Atm Of Air Research Articles

Experimental and theoretical investigation of benzothiazole oxidation by OH in air and the role of O2.

Benzothiazole (BTH) and its derivatives are amongst a group of emerging contaminants that are widely distributed in the environment due to their extensive use in many different consumer products. In air, reaction with the hydroxyl radical (OH) is expected to be a major loss process for BTH in the gas phase, but the kinetics and mechanisms are unknown. Here, we report a combination of experiments and theory to determine both the rate constant and products of the reaction of OH with the smallest member of the series, benzothiazole, in the gas phase. The mechanism first involves an attack by OH on BTH to produce several OHBTH intermediates. This is followed by O2 reactions with OHBTH, leading to several stable products successfully predicted by theory. Relative rate studies at 1 atm in air and 298 K using benzene as a reference gave a rate constant for the BTH + OH reaction of 2.1 ± 0.1 × 10-12 (1σ) cm3 per molecule per s, which translates to a lifetime in air of 5.5 days at 1 × 106 OH cm-3. Four hydroxybenzothiazole products reflecting attack on different carbon atoms of the benzene ring were measured (n-OHBTH, where n = 4, 5, 6, 7), with the relative product yields well predicted by the calculated formation energies of the pre-reaction OH⋯BTH complex. Attack of OH on the -CH of the thiazole ring leads to the formation of 2-OHBTH, representing a smaller fraction of the overall reaction, and is shown to proceed through a more complex mechanism than attack on the benzene ring. A theoretical approach to predicting chromatographic retention times of the products based on solvation free energies (ΔGsolv) was successful for most of the products. These studies illustrate how the powerful combination of experiment and theory can be used to predict products of atmospheric oxidation of emerging contaminants and ultimately used to assess their impacts on the environment.

The [(Bn-tpen)FeII]2+ Complex as a Catalyst for the Oxidation of Cyclohexene and Limonene with Dioxygen.

[(Bn-tpen)FeII(MeCN)](ClO4)2, containing the pentadentate Bn-tpen-N-benzyl-N,N',N'-tris(2-pyridylmethyl)-1,2-diaminoethane ligand, was studied in the oxygenation of cyclohexene and limonene using low-pressure dioxygen (0.2 atm air or 1 atm pure O2) in acetonitrile. 2-Cyclohexen-1-one and 2-cyclohexen-1-ol are the main products of cyclohexene oxidations, with cyclohexene oxide as a minor product. Limonene is oxidized to limonene oxide, carvone, and carveol. Other oxidation products such as perillaldehyde and perillyl alcohol are found in trace amounts. This catalyst is slightly less active than the previously reported [(N4Py)FeII(MeCN)](ClO4)2 (N4Py-N,N-bis(2-pyridylmethyl)-N-(bis-2-pyridylmethyl)amine). Based on cyclic voltammetry experiments, it is postulated that [(Bn-tpen)FeIV=O]2+ is the active species. The induction period of approx. 3 h during cyclohexene oxygenation is probably caused by deactivation of the reactive Fe(IV)=O species by the parent Fe(II) complex. Equimolar mixtures of Fe(II) salt and the ligand (in situ-formed catalyst) gave catalytic performance similar to that of the synthesized catalyst.

CO2 Promoting Polymorphic Transformation of Clarithromycin: Polymorph Characterization, Pathway Design, and Mechanism Study

Carbon dioxide (CO2) has a wide range of uses such as food additives and raw materials for synthetic chemicals, while its application in the solid-state transformation of pharmaceutical crystals is rare. In this work, we report a case of using 1 atm CO2 as an accelerator to promote the polymorphic transformation of clarithromycin (CLA). Initially, crystal structures of Form 0′ and three solvates were successfully determined by single crystal X-ray diffraction (SCXRD) analysis for the first time and found to be isomorphous. Powder X-ray diffraction (PXRD) and thermal analysis indicated that the solvate desolvates and transforms into the structurally similar non-solvated Form 0′ at room temperature to ~50 °C. Form 0′ and Form II are monotropically related polymorphs with Form II being the most stable. Subsequently, the effect of CO2 on the transformation of CLA solvates to Form II was studied. The results show that CO2 can significantly facilitate the transformation of Form 0′ to Form II, despite no significant effect on the desolvation process. Finally, the molecular mechanism of CO2 promoting the polymorphic transformation was revealed by the combination of the measurement of adsorption capacity, theoretical calculations as well as crystal structure analysis. Based on the above results, a new pathway of preparing CLA Form II was designed: transform CLA solvates into Form 0′ in 1 atm air at 50 °C followed by the transformation of Form 0′ to Form II in 1 atm CO2 at 50 °C. This work provides a new idea for promoting the phase transformation of pharmaceutical crystals as well as a new scenario for the utilization of CO2.

Numerical study on three-stage ignition of dimethyl ether by hot air under engine-relevant conditions

Non-premixed combustion often occurs in practical engines, and it is affected by the coupling effects of chemical kinetics and transport. This study aims to elucidate the individual effect of chemical kinetics, molecular diffusion, and convective transport on non-premixed combustion. To this end, three types of reactive systems are investigated by numerical simulations considering detailed chemistry and transport: (1) thermochemical system: 0D homogeneous autoignition, (2) thermochemical-diffusive system: 1D non-premixed ignition in a static diffusion layer, (3) thermochemical-diffusive-convective system: 1D non-premixed ignition in a counterflow and 2D lifted flame in a coflow. The simulations are carried out for diluted dimethyl ether and hot air under engine-relevant conditions with a pressure of 40 atm and hot air temperatures of 700∼1500 K. First, homogeneous ignition process of DME/air premixture is investigated. It is found that, apart from the low- and high-temperature chemistry which are essential in the typical two-stage ignition, the intermediate-temperature chemistry can also play an important role, especially for slow reaction process in fuel rich regions. Then, the effects of thermochemical conditions and molecular diffusion are assessed for non-premixed ignition process in the 1D diffusion layer. The results show that, the reaction front always initiates from local autoignition in most reactive regions; then it propagates either in sequential auto-ignition mode or in diffusion-driven mode as a deflagration wave. With various thermochemical conditions, the chemical kinetics behave differently and produce complex multibrachial (tetrabrachial, pentabrachial and hexbrachial) structures during the reaction front propagation. Decreasing the diffusion layer thickness generally delays the reaction front initiation but enhances its transition into a diffusion-driven flame. Finally, it is shown that 1D diffusion layer simulations can qualitatively reproduce the complex multibrachial structures in 1D counterflow and 2D coflow at certain conditions. A regime diagram is proposed to separate the effects of chemical kinetics, molecular diffusion, and convective transport.

Carbonaceous Material Modified MoO2 Nanospheres with Oxygen Vacancies for Enhanced Visible-Light Photocatalytic Oxidative Coupling of Benzylamine.

Surface oxygen vacancy (OV) plays a pivotal role in the activation of molecular oxygen and separation of electrons and holes in photocatalysis. Herein, carbonaceous materials-modified MoO2 nanospheres with abundant surface OVs (MoO2/C-OV) were successfully synthesized via glucose hydrothermal processes. In situ introduction of carbonaceous materials triggered a reconstruction of the MoO2 surface, which introduced abundant surface OVs on the MoO2/C composites. The surface oxygen vacancies on the obtained MoO2/C-OV were confirmed via electron spin resonance spectroscopy (ESR) and X-ray photoelectron spectroscopy (XPS). The surface OVs and carbonaceous materials boosted the activation of molecular oxygen to singlet oxygen (1O2) and superoxide anion radical (•O2-) in selectively photocatalytic oxidation of benzylamine to imine. The conversion of benzylamine was 10 times that of pristine MoO2 nanospheres with a high selectivity under visible light irradiation at 1 atm air pressure. These results open an avenue to modify Mo-based materials for visible light-driven photocatalysis.

Effect of SnCl2 heat treatment on SnS thin films deposited by RF sputtering

In this study, the effect of SnCl2 treatment on SnS thin films was investigated. SnS thin films were grown by RF sputtering and SnCl2 treatment was applied by wet chemical processing. The samples grouped as SnCl2 heat treated, annealed, as dep. were subjected to annealing in air atm. The as dep. sample grew in the orthorhombic SnS phase. Annealing of the SnS sample in air environment led to the formation of orthorhombic SnS as well as non-dominant SnS2 and SnO2 phases. It was found that applying SnCl2 heat treatment to SnS deteriorated the crystallization and especially the SnO2 oxide phase became more dominant. Raman spectra confirmed the presence of SnS and SnS2 phases in the samples, but no evidence of SnO2 phase was found. SEM images showed bladelike, dense grain formation in the as dep. and annealed samples. However, SnCl2 heat treatment completely changed the surface morphology of the sample, causing it to transform into a structure consisting of several domains split by deep fractures. EDS revealed a distinct Sn-rich composition of the as dep. and annealed samples (Sn/S~1.2). On the other hand, SnCl2 heat treatment caused a massive loss of sulfur in the atomic distribution of the SnS and it was seen that the Sn/S ratio increased to around 7.5. The band gaps of the as dep. and annelaed samples were calculated as 1.43 eV and 1.45, respectively. However, SnCl2 heat treatment led to an increase to 1.56 eV of the band gap. Analysis results show that SnCl2 treatment by the wet processing causes a significant change on the characteristics of SnS thin film. In this context, it can be said that SnCl2 heat treatment can be further improved with optimization processes.

Oxygen-Ion and Proton Transport of Origin and Ca-Doped La2ZnNdO5.5 Materials

Oxygen-ionic and proton-conducting oxides are widely studied materials for their application in various electrochemical devices such as solid oxide fuel cells and electrolyzers. Rare earth oxides are known as a class of ionic conductors. In this paper, La2ZnNdO5.5 and its Ca-doped derivatives La2Nd0.9Ca0.1ZnO5.45 and La2ZnNd0.9Ca0.1O5.45 were obtained by a solid-state reaction route. Phase composition, lattice parameters, and hydration capability were investigated by X-ray diffraction and thermogravimetric analyses. The conductivities of these materials were measured by the electrochemical impedance spectroscopy technique in dry (pH2O = 3.5 × 10−5 atm) and wet (pH2O = 2 × 10−2 atm) air. All phases crystallized in a trigonal symmetry with P3m1 space group. The conductivity difference between undoped and calcium-doped samples is more than two orders of magnitude due to the appearance of oxygen vacancies during acceptor doping, which are responsible for a higher ionic conductivity. The La2Nd0.9Ca0.1ZnO5.45 sample shows the highest conductivity of about 10−3 S∙cm−1 at 650 °C. The Ca-doped phases are capable of reversible water uptake, confirming their proton-conducting nature.

Nickel(II) Complexes of Tripodal Ligands as Catalysts for Fixation of Atmospheric CO2 as Organic Carbonates.

The fixation of atmospheric CO2 into value-added products is a promising methodology. A series of novel nickel(II) complexes of the type [Ni(L)(CH3 CN)2 ](BPh4 )2 1-5, where L=N,N-bis(2-pyridylmethyl)-N', N'-dimethylpropane-1,3-diamine (L1), N,N-dimethyl-N'-(2-(pyridin-2-yl)ethyl)-N'-(pyridin-2-ylmethyl) propane-1,3-diamine (L2), N,N-bis((4-methoxy-3,5-dimethylpyridin-2-ylmethyl)-N',N'-dimethylpropane-1,3-diamine (L3), N-(2-(dimethylamino) benzyl)-N',N'-dimethyl-N-(pyridin-2-ylmethyl) propane-1,3-diamine (L4) and N,N-bis(2-(dimethylamino)benzyl)-N', N'-dimethylpropane-1,3-diamine (L5) have been synthesized and characterized as the catalysts for the conversion of atmospheric CO2 into organic cyclic carbonates. The single-crystal X-ray structure of 2 was determined and exhibited distorted octahedral coordination geometry with cis-α configuration. The complexes have been used as a catalyst for converting CO2 and epoxides into five-membered cyclic carbonates under 1 atmospheric (atm) pressure at room temperature in the presence of Bu4 NBr. The catalyst containing electron-releasing -Me and -OMe groups afforded the maximum yield of cyclic carbonates, 34% (TON, 680) under 1 atm air. It was drastically enhanced to 89% (TON, 1780) under pure CO2 gas at 1 atm. It is the highest catalytic efficiency known for CO2 fixation using nickel-based catalysts at room temperature and 1 atm pressure. The electronic and steric factors of the ligands strongly influence the catalytic efficiency. Furthermore, all the catalysts can convert a wide range of epoxides (ten examples) into corresponding cyclic carbonate with excellent selectivity (>99%) under this mild condition.

Mechanism and effect assessment of sub-atmospheric pressure and co-flow air to suppress the flicker of buoyancy-driven methane laminar diffusion flame

To further reduce the combustion instability behavior in high-altitude areas, a synergistic suppression of buoyancy-driven methane laminar diffusion flame flicker was achieved by sub-atmospheric pressure combined with co-flow air, and the suppression mechanism was revealed through the schlieren technique. As the pressure decreases, the fluid density gradient within the shear layer decreases, slowing down the formation of vortices. When the co-flow air increases, the vortex is accelerated to rise until the vortex forms downstream of the flame and the flame flicker is completely suppressed. The suppression of flame flicker by sub-atmospheric pressure and co-flow air was nonlinear. The flicker frequency, oscillation amplitude, and flame mean height of flames were assessed for a pressure of 0.5–1.0 atm and co-flow air of 4–16 L/min. The sub-atmospheric pressure reduces the flicker frequency, which increases with increasing co-flow air. The reduction rate of oscillation amplitude at sub-atmospheric pressure varied among different co-flow air flow rates. The initial and that almost realize flame stabilization co-flow air flow rates are more effective than the intermediate flow rate in reducing the oscillation amplitude. The flame mean height decreases monotonically with decreasing pressure, but there is a small peak in the downward trend with increasing co-flow air.

High temperature fuel impacts on combustion characteristics of a swirl-stabilized combustor

Future aircraft will require advanced thermal management systems to manage the increased heat loads resulting from the avionics, turbomachinery and other subsystems of higher performance, and high speed flight systems. Fuel is the primary coolant to alleviate these thermal management challenges. Heated fuel entering the combustor is likely to affect combustion performance due to dramatic changes in properties that impact fuel atomization, distribution, vaporization and fuel/air mixing. In this study, the combustion performance, emissions, and flame characteristics of a single-nozzle, swirl-stabilized combustor operating with high temperature fuels were investigated. Four fuels representing a wide range of jet fuel physical and chemical properties were studied at injection temperatures of 32, 121 and 260 °C. The test fuels included a conventional Jet A (A-2), a low cetane number alcohol-to-jet (ATJ) alternative fuel (C-1), n-dodecane (n-C12) and a high viscosity jet fuel blend (C-3A). Tests were conducted at a combustor pressure of 2 atm and inlet air temperature of 121 °C at global equivalence ratios (ϕ) of 0.10–0.24 for most fuel temperatures. Particulate matter (PM) emissions (concentrations and size distributions), and primary gaseous emissions were measured. High frequency pressure measurements and high-speed video were collected to assess fuel temperature impacts on combustion stability and flame characteristics, respectively. Results show that the heated fuel impacts on combustion were highly dependent on fuel type, temperature and ϕ. Qualitative results show that as fuel temperature increased, the flame in the primary zone appeared more compact, and less thermally radiant (lower soot). PM emissions were significantly impacted with reductions exceeding 95 % in particle number density for all fuels, and between 20 and 55 % reductions in mean particle diameters for aromatic-containing fuels. Gaseous emissions show up to ∼ 90 % reduction in unburned hydrocarbons (UHC) and up to 60 % reduction in carbon monoxide (CO), and corresponding moderate increases in NOx and CO2 with the heated fuel. The combustor acoustic response was slightly suppressed in frequencies of interest as fuel temperature increased. In general, the impacts of heated fuel on combustion were mostly beneficial and are primarily attributed to improved fuel atomization and reduced fuel evaporation timescales of the heated fuel. Specific impacts of fuel physical and chemical properties, and potential implications of heated fuel combustion are discussed.

Surface coordination enhanced visible-light photocatalytic coupling of benzylamine to N-benzylidene benzylamine over the Pd/NH2-MIL-125(Ti) nanosheets

The two-dimensional (2D) Metal Organic Framework (MOF) of NH2-MIL-125(Ti) nanosheets with oxygen vacancies were prepared to construct a multifunctional photocatalyst via surface modification of Pd nanoparticles (Pd/MTNs). The obtained photocatalyst showed the highly efficiency for precisely transformation of benzylamine to N-benzylidene benzylamine under visible light irradiation and 1 atm air pressure at room temperature. With the assistance of theoretical mathematical model, the MTNs loaded 0.5% wt Pd completed the transformation for benzylamine (>99%) precisely to N-Benzylidenebenzylamine (99%). However, the Bulk loaded 0.5% wt Pd exhibits decreased conversion (80.5%) and selectivity (85.9%). AFM, XPS and UV–vis DRS experiments indicated that the open 2D structure of MTNs would contribute to the generation of surface oxygen vacancies (OV) sites and abundant Ti metal sites with underfilling electrons 3d orbit, enhancing the light absorption. In-situ FTIR revealed that these exposed Ti atoms would act as the discriminating sites to specifically adsorb the benzylamine molecules forming chemical coordination bonds -C-N⋯Ti- on interface, polarizing and activating -C-N-bonds in benzylamine. Additionally, series of in-situ EPR and experimental results elucidated that the surface OV sites would act as the functional sites to capture the O2 molecules from air. Furthermore, surface Pd sites would as an active site to accelerate the photo-generated electrons transfer from inside to interface, inducing the activation of adsorbed O2 molecules to O2–. Based on these cooperating function sites in MTNs, a possible catalytic mechanism was discussed in a molecular scale. This work highlights the rational construction of a multifunctional photocatalyst and the synergistic effects of the surface coordination and photocatalysis.

Oxygen vacancy enhanced visible light photocatalytic selective oxidation of benzylamine over ultrathin Pd/BiOCl nanosheets

Two atomic layered BiOCl nanosheets with rich oxygen vacancies (NS-OV) were constructed via surface Pd deposition (0.5 wt%) as a multifunctional photocatalyst (Pd0.5/NS-OV), which exhibits high conversion (>95%) and precise selectivity (>98%) for benzylamine coupling to N-benzylidenebenzylamine under visible light irradiation and 1 atm air pressure. XPS and UV–vis DRS indicated that ultrathin structure of the nanosheets induces the formation of surface oxygen vacancies (OV), resulting in abundant surface low-coordinated Bi atoms and expanded visible light absorpion. Moreover, in-situ EPR results revealed that surface OV sites contribute to assemble O2 molecules from air to surface of NS-OV. Additionally, in-situ FTIR suggested that low-coordinated Bi selectively adsorb benzylamine molecules via -N···Bi- coordination bonds at the interfaces, inducing polarization and activation of -C-N bonds. Furthermore, Pd sites were observed to crucially participate in formation of active ∙O2- species under visible light irradiation. Based on multifunctional features, a possible synergistic mechanism was proposed.

Aerobic oxidation of syringyl alcohol over N-doped carbon nanotubes

Carbon nanotubes (CNTs) doped with nitrogen were prepared using two methodologies, chemical vapor deposition (N-CNTs) and post-modification (N-CNTs-P), and characterized by N2 adsorption, TEM, XPS, Raman spectroscopy, and water capacity measurements. Their catalytic performance was assessed for aerobic oxidation of syringyl alcohol, a model of syringyl unit of lignin. With N-CNTs, the reaction readily proceeds under mild conditions (40–80 °C, 1 atm of air, isopropanol, ethanol, or water as solvents), leading to syringaldehyde with 95–97% yield. A correlation between N content in N-CNTs and oxidation rate has been established. Spectroscopic studies coupled with water capacity measurements implicated that a blend of graphitic and pyridinic nitrogen species is crucial for catalytic activity. The catalysts can be easily recovered, regenerated, and reused without significant loss of the catalytic performance. N-CNTs-P catalysts, which endow high content of quinone-type oxygen groups, provide significantly lower syringaldehyde yield due to fast deactivation.

Room Temperature Aerobic Peroxidation of Organic Substrates Catalyzed by Cobalt(III) Alkylperoxo Complexes

Room temperature aerobic oxidation of hydrocarbons is highly desirable and remains a great challenge. Here we report a series of highly electrophilic cobalt(III) alkylperoxo complexes, CoIII(qpy)OOR supported by a planar tetradentate quaterpyridine ligand that can directly abstract H atoms from hydrocarbons (R'H) at ambient conditions (CoIII(qpy)OOR + R'H → CoII(qpy) + R'• + ROOH). The resulting alkyl radical (R'•) reacts rapidly with O2 to form alkylperoxy radical (R'OO•), which is efficiently scavenged by CoII(qpy) to give CoIII(qpy)OOR' (CoII(qpy) + R'OO• → CoIII(qpy)OOR'). This unique reactivity enables CoIII(qpy)OOR to function as efficient catalysts for aerobic peroxidation of hydrocarbons (R'H + O2 → R'OOH) under 1 atm air and at room temperature.

Efficient Syntheses of Biobased Terephthalic Acid, p-Toluic Acid, and p-Methylacetophenone via One-Pot Catalytic Aerobic Oxidation of Monoterpene Derived Bio-p-cymene.

An efficient elevated-pressure catalytic oxidative process (2.5 mol % Co(NO3)2, 2.5 mol % MnBr2, air (30 bar), 125 °C, acetic acid, 6 h) has been developed to oxidize p-cymene into crystalline white terephthalic acid (TA) in ∼70% yield. Use of this mixed Co2+/Mn2+ catalytic system is key to obtaining high 70% yields of TA at relatively low reaction temperatures (125 °C) in short reaction times (6 h), which is likely to be due to the synergistic action of bromine and nitrate radicals in the oxidative process. Recycling studies have demonstrated that the mixed metal catalysts present in recovered mother liquors could be recycled three times in successive p-cymene oxidation reactions with no loss in catalytic activity or TA yield. Partial oxidation of p-cymene to give p-methylacetophenone (p-MA) in 55–60% yield can be achieved using a mixed CoBr2/Mn(OAc)2 catalytic system under 1 atm air for 24 h, while use of Co(NO3)2/MnBr2 under 1 atm O2 for 24 h gave p-toluic acid in 55–60% yield. Therefore, access to these simple catalytic aerobic conditions enables multiple biorenewable bulk terpene feedstocks (e.g., crude sulfate turpentine, turpentine, cineole, and limonene) to be converted into synthetically useful bio-p-MA, bio-p-toluic acid, and bio-TA (and hence bio-polyethylene terephthalate) as part of a terpene based biorefinery.

Effect of Oxygen on the Oxidation of Methane with Hydrogen Peroxide to Methanol in the Presence of Glutathione-Stabilized Gold Nanoclusters

The catalytic activity of glutathione-stabilized gold thiolate nanoclusters (1–2 nm) in the oxidation of methane with H2O2 and air oxygen in aqueous medium at 70°C in 30 atm CH4 was studied. The ratio and yield of the oxidation products CH3OH and CH3OOH depends on the content of H2O2 and oxygen in the reactor. At increased partial pressure of oxygen, the total yield of products increases compared with the total yield of independent oxidations with H2O2 or O2 at 5 atm of air, but decreases at 10 atm. A molecular mechanism of methane oxidation was proposed, which describes well the kinetic curves of accumulation and consumption of CH3OH and CH3OOH and the effect of oxygen on their yield. A molecular model of active site was proposed based on the literature data about the structure of glutathione-stabilized Au25 clusters and the results of quantum chemical modeling. The experiments with re-introduction of the gas phase and renewal of the H2O2 content demonstrated 100% conservation of the catalytic activity. The yield of CH3OH reached 60 mol per mole of Au25 clusters.

Copper-Catalyzed Oxalamide-Directed ortho-C-H Amination of Anilines with Alkylamines.

A copper-catalyzed oxalamide-directed ortho-C-H amination of anilines has been developed by using 1 atm of air as the sole oxidant. The protocol shows excellent functional group tolerance, and some heterocyclic amines including indole, benzothiophene, benzothiazole, quinoline, isoquinoline, and quinoxaline could be compatible in the reaction. The late-stage diversification of medicinal drugs demonstrates the synthetic utility of this protocol.

Dependence of mechanical properties of mitral valve annuloplasty rings on annealing modes

Objective : to investigate dependence of the mechanical properties of mitral annuloplasty rings on heat annealing modes. Materials and methods . The study evaluates the nature of change in stress–strain curves under uniaxial compression of experimental samples processed at varying annealing temperature, duration and pressure. Results . It was noted that higher exposure, temperature, and lower pressure led to increased structural rigidity and strength for small strains. Moreover, the extent of influence of annealing temperature and duration was comparable. A 40% (500–700 °C) change in temperature altered the mechanical properties of the ring – 20% increase in strength. A similar change in heat treatment time (4.5–6.5 min) resulted in a 27% increase in the force required for a 15% compression. Conclusion . The experimental dependences presented in the work allow recommending main parameters for heat treatment mode: temperature range 600–700 °C, 10.5 minutes exposure time, and 0.1–0.5 atm air pressure in the furnace chamber.

Changes in Motor Function in Response to Living in an Extreme Underwater Saturation Environment under High Stress and Increased Workload

Understanding changes in individual motor function and how it relates to workload, personality types, and shared knowledge is vital to the success of team‐based missions. Such changes may present a challenge in long duration spaceflight and other missions in extreme environments. Therefore, we studied grip strength, dexterity, stress level, task load and the personality types of participants living in an extreme environment during the NASA Extreme Environment Mission Operation (NEEMO) 23 in June 2019. The Aquarius Reef Base is home to NEEMO missions and is located at 20 m (66 ft) with 2.6 atm (air) pressure inside the habitat, where CO2 levels are often elevated similar to the International Space Station.Motor strength was assessed using a grip dynanometer and dexterity was measured using a pegboard. The tests were performed by 6 subjects (2 males, 4 females) 1 day pre‐mission, during the mission (grip test twice) and 1 day post‐mission. Dexterity test was also performed at the beginning and at end of Extravehicular Activities (EVAs). NASA TLX tests measuring mental, physical, temporal effort, performance, general effort and frustration, were assessed immediately after returning from EVAs. To monitor changes in stress level, Short Stress State Questionnaire (SSSQ) and Generalized Anxiety Disorder (GAD7) scores were collected. Measures of social cognition, including Reading the Mind in Eyes and Big 5 personality tests, were performed once before the mission.There was a trend of decreased grip strength at the end of mission and post‐mission, compared to baseline and beginning of mission. The dexterity scores at the beginning of EVAs were significantly higher, compared to before and during mission. This suggests that tasks with fine motor function can be affected by context such as in‐water performance. At the end of the EVAs, the dexterity score was significantly higher compared to before mission and during mission as well. There was a trend of worse performance on the dexterity test at the end of EVA, compared to the beginning of EVA. A trend of increasing GAD7 scores at half time of the mission and post‐mission could be observed. There were several differences in NASA TLX scores between different subjects.These results indicate that strength and dexterity was influenced during EVAs. This may have been due to both physical and psychological stress during the extreme underwater mission in a saturation environment. Further examination of these trends is recommended.Support or Funding InformationKetone Technologies LLC provided partial funding for the study. SIFT provided partial salary for CA.

Changes in Sensory Functions in Response to Living in an Extreme Underwater Saturation Environment

The present challenges of long duration spaceflight and other missions in extreme environments include changes of sensory functions, including vision impairment and changes in taste perception. In order to monitor and improve astronaut health and performance during long duration spaceflight and future spaceflight missions we studied sensory functions in response to living in an extreme environment during the NASA Extreme Environment Mission Operation (NEEMO) 23. The Aquarius Reef Base is located at 20 m (66 ft) with 2.6 atm (air) pressure inside the habitat, while levels of CO2 are elevated similarly to the International Space Station.This study assessed the changes in visual acuity and taste perception in 6 NEEMO 23 subjects (2 males, 4 females) 1 day before the mission, during the mission at half time and 1 day post mission. Visual changes were assessed using the NIH Toolbox protocol, while changes in taste perception were measured using solutions containing concentrations of either salty, sweet and bitter flavors in three different concetrations on the side of the tongue and in full mouth.We observed a trend of decreased salty and bitter taste sensation in the habitat and post mission, compared to baseline, while the sweet taste sensation did not change. When testing the full mouth, the salty taste sensation significantly decreased post mission, compared to baseline at low or medium concentration. Bitter taste sensation significantly decreased at low concentration in habitat and post mission, compared to baseline. At medium concentration the bitter taste sensation significantly decreased post mission, compared to baseline and in‐habitat, while at high concentration it significantly decreased post mission, compared to baseline. There was a signifcant reduction in the Overall Raw and in Overall Uncorrected Vision Scores between baseline and post mission indicating a significant reduction in visual acuity during the 9 days mission that was not restored immediately after the mission.Living in a saturation environment decreases certain sensory modalities that may persist for an unknown length of time after the exposure. Diminished sensitivity to taste can alter nutritional status and chemosensory changes may also relate to space sickness, stress and psychological factors, while changes in vision may impair operational tasks. These data indicate that mitigation strategies need to be developed and tested in space analog environments.Support or Funding InformationKetone Technologies LLC provided partial funding for the study. SIFT provided partial salary for CA.