3,031 research outputs found
Environmental, developmental, and genetic factors controlling root system architecture
A better understanding of the development and architecture of roots is essential to develop strategies to increase crop yield and optimize agricultural land use. Roots control nutrient and water uptake, provide anchoring and mechanical support and can serve as important storage organs. Root growth and development is under tight genetic control and modulated by developmental cues including plant hormones and the environment. This review focuses on root architecture and its diversity and the role of environment, nutrient, and water as well as plant hormones and their interactions in shaping root architecture
The importance of context and the effect of information and deliberation on opinion change regarding environmental issues in citizensâ juries
Citizensâ juries have become a popular method for engaging citizens in deliberation about complex public policy issues, such as climate action and sustainable development. Empirical evidence routinely indicates that jurors change their minds throughout the process. What is less clear is when and why this occurs and whether the causes are consistent across juries that consider the same topic but are situated within different contexts. We present evidence of opinion change in citizensâ juries through a natural experiment, contrasting three local contexts of onshore windfarm development in Scotland; viz. existing, planned, and absent. Jurorsâ individual opinions of climate change, wind energy, and windfarms were measured through questionnaires at four time points: the start, following information-giving, reflection, and deliberation. Statistical examination of jurorsâ responses, through paired sample t-tests, Wilcoxon sign-tests, and Generalised Least Squares regression, reveals to what extent substantive changes were associated with different phases and locational contexts. In all three juries, opinion change occurs throughout the process, on different topics, and to different degrees. While the information phase consistently influences jurorsâ opinions the most, jury composition affects the magnitude and direction of opinion change, with outcomes contingent on contexts. Our findings are important for informing how mini-publics are designed and used to inform environmental policy-making at different scales
Intergovernmentalists in the Commission:Foxes in the Henhouse?
Contrary to the dominant view in the scholarly literature on European institutions, where the European Commission is generally described as a unitary actor whose acts are primarily influenced by a political agenda and/or considerations of self-interest, this article argues that a variety of opinions coexist within the Commission staff. Based on the largest attitudinal survey ever conducted on Commission officials, it documents the existence of a sizeable minority of intergovernmentalists and analyzes their attitude towards the institution they serve and their views on its place in the integration process
Lower bounds on the complexity of simulating quantum gates
We give a simple proof of a formula for the minimal time required to simulate
a two-qubit unitary operation using a fixed two-qubit Hamiltonian together with
fast local unitaries. We also note that a related lower bound holds for
arbitrary n-qubit gates.Comment: 6 page
An Unbiased Survey of 500 Nearby Stars for Debris Disks: A JCMT Legacy Program
We present the scientific motivation and observing plan for an upcoming
detection survey for debris disks using the James Clerk Maxwell Telescope. The
SCUBA-2 Unbiased Nearby Stars (SUNS) Survey will observe 500 nearby main
sequence and sub-giant stars (100 of each of the A, F, G, K and M spectral
classes) to the 850 micron extragalactic confusion limit to search for evidence
of submillimeter excess, an indication of circumstellar material. The survey
distance boundaries are 8.6, 16.5, 22, 25 and 45 pc for M, K, G, F and A stars,
respectively, and all targets lie between the declinations of -40 deg to 80
deg. In this survey, no star will be rejected based on its inherent properties:
binarity, presence of planetary companions, spectral type or age. This will be
the first unbiased survey for debris disks since IRAS. We expect to detect ~125
debris disks, including ~50 cold disks not detectable in current shorter
wavelength surveys. A substantial amount of complementary data will be required
to constrain the temperatures and masses of discovered disks. High resolution
studies will likely be required to resolve many of the disks. Therefore, these
systems will be the focus of future observational studies using a variety of
observatories to characterize their physical properties. For non-detected
systems, this survey will set constraints (upper limits) on the amount of
circumstellar dust, of typically 200 times the Kuiper Belt mass, but as low as
10 times the Kuiper Belt mass for the nearest stars in the sample
(approximately 2 pc).Comment: 11 pages, 7 figures (3 color), accepted by the Publications of the
Astronomical Society of the Pacifi
Questioning policy, youth participation and lifestyle sports
Young people have been identified as a key target group for whom participation in sport and physical activity could have important benefits to health and wellbeing and consequently have been the focus of several government policies to increase participation in the UK. Lifestyle sports represent one such strategy for encouraging and sustaining new engagements in sport and physical activity in youth groups, however, there is at present a lack of understanding of the use of these activities within policy contexts. This paper presents findings from a government initiative which sought to increase participation in sport for young people through provision of facilities for mountain biking in a forest in south-east England. Findings from qualitative research with 40 young people who participated in mountain biking at the case study location highlight the importance of non-traditional sports as a means to experience the natural environments through forms of consumption which are healthy, active and appeal to their identities. In addition, however, the paper raises questions over the accessibility of schemes for some individuals and social groups, and the ability to incorporate sports which are inherently participant-led into state-managed schemes. Lifestyle sports such as mountain biking involve distinct forms of participation which present a challenge for policy-makers who seek to create and maintain sustainable communities of youth participants
Homologous and heterologous desensitization of guanylyl cyclase-B signaling in GH3 somatolactotropes
The guanylyl cyclases, GC-A and GC-B, are selective receptors for atrial and C-type natriuretic peptides (ANP and CNP, respectively). In the anterior pituitary, CNP and GC-B are major regulators of cGMP production in gonadotropes and yet mouse models of disrupted CNP and GC-B indicate a potential role in growth hormone secretion. In the current study, we investigate the molecular and pharmacological properties of the CNP/GC-B system in somatotrope lineage cells. Primary rat pituitary and GH3 somatolactotropes expressed functional GC-A and GC-B receptors that had similar EC50 properties in terms of cGMP production. Interestingly, GC-B signaling underwent rapid homologous desensitization in a protein phosphatase 2A (PP2A)-dependent manner. Chronic exposure to either CNP or ANP caused a significant down-regulation of both GC-A- and GC-B-dependent cGMP accumulation in a ligand-specific manner. However, this down-regulation was not accompanied by alterations in the sub-cellular localization of these receptors. Heterologous desensitization of GC-B signaling occurred in GH3 cells following exposure to either sphingosine-1-phosphate or thyrotrophin-releasing hormone (TRH). This heterologous desensitization was protein kinase C (PKC)-dependent, as pre-treatment with GF109203X prevented the effect of TRH on CNP/GC-B signaling. Collectively, these data indicate common and distinct properties of particulate guanylyl cyclase receptors in somatotropes and reveal that independent mechanisms of homologous and heterologous desensitization occur involving either PP2A or PKC. Guanylyl cyclase receptors thus represent potential novel therapeutic targets for treating growth-hormone-associated disorders
X-ray and Radio Timing of the Pulsar in 3C 58
We present timing data spanning 6.4 yr for the young and energetic PSR
J0205+6449, in the supernova remnant 3C 58. Data were obtained with the Rossi
X-ray Timing Explorer, the Jodrell Bank Observatory and the Green Bank
Telescope. We present phase-coherent timing analyses showing timing noise and
two spin-up glitches with fractional frequency increases of ~3.4E-7 near MJD
52555, and ~3.8E-6 between MJDs 52777 and 53062. These glitches are unusually
large if the pulsar was created in the historical supernova in 1181 as has been
suggested. For the X-ray timing we developed a new unbinned maximum-likelihood
method for determining pulse arrival times which performs significantly better
than the traditional binned techniques. In addition, we present an X-ray pulse
profile analysis of four years of RXTE data showing that the pulsar is detected
up to ~40 keV. We also present the first measurement of the phase offset
between the radio and X-ray pulse for this source, showing that the radio pulse
leads the X-ray pulse by phi=0.10+/-0.01 in phase. We compile all known
measurements of the phase offsets between radio and X-ray and radio and
gamma-ray pulses for X-ray and gamma-ray pulsars. We show that there is no
relationship between pulse period and phase offset, supported by our
measurement of the phase offset for PSR J0205+6449.Comment: 19 pages, 12 figures. Published in the Astrophysical Journal.
Includes additional data analysis and two new figure
Radioactive 26Al and massive stars in the Galaxy
Gamma-rays from radioactive 26Al (half life ~7.2 10^5 yr) provide a
'snapshot' view of ongoing nucleosynthesis in the Galaxy. The Galaxy is
relatively transparent to such gamma-rays, and emission has been found
concentrated along the plane of the Galaxy. This led to the conclusion1 that
massive stars throughout the Galaxy dominate the production of 26Al. On the
other hand, meteoritic data show locally-produced 26Al, perhaps from spallation
reactions in the protosolar disk. Furthermore, prominent gamma-ray emission
from the Cygnus region suggests that a substantial fraction of Galactic 26Al
could originate in localized star-forming regions. Here we report high spectral
resolution measurements of 26Al emission at 1808.65 keV, which demonstrate that
the 26Al source regions corotate with the Galaxy, supporting its Galaxy-wide
origin. We determine a present-day equilibrium mass of 2.8 (+/-0.8) M_sol of
26Al. We use this to estimate that the frequency of core collapse (i.e. type
Ib/c and type II) supernovae to be 1.9(+/- 1.1) events per century.Comment: accepted for publication in Nature, 24 pages including Online
Supplements, 11 figures, 1 tabl
Ages for exoplanet host stars
Age is an important characteristic of a planetary system, but also one that
is difficult to determine. Assuming that the host star and the planets are
formed at the same time, the challenge is to determine the stellar age.
Asteroseismology provides precise age determination, but in many cases the
required detailed pulsation observations are not available. Here we concentrate
on other techniques, which may have broader applicability but also serious
limitations. Further development of this area requires improvements in our
understanding of the evolution of stars and their age-dependent
characteristics, combined with observations that allow reliable calibration of
the various techniques.Comment: To appear in "Handbook of Exoplanets", eds. Deeg, H.J. & Belmonte,
J.A, Springer (2018
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