1,297 research outputs found
Refugial peatlands in the Northern Apennines. Vegetation-environment relationships and future perspectives
Aims: We aimed to detect the environmental drivers conditioning plant diversity and to predict how modifications in habitat conditions and ongoing global warming could lead to vegetation changes or biodiversity losses in a region especially rich in peatlands despite its relatively low latitude. Study area: The study area was located in the Northern Apennines, Northern Italy (about 44 degrees 45' N; 10 degrees 20' E). The vegetation study was carried out at 12 peatland sites where 206 plots were set up. Species composition in the 206 plots were recorded in the field and classified with cluster analysis. Data on hydrology, water chemistry and peat chemistry were collected at a subset of 127 plots and statistically analysed by a multivariate ordination method. Species richness and evenness were calculated for all plots. Relationships between species composition and environmental variables were analysed by stepwise multiple regression. Results: The cluster analysis defined 17 vegetation units. Water table depth represented the major environmental factors accounting for vegetation patterns, with the vegetation units being grouped in four main blocks based on vegetation physiognomy and species composition: Sphagnum hummocks, Sphagnum lawns, fens and pools. Water chemistry and peat chemistry both presented moderate variations among the vegetation units with mean water pH ranging from 4.9 to 6.3. Concentrations of major cations in the pore water showed that all of the habitats investigated were influenced by telluric water, with no evidence of ombrotrophic conditions. Species richness and evenness both presented poor relations with the environment while responses of individual species to environmental factors were more informative on vegetation changes triggered by climate change. Conclusions: Prolonged drought events associated with high temperature in summer months are expected to exert a strong impact on peatland vegetation. The main effect of climate change on the vegetation of the peatlands investigated consists in the spreading of vascular plants at the expense of Sphagnum mosses
Mode identification in the high-amplitude {\delta} Scuti star V2367 Cyg
We report on a multi-site photometric campaign on the high-amplitude
Scuti star V2367 Cyg in order to determine the pulsation modes. We also used
high-dispersion spectroscopy to estimate the stellar parameters and projected
rotational velocity. Time series multicolour photometry was obtained during a
98-d interval from five different sites. These data were used together with
model atmospheres and non-adiabatic pulsation models to identify the spherical
harmonic degree of the three independent frequencies of highest amplitude as
well as the first two harmonics of the dominant mode. This was accomplished by
matching the observed relative light amplitudes and phases in different
wavebands with those computed by the models. In general, our results support
the assumed mode identifications in a previous analysis of Kepler data.Comment: 9 pages, 5 figures, 4 tables. Accepted for publication in MNRA
Genetic and ecological consequences of recent habitat fragmentation in a narrow endemic plant species within an urban context
Understanding the timescales that shape spatial genetic structure is pivotal to ascertain the impact of habitat fragmentation on the genetic diversity and reproductive viability of long-lived plant populations. Combining genetic and ecological information with current and past fragmentation conditions allows the identification of the main drivers important in shaping population structure and declines in reproduction, which is crucial for informing conservation strategies. Using historic aerial photographs, we defined the past fragmentation conditions for the shrub Conospermum undulatum, a species now completely embedded in an urban area. We explored the impact of current and past conditions on its genetic layout and assessed the effects of genetic and environmental factors on its reproduction. The historically high structural connectivity was evident in the genetics of the species. Despite the current intense fragmentation, we found similar levels of genetic diversity across populations and a weak spatial genetic structure. Historical connectivity was negatively associated with genetic differentiation among populations and positively related to within-population genetic diversity. Variation partitioning of reproductive performance explained ~ 66% of the variance, showing significant influences for genetic (9%), environmental (15%), and combined (42%) fractions. Our study highlights the importance of considering the historical habitat dynamics when investigating fragmentation consequences in long-lived plants. A detailed characterization of fragmentation from 1953 has shown how low levels of genetic fixation are due to extensive gene flow through the non-fragmented landscape. Moreover, knowledge of the relationships between genetic and environmental variation and reproduction can help to implement effective conservation strategies, particularly in highly dynamic landscapes
Genetic and ecological consequences of recent habitat fragmentation in a narrow endemic plant species within an urban context
Understanding the timescales that shape spatial genetic structure is pivotal to ascertain the impact of habitat fragmentation on the genetic diversity and reproductive viability of long-lived plant populations. Combining genetic and ecological information with current and past fragmentation conditions allows the identification of the main drivers important in shaping population structure and declines in reproduction, which is crucial for informing conservation strategies. Using historic aerial photographs, we defined the past fragmentation conditions for the shrub Conospermum undulatum, a species now completely embedded in an urban area. We explored the impact of current and past conditions on its genetic layout and assessed the effects of genetic and environmental factors on its reproduction. The historically high structural connectivity was evident in the genetics of the species. Despite the current intense fragmentation, we found similar levels of genetic diversity across populations and a weak spatial genetic structure. Historical connectivity was negatively associated with genetic differentiation among populations and positively related to within-population genetic diversity. Variation partitioning of reproductive performance explainedâ~â66% of the variance, showing significant influences for genetic (9%), environmental (15%), and combined (42%) fractions. Our study highlights the importance of considering the historical habitat dynamics when investigating fragmentation consequences in long-lived plants. A detailed characterization of fragmentation from 1953 has shown how low levels of genetic fixation are due to extensive gene flow through the non-fragmented landscape. Moreover, knowledge of the relationships between genetic and environmental variation and reproduction can help to implement effective conservation strategies, particularly in highly dynamic landscapes
Hydrogen sulfide inhibits tmprss2 in human airway epithelial cells: Implications for sarsâcovâ2 infection
The COVIDâ19 pandemic has now affected around 190 million people worldwide, accounting for more than 4 million confirmed deaths. Besides ongoing global vaccination, finding protective and therapeutic strategies is an urgent clinical need. SARSâCoVâ2 mostly infects the host organism via the respiratory system, requiring angiotensinâconverting enzyme 2 (ACE2) and transmembrane protease serine 2 (TMPRSS2) to enter target cells. Therefore, these surface proteins are considered potential druggable targets. Hydrogen sulfide (H2S) is a gasotransmitter produced by several cell types and is also part of natural compounds, such as sulfurous waters that are often inhaled as lowâintensity therapy and prevention in different respiratory conditions. H2S is a potent biological mediator, with antiâoxidant, antiâinflammatory, and, as more recently shown, also antiviral activities. Considering that respiratory epithelial cells can be directly exposed to H2S by inhalation, here we tested the in vitro effects of H2Sâdonors on TMPRSS2 and ACE2 expression in human upper and lower airway epithelial cells. We showed that H2S significantly reduces the expression of TMPRSS2 without modifying ACE2 expression both in respiratory cell lines and primary human upper and lower airway epithelial cells. Results suggest that inhalational exposure of respiratory epithelial cells to natural H2S sources may hinder SARSâCoVâ2 entry into airway epithelial cells and, consequently, potentially prevent the virus from spreading into the lower respiratory tract and the lung
The APACHE survey hardware and software design: Tools for an automatic search of small-size transiting exoplanets
Small-size ground-based telescopes can effectively be used to look for transiting rocky planets around nearby low-mass M stars using the photometric transit method, as recently demonstrated for example by the MEarth project. Since 2008 at the Astronomical Observatory of the Autonomous Region of Aosta Valley (OAVdA), we have been preparing for the long-term photometric survey APACHE, aimed at finding transiting small-size planets around thousands of nearby early and mid-M dwarfs. APACHE (A PAthway toward the Characterization of Habitable Earths) is designed to use an array of five dedicated and identical 40-cm Ritchey-Chretien telescopes and its observations started at the beginning of summer 2012. The main characteristics of the survey final set up and the preliminary results from the first weeks of observations will be discussed
HADES RV Programme with HARPS-N at TNG VI. GJ 3942 b behind dominant activity signals
Short- to mid-term magnetic phenomena on the stellar surface of M-type stars
cannot only resemble the effects of planets in radial velocity data, but also
may hide them. We analyze 145 spectroscopic HARPS-N observations of GJ 3942
taken over the past five years and additional photometry to disentangle stellar
activity effects from genuine Doppler signals as a result of the orbital motion
of the star around the common barycenter with its planet. To achieve this, we
use the common methods of pre-whitening, and treat the correlated red noise by
a first-order moving average term and by Gaussian-process regression following
an MCMC analysis. We identify the rotational period of the star at 16.3 days
and discover a new super-Earth, GJ 3942 b, with an orbital period of 6.9 days
and a minimum mass of 7.1 Me. An additional signal in the periodogram of the
residuals is present but we cannot claim it to be related to a second planet
with sufficient significance at this point. If confirmed, such planet candidate
would have a minimum mass of 6.3 Me and a period of 10.4 days, which might
indicate a 3:2 mean-motion resonance with the inner planet
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