Pathogenic Potential to Humans of Bovine Escherichia coli O26, Scotland

Escherichia coli O26 and O157 have similar overall prevalences in cattle in Scotland, but in humans, Shiga toxin–producing E. coli O26 infections are fewer and clinically less severe than E. coli O157 infections. To investigate this discrepancy, we genotyped E. coli O26 isolates from cattle and humans in Scotland and continental Europe. The genetic background of some strains from Scotland was closely related to that of strains causing severe infections in Europe. Nonmetric multidimensional scaling found an association between hemolytic uremic syndrome (HUS) and multilocus sequence type 21 strains and confirmed the role of stx<sub>2</sub> in severe human disease. Although the prevalences of E. coli O26 and O157 on cattle farms in Scotland are equivalent, prevalence of more virulent strains is low, reducing human infection risk. However, new data on E. coli O26–associated HUS in humans highlight the need for surveillance of non-O157 enterohemorrhagic E. coli and for understanding stx<sub>2</sub> phage acquisition

Galaxies in box: A simulated view of the interstellar medium

We review progress in the development of physically realistic three dimensional simulated models of the galaxy.We consider the scales from star forming molecular clouds to the full spiral disc. Models are computed using hydrodynamic (HD) or magnetohydrodynamic (MHD) equations and may include cosmic ray or tracer particles. The range of dynamical scales between the full galaxy structure and the turbulent scales of supernova (SN) explosions and even cloud collapse to form stars, make it impossible with current computing tools and resources to resolve all of these in one model. We therefore consider a hierarchy of models and how they can be related to enhance our understanding of the complete galaxy.Comment: Chapter in Large Scale Magnetic Fields in the Univers

Nonlinear force-free magnetic field extrapolations: comparison of the Grad-Rubin and Wheatland-Sturrock-Roumeliotis algorithm

We compare the performance of two alternative algorithms which aim to construct a force-free magnetic field given suitable boundary conditions. For this comparison, we have implemented both algorithms on the same finite element grid which uses Whitney forms to describe the fields within the grid cells. The additional use of conjugate gradient and multigrid iterations result in quite effective codes. The Grad-Rubin and Wheatland-Sturrock-Roumeliotis algorithms both perform well for the reconstruction of a known analytic force-free field. For more arbitrary boundary conditions the Wheatland-Sturrock-Roumeliotis approach has some difficulties because it requires overdetermined boundary information which may include inconsistencies. The Grad-Rubin code on the other hand loses convergence for strong current densities. For the example we have investigated, however, the maximum possible current density seems to be not far from the limit beyond which a force free field cannot exist anymore for a given normal magnetic field intensity on the boundary.Comment: 21 pages, 13 figure

Coherent QCD phenomena in the Coherent Pion-Nucleon and Pion-Nucleus Production of Two Jets at High Relative Momenta

We use QCD to compute the cross section for coherent production of a di-jet (treated as a $q\bar q$ moving at high relative transverse momentum,$\kappa_t$). In the target rest frame,the space-time evolution of this reaction is dominated by the process in which the high $\kappa_t$ $q\bar q$ component of the pion wave function is formed before reaching the target. It then interacts through two gluon exchange. In the approximation of keeping the leading order in powers of $\alpha_s$ and all orders in $\alpha_{s}\ln(\kappa_{t}^2/k_{0}^2),$ the amplitudes for other processes are shown to be smaller at least by a power of $\alpha_{s}$. The resulting dominant amplitude is proportional to $z(1-z) \kappa_t^{-4}$ ($z$ is the fraction light-cone(+)momentum carried by the quark in the final state) times the skewed gluon distribution of the target. For the pion scattering by a nuclear target, this means that at fixed $x_{N}= 2\kappa_{t}^2/s$ (but $\kappa_{t}^2\to \infty$) the nuclear process in which there is only a single interaction is the most important one to contribute to the reaction. Thus in this limit color transparency phenomena should occur.These findings are in accord with E971 experiment at FNAL. We also re-examine a potentially important nuclear multiple scattering correction which is positive and $\propto A^{1/3}/\kappa_t^4$. The meaning of the signal obtained from the experimental measurement of pion diffraction into two jets is also critically examined and significant corrections are identified.We show also that for values of $\kappa_t$ achieved at fixed target energies, di-jet production by the e.m. field of the nucleus leads to an insignificant correction which gets more important as $\kappa_t$ increases.Comment: 23 pages, 9 figure

Improving farmers' access to clean planting material through partnership in the value chain.

Sweetpotato is an important food security crop in Rwanda grown mainly by women for household consumption and as a source of family income Sweetpotato production is faced with several constraints, among them the availability of clean planting of most varieties but more so of the new Vitamin A richOrange Fleshed Sweetpotato. This is limiting their potential to benefits producers, processors, and consumers as a source of food based vitamin A. Therefore an efficient sustainable seed system for multiplication and distribution of cleaning planting material to users is vital. Through a thorough need assessment, four districts were identified for OFSP promotion. Farmer based approach was used to develop an effective, rapid and sustainable chain for multiplication and to disseminate clean basic sweetpotato planting material from in vitro lab to subsequent multiplication sites. Public, research, private, development organization, and farmer group's partnership was paramount to clean, multiply, identify, organize and train farmers' groups in different modules. Most of the new varieties namely, Cacearpedo, Gihingamukungu, and Ukerewe possess preferred traits by farmers compared to their local ones. Now farmers know the importance of using clean planting cuttings as a factor to increase productivity when planted at right time. Initial comparison of harvest from two consecutive seasons, May to July 2011 and July to December 2011 the study finds an increase of yield of 27% for Cacearpedo, 22% for Ukerewe and 71% for 97-062. This can be attributed to improved technical support, adoption of better agriculture techniques, healthy vines, and on time vines availability

Exogenous NG-hydroxy-l-arginine causes nitrite production in vascular smooth muscle cells in the absence of nitric oxide synthase activity

AbstractNitric oxide (NO) production from exogenous NG-hydroxy-l-arginine (OH-l-Arg) was investigated in rat aortic smooth muscle cells in culture by measuring nitrite accumulation in the culture medium. As well, the interaction between OH-l-Arg and l-arginine uptake via the y+ cationic amino acid transporter was studied. In cells without NO-synthase activity, OH-l-Arg (1–1000 μM) induced a dose-dependent nitrite production with a half-maximal effective concentration (EC50) of 18.0 ± 1.5 μM (n = 4–7). This nitrite accumulation was not inhibited by the NO-synthase inhibitor NG-nitro-l-arginine methyl ester, l-NAME (300 μM). In contrast, it was abolished by miconazole (100 μM), an inhibitor of cytochrome P450. Incubation of vascular smooth muscle cells with LPS (10 μgml) induced an l-name inhibited nitrite accumulation, but did not enhance the OH-l-Arg induced nitrite production. OH-l-Arg and other cationic amino acids, L-lysine and l-ornithine, competitively inhibited [3H]-l-arginine uptake m rat aortic smooth muscle cells, with inhibition constants of 195 ± 23 μM(n = 12), 260 ± 40 μM(n= 5) and 330 ± 10 μM(n = 5), respectively. These results show that OH-l-Arg is recognized by the cationic l-amino acid carrier present in vascular smooth muscle cells and can be oxidized to NO and nitrite in these cells in the absence of NO-synthase, probably by cytochrome P450 or by a reaction involving a cytochrome P450 byproduct

Diffusion in supersonic, turbulent, compressible flows

We investigate diffusion in supersonic, turbulent, compressible flows. Supersonic turbulence can be characterized as network of interacting shocks. We consider flows with different rms Mach numbers and where energy necessary to maintain dynamical equilibrium is inserted at different spatial scales. We find that turbulent transport exhibits super-diffusive behavior due to induced bulk motions. In a comoving reference frame, however, diffusion behaves normal and can be described by mixing length theory extended into the supersonic regime.Comment: 11 pages, incl. 5 figures, accepted for publication in Physical Review E (a high-resolution version is available at http://www.aip.de./~ralf/Publications/p21.abstract.html

Multiwavelength Studies of Young OB Associations

We discuss how contemporary multiwavelength observations of young OB-dominated clusters address long-standing astrophysical questions: Do clusters form rapidly or slowly with an age spread? When do clusters expand and disperse to constitute the field star population? Do rich clusters form by amalgamation of smaller subclusters? What is the pattern and duration of cluster formation in massive star forming regions (MSFRs)? Past observational difficulties in obtaining good stellar censuses of MSFRs have been alleviated in recent studies that combine X-ray and infrared surveys to obtain rich, though still incomplete, censuses of young stars in MSFRs. We describe here one of these efforts, the MYStIX project, that produced a catalog of 31,784 probable members of 20 MSFRs. We find that age spread within clusters are real in the sense that the stars in the core formed after the cluster halo. Cluster expansion is seen in the ensemble of (sub)clusters, and older dispersing populations are found across MSFRs. Direct evidence for subcluster merging is still unconvincing. Long-lived, asynchronous star formation is pervasive across MSFRs.Comment: 22 pages, 9 figures. To appear in "The Origin of Stellar Clusters", edited by Steven Stahler, Springer, 2017, in pres

Electric current circuits in astrophysics

Cosmic magnetic structures have in common that they are anchored in a dynamo, that an external driver converts kinetic energy into internal magnetic energy, that this magnetic energy is transported as Poynting fl ux across the magnetically dominated structure, and that the magnetic energy is released in the form of particle acceleration, heating, bulk motion, MHD waves, and radiation. The investigation of the electric current system is particularly illuminating as to the course of events and the physics involved. We demonstrate this for the radio pulsar wind, the solar flare, and terrestrial magnetic storms