550 research outputs found
Dynamic routing problems with fruitful regions: models and evolutionary computation
We introduce the concept of fruitful regions in a dynamic routing context: regions that have a high potential of generating loads to be transported. The objective is to maximise the number of loads transported, while keeping to capacity and time constraints. Loads arrive while the problem is being solved, which makes it a real-time routing problem. The solver is a self-adaptive evolutionary algorithm that ensures feasible solutions at all times. We investigate under what conditions the exploration of fruitful regions improves the effectiveness of the evolutionary algorith
Change in fatty liver status and 5-year risk of incident metabolic syndrome: a retrospective cohort study
INTRODUCTION: Fatty liver is associated with metabolic syndrome (MetS) but it may also occur without MetS. Whether resolution of fatty liver in the general population affects risk of MetS is unknown. Our aim was to determine whether a change in fatty liver status (either the development of new fatty liver or the resolution of existing fatty liver) would modify the risk of de novo MetS.METHODS:Two thousand eighty-nine people without hypertension, diabetes, and MetS were examined at baseline and at 5-year follow-up using a retrospective cohort study design. Fatty liver status was assessed at baseline and at follow-up by ultrasonography. Adjusted hazard ratios (aHR) and 95 % confidence intervals (CIs) for de novo MetS at follow-up were calculated controlling for the potential confounders, compared to the reference group (people who never had fatty liver at baseline and follow-up).RESULTS:During follow-up, fatty liver developed in 251 people and fatty liver resolved in 112 people. After the adjustment for multiple confounders, persisting fatty liver and incident fatty liver development were associated with de novo MetS, with aHR of 2.60 (95 % CIs [1.61,4.20]) and 3.31 (95 % CIs [1.99,5.51]), respectively. Risk of new MetS in resolved fatty liver group was attenuated with insignificant aHR of 1.29 accompanying 95 % CIs of 0.60 and 2.80.DISCUSSION:Development or maintenance of fatty liver is positively associated with occurrence of new MetS. Resolution of fatty liver status has similar risk of de novo MetS with those who never had fatty liver. Therefore, cautious management is needed with those with fatty liver
Cooling atomic motion with quantum interference
We theoretically investigate the quantum dynamics of the center of mass of
trapped atoms, whose internal degrees of freedom are driven in a
-shaped configuration with the lasers tuned at two-photon resonance.
In the Lamb-Dicke regime, when the motional wave packet is well localized over
the laser wavelenght, transient coherent population trapping occurs, cancelling
transitions at the laser frequency. In this limit the motion can be efficiently
cooled to the ground state of the trapping potential. We derive an equation for
the center-of-mass motion by adiabatically eliminating the internal degrees of
freedom. This treatment provides the theoretical background of the scheme
presented in [G. Morigi {\it et al}, Phys. Rev. Lett. {\bf 85}, 4458 (2000)]
and implemented in [C.F. Roos {\it et al}, Phys. Rev. Lett. {\bf 85}, 5547
(2000)]. We discuss the physical mechanisms determining the dynamics and
identify new parameters regimes, where cooling is efficient. We discuss
implementations of the scheme to cases where the trapping potential is not
harmonic.Comment: 11 pages, 3 figure
Galaxy rotation curves: the effect of j x B force
Using the Galaxy as an example, we study the effect of j x B force on the
rotational curves of gas and plasma in galaxies. Acceptable model for the
galactic magnetic field and plausible physical parameters are used to fit the
flat rotational curve for gas and plasma based on the observed baryonic
(visible) matter distribution and j x B force term in the static MHD equation
of motion. We also study the effects of varied strength of the magnetic field,
its pitch angle and length scale on the rotational curves. We show that j x B
force does not play an important role on the plasma dynamics in the
intermediate range of distances 6-12 kpc from the centre, whilst the effect is
sizable for larger r (r > 15 kpc), where it is the most crucial.Comment: Accepted for publication in Astrophysics & Space Science (final
printed version, typos in proofs corrected
Precise limits from lepton flavour violating processes on the Littlest Higgs model with T-parity
We recalculate the leading one-loop contributions to mu > e gamma and mu ->
eee in the Littlest Higgs model with T-parity, recovering previous results for
the former. When all the Goldstone interactions are taken into account, the
latter is also ultraviolet finite. The present experimental limits on these
processes require a somewhat heavy effective scale ~2.5 TeV, or the flavour
alignment of the Yukawa couplings of light and heavy leptons at the ~10% level,
or the splitting of heavy lepton masses to a similar precision. Present limits
on tau decays set no bounds on the corresponding parameters involving the tau
leptonComment: 41 pages, 11 figures; v3: matches published version in JHE
Theoretical study of electronic Raman scattering of Borocarbide superconductors
The electronic Raman scattering of Borocarbide superconductors is studied
based on the weak coupling theory with -wave gap symmetry. The low energy
behaviors and the relative peak positions can be naturally understood, while
the explanation of the detailed shape of the peak seems to require a
strong inelastic interaction not present in the weak coupling theory.Comment: Revtex 4 file, 9 pages and 5 figure
Experimental Implementation of the Quantum Random-Walk Algorithm
The quantum random walk is a possible approach to construct new quantum
algorithms. Several groups have investigated the quantum random walk and
experimental schemes were proposed. In this paper we present the experimental
implementation of the quantum random walk algorithm on a nuclear magnetic
resonance quantum computer. We observe that the quantum walk is in sharp
contrast to its classical counterpart. In particular, the properties of the
quantum walk strongly depends on the quantum entanglement.Comment: 5 pages, 4 figures, published versio
Nuclear Magnetic Resonance and Magnetization Studies of the Ferromagnetic Ordering Temperature Suppression in Ru Deficient SrRuO3
The synthesis of SrRuO3 under high-pressure oxygen produces a
nonstoichiometric form with randomly distributed vacancies on the Ru-sites,
along with a significantly reduced ferromagnetic ordering temperature. In order
to gain additional insight into the suppression of the ferromagnetism, local
studies utilizing 99,101 Ru zero-field spin-echo NMR, and Ru K-edge XAFS, along
with complimentary magnetization and x-ray diffraction measurements, have been
carried out on samples of SrRuO3 annealed at both ("ambient") atmospheric
pressure and "high-pressure" oxygen (600 atm). Consistent with previous work,
the NMR spectrum for "ambient" SrRuO3 consists of two well-defined peaks at
64.4 MHz and 72.2 MHz corresponding to the 99Ru and 101Ru isotopes,
respectively, and a hyperfine field of 329 kG. Although the magnetization
measurements show a lower ferromagnetic ordering temperature for the
"high-pressure" oxygen sample (90 K compared to 160 K for the "ambient"
sample), the NMR spectrum shows no significant shift in the two peak
frequencies. However, the two peaks exhibit considerable broadening, along with
structure on both the low and high frequency sides which is believed to be
quadrupolar in origin. Analysis of the Ru K-edge XAFS reveals more disorder in
the Ru-O bond for the "high-pressure" oxygen sample compared to the "ambient"
sample. Furthermore, XANES of Ru K-edge analysis indicates no difference in the
valence of Ru between the two samples. The magnetic behavior indicates the
existence of some vacancies on the Ru sites for the "high-pressure" oxygen
sample.Comment: Proceedings of the 3rd Polish-US Workshop on Magnetism and
Superconductivity of Advanced Materials, July 14-19, 2002, Ladek Zdroj
(Poland), to appear in Physica
Electroweak Symmetry Breaking at the LHC
One of the major goals of the Large Hadron Collider is to probe the
electroweak symmetry breaking mechanism and the generation of the masses of the
elementary particles. We review the physics of the Higgs sector in the Standard
Model and some of its extensions such as supersymmetric theories and models of
extra dimensions. The prospects for discovering the Higgs particles at the LHC
and the study of their fundamental properties are summarised.Comment: 27 pages, 45 figures, uses LaTeX (insa.sty). Invited review for
volume on LHC physics to celebrate the Platinum Jubilee of the Indian
National Science Academy, edited by Amitava Datta, Biswarup Mukhopadhyaya and
Amitava Raychaudhuri. Expanded the acronym in the title in the annoncement.
No other change in the text or reference
Competing orders in a magnetic field: spin and charge order in the cuprate superconductors
We describe two-dimensional quantum spin fluctuations in a superconducting
Abrikosov flux lattice induced by a magnetic field applied to a doped Mott
insulator. Complete numerical solutions of a self-consistent large N theory
provide detailed information on the phase diagram and on the spatial structure
of the dynamic spin spectrum. Our results apply to phases with and without
long-range spin density wave order and to the magnetic quantum critical point
separating these phases. We discuss the relationship of our results to a number
of recent neutron scattering measurements on the cuprate superconductors in the
presence of an applied field. We compute the pinning of static charge order by
the vortex cores in the `spin gap' phase where the spin order remains
dynamically fluctuating, and argue that these results apply to recent scanning
tunnelling microscopy (STM) measurements. We show that with a single typical
set of values for the coupling constants, our model describes the field
dependence of the elastic neutron scattering intensities, the absence of
satellite Bragg peaks associated with the vortex lattice in existing neutron
scattering observations, and the spatial extent of charge order in STM
observations. We mention implications of our theory for NMR experiments. We
also present a theoretical discussion of more exotic states that can be built
out of the spin and charge order parameters, including spin nematics and phases
with `exciton fractionalization'.Comment: 36 pages, 33 figures; for a popular introduction, see
http://onsager.physics.yale.edu/superflow.html; (v2) Added reference to new
work of Chen and Ting; (v3) reorganized presentation for improved clarity,
and added new appendix on microscopic origin; (v4) final published version
with minor change
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