52 research outputs found
Preoperative serum sodium measurements and postoperative inpatient mortality: A casecontrol analysis of data from the South African Surgical Outcomes Study
Background. Abnormal preoperative serum sodium measurements have been shown to be associated with increased postoperative mortality in US and European surgical populations. It is possible that such measurements are also associated with increased postoperative mortality in a South African (SA) setting, but this is yet to be confirmed. Establishing whether preoperative serum sodium measurements are associated with postoperative mortality could have implications for perioperative risk stratification in SA settings.Objectives. To determine whether preoperative serum sodium measurements are associated with postoperative mortality in SA surgical patients.Methods. This was an unmatched case-control study of patient data (demographics, comorbidities, procedure-related variables, and preoperative serum sodium measurements) collected during the South African Surgical Outcomes Study. Data were analysed using recommended statistical methods for unmatched case-control studies.Results. The study population comprised 103 patients and 410 controls. Cases were defined as patients who suffered postoperative inpatient mortality, while controls were defined as patients who did not suffer postoperative inpatient mortality. Preoperative hypernatraemia (i.e. a preoperative serum sodium measurement >144 mEq/L) was independently associated with a four-fold higher risk of postoperative inpatient mortality compared with a normal preoperative serum sodium measurement of 135 - 144 mEq/L (odds ratio (OR) 4.21, 95% confidence interval (CI) 1.19 - 14.83, p=0.025). Preoperative hyponatraemia (i.e. a preoperative serum sodium measurement <135 mEq/L) was not independently associated with a higher or lower risk of postoperative inpatient mortality compared with a normal preoperative serum sodium measurement (OR 1.39, 95% CI 0.70 - 2.76, p=0.346).Conclusions. Preoperative hypernatraemia, but not preoperative hyponatraemia, is a risk factor for postoperative inpatient mortality in SA surgical patients
Chemical diversity of gas in distant galaxies: The metal and dust enrichment and variations within absorbing galaxies
The chemical composition of gas in galaxies can be measured in detail from
absorption spectroscopy. By studying gas in galaxies in this way, it is
possible to investigate the small and faint galaxies, which are the most
numerous in the universe. In particular, the chemical distribution of gas in
absorbing systems gives us insight into cycles of gas in and around galaxies.
Here we study chemical enrichment within 64 Damped Lyman-alpha Absorption (DLA)
systems between . We use high-resolution spectra from VLT/UVES
to infer dust depletion from relative abundances of several metals. We perform
a component-by-component analysis within DLAs, and characterise variations in
their chemical enrichment. Unlike hydrogen, the metal columns can be
characterised for individual components. We use them to derive the dust
depletion ([Zn/Fe]fit), as an indicator for chemical enrichment. We find that
some DLAs are chemically diverse within themselves, with [Zn/Fe]fit ranging up
to 0.62 dex within a single system. This suggests that absorbing gas within
these galaxies is chemically diverse. Although we do not find a clear trend of
decreasing dust depletion with redshift, we do see that the most chemically
enriched systems are at lower redshifts. We also observe evidence for dust-poor
components at all redshifts, which may be due to the accretion of pristine gas
onto galaxies. We combine the chemical and kinematic properties of the
individual gas components and observe potential signatures of infalling gas,
with low depletion at velocities below 100km/s, and outflows, with high
depletion and velocities of 600km/s. We find over-abundances of
alpha-elements (an enhancement of 0.3dex) and under-abundances of Mn in
several components, which is likely a signature of core-collapse SNe
nucleosythesis in the ISM. We observe these effects mostly at lower levels of
chemical enrichment.Comment: 56 pages, 99 figures, Accepted for publication in A&A, Abstract
abridged for arXi
Dust depletion of of metals from local to distant galaxies II: Cosmic dust-to-metal ratio and dust composition
The evolution of the cosmic dust content and the cycle between metals and
dust in the interstellar medium (ISM) play a fundamental role in galaxy
evolution. The chemical enrichment of the Universe can be traced through the
evolution of the dust-to-metals ratio (DTM) and the dust-to-gas ratio (DTG)
with metallicity. We use a novel method to determine mass estimates of the DTM,
DTG and dust composition based on our previous measurements of the depletion of
metals in different environments (the Milky Way, the Magellanic Clouds, and
damped Lyman- absorbers, DLAs, toward quasars and towards gamma-ray
bursts, GRBs), which were calculated from the relative abundances of metals in
the ISM through absorption-line spectroscopy column densities observed mainly
from VLT/UVES and X-shooter, and HST/STIS. We derive the dust extinction from
the estimated dust depletion () and compare with the
from extinction. We find that the DTM and DTG ratios increase with metallicity
and with the dust tracer [Zn/Fe]. This suggests that grain growth in the ISM is
a dominant process of dust production. The increasing trend of the DTM and DTG
with metallicity is in good agreement with a dust production and evolution
model. Our data suggest that the stellar dust yield is much lower than the
metal yield and thus that the overall amount of dust in the warm neutral medium
that is produced by stars is much lower. We find that is
overall lower than for the Milky Way and a few Magellanic
Clouds lines of sight, a discrepancy that is likely related to the presence of
carbonaceous dust. We show that the main elements that contribute to the dust
composition are, O, Fe, Si, Mg, C, S, Ni and Al for all the environments.
Abundances at low dust regimes suggest the presence of pyroxene and metallic
iron in dust.Comment: Accepted for publication in A&A. Abstract abridge
Dissecting the interstellar medium of a z=6.3 galaxy: X-shooter spectroscopy and HST imaging of the afterglow and environment of the Swift GRB 210905A
The study of the properties of galaxies in the first billion years after the
Big Bang is one of the major topic of current astrophysics.
Optical/near-infrared spectroscopy of the afterglows of long Gamma-ray bursts
(GRBs) provide a powerful diagnostic tool to probe the interstellar medium
(ISM) of their host galaxies and foreground absorbers, even up to the highest
redshifts. We analyze the VLT/X-shooter afterglow spectrum of GRB 210905A,
triggered by the Swift Neil Gehrels Observatory, and detect neutral-hydrogen,
low-ionization, high-ionization, and fine-structure absorption lines from a
complex system at z=6.3118, that we associate with the GRB host galaxy. We
study the ISM properties of the host system, revealing the metallicity,
kinematics and chemical abundance pattern. The total metallicity of the z~6.3
system is [M/H]=-1.72+/-0.13, after correcting for dust-depletion and taking
into account alpha-element enhancement. In addition, we determine the overall
amount of dust and dust-to-metal mass ratio (DTM) ([Zn/Fe]_fit=0.33+/-0.09,
DTM=0.18+/-0.03). We find indications of nucleosynthesis due to massive stars
and evidence of peculiar over-abundance of aluminium. From the analysis of
fine-structure lines, we determine distances of several kpc for the
low-ionization gas clouds closest to the GRB. Those farther distances are
possibly due to the high number of ionizing photons. Using the HST/F140W image
of the GRB field, we show the GRB host galaxy as well as multiple objects
within 2" from the GRB. We discuss the galaxy structure and kinematics that
could explain our observations, also taking into account a tentative detection
of Lyman-alpha emission. Deep spectroscopic observations with VLT/MUSE and JWST
will offer the unique possibility of combining our results with the ionized-gas
properties, with the goal of better understanding how galaxies in the
reionization era form and evolve.Comment: Accepted Publication (In Press on A&A) - 22 pages, 10 figures, 6
tables - Appendix: 6 figures, 3 table
Ethical preferences for influencing superiors: A 41-society study
With a 41-society sample of 9990 managers and professionals, we used hierarchical linear modeling to investigate the impact of both macro-level and micro-level predictors on subordinate influence ethics. While we found that both macro-level and micro-level predictors contributed to the model definition, we also found global agreement for a subordinate influence ethics hierarchy. Thus our findings provide evidence that developing a global model of subordinate ethics is possible, and should be based upon multiple criteria and multilevel variables
A Twenty-First Century Assessment of Values Across the Global
This article provides current Schwartz Values Survey (SVS) data from samples of business managers and professionals across 50 societies that are culturally and socioeconomically diverse. We report the society scores for SVS values dimensions for both individual- and societallevel analyses. At the individual-level, we report on the ten circumplex values sub-dimensions and two sets of values dimensions (collectivism and individualism; openness to change, conservation, self-enhancement, and self- transcendence). At the societal-level, we report on the values dimensions of embeddedness, hierarchy, mastery, affective autonomy, intellectual autonomy, egalitarianism, and harmony. For each society, we report the Cronbach’s a statistics for each values dimension scale to assess their internal consistency (reliability) as well as report interrater agreement (IRA) analyses to assess the acceptability of using aggregated individual level values scores to represent country values. We also examined whether societal development level is related to systematic variation in the measurement and importance of values. Thus, the contributions of our evaluation of the SVS values dimensions are two-fold. First, we identify the SVS dimensions that have cross-culturally internally reliable structures and withinsociety agreement for business professionals. Second, we report the society cultural values scores developed from the twenty-first century data that can be used as macro-level predictors in multilevel and single-level international business research
Societal-level versus individual-level predictions of ethical behavior: a 48-society study of collectivism and individualism
Is the societal-level of analysis sufficient today to understand the values of those in the global workforce? Or are individual-level analyses more appropriate for assessing the influence of values on ethical behaviors across country workforces? Using multi-level analyses for a 48-society sample, we test the utility of both the societal-level and individual-level dimensions of collectivism and individualism values for predicting ethical behaviors of business professionals. Our values-based behavioral analysis indicates that values at the individual-level make a more significant contribution to explaining variance in ethical behaviors than do values at the societal-level. Implicitly, our findings question the soundness of using societal-level values measures. Implications for international business research are discussed
South African Paediatric Surgical Outcomes Study : a 14-day prospective, observational cohort study of paediatric surgical patients
BACKGROUND : Children comprise a large proportion of the population in sub-Saharan Africa. The burden of paediatric surgical disease exceeds available resources in Africa, potentially increasing morbidity and mortality. There are few prospective paediatric perioperative outcomes studies, especially in low- and middle-income countries (LMICs).
METHODS : We conducted a 14-day multicentre, prospective, observational cohort study of paediatric patients (aged <16 yrs) undergoing surgery in 43 government-funded hospitals in South Africa. The primary outcome was the incidence of in-hospital postoperative complications.
RESULTS : We recruited 2024 patients at 43 hospitals. The overall incidence of postoperative complications was 9.7% [95% confidence interval (CI): 8.4–11.0]. The most common postoperative complications were infective (7.3%; 95% CI: 6.2–8.4%). In-hospital mortality rate was 1.1% (95% CI: 0.6–1.5), of which nine of the deaths (41%) were in ASA physical status 1 and 2 patients. The preoperative risk factors independently associated with postoperative complications were ASA physcial status, urgency of surgery, severity of surgery, and an infective indication for surgery.
CONCLUSIONS : The risk factors, frequency, and type of complications after paediatric surgery differ between LMICs and high-income countries. The in-hospital mortality is 10 times greater than in high-income countries. These findings should be used to develop strategies to improve paediatric surgical outcomes in LMICs, and support the need for larger prospective, observational paediatric surgical outcomes research in LMICs.
CLINICAL TRIAL REGISTRATION : NCT03367832.Jan Pretorius Research Fund; Discipline of Anaesthesiology and Critical Care, Nelson R Mandela School of Medicine, University of KwaZulu-Natal; Department of Anaesthesia and Perioperative Medicine, Groote Schuur Hospital and University of Cape Town; Department of Anaesthesia, University of the Witwatersrand; and the Paediatric Anaesthesia Community of South Africa (PACSA).https://bjanaesthesia.org2020-02-01gl2019Anaesthesiolog
- …