16,565 research outputs found
Shape instabilities in vesicles: a phase-field model
A phase field model for dealing with shape instabilities in fluid membrane
vesicles is presented. This model takes into account the Canham-Helfrich
bending energy with spontaneous curvature. A dynamic equation for the
phase-field is also derived. With this model it is possible to see the vesicle
shape deformation dynamically, when some external agent instabilizes the
membrane, for instance, inducing an inhomogeneous spontaneous curvature. The
numerical scheme used is detailed and some stationary shapes are shown together
with a shape diagram for vesicles of spherical topology and no spontaneous
curvature, in agreement with known results
Banco de Portugal Conference on "Portuguese Economic Development in the European Union": A Personal Summary
Chiral symmetry breaking in QCD-like gauge theories with a confining propagator and dynamical gauge boson mass generation
We study chiral symmetry breaking in QCD-like gauge theories introducing a
confining effective propagator, as proposed recently by Cornwall, and
considering the effect of dynamical gauge boson mass generation. The effective
confining propagator has the form and we study the bifurcation
equation finding limits on below which a satisfactory fermion mass solution
is generated. Since the coupling constant and gauge boson propagator are damped
in the infrared, due to the presence of dynamically massive gauge bosons, the
major part of the chiral breaking is only due to the confining propagator. We
study the asymptotic behavior of the gap equation containing confinement and
massive gauge boson exchange, and find that the symmetry breaking can be
approximated at some extent by an effective four-fermion interaction generated
by the confining propagator. We compute some QCD chiral parameters as a
function of , finding values compatible with the experimental data. Within
this approach we expect that lattice simulations should not see large
differences between the confinement and chiral symmetry breaking scales
independent of the fermionic representation and we find a simple approximate
relation between the fermion condensate and dynamical mass for a given
representation as a function of the parameters appearing in the effective
confining propagator.Comment: 32 pages, 9 figures, new references added, matchs published versio
Chiral symmetry breaking with a confining propagator and dynamically massive gluons
Chiral symmetry breaking in QCD is studied introducing a confining effective
propagator, as proposed recently by Cornwall, and considering the effect of
dynamically massive gluons. The effective confining propagator has the form
and we study the bifurcation equation finding limits on the
parameter below which a satisfactory fermion mass solution is generated.
Since the coupling constant and gluon propagator are damped in the infrared,
due to the presence of a dynamical gluon mass, the major part of the chiral
breaking is only due to the confining propagator and related to the low
momentum region of the gap equation. We study the asymptotic behavior of the
gap equation containing this confinement effect and massive gluon exchange, and
find that the symmetry breaking can be approximated by an effective
four-fermion interaction generated by the confining propagator. We compute some
QCD chiral parameters as a function of , finding values compatible with the
experimental data. We find a simple approximate relation between the fermion
condensate and dynamical mass for a given representation as a function of the
parameters appearing in the effective confining propagator.Comment: 12 pages, 2 figures. Talk presented at the International Workshop on
QCD Green's Functions, Confinement, and Phenomenology - QCD-TNT II, September
05-09 2011, ECT* Trento, Italy; ANN.PHYS.(NY, 2011
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Algorithms for network piecewise-linear programs
In this paper a subarea of Piecewise-Linear Programming named network Piecewise-Linear Programming (NPLP) is discussed. Initially the problem formulation, main efinitins and related Concepts are presented. In the sequence of the paper, four specialized algorithms for NPLP, as well as the results of a preliminary computational study, are presented
Quasi-Dirac neutrinos and solar neutrino data
We present an analysis of the solar neutrino data in the context of a
quasi-Dirac neutrino model in which the lepton mixing matrix is given at tree
level by the tribimaximal matrix. When radiative corrections are taken into
account, new effects in neutrino oscillations, as , appear.
This oscillation is constrained by the solar neutrino data. In our analysis, we
have found an allowed region for our two free parameters and .
The radiative correction, , can vary approximately from to and the calculated fourth mass eigenstate, , 0.01 eV
to 0.2 eV at 2 level. These results are very similar to the ones
presented in the literature.Comment: 24 pages, 7 figures and 2 tables. Results and conclusion unchanged.
Version published in EPJC. Figures improve
Experimental joint immobilization in guinea pigs. Effects on the knee joint
In young and adult guinea pigs, the aftermath experimentally induced by the immobilization of the knee joint in hyperextended forced position was studied. Joint immobilization which varied from one to nine weeks was attained by plaster. Eighty knee joints were examined macro and microscopically. Findings included: (1) muscular hypotrophy and joint stiffness in all animals, directly proportional to the length of immobilization; (2) haemoarthrosis in the first week; (3) intra-articular fibrous tissue proliferation ending up with fibrous ankylosis; (4) hyaline articular cartilage erosions; (5) various degrees of destructive menisci changes. A tentative explanation of the fibrous tissue proliferation and of the cartilage changes is offered
Optimal Time-dependent Sequenced Route Queries in Road Networks
In this paper we present an algorithm for optimal processing of
time-dependent sequenced route queries in road networks, i.e., given a road
network where the travel time over an edge is time-dependent and a given
ordered list of categories of interest, we find the fastest route between an
origin and destination that passes through a sequence of points of interest
belonging to each of the specified categories of interest. For instance,
considering a city road network at a given departure time, one can find the
fastest route between one's work and his/her home, passing through a bank, a
supermarket and a restaurant, in this order. The main contribution of our work
is the consideration of the time dependency of the network, a realistic
characteristic of urban road networks, which has not been considered previously
when addressing the optimal sequenced route query. Our approach uses the A*
search paradigm that is equipped with an admissible heuristic function, thus
guaranteed to yield the optimal solution, along with a pruning scheme for
further reducing the search space. In order to compare our proposal we extended
a previously proposed solution aimed at non-time dependent sequenced route
queries, enabling it to deal with the time-dependency. Our experiments using
real and synthetic data sets have shown our proposed solution to be up to two
orders of magnitude faster than the temporally extended previous solution.Comment: 10 pages, 12 figures To be published as a short paper in the 23rd ACM
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