967 research outputs found
La Marca del Artífice. Descartes, Plinio y las Líneas de Apeles
Nas Quintas Respostas Descartes torna explícita a analogia entre a semelhança ego-Deus e a semelhança obra-pintor. É pertinente considerar o exemplum que (seguindo uma rica tradição iniciada na Historia Natural de Plinio o Velho) Descartes evoca para fazer referência à absoluta perfeição da obra. Trata-se de Apeles de Cós. Pretendemos mostrar: 1) Que a obra de Apeles é a única que pode sustentar à analogia com a ideia de Deus, já que é a única que revela os dois nomes que presidem as provas da Sua existência, a saber: ens infinitus; ens perfectissimum. 2) Que esta analogía refere-se a uma obra particular de Apeles, a mais célebre, cuja descrição por parte de Plinio era já e ainda é um locus classicus. Em primeiro lugar, é a única que não representa, nem tem a pretensão de representar, outra coisa que não seja a marca do Artífice; e em segundo lugar, é a única que, como a ideia de Deus, contém, após seis séculos de interpretações, toda a perfeição concebível, isto é, toda perfeição da arte passada e da ainda por vir.AbstractIn the Fifth Replies, Descartes explains the analogy between the ego-God likeness and the work-painter likeness. It is worth considering the exemplum evoked by Descartes (following a strong tradition which started in the Natural History by Pliny the Elder) to refer to the absolute perfection of the work, i.e., Apelles of Kos. We intend to show that: (1) Apelles' is the only work that can claim the analogy with the idea of God, since it is the only one revealing the two terms prevailing over the proofs of His existence, namely: ens infinitum; ens perfectissimum; (2) this analogy refers to a specific work of Apelles, the most famous one, whose description by Pliny was, and still is, a locus classicus. First of all, it is the only one not representing —nor intending to represent— anything but the Author's sign; secondly, it is the only one that, like the idea of God, and after six centuries of interpretations, still contains every conceivable perfection, that is, all perfections of past and future art. Recebido em 12/2013Aprovado em 02/201
El organismo como república. Georges Cabanis y los fundamentos de la psicofisiología
Este trabajo pretende examinar los fundamentos de la psicofisiología moderna, tal como ella se formula en los Rapports du Physique et du Moral dans l'homme ( 1802) de Georges Cabanis (1757-1808)
Análisis y ejecución de estrategias en la industria de sensores mediante la simulación CAPSIM
Documento en el que se muestra el trabajo realizado en la dirección de una empresa de la industria de sensores dentro del simulador de negocios Capsim. Se presenta un análisis de la industria de los sensores, se describe la empresa en la que se trabajó, las estrategias de negocio y el proceso de su implementación, así como los resultados finales
Monte-Carlo simulations of the recombination dynamics in porous silicon
A simple lattice model describing the recombination dynamics in visible light
emitting porous Silicon is presented. In the model, each occupied lattice site
represents a Si crystal of nanometer size. The disordered structure of porous
Silicon is modeled by modified random percolation networks in two and three
dimensions. Both correlated (excitons) and uncorrelated electron-hole pairs
have been studied. Radiative and non-radiative processes as well as hopping
between nearest neighbor occupied sites are taken into account. By means of
extensive Monte-Carlo simulations, we show that the recombination dynamics in
porous Silicon is due to a dispersive diffusion of excitons in a disordered
arrangement of interconnected Si quantum dots. The simulated luminescence decay
for the excitons shows a stretched exponential lineshape while for uncorrelated
electron-hole pairs a power law decay is suggested. Our results successfully
account for the recombination dynamics recently observed in the experiments.
The present model is a prototype for a larger class of models describing
diffusion of particles in a complex disordered system.Comment: 33 pages, RevTeX, 19 figures available on request to
[email protected]
Hidden in plain sight: a massive, dusty starburst in a galaxy protocluster at z=5.7 in the COSMOS field
We report the serendipitous discovery of a dusty, starbursting galaxy at
(hereafter called CRLE) in close physical association with the
"normal" main-sequence galaxy HZ10 at . CRLE was identified by
detection of [CII], [NII] and CO(2-1) line emission, making it the highest
redshift, most luminous starburst in the COSMOS field. This massive, dusty
galaxy appears to be forming stars at a rate of at least 1500
yr in a compact region only kpc in diameter. The dynamical and
dust emission properties of CRLE suggest an ongoing merger driving the
starburst, in a potentially intermediate stage relative to other known dusty
galaxies at the same epoch. The ratio of [CII] to [NII] may suggest that an
important () contribution to the [CII] emission comes from a diffuse
ionized gas component, which could be more extended than the dense,
starbursting gas. CRLE appears to be located in a significant galaxy
overdensity at the same redshift, potentially associated with a large-scale
cosmic structure recently identified in a Lyman Alpha Emitter survey. This
overdensity suggests that CRLE and HZ10 reside in a protocluster environment,
offering the tantalizing opportunity to study the effect of a massive starburst
on protocluster star formation. Our findings support the interpretation that a
significant fraction of the earliest galaxy formation may occur from the inside
out, within the central regions of the most massive halos, while rapidly
evolving into the massive galaxy clusters observed in the local Universe.Comment: 16 pages, 9 figures, 4 tables, final version to appear on ApJ
(accepted May 19, 2018
Relationship among expression, amplification, and methylation of FE4 esterase genes in Italian populations of Myzus persicae (Sulzer) (Homoptera : Aphididae)
The wide use of insecticides containing an esteric group selected resistant Myzus persicae populations characterised by the overproduction of one of two closely related carboxylesterases (E4 and FE4). In this paper, we present data collected from Italian population indicating that all the 22 populations analysed possess amplified FE4 gene only. The estimation of FE4 copy number, carried out by densitometric scanning of dot and Southern blots, puts in evidence that the different populations possess a gene copy number ranging from 6 to 104. Statistical analysis shows the existence of a high positive correlation between gene copy number and total esterase activity. In aphid strain with low FE4 copy number, these genes are almost totally methylated. On the contrary, aphid strains with high FE4 gene number evidenced highly variable methylation levels and absence of correlation between the number of genes and their methylation state. The same result has been observed when comparing FE4 methylation levels and esterase activity
Photon recycling in Fabry-Perot micro-cavities based on SiN waveguides
We present a numerical analysis and preliminary experimental results on
one-dimensional Fabry-Perot micro-cavities in SiN waveguides. The
Fabry-Perot micro-cavities are formed by two distributed Bragg reflectors
separated by a straight portion of waveguide. The Bragg reflectors are composed
by a few air slits produced within the SiN waveguides. In order to
increase the quality factor of the micro-cavities, we have minimized, with a
multiparametric optimization tool, the insertion loss of the reflectors by
varying the length of their first periods (those facing the cavity). To explain
the simulation results the coupling of the fundamental waveguide mode with
radiative modes in the Fabry-Perot micro-cavities is needed. This effect is
described as a recycling of radiative modes in the waveguide. To support the
modelling, preliminary experimental results of micro-cavities in SiN
waveguides realized with Focused Ion Beam technique are reported.Comment: 5 pages, 5 figure
Temporal Lobe Spikes Affect Distant Intrinsic Connectivity Networks
Objective: To evaluate local and distant blood oxygen level dependent (BOLD) signal changes related to interictal epileptiform discharges (IED) in drug-resistant temporal lobe epilepsy (TLE). Methods: Thirty-three TLE patients undergoing EEG–functional Magnetic Resonance Imaging (fMRI) as part of the presurgical workup were consecutively enrolled. First, a single-subject spike-related analysis was performed: (a) to verify the BOLD concordance with the presumed Epileptogenic Zone (EZ); and (b) to investigate the Intrinsic Connectivity Networks (ICN) involvement. Then, a group analysis was performed to search for common BOLD changes in TLE. Results: Interictal epileptiform discharges were recorded in 25 patients and in 19 (58%), a BOLD response was obtained at the single-subject level. In 42% of the cases, BOLD changes were observed in the temporal lobe, although only one patient had a pure concordant finding, with a single fMRI cluster overlapping (and limited to) the EZ identified by anatomo-electro-clinical correlations. In the remaining 58% of the cases, BOLD responses were localized outside the temporal lobe and the presumed EZ. In every patient, with a spike-related fMRI map, at least one ICN appeared to be involved. Four main ICNs were preferentially involved, namely, motor, visual, auditory/motor speech, and the default mode network. At the single-subject level, EEG–fMRI proved to have high specificity (above 65%) in detecting engagement of an ICN and the corresponding ictal/postictal symptom, and good positive predictive value (above 67%) in all networks except the visual one. Finally, in the group analysis of BOLD changes related to IED revealed common activations at the right precentral gyrus, supplementary motor area, and middle cingulate gyrus. Significance: Interictal temporal spikes affect several distant extra-temporal areas, and specifically the motor/premotor cortex. EEG–fMRI in patients with TLE eligible for surgery is recommended not for strictly localizing purposes rather it might be useful to investigate ICNs alterations at the single-subject level
Single-particle states in spherical Si/SiO quantum dots
We calculate ground and excited electron and hole levels in spherical Si
quantum dots inside SiO in a multiband effective mass approximation.
Luttinger Hamiltonian is used for holes and the strong anisotropy of the
conduction electron effective mass in Si is taken into account. As boundary
conditions for electron and hole wave functions we use continuity of the wave
functions and the velocity density at the boundary of the quantum dots.Comment: 8 pages, 5 figure
Electronic structure of intentionally disordered AlAs/GaAs superlattices
We use realistic pseudopotentials and a plane-wave basis to study the
electronic structure of non-periodic, three-dimensional, 2000-atom
(AlAs)_n/(GaAs)_m (001) superlattices, where the individual layer thicknesses
n,m = {1,2,3} are randomly selected. We find that while the band gap of the
equivalent (n = m = 2) ordered superlattice is indirect, random fluctuations in
layer thicknesses lead to a direct gap in the planar Brillouin zone, strong
wavefunction localization along the growth direction, short radiative
lifetimes, and a significant band-gap reduction, in agreement with experiments
on such intentionally grown disordered superlattices.Comment: 10 pages, REVTeX and EPSF macros, 4 figures in postscript. e-mail to
[email protected]
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