13 research outputs found
A Floristic Study of Halmahera, Indonesia Focusing on Palms (Arecaceae) and Their Seed Dispersal
The dispersal services of frugivores affect plant community assembly, persistence, and gene flow in the short-term, and in the long-term are critical to ensuring that tropical trees and palms can regenerate in disturbed areas and can migrate amidst climate change. Halmahera is the largest Moluccan island within the Wallacea biodiversity hotspot, yet data on its plant and animal distributions and interactions are almost null. I studied the tropical trees and palms of Halmahera and their seed dispersal dynamics. Chapter I explores the palms of the Moluccan islands through field-, herbarium-, and literature- based studies. The results of herbarium specimen collections are presented within a preliminary list of palms for Halmahera’s Aketajawe-Lolobata National Park, and contextualized in a review of regional palm biogeography. Expanding beyond the study of one plant family, Chapter II compiles and examines all the tree and palm taxa of the Moluccan islands in order to infer seed dispersal syndromes for each taxon, resulting in an analysis of over 900 taxa. Zoochory was found in 93% of plant families, and nearly 30% of endemic taxa rely primarily on dispersal by large-bodied frugivores. The role of a hypothesized keystone disperser (the Papuan hornbill, Rhyticeros plicatus ruficollis) is confirmed experimentally to disperse about 10% of Halmahera’s tropical tree and palm taxa. The final chapter encompasses an ex-situ germination trial and a year-long in-situ experimental study that examines the germination and recruitment of three palm species post-ingestion by Papuan hornbills, in four different habitat types representative of Halmahera’s landscape. Palms dispersed by hornbills into disturbed habitats and primary forests resulted in enhanced recruitment, although results varied by habitat and species. Hornbills aid both in forest conservation and recovery/assembly after disturbance. The results of this dissertation provide a foundation for further ecological studies and for enhanced conservation of Halmahera island
STUDIES ON BEGONIA(BEGONIACEAE) OF THE MOLUCCA ISLANDS I: TWO NEW SPECIES FROM HALMAHERA, INDONESIA AND AN UPDATED DESCRIPTION OF BEGONIA HOLOSERICEA
Two new species of Begonia, Begonia holosericeoides Ardi & D. C. Thomas and B. aketajawensis Ardi & D. C. Thomas, are described from Aketajawe Lolobata National Park, Halmahera, Indonesia. The two species belong to Begonia section Petermannia. Begonia holosericea, previously only tentatively assigned to a section, is here assigned to section Petermannia based on the examination of newly available material. Additionally, a revised description and an illustration are provided. A key to the Moluccan species of Begonia is presented.</p
SN 2009bb: a Peculiar Broad-Lined Type Ic Supernova
Ultraviolet, optical, and near-infrared photometry and optical spectroscopy
of the broad-lined Type Ic supernova (SN) 2009bb are presented, following the
flux evolution from -10 to +285 days past B-band maximum. Thanks to the very
early discovery, it is possible to place tight constraints on the SN explosion
epoch. The expansion velocities measured from near maximum spectra are found to
be only slightly smaller than those measured from spectra of the prototype
broad-lined SN 1998bw associated with GRB 980425. Fitting an analytical model
to the pseudo-bolometric light curve of SN 2009bb suggests that 4.1+-1.9 Msun
of material was ejected with 0.22 +-0.06 Msun of it being 56Ni. The resulting
kinetic energy is 1.8+-0.7x10^52 erg. This, together with an absolute peak
magnitude of MB=-18.36+-0.44, places SN 2009bb on the energetic and luminous
end of the broad-lined Type Ic (SN Ic) sequence. Detection of helium in the
early time optical spectra accompanied with strong radio emission, and high
metallicity of its environment makes SN 2009bb a peculiar object. Similar to
the case for GRBs, we find that the bulk explosion parameters of SN 2009bb
cannot account for the copious energy coupled to relativistic ejecta, and
conclude that another energy reservoir (a central engine) is required to power
the radio emission. Nevertheless, the analysis of the SN 2009bb nebular
spectrum suggests that the failed GRB detection is not imputable to a large
angle between the line-of-sight and the GRB beamed radiation. Therefore, if a
GRB was produced during the SN 2009bb explosion, it was below the threshold of
the current generation of gamma-ray instruments.Comment: Accepted for publication in Ap
A population of gamma-ray emitting globular clusters seen with the Fermi Large Area Telescope
Globular clusters with their large populations of millisecond pulsars (MSPs)
are believed to be potential emitters of high-energy gamma-ray emission. Our
goal is to constrain the millisecond pulsar populations in globular clusters
from analysis of gamma-ray observations. We use 546 days of continuous
sky-survey observations obtained with the Large Area Telescope aboard the Fermi
Gamma-ray Space Telescope to study the gamma-ray emission towards 13 globular
clusters. Steady point-like high-energy gamma-ray emission has been
significantly detected towards 8 globular clusters. Five of them (47 Tucanae,
Omega Cen, NGC 6388, Terzan 5, and M 28) show hard spectral power indices and clear evidence for an exponential cut-off in the range
1.0-2.6 GeV, which is the characteristic signature of magnetospheric emission
from MSPs. Three of them (M 62, NGC 6440 and NGC 6652) also show hard spectral
indices , however the presence of an exponential cut-off
can not be unambiguously established. Three of them (Omega Cen, NGC 6388, NGC
6652) have no known radio or X-ray MSPs yet still exhibit MSP spectral
properties. From the observed gamma-ray luminosities, we estimate the total
number of MSPs that is expected to be present in these globular clusters. We
show that our estimates of the MSP population correlate with the stellar
encounter rate and we estimate 2600-4700 MSPs in Galactic globular clusters,
commensurate with previous estimates. The observation of high-energy gamma-ray
emission from a globular cluster thus provides a reliable independent method to
assess their millisecond pulsar populations that can be used to make
constraints on the original neutron star X-ray binary population, essential for
understanding the importance of binary systems in slowing the inevitable core
collapse of globular clusters.Comment: Accepted for publication in A&A. Corresponding authors: J.
Kn\"odlseder, N. Webb, B. Pancraz
Fermi Large Area Telescope Constraints on the Gamma-ray Opacity of the Universe
The Extragalactic Background Light (EBL) includes photons with wavelengths
from ultraviolet to infrared, which are effective at attenuating gamma rays
with energy above ~10 GeV during propagation from sources at cosmological
distances. This results in a redshift- and energy-dependent attenuation of the
gamma-ray flux of extragalactic sources such as blazars and Gamma-Ray Bursts
(GRBs). The Large Area Telescope onboard Fermi detects a sample of gamma-ray
blazars with redshift up to z~3, and GRBs with redshift up to z~4.3. Using
photons above 10 GeV collected by Fermi over more than one year of observations
for these sources, we investigate the effect of gamma-ray flux attenuation by
the EBL. We place upper limits on the gamma-ray opacity of the Universe at
various energies and redshifts, and compare this with predictions from
well-known EBL models. We find that an EBL intensity in the optical-ultraviolet
wavelengths as great as predicted by the "baseline" model of Stecker et al.
(2006) can be ruled out with high confidence.Comment: 42 pages, 12 figures, accepted version (24 Aug.2010) for publication
in ApJ; Contact authors: A. Bouvier, A. Chen, S. Raino, S. Razzaque, A.
Reimer, L.C. Reye
Carnegie Supernova Project-I and -II: Measurements of using Cepheid, TRGB, and SBF Distance Calibration to Type Ia Supernovae
We present an analysis of Type Ia Supernovae (SNe~Ia) from both the Carnegie
Supernova Project~I (CSP-I) and II (CSP-II), and extend the Hubble diagram from
the optical to the near-infrared wavelengths (). We calculate the
Hubble constant, , using various distance calibrators: Cepheids, Tip of
the Red Giant Branch (TRGB), and Surface Brightness Fluctuations (SBF).
Combining all methods of calibrations, we derive $\rm H_0=71.76 \pm 0.58 \
(stat) \pm 1.19 \ (sys) \ km \ s^{-1} \ Mpc^{-1}B\rm
H_0=73.22 \pm 0.68 \ (stat) \pm 1.28 \ (sys) \ km \ s^{-1} \ Mpc^{-1}H1.2\sim 1.3 \rm \ km \
s^{-1} \ Mpc^{-1}H_0H_0H_0Y0.12\pm0.01\sigma_{int}$). We revisit SN~Ia Hubble residual-host mass correlations and
recover previous results that these correlations do not change significantly
between the optical and the near-infrared wavelengths. Finally, SNe~Ia that
explode beyond 10 kpc from their host centers exhibit smaller dispersion in
their luminosity, confirming our earlier findings. Reduced effect of dust in
the outskirt of hosts may be responsible for this effect.Comment: Revised calculations are made. Will be resubmitted to Ap
The Gravity Collective: A Search for the Electromagnetic Counterpart to the Neutron Star-Black Hole Merger GW190814
We present optical follow-up imaging obtained with the Katzman Automatic
Imaging Telescope, Las Cumbres Observatory Global Telescope Network, Nickel
Telescope, Swope Telescope, and Thacher Telescope of the LIGO/Virgo
gravitational wave (GW) signal from the neutron star-black hole (NSBH) merger
GW190814. We searched the GW190814 localization region (19 deg for the
90th percentile best localization), covering a total of 51 deg and 94.6%
of the two-dimensional localization region. Analyzing the properties of 189
transients that we consider as candidate counterparts to the NSBH merger,
including their localizations, discovery times from merger, optical spectra,
likely host-galaxy redshifts, and photometric evolution, we conclude that none
of these objects are likely to be associated with GW190814. Based on this
finding, we consider the likely optical properties of an electromagnetic
counterpart to GW190814, including possible kilonovae and short gamma-ray burst
afterglows. Using the joint limits from our follow-up imaging, we conclude that
a counterpart with an -band decline rate of 0.68 mag day, similar to
the kilonova AT 2017gfo, could peak at an absolute magnitude of at most
mag (50% confidence). Our data are not constraining for ''red'' kilonovae and
rule out ''blue'' kilonovae with (30% confidence). We
strongly rule out all known types of short gamma-ray burst afterglows with
viewing angles 17 assuming an initial jet opening angle of
and explosion energies and circumburst densities similar to
afterglows explored in the literature. Finally, we explore the possibility that
GW190814 merged in the disk of an active galactic nucleus, of which we find
four in the localization region, but we do not find any candidate counterparts
among these sources.Comment: 86 pages, 9 figure
Gamma-ray and radio properties of six pulsars detected by the fermi large area telescope
We report the detection of pulsed γ-rays for PSRs J0631+1036, J0659+1414, J0742-2822, J1420-6048, J1509-5850, and J1718-3825 using the Large Area Telescope on board the Fermi Gamma-ray Space Telescope (formerly known as GLAST). Although these six pulsars are diverse in terms of their spin parameters, they share an important feature: their γ-ray light curves are (at least given the current count statistics) single peaked. For two pulsars, there are hints for a double-peaked structure in the light curves. The shapes of the observed light curves of this group of pulsars are discussed in the light of models for which the emission originates from high up in the magnetosphere. The observed phases of the γ-ray light curves are, in general, consistent with those predicted by high-altitude models, although we speculate that the γ-ray emission of PSR J0659+1414, possibly featuring the softest spectrum of all Fermi pulsars coupled with a very low efficiency, arises from relatively low down in the magnetosphere. High-quality radio polarization data are available showing that all but one have a high degree of linear polarization. This allows us to place some constraints on the viewing geometry and aids the comparison of the γ-ray light curves with high-energy beam models
Burnout among surgeons before and during the SARS-CoV-2 pandemic: an international survey
Background: SARS-CoV-2 pandemic has had many significant impacts within the surgical realm, and surgeons have been obligated to reconsider almost every aspect of daily clinical practice. Methods: This is a cross-sectional study reported in compliance with the CHERRIES guidelines and conducted through an online platform from June 14th to July 15th, 2020. The primary outcome was the burden of burnout during the pandemic indicated by the validated Shirom-Melamed Burnout Measure. Results: Nine hundred fifty-four surgeons completed the survey. The median length of practice was 10 years; 78.2% included were male with a median age of 37 years old, 39.5% were consultants, 68.9% were general surgeons, and 55.7% were affiliated with an academic institution. Overall, there was a significant increase in the mean burnout score during the pandemic; longer years of practice and older age were significantly associated with less burnout. There were significant reductions in the median number of outpatient visits, operated cases, on-call hours, emergency visits, and research work, so, 48.2% of respondents felt that the training resources were insufficient. The majority (81.3%) of respondents reported that their hospitals were included in the management of COVID-19, 66.5% felt their roles had been minimized; 41% were asked to assist in non-surgical medical practices, and 37.6% of respondents were included in COVID-19 management. Conclusions: There was a significant burnout among trainees. Almost all aspects of clinical and research activities were affected with a significant reduction in the volume of research, outpatient clinic visits, surgical procedures, on-call hours, and emergency cases hindering the training. Trial registration: The study was registered on clicaltrials.gov "NCT04433286" on 16/06/2020
STUDIES ON BEGONIA(BEGONIACEAE) OF THE MOLUCCA ISLANDS I: TWO NEW SPECIES FROM HALMAHERA, INDONESIA AND AN UPDATED DESCRIPTION OF BEGONIA HOLOSERICEA
Two new species of Begonia, Begonia holosericeoides Ardi & D. C. Thomas and B. aketajawensis Ardi & D. C. Thomas, are described from Aketajawe Lolobata National Park, Halmahera, Indonesia. The two species belong to Begonia section Petermannia. Begonia holosericea, previously only tentatively assigned to a section, is here assigned to section Petermannia based on the examination of newly available material. Additionally, a revised description and an illustration are provided. A key to the Moluccan species of Begonia is presented