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Understanding the properties of molecular nitrogen N2 at extreme conditions is the fundamental problem for atomistic theory and the important benchmark for the capabilities of first-principles molecular dynamics (FPMD) methods. In this work, we focus on the connection between the dynamics of ions and electronic excitations in warm dense N2. The restricted open-shell Kohn–Sham method gives us the possibility to reach relevant time and length scales for FPMD modeling of an isolated exciton dynamics in warm dense N2. Wannier localization sheds light on the corresponding mechanisms of covalent bond network rearrangements that stand behind polymerization kinetics. FPMD results suggest a concept of energy transfer from the thermal energy of ions into the internal energy of polymeric structures that form in warm dense N2 at extreme conditions. Our findings agree with the thermobaric conditions for the onset of absorption in the optical spectroscopy study of Jiang et al. [Nat. Commun. 9, 2624 (2018)]. [ABSTRACT FROM AUTHOR]

Up to 17 GPa, the crystalline phases of N2 are characterized by pronounced orientational disorder, whereas the higher-pressure phases of molecular N2 are ordered. This raises the question about long-term relaxation of orientational disorder within the low- to intermediate-pressure regime. Here, this question is addressed by comparing synthetic with natural, chemically pure, solid N2 that resides as inclusions in diamonds at 300 K for about 108 years at pressures up to 11 GPa. It is shown that disorder prevails at 8.7 GPa, 300 K, where both synthetic and natural N2 assume the same structure. However, at 10.8 GPa, natural solid N2 exhibits monoclinic distortion and partial orientational ordering of the molecules, both of which are not observed in synthetic material. This difference is interpreted as the result of long-term structural relaxation. The ordering mechanism is examined and placed into the context of the δ- to ε-N2 transition. We present explanations for the absence of complete ordering of δ-N2. [ABSTRACT FROM AUTHOR]

The contribution of atomic nitrogen is fairly possible in plasma-assisted catalytic synthesis of ammonia since it has high adsorption probabilities on solid surfaces. On the other hand, recently, the contribution of vibrational excited molecular nitrogen to ammonia synthesis has been discussed. In this work, we compared the fluxes of atomic nitrogen and vibrational excited molecular nitrogen with the rate of plasma-assisted ammonia synthesis. We employed an atmospheric-pressure nitrogen plasma jet, and the spatial afterglow of the plasma jet and a hydrogen flow irradiated the surface of a ruthenium catalyst. The fluxes of atomic nitrogen and vibrational excited molecular nitrogen were measured by two-photon absorption laser-induced fluorescence spectroscopy and laser Raman scattering, respectively. The synthesis rate of ammonia had a positive correlation with the flux of vibrational excited molecular nitrogen, while the variation of the synthesis rate with the gas flow rate was opposite to the flux of atomic nitrogen. The experimental results indicate the contribution of vibrational excited molecular nitrogen to the synthesis of ammonia using the atmospheric-pressure plasma, where the flux of vibrational excited molecular nitrogen is more than four orders of magnitude higher than that of atomic nitrogen. [ABSTRACT FROM AUTHOR]

Unlike naturally occurring oxide crystals such as ruby and gemstones, there are no naturally occurring nitride crystals because the triple bond of the nitrogen molecule is one of the strongest bonds in nature. Here, we report that when the transition metal scandium is subjected to molecular nitrogen, it self-catalyzes to break the nitrogen triple bond to form highly crystalline layers of ScN, a semiconductor. This reaction proceeds even at room temperature. Self-activated ScN films have a twin cubic crystal structure, atomic layering, and electronic and optical properties comparable to plasma-based methods. We extend our research to showcase Sc’s scavenging effect and demonstrate self-activated ScN growth under various growth conditions and on technologically significant substrates, such as 6H–SiC, AlN, and GaN. Ab initio calculations elucidate an energetically efficient pathway for the self-activated growth of crystalline ScN films from molecular N2. The findings open a new pathway to ultralow-energy synthesis of crystalline nitride semiconductor layers and beyond.

Wave packet interferometry with vacuum ultraviolet light has been used to probe a complex region of the electronic spectrum of molecular nitrogen, N2. Wave packets of Rydberg and valence states were excited by using double pulses of vacuum ultraviolet (VUV), free-electron-laser (FEL) light. These wave packets were composed of contributions from multiple electronic states with a moderate principal quantum number (n ∼ 4–9) and a range of vibrational and rotational quantum numbers. The phase relationship of the two FEL pulses varied in time, but as demonstrated previously, a shot-by-shot analysis allows the spectra to be sorted according to the phase between the two pulses. The wave packets were probed by angle-resolved photoionization using an infrared pulse with a variable delay after the pair of excitation pulses. The photoelectron branching fractions and angular distributions display oscillations that depend on both the time delays and the relative phases of the VUV pulses. The combination of frequency, time delay, and phase selection provides significant control over the ionization process and ultimately improves the ability to analyze and assign complex molecular spectra. [ABSTRACT FROM AUTHOR]

We studied luminescence accompanied an injection of the nitrogen-helium gas mixture after passing discharge into dense cold helium gas. Initially, when the experimental beaker was filled with superfluid helium and the nitrogen-helium gas was injected into bulk superfluid helium at T ≈ 1.5 K, the dominant band in the emission spectra was the α-group of nitrogen atoms. At these conditions, the nanoclusters of molecular nitrogen with high concentrations of stabilized nitrogen atoms were formed. When superfluid helium was evaporated from the beaker and the temperature at the bottom of the beaker was increased to T ≈ 20 K, we observed a drastic change in the luminescence spectra. The β-group of oxygen atoms was dominated in the luminescence spectra, and the emission of the α-group became small. At high temperatures (T ≈ 20 K), most of the nitrogen atoms recombine on the surface of N2 nanoclusters with the formation of excited nitrogen molecules. We explained the effect of the enhancement of β-group emission by effective energy transfer from excited nitrogen molecules to the stabilized impurity oxygen atom inside N2 nanoclusters. [ABSTRACT FROM AUTHOR]

Unlike naturally occurring oxide crystals such as ruby and gemstones, there are no naturally occurring nitride crystals because the triple bond of the nitrogen molecule is one of the strongest bonds in nature. Here, we report that when the transition metal scandium is subjected to molecular nitrogen, it self-catalyzes to break the nitrogen triple bond to form highly crystalline layers of ScN, a semiconductor. This reaction proceeds even at room temperature. Self-activated ScN films have a twin cubic crystal structure, atomic layering, and electronic and optical properties comparable to plasma-based methods. We extend our research to showcase Sc's scavenging effect and demonstrate self-activated ScN growth under various growth conditions and on technologically significant substrates, such as 6H–SiC, AlN, and GaN. Ab initio calculations elucidate an energetically efficient pathway for the self-activated growth of crystalline ScN films from molecular N2. The findings open a new pathway to ultralow-energy synthesis of crystalline nitride semiconductor layers and beyond. [ABSTRACT FROM AUTHOR]

In the present study, a Cu2O@PCz electrode for the nitrogen reduction reaction is proposed; this electrode takes advantage of the catalytic properties of Cu2O in conjunction with conducting polymers such as polycarbazole (PCz). This combination demonstrates an improvement in the catalytic activity and higher stability of this metal oxide in nitrogen electro-reduction reaction (NRR) and nitrogen oxoanion electro-reduction reaction (NORR) processes under aqueous conditions. On this basis, the material synthesized on FTO (SnO2 : F), Cu2O@PCz, exhibits a faradaic efficiency of around 38.83%, together with an NH3 productivity of 1.83 μg h−1 cm−2 in NRR type processes, on applying a potential of −0.8 V (V vs. Ag/AgCl). Similarly, in NORR type processes, the material exhibits NH3 and N2H4 productivity. The latter is the most relevant in terms of the yields obtained. Specifically, using nitrite (NO2−), an efficiency of around 77.72% was obtained, together with a formation rate of 37.02 μg h−1 cm−2 at a potential of −0.8 V (V vs. Ag/AgCl). Although N2H4 is a by-product of ammonia formation, this molecule can be considered an intermediate, which broadens the scope of this study for future research into the production of green chemicals. Finally, this research presents promising new routes for the production of NH3 at room temperature, highlighting the potential of low-cost materials, easy synthesis, and enhanced stability. [ABSTRACT FROM AUTHOR]

Based on a modified numerical model of the ionosphere and plasmasphere developed at the Institute of Solar–Terrestrial Physics (ISTP), Siberian Branch, Russian Academy of Sciences, the altitude profiles of the Ne electron density for the quiet and disturbed states of the thermosphere were calculated for the conditions of January 25, 2009, at a geographical point with the coordinates 52.4° N, 104.3° E (Irkutsk). The disturbed conditions were set by varying the temperature of neutral particles T in the thermosphere. At altitudes below 180 km and above 250 km, with an increase/decrease in T, an increase/decrease in Ne occurs. At altitudes of 180–250 km, the opposite picture is observed: an increase/decrease in T causes a decrease/increase in Ne. The opposite nature of the change in the Ne profile is associated with the influence of the ratio of concentrations of atomic oxygen and molecular nitrogen [O]/[N2] at the altitudes of region F. Quantitative estimates of the change in Ne at different altitudes with changes in the temperature of neutral particles were obtained. It has been established that a change in T by 1 K leads to a change in Ne by 0.2–0.3%. The modeling results are compared with observations of the peak electron density NmF2 obtained on the Irkutsk ionosonde during sudden stratospheric warming in January 2009. [ABSTRACT FROM AUTHOR]

In this article we present a quantitative analysis of the second positive system of molecular nitrogen and the first negative system of the molecular nitrogen cation excited in the presence of ionizing radiation. Optical emission spectra of atmospheric air and nitrogen surrounding 210Po sources were measured from 250 to 400 nm. Multi-Boltzmann and non-Boltzmann vibrational distribution spectral models were used to determine the vibrational temperature and vibrational distribution function of the emitting N2(C³Pu) and N2+(B²S+u) states. A zero-dimensional kinetic model, based on the electron energy distribution function (EEDF) and steady-state excitation and de-excitation of N2(X1S+g), N2 +(B2S+u), N2+(X2S+g), N4+, O2 +, and N2(C3Pu, v), was developed for the prediction of the relative spectral intensity of both the N2+(B2S+u - X2S+ g) emission band and the vibrational bands of N2(C3Pu - B3Pg) for comparison with the experimental data. [ABSTRACT FROM AUTHOR]

Green ammonia is assumed to be an important part of the European hydrogen economy and one of the most important substrates of chemical industry. The future development of its manufacturing processes can be related to the electrocatalytic studies yielding in the development of the catalytic materials that would effectively break the nitrogen-nitrogen bond to successfully drive the N2RR—a process of molecular nitrogen electroreduction to ammonia. Molecular nitrogen is characterized with strong triple bond energies (942 kJ/mol) which leading into large dissociation energy of N2 (9,76 eV) and also large energy barrier of the first step of triple bond dissociation 410 kJ/mol (4,25 eV). Those large energies makes reduction to ammonia an extremely difficult task. Metal nitrides of d and f block became in interest due to their activity in ammonia production from molecular nitrogen and hydrogen. Practically all the transition elements occurs in one of the four types of crystalline structures: regular, regular face cantered, hexagonal and hexagonal close packed. The reactions of these metals with nitrogen (or ammonia) typically yields in nitride compounds of an identical type of crystalline structure as the initial metal. Dealing with single metal systems, their ternary counterparts and metal–metal nitride heterostructures, the presented review shows that nitrides are promising groups of electrocatalytic materials. Being property-prone to their internal structural features such as non-stoichiometry and correlated concentration of nitrogen vacancies, metal nitrides are a good candidate for joined investigations spanned between electrochemistry, inorganic chemistry and material engineering. [ABSTRACT FROM AUTHOR]

The reactivity of nitrogen oxide, NO, as a ligand in complexes with [Fe2-S2] and [Co2-S2] non-planar rhombic cores is examined by density functional theory (DFT). The cobalt-containing nitrosyl complexes are less stable than the iron complexes because the Co-S bonds in the [Co2-S2] core are weakened upon NO coordination. Various positions of NO were examined, including its binding to sulfur centers. The release of NO molecules can be monitored photochemically. The ability of NO to form a (NO)2 dimer provides a favorable route of electrochemical reduction, as protonation significantly stabilizes the dimeric species over the monomers. The quasilinear dimer ONNO, with trans-orientation of oxygen atoms, gains higher stability under protonation and reduction via proton–electron transfer. The first two reduction steps lead to an N2O intermediate, whose reduction is more energy demanding: in the two latter reaction steps the highest energy barrier for Co2S2(CO)6 is 109 kJ mol−1, and for Fe2S2(CO)6, it is 133 kJ mol−1. Again, the presence of favorable light absorption bands allows for a photochemical route to overcome these energy barriers. All elementary steps are exothermic, and the final products are molecular nitrogen and water. [ABSTRACT FROM AUTHOR]

In this paper, the degradation of nitric oxide (NO) in an annular laboratory reactor is presented. Preliminary experiments were performed in an annular reactor (AR) under simulated solar irradiation. Titanium dioxide (TiO2 P25) was used as a photocatalyst and immobilized on glass fibers mesh (GM) by the sol–gel method prepared from commercially available materials. The aim of the experiments was to remove NO from the air stream. The initial rate constant of the NO photocatalytic degradation was recognized to follow mass-transfer-controlled first-order kinetics. The results confirmed the photocatalytic reduction of NO to molecular nitrogen (N2) and oxidation to nitrate. Therefore, the preliminary results obtained in this work are used for the development of a computational fluid dynamics (CFD) model (COMSOL Multiphysics v6.2). CFD calculations provide a good basis for sizing reactors at the semi-pilot and pilot levels for both indoor and outdoor air purification systems. [ABSTRACT FROM AUTHOR]

Nitrogen is a highly stable element that exists in the form of nitrogen molecules under ambient pressure. Researchers have found that nitrogen can form polymeric structures under high temperature and pressure, which have extremely high energy density and decompose into pollution-free nitrogen. From the perspective of application, it can be used as a new type of environmentally friendly high-energy-density material. Subsequently, a large number of studies have been conducted on nitrogen, resulting in phase diagrams of nitrogen under high-pressure conditions and the synthesis of structures such as cubic gauche nitrogen and layered polymeric nitrogen. However, the synthesis conditions for pure nitrogen polymeric structures are relatively harsh, and it is also difficult to preserve them under ambient pressure. People have turned to methods such as molecular nitrogen and inert gas nitrides in the hope of obtaining stable high-energy-density nitrogen structures under normal pressure. This article briefly introduces the current theoretical and experimental progress of high-energy-density nitrogen and discusses the future development direction of high-energy-density nitrogen. [ABSTRACT FROM AUTHOR]

Under the extreme conditions of high temperature and high pressure, molecular crystal nitrogen breaks the traditional three-bond mechanism and transforms into a single-bond polymerization state. The unique dissociation mechanism of nitrogen under high pressure makes the research significance of polymeric nitrogen beyond the scope of energetic materials, and also has profound scientific significance in the field of fundamental physics. Following the cubic gauche polymeric nitrogen cg-N (space group I213), the second experimentally discovered layered structure polymeric nitrogen LP-N (space group Pba2) has been controversial. The main problem is that, in addition to not being verified by other high-pressure X-ray diffraction experiments, LP-N structure has the similar synthesis temperature and pressure conditions and synthesis pathways, as well as almost the same Raman spectral characteristics as the subsequently discovered black phosphorus structure polymeric nitrogen BP-N (space group Cmca). The high-temperature and highpressure synthesis of LP-N is likely to have a unique phase transition kinetic barrier. In this work, we started from the low-temperature solid-state molecular nitrogen λ-N2, used double-sided laser-heated diamond anvil cell (LHDAC) technology, combined with high-pressure X-ray diffraction based on the synchrotron radiation and high-pressure Raman scattering spectroscopy, supplemented by first-principles calculations, and observed the Pba2 structure of polymeric nitrogen LP-N at the conditions of about 141 GPa and about 2 600 K. Combined with first-principles calculations, we compared and analyzed its pressure-dependent evolution of the volume per atom (p-V curve) and discussed the kinetic factors of LP-N synthesis at high temperature and high pressure. In addition to a more comprehensive understanding of LP-N, this paper further reveals the high-pressure path-dependent characteristics of polymeric nitrogen. [ABSTRACT FROM AUTHOR]

Two solar eclipse events in 2023 appeared to produce considerable enhancements in the thermospheric column density ratio of monatomic oxygen to molecular nitrogen (ΣO/N2) as measured by TIMED GUVI. We quantify potential sources for eclipse‐induced ΣO/N2 changes and find that the observed enhancements arise from the ionospheric O+ radiative recombination contribution to the OI 135.6 nm emission from which ΣO/N2 is derived. Variations in the solar Extreme Ultra Violet (EUV) and X‐ray spectrum, due to the difference between the disk spectrum and the coronal spectrum, are also considered but shown to have negligible contributions to the ΣO/N2 enhancements. After accounting for the radiative recombination contribution, we constrain the real thermospheric compositional change to the uncertainty level of the measurements of 5%–10%. These results are valuable for the interpretation of eclipse‐induced ΣO/N2 changes that will further first‐principle model comparisons and lead to a better understanding of the response of the thermosphere to localized variations in solar EUV and X‐ray forcing. Plain Language Summary: The Thermosphere Ionosphere Mesosphere Energetics and Dynamics' Global Ultraviolet Imager provides an estimate of the column ratio of monatomic oxygen (O) to molecular nitrogen (N2) in the upper atmosphere (ΣO/N2) as a data product under normal, sunlit conditions. Eclipses are special conditions. In this paper, we model the measured ultraviolet emissions from O and N2 that go into the retrieval algorithm to understand why this increase in the radiance ratio occurs within the totality of the eclipse. There are two components to the O emission, the glow created by electrons (photoelectrons) that result from the ionization of the upper atmosphere and the glow created by recombination of ionospheric O+ ions. We find that the photoelectron source decreases significantly during the eclipse, but near the magnetic equator, the ionospheric recombination emission does not, which causes the retrieval algorithm to overestimate the ΣO/N2 column density ratio during eclipses. The observations and models are consistent with this explanation. Key Points: The apparent thermospheric ΣO/N2 enhancements (10%–30%) for two eclipse events are found to be predominantly of ionospheric originVariations in the solar spectrum due to wavelength‐dependent attenuation are found to have a negligible impact on ΣO/N2 during the eclipseThe true eclipsed‐induced thermosphere compositional changes are determined to be within 5%–10% of the pre‐eclipse values [ABSTRACT FROM AUTHOR]

The balance of processes affecting electron density drives the dynamics of upper‐atmospheric electrical events, such as sprites. We examine the detachment of electrons from negatively charged atomic oxygen (O−) via collisions with neutral molecular nitrogen (N2) leading to the formation of nitrous oxide (N2O). Past research posited that this process, even without significant vibrational excitation of N2, strongly impacts the dynamics of sprites. We introduce updated rate coefficients derived from recent experimental measurements which suggest a negligible influence of this reaction on sprite dynamics. Given that previous rates were incompatible with the observed decay of the light emissions from sprite glows, our findings support that glows actually result from electron depletion in sprite columns. Plain Language Summary: Sprites are transient, filamentary luminous structures appearing between approximately 50 and 85 km above Earth's surface. While the primary sprite activity is ephemeral, lasting mere thousandths of a second, certain luminous features persist up to a hundred times longer. The key to understanding these enduring structures lies in the evolution of free electron populations that facilitate electrical conductivity. Here we show that a process that influences this population is slower than previously thought. This may explain why luminous structures can persist for so long. Key Points: Associative detachment of electrons in sprites proceeds almost exclusively from vibrationally excited N2We provide updated rate coefficients for electron associative detachmentIn models with the updated rates, sprite glows persist tens of milliseconds, in agreement with observations [ABSTRACT FROM AUTHOR]

The combination of compositional versatility and topological diversity for the integration of electroactive species into high-porosity molecular architectures is perhaps one of the main appeals of metal–organic frameworks (MOFs) in the field of electrocatalysis. This premise has attracted much interest in recent years, and the results generated have also revealed one of the main limitations of molecular materials in this context: low stability under electrocatalytic conditions. Using zirconium MOFs as a starting point, in this work, we use this stability as a variable to discriminate between the most suitable electrocatalytic reaction and specific topologies within this family. Our results revealed that the PCN-224 family is particularly suitable for the electroreduction of molecular nitrogen for the formation of ammonia with faradaic efficiencies above 30% in the presence of Ni2+ sites, an activity that improves most of the catalysts described. We also introduce the fluorination of porphyrin at the meso position as a good alternative to improve both the activity and stability of this material under electrocatalytic conditions. [ABSTRACT FROM AUTHOR]

Background and purpose: Sesame (Sesamum indicum L.) is considered the queen of oil plants and is a crucial food source in traditional agriculture in hot regions. Legumes play a role in stabilizing molecular nitrogen in the air and reducing the need for chemical fertilizers in intercropping. Utilizing intercropping of plants from different species in agriculture is an effective way to increase diversity. In order to promote sustainable agriculture, it is essential to implement agricultural systems that combine sufficient input with the use of chemical, biological, and organic fertilizers to produce crops and maintain yield at an acceptable level. Therefore, this research was conducted to address the necessity of using organic and biological fertilizers alongside chemical fertilizers in agricultural ecosystems to produce healthy, high-quality products, and to emphasize the importance of increasing production efficiency in intercropping. Materials and methods: The factorial experiment was conducted using a randomized complete block design with three replications on a farm affiliated with the Organization of Agricultural Jihad, Khondab, in the Central Province, during the 2018 and 2019 crop years. the first factor is different sources of fertilizer in six levels (control, poultry manure, chemical fertilizer, mycorrhiza, combination of poultry manure and mycorrhiza, combination of chemical and mycorrhiza) and the second factor is the cultivation pattern in six levels (sole sesame (S), sole green bean (GB), two rows of sesame and two rows of green beans (2S: 2GB), 2S: 3GB, 3S: 2GB, 3S: 3GB). Sesame seed yield and yield components, green bean pod yield, sesame and green bean biological yield, growth indices and percentage and yield of sesame oil were evaluated. Findings: The results of variance analysis of the data confirmed the significant effect of the main effects of intercropping and fertilizer treatments on all the measured traits at the probability level of 1%. The interaction between them (except root colonization percentage) also showed a statistically significant difference at the probability level of 1%. Compared to pure sesame cultivation, intercropping obtained the highest amount in all the measured traits. In such a way that the highest percentage of symbiosis of mycorrhiza with sesame roots and green beans, 43.12 and 44.06%, respectively, was observed in the intercropping of 2S:3GB. Among the fertilizer treatments, the highest rate of mycorrhiza coexistence with sesame and green beans was obtained from the chicken manure + mycorrhiza treatment, 78.57% and 79.22%, respectively. The highest seed yield and biological yield of sesame (257 and 928 g m-2, respectively) were obtained from intercropping of 3S:2GB using chicken manure + mycorrhiza. The highest yield of green pods (1204 g m-2) was awarded to the pure cultivation of green beans with the application of chicken manure + mycorrhiza. According to the means comparison, intercropping of 2S:2GB using chicken manure + mycorrhiza produced the highest percentage of sesame seed oil (49.94% and 52.54%, respectively). The highest yield of sesame seed oil (1350 kg ha-1) was also observed in intercropping of three 2S: 2GB using chicken manure + mycorrhiza. According to the results, the highest amount of land equality ratio (1.62) was awarded to intercropping of 3S:3GB along with the application of chemical fertilizers. Conclusion: Considering the superiority of poultry manure + mycorrhiza along with various types of intercropping for sesame plant, it seems that the application of this treatment in the bed of intercropping of plants is suggested to achieve proper performance in the tested area. Also, the combined use of organic, biological and chemical fertilizers in the intercropping bed can be a suitable alternative to reduce the consumption of chemical inputs. [ABSTRACT FROM AUTHOR]

The propulsion research lab at Utah State University has developed a minimally-intrusive optical sensing system for high-temperature/high-velocity gas-generator exhaust plumes. For this application glass fiber-optic cables, acting as radiation conduits, are inserted through the combustion chamber or nozzle wall and look directly into the flow core. The cable transmits data from the flame zone to externally-mounted spectrometers. In order to capture the full-optical spectrum, a blended dual-spectrum system was employed, with one spectrometer system tuned for best-response across the visible-light and near-infrared spectrum, and one spectrometer tuned for best-response in the near- and mid-infrared spectrum. The dual-band sensors are radiometrically-calibrated and the sensed-spectra are spliced together using an optimal Wiener filtering algorithm to perform the deconvolution. The merged spectrum is subsequently curve-fit to Planck's black-body radiation law, and flame temperature is calculated from associated curve maxima (Wien's law). The presented fiber-optic sensing systems performs a function that is analogous to Raman spectroscopy. The system non-contact, high-temperature measurement, and does not interfere with the heat transfer processes. In this report data collected from a lab-scale (200 N) hybrid rocket system are analyzed using the described method. Optically-sensed flame-temperatures are correlated to analytical predictions, and shown to generally agree within a few degrees. Additionally, local maxima in the optical spectra are shown to correspond to emission frequencies of atomic and molecular oxygen, water vapor, and molecular nitrogen; all species known to exist in the hybrid combustion plume. Presented data demonstrate that selected fiber-optics can survive temperature greater than 3000 ℃, for durations of up to 25 seconds. [ABSTRACT FROM AUTHOR]

Kojic acid is a valuable compound that contributes to various therapeutic and cosmetic applications. Organic nitrogen partially contributes to fermentation and mostly prefers cell growth as well as increases production costs. This study aims to find the effect of low-cost inorganic nitrogen in the form of ammonium chloride on kojic acid production from fungal isolate Aspergillus sp. BU20S. A 3.63-times increase in the kojic acid (4.43 ± 0.47 g/L) was found when only the ammonium chloride was supplemented in glucose (10 g/L) medium than other minimal salts. The product formation was 2.52 ± 0.56 g/L in ammonium chloride as compared to 2.02 ± 0.06 g/L yeast extract after 10 days. The carbon/nitrogen ratio (C/N) was found optimal as 15 (molecular C/N: 23.58) which gives a high titer of 5.17 ± 0.84 g/L from 10 g/L of glucose. At this optimal molecular nitrogen value, the nitrogen supplement cost can be reduced by 93–99% compared to yeast extract. The antimicrobial potential of kojic acid purified from the fermented broth was also studied against methicillin-resistant Staphylococcus aureus (MRSA). The purified kojic acid showed a ~ 20 mm zone of inhibition at a 2.5 mg dose loaded over 7.4 × 109 CFU/mL of MRSA. This study concludes that only ammonium chloride is a sufficient inorganic nitrogen source to produce kojic acid and is useful in reducing production costs. The purified kojic acid is also an effective antimicrobial agent. [ABSTRACT FROM AUTHOR]

Estuaries can remove and/or retain land-derived nitrogen (N) and act as filters buffering N loads to the open sea. The N coastal filter can be seasonally variable depending on water temperature and transported loads, two factors acting in synergy and strongly influenced by climate change. The capacity of sediments to mitigate riverine N loads was investigated at four sites in the Vistula River plume area (Gulf of Gdańsk, Southern Baltic Sea). Samplings were carried out in two contrasting seasons: spring and summer, characterized by different water temperatures and nitrate (NO3 -) levels. Inorganic N fluxes, and rates of denitrification and dissimilatory nitrate reduction to ammonium (DNRA) were measured in intact sediment cores by means of dark incubations and 15N-nitrate concentration-series experiments. Sampling sites were selected along a gradient of depth (5 to 24 m), that was also a gradient of sediment organic matter content. In both seasons, denitrification rates increased along with depth and from spring (6.5 ± 7.0 µmolm-2 h-1) to summer (20.4 ± 15.4 µmolm-2 h-1), despite lower NO3 - concentrations in summer. In spring, at higher NO3 -. The denitrification efficiency (DE), calculated as the ratio between molecular nitrogen (N2) flux and dissolved inorganic N effluxes from sediments, ranged from 0 to 37% in spring, whereas in summer DE did not exceed 16%. Despite the dominance of denitrification over DNRA, the analyzed sediments acted as weak N buffers under in situ dark conditions. However, concentrationseries experiments suggested high potential denitrification capacity, exceeding 400 µmol m3 - across all sites and seasons, contributing to over 80% of the total denitrification. Notably, no anammox was detected at the sampling sites. DNRA exhibited low to undetectable rates in spring, especially at the shallowest sites. However, during summer, N recycling via DNRA increased and ranged from 0.7 to 14.9 µmol m-2 h-1. The denitrification efficiency (DE), calculated as the ratio between molecular nitrogen (N2) flux and dissolved inorganic N effluxes from sediments, ranged from 0 to 37% in spring, whereas in summer DE did not exceed 16%. Despite the dominance of denitrification over DNRA, the analyzed sediments acted as weak N buffers under in situ dark conditions. However, concentrationseries experiments suggested high potential denitrification capacity, exceeding 400 µmol m-2 h-1, in response to short-term, large riverine inputs of NO³ -. [ABSTRACT FROM AUTHOR]

Denitrifying bacteria harboring the nitrate reductase S (nirS) gene convert active nitrogen into molecular nitrogen, and alleviate eutrophication in aquaculture water. Suspended particulate matter (SPM) is an important component of aquaculture water and a carrier for denitrification. SPM with different particle sizes were collected from a coastal high-altitude aquaculture pond in Maoming City, China. Diversity, community structure, abundance of nirS-type denitrifying bacteria on SPM and environmental influencing factors were studied using high-throughput sequencing, fluorescence quantitative PCR, and statistical analysis. Pseudomonas, Halomonas, and Wenzhouxiangella were the dominant genera of nirS-type denitrifying bacteria on SPM from the ponds. Network analysis revealed Pseudomonas and Halomonas as the key genera involved in the interaction of nirS-type denitrifying bacteria on SPM in the ponds. qPCR indicated a trend toward greater nirS gene abundance in progressively larger SPM. Dissolved oxygen, pH, temperature, and SPM particle size were the main environmental factors influencing changes in the nirS-type denitrifying bacterial community on SPM in coastal high-altitude aquaculture pond water. These findings increase our understanding of the microbiology of nitrogen cycle processes in aquaculture ecosystem, and will help optimize aquatic tailwater treatment strategies. [ABSTRACT FROM AUTHOR]

The growth and sustainable development of humanity is heavily dependent upon molecular nitrogen (N2) fixation. Herein we discover ambient catalyst-free disproportionation of N2 by water plasma which occurs via the distinctive HONH-HNOH+• intermediate to yield economically valuable nitroxyl (HNO) and hydroxylamine (NH2OH) products. Calculations suggest that the reaction is prompted by the coordination of electronically excited N2 with water dimer radical cation, (H2O)2+•, in its two-center-three-electron configuration. The reaction products are collected in a 76-needle array discharge reactor with product yields of 1.14 μg cm–2 h–1 for NH2OH and 0.37 μg cm–2 h–1 for HNO. Potential applications of these compounds are demonstrated to make ammonia (for NH2OH), as well as to chemically react and convert cysteine, and serve as a neuroprotective agent (for HNO). The conversion of N2 into HNO and NH2OH by water plasma could offer great profitability and reduction of polluting emissions, thus giving an entirely look and perspectives to the problem of green N2 fixation. The growth and sustainable development of humanity is heavily dependent upon N2 fixation. Herein, authors developed an ambient catalyst-free disproportionation of N2 by water plasma to yield economically valuable nitroxyl and hydroxylamine products. [ABSTRACT FROM AUTHOR]

The high‐resolution Whole Atmosphere Community Climate Model with thermosphere/ionosphere extension (WACCM‐X) is used to study the impacts of gravity waves (GWs) on the thermospheric circulation and composition. The resolved GWs are found to propagate anisotropically with stronger eastward components at most altitudes. The dissipation of these waves in the thermosphere produces a net eastward forcing that reaches peak values between 200 and 250 km at mid‐high latitudes in both hemispheres. Consequently, the mean circulation is weakened in the winter hemisphere and enhanced in the summer, which in turn impacts the thermospheric composition. Most notably, the column integrated O/N2 in both hemispheres is reduced and agrees better with observations. The mean thermospheric GW forcing in the meridional direction has comparable amplitude and acts to modify the gradient‐wind relationship. Plain Language Summary: Small‐scale waves originate from the lower atmosphere have been shown to propagate into the thermosphere. To study their effects a high‐resolution whole atmosphere model has been employed. Using this high‐resolution model, which can partially resolve the small‐scale waves, we can directly quantify the force exerted by these waves on the general circulation in the thermosphere. We found that such force is strong, and affects the thermospheric circulation in both winter and summer hemisphere. This consequently changes the distribution of important thermospheric species. One measure of the thermospheric composition is the ratio of atomic oxygen and molecular nitrogen, which is an indicator of the relative abundance of atomic and molecular species. This ratio has been grossly over‐estimated in previous modeling studies. It is reduced as a result of the circulation change, and is much better agreement with observations. Key Points: Gravity waves (GWs) resolved by high‐resolution WACCM‐X displays anisotropic propagationGW forcing alters thermospheric circulationThe circulation change leads to a much improved thermospheric O/N2 [ABSTRACT FROM AUTHOR]

Leveraging observations by two NASA missions—GOLD (Global‐scale Observations of the Limb and Disk) and ICON (Ionospheric Connection Explorer), we investigate concurrent responses of thermospheric composition, temperatures, and neutral winds to the geomagnetic storm on 3–4 November 2021, as well as their interplay at low and middle latitudes. The synergetic observations reveal remarkable depletions up to 60%–70% in GOLD O/N2, along with large enhancements in GOLD temperatures poleward of 30° in the middle thermosphere. Meridional winds from ICON observations are altered by ∼100 m/s equatorward of 25°N latitude and at 250 km, characterized by a reversal of prevailing northward winds to geomagnetic storm‐driven southward winds. This study fills a need, after a decade‐long gap, for observing concurrent and co‐located responses of composition, temperatures, and neutral winds in the thermosphere to geomagnetic storms. Plain Language Summary: Geomagnetic storms, arising from solar wind shocks emitted from the Sun, deposit a large portion of the absorbed solar energy into the Earth's high‐latitude atmosphere through Joule heating and high energy particle heating. Accurate prediction of the responses to geomagnetic storms in the thermosphere‐ionosphere is one of the core scientific objectives of space weather. The recently launched Global‐scale Observations of the Limb and Disk (GOLD) and Ionospheric Connection Explorer (ICON) missions provides an unparalleled opportunity to assess storm‐induced concurrent changes in multiple key parameters. During a G3 geomagnetic storm on 3 November 2021, GOLD observed the substantial changes of 60%–70% in thermosphere column density ratios of atomic oxygen to molecular nitrogen and temperatures. Exceptional meridional winds of 100–200 m/s were also seen by ICON over a broad altitude range. Such observations fill a decades‐long need for simultaneous observations of the key variables in the ionosphere‐thermosphere system. Key Points: Remarkable depletions in O/N2 and enhancements in temperature, up to 60%–70%, are seen by Global‐scale Observations of the Limb and Disk during the geomagnetic stormAveraged southward wind deviations of ∼100 m/s are observed by Ionospheric Connection Explorer, coincident with the largest gradient in O/N2 depletionsBoth O/N2 and temperatures recover rapidly from the disturbed states to pre‐storm states [ABSTRACT FROM AUTHOR]

Molecular nitrogen is often used as a buffer gas in cells with alkali metals due to its known ability to quench resonant fluorescence. It is widely believed that the suppression of spontaneous emission decreases the width of coherent population trapping resonance. However, our recent results have not confirmed this positive action of molecular nitrogen within the typical range of 87Rb concentrations and buffer gas pressures. On the opposite, we have observed the negative influence of quenching, the decrease in contrast of the coherent population trapping resonance in – configuration. In this work, we further confirm these results implementing the Ramsey spectroscopy, and compare the characteristics of the central fringe in nitrogen and neon, and show that the latter provides a significantly better contrast-to-width ratio. [ABSTRACT FROM AUTHOR]

Catalysts for the selective oxidation of ammonia to molecular nitrogen are essential for the fight against environmental pollution due to vehicle and industrial emissions. This work reports a study of Pt/TiO2-based K-modified catalysts for the selective oxidation of ammonia. The Pt/TiO2 catalysts are prepared by impregnating a commercial TiO2 support (Degussa, P25 Aeroxide) by a platinum nitrate precursor followed by depositing small amounts of potassium with variation of the precursor nature (KOH, KNO3, KCl). The influence of a promoting additive on the catalysts properties is considered using a complex of physicochemical and kinetic methods such as powder XRD, X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption of NH3 (NH3-TPD), NH3+O2 temperature programmed reaction (NH3+O2-TPR). According to the XRD data, dispersed platinum particles with a coherent scattering region of no more than 5 nm are formed in the samples. The XPS data indicate that the oxidation state of platinum can be changed by varying the potassium precursor. It is shown that the potassium chloride precursor enhances the selectivity to molecular nitrogen in the temperature range up to 200 °C. The changes in the acidic properties of the sample surfaces are revealed using the NH3-TPD data, and the changes are compared with catalytic characteristics of the samples in the reaction of ammonia oxidation. [ABSTRACT FROM AUTHOR]

In air at a pressure of 1 Torr, the regime of collision of plasma diffuse jets (PDJ) that consist of red streamers was studied. The PDJ were formed by sending voltage pulses at a frequency of 21 kHz in a quartz tube, and they started from the plasma of a capacitive discharge that was created by the voltage pulses of positive and negative polarity. It is shown that when the pulse polarity is the same, the opposite PDJs in air suppress each other's radiation from the 2+ and 1+ systems of molecular nitrogen. It is also shown that at the opposite polarity of the voltage pulses, the intensity of radiation in the PDJ collision region increases substantially. The data is provided on the effect of the delay between the switching on of the generators of opposite polarity on the PDJ radiation spectra. It is shown that, when the relative air humidity is increased, lines of atomic nitrogen Hα appear in the spectrum as well as the hydroxyl molecular bands OH and OH+, whose spectral radiation energy density is commensurate with the energy density of the second positive (2+) system of molecular nitrogen. [ABSTRACT FROM AUTHOR]

Nitrogenases are the only enzymes that reduce molecular nitrogen (N2) to ammonia. Recently, we could demonstrate that nitrogenases also reduce the greenhouse gas carbon dioxide (CO2), suggesting CO2 to be substrate. Indeed, the iron nitrogenase reduces CO2 into formate and CH4 under physiological conditions. Based on Rhodobacter capsulatus, we could establish a light-driven formation of these products, which serve as substrates for other microbes and feedstock chemicals for a green economy. [ABSTRACT FROM AUTHOR]

Because of its current and future intensive use, the synthesis of sustainable ammonia is of major concern. This study focuses on highlighting the mechanistic behaviours of NH3 production from molecular nitrogen and hydrogen on ruthenium materials supported on cerium‐based ternary intermetallics. An interesting activity is reported for Ru/CeTX materials (T=Sc, Ti; X=Si, Ge) with an ammonia production rate around 0.60 mmolNH3 h−1 g−1 at only 300 °C and 1 bar. While the activity at 400 °C appeared attributable to the N≡N cleavage activation, this low‐temperature activity is no longer correlated with this parameter, but rather to the behaviour regarding hydrogen and especially the ability of cerium‐based intermetallic materials to desorb hydrogen from the structure, supporting an associative‐type mechanism. [ABSTRACT FROM AUTHOR]

In this work, we investigate the structural parameters that affect water adsorption on amorphous carbon nitride thin films synthesized by pulsed laser deposition. The study includes the case of ablation of graphite targets within molecular nitrogen and within a stream of nitrogen plasma afterglow. The results obtained showed that, the effect of Csp2-Csp2 bonds concentration on the adsorption of water molecules depends strongly on the ratio and distortion of the hexagonal rings. Furthermore, analysis of the spectral data showed that, the relationship between the hydrogen bonding strength of water molecules with the film surface and the concentration of Csp2-Csp2 bonds takes a specific mathematical formula in the case of structures composed mainly of hexagonal rings. [ABSTRACT FROM AUTHOR]