, we estimate its mass to be 0.168+/-.016 solar masses, giving a mass
ratio for this system q = 0.082. Assuming the two objects are coeval, this mass
suggests a M4V-M7V spectral type for the companion, which is confirmed through
integral field spectroscopic measurements. We see clear evidence for orbital
motion from this companion and are able to constrain the semi-major axis to be
greater than 24.9 AU, the period > 124$ yrs, and eccentricity > 0.16.
Multiplicity studies of higher mass stars are relatively rare, and binary
companions such as this one at the extreme low end of the mass ratio
distribution are useful additions to surveys incomplete at such a low mass
ratio. Moreover, the frequency of binary companions can help to discriminate
between binary formation scenarios that predict an abundance of low-mass
companions forming from the early fragmentation of a massive circumstellar
disk. A system such as this may provide insight into the anomalous X-ray
emission from A stars, hypothesized to be from unseen late-type stellar
companions. Indeed, we calculate that the presence of this M-dwarf companion
easily accounts for the X-ray emission from this star detected by ROSAT.Comment: 9 pages, 6 figures, Accepted to Ap