Diet Specialization by the Scarlet Kingsnake, Lampropeltis elapsoides (Colubridae)

Based on 34 natural prey items, Lampropeltis elapsoides eats primarily elongate squamates (97%), especially skinks (74%) and colubroid snakes (15%). N o ontogenetic or geographic variation is evident; prey items are swallowed headfirst and average 19% of predator mass. The diet substantially overlaps that of juveniles of some other lampropeltines, including sympatric L. triangulum, but is unusually narrow compared to adults of most other species

Diet Specialization by the Scarlet Kingsnake, Lampropeltis elapsoides (Colubridae)

Based on 34 natural prey items, Lampropeltis elapsoides eats primarily elongate squamates (97%), especially skinks (74%) and colubroid snakes (15%). N o ontogenetic or geographic variation is evident; prey items are swallowed headfirst and average 19% of predator mass. The diet substantially overlaps that of juveniles of some other lampropeltines, including sympatric L. triangulum, but is unusually narrow compared to adults of most other species

Spectroscopy of Brown Dwarf Candidates in the rho Ophiuchi Molecular Core

We present an analysis of low resolution infrared spectra for 20 brown dwarf candidates in the core of the $\rho$ Ophiuchi molecular cloud. Fifteen of the sources display absorption-line spectra characteristic of late-type stars. By comparing the depths of water vapor absorption bands in our candidate objects with a grid of M dwarf standards, we derive spectral types which are independent of reddening. Optical spectroscopy of one brown dwarf candidate confirms the spectral type derived from the water bands. Combining their spectral types with published near-infrared photometry, effective temperatures and bolometric stellar luminosities are derived enabling us to place our sample on the Hertzsprung-Russell diagram. We compare the positions of the brown dwarf candidates in this diagram with two sets of theoretical models in order to estimate their masses and ages. Considering uncertainties in placing the candidates in the H-R diagram, six objects consistently lie in the brown dwarf regime and another five objects lie in the transition region between stellar and substellar objects. The ages inferred for the sample are consistent with those derived for higher mass association members. Three of the newly identified brown dwarfs display infrared excesses at $\lambda$=2.2 $\mu$m suggesting that young brown dwarfs can have active accretion disks. Comparing our mass estimates of the brown dwarf candidates with those derived from photometric data alone suggests that spectroscopy is an essential component of investigations of the mass functions of young clusters.Comment: Astronomical Journal, in press: 25 pages, latex, 5 tables and 6 figures (separate

Conservation and Use of the North American Plant Cornucopia: The Way Forward

The pages of this extensive book document the potential of a great many North American plants to enhance the productivity, sustainability, and nutritional quality of crops or to be further developed into important cultivated species in their own right. But this potential can only be realized if the plants are adequately conserved to ensure their survival and availability for research, invested in to promote their development, and marketed so as to be attractive to producers and consumers. We outline some of the key steps needed to boost the conservation and use of our regional cornucopia. In situ and ex situ conservation of North America’s useful plants are being accomplished by a variety of institutions with different mandates, but habitat destruction and other threats to wild populations continue to negatively impact many species. Information sharing, coordinating efforts, filling research gaps for wild plants, and increasing support for conservation will be necessary to more comprehensively safeguard these plants and to make them available for use. Technologies enabling more efficient exploration of the diversity within these species are rapidly advancing and offer the potential to contribute to quick advances in improvement of cultivars, but considerable further research and partnerships are needed to generate and share the results widely. Marketing of new crops can take advantage of the increasing public interest in diverse and nutritious foods, learning from successful collaborations between producers, researchers, and consumers. As a whole, North America already possesses a strong foundation from which the conservation and use of its flora can be enhanced. This includes many protected areas, strong conservation institutions, innovative research, and the willingness to collaborate across fields, institutions, and borders. There are still many silos that need to be broken down and reorganized through innovative partnerships to better conserve and benefit from the North American cornucopia. But given the incredible diversity of interesting and useful plants in the region, the remarkable efforts for many decades by many organizations to care for these plants and share them with humanity, and the increasing public interest in more diverse, healthy, and resilient food and agricultural systems, there is reason for hope

Genetic contribution to postpartum haemorrhage in Swedish population: cohort study of 466 686 births

Objective: To investigate the familial clustering of postpartum haemorrhage in the Swedish population, and to quantify the relative contributions of genetic and environmental effects. Design: Register based cohort study. Setting: Swedish population (multi-generation and medical birth registers). Main outcome measure Postpartum haemorrhage, defined as >1000 mL estimated blood loss. Participants: The first two live births to individuals in Sweden in 1997-2009 contributed to clusters representing intact couples (n=366 350 births), mothers with separate partners (n=53 292), fathers with separate partners (n=47 054), sister pairs (n=97 228), brother pairs (n=91 168), and mixed sibling pairs (n=177 944). Methods: Familial clustering was quantified through cluster specific tetrachoric correlation coefficients, and the influence of potential sharing of known risk factors was evaluated with alternating logistic regression. Relative contributions of genetic and environmental effects to the variation in liability for postpartum haemorrhage were quantified with generalised linear mixed models. Results: The overall prevalence of postpartum haemorrhage after vaginal deliveries in our sample was 4.6%. Among vaginal deliveries, 18% (95% confidence interval 9% to 26%) of the variation in postpartum haemorrhage liability was attributed to maternal genetic factors, 10% (1% to 19%) to unique maternal environment, and 11% (0% to 26%) to fetal genetic effects. Adjustment for known risk factors only partially explained estimates of familial clustering, suggesting that the observed shared genetic and environmental effects operate in part through pathways independent of known risk factors. There were similar patterns of familial clustering for both of the main subtypes examined (atony and retained placenta), though strongest for haemorrhage after retained placenta. Conclusions: There is a maternal genetic predisposition to postpartum haemorrhage, but more than half of the total variation in liability is attributable to factors that are not shared in families

Optical Spectroscopy of the Surface Population of the rho Ophiuchi Molecular Cloud: The First Wave of Star Formation

We present the results of optical spectroscopy of 139 stars obtained with the Hydra multi-object spectrograph. The objects extend over a 1.3 square degree area surrounding the main cloud of the rho Oph complex. The objects were selected from narrowband images to have H alpha in emission. Using the presence of strong H alpha emission, lithium absorption, location in the Hertzsprung-Russell diagram, or previously reported x-ray emission, we were able to identify 88 objects as young stars associated with the cloud. Strong H alpha emission was confirmed in 39 objects with line widths consistent with their origin in magnetospheric accretion columns. Two of the strongest emission-line objects are young, x-ray emitting brown dwarf candidates with M8 spectral types. Comparisons of the bolometric luminosities and effective temperatures with theoretical models suggest a medianage for this population of 2.1 Myr which is signifcantly older than the ages derived for objects in the cloud core. It appears that these stars formed contemporaneously with low mass stars in the Upper Scorpius subgroup, likely triggered by massive stars in the Upper-Centaurus subgroup.Comment: 35 pages of postscript which includes seven figures (some of which are multi-panel) and four postscript tables. Astronomical Journal (in press

Towards an Understanding of Changing-Look Quasars: An Archival Spectroscopic Search in SDSS

The uncertain origin of the recently-discovered `changing-looking' quasar phenomenon -- in which a luminous quasar dims significantly to a quiescent state in repeat spectroscopy over ~10 year timescales -- may present unexpected challenges to our understanding of quasar accretion. To better understand this phenomenon, we take a first step to building a sample of changing-look quasars with a systematic but simple archival search for these objects in the Sloan Digital Sky Survey Data Release 12. By leveraging the >10 year baselines for objects with repeat spectroscopy, we uncover two new changing-look quasars, and a third discovered previously. Decomposition of the multi-epoch spectra and analysis of the broad emission lines suggest that the quasar accretion disk emission dims due to rapidly decreasing accretion rates (by factors of >2.5), while disfavoring changes in intrinsic dust extinction for the two objects where these analyses are possible. Broad emission line energetics also support intrinsic dimming of quasar emission as the origin for this phenomenon rather than transient tidal disruption events or supernovae. Although our search criteria included quasars at all redshifts and transitions from either quasar-like to galaxy-like states or the reverse, all of the clear cases of changing-look quasars discovered were at relatively low-redshift (z ~ 0.2 - 0.3) and only exhibit quasar-like to galaxy-like transitions.Comment: 15 pages, 8 figures. Updated to accepted versio

Discovery of a close-separation binary quasar at the heart of a z~0.2 merging galaxy and its implications for low-frequency gravitational waves

Supermassive black hole (SMBH) binaries with masses of ~10^8--10^9 Msun are expected to dominate the contribution to the as-yet undetected gravitational wave background (GWB) signal at the nanohertz frequencies accessible to Pulsar Timing Arrays (PTA). We currently lack firm empirical constraints on the amplitude of the GWB due to the dearth of confirmed SMBH binaries in the required mass range. Using HST/WFC3 images, we have discovered a z~0.2 quasar hosted in a merger remnant with two closely separated (0.13'' or ~430pc) continuum cores at the heart of the galaxy SDSSJ1010+1413. The two cores are spatially coincident with two powerful [OIII]-emitting point sources with quasar-like luminosities (L_AGN ~ 5x10^46 erg/s, suggesting the presence of a bound SMBH system, each with M_BH > 4x10^8 Msun. We place an upper limit on the merging timescale of the SMBH pair of 2.5 billion years, roughly the Universe lookback time at z~0.2. There is likely a population of quasar binaries similar to SDSSJ1010+1413 that contribute to a stochastic GWB that should be detected in the next several years. If the GWB is not detected this could indicate that SMBHs merge only over extremely long timescales, remaining as close separation binaries for many Hubble times, the so-called `final-parsec problem'.Comment: Accepted to ApJL (in press), 9 pages, 5 figure

Now You See It, Now You Don't: The Disappearing Central Engine of the Quasar J1011+5442

We report the discovery of a new "changing-look" quasar, SDSS J101152.98+544206.4, through repeat spectroscopy from the Time Domain Spectroscopic Survey. This is an addition to a small but growing set of quasars whose blue continua and broad optical emission lines have been observed to decline by a large factor on a time scale of approximately a decade. The 5100 Angstrom monochromatic continuum luminosity of this quasar drops by a factor of > 9.8 in a rest-frame time interval of < 9.7 years, while the broad H-alpha luminosity drops by a factor of 55 in the same amount of time. The width of the broad H-alpha line increases in the dim state such that the black hole mass derived from the appropriate single-epoch scaling relation agrees between the two epochs within a factor of 3. The fluxes of the narrow emission lines do not appear to change between epochs. The light curve obtained by the Catalina Sky Survey suggests that the transition occurs within a rest-frame time interval of approximately 500 days. We examine three possible mechanisms for this transition suggested in the recent literature. An abrupt change in the reddening towards the central engine is disfavored by the substantial difference between the timescale to obscure the central engine and the observed timescale of the transition. A decaying tidal disruption flare is consistent with the decay rate of the light curve but not with the prolonged bright state preceding the decay, nor can this scenario provide the power required by the luminosities of the emission lines. An abrupt drop in the accretion rate onto the supermassive black hole appears to be the most plausible explanation for the rapid dimming.Comment: Submitted to MNRA

Low Mass Stars and Substellar Objects in the NGC 1333 Molecular Cloud

We present the results of near-infrared imaging and low-resolution near- infrared spectroscopy of low mass objects in the NGC 1333 molecular cloud. A JHK survey of an 11.4' x 11.7' area of the northern cluster was conducted to a sensitivity of K < 16 mag. Using near-infrared magnitudes and colors from this and previously published surveys, twenty-five brown dwarf candidates were selected toward the high extinction cloud core. Spectra in the K band were obtained and comparisons of the depths of water vapor absorption bands in our candidate objects with a grid of dwarf,subgiant, and giant standards were made to derive spectral types. These data were then used to derive effective temperatures and stellar luminosities which, when combined with theoretical tracks and isochrones for pre-main sequence objects, resulted in estimates for their masses and ages. The models suggest a median age for the sample of < 1 Myr with substellar masses for at least 9 of the candidates including the x-ray flare source ASR 24. Surface gravities have been estimated for the brown dwarf candidates and, for a given spectral type,found to resemble more closely dwarfs than giants. Using the near-infrared imaging data and age estimates from the spectroscopic sample, an extinction-limited sample in the northern cluster was defined. Consistent with recent studies of other young clusters, this sample exhibits an accretion disk frequency of 0.75 +-0.20 and a mass spectrum slope across the hydrogen-burning limit of alpha < 1.6 where dN/dM ~ M^-(alpha).Comment: 22 postscript pages, 12 postscript figures, and 3 postscript tables. Accepted for publication in the Astronomical Journal (February, 2004