1,400 research outputs found
Control of conditional pattern with polarization entanglement
Conditional interference patterns can be obtained with twin photons from
spontaneous parametric down-conversion and the phase of the pattern can be
controlled by the relative transverse position of the signal and idler
detectors. Using a configuration that produces entangled photons in both
polarization and transverse momentum we report on the control of the
conditional patterns by acting on the polarization degree of freedom.Comment: Submitted for publication in Optics Communication
Confined Placental Mosaicism in Chorionic Vilus Sampling - Case Report
Objectives: Chorionic Vilus Sampling (CVS) has several advantages over amniocentesis: it may be performed at an earlier gestational age, the results are quicker to obtain and there’s a lower miscarriage risk – 1%. However, the higher prevalence of discrepant fetal and vilus sampling material’s karyotype findings is a disadvantage of this technique – 0.5%. This is caused, amongst other causes, by placental mosaicism which consists of two genetically different cell lines. There are three types of placental mosaicism according to the abnormal cell line location: Type I – in the cytotrophoblast; Type II – in the vilus’ stroma; Type III – in both the above locations. Material and Methods: We present a case report about a 36-year-old pregnant woman going through our Department’s 1st trimester combined screening program; a CVS was performed, which showed Confined Placental Mosaicism (CPM).
Results and Conclusion: Although the pregnant woman was in the low-risk group for aneuploidy, the patient wanted the cytogenetic study to be performed in order to reduce maternal anxiety. CVS was performed at the gestational age of 12 weeks + 5 days and the karyotype was 47XY+2/46XY. For the correct interpretation of this data an amniocentesis was performed at the gestational age of 15 weeks + 6 days, which showed a 46XY karyotype. We therefore conclude that the cytogenetic analysis of the CVS was the result of a CPM. A careful follow-up including fetal echocardiogram and seriated ultrasonographic monitoring was used to safely exclude malformations and fetal growth restriction. We verified no occurences throughout pregnancy, delivery and perinatal period. CVS practice was recently implemented in our country and has many advantages over amniocentesis. Besides the fact that an earlier gestational age usually means less affective bonding to the fetus and therefore makes medical termination of pregnancy somewhat less difficult, one should consider specific situations like the one reported in which CPM may be diagnosed. This condition is associated with increased risk of fetal growth restriction, so the clinician should be aware of the need for a more careful follow-up, since perinatal complications, which should be anticipated and treated, can be expected in 16-21% of these cases
Experimental methods on the determination of the mechanical properties of concrete at high temperatures
Até ao momento não existem ainda procedimentos padrão para ensaios a altas temperaturas no betão, pelo que têm sido realizados ensaios a temperaturas elevadas adaptados de ensaios à temperatura ambiente. Os ensaios têm-se dividido entre ensaios a altas temperaturas e residuais após aquecimento e arrefecimento. O primeiro procedimento é mais adequado para a determinação das propriedades mecânicas do betão durante um incêndio enquanto o segundo procedimento é usado para determinar a resistência residual do betão após incêndio. Nesta comunicação apresentam-se os resultados de ensaios realizados por diferentes autores para a determinação das propriedades mecânicas residuais do betão após aquecimento e arrefecimento. Os resultados apresentados dizem respeito a resistências residuais à compressão, tração e flexão e módulo de elasticidade. Os métodos de ensaio aplicados são devidamente descritos e os resultados obtidos são objeto de análises comparativas.ABSTRACT: So far there are no standard procedures for testing concrete at high temperatures which have been conducted according to the ones at ambient temperature. The tests have been divided between tests at high temperatures and residual after heating and cooling. The first procedure is appropriate for determining the mechanical properties of concrete during fire while the second is used to determine the residual mechanical properties of concrete after fire. In this paper are presented the results of tests carried out by different authors for assessing the residual mechanical properties of concrete after heating and cooling. The results presented are respecting to residual compressive, tensile and flexural strength and elasticity modulus. The test methods are described and results obtained are compared
Conservation of Orbital Angular Momentum in Stimulated Down-Conversion
We report on an experiment demonstrating the conservation of orbital angular
momentum in stimulated down-conversion. The orbital angular momentum is not
transferred to the individual beams of the spontaneous down-conversion, but it
is conserved when twin photons are taken individually. We observe the
conservation law for an individual beam of the down-conversion through
cavity-free stimulated emission.Comment: Submitted for publication in Phys. Rev. Let
Structural fluctuations and quantum transport through DNA molecular wires: a combined molecular dynamics and model Hamiltonian approach
Charge transport through a short DNA oligomer (Dickerson dodecamer) in
presence of structural fluctuations is investigated using a hybrid
computational methodology based on a combination of quantum mechanical
electronic structure calculations and classical molecular dynamics simulations
with a model Hamiltonian approach. Based on a fragment orbital description, the
DNA electronic structure can be coarse-grained in a very efficient way. The
influence of dynamical fluctuations arising either from the solvent
fluctuations or from base-pair vibrational modes can be taken into account in a
straightforward way through time series of the effective DNA electronic
parameters, evaluated at snapshots along the MD trajectory. We show that charge
transport can be promoted through the coupling to solvent fluctuations, which
gate the onsite energies along the DNA wire
Complex Network Tools to Understand the Behavior of Criminality in Urban Areas
Complex networks are nowadays employed in several applications. Modeling
urban street networks is one of them, and in particular to analyze criminal
aspects of a city. Several research groups have focused on such application,
but until now, there is a lack of a well-defined methodology for employing
complex networks in a whole crime analysis process, i.e. from data preparation
to a deep analysis of criminal communities. Furthermore, the "toolset"
available for those works is not complete enough, also lacking techniques to
maintain up-to-date, complete crime datasets and proper assessment measures. In
this sense, we propose a threefold methodology for employing complex networks
in the detection of highly criminal areas within a city. Our methodology
comprises three tasks: (i) Mapping of Urban Crimes; (ii) Criminal Community
Identification; and (iii) Crime Analysis. Moreover, it provides a proper set of
assessment measures for analyzing intrinsic criminality of communities,
especially when considering different crime types. We show our methodology by
applying it to a real crime dataset from the city of San Francisco - CA, USA.
The results confirm its effectiveness to identify and analyze high criminality
areas within a city. Hence, our contributions provide a basis for further
developments on complex networks applied to crime analysis.Comment: 7 pages, 2 figures, 14th International Conference on Information
Technology : New Generation
Evaluation of Xgboost and Lgbm Performance in Tree Species Classification with Sentinel-2 Data
Los, H., Mendes, G. S., Cordeiro, D., Grosso, N., Costa, H., Benevides, P., & Caetano, M. (2021). Evaluation of Xgboost and Lgbm Performance in Tree Species Classification with Sentinel-2 Data. In IGARSS 2021 - 2021 IEEE International Geoscience and Remote Sensing Symposium: Proceedings (pp. 5803-5806). IEEE. https://doi.org/10.1109/IGARSS47720.2021.9553031Tree species classification with satellite data has become more and more popular since Sentinel-2 launch. We compared efficacy and effectiveness of Extreme Gradient Boosting (XGBoost) and Light Gradient Boosting Machine (LGBM) with widely used in remote sensing Random Forest (RF), Support Vector Machine (SVM) and K-Nearest Neighbour (KNN) algorithms. Analyses were performed over an area in Portugal with multi-temporal Sentinel-2 data registered in April, June, August and October 2018. The selected classes were: cork oak, holm oak, eucalyptus, other broadleaved, maritime pine, stone pine and other coniferous. Algorithm efficacy was measured through F1-score and accuracy while efficiency was measured through the median time needed for each fit. XGBoost and LGBM outperformed efficacy of other algorithms, which was already high (above 90% for the best variant of each algorithm). In terms of efficacy, LGBM overcame all algorithms, including XGBoost.authorsversionpublishe
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