| 1. |
- Neumann, J. T., et al.
(författare)
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Application of High-Sensitivity Troponin in Suspected Myocardial Infarction
- 2019
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Ingår i: New England Journal of Medicine. - : MASSACHUSETTS MEDICAL SOC. - 0028-4793 .- 1533-4406. ; 380:26, s. 2529-2540
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundData regarding high-sensitivity troponin concentrations in patients presenting to the emergency department with symptoms suggestive of myocardial infarction may be useful in determining the probability of myocardial infarction and subsequent 30-day outcomes. MethodsIn 15 international cohorts of patients presenting to the emergency department with symptoms suggestive of myocardial infarction, we determined the concentrations of high-sensitivity troponin I or high-sensitivity troponin T at presentation and after early or late serial sampling. The diagnostic and prognostic performance of multiple high-sensitivity troponin cutoff combinations was assessed with the use of a derivation-validation design. A risk-assessment tool that was based on these data was developed to estimate the risk of index myocardial infarction and of subsequent myocardial infarction or death at 30 days. ResultsAmong 22,651 patients (9604 in the derivation data set and 13,047 in the validation data set), the prevalence of myocardial infarction was 15.3%. Lower high-sensitivity troponin concentrations at presentation and smaller absolute changes during serial sampling were associated with a lower likelihood of myocardial infarction and a lower short-term risk of cardiovascular events. For example, high-sensitivity troponin I concentrations of less than 6 ng per liter and an absolute change of less than 4 ng per liter after 45 to 120 minutes (early serial sampling) resulted in a negative predictive value of 99.5% for myocardial infarction, with an associated 30-day risk of subsequent myocardial infarction or death of 0.2%; a total of 56.5% of the patients would be classified as being at low risk. These findings were confirmed in an external validation data set. ConclusionsA risk-assessment tool, which we developed to integrate the high-sensitivity troponin I or troponin T concentration at emergency department presentation, its dynamic change during serial sampling, and the time between the obtaining of samples, was used to estimate the probability of myocardial infarction on emergency department presentation and 30-day outcomes.
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| 2. |
- Arevalo-Martinez, D. L., et al.
(författare)
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Ideas and perspectives: Land-ocean connectivity through groundwater
- 2023
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 20:3, s. 647-662
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Tidskriftsartikel (refereegranskat)abstract
- For millennia, humans have gravitated towards coastlines for theirresource potential and as geopolitical centres for global trade. A basicrequirement ensuring water security for coastal communities relies on adelicate balance between the supply and demand of potable water. Theinteraction between freshwater and saltwater in coastal settings is,therefore, complicated by both natural and human-driven environmentalchanges at the land-sea interface. In particular, ongoing sea-level rise,warming and deoxygenation might exacerbate such perturbations. In thiscontext, an improved understanding of the nature and variability ofgroundwater fluxes across the land-sea continuum is timely yet remains outof reach. The flow of terrestrial groundwater across the coastal transitionzone and the extent of freshened groundwater below the present-dayseafloor are receiving increased attention in marine and coastal sciencesbecause they likely represent a significant yet highly uncertain componentof (bio)geochemical budgets and because of the emerging interest in thepotential use of offshore freshened groundwater as a resource. At the sametime, "reverse" groundwater flux from offshore to onshore is of prevalentsocio-economic interest, as terrestrial groundwater resources arecontinuously pressured by over-pumping and seawater intrusion in many coastalregions worldwide. An accurate assessment of the land-ocean connectivitythrough groundwater and its potential responses to future anthropogenicactivities and climate change will require a multidisciplinary approachcombining the expertise of geophysicists, hydrogeologists, (bio)geochemistsand modellers. Such joint activities will lay the scientific basis forbetter understanding the role of groundwater in societally relevant issuessuch as climate change, pollution and the environmental status of thecoastal oceans within the framework of the United Nations SustainableDevelopment Goals. Here, we present our perspectives on future researchdirections to better understand land-ocean connectivity through groundwater,including the spatial distributions of the essential hydrogeologicalparameters, highlighting technical and scientific developments and brieflydiscussing the societal relevance of that connectivity in rapidly changing coastal oceans.
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| 3. |
- Rehkämper, Mark, et al.
(författare)
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Thallium isotope variations in seawater and hydrogenetic, diagenetic, and hydrothermal ferromanganese deposits
- 2002
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Ingår i: Earth and Planetary Science Letters. - 0012-821X .- 1385-013X. ; 197:1-2
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Tidskriftsartikel (refereegranskat)abstract
- Results are presented for the first in-depth investigation of Tl isotope variations in marine materials. The Tl isotopic measurements were conducted by multiple collector-inductively coupled plasma mass spectrometry for a comprehensive suite of hydrogenetic ferromanganese crusts, diagenetic Fe-Mn nodules, hydrothermal manganese deposits and seawater samples. The natural variability of Tl isotope compositions in these samples exceeds the analytical reproducibility (±0.05‰) by more than a factor of 40. Hydrogenetic Fe-Mn crusts have ε205Tl of +10 to +14, whereas seawater is characterized by values as low as -8 (ε205Tl represents the deviation of the 205Tl/203Tl ratio of a sample from the NIST SRM 997 Tl isotope standard in parts per 104). This 2‰ difference in isotope composition is thought to result from the isotope fractionation that accompanies the adsorption of Tl onto ferromanganese particles. An equilibrium fractionation factor of α1.0021 is calculated for this process. Ferromanganese nodules and hydrothermal manganese deposits have variable Tl isotope compositions that range between the values obtained for seawater and hydrogenetic Fe-Mn crusts. The variability in ε205Tl in diagenetic nodules appears to be caused by the adsorption of Tl from pore fluids, which act as a closed-system reservoir with a Tl isotope composition that is inferred to be similar to seawater. Nodules with ε205Tl values similar to seawater are found if the scavenging of Tl is nearly quantitative. Hydrothermal manganese deposits display a positive correlation between ε205Tl and Mn/Fe. This trend is thought to be due to the derivation of Tl from distinct hydrothermal sources. Deposits with low Mn/Fe ratios and low ε205Tl are produced by the adsorption of Tl from fluids that are sampled close to hydrothermal sources. Such fluids have low Mn/Fe ratios and relatively high temperatures, such that only minor isotope fractionation occurs during adsorption. Hydrothermal manganese deposits with high Mn/Fe and high ε205Tl are generated by scavenging of Tl from colder, more distal hydrothermal fluids. Under such conditions, adsorption is
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| 4. |
- Sprenk, D., et al.
(författare)
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Southern Ocean bioproductivity during the last glacial cycle - new detection method and decadal-scale insight from the Scotia Sea
- 2013
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Ingår i: ANTARCTIC PALAEOENVIRONMENTS AND EARTH-SURFACE PROCESSES. - : The Geological Society Publishing House. ; , s. 245-261
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Bokkapitel (refereegranskat)abstract
- We present biogenic opal flux records from two deep-sea sites in the Scotia Sea (MD07-3133 and MD07-3134) at decadal-scale resolution, covering the last glacial cycle. In addition to conventional and time-consuming biogenic opal measuring methods, we introduce new biogenic opal estimation methods derived from sediment colour b*, wet bulk density, Si/Ti-count ratio and Fourier transform infrared spectroscopy (FTIRS). All methods capture the biogenic opal amplitude; however, FTIRS-a novel method for marine sediment -yields the most reliable results. Th-230 normalization data show strong differences in sediment focusing with intensified sediment focusing during glacial times. At MD07-3134 Th-230 normalized biogenic opal fluxes vary between 0.2 and 2.5 g cm(-2) kyr(-1). Our biogenic opal flux records indicate bioproductivity changes in the Southern Ocean, strongly influenced by sea ice distribution and also summer sea surface temperature changes. South of the Antarctic Polar Front, lowest bioproductivity occurred during the Last Glacial Maximum when upwelling of mid-depth water was reduced and sea ice cover intensified. Around 17 ka, bioproductivity increased abruptly, corresponding to rising atmospheric CO2 and decreasing seasonal sea ice coverage.
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