1,788,534 research outputs found
A coil-globule transition of a semiflexible polymer driven by the addition of spherical particles
The phase behaviour of a single large semiflexible polymer immersed in a
suspension of spherical particles is studied. All interactions are simple
excluded volume interactions and the diameter of the spherical particles is an
order of magnitude larger than the diameter of the polymer. The spherical
particles induce a quite long ranged depletion attraction between the segments
of the polymer and this induces a continuous coil-globule transition in the
polymer. This behaviour gives an indication of the condensing effect of
macromolecular crowding on DNA.Comment: 12 pages, 4 figure
Nonequilibrium dynamics and magnetoviscosity of moderately concentrated magnetic liquids: A dynamic mean--field study
A mean-field Fokker-Planck equation approach to the dynamics of ferrofluids
in the presence of a magnetic field and velocity gradients is proposed that
incorporates magnetic dipole-dipole interactions of the colloidal particles.
The model allows to study the combined effect of a magnetic field and dipolar
interactions on the viscosity of the ferrofluid. It is found that dipolar
interactions lead to additional non-Newtonian contributions to the stress
tensor, which modify the behavior of the non-interacting system. The
predictions of the present model are in qualitative agreement with experimental
results, such as presence of normal stress differences, enhancement and
different anisotropy of magnetoviscous effect and the dependence of the
viscosity on the hydrodynamic volume fraction. A quantitative comparison of the
concentration dependence of the magnetoviscosity shows good agreement with
experimental results for low concentrations.Comment: 12 pages, 5 figure
Nucleon-nucleon interactions via Lattice QCD: Methodology --HAL QCD approach to extract hadronic interactions in lattice QCD--
We review the potential method in lattice QCD, which has recently been
proposed to extract nucleon-nucleon interactions via numerical simulations. We
focus on the methodology of this approach by emphasizing the strategy of the
potential method, the theoretical foundation behind it, and special numerical
techniques. We compare the potential method with the standard finite volume
method in lattice QCD, in order to make pros and cons of the approach clear. We
also present several numerical results for the nucleon-nucleon potentials.Comment: 12 pages, 10 figure
Phosphorus donors in highly strained silicon
The hyperfine interaction of phosphorus donors in fully strained Si thin
films grown on virtual SiGe substrates with is
determined via electrically detected magnetic resonance. For highly strained
epilayers, hyperfine interactions as low as 0.8 mT are observed, significantly
below the limit predicted by valley repopulation. Within a Green's function
approach, density functional theory (DFT) shows that the additional reduction
is caused by the volume increase of the unit cell and a local relaxation of the
Si ligands of the P donor.Comment: 12 pages, 3 figure
Effect of polymer-polymer interactions on the surface tension of colloid-polymer mixtures
The density profile and surface tension for the interface of phase-separated
colloid-polymer mixtures have been studied in the framework of the square
gradient approximation for both ideal and interacting polymers in good solvent.
The calculations show that in the presence of polymer-polymer excluded volume
interactions the interfaces have lower widths and surface tensions compared to
the case of ideal polymers. These results are a direct consequence of the
shorter range and smaller depth of the depletion potential between colloidal
particles induced by interacting polymers.Comment: 12 pages, 5 figures, accepted for J. Chem. Phy
Use of inverse gas chromatography to account for the pervaporation performance in the microemulsion breakdown
Mass transfer phenomenon that occurs in the pervaporation process when applied to the microemulsion breakdown, was confirmed by the results of inverse gas chromatography. The stationary phase for this study was polydimethylsiloxane (PDMS), a hydrophobic polymer employed as a membrane in the pervaporation technique. The retention times of the different molecule probes (toluene, cyclohexane, and n-butanol) gave an insight into the extent of the interactions between each of these molecules and the stationary phase; these molecules were the components of the two microemulsions in study. The infinite dilution conditions allowed to determine the thermodynamic and the chromatographic parameters γ∞ (the infinite dilution activity coefficient), the Flory-Huggins parameter interactions χ∞12, and V0g (the specific retention volume), respectively. The magnitudes of the latter parameters threw some light on the permselectivity of the membrane in the
pervaporation operation
ANTARES and other Neutrino Telescopes in the Northern Hemisphere
Several projects are concentrating their efforts on opening the high energy
neutrino window on the Universe with km-scale detectors. The detection
principle relies on the observation, using photomultipliers, of the Cherenkov
light emitted by charged leptons induced by neutrino interactions in the
surrounding detector medium. In the Northern hemisphere, while the pioneering
Baikal telescope, has been operating for 10 years, most of the activity now
concentrates in the Mediterranean sea. Recently, the Antares collaboration has
completed the construction of a 12 line array comprising ~ 900
photomultipliers. In this paper we will review the main results achieved with
the detectors currently in operation in the Northern hemisphere, as well as the
R&D efforts towards the construction of a large volume neutrino telescope in
the Mediterranean.Comment: To Appear in proceedings of the XV International Symposium on Very
High Energy Cosmic Ray Interactions (ISVHECRI 2008
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