3,599 research outputs found
Holographic fermions in external magnetic fields
We study the Fermi level structure of 2+1-dimensional strongly interacting
electron systems in external magnetic field using the AdS/CFT correspondence.
The gravity dual of a finite density fermion system is a Dirac field in the
background of the dyonic AdS-Reissner-Nordstrom black hole. In the probe limit
the magnetic system can be reduced to the non-magnetic one, with
Landau-quantized momenta and rescaled thermodynamical variables. We find that
at strong enough magnetic fields, the Fermi surface vanishes and the
quasiparticle is lost either through a crossover to conformal regime or through
a phase transition to an unstable Fermi surface. In the latter case, the
vanishing Fermi velocity at the critical magnetic field triggers the non-Fermi
liquid regime with unstable quasiparticles and a change in transport properties
of the system. We associate it with a metal-"strange metal" phase transition.
Next we compute the DC Hall and longitudinal conductivities using the
gravity-dressed fermion propagators. For dual fermions with a large charge,
many different Fermi surfaces contribute and the Hall conductivity is quantized
as expected for integer Quantum Hall Effect (QHE). At strong magnetic fields,
as additional Fermi surfaces open up, new plateaus typical for the fractional
QHE appear. The somewhat irregular pattern in the length of fractional QHE
plateaus resemble the outcomes of experiments on thin graphite in a strong
magnetic field. Finally, motivated by the absence of the sign problem in
holography, we suggest a lattice approach to the AdS calculations of finite
density systems.Comment: 34 pages, 14 figure
Thermalisation time and specific heat of neutron stars crust
We discuss the thermalisation process of the neutron stars crust described by
solving the heat transport equation with a microscopic input for the specific
heat of baryonic matter. The heat equation is solved with initial conditions
specific to a rapid cooling of the core. To calculate the specific heat of
inner crust baryonic matter, i.e., nuclear clusters and unbound neutrons, we
use the quasiparticle spectrum provided by the Hartree-Fock-Bogoliubov approach
at finite temperature. In this framework we analyse the dependence of the crust
thermalisation on pairing properties and on cluster structure of inner crust
matter. It is shown that the pairing correlations reduce the crust
thermalisation time by a very large fraction. The calculations show also that
the nuclear clusters have a non-negligible influence on the time evolution of
the surface temperature of the neutron star.Comment: 7 pages, 5 figures, submitted to Phys. Rev.
Model for resonant photon creation in a cavity with time dependent conductivity
In an electromagnetic cavity, photons can be created from the vacuum state by
changing the cavity's properties with time. Using a simple model based on a
massless scalar field, we analyze resonant photon creation induced by the
time-dependent conductivity of a thin semiconductor film contained in the
cavity. This time dependence may be achieved by irradiating periodically the
film with short laser pulses. This setup offers several experimental advantages
over the case of moving mirrors.Comment: 9 pages, 1 figure. Minor changes. Version to appear in Phys. Rev.
Nicastrin and Notch4 drive endocrine therapy resistance and epithelial to mesenchymal transition in MCF7 breast cancer cells
Introduction Resistance to anti-estrogen therapies is a major cause of disease relapse and mortality in estrogen receptor alpha (ERα)-positive breast cancers. Tamoxifen or estrogen withdrawal increases the dependence of breast cancer cells on Notch signalling. Here, we investigated the contribution of Nicastrin and Notch signalling in endocrine-resistant breast cancer cells. Methods We used two models of endocrine therapies resistant (ETR) breast cancer: tamoxifen-resistant (TamR) and long-term estrogen-deprived (LTED) MCF7 cells. We evaluated the migratory and invasive capacity of these cells by Transwell assays. Expression of epithelial to mesenchymal transition (EMT) regulators as well as Notch receptors and targets were evaluated by real-time PCR and western blot analysis. Moreover, we tested in vitro anti-Nicastrin monoclonal antibodies (mAbs) and gamma secretase inhibitors (GSIs) as potential EMT reversal therapeutic agents. Finally, we generated stable Nicastrin overexpessing MCF7 cells and evaluated their EMT features and response to tamoxifen. Results We found that ETR cells acquired an epithelial to mesenchymal transition (EMT) phenotype and displayed increased levels of Nicastrin and Notch targets. Interestingly, we detected higher level of Notch4 but lower levels of Notch1 and Notch2 suggesting a switch to signalling through different Notch receptors after acquisition of resistance. Anti-Nicastrin monoclonal antibodies and the GSI PF03084014 were effective in blocking the Nicastrin/Notch4 axis and partially inhibiting the EMT process. As a result of this, cell migration and invasion were attenuated and the stem cell-like population was significantly reduced. Genetic silencing of Nicastrin and Notch4 led to equivalent effects. Finally, stable overexpression of Nicastrin was sufficient to make MCF7 unresponsive to tamoxifen by Notch4 activation. Conclusions ETR cells express high levels of Nicastrin and Notch4, whose activation ultimately drives invasive behaviour. Anti-Nicastrin mAbs and GSI PF03084014 attenuate expression of EMT molecules reducing cellular invasiveness. Nicastrin overexpression per se induces tamoxifen resistance linked to acquisition of EMT phenotype. Our finding suggest that targeting Nicastrin and/or Notch4 warrants further clinical evaluation as valid therapeutic strategies in endocrine-resistant breast cancer
Transient Analysis of Warm Electron Injection Programming of Double Gate SONOS Memories by means of Full Band Monte Carlo Simulation
In this paper we investigate "Warm Electron Injection" as a mechanism for NOR
programming of double-gate SONOS memories through 2D full band Monte Carlo
simulations. Warm electron injection is characterized by an applied VDS smaller
than 3.15 V, so that electrons cannot easily accumulate a kinetic energy larger
than the height of the Si/SiO2 barrier. We perform a time-dependent simulation
of the program operation where the local gate current density is computed with
a continuum-based method and is adiabatically separated from the 2D full Monte
Carlo simulation used for obtaining the electron distribution in the phase
space. In this way we are able to compute the time evolution of the charge
stored in the nitride and of the threshold voltages corresponding to forward
and reverse bias. We show that warm electron injection is a viable option for
NOR programming in order to reduce power supply, preserve reliability and CMOS
logic level compatibility. In addition, it provides a well localized charge,
offering interesting perspectives for multi-level and dual bit operation, even
in devices with negligible short channel effects
Effects of electron-electron interactions on the electronic Raman scattering of graphite in high magnetic fields
We report the observation of strongly temperature-dependent, asymmetric
spectral lines in electronic Raman scattering spectra of graphite in a high
magnetic field up to 45 T applied along the c-axis. The magnetic field
quantizes the in-plane motion, while the out-of-plane motion remains free,
effectively reducing the system dimension from three to one. Optically created
electron-hole pairs interact with, or shake up, the one-dimensional Fermi sea
in the lowest Landau subbands. Based on the Tomonaga-Luttinger liquid theory,
we show that interaction effects modify the van Hove singularity to the form
at zero temperature. At finite temperature, we
predict a thermal broadening factor that increases linearly with the
temperature. Our model reproduces the observed temperature-dependent
line-shape, determining to be 0.05 at 40 T
Magnetophonon resonance in graphite: High-field Raman measurements and electron-phonon coupling contributions
We perform Raman scattering experiments on natural graphite in magnetic fields up to 45 T, observing a series of peaks due to interband electronic excitations over a much broader magnetic field range than previously reported. We also explore electron-phonon coupling in graphite via
magnetophonon resonances
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Brain Routes for Reading in Adults with and without Autism: EMEG Evidence
Reading utilises at least two neural pathways. The temporal lexical route visually maps whole words to their lexical entries, whilst the nonlexical route decodes words phonologically via parietal cortex. Readers typically employ the lexical route for familiar words, but poor comprehension plus precocity at mechanically ‘sounding out’ words suggests that differences might exist in autism. Combined MEG/EEG recordings of adults with autistic spectrum conditions (ASC) and controls while reading revealed preferential recruitment of temporal areas in controls and additional parietal recruitment in ASC. Furthermore, a lack of differences between semantic word categories was consistent with previous suggestion that people with ASC may lack a ‘default’ lexical-semantic processing mode. These results are discussed with reference to dual-route models of reading
Primeros pasos en la docencia y la Investigación. Escuela de ayudantes de Histología de la Facultad de Ciencias Veterinarias de la Universidad de Buenos Aires.
Desde el año 2000 y por resolución (CD) 651 de octubre de 1999 se implementa en la Cátedra de Histología y Embriología de la Facultad de Ciencias Veterinarias de la UBA la escuela de ayudantes como paso previo para la incorporación como docente auxiliar. Interrumpida por la pandemia de Covid19 se retomó en el año 2022 con nuevas modificaciones. El curso está abierto a alumnos de la carrera de grado tanto de Veterinaria como de Bioterio de nuestra facultad, como así también, para aquellos alumnos de postgrado o profesionales interesados en la enseñanza de las ciencias morfológicas de otras facultades de Veterinaria, Medicina, Odontología y Ciencias Naturales que quieran perfeccionarse en el área. El objetivo es brindar a los nuevos aspirantes los elementos básicos necesarios no sólo desde lo curricular, sino también proveer elementos pedagógicos y de laboratorio como componentes necesarios que faculte a los asistentes para el trabajo diario en contacto con los alumnos. El llamado se realiza anualmente en donde los nuevos integrantes son seleccionados según su curriculum e intereses y teniendo en cuenta como condiciones para su admisión tener aprobada la asignatura Histología en sus respectivas casas de estudio con un valor no inferior a 8 y un promedio general no menor a 7 al momento del llamado. El curso se implementa en módulos teórico-prácticos y referidos a la observación de preparaciones de manera descriptiva y fundamentada en el diagnóstico. Además, se estructura un módulo dedicado a recibir conocimientos de pedagogía, aplicables al abordaje teórico-práctico de la materia y un módulo en laboratorio, en donde se desarrollan las técnicas histológicas de rutina. La evaluación del curso se realiza de manera continua y permanente. Esta nueva modalidad ha incorporado ya nuevas generaciones de docentes e investigadores con una formación más completa e integradora que repercute en una mejor implementación del proceso enseñanza-aprendizaje
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