21 research outputs found
The mass-metallicity-star formation rate relation at z > 2 with 3D <i>Hubble Space Telescope</i>
We present new accurate measurements of the physical properties of a
statistically significant sample of 103 galaxies at z~2 using near-infrared
spectroscopy taken as part of the 3D-HST survey. We derive redshifts,
metallicities and star formation rates (SFRs) from the [OII], [OIII] and Hbeta
nebular emission lines and exploit the multi-wavelength photometry available in
CANDELS to measure stellar masses. We find the mass-metallicity relation (MZR)
derived from our data to have the same trend as previous determinations in the
range 0<z<3, with lower mass galaxies having lower metallicities. However we
find an offset in the relation compared to the previous determination of the
z~2 MZR by Erb et al. 2006b, who measure metallicities using the [NII]/Halpha
ratio, with metallicities lower at a given mass. Incorporating our SFR
information we find that our galaxies are offset from the Fundamental
Metallicity Relation (FMR) by ~0.3 dex. We investigate the photoionization
conditions and find that our galaxies are consistent with the elevated
ionization parameter previously reported in high-redshift galaxies. Using the
BPT diagram we argue that, if this is the case, metallicity indicators based on
[NII] and Halpha may not be consistent with the ones obtained via oxygen lines
and Hbeta. Using a recent determination of the theoretical evolution of the
star forming sequence in the BPT diagram we convert our measured [OIII]/Hbeta
line ratios to [NII]/Halpha ratios. From the [NII]/Halpha ratio we infer
systematically higher metallicities in better agreement with the FMR. Our
results thus suggest the evolution of the FMR previously reported at z~2-3 may
be an artifact of the differential evolution in metallicity indicators, and
caution against using locally calibrated metallicity relations at high redshift
which do not account for evolution in the physical conditions of star-forming
regions.Comment: 15 pages, 13 figures, acccpted for publication in MNRA
Mortality rate and risk factors for gastrointestinal bleeding in elderly patients
Background: Gastrointestinal bleeding (GIB) is burdened by high mortality rate that increases with aging. Elderly patients may be exposed to multiple risk factors for GIB. We aimed at defining the impact of GIB in elderly patients. Methods: Since 2008, samples of elderly patients (age 65 65 years) with multimorbidity admitted to 101 internal medicine wards across Italy have been prospectively enrolled and followed-up (REPOSI registry). Diagnoses of GIB, length of stay (LOS), mortality rate, and possible risk factors, including drugs, index of comorbidity (Cumulative Illness Rating Scale [CIRS]), polypharmacy, and chronic diseases were assessed. Adjusted multivariate logistic regression models were computed. Results: 3872 patients were included (mean age 79 \ub1 7.5 years, F:M ratio 1.1:1). GIB was reported in 120 patients (mean age 79.6 \ub1 7.3 years, F:M 0.9:1), with a crude prevalence of 3.1%. Upper GIB occurred in 72 patients (mean age 79.3 \ub1 7.6 years, F:M 0.8:1), lower GIB in 51 patients (mean age 79.4 \ub1 7.1 years, F:M 0.9:1), and both upper/lower GIB in 3 patients. Hemorrhagic gastritis/duodenitis and colonic diverticular disease were the most common causes. The LOS of patients with GIB was 11.7 \ub1 8.1 days, with a 3.3% in-hospital and a 9.4% 3-month mortality rates. Liver cirrhosis (OR 5.64; CI 2.51\u201312.65), non-ASA antiplatelet agents (OR 2.70; CI 1.23\u20135.90), and CIRS index of comorbidity >3 (OR 2.41; CI 1.16\u20134.98) were associated with GIB (p < 0.05). Conclusions: A high index of comorbidity is associated with high odds of GIB in elderly patients. The use of non-ASA antiplatelet agents should be discussed in patients with multimorbidity