16,453 research outputs found
Cross-Border Investment, Conflict of Laws, and the Privatization of Securities Law
The rapid acceleration of transnational investing is occurring in an environment in which emerging markets, and foreign interest in these markets, are exploding. The issues involved with cross-border investment, conflict of laws and the privatization of securities law are examined
Quantum-enhanced gyroscopy with rotating anisotropic Bose–Einstein condensates
High-precision gyroscopes are a key component of inertial navigation systems. By considering matter wave gyroscopes that make use of entanglement it should be possible to gain some advantages in terms of sensitivity, size, and resources used over unentangled optical systems. In this paper we consider the details of such a quantum-enhanced atom interferometry scheme based on atoms trapped in a carefully-chosen rotating trap. We consider all the steps: entanglement generation, phase imprinting, and read-out of the signal and show that quantum enhancement should be possible in principle. While the improvement in performance over equivalent unentangled schemes is small, our feasibility study opens the door to further developments and improvements
Stabilization of microbial communities by responsive phenotypic switching
Clonal microbes can switch between different phenotypes and recent theoretical work has shown that stochas-tic switching between these subpopulations can stabilize microbial communities. This phenotypic switching need not be stochastic, however, but could also be in response to environmental factors, both biotic and abiotic. Here, motivated by the bacterial persistence phenotype, we explore the ecological effects of such responsive switching by analyzing phenotypic switching in response to competing species. We show that the stability of microbial communities with responsive switching differs generically from that of communities with stochastic switching only. To understand the mechanisms by which responsive switching stabilizes coexistence, we go on to analyze simple two-species models. Combining exact results and numerical simulations, we extend the classical stability results for the competition of two species without phenotypic variation to the case in which one species switches, stochastically and responsively, between two phenotypes. In particular, we show that responsive switching can stabilize coexistence even when stochastic switching on its own does not affect the stability of the community
Lorentz Beams
A new kind of tridimensional scalar optical beams is introduced. These beams
are called Lorentz beams because the form of their transverse pattern in the
source plane is the product of two independent Lorentz functions. Closed-form
expression of free-space propagation under paraxial limit is derived and pseudo
non-diffracting features pointed out. Moreover, as the slowly varying part of
these fields fulfils the scalar paraxial wave equation, it follows that there
exist also Lorentz-Gauss beams, i.e. beams obtained by multipying the original
Lorentz beam to a Gaussian apodization function. Although the existence of
Lorentz-Gauss beams can be shown by using two different and independent ways
obtained recently from Kiselev [Opt. Spectr. 96, 4 (2004)] and Gutierrez-Vega
et al. [JOSA A 22, 289-298, (2005)], here we have followed a third different
approach, which makes use of Lie's group theory, and which possesses the merit
to put into evidence the symmetries present in paraxial Optics.Comment: 11 pages, 1 figure, submitted to Journal of Optics
Charge transport through bio-molecular wires in a solvent: Bridging molecular dynamics and model Hamiltonian approaches
We present a hybrid method based on a combination of quantum/classical
molecular dynamics (MD) simulations and a mod el Hamiltonian approach to
describe charge transport through bio-molecular wires with variable lengths in
presence o f a solvent. The core of our approach consists in a mapping of the
bio-molecular electronic structure, as obtained f rom density-functional based
tight-binding calculations of molecular structures along MD trajectories, onto
a low di mensional model Hamiltonian including the coupling to a dissipative
bosonic environment. The latter encodes fluctuat ion effects arising from the
solvent and from the molecular conformational dynamics. We apply this approach
to the c ase of pG-pC and pA-pT DNA oligomers as paradigmatic cases and show
that the DNA conformational fluctuations are essential in determining and
supporting charge transport
A Systematic Study of Projection Biases in Weak Lensing Analysis
We present a systematic study of projection biases in the weak lensing
analysis of the first year of data from the Dark Energy Survey (DES)
experiment. In the analysis we used a CDM model and three two-point
correlation functions. We show that these biases are a consequence of
projecting, or marginalizing, over parameters like , , and
that are both poorly constrained and correlated with the
parameters of interest like , and . Covering the
relevant parameter space we show that the projection biases are a function of
where the true values of the poorly constrained parameters lie with respect to
the parameter priors. For example, biases in the position of the posteriors can
exceed the 1.5 level if the true values of and are close to
the top of the prior's range and the true values of and are close to the bottom of the range of their priors. We also show that in
some cases the 1D credible intervals can be over-specified by as much as 30%
and coverage can be as low as 27%. Finally we estimate these projection biases
for the analysis of three and six years worth of DES data
The Tenerife Cosmic Microwave Background Maps: Observations and First Analysis
The results of the Tenerife Cosmic Microwave Background (CMB) experiments are
presented. These observations cover 5000 and 6500 square degrees on the sky at
10 and 15 GHz respectively centred around Dec.~ +35 degrees. The experiments
are sensitive to multipoles l=10-30 which corresponds to the Sachs-Wolfe
plateau of the CMB power spectra. The sensitivity of the results are ~31 and
\~12 microK at 10 and 15 GHz respectively in a beam-size region (5 degrees
FWHM). The data at 15 GHz show clear detection of structure at high Galactic
latitude; the results at 10 GHz are compatible with these, but at lower
significance. A likelihood analysis of the 10 and 15 GHz data at high Galactic
latitude, assuming a flat CMB band power spectra gives a signal Delta
T_l=30+10-8 microK (68 % C.L.). Including the possible contaminating effect due
to the diffuse Galactic component, the CMB signal is Delta T_l=30+15-11 microK.
These values are highly stable against the Galactic cut chosen. Assuming a
Harrison-Zeldovich spectrum for the primordial fluctuations, the above values
imply an expected quadrupole Q_RMS-PS=20+10-7 microK which confirms previous
results from these experiments, and which are compatible with the COBE DMR.Comment: 17 pages, 7 figures. Submitted to Ap
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