Effect of cation structure on the oxygen solubility and diffusivity in a range of bis{(trifluoromethyl)sulfonyl}imide anion based ionic liquids for lithium-air battery electrolytes

This paper reports on the solubility and diffusivity of dissolved oxygen in a series of ionic liquids (ILs) based on the bis{(trifluoromethyl)sulfonyl}imide anion with a range of related alkyl and ether functionalised cyclic alkylammonium cations. Cyclic voltammetry has been used to observe the reduction of oxygen in ILs at a microdisk electrode and chronoamperometric measurements have then been applied to simultaneously determine both the concentration and the diffusion coefficient of oxygen in the different ILs. The viscosity of the ILs and the calculated molar volume and free volume is also reported. It is found that, within this class of ILs, the oxygen diffusivity generally increases with decreasing viscosity of the neat IL. An inverse relationship between oxygen solubility and IL free volume is reported for the two IL families implying oxygen is not simply occupying the available empty space. In addition, it is reported that the introduction of ether-group into the IL cation structure promotes the diffusivity of dissolved oxygen but reduces the solubility of the gas.

Fear of oxygen therapy for children in Malawi

BACKGROUND: Although pneumonia is a common cause of death in children in Malawi, healthcare staff frequently encounter patients or carers who refuse oxygen therapy. This qualitative study documents factors that influence acceptance or refusal of oxygen therapy for children in Malawi.

METHODS: Nine group interviews involving 86 participants were held in community and hospital settings in rural and urban Malawi. Eleven in-depth interviews of healthcare staff providing oxygen were held in a central hospital. Thematic analysis of transcripts of the audio recordings was carried out to identify recurring themes.

RESULTS: Similar ideas were identified in the group interviews and in-depth staff interviews. Past experiences of oxygen use (direct and indirect, positive and negative) had a strong influence on views of oxygen. A recurrent theme was fear of oxygen, often due to a perceived association between death and recent oxygen use. Fears were intensified by a lack of familiarity with equipment used to deliver oxygen, distrust of medical staff and concerns about cost of oxygen.

CONCLUSIONS: This study identifies reasons for refusal of oxygen therapy for children in a low-income country. Findings from the study suggest that training of healthcare staff to address fears of parents, and information, education and communication (IEC) approaches that improve public understanding of oxygen and provide positive examples of its use are likely to be helpful in improving uptake of oxygen therapy in Malawi.

Long-term changes in oxygen depletion in a small temperate lake: effects of climate change and eutrophication

1. We analysed 41 years of data (1968–2008) from Blelham Tarn, U.K., to determine the consequences of eutrophication and climate warming on hypolimnetic dissolved oxygen (DO).
2. The establishment of thermal stratification was strongly related to the onset of DO depletion in the lower hypolimnion. As a result of a progressively earlier onset of stratification and later overturn, the duration of stratification increased by 38 ± 8 days over the 41 years.
3. The observed rate of volumetric hypolimnetic oxygen depletion (VHODobs) ranged from 0.131 to 0.252 g O2 m−3 per day and decreased significantly over the study period, despite the increase in the mean chlorophyll a (Chl a) concentration in the growing season. The vertical transport of DO represented from 0 to 30% of VHODobs, while adjustments for interannual differences in hypolimnetic temperature were less important, ranging from −11 to 9% of VHODobs.
4. The mean wind speed during May made the strongest significant contribution to the variation in VHODobs. VHODobs adjusted for the vertical transport of DO and hypolimnetic temperature differences, VHODadj, was significantly related to the upper mixed layer Chl a concentration during spring.
5. Hypolimnetic anoxia (HA) ranged from 27 to 168 days per year and increased significantly over time, which undoubtedly had negative ecological consequences for the lake.
6. In similar small temperate lakes, the negative effects of eutrophication on hypolimnetic DO are likely to be exacerbated by changes in lake thermal structure brought about by a warming climate, which may undermine management efforts to alleviate the effects of anthropogenic eutrophication.

Deriving ecological quality standards for lakes using hypolimnetic oxygen depletion

The ecological quality of lakes and other surface water bodies in the European Union is determined by the quality of the structure and functioning of the aquatic ecosystem. The depletion rate of oxygen in the hypolimnion is an important process in thermally stratified lakes and the distribution of consumption between water and sediment an important structural characteristic. It is shown that the variation of volumetric oxygen consumption rate with trophic state can be used to select lake water total phosphorus and chlorophyll concentrations that correspond to changes in the functioning of the lake. Lake morphometry has little effect on this aspect of lake function and the relative amount of oxygen consumption in the water and sediment changes only a little with trophic state, most of the consumption being in the water. Suggestions for the reference condition, good and moderate ecological quality are made using the changes in this aspect of lake function and they are presented as lake water total phosphorus and chlorophyll concentration.