bluuebunny/crossref_metadata_2025 huggingface dataset:
Parechovirus A Infections in Healthy Australian Children During the First 2 Years of Life: A Community-based Longitudinal Birth Cohort Study
Authors: Wang Claire Y T , Ware Robert S , Lambert Stephen B , Mhango Lebogang P , Tozer Sarah , Day Rebecca , Grimwood Keith , Bialasiewicz Seweryn
Published: August 2019

Background

Hospital-based studies identify parechovirus (PeV), primarily PeV-A3, as an important cause of severe infections in young children. However, few community-based studies have been published and the true PeV infection burden is unknown. We investigated PeV epidemiology in healthy children participating in a community-based, longitudinal birth cohort study.

Methods

Australian children (n = 158) enrolled in the Observational Research in Childhood Infectious Diseases (ORChID) study were followed from birth until their second birthday. Weekly stool and nasal swabs and daily symptom diaries were collected. Swabs were tested for PeV by reverse-transcription polymerase chain reaction and genotypes determined by subgenomic sequencing. Incidence rate, infection characteristics, clinical associations, and virus codetections were investigated.

Results

PeV was detected in 1423 of 11 124 (12.8%) and 17 of 8100 (0.2%) stool and nasal swabs, respectively. Major genotypes among the 306 infection episodes identified were PeV-A1 (47.9%), PeV-A6 (20.1%), and PeV-A3 (18.3%). The incidence rate was 144 episodes (95% confidence interval, 128–160) per 100 child-years. First infections appeared at a median age of 8 (interquartile range, 6.0–11.7) months. Annual seasonal peaks changing from PeV-A1 to PeV-A3 were observed. Infection was positively associated with age ≥6 months, summer season, nonexclusive breastfeeding at age <3 months, and formal childcare attendance before age 12 months. Sole PeV infections were either asymptomatic (38.4%) or mild (32.7%), while codetection with other viruses in stool swabs was common (64.4%).

Conclusions

In contrast with hospital-based studies, this study showed that diverse and dynamically changing PeV genotypes circulate in the community causing mild or subclinical infections in children.

Parechovirus can cause severe illnesses in children. However, studies focus mainly on hospitalized populations. True disease burden in the community remains largely unknown. From our community-based cohort, we found diverse parechovirus genotypes in the community, causing mild or subclinical infections in children.

Clinical Trials Registration

NCT01304914.
Intranasal desmopressin reduces renal biopsy-related bleeding and serum sodium levels in patients with reduced renal function
Authors: Rao Namrata S , Chandra Abhilash
Published: August 2019

Background

The use of desmopressin in preventing renal biopsy-related bleeding is not established and its effects on serum sodium levels are not well studied. The study aimed to compare the bleeding complication rates between the groups with and without desmopressin use prebiopsy and to observe the effect of desmopressin on postbiopsy serum sodium levels.

Methods

In this single-center, prospective and retrospective interventional study, from June 2018 onwards, patients with serum creatinine >132.6 μmol/L but not on dialysis and undergoing ultrasound-assisted needle-guided renal biopsy received 150 μg of desmopressin (D-amino D-arginine vasopressin (DDAVP)) (Group II). Data from patients from June 2017 to May 2018 were included in Group I in whom desmopressin was not used. Bleeding complications were monitored by clinical and ultrasound surveillance. Serum sodium levels were checked prior to and 24 h following desmopressin in Group II.

Results

A total of 194 patients were included in the study: 105 in Group I and 89 in Group II. Group II had lower overall minor bleeding complications and perinephric hematomas than Group I (15.7% versus 31.4%, 14% versus 27% and 7.8% versus 19% in Group II and Group I, respectively, with P < 0.05). Not using desmopressin and female sex were significant predictors for overall risk of bleeding on multivariate logistic regression. Serum sodium levels fell in 94% of patients in Group II. Lower prebiopsy serum sodium, higher estimated glomerular function rate and higher spot urine sodium values were associated with a greater decrease in serum sodium after desmopressin.

Conclusion

Intranasal desmopressin reduces bleeding complications during renal biopsies performed in patients with reduced renal function not requiring dialysis, albeit with a risk of developing hyponatremia.
Enhanced E. coli LF82 Translocation through the Follicle-associated Epithelium in Crohn’s Disease is Dependent on Long Polar Fimbriae and CEACAM6 expression, and Increases Paracellular Permeability
Authors: Keita Åsa V , Alkaissi Lina Yakymenko , Holm Elin B , Heil Stéphanie D S , Chassaing Benoit , Darfeuille-Michaud Arlette , McKay Derek M , Söderholm Johan D
Published: August 2019

Background and Aims

Patients with Crohn’s disease [CD] harbour an increased number of adherent-invasive E. coli [AIEC]. The strain LF82, identified in the ileal mucosa of CD patients, has been extensively studied for pathogenic mechanisms. However, understanding of the interaction of LF82 with the intestinal mucosa of CD patients is lacking.

Methods

Here, we investigated the importance of long polar fimbriae [LPF] type 1 pili and the carcinoembryonic antigen-related cell-adhesion molecule 6 [CEACAM6] for translocation of LF82 in an in vitro model of follicle-associated epithelium [FAE], and in the FAE and villus epithelium [VE] of patients with CD and controls, using Ussing chambers.

Results

Significantly greater LF82 passage occurred in the FAE model compared with in the VE Caco-2cl1 mono-culture. Moreover, bacterial translocation was inhibited by either LPF disruption or pre-incubation with anti-CEACAM6 antibody. Tissue mounted in Ussing chambers showed significantly higher LF82 passage in FAE from patients with CD compared with control FAE, that was diminished in LF82 lacking LPF and by blocking host CEACAM6. Interestingly, addition of LF82 to the CD FAE tissues significantly increased paracellular permeability [of 51Chromium-EDTA] compared with baseline, and the increase was inhibited by anti-CEACAM6. Immunofluorescence and immunoblots showed higher expression of CEACAM6 in FAE of patients with CD compared with in FAE from controls.

Conclusions

These data suggest that the FAE of CD patients is a site of vulnerability for invasion by LF82 via a mechanism that requires both bacterial LPF and host CEACAM6. Further, LF82 has the ability to increase paracellular passage through the FAE of patients with CD. These data can help define novel therapeutic targets in CD for the prevention of clinical recurrence.
Clonal haematopoiesis in patients with degenerative aortic valve stenosis undergoing transcatheter aortic valve implantation
Authors: Mas-Peiro Silvia , Hoffmann Jedrzej , Fichtlscherer Stephan , Dorsheimer Lena , Rieger Michael A , Dimmeler Stefanie , Vasa-Nicotera Mariuca , Zeiher Andreas M
Published: August 2019

Aims

Clonal haematopoiesis of indeterminate potential (CHIP), defined as the presence of an expanded somatic blood cell clone without other haematological abnormalities, was recently shown to increase with age and is associated with coronary artery disease and calcification. The most commonly mutated CHIP genes, DNMT3A and TET2, were shown to regulate inflammatory potential of circulating leucocytes. The incidence of degenerative calcified aortic valve (AV) stenosis increases with age and correlates with chronic inflammation. We assessed the incidence of CHIP and its association with inflammatory blood cell phenotypes in patients with AV stenosis undergoing transfemoral aortic valve implantation (TAVI).

Methods and results

Targeted amplicon sequencing for DNMT3A and TET2 was performed in 279 patients with severe AV stenosis undergoing TAVI. Somatic DNMT3A- or TET2-CHIP-driver mutations with a VAF ≥ 2% were detected in 93 out of 279 patients (33.3%), with an age-dependent increase in the incidence from 25% (55–69 years) to 52.9% (90–100 years). Patients with DNMT3A- or TET2-CHIP-driver mutations did not differ from patients without such mutations in clinical parameters, concomitant atherosclerotic disease, blood cell counts, inflammatory markers, or procedural characteristics. However, patients with DNMT3A- or TET2-CHIP-driver mutations had a profoundly increased medium-term all-cause mortality following successful TAVI. Differential myeloid and T-cell distributions revealed pro-inflammatory T-cell polarization in DNMT3A-mutation carriers and increased pro-inflammatory non-classical monocytes in TET2-mutation carriers.

Conclusion

This is the first study to show that acquired somatic mutations in the most commonly mutated CHIP-driver genes occur frequently in patients with severe degenerative AV stenosis, are associated with increased pro-inflammatory leucocyte subsets, and confer a profound increase in mortality following successful TAVI.
Gene Fusions Derived by Transcriptional Readthrough are Driven by Segmental Duplication in Human
Authors: McCartney Ann M , Hyland Edel M , Cormican Paul , Moran Raymond J , Webb Andrew E , Lee Kate D , Hernandez-Rodriguez Jessica , Prado-Martinez Javier , Creevey Christopher J , Aspden Julie L , McInerney James O , Marques-Bonet Tomas , O’Connell Mary J
Published: August 2019

Gene fusion occurs when two or more individual genes with independent open reading frames becoming juxtaposed under the same open reading frame creating a new fused gene. A small number of gene fusions described in detail have been associated with novel functions, for example, the hominid-specific PIPSL gene, TNFSF12, and the TWE-PRIL gene family. We use Sequence Similarity Networks and species level comparisons of great ape genomes to identify 45 new genes that have emerged by transcriptional readthrough, that is, transcription-derived gene fusion. For 35 of these putative gene fusions, we have been able to assess available RNAseq data to determine whether there are reads that map to each breakpoint. A total of 29 of the putative gene fusions had annotated transcripts (9/29 of which are human-specific). We carried out RT-qPCR in a range of human tissues (placenta, lung, liver, brain, and testes) and found that 23 of the putative gene fusion events were expressed in at least one tissue. Examining the available ribosome foot-printing data, we find evidence for translation of three of the fused genes in human. Finally, we find enrichment for transcription-derived gene fusions in regions of known segmental duplication in human. Together, our results implicate chromosomal structural variation brought about by segmental duplication with the emergence of novel transcripts and translated protein products.
The perioperative period: a critical yet neglected time window for reducing the recurrence risk of endometriosis?
Authors: Guo Sun-Wei , Martin Dan C
Published: August 2019

While surgery is commonly the management of symptomatic endometriosis when patients do not respond to medical or supportive therapy, recurrence after surgery poses a serious challenge, and repeat surgery increases the risk of premature ovarian failure, adhesion and organ injury. Conceivably, the recurrent endometriotic lesions could arise from minimal residual lesions (MRLs) or from de novo lesions. However, several lines of evidence suggest that the former is more likely. So far, most, if not all, efforts to combat recurrence have been focused on postoperative medication of hormonal drugs to reduce recurrence risk through lesional dormancy and possibly atrophy. However, the perioperative period may exert a disproportionally high impact on the risk of recurrence; it is likely to be amendable for possible intervention but has been generally neglected. Indeed, many perioperative factors are known to or conceivably could facilitate the recurrence of endometriosis through the suppression of cell-mediated immunity due to the activation of adrenergic signaling and the release of prostaglandins. Perioperative use of β-blockers and/or nuclear factor κB/jCycloxygenase 2 (NF-κB/COX-2) inhibitors may boost the cell-mediated immunity suppressed by surgery, resulting in the partial or even complete removal of MRLs and reduced recurrence risk. This is both biologically plausible and supported by a recent experimental study. We call for more research on possible perioperative interventions to reduce the recurrence risk of endometriosis. The potential payoff might be a substantial reduction in the risk of recurrence and cost when compared with the traditional approach of postoperative intervention.
Generalizations of Stillman’s Conjecture via Twisted Commutative Algebra
Authors: Erman Daniel , Sam Steven V , Snowden Andrew
Published: August 2019

Combining recent results on Noetherianity of twisted commutative algebras by Draisma and the resolution of Stillman’s conjecture by Ananyan–Hochster, we prove a broad generalization of Stillman’s conjecture. Our theorem yields an array of boundedness results in commutative algebra that only depend on the degrees of the generators of an ideal and not the number of variables in the ambient polynomial ring.
Establishment of a Seronegative Occult Infection With an Active Hepatitis B Virus Reservoir Enriched of Vaccine Escape Mutations in a Vaccinated Infant After Liver Transplantation
Authors: Salpini Romina , Pietrobattista Andrea , Piermatteo Lorenzo , Basso Maria Sole , Bellocchi Maria C , Liccardo Daniela , Carioti Luca , Francalanci Paola , Aragri Marianna , Alkhatib Mohammed , Scutari Rossana , Candusso Manila , Ciotti Marco , Svicher Valentina
Published: August 2019

We describe the establishment of a seronegative occult hepatitis B virus (HBV) infection (OBI) in a successfully vaccinated infant who underwent liver transplantation from an donor positive for antibody to hepatitis B core antigen (anti-HBc). The use of highly sensitive droplet digital polymerase chain reaction assays revealed a not negligible and transcriptionally active intrahepatic HBV reservoir (circular covalently closed DNA, relaxed circular DNA, and pregenomic RNA: 5.6, 2.4, and 1.1 copies/1000 cells, respectively), capable to sustain ongoing viral production and initial liver damage. Next-generation sequencing revealed a peculiar enrichment of hepatitis B surface antigen vaccine-escape mutations that could have played a crucial role in OBI transmission. This clinical case highlights the pathobiological complexity and the diagnostic challenges underlying OBI.
Contextual factors affecting the integration of community health workers into the health system in Limpopo Province, South Africa
Authors: Jobson Geoffrey , Naidoo Nireshni , Matlakala Nthabiseng , Marincowitz Gert , Railton Jean , McIntyre James A , Struthers Helen E , Peters Remco P H
Published: August 2019

Background

Community health workers (CHWs) are an essential cadre in the health systems of many low- and middle-income countries. These workers provide a wide variety of services and are key to ongoing processes of task shifting within human immunodeficiency virus programmes in particular. Ward-based outreach teams (WBOTs) are South Africa’s latest iteration of the CHW programme and have been introduced as part of the National Department of Health’s Primary Health Care Re-engineering programme.

Methods

In order to assess the perceived effectiveness of the WBOTs in supporting the ongoing rollout of antiretroviral therapy, tuberculosis care and patient support, we conducted a qualitative investigation focusing on the perceived successes and challenges of the programme among CHWs, community leaders, healthcare workers and community members in the Mopani district, Limpopo province, South Africa.

Results

The CHW programme operates across these contexts, each associated with its own set of challenges and opportunities.

Conclusions

While these challenges may be interrelated, a contextual analysis provides a useful means of understanding the programme’s implementation as part of ongoing decision-making processes.
How to Investigate the Origins of Novelty: Insights Gained from Genetic, Behavioral, and Fitness Perspectives
Authors: Martin C H , McGirr J A , Richards E J , St. John M E
Published: August 2019

Synopsis

Biologists are drawn to the most extraordinary adaptations in the natural world, often referred to as evolutionary novelties, yet rarely do we understand the microevolutionary context underlying the origins of novel traits, behaviors, or ecological niches. Here we discuss insights gained into the origins of novelty from a research program spanning biological levels of organization from genotype to fitness in Caribbean pupfishes. We focus on a case study of the origins of novel trophic specialists on San Salvador Island, Bahamas and place this radiation in the context of other rapid radiations. We highlight questions that can be addressed about the origins of novelty at different biological levels, such as measuring the isolation of novel phenotypes on the fitness landscape, locating the spatial and temporal origins of adaptive variation contributing to novelty, detecting dysfunctional gene regulation due to adaptive divergence, and connecting behaviors with novel traits. Evolutionary novelties are rare, almost by definition, and we conclude that integrative case studies can provide insights into this rarity relative to the dynamics of adaptation to more common ecological niches and repeated parallel speciation, such as the relative isolation of novel phenotypes on fitness landscapes and the transient availability of ecological, genetic, and behavioral opportunities.
A Phylogenetic Analysis of the Dirt Ants, Basiceros (Formicidae: Myrmicinae): Inferring Life Histories Through Morphological Convergence
Authors: Probst Rodolfo S , Wray Brian D , Moreau Corrie S , Brandão Carlos R F
Published: August 2019

Ants of the genus Basiceros Schulz, 1906 are elusive species known only from Neotropical rainforests. Little information is available regarding their natural history, and nothing is known about the phylogenetic relationships among species within the genus. The genus has been the subject of some controversy regarding generic delimitation but is currently a member of the ‘Basiceros-genus group’ following recent classification changes. For mouthparts, labral and mandibular morphologies present considerable variation in the Basiceros-genus group, likely a result of adaptive evolution. In Basiceros, those differences can be observed in the labrum shape and the various degrees of development of the labral cleft and the clypeomandibular space. Here, in an attempt to illuminate the evolution of the group, species boundaries are tested for Basiceros. The evolutionary relationships of its species are investigated using molecular and morphological data. Bayesian inference and maximum likelihood analyses of a molecular dataset consisting of up to nine genes (three mitochondrial, six nuclear) and including samples from multiple populations of all known Basiceros taxa recovered the monophyly of the genus and of its species, with two well-resolved internal clades: the singularis clade and the disciger clade. Focusing on the female castes of Basiceros, an ancestral state reconstruction is presented for mandibles and labrum morphology. The results suggest that the labrum and clypeomandibular morphologies are highly labile, although phylogenetically important characters in the genus. Mouthpart traits indicate a strong correlated evolutionary history potentially associated with specialized feeding habits.
Civilians, Control, and Collaboration during Civil Conflict
Authors: Condra Luke N , Wright Austin L
Published: August 2019

What affects civilian collaboration with armed actors during civil war? While theory and evidence confirm that harm by armed actors influences when and with whom civilians collaborate, we argue that collaboration is also a function of civilians’ perceptions of armed actors’ efforts to minimize collateral casualties. We test this argument using a series of nationwide surveys of Afghan civilians conducted quarterly between 2013 and 2015. Our data record civilian willingness to report roadside bombs to government authorities and perceptions of government and Taliban efforts to minimize civilian harm. Civilians are less (more) willing to collaborate with the government when they perceive the government (Taliban) carelessly using force, even after accounting for political sentiment, local security conditions, and a range of additional confounding factors. Moreover, our evidence suggests that perceived carelessness in the rival’s area of control influences collaboration. We discuss how these empirical results inform broader literatures on collaboration, conquest, occupation, and control.
Consumer health information and question answering: helping consumers find answers to their health-related information needs
Authors: Demner-Fushman Dina , Mrabet Yassine , Ben Abacha Asma
Published: August 2019

Objective

Consumers increasingly turn to the internet in search of health-related information; and they want their questions answered with short and precise passages, rather than needing to analyze lists of relevant documents returned by search engines and reading each document to find an answer. We aim to answer consumer health questions with information from reliable sources.

Materials and Methods

We combine knowledge-based, traditional machine and deep learning approaches to understand consumers’ questions and select the best answers from consumer-oriented sources. We evaluate the end-to-end system and its components on simple questions generated in a pilot development of MedlinePlus Alexa skill, as well as the short and long real-life questions submitted to the National Library of Medicine by consumers.

Results

Our system achieves 78.7% mean average precision and 87.9% mean reciprocal rank on simple Alexa questions, and 44.5% mean average precision and 51.6% mean reciprocal rank on real-life questions submitted by National Library of Medicine consumers.

Discussion

The ensemble of deep learning, domain knowledge, and traditional approaches recognizes question type and focus well in the simple questions, but it leaves room for improvement on the real-life consumers’ questions. Information retrieval approaches alone are sufficient for finding answers to simple Alexa questions. Answering real-life questions, however, benefits from a combination of information retrieval and inference approaches.

Conclusion

A pilot practical implementation of research needed to help consumers find reliable answers to their health-related questions demonstrates that for most questions the reliable answers exist and can be found automatically with acceptable accuracy.
The Parentage Disruption: A Comparative Approach
Authors: Kessler Guillaume
Published: August 2019

The bionormative and heteronormative models of parentage has been challenged by multiple factors: a cultural shift, which has led to the decline of marriage and the development of cohabitation, a technological evolution, which has made it possible to develop new reproductive technologies, and a legal change that has led to the recognition of same-sex relationships. However, the extent of this development has not yet been fully assessed. Rather than simply adapting the rules designed according to an outdated model, it would be better to break with it permanently. This article proposes to build a new system based on intent and care, on the basis of case law and doctrinal proposals from several countries. Drawing from the best interests of the child standard, it operates a distinction between the status of parent and progenitor: whatever the circumstances of the birth (natural procreation, adoption, assisted reproduction technology, or surrogacy) and the nature of the parents' relationship (same-sex or heterosexual, married or unmarried, engaged in a romantic relationship or not), parentage would be based on a formal statement and the question of genetics limited to the determination of identity and the right to know one's origins.
Reproduction of marginality: The labour market position of unemployed foreign citizens during economic recession in Iceland
Authors: Wojtyńska Anna , Skaptadóttir Unnur Dís
Published: August 2019

Following the economic crash in 2008, many migrants in Iceland lost their jobs and experienced deteriorating working conditions. In 2011, four years after the onset of the recession, the unemployment rates among the foreign population remained significantly higher than among Icelanders. In this article, we discuss experiences of unemployed migrants concerning their changed position on the labour market in order to highlight the different mechanisms of labour market exclusion. On the basis of research among registered unemployed foreign citizens, we analyse the main reasons for their difficulties in finding new employment. The main obstacles as reported by survey respondents and focus groups participants were limited knowledge of Icelandic, increased reluctance among Icelandic employers to hire foreigners and insufficient social networking with the native population.
Modelling the Effects of Dark Matter Substructure on Globular Cluster Evolution with the Tidal Approximation
Authors: Webb Jeremy J , Bovy Jo , Carlberg Raymond G , Gieles Mark
Published: August 2019

We present direct N-body simulations of tidally filling 30,000 M⊙ star clusters orbiting between 10 kpc and 100 kpc in galaxies with a range of dark matter substructure properties. The time-dependent tidal force is determined based on the combined tidal tensor of the galaxy’s smooth and clumpy dark matter components, the latter of which causes fluctuations in the tidal field that can heat clusters. The strength and duration of these fluctuations are sensitive to the local dark matter density, substructure fraction, sub-halo mass function, and the sub-halo mass-size relation. Based on the cold dark matter framework, we initially assume sub-halos are Hernquist spheres following a power-law mass function between 105 and 1011M⊙ and find that tidal fluctuations are too weak and too short to affect star cluster evolution. Treating sub-halos as point masses, to explore how denser sub-halos affect clusters, we find that only sub-halos with masses greater than 106M⊙ will cause cluster dissolution times to decrease. These interactions can also decrease the size of a cluster while increasing the velocity dispersion and tangential anisotropy in the outer regions via tidal heating. Hence increased fluctuations in the tidal tensor, especially fluctuations that are due to low-mass halos, do not necessarily translate into mass loss. We further conclude that the tidal approximation can be used to model cluster evolution in the tidal fields of cosmological simulations with a minimum cold dark matter sub-halo mass of 106M⊙, as the effect of lower-mass sub-halos on star clusters is negligible.
Arecibo 4.5/1.4/0.33-GHz polarimetric single-pulse emission survey
Authors: Olszanski Timothy E E , Mitra Dipanjan , Rankin Joanna M
Published: August 2019

We report on an Arecibo 4.5-GHz polarimetric single-pulse survey of the brightest pulsars at high frequency within its sky. The high-frequency profiles are accompanied by a collection of both previously published and unpublished high quality 1.4- and 0.33-GHz observations. Here our analyses and discussion primarily involve the average and statistical properties of the 46 pulsars polarimetric pulse sequences, profile classification and frequency evolution, and polarimetric profiles and peak-occurrence histograms. In most cases both the fractional linear polarization and profile widths decrease with frequency as expected, but there are some exceptions. Similarly, we were able to review and/or extend the profile classifications for this population of pulsars and work out their beaming characteristics quantitatively showing that almost all show properties compatible with the core/double-cone emission beam model. The entirety of these observations’ average profiles are accessible for download.
Studying the morphology of reionization with the triangle correlation function of phases
Authors: Gorce Adélie , Pritchard Jonathan R
Published: August 2019

We present a new statistical tool, called the triangle correlation function (TCF), inspired by the earlier work of Obreschkow et al. It is derived from the three-point correlation function and aims to probe the characteristic scale of ionized regions during the epoch of reionization from 21cm interferometric observations. Unlike most works, which focus on power spectrum, i.e. amplitude information, our statistic is based on the information we can extract from the phases of the Fourier transform of the ionization field. In this perspective, it may benefit from the well-known interferometric concept of closure phases. We find that this statistical estimator performs very well on simple ionization fields. For example, with well-defined fully ionized discs, there is a peaking scale, which we can relate to the radius of the ionized bubbles. We explore the robustness of the TCF when observational effects such as angular resolution and noise are considered. We also get interesting results on fields generated by more elaborate simulations such as 21CMFAST. Although the variety of sources and ionized morphologies in the early stages of the process make its interpretation more challenging, the nature of the signal can tell us about the stage of reionization. Finally, and in contrast to other bubble size distribution algorithms, we show that the TCF can resolve two different characteristic scales in a given map.
Probing the origin of stellar flares on M dwarfs using TESS data sectors 1–3
Authors: Doyle L , Ramsay G , Doyle J G , Wu K
Published: August 2019

Detailed studies of the Sun have shown that sunspots and solar flares are closely correlated. Photometric data from Kepler/K2 has allowed similar studies to be carried out on other stars. Here, we utilize Transiting Exoplanet Survey Satellite (TESS) photometric 2-min cadence of 167 low-mass stars from Sectors 1 to 3 to investigate the relationship between star-spots and stellar flares. From our sample, 90 per cent show clear rotational modulation likely due to the presence of a large, dominant star-spot and we use this to determine a rotational period for each star. Additionally, each low-mass star shows one or more flares in its light curve and using Gaia Data Release 2 parallaxes and SkyMapper magnitudes we can estimate the energy of the flares in the TESS band-pass. Overall, we have 1834 flares from the 167 low-mass stars with energies from 6.0 × 1029 to 2.4 × 1035 erg. We find none of the stars in our sample show any preference for rotational phase, suggesting the lack of a correlation between the large, dominant star-spot, and flare number. We discuss this finding in greater detail and present further scenarios to account for the origin of flares on these low-mass stars.
K2 observations of the sdBV + dM/bd binaries PHL 457 and EQ Psc
Authors: Baran A S , Telting J H , Jeffery C S , Østensen R H , Vos J , Reed M D , Vŭcković M
Published: August 2019

We present an analysis of two pulsating subdwarf B stars PHL 457 and EQ Psc observed during the K2 mission. The K2 light curves of both stars show variation consistent with irradiation of a cooler companion by the hot subdwarf. They also show higher frequency oscillations consistent with pulsation. Using new spectroscopic data, we measured the radial velocity, effective temperature, surface gravity, and helium abundance of both hot subdwarfs as a function of orbital phase. We confirm the previously published spectroscopic orbit of PHL 457, and present the first spectroscopic orbit of EQ Psc. The orbital periods are 0.313 and 0.801 d, respectively. For EQ Psc, we find a strong correlation between Teff and orbital phase, due to contribution of light from the irradiated companion. We calculated amplitude spectra, identified significant pulsation frequencies, and searched for multiplets and asymptotic period spacings. By means of multiplets and period spacing, we identified the degrees of several pulsation modes in each star. The g-mode multiplets indicate subsynchronous core rotation with periods of 4.6 d (PHL 457) and 9.4 d (EQ Psc). We made spectral energy disctribution (SED) fits of PHL 457 and EQ Psc using available broad-band photometry and Gaia data. While the SED of PHL 457 shows no evidence of a cool companion, the SED for EQ Psc clearly shows an infrared (IR) access consistent with a secondary with a temperature of about 6800 K and a radius of 0.23 R⊙. This is the first detection of an IR access in any sdB + dM binary.
There is no magnetic braking catastrophe: low-mass star cluster and protostellar disc formation with non-ideal magnetohydrodynamics
Authors: Wurster James , Bate Matthew R , Price Daniel J
Published: August 2019

We present results from the first radiation non-ideal magnetohydrodynamics (MHD) simulations of low-mass star cluster formation that resolve the fragmentation process down to the opacity limit. We model 50 M⊙ turbulent clouds initially threaded by a uniform magnetic field with strengths of 3, 5 10, and 20 times the critical mass-to-magnetic flux ratio, and at each strength, we model both an ideal and non-ideal (including Ohmic resistivity, ambipolar diffusion, and the Hall effect) MHD cloud. Turbulence and magnetic fields shape the large-scale structure of the cloud, and similar structures form regardless of whether ideal or non-ideal MHD is employed. At high densities (106 ≲ nH ≲ 1011 cm−3), all models have a similar magnetic field strength versus density relation, suggesting that the field strength in dense cores is independent of the large-scale environment. Albeit with limited statistics, we find no evidence for the dependence of the initial mass function on the initial magnetic field strength, however, the star formation rate decreases for models with increasing initial field strengths; the exception is the strongest field case where collapse occurs primarily along field lines. Protostellar discs with radii ≳ 20 au form in all models, suggesting that disc formation is dependent on the gas turbulence rather than on magnetic field strength. We find no evidence for the magnetic braking catastrophe, and find that magnetic fields do not hinder the formation of protostellar discs.
SDSS-IV MaNGA: environmental dependence of gas metallicity gradients in local star-forming galaxies
Authors: Lian Jianhui , Thomas Daniel , Li Cheng , Zheng Zheng , Maraston Claudia , Bizyaev Dmitry , Lane Richard R , Yan Renbin
Published: August 2019

Within the standard model of hierarchical galaxy formation in a Λ cold dark matter universe, the environment of galaxies is expected to play a key role in driving galaxy formation and evolution. In this paper, we investigate whether and how the gas metallicity and the star formation surface density (ΣSFR) depend on galaxy environment. To this end, we analyse a sample of 1162 local, star-forming galaxies from the galaxy survey Mapping Nearby Galaxies at APO (MaNGA). Generally, both parameters do not show any significant dependence on environment. However, in agreement with previous studies, we find that low-mass satellite galaxies are an exception to this rule. The gas metallicity in these objects increases while their ΣSFR decreases slightly with environmental density. The present analysis of MaNGA data allows us to extend this to spatially resolved properties. Our study reveals that the gas metallicity gradients of low-mass satellites flatten and their ΣSFR gradients steepen with increasing environmental density. By extensively exploring a chemical evolution model, we identify two scenarios that are able to explain this pattern: metal-enriched gas accretion or pristine gas inflow with varying accretion time-scales. The latter scenario better matches the observed ΣSFR gradients, and is therefore our preferred solution. In this model, a shorter gas accretion time-scale at larger radii is required. This suggests that ‘outside–in quenching’ governs the star formation processes of low-mass satellite galaxies in dense environments.
Comet C/2018 V1 (Machholz–Fujikawa–Iwamoto): dislodged from the Oort Cloud or coming from interstellar space?
Authors: de la Fuente Marcos C , de la Fuente Marcos R
Published: August 2019

The chance discovery of the first interstellar minor body, 1I/2017 U1 (‘Oumuamua), indicates that we may have been visited by such objects in the past and that these events may repeat in the future. Unfortunately, minor bodies following nearly parabolic or hyperbolic paths tend to receive little attention: over 3/4 of those known have data-arcs shorter than 30 d and, consistently, rather uncertain orbit determinations. This fact suggests that we may have observed interstellar interlopers in the past, but failed to recognize them as such due to insufficient data. Early identification of promising candidates by using N-body simulations may help in improving this situation, triggering follow-up observations before they leave the Solar system. Here, we use this technique to investigate the pre- and post-perihelion dynamical evolution of the slightly hyperbolic comet C/2018 V1 (Machholz–Fujikawa–Iwamoto) to understand its origin and relevance within the context of known parabolic and hyperbolic minor bodies. Based on the available data, our calculations suggest that although C/2018 V1 may be a former member of the Oort Cloud, an origin beyond the Solar system cannot be excluded. If extrasolar, it might have entered the Solar system from interstellar space at low relative velocity with respect to the Sun. The practical feasibility of this alternative scenario has been assessed within the kinematic context of the stellar neighbourhood of the Sun, using data from Gaia second data release, and two robust solar sibling candidates have been identified. Our results suggest that comets coming from interstellar space at low heliocentric velocities may not be rare.
Lack of close-in, massive planets of main-sequence A-type stars from Kepler
Authors: Sabotta Silvia , Kabath Petr , Korth Judith , Guenther Eike W , Dupkala Daniel , Grziwa Sascha , Klocova Tereza , Skarka Marek
Published: August 2019

Some theories of planet formation and evolution predict that intermediate-mass stars host more hot Jupiters than Sun-like stars, others reach the conclusion that such objects are very rare. By determining the frequencies of those planets we can test those theories.

Based on the analysis of Kepler light curves it has been suggested that about 8 per cent of the intermediate-mass stars could have a close-in substellar companion. This would indicate a very high frequency of such objects. Up to now, there was no satisfactory proof or test of this hypothesis.

We studied a previously reported sample of 166 planet candidates around main-sequence A-type stars in the Kepler field. We selected six of them for which we obtained extensive long-term radial velocity measurements with the Alfred Jensch 2-m telescope in Tautenburg and the Perek 2-m telescope in Ondřejov. We derive upper limits of the masses of the planet candidates. We show that we are able to detect this kind of planet with our telescopes and their instrumentation using the example of MASCARA-1 b.

With the transit finding pipeline Extrans we confirm that there is no single transit event from a Jupiter-like planet in the light curves of those 166 stars. We furthermore determine that the upper limit for the occurrence rate of close-in, massive planets for A-type stars in the Kepler sample is around 0.75 per cent.

We argue that there is currently little evidence for a very high frequency of close-in, massive planets of intermediate-mass stars.
On the nature of radio filaments near the Galactic Centre
Authors: Barkov Maxim V , Lyutikov Maxim
Published: August 2019

We suggest that narrow, long radio filaments near the Galactic Centre arise as kinetic jets – streams of high-energy particles escaping from ram pressure confined pulsar wind nebulae (PWNe). The reconnection between the PWN and interstellar magnetic field allows pulsar wind particles to escape, creating long narrow features. They are the low-frequency analogues of kinetic jets seen around some fast-moving pulsars, such as The Guitar and The Lighthouse PWNe. The radio filaments trace a population of pulsars also responsible for the Fermi GeV excess produced by the Inverse Compton scattering by the pulsar wind particles. The magnetic flux tubes are stretched radially by the large-scale Galactic winds. In addition to PWNe accelerated particles can be injected at supernovae remnants. The model predicts variations of the structure of the largest filaments on scales of ∼dozens of years – smaller variations can occur on shorter time-scales. We also encourage targeted observations of the brightest sections of the filaments and of the related unresolved point sources in search of the powering PWNe and pulsars.
Unexpected behavior of DNA polymerase Mu opposite template 8-oxo-7,8-dihydro-2′-guanosine
Authors: Kaminski Andrea M , Chiruvella Kishore K , Ramsden Dale A , Kunkel Thomas A , Bebenek Katarzyna , Pedersen Lars C
Published: August 2019

DNA double-strand breaks (DSBs) resulting from reactive oxygen species generated by exposure to UV and ionizing radiation are characterized by clusters of lesions near break sites. Such complex DSBs are repaired slowly, and their persistence can have severe consequences for human health. We have therefore probed DNA break repair containing a template 8-oxo-7,8-dihydro-2′-guanosine (8OG) by Family X Polymerase μ (Pol μ) in steady-state kinetics and cell-based assays. Pol μ tolerates 8OG-containing template DNA substrates, and the filled products can be subsequently ligated by DNA Ligase IV during Nonhomologous end-joining. Furthermore, Pol μ exhibits a strong preference for mutagenic bypass of 8OG by insertion of adenine. Crystal structures reveal that the template 8OG is accommodated in the Pol μ active site with none of the DNA substrate distortions observed for Family X siblings Pols β or λ. Kinetic characterization of template 8OG bypass indicates that Pol μ inserts adenosine nucleotides with weak sugar selectivity and, given the high cellular concentration of ATP, likely performs its role in repair of complex 8OG-containing DSBs using ribonucleotides.
Specificity of MYB interactions relies on motifs in ordered and disordered contexts
Authors: Millard Peter S , Weber Konrad , Kragelund Birthe B , Burow Meike
Published: August 2019

Physical interactions between members of the MYB and bHLH transcription factor (TF) families regulate many important biological processes in plants. Not all reported MYB–bHLH interactions can be explained by the known binding sites in the R3 repeat of the MYB DNA-binding domain. Noteworthy, most of the sequence diversity of MYB TFs lies in their non-MYB regions, which contain orphan small subgroup-defining motifs not yet linked to molecular functions. Here, we identified the motif mediating interaction between MYB TFs from subgroup 12 and their bHLH partners. Unlike other known MYB–bHLH interactions, the motif locates to the centre of the predicted disordered non-MYB region. We characterised the core motif, which enabled accurate prediction of previously unknown bHLH-interacting MYB TFs in Arabidopsis thaliana, and we confirmed its functional importance in planta. Our results indicate a correlation between the MYB–bHLH interaction affinity and the phenotypic output controlled by the TF complex. The identification of an interaction motif outside R3 indicates that MYB–bHLH interactions must have arisen multiple times, independently and suggests many more motifs of functional relevance to be harvested from subgroup-specific studies.
Post-transcriptional negative feedback regulation of proteostasis through the Dis3 ribonuclease and its disruption by polyQ-expanded Huntingtin
Authors: Kong Ka-Yiu Edwin , Hung Ting-Ngai Felix , Man Pui-Hei Marcus , Wong Tin-Ning , Cheng Tao , Jin Dong-Yan
Published: August 2019

When proteostasis is disrupted by stresses such as heat shock, the heat stress response will be stimulated, leading to up-regulation of molecular chaperones by transcriptional activation and mRNA stabilization for restoring proteostasis. Although the mechanisms for their transcriptional activation have been clearly defined, how chaperone mRNAs are stabilized remains largely unknown. Starting by exploring the coupling between the apparently unrelated RNA degradation and protein quality control (PQC) systems, we show that the Dis3 ribonuclease, catalytic subunit of the RNA exosome required for RNA degradation, suppresses PQC activity in unstressed cells by degrading mRNAs encoding the Hsp70 cofactors Sis1, Ydj1 and Fes1, as well as some other chaperones or PQC factors, thereby limiting their protein expression. Dis3 is stabilized through its binding to Sis1 and the Hsp70s Ssa1/2. Upon heat stress, loss of Sis1 and Ssa1/2 availability triggers Dis3 ubiquitination and degradation, leading to stabilization of those chaperone mRNAs originally targeted by Dis3. We further demonstrate that polyQ-expanded huntingtin delays Dis3 degradation during heat stress and thus hinders chaperone mRNA stabilization. Our findings not only reveal a post-transcriptional negative feedback loop for maintaining proteostasis, but also uncover a mechanism that contributes to the impaired heat stress response in Huntington's disease.
Neural substrates for anticipation and consumption of social and monetary incentives in depression
Authors: He Zhenhong , Zhang Dandan , Muhlert Nils , Elliott Rebecca
Published: August 2019

Depression has been reliably associated with abnormalities in the neural representation of reward and loss. However, most studies have focused on monetary incentives; fewer studies have considered neural representation of social incentives. A direct comparison of non-social and social incentives within the same study would establish whether responses to the different incentives are differentially affected in depression. The functional magnetic resonance imaging study presented here investigated the neural activity of individuals with subthreshold depression (SD) and healthy controls (HCs) while they participated in an incentive delay task offering two types of reward (monetary gain vs social approval) and loss (monetary loss vs social disapproval). Compared to HCs, individuals with SD showed increased subgenual anterior cingulate cortex (sgACC) activity during anticipation of social loss, whereas the response in the putamen was decreased during consumption of social gain. Individuals with SD also exhibited diminished insula responses in consuming social loss. Furthermore, positive connectivity between the insula and ventral lateral pre-frontal cortex (VLPFC) was observed in individuals with SD while negative connectivity was found in HCs when consuming social loss. These results demonstrate neural alterations in individuals with depression, specific to the processing of social incentives, mainly characterised by dysfunction within the ‘social pain network’ (sgACC, insula and VLPFC).