Spatial distribution of HOCN around Sagittarius B2

HOCN and HNCO abundance ratio in molecular gas can tell us the information of their formation mechanism. We performed high-sensitivity mapping observations of HOCN, HNCO, and HNC18O lines around Sagittarius B2 (Sgr B2) with IRAM 30m telescope at 3-mm wavelength. HNCO 404-303 and HOCN 404-303 are used to obtain the abundance ratio of HNCO to HOCN. The ratio of HNCO 404-303 to HNC18O 404-303 is used to calculate the optical depth of HNCO 04-303. The abundance ratio of HOCN and HNCO is observed to range from 0.4% to 0.7% toward most positions, which agrees well with the gas-grain model. However, the relative abundance of HOCN is observed to be enhanced toward the direction of Sgr B2 (S), with HOCN to HNCO abundance ratio of ∼ 0.9%. The reason for that still needs further investigation. Based on the intensity ratio of HNCO and HNC18O lines, we updated the isotopic ratio of 16O/18O to be 296 ± 54 in Sgr B2.

Isotope geochemistry in archaeology

Isotope geochemistry is an important scientific technique that has made a significant contribution to archaeological research. Isotope techniques measure the relative abundance of a number of nuclides of the same (or derivative) element as a means of investigating a variety of natural processes. Both stable (H, O, C, N, Ca, Sr, Cu, Pb, S) and unstable (U, Th, K, Ar) isotope systems are analyzed as part of archaeological investigations.Isotopes (often referred to as a nuclide in the singular) are variants of a particular element, which share the same number of protons but have varying numbers of neutrons. Isotopes are referred to as stable or unstable, depending on whether they undergo radioactive decay. Some nuclides are primordial, meaning they have existed since the beginning of the universe, while others are the product of the decay of other elements. Isotopes of the same element generally share the same chemical behavior.Stable isotopes can be applied to studying a variety of processes with their applicability to specific problems depending on the mechanism by which one nuclide becomes naturally enriched or depleted. The basis of the application of some stable isotopes is that the variation in their atomic mass leads them to behave differently during processes such as evaporation, precipitation, freezing, photosynthesis, and incorporation into the body. Another approach is based on taking advantage of the varying abundance of some stable isotopes within different geological units to allow proveniencing of various materials. This can only be achieved if the isotope ratios remain unchanged after incorporation into the sample.Unstable isotopes are most commonly used as a geochronological tool for establishing the age of materials such as organics, calcium carbonates, and igneous rocks. Unstable nuclides that have either too many or too few neutrons spontaneously transform by beta decay, alpha decay, or spontaneous nuclear fission. The decay speed can be calibrated to time and is usually expressed as a “half-life.” On the basis of a known decay rate and original abundance ratio, the comparison of the relative abundance of a stable nuclide to an unstable nuclide can provide an age estimation of the material studied. In the case of radiocarbon dating, the abundance of 14C in the sample is compared to modern levels of 14C.Isotope analysis can be performed directly on archaeological materials or on geological materials to provide a context for archaeological sites. A particular advantage of using isotopic methods in archaeological investigations is that it provides quantifiable information that can be compared to the material culture record.

Big Three Dragons: A [N ii] 122 μm Constraint and New Dust-continuum Detection of a z = 7.15 Bright Lyman-break Galaxy with ALMA

We present new Atacama Large Millimeter/submillimeter Array Band 7 observational results of a Lyman-break galaxy at z = 7.15, B14-65666 (“Big Three Dragons”), which is an object detected in [O iii] 88 μm, [C ii] 158 μm, and dust continuum emission during the epoch of reionization. Our targets are the [N ii] 122 μm fine-structure emission line and the underlying 120 μm dust continuum. The dust continuum is detected with a ∼19σ significance. From far-infrared spectral energy distribution sampled at 90, 120, and 160 μm, we obtain a best-fit dust temperature of 40 K (79 K) and an infrared luminosity of log 10 ( L IR / L ⊙ ) = 11.6 (12.1) at the emissivity index β = 2.0 (1.0). The [N ii] 122 μm line is not detected. The 3σ upper limit of the [N ii] luminosity is 8.1 × 107 L ⊙. From the [N ii], [O iii], and [C ii] line luminosities, we use the Cloudy photoionization code to estimate nebular parameters as functions of metallicity. If the metallicity of the galaxy is high (Z > 0.4 Z ⊙), the ionization parameter and hydrogen density are log 10 U ≃ − 2.7 ± 0.1 and n H ≃ 50–250 cm−3, respectively, which are comparable to those measured in low-redshift galaxies. The nitrogen-to-oxygen abundance ratio, N/O, is constrained to be subsolar. At Z < 0.4 Z ⊙, the allowed U drastically increases as the assumed metallicity decreases. For high ionization parameters, the N/O constraint becomes weak. Finally, our Cloudy models predict the location of B14-65666 on the BPT diagram, thereby allowing a comparison with low-redshift galaxies.

Possible Detection of X-Ray Emitting Circumstellar Material in the Synchrotron-dominated Supernova Remnant RX J1713.7−3946

We report on a discovery of an X-ray emitting circumstellar material (CSM) knot inside the synchrotron dominant supernova remnant RX J1713.7−3946. This knot was previously thought to be a Wolf–Rayet star (WR 85), but we realized that it is in fact ∼40″ away from WR 85, indicating no relation to WR 85. We performed high-resolution X-ray spectroscopy with the Reflection Grating Spectrometer (RGS) on board XMM-Newton. The RGS spectrum clearly resolves a number of emission lines, such as N Lyα, O Lyα, Fe xviii, Ne x, Mg xi, and Si xiii. The spectrum can be well represented by an absorbed thermal-emission model with a temperature of k B T e = 0.65 ± 0.02 keV. The elemental abundances are obtained to be N / H = 3.5 ± 0.8 N / H ⊙ , O / H = 0.5 ± 0.1 O / H ⊙ , Ne / H = 0.9 ± 0.1 Ne / H ⊙ , Mg / H = 1.0 ± 0.1 Mg / H ⊙ , Si / H = 1.0 ± 0.2 Si / H ⊙ , and Fe / H = 1.3 ± 0.1 Fe / H ⊙ . The enhanced N abundance with others being about the solar values allows us to infer that this knot is CSM ejected when the progenitor star evolved into a red supergiant. The abundance ratio of N to O is obtained to be N / O = 6.8 − 2.1 + 2.5 N / O ⊙ . By comparing this to those in outer layers of red supergiant stars expected from stellar evolution simulations, we estimate the initial mass of the progenitor star to be 15 M ⊙ ≲ M ≲ 20 M ⊙.

Improvement of 1,3-Propanediol Production From Crude Glycerol by Co-cultivation of Anaerobic and Facultative Microbes Under Non-strictly Anaerobic Conditions

Background: Natural microbial consortia could efficiently produce 1,3-propanediol, the most promising bulk biochemical derived from glycerol that can be used as a monomer in the synthesis of polytrimethylene terephthalate (PTT). While natural microbial communities are made up of a diverse range of microbes with frequently unknown functions, the construction of synthetic microbial consortia allows for creating more defined systems with lower complexity.Results: In this study, the synthetic microbial consortia were constructed by combing facultative microbes of Klebsiella pneumoniae DUT2 (KP) and/or Escherichia coli DUT3 (EC) cultures with the strict anaerobic microbe of Clostridium butyricum DUT1 (CB) cultures under micro-aerobic conditions. The function of EC and KP during the fermentation process was to deplete oxygen and provide an anaerobic environment for CB. Furthermore, KP competes with CB to consume crude glycerol and produce 1,3-PDO. The interaction of commensalism and competition resulted in synthetic microbial consortia that could efficiently convert crude glycerol to 1,3-PDO even under micro-aerobic conditions. In a batch fermentation, the synthetic CB:KP co-culture at an initial abundance ratio of 92.5:7.5 yielded a maximum 1,3-PDO concentration of 52.08 g/L, with a yield of 0.49 g/g and a productivity of 1.80 g/(L.h), which increased by 10%, 9%, and 12%, respectively, when compared to the CB mono-culture under strictly anaerobic conditions. Compared to the KP mono-culture, the final 1,3-PDO concentration, yield, and productivity by the synthetic CB:KP consortia increased by 16%, 19%, and 84%, respectively. The synthetic CB:KP:EC co-culture achieved the highest 1,3-PDO flux of 49.17% at an initial abundance ratio of 85:7.5:7.5, while 7.43%, 5.77%, 3.15% 4.24%, and 2.13% of flux was distributed to butyric acid, acetic acid, lactic acid, ethanol, and succinic acid pathways. In a fed-batch fermentation, synthetic CB:KP:EC co-culture demonstrated a maximum 1,3-PDO concentration of 77.68 g/L with a yield of 0.51 g/g which is 30% and 13% higher than the production by the CB mono-culture at 0.02 vvm N2 supply. The initial abundance of CB guaranteed to be at least 85% facilitates 1,3-PDO production from crude glycerol efficiently by the development of synthetic microbial consortia. Conclusion: Under micro-aerobic conditions, the synthetic microbial consortia demonstrated excellent performance on 1,3-propanediol production via the interaction of commensalism and competition. The experimental results demonstrated the potential benefit of using the synthetic microbial consortia to produce 1,3-propanediol from crude glycerol.

Atomic Iron and Nickel in the Coma of C/1996 B2 (Hyakutake): Production Rates, Emission Mechanisms, and Possible Parents

Two papers recently reported the detection of gaseous nickel and iron in the comae of over 20 comets from observations collected over two decades, including interstellar comet 2I/Borisov. To evaluate the state of the laboratory data in support of these identifications, we reanalyzed archived spectra of comet C/1996 B2 (Hyakutake), one of the nearest and brightest comets of the past century, using a combined experimental and computational approach. We developed a new, many-level fluorescence model that indicates that the fluorescence emissions of Fe I and Ni I vary greatly with heliocentric velocity. Combining this model with laboratory spectra of an Fe-Ni plasma, we identified 22 lines of Fe I and 14 lines of Ni I in the spectrum of Hyakutake. Using Haser models, we estimate the nickel and iron production rates as Q Ni = (2.6–4.1) × 1022 s−1 and Q Fe = (0.4–2.8) × 1023 s−1. From derived column densities, the Ni/Fe abundance ratio log10[Ni/Fe] = −0.15 ± 0.07 deviates significantly from solar abundance ratios, and it is consistent with the ratios observed in solar system comets. Possible production and emission mechanisms are analyzed in the context of existing laboratory measurements. Based on the observed spatial distributions, excellent fluorescence model agreement, and Ni/Fe ratio, our findings support an origin consisting of a short-lived unknown parent followed by fluorescence emission. Our models suggest that the strong heliocentric velocity dependence of the fluorescence efficiencies can provide a meaningful test of the physical process responsible for the Fe I and Ni I emission.

Microbial Surface Biofilm Responds to the Growth-Reproduction-Senescence Cycle of the Dominant Coral Reef Macroalgae Sargassum spp.

Macroalgae play an intricate role in microbial-mediated coral reef degradation processes due to the release of dissolved nutrients. However, temporal variabilities of macroalgal surface biofilms and their implication on the wider reef system remain poorly characterized. Here, we study the microbial biofilm of the dominant reef macroalgae Sargassum over a period of one year at an inshore Great Barrier Reef site (Magnetic Island, Australia). Monthly sampling of the Sargassum biofilm links the temporal taxonomic and putative functional metabolic microbiome changes, examined using 16S rRNA gene amplicon and metagenomic sequencing, to the pronounced growth-reproduction-senescence cycle of the host. Overall, the macroalgal biofilm was dominated by the heterotrophic phyla Firmicutes (35% ± 5.9% SD) and Bacteroidetes (12% ± 0.6% SD); their relative abundance ratio shifted significantly along the annual growth-reproduction-senescence cycle of Sargassum. For example, Firmicutes were 1.7 to 3.9 times more abundant during host growth and reproduction cycles than Bacteroidetes. Both phyla varied in their carbohydrate degradation capabilities; hence, temporal fluctuations in the carbohydrate availability are potentially linked to the observed shift. Dominant heterotrophic macroalgal biofilm members, such as Firmicutes and Bacteroidetes, are implicated in exacerbating or ameliorating the release of dissolved nutrients into the ambient environment, though their contribution to microbial-mediated reef degradation processes remains to be determined.

Inhibition of Rho Kinase by Fasudil Ameliorates Cognition Impairment in APP/PS1 Transgenic Mice via Modulation of Gut Microbiota and Metabolites

Background: Fasudil, a Rho kinase inhibitor, exerts therapeutic effects in a mouse model of Alzheimer's disease (AD), a chronic neurodegenerative disease with progressive loss of memory. However, the mechanisms remain unclear. In addition, the gut microbiota and its metabolites have been implicated in AD.Methods: We examined the effect of fasudil on learning and memory using the Morris water-maze (MWM) test in APPswe/PSEN1dE9 transgenic (APP/PS1) mice (8 months old) treated (i.p.) with fasudil (25 mg/kg/day; ADF) or saline (ADNS) and in age- and gender-matched wild-type (WT) mice. Fecal metagenomics and metabolites were performed to identify novel biomarkers of AD and elucidate the mechanisms of fasudil induced beneficial effects in AD mice.Results: The MWM test showed significant improvement of spatial memory in APP/PS1 mice treated with fasudil as compared to ADNS. The metagenomic analysis revealed the abundance of the dominant phyla in all the three groups, including Bacteroidetes (23.7–44%) and Firmicutes (6.4–26.6%), and the increased relative abundance ratio of Firmicutes/Bacteroidetes in ADNS (59.1%) compared to WT (31.7%). In contrast, the Firmicutes/Bacteroidetes ratio was decreased to the WT level in ADF (32.8%). Lefse analysis of metagenomics identified s_Prevotella_sp_CAG873 as an ADF potential biomarker, while s_Helicobacter_typhlonius and s_Helicobacter_sp_MIT_03-1616 as ADNS potential biomarkers. Metabolite analysis revealed the increment of various metabolites, including glutamate, hypoxanthine, thymine, hexanoyl-CoA, and leukotriene, which were relative to ADNS or ADF microbiota potential biomarkers and mainly involved in the metabolism of nucleotide, lipids and sugars, and the inflammatory pathway.Conclusions: Memory deficit in APP/PS1 mice was correlated with the gut microbiome and metabolite status. Fasudil reversed the abnormal gut microbiota and subsequently regulated the related metabolisms to normal in the AD mice. It is believed that fasudil can be a novel strategy for the treatment of AD via remodeling of the gut microbiota and metabolites. The novel results also provide valuable references for the use of gut microbiota and metabolites as diagnostic biomarkers and/or therapeutic targets in clinical studies of AD.

Chemical abundances in Seyfert galaxies– VIII. Argon abundance estimates

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 &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 $\rm 0.2 \: \lesssim \: (Z/{\rm Z_{\odot }}) \: \lesssim \: 2.0$, 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 disk 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.