Hydrogen Abundance Research Articles

Efficacy evaluation of probiotics combined with prebiotics in patients with clinical hypothyroidism complicated with small intestinal bacterial overgrowth during the second trimester of pregnancy.

ObjectiveTo explore the effect of probiotics combined with prebiotics on clinical hypothyroidism during pregnancy combined with small intestinal bacterial overgrowth.Methods(1) In total, 441 pregnant women were included in this study. A total of 231 patients with clinical hypothyroidism during the second trimester of pregnancy and 210 normal pregnant women were enrolled in the lactulose methane-hydrogen breath test. The positive rate of intestinal bacterial overgrowth (SIBO), gastrointestinal symptoms, thyroid function and inflammatory factors were compared between the two groups by chi-square test and two independent sample t-test. (2) SIBO-positive patients in the clinical hypothyroidism group during pregnancy (n=112) were treated with probiotics combined with prebiotics based on conventional levothyroxine sodium tablets treatment. The changes in the methane-hydrogen breath test, gastrointestinal symptoms, thyroid function and inflammatory factors were compared before treatment (G0) and 21 days after treatment (G21) by chi-square test and paired sample t test.Results(1) The positive rates of SIBO in pregnant women in the clinical hypothyroidism group and control group were 48.5% and 24.8%, respectively. (2) The incidence of abdominal distention and constipation in the clinical hypothyroidism group was significantly higher than that in the control group, and the risk of abdominal distention and constipation in SIBO-positive pregnant women was higher than that in SIBO-negative pregnant women. (3) The serum levels of hypersensitive C-reactive protein (hsCRP), IL-10, IL-6, TNF-α, low-density lipoprotein (LDL), total cholesterol (TC), free fatty acids (FFAs) and apolipoprotein B (ApoB) in the hypothyroidism group during pregnancy were higher than those in the control group. (4) After 21 days of probiotics combined with prebiotics, the incidence of pure methane positivity in the methane-hydrogen breath test in the G21 group was significantly reduced, and the average abundance of hydrogen and methane at each time point in the G21 group was lower than that in the G0 group. (5) The incidence of constipation in the G21 group was significantly lower than before treatment. (6) The levels of serum TSH, hsCRP, IL-6, TNF-α, TC and LDL in pregnant women after probiotics combined with prebiotics were lower than those before treatment.ConclusionProbiotics combined with prebiotics are effective in the treatment of pregnant patients with clinical hypothyroidism complicated with SIBO, providing a new idea to treat pregnant patients with clinical hypothyroidism complicated with SIBO.

A pristine record of outer Solar System materials from asteroid Ryugu’s returned sample

Volatile and organic-rich C-type asteroids may have been one of the main sources of Earth’s water. Our best insight into their chemistry is currently provided by carbonaceous chondritic meteorites, but the meteorite record is biased: only the strongest types survive atmospheric entry and are then modified by interaction with the terrestrial environment. Here we present the results of a detailed bulk and microanalytical study of pristine Ryugu particles, brought to Earth by the Hayabusa2 spacecraft. Ryugu particles display a close compositional match with the chemically unfractionated, but aqueously altered, CI (Ivuna-type) chondrites, which are widely used as a proxy for the bulk Solar System composition. The sample shows an intricate spatial relationship between aliphatic-rich organics and phyllosilicates and indicates maximum temperatures of ~30 °C during aqueous alteration. We find that heavy hydrogen and nitrogen abundances are consistent with an outer Solar System origin. Ryugu particles are the most uncontaminated and unfractionated extraterrestrial materials studied so far, and provide the best available match to the bulk Solar System composition.

The Determination of the Water Content and Hydrogen Abundance of Two CK- and CV-type Carbonaceous Chondrites Using Thermogravimetric Analysis

The Determination of the Water Content and Hydrogen Abundance of Two CK- and CV-type Carbonaceous Chondrites Using Thermogravimetric Analysis

Global Hydrogen Abundances on the Lunar Surface

AbstractA global map of bulk hydrogen abundances on the Moon is presented. This map was generated using data from the Lunar Prospector Neutron Spectrometer. This map required corrections for variations due to rare‐earth elements, and was calibrated to Apollo sample hydrogen abundances. Since neutron‐derived measurements sample hydrogen content to a depth of tens of cm, these results provide complementary insights to those provided by studies using spectral reflectance data, which sample depths of order μm. Comparison of these abundances to Apollo sample values suggest that the samples reflect actual hydrogen content on the lunar surface, not dominantly from non‐lunar contamination. The average lunar hydrogen abundance is 47 ppm with a systematic uncertainty of ∼10 ppm. This is consistent with bulk hydrogen from solar wind emplacement. A bulk hydrogen enhancement (50–68 ppm) has been identified at the Moon's largest pyroclastic deposit (Aristarchus Plateau), which corroborates prior observations that hydrogen and/or water plays a role in lunar magmatic events. Global data show a correlation between hydrogen and evolved materials rich in incompatible trace elements (i.e., KREEP type rocks), with a hydrogen excess of 14–36 ppm in these materials. Based on this hydrogen enhancement, we estimate a lower‐limit water abundance within urKREEP materials (i.e., the final ∼2% of the lunar magma ocean) of 320–820 ppm H2O. This observation implies that water played a role in the original magma‐ocean formation and solidification with a lower‐limit water content in the original lunar magma ocean of 7–16 ppm or higher.

Numerical modeling of mapping of Martian epithermal neutron emission: Applications to FREND investigation onboard ESA’s Trace Gas Orbiter

Neutron telescope FREND is operating onboard ESA TGO mission from May 2018 till present. The instrument measures epithermal neutron flux from the Martian surface. Measured variations of the neutron flux may be used to determine hydrogen abundance in the soil usually interpreted as a water/water ice. The unique design of the instrument provides measurements of the neutron flux with a spatial resolution that is much higher than the resolution of previous neutron spectrometers operating on orbit around Mars on board the NASA Mars Odyssey spacecraft. It is known that the spatial resolution of a neutron spectrometer in an orbit around Mars is determined not only by the parameters of the detectors, presence or absence of additional modules to improve the resolution, the orbital altitude of the spacecraft, but also by the fact that Mars has an atmosphere that scatters some of the neutrons that emerge from the Martian surface. One of the ways to increase the spatial resolution of orbital neutron detectors is the passive collimation method using neutron-absorbing substances. In this paper we consider the results of numerical modeling of parameters of the collimated instrument in order to determine its spatial resolution, taking into account the presence of the Martian atmosphere. The contribution of neutrons passing through the collimator walls to the total counting rate and how they affect the estimation of the hydrogen/water concentration in the soil are also considered. Therefore, a method was developed to take into account the imperfect absorbing properties of the collimator and to clear the measured signal from the contribution of neutrons that passed through the collimator wall. Comparison of the spatial resolution of non-collimated and collimated instruments is discussed. Moreover, the results obtained with the conventional method of data processing are compared with the results of developed method, which takes into account the contribution of non-collimated neutrons. The advantage of the results obtained by the developed method is shown.

Mass-loss implementation and temperature evolution of very massive stars

ABSTRACT Very massive stars (VMS) dominate the physics of young clusters due to their ionizing radiation and extreme stellar winds. It is these winds that determine their lifepaths until expiration. Observations in the Arches Cluster show that VMS all have similar temperatures. The VLT-FLAMES Tarantula Survey analysed VMS in the 30 Doradus (30 Dor) region of the Large Magellanic Cloud (LMC) also finding a narrow range of temperatures, albeit at higher values – likely a metallicity effect. Using mesa, we study the main-sequence evolution of VMS with a new mass-loss recipe that switches from optically thin O-star winds to optically thick Wolf–Rayet-type winds through the model-independent transition mass-loss rate of Vink & Gräfener. We examine the temperature evolution of VMS with mass loss that scales with the luminosity-over-mass (L/M) ratio and the Eddington parameter (Γe), assessing the relevance of the surface hydrogen (H) abundance that sets the number of free electrons. We present grids of VMS models at Galactic and LMC metallicity and compare our temperature predictions with empirical results. Models with a steep Γe dependence evolve horizontally in the Hertzsprung–Russel (HR) diagram at nearly constant luminosities, requiring a delicate and unlikely balance between envelope inflation and enhanced mass loss over the entire VMS mass range. By contrast, models with a steep L/M-dependent mass loss are shown to evolve vertically in the HR diagram at nearly constant Teff, naturally reproducing the narrow range of observed temperatures, as well as the correct trend with metallicity. This distinct behaviour of a steeply dropping luminosity is a self-regulatory mechanism that keeps temperatures constant during evolution in the HR diagram.

The Effects of Elemental Abundances on Fitting Supernova Remnant Models to Data

Models for supernova remnant (SNR) evolution can be used to determine the energy of the explosion, the age of the SNR, and the density of the surrounding medium by matching observations. Observed SNR properties derived from the X-ray spectrum include the electron temperature (kTe) and emission measure (EM) of the shocked gas. SNR models are based on hydrodynamic solutions for density, pressure, and velocity. The relations between these and kTe or EM depend on the three inputs of composition, ionization state, and electron-ion temperature ratio (Te/TI). The standard definitions and the XSPEC definitions for kTe and EM have important differences that are not well-known. The same definition used by observers of SNRs must be used in models for correct interpretation. Here, the effects of the three inputs on standard and on XSPEC versions of kTe and EM are investigated, with examples. The ratio of standard EM to the XSPEC value ranges widely, between ∼10−3 to ∼1, with smallest ratios for gas with low hydrogen abundance. The standard kTe differs from the XSPEC value by less than a few percent. For the illustrative example SNR J0049-7314, the ejecta component is shown to be consistent with core-collapse composition and a stellar wind environment.

Discovery and analysis of three magnetic hot subdwarf stars: evidence for merger-induced magnetic fields

ABSTRACT Magnetic fields can play an important role in stellar evolution. Among white dwarfs, the most common stellar remnant, the fraction of magnetic systems is more than 20 per cent. The origin of magnetic fields in white dwarfs, which show strengths ranging from 40 kG to hundreds of MG, is still a topic of debate. In contrast, only one magnetic hot subdwarf star has been identified out of thousands of known systems. Hot subdwarfs are formed from binary interaction, a process often associated with the generation of magnetic fields, and will evolve to become white dwarfs, which makes the lack of detected magnetic hot subdwarfs a puzzling phenomenon. Here we report the discovery of three new magnetic hot subdwarfs with field strengths in the range 300–500 kG. Like the only previously known system, they are all helium-rich O-type stars (He-sdOs). We analysed multiple archival spectra of the three systems and derived their stellar properties. We find that they all lack radial velocity variability, suggesting formation via a merger channel. However, we derive higher than typical hydrogen abundances for their spectral type, which are in disagreement with current model predictions. Our findings suggest a lower limit to the magnetic fraction of hot subdwarfs of $0.147^{+0.143}_{-0.047}$ per cent, and provide evidence for merger-induced magnetic fields which could explain white dwarfs with field strengths of 50–150 MG, assuming magnetic flux conservation.

Recyclable and biodegradable pectin-based film with high mechanical strength

Pectin, a promising polysaccharide, has drawn increasing attention due to its renewability and abundance, but the poor mechanical properties and moisture resistance limit its applications. In this study, we proposed a facile method to prepare a pectin-based film with high mechanical strength and satisfactory moisture resistance via introducing strong bonds, including ionic bond and crystalline domain, counting itself abundance hydrogen bond forming multiple sacrifice bond synergistically for energy dissipation. Thus, pectin-based film exhibits an outstanding fracture stress of 12.7 MPa, which is 200% increase compared to that of original one. Due to the reversible property of these bonds, the pectin-based film appears perfect recyclability (three recycling cycles). Additionally, the hybrid pectin-based film also demonstrates satisfactory moisture resistance, good light transmittance, and favorable biodegradability in natural soil. Considering the demonstrated pectin-based film is eco-friendly and reliable, which represents a promising alternative to replace the non-biodegradable food packaging film.

Collision-induced satellite in the blue wing of the Balmer-β line and consequences on the Balmer series

In this paper we emphasize the non-Lorentzian behavior of the Balmer series in helium-dominated DBA white dwarf stars for which the decades-old problem exists for the determination of the hydrogen abundance. In a very recent work, we have shown that quasi-molecular line satellites due to H-He and H-H collisions are responsible for the asymmetrical shape of the Lyman-α lines observed with the Cosmic Origin Spectrograph and that a similar asymmetry exists for the Balmer-α line profiles. In continuation with very recent work, where the n = 2, 3 potential energies and transition dipole moments from the ground state were determined, here, we present accurate H-He potential energies and electronic transition dipole moments concerning the molecular states correlated with H(n = 4)+He and their transition dipole moments with the states correlated with H(n = 2)+He. Those new data are used to provide a theoretical investigation of the collisional effects in the blue wing of the Balmer-β line of H perturbed by He. Because of the general trend characterizing the repulsive Σ states of the potential energies involved in the Balmer series, the amplitude in the core of the line is decreasing very fast with the order of the series when the helium density gets as large as 1021 cm−3. This study is undertaken by applying a unified theory of spectral line broadening that is valid at very high helium densities found in DZA white dwarf stars. The treatment includes collision-induced line satellites due to asymptotically forbidden transitions, and it explains the asymmetry observed in their spectra.

Intrinsic Lyα Profiles of High-velocity G, K, and M Dwarfs

Abstract Observations of H i Lyman α, the brightest UV emission line of late-type stars, are critical for understanding stellar chromospheres and transition regions, modeling photochemistry in exoplanet atmospheres, and measuring the abundances of neutral hydrogen and deuterium in the interstellar medium. Yet Lyα observations are notoriously challenging owing to severe attenuation from interstellar gas, hindering our understanding of this important emission line’s basic morphology. We present high-resolution far- and near-UV spectroscopy of five G, K, and M dwarfs with radial velocities large enough to Doppler-shift the stellar Lyα emission line away from much of the interstellar attenuation, allowing the line core to be directly observed. We detect self-reversal in the Lyα emission-line core for all targets, and we show that the self-reversal depth decreases with increasing surface gravity. Mg ii self-reversed emission-line profiles provide some useful information to constrain the Lyα line core, but the differences are significant enough that Mg ii cannot be used directly as an intrinsic Lyα template during reconstructions. We show that reconstructions that neglect self-reversal could overestimate intrinsic Lyα fluxes by as much as 60%–100% for G and K dwarfs and 40%–170% for M dwarfs. The five stars of our sample have low magnetic activity and subsolar metallicity; a larger sample size is needed to determine how sensitive these results are to these factors.

Resource potential of lunar permanently shadowed regions

The lunar polar regions contain permanently shadowed regions (PSRs) or local topographic depressions that never receive direct sunlight. These environments (<110 K) have the potential to cold-trap volatile materials in the form of ice, which are essential resources for exploration and industrialization of cislunar space and the Solar System. Orbital observations and those from the LCROSS impactor experiment provide evidence of the existence of water ice and other cold-trapped volatiles in PSRs; however, constraints on volatile abundance and distribution remain ambiguous as individual observations are not always in concord. Here we compile observations indicating the presence of volatiles from ten remotely sensed datasets in 65 PSRs to estimate the locations and mass of water ice deposits. Faustini, Cabeus, de Gerlache, Shoemaker, Haworth, Sverdrup, Slater, and Amundsen are likely the most resource-rich PSRs. Based on co-locations of observations indicative of surface frost and subsurface hydrogen abundance, we find that the craters with the highest potential mass in metric tons (t) of water ice include Cabeus (~11 × 106 t), Shoemaker (~5 × 106 t), Faustini (~4 × 106 t), de Gerlache (~3 × 106 t), and Haworth (~3 × 106 t). Future prospecting of lunar volatiles and water ice is contingent on filling knowledge gaps in resource potential, notably accurate measurements of grade and depth of volatiles. Our proposed ranking and estimates for resource tonnage are a tool to guide future orbital and landed missions that could accurately determine the resource potential of PSR deposits.

Equilibrium and kinetic controls on molecular hydrogen abundance and hydrogen isotope fractionation in hydrothermal fluids

Molecular hydrogen (H2) is among the main components in hydrothermal fluids and exerts a major role in geochemical and biological processes. Nevertheless, the understanding and quantification of factors controlling H2 abundance and isotope composition remain uncertain. Sub-aerial hydrothermal systems provide a unique opportunity to study sources and reactions of H2. Here, we present hydrogen fugacity (fH2) and δD values of H2 and H2O in hydrothermal fluids from such systems worldwide (Greece, Iceland, Kenya and New Zealand), representative of mid-ocean ridge and arc systems and sourced by seawater and meteoric water. The hydrothermal fluid temperatures are 226-359°C, and the fH2, δD-H2 and δD-H2O values are 0.002-3.3 bar, -646 to -391‰ and -94.1 to +11.3‰, respectively. Comparison of measured data with geochemical modeling reveals that H2 is predominantly sourced from the reduction of H2O, enabled through the oxidation of aqueous Fe+II to Fe+III and precipitation of Fe+III-bearing hydrothermal minerals (e.g., epidote). We argue that fH2 in hydrothermal fluids is controlled by metastable mineral-fluid and fluid-fluid equilibria upon progressive rock alteration and depend on temperature, rock-to-water ratio (r/w), source water composition and volcanic gas input. Consequently, fH2 in these systems is not fixed by a sole redox buffer. Our data demonstrate that δD-H2 values of reservoir fluids at depth are controlled by the δD value of the source water and the equilibrium isotope fractionation characteristic of the hydrothermal reservoir temperatures. Attainment of isotopic equilibrium at reservoir conditions is supported by fast isotopic equilibration times at T > 200°C, on the order of minutes to few hours, relative to hydrothermal fluid residence times within the reservoirs of years to decades or even longer. During its ascent to the surface, the isotopic composition of H2 can be modified due to isotopic re-equilibration with H2O. The extent of re-equilibration depends on the interplay between fluid flow velocity, cooling rate and kinetics of D-H exchange between H2 and H2O. For fast flowing well discharges (∼0.1 to >10 m/s), negligible changes occur, whereas for slowly flowing (<0.06 m/s) fumaroles, complete re-equilibration at surface temperatures (∼100°C) is sometimes observed. Based on the extent of hydrogen isotope disequilibrium relative to reservoir conditions, fluid reservoir-to-surface travel times are estimated to range from few minutes to <3 hrs for well fluids and few hours to days for fumarolic vapor.

Formation of the Double White Dwarf Binary PTF J0533+0209 through Stable Mass Transfer?

Abstract Double white dwarf (DWD) binaries are important for studies of common-envelope (CE) evolution, Type Ia supernova progenitors and Galactic sources of low-frequency gravitational waves. PTF J0533+0209 is a DWD system with a short orbital period of P orb ∼ 20 minutes and thus a so-called LISA verification source. The formation of this system and other DWDs is still under debate. In this paper, we discuss the possible formation scenarios of this binary and argue that it is not likely to have formed through CE evolution. Applying a new magnetic-braking prescription, we use the MESA code to model the formation of this system through stable mass transfer. We find a model that can well reproduce the observed WD masses and orbital period but not the effective temperature and hydrogen abundance of the low-mass He WD component. We discuss the possibility of using H flashes to mitigate this discrepancy. Finally, we discuss the future evolution of this system into an AM CVn binary such as those that will be detected by spaceborne GW observatories like LISA, TianQin, and Taiji.

Nonstandard Modeling of a Possible Blue Straggler Star, KIC 11145123

Abstract Nonstandard modeling of KIC 11145123, a possible blue straggler star, has been asteroseismically carried out based on a scheme to compute stellar models with the chemical compositions in their envelopes arbitrarily modified, mimicking the effects of some interactions with other stars through which blue straggler stars are thought to be born. We have constructed a nonstandard model of the star with the following parameters: M = 1.36 M ⊙, Y init = 0.26, Z init = 0.002, and f ovs = 0.027, where f ovs is the extent of overshooting described as an exponentially decaying diffusive process. The modification is down to the depth of r/R ∼ 0.6 and the extent ΔX, which is a difference in surface hydrogen abundance between the envelope-modified and unmodified models, is 0.06. The residuals between the model and the observed frequencies are comparable with those for the previous model computed assuming standard single-star evolution, suggesting that it is possible that the star was born with a relatively ordinary initial helium abundance of ∼0.26 compared with that of the previous models (∼0.30–0.40), then experienced some modification of the chemical compositions and gained helium in the envelope. Detailed analyses of the nonstandard model have implied that the elemental diffusion in the deep radiative region of the star might be much weaker than that assumed in current stellar evolutionary calculations; we need some extra mechanisms inside the star, rendering the star a much more intriguing target to be further investigated.

The evidence for unusually high hydrogen abundances in the central part of Valles Marineris on Mars

Studies of hydrogen deposition in the shallow Martian subsurface have been conducted by two neutron and one gamma-ray detectors in the past and provided global hydrogen maps (Boynton et al., 2002; Feldman et al., 2002; Mitrofanov et al., 2002). It is known from these maps that hydrogen is most abundant in the polar permafrost areas compared to the equatorial band where frozen water is not stable on the surface. However, the spatial resolution of hundreds of kilometres typical for these maps does not allow for detection of local hydrogen-rich features that can be associated with geological structures. The FREND neutron telescope (Mitrofanov et al., 2018) onboard ExoMars TGO (Vago et al., 2015) is capable of a much better spatial resolution for mapping neutron emission of Mars. In this Report we present an analysis of the most intriguing local area of highly suppressed neutron emission in the vicinity of the Martian equator, which coincides with Candor Chaos in the central area of Valles Marineris, thought to be promising for testing water ice (Gourronc et al., 2014). Provided such suppression would be interpreted as the evidence for very high content of hydrogen in the soil, the mean water equivalent hydrogen value in the local suppression area should be as large as 40.3 wt%. This finding is thought to be uncommon for equatorial regions, but is probably associated with particular geomorphological conditions inside Valles Marineris.

Warm Plasma Application in Tar Conversion and Syngas Valorization: The Fate of Hydrogen Sulfide

Warm plasma techniques are considered a promising method of tar removal in biomass-derived syngas. The fate of another problematic syngas impurity—hydrogen sulfide—is studied in this work. It is revealed that processing simulated syngas with a microwave plasma results in hydrogen sulfide conversion. For different gas flow rates (20–40 NLPM) and hydrogen sulfide concentrations ranging from 250 ppm to 750 ppm, the conversion rate varies from ca. 26% to 45%. The main sulfur-containing products are carbon disulfide (ca. 30% of total sulfur) and carbonyl sulfide (ca. 8% of total sulfur). Besides them, significantly smaller quantities of sulfates and benzothiophene are also detected. The main components of syngas have a tremendous impact on the fate of hydrogen sulfide. While the presence of carbon monoxide, methane, carbon dioxide, and tar surrogate (toluene) leads to the formation of carbonyl sulfide, carbon disulfide, sulfur dioxide, and benzothiophene, respectively, the abundance of hydrogen results in the recreation of hydrogen sulfide. Consequently, the presence of hydrogen in the simulated syngas is the main factor that determines the low conversion rate of hydrogen sulfide. Conversion of hydrogen sulfide into various sulfur compounds might be problematic in the context of syngas purification and the application of the right technique for sulfur removal.

Specific heat and thermal history of the Sariçiçek howardite

AbstractMeteorites are excavated fragments from asteroid surfaces and planets, and determining their thermophysical properties is important since they contain valuable information about internal structures of their parent bodies. We investigated thermophysical properties of the Sariçiçek meteorite by differential scanning calorimetry (DSC), measuring phase transition temperatures, enthalpy changes and specific heat capacities of samples and thermogravimetric analysis (TGA), investigating weight change in a sample as a function of temperature or time. DSC results indicate that troilite α/β and β/γ phase transition temperatures of the interior part of the meteorite were at 421.98 ± 0.02 and 581.74 ± 1.71 K, and troilite content of interior and crust parts of the meteorite were 0.28 and 0.02 wt%, respectively. Relict temperatures were calculated as 453 ± 10, 465 ± 17, and 588 ± 55 K; specific heat capacities were measured as 779, 745, and 663 J kg–1 K–1 at 300 K; and predicted as 568, 537, and 480 J kg–1 K–1 at 200 K, for interior, edge, and crust, respectively. TGA results revealed that Sariçiçek's weight loss was 0.98% at 1170 °C, and water content and hydrogen abundance at 200–800 °C were 0.34% and 0.04%, respectively. Obtained results shed light on a thermal history of Sariçiçek’s parent body and provide further knowledge on thermal alteration of 4 Vesta.

Active neutron interrogation experiments and simulation verification using the SIngle-scintillator Neutron and Gamma-Ray spectrometer (SINGR) for geosciences

We present a new SIngle-scintillator Neutron and Gamma-Ray spectrometer (SINGR) instrument for use with both passive and active measurement techniques. Here we discuss, the application of SINGR for planetary exploration missions; however, hydrology, nuclear non-proliferation, and resource prospecting are all potential areas where the instrument could be applied. SINGR uses an elpasolite scintillator, Cs2YLiCl6:Ce (CLYC), that has been shown to have high neutron efficiency even at small volumes, with a gamma-ray energy resolution of approximately 4% full-width-at-half-maximum at 662 keV. Active gamma-ray and neutron (GRNS) measurements were performed with SINGR at the NASA Goddard Space Flight Center (GSFC) Goddard Geophysical and Astronomical Observatory (GGAO) outdoor test site using a pulsed neutron generator (PNG) to interrogate geologically relevant materials (basalt and granite monuments). These experimental results, combined with simulations, demonstrate that SINGR is capable of generating neutron die-away curves that can be used to reconstruct the bulk hydrogen abundance and the depth distribution of hydrogen within the monuments. We compare our experimental results with Monte Carlo N-Particle (MCNP) 6.1 transport simulations to constrain the uncertainties in depth and hydrogen abundance from the neutron die-away data generated by SINGR. For future planetary exploration missions, SINGR provides a single detector system for interrogating the shallow subsurface to characterize the presence and abundance of hydrated phases and to provide bulk elemental analysis.

Chemical abundances in Seyfert galaxies – VIII. Argon abundance estimates

ABSTRACT For the first time, the argon abundance relative to hydrogen abundance (Ar/H) in the narrow line region of a sample of Seyfert 2 nuclei has been derived. In view of this, optical narrow emission line intensities of a sample of 64 local Seyfert 2 nuclei (z &amp;lt; 0.25) taken from Sloan Digital Sky Survey DR7 and measured by the MPA/JHU group were considered. We adopted the Te-method for AGNs, which is based on direct determination of the electron temperature, together with a grid of photoionization model results, built with the cloudy code, to obtain a method for the derivation of the Ar/H abundance. We find that for a metallicity range of $\rm 0.2 \: \lesssim \: (\mathit{ Z}/{\rm Z_{\odot }}) \: \lesssim \: 2.0$, Seyfert 2 nuclei present Ar/H abundance ranging from ∼0.1 to ∼3 times the argon solar value, adopting $\rm log(O/H)_{\odot }=-3.31$ and $\rm log(Ar/H)_{\odot }=-5.60$. These range of values correspond to $\rm 8.0 \: \lesssim \: (12+log(O/H) \: \lesssim \: 9.0$ and $\rm 5.4 \: \lesssim \: (12+log(Ar/H) \: \lesssim \: 6.9$, respectively. The range of Ar/H and Ar/O abundance values obtained from our sample are in consonance with estimations from extrapolations of the radial abundance gradients to the central parts of the disc for four spiral galaxies. We combined our abundance results with estimates obtained from a sample of H ii galaxies, which were taken from the literature, and found that the Ar/O abundance ratio decreases slightly as the O/H abundance increases.