115,592 research outputs found
Sequence-specific double-strand cleavage of DNA by penta-N-methylpyrrolecarboxamide-EDTA·Fe(II)
In the presence of O2 and 5 mM dithiothreitol, penta-N-methylpyrrolecarboxamide-EDTA·Fe(II) [P5E·Fe(II)] at 0.5 µ M cleaves pBR322 plasmid DNA (50 µ M in base pairs) on opposite strands to afford discrete DNA fragments as analyzed by agarose gel electrophoresis. High-resolution denaturing gel electrophoresis of a 32P-end-labeled 517-base-pair restriction fragment containing a major cleavage site reveals that P5E·Fe(II) cleaves 3-5 base pairs contiguous to a 6-base-pair sequence, 5'-T-T-T-T-T-A-3' (4,323-4,328 base pairs). The major binding orientation of the pentapeptide occurs with the amino terminus at the adenine side of this sequence. In the presence of 5 mM dithiothreitol, 0.01 µ M P5E·Fe(II) converts form I pBR322 DNA at 0.22 µ M plasmid (1.0 mM in base pairs) to 40% form II, indicating the cleavage reaction is catalytic, turning over a minimum of nine times. This synthetic molecule achieves double-strand cleavage of DNA (pH 7.9, 25 degrees C) at the 6-base-pair recognition level and may provide an approach to the design of "artificial restriction enzymes.
Comment on "Central limit behavior in deterministic dynamical systems"
We check claims for a generalized central limit theorem holding at the
Feigenbaum (infinite bifurcation) point of the logistic map, made recently by
U. Tirnakli, C. Beck, and C. Tsallis (Phys. Rev. {\bf 75}, 040106(R) (2007)).
We show that there is no obvious way that these claims can be made consistent
with high statistics simulations. We also refute more recent claims by the same
authors that extend the claims made in the above reference.Comment: 3 pages, including 3 figure
Higgs bundles and the real symplectic group
We give an overview of the work of Corlette, Donaldson, Hitchin and Simpson
leading to the non-abelian Hodge theory correspondence between representations
of the fundamental group of a surface and the moduli space of Higgs bundles. We
then explain how this can be generalized to a correspondence between character
varieties for representations of surface groups in real Lie groups G and the
moduli space of G-Higgs bundles. Finally we survey recent joint work with
Bradlow, Garc\'ia-Prada and Mundet i Riera on the moduli space of maximal
Sp(2n,R)-Higgs bundles.Comment: 12 page
Validation of Advanced EM Models for UXO Discrimination
The work reported here details basic validation of our advanced physics-based
EMI forward and inverse models against data collected by the NRL TEMTADS
system. The data was collected under laboratory-type conditions using both
artificial spheroidal targets and real UXO. The artificial target models are
essentially exact, and enable detailed comparison of theory and data in support
of measurement platform characterization and target identification. Real UXO
targets cannot be treated exactly, but it is demonstrated that quantitative
comparisons of the data with the spheroid models nevertheless aids in
extracting key target discrimination information, such as target geometry and
hollow target shell thickness.Comment: 15 pages, 16 figure
Second sound spectroscopy of a nonequilibrium superfluid-normal interface
An experiment is proposed to test a previously developed theory of the
hydrodynamics of a nonequilibrium heat current-induced superfluid-normal
interface. It is shown that the interfacial ``trapped'' second sound mode
predicted by the theory leads to a sharp resonant dip in the reflected signal
from an external second sound pulse propagated towards the interface when its
horizontal phase speed matches that of the interface mode. The influence of the
interface on thermal fluctuations in the bulk superfluid is shown to lead to
slow power dependence of the order parameter, and other quantities, on distance
from it.Comment: 4 pages, 3 figure
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