3,988 research outputs found
On the sensitivity of extrasolar mass-loss rate ranges: HD 209458b a case study
We present a 3D hydrodynamic study of the effects that different stellar wind
conditions and planetary wind structures have on the calculated Ly-
absorptions produced during the transit of HD 209458b. Considering a range of
stellar wind speeds [350-800] km s, coronal temperature
[3-7] K and two values of the polytropic index
[1.01-1.13], while keeping fixed the stellar mass loss rate, we found a
that a range between [3-5] g s give
account for the observational absorption in Ly- measured for the
planetary system. Also, several models with anisotropic evaporation profiles
for the planetary escaping atmosphere were carried out, showing that both, the
escape through polar regions and through the night side yields larger
absorptions than an isotropic planetary wind
Photo-ionization of planetary winds: case study HD209458b
Close-in hot Jupiters are exposed to a tremendous photon flux that ionizes
the neutral escaping material from the planet leaving an observable imprint
that makes them an interesting laboratory for testing theoretical models. In
this work we present 3D hydrodynamic simulations with radiation transfer
calculations of a close-in exoplanet in a blow-off state. We calculate the
Ly- absorption and compare it with observations of HD 209458b an
previous simplified model results.Our results show that the hydrodynamic
interaction together with a proper calculation of the photoionization proccess
are able to reproduce the main features of the observed Ly- absorption,
in particular at the blue-shifted wings of the line. We found that the ionizing
stellar flux produce an almost linear effect on the amount of absorption in the
wake. Varying the planetary mass loss rate and the radiation flux, we were able
to reproduce the absorption observed at .Comment: 9 pages, 6 figure
Multi-year particle fluxes in Kongsfjorden, Svalbard
Abstract. High-latitude regions are
warming faster than other areas due to reduction of snow cover and sea ice
loss and changes in atmospheric and ocean circulation. The combination of
these processes, collectively known as polar amplification, provides an
extraordinary opportunity to document the ongoing thermal destabilisation of
the terrestrial cryosphere and the release of land-derived material into the
aquatic environment. This study presents a 6-year time series (2010–2016) of
physical parameters and particle fluxes collected by an oceanographic mooring
in Kongsfjorden (Spitsbergen, Svalbard). In recent decades, Kongsfjorden has
been experiencing rapid loss of sea ice coverage and retreat of local
glaciers as a result of the progressive increase in ocean and air
temperatures. The overarching goal of this study was to continuously monitor
the inner fjord particle sinking and to understand to what extent the
temporal evolution of particulate fluxes was linked to the progressive
changes in both Atlantic and freshwater input. Our data show high peaks of
settling particles during warm seasons, in terms of both organic and
inorganic matter. The different sources of suspended particles were described
as a mixing of glacier carbonate, glacier siliciclastic and autochthonous marine input. The glacier releasing
sediments into the fjord was the predominant source, while the sediment input
by rivers was reduced at the mooring site. Our time series showed that the
seasonal sunlight exerted first-order control on the particulate fluxes in
the inner fjord. The marine fraction peaked when the solar radiation was at a
maximum in May–June while the land-derived fluxes exhibited a 1–2-month lag
consistent with the maximum air temperature and glacier melting. The
inter-annual time-weighted total mass fluxes varied by 2 orders of magnitude
over time, with relatively higher values in 2011, 2013, and 2015. Our results
suggest that the land-derived input will remarkably increase over time in a
warming scenario. Further studies are therefore needed to understand the
future response of the Kongsfjorden ecosystem alterations with respect to the
enhanced release of glacier-derived material
Dark Matter investigation by DAMA at Gran Sasso
Experimental observations and theoretical arguments at Galaxy and larger
scales have suggested that a large fraction of the Universe is composed by Dark
Matter particles. This has motivated the DAMA experimental efforts to
investigate the presence of such particles in the galactic halo by exploiting a
model independent signature and very highly radiopure set-ups deep underground.
Few introductory arguments are summarized before presenting a review of the
present model independent positive results obtained by the DAMA/NaI and
DAMA/LIBRA set-ups at the Gran Sasso National Laboratory of the INFN.
Implications and model dependent comparisons with other different kinds of
results will be shortly addressed. Some arguments put forward in literature
will be confuted.Comment: review article, 71 pages, 25 figures, 8 tables; v2: minor
modifications. In publication on the International Journal of Modern Physics
Final model independent result of DAMA/LIBRA-phase1
The results obtained with the total exposure of 1.04 ton x yr collected by
DAMA/LIBRA-phase1 deep underground at the Gran Sasso National Laboratory (LNGS)
of the I.N.F.N. during 7 annual cycles (i.e. adding a further 0.17 ton x yr
exposure) are presented. The DAMA/LIBRA-phase1 data give evidence for the
presence of Dark Matter (DM) particles in the galactic halo, on the basis of
the exploited model independent DM annual modulation signature by using highly
radio-pure NaI(Tl) target, at 7.5 sigma C.L.. Including also the first
generation DAMA/NaI experiment (cumulative exposure 1.33 ton x yr,
corresponding to 14 annual cycles), the C.L. is 9.3 sigma and the modulation
amplitude of the single-hit events in the (2-6) keV energy interval is: (0.0112
\pm 0.0012) cpd/kg/keV; the measured phase is (144 \pm 7) days and the measured
period is (0.998 \pm 0.002) yr, values well in agreement with those expected
for DM particles. No systematic or side reaction able to mimic the exploited DM
signature has been found or suggested by anyone over more than a decade.Comment: 20 pages, 13 figures, 6 tables; in publication on Eur. Phys. J.
Model independent result on possible diurnal effect in DAMA/LIBRA-phase1
The results obtained in the search for possible diurnal effect in the
single-hit low energy data collected by DAMA/LIBRA-phase1 (total exposure: 1.04
ton x yr) deep underground at the Gran Sasso National Laboratory (LNGS) of the
I.N.F.N. are presented. At the present level of sensitivity the presence of any
significant diurnal variation and of diurnal time structures in the data can be
excluded for both the cases of solar and sidereal time. In particular, the
diurnal modulation amplitude expected, because of the Earth diurnal motion, on
the basis of the DAMA Dark Matter annual modulation results is below the
present sensitivity.Comment: 14 pages, 5 figures, 2 tables; in publication on Eur. Phys. J.
No role for neutrons, muons and solar neutrinos in the DAMA annual modulation results
This paper summarizes in a simple and intuitive way why the neutrons, the
muons and the solar neutrinos cannot give any significant contribution to the
DAMA annual modulation results. A number of these elements have already been
presented in individual papers; they are recalled here. Afterwards, few simple
considerations are summarized which already demonstrate the incorrectness of
the claim reported in PRL 113 (2014) 081302.Comment: 11 pages, 1 tabl
Investigating Earth shadowing effect with DAMA/LIBRA-phase1
In the present paper the results obtained in the investigation of possible
diurnal effects for low-energy single-hit scintillation events of
DAMA/LIBRA-phase1 (1.04 ton yr exposure) have been analysed in terms
of an effect expected in case of Dark Matter (DM) candidates inducing nuclear
recoils and having high cross-section with ordinary matter, which implies low
DM local density in order to fulfill the DAMA/LIBRA DM annual modulation
results. This effect is due to the different Earth depths crossed by those DM
candidates during the sidereal day.Comment: 22 pages, 9 figures, 1 table; in publication on Eur. Phys. J.
The Epigenetics of the Endocannabinoid System
The endocannabinoid system (ES) is a cell-signalling system widely distributed in biological tissues that includes endogenous ligands, receptors, and biosynthetic and hydrolysing machineries. The impairment of the ES has been associated to several pathological conditions like behavioural, neurological, or metabolic disorders and infertility, suggesting that the modulation of this system may be critical for the maintenance of health status and disease treatment. Lifestyle and environmental factors can exert long-term effects on gene expression without any change in the nucleotide sequence of DNA, affecting health maintenance and influencing both disease load and resistance. This potentially reversible "epigenetic" modulation of gene expression occurs through the chemical modification of DNA and histone protein tails or the specific production of regulatory non-coding RNA (ncRNA). Recent findings demonstrate the epigenetic modulation of the ES in biological tissues; in the same way, endocannabinoids, phytocannabinoids, and cannabinoid receptor agonists and antagonists induce widespread or gene-specific epigenetic changes with the possibility of trans-generational epigenetic inheritance in the offspring explained by the transmission of deregulated epigenetic marks in the gametes. Therefore, this review provides an update on the epigenetics of the ES, with particular attention on the emerging role in reproduction and fertility
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