Propagation of generalized vector Helmholtz-Gauss beams through paraxial optical systems

We introduce the generalized vector Helmholtz-Gauss (gVHzG) beams that constitute a general family of localized beam solutions of the Maxwell equations in the paraxial domain. The propagation of the electromagnetic components through axisymmetric ABCD optical systems is expressed elegantly in a coordinate-free and closed-form expression that is fully characterized by the transformation of two independent complex beam parameters. The transverse mathematical structure of the gVHzG beams is form-invariant under paraxial transformations. Any paraxial beam with the same waist size and transverse spatial frequency can be expressed as a superposition of gVHzG beams with the appropriate weight factors. This formalism can be straightforwardly applied to propagate vector Bessel-Gauss, Mathieu-Gauss, and Parabolic-Gauss beams, among others

Introduction to Special Issue of Molecular Plant Pathology - "Extracellular and intracellular perception of plant viruses"

Non peer reviewe

A comparative study of experimental configurations in synchrotron pair distribution function

The identification and quantification of amorphous components and nanocrystalline phases with very small crystal sizes, smaller than ~3 nm, within samples containing crystalline phases is very challenging. However, this is important as there are several types of systems that contain these matrices: building materials, glass-ceramics, some alloys, etc. The total scattering synchrotron pair distribution function (PDF) can be used to characterize the local atomic order of the nanocrystalline components and to carry out quantitative analyses in complex mixtures. Although the resolution in momentum transfer space has been widely discussed, the resolution in the interatomic distance space has not been discussed to the best of our knowledge. Here, we report synchrotron PDF data collected at three beamlines in different experimental configurations and X-ray detectors. We not only discuss the effect of the resolution in Q-space, Qmax ins of the recorded data and Qmax of the processed data, but we also discuss the resolution in the interatomic distance (real) space. A thorough study of single-phase crystalline nickel used as standard was carried out. Then, selected cement-related samples including anhydrous tricalcium and dicalcium silicates, and pastes derived from the hydration of tricalcium silicate and ye’elimite with bassanite were analyzed.This work is part of the PhD of Mr. Jesus D. Zea-Garcia. This work was supported by Spanish MINECO and FEDER [BIA2017-82391-R research project and I3 [IEDI-2016-0079] program]

Non-canonical Translation in Plant RNA Viruses

Viral protein synthesis is completely dependent upon the host cell's translational machinery. Canonical translation of host mRNAs depends on structural elements such as the 5′ cap structure and/or the 3′ poly(A) tail of the mRNAs. Although many viral mRNAs are devoid of one or both of these structures, they can still translate efficiently using non-canonical mechanisms. Here, we review the tools utilized by positive-sense single-stranded (+ss) RNA plant viruses to initiate non-canonical translation, focusing on cis-acting sequences present in viral mRNAs. We highlight how these elements may interact with host translation factors and speculate on their contribution for achieving translational control. We also describe other translation strategies used by plant viruses to optimize the usage of the coding capacity of their very compact genomes, including leaky scanning initiation, ribosomal frameshifting and stop-codon readthrough. Finally, future research perspectives on the unusual translational strategies of +ssRNA viruses are discussed, including parallelisms between viral and host mRNAs mechanisms of translation, particularly for host mRNAs which are translated under stress conditions.The research program in Aranda's lab is supported by grants AGL2015-65838 (MINECO, Spain) and ARIMNet2-EMERAMB(ERA-Net-618127, EU FP7). WM is funded by NIH grant number R01 GM067104.Peer reviewedPeer Reviewe

Recent studies of cements and concretes by synchrotron radiation crystallographic and cognate methods

The portfolio of available synchrotron radiation techniques is increasing notably for cements and pastes. Furthermore, sometimes the terminology is confusing and an overall picture highlighting similarities and differences of related techniques was lacking. Therefore, the main objective of this work is to review recent advances in synchrotron techniques providing a comprehensive overview. This work is not intended to gather all publications in cement chemistry but to give a unified picture through selected examples. Crystallographic techniques are used for structure determination, quantitative phase analyses and microstructure characterization. These studies are not only carried out in standard conditions but synchrotron techniques are especially suited to non-ambient conditions: high temperatures and pressures, hydration, etc., and combinations. Related crystallographic techniques, like Pair Distribution Function, are being used for the analysis of ill-crystalline phase(s). Furthermore, crystallographic tools are also employed in imaging techniques including scanning diffraction microscopy and tomography and coherent diffraction imaging. Other synchrotron techniques are also reviewed including X-rays absorption spectroscopy for local structure and speciation characterizations; small angle X-ray scattering for microstructure analysis and several imaging techniques for microstructure quantification: full-field soft and hard X-ray nano-tomographies; scanning infrared spectro-microscopy; scanning transmission and fluorescence X-ray tomographies. Finally, a personal outlook is provided.I am grateful to all my coauthors, collaborators, colleagues and PhD students, for all our work together during more than two decades. I thank the University of Malaga and ALBA Synchrotron Light Source for the support and the stirring environments. I acknowledge the Spanish science funding agencies (they change the name quite often) for funding my studentship, to do the PhD and the three summer research stays at Oxford University, to the last ongoing research project. To all synchrotrons I have been allowed to enjoy carrying out experiments: SRS, ESRF, Max-Lab, DLS, APS, SLS and ALBA. Finally, this work has been supported by the Spanish MINECO through the BIA2014-57658-C2-1-R research grant

Development of expression vectors based on pepino mosaic virus

<p>Abstract</p> <p>Background</p> <p>Plant viruses are useful expression vectors because they can mount systemic infections allowing large amounts of recombinant protein to be produced rapidly in differentiated plant tissues. Pepino mosaic virus (PepMV) (genus <it>Potexvirus</it>, family <it>Flexiviridae</it>), a widespread plant virus, is a promising candidate expression vector for plants because of its high level of accumulation in its hosts and the absence of severe infection symptoms. We report here the construction of a stable and efficient expression vector for plants based on PepMV.</p> <p>Results</p> <p>Agroinfectious clones were produced from two different PepMV genotypes (European and Chilean), and these were able to initiate typical PepMV infections. We explored several strategies for vector development including coat protein (CP) replacement, duplication of the CP subgenomic promoter (SGP) and the creation of a fusion protein using the foot-and-mouth disease virus (FMDV) 2A catalytic peptide. We found that CP replacement vectors were unable to move systemically and that vectors with duplicated SGPs (even heterologous SGPs) suffered from significant transgene instability. The fusion protein incorporating the FMDV 2A catalytic peptide gave by far the best results, maintaining stability through serial passages and allowing the accumulation of GFP to 0.2-0.4 g per kg of leaf tissue. The possible use of PepMV as a virus-induced gene silencing vector to study gene function was also demonstrated. Protocols for the use of this vector are described.</p> <p>Conclusions</p> <p>A stable PepMV vector was generated by expressing the transgene as a CP fusion using the sequence encoding the foot-and-mouth disease virus (FMDV) 2A catalytic peptide to separate them. We have generated a novel tool for the expression of recombinant proteins in plants and for the functional analysis of virus and plant genes. Our experiments have also highlighted virus requirements for replication in single cells as well as intercellular and long-distance movement.</p

Propagation dynamics of vector Mathieu-Gauss beams

The vector Mathieu-Gauss beams of integer order are examined as the solutions of the vector paraxial wave equation in elliptical coordinates. The propagation of the vector components and the three-dimensional intensity distribution of focused vector Mathieu-Gauss beams are analyzed for a variety of polarizations. Conditions in which the linearly polarized Mathieu-Gauss beams can be approximated by the scalar solutions of the paraxial wave equation are also discussed

Prototyping a Conductive Polymer Steering Pad for Rail Freight Service

The AdapterPlus™ steering pad is a polymer component on a railcar that helps to reduce stresses on the axle as a railcar rounds a curve. One railway application requires a minimum of 240 mA to be passed through the steering pad to the rail, which activates air valves that control automated cargo gates. Currently, two copper studs are inserted into the pad to provide a conductive path. However, after continuous cyclic loading caused by normal service operation, the copper studs deform, wear, and eventually lose contact between the two surfaces rendering the pad nonconductive. One proposed solution to this problem is to create a steering pad made entirely from an electrically conductive material. The University Transportation Center for Railway Safety (UTCRS) research team has successfully created a conductive nanocomposite made from vapor grown carbon nanofibers (CNFs) and a modified form of Elastollan 1195A thermoplastic polyurethane (TPU). Previous attempts to create this material were promising but failed to produce an electrically conductive specimen when injection molded. Preliminary results have shown that the new material can be injection molded to create an electrically conductive test specimen. An injection molded insert was designed, fabricated, and incorporated into the existing steering pad design for further testing. Pressure measurement film had previously been used to find the points of maximum stress inside the pad to optimize the design of the composite insert. Characterization of the resistivity of the composite material was carried out in order to verify functionality in future iterations of this product. The resistance of the composite material is expected to be non-linear with a strong dependence on load and voltage. Conductivity tests were performed using a material testing system with a compressive load ranging from 1500 pounds to 5500 pounds. The voltage at each load was also varied between 10V to 20V and the nonlinear resistance of the material was examined. The results have shown that the CNF/TPU composite is a potential replacement for the current TPU used for the pad and, with minimal modifications, can be implemented in field service operation