275 research outputs found
The unmixed kinematics and origins of diffuse stellar light in the core of the Hydra I cluster (Abell 1060)
Diffuse intracluster light (ICL) and cD galaxy halos are believed to
originate from galaxy evolution and disruption. We present a kinematic study of
the ICL in the Hydra I cluster core, using planetary nebulas (PNs) as tracers.
We used multi-slit imaging spectroscopy with FORS2 on VLT-UT1 to detect 56 PNs
associated with diffuse light in the central 100 x 100 kpc^2 of Hydra I. We
measured their [OIII] magnitudes, sky positions, and velocity distribution
(LOSVD), and compared with the phase-space distribution of nearby galaxies. The
luminosity function of the detected PNs is consistent with that expected at a
distance of ~50 Mpc. Their number density is ~4 times lower for the light seen
than expected, and we discuss ram pressure stripping of the PNs by the hot ICM
as one of the possible explanations. The LOSVD histogram of the PNs is highly
non-Gaussian and multipeaked: it is dominated by a broad central component with
sigma~500 km/s at around the average velocity of the cluster, and shows two
additional narrower peaks at 1800 km/s and 5000 km/s. The main component is
broadly consistent with the outward continuation of the intracluster halo of
NGC 3311, which was earlier shown to have a velocity dispersion of ~470 km/s at
radii of >50". Galaxies with velocities in this range are absent in the central
100 x 100 kpc^2 and may have been disrupted earlier to build this component.
The PNs in the second peak in the LOSVD at 5000 km/s are coincident spatially
and in velocities with a group of dwarf galaxies in the MSIS field. They may
trace the debris from the ongoing tidal disruption of these galaxies. Most of
the diffuse light in the core of Hydra is still not phase-mixed. The build-up
of ICL and the dynamically hot cD halo around NGC 3311 are ongoing, through the
accretion of material from galaxies falling into the cluster core and tidally
interacting with its potential well.Comment: 12 pages, 7 figures, accepted for publication in A&
Stellar population and the origin of intra-cluster stars around brightest cluster galaxies: the case of NGC 3311
Context. We investigate the stellar population and the origin of diffuse
light around brightest cluster galaxies.
Aims. We study the stellar population of the dynamically hot stellar halo of
NGC 3311, the brightest galaxy in the Hydra I cluster, and that of photometric
substructures in the diffuse light to constrain the origin of these components.
Methods. We analyze absorption lines in medium-resolution, long-slit spectra
in the wavelength range 4800-5800 angstrom obtained with FORS2 at the Very
Large Telescope. We measure the equivalent width of Lick indices out to 20 kpc
from the center of NGC 3311 and fit them with stellar population models that
account for the [alpha/Fe] overabundance.
Results. Stars in the dynamically hot halo of NGC 3311 are old (age > 13
Gyr), metal-poor ([Z/H] ~ -0.35), and alpha-enhanced ([alpha/Fe] ~ 0.48).
Together with the high velocity dispersion, these measurements indicate that
the stars in the halo were accreted from the outskirts of other early-type
galaxies, with a possible contribution from dwarf galaxies. We identify a
region in the halo of NGC 3311 associated with a photometric substructure where
the stellar population is even more metal-poor ([Z/H] ~ -0.73). In this region,
our measurements are consistent with a composite stellar population superposed
along the line of sight, consisting of stars from the dynamically hot halo of
NGC 3311 and stars stripped from dwarf galaxies. The latter component
contributes < 28% to the local surface brightness.
Conclusions. The build-up of diffuse light around NGC 3311 is on-going. Based
on the observed stellar population properties, the dominant part of these stars
may have come from the outskirts of bright early-type galaxies, while stars
from stripped dwarf galaxies are presently being added.Comment: 8 pages, 4 figures. Accepted for publication in Astronomy &
Astrophysic
An integrated technological approach to the selection of lactic acid bacteria of flour origin for sourdough production
Several lactic acid bacteria (LAB) were evaluated in situ for their potential in sourdough fermentation. The
strains belonged to Lactobacillus plantarum, Lactobacillus sakei, Lactobacillus sanfranciscensis, Leuconostoc citreum,
Leuconostoc mesenteroides, Leuconostoc pseudomesenteroides and Weissella cibaria. LAB were used, in individual
inocula, to carry out the fermentation of \u3b3-ray treated (sterile) flour and untreated commercial flour, in order
to evaluate their performances both in the absence and presence of the native microbiota of flour. The pH and
total titratable acidity (TTA) showed a strong and fast acidification of the experimental sourdough determined
by W. cibaria and Ln. citreum strains. All strains were followed during fermentation by plate count. Randomly
amplified polymorphic DNA (RAPD)-PCR analysis applied on the colonies isolated from the highest dilution of
samples confirmed the dominance of the added strains in all sourdoughs prepared with sterile and non-sterile
flour. The analysis of organic acids, performed by high-performance liquid chromatography (HPLC), confirmed
that some W. cibaria and Ln. citreum strains showed an optimal fermentation quotient. The volatile organic
compound (VOC) composition resulting from the gas chromatography coupled with mass spectrometry (GC/MS)
analysis of sourdough headspace recognised 51 chemical compounds including acids, alcohols, aldehydes, esters,
ketones, lactones, acetate, alkane, and phenol, most of which are of LAB origin and are relevant for the final bread.
After baking, the breads were evaluated for the height of the central slices, colour of crust and crumb, hardness
and number and distribution of alveolus. The combination of these results indicated that strains Ln. citreum
PON10079 and PON10080 and W. cibaria PON10030 and PON10032 are suitable cultures to use in industrial
production
The dark halo of the Hydra I galaxy cluster: core, cusp, cosmological? Dynamics of NGC 3311 and its globular cluster system
NGC 3311 is the central cD galaxy of the Hydra I cluster. We use globular
clusters around NGC 3311, combined with kinematical data of the galaxy itself,
to investigate the dark matter distribution in the central region of Hydra I.
Radial velocities of 118 bright globular clusters, based on VLT/VIMOS mask
spectroscopy, are used to calculate velocity dispersions which are well defined
out to 100 kpc. NGC 3311 is the most distant galaxy for which this kind of
study has been performed. We also determine velocity dispersions of the stellar
component from long slit spectroscopy out to 20 kpc. Moreover, we present a new
photometric model for NGC 3311 in the V-band. We search for a dark halo which
in the context of a spherical Jeans model. We also compare the radial velocity
distributions of globular clusters and planetary nebulae. The projected stellar
velocity dispersion rises from 185 km/s to 350 km/s at a radius of 20 kpc. The
globular cluster dispersion rises as well from 500 km/s at 10 kpc to about 800
km/s at 100 kpc, comparable to the velocity dispersion of the cluster galaxies.
A dark matter halo with a core reproduces well the velocity dispersions of
stars and globular clusters simultaneously under isotropy. The central stellar
velocity dispersions predicted by cosmological NFW halos are less good
representations, while the globular clusters allow a wide range of halo
parameters. A suspected radial anisotropy of the stellar population aggravates
the deviations. However, we find discrepancies with previous kinematical data,
which we cannot resolve and may indicate a more complicated velocity pattern.
Although one cannot conclusively demonstrate that the dark matter halo of NGC
3311 has a core rather than a cusp, a core seems to be preferred by the present
data. A more complete velocity field and an analysis of the anisotropy is
required to reach firm conclusions.Comment: 8 pages, 5 figures, abstract abridged, accepted for publication in
A&
The dynamically hot stellar halo around NGC 3311: a small cluster-dominated central galaxy
An important open question is the relation between intracluster light and the
halos of central galaxies in galaxy clusters. Here we report results from an on
going project with the aim to characterize the dynamical state in the core of
the Hydra I (Abell 1060) cluster around NGC 3311. Methods: We analyze deep
long-slit absorption line spectra reaching out to ~25 kpc in the halo of NGC
3311. Results: We find a very steep increase in the velocity dispersion profile
from a central sigma_0=150 km/s to sigma_out ~450 km/s at R ~ 12 kpc. Farther
out, to ~25 kpc, sigma appears to be constant at this value, which is ~60% of
the velocity dispersion of the Hydra I galaxies. With its dynamically hot halo
kinematics, NGC 3311 is unlike other normal early-type galaxies. Conclusions:
These results and the large amount of dark matter inferred from X-rays around
NGC 3311 suggest that the stellar halo of this galaxy is dominated by the
central intracluster stars of the cluster, and that the transition from
predominantly galaxy-bound stars to cluster stars occurs in the radial range 4
to 12 kpc from the center of NGC 3311. We comment on the wide range of halo
kinematics observed in cluster central galaxies, depending on the evolutionary
state of their host clusters.Comment: 5 pages, 4 figures, 1 table, accepted for publication in A&
Efficacy and safety of dapoxetine in treatment of premature ejaculation: an evidence‐based review
SummaryBackground Premature ejaculation (PE) is a major issue in male sexual health, with a global prevalence estimated to be between 20% and 40%, making it the most common sexual dysfunction in men. PE causes distress and reduced quality of life for patients and has a negative impact on interpersonal relationships. Historically, it has been treated with cognitive therapy, behavioural methods and off-label use of selective serotonin reuptake inhibitors (SSRIs) usually used to treat depression and other psychological disorders. Dapoxetine is the only SSRI specifically designed to treat PE. Mechanism of action Dapoxetine hydrochloride is a potent inhibitor of serotonin reuptake transporters. Dapoxetine is suited for 'on-demand' treatment of PE because of its rapid absorption and short initial half-life. Efficacy Evidence from published studies showed that dapoxetine 30 mg or 60 mg taken 'on-demand' results in a significant increase in intravaginal ejaculatory latency time (IELT) when compared with placebo. Most patient-reported outcomes are clearly improved relative to placebo following dapoxetine therapy, indicating greater control over ejaculation, more satisfaction with intercourse, less ejaculation-related distress and significantly reduced interpersonal difficulties. Safety The most common adverse events with dapoxetine are nausea, dizziness, somnolence, headache, diarrhoea and insomnia. Usually they do not lead to drug discontinuation. Conclusion Dapoxetine is the only effective and safe available on-label oral treatment for PE, and its use can result in better quality of life for the patient and their sexual partner
Codominance of Lactobacillus plantarum and obligate heterofermentative lactic acid bacteria during sourdough fermentation
Fifteen sourdoughs produced in western Sicily (southern Italy) were analysed by classical methods for their chemico-physical characteristics and the levels of lactic acid bacteria (LAB). pH and total titratable acidity (TTA) were mostly in the range commonly reported for similar products produced in Italy, but the fermentation quotient (FQ) of the majority of samples was above 4.0, due to the low concentration of acetic acid estimated by high performance liquid chromatography (HPLC). Specific counts of LAB showed levels higher than 108CFUg-1 for many samples. The colonies representing various morphologies were isolated and, after the differentiation based on phenotypic characteristics, divided into 10 groups. The most numerous group was composed of facultative heterofermentative isolates, indicating a relevance of this bacterial group during fermentation. The genetic analysis by randomly amplified polymorphic DNA (RAPD)-PCR, 16S rRNA gene sequencing and species-specific PCRs identified 33 strains as Lactobacillus plantarum, Lactobacillus curvatus and Lactobacillus graminis. Due to the consistent presence of L.plantarum, it was concluded that this species codominates with obligate heterofermentative LAB in sourdough production in this geographical area. In order to evaluate the performances at the basis of their fitness, the 29 L.plantarum strains were investigated for several technological traits. Twelve cultures showed good acidifying abilities invitro and L.plantarum PON100148 produced the highest concentrations of organic acids. Eleven strains were positive for extracellular protease activity. Bacteriocin-like inhibitory substances (BLIS) production and antifungal activity was scored positive for several strains, included L.plantarum PON100148 which was selected as starter for experimental sourdough production. The characteristics of the sourdoughs and the resulting breads indicated that the best productions were obtained in presence of L.plantarum PON100148
Industrial application of selected lactic acid bacteria isolated from local semolinas for typical sourdough bread production
Four obligate heterofermentative lactic acid bacteria (LAB) strains (Weissella cibaria PON10030 and
PON10032 and Leuconostoc citreum PON 10079 and PON10080) were tested as single strain starters,
mono-species dual strain starters, and multiple strain starter for the preparation and propagation of
sourdoughs for the production of a typical bread at industrial level. The kinetics of pH and TTA during the
daily sourdough refreshments indicated a correct acidification process for all trials. The concentration of
lactic and acetic acid increased consistently during fermentation. The resulting molar ratios between
these two organic acids in the experimental trials were lower than those observed in the control trial.
The microbiological investigation showed levels of approximately 109 CFU/mL in almost all sourdoughs
and the comparison of the genetic polymorphisms of the dominating LAB with those of the pure cultures
evidenced the persistence of the added strains over time. The resulting breads were evaluated for several
quality parameters. The breads with the greatest height were obtained with the quadruple combination
of leuconostocs and weissellas. The highest softness was registered for the breads obtained from fermentations
performed by W. cibaria PON10032 alone and in combination. The different inocula influenced
also the color, the void fraction, the cell density and the mean cell area of the breads. Different
levels of acids, alcohols, aldehydes, esters, hydrocarbons, ketones, terpenes, furans and phenol were
emitted by the breads. The sensory tests indicated the breads from the sourdoughs fermented with the
seven LAB inocula as sweeter and less acidic than control breads and the breads from the trials with the
highest complexity of LAB inoculums were those more appreciated by tasters. A multivariate approach
found strong differences among the trials. In particular, control breads and the breads obtained with
different starter LAB were quite distant and a more strict relation was found among the productions
carried out by W. cibaria strains. This study proved the suitability of the selected strains of L. citreum and
W. cibaria for industrial-scale level applications in sourdough bread production
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