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Potent Attractant for Root-Knot Nematodes in Exudates from Seedling Root Tips of Two Host Species.
Root-knot nematodes (RKN; Meloidogyne spp.) can parasitize over 2,000 plant species and are generally considered to be the most agriculturally damaging group of plant-parasitic nematodes worldwide. Infective juveniles (J2) are non-feeding and must locate and invade a host before their reserves are depleted. However, what attracts J2 to appropriate root entry sites is not known. An aim of this research is to identify semiochemicals that attract RKN to roots. J2 of the three RKN species tested are highly attracted to root tips of both tomato and Medicago truncatula. For both hosts, mutants defective in ethylene signaling were found to be more attractive than those of wild type. We determined that cell-free exudates collected from tomato and M. truncatula seedling root tips were highly attractive to M. javanica J2. Using a pluronic gel-based microassay to monitor chemical fractionation, we determined that for both plant species the active component fractionated similarly and had a mass of ~400 based on size-exclusion chromatography. This characterization is a first step toward identification of a potent and specific attractant from host roots that attracts RKN. Such a compound is potentially a valuable tool for developing novel and safe control strategies
Radio-wave propagation in the non-Gaussian interstellar medium
Radio waves propagating from distant pulsars in the interstellar medium
(ISM), are refracted by electron density inhomogeneities, so that the intensity
of observed pulses fluctuates with time. The theory relating the observed pulse
time-shapes to the electron-density correlation function has developed for 30
years, however, two puzzles have remained. First, observational scaling of
pulse broadening with the pulsar distance is anomalously strong; it is
consistent with the standard model only when non-uniform statistics of electron
fluctuations along the line of sight are assumed. Second, the observed pulse
shapes are consistent with the standard model only when the scattering material
is concentrated in a narrow slab between the pulsar and the Earth.
We propose that both paradoxes are resolved at once if one assumes stationary
and uniform, but non-Gaussian statistics of the electron-density distribution.
Such statistics must be of Levy type, and the propagating ray should exhibit a
Levy flight. We propose that a natural realization of such statistics may be
provided by the interstellar medium with random electron-density
discontinuities. We develop a theory of wave propagation in such a non-Gaussian
random medium, and demonstrate its good agreement with observations. The
qualitative introduction of the approach and the resolution of the
anomalous-scaling paradox was presented earlier in [PRL 91, 131101 (2003); ApJ
584, 791 (2003)].Comment: 27 pages, changes to match published versio
Diurnal variation in harbour porpoise detection – potential implications for management
Peer reviewedPublisher PD
Nitrate and phosphate availability and distribution have different effects on root system architecture of Arabidopsis
Plant root systems can respond to nutrient availability and distribution by changing the three-dimensional deployment of their roots: their root system architecture (RSA). We have compared RSA in homogeneous and heterogeneous nitrate and phosphate supply in Arabidopsis. Changes in nitrate and phosphate availability were found to have contrasting effects on primary root length and lateral root density, but similar effects on lateral root length. Relative to shoot dry weight (DW), primary root length decreased with increasing nitrate availability, while it increased with increasing phosphate supply. Lateral root density remained constant across a range of nitrate supplies, but decreased with increasing phosphate supply. In contrast, lateral root elongation was suppressed both by high nitrate and high phosphate supplies. Local supplies of high nitrate or phosphate in a patch also had different effects. Primary root growth was not affected by a high nitrate patch, but growth through a high phosphate patch reduced primary root growth after the root left the patch. A high nitrate patch induced an increase in lateral root density in the patch, whereas lateral root density was unaffected by a high phosphate patch. However, both phosphate- and nitrate-rich patches induced lateral root elongation in the patch and suppressed it outside the patch. This co-ordinated response of lateral roots also occurs in soil-grown plants exposed to a nutrient-rich patch. The auxin-resistant mutants axr1, axr4 and aux1 all showed the wild-type lateral root elongation responses to a nitrate-rich patch, suggesting that auxin is not required for this response
Anxious to see you: Neuroendocrine mechanisms of social vigilance and anxiety during adolescence.
Social vigilance is a behavioral strategy commonly used in adverse or changing social environments. In animals, a combination of avoidance and vigilance allows an individual to evade potentially dangerous confrontations while monitoring the social environment to identify favorable changes. However, prolonged use of this behavioral strategy in humans is associated with increased risk of anxiety disorders, a major burden for human health. Elucidating the mechanisms of social vigilance in animals could provide important clues for new treatment strategies for social anxiety. Importantly, during adolescence the prevalence of social anxiety increases significantly. We hypothesize that many of the actions typically characterized as anxiety behaviors begin to emerge during this time as strategies for navigating more complex social structures. Here, we consider how the social environment and the pubertal transition shape neural circuits that modulate social vigilance, focusing on the bed nucleus of the stria terminalis and prefrontal cortex. The emergence of gonadal hormone secretion during adolescence has important effects on the function and structure of these circuits, and may play a role in the emergence of a notable sex difference in anxiety rates across adolescence. However, the significance of these changes in the context of anxiety is still uncertain, as not enough studies are sufficiently powered to evaluate sex as a biological variable. We conclude that greater integration between human and animal models will aid the development of more effective strategies for treating social anxiety
The silence of self-knowledge
Gareth Evans famously affirmed an explanatory connection between answering the question whether p and knowing whether one believes that p. This is commonly interpreted in terms of the idea that judging that p constitutes an adequate basis for the belief that one believes that p. This paper formulates and defends an alternative, more modest interpretation, which develops from the suggestion that one can know that one believes that p in judging that p
Time dependent spectral modeling of Markarian 421 during a violent outburst in 2010
We present the results of extensive modeling of the spectral energy
distributions (SEDs) of the closest blazar (z=0.031) Markarian 421 (Mrk 421)
during a giant outburst in February 2010. The source underwent rapid flux
variations in both X-rays and very high energy (VHE) gamma-rays as it evolved
from a low-flux state on 2010 February 13-15 to a high-flux state on 2010
February 17. During this period, the source exhibited significant spectral
hardening from X-rays to VHE gamma-rays while exhibiting a "harder when
brighter" behavior in these energy bands. We reproduce the broadband SED using
a time-dependent multi-zone leptonic jet model with radiation feedback. We find
that an injection of the leptonic particle population with a single power-law
energy distribution at shock fronts followed by energy losses in an
inhomogeneous emission region is suitable for explaining the evolution of Mrk
421 from low- to high-flux state in February 2010. The spectral states are
successfully reproduced by a combination of a few key physical parameters, such
as the maximum minimum cutoffs and power-law slope of the electron
injection energies, magnetic field strength, and bulk Lorentz factor of the
emission region. The simulated light curves and spectral evolution of Mrk 421
during this period imply an almost linear correlation between X-ray flux at
1-10 keV energies and VHE gamma-ray flux above 200 GeV, as has been previously
exhibited by this source. Through this study, a general trend that has emerged
for the role of physical parameters is that, as the flare evolves from a low-
to a high-flux state, higher bulk kinetic energy is injected into the system
with a harder particle population and a lower magnetic field strength.Comment: 13 pages, 5 figures, accepted for publication in MNRA
Meson-exchange Currents and Quasielastic Neutrino Cross Sections
We illustrate and discuss the role of meson-exchange currents in quasielastic
neutrino-nucleus scattering induced by charged currents, comparing the results
with the recent MiniBooNE data for differential and integrated cross sections.Comment: 9 pages, 8 figures; Proceedings of the 30th International Workshop on
Nuclear Theory IWNT30, Rila Mountains, Bulgaria, June 27 - July 2, 201
Photon-Number-Splitting versus Cloning Attacks in Practical Implementations of the Bennett-Brassard 1984 protocol for Quantum Cryptography
In practical quantum cryptography, the source sometimes produces multi-photon
pulses, thus enabling the eavesdropper Eve to perform the powerful
photon-number-splitting (PNS) attack. Recently, it was shown by Curty and
Lutkenhaus [Phys. Rev. A 69, 042321 (2004)] that the PNS attack is not always
the optimal attack when two photons are present: if errors are present in the
correlations Alice-Bob and if Eve cannot modify Bob's detection efficiency, Eve
gains a larger amount of information using another attack based on a 2->3
cloning machine. In this work, we extend this analysis to all distances
Alice-Bob. We identify a new incoherent 2->3 cloning attack which performs
better than those described before. Using it, we confirm that, in the presence
of errors, Eve's better strategy uses 2->3 cloning attacks instead of the PNS.
However, this improvement is very small for the implementations of the
Bennett-Brassard 1984 (BB84) protocol. Thus, the existence of these new attacks
is conceptually interesting but basically does not change the value of the
security parameters of BB84. The main results are valid both for Poissonian and
sub-Poissonian sources.Comment: 11 pages, 5 figures; "intuitive" formula (31) adde
Efficient calibration for high-dimensional computer model output using basis methods
Calibration of expensive computer models with high-dimensional output fields
can be approached via history matching. If the entire output field is matched,
with patterns or correlations between locations or time points represented,
calculating the distance metric between observational data and model output for
a single input setting requires a time intensive inversion of a
high-dimensional matrix. By using a low-dimensional basis representation rather
than emulating each output individually, we define a metric in the reduced
space that allows the implausibility for the field to be calculated
efficiently, with only small matrix inversions required, using projection that
is consistent with the variance specifications in the implausibility. We show
that projection using the norm can result in different conclusions, with
the ordering of points not maintained on the basis, with implications for both
history matching and probabilistic methods. We demonstrate the scalability of
our method through history matching of the Canadian atmosphere model, CanAM4,
comparing basis methods to emulation of each output individually, showing that
the basis approach can be more accurate, whilst also being more efficient
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