Effects of leaf wetness duration and temperature on infection of Prunus by Xanthomonas arboricola pv. pruni

Xanthomonas arboricola pv. pruni is the causal agent of bacterial spot disease of stone fruits and almond. The bacterium is distributed throughout the major stone-fruit-producing areas of the World and is considered a quarantine organism in the European Union according to the Council Directive 2000/29/EC, and by the European and Mediterranean Plant Protection Organization. The effect of leaf wetness duration and temperature on infection of Prunus by X. arboricola pv. pruni was determined in controlled environment experiments. Potted plants of the peach-almond hybrid GF-677 were inoculated with bacterial suspensions and exposed to combinations of six leaf wetness durations (from 0 to 24 h) and seven fixed temperatures (from 5 to 35°C) during the infection period. Then, plants were transferred to a biosafety greenhouse, removed from bags, and incubated at optimal conditions for disease development. Although leaf wetness was required for infection of Prunus by X. arboricola pv. pruni, temperature had a greater effect than leaf wetness duration on disease severity. The combined effect of wetness duration and temperature on disease severity was quantified using a modification of the Weibull equation proposed by Duthie. The reduced-form of Duthie's model obtained by nonlinear regression analysis fitted well to data (R = 0.87 and R2adj = 0.85), and all parameters were significantly different from 0. The estimated optimal temperature for infection by X. arboricola pv. pruni was 28.9°C. Wetness periods longer than 10 h at temperatures close to 20°C, or 5 h at temperatures between 25 and 35°C were necessary to cause high disease severity. The predictive capacity of the model was evaluated using an additional set of data obtained from new wetness duration-temperature combinations. In 92% of the events the observed severity agreed with the predicted level of infection risk. The risk chart derived from the reduced form of Duthie's model can be used to estimate the potential risk for infection of Prunus by X. arboricola pv. pruni based on observed or forecasted temperature and wetness durationMinisterio de Educación, Ciencia y Deporte (AGL2013-41405-R, FPU13/04123) of Spain (https://www.mecd.gob.es/). University of Girona (SING12/13, MPCUdG2016/085) (www. udg.edu). European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement number 613678 (DROPSA

Basis for a predictive model of Xanthomonas arboricola pv pruni growth and infections in host plants

Xanthomonas arboricola pv. pruni (Xap) is the causal agent of bacterial spot disease of stone fruits and almond. The bacterium is considered a quarantine pathogen in Europe and it has become a new and emerging threat for European crops. As the disease is strongly influenced by the weather, a forecasting model that predicts Xap infections based on climatic conditions could be implemented in stone fruit integrated pest management. The objective of this work was to constrain the basis for the development of a predictive model of Xap growth and infections, determining the effects of pathogen, host and climatic parameters on infection and disease development. A non-pathogenic specialization of Xap and cross-infection among host species was observed, although strains isolated from peach were the most virulent in peach leaves. Xap was able to infect unwounded leaves and it was observed that the presence of wounds on the leave surface did not favour Xap penetration in peach leaves. Otherwise, the water condition of plants played an important role in Xap infections and disease development in peach. The presence of water congestion and leaf wetness 48 h before inoculation favoured Xap infections and the duration of leaf wetness after inoculation was directly correlated to disease severity. Temperature and leaf age had a significant effect on Xap infections. Temperatures above 20°C favoured Xap infections, which were basically produced in young leaves; whereas severity was significantly lower at temperatures below 15°C and in mature leavesSupported by research grants BR 2013/31 from University of Girona and FPU13/04123 from Spain MECD, and the projects AGL2013-41405-R from Spain MINECO and the European Union Seventh Framework (FP7 / 2007-2013) under the agreement n°613678 (DROPSA

3D hp-Adaptive Finite Element Simulations of Bend, Step, and Magic-T Electromagnetic Waveguide Structures

Metallic rectangular waveguides are often the preferred choice on telecommunication systems and medical equipment working on the upper microwave and millimeter wave frequency bands due to the simplicity of its geometry, low losses, and the capacity to handle high powers. Waveguide translational symmetry is interrupted by the unavoidable presence of bends, transitions, and junctions, among others. This paper employs a 3D hp self-adaptive grid-refinement finite element strategy for the solution of these relevant electromagnetic waveguide problems. These structures often incorporate dielectrics, metallic screws, round corners, and so on, which may facilitate its construction or improve its design, but significantly difficult its modeling when employing semi-analytical techniques. The hp-adaptive finite element method enables accurate modeling of these structures even in the presence of complex materials and geometries. Numerical results demonstrate the suitability of the hp-adaptive method for modeling these waveguide structures, delivering errors below 0.5% with a limited number of unknowns. Solutions of waveguide problems obtained with the self-adaptive hp-FEM are of comparable accuracy to those obtained with semi-analytical techniques such as the Mode Matching method, for problems where the latest methods can be applied. At the same time, the hp-adaptive FEM enables accurate modeling of more complex waveguide structures.TEC2010-18175/TCM MTM2010-1651

Single-Molecule Super-Resolution Imaging of T-Cell Plasma Membrane CD4 Redistribution upon HIV-1 Binding

The first step of cellular entry for the human immunodeficiency virus type-1 (HIV-1) occurs through the binding of its envelope protein (Env) with the plasma membrane receptor CD4 and co-receptor CCR5 or CXCR4 on susceptible cells, primarily CD4+ T cells and macrophages. Although there is considerable knowledge of the molecular interactions between Env and host cell receptors that lead to successful fusion, the precise way in which HIV-1 receptors redistribute to sites of virus binding at the nanoscale remains unknown. Here, we quantitatively examine changes in the nanoscale organisation of CD4 on the surface of CD4+ T cells following HIV-1 binding. Using singlemolecule super-resolution imaging, we show that CD4 molecules are distributed mostly as either individual molecules or small clusters of up to 4 molecules. Following virus binding, we observe a local 3-to-10-fold increase in cluster diameter and molecule number for virus-associated CD4 clusters. Moreover, a similar but smaller magnitude reorganisation of CD4 was also observed with recombinant gp120. For one of the first times, our results quantify the nanoscale CD4 reorganisation triggered by HIV-1 on host CD4+ T cells. Our quantitative approach provides a robust methodology for characterising the nanoscale organisation of plasma membrane receptors in general with the potential to link spatial organisation to function

Polarization build up in COMPASS 6LiD target

The CERN COMPASS experiment uses a large double 424 cm3 cell polarized 6LiD target for the muon program. High nuclear spin polarization |P| > 50 % is obtained, typically in five days. The high cooling power of the COMPASS dilution refrigerator helps to build up the polarization fast at temperatures around 300 mK. At lower microwave power with lower spin and lattice temperatures, the polarization build up is slower. We discuss these features of the dynamic nuclear polarization of our 6LiD target

Permanent-magnet atom chips for the study of long, thin atom clouds

Atom-chip technology can be used to confine atoms tightly using permanently magnetised videotape along with external magnetic fields. The one-dimensional (1D) gas regime can be realised and studied by trapping the atoms in high-aspect-ratio traps in which the radial motion of the system is confined to zero-point oscillation

Magnetic control of graphitic microparticles in aqueous solutions

Graphite is an inexpensive material with useful electrical, magnetic, thermal, and optical properties. It is also biocompatible and used universally as a substrate. Micrometer-sized graphitic particles in solution are therefore ideal candidates for novel lab-on-a-chip and remote manipulation applications in biomedicine, biophysics, chemistry, and condensed-matter physics. However, submerged graphite is not known to be amenable to magnetic manipulation, the optimal manipulation method for such applications. Here, we exploit the diamagnetism of graphite and demonstrate contactless magnetic positioning control of graphitic microflakes in diamagnetic aqueous solutions. We develop a theoretical model for magnetic manipulation of graphite microflakes and demonstrate experimentally magnetic transport of such particles over distances [Formula: see text] with peak velocities [Formula: see text] in inhomogeneous magnetic fields. We achieve fully biocompatible transport for lipid-coated graphite in NaCl aqueous solution, paving the way for previously undiscovered biomedical applications. Our results prove that micrometer-sized graphite can be magnetically manipulated in liquid media

Bose-Einstein Condensation on a Permanent-Magnet Atom Chip

We have produced a Bose-Einstein condensate on a permanent-magnet atom chip based on periodically magnetized videotape. We observe the expansion and dynamics of the condensate in one of the microscopic waveguides close to the surface. The lifetime for atoms to remain trapped near this dielectric material is significantly longer than above a metal surface of the same thickness. These results illustrate the suitability of microscopic permanent-magnet structures for quantum-coherent preparation and manipulation of cold atoms.Comment: 4 pages, 6 figures, Published in Phys. Rev. A, Rapid Com

Bose-Einstein Condensation on a Permanent-Magnet Atom Chip

We have produced a Bose-Einstein condensate on a permanent-magnet atom chip based on periodically magnetized videotape. We observe the expansion and dynamics of the condensate in one of the microscopic waveguides close to the surface. The lifetime for atoms to remain trapped near this dielectric material is significantly longer than above a metal surface of the same thickness. These results illustrate the suitability of microscopic permanent-magnet structures for quantum-coherent preparation and manipulation of cold atoms.Comment: 4 pages, 6 figures, Published in Phys. Rev. A, Rapid Com

Cold atoms in videotape micro-traps

We describe an array of microscopic atom traps formed by a pattern of magnetisation on a piece of videotape. We describe the way in which cold atoms are loaded into one of these micro-traps and how the trapped atom cloud is used to explore the properties of the trap. Evaporative cooling in the micro-trap down to a temperature of 1 microkelvin allows us to probe the smoothness of the trapping potential and reveals some inhomogeneity produced by the magnetic film. We discuss future prospects for atom chips based on microscopic permanent-magnet structures.Comment: Submitted for EPJD topical issue "Atom chips: manipulating atoms and molecules with microfabricated structures