10 research outputs found
Data set_Phytoplankton pigment dynamics in marine lake fluctuating between stratified and holomictic euxinic conditions
No full text<p>Study site: Zmajevo oko - Rogoznica Lake small karstified sea lake on the eastern Adriatic coast of Croatia (43o32" N, 15o58" E) Physico-chemical parameters: Temperature (T, oC), salinity (S), dissolved oxygen (DO, mg/L) were measured in situ during sampling using a HQ40d multimeter probe (Hach Lange, Germany). For the determination of photosynthetic pigments, one liter of water was filtered at low vacuum onto glass fiber filters (0.7 μm GF/F) and stored at -80 oC until analysis. The filters were extracted by sonication in 4 mL of cold 90% acetone, followed by centrifugation to clarify the extracts. Chlorophylls and carotenoids were analyzed by reversed-phase HPLC according to Barlow et al. (1997). In brief, the extracts were mixed with 1 M ammonium acetate (1:1; v/v) and injected into an HPLC system, which consisted of a gradient solvent delivery system (Varian Star 9010), an injector (Rheodyne, model 7125), a Hypersil™ MOS -2 C8 HPLC column (150 x 4.6 mm, Thermo Scientific) and serially coupled spectrophotometric and spectrofluorimetric detectors. A binary linear gradient was used to separate the pigments. Solvent A was a mixture of methanol / 1 M ammonium acetate (70/30), while solvent B was methanol. Chlorophylls and carotenoids were detected by absorbance at 440 nm (Spectra Physics UV 2000), while phaeopigments were detected by fluorescence (Spectra Physics FL 3000) with excitation at 420 nm and emission at 672 nm. Data was acquired and processed using Varian Star 4.0 software. The qualitative and quantitative analyzes of the individual pigments were performed by external standard calibration with authentic pigment standards (VKI, Denmark). The total reduced sulfur species (RSStotal) were analyzed by electrochemical methods as previously described (Bura-Nakić et al. 2009; Marguš et al. 2015). The DOC and POC were analyzed using a TOC-Vcph analyzer (Schimadzu, Japan). The fractions were separated immediately after sampling by filtration through a pre-combusted 0.7 μm GF/F filter and stored until analysis (at -20°C). Samples for nutrient measurements were stored at -20 oC prior to analysis. Nitrate (NO3-), nitrite (NO2-), ammonium (NH4+), orthophosphate (PO43-) and silicate (SiO44-) were analyzed in unfiltered samples using a spectrophotometer (Strickland and Parsons, 1972).</p>
Extraction and Characterization of Surfactants from Atmospheric Aerosols
No full textThe authors also warmly thank Marija Margus, Ana Cvitesic, Sanja Frka Milosavljevic and Irena Ciglenecki, from Rudjer Boskovic Institute of Zagreb, Croatia for the help with the aerosol sampling at Marina Frapa, Rogoznica, Croatia.International audienceSurface-active compounds, or surfactants, present in atmospheric aerosols are expected to play important roles in the formation of liquid water clouds in the Earth's atmosphere, a central process in meteorology, hydrology, and for the climate system. But because specific extraction and characterization of these compounds have been lacking for decades, very little is known on their identity, properties, mode of action and origins, thus preventing the full understanding of cloud formation and its potential links with the Earth's ecosystems.In this paper we present recently developed methods for 1) the targeted extraction of all the surfactants from atmospheric aerosol samples and for the determination of 2) their absolute concentrations in the aerosol phase and 3) their static surface tension curves in water, including their Critical Micelle Concentration (CMC). These methods have been validated with 9 references surfactants, including anionic, cationic and non-ionic ones. Examples of results are presented for surfactants found in fine aerosol particles (diameter < 1 mu m) collected at a coastal site in Croatia and suggestions for future improvements and other characterizations than those presented are discussed
Electrochemical nanogravimetric studies of sulfur/sulfide redox processes on gold surface
No full textElectrochemical Quartz Crystal Microbalance Study of FeS Particles Attached to Au Surface
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Biogeochemical sulfur cycling in the water column of a shallow stratified sea-water lake: Speciation and quadruple sulfur isotope composition
No full textConcentrations of sulfate, sulfide and intermediate sulfur species as well as quadruple sulfur isotope compositions of sulfate, sulfide and zero-valent sulfur (ZVS) were analyzed in the water column of Lake Rogoznica (Croatia), a stratified marine euxinic lake. The chemocline in the lake, which was located at 8.5–9.5 m depth, supports a dense population of purple phototrophic sulfide oxidizing bacteria from the genus Chromatium. The highest ZVS (5.42 μmol L−1) and sulfite (1.13 μmol L−1) concentrations were detected at the chemocline. Thiocyanate concentrations up to 288 nmol L−1 were detected near the bottom of the lake. The thiocyanate profile suggests that it diffuses up from the sediment, where it may be produced by the reaction of cyanide with sulfide oxidation intermediates. Multiple sulfur isotope fractionations between sulfate and sulfide were consistent with a model finding that disproportionation is not a dominant process below the chemocline. Microbial sulfide oxidation was found to be the dominant process of the reoxidative part of the sulfur cycle. Despite the absence of a clear signal for sulfur disproportionation in multiple sulfur isotope values, δ34S fractionations between sulfate and sulfide were in the range of 43.8–45.2‰, is relatively large in comparison to most laboratory culturing studies. Our results suggest that such fractionation is achieved by microbial sulfate reduction alone, which is in agreement with metabolic models and recent laboratory studies
Ocean Oxygen: the role of the Ocean in the oxygen we breathe and the threat of deoxygenation
No full textEMB Future Science Brief No. 10 highlights the most recent science on Ocean oxygen, including causes, impacts and mitigation strategies of Ocean oxygen loss, and discusses whether “every second breath we take comes from the Ocean”. It closes with key policy, management and research recommendations to address Ocean deoxygenation and communicate more accurately about the role of the Ocean in Earth’s oxygen.
The sentence “every second breath you take comes from the Ocean” is commonly used in Ocean Literacy and science communication to highlight the importance of Ocean oxygen. However, despite its widespread use, it is often not phrased correctly. In contrast, there is little awareness about the threat of the global oxygen loss in the Ocean, called deoxygenation, particularly in comparison with other important stressors, such as Ocean acidification or increasing seawater temperatures.
Deoxygenation is increasing in the coastal and open Ocean, primarily due to human-induced global warming and nutrient run-off from land, and projections show that the Ocean will continue losing oxygen as global warming continues. The consequences of oxygen loss in the Ocean are extensive and include decreased biodiversity, shifts in species distributions, displacement or reduction in fisheries resources, changes in biogeochemical cycling and mass mortalities. Low oxygen conditions also drive other chemical processes which produce greenhouse gases, toxic compounds and further degrade water quality. The degraded water quality directly affects marine ecosystems, but also indirectly impacts ecosystem services supporting local communities, regional economies and tourism. Although there are still gaps in our knowledge, we know enough to be very concerned about the consequences: the impacts might even be larger than from Ocean acidification or heat waves, and three out of the five global mass extinctions were linked to Ocean deoxygenation.
The sense of urgency to improve Ocean health is reflected in the UN Decade of Ocean Science for Sustainable Development (Ocean Decade) and the EU Mission: Restore our Ocean and Waters (Mission Ocean), and tackling the loss of oxygen in the Ocean is critical to achieving the aims of these two initiatives
Comparison of Fatal or Irreversible Events With Extended-Duration Betrixaban Versus Standard Dose Enoxaparin in Acutely III Medical Patients: An APEX Trial Substudy
Get PDFBACKGROUND: Extended-duration betrixaban showed a significant reduction in venous thromboembolism in the APEX trial (Acute Medically Ill VTE Prevention With Extended Duration Betrixaban Study). Given the variable clinical impact of different efficacy and safety events, one approach to assess net clinical outcomes is to include only those events that are either fatal or cause irreversible harm. METHODS AND RESULTS: This was a post hoc analysis of the APEX trial-a multicenter, double-blind, randomized controlled trial comparing extended-duration betrixaban versus standard-of-care enoxaparin. A composite of all fatal or irreversible safety (fatal bleeding or intracranial hemorrhage) and efficacy events (cardiopulmonary death, myocardial infarction, pulmonary embolism, and ischemic stroke) was evaluated in a time-to-first event analysis. In patients with positive D-dimer results, betrixaban reduced fatal or irreversible events at 35 to 42 days (4.80% versus 3.54%; hazard ratio, 0.73; absolute risk reduction, 1.26%; number needed to treat, 79 [P=0.033]) and at study end at 77 days (6.27% versus 4.36%; hazard ratio, 0.70; absolute risk reduction, 1.91%; number needed to treat, 52 [P=0.005]) versus enoxaparin. In all patients, betrixaban reduced fatal or irreversible events at 35 to 42 days (4.08% versus 2.90%; hazard ratio, 0.71; absolute risk reduction, 1.18%; number needed to treat, 86 [P=0.006]) and 77 days (5.17% versus 3.64%; hazard ratio, 0.70; absolute risk reduction, 1.53%; number needed to treat, 65 [P=0.002]). CONCLUSIONS: Among hospitalized medically ill patients, extended-duration betrixaban demonstrated an ≈30% reduction in fatal or irreversible ischemic or bleeding events compared with standard-duration enoxaparin. A total of 65 patients would require treatment with betrixaban to prevent 1 fatal or irreversible event versus enoxaparin. CLINICAL TRIAL REGISTRATION: URL: http://www.ClinicalTrials.gov. Unique identifier: NCT01583218.sponsorship: The study was funded by Portola Pharmaceuticals; APEX ClinicalTrials gov number NCT01583218. The corresponding author had full access to all of the data in the study and had final responsibility for the decision to submit for publication. The authors wrote all drafts of the article and take responsibility for its content. The sponsors had the opportunity to review and comment on this article but had no editorial authority. (Portola Pharmaceuticals, APEX ClinicalTrials|NCT01583218)status: Publishe
Abstracts of The Second Eurasian RISK-2020 Conference and Symposium
Get PDFThis abstract book contains abstracts of the various research ideas presented at The Second Eurasian RISK-2020 Conference and Symposium.The RISK-2020 Conference and Symposium served as a perfect venue for practitioners, engineers, researchers, scientists, managers and decision-makers from all over the world to exchange ideas and technology about the latest innovation developments dealing with risk minimization
