366 research outputs found
A preliminary survey of marine cave habitats in the Maltese Islands
The Mediterranean Sea is a hotspot for marine biodiversity. Past studies of Mediterranean marine
caves have revealed the unique biocoenotic and ecological characteristics of these habitats, which are protected by European Union legislation. The Maltese Islands
have an abundance of partially and fully submerged
marine caves with di fferent geomorphological characteristics, yet there have been no systematic studies on these
habitats and their associated species. This study is a
firrst synthesis of existing information on the biotic assemblages and physical characteristics of Maltese marine caves. The work combines a review of the available
information with a preliminary survey of some marine
caves in Gozo, during which several species were recorded for the first time for the Maltese Islands. Characteristic species recorded from local marine caves are highlighted, including several species of red and brown algae,
sessile invertebrates including bryozoans, ascidians and
sponges, and mobile forms including crustaceans and
fi sh. A marked zonation from the cave entrance to the
inside of the caves was identifi ed: photophilic algae at
the mouth of the cave are progressively replaced by more
sciaphilic species, followed by a middle section dominated by sessile invertebrates, and then a completely dark
inner section that is mostly devoid of sessile organisms.
Several species protected by national and international
legislation were found to occur.peer-reviewe
Effects of standard coagulant agents on the dielectric properties of fresh human blood
In this paper, the effects of coagulation and temperature on the dielectric properties of human blood are investigated over the frequency range of 400 MHz-20 GHz using freshly extracted blood samples. The dielectric properties are measured using blood in four different sample collection tubes (bottles): one containing pure whole blood, two containing different anticoagulant agents, and one containing clot activator and serum separator. The collected data indicates that additive agents can have a significant impact on the measured dielectric properties of blood, both immediately after the sample is taken, and over longer time periods. This is an important finding as it suggests that measurements of blood properties conducted on sample repositories, or tissue banks, may not be representative of natural blood properties. Further, the results demonstrate that the dielectric properties of normal blood vary over time due to coagulation. Different clotting rates lead to dielectric properties of female and male blood samples that vary distinctly over time. The results also show that the relative permittivity of the anti-coagulated blood decreases with increasing temperature, up to the cross-over point around 10 GHz where the trend reverses.peer-reviewe
Spatial distribution of demersal fishery resources, environmental factors and fishing activities in GSA 15 (Malta Island)
The FAOâMedSudMed Regional Project has promoted research on the improvement of knowledge on fishery ecosystems, with a view to the sustainable management of living marine resources in the central Mediterranean (Straits of Sicily). A pilot study focused on the waters around the Maltese Islands (GSA 15), with the aim of providing a comprehensive overview of the spatial distribution of the different life stages of exploitable demersal fishes in relation to the type and distribution of fishing, as well as to the oceanographic factors characteristic of the area of study. Critical zones for their role in the ecology of the main demersal fishery target species were investigated using species abundance data disaggregated by life stage. Spatial analysis and the application of GIS techniques allowed the identification of preferred habitats (e.g. nursery, feeding and spawning areas) for Merluccius merluccius, Mullus barbatus, Parapenaeus longirostris, Raja clavata and Raja miraletus. The impact of fishing on these species was assessed, particularly in terms of fish assemblages. The transport paths of early life stages were also hypothesized on the basis of oceanographic factors typical of the area. The results revealed that the spatial distribution of the main fishery resources overlaps the limits of the current GSAs. The analysis of oceanographic factors showed that some fishery resources are sustained by young individuals transported from adjacent GSAs. The results also demonstrated that the spatial distribution of the main demersal fishery resources in the Mediterranean GSA 15 straddle other GSAs, in particular as concerns nursery and spawning areas, indicating that some fishery resources are shared. This implies that harmonized fishery management should be applied over a larger area than is implied by the GSA concept. Finally, the study showed how data provided by different methods could be integrated to enhance the available scientific information in a data-limited situation.peer-reviewe
The detection of neutrino interactions in the emulsion/lead target of the OPERA experiment
The OPERA neutrino detector in the underground Gran Sasso Laboratory (LNGS)
was designed to perform the first detection of neutrino oscillations in
appearance mode through the study of oscillations. The
apparatus consists of an emulsion/lead target complemented by electronic
detectors and it is placed in the high energy long-baseline CERN to LNGS beam
(CNGS) 730 km away from the neutrino source. Runs with CNGS neutrinos were
successfully carried out in 2007 and 2008 with the detector fully operational
with its related facilities for the emulsion handling and analysis. After a
brief description of the beam and of the experimental setup we report on the
collection, reconstruction and analysis procedures of first samples of neutrino
interaction events
Emulsion sheet doublets as interface trackers for the OPERA experiment
New methods for efficient and unambiguous interconnection between electronic
counters and target units based on nuclear photographic emulsion films have
been developed. The application to the OPERA experiment, that aims at detecting
oscillations between mu neutrino and tau neutrino in the CNGS neutrino beam, is
reported in this paper. In order to reduce background due to latent tracks
collected before installation in the detector, on-site large-scale treatments
of the emulsions ("refreshing") have been applied. Changeable Sheet (CSd)
packages, each made of a doublet of emulsion films, have been designed,
assembled and coupled to the OPERA target units ("ECC bricks"). A device has
been built to print X-ray spots for accurate interconnection both within the
CSd and between the CSd and the related ECC brick. Sample emulsion films have
been extensively scanned with state-of-the-art automated optical microscopes.
Efficient track-matching and powerful background rejection have been achieved
in tests with electronically tagged penetrating muons. Further improvement of
in-doublet film alignment was obtained by matching the pattern of low-energy
electron tracks. The commissioning of the overall OPERA alignment procedure is
in progress.Comment: 19 pages, 19 figure
First events from the CNGS neutrino beam detected in the OPERA experiment
The OPERA neutrino detector at the underground Gran Sasso Laboratory (LNGS)
was designed to perform the first detection of neutrino oscillations in
appearance mode, through the study of nu_mu to nu_tau oscillations. The
apparatus consists of a lead/emulsion-film target complemented by electronic
detectors. It is placed in the high-energy, long-baseline CERN to LNGS beam
(CNGS) 730 km away from the neutrino source. In August 2006 a first run with
CNGS neutrinos was successfully conducted. A first sample of neutrino events
was collected, statistically consistent with the integrated beam intensity.
After a brief description of the beam and of the various sub-detectors, we
report on the achievement of this milestone, presenting the first data and some
analysis results.Comment: Submitted to the New Journal of Physic
Measurement of the atmospheric muon charge ratio with the OPERA detector
The OPERA detector at the Gran Sasso underground laboratory (LNGS) was used
to measure the atmospheric muon charge ratio in the TeV energy region. We
analyzed 403069 atmospheric muons corresponding to 113.4 days of livetime
during the 2008 CNGS run. We computed separately the muon charge ratio for
single and for multiple muon events in order to select different energy regions
of the primary cosmic ray spectrum and to test the charge ratio dependence on
the primary composition. The measured charge ratio values were corrected taking
into account the charge-misidentification errors. Data have also been grouped
in five bins of the "vertical surface energy". A fit to a simplified model of
muon production in the atmosphere allowed the determination of the pion and
kaon charge ratios weighted by the cosmic ray energy spectrum.Comment: 14 pages, 10 figure
Electron/pion separation with an Emulsion Cloud Chamber by using a Neural Network
We have studied the performance of a new algorithm for electron/pion
separation in an Emulsion Cloud Chamber (ECC) made of lead and nuclear emulsion
films. The software for separation consists of two parts: a shower
reconstruction algorithm and a Neural Network that assigns to each
reconstructed shower the probability to be an electron or a pion. The
performance has been studied for the ECC of the OPERA experiment [1].
The separation algorithm has been optimized by using a detailed Monte
Carlo simulation of the ECC and tested on real data taken at CERN (pion beams)
and at DESY (electron beams). The algorithm allows to achieve a 90% electron
identification efficiency with a pion misidentification smaller than 1% for
energies higher than 2 GeV
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