83 research outputs found
The lenticular galaxy NGC3607: stellar population, metallicity and ionised gas
In this work we derive clues to the formation scenario and ionisation source
of the lenticular galaxy NGC 3607 by means of metallicity gradients, stellar
population and emission lines properties. We work with long-slit spectroscopy
from which we (i) study the radial distribution of the equivalent widths of
conspicuous metallic absorption features, (ii) infer on the star-formation
history (with a stellar population synthesis algorithm), and (iii) investigate
the ionisation source responsible for a few strong emission lines. Negative
radial gradients are observed for most of the absorption features of NGC 3607.
Compared to the external parts, the central region has a deficiency of alpha
elements and higher metallicity, which implies different star-formation
histories in both regions. At least three star formation episodes are detected,
with ages within 1-13 Gyr. The dynamical mass and the gradient slope are
consistent with mergers being important contributors to the formation mechanism
of NGC 3607. Emission-line ratios indicate the presence of a LINER at the
centre of NGC 3607. Contribution of hot, old stars to the gas ionisation
outside the central region is detected. Evidence drawn from this work suggest
small mergers as important contributors to the formation of NGC 3607, a
scenario consistent with the star-formation episodes.Comment: 10 pages, 11 figs; accepted for publication in A&
Counterintuitive transitions between crossing energy levels
We calculate analytically the probabilities for intuitive and
counterintuitive transitions in a three-state system, in which two parallel
energies are crossed by a third, tilted energy. The state with the tilted
energy is coupled to the other two states in a chainwise linkage pattern with
constant couplings of finite duration. The probability for a counterintuitive
transition is found to increase with the square of the coupling and decrease
with the squares of the interaction duration, the energy splitting between the
parallel energies, and the tilt (chirp) rate. Physical examples of this model
can be found in coherent atomic excitation and optical shielding in cold atomic
collisions
On the topology of adiabatic passage
We examine the topology of eigenenergy surfaces characterizing the population
transfer processes based on adiabatic passage. We show that this topology is
the essential feature for the analysis of the population transfers and the
prediction of its final result. We reinterpret diverse known processes, such as
stimulated Raman adiabatic passage (STIRAP), frequency-chirped adiabatic
passage and Stark-chirped rapid adiabatic passage (SCRAP). Moreover, using this
picture, we display new related possibilities of transfer. In particular, we
show that we can selectively control the level which will be populated in
STIRAP process in Lambda or V systems by the choice of the peak amplitudes or
the pulse sequence
The elliptical galaxy NGC 5044: Stellar population and ionized gas
In this work we investigate the stellar population, metallicity distribution
and ionized gas in the elliptical galaxy NGC 5044, using long-slit spectroscopy
and a stellar population synthesis method. We found differences in the slope of
metal-line profiles along the galaxy which suggests an enhancement of alpha
elements, particularly towards the central region. The presence of a
non-thermal ionization source, such as a low-luminosity AGN and/or shock
ionization, is implied by the large values of the ratio (N II])Ha observed in
all sampled regions. However, the emission lines observed in the external
regions indicate the presence of an additional ionization source, probably hot,
post-AGB stars.Comment: Accepted by A&
Panchromatic Averaged Stellar Populations: PaasP
We study how the spectral fitting of galaxies, in terms of light fractions
derived in one spectral region translates into another region, by using results
from evolutionary synthesis models. In particular, we examine propagation
dependencies on Evolutionary Population Synthesis (EPS, {\sc grasil}, {\sc
galev}, Maraston and {\sc galaxev}) models, age, metallicity, and stellar
evolution tracks over the near-UV---near infrared (NUV---NIR, 3500\AA\ to
2.5\mc) spectral region. Our main results are: as expected, young (
400 Myr) stellar population fractions derived in the optical cannot be directly
compared to those derived in the NIR, and vice versa. In contrast, intermediate
to old age ( 500 Myr) fractions are similar over the whole spectral
region studied. The metallicity has a negligible effect on the propagation of
the stellar population fractions derived from NUV --- NIR. The same applies to
the different EPS models, but restricted to the range between 3800 \AA\ and
9000 \AA. However, a discrepancy between {\sc galev}/Maraston and {\sc
grasil}/{\sc galaxev} models occurs in the NIR. Also, the initial mass function
(IMF) is not important for the synthesis propagation. Compared to {\sc
starlight} synthesis results, our propagation predictions agree at 95%
confidence level in the optical, and 85% in the NIR. {\bf In summary,
spectral fitting} performed in a restricted spectral range should not be
directly propagated from the NIR to the UV/Optical, or vice versa. We provide
equations and an on-line form ({\bf Pa}nchromatic {\bf A}veraged {\bf S}tellar
{\bf P}opulation - \paasp) to be used for this purpose.Comment: 13 pages and 10 figures. Accepted by MNRA
The elliptical galaxies NGC 1052 and NGC 7796: stellar populations and abundance alpha/Fe ratio
Context: The spatial distribution of the stellar populations inside a
spheroidal system and their kinematical properties supply important
informations about the formation process. Aims: We have performed a detailed
stellar population analysis using long slit spectroscopic observations up to
almost one effective radius of two different early-type galaxies of low density
regions of the local Universe: NGC 1052, a E4 Liner prototype of a loose group
that has a stellar rotating disc, and NGC 7796, a E1 of the field which shows a
kinematically distinct core. The mean luminosity-weighted stellar age,
metallicity, and alpha/Fe ratio along both photometric axes of them have been
obtained in order to reconstruct the star formation history in their
kinematically distinct subsystems. Methods: We have measured Lick indices and
computed their radial gradients. They were compared with the predicted ones of
simple stellar population models. We have also applied a stellar population
synthesis. Results: The star characteristics are associated with their
kinematics: they are older and alpha-enhanced in the bulge of NGC 1052 and core
of NGC 7796, while they show a strong spread of alpha/Fe and age along the disc
of NGC 1052 and an outwards radial decreasing of them outside the core of NGC
7796. The age variation is possibly connected to the alpha/Fe one. Conclusions:
Both galaxies were formed by processes in which the star formation occurred
firstly at the bulge (NGC 1052) and nucleus (NGC 7796) 12-15 Gyr ago on short
timescales (0.1-1 Gyr) providing an efficient chemical enrichment by SN-II. In
the disc of NGC 1052, there is some spread of age and formation timescales
around its stars. In NGC 7796, the star formation timescale had some outwards
radial increasing along both axes.Comment: 26 pages, 27 figures, accepted for publication in A&
Comparison of DNA histograms by standard flow cytometry and image cytometry on sections in Barrett's adenocarcinoma
<p>Abstract</p> <p>Background</p> <p>The purpose of this study was to compare DNA histograms obtained by standard flow cytometry (FC) and high fidelity image cytometry on sections (ICS) in normal gastrointestinal mucosa and Barrett's adenocarcinoma (BAC).</p> <p>Methods</p> <p>Archival formalin-fixed paraffin-embedded tissue blocks of 10 normal controls from 10 subjects and 42 BAC tissues from 17 patients were examined. DNA FC was performed using standard techniques and ICS was carried out by Automated Cellular Imaging System (ACIS). DNA ploidy histograms were classified into diploid with peak DNA index (DI) at 0.9–1.1, and aneuploid with peak DI > 1.1. DI values of aneuploid peaks were determined. Additionally, for DNA ICS, heterogeneity index (HI) representing DNA content heterogeneity, and histograms containing cells with DI > G2 were also identified.</p> <p>Results</p> <p>All control samples were diploid by both FC and ICS analyses. In BAC, FC showed diploid peaks in 29%, diploid peaks with additional aneuploid or tetraploid peaks in 57%, and 14% of the samples, respectively. In contrast, ICS showed aneuploid peaks in all the cases with peak DI > 1.25; 37 cases had peak DI between 1.25 and 2.25; and 5 cases had peak DI > 2.25. HI values (mean ± SD) were 11.3 ± 1.1 in controls and 32.4 ± 8.5 in BAC (p < 0.05). Controls had no G2 exceeding cells. However, 19/37 (51%) of the cases with primary peak DI < 2.25 had cells exceeding 9N.</p> <p>Conclusion</p> <p>ICS detects DNA aneuploidy in all BAC samples while FC missed the diagnosis of aneuploidy in 29%. In addition, ICS provides more information on HI and G2 exceeding rates.</p
Subnormal vitamin B12 concentrations and anaemia in older people: a systematic review
<p>Abstract</p> <p>Background</p> <p>Pernicious anaemia is undeniably associated with vitamin B12 deficiency, but the association between subnormal vitamin B12 concentrations and anaemia in older people is unclear. The aim of this systematic review was to evaluate the association between subnormal vitamin B12 concentrations and anaemia in older people.</p> <p>Methods</p> <p>Clinical queries for aetiology and treatment in bibliographic databases (PubMed [01/1949-10/2009]; EMBASE [01/1980-10/2009]) were used. Reference lists were checked for additional relevant studies. Observational studies (≥50 participants) and randomized placebo-controlled intervention trials (RCTs) were considered.</p> <p>Results</p> <p>25 studies met the inclusion criteria. Twenty-one observational cross-sectional studies (total number of participants n = 16185) showed inconsistent results. In one longitudinal observational study, low vitamin B12 concentrations were not associated with an increased risk of anaemia (total n = 423). The 3 RCTs (total n = 210) were well-designed and showed no effect of vitamin B12 supplementation on haemoglobin concentrations during follow-up in subjects with subnormal vitamin B12 concentrations at the start of the study. Due to large clinical and methodological heterogeneity, statistical pooling of data was not performed.</p> <p>Conclusions</p> <p>Evidence of a positive association between a subnormal serum vitamin B12 concentration and anaemia in older people is limited and inconclusive. Further well-designed studies are needed to determine whether subnormal vitamin B12 is a risk factor for anaemia in older people.</p
Primary biliary cirrhosis
Primary biliary cirrhosis (PBC) is a chronic and slowly progressive cholestatic liver disease of autoimmune etiology characterized by injury of the intrahepatic bile ducts that may eventually lead to liver failure. Affected individuals are usually in their fifth to seventh decades of life at time of diagnosis, and 90% are women. Annual incidence is estimated between 0.7 and 49 cases per million-population and prevalence between 6.7 and 940 cases per million-population (depending on age and sex). The majority of patients are asymptomatic at diagnosis, however, some patients present with symptoms of fatigue and/or pruritus. Patients may even present with ascites, hepatic encephalopathy and/or esophageal variceal hemorrhage. PBC is associated with other autoimmune diseases such as Sjogren's syndrome, scleroderma, Raynaud's phenomenon and CREST syndrome and is regarded as an organ specific autoimmune disease. Genetic susceptibility as a predisposing factor for PBC has been suggested. Environmental factors may have potential causative role (infection, chemicals, smoking). Diagnosis is based on a combination of clinical features, abnormal liver biochemical pattern in a cholestatic picture persisting for more than six months and presence of detectable antimitochondrial antibodies (AMA) in serum. All AMA negative patients with cholestatic liver disease should be carefully evaluated with cholangiography and liver biopsy. Ursodeoxycholic acid (UDCA) is the only currently known medication that can slow the disease progression. Patients, particularly those who start UDCA treatment at early-stage disease and who respond in terms of improvement of the liver biochemistry, have a good prognosis. Liver transplantation is usually an option for patients with liver failure and the outcome is 70% survival at 7 years. Recently, animal models have been discovered that may provide a new insight into the pathogenesis of this disease and facilitate appreciation for novel treatment in PBC
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