796 research outputs found
Sea turtle nesting in the Ten Thousand Islands of Florida
Loggerhead sea turtles (Caretta caretta) nest in numerous substrate and beach
types within the Ten Thousand Islands (TTl) of southwest Florida. Nesting beach
selection was analyzed on 12 islands within this archipelago. Numerous physical
characteristics were recorded to identify the relatedness of these variables and determine
their importance for nesting beach selection in C. caretta. These variables were chosen
after evaluating the islands, conducting literature searches and soliciting personal
communications. Along transects, data were collected, on the following: height of
canopy, beach width, overall slope (beach slope and slope of offshore approach) and sand
samples analyzed for pH, percentage of water, percentage of organic content, percentage
of carbonate and particle size (8 size classes). Data on ordinal aspect of beaches and
beach length were also recorded and included in the analysis. All of the variables were
analyzed by tree regression, incorporating the nesting data into the analysis. In the TTl,
loggerheads appear to prefer wider beaches (p< 0.001; R2
= 0.56) that inherently have less
slope, and secondarily, wider beaches that have low amounts of carbonate (p< O.00 1). In
addition, C. caretta favors nest sites within or in close proximity to the supra-littoral
vegetation zone of beaches in the TTl (p< 0.001). (86 page document
Robust quantum coherence above the Fermi sea
In this paper we present an experiment where we measured the quantum
coherence of a quasiparticle injected at a well-defined energy above the Fermi
sea into the edge states of the integer quantum Hall regime. Electrons are
introduced in an electronic Mach-Zehnder interferometer after passing through a
quantum dot that plays the role of an energy filter. Measurements show that
above a threshold injection energy, the visibility of the quantum interferences
is almost independent of the energy. This is true even for high energies, up to
130~eV, well above the thermal energy of the measured sample. This result
is in strong contradiction with our theoretical predictions, which instead
predict a continuous decrease of the interference visibility with increasing
energy. This experiment raises serious questions concerning the understanding
of excitations in the integer quantum Hall regime
Frequency shifts of photoassociative spectra of ultracold metastable Helium atoms : a new measurement of the s-wave scattering length
We observe light-induced frequency shifts in one-color photoassociative
spectra of magnetically trapped He atoms in the metastable
state. A pair of ultracold spin-polarized helium atoms is excited into
a molecular bound state in the purely long range potential connected to
the asymptote. The shift arises from the optical coupling of
the molecular excited bound state with the scattering states and the bound
states of two colliding atoms. We measure the frequency-shifts for
several ro-vibrational levels in the potential and find a linear
dependence on the photoassociation laser intensity. Comparison with a
theoretical analysis provides a good indication for the s-wave scattering
length of the quintet () potential, nm, which
is significantly lower than most previous results obtained by non-spectroscopic
methods.Comment: 7 pages, 4 figure
Accurate determination of the scattering length of metastable Helium atoms using dark resonances between atoms and exotic molecules
We present a new measurement of the s-wave scattering length a of
spin-polarized helium atoms in the 2^3S_1 metastable state. Using two-photon
photoassociation spectroscopy and dark resonances we measure the energy
E_{v=14}= -91.35 +/- 0.06 MHz of the least bound state v=14 in the interaction
potential of the two atoms. We deduce a value of a = 7.512 +/- 0.005 nm, which
is at least one hundred times more precise than the best previous
determinations and is in disagreement with some of them. This experiment also
demonstrates the possibility to create exotic molecules binding two metastable
atoms with a lifetime of the order of 1 microsecond.Comment: 4 pages, 4 figure
Model counting for CNF formuals of bounded module treewidth
The modular treewidth of a graph is its treewidth after the contraction of modules. Modular treewidth properly generalizes treewidth and is itself properly generalized by clique-width. We show that the number of satisfying assignments of a CNF formula whose incidence graph has bounded modular treewidth can be computed in polynomial time. This provides new tractable classes of formulas for which #SAT is polynomial. In particular, our result generalizes known results for the treewidth of incidence graphs and is incomparable with known results for clique-width (or rank-width) of signed incidence graphs. The contraction of modules is an effective data reduction procedure. Our algorithm is the first one to harness this technique for #SAT. The order of the polynomial time bound of our algorithm depends on the modular treewidth. We show that this dependency cannot be avoided subject to an assumption from Parameterized Complexity
Key parameters design for online battery electrochemical impedance tracker
International audienceNew applications in transport and energy storage require the use of Lithium-ion batteries. Advanced battery management systems including electrochemical impedance measurement are studied for the determination of the state of the battery, the prediction of the autonomy, the failure and security management. Taking into account constraints of cost and simplicity, we propose to use the existing electronics of current control and we evaluate the effect of the electronics design on the performance of a frequency evolutionary estimation of the electrochemical impedance. This recursive method relies on a wideband active approach and provides both an accurate estimate of the impedance in the frequency area and a tracking of its temporal variations. Benefits are the limitation of the data memory required and the amount of operations that can be completely carried out by a target such as a microcontroller. We propose a methodology to design the key parameters of electronics in function of the frequency band of interest and the desired accuracy. We highlighted that electronics of conventional BMS can host this tracking algorithm, with analog to digital converters of 10 bits or more, having an analog stage to adapt their dynamics, and that microcontrollers can be enough powerful to perform calculations, both in terms of number of operations and speed of execution. This design strategy has been applied to define a prototyping environment for a BMS based on an ARM microcontroller which is expected to provide the tracking impedance of a battery every 250 ms with less than 0,5 % of error
Carrier drift velocity and edge magnetoplasmons in graphene
We investigate electron dynamics at the graphene edge by studying the
propagation of collective edge magnetoplasmon (EMP) excitations. By timing the
travel of narrow wave-packets on picosecond time scales around exfoliated
samples, we find chiral propagation with low attenuation at a velocity which is
quantized on Hall plateaus. We extract the carrier drift contribution from the
EMP propagation and find it to be slightly less than the Fermi velocity, as
expected for an abrupt edge. We also extract the characteristic length for
Coulomb interaction at the edge and find it to be smaller than for soft,
depletion edge systems.Comment: 5 pages, 3 figures of main text and 6 pages, 6 figures of
supplemental materia
Genome Sequences of the Race 1 and Race 4 Xanthomonas campestris pv. campestris Strains CFBP 1869 and CFBP 5817
Xanthomonas campestris pv. campestris is the causal agent of black rot on Brassicaceae. The draft genome sequences of strains CFBP 1869 and CFBP 5817 have been determined and are the first ones corresponding to race 1 and race 4 strains, which have a predominant agronomic and economic impact on cabbage cultures worldwide
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