1,336 research outputs found
Variation in Environmental Parameters in Research and Aquaculture: Effects on Behaviour, Physiology and Cell Biology of Teleost Fish
Over the last few years the increasing use of fish as animal models in scientific research and the increased fish breeding for human consumption have stressed the need for more knowledge on the effect of variations in environmental parameters on fish biology and on the welfare of specimens used both in research and aquaculture contexts. Experimental evidence shows that environmental variations can affect fish biology at various levels, from the molecular to that of the population, sometimes in a different way depending on the species considered. In order to achieve reproducible results in experiments involving fish it is necessary to set and maintain all environmental parameters constant at the optimal value to guarantee the wellness of the animal. The effects of the variation in environmental parameters on the behaviour, physiology and cell biology of teleosts are here discussed in order to provide useful information for research based on fish models
The AGB population of NGC 6822: distribution and the C/M ratio from JHK photometry
NGC 6822 is an irregular dwarf galaxy and part of the Local Group. Its close
proximity and apparent isolation provide a unique opportunity to study galactic
evolution without any obvious strong external influences. This paper aims to
study the spatial distribution of the asymptotic giant branch (AGB) population
and metallicity in NGC 6822. Using deep, high quality JHK photometry, taken
with WFCAM on UKIRT, carbon- and oxygen-rich AGB stars have been isolated. The
ratio between their number, the C/M ratio, has then been used to derive the
[Fe/H] abundance across the galaxy. The tip of the red giant branch is located
at K0 = 17.41 \pm 0.11 mag and the colour separation between carbon- and
oxygen-rich AGB stars is at (J - K)0 = 1.20 \pm 0.03 mag (i.e. (J - K)2MAS S
{\guillemotright} 1.28 mag). A C/M ratio of 0.62 \pm 0.03 has been derived in
the inner 4 kpc of the galaxy, which translates into an iron abundance of
[Fe/H] = -1.29\pm0.07 dex. Variations of these parameters were investigated as
a function of distance from the galaxy centre and azimuthal angle. The AGB
population of NGC 6822 has been detected out to a radius of 4 kpc giving a
diameter of 56 arcmin. It is metal-poor, but there is no obvious gradient in
metallicity with either radial distance from the centre or azimuthal angle. The
detected spread in the TRGB magnitude is consistent with that of a galaxy
surrounded by a halo of old stars. The C/M ratio has the potential to be a very
useful tool for the determination of metallicity in resolved galaxies but a
better calibration of the C/M vs. [Fe/H] relation and a better understanding of
the sensitivities of the C/M ratio to stellar selection criteria is first
required
Localization of α-synuclein in teleost central nervous system: immunohistochemical and Western blot evidence by 3D5 monoclonal antibody in the common carp, Cyprinus carpio
Alpha synuclein (α-syn) is a 140 amino acid vertebrate-specific protein, highly expressed in the human nervous system and abnormally accumulated in Parkinson's disease and other neurodegenerative disorders, known as synucleinopathies. The common occurrence of α-syn aggregates suggested a role for α-syn in these disorders, although its biological activity remains poorly understood. Given the high degree of sequence similarity between vertebrate α-syns, we investigated this proteins in the CNS of the common carp Cyprinus carpio, with the aim of comparing its anatomical and cellular distribution with that of mammalian α-syn. The distribution of α-syn was analyzed by semiquantitative Western blot, immunohistochemistry and immunofluorescence by a novel monoclonal antibody (3D5) against a fully conserved epitope between carp and human α-syn. The distribution of 3D5 immunoreactivity was also compared with that of ChAT, TH and 5HT by double immunolabelings. Results show that α-syn-like protein of about 17 kDa is expressed to different levels in several brain regions and in the spinal cord. Immunoreactive materials were localized in neuronal perikarya and varicose fibers but not in the nucleus. Present findings indicate that α-syn-like proteins may be expressed in few subpopulations of catecholaminergic and serotoninergic neurons in the carp brain. However, evidence of cellular colocalization 3D5/TH or 3D5/5HT was rare. Differently, the same proteins appear to be co-expressed with ChAT by cholinergic neurons in several motor and reticular nuclei. These results sustain the functional conservation of the α-syn expression in cholinergic systems and suggest that α-syn modulates similar molecular pathways in phylogenetically distant vertebrates. This article is protected by copyright. All rights reserved
Feeding behaviour of larval European sea bass (Dicentrarchus labrax L.) in relation to temperature and prey density
The feeding behaviour of larval European sea bass (Dicentrarchus labrax, L.) was analysed in relation to temperature and prey
density under controlled laboratory conditions with the aim to assess the ability of larval fish to change the feeding tactic as a
response to environmental changes. Larvae were acclimated for 20 days at three different temperatures (19, 22 and 26°C), and
their feeding behaviour was then video-recorded in experimental trials, at two prey densities, consisting of swarms of 400/l
and 1440/l Artemia nauplii. Results showed that there was a significant effect of the interaction between temperature and prey
density on the proportion of swimming activity that was reduced at the high temperature-high prey density combination. This
suggested a switching in the larval feeding behaviour from an active to an ambush tactic, when the temperature reached 26°C
and the prey density was 1440 /l Artemia nauplii. These results are consistent with the current literature on fish larval behaviour
in showing that the foraging tactic can be modulated by the interaction of different abiotic and biotic factors characterising the
rearing environment
Three aspects of red giant studies in the Magellanic Clouds
There are three important aspects concerning the study of the red giant and
in particular of the asymptotic giant branch (AGB) stars in the Magellanic
Clouds. These are: the surface distribution, the luminosity function and the
variability. The spatial distribution of AGB stars is an efficient tool to
study the structure of the galaxies and their metalicity by analysing the ratio
between carbon- and oxygen-rich AGB stars. The shape of the luminosity function
carries informations about the star formation rate in the Clouds and it can be
mathematically related to their history. Most AGB stars vary their magnitude in
a few to several hundred years time; the one epoch DENIS magnitudes for both
Large and Small Magellanic Cloud AGB stars outline the same relations as a
function of period.Comment: 8 pages, 6 figures, invited talk, to be published in: Mass-Losing
Pulsating Stars and their Circumstellar Matter, Y. Nakada & M. Honma (eds)
Kluwer ASSL serie
Photometric Properties of Long-period Variables in the Large Magellanic Cloud
Approximately four thousand light curves of red variable stars in the LMC
were selected from the 2.3-years duration MOA database by a period analysis
using the Phase Dispersion Minimization method. Their optical features
(amplitudes, periodicities, position in CMD) were investigated. Stars with
large amplitues and high periodicities were distributed on the only one strip
amongst multiple structure on the LMC period-luminosity relation. In the CMD,
the five strips were located in the order of the period. The stars with
characterized light curves were also discussed.Comment: 8 pages, 5 figures, Proceeding of WS on Mass-Losing Pulsating Stars
and Their Circumstellar Matter, Sendai, Japa
Nova Sco 2001 (V1178 Sco)
We present intermediate resolution spectroscopy and near infrared photometry
of NOVA Sco 2001 (V1178 Sco), which was first detected May 13th 2001 and
reported June 21th 2001, and obtained by us the same day. We also retrieved
very accurate astrometry of the target in this very crowded field. This is
needed to be able to do follow up observations of the postnova during the next
years. The spectrum shows an overall expansion of 2100 km/s and has clearly
complex, and most likely nonsymmetric, outflow substructures. We clearly
identify this object as classical nova, "Fe II" subclass.Comment: 4 pages, TeX, accepted for Publication in A&A (Letter
Transcranial direct current stimulation (tDCS) in unilateral cerebral palsy: A pilot study of motor effect
Transcranial Direct Current Stimulation (tDCS) is an emerging tool to improve upper limb motor functions after stroke acquired in adulthood; however, there is a paucity of reports on its efficacy for upper limb motor rehabilitation in congenital or early-acquired stroke. In this pilot study we have explored, for the first time, the immediate effects, and their short-term persistence, of a single application of anodal tDCS on chronic upper limb motor disorders in children and young individuals with Unilateral Cerebral Palsy (UCP). To this aim, in a crossover sham-controlled study, eight subjects aged 10-28 years with UCP underwent two sessions of active and sham tDCS. Anodal tDCS (1.5 mA, 20 min) was delivered over the primary motor cortex (M1) of the ipsilesional hemisphere. Results showed, only following the active stimulation, an immediate improvement in unimanual gross motor dexterity of hemiplegic, but not of nonhemiplegic, hand in Box and Block test (BBT). Such improvement remained stable for at least 90 minutes. Performance of both hands in Hand Grip Strength test was not modified by anodal tDCS. Improvement in BBT was unrelated to participants’ age or lesion size, as revealed by MRI data analysis. No serious adverse effects occurred after tDCS; some mild and transient side effects (e.g., headache, tingling, and itchiness) were reported in a limited number of cases. This study provides an innovative contribution to scientific literature on the efficacy and safety of anodal tDCS in UCP
Architectures and Key Technical Challenges for 5G Systems Incorporating Satellites
Satellite Communication systems are a promising solution to extend and
complement terrestrial networks in unserved or under-served areas. This aspect
is reflected by recent commercial and standardisation endeavours. In
particular, 3GPP recently initiated a Study Item for New Radio-based, i.e., 5G,
Non-Terrestrial Networks aimed at deploying satellite systems either as a
stand-alone solution or as an integration to terrestrial networks in mobile
broadband and machine-type communication scenarios. However, typical satellite
channel impairments, as large path losses, delays, and Doppler shifts, pose
severe challenges to the realisation of a satellite-based NR network. In this
paper, based on the architecture options currently being discussed in the
standardisation fora, we discuss and assess the impact of the satellite channel
characteristics on the physical and Medium Access Control layers, both in terms
of transmitted waveforms and procedures for enhanced Mobile BroadBand (eMBB)
and NarrowBand-Internet of Things (NB-IoT) applications. The proposed analysis
shows that the main technical challenges are related to the PHY/MAC procedures,
in particular Random Access (RA), Timing Advance (TA), and Hybrid Automatic
Repeat reQuest (HARQ) and, depending on the considered service and
architecture, different solutions are proposed.Comment: Submitted to Transactions on Vehicular Technologies, April 201
Simulation of a flash-flood event over the Adriatic Sea with a high-resolution atmosphere–ocean–wave coupled system
On the morning of September 26, 2007, a heavy precipitation event (HPE) affected the Venice lagoon and the neighbouring coastal zone of the Adriatic Sea, with 6-h accumulated rainfall summing up to about 360 mm in the area between the Venetian mainland, Padua and Chioggia. The event was triggered and maintained by the uplift over a convergence line between northeasterly flow from the Alps and southeasterly winds from the Adriatic Sea. Hindcast modelling experiments, using standalone atmospheric models, failed to capture the spatial distribution, maximum intensity and timing of the HPE. Here we analyze the event by means of an atmosphere-wave-ocean coupled numerical approach. The combined use of convection permitting models with grid spacing of 1 km, high-resolution sea surface temperature (SST) fields, and the consistent treatment of marine boundary layer fluxes in all the numerical model components are crucial to provide a realistic simulation of the event. Inaccurate representations of the SST affect the wind magnitude and, through this, the intensity, location and time evolution of the convergence zone, thus affecting the HPE prediction. © 2021, The Author(s)
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