University of Bordeaux

About: University of Bordeaux is a education organization based out in Bordeaux, France. It is known for research contribution in the topics: Population & Laser. The organization has 28811 authors who have published 55536 publications receiving 1619635 citations. The organization is also known as: UB.

Detection of the characteristic pion-decay signature in supernova remnants

Abstract: Cosmic rays are particles (mostly protons) accelerated to relativistic speeds. Despite wide agreement that supernova remnants (SNRs) are the sources of galactic cosmic rays, unequivocal evidence for the acceleration of protons in these objects is still lacking. When accelerated protons encounter interstellar material, they produce neutral pions, which in turn decay into gamma rays. This offers a compelling way to detect the acceleration sites of protons. The identification of pion-decay gamma rays has been difficult because high-energy electrons also produce gamma rays via bremsstrahlung and inverse Compton scattering. We detected the characteristic pion-decay feature in the gamma-ray spectra of two SNRs, IC 443 and W44, with the Fermi Large Area Telescope. This detection provides direct evidence that cosmic-ray protons are accelerated in SNRs.

Top 10 plant viruses in molecular plant pathology

Abstract: Many scientists, if not all, feel that their particular plant virus should appear in any list of the most important plant viruses. However, to our knowledge, no such list exists. The aim of this review was to survey all plant virologists with an association with Molecular Plant Pathology and ask them to nominate which plant viruses they would place in a 'Top 10' based on scientific/economic importance. The survey generated more than 250 votes from the international community, and allowed the generation of a Top 10 plant virus list for Molecular Plant Pathology. The Top 10 list includes, in rank order, (1) Tobacco mosaic virus, (2) Tomato spotted wilt virus, (3) Tomato yellow leaf curl virus, (4) Cucumber mosaic virus, (5) Potato virus Y, (6) Cauliflower mosaic virus, (7) African cassava mosaic virus, (8) Plum pox virus, (9) Brome mosaic virus and (10) Potato virus X, with honourable mentions for viruses just missing out on the Top 10, including Citrus tristeza virus, Barley yellow dwarf virus, Potato leafroll virus and Tomato bushy stunt virus. This review article presents a short review on each virus of the Top 10 list and its importance, with the intent of initiating discussion and debate amongst the plant virology community, as well as laying down a benchmark, as it will be interesting to see in future years how perceptions change and which viruses enter and leave the Top 10.

High harmonic interferometry of multi-electron dynamics in molecules

Abstract: High harmonic emission occurs when an electron, liberated from a molecule by an incident intense laser field, gains energy from the field and recombines with the parent molecular ion. The emission provides a snapshot of the structure and dynamics of the recombining system, encoded in the amplitudes, phases and polarization of the harmonic light. Here we show with CO2 molecules that high harmonic interferometry can retrieve this structural and dynamic information: by measuring the phases and amplitudes of the harmonic emission, we reveal ‘fingerprints’ of multiple molecular orbitals participating in the process and decode the underlying attosecond multi-electron dynamics, including the dynamics of electron rearrangement upon ionization. These findings establish high harmonic interferometry as an effective approach to resolving multi-electron dynamics with sub-Angstrom spatial resolution arising from the de Broglie wavelength of the recombining electron, and attosecond temporal resolution arising from the timescale of the recombination event. The high harmonic emission that accompanies the recombination of an electron with its parent molecular ion in an intense laser field provides a snapshot of the structure and dynamics of the recombining system. Experiments with CO2 molecules now show that high harmonic interferometry can retrieve this structural and dynamic information by measuring the phases and amplitudes of the harmonic emission. The resulting 'fingerprints' of the multiple molecular orbitals participating in the process can be used to decode the underlying attosecond multi-electron dynamics, including the dynamics of electron rearrangement upon ionization. The light emitted from the system contains images of moving electrons that can be processed into a movie. These findings establish high harmonic interferometry as an effective approach to resolving multi-electron dynamics with sub-Angstrom spatial resolution arising from the de-Broglie wavelength of the recombining electron, and attosecond temporal resolution arising from the timescale of the recombination event. The high harmonic emission that accompanies the recombination of an electron with its parent molecular ion in an intense laser field provides a snapshot of the structure and dynamics of the recombining system. Experiments on CO2 molecules now show how to extract information from the properties of the emitted light about the underlying multi-electron dynamics with sub-Angstrom spatial resolution and attosecond temporal resolution