Types of pulsating aurora: comparison of model and EISCAT electron density observations

Energetic particle precipitation associated with pulsating aurora (PsA) can reach down to lower mesospheric altitudes and deplete ozone. It is well documented that pulsating aurora is a common phenomenon during substorm recovery phases. This indicates that using magnetic indices to model the chemistry induced by PsA electrons could underestimate the energy deposition in the atmosphere. Integrating satellite measurements of precipitating electrons in models is considered to be an alternative way to account for such an underestimation. One way to do this is to test and validate the existing ion chemistry models using integrated measurements from satellite and ground-based observations. By using satellite measurements, an average or typical spectrum of PsA electrons can be constructed and used as an input in models to study the effects of the energetic electrons in the atmosphere. In this study, we compare electron densities from the EISCAT (European Incoherent Scatter scientific radar system) radars with auroral ion chemistry and the energetics model by using pulsating aurora spectra derived from the Polar Operational Environmental Satellite (POES) as an energy input for the model. We found a good agreement between the model and EISCAT electron densities in the region dominated by patchy pulsating aurora. However, the magnitude of the observed electron densities suggests a significant difference in the flux of precipitating electrons for different pulsating aurora types (structures) observed.

Gas phase ion chemistry of titanium–oxofullerene with ligated solvents

Gas phase fragmentation events of fullerene-like titanium oxo-cluster anions were investigated in detail. The fragmentation channel of the ions was comparable to the fragmentation of C60 ions with systematic C2 losses which is a consequence of topological similarity.

Temperature-dependent ion chemistry in nanosecond discharge plasma-assisted CH4 oxidation

Ion chemistry with temperature evolution in weakly ionized plasma is important in plasma-assisted combustion and plasma-assisted catalysis, fuel reforming, and material synthesis due to its contribution to plasma generation and state transition. In this study, the kinetic roles of ionic reactions in nanosecond discharge (NSD) plasma-assisted temperature-dependent decomposition and oxidation of methane are investigated by integrated studies of experimental measurements and mathematical simulations. A detailed plasma chemistry mechanism governing the decomposition and oxidation processes in a He/CH4/O2 combustible mixture is proposed and studied by including a set of electron impact reactions, reactions involving excited species, and ionic reactions. A zero-dimensional model incorporating the plasma kinetics solver ZDPlasKin and the combustion chemical kinetics solver CHEMKIN is used to calculate the time evolution of the ion density. Uncertainty analysis of ionic reactions on key species generation is conducted by using different referenced data, and insignificant sensitivity is found. The numerical model is consistent with experimental data for methane consumption and generation of major species including CO, CO2, and H2. By modeling the temporal evolution of key ions, it is observed that O2+ presents the largest concentration in the discharge stage, followed by CH4+, CH3+, and CH2+, which is in accordance with the traditional ion chemistry in hydrocarbon flames and agrees well with molecular-beam mass spectrometer investigations. The path flux shows that the concentrations of key species, including electrons, O, OH, H, O(1D), O2(a1Δg), O2+, CH3+, and CH4+, change within 1–2 orders of magnitude and that the transition from a homogeneous state to a contracted/constricted state does not occur. The path flux and sensitivity analysis reveal the significant roles of cations in the stimulation of active radical generation, including CH, O, OH, and O(1D), thus accelerating methane oxidation. This work provides a deep insight into the ion chemistry of temperature-dependent plasma-assisted CH4 oxidation.

A Novel Approach to Characterize the Lipidome of Marine Archaeon Nitrosopumilus maritimus by Ion Mobility Mass Spectrometry

Archaea are differentiated from the other two domains of life by their biomolecular characteristics. One such characteristic is the unique structure and composition of their lipids. Characterization of the whole set of lipids in a biological system (the lipidome) remains technologically challenging. This is because the lipidome is innately complex, and not all lipid species are extractable, separable, or ionizable by a single analytical method. Furthermore, lipids are structurally and chemically diverse. Many lipids are isobaric or isomeric and often indistinguishable by the measurement of mass or even their fragmentation spectra. Here we developed a novel analytical protocol based on liquid chromatography ion mobility mass spectrometry to enhance the coverage of the lipidome and characterize the conformations of archaeal lipids by their collision cross-sections (CCSs). The measurements of ion mobility revealed the gas-phase ion chemistry of representative archaeal lipids and provided further insights into their attributions to the adaptability of archaea to environmental stresses. A comprehensive characterization of the lipidome of mesophilic marine thaumarchaeon, Nitrosopumilus maritimus (strain SCM1) revealed potentially an unreported phosphate- and sulfate-containing lipid candidate by negative ionization analysis. It was the first time that experimentally derived CCS values of archaeal lipids were reported. Discrimination of crenarchaeol and its proposed stereoisomer was, however, not achieved with the resolving power of the SYNAPT G2 ion mobility system, and a high-resolution ion mobility system may be required for future work. Structural and spectral libraries of archaeal lipids were constructed in non-vendor-specific formats and are being made available to the community to promote research of Archaea by lipidomics.

Groundwater geochemistry and hydrogeochemical processes assessment in Bantul, Yogyakarta, Indonesia

In Bantul, Southern Yogyakarta, groundwater is the main source of domestic water needs. Therefore, knowing the hydrogeochemistry of groundwater is crucial in order to manage a sustainable groundwater resource. To characterize the compelling geochemical processes that control the groundwater chemistry, further hydrogeochemical examinations were directed in the area. Thirty groundwater samples were collected from shallow dug wells during the early dry season (April 2021). Sampling procedures and chemical analysis were carried out as per standard methods with secondary data obtained in 2006. The geochemical evaluations were depicted using several graphical plots dependent on the ionic constituents, hydrochemical facies, and controlling factors of groundwater quality. Two major hydrochemical facies were identified: alkaline-earth water with higher alkali; bicarbonate predominated (62%) and alkaline-earth water; bicarbonate predominated (32%). Weathering of silicate minerals occurs in 70% of recent samples and predominantly regulates major ion chemistry such as calcium, magnesium, sodium, and potassium. Chloro-alkaline indices 1,2 values signify that there are two potential rock-water interaction processes in the study region, namely the ion exchange and reverse ion exchange. Concentrations of nitrate, sulfate, and chloride indicate that the water chemistry has not been heavily contaminated by the land use in the area and is still mainly controlled by geogenic processes rather than anthropogenic activities.

Mechanisms controlling major ion chemistry and its suitability for irrigation of Narmada River, India

Surface water chemistry of the upper Narmada River was investigated at 13 different locations for 4 consecutive years (2017 to 2020) during pre- and post-monsoon seasons. The main objective of the study was to identify the processes governing the water chemistry of Narmada River and evaluate its suitability for irrigation. The physical parameters estimated were; pH (7.9 ± 0.4 for pre- and 8 ± 0.4 for post-monsoon seasons), EC (322.8±93.3 μS/cm for pre- and 312.1±80.2 μS/cm for post-monsoon) and TDS (203.4±41.5 mg/L for pre-and 213.4±48 mg/L for post-monsoon). The obtained concentration of cations and anions were in the order of Ca++ > Na+ > Mg++> K+ and HCO3−> Cl−>SO4−> NO3−> PO4− respectively. Thus, the water of Narmada was found to be alkaline in nature. Piper diagram inferred that the water was dominated by Ca-Mg-HCO3− type of hydrochemical faces. Gibb's plot clarified that rock-water interaction regulates the ion chemistry of the Narmada. Various indices like sodium percentage (Na%), sodium absorption ration (SAR), Kelly index (Ki), permeability index (PI), magnesium hazard (MH) was calculated which showed that the surface water was suitable for irrigation. Lastly, one-way ANOVA (p < 0.05) confirmed no significant differences in water quality except for temperature, EC and SO4−, for pre- and post-monsoon season.

Recent Advances in the Synthesis of Diverse Libraries of Small-Molecule Building Blocks in Ionic Liquids (ILs)

The Account describes recent advances, from the authors’ laboratories, in the synthesis of diverse libraries of small-molecule building blocks employing ionic liquids (ILs). The ability of ILs to act as catalysts/promoters/solvents for electrophilic and onium ion chemistry, as well as in metal-mediated cross-coupling reactions, and the potential to sequence/hyphenate these methods, have opened up new opportunities for facile assembly of functional small molecules with increased complexity from readily available precursors. While Brønsted acidic IL/IL solvent mixtures are suitable media for carbocation and onium ion chemistry, piperidine-appended IL/IL solvent mixtures can successfully catalyze a variety of base-catalyzed reactions. Several widely practiced transformations including ‘name reactions’ were adapted and performed efficiently in ILs.1 Introduction2 Aryldiazonium Salts and Aryltriazenes as Coupling Partners in Metal-Mediated C–C Cross-Coupling Reactions in ILs3 Expanding the Scope of Metal-Mediated Cross-Coupling Reactions in ILs4 Application of ILs in Synthesis and Functionalization of Hetero­cycles5 Expanding the Scope of Amide Synthesis in ILs6 Generation and Chemistry of ‘Tamed’ Propargylic Cations in ILs7 Newer Nitration Methods for Arenes and Heteroarenes in ILs8 Halofunctionalization in ILs9 ‘Name Reactions’and Other Widely Practiced Synthetic Transformations in ILs9.1 The Biginelli Reaction9.2 Nitrile Synthesis by the Schmidt Reaction9.3 Rupe Rearrangement9.4 Synthesis of 1,3-Dioxanes via Prins Reaction in [BMIM(SO3H)][OTf]9.5 Synthesis of Cyclopropanes and Oxiranes by the Corey–Chaykovsky (CC) Reaction10 Conclusions and Closing Remarks