Asteroseismological Analysis of the DAV HS 0507+0434B: The Influence of Chemical Profile on the Pulsation Periods

Asteroseismology is a powerful tool to infer the details of the inner chemical structure of white dwarfs. Using the nine observed frequencies of HS 0507+0434B, we explore the influence of the inner chemical profile on the pulsation periods. Based on the evolutionary C/O profile, we modify slightly the C/O core profile and make an asteroseismic analysis for HS 0507+0434B. We find that the trapped mode with the period of 445.3 s is mainly affected by the hydrogen and helium mass fraction. The inner C/O core profile has an influence on all modes extending into the inner core. When we use the iteration method with the optimal C/O core profile, the fit between the theoretical periods and observed ones is significantly improved. For the best-fitting model with the optimal parametric C/O core, there is a smaller C/O ratio and a smaller overshooting zone in the stellar interior. The fundamental parameters of the model with the optimal C/O core are M */M ⊙ ∼ 0.710 ± 0.005, T eff ∼ 12570 ± 106K, log M H / M * ∼ − 8.01 ± 0.08 , and log M He / M * ∼ − 2.51 ± 0.08 .

Dual RNASeq Reveals NTHi-Macrophage Transcriptomic Changes During Intracellular Persistence

Nontypeable Haemophilus influenzae (NTHi) is a pathobiont which chronically colonises the airway of individuals with chronic respiratory disease and is associated with poor clinical outcomes. It is unclear how NTHi persists in the airway, however accumulating evidence suggests that NTHi can invade and persist within macrophages. To better understand the mechanisms of NTHi persistence within macrophages, we developed an in vitro model of NTHi intracellular persistence using human monocyte-derived macrophages (MDM). Dual RNA Sequencing was used to assess MDM and NTHi transcriptomic regulation occurring simultaneously during NTHi persistence. Analysis of the macrophage response to NTHi identified temporally regulated transcriptomic profiles, with a specific ‘core’ profile displaying conserved expression of genes across time points. Gene list enrichment analysis identified enrichment of immune responses in the core gene set, with KEGG pathway analysis revealing specific enrichment of intracellular immune response pathways. NTHi persistence was facilitated by modulation of bacterial metabolic, stress response and ribosome pathways. Levels of NTHi genes bioC, mepM and dps were differentially expressed by intracellular NTHi compared to planktonic NTHi, indicating that the transcriptomic adaption was distinct between the two different NTHi lifestyles. Overall, this study provides crucial insights into the transcriptomic adaptations facilitating NTHi persistence within macrophages. Targeting these reported pathways with novel therapeutics to reduce NTHi burden in the airway could be an effective treatment strategy given the current antimicrobial resistance crisis and lack of NTHi vaccines.

Deposition of Polycyclic Aromatic Hydrocarbons (PAHs) into Northern Ontario Lake Sediments

Polycyclic aromatic hydrocarbons (PAHs) are priority pollutants that are produced through incomplete combustion of modern biomass and fossil fuels. In aquatic systems PAHs are absorbed by suspended matter and ultimately deposited into sediments. PAH fluxes to sediments have been declining in North American since the mid 1960s. Improving technology and regulations were expected to contribute to declining PAH concentrations; however, in some urban sediment there are recent increases in deposition. Trends in concentrations of pyrogenic PAHs and perylene were determined in the sediment of two lakes, in central Ontario. Intact piston cores that preserve the depositional history were collected from each site, sliced into 1 cm intervals and analyzed using gas-chromatography/ mass-spectrometry. Pyrogenic PAH trends at each site displayed unique characteristics suggesting differing extents of influence from various atmospheric sources. The upper core profile (above 8.5 cm) in the more remote site had decreasing PAH concentrations consistent with observations from Siskitwit Lake. The more urban site (above 3.5 cm) had increasing PAH concentrations suggesting modern anthropogenic activities have a larger influence in this region. Perylene fluxes at both sites do not correlate with the observed PAH fluxes, increasing in concentration with depth, thus indicating separate sources for this PAH, likely diagenesis within the sediments. Both sites had PAH concentrations exceeding the interim sediment quality guidelines in the uppermost sediment deposits. This study provides insights into the differential atmospheric deposition in Ontario and may aid in establishing strategies for reducing or mitigating the production of PAHs.

Parallel structural interpretation of drill cores and microresistivity scanner images from gas-bearing shale (Baltic Basin, Poland)

Having access to drill cores and microresistivity scanner images from five shale gas exploration boreholes, we were able to compare the results of structural interpretation based on two data sets. The most frequent structures observed in shale complexes are subvertical strata-bound joints that commonly create calcite veins. We have applied a modified approach for statistical analysis of strata-bound fractures taking into account their height. For comparison of cores and scanner image log structural interpretations, we used the fracture number and fracture intensity parameters. We found significant discrepancies between results of cores and image log interpretations. The much greater number of fractures recognized in the image log than in the core is explained by differences in the observation space related to the core and borehole diameters. To predict which fracture that was visible in the scanner image should be represented in the core, we introduced a “critical angle” parameter and used it in the filtering procedure, which gave satisfactory results. In general, the systematically observed superiority of fracture intensity in the scanner image over the core profile is explained by a large number of tiny noncracked veins that are better recorded by a scanner then are visible by the unaided eye. The most striking difference was found in carbonate-rich formations, in which noncracked veins are more numerous. On the contrary, fracture intensity in intervals enriched in total organic carbon (TOC) is always higher in core than in the scanner image, due to a resistivity enhancement related to gas presence. We also compared a record of en echelon arrays of open fractures that allow us to discriminate enhanced natural fractures from borehole-induced tensile fractures. A major difference in the bedding fracture density between the core and image log we attribute to core relaxation during its extraction to the surface. A tectonic inversion phase was also possible to recognize based on the integrated core and scanner interpretation.

The distribution of stars around the Milky Way’s central black hole

Context. The existence of dynamically relaxed stellar density cusps in dense clusters around massive black holes is a long-standing prediction of stellar dynamics, but it has so far escaped unambiguous observational confirmation. Aims. In this paper we aim to revisit the problem of inferring the innermost structure of the Milky Way’s nuclear star cluster via star counts, to clarify whether it displays a core or a cusp around the central black hole. Methods. We used judiciously selected adaptive optics assisted high angular resolution images obtained with the NACO instrument at the ESO VLT. Through image stacking and improved point spread function fitting we pushed the completeness limit about one magnitude deeper than in previous, comparable work. Crowding and extinction corrections were derived and applied to the surface density estimates. Known young, and therefore dynamically not relaxed stars, are excluded from the analysis. Contrary to previous work, we analyse the stellar density in well-defined magnitude ranges in order to be able to constrain stellar masses and ages. Results. We focus on giant stars, with observed magnitudes K = 12.5−16, and on stars with observed magnitudes K ≈ 18, which may have similar mean ages and masses than the former. The giants display a core-like surface density profile within a projected radius R ≤ 0.3 pc of the central black hole, in agreement with previous studies, but their 3D density distribution is not inconsistent with a shallow cusp if we take into account the extent of the entire cluster, beyond the radius of influence of the central black hole. The surface density of the fainter stars can be described well by a single power-law at R < 2 pc. The cusp-like profile of the faint stars persists even if we take into account the possible contamination of stars in this brightness range by young pre-main sequence stars. The data are inconsistent with a core-profile for the faint stars. Finally, we show that a 3D Nuker law provides a good description of the cluster structure. Conclusions. We conclude that the observed density of the faintest stars detectable with reasonable completeness at the Galactic centre, is consistent with the existence of a stellar cusp around the Milky Way’s central black hole, Sagittarius A*. This cusp is well developed inside the influence radius of Sagittarius A* and can be described by a single three-dimensional power-law with an exponent γ = 1.43 ± 0.02 ± 0.1sys. This corroborates existing conclusions from Nbody simulations performed in a companion paper. An important caveat is that the faint stars analysed here may be contaminated significantly by dynamically unrelaxed stars that formed about 100 Myr ago. The apparent lack of giants at projected distances of R ≲ 0.3 pc (R ≲ 8′′) of the massive black hole may indicate that some mechanism may have altered their distribution or intrinsic luminosity. We roughly estimate the number of possibly missing giants to about 100.

Core/Double-Cone Emission-Beam Structure in a Millisecond Pulsar

Slow pulsars show a great deal of qualitative and quantitative regularity in the structure of their radio emission beams as described by the core/double-cone model; however, millisecond pulsars (MSPs) have shown little. It is thus arresting to encounter a 2.7-s MSP with what appears to be a double-cone/core profile—and even more so to find that the arrangement of the cones around the core suggest aberration/retardation emission heights that are very reasonable. This and several other pulsars then represent rare opportunities for analysis and raise questions about why a few MSPs show such orderly beam structure while so many do not.

Rapid thermokarst evolution during the mid-Holocene in Central Yakutia, Russia

The reconstruction of Holocene thermokarst landform evolution is important to understand the potential impact of current global climate change on permafrost regions. A multi-proxy approach was applied to analyse the sedimentological and biogeochemical characteristics as well as pollen and lacustrine microfossils of a core profile drilled in a small pingo within a large Central Yakutian thermokarst basin (alas). Age–depth modelling with macrofossil 14C ages reveals high thermokarst deposit sedimentation rates and a complete thermokarst sequence spanning about 900 years during the mid-Holocene between ~6750 and 5870 cal. yr BP. In total, three stages of thermokarst landscape evolution have been identified. Thermokarst processes were initiated at ⩽6750 to 6500 cal. yr BP. Terrestrial conditions changed quickly to lacustrine conditions, and a thermokarst lake rapidly emerged and grew to an estimated size of 120–600 m diameter and 7.5–15 m depth during only ~150 years between ~6500 and 6350 cal. yr BP. The decline of thermokarst processes and lake decrease may have been affected by local hydrological conditions between ~6350 and 5870 cal. yr BP but ceased completely after 5870 cal. yr BP, likely due to climatic changes. Clear evidence for long-lasting and stable lacustrine conditions was not obtained. The study emphasises that short-term warming led to very active permafrost degradation and rapid but locally variable modification of alas and thermokarst evolution.