273 research outputs found
Label-free detection of anticancer drug paclitaxel in living cells by confocal Raman microscopy
Confocal Raman microscopy, a non-invasive, label-free, and high spatial resolution imaging technique is employed to trace the anticancer drug paclitaxel in living Michigan Cancer Foundation-7 (MCF-7) cells. The Raman images were treated by K-mean cluster analysis to detect the drug in cells. Distribution of paclitaxel in cells is verified by calculating the correlation coefficient between the reference spectrum of the drug and the whole Raman image spectra. A time dependent gradual diffusion of paclitaxel all over the cell is observed suggesting a complementary picture of the pharmaceutical action of this drug based on rapid binding of free tubulin to crystallized paclitaxel. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4794871
Landau Levels, Magnetic Fields and Holographic Fermi Liquids
We further consider a probe fermion in a dyonic black hole background in
anti-de Sitter spacetime, at zero temperature, comparing and contrasting two
distinct classes of solution that have previously appeared in the literature.
Each class has members labeled by an integer n, corresponding to the n-th
Landau level for the fermion. Our interest is the study of the spectral
function of the fermion, interpreting poles in it as indicative of
quasiparticles associated with the edge of a Fermi surface in the
holographically dual strongly coupled theory in a background magnetic field H
at finite chemical potential. Using both analytical and numerical methods, we
explicitly show how one class of solutions naturally leads to an infinite
family of quasiparticle peaks, signaling the presence of a Fermi surface for
each level n. We present some of the properties of these peaks, which fall into
a well behaved pattern at large n, extracting the scaling of Fermi energy with
n and H, as well as the dispersion of the quasiparticles.Comment: 23 pages, 4 figures. Changed some of the terminology: non-separable
-> infinite-sum. Clarified the relationship between our ansatz and the
separable ansat
Non-relativistic metrics from back-reacting fermions
It has recently been pointed out that under certain circumstances the
back-reaction of charged, massive Dirac fermions causes important modifications
to AdS_2 spacetimes arising as the near horizon geometry of extremal black
holes. In a WKB approximation, the modified geometry becomes a non-relativistic
Lifshitz spacetime. In three dimensions, it is known that integrating out
charged, massive fermions gives rise to gravitational and Maxwell Chern-Simons
terms. We show that Schrodinger (warped AdS_3) spacetimes exist as solutions to
a gravitational and Maxwell Chern-Simons theory with a cosmological constant.
Motivated by this, we look for warped AdS_3 or Schrodinger metrics as exact
solutions to a fully back-reacted theory containing Dirac fermions in three and
four dimensions. We work out the dynamical exponent in terms of the fermion
mass and generalize this result to arbitrary dimensions.Comment: 26 pages, v2: typos corrected, references added, minor change
Deconstructing holographic liquids
We argue that there exist simple effective field theories describing the
long-distance dynamics of holographic liquids. The degrees of freedom
responsible for the transport of charge and energy-momentum are Goldstone
modes. These modes are coupled to a strongly coupled infrared sector through
emergent gauge and gravitational fields. The IR degrees of freedom are
described holographically by the near-horizon part of the metric, while the
Goldstone bosons are described by a field-theoretical Lagrangian. In the cases
where the holographic dual involves a black hole, this picture allows for a
direct connection between the holographic prescription where currents live on
the boundary, and the membrane paradigm where currents live on the horizon. The
zero-temperature sound mode in the D3-D7 system is also re-analyzed and
re-interpreted within this formalism.Comment: 21 pages, 2 figure
A conical deficit in the AdS4/CFT3 correspondence
Inspired by the AdS/CFT correspondence we propose a new duality that allow
the study of strongly coupled field theories living in a 2+1 conical
space-time. Solving the 4-d Einstein equations in the presence of an infinite
static string and negative cosmological constant we obtain a conical AdS4
space-time whose boundary is identified with the 2+1 cone found by Deser,
Jackiw and 't Hooft. Using the AdS4/CFT3 correspondence we calculate retarded
Green's functions of scalar operators living in the cone.Comment: v3, 14 pages. We reinterpret our results for the Green's functions in
the con
Diversidad de vertebrados acuáticos de tres humedales urbanos de la ciudad de Buenos Aires
The urban wetlands are sites of high biodiversity that are under a great anthropogenic pressure. In the city of Buenos Aires, one of the more important areas of recreation is constituted by Parque Tres de Febrero (well-known as like “Bosques de Palermo”), that conforms a green zone of 25 ha. In this area there are artificial wetlands of diverse physical characteristics. In the present work, the goal is to determine vertebrate’s diversity in these urban aquatic enviroments in order to evaluate the degree of impact of the recreational activity on the conservation of the vertebrates associated to the water bodies.
The study was carried out in three artificial lagoons included in the park: Regatas, Rosedal and Planetario.
Altogether, seventeen species of fish (Prochilodus lineatus, Oligosarcus jenynsii, Cheirodon interruptus, Bryconamericus iheringii, Hoplias malabaricus, Hypostomus commersoni, Rhamdia quelen, Pimelodus albicans, Pimelodus maculatus, Cyprinus carpio carpio, Cnesterodon decemmaculatus, Gambusia affinis, Jenynsia multidentata, Synbranchus marmoratus, Australoheros facetus, Gymnogeophagus meridionalis and Crenicichla scottii), eighteen species of birds (Podiceps rolland, Podilymbus podiceps, Podiceps major, Phalacrocorax olivaceus, Ardea alba, Egretta thula, Butorides striatus, Nycticorax nycticorax, Anas georgica, Anas platyrhynchos, Anas platyrhynchos domesticus, Anser anser, Cairina moschata, Netta peposaca, Aramus guarauna, Fulica armillata, Fulica leucoptera and Chloroceyle amazona), three species of turtles (Phrynops hilarii, Trachemys scripta elegans and Trachemys venusta) and one species of mammal were registered (Myocastor coipo). Among these species, eight are introduced: two fishes (Cyprinus carpio carpio and Gambusia affinis), two turtles (Trachemys scripta elegans and Trachemys venusta) and four birds (Anas platyrhynchos, Anas platyrhynchos domesticus, Anser anser and Cairina moschata). Regatas was the site with greater diversity of fishes (n=17) that represents a 10.43% of RĂo de la Plata’s ichthyofauna (n=163). This site lodges a 13% of the bird species associated to registered water bodies in the City of Buenos Aires (n=107). When comparing the specific richness among lagoons, we found high similarity between Regatas and Planetarium. Also, both sites presented the greatest specific richness of fish during the months of January and February. From this preliminary study it was possible to describe and to differentiate each lagoon by its fauna and physical characteristics, and also it constitutes the base to continue with further studies of communities which allow the development of the necessary guidelines of handling for the protection of Lagos Tres de Febrero.Instituto de LimnologĂa "RaĂşl A. Ringuelet
Diversidad de vertebrados acuáticos de tres humedales urbanos de la ciudad de Buenos Aires
The urban wetlands are sites of high biodiversity that are under a great anthropogenic pressure. In the city of Buenos Aires, one of the more important areas of recreation is constituted by Parque Tres de Febrero (well-known as like “Bosques de Palermo”), that conforms a green zone of 25 ha. In this area there are artificial wetlands of diverse physical characteristics. In the present work, the goal is to determine vertebrate’s diversity in these urban aquatic enviroments in order to evaluate the degree of impact of the recreational activity on the conservation of the vertebrates associated to the water bodies.
The study was carried out in three artificial lagoons included in the park: Regatas, Rosedal and Planetario.
Altogether, seventeen species of fish (Prochilodus lineatus, Oligosarcus jenynsii, Cheirodon interruptus, Bryconamericus iheringii, Hoplias malabaricus, Hypostomus commersoni, Rhamdia quelen, Pimelodus albicans, Pimelodus maculatus, Cyprinus carpio carpio, Cnesterodon decemmaculatus, Gambusia affinis, Jenynsia multidentata, Synbranchus marmoratus, Australoheros facetus, Gymnogeophagus meridionalis and Crenicichla scottii), eighteen species of birds (Podiceps rolland, Podilymbus podiceps, Podiceps major, Phalacrocorax olivaceus, Ardea alba, Egretta thula, Butorides striatus, Nycticorax nycticorax, Anas georgica, Anas platyrhynchos, Anas platyrhynchos domesticus, Anser anser, Cairina moschata, Netta peposaca, Aramus guarauna, Fulica armillata, Fulica leucoptera and Chloroceyle amazona), three species of turtles (Phrynops hilarii, Trachemys scripta elegans and Trachemys venusta) and one species of mammal were registered (Myocastor coipo). Among these species, eight are introduced: two fishes (Cyprinus carpio carpio and Gambusia affinis), two turtles (Trachemys scripta elegans and Trachemys venusta) and four birds (Anas platyrhynchos, Anas platyrhynchos domesticus, Anser anser and Cairina moschata). Regatas was the site with greater diversity of fishes (n=17) that represents a 10.43% of RĂo de la Plata’s ichthyofauna (n=163). This site lodges a 13% of the bird species associated to registered water bodies in the City of Buenos Aires (n=107). When comparing the specific richness among lagoons, we found high similarity between Regatas and Planetarium. Also, both sites presented the greatest specific richness of fish during the months of January and February. From this preliminary study it was possible to describe and to differentiate each lagoon by its fauna and physical characteristics, and also it constitutes the base to continue with further studies of communities which allow the development of the necessary guidelines of handling for the protection of Lagos Tres de Febrero.Instituto de LimnologĂa "RaĂşl A. Ringuelet
Black hole determinants and quasinormal modes
We derive an expression for functional determinants in thermal spacetimes as
a product over the corresponding quasinormal modes. As simple applications we
give efficient computations of scalar determinants in thermal AdS, BTZ black
hole and de Sitter spacetimes. We emphasize the conceptual utility of our
formula for discussing `1/N' corrections to strongly coupled field theories via
the holographic correspondence.Comment: 28 pages. v2: slightly improved exposition, references adde
Strange metals and the AdS/CFT correspondence
I begin with a review of quantum impurity models in condensed matter physics,
in which a localized spin degree of freedom is coupled to an interacting
conformal field theory in d = 2 spatial dimensions. Their properties are
similar to those of supersymmetric generalizations which can be solved by the
AdS/CFT correspondence; the low energy limit of the latter models is described
by a AdS2 geometry. Then I turn to Kondo lattice models, which can be described
by a mean- field theory obtained by a mapping to a quantum impurity coupled to
a self-consistent environment. Such a theory yields a 'fractionalized Fermi
liquid' phase of conduction electrons coupled to a critical spin liquid state,
and is an attractive mean-field theory of strange metals. The recent
holographic description of strange metals with a AdS2 x R2 geometry is argued
to be related to such mean-field solutions of Kondo lattice models.Comment: 19 pages, 4 figures; Plenary talk at Statphys24, Cairns, Australia,
July 2010; (v2) added refs; (v3) more ref
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