2,789 research outputs found

    Elastic-Net Regularization in Learning Theory

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    Within the framework of statistical learning theory we analyze in detail the so-called elastic-net regularization scheme proposed by Zou and Hastie for the selection of groups of correlated variables. To investigate on the statistical properties of this scheme and in particular on its consistency properties, we set up a suitable mathematical framework. Our setting is random-design regression where we allow the response variable to be vector-valued and we consider prediction functions which are linear combination of elements ({\em features}) in an infinite-dimensional dictionary. Under the assumption that the regression function admits a sparse representation on the dictionary, we prove that there exists a particular ``{\em elastic-net representation}'' of the regression function such that, if the number of data increases, the elastic-net estimator is consistent not only for prediction but also for variable/feature selection. Our results include finite-sample bounds and an adaptive scheme to select the regularization parameter. Moreover, using convex analysis tools, we derive an iterative thresholding algorithm for computing the elastic-net solution which is different from the optimization procedure originally proposed by Zou and HastieComment: 32 pages, 3 figure

    Microstructure and chemical composition of Roman orichalcum coins emitted after the monetary reform of Augustus (23 B.C.)

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    A collection of ancient Roman orichalcum coins, i.e., a copper-zinc alloy, minted under the reigns from Caesar to Domitianus, have been characterised using scanning electron microscopy (SEM-EDS) and electron microprobe analysis (EMPA). We studied, for the first time, coins emitted by Romans after the reforms of Augustus (23 B.C.) and Nero (63-64 A.D). These coins, consisting of asses, sestertii, dupondii and semisses, were analysed using non- and invasive analyses, aiming to explore microstructure, corrosive process and to acquire quantitative chemical analysis. The results revealed that the coins are characterized by porous external layers, which are affected by dezincification and decuprification processes. As pictured by the X-ray maps, the elemental distribution of Cu and Zn shows patterns of depletion that in some cases penetrate in deep up to 1 mm. The composition of the un-corroded nucleus is a Cu-Zn alloy containing up to 30% of Zn, typical of coins produced via cementation process

    Effect of Scatterering on Coherent Anti-Stokes Raman Scattering (CARS) signals

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    We develop a computational framework to examine the factors responsible for scattering-induced distortions of coherent anti-Stokes Raman scattering (CARS) signals in turbid samples. We apply the Huygens-Fresnel Wave-based Electric Field Superposition (HF-WEFS) method combined with the radiating dipole approximation to compute the effects of scattering-induced distortions of focal excitation fields on the far-field CARS signal. We analyze the effect of spherical scatterers, placed in the vicinity of the focal volume, on the CARS signal emitted by different objects (2{\mu}m diameter solid sphere, 2{\mu}m diameter myelin cylinder and 2{\mu}m diameter myelin tube). We find that distortions in the CARS signals arise not only from attenuation of the focal field but also from scattering-induced changes in the spatial phase that modifies the angular distribution of the CARS emission. Our simulations further show that CARS signal attenuation can be minimized by using a high numerical aperture condenser. Moreover, unlike the CARS intensity image, CARS images formed by taking the ratio of CARS signals obtained using x- and y-polarized input fields is relatively insensitive to the effects of spherical scatterers. Our computational framework provide a mechanistic approach to characterizing scattering-induced distortions in coherent imaging of turbid media and may inspire bottom-up approaches for adaptive optical methods for image correction.Comment: 15 pages, 7 figure

    Respirando en la cima del mundo

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    Desde la antigüedad, el hombre se ha sentido atraído por la superación de los obstáculos naturales y por la exploración de lo desconocido, tanto en la geografía como en la ciencia. Es posible que las emociones de un montañista que alcanza su cumbre y las de un científico que llega a su descubrimiento sean muy similares. Para quien haya hecho sus intentos en cualquiera de estos campos, es factible evocarlas, aunque resulta difícil imaginar la suma de ambas. Quizás habría que preguntar a los investigadores de la expedición Caudwell Xtreme Everest (CXE), así como a sus predecesores, que consiguieron ambas metas. CXE es una mega-expedición científica que involucró a más de 200 montañistas y científicos instalados entre abril y mayo de 2007 en el pico más alto del mundo, con la intención de recabar múltiples datos fisiológicos en tan difíciles condiciones. Resulta admirable el esfuerzo logístico de semejante expedición, que involucró la instalación de varias toneladas de equipo técnico y médico y el transporte de muestras entre campamentos.Fil: de Vito, Eduardo. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Médicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Arce, Santiago C.. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Médicas; Argentin

    Factors affecting the vaccination choices of pregnant women for their children. A systematic review of the literature

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    In recent years, an increase in vaccine hesitancy has led to a decrease in vaccination coverage in several countries. We conducted a systematic review of studies that assessed knowledge of and attitudes toward pediatric vaccinations, and the vaccination choices and their determinants among pregnant women. A total of 6,277 records were retrieved, and 16 full texts were included in the narrative synthesis. The published literature on the topic shows that, overall, pregnant women believe that vaccines are important for the protection of their children and the community, but various concerns and misunderstandings persist around vaccine safety and efficacy, which reduce the trust of expectant mothers in immunization. Nevertheless, such attitudes and choices vary depending on the vaccine being considered and the corresponding determinants should therefore be studied in the context of each specific vaccination. Further research on this topic is needed, particularly in non-western countries

    Emergency Department Overcrowding. A Retrospective Spatial Analysis and the Geocoding of Accesses. A Pilot Study in Rome

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    The overcrowding of first aid facilities creates considerable hardship and problems which have repercussions on patients’ wellbeing, the time needed for a diagnosis, and on the quality of the assistance. The basic objective of this contribution, based on the data collected by the Hospital Policlinico Umberto I in Rome (Lazio region, Italy), is to carry out a territorial screening of the municipality using GIS applications and spatial analyses aimed at reducing—in terms of triage—code white (inappropriate) attendances, after having identified the areas of greatest provenance of improperly used emergency room access. Working in a GIS environment and using functions for geocoding, we have tested an experimental model aimed at giving a close-up geographical-sanitary look at the situation: recognizing the territorial sectors in Rome which contribute to amplifying the Policlinico Umberto I emergency room overcrowding; leading up to an improvement of the situation; promoting greater awareness and knowledge of the services available on the territory, a closer relationship between patient and regular doctor (general practitioner, GP) or Local Healthcare Unit and a more efficient functioning of the emergency room. In particular, we have elaborated a “source” map from which derive all the others and it is a dot map on which all the codes white have been geolocalized on a satellite image through geocoding. We have produced three sets made up of three digital cartographic elaborations each, constructed on the census sections, the census areas and the sub-municipal areas, according to data aggregation, for absolute and relative values, and using different templates. Finally, following the same methodology and steps, we elaborated another dot map about all the codes red to provide another kind of information and input for social utility. In the near future, this system could be tested on a platform that spatially analyzes the emergency department (ED) accesses in near-real-time in order to facilitate the identification of critical territorial issues and intervene in a shorter time to regulate the influx of patients to the ED

    Measles among healthcare workers in Italy. Is it time to act?

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    Vaccination of healthcare workers (HCWs) against measles is strongly recommended in Europe. In this study, we examined the impact of measles on Italian HCWs by systematically and quantitatively analyzing measles cases involving HCWs over time and by identifying the epidemiological characteristics of the respective measles outbreaks. We retrieved data on measles cases from the Italian national integrated measles and rubella surveillance system from January 2013 to May 2019. Additionally, we performed a systematic review of the literature and an analysis of the measles and rubella aggregate outbreaks reporting forms from 2014 to 2018. Our review suggests that preventing measles infection among HCWs in disease outbreaks may be crucial for the elimination of measles in Italy. National policies aiming to increase HCW immunization rates are fundamental to the protection of HCWs and patients, will limit the economic impact of outbreaks on the institutions affected and will help achieve the elimination goal

    Impairment of the autophagic flux in astrocytes intoxicated by trimethyltin

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    Autophagy is a lysosomal catabolic route for protein aggregates and damaged organelles which in different stress conditions, such as starvation, generally improves cell survival. An impairment of this degradation pathway has been reported to occur in many neurodegenerative processes. Trimethyltin (TMT) is a potent neurotoxin present as an environmental contaminant causing tremors, seizures and learning impairment in intoxicated subjects. The present data show that in rat primary astrocytes autophagic vesicles (AVs) appeared after few hours of TMT treatment. The analysis of the autophagic flux in TMT-treated astrocytes was consistent with a block of the late stages of autophagy and was accompanied by a progressive accumulation of the microtubule associated protein light chain 3 (LC3) and of p62/SQSTM1. Interestingly, an increased immunoreactivity for p62/SQSTM1 was also observed in hippocampal astrocytes detected in brain slices of TMT-intoxicated rats. The time-lapse recordings of AVs in EGFP-mCherry-LC3B transfected astrocytes demonstrated a reduced mobility of autophagosomes after TMT exposure respect to control cells. The observed block of the autophagic flux cannot be overcome by known autophagy inducers such as rapamycin or 0.5mM lithium. Although ineffective when used at 0.5mM, lithium at higher concentrations (2mM) was able to protect astrocyte cultures from TMT toxicity. This effect correlated well with its ability to determine the phosphorylation/inactivation of glycogen kinase synthase-3β (GSK-3β)

    Genomics knowledge and attitudes among European public health professionals. Results of a cross-sectional survey

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    Background The international public health (PH) community is debating the opportunity to incorporate genomic technologies into PH practice. A survey was conducted to assess attitudes of the European Public Health Association (EUPHA) members towards their role in the implementation of public health genomics (PHG), and their knowledge and attitudes towards genetic testing and the delivery of genetic services. Methods EUPHA members were invited via monthly newsletter and e-mail to take part in an online survey from February 2017 to January 2018. A descriptive analysis of knowledge and attitudes was conducted, along with a univariate and multivariate analysis of their determinants. Results Five hundred and two people completed the questionnaire, 17.9% were involved in PHG activities. Only 28.9% correctly identified all medical conditions for which there is (or not) evidence for implementing genetic testing; over 60% thought that investing in genomics may divert economic resources from social and environmental determinants of health. The majority agreed that PH professionals may play different roles in incorporating genomics into their activities. Better knowledge was associated with positive attitudes towards the use of genetic testing and the delivery of genetic services in PH (OR = 1.48; 95% CI 1.01–2.18). Conclusions Our study revealed quite positive attitudes, but also a need to increase awareness on genomics among European PH professionals. Those directly involved in PHG activities tend to have a more positive attitude and better knowledge; however, gaps are also evident in this group, suggesting the need to harmonize practice and encourage greater exchange of knowledge among professionals
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