448 research outputs found
Coastal evolution in a Mediterranean microtidal zone: mid to late Holocene natural dynamics and human management of the Castelló lagoon, NE Spain
© 2016 Ejarque et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. We present a palaeoenvironmental study of the Castelló lagoon (NE Spain), an important archive for understanding long-term interactions between dynamic littoral ecosystems and human management. Combining geochemistry, mineralogy, ostracods, diatoms, pollen, non-pollen palynomorphs, charcoal and archaeo-historical datasets we reconstruct: 1) the transition of the lagoon from a marine to a marginal environment between ∼ 3150 cal BC to the 17 th century AD; 2) fluctuations in salinity; and 3) natural and anthropogenic forces contributing to these changes. From the Late Neolithic to the Medieval period the lagoon ecosystem was driven by changing marine influence and the land was mainly exploited for grazing, with little evidence for impact on the natural woodland. Land-use exploitation adapted to natural coastal dynamics, with maximum marine flooding hampering agropastoral activities between ∼ 1550 and ∼ 150 cal BC. In contrast, societies actively controlled the lagoon dynamics and become a major agent of landscape transformation after the Medieval period. The removal of littoral woodlands after the 8 th century was followed by the expansion of agrarian and industrial activities. Regional mining and smelting activities polluted the lagoon with heavy metals from the ∼ 11 th century onwards. The expansion of the milling industry and of agricultural lands led to the channelization of the river Muga into the lagoon after ∼ 1250 cal AD. This caused its transformation into a freshwater lake, increased nutrient load, and the infilling and drainage of a great part of the lagoon. By tracking the shift towards an anthropogenically-controlled system around∼ 750 yr ago, this study points out Mediterranean lagoons as ancient and heavily-modified systems, with anthropogenic impacts and controls covering multi-centennial and even millennial timescales. Finally, we contributed to the future construction of reliable seashell-based chronologies in NE Spain by calibrating the Banyuls-sur-Mer ▵ R offset with ceramic imports from the Emporiae archaeological site
The role of subsidies in promoting italian joint ventures in least developed and transition economies
This paper analyses the impact of subsidies to promote Italian joint ventures (JVs) with firms in LDC and transition economies. The empirical analysis is carried out on a unique dataset of 172 JVs interviewed during 1998 by means of a closed-answer qualitative-quantitative questionnaire. The main finding of the study is that although there is a significant deadweight component in incentive policy, subsidised firms are significantly more likely to grow. Moreover, JVs comprising new firms (which need to grow to survive) also achieve a higher-than- average employment performance, and so too do (labour intensive) JVs motivated by the search for lower labour costs, and JVs in East European countries
Low-Voltage GaN Based Inverter for Power Steering Application
In the paper, an experimental evaluation of a low voltage Gallium Nitride (GaN) based inverter suitable for power steering application is presented. The inverter switches belong to the last generation of low voltage enhancement-mode normally-off GaN Field-Effect Transistor (FET). The main advantage in the usage of these devices is the high switching frequency capability with consequently volume reduction of the passive components. On the other hand, the layout and the device packaging solution are a challenge to reduce the parasitic inductances. Furthermore, the dv/dt increasing with the switching frequency need a deep investigation in a motor drive
application. The paper deals with the advances and drawbacks of the GaN FETs in two-level Pulse Width Modulation (PWM) motor drive applications providing a piece of detailed experimental evidence and design guidelines
Ecología y geoquímica de ostrácodos como indicadores paleoambientales en ambientes marginales marinos.: Un ejemplo de estudio. La Albufera de Valencia
El presente estudio paleolimnológico se centra en la evolución Holocena de la Albufera de
Valencia, el mayor lago costero oligohalino de la Península Ibérica. Este lago costero ha sido el punto de
mira de numerosos estudios durante el último siglo, sin embargo, se sabía muy poco sobre el origen y
evolución del mismo. Se utilizaron los restos subfósiles de ostrácodos como los mejores bioindicadores
ambientales. Se emprendió un estudio basado en la calibración de una especie de ostrácodo eurihalino
clave, Cyprideis torosa. Los resultados mostraron que la combinación de los nodos de las valvas junto
con los isótopos de oxígeno (δ18O), nos proporcionaba un modelo cuantitativo certero para reconstruir
salinidades. Por otro lado, el Sr/Ca de las valvas de C. torosa estaba altamente correlacionado con el
Sr/Ca del agua, permitiendo así la posibilidad de reconstruir el Sr/Ca de aguas pasadas. Además, se
reafirmó que el δ13CDIC puede ser inferido a partir del δ13C del ostrácodo. Estos resultados, junto con las
técnicas de análisis paleoecológicos se aplicaron en tres secuencias sedimentarias de la Albufera con
distintas longitudes (850 cm, 240 cm y 63 cm). Los sondeos más largos aportaron información sobre las
principales transgresiones marinas que se produjeron durante el Holoceno. Sin embargo, no se encontró
ninguna asociación típicamente marina, sugiriendo así que el lago no estuvo totalmente abierto al mar
durante este periodo. El estudio de los sondeos cortos mostro que la desalinización de la Albufera se
produjo más tarde de lo postulado en estudios previos, probablemente en el último cuarto del siglo XIX.
Las aguas no tratadas de la de las ciudades de alrededor incrementaron la carga de nutrientes en el lago
provocando un proceso drástico de eutrofización durante la mitad y la parte final del siglo XX. La
densa pradera de macrófitos que poblaba el lago desapareció hacia finales de los años 60. Así mismo, los
vertidos incontrolados de las industrias de alrededor del lago y probablemente el incremento de las
actividades cinegéticas en el lago, desde principios del siglo XIX, incrementaron la carga de metales
pesados que todavía hoy permanecen en los sedimentos de la AlbuferaWe undertook a paleolimnological study on the Holocene evolution of the
Albufera de Valencia, the largest coastal oligohaline lake in the Iberian Peninsula,
enclosed in the Albufera Natural Park. The lake has been the focus of many
studies during the last century; however, the origin and the evolution of the
lake remained unknown. Subfossil ostracod remains preserved in lake sediments
were considered as the most suitable bioindicators owing to the significant
relationships between the species distribution and shell chemistry (trace
elements and isotopes) of ostracods and water physical and chemical variables.
The paleolimnology of coastal lakes is a complex and difficult task; hence,
prior to this we undertook a study to calibrate the euryhaline ostracod target
species Cyprideis torosa as a quantitative paleoenvironmental proxy. The results
showed that the combination of both shell nodes and !18O provided an accurate
quantitative model for salinity reconstruction. On the other hand, C. torosa
shell Sr/Ca was highly correlated with water Sr/Ca, allowing the possibility to
reconstruct past water Sr/Ca in a quantitative manner. Additionally, we support
the previous findings that !13CDIC can be inferred from ostracod shell !13C. These
results, together with classical paleoecological analyses and interpretations
based on ostracod paleoassemblages and sediment characteristics were applied
to study three sedimentary sequences from lake Albufera of various lengths (850
cm, 240 cm and 63 cm). The longest two cores provided information about the
main transgressive phases occurred during the mid to late Holocene. However,
a typical marine ostracod fauna was not recorded at a certain unit of the core,
suggesting that the lake was not totally open to the sea during this period. The
highest resolution of the shorter two cores, allowed to establish that the main
desalinization of the Albufera took place later than thought before, probably
in the last quarter of the XIXth century, when an important rice field expansion
took place around the lake. The untreated sewage waters and the change of rice
cultivation methods from surrounding towns increased the nutrient load onto
the lake favoring a drastic eutrophication process during the mid to late XX
century. The dense macrophyte cover disappeared from the lake by the end of
1960 resulting in marked sediment differences (disturbed and anoxic sediment
layer). Furthermore, the uncontrolled spills from the nearby industries and
probably also the increasing hunting activities since the beginning of the XIXth
century increased the heavy metals load remaining in the sediment
Study and micro-Raman characterization of pigments present on majolicas of historical and artistic interest from Gerace, Italy
AbstractIn this work, pigments of majolicas made between the sixteenth century and eighteenth century from Gerace have been characterized by micro-Raman spectroscopy. Majolica, known also as pottery, was originally used to identify all objects made from clay materials. In this work, ten samples were analyzed: two vases, six majolica fragments made in Gerace, one vase of uncertain origin (probably Gerace or Caltagirone) and one vase of Venetian origin. The Raman spectroscopic analysis allowed to identify most of the pigments present on the studied cultural heritage pottery above described. Pigments white, yellow, orange, red, blue, and green have been characterized and their attribution allowed to divide the artwork made in Gerace with those made wherever.
Graphical Abstrac
Convolutional Neural Network-Based Automatic Analysis of Chest Radiographs for the Detection of COVID-19 Pneumonia: A Prioritizing Tool in the Emergency Department, Phase I Study and Preliminary “Real Life” Results
The aim of our study is the development of an automatic tool for the prioritization of COVID-19 diagnostic workflow in the emergency department by analyzing chest X-rays (CXRs). The Convolutional Neural Network (CNN)-based method we propose has been tested retrospectively on a single-center set of 542 CXRs evaluated by experienced radiologists. The SARS-CoV-2 positive dataset (n = 234) consists of CXRs collected between March and April 2020, with the COVID-19 infection being confirmed by an RT-PCR test within 24 h. The SARS-CoV-2 negative dataset (n = 308) includes CXRs from 2019, therefore prior to the pandemic. For each image, the CNN computes COVID-19 risk indicators, identifying COVID-19 cases and prioritizing the urgent ones. After installing the software into the hospital RIS, a preliminary comparison between local daily COVID-19 cases and predicted risk indicators for 2918 CXRs in the same period was performed. Significant improvements were obtained for both prioritization and identification using the proposed method. Mean Average Precision (MAP) increased (p < 1.21 × 10(−21) from 43.79% with random sorting to 71.75% with our method. CNN sensitivity was 78.23%, higher than radiologists’ 61.1%; specificity was 64.20%. In the real-life setting, this method had a correlation of 0.873. The proposed CNN-based system effectively prioritizes CXRs according to COVID-19 risk in an experimental setting; preliminary real-life results revealed high concordance with local pandemic incidence
Optical properties of two complementary samples of intermediate Seyfert galaxies
We present preliminary results of the analysis of optical spectra of two
complementary samples of Seyfert galaxies. The first sample was extracted from
a selection of the 4th Fermi Gamma-ray Large Area Telescope (4FGL) catalog, and
consists of 9 -ray emitting jetted Seyfert galaxies. The second one was
extracted from the Swift-BAT AGN Spectroscopic Survey (BASS), and is composed
of 38 hard-X ray selected Active Galactic Nuclei (AGN). These two samples are
complementary, with the former expected to have smaller viewing angles, while
the latter may include objects with larger viewing angles. We measured emission
line ratios to investigate whether the behavior of these Seyferts can be
explained in terms of obscuration, as suggested by the well-known Unified Model
(UM) of AGN, or if there are intrinsic differences due to the presence of jets,
outflows, or the evolution. We found no indications of intrinsic differences.
The UM remains the most plausible interpretation for these classes of objects
even if some results can be challenging for this model.Comment: 24 pages, 10 figures, conference proceeding "14th Serbian Conference
on Spectral Line Shapes in Astrophysics
An interface capturing method for liquid-gas flows at low-Mach number
Multiphase, compressible and viscous flows are of crucial importance in a
wide range of scientific and engineering problems. Despite the large effort
paid in the last decades to develop accurate and efficient numerical techniques
to address this kind of problems, current models need to be further improved to
address realistic applications. In this context, we propose a numerical
approach to the simulation of multiphase, viscous flows where a compressible
and an incompressible phase interact in the low-Mach number regime. In this
frame, acoustics is neglected but large density variations of the compressible
phase can be accounted for as well as heat transfer, convection and diffusion
processes. The problem is addressed in a fully Eulerian framework exploiting a
low-Mach number asymptotic expansion of the Navier-Stokes equations. A Volume
of Fluid approach (VOF) is used to capture the liquid-gas interface, built on
top of a massive parallel solver, second order accurate both in time and space.
The second-order-pressure term is treated implicitly and the resulting pressure
equation is solved with the eigenexpansion method employing a robust and novel
formulation. We provide a detailed and complete description of the theoretical
approach together with information about the numerical technique and
implementation details. Results of benchmarking tests are provided for five
different test cases
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