189 research outputs found
Aeschylus fr. 486 Radt, tragic homerisms, and ancient scholarship on Sophocles
No full textThe paper contends that the gloss μενοινᾷ... ὀρέγεται attributed to Aeschylus (fr. 486) by Schol. M Od. 13.381 actually refers to Sophocles Ajax 341, as once suggested by Ludwich. The gloss was probably meant to explain μενοινᾷ by means o fὀρέξατο (Il. 6.466) and may be another relic of a broader comparison between S. Aj. 333-595 and Il. 6.369-502 attested in the scholia vetera to Sophocles
Determination of semi-volatile organic compounds adsorbed on the surface of suspended particulate matter
No full textComparing the Performance of Teflon and Quartz Membrane Filters Collecting Atmospheric PM: Influence of Atmospheric Water
No full textMass concentration and chemical composition of PM10 and PM2.5 was measured during eight one-month winter and summer field studies carried out in the Po Valley (Northern Italy). PM was daily collected on Teflon (T) and on quartz (Q) filters set side-by-side. During the summer periods the differences between the mass concentrations measured on the two filters (T-Q) were within the range of experimental error, while statistically significant positive differences were detected during the winter periods. The sum of the chemical analyses (elements, ions, elemental and organic carbon) allowed the achievement of satisfactory mass closure during the summer periods, while unaccounted masses of the order of 10-20% of the PM mass measured on Teflon were detected during the winter periods. Unaccounted mass and T-Q differences increased during periods of high atmospheric stability, when the ammonium nitrate concentration also increased rapidly. Unaccounted masses and T-Q differences can be attributed to PM-bound and PM-adsorbed water
Performance evaluation of a very-low-volume sampler for atmospheric particulate matter
No full textA cheap and small device for sampling atmospheric particulate matter (PM) has been recently developed. It works at a very low flow rate (0.5 L min–1) and is able to collect the atmospheric aerosol on filters, allowing subsequent chemical analyses. The samplings have a long duration (1–2 months), and the devices can be used to make cheap networks over a territory. These very-low-volume samplers (VLVS) can be used to trace long-term concentration variations and to draw up concentration maps of PM and its chemical components. The performance of the VLVS was evaluated in terms of measurement repeatability and of agreement with the results obtained when using a 2.3 m3 h–1 reference sampler (REF). The study period was 1 year. The considered PM components were ions, polycyclic aromatic hydrocarbons (PAHs), levoglucosan and elements. The repeatability of the measurements was very good for all the examined PM components: the standard deviation of 3 replicates (co-located samplers) over 9 measurement periods was in the range 2.0–5.5% for ions, 10–17% for PAH, 5.2% for levoglucosan and 5.6–16% for elements. It was 8.2% for the PM mass concentration. This satisfactory performance indicates that the VLVSs can be reliably used to evaluate the spatial variability and to draw concentration maps of PM and PM components. A very good agreement with the reference sampler was obtained for ions, with the only exception of ammonium nitrate and ammonium chloride (VLVS values were up to 10–20% lower than the reference values), levoglucosan and elements. In the case of PAH, instead, the ratio VLVS/REF was in the range 1.2–1.6 for 4-ring congeners and 0.4–0.8 for 5-and 6-ring congeners. For all the congeners, anyway, these typical ratios were kept, with small variations, during the whole study period
Inorganic constituents of urban air pollution in the Lazio region (Central Italy)
No full textA field study was carried out at six locations
in the Lazio region (Central Italy) aimed at characterising
atmospheric particulate matter (PM10 and PM2.5)
from the point of viewof the chemical composition and
grain size distribution of the particles, the mixing properties
of the atmosphere, the frequency and relevance
of natural events. The combination of four different
analytical techniques (ion chromatography, X-ray fluorescence
and ICP for inorganic components, thermooptical
analysis for carbon compounds) yielded sound
results in terms of characterisation of the air masses.
During the first three months of the study (October-
December 2004), many pollution events of natural (seasalt
or desert dust episodes) or anthropogenic nature
were identified and characterised. More than 90% of
the collected mass was identified by chemical analysis.
The central role played by the mixing properties of the
lower atmosphere when pollution events occurred was
highlighted. The results show a major impact of primary
anthropogenic pollutants on traffic stations and a
homogeneous distribution of secondary pollutants over
the regional area. An evaluation of the sources of PM and an identification of possible reliable tracers were
obtained using a chemical fractionation procedure
Polveri fini” project:atmospheric pollution from natural and anthropogenic sources in the lazio region
No full textToward brain-heart computer interfaces: A study on the classification of upper limb movements using multisystem directional estimates
No full textObjective. Brain-computer interfaces (BCIs) exploit computational features from brain signals to perform a given task. Despite recent neurophysiology and clinical findings indicating the crucial role of functional interplay between brain and cardiovascular dynamics in locomotion, heartbeat information remains to be included in common BCI systems. In this study, we exploit the multidimensional features of directional and functional interplay between electroencephalographic and heartbeat spectra to classify upper limb movements into three classes. Approach. We gathered data from 26 healthy volunteers that performed 90 movements; the data were processed using a recently proposed framework for brain-heart interplay (BHI) assessment based on synthetic physiological data generation. Extracted BHI features were employed to classify, through sequential forward selection scheme and k-nearest neighbors algorithm, among resting state and three classes of movements according to the kind of interaction with objects. Main results. The results demonstrated that the proposed brain-heart computer interface (BHCI) system could distinguish between rest and movement classes automatically with an average 90% of accuracy. Significance. Further, this study provides neurophysiology insights indicating the crucial role of functional interplay originating at the cortical level onto the heart in the upper limb neural control. The inclusion of functional BHI insights might substantially improve the neuroscientific knowledge about motor control, and this may lead to advanced BHCI systems performances
Assessing the contribution of water to the mass closure of PM10
No full textThe data obtained during a number of field studies aimed at determining the chemical composition of atmospheric particulate matter (PM) have shown that the measurement of the main PM components (main elements, ions, elemental carbon, organic carbon) was generally sufficient to obtain a reasonable mass closure. Notwithstanding, a wide gap between PM mass concentration and reconstructed mass was observed in two peculiar environmental conditions: desert dust intrusion and severe atmospheric stability episodes characterized by very high ammonium nitrate concentration. In these two cases, the mass closure improved significantly by adding the concentration of PM-bound water. Water was determined by using a coulometric Karl-Fisher system equipped with a controlled heating device; the method was able to separate different water contributions released in different temperature ranges from 50 to 250 °C. In our field studies the amount of water associated to ammonium salts in winter stability conditions was mostly dependent on ammonium nitrate concentration and constituted up to 22% of the total PM10 mass; the specific water contribution linked to ammonium salts (released in the temperature range 180-250 °C) constituted up to 30% of the ammonium nitrate mass. It was confirmed that in these extreme conditions quartz and Teflon filters behave differently: when measured on quartz filters, PM concentration was lower than on Teflon, the mass closure was satisfactory and the concentration of water was presumably very low. In the case of desert dust episodes, water was up to 10% of total PM10 mass; the specific water contribution linked to desert dust (released in the temperature range 100-180 °C) constituted about 5% of the mass of soil components. In other environmental situations, such as urban environments, marine atmosphere and rural areas, the concentration of PM-bound water was below 2-3 μg/m3
Fulvic acids in microlayer waters of the Gerlache Inlet Sea (Anmtartica):Their distribution in dissolved and particulate phases
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