4,013 research outputs found
Retinal biomarkers of Alzheimer’s disease: insights from transgenic mouse models
In this paper, we use the retina as a window into the central nervous system and in particular to assess changes in the retinal tissue associated with the Alzheimer’s disease. We imaged the retina of wild-type (WT) and transgenic mouse model (TMM) of Alzheimer’s disease with optical coherence tomography and classify retinas into the WT and TMM groups using support vector machines with the radial basis function kernel. Predictions reached an accuracy over 80% at the age of 4 months and over 90% at the age of 8 months. Texture analysis of computed fundus reference images suggests a more heterogeneous organization of the retina in transgenic mice at the age of 8 months in comparison to controls.This study was supported by the Neuroscience Mantero Belard Prize 2015 (Santa
Casa da Misericórdia)(MB-1049-2015), by The Portuguese Foundation for Science
and Technology (PEst-UID/NEU/04539/2013), by FEDER-COMPETE
(POCI-01-0145-FEDER-007440) and Centro 2020 Regional Operational Programme
(CENTRO-01-0145-FEDER-000008: BrainHealth 2020).info:eu-repo/semantics/publishedVersio
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Coherent control of the photoinduced transition in a strongly correlated material
The use of intense tailored light fields is the perfect tool to achieve ultrafast control of electronic properties in quantum materials. Among them, Mott insulators are materials in which strong electron-electron interactions drive the material into an insulating phase. When shining a Mott insulator with a strong laser pulse, the electric field may induce the creation of doublon-hole pairs, triggering a photoinduced transition into a metallic state. In this paper, we take advantage of the threshold character of this photoinduced transition and we propose a setup that consists of a midinfrared laser pulse and a train of short pulses separated by a half period of the midinfrared with alternating phases. By varying the time delay between the two pulses and the internal carrier envelope phase of the short pulses, we achieve control of the phase transition, which leaves its fingerprint at its high harmonic spectrum
Dialectical polyptych: an interactive movie
Most of the known video games developed by big software companies usually establish an approach to the cinematic language in an attempt to create a perfect combination of narrative, visual technique and interaction. Unlike most video games, interactive film narratives normally involve an interruption in time whenever the spectator has to make choices. “Dialectical Polyptych” is an interactive movie included in a project called “Characters looking for a spect-actor”, which aims to give the spectator on-the-fly control over film editing, thus exploiting the role of the spectator as an active subject in the presented narrative. This paper presents a system based on a 3D sensor for tracking the spectator's movements and positions, which allows seamless real-timeinteractivity with the movie. Different positions of the body prompt a change in the angle or shot within each narrative, and hand swipes allow the spectator to alternate between the two parallel narratives, both producing a complementary narrative.info:eu-repo/semantics/publishedVersio
Mass-degenerate Higgs bosons at 125 GeV in the Two-Higgs-Doublet Model
The analysis of the Higgs boson data by the ATLAS and CMS Collaborations
appears to exhibit an excess of h --> gamma\gamma events above the Standard
Model (SM) expectations; whereas no significant excess is observed in h --> ZZ*
--> {four lepton} events, albeit with large statistical uncertainty due to the
small data sample. These results (assuming they persist with further data)
could be explained by a pair of nearly mass-degenerate scalars, one of which is
a SM-like Higgs boson and the other is a scalar with suppressed couplings to
W+W- and ZZ. In the two Higgs doublet model, the observed \gamma\gamma and ZZ*
--> {four lepton} data can be reproduced by an approximately degenerate CP-even
(h) and CP-odd (A) Higgs boson for values of \sin(\beta-\alpha) near unity and
0.7 < \tan\beta < 1. An enhanced \gamma\gamma signal can also arise in cases
where m_h ~ m_H, m_H ~ m_A, or m_h ~ m_H ~ m_A. Since the ZZ* --> {four lepton}
signal derives primarily from a SM-like Higgs boson whereas the \gamma\gamma
signal receives contributions from two (or more) nearly mass-degenerate states,
one would expect a slightly different invariant mass peak in the ZZ* --> {four
lepton} and \gamma\gamma channels. The phenomenological consequences of such
models can be tested with additional Higgs data that will be collected at the
LHC in the near future.Comment: 18 pages, 19 pdf figures, v2: references added, v3&v4: added refs and
explanation
All-optical valley switch and clock of electronic dephasing
2D materials with broken inversion symmetry posses an extra degree of
freedom, the valley pseudospin, that labels in which of the two
energy-degenerate crystal momenta, or , the conducting carriers are
located. It has been shown that shining circularly-polarized light allows to
achieve close to 100% of valley polarization, opening the way to valley-based
transistors. Yet, switching of the valley polarization is still a key challenge
for the practical implementation of such devices due to the short coherence
lifetimes. Recent progress in ultrashort laser technology now allows to produce
trains of attosecond pulses with controlled phase and polarization between the
pulses. Taking advantage of such technology, we introduce a coherent control
protocol to turn on, off and switch the valley polarization at faster
timescales than electronic and valley decoherence, that is, an ultrafast
optical valley switch. We theoretically demonstrate the protocol for hBN and
MoS monolayers calculated from first principles. Additionally, using two
time-delayed linearly-polarized pulses with perpendicular polarization, we show
that we can extract the electronic dephasing time from the valley Hall
conductivity.Comment: 19 pages; 4 figure
Reconstruction of attosecond beating by interference of two-photon transitions in bulk solids
The reconstruction of attosecond beating by interference of two-photon
transitions (RABBIT) is one of the most widely used techniques for resolving
ultrafast electronic dynamics in atomic and molecular systems. As it relies on
the interference of photo-electrons in vacuum, similar interference has never
been contemplated in the bulk of crystals. Here we show that the interference
of two-photon transitions can be recorded directly in the bulk of solids and
read out with standard angle-resolved photo-emission spectroscopy. The phase of
the RABBIT beating in the photoelectron spectra coming from the bulk of solids
is sensitive to the relative phase of the Berry connection between bands and it
experiences a shift of as one of the quantum paths crosses a band. For
resonant interband transitions, the amplitude of the RABBIT oscillation decays
as the pump and probe pulses are separated in time due to electronic
decoherence, providing a simple interferometric method to extract dephasing
times
Assessment of lot shape in business park design
Planning and developing a business park is a complex task, whichdemands integration across various
fields of design and knowledge. The first choice to be made in the design process is relate to the zoning process
and the definition of the lot layout and landscape. These first decisions will constrain all subsequent decisions
concerning utilities, facilities and amenities. For this reason, the assessment of those issues is crucial for the
perception of the overall quality of the business park design. The main goal of this work is to present a simple
indicator which can assess the lot shape in order to optimize the building form and costs, the use of its open
areas, the layout and the economic spacing of roads and the service routes. The indicator lot shape evaluatesthe
performance of the lot design solutions according to the concept of compactness
Urban air dispersion model of a mid-sized city. Validation methodology
Viana do Castelo is a mid-sized city located on the northwest Portuguese seaside, which undertook the challenge of developing an environmental program leading to the integration in the Healthy Cities
European Network. Within this program includes prediction of pollutant concentration for NO2, CO, PM10,
O3 and C6H6. This paper presents the methodology developed to validate the modelled results. Predicted
concentrations were compared against measured concentrations of a chosen pollutant: Carbon Monoxide, CO.
The methodology adopted was based in BOOT statistical approach. Five comparison statistics were calculated
for three test points in order to find out the quality of the modelled results. Additionally, a hourly profile of
predicted versus measured concentrations was developed.(undefined
Os inventários de recursos hídricos subterrâneos como ferramenta de suporte à gestão dos recursos hídricos à escala local
Nos últimos anos a União Europeia produziu diversa legislação relativa aos recursos hídricos subterrâneos, tendo por base a sua preservação, conservação e gestão eficiente. Portugal transpôs e implementou estas orientações, incorporando assim a questão da proteção das águas subterrâneas no planeamento, nomeadamente à escala municipal.Este trabalho pretende evidenciar a utilidade dos inventários de emergências, bem como a sua relação com a análise de vulnerabilidade preconizada na Lei Portuguesa, constituindo assim, metodologias importantes de suporte à gestão destes importantes recursos, tanto a nível municipal como local.Deste modo, apresentam-se os resultados de um inventário de recursos hídricos subterrâneos realizado na pequena bacia hidrográfica da Ribeira de Sá, localizada no concelho de Castelo de Paiva, em Portugal.Os resultados obtidos nesta área reforçam claramente a importância do conhecimento inicial dos recursos existentes, nomeadamente através da inventariação, para que se definam medidas proteção e gestão adequada
Validation study of urban air dispersion model of Viana do Castelo
The City of Viana do Castelo in Portugal has developed an air quality program, which includes
prediction of pollutant concentration for NO2, CO, PM10, O3 and C6H6. A range of numerical models were
used to produce the concentration maps: the ADMS-Urban model for the pollutants dispersion; the Hills
model to calculate air flow and turbulence over complex terrain, including the effects of variable surface
roughness; the CORINAIR v.5 to estimate traffic emissions.
This paper presents the methodology developed to validate the modelled results. Predicted concentrations
were compared against measured concentrations of a chosen pollutant: Carbon Monoxide, CO. Five
comparison statistics were calculated for three test points in order to find out the quality of the modelled
results. Additionally, a hourly profile of predicted versus measured concentrations was developed
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