344 research outputs found
Argumentación y habilidades en el proceso educativo
Miguel Ángel Campos Hernández. Argumentación y habilidades en el proceso educativo. Colección: Educación. México: IISUE / Plaza y Valdés, 2008, 428 págs. ISBN:978-607-402-048-9 (Plaza de Valdés); 978-970-32-5443-9 (UNAM)
Single-Particle Density of States of a Superconductor with a Spatially Varying Gap and Phase Fluctuations
Recent experiments have shown that the superconducting energy gap in some
cuprates is spatially inhomogeneous. Motivated by these experiments, and using
exact diagonalization of a model d-wave Hamiltonian, combined with Monte Carlo
simulations of a Ginzburg-Landau free energy functional, we have calculated the
single-particle density of states LDOS of a model high-T
superconductor as a function of temperature. Our calculations include both
quenched disorder in the pairing potential and thermal fluctuations in both
phase and amplitude of the superconducting gap. Most of our calculations assume
two types of superconducting regions: , with a small gap and large
superfluid density, and , with the opposite. If the regions are
randomly embedded in an host, the LDOS on the sites still has
a sharp coherence peak at , but the component does not, in
agreement with experiment. An ordered arrangement of regions leads to
oscillations in the LDOS as a function of energy. The model leads to a
superconducting transition temperature well below the pseudogap
temperature , and has a spatially varying gap at very low , both
consistent with experiments in underdoped Bi2212. Our calculated
LDOS shows coherence peaks for , in agreement with previous work considering phase but not amplitude
fluctuations in a homogeneous superconductor. Well above , the gap in the
LDOS disappears.Comment: 37 pages, 12 figures. Accepted by Phys. Rev. B. Scheduled Issue: 01
Nov 200
Importance of molecular interactions in colloidal dispersions
We review briefly the concept of colloidal dispersions, their general
properties and some of their most important applications, as well as the basic
molecular interactions that give rise to their properties in equilibrium.
Similarly, we revisit Brownian motion and hydrodynamic interactions associated
with the concept of viscosity of colloidal dispersion. It is argued that the
use of modern research tools, such as computer simulations, allows one to
predict accurately some macroscopically measurable properties by solving
relatively simple models of molecular interactions for a large number of
particles. Lastly, as a case study, we report the prediction of rheological
properties of polymer brushes using state of the art, coarse grained computer
simulations, which are in excellent agreement with experiments.Comment: 8 pages, 10 figure
Medicinal Plant Extracts and Their Use As Wound Closure Inducing Agents
Skin insult and damage start a complex healing process that involves a myriad of coordinated reactions at both the cellular and molecular level occurring simultaneously. These processes can be divided into that of cell migration and tissue remodeling of the wound. In addition, it is well known that deep wounds that derive from surgical procedures need a multidisciplinary approach to have a successful wound healing process. Recently, there has been a renowned interest in the identification of active compounds derived from ornamental, edible, and wild plants being used in the cosmetic and skin product industry. Recent reports suggest that active components of several plants such as Propolis and Aloe vera could be used
to induce the process of wound healing and tissue regeneration and reducing therefore the time to complete wound closure.
Other plant species such as Achillea millefolium or Salvia officinalis have anti-inflammatory properties and promote cellular proliferation contributing to faster tissue regeneration. It has been described that Malva sylvestris influences the formation of fibrosis-free granulation tissue in the skin. Recent observations suggest that Casearia sylvestris induces the angiogenic process. These effects have been evaluated in cell lines, different animal models, and some in randomized clinical trials. In this review we summarize the evidence of plant extracts and their active components (when known) in the acceleration of the wound closure process and tissue repair
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