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Abstract The physics of recombination lines in the Heisinglet system is expected to be relatively simple, supported by accurate atomic models. We examine the intensities of Heisingletsλ3614, λ3965, λ5016, λ6678, and λ7281 and the triplet Heiλ5876 in various types of ionized nebulae and compare them with theoretical predictions to test the validity of the “Case B” recombination scenario and the assumption of thermal homogeneity. Our analysis includes 85 spectra from Galactic and extragalactic Hiiregions, 90 from star-forming galaxies, and 218 from planetary nebulae, all compiled by the Deep Spectra of Ionized Regions Database Extended (DESIRED-E) project. By evaluating the ratios Heiλ7281/λ6678 and Heiλ7281/λ5876, we determineTe(Hei) and compare it with direct measurements ofTe([Oiii]λ4363/λ5007). We find thatTe(Hei) is systematically lower thanTe([Oiii]) across most objects and nebula types. Additionally, we identify a correlation between the abundance discrepancy factor (ADF(O2+)) and the differenceTe([Oiii]) –Te(Hei) for planetary nebulae. We explore two potential explanations: photon loss fromn1P → 11Stransitions and temperature inhomogeneities. Deviations from “Case B” may indicate photon absorption by Hirather than Heiand/or generalized ionizing photon escape, highlighting the need for detailed consideration of radiative transfer effects. If temperature inhomogeneities are widespread, identifying a common physical phenomenon affecting all ionized nebulae is crucial. Our results suggest that both scenarios can contribute to the observed discrepancies.
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Production of diverse brGDGTs by Acidobacterium Solibacter usitatus in response to temperature, pH, and O 2 provides a culturing perspective on br GDGT proxies and biosynthesis
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Abstract Polymeric donors of gasotransmitters, gaseous signaling molecules such as hydrogen sulfide, nitric oxide, and carbon monoxide, hold potential for localized and extended delivery of these reactive gases. Examples of gasotransmitter donors based on polysaccharides are limited despite the availability and generally low toxicity of this broad class of polymers. In this work, we sought to create a polysaccharide H2S donor by covalently attachingN‐thiocarboxyanhydrides (NTAs) to amylopectin, the major component of starch. To accomplish this, we added an allyl group to an NTA, which can spontaneously hydrolyze to release carbonyl sulfide and ultimately H2S via the ubiquitous enzyme carbonic anhydrase, and then coupled it to thiol‐functionalized amylopectin of three different molecular weights (MWs) through thiol‐ene “click” photochemistry. We also varied the degree of substitution (DS) of the NTA along the amylopectin backbone. H2S release studies on the six samples, termed amyl‐NTAs, with variable MWs (three) and DS values (two), revealed that lower MW and higher DS led to faster release. Finally, dynamic light scattering experiments suggested that aggregation increased with MW, which may also have affected H2S release rates. Collectively, these studies present a new synthetic method to produce polysaccharide H2S donors for applications in the biomedical field.more » « less
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Abstract In 2021, the Ocean Thematic Centre of the European Research Infrastructure “Integrated Carbon Observation System” conducted an international partial pressure of carbon dioxide (pCO2) instrument intercomparison. The goal was to understand how different types of instrumentation for the measurement of oceanpCO2compare to each other. During the two‐week long experiment, we installed various instruments in a tank facility using natural sea water (North Sea). These included direct air–water equilibration systems and membrane‐based flow‐through instruments along with submersible sensors and instruments that are normally installed on buoys and autonomous surface vehicles. In situ instruments were installed inside the tank and the flow‐through instruments were fed the same water using a pumping system. We changed the temperature (between 10°C and 28°C) and the seawaterpCO2(between 250 and 800μatm) to observe instrument responses over a wide range. Since there is no reference for surface oceanpCO2measurements, we agreed on a set of instruments serving as intercomparison reference. All data from the different instruments were then compared against the intercomparison reference during periods of stable temperature andpCO2. The study provides important information to enhance future ocean carbon monitoring networks, but makes no direct recommendation for the use of any specific sensor. A major finding is that equilibration through direct air–water contact appears to be more consistent and independent of external factors than equilibration through a membrane or photometric detection. We found several instruments with no temperature measurements at the location of equilibration or with uncalibrated temperature sensors introducing significant uncertainty in the results.more » « less
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1111/gbi.12525
