8 research outputs found
Latest Miocene restriction of the Mediterranean Outflow Water:a perspective from the Gulf of CĂĄdiz
The Mediterranean-Atlantic water mass exchange provides the ideal setting for deciphering the role of gateway evolution in ocean circulation. However, the dynamics of Mediterranean Outflow Water (MOW) during the closure of the Late Miocene Mediterranean-Atlantic gateways are poorly understood. Here, we define the sedimentary evolution of Neogene basins from the Gulf of CĂĄdiz to the West Iberian margin to investigate MOW circulation during the latest Miocene. Seismic interpretation highlights a middle to upper Messinian seismic unit of transparent facies, whose base predates the onset of the Messinian salinity crisis (MSC). Its facies and distribution imply a predominantly hemipelagic environment along the Atlantic margins, suggesting an absence or intermittence of MOW preceding evaporite precipitation in the Mediterranean, simultaneous to progressive gateway restriction. The removal of MOW from the Mediterranean-Atlantic water mass exchange reorganized the Atlantic water masses and is correlated to a severe weakening of the Atlantic Meridional Overturning Circulation (AMOC) and a period of further cooling in the North Atlantic during the latest Miocene
Evaluation of appendicitis risk prediction models in adults with suspected appendicitis
Background
Appendicitis is the most common general surgical emergency worldwide, but its diagnosis remains challenging. The aim of this study was to determine whether existing risk prediction models can reliably identify patients presenting to hospital in the UK with acute right iliac fossa (RIF) pain who are at low risk of appendicitis.
Methods
A systematic search was completed to identify all existing appendicitis risk prediction models. Models were validated using UK data from an international prospective cohort study that captured consecutive patients aged 16â45âyears presenting to hospital with acute RIF in March to June 2017. The main outcome was best achievable model specificity (proportion of patients who did not have appendicitis correctly classified as low risk) whilst maintaining a failure rate below 5 per cent (proportion of patients identified as low risk who actually had appendicitis).
Results
Some 5345 patients across 154 UK hospitals were identified, of which twoâthirds (3613 of 5345, 67·6 per cent) were women. Women were more than twice as likely to undergo surgery with removal of a histologically normal appendix (272 of 964, 28·2 per cent) than men (120 of 993, 12·1 per cent) (relative risk 2·33, 95 per cent c.i. 1·92 to 2·84; Pâ<â0·001). Of 15 validated risk prediction models, the Adult Appendicitis Score performed best (cutâoff score 8 or less, specificity 63·1 per cent, failure rate 3·7 per cent). The Appendicitis Inflammatory Response Score performed best for men (cutâoff score 2 or less, specificity 24·7 per cent, failure rate 2·4 per cent).
Conclusion
Women in the UK had a disproportionate risk of admission without surgical intervention and had high rates of normal appendicectomy. Risk prediction models to support shared decisionâmaking by identifying adults in the UK at low risk of appendicitis were identified
Rare earth elements and Nd isotopes as tracers of modern ocean circulation in the central Mediterranean Sea
Seawater rare earth element (REE) concentrations and Nd isotopic composition (ΔNd) are increasingly applied as valuable tracers of oceanographic processes such as
water mass mixing and lithogenic inputs to seawater. However, their measurements are basically lacking in the Mediterranean Sea water column. This study analyzes
9 seawater stations around the central Mediterranean Sea to clarify the relative importance of external sources, vertical (biogeochemical) processes and lateral water
mass transport in controlling REE and ΔNd distributions. Concentrations of REE do not show nutrient-like profiles with depth, likely indicative of relatively young
waters with limited accumulation of remineralized REE. Light REE (LREE) present a non-conservative behavior, which largely peak at surface waters and rapidly
decrease with depth. The negative correlation of surface LREE enrichment with offshore distance highlights the influence of continental input from the western
Italian coast to the Tyrrhenian surface waters. In contrast to other regions with reported boundary exchange, this process does not modify the ΔNd values here. On the
other side, distributions of dissolved heavy REE (HREE) and ΔNd display a conservative behavior that can be explained by mixing of western- (MAW and WMDW) and
eastern- (LIW and EMDW) originated waters. We test this hypothesis with an Optimum Multi-Parameter Analysis (OMPA) including HREE and ΔNd parameters. Even
though the limited data set, consistent results of water mass fractions are obtained for the four main water masses although with some particularities. While LIW takes
on major importance when considering HREE in the model, EMDW fractions are preferentially detected with ΔNd. This latter finding implies a noticeable deep water
flux across the Sicily Strait into the Western Mediterranean that was not clearly evidenced before
Eastern Mediterranean water outflow during the Younger Dryas was twice that of the present day
Eastern Mediterranean deep-intermediate convection was highly sensitive to varying inputs
of fresh water fluxes associated with increased rainfall during the African Humid period (15-6
kyr Before Present). Here we investigate changes in the water-outflow from the Eastern
Mediterranean Sea since the last deglaciation using neodymium isotope ratios. Our results
indicate enhanced outflow during the Younger Dryas, two times higher than present-day
outflow and about three times higher than during the last Sapropel. We propose that the
increased outflow into the western Mediterranean over the Younger Dryas was the result of
the combined effect of 1) enhanced climate-driven convection in the Aegean Sea and 2)
reduced convection of western deep water during this period. Our results provide solid
evidence for an enhanced Younger Dryas westward flow of Eastern Mediterranean sourced
waters in consonance with an intensification of Mediterranean water-outflow during a
weakened state of the Atlantic circulation