1,404 research outputs found
A methodology to allow avalanche forecasting on an information retrieval system
This paper presents adaptations and tests undertaken to allow an information retrieval (IR) system to forecast the likelihood of avalanches on a particular day. The forecasting process uses historical data of the weather and avalanche conditions for a large number of days. A method for adapting these data into a form usable by a text-based IR system is first described, followed by tests showing the resulting system’s accuracy to be equal to existing ‘custom built’ forecasting systems. From this, it is concluded that the adaptation methodology is effective at allowing such data to be used in a text-based IR system. A number of advantages in using an IR system for avalanche forecasting are also presented
Exploration of the BaSeL stellar library for 9 F-type stars COROT potential targets
The Basel Stellar Library (BaSeL models) is constituted of the merging of
various synthetic stellar spectra libraries, with the purpose of giving the
most comprehensive coverage of stellar parameters. It has been corrected for
systematic deviations detected in respect to UBVRIJHKLM photometry at solar
metallicity, and can then be considered as the state-of-the-art knowledge of
the broad band content of stellar spectra. In this paper, we consider a sample
of 9 F-type stars with detailed spectroscopic analysis to investigate the Basel
Stellar Library in two photometric systems simultaneously, Johnson (B-V, U-B)
and Stromgren (b-y, m_1, and c_1). The sample corresponds to potential targets
of the central seismology programme of the COROT space experiment, which have
been recently observed at OHP. The atmospheric parameters T_eff, [Fe/H], and
log g obtained from the BaSeL models are compared with spectroscopic
determinations as well as with results of other photometric calibrations. For a
careful interpretation of the BaSeL solutions, we computed confidence regions
around the best ^2-estimates and projected them on T_eff-[Fe/H],
T_eff-log g, and log g-[Fe/H] diagrams. (Abridged)Comment: 16 pages, LaTeX2e; version accepted for publication in the new A&A
Journal: minor changes + figures in black and white for better readabilit
Gas and stellar metallicities in H ii galaxies
We examine the gas and stellar metallicities in a sample of H ii galaxies from the Sloan Digital Sky Survey, which possibly contains the largest homogeneous sample of H ii galaxy spectra to date. We eliminated all spectra with an insufficient signal-to-noise ratio, without strong emission lines and without the [O ii] λ3727 Å line, which is necessary for the determination of the gas metallicity. This excludes galaxies with redshift ≲ 0.033. Our final sample contains ∼700 spectra of H ii galaxies. Through emission line strength calibrations and a detailed stellar population analysis employing evolutionary stellar synthesis methods, which we already used in previous works, we determined the metallicities of both the gas and the stellar content of these galaxies. We find that in H ii galaxies up to stellar masses of 5 × 109 M⊙, enrichment mechanisms do not vary with galactic mass, being the same for low- and high-mass galaxies on average. They do seem to present a greater variety at the high-mass end, though, indicating a more complex assembly history for high-mass galaxies. In around 23 per cent of our H ii galaxies, we find a metallicity decrease over the last few Gyr. Our results favour galaxy evolution models featuring constantly infalling low-metallicity clouds that retain part of the galactic winds. Above 5 × 109 M⊙ stellar mass, the retention of high-metallicity gas by the galaxies' gravitational potential dominate
Differences of disease progression in congestive heart failure due to alcoholic as compared to idiopathic dilated cardiomyopathy
In patients with alcoholic cardiomyopathy there is evidence that mild heart failure is reversible if patients abstain from alcohol, but there is no consensus whether the disease is progressive once structural myocardial dilatation has evolved. The aim of the present study was to compare the long-term course of congestive heart failure due to alcoholic and idiopathic dilated cardiomyopathy. Of 75 patients with overt congestive heart failure, 23 had alcoholic cardiomyopathy and were compared to 52 patients with idiopathic cardiomyopathy. The mean age was 48 ± 12 years. Despite medical therapy, heart failure class New York Heart Association III-IV was present in 52% of patients with alcoholic and 47% of patients with idiopathic cardiomyopathy (not significant). Their mean left ventricular ejection fraction was 30 ± l2% vs 28 ± 12% and left ventricular end-diastolic volumes were 264 ± 125 ml and 254 ± 100 ml respectively (not significant). Overall survival at 1, 5 and 10 years was l00%, 81% and 81% for the group with alcoholic dilated cardiomyopathy and 89%, 48% and 30% for the group with idiopathic cardiomyopathy, respectively (P=0·041 and the difference was even greater for transplant-free survival P=0·005 Clinical and invasive signs of left and right heart failure as well as left ventricular dimensions were predictive of a fatal outcome; however, symptom duration and left ventricular volumes were only predictive in patients with idiopathic cardiomyopathy, suggesting that in the two patient groups different mechanisms may lead to death. Mortality in patients with severe congestive heart failure and left ventricular dilatation due to alcoholic cardiomyopathy is significantly lower than that in patients with idiopathic cardiomyopathy and similar degrees of heart failure. Thus, despite structural changes mherent in marked left ventricular dilatation, disease progression in alcoholic dilated cardiomyopathy is different from that in idiopathic cardiomyopathy and thus may have implications for the choice of therap
Uncertainty-principle noise in vacuum-tunneling transducers
The fundamental sources of noise in a vacuum-tunneling probe used as an
electromechanical transducer to monitor the location of a test mass are
examined using a first-quantization formalism. We show that a tunneling
transducer enforces the Heisenberg uncertainty principle for the position and
momentum of a test mass monitored by the transducer through the presence of two
sources of noise: the shot noise of the tunneling current and the momentum
fluctuations transferred by the tunneling electrons to the test mass. We
analyze a number of cases including symmetric and asymmetric rectangular
potential barriers and a barrier in which there is a constant electric field.
Practical configurations for reaching the quantum limit in measurements of the
position of macroscopic bodies with such a class of transducers are studied
Old stellar Galactic disc in near-plane regions according to 2MASS: scales, cut-off, flare and warp
We have pursued two different methods to analyze the old stellar population
near the Galactic plane, using data from the 2MASS survey. The first method is
based on the isolation of the red clump giant population in the color-magnitude
diagrams and the inversion of its star counts to obtain directly the density
distribution along the line of sight. The second method fits the parameters of
a disc model to the star counts in 820 regions. Results from both independent
methods are consistent with each other. The qualitative conclusions are that
the disc is well fitted by an exponential distribution in both the
galactocentric distance and height. There is not an abrupt cut-off in the
stellar disc (at least within R<15 kpc). There is a strong flare (i.e. an
increase of scale-height towards the outer Galaxy) which begins well inside the
solar circle, and hence there is a decrease of the scale-height towards the
inner Galaxy. Another notable feature is the existence of a warp in the old
stellar population whose amplitude is coincident with the amplitude of the gas
warp.
It is shown for low latitude stars (mean height: |z|~300 pc) in the outer
disc (galactocentric radius R>6 kpc) that: the scale-height in the solar circle
is h_z(R_sun)=3.6e-2 R_sun, the scale-length of the surface density is h_R=0.42
R_sun and the scale-length of the space density in the plane (i.e. including
the effect of the flare) is H=0.25 R_sun. The variation of the scale-height due
to the flare follows roughly a law h_z(R) =~ h_z(R_sun) exp
[(R-R_\odot)/([12-0.6R(kpc)] kpc)] (for R<~15 kpc; R_sun=7.9 kpc). The warp
moves the mean position of the disc to a height z_w=1.2e-3 R(kpc)^5.25
sin(phi+(5 deg.)) pc (for R<~13 kpc; R_sun=7.9 kpc).Comment: LaTEX, 20 pages, 23 figures, accepted to be published in A&
A review of implant provision for hypodontia patients within a Scottish referral centre
Background: Implant treatment to replace congenitally missing teeth often involves multidisciplinary input in a secondary care environment. High quality patient care requires an in-depth knowledge of treatment requirements.
Aim: This service review aimed to determine treatment needs, efficiency of service and outcomes achieved in hypodontia patients. It also aimed to determine any specific difficulties encountered in service provision, and suggest methods to overcome these.
Methods: Hypodontia patients in the Unit of Periodontics of the Scottish referral centre under consideration, who had implant placement and fixed restoration, or review completed over a 31 month period, were included. A standardised data collection form was developed and completed with reference to the patient's clinical record. Information was collected with regard to: the indication for implant treatment and its extent; the need for, complexity and duration of orthodontic treatment; the need for bone grafting and the techniques employed and indicators of implant success.
Conclusion: Implant survival and success rates were high for those patients reviewed. Incidence of biological complications compared very favourably with the literature
The Star Formation Epoch of the Most Massive Early-Type Galaxies
We present new Keck spectroscopy of early-type galaxies in three galaxy
clusters at z~0.5. We focus on the fundamental plane (FP) relation, and combine
the kinematics with structural parameters determined from HST images. The
galaxies obey clear FP relations, which are offset from the FP of the nearby
Coma cluster due to passive evolution of the stellar populations. The z~0.5
data are combined with published data for 11 additional clusters at
0.18<z<1.28, to determine the evolution of the mean M/L(B) ratio of cluster
galaxies with masses M>10^11 M_sun, as implied by the FP. We find
dlog(M/L(B))/dz = -0.555+-0.042, stronger evolution than was previously
inferred from smaller samples. The observed evolution depends on the
luminosity-weighted mean age of the stars in the galaxies, the initial mass
function (IMF), selection effects due to progenitor bias, and other parameters.
Assuming a normal IMF but allowing for various other sources of uncertainty we
find z* = 2.01+-0.20 for the luminosity-weighted mean star formation epoch. The
main uncertainty is the slope of the IMF in the range 1-2 Solar masses: we find
z* = 4.0 for a top-heavy IMF with slope x=0. The M/L(B) ratios of the cluster
galaxies are compared to those of recently published samples of field
early-type galaxies at 0.32<z<1.14. Assuming that progenitor bias and the IMF
do not depend on environment we find that the present-day age of stars in
massive field galaxies is 4.1 +- 2.0 % (~0.4 Gyr) less than that of stars in
massive cluster galaxies, consistent with most, but not all, previous studies
of local and distant early-type galaxies. This relatively small age difference
is surprising in the context of expectations from ``standard'' hierarchical
galaxy formation models. [ABRIDGED]Comment: Accepted for publication in ApJ. Minor corrections to match published
versio
Breast cancer: Pretreatment drug resistance parameters (GSH-system, ATase, P-glycoprotein) in tumor tissue and their correlation with clinical and prognostic characteristics
Background: The identification of new factors predicting relapse, outcome and response to systemic therapy in breast cancer is warranted. The measurement of biological markers such as drug resistance parameters (DRPs), which are part of the phenotype of malignant cells and contribute to resistance to anti-cancer drugs may be a possibility, which may ultimately lead to improvement of therapeutic results. Patients and methods: The level of glutathione (GSH), activities of glutathione-S-transferase (GST), glutathione-peroxidase (GPx), 06-alkylguanine-DNA-alkyltransferase (ATase), and P-glycoprotein (PGP) were measured in tumor and adjacent tumor free tissue samples from 89 consecutive, untreated females with breast cancer and correlated with clinical and prognostic factors. Early breast cancer (EBC) was diagnosed in 56 patients, 22 patients had locally advanced (LABC) and 11 patients metastatic breast cancer. Results: All DRPs showed significantly higher expression in tumor than in tumor free tissues. GPx was positively correlated with GST (r = 0.3, P = 0.0048) and with GSH (r = 0.5, P = 0.0001) in tumor as well as in normal tissue. GST activity was significantly higher in EBC than in LABC or metastatic breast cancer (P = 0.02). GSH level was significantly higher in grade I than in grade 2 or grade 3 tumors (P = 0.01). When clinical characteristics were related to the level of DRP, ‘high' GSH was associated with age >60 years (P = 0.01) in EBC, and with grade 1-2 tumors (P = 0.05) in LABC. No differences in OS were apparent between groups of ‘high' and ‘low' DRP-expression. However, the four-year estimated disease-free survival of EBC tended to be higher in patients with ‘high' GST (P = 0.10) and of LABC in patients with ‘high' GPx levels (P = 0.06). Conclusion: We conclude that ‘high' levels of DRP in tumor tissue of breast cancer patients are part of the initial phenotype of the malignant cells. Due to its high prevalence (83% in EBC, 100% in primarily metastatic breast cancer), PGP did not add to prognostic information. High levels of GSH, GST and and GPx were associated with favorable clinical characteristics and good prognosis, whereas low levels of GSH and GST activity were associated with more aggressive or more advanced diseas
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