Investigating the OH-H2 relation in diffuse Galactic clouds

We investigate the correlation between OH and H2 column densities in diffuse Galactic clouds, in order to identify potential molecular tracers of interstellar H2. For this, we analyse near-UV spectra extracted from the ESO/VLT archives towards seventeen sightlines (five of them new) with known N(H2), along with nine sightlines with no H2 information. N(OH) shows only marginal correlation with N(H2) (10$^{20}$ to 2 x 10$^{21}$ cm$^{-2}$), at the 95 per cent confidence level. We use orthogonal distance regression analysis to obtain N(OH)/N(H2) = (1.32+/-0.15) x 10$^{-7}$, which is ~ 33 per cent higher than the previous estimates based on near-UV data. We also obtain N(CH)/N(H2) = (3.83+/-0.23) x 10$^{-8}$ and a significant correlation between N(OH) and N(CH), with N(OH) = (2.61+/-0.19) x N(CH), both of which are consistent with previous results. Comparison with predictions of numerical models indicate that OH absorption arises from diffuse gas (nH ~ 50 cm$^{-3}$) illuminated by radiation fields ~ 0.5-5 G0, while CH is associated with higher density of 500 cm$^{-3}$. We posit that the apparent dichotomy in the properties of the diffuse clouds giving rise to OH and CH absorption could be due to either (a) the presence of multiple spectroscopically unresolved clouds along the line-of-sight, or, (b) density gradients along the line-of-sight within a single cloud.Comment: 10 pages, 3 figures, 5 tables; accepted for publication in MNRA

Unbiased cut selection for optimal upper limits in neutrino detectors: the model rejection potential technique

We present a method for optimising experimental cuts in order to place the strongest constraints (upper limits) on theoretical signal models. The method relies only on signal and background expectations derived from Monte-Carlo simulations, so no bias is introduced by looking at actual data, for instance by setting a limit based on expected signal above the ``last remaining data event.'' After discussing the concept of the ``average upper limit,'' based on the expectation from an ensemble of repeated experiments with no true signal, we show how the best model rejection potential is achieved by optimising the cuts to minimise the ratio of this ``average upper limit'' to the expected signal from the model. As an example, we use this technique to determine the limit sensitivity of kilometre scale neutrino detectors to extra-terrestrial neutrino fluxes from a variety of models, e.g. active galaxies and gamma-ray bursts. We suggest that these model rejection potential optimised limits be used as a standard method of comparing the sensitivity of proposed neutrino detectors.Comment: 18 pages, 7 figures, submitted to Astroparticle Physic

The dental calculus metabolome in modern and historic samples.

INTRODUCTION: Dental calculus is a mineralized microbial dental plaque biofilm that forms throughout life by precipitation of salivary calcium salts. Successive cycles of dental plaque growth and calcification make it an unusually well-preserved, long-term record of host-microbial interaction in the archaeological record. Recent studies have confirmed the survival of authentic ancient DNA and proteins within historic and prehistoric dental calculus, making it a promising substrate for investigating oral microbiome evolution via direct measurement and comparison of modern and ancient specimens. OBJECTIVE: We present the first comprehensive characterization of the human dental calculus metabolome using a multi-platform approach. METHODS: Ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) quantified 285 metabolites in modern and historic (200 years old) dental calculus, including metabolites of drug and dietary origin. A subset of historic samples was additionally analyzed by high-resolution gas chromatography-MS (GC-MS) and UPLC-MS/MS for further characterization of metabolites and lipids. Metabolite profiles of modern and historic calculus were compared to identify patterns of persistence and loss. RESULTS: Dipeptides, free amino acids, free nucleotides, and carbohydrates substantially decrease in abundance and ubiquity in archaeological samples, with some exceptions. Lipids generally persist, and saturated and mono-unsaturated medium and long chain fatty acids appear to be well-preserved, while metabolic derivatives related to oxidation and chemical degradation are found at higher levels in archaeological dental calculus than fresh samples. CONCLUSIONS: The results of this study indicate that certain metabolite classes have higher potential for recovery over long time scales and may serve as appropriate targets for oral microbiome evolutionary studies

Author Correction: Multi-ancestry genome-wide association analyses improve resolution of genes and pathways influencing lung function and chronic obstructive pulmonary disease risk

Correction to: Nature Geneticshttps://doi.org/10.1038/s41588-023-01314-0, published online 13 March 2023. In the version of the article initially published, the sample sizes in the main text and Supplementary Tables 1 and 2 were incorrect. In the abstract, the last paragraph of the Introduction, the first paragraph of the Results, the top box in Figure 1a and the Supplementary Information, the total sample size has been corrected from 580,869 to 588,452 participants and the size of the European cohort from 468,062 to 475,645. Some of the effect sizes in Supplementary Table 14 (columns W, Z, AC, AF) had the wrong sign. There was also an error in Supplementary Table 3 where the sample size instead of the variant count was shown for EXCEED. The errors do not affect the conclusions of the study. Additionally, two acknowledgments for use of INTERVAL pQTL and Lung eQTL consortium data were omitted from the Supplementary Information. These errors have been corrected in the Supplementary Information and HTML and PDF versions of the article

In-situ estimation of ice crystal properties at the South Pole using LED calibration data from the IceCube Neutrino Observatory

The IceCube Neutrino Observatory instruments about 1 km3 of deep, glacial ice at the geographic South Pole using 5160 photomultipliers to detect Cherenkov light emitted by charged relativistic particles. A unexpected light propagation effect observed by the experiment is an anisotropic attenuation, which is aligned with the local flow direction of the ice. Birefringent light propagation has been examined as a possible explanation for this effect. The predictions of a first-principles birefringence model developed for this purpose, in particular curved light trajectories resulting from asymmetric diffusion, provide a qualitatively good match to the main features of the data. This in turn allows us to deduce ice crystal properties. Since the wavelength of the detected light is short compared to the crystal size, these crystal properties do not only include the crystal orientation fabric, but also the average crystal size and shape, as a function of depth. By adding small empirical corrections to this first-principles model, a quantitatively accurate description of the optical properties of the IceCube glacial ice is obtained. In this paper, we present the experimental signature of ice optical anisotropy observed in IceCube LED calibration data, the theory and parametrization of the birefringence effect, the fitting procedures of these parameterizations to experimental data as well as the inferred crystal properties.</p

In situ estimation of ice crystal properties at the South Pole using LED calibration data from the IceCube Neutrino Observatory

The IceCube Neutrino Observatory instruments about 1 km3 of deep, glacial ice at the geographic South Pole. It uses 5160 photomultipliers to detect Cherenkov light emitted by charged relativistic particles. An unexpected light propagation effect observed by the experiment is an anisotropic attenuation, which is aligned with the local flow direction of the ice. We examine birefringent light propagation through the polycrystalline ice microstructure as a possible explanation for this effect. The predictions of a first-principles model developed for this purpose, in particular curved light trajectories resulting from asymmetric diffusion, provide a qualitatively good match to the main features of the data. This in turn allows us to deduce ice crystal properties. Since the wavelength of the detected light is short compared to the crystal size, these crystal properties include not only the crystal orientation fabric, but also the average crystal size and shape, as a function of depth. By adding small empirical corrections to this first-principles model, a quantitatively accurate description of the optical properties of the IceCube glacial ice is obtained. In this paper, we present the experimental signature of ice optical anisotropy observed in IceCube light-emitting diode (LED) calibration data, the theory and parameterization of the birefringence effect, the fitting procedures of these parameterizations to experimental data, and the inferred crystal properties.Peer Reviewe