46 research outputs found
Explanation for the increase in high altitude water on Mars observed by NOMAD during the 2018 global dust storm
The Nadir and Occultation for MArs Discovery (NOMAD) instrument on board ExoMars Trace Gas Orbiter (TGO) measured a large increase in water vapor at altitudes in the range of 40â100 km during the 2018 global dust storm on Mars. Using a threeâdimensional general circulation model, we examine the mechanism responsible for the enhancement of water vapor in the upper atmosphere. Experiments with different prescribed vertical profiles of dust show that when more dust is present higher in the atmosphere the temperature increases and the amount of water ascending over the tropics is not limited by saturation until reaching heights of 70â100 km. The warmer temperatures allow more water to ascend to the mesosphere. Photochemical simulations show a strong increase in highâaltitude atomic hydrogen following the highâaltitude water vapor increase by a few days
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Water Vapor Vertical Profiles on Mars in Dust Storms Observed by TGO/NOMAD
It has been suggested that dust storms efficiently transport water vapor from the nearâsurface to the middle atmosphere on Mars. Knowledge of the water vapor vertical profile during dust storms is important to understand water escape. During Martian Year 34, two dust storms occurred on Mars: a global dust storm (June to midâSeptember 2018) and a regional storm (January 2019). Here we present water vapor vertical profiles in the periods of the two dust storms (Ls = 162â260° and Ls = 298â345°) from the solar occultation measurements by Nadir and Occultation for Mars Discovery (NOMAD) onboard ExoMars Trace Gas Orbiter (TGO). We show a significant increase of water vapor abundance in the middle atmosphere (40â100 km) during the global dust storm. The water enhancement rapidly occurs following the onset of the storm (Ls~190°) and has a peak at the most active period (Ls~200°). Water vapor reaches very high altitudes (up to 100 km) with a volume mixing ratio of ~50 ppm. The water vapor abundance in the middle atmosphere shows high values consistently at 60°Sâ60°N at the growth phase of the dust storm (Ls = 195°â220°), and peaks at latitudes greater than 60°S at the decay phase (Ls = 220°â260°). This is explained by the seasonal change of meridional circulation: from equinoctial Hadley circulation (two cells) to the solstitial one (a single poleâtoâpole cell). We also find a conspicuous increase of water vapor density in the middle atmosphere at the period of the regional dust storm (Ls = 322â327°), in particular at latitudes greater than 60°S
Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries
Background
Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres.
Methods
This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and lowâmiddle-income countries.
Results
In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of âsingle-useâ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for lowâmiddle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia.
Conclusion
This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both highâ and lowâmiddleâincome countries
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Effect of external acidosis on basal and ATP-evoked calcium influx in cultured astrocytes
The effect of lactic acidosis on calcium influx, accumulation and efflux was studied in primary cultures of neonatal cortical rat astrocytes. Treatment of cultures with 20 mM sodium lactate, pH 6.0, for 10â60 min resulted in a 35% reduction of
45Ca
2+ influx. The decrease in calcium influx was pH dependent because a similar reduction was observed in cultures exposed to pH 6.0 without lactate, while no difference was observed in cultures treated with sodium lactate at pH 7.4. Calcium accumulation was also decreased by lactic acidosis (20% reduction), while calcium efflux was unaffected. Studies with lanthanum, an inhibitor of calcium transport, indicated that the effect of lactic acidosis was not due to non-specific leakage of calcium. The reduction in calcium influx was reversible, thereby indicating that the cells were not permenantly damaged by lactic acidosis. In addition to basal calcium influx, stimulated influx (mediated by extracellular ATP, 100 ÎŒM) was also reduced by 20 mM sodium lactate, pH 6. These findings suggest that protonization of calcium channels or other calcium entry pathways leads to a reduction in calcium influx in astrocytes. This diminished calcium entry, by affecting calcium-dependent mechanisms necessary for such processes as volume regulation, glycogen metabolism, or regulation of ionic permeability, may alter the ability of astrocytes to elicit appropriate responses following CNS injury
Traumatic Injury Activates Protein Kinase B/Akt in Cultured Astrocytes: Role of Extracellular ATP and P2 Purinergic Receptors
Destabilization of glial fibrillary acidic protein mRNA in astrocytes by ammonia and protection by extracellular ATP
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Effect of ammonia on calcium homeostasis in primary astrocyte cultures
Calcium influx, accumulation and efflux were studied in primary cultures of rat astrocytes treated with ammonium chloride. Treatment of the cells for 3 days with 10 mM NH
4Cl resulted in a 35% reduction in
45Ca influx. The decrease in calcium influx was dose-dependent between 2 and 10 mM NH
4Cl. Short-term (30 min) exposure to ammonia had no effect on calcium influx. Calcium accumulation, as measured by 20-min exposure to
45Ca, decreased after treating cultures with 10 mM NH
4Cl for one or 3 days; a greater effect was observed after the 3-day treatment. Studies with lanthanum, an inhibitor of calcium transport, indicated that the effect of ammonia was not due to non-specific leakage of calcium. Calcium efflux was not affected by exposure of the cultures to ammonium chloride. Purinergic-evoked calcium influx and mobilization was not altered by ammonia. While the mechanism(s) of calcium homeostasis affected by long-term hyperammonemia remain to be defined, these results suggest that reduced astrocytic calcium may be related to the pathogenesis of ammonia-related disorders such as hepatic encephalography
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ATP stimulates calcium influx in primary astrocyte cultures
The effect of ATP and other purines on
45Ca uptake was studied in primary cultures of rat astrocytes. Treatment of the cells with ATP for 1 to 30 min brought about an increase in cellular
45Ca. Stimulation of calcium influx by ATP was investigated using a 90 sec exposure to
45Ca and over a concentration range of 0.1 nM to 3 mM; a biphasic dose-response curve was obtained with EC
50 values of 0.3 nM and 9 uM, indicating the presence of low and high affinity purinergic binding sites. Similar levels of
45Ca influx at 90 sec were observed with ATP, ADP and adenosine (all at 100 uM). Prior treatment of the cultures with LaCl
3 blocked the purine-induced
45Ca influx. These findings indicate that one pathway for calcium entry in astrocytes involves purinergic receptor-operated, calcium channels