Ill-posedness of the mean-field model of superconducting vortices and a possible regularisation

We conjecture that the mean-field model of superconducting vortices given in [10] is ill-posed wherever the electric current j has some component in the same direction as the vorticity vector ? (which gives the average density and direction of the superconducting vortices). The conjecture is illustrated with a linear stability analysis of a certain solution to the model. A regularised model is then proposed, and this is used to demonstrate the instability of force-free steady states in a certain geometry

Partnerships Form the Basis for Implementing a National Space Weather Plan

The 2017 Space Weather Enterprise Forum, held June 27, focused on the vital role of partnerships in order to establish an effective and successful national space weather program. Experts and users from the many government agencies, industry, academia, and policy makers gathered to discuss space weather impacts and mitigation strategies, the relevant services and supporting infrastructure, and the vital role cross-cutting partnerships must play for successful implementation of the National Space Weather Action Plan

Characterization of transposon insertion mutants in desulfovibrio vulgaris hilderborough by sequencing genomic DNA [abstract]

Abstract only availableTn5 transposon mutagenesis occurs by a mechanism in which a segment of DNA (transposon) encoded in a plasmid is inserted into genomic DNA (the target) by a conservative (cut-and-paste) mechanism. When the insertion position is in a coding sequence or regulatory region of DNA, the insertion results in a mutation. The plasmid pRL27 encodes a mini-Tn5 transposon, Tn5 transposase, and kanamycin resistance, (Metcalf, William W. et al, 2002 Arch Microbiol 178 :193-201) and was used to transform Desulfovibrio vulgaris Hildenborough by electroporation. Transposon insertion mutants were identified by their ability to grow in the presence of kanamycin. To identify the insertion sites of the transposons, in theory one should be able to sequence from the transposon into chromosomal DNA and identify the mutation site by comparison with the known genome. Unlike sequencing of plasmid DNA or PCR products, direct genomic sequencing has a limited success rate. Direct genomic sequencing is sensitive to DNA quality, interference of secondary DNA structures, salt concentration, and the availability of primer binding sites. Because of these difficulties, in our attempts to identify insertion sites of mini-Tn5, we examined template DNA quality as well as modifying sequencing reaction conditions. Our objective is to develop an effective, reliable method for sequencing genomic DNA to identify where transposon insertion sites have occurred in each mutant.Department of Energy Genomics: Genomes to Life Progra

Rapid automated characterization of transposon insertion mutants in Desulfovibrio vulgaris Hildenborough by srnPCR [abstract]

Abstract only availableTn5 transposon mutagenesis occurs by a mechanism in which a segment of DNA (transposon) encoded in a plasmid is inserted into genomic DNA (the target) by a conservative (cut-and-paste) mechanism (Fig. 2). When the insertion position is in a coding sequence or regulatory region of DNA, the insertion results in a mutation. The plasmid pRL27 (a generous gift from Bill Metcalf) encodes a mini-Tn5 transposon, Tn5 transposase, and kanamycin resistance (neo), and was used to transform Desulfovibrio vulgaris Hildenborough by electroporation. Transposon insertion mutants were identified by their ability to grow in the presence of kanamycin. To locate the insertion site of the transposon, in theory, one should be able to directly sequence from the transposon into chromosomal DNA (Fig. 3.1) and identify the mutation site by comparison with the known genome BLAST. Unlike sequencing of plasmid DNA or PCR products, direct genomic sequencing has a limited success rate. Therefore, a method of enriching the transposon-flanking sequence is needed. Nested semi-random PCR (Fig. 3.2) is an efficient and cost effective enrichment method. Sequencing these enriched products allows us to identify the transposon insertion site. The factors that influence characterization success rate are: frequency and location of priming sites, reaction volume, and reaction conditions (annealing temperature, extension time, etc.). By varying these factors, we have developed an efficient and reliable method for characterizing transposon insertion mutants. Utilizing high-throughput robotics and nested semi-random PCR, we have generated single gene mutants that may provide valuable biological data.U.S. Department of Energy Genomes to Life gran

Differentiating EDRs from the Background Magnetopause Current Sheet: A Statistical Study

The solar wind is a continuous outflow of charged particles from the Sun's atmosphere into the solar system. At Earth, the solar wind's outward pressure is balanced by the Earth's magnetic field in a boundary layer known as the magnetopause. Plasma density and temperature differences across the boundary layer generate the Chapman-Ferraro current which supports the magnetopause. Along the dayside magnetopause, magnetic reconnection can occur in electron diffusion regions (EDRs) embedded into the larger ion diffusion regions (IDRs). These diffusion regions form when opposing magnetic field lines in the solar wind and Earth's magnetic field merge, releasing magnetic energy into the surrounding plasma. While previous studies have given us a general understanding of the structure of the diffusion regions, we still do not have a good grasp of how they are statistically differentiated from the non-diffusion region magnetopause. By investigating 251 magnetopause crossings from NASA's Magnetospheric Multiscale (MMS) Mission, we demonstrate that EDR magnetopause crossings show current densities an order of magnitude higher than regular magnetopause crossings - crossings that either passed through the reconnection exhausts or through the non-reconnecting magnetopause, providing a baseline for the magnetopause current sheet under a wide range of driving conditions. Significant current signatures parallel to the local magnetic field in EDR crossings are also identified, which is in contrast to the dominantly perpendicular current found in the regular magnetopause. Additionally, we show that the ion velocity along the magnetopause is highly correlated with a crossing's location, indicating the presence of magnetosheath flows inside the magnetopause