1,651 research outputs found
Egg parasitoid exploitation of plant volatiles induced by single or concurrent attack of a zoophytophagous predator and an invasive phytophagous pest
Zoophytophagous insect predators can induce physiological responses in plants by activating defence signalling pathways, but whether plants can respond to facultative phytophagy by recruiting natural enemies remains to be investigated. In Y-tube olfactometer bioassays, using a system including a Vicia faba plant, the zoophytophagous predator Podisus maculiventris and the egg parasitoid Telenomus podisi, we first demonstrated that T. podisi females are attracted by broad bean plants damaged by feeding activity of P. maculiventris and on which host egg masses had been laid, while they are not attracted by undamaged plants or plants damaged by feeding activity alone. In a second experiment, we evaluated the impact of the invasive phytophagous pest Halyomorpha halys on this plant volatile-mediated tritrophic communication. Results showed that the invasive herbivorous adults do not induce plants to recruit the native egg parasitoid, but they can disrupt the local infochemical network. In fact, T. podisi females are not attracted by volatiles emitted by plants damaged by H. halys feeding alone or combined with oviposition activity, nor are they attracted by plants concurrently infested by P. maculiventris and H. halys, indicating the specificity in the parasitoid response and the ability of the invasive herbivore in interrupting the semiochemical communication between plants and native egg parasitoids. To the best of our knowledge, this is the first study showing that zoophytophagous predator attacks induce indirect plant defences similarly to those defence strategies adopted by plants as a consequence of single or concurrent infestations of herbivorous insects
Control of the Onset of Filamentation in Condensed Media
Propagation of intense, ultrashort laser pulses through condensed media like
crystals of BaF and sapphire results in the formation of filaments. We
demonstrate that the onset of filamentation may be controlled by rotating the
plane of polarization of incident light. We directly visualize filamentation in
BaF_2 via six-photon absorption-induced fluorescence and, concomitantly, by
probing the spectral and spatial properties of white light that is generated.Comment: To appear in Phys. Rev.
Dynamic Nonlinear X-waves for Femtosecond Pulse Propagation in Water
Recent experiments on femtosecond pulses in water displayed long distance
propagation analogous to that reported in air. We verify this phenomena
numerically and show that the propagation is dynamic as opposed to self-guided.
Furthermore, we demonstrate that the propagation can be interpreted as due to
dynamic nonlinear X-waves whose robustness and role in long distance
propagation is shown to follow from the interplay between nonlinearity and
chromatic dispersion.Comment: 4 page
Highly charged ions in Penning traps, a new tool for resolving low lying isomeric states
The use of highly charged ions increases the precision and resolving power,
in particular for short-lived species produced at on-line radio-isotope beam
facilities, achievable with Penning trap mass spectrometers. This increase in
resolving power provides a new and unique access to resolving low-lying
long-lived ( ms) nuclear isomers. Recently, the keV
(determined from -ray spectroscopy) isomeric state in Rb has
been resolved from the ground state, in a charge state of with the TITAN
Penning trap at the TRIUMF-ISAC facility. The excitation energy of the isomer
was measured to be keV above the ground state. The extracted
masses for both the ground and isomeric states, and their difference, agree
with the AME2003 and Nuclear Data Sheet values. This proof of principle
measurement demonstrates the feasibility of using Penning trap mass
spectrometers coupled to charge breeders to study nuclear isomers and opens a
new route for isomer searches.Comment: 8 pages, 6 figure
First direct mass-measurement of the two-neutron halo nucleus 6He and improved mass for the four-neutron halo 8He
The first direct mass-measurement of He has been performed with the
TITAN Penning trap mass spectrometer at the ISAC facility. In addition, the
mass of He was determined with improved precision over our previous
measurement. The obtained masses are (He) = 6.018 885 883(57) u and
(He) = 8.033 934 44(11) u. The He value shows a deviation from
the literature of 4. With these new mass values and the previously
measured atomic isotope shifts we obtain charge radii of 2.060(8) fm and
1.959(16) fm for He and He respectively. We present a detailed
comparison to nuclear theory for He, including new hyperspherical harmonics
results. A correlation plot of the point-proton radius with the two-neutron
separation energy demonstrates clearly the importance of three-nucleon forces.Comment: 4 pages, 2 figure
Light Filaments Without Self Guiding
An examination of the propagation of intense 200 fs pulses in water reveals
light filaments not sustained by the balance between Kerr-induced self-focusing
and plasma-induced defocusing. Their appearance is interpreted as the
consequence of a spontaneous reshaping of the wave packet form a gaussian into
a conical wave, driven by the requirement of maximum localization, minimum
losses and stationarity in the presence of non-linear absorption.Comment: Submitted to Phys. Rev. Lett. on July 7th, 200
TriSol: a major upgrade of the TwinSol RNB facility
We report here on the recent upgrade of the TwinSol radioactive nuclear beam
(RNB) facility at the University of Notre Dame. The new TriSol system includes
a magnetic dipole to provide a second beamline and a third solenoid which acts
to reduce the size of the radioactive beam on target.Comment: submitted to Nuclear Instruments and Methods
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