9,667 research outputs found
LAGOON LITTER: PRELIMINARY APPROACH AND PROPOSAL OF SAMPLING METHODS FOR THE FUTURE IMPLEMENTATION OF WFD
Lagoons are one of the most productive ecosystems in the world, with unique
hydrodynamic and ecological conditions. They provide many goods and services,
otherwise they are located along coastal areas in which the anthropogenic pressures
are very high, especially for what concerns plastic pollution. These transitional water
ecosystems act as a trap for litter; in particular the impact of plastics could be higher
with respect to marine litter because of the âtrapping effectâ of the lagoons.
For this reason, the aims of this research are to analyze the methods for sampling
plastics in respect to the dimension of the particles, sedimentation and suspension
processes, and water circulation. Up to now, implementation methods for sampling
plastics in order to measure their abundance and distribution are not well investigated,
more efforts should be addressed in achieving consistency of the sampling techniques
as well as standardization.
The research was carried out in the Aquatina Lagoon (South Adriatic Sea, Apulia, Italy).
The investigated plastics were divided in 3 main categories: microplastics (smaller than
5 mm), mesoplastics (between 5 mm and 2.5 cm) and macroplastics (bigger than 2.5
cm).
The lagoon has been divided in different compartments that were separately
considered and sampled: water surface, bottom and banks.
Each compartment was sampled with different sampling methods such as: i) plankton
net (200 ÎŒm) for the water surface, in order to have a better precision about the
abundance and distribution of microplastic; ii) square method was applied for sampling
bottom and banks. Bottom samples were collected using a grab while bank samples
were collected by hand.
Since the quantifying of the plastics is the first step to analyze the consequences of this
anthropogenic impact on human-health, food chain, supply natural and goods and
services of lagoons, here we propose and applied sampling methods for collecting
plastics in different compartments and in order to catch the most common dimensional
categories of plastic particles
Dependencies and Simultaneity in Membrane Systems
Membrane system computations proceed in a synchronous fashion: at each step
all the applicable rules are actually applied. Hence each step depends on the
previous one. This coarse view can be refined by looking at the dependencies
among rule occurrences, by recording, for an object, which was the a rule that
produced it and subsequently (in a later step), which was the a rule that
consumed it. In this paper we propose a way to look also at the other main
ingredient in membrane system computations, namely the simultaneity in the rule
applications. This is achieved using zero-safe nets that allows to synchronize
transitions, i.e., rule occurrences. Zero-safe nets can be unfolded into
occurrence nets in a classical way, and to this unfolding an event structure
can be associated. The capability of capturing simultaneity of zero-safe nets
is transferred on the level of event structure by adding a way to express which
events occur simultaneously
Optical measurements of phase steps in segmented mirrors - fundamental precision limits
Phase steps are an important type of wavefront aberrations generated by large
telescopes with segmented mirrors. In a closed-loop correction cycle these
phase steps have to be measured with the highest possible precision using
natural reference stars, that is with a small number of photons. In this paper
the classical Fisher information of statistics is used for calculating the
Cramer-Rao bound, which determines the limit to the precision with which the
height of the steps can be estimated in an unbiased fashion with a given number
of photons and a given measuring device. Four types of measurement devices are
discussed: a Shack-Hartmann sensor with one small cylindrical lenslet covering
a sub-aperture centred over a border, a modified Mach-Zehnder interferometer, a
Foucault test, and a curvature sensor. The Cramer-Rao bound is calculated for
all sensors under ideal conditions, that is narrowband measurements without
additional noise or disturbances apart from the photon shot noise. This limit
is compared with the ultimate quantum statistical limit for the estimate of
such a step which is independent of the measuring device. For the
Shack-Hartmann sensor, the effects on the Cramer-Rao bound of broadband
measurements, finite sampling, and disturbances such as atmospheric seeing and
detector readout noise are also investigated. The methods presented here can be
used to compare the precision limits of various devices for measuring phase
steps and for optimising the parameters of the devices. Under ideal conditions
the Shack-Hartmann and the Foucault devices nearly attain the ultimate quantum
statistical limits, whereas the Mach-Zehnder and the curvature devices each
require approximately twenty times as many photons in order to reach the same
precision.Comment: 23 pages, 19 figures, to be submitted to Journal of Modern Optic
Romanesque and territory. The construction materials of Sardinian medieval churches: new approaches to the valorization, conservation and restoration
This paper is intended to illustrate a multidisciplinary research project devoted to the study of the constructive materials of the Romanesque churches in Sardinia during the âGiudicatiâ period (11th -13th centuries). The project focuses on the relationship between a selection of monuments and their territory, both from a historical-architectural perspective and from a more modern perspective addressing future restoration works. The methodologies of the traditional art-historical research (study of bibliographic, epigraphic and archival sources, formal reading of artifacts) are flanked by new technologies: digital surveys executed with a 3D laser-scanner, analyses of the materials (stones, mortars, bricks) with different instrumental methods: X-ray fluorescence (XRF) and inductively coupled mass spectrometry (ICP-MS) for chemical composition, X-ray diffractometer (XRD) to determine the alteration phases (e.g., soluble salts), optical microscopy and electronic (SEM) to study textures, mineral assemblages and microstructures, termogravimetric/differential scanning, calorimetric analysis (TG/DTA) for the composition of the binder mortars.
This multidisciplinary approach allows the achieving of important results in an archaeometric context: 1) from a historical point of view, with the possible identification of ancient traffics, trade routes, sources of raw materials, construction phases, wall textures; 2) from a conservative point of view, by studying chemical and physical weathering processes of stone materials compatible for replacement in case of future restoration works.
Sardinian Romanesque architectural heritage is particularly remarkable: about 200 churches of different types and sizes, with the almost exclusive use of cut stones. Bi- or poly-chromy, deriving from the use of different building materials, characterizes many of these monuments, becoming also a vehicle for political and cultural meanings. The paper will present some case studies aimed to illustrate the progress of the project and the results achieved
Leave-one-out prediction error of systolic arterial pressure time series under paced breathing
In this paper we show that different physiological states and pathological
conditions may be characterized in terms of predictability of time series
signals from the underlying biological system. In particular we consider
systolic arterial pressure time series from healthy subjects and Chronic Heart
Failure patients, undergoing paced respiration. We model time series by the
regularized least squares approach and quantify predictability by the
leave-one-out error. We find that the entrainment mechanism connected to paced
breath, that renders the arterial blood pressure signal more regular, thus more
predictable, is less effective in patients, and this effect correlates with the
seriousness of the heart failure. The leave-one-out error separates controls
from patients and, when all orders of nonlinearity are taken into account,
alive patients from patients for which cardiac death occurred
Hepatocellular carcinoma locoregional therapies for patients in the waiting list. Impact on transplantability and recurrence rate
The practice of treating candidates to liver transplantation (LT) for hepatocellular carcinoma (HCC) with locoregional therapies is common in most transplant centers. However, for T1 tumors and expected waiting times to LT <6 months, there is no evidence that these treatments are beneficial. For T2 tumors and for longer waiting times, neo-adjuvant treatments are usually performed with transarterial chemoembolization (TACE), ablation techniques, and liver resection in selected cases. The treatment choice should be based on the BCLC staging system. At present, there is no evidence of the superiority of ablation/resection vs. TACE, but some studies showed better results of the former in achieving a complete response. The response to neo-adjuvant treatments should be evaluated through mRECIST criteria, but few studies adopted these criteria and properly analyzed factors affecting response. The simultaneous evaluation of the impact of neo-adjuvant therapies on dropout rate, post-LT HCC recurrence and patient survival is rarely reported. Tumor stage and volume, alpha-fetoprotein levels, response to treatments and liver function affect pre-LT outcomes. These same factors, together with vascular invasion and poor tumor differentiation are major determinants of poor post-LT outcomes. Due to the low number of prospective studies with well defined entry criteria and the variability of results, the role of downstaging is still to be defined. Novel molecular markers seem promising for the estimation of prognosis and/or response to treatments. With a persistent scarcity of organ donors, neo-adjuvant treatments can help in identifying patients with different probabilities of cancer progression, and consequently in balancing the priority of HCC and non-HCC-candidates through revised additional scores for HCC
Relationships between size and abundance in beach plastics: A power-law approach
Sandy beaches are one of the most relevant coastal environments in terms of socio-ecological and economical
value. So, the presence and accumulation of plastic litter determines a degradation of these values, and calls for
management actions for cleaning are required. In this research, we investigated the features of plastic litter
distribution on a Mediterranean beach in relation to size and abundance of the sampled items. Simple allometric
models were applied with the aim to provide a parsimonious tool for estimating the amount and sizes of the
beach plastic litter. The results show effective relations between size and abundance of plastic items according to
the power-law distribution. This relationship could support decision-makers to estimate the total amount of
beach plastics through the application of a simple model instead of more complex models requiring the estimation
of many parameters and the availability of large datasets
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