422 research outputs found

    Nodule Initiation Elicited by Noninfective Mutants of \u3cem\u3eRhizobium phaseoli\u3c/em\u3e

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    Rhizobium phaseoli CE106, CE110, and CE115, originally derived by transposon mutagenesis (Noel et al., J. Bacteriol. 158:149-155, 1984), induced the formation of uninfected root nodule-like swellings on bean (Phaseolus vulgaris). Bacteria densely colonized the root surface, and root hair curling and initiation of root cortical-cell divisions occurred normally in mutant-inoculated seedlings, although no infection threads formed. The nodules were ineffective, lacked leghemoglobin, and were anatomically distinct from normal nodules. Ultrastructural specialization for ureide synthesis, characteristic of legumes that form determinate nodules, was absent. Colony morphology of the mutant strains on agar plates was less mucoid than that of the wild type, and under some cultural conditions, the mutants did not react with Cellufluor, a fluorescent stain for β-linked polysaccharide. These observations suggest that the genetic lesions in these mutants may be related to extracellular polysaccharide synthesis

    The Stochastic State Selection Method Combined with the Lanczos Approach to Eigenvalues in Quantum Spin Systems

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    We describe a further development of the stochastic state selection method, a new Monte Carlo method we have proposed recently to make numerical calculations in large quantum spin systems. Making recursive use of the stochastic state selection technique in the Lanczos approach, we estimate the ground state energy of the spin-1/2 quantum Heisenberg antiferromagnet on a 48-site triangular lattice. Our result for the upper bound of the ground state energy is -0.1833 +/- 0.0003 per bond. This value, being compatible with values from other work, indicates that our method is efficient in calculating energy eigenvalues of frustrated quantum spin systems on large lattices.Comment: 11 page

    A constrained stochastic state selection method applied to quantum spin systems

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    We describe a further development of the stochastic state selection method, which is a kind of Monte Carlo method we have proposed in order to numerically study large quantum spin systems. In the stochastic state selection method we make a sampling which is simultaneous for many states. This feature enables us to modify the method so that a number of given constraints are satisfied in each sampling. In this paper we discuss this modified stochastic state selection method that will be called the constrained stochastic state selection method in distinction from the previously proposed one (the conventional stochastic state selection method) in this paper. We argue that in virtue of the constrained sampling some quantities obtained in each sampling become more reliable, i.e. their statistical fluctuations are less than those from the conventional stochastic state selection method. In numerical calculations of the spin-1/2 quantum Heisenberg antiferromagnet on a 36-site triangular lattice we explicitly show that data errors in our estimation of the ground state energy are reduced. Then we successfully evaluate several low-lying energy eigenvalues of the model on a 48-site lattice. Our results support that this system can be described by the theory based on the spontaneous symmetry breaking in the semiclassical Neel ordered antiferromagnet.Comment: 15 pgaes, 5 figure

    Proton acceleration beyond 100 EeV by an oblique shock wave in the jet of 3C 273

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    We estimate the highest energy of proton diffusively accelerated by shock in knot A1 of the jet in luminous nearby quasar 3C 273. Referring to the recent polarization measurements using very long baseline interferometry (VLBI), we consider the shock propagation across magnetic field lines, namely, configuration of the oblique shock. For larger inclination of the field lines, the effects of particle reflection at the shock front are more pronounced, to significantly increase acceleration efficiency. The quasiperpendicular shock turns out to be needed for safely achieving the proton acceleration to the energy above 100 EeV (10^20 eV) in a parameter domain reflecting conceivable energy restrictions.Comment: 12 pages, 2 figures, accepted for publication in Astrophysical Journal Letter

    An updated revision of shortfin mako size distributions in the Atlantic

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    As part of an ongoing cooperative program for fisheries and biological data collection within the ICCAT Sharks Working Group, information collected by fishery observers and scientific projects from several fishing nations in the Atlantic were analyzed. Datasets included information on geographic location, size and sex. A total of 42,979 shortfin mako records collected between 1989 and 2017 were compiled. Sizes considered ranged between 60 and 353 cm FL (fork length). Of those, sex information was available for 24,316 specimens. Considerable variability was observed in the size distribution by region and season, with larger sizes tending to occur in equatorial and tropical regions and smaller sizes in higher latitudes. Variability between coastal and more oceanic waters is also likely. Most fleets showed unimodal distributions, but in some cases there were bimodal patterns. The distributional patterns presented in this study provide an advance in the understanding of shortfin mako size distribution in the Atlantic, and can be used in the next update of the ICCAT shortfin mako stock assessment.info:eu-repo/semantics/publishedVersio
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