Oxygen-deficient Environments Research Articles

All organic nanomedicine for PDT–PTT combination therapy of cancer cells in hypoxia

Photodynamic and photothermal therapies are promising treatments for cancer, dermatological, and ophthalmological conditions. However, photodynamic therapy (PDT) is less effective in oxygen-deficient tumor environments. Combining PDT with photothermal therapy (PTT) can enhance oxygen supply and treatment efficacy. Inorganic PTT agents pose toxicity risks, limiting their clinical use despite their high performance. In this study, we developed a novel nanomedicine integrating an all-organic photothermal agent and an organic photosensitizer, creating a colocalized nanoplatform to enhance phototherapy efficacy in cancer treatment. PTT nanoparticles (NPs) were synthesized through a thermal phase transition of organic chromophores, demonstrating superior photothermal properties and photostability. Utilizing this nanoplatform, we devised ‘Combi NPs’ for combined PDT–PTT nanomedicine. Tests on A549 cancer cell lines have revealed that Combi NPs exhibit superior cytotoxicity and induce apoptosis in hypoxic conditions, outperforming PTT-only NPs. The all-organic Combi NPs show significant potential for clinical cancer phototherapy in hypoxic microenvironments, potentially mitigating long-term nanomedicine accumulation and associated toxicity.

Redirecting the electron flow to coordinate oxidation and reduction reactions for efficient photocatalytic H2O2 production

Energy-efficient photocatalytic production of H2O2 from water holds the potential to replace the anthraquinone process. However, the impracticality of oxygen bubbling in such processes necessitates addressing the H2O2 production in oxygen-deficient environments. Here, we demonstrated the generation of singlet oxygen (1O2) as a highly active water oxidation derivative that redirects the electron flow for H2O2 production in oxygen-deficient environments. Ground-state oxygen was in-situ generated on photocatalysts and undergoes transition to 1O2, surpassing other competitive electron-consuming reactions. Self-generated 1O2 undergoes preferential photo-reduction to H2O2, benefiting from a small activation energy (0.2 eV), facilitated electron trapping rate, adjacent oxidation/reduction sites and suppressed competitive energy transfer from excited-states to air 3O2. A remarkable solar-to-chemical conversion (SCC) efficiency of 0.25 % was obtained for H2O2 generation in oxygen-deficient conditions. This work unveils a novel concept of redirecting electron flow towards H2O2 production, taking advantage of highly active in-situ generated 1O2.

Preserved particulate organic carbon is likely derived from the subsurface sulfidic photic zone of the Proterozoic Ocean: evidence from a modern, oxygen-deficient lake.

Biological processes in the Proterozoic Ocean are often inferred from modern oxygen-deficient environments (MODEs) or from stable isotopes in preserved sediment. To date, few MODE studies have simultaneously quantified carbon fixation genes and attendant stable isotopic signatures. Consequently, how carbon isotope patterns reflect these pathways has not been thoroughly vetted. Addressing this, we profiled planktonic productivity and quantified carbon fixation pathway genes and associated organic carbon isotope values (δ13 CPOC ) of size-fractionated (0.2-2.7 and >2.7 μm) particulate matter from meromictic Fayetteville Green Lake, NY, USA. The high-O2 Calvin-Benson-Bassham (CBB) gene (cbbL) was most abundant in the <2.7 μm size fraction in shallow oxic and deep hypoxic waters, corresponding with cyanobacterial and eukaryote algal populations. The low-O2 CBB gene (cbbM) was most abundant near the lower oxycline boundary in the larger size fraction, coincident with purple sulfur bacteria populations. The reverse citric acid cycle gene (aclB) was equally abundant in both size fractions in the deepest photic zone, coinciding with green sulfur bacteria populations. Methane coenzyme reductase A (mcrA), of anaerobic methane cyclers, was most abundant at the lower oxycline boundary in both size fractions, coinciding with Methanoregula populations. δ13 CPOC values overlapped with the high-O2 CBB fixation range except for two negative excursions near the lower oxycline boundary, likely reflecting assimilation of isotopically-depleted groundwater-derived carbon by autotrophs and sulfate-reducers. Throughout aphotic waters, δ13 CPOC values of the large size fraction became 13 C-enriched, likely reflecting abundant purple sulfur bacterial aggregates. Eukaryote algae- or cyanobacteria-like isotopic signatures corresponded with increases in cbbL, cbbM, and aclB, and enrichment of exopolymer-rich prokaryotic photoautotrophs aggregates. Results suggest that δ13 CPOC values of preserved sediments from areas of the Proterozoic Ocean with sulfidic photic zones may reflect a mixture of alternate carbon-fixing populations exported from the deep photic zone, challenging the paradigm that sedimentary stable carbon isotope values predominantly reflect oxygenic photosynthesis from surface waters.

Respiratory protective equipment fit tests for researchers at the national synchrotron radiation research center

Researchers at the National Synchrotron Radiation Research Center should use respiratory protective equipment to prevent respiratory damage caused by gases, steam, solvents, chemicals, materials containing toxic substances, and oxygen-deficient environments. Those working with organic matter and certain chemical substances and those exposed to occupation dust should use respiratory protective gear to ensure their health. This study conducted qualitative and quantitative fit tests for various mask brands and sizes, namely 3M-9042, N95-9211, P95-8576, and 3M-6200 masks. The gear worn by all 18 participants in the qualitative fit test passed. By contrast, the gear worn by 12 of the 15 participants in the quantitative test passed; the failure of the remaining gear was due to differences in face shape. The N95-9211 mask can be used in three-piece protective gear because it exhibited a tight fit. Additionally, the 3M-6200 negative-pressure half-face mask exhibited the most satisfactory fit and can be used in protective gear.

A general strategy to enhance hydrogen peroxide generation via two-electron water oxidation by antimony modification for removal of triethyl phosphate and hexavalent chromium

Two-electron water oxidation has attracted more and more attention for H2O2 production. This strategy mainly uses water and does not require bubbling of oxygen gas, which can be widely used in oxygen-deficient environments. Currently, the most important research for two-electron water oxidation is the design of high-efficiency anode materials. Herein, a general method is developed to enhance the activity of two-electron water oxidation for H2O2 production via Sb2O3 modification. This strategy is suitable for a series of electrodes, including carbon fiber paper, graphite plate, WO3, CuWO4 and WO3&CuWO4 composite. The mechanism for Sb2O3 modification toward enhanced H2O2 generation is clearly demonstrated. It should be due to three factors: 1) enhance the reaction kinetic, 2) enlarge the specific surface area and 3) suppress H2O2 decomposition. According to density function calculation, it is firstly found that the Sb optimizes the Gibbs free energy of adsorbed *OH intermediate of its nearby atom, making its adjacent atom (such as W) the active site. Finally, these Sb-modified electrodes are firstly used to produce H2O2 for high-efficiency removal of triethyl phosphate, an environmental pollutant that are difficult to be degraded. It can also be used for the removal of hexavalent chromium, one kind of heavy metal.

Effect of Oxygen and Moisture on the Friction and Wear of Carbon Fiber-Reinforced Polymers

Carbon fiber-reinforced polytetrafluoroethylene (CF/PTFE) composites are frequently used in tribological dry gas applications, such as in dynamic seals in reciprocating hydrogen gas compressors and Stirling engines, due to their superior friction and wear. Due to the increasing concerns regarding fluoropolymers as possible pollutants of harmful per- and poly-fluoroalkyl substances (PFAS) emissions, replacements for PTFE should be investigated. The literature indicates that CF-reinforced polyetheretherketone (CF/PEEK) may have similar favorable tribological properties to CF/PTFE. However, the tribological behavior of CF/PEEK in dry gas is poorly understood, and no direct comparison has been made between the two materials. The aim of this study was to compare the effect of oxygen and moisture on the friction and wear of CF/PTFE and CF/PEEK. Tribological tests were carried out with a tri-pin-on-disc tribometer in a nitrogen environment with individually controlled contents of oxygen and moisture. The results showed that the effect of oxygen and moisture are distinctly different for CF/PTFE and CF/PEEK. While CF/PTFE performs best in oxygen-deficient environments, CF/PEEK performs best in moisture-enriched environments. Complementary tests with a PTFE composite filled with both CF and PEEK suggested that the environmental sensitivity can be significantly reduced by combining the two polymers.

Palaeoenvironmental Evolution Based on Elemental Geochemistry of the Wufeng-Longmaxi Shales in Western Hubei, Middle Yangtze, China

The organic-rich shales found in the Wufeng–Longmaxi Formation are typically deposited in oxygen-deficient reducing environments. One of the primary sources of debate revolves around the question of whether the anoxic bottom water found in these shales is either euxinic or ferruginous, and this matter remains unresolved. Previous studies have mostly focused on the Wufeng–Longmaxi Formation as a whole in order to understand the key factors that control organic matter accumulation (OMA). However, research on OMA for each member, including the Wufeng Formation (WF), the lower Longmaxi Formation (LLM), and the upper Longmaxi Formation (ULM), has been insufficient. This paper aims to investigate the palaeoenvironmental conditions and OMA mechanisms of the Wufeng–Longmaxi shales in western Hubei by integrating data on total organic carbon (TOC) content, mineral compositions, major and trace elements, and iron speciation. The results indicate that the Wufeng–Longmaxi shales were deposited under highly restricted hydrographic conditions, except for relatively open and upwelling conditions in the upper WF. Silica in the upper WF was primarily biogenic origin and not hydrothermal. Ferruginous conditions were the primary redox conditions for organic-rich shales except for minor formations in the lower LLM that were deposited under euxinic conditions. Due to the tectonic uplift caused by the Kwangsian Orogeny in the upper LLM, the palaeoenvironment was characterized by a warmer and wetter climate, high terrigenous influx, oxic conditions, and low productivity as the result of the insufficient nutrients caused by the weak upwelling, leading to the turnover of graptolite biozones from LM5 to LM6. The factors influencing OMA changed vertically. TOC contents have a highly positive correlation with Al content, indicating that terrigenous influx was the main factor affecting OMA in the WF, which significantly differed from patterns found in other regions. This suggests that the sedimentation rate of organic matter was higher than the terrigenous dilution rate during the WF stage. The combination of redox conditions and productivity were the main factors affecting OMA in the LLM, while terrigenous influx was the key factor controlling OMA in the ULM, resulting in the dilution of organic matter. Regions in the eastern Yiling block, which are close to the Qinling Ocean, show better prospects for shale gas exploration. This research will further facilitate the development of shale gas in this area.

Aluminum/Bromate and Aluminum/Iodate Mechanically Rechargeable Batteries

The ever-increasing characteristics of microcomputers, sensors, actuators, and communication systems require more powerful and more compact autonomous power sources. Al/bromate and Al/iodate flow batteries are proposed as new power supply units for use in oxygen-deficient environments. The batteries employ a mechanically rechargeable aluminum anode flooded with aqueous salt electrolytes or seawater, a cation-exchange membrane, and a carbonaceous porous cathode, where acidified alkali metal bromate, or iodate, is reduced in a six-electron process. The theoretical energy density of an Al/bromate flow cell per reactants is 0.65 kWh kg−1. Seawater is assumed as an electrolyte for the anode compartment. Using a H2/iodate flow cell, it is shown that iodate–iodine–iodide electrochemical transformations can be realized in both directions in acidic media at carbonaceous electrodes. At 30 °C, the area-specific power of the single cells of the Al/bromate and Al/iodate flow batteries reaches 0.26 W cm−2 and 0.075 W cm−2, respectively.

Research progress on the corrosion behavior of titanium alloys

Abstract Titanium and its alloys show outstanding application prospects in many industrial fields due to their high specific strength, good corrosion resistance, high temperature resistance, etc. However, at present the corrosion failure of Ti alloys is attracted great attention with gradual increasing applications. The different localized corrosion forms are introduced in this review, including galvanic corrosion, crevice corrosion, pitting corrosion, hydrogen-induced cracking, stress corrosion crack, microbiological corrosion, corrosion fatigue, and corrosion wear. Among them, the corrosion failure caused by stress corrosion crack and hydrogen-induced cracking is the most serious, accounting for about 40–60% of the actual failure accidents. The effects of temperature, pressure, corrosive media and microstructure on the failure of titanium alloys are discussed. Particularly noteworthy, F− is extremely aggressive to the passive film of titanium alloys. The corrosion behavior of titanium alloys applied in aerospace, marine, petrochemical industries and biomedical environments are introduced. In the above environments, the passive film is most easily damaged and difficult to passive in high temperature and oxygen-deficient environments. The current controversies in the corrosion mechanism have also been proposed, especially the stress corrosion that has the most serious impact on titanium alloys, and its mechanism will be the focus of future research.

Effect of sulfate-reducing bacteria from salt scale of water flooding pipeline on corrosion behavior of X80 steel

As a means to enhance the recovery of oil reservoirs, waterflooding is widely employed in field development. However, because injected water contains solid impurities and incompatible characteristics, water injection pipelines often suffer from scaling and blocking. In addition, because these pipelines are typically buried in underground soil, microbial bacteria are derived from humid and oxygen-deficient environments, causing serious microbial corrosion on the basis of scaling corrosion. The objective of this study was to analyze the corrosion behavior under the combined effect of sulfate-reducing bacteria (SRB) and the scale layer (CaCO3) induced inside a water injection pipeline. With an X80 steel pipeline as the experimental material and an oilfield injected water simulation solution as the experimental medium, this study conducted weight-loss tests and electrochemical experiments. Combined with the experimental results, scanning electron microscopy, electrochemical impedance spectroscopy, element and phase analyses, and 3D corrosion morphology reconstruction technology were used to explore the changes and mechanism of corrosion behavior under the combined effect of CaCO3 scale layer and SRB in water injection pipelines used in oilfields. The study results showed that a nonuniformly distributed CaCO3 scale layer can provide sites for SRB metabolic activity and also serve as a channel for the exchange of corrosion ions. The corrosion rate of the water injection pipeline increased significantly under the combined effect of the CaCO3 scale layer and SRB, and pitting corrosion under the biofilm/scale layer was serious. In the presence of iron oxides, SRB could interact with CaCO3, causing microbial dissimilation and reduction of iron oxides, forming a loose FeS product film, and accelerating the corrosion process of steel pipelines.

How to simply and efficiently screen microbial strains capable of anaerobic biosynthesis of biosurfactants: Method establishment, influencing factors and application example evaluation.

Microbial resources capable of anaerobic biosynthesis of biosurfactants are increasingly interested for their application in oxygen-deficient environments, such as in-situ microbial enhanced oil recovery and anaerobic bioremediation. How to simply and efficiently screen microbial strains capable of anaerobic biosynthesis of biosurfactants need be further studied in depth. In this study, an efficient and simple screening method was established based on the oil displacement characteristic of biosurfactants combined with the anaerobic culture technology using microplate assays. Strains whose anaerobic culture in microwells can form oil displacement circles with diameters larger than 10 mm were screened for scale-up culture in anaerobic tubes. The screened strains which can reduce the surface tension of anaerobic culture to lower than 45 mN/m were verified as positive strains. Using this screening method, eight positive strains and thirteen positive strains were screened from oil reservoir produced water and oily sludge, respectively. Through phylogenetic analysis, some screened strains were identified as Pseudomonas sp., Bacillus sp., and Enterobacter sp. This study also found that more microbial strains might be isolated after enrichment culture of environmental samples, whereas more microbial species would be isolated without enrichment. Suspension of environmental samples prepared with distilled water or normal saline had no significant effect. The established screening method is highly targeted and efficient for microbial strains capable of anaerobic biosynthesis of biosurfactants. The diameter of oil displacement circle is a reliable screening indicator. This study will contribute to explore more microbial resources which can anaerobically biosynthesize biosurfactants.

Abstract P1040: The Protective Effects Of Sialidase Neu3 Against Cardiac Ischemia And Reperfusion Injury

The salvage of myocardium after acute myocardial infarction (AMI) can only be achieved by timely reperfusion. This is life-saving, however it may also lead to additional damage in the form of ischemia and reperfusion injury (IRI). Protecting cardiac tissue from IRI remains one of the greatest unmet clinical needs in cardiology. Therefore, a better understanding of IRI pathophysiology is necessary. There has been increasing recognition that the activation of specific molecular mechanisms, including the Reperfusion Injury Salvage Kinase (RISK) pathway and HIF-1&amp;#945; contributes to cardioprotection against IRI. Along this line, we previously reported that sialidase Neu3, which removes sialic acid from glycosphingolipids, controls HIF-1&amp;#945; activation via a prolyl hydroxylase-independent pathway. In fact, we found that Neu3 was up-regulated under chronic hypoxia in cyanotic congenital cardiac patients and its overexpression increased muscle cells’ resistance to hypoxic stress by activating the RISK pathway. In light of these premises, the goal of this study was to determine Neu3's involvement in the cardiac response to IRI and establish whether its inducible activation could promote cardioprotection. An IRI model in mice, obtained by temporarily blocking the LAD coronary artery, showed that Neu3 is modulated during this process. Notably, Neu3 showed progressive downregulation during the ischemic phase followed by its reactivation during reperfusion. These results were similar to the Neu3 modulation we observed in human cardiac cells (AC16) exposed to an IRI model in vitro . The overexpression of Neu3 during ischemia had beneficial effects both in terms of cell proliferation and reduction of oxidative stress after reperfusion. We found that Neu3 promotes the activation of glycolytic enzymes during the ischemic phase as well as the maintenance of the mitochondrial membrane potential, suggesting that the Neu3-overexpressing human cardiomyocyte undergoes more aerobic metabolism even in oxygen-deficient environments. In conclusion, these results support a role for Neu3 in cardioprotection against IRI, suggesting that it may be a useful therapeutic target for improving the recovery of patients who have undergone acute myocardial infarction.

Tailoring the free carrier and optoelectric properties of indium tin oxide film via quasi-continuous-wave laser annealing

In this study, a 1064-nm quasi-continuous-wave laser was employed to anneal the indium tin oxide (ITO) films, thereby prominently prompting transparency in the near-infrared region with insignificant variation in resistivity. The decrease in carrier density due to laser annealing contributed to the improvement in transparency. Interestingly, the depth-resolved X-ray photoelectron spectroscopy distinguishes between two different mechanisms for tailoring the properties of the free carriers. Tin oxide reduction in the oxygen-deficient zone of the ITO films at a depth of approximately more than 80 nm was more significant than that in the oxygen-rich zone within the top 80-nm thin layer. In addition, the elimination of oxygen vacancies in the oxygen-rich environments did not indicate apparent advantage when compared with that in the oxygen-deficient environments owing to the oxygen supplied during the tin oxide reduction process. These results provide an alternative laser annealing technologies for tailoring the properties of the free carriers and elucidating the fundamental mechanisms in oxygen-rich and oxygen-deficient environments in an annealing process.

The Effect of the Crystalline Structure Transformation in VO2|Glass by Inserting TiO2 Buffer Layer and Its Application in Smart Windows

Vanadium dioxide (VO2) undergoes a reversible metal-insulator transition at low temperature, which has wide range of applications in smart windows and infrared detectors. However, the preparation of VO2 films with controllable phase on glass substrate is still limited. In this paper, it is shown that B-phase can be transformed into M-phase with monoclinic structure by inserting TiO2 buffer layer on glass substrate at low temperature of 400°C. This crystalline transformation might be attributed to that Ti atoms diffuse and form oxygen-deficient environments. Different thicknesses of buffer layers have different effect on characteristic of VO2 film. With 50-nm TiO2 buffer layer, the VO2|TiO2|glass film showed an abrupt resistance change with more than 2.5-order of magnitude across metal–insulator transition, and the visible-light transmittance value is as high as 55.5% with the solar modulation capability up to 8.6%. The current results are very important for the application in smart windows.

Discovery of Novel Pseudomonas putida Flavin-Binding Fluorescent Protein Variants with Significantly Improved Quantum Yield.

Oxygen-independent, flavin-binding fluorescent proteins (FbFPs) are emerging as alternatives to green fluorescent protein (GFP), which has limited applicability in studying anaerobic microorganisms, such as human gastrointestinal bacteria, which grow in oxygen-deficient environments. However, the utility of these FbFPs has been compromised because of their poor fluorescence emission. To overcome this limitation, we have employed a high-throughput library screening strategy and engineered an FbFP derived from Pseudomonas putida (SB2) for enhanced quantum yield. Of the resulting SB2 variants, KOFP-7 exhibited a significantly improved quantum yield (0.61) compared to other reported engineered FbFPs, which was even higher than that of enhanced GFP (EGFP, 0.60), with significantly enhanced tolerance against a strong reducing agent.

Statistical Analysis of Tri-Cresyl Phosphate Conversion on an Iron Oxide Surface Using Reactive Molecular Dynamics Simulations

Parallel reactive molecular dynamics simulations were used to statistically analyze chemical reactions between tri-cresyl phosphate (TCP) and an amorphous iron oxide surface. To accurately model this system, a new parameter set for Fe/P/O interactions within the ReaxFF framework was developed. Using the new parameter set, 100 parallel simulations of a single TCP molecule on an amorphous iron oxide surface were run to capture multiple possible reactions at temperatures ranging from 300 to 700 K. The frequency of TCP–surface reactions for each atom type and each unique reaction site on the TCP was analyzed across the range of temperatures. Finally, the composition of the material chemisorbed to the surface was determined and analyzed in the context of previously reported experimental measurements of TCP films in oxygen-deficient environments. The results are specifically relevant to TCP, but the parallel reactive simulation approach and statistical analysis of reaction sites can be applied more generally to...

Influence of coupling action of oxygenated fuel and gas circuit oxygen on hydrocarbons formation in diesel engine

In this paper, by comparing the effect of three fuels (B0, B20 and B20 + EHN) on engine hydrocarbon (HC) emissions in different oxygen concentrations, the relationship between the HC formation and the coupling effect of three factors: the fuel oxygen content, the combustion duration and the in-cylinder combustion temperature was analyzed. The result shows that the combustion temperature is the main influencing factor of HC emissions in the oxygen-enriched environment. However, in the medium-oxygen and oxygen-deficient environments, the fuel oxygen content factor has a greater effect than the combustion temperature. In view of the difference between the B20 fuel and the B20 + EHN fuel on HC emissions, the influence of the combustion duration on the HC emissions is much greater than that of the combustion temperature and with the decrease of the oxygen concentration, the influence weight of the combustion duration is weakened. In addition, the HC emissions from the B0 and the B20 fuels were compared. The result shows that the combustion duration is the main factor for HC emissions reduction, and the influence weight of the factor of combustion duration is greater than the sum of the oxygen content in the fuel and the combustion temperature.

Postdepositional aerobic and anaerobic particulate organic matter degradation succession reflected by dinoflagellate cysts: The Madeira Abyssal Plain revisited

We report on the succession of selective degradation of dinoflagellate cyst species that can be considered representative for discrete particulate organic matter (POM) classes of different degradability. The effects of anaerobic and aerobic degradation as well as bioturbation in a natural setting are documented in high resolution by means of palynological and geochemical analyses on Madeira Abyssal Plain A- and F-turbidites. These turbidites are unique as their initial ungraded sediments are affected by a downward penetrating oxydation front.Geochemical analyses document the presence of an active downward penetrating oxidation front in the A turbidite, and a palaeo-oxidation front in the F-turbidite. In this latter turbidite, several zones can be distinguished from top to bottom: an oxidised bioturbated zone, an oxidised but not-bioturbated zone, a visible paleo-oxidation front, and a narrow nitrogenous zone overlying unoxidised sediments.We are the first to report that anaerobic degradation within the nitrogenous zones in both turbidites affects cysts of some heterotrophic dinoflagellates. The cyst species affected (Echinidinium aculeatum, Echinidinium spp., cysts of Protoperidinium monospinum and Brigantedinium spp.) exponentially decrease in this zone that is further characterised by a strong decrease in sulphur content due to sulphide oxidation. Degradation rates are different for each species. These cysts of heterotrophic dinoflagellates consist of a nitrogen-rich glycan in contrast to the cellulosic cysts walls of phototrophic dinoflagellates. Therefore, our observation supports the hypothesis that the quality of organic matter plays an important role in OM degradation in oxygen deficient environments with N-rich OM being more labile than other components in these environments.All heterotrophic species are strongly affected by aerobic degradation with their cyst concentrations exponentially decreasing with increasing oxygen exposure. Degradation rates vary between species and range von highly degradable to slightly degradable. Most strongly affected are cysts of Protoperidinium monospinum, Brigantedinium spp., and Echinidinium spp. Increasingly less affected are: Selenopemphix nephroides, Selenopemphix quanta, other Peridinioids and Echinidinium aculeatum. An effect of aerobic degradation on photosynthetic species could only be observed for Pentapharsodinium dalei. All Impagidinium species appeared to be resistant to aerobic degradation.Despite having analysed only a limited number of samples in the bioturbated zone of the F-turbidite, we have strong indications that the bioturbation can lead to the degradation of POM that is not affected by aerobic degradation alone. The cyst species Spiniferites ramosus, Impagidinium paradoxum, Lingulodinium machaerophorum, Nematosphaeropsis labyrinthus, Spiniferites spp., Impagidinium sphaericum, Spiniferites elongates and Spiniferites mirabilis do not show concentration changes in the non-bioturbated aerobic sediments but their concentrations are considerably decreased in the bioturbated part of the F-turbidite. This supports the hypothesis that bioturbation can increase the degradation of POM by e.g. increasing oxygen exposure time and/or by an alteration of aerobic and anaerobic conditions.We furthermore show that the degradation rates of POM components represented by individual cyst species differ between zones with different redox and biological conditions. This implies that POM degradation reaction rate coefficients are environment dependent. Our observation that dinoflagellate cyst species have different degradation rates ranging from extremely labile to extremely recalcitrant within the individual redox/bioturbation zones supports the hypothesis that cyst walls have a species specific molecular structure. Our results support continuum models of organic matter degradation that assume a continuous distribution of organic matter reactivity.

Cathodic modification of stainless steels with ruthenium: a review of recent advances in making the cheaper option cheaper

AbstractCorrosion resistance of stainless steels is significantly compromised in oxygen-deficient environments, leading to limited service life as well as unsatisfactory performance of the structures made of these alloys. Cathodic modification with ruthenium has been demonstrated to remarkably improve the corrosion resistance of stainless steels in reducing acidic media, even in the presence of an abrasive suspension. Although ruthenium is several times cheaper than other platinum group metals (PGMs), alloying with ruthenium remains prohibitively more expensive than alloying with conventional, although less effective, metals. A number of strategies have been explored to reduce the amount of ruthenium required to cathodically modify stainless steels in a bid to make this cheaper option much cheaper and thus increase the cost-benefits of using these alloys. Some of the strategies include partially substituting ruthenium with cheaper metals, as well as introducing the PGM as a surface alloy.

Intracellular nitrate in sediments of an oxygen-deficient marine basin is linked to pelagic diatoms.

Intracellular nitrate is an important electron acceptor in oxygen-deficient aquatic environments, either for the nitrate-storing microbes themselves, or for ambient microbial communities through nitrate leakage. This study links the spatial distribution of intracellular nitrate with the abundance and identity of nitrate-storing microbes in sediments of the Bornholm Basin, an environmental showcase for severe hypoxia. Intracellular nitrate (up to 270 nmol cm-3 sediment) was detected at all 18 stations along a 35-km transect through the basin and typically extended as deep as 1.6 cm into the sediment. Intracellular nitrate contents were particularly high at stations where chlorophyll contents suggested high settling rates of pelagic primary production. The depth distribution of intracellular nitrate matched that of the diatom-specific photopigment fucoxanthin in the upper 1.6 cm and calculations support that diatoms are the major nitrate-storing microbes in these sediments. In contrast, other known nitrate-storing microbes, such as sulfide-oxidizing bacteria and foraminifers, played only a minor role, if any. Strikingly, 18S rRNA gene sequencing revealed that the majority of the diatoms in the sediment were pelagic species. We conclude that intracellular nitrate stored by pelagic diatoms is transported to the seafloor by settling phytoplankton blooms, implying a so far overlooked 'biological nitrate pump'.