bluuebunny/crossref_metadata_2025_split huggingface dataset:
Antibacterial and antioxidant activities of Streptomyces sp. strain FR7 isolated from forest soil
Authors: Weslati Imen , Simões Luara , Teixeira Ana , Parpot Pier , Raies Aly , Oliveira Rui 
Published: March 2023

Abstract
Actinomycetes produce secondary metabolites with many bioactivities such as antimicrobial, which can be useful as alternatives against resistant bacterial strains. Therefore, the screening of new habitats is likely to provide new strains with high potential. In this work, the antimicrobial capacity was used to select Streptomyces sp. strains isolated from Raf Raf forest (Tunisia). From the strain displaying higher activity, FR7, an ethyl acetate extract was prepared under optimized culturing conditions (10 days at 30°C in ISP2 medium with initial pH 8), showing significant antimicrobial activity against Micrococcus luteus and Staphylococcus aureus (MIC = 5 μg ml−1), and Listeria monocytogenes and Pseudomonas aeruginosa (MIC = 20 μg ml−1). The extract displayed strong DPPH radical scavenging activity (IC50 = 1.3 μg ml−1) and protection of yeast cells from H2O2-induced oxidative stress determined by flow cytometry with dichlorofluorescein diacetate. The crude extract showed the presence of polyketides, with methylsalicylic acid as moiety, a large and diverse group of secondary metabolites with a wide range of bioactivities, including antioxidant and antibacterial. Based on 16S RNA gene sequences, strain FR7 was identified as belonging to genus Streptomyces with high resemblance to S. iakyrus. Streptomyces sp. FR7 has great potential as a source of antibacterial and antioxidant metabolites.
Determining Stress in Metallic Conducting Layers of Microelectronics Devices Using High Resolution Electron Backscatter Diffraction and Finite Element Analysis
Authors: Ruggles Timothy , Grutzik Scott , Stephens Kelly , Michael Joseph 
Published: March 2023

AbstractDelayed failure due to stress voiding is a concern with some aging microelectronics, as these voids can grow large enough to cause an open circuit. Local measurements of stress in the metallic layers are crucial to understanding and predicting this failure, but such measurements are complicated by the fact that exposing the aluminum conducting lines will relieve most of their stress. In this study, we instead mechanically thin the device substrate and measure distortions on the thinned surface using high resolution electron backscatter diffraction (HREBSD). These measurements are then related to the stresses in the metallic layers through elastic simulations. This study found that in legacy components that had no obvious voids, the stresses were comparable to the theoretical stresses at the time of manufacture (≈300 MPa). Distortion fields in the substrate were also determined around known voids, which may be directly compared to stress voiding models. The technique presented here for stress determination, HREBSD coupled with finite element analysis to infer subsurface stresses, is a valuable tool for assessing failure in layered microelectronics devices.
The properties of RR Lyrae variable stars in the isolated Local Group dwarf galaxy WLM
Authors: Sarajedini Ata 
Published: March 2023

ABSTRACTWe present an analysis of 50 F475W (≈B filter) and F814W (≈I filter) archival images taken with the Hubble Space Telescope (HST)/Advanced Camera for Surveys of one field in the isolated Local Group dwarf galaxy Wolf–Lundmark–Melotte (WLM). From point spread function fitting photometry of these images, we construct a colour–magnitude diagram and identify and characterize 90 RR Lyrae variables (76 ab-type and 14 c-type) determining their mean magnitudes, colours, periods, and amplitudes in the HST passbands. We have also uncovered 79 Cepheid-type variables, but because of the short time window of our observations (1.85 d), we are not confident in their period determinations. The mean period of the ab-type RR Lyraes is found to be 〈Pab〉 = 0.609 ± 0.058 (ran) corresponding to a mean metallicity of 〈[Fe/H]〉 = −1.74 ± 0.02 (ran) on the Carretta et al. scale. We also present a re-analysis of the Hodge et al. colour–magnitude diagram of the WLM globular cluster and conclude that it is much more metal-poor than Hodge et al. quote. Based on a comparison of the WLM RR Lyraes with those in the other seven ‘isolated’ dwarf galaxies of the Local Group (i.e. Leo A, LGS 3, Cetus, IC 1613, Aquarius, Tucana, and Phoenix), we conclude that there was one unique epoch of early star formation common to all of these isolated dwarfs.
TESS shines light on the origin of the ambiguous nuclear transient ASASSN-18el
Authors: Hinkle Jason T , Kochanek Christopher S , Shappee Benjamin J , Vallely Patrick J , Auchettl Katie , Fausnaugh Michael , Holoien Thomas W-S , Treiber Helena P , Payne Anna V , Gaudi B Scott , Stassun Keivan G , Thompson Todd A , Tonry J L , Villanueva Steven 
Published: March 2023

ABSTRACT
We analyse high-cadence data from the Transiting Exoplanet Survey Satellite (TESS) of the ambiguous nuclear transient (ANT) ASASSN-18el. The optical changing-look phenomenon in ASASSN-18el has been argued to be due to either a drastic change in the accretion rate of the existing active galactic nucleus (AGN) or the result of a tidal disruption event (TDE). Throughout the TESS observations, short-time-scale stochastic variability is seen, consistent with an AGN. We are able to fit the TESS light curve with a damped-random-walk (DRW) model and recover a rest-frame variability amplitude of $\hat{\sigma } = 0.93 \pm 0.02$ mJy and a rest-frame time-scale of $\tau _{DRW} = 20^{+15}_{-6}$ d. We find that the estimated τDRW for ASASSN-18el is broadly consistent with an apparent relationship between the DRW time-scale and central supermassive black hole mass. The large-amplitude stochastic variability of ASASSN-18el, particularly during late stages of the flare, suggests that the origin of this ANT is likely due to extreme AGN activity rather than a TDE.
A closer look at dark photon explanations of the excess radio background
Authors: Acharya Sandeep Kumar , Chluba Jens 
Published: March 2023

ABSTRACT
The observed excess radio background has remained a puzzle for over a decade. A recent new physics solution involves dark matter that decays into dark photons in the presence of a thermal dark photon background. The produced non-thermal dark photon spectrum then converts into standard photons around the reionization era, yielding an approximate power-law radio excess with brightness temperature T(ν) ≃ ν−2.5 over a wide range of frequencies, ν. This simple power-law model comes intriguingly close to the current data, even if several ingredients are required to make it work. In this paper, we investigate some of the details of this model, showcasing the importance of individual effects. In particular, significant deviation from a power law is present at $\nu \lesssim 100\, {\rm MHz}$ and $\nu \gtrsim 1\, {\rm GHz}$. These effects result in improving the fit to data compared to a power-law spectrum, and may become testable in future observations. We also highlight independent signatures that can be tested with future cosmic microwave background spectral distortion experiments such as PIXIE. However, there are challenges for the model from the observed radio background anisotropies, as discussed here. We furthermore highlight a possible runaway process due to the finite width of the dark matter decay profile, which suggests that additional work might be required to obtain a viable model.
Computational fluid dynamics with the coupled discrete unified gas kinetic scheme (CDUGKS)
Authors: Zamora Alvaro , Slaughter Elliott , Abel Tom 
Published: March 2023

ABSTRACTIn this paper, we introduce our open source implementation of the Coupled Discrete Unified Gas Kinetic Scheme (CDUGKS), a phase space scheme capable of handling a wide range of flow regimes. We demonstrate its performance on several well known test problems from the astrophysical fluid dynamics literature such as the 1D Sod shock tube and Einfeldt rarefaction, 2D Kelvin-Helmholtz instability, 1D thermoacoustic wave, a triangular Gresho vortex, a sine wave velocity perturbation. For these problems, we show that the code can simulate flows ranging from the inviscid/Eulerian regime to the free-streaming regime, capturing shocks and emergent diffusive processes in the appropriate regimes. We also use a variety of Prandtl numbers to demonstrate the scheme’s ability to simulate different thermal conductivities at fixed viscosity. The scheme is second-order accurate in space and time and, unlike many solvers, uses a time-step that is independent of the mean free path of the gas. Our code (mp-cdugks) is public under a CC0 1.0 Universal license and is available on GitHub.
NGC 4388: a test case for relativistic disc reflection and Fe K fluorescence features
Authors: Yaqoob Tahir , Tzanavaris P , LaMassa S 
Published: March 2023

ABSTRACT
We present a new analysis of the Suzaku X-ray spectrum of the Compton-thin Seyfert 2 galaxy NGC 4388. The spectrum above ∼2 keV can be described by a remarkably simple and rather mundane model, consisting of a uniform, neutral spherical distribution of matter, with a radial column density of $2.58\pm 0.02 \times 10^{23} \ \rm cm^{-2}$, and an Fe abundance of $1.102^{+0.024}_{-0.021}$ relative to solar. The model does not require any phenomenological adjustments to self-consistently account for the low-energy extinction, the Fe Kα and Fe Kβ fluorescent emission lines, the Fe K edge, and the Compton-scattered continuum from the obscuring material. The spherical geometry is not a unique description, however, and the self-consistent, solar abundance MYTORUS model, applied with toroidal and non-toroidal geometries, gives equally good descriptions of the data. In all cases, the key features of the spectrum are so tightly locked together that for a wide range of parameters, a relativistic disc-reflection component contributes no more than $\sim 2{{\ \rm per\ cent}}$ to the net spectrum in the 2–20 keV band. We show that the commonly invoked explanations for weak X-ray reflection features, namely a truncated and/or very highly ionized disc, do not work for NGC 4388. If relativistically broadened Fe Kα lines and reflection are ubiquitous in Seyfert 1 galaxies, they should also be ubiquitous in Compton-thin Seyfert 2 galaxies. The case of NGC 4388 shows the need for similar studies of more Compton-thin AGN to ascertain whether this is true.
Study with WhoSGlAd of the acoustic depth of the helium glitch across the seismic HR diagram and its impact on the inferred helium abundance
Authors: Farnir M , Valentino A , Dupret M-A , Broomhall A-M 
Published: March 2023

ABSTRACTThe acoustic glitches’ signature present in solar-like stars holds invaluable information. Indeed, it is caused by a sharp variation in the sound speed, therefore carrying localized information. One such glitch is the helium glitch caused by the hydrogen and first and second partial helium ionization region, allowing us to constrain the surface helium abundance. However, the function adjusted to the glitch signature depends non-linearly on the acoustic depth at which it occurs, He. Retrieving the faint glitch signature and estimating τHe are difficult but crucial tasks to accurately measure the glitch parameters and, ultimately, accurately infer the helium abundance. In this paper, we aim at providing a way to estimate τHe using precise seismic indicators, independent of stellar modelling. Consequently, we aim at improving the WhoSGlAd (Whole Spectrum and Glitches Adjustment) method by automatically providing a model-independent measure of the glitch’s parameters. We compute the evolution of THe, a dimensionless form of the acoustic depth, along a grid of models and adjust an empirical linear relation between THe and the mean large separation and frequency ratio as defined in WhoSGlAd. We further optimize over the value of this estimate to ensure the stability and accuracy of the approach. The proposed approach provides an excellent estimate of the acoustic depth and allows us to swiftly retrieve the glitch signature of observed spectra. We demonstrate that the we can accurately model the helium abundance of four Kepler targets by comparing model (both versions of WhoSGlAd) and literature values.
The connection between starspots and superflares: a case study of two stars
Authors: Araújo Alexandre , Valio Adriana 
Published: March 2023

ABSTRACT
How do the characteristics of starspots influence the triggering of stellar flares? Here, we investigate the activity of two K-type stars, similar in every way from mass to rotation periods and planetary systems. Both stars exhibit about a hundred spots; however, Kepler-411 produced 65 superflares, while Kepler-210 presented none. The spots of both stars were characterized using the planetary transit mapping technique, which yields the intensity, temperature, and radius of starspots. The average radius was (17 ± 7) × 103  and (58 ± 23) × 103 km, while the intensity ratio with respect to the photosphere was (0.35 ± 0.24) and (0.64 ± 0.15) Ic, and the temperature was (3800 ± 700) and (4180 ± 240) K for spots of Kepler-411 and Kepler-210, respectively. Therefore, spots on the star with no superflares, Kepler-210, are mostly larger, less dark, and warmer than those on the flaring star, Kepler-411. This may be an indication of magnetic fields with smaller magnitude and complexity of the spots on Kepler-210 when compared to those on Kepler-411. Thus, starspot area appears not to be the main culprit of superflares triggering. Perhaps the magnetic complexity of active regions is more important.
Restoration of mitochondrial function through activation of hypomodified tRNAs with pathogenic mutations associated with mitochondrial diseases
Authors: Tomoda Ena , Nagao Asuteka , Shirai Yuki , Asano Kana , Suzuki Takeo , Battersby Brendan J , Suzuki Tsutomu 
Published: March 2023

Abstract
Mutations in mitochondrial (mt-)tRNAs frequently cause mitochondrial dysfunction. Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS), and myoclonus epilepsy associated with ragged red fibers (MERRF) are major clinical subgroups of mitochondrial diseases caused by pathogenic point mutations in tRNA genes encoded in mtDNA. We previously reported a severe reduction in the frequency of 5-taurinomethyluridine (τm5U) and its 2-thiouridine derivative (τm5s2U) in the anticodons of mutant mt-tRNAs isolated from the cells of patients with MELAS and MERRF, respectively. The hypomodified tRNAs fail to decode cognate codons efficiently, resulting in defective translation of respiratory chain proteins in mitochondria. To restore the mitochondrial activity of MELAS patient cells, we overexpressed MTO1, a τm5U-modifying enzyme, in patient-derived myoblasts. We used a newly developed primer extension method and showed that MTO1 overexpression almost completely restored the τm5U modification of the MELAS mutant mt-tRNALeu(UUR). An increase in mitochondrial protein synthesis and oxygen consumption rate suggested that the mitochondrial function of MELAS patient cells can be activated by restoring the τm5U of the mutant tRNA. In addition, we confirmed that MTO1 expression restored the τm5s2U of the mutant mt-tRNALys in MERRF patient cells. These findings pave the way for epitranscriptomic therapies for mitochondrial diseases.
7-Deazaguanines in DNA: functional and structural elucidation of a DNA modification system
Authors: Gedara Samanthi Herath , Wood Evan , Gustafson Andrew , Liang Cui , Hung Shr-Hau , Savage Joshua , Phan Phuc , Luthra Amit , de Crécy-Lagard Valérie , Dedon Peter , Swairjo Manal A , Iwata-Reuyl Dirk 
Published: March 2023

Abstract
The modified nucleosides 2′-deoxy-7-cyano- and 2′-deoxy-7-amido-7-deazaguanosine (dPreQ0 and dADG, respectively) recently discovered in DNA are the products of the bacterial queuosine tRNA modification pathway and the dpd gene cluster, the latter of which encodes proteins that comprise the elaborate Dpd restriction–modification system present in diverse bacteria. Recent genetic studies implicated the dpdA, dpdB and dpdC genes as encoding proteins necessary for DNA modification, with dpdD–dpdK contributing to the restriction phenotype. Here we report the in vitro reconstitution of the Dpd modification machinery from Salmonella enterica serovar Montevideo, the elucidation of the roles of each protein and the X-ray crystal structure of DpdA supported by small-angle X-ray scattering analysis of DpdA and DpdB, the former bound to DNA. While the homology of DpdA with the tRNA-dependent tRNA-guanine transglycosylase enzymes (TGT) in the queuosine pathway suggested a similar transglycosylase activity responsible for the exchange of a guanine base in the DNA for 7-cyano-7-deazaguanine (preQ0), we demonstrate an unexpected ATPase activity in DpdB necessary for insertion of preQ0 into DNA, and identify several catalytically essential active site residues in DpdA involved in the transglycosylation reaction. Further, we identify a modification site for DpdA activity and demonstrate that DpdC functions independently of DpdA/B in converting preQ0-modified DNA to ADG-modified DNA.
Recovery From Nicotine Addiction: A Diffusion Model Decomposition of Value-Based Decision-Making in Current Smokers and Ex-smokers
Authors: Copeland Amber , Stafford Tom , Field Matt 
Published: March 2023

AbstractIntroductionA considerable number of people successfully give up tobacco smoking. In nicotine-dependent individuals, tobacco choice is determined by greater expected drug value; however, less is known about the underlying mechanisms through which people quit smoking.Aims and MethodsThis study aimed to explore whether computational parameters of value-based decision-making (VBDM) characterize recovery from nicotine addiction. Using a preregistered, between-subject design, current daily smokers (n = 51) and ex-smokers who used to smoke daily (n = 51) were recruited from the local community. Participants completed a two-alternative forced choice task in which they chose between either two tobacco-related images (in one block) or tobacco-unrelated images (in a different block). During each trial, participants pressed a computer key to select the image they rated most positively during a previous task block. To estimate evidence accumulation (EA) processes and response thresholds during the different blocks, a drift-diffusion model was fitted to the reaction time and error data.ResultsEx-smokers had significantly higher response thresholds when making tobacco-related decisions (p = .01, d = 0.45) compared to current smokers, although there were no significant group differences during tobacco-unrelated decisions. Furthermore, there were no significant group differences in EA rates when making tobacco or tobacco-unrelated decisions.ConclusionsGreater cautiousness when making value-based decisions about tobacco-related cues characterized recovery from nicotine addiction.ImplicationsThe number of people dependent on nicotine has decreased steadily during the past decade; however, the mechanisms that underlie recovery are currently less well understood. The present study applied advances in the measurement of value-based choice. The aim was to explore whether the internal processes that underpin VBDM discriminate current daily tobacco smokers from ex-tobacco smokers who used to smoke daily. Findings revealed that recovery from nicotine addiction was characterized by higher response thresholds when making value-based decisions about tobacco-related cues; this may serve as a novel target for treatment interventions that focus on helping people to stop smoking.
Effects of very low-carbohydrate ketogenic diets on lipid profiles in normal-weight (body mass index &lt; 25 kg/m2) adults: a meta-analysis
Authors: Joo Minjin , Moon Sumin , Lee Young Seo , Kim Myeong Gyu 
Published: March 2023

Abstract

Context
Very low-carbohydrate diets or ketogenic diets (KDs) have garnered attention for weight loss in patients with overweight or obesity as well as for normal-weight adults, yet the adverse effects of KDs, such as dyslipidemia in normal-weight adults, have not been studied extensively.

Objective
This meta-analysis aimed to identify the effects of KDs on the lipid profile in normal-weight (body mass index [BMI] &lt; 25 kg/m2) adults from randomized controlled trials.

Data Sources
PubMed and Embase databases were searched on November 21, 2021, using search terms representing KDs and lipid profiles. Two researchers independently screened articles according to PICOS inclusion criteria.

Data Extraction
General study information, dietary data, and lipid profiles were extracted from eligible studies. Risk of bias was assessed using the Cochrane risk of bias 2 tool.

Data Analysis
Fixed- or random-effects meta-analysis was performed to estimate the effects of KDs on total cholesterol (TC), high-density lipoprotein-cholesterol (HDL-C), low-density lipoprotein-cholesterol (LDL-C), triglycerides, apolipoprotein A (apoA), and apolipoprotein B (apoB), considering heterogeneity across studies. The certainty of evidence was assessed using the GRADE (Grading of Recommendations, Assessment, Development and Evaluation) approach.

Results
Three studies were selected for meta-analysis. A KD significantly increased TC by 1.47 mmol/L (95%CI, 0.72–2.22 mmol/L), LDL-C by 1.08 mmol/L (95%CI, 0.37–1.79 mmol/L), and apoB by 0.35 g/L (95%CI, 0.06–0.65 g/L). In addition, a KD significantly increased HDL-C by 0.35 mmol/L (95%CI, 0.27–0.42 mmol/L) and apoA by 0.34 g/L (95%CI, 0.28–0.41 g/L) compared with control diets. Triglyceride levels were not significantly different between KDs and control diets (P = 0.63).

Conclusion
This study suggests unfavorable effects of KDs on TC and LDL-C in normal-weight adults. Although an increase in HDL-C can compensate for unfavorable changes in lipids, normal-weight individuals should consider the risk of hypercholesterolemia when consuming a KD. Results for triglycerides were inconsistent.