36 research outputs found
Experiences with designing and managing organic rotation trials
This report was presented at the UK Organic Research 2002 Conference. Practical problems encountered in two long-term organic rotation trials at Aberdeen and Elgin are discussed. Compromises have had to be made in designing and managing the trials: how to include livestock and measure output, plot size, marking and fencing, discards and paths, replication, rotation length, randomisation of crop sequence, site uniformity, manoeuvrability of machines, soil compaction and exposure to pest damage
Effect of organic crop rotations on long-term development of the weed seedbank
Changes in the weed seedbank were monitored between 1991 and 1998 in two experiments that were established to compare organic crop rotations at two sites in NE Scotland. Two rotations, replicated twice at each site, were compared and all courses of both rotations were present every year. There were relatively minor changes in weed species diversity over time, but major changes in seedbank abundance. Weed seed numbers were relatively low in rotations with a high proportion of grass/clover ley. Differences in level of seedbank across the rotation were relatively predictable at Tulloch but much less so at Woodside where factors such as the effect of the grass/clover ley seemed to play a lesser role. Other factors, such as weather and its influence on the effectiveness of weed control operations, and higher populations of ground-living arthropods, may be affecting the Woodside seedbanks
The variable X-ray light curve of GRB 050713A: the case of refreshed shocks
We present a detailed study of the spectral and temporal properties of the
X-ray and optical emission of GRB050713a up to 0.5 day after the main GRB
event. The X-ray light curve exhibits large amplitude variations with several
rebrightenings superposed on the underlying three-segment broken powerlaw that
is often seen in Swift GRBs. Our time-resolved spectral analysis supports the
interpretation of a long-lived central engine, with rebrightenings consistent
with energy injection in refreshed shocks as slower shells generated in the
central engine prompt phase catch up with the afterglow shock at later times.
Our sparsely-sampled light curve of the optical afterglow can be fitted with a
single power law without large flares. The optical decay index appears flatter
than the X-ray one, especially at later times.Comment: few changes, to be published in A&
Three Gravitationally Lensed Supernovae Behind CLASH Galaxy Clusters
We report observations of three gravitationally lensed supernovae (SNe) in
the Cluster Lensing And Supernova survey with Hubble (CLASH) Multi-Cycle
Treasury program. These objects, SN CLO12Car (z = 1.28), SN CLN12Did (z =
0.85), and SN CLA11Tib (z = 1.14), are located behind three different clusters,
MACSJ1720.2+3536 (z = 0.391), RXJ1532.9+3021 (z = 0.345), and Abell 383 (z =
0.187), respectively. Each SN was detected in Hubble Space Telescope (HST)
optical and infrared images. Based on photometric classification, we find that
SNe CLO12Car and CLN12Did are likely to be Type Ia supernovae (SNe Ia), while
the classification of SN CLA11Tib is inconclusive. Using multi-color
light-curve fits to determine a standardized SN Ia luminosity distance, we
infer that SN CLO12Car was approximately 1.0 +/- 0.2 mag brighter than field
SNe Ia at a similar redshift and ascribe this to gravitational lens
magnification. Similarly, SN CLN12Did is approximately 0.2 +/- 0.2 mag brighter
than field SNe Ia. We derive independent estimates of the predicted
magnification from CLASH strong+weak lensing maps of the clusters: 0.83 +/-
0.16 mag for SN CLO12Car, 0.28 +/- 0.08 mag for SN CLN12Did, and 0.43 +/- 0.11
mag for SN CLA11Tib. The two SNe Ia provide a new test of the cluster lens
model predictions: we find that the magnifications based on the SN Ia
brightness and those predicted by the lens maps are consistent. Our results
herald the promise of future observations of samples of cluster-lensed SNe Ia
(from the ground or space) to help illuminate the dark-matter distribution in
clusters of galaxies, through the direct determination of absolute
magnifications.Comment: ApJ in pres
Intrinsic and dust-induced polarization in gamma-ray burst afterglows: the case of GRB 021004
Polarization measurements for the optical counterpart to GRB 021004 are
presented and discussed. Our observations were performed with the TNG and the
VLT-UT3 (Melipal) during the first and fourth night after the gamma-ray burst
discovery. We find robust evidence of temporal evolution of the polarization,
which is therefore, at least partially, intrinsic to the optical transient. We
do not find convincing evidence of wavelength dependence for the intrinsic
polarization of the transient, in agreement with current polarization models
for optical afterglows. We discuss the role of dust, both in our galaxy and in
the host, in modifying the transmitted polarization vector, showing how a
sizable fraction of the observed polarized flux is due to Galactic selective
extinction, while it is not possible to single out any clear contribution from
dust in the host galaxy. We discuss how our data compare to those obtained by
different groups showing that a two-component model is required to describe the
complete dataset. This is not surprising given the complex lightcurve of GRB
021004.Comment: 9 pages, 6 postscript figures, A&A in pres
Out of the darkness: the infrared afterglow of the INTEGRAL burst GRB 040422 observed with the VLT
GRB 040422 was detected by the INTEGRAL satellite at an angle of only 3
degrees from the Galactic plane. Analysis of the prompt emission observed with
the SPI and IBIS instruments on INTEGRAL are presented. The IBIS spectrum is
well fit by the Band model with a break energy of Eo=56+/-2 keV and
Epeak=41+/-3 keV. The peak flux is 1.8 10^(-7) erg/cm2/s and fluence 3.4
10^(-7) erg/cm2 in the range 20-200 keV. We then present the observations of
the afterglow of GRB 040422, obtained with the ISAAC and FORS 2 instruments at
the VLT less than 2 hours after the burst. We report the discovery of its
near-infrared afterglow, for which we give here the astrometry and photometry.
No detection could have been obtained in the R and I bands, partly due to the
large extinction in the Milky Way. We re-imaged the position of the afterglow
two months later in the Ks band, and detected a likely bright host galaxy. We
compare the magnitude of the afterglow with a those of a compilation of
promptly observed counterparts of previous GRBs, and show that the afterglow of
GRB 040422 lies at the very faint end of the distribution, brighter only than
that of GRB 021211, singled out later and in the optical bands, and GRB 040924
after accounting for Milky Way extinction. This observation suggests that the
proportion of dark GRBs can be significantly lowered by a more systematic use
of 8-m class telescopes in the infrared in the very early hours after the
burst.Comment: 9 pages, 7 figures, accepted in A&
Electromagnetic priors for black hole spindown in searches for gravitational-waves from supernovae and long GRBs
Some core-collapse supernovae appear to be hyper-energetic, and a subset of
these are aspherical and associated with long GRBs. We use observations of
electromagnetic emission from core-collapse supernovae and GRBs to impose
constraints on their free energy source as a prior to searches for their
gravitational wave emission. We review these events based on a finite
efficiency for the conversion of spin energy to magnetic winds powering
supernovae. We find that some of the hyper-energetic events cannot be powered
by the spindown of rapidly rotating proto-neutron stars by virtue of their
limited rotational energy. They can, instead, be produced by the spindown of
black holes providing a distinct prospect for gravitational-wave emission of
interest to LIGO, Virgo, and the LCGT.Comment: A&A Lett., to appea
Supplement: "Localization and broadband follow-up of the gravitational-wave transient GW150914" (2016, ApJL, 826, L13)
This Supplement provides supporting material for Abbott et al. (2016a). We briefly summarize past electromagnetic (EM) follow-up efforts as well as the organization and policy of the current EM follow-up program. We compare the four probability sky maps produced for the gravitational-wave transient GW150914, and provide additional details of the EM follow-up observations that were performed in the different bands
Evidence-based Kernels: Fundamental Units of Behavioral Influence
This paper describes evidence-based kernels, fundamental units of behavioral influence that appear to underlie effective prevention and treatment for children, adults, and families. A kernel is a behavior–influence procedure shown through experimental analysis to affect a specific behavior and that is indivisible in the sense that removing any of its components would render it inert. Existing evidence shows that a variety of kernels can influence behavior in context, and some evidence suggests that frequent use or sufficient use of some kernels may produce longer lasting behavioral shifts. The analysis of kernels could contribute to an empirically based theory of behavioral influence, augment existing prevention or treatment efforts, facilitate the dissemination of effective prevention and treatment practices, clarify the active ingredients in existing interventions, and contribute to efficiently developing interventions that are more effective. Kernels involve one or more of the following mechanisms of behavior influence: reinforcement, altering antecedents, changing verbal relational responding, or changing physiological states directly. The paper describes 52 of these kernels, and details practical, theoretical, and research implications, including calling for a national database of kernels that influence human behavior
Multi-messenger observations of a binary neutron star merger
On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta