4,289 research outputs found
elemental concentration in atmospheric particulate matter estimation of nanoparticle contribution
Atmospheric nanoparticles (NPs) are often contained in aggregates or included in larger particles. We show that some of these structures can be crushed in water media by the application of ultrasounds, leading to a suspension of insoluble NPs. The contribution of these NPs to the total elemental concentration is evaluated as the difference between the inductively coupled plasma (ICP-MS) analysis before and after the elution of the suspension from an ion exchange cartridge. Total elemental content in PM can be therefore fractionated into three contributions - soluble species, solid NPs released from larger structures, insoluble particles - that may likely have different health and environmental effects. The method was applied to both Certified Material NIST 1649a and size-segregated atmospheric PM samples collected by a 13-stage impactor. The results indicate that alkaline and alkaline earth metals are found in the suspension only as watersoluble species, also when they are contained in the fine fraction of PM. Instead, a significant fraction of most elements typically emitted from combustion sources (Pb, Sb, Sn, Cd, V and As) is present in fine PM as insoluble nanoparticles that are easily dispersed in water under ultrasound application
Gastroenteritis Outbreak at Holiday Resort, Central Italy
Gastroenteritis Outbreak at Holiday Resort, Central Ital
Synchrotron radiation microtomography of musical instruments: a non-destructive monitoring technique for insect infestations
X-ray computed tomography is becoming a common technique for the structural analysis of samples of cultural relevance, providing luthiers, art historians, conservators and restorators with a unique tool for the characterization of musical instruments. Synchrotron-radiation phase-contrast microtomography is an ideal technique for the non-destructive 3D analysis of samples where small lowabsorbing details such as larvae and eggs can be detected. We report results from the first feasibility studies performed at the Elettra synchrotron laboratory, where the 1494 organ by Lorenzo Gusnasco da Pavia has been studied. Together with important information about the structural conditions, the presence of xylophages could be detected and characterized
Characterization of PM10 sources in the central Mediterranean
The Mediterranean Basin atmosphere is influenced by both strong natural and
anthropogenic aerosol emissions and is also subject to important climatic
forcings. Several programs have addressed the study of the Mediterranean
basin; nevertheless important pieces of information are still missing. In
this framework, PM10 samples were collected on a daily basis on the
island of Lampedusa (35.5° N, 12.6° E; 45 m a.s.l.),
which is far from continental pollution sources (the nearest coast, in
Tunisia, is more than 100 km away). After mass gravimetric measurements,
different portions of the samples were analyzed to determine the ionic
content by ion chromatography (IC), the soluble metals by inductively
coupled plasma atomic emission spectrometry (ICP-AES), and the total
(soluble + insoluble) elemental composition by particle-induced x-ray
emission (PIXE). Data from 2007 and 2008 are used in this study.
The Positive Matrix Factorization (PMF) model was applied to the 2-year long
data set of PM10 mass concentration and chemical composition to assess
the aerosol sources affecting the central Mediterranean basin. Seven sources
were resolved: sea salt, mineral dust, biogenic emissions, primary
particulate ship emissions, secondary sulfate, secondary nitrate, and
combustion emissions. Source contributions to the total PM10 mass were
estimated to be about 40 % for sea salt, around 25 % for mineral dust,
10 % each for secondary nitrate and secondary sulfate, and 5 % each for
primary particulate ship emissions, biogenic emissions, and combustion
emissions. Large variations in absolute and relative contributions are found
and appear to depend on the season and on transport episodes. In addition,
the secondary sulfate due to ship emissions was estimated and found to
contribute by about one-third to the total sulfate mass. Results for the
sea-salt and mineral dust sources were compared with estimates of the same
contributions obtained from independent approaches, leading to an estimate
of the water content bound to the sea salt in the marine source
Constraining the ship contribution to the aerosol of the Central Mediterranean
Abstract. Particulate matter with aerodynamic diameters lower than 10 µm, (PM10) aerosol samples were collected during summer 2013 within the framework of the Chemistry and Aerosol Mediterranean Experiment (ChArMEx) at two sites located north (Capo Granitola) and south (Lampedusa Island), respectively, of the main Mediterranean shipping route in the Straight of Sicily. The PM10 samples were collected with 12 h time resolutions at both sites. Selected metals, main anions, cations and elemental and organic carbon were determined. The evolution of soluble V and Ni concentrations (typical markers of heavy fuel oil combustion) was related to meteorology and ship traffic intensity in the Straight of Sicily, using a high-resolution regional model for calculation of back trajectories. Elevated concentration of V and Ni at Capo Granitola and Lampedusa are found to correspond with air masses from the Straight of Sicily and coincidences between trajectories and positions of large ships; the vertical structure of the planetary boundary layer also appears to play a role, with high V values associated with strong inversions and a stable boundary layer. The V concentration was generally lower at Lampedusa than at Capo Granitola V, where it reached a peak value of 40 ng m−3. Concentrations of rare earth elements (REEs), La and Ce in particular, were used to identify possible contributions from refineries, whose emissions are also characterized by elevated V and Ni amounts; refinery emissions are expected to display high La ∕ Ce and La ∕ V ratios due to the use of La in the fluid catalytic converter systems. In general, low La ∕ Ce and La ∕ V ratios were observed in the PM samples. The combination of the analyses based on chemical markers, air mass trajectories and ship routes allows us to unambiguously identify the large role of the ship source in the Straight of Sicily. Based on the sampled aerosols, ratios of the main aerosol species arising from ship emission with respect to V were estimated with the aim of deriving a lower limit for the total ship contribution to PM10. The estimated minimum ship emission contributions to PM10 were 2.0 µg m−3 at Lampedusa and 3.0 µg m−3 at Capo Granitola, corresponding with 11 and 8.6 % of PM10, respectively
Dense gas in nearby galaxies XVI. The nuclear starburst environment in NGC4945
A multi-line millimeter-wave study of the nearby starburst galaxy NGC 4945
has been carried out using the Swedish-ESO Submillimeter Telescope (SEST). The
study covers the frequency range from 82 GHz to 354 GHz and includes 80
transitions of 19 molecules. 1.3 mm continuum data of the nuclear source are
also presented. A large number of molecular species indicate the presence of a
prominent high density interstellar gas component characterized by cm. Abundances of molecular species are calculated and
compared with abundances observed toward the starburst galaxies NGC 253 and M
82 and galactic sources. Apparent is an `overabundance' of HNC in the nuclear
environment of NGC 4945. While the HNC/HCN =1--0 line intensity ratio is
0.5, the HNC/HCN abundance ratio is 1. While HCN is subthermally
excited (8 K), CN is even less excited (3--4
K), indicating that it arises from a less dense gas component and that its
=2--1 line can be optically thin even though its =1--0 emission is
moderately optically thick. Overall, fractional abundances of NGC 4945 suggest
that the starburst has reached a stage of evolution that is intermediate
between those observed in NGC 253 and M 82. Carbon, nitrogen, oxygen and sulfur
isotope ratios are also determined. Within the limits of uncertainty, carbon
and oxygen isotope ratios appear to be the same in the nuclear regions of NGC
4945 and NGC 253. High O/O, low O/O and
N/N and perhaps also low S/S ratios appear to be
characteristic properties of a starburst environment in which massive stars
have had sufficient time to affect the isotopic composition of the surrounding
interstellar medium.Comment: 26 pages, 16 figures, accepted bt A&
An Overview of the 2014 ALMA Long Baseline Campaign
A major goal of the Atacama Large Millimeter/submillimeter Array (ALMA) is to
make accurate images with resolutions of tens of milliarcseconds, which at
submillimeter (submm) wavelengths requires baselines up to ~15 km. To develop
and test this capability, a Long Baseline Campaign (LBC) was carried out from
September to late November 2014, culminating in end-to-end observations,
calibrations, and imaging of selected Science Verification (SV) targets. This
paper presents an overview of the campaign and its main results, including an
investigation of the short-term coherence properties and systematic phase
errors over the long baselines at the ALMA site, a summary of the SV targets
and observations, and recommendations for science observing strategies at long
baselines. Deep ALMA images of the quasar 3C138 at 97 and 241 GHz are also
compared to VLA 43 GHz results, demonstrating an agreement at a level of a few
percent. As a result of the extensive program of LBC testing, the highly
successful SV imaging at long baselines achieved angular resolutions as fine as
19 mas at ~350 GHz. Observing with ALMA on baselines of up to 15 km is now
possible, and opens up new parameter space for submm astronomy.Comment: 11 pages, 7 figures, 2 tables; accepted for publication in the
Astrophysical Journal Letters; this version with small changes to
affiliation
Study of decays to the final state and evidence for the decay
A study of decays is performed for the first time
using data corresponding to an integrated luminosity of 3.0
collected by the LHCb experiment in collisions at centre-of-mass energies
of and TeV. Evidence for the decay
is reported with a significance of 4.0 standard deviations, resulting in the
measurement of
to
be .
Here denotes a branching fraction while and
are the production cross-sections for and mesons.
An indication of weak annihilation is found for the region
, with a significance of
2.4 standard deviations.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2016-022.html,
link to supplemental material inserted in the reference
Model-independent evidence for contributions to decays
The data sample of decays acquired with the
LHCb detector from 7 and 8~TeV collisions, corresponding to an integrated
luminosity of 3 fb, is inspected for the presence of or
contributions with minimal assumptions about
contributions. It is demonstrated at more than 9 standard deviations that
decays cannot be described with
contributions alone, and that contributions play a dominant role in
this incompatibility. These model-independent results support the previously
obtained model-dependent evidence for charmonium-pentaquark
states in the same data sample.Comment: 21 pages, 12 figures (including the supplemental section added at the
end
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