2,454 research outputs found
Front dynamics in turbulent media
A study of a stable front propagating in a turbulent medium is presented. The
front is generated through a reaction-diffusion equation, and the turbulent
medium is statistically modeled using a Langevin equation. Numerical
simulations indicate the presence of two different dynamical regimes. These
regimes appear when the turbulent flow either wrinkles a still rather sharp
propagating interfase or broadens it. Specific dependences of the propagating
velocities on stirring intensities appropriate to each case are found and
fitted when possible according to theoretically predicted laws. Different
turbulent spectra are considered.Comment: 8 pages, REVTEX, 6 postscript figures included. To appear in Phys.
Fluids (1997
Transverse transport in graphite
Graphite is a layered material showing a strong anisotropy. Among the
unconventional properties reported by experiments, the electronic transport
along the c-axis, which has direct implications in order to build graphitic
devices, remains a controversial topic. We study the influence of inelastic
scattering on the electron tunnelling between layers. In the presence of
electron electron interactions, tunnelling processes are modified by inelastic
scattering events.Comment: 9 pages, no figures Proceedings of the Graphene Conference, MPI PKS
Dresden, September 200
Langevin approach to generate synthetic turbulence
We present an analytical scheme, easily implemented numerically, to generate
synthetic Gaussian turbulent flows by using a linear Langevin equation, where
the noise term acts as a stochastic stirring force. The characteristic
parameters of the velocity field are well introduced, in particular the
kinematic viscosity and the spectrum of energy. As an application, the
diffusion of a passive scalar is studied for two different energy spectra.
Numerical results are compared favorably with analytical calculations.Comment: 7 pages, REVTEX, 6 figures. To appear in Physics of Fluids (April
1997
Physics for non-physicists - Two bio-degrees reforms in Spanish universities: Health Biology and Biology
We present a review of two different innovative experiences of Physics education for Bio-Sciences in two Spanish Universities - the Health Biology degree of the Universidad de Alcalá de Henares (UAH) and the Biology degree of the Universidad Autónoma de Madrid (UAM). Both experiences took place simultaneously and coincident with the implementation of Bologna Plan. Although they were developed under different contextual constraints, set by the respective Faculties, they share a number of similar pedagogical strategies which are analyzed. In both cases the reforms allowed a substantial improvement in learning results compared to those obtained in the previous Physics courses in the respective degreesLHM participated in the GIREP-MPTL 2018 on behalf of the project IPLS-Spain, promoted and supported by an inter-university group of physics teachers and young biologist
Crosstalk between nanotube devices: contact and channel effects
At reduced dimensionality, Coulomb interactions play a crucial role in
determining device properties. While such interactions within the same carbon
nanotube have been shown to have unexpected properties, device integration and
multi-nanotube devices require the consideration of inter-nanotube
interactions. We present calculations of the characteristics of planar carbon
nanotube transistors including interactions between semiconducting nanotubes
and between semiconducting and metallic nanotubes. The results indicate that
inter-tube interactions affect both the channel behavior and the contacts. For
long channel devices, a separation of the order of the gate oxide thickness is
necessary to eliminate inter-nanotube effects. Because of an exponential
dependence of this length scale on dielectric constant, very high device
densities are possible by using high-k dielectrics and embedded contacts
Compositeness effects, Pauli's principle and entanglement
We analyse some compositeness effects and their relation with entanglement.
We show that the purity of a composite system increases, in the sense of the
expectation values of the deviation operators, with large values of the
entanglement between the components of the system. We also study the validity
of Pauli's principle in composite systems. It is valid within the limits of
application of the approach presented here. We also present an example of two
identical fermions, one of them entangled with a distinguishable particle,
where the exclusion principle cannot be applied. This result can be important
in the description of open systems
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