1,107 research outputs found
A flexible polymer chain in a critical solvent: Coil or globule?
We study the behavior of a flexible polymer chain in the presence of a
low-molecular weight solvent in the vicinity of a liquid-gas critical point
within the framework of a self-consistent field theory. The total free energy
of the dilute polymer solution is expressed as a function of the radius of
gyration of the polymer and the average solvent number density within the
gyration volume at the level of the mean-field approximation. Varying the
strength of attraction between polymer and solvent we show that two
qualitatively different regimes occur at the liquid-gas critical point. In case
of weak polymer-solvent interactions the polymer chain is in a globular state.
On the contrary, in case of strong polymer-solvent interactions the polymer
chain attains an expanded conformation. We discuss the influence of the
critical solvent density fluctuations on the polymer conformation. The reported
effect could be used to excert control on the polymer conformation by changing
the thermodynamic state of the solvent. It could also be helpful to estimate
the solvent density within the gyration volume of the polymer for drug delivery
and molecular imprinting applications
Estimation of reliability of seismic and electromagnetic monitoring in seismic active areas by diffraction tomography
International audienceThis paper presents the algorithms and results of the numerical simulation of the solution of a 2-D inverse problem on the restoration of seismic parameters and electrical conductivity of local inhomogeneities by the diffraction tomography method based upon the first order Born approximation. The direct problems for the Lame and Maxwell equations are solved by the finite difference method. Restoration of inhomogeneities which are not very weak is implemented with the use of a small number of receivers (source-receiver pairs)
The local phase transitions of the solvent in the neighborhood of a solvophobic polymer at high pressures
We investigate local phase transitions of the solvent in the neighborhood of
a solvophobic polymer chain which is induced by a change of the polymer-solvent
repulsion and the solvent pressure in the bulk solution. We describe the
polymer in solution by the Edwards model, where the conditional partition
function of the polymer chain at a fixed radius of gyration is described by a
mean-field theory. The contributions of the polymer-solvent and the
solvent-solvent interactions to the total free energy are described within the
mean-field approximation. We obtain the total free energy of the solution as a
function of the radius of gyration and the average solvent number density
within the gyration volume. The resulting system of coupled equations is solved
varying the polymer-solvent repulsion strength at high solvent pressure in the
bulk. We show that the coil-globule (globule-coil) transition occurs
accompanied by a local solvent evaporation (condensation) within the gyration
volum
Semileptonic transition in three--point QCD sum rules and HQET with gluon condensate corrections
Taking into account the gluon condensate contributions, the form factors of
the semileptonic transition with are
calculated in the framework of the three point QCD sum rules. The heavy quark
effective theory limit of the form factors are also computed. The relevant
total decay width as well as the branching ratio are evaluated and compared
with the predictions of the other non-perturbative approaches.Comment: 27 Pages, 4 Figures and 4 Table
Subthreshold and near-threshold kaon and antikaon production in proton-nucleus reactions
The differential production cross sections of K^+ and K^- mesons have been
measured at the ITEP proton synchrotron in p+Be, p+Cu collisions under lab
angle of 10.5^0, respectively, at 1.7 and 2.25, 2.4 GeV beam energies. A
detailed comparison of these data with the results of calculations within an
appropriate folding model for incoherent primary proton-nucleon, secondary
pion-nucleon kaon and antikaon production processes and processes associated
with the creation of antikaons via the decay of intermediate phi mesons is
given. We show that the strangeness exchange process YN->NNK^- gives a small
contribution to the antikaon yield in the kinematics of the performed
experiment. We argue that in the case when antikaon production processes are
dominated by the channels with KK^- in the final state, the cross sections of
the corresponding reactions are weakly influenced by the in-medium kaon and
antikaon mean fields.Comment: 24 pages. accepted for publication at J.Phys.
Two-particle decays of B_c meson into charmonium states
The factorization of hard and soft contributions into the hadronic decays of
B_c meson at large recoils is explored in order to evaluate the decay rates
into the S, P and D-wave charmonia associated with rho and pi. The constraints
of approach applicability and uncertainties of numerical estimates are
discussed. The mode with the J/psi in the final state is evaluated taking into
account the cascade radiative electromagnetic decays of excited P-wave states,
that enlarges the branching ratio by 20-25%.Comment: 13 pages, LaTeX axodraw-style, 1 figure, 2 table
Reply to the "Comment on `Once more about the molecule approach to the light scalars' "
The need to regularize loop integrals in a manner that preserves gauge
invariance, for example, using the Pauli-Villars method, requires a subtraction
that in the large mass limit hides its high momentum origin. This gives rise to
the illusion that only nonrelativistic kaon loop momenta are relevant, when in
fact this is not the case, as we show.Comment: 4 pages, 1 figure, there are specified the title, the abstract, and
the first paragraph, typos are remove
Variational Lie algebroids and homological evolutionary vector fields
We define Lie algebroids over infinite jet spaces and establish their
equivalent representation through homological evolutionary vector fields.Comment: Int. Workshop "Nonlinear Physics: Theory and Experiment VI"
(Gallipoli, Italy; June-July 2010). Published v3 = v2 minus typos, to appear
in: Theoret. and Mathem. Phys. (2011) Vol.167:3 (168:1), 18 page
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