A method to obtain disinfected Globodera infective juveniles directly from cysts

Les systèmes d'inoculation in vitro sont des outils performants et précis pour l'étude des interactions plantes-nématodes. L'obtention de juvéniles stériles est une étape cruciale pour la plupart de ces systèmes. La majorité des protocoles publiés comprennent une désinfection des juvéniles, ce qui conduit à une mortalité élevée. Nous décrivons ici une nouvelle méthode pour désinfecter, rapidement, facilement, et à faible coût des nématodes du genre #Globodera$, en partant de kystes. La mortalité des juvéniles désinfectés est faible (entre 10 et 40% au maximum). Les juvéniles stérilisés infestent les racines de pomme de terre cultivées in vitro et s'y développent normalement. (Résumé d'auteur

A High-Resolution Combined Scanning Laser- and Widefield Polarizing Microscope for Imaging at Temperatures from 4 K to 300 K

Polarized light microscopy, as a contrast-enhancing technique for optically anisotropic materials, is a method well suited for the investigation of a wide variety of effects in solid-state physics, as for example birefringence in crystals or the magneto-optical Kerr effect (MOKE). We present a microscopy setup that combines a widefield microscope and a confocal scanning laser microscope with polarization-sensitive detectors. By using a high numerical aperture objective, a spatial resolution of about 240 nm at a wavelength of 405 nm is achieved. The sample is mounted on a $^4$He continuous flow cryostat providing a temperature range between 4 K and 300 K, and electromagnets are used to apply magnetic fields of up to 800 mT with variable in-plane orientation and 20 mT with out-of-plane orientation. Typical applications of the polarizing microscope are the imaging of the in-plane and out-of-plane magnetization via the longitudinal and polar MOKE, imaging of magnetic flux structures in superconductors covered with a magneto-optical indicator film via Faraday effect or imaging of structural features, such as twin-walls in tetragonal SrTiO$_3$. The scanning laser microscope furthermore offers the possibility to gain local information on electric transport properties of a sample by detecting the beam-induced voltage change across a current-biased sample. This combination of magnetic, structural and electric imaging capabilities makes the microscope a viable tool for research in the fields of oxide electronics, spintronics, magnetism and superconductivity.Comment: 14 pages, 11 figures. The following article has been accepted by Review of Scientific Instruments. After it is published, it will be found at http://aip.scitation.org/journal/rs

EP-1502: High resolution portal image prediction for radiotherapy treatment verification & in vivo dosimetry

International audiencePurpose/Objective: Historically designed as a control system for patient positioning for radiotherapy treatment, Electronic Portal Imaging Devices (EPIDs) are nowadays widely used for quality assurance and dosimetric verifications in new irradiation techniques. One of the main advantages of the EPID is its high resolution which can detect small details. The objective of this study is to compare the EPID image acquired during the treatment with a predicted high resolution portal image computed by Monte Carlo (MC) simulation. A new method for prediction of high resolution EPID images is tested for in vivo treatment verification. Materials and Methods: Experiments were carried out on a Siemens ARTISTETM, equipped with a 160-MLCTM, and its Siemens OptivueTM 1000 EPID. This EPID has an active detection area of 41 x 41 cm2 and a matrix of 1024 x 1024 pixels. A model of this linac and the EPID was developed with the MC code Penelope, and commissioned. We focus on a breast treatment conformational beam (6 MV) on the CIRS adult female phantom. The CT-scan of the phantom was used as input, and Hounsfield numbers were converted in density and atomic composition, so as to obtain a voxelized geometry used in the Penelope code. Particles exiting the phantom and impinging on the EPID are simulated up to the EPID in order to compute the predicted portal image by scoring the energy deposited in the phosphor layer on a 1024 x 1024 virtual grid. The simulated image was then smoothed using a denoising algorithm in order to keep the high resolution advantage. Several denoising algorithms were tested, among them IRON, LASG and a recently developed one called DPGLM. For now, we use the gamma-index technique to evaluate the accuracy of the simulated image against the experimental one. Results: Figure 1 shows the acquired image and the simulated one. The gamma-index is satisfied for 94.4 % of the pixels for 3.5 % and 3.5 mm criterion. The DPGLM gives the best result toward accuracy and computed time. Indeed, the denoising of 1024 x 1024 images takes about 1h30 mn, 2h and 5 mn using DPGLM, IRON, and LASG, respectively. The LASG algorithm is really fast but the result is too smoothed for the high resolution purpose. Conclusions: This work is the first step in the aim of in vivo dosimetry by comparing experimental portal images with high resolution predicted images obtained using MC simulations in a voxelized geometry. First results obtained on a breast treatment are encouraging, and we can expect to detect treatment errors

Formation of a non-magnetic, odd-denominator fractional quantized conductance in a quasi-one-dimensional electron system

We have investigated the transport properties of a two-dimensional electron gas confined to one dimension by voltages applied to a pair of split gates and an additional top gate deposited on the surface of the GaAs/AlGaAs heterostructure. At low carrier concentrations, <5 × 1010 cm−2, in a wide 1D channel (700 nm), with an asymmetric confinement potential, the conductance plateaux in units of e2/h at 1 and 2/3 were observed. In the presence of a fixed in-plane magnetic field of 10 T, additional plateaux at 2/5 and 2/7 appeared with increasing asymmetry in confinement potential. The appearance of odd-denominator fractional states seems to originate from the zigzag formed when electrons are allowed to relax in the second dimension at the boundary of the 1D-2D transition

Mitigation of carbon using Atriplex nummularia revegetation

The use of abandoned or marginally productive land to mitigate greenhouse gas emissions may avoid competition with food and water production. Atriplex nummularia Lindl. is a perennial shrub commonly established for livestock forage on saline land, however, its potential for carbon mitigation has not been systematically evaluated. Similarly, although revegetation is an allowable activity to mitigate carbon within Article 3.4 of the United Nations Framework Convention on Climate Change's Kyoto Protocol, there is a paucity of information on rates of carbon mitigation in soils and biomass through this mechanism. For six sites where A. nummularia had been established across southern Australia four were used to assess changes in soil carbon storage and four were used to develop biomass carbon sequestration estimates. A generalised allometric equation for above and below ground biomass was developed, with a simple crown volume index explaining 81% of the variation in total biomass. There were no significant differences in soil organic carbon storage to 0.3 m or 2 m depth compared to existing agricultural land-use. Between 2.2 and 8.3 Mg C ha−1 or 0.2–0.6 Mg C ha−1 yr−1 was sequestered in above and below ground biomass and this translates to potential total sequestration of 1.1–3.6 Tg C yr−1 on saline land across Australia. Carbon income and forage grazing may thus provide a means to finance the stabilization of compromised land