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Peculiarly pleasant weather for US maize.
Continuation of historical trends in crop yield are critical to meeting the demands of a growing and more affluent world population. Climate change may compromise our ability to meet these demands, but estimates vary widely, highlighting the importance of understanding historical interactions between yield and climate trends. The relationship between temperature and yield is nuanced, involving differential yield outcomes to warm ([Formula: see text]C) and hot ([Formula: see text]C) temperatures and differing sensitivity across growth phases. Here, we use a crop model that resolves temperature responses according to magnitude and growth phase to show that US maize has benefited from weather shifts since 1981. Improvements are related to lengthening of the growing season and cooling of the hottest temperatures. Furthermore, current farmer cropping schedules are more beneficial in the climate of the last decade than they would have been in earlier decades, indicating statistically significant adaptation to a changing climate of 13 kg·ha-1· decade-1 All together, the better weather experienced by US maize accounts for 28% of the yield trends since 1981. Sustaining positive trends in yield depends on whether improvements in agricultural climate continue and the degree to which farmers adapt to future climates
Gamma-ray Bursts, Classified Physically
From Galactic binary sources, to extragalactic magnetized neutron stars, to
long-duration GRBs without associated supernovae, the types of sources we now
believe capable of producing bursts of gamma-rays continues to grow apace. With
this emergent diversity comes the recognition that the traditional (and newly
formulated) high-energy observables used for identifying sub-classes does not
provide an adequate one-to-one mapping to progenitors. The popular
classification of some > 100 sec duration GRBs as ``short bursts'' is not only
an unpalatable retronym and syntactically oxymoronic but highlights the
difficultly of using what was once a purely phenomenological classification to
encode our understanding of the physics that gives rise to the events. Here we
propose a physically based classification scheme designed to coexist with the
phenomenological system already in place and argue for its utility and
necessity.Comment: 6 pages, 3 figures. Slightly expanded version of solicited paper to
be published in the Proceedings of ''Gamma Ray Bursts 2007,'' Santa Fe, New
Mexico, November 5-9. Edited by E. E. Fenimore, M. Galassi, D. Palme
Predicting Short-duration GRB Rates in the Advanced LIGO Volume
Starting with models for the compact object merger event rate, the
short-duration Gamma-ray Burst (sGRB) luminosity function, and the Swift/BAT
detector, we calculate the observed Swift sGRB rate and its uncertainty. Our
probabilistic sGRB world model reproduces the observed number distributions in
redshift and flux for 123 Swift/BAT detected sGRBs and can be used to predict
joint sGRB/LIGO detection rates. We discuss the dependence of the rate
predictions on the model parameters and explore how they vary with increasing
experimental sensitivity. In particular, the number of bursts in the LIGO
volume depends strongly on the parameters that govern sGRB beaming. Our results
suggest that nearby sGRBs should be observed to have broader jets on average
( degrees), as compared to the narrowly-beamed
appearance of cosmological sGRBs due to detection selection effect driving
observed jet angle. Assuming all sGRBs are due to compact object mergers,
within a Mpc aLIGO volume, we predict sGRB/GW
associations all-sky per year for on-axis events at Swift sensitivities,
increasing to with the inclusion of off-axis events. We
explore the consistency of our model with GW170817/GRB~170817A in the context
of structured jets. Predictions for future experiments are made.Comment: ApJ accepte
First Results from the rapid-response spectrophotometric characterization of Near-Earth Objects
As part of our multi-observatory, multi-filter campaign, we present \rmi
color observations of 82 Near-Earth Objects (NEOs) obtained with the RATIR
instrument on the 1.5m robotic telescope at the San Pedro Martir's National
Observatory in Mexico. Our project is particularly focused on rapid response
observations of small ( m) NEOs. The rapid response and the use
of spectrophotometry allows us to constrain the taxonomic classification of
NEOs with high efficiency. Here we present the methodology of our observations
and our result, suggesting that the ratio of C-type to S-type asteroids in a
size range of 30-850m is 1.1, which is in accordance with our previous
results. We also find that 10 of all NEOs in our sample are neither C- nor
S-type asteroidsComment: 31 pages, 4 tables, 10 figure
GRB Energetics in the Swift Era
We examine the rest frame energetics of 76 gamma-ray bursts (GRBs) with known
redshift that were detected by the Swift spacecraft and monitored by the
satellite's X-ray Telescope (XRT). Using the bolometric fluence values
estimated in Butler et al. 2007b and the last XRT observation for each event,
we set a lower limit the their collimation corrected energy Eg and find that a
68% of our sample are at high enough redshift and/or low enough fluence to
accommodate a jet break occurring beyond the last XRT observation and still be
consistent with the pre-Swift Eg distribution for long GRBs. We find that
relatively few of the X-ray light curves for the remaining events show evidence
for late-time decay slopes that are consistent with that expected from post jet
break emission. The breaks in the X-ray light curves that do exist tend to be
shallower and occur earlier than the breaks previously observed in optical
light curves, yielding a Eg distribution that is far lower than the pre-Swift
distribution. If these early X-ray breaks are not due to jet effects, then a
small but significant fraction of our sample have lower limits to their
collimation corrected energy that place them well above the pre-Swift Eg
distribution. Either scenario would necessitate a much wider post-Swift Eg
distribution for long cosmological GRBs compared to the narrow standard energy
deduced from pre-Swift observations. We note that almost all of the pre-Swift
Eg estimates come from jet breaks detected in the optical whereas our sample is
limited entirely to X-ray wavelengths, furthering the suggestion that the
assumed achromaticity of jet breaks may not extend to high energies.Comment: 30 pages, 10 figures, Accepted to Ap
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