bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative methods for the determination of abundance of mobile prey of ghost crabs, Ocypode Weber, 1795 (Decapoda: Brachyura: Ocypodidae), a top predator on sandy shores
Authors: Yong Adeline Y P , Lim Shirley S L
Published: July 2019

Ghost crabs, OcypodeWeber, 1795 (Decapoda: Brachyura: Ocypodidae) are the top-benthic predators on sandy beaches in the sub-tropical and tropical regions around the world. They are omnivores and opportunistic feeders with varied feeding modes, such that they can exert cascading trophic effects on intertidal communities. Although there is a wealth of literature on the diet of ghost crabs based on qualitative reports of direct observation of predation, tracks/signs of feeding activities, or presence/absence data of prey items in foregut content analyses, there is hardly any quantitative analyses of food resources in the field that are available to these top predators on the sandy shore. While the abundance of immobile food resources can be ascertained by sediment sample assays, specialized sampling methods have been used for the collection and enumeration of mobile prey items. There is a need also to understand the period of foraging activity of the study species in order to track the predator-prey interaction at the appropriate time of the day. We outline three techniques suitable for the collection of prey types with different distribution, activity period and mobility: 1) surface-dwelling prey, 2) prey that burrow, and 3) prey that are capable of flying, a novel method that has not been utilized and described before.
Nuclear Humanitarianism
Authors: Chiam Madelaine , Hood Anna
Published: July 2019

In recent years, humanitarianism has been portrayed as a revolutionary new force in the anti-nuclear movement. This article challenges this progressive understanding of humanitarianism’s role in nuclear affairs by exploring how the language and concept of humanitarianism have been deployed by two states that have been deeply involved in international nuclear law projects over the last 50 years: Australia and New Zealand. It argues that contrary to popular perceptions about the radical potential of humanitarianism in nuclear affairs, the phenomenon’s track record in Australia and New Zealand is chequered. Indeed, in certain key respects, humanitarianism has impeded anti-nuclear agendas in Australia and New Zealand: first, the ambiguity inherent in the language of humanitarianism has allowed it to be deployed to support the maintenance of nuclear weapons; and secondly, humanitarianism has generated outcomes that often support and reinforce the status quo legally and structurally. The article also offers some reflections on the relationship between humanitarianism and international law in the nuclear context. Specifically, it shows how the Australian and New Zealand case studies reveal contradictory approaches to, and understandings of, humanitarianism as law.
The South America Tomato Leafminer, Tuta absoluta (Lepidoptera: Gelechiidae), Spreads Its Wings in Eastern Africa: Distribution and Socioeconomic Impacts
Authors: Aigbedion-Atalor Pascal Osa , Hill Martin P , Zalucki Myron P , Obala Francis , Idriss Gamal E , Midingoyi Soul-Kifouly , Chidege Maneno , Ekesi Sunday , Mohamed Samira Abuelgasim
Published: July 2019

Following the arrival of Tuta absoluta Meyrick in the eastern African subregion in 2012, several studies have shown numerous ecological aspects of its invasion. We investigated the impact of T. absoluta on people’s livelihoods across four counties of Kenya. Here, 200 farmers in the country were interviewed in person using semistructured questionnaires. In addition to livelihood surveys, T. absoluta distribution was mapped between 2016 and 2018 to determine its current distribution across four countries (Kenya, Sudan, Tanzania, and Uganda) in the subregion. Albeit a recent invader, T. absoluta is abundant and distributed throughout the subregion and is viewed as the worst invasive alien species of agriculturally sustainable livelihoods by tomato farmers. The arrival of T. absoluta in the subregion has resulted in livelihood losses and increased both the cost of tomato production and frequency of pesticide application. We recommend the implementation of biological control along, with other control measures in an integrated approach, against T. absoluta in the subregion, where its impact on sustainable livelihoods is serious and long-term control strategies are required to curb its detrimental effects.
Struggles for Human Rights in Health in an Age of Neoliberalism: From Civil Disobedience to Epistemic Disobedience
Authors: Yamin Alicia Ely
Published: July 2019

Like other contributors to this special issue and beyond, I believe we are at a critical inflection point in human rights and need to re-energize our work broadly to address growing economic inequality as well as inequalities based on different axes of identity. In relation to the constellation of fields involved in ‘health and human rights’ specifically—which link distinct communities with dissonant values, methods and orthodoxies—I argue that we also need to challenge ideas that are taken for granted in the fields that we are trying to transform. After setting out a personal and subjective account of why human rights-based approaches (HRBAs) are unlikely to be meaningful tools for social change as they are now generally being deployed, I suggest we collectively—scholars, practitioners and advocates—need to grapple with how to think about: (1) biomedicine in relation to the social as well as biological nature of health and well-being; and (2) conventional public health in relation to the social construction of health within and across borders and health systems. In each case, I suggest that challenging accepted truths in different disciplines, and in turn in the political economy of global health, have dramatic implications for not just theory but informing different strategies for advancing health (and social) justice through rights in practice.
HARK the SHARK: Realized Volatility Modeling with Measurement Errors and Nonlinear Dependencies
Authors: Buccheri Giuseppe , Corsi Fulvio
Published: July 2019

Despite their effectiveness, linear models for realized variance neglect measurement errors on integrated variance and exhibit several forms of misspecification due to the inherent nonlinear dynamics of volatility. We propose new extensions of the popular approximate long-memory heterogeneous autoregressive (HAR) model apt to disentangle these effects and quantify their separate impact on volatility forecasts. By combining the asymptotic theory of the realized variance estimator with the Kalman filter and by introducing time-varying HAR parameters, we build new models that account for: (i) measurement errors (HARK), (ii) nonlinear dependencies (SHAR) and (iii) both measurement errors and nonlinearities (SHARK). The proposed models are simply estimated through standard maximum likelihood methods and are shown, both on simulated and real data, to provide better out-of-sample forecasts compared to standard HAR specifications and other competing approaches.
Taxonomic revision of the long-tailed shrew, Sorex dispar Batchelder, 1911, from the Appalachian Region of North America, with the description of a new subspecies
Authors: Diersing Victor E
Published: July 2019

The long-tailed shrew, Sorex dispar Batchelder, 1911, and Gaspe shrew, S. gaspensis Anthony and Goodwin, 1924, from the Appalachian Mountains of North America have been characterized as genetically highly similar, and that one is morphologically a clinal variate of the other, i.e., there is a single species. I measured 24 characters of the skull on 196 shrews from throughout the range of the species. Geographic variation in skull shape and size was not gradual or continuous, but abrupt. These abrupt changes in morphology are associated with major water barriers, primarily the Connecticut River, middle Saint John River, and the Strait of Canso, which separates mainland Nova Scotia from Cape Breton Island. The morphological analyses presented here and previous genetic studies indicate that S. dispar and S. gaspensis are likely conspecific. Shrews with the largest skull occur from North Carolina north to Vermont and are referable to S. d. dispar with S. d. blitchi as a synonym. Shrews from New Hampshire northeast to southern New Brunswick and mainland Nova Scotia have a medium-sized skull and are referable to a new subspecies. Those from northern New Brunswick, Gaspe Peninsula of Quebec, and Cape Breton Island have a small skull and are referable to S. d. gaspensis. The skull morphology of S. d. gaspensis and the new subspecies are more similar to each other than to S. d. dispar. Results of this study differ from those of previous morphological studies because measurement error and within-group variation were reduced, which allowed for visibility of otherwise “hidden” between-group differences, or geographic variation.
Sex-Based Disparities Among Cancer Clinical Trial Participants
Authors: Ludmir Ethan B , Fuller C David , Moningi Shalini , Mainwaring Walker , Lin Timothy A , Miller Austin B , Jethanandani Amit , Espinoza Andres F , Verma Vivek , Smith Benjamin D , Smith Grace L , VanderWalde Noam A , Holliday Emma B , Guadagnolo B Ashleigh , Stinchcombe Thomas E , Jagsi Reshma , Gomez Daniel R , Minsky Bruce D , Rödel Claus , Fokas Emmanouil
Published: July 2019

Landmark investigation two decades ago demonstrated sex-based disparities among participants in cancer cooperative group trials. Although federal efforts have aimed to improve representation of female patients in government-sponsored research, less is known about sex disparities in the broader landscape of modern oncologic randomized controlled trials. Using ClinicalTrials.gov, we identified randomized controlled trials related to colorectal or lung cancer (the two most common non-sex-specific disease sites). Among the 147 included trials, the proportion of female patients enrolled on trial was on average 6.8% (95% confidence interval = −8.8% to –4.9%) less than the proportion of female patients in the population by disease site (P < .001). Whereas no statistically significant underrepresentation of women was noted within the 26 cooperative group trials, sex disparities were markedly heightened for the 121 noncooperative-group-sponsored trials. Furthermore, underrepresentation of women did not improve with time. Future efforts should therefore focus on addressing these pervasive sex-based enrollment disparities beyond cooperative group trials alone.
Root production, mortality and turnover in soil profiles as affected by clipping in a temperate grassland on the Loess Plateau
Authors: Wei Lin , Yao Pengwei , Jing Guanghua , Ye Xiefeng , Cheng Jimin
Published: July 2019

Aims

Clipping or mowing for hay, as a prevalent land-use practice, is considered to be an important component of global change. Root production and turnover in response to clipping have great implications for the plant survival strategy and grassland ecosystem carbon processes. However, our knowledge about the clipping effect on root dynamics is mainly based on root living biomass, and limited by the lack of spatial and temporal observations. The study aim was to investigate the effect of clipping on seasonal variations in root length production and mortality and their distribution patterns in different soil layers in semiarid grassland on the Loess Plateau.

Methods

Clipping was performed once a year in June to mimic the local spring livestock grazing beginning from 2014. The minirhizotron technique was used to monitor the root production, mortality and turnover rate at various soil depths (0–10, 10–20, 20–30 and 30–50 cm) in 2014 (from 30 May to 29 October) and 2015 (from 22 April to 25 October). Soil temperature and moisture in different soil layers were also measured during the study period.

Important Findings

Our results showed that: (i) Clipping significantly decreased the cumulative root production (P < 0.05) and increased the cumulative root mortality and turnover rates of the 0–50 cm soil profile for both years. (ii) Clipping induced an immediate and sharp decrease in root length production and an increase in root length mortality in all soil layers. However, with plant regrowth, root production increased and root mortality decreased gradually, with the root production at a depth of 30–50 cm even exceeding the control in September–October 2014 and April–May 2015. (iii) Clipping mainly reduced root length production and increased root length mortality in the upper 0–20 cm soil profile with rapid root turnover. However, roots at deeper soil layers were either little influenced by clipping or exhibited an opposite trend with slower turnover rate compared with the upper soil profile, leading to the downward transport of root production and living root biomass. These findings indicate that roots in deeper soil layers tend to favour higher root biomass and longer fine root life spans to maximize the water absorption efficiency under environmental stress, and also suggest that short-term clipping would reduce the amount of carbon through fine root litter into the soil, especially in the shallow soil profile.
An unusual presentation of sphenoid Candida fungal ball: a case report
Authors: Tuang Geng Ju , Zahedi Farah Dayana , Akashah Izzah , Lee Jennifer Peak Hui , Abidin Zainal Azmi Zainal
Published: July 2019

The clinical presentation of a sphenoid fungal ball (FB) is often non-specific and tends to be overlooked, particularly in hosts with an intact immune status. Rarely, potentially life-threatening complications may arise, owning its anatomical characteristics with contiguous structures. Herein, we present an unusual case of sphenoid FB complicated with orbital apex syndrome in an immunocompetent patient. The diagnosis dilemma and subsequent management are further discussed.
On the move: redox-dependent protein relocation in plants
Authors: Foyer Christine H , Baker Alison , Wright Megan , Sparkes Imogen A , Mhamdi Amna , Schippers Jos H M , Van Breusegem Frank
Published: July 2019

Some proteins move between different intracellular compartments such as the cytosol or chloroplasts and the nucleus in response to redox triggers. Redox post-translational modifications control the intercompartmental switching of proteins.
An uncertainty principle for star formation – IV. On the nature and filtering of diffuse emission
Authors: Hygate Alexander P S , Kruijssen J M Diederik , Chevance Mélanie , Schruba Andreas , Haydon Daniel T , Longmore Steven N
Published: July 2019

Diffuse emission is observed in galaxies in many tracers across the electromagnetic spectrum, including tracers of star formation, such as H α and ultraviolet (UV), and tracers of gas mass, such as carbon monoxide (CO) transition lines and the 21-cm line of atomic hydrogen (H i). Its treatment is key to extracting meaningful information from observations such as cloud-scale star formation rates. Finally, studying diffuse emission can reveal information about the physical processes taking place in the interstellar medium, such as chemical transitions and the nature of stellar feedback (through the photon escape fraction). We present a physically motivated method for decomposing astronomical images containing both diffuse emission and compact regions of interest, such as H ii regions or molecular clouds, into diffuse and compact component images through filtering in Fourier space. We have previously presented a statistical method for constraining the evolutionary timeline of star formation and mean separation length between compact star-forming regions with galaxy-scale observations. We demonstrate how these measurements are biased by the presence of diffuse emission in tracer maps and that by using the mean separation length as a critical length-scale to separate diffuse emission from compact emission, we are able to remove its biasing effect. Furthermore, this method provides, without the need for interferometry or ancillary spectral data, a measurement of the diffuse emission fraction in input tracer maps and decomposed diffuse and compact emission maps for further analysis.
Low-eccentricity migration of ultra-short-period planets in multiplanet systems
Authors: Pu Bonan , Lai Dong
Published: July 2019

Recent studies suggest that ultra-short-period planets (USPs), Earth-sized planets with sub-day periods, constitute a statistically distinct sub-sample of Kepler planets: USPs have smaller radii (1–1.4R⊕) and larger mutual inclinations with neighbouring planets than nominal Kepler planets, and their period distribution is steeper than longer period planets. We study a ‘low-eccentricity’ migration scenario for the formation of USPs, in which a low-mass planet with initial period of a few days maintains a small but finite eccentricity due to secular forcings from exterior companion planets, and experiences orbital decay due to tidal dissipation. USP formation in this scenario requires that the initial multiplanet system have modest eccentricities (≳0.1) or angular momentum deficit. During the orbital decay of the innermost planet, the system can encounter several apsidal and nodal precession resonances that significantly enhance eccentricity excitation and increase the mutual inclination between the inner planets. We develop an approximate method based on eccentricity and inclination eigenmodes to efficiently evolve a large number of multiplanet systems over Gyr time-scales in the presence of rapid (as short as ∼100 yr) secular planet–planet interactions and other short-range forces. Through a population synthesis calculation, we demonstrate that the ‘low-e migration’ mechanism can naturally produce USPs from the large population of Kepler multis under a variety of conditions, with little fine-tuning of parameters. This mechanism favours smaller inner planets with more massive and eccentric companion planets, and the resulting USPs have properties that are consistent with observations.
CRTS J035010.7 + 323230, a new eclipsing polar in the cataclysmic variable period gap
Authors: Mason Paul A , Wells Natalie K , Motsoaledi Mokhine , Szkody Paula , Gonzalez Emmanuel
Published: July 2019

We report the discovery of a new eclipsing polar, CRTS J035010.7+323230 (hereafter CRTS J0350+3232). We identified this cataclysmic variable (CV) candidate as a possible polar from its multiyear Catalina Real-Time Transient Survey (CRTS) optical light curve. Photometric monitoring of 22 eclipses in 2015 and 2017 was performed with the 2.1-m Otto Struve Telescope at McDonald Observatory. We derive an unambiguous high-precision ephemeris. Strong evidence that CRTS J0350 + 3232 is a polar comes from optical spectroscopy obtained over a complete orbital cycle using the Apache Point Observatory 3.5-m telescope. High velocity Balmer and He ii λ4686Å emission-line equivalent width ratios, structures, and variations are typical of polars and are modulated at the same period, 2.37 h (142.3 min), as the eclipse to within uncertainties. The spectral energy distribution and luminosity is found to be comparable to that of AM Herculis. Pre-eclipse dips in the light curve show evidence for stream accretion. We derive the following tentative binary and stellar parameters assuming a helium composition white dwarf and a companion mass of 0.2 M⊙: inclination i  = 74.68° ± 0.03°, semimajor axis a  = 0.942 ± 0.024 R⊙, and masses and radii of the white dwarf and companion, respectively: M1  = 0.948 $^{+0.006}_{-0.012}$ M⊙, R1  = 0.00830 $^{+0.00012}_{-0.00006}$ R⊙, and R2  = 0.249 ± 0.002 R⊙. As a relatively bright (V ∼ 17–19 mag), eclipsing, period-gap polar, CRTS J0350 + 3232 will remain an important laboratory for the study of accretion and angular momentum evolution in polars.
Stellar activity analysis of Barnard’s Star: Very slow rotation and evidence for long-term activity cycle
Authors: Toledo-Padrón B , Hernández J I González , Rodríguez-López C , Mascareño A Suárez , Rebolo R , Butler R P , Ribas I , Anglada-Escudé G , Johnson E N , Reiners A , Caballero J A , Quirrenbach A , Amado P J , Béjar V J S , Morales J C , Perger M , Jeffers S V , Vogt S , Teske J , Shectman S , Crane J , Díaz M , Arriagada P , Holden B , Burt J , Rodríguez E , Herrero E , Murgas F , Pallé E , Morales N , López-González M J , Alonso E Díez , Tuomi M , Kiraga M , Engle S G , Guinan E F , Strachan J B P , Aceituno F J , Aceituno J , Casanova V M , Martín-Ruiz S , Montes D , Ortiz J L , Sota A , Briol J , Barbieri L , Cervini I , Deldem M , Dubois F , Hambsch F-J , Harris B , Kotnik C , Logie L , Lopez J , McNeely M , Ogmen Y , Pérez L , Rau S , Rodríguez D , Urquijo F S , Vanaverbeke S
Published: July 2019

The search for Earth-like planets around late-type stars using ultra-stable spectrographs requires a very precise characterization of the stellar activity and the magnetic cycle of the star, since these phenomena induce radial velocity (RV) signals that can be misinterpreted as planetary signals. Among the nearby stars, we have selected Barnard’s Star (Gl 699) to carry out a characterization of these phenomena using a set of spectroscopic data that covers about 14.5 years and comes from seven different spectrographs: HARPS, HARPS-N, CARMENES, HIRES, UVES, APF, and PFS; and a set of photometric data that covers about 15.1 years and comes from four different photometric sources: ASAS, FCAPT-RCT, AAVSO, and SNO. We have measured different chromospheric activity indicators (Hα, Ca II HK and Na I D), as well as the FWHM of the cross-correlation function computed for a sub-set of the spectroscopic data. The analysis of Generalized Lomb-Scargle periodograms of the time series of different activity indicators reveals that the rotation period of the star is 145 ± 15 days, consistent with the expected rotation period according to the low activity level of the star and previous claims. The upper limit of the predicted activity-induced RV signal corresponding to this rotation period is about 1 m/s. We also find evidence of a long-term cycle of 10 ± 2 years that is consistent with previous estimates of magnetic cycles from photometric time series in other M stars of similar activity levels. The available photometric data of the star also support the detection of both the long-term and the rotation signals.
SN 2012dn from early to late times: 09dc-like supernovae reassessed★
Authors: Taubenberger S , Floers A , Vogl C , Kromer M , Spyromilio J , Aldering G , Antilogus P , Bailey S , Baltay C , Bongard S , Boone K , Buton C , Chotard N , Copin Y , Dixon S , Fouchez D , Fransson C , Gangler E , Gupta R R , Hachinger S , Hayden B , Hillebrandt W , Kim A G , Kowalski M , Leget P-F , Leibundgut B , Mazzali P A , Noebauer U M , Nordin J , Pain R , Pakmor R , Pecontal E , Pereira R , Perlmutter S , Ponder K A , Rabinowitz D , Rigault M , Rubin D , Runge K , Saunders C , Smadja G , Tao C , Thomas R C
Published: July 2019

As a candidate ‘super-Chandrasekhar’ or 09dc-like Type Ia supernova (SN Ia), SN 2012dn shares many characteristics with other members of this remarkable class of objects but lacks their extraordinary luminosity. Here, we present and discuss the most comprehensive optical data set of this SN to date, comprised of a densely sampled series of early-time spectra obtained within the Nearby Supernova Factory project, plus photometry and spectroscopy obtained at the VLT about 1 yr after the explosion. The light curves, colour curves, spectral time series and ejecta velocities of SN 2012dn are compared with those of other 09dc-like and normal SNe Ia, the overall variety within the class of 09dc-like SNe Ia is discussed, and new criteria for 09dc-likeness are proposed. Particular attention is directed to additional insight that the late-phase data provide. The nebular spectra show forbidden lines of oxygen and calcium, elements that are usually not seen in late-time spectra of SNe Ia, while the ionisation state of the emitting iron plasma is low, pointing to low ejecta temperatures and high densities. The optical light curves are characterised by an enhanced fading starting ∼60 d after maximum and very low luminosities in the nebular phase, which is most readily explained by unusually early formation of clumpy dust in the ejecta. Taken together, these effects suggest a strongly perturbed ejecta density profile, which might lend support to the idea that 09dc-like characteristics arise from a brief episode of interaction with a hydrogen-deficient envelope during the first hours or days after the explosion.
Spectral analysis of the hybrid PG 1159-type central stars of the planetary nebulae Abell 43 and NGC 7094
Authors: Löbling L , Rauch T , Miller Bertolami M M , Todt H , Friederich F , Ziegler M , Werner K , Kruk J W
Published: July 2019

Stellar post asymptotic giant branch (post-AGB) evolution can be completely altered by a final thermal pulse (FTP) which may occur when the star is still leaving the AGB (AFTP), at the departure from the AGB at still constant luminosity (late TP, LTP) or after the entry to the white-dwarf cooling sequence (very late TP, VLTP). Then convection mixes the He-rich material with the H-rich envelope. According to stellar evolution models the result is a star with a surface composition of $\mathrm{H}\approx \, 20$ per cent by mass (AFTP), ≈ 1 per cent (LTP), or (almost) no H (VLTP). Since FTP stars exhibit intershell material at their surface, spectral analyses establish constraints for AGB nucleosynthesis and stellar evolution. We performed a spectral analysis of the so-called hybrid PG 1159-type central stars (CS) of the planetary nebulae Abell 43 and NGC 7094 by means of non-local thermodynamical equilibrium models. We confirm the previously determined effective temperatures of $\mbox{$T_\mathrm{eff}$}\, = 115\, 000\pm 5\, 000 \, \mathrm{K}$ and determine surface gravities of $\log\,(g\,/\,(\mathrm{cm}\,\mathrm{s}^{-2} )) = 5.6\pm 0.1$ for both. From a comparison with AFTP evolutionary tracks, we derive stellar masses of $0.57^{+0.07}_{-0.04}$ M⊙ and determine the abundances of H, He, and metals up to Xe. Both CS are likely AFTP stars with a surface H mass fraction of 0.25 ± 0.03 and 0.15 ± 0.03, respectively, and an Fe deficiency indicating subsolar initial metallicities. The light metals show typical PG 1159-type abundances and the elemental composition is in good agreement with predictions from AFTP evolutionary models. However, the expansion ages do not agree with evolution time-scales expected from the AFTP scenario and alternatives should be explored.
Ultraviolet Mg ii emission from fast neutral ejecta around Eta Carinae
Authors: Smith Nathan , Morse Jon A
Published: July 2019

We present the first images of the nebula around η Carinae obtained with the Wide Field Camera 3 (WFC3) onboard the Hubble Space Telescope (HST), including an ultraviolet (UV) image in the F280N filter that traces Mg ii emission, plus contemporaneous imaging in the F336W, F658N, and F126N filters that trace near-UV continuum, [N ii], and [Fe ii], respectively. The F336W and F658N images are consistent with previous images in these filters, and F126N shows that for the most part, [Fe ii] λ12567 traces clumpy shocked gas seen in [N ii]. The F280N image, however, reveals Mg ii emission from structures that have not been seen in any previous line or continuum images of η Carinae. This image shows diffuse Mg ii emission immediately outside the bipolar Homunculus nebula in all directions, but with the strongest emission concentrated over the poles. The diffuse structure with prominent radial streaks, plus an anticorrelation with ionized tracers of clumpy shocked gas, leads us to suggest that this is primarily Mg ii resonant scattering from unshocked, neutral atomic gas. We discuss the implied structure and geometry of the Mg ii emission, and its relation to the Homunculus lobes and various other complex nebular structures. An order of magnitude estimate of the neutral gas mass traced by Mg ii is 0.02 M⊙, with a corresponding kinetic energy around 1047 erg. This may provide important constraints on polar mass-loss in the early phases of the great eruption. We argue that the Mg ii line may be an excellent tracer of significant reservoirs of freely expanding, unshocked, and otherwise invisible neutral atomic gas in a variety of stellar outflows.
The Lense–Thirring timing-accretion plane for ULXs
Authors: Middleton M J , Fragile P C , Ingram A , Roberts T P
Published: July 2019

Identifying the compact object in ultraluminous X-ray sources (ULXs) has to date required detection of pulsations or a cyclotron resonance scattering feature (CRSF), indicating a magnetized neutron star. However, pulsations are observed to be transient and it is plausible that accretion on to the neutron star may have suppressed the surface magnetic field such that pulsations and CRSFs will be entirely absent. We may therefore lack direct means to identify neutron star systems whilst we presently lack an effective means by which to identify black hole ULXs. Here we present a possible method for separating the ULX population by assuming the X-ray, mHz quasi-periodic oscillations (QPOs), and day time-scale periods/QPOs are associated with Lense–Thirring precession of the inflow and outflowing wind, respectively. The precession time-scales combined with the temperature of the soft X-ray component produce planes where the accretor mass enters as a free parameter. Depending on the properties of the wind, use of these planes may be robust to a range in the angular momentum (spin) and, for high accretion rates, essentially independent of the neutron star’s surface dipole field strength. Our model also predicts the mHz QPO frequency and magnitude of the phase lag imprinted due to propagation through the optically thick wind; in the case of NGC 5408 X-1 we subsequently infer a black hole mass and moderate-to-high spin. Finally, we note that observing secular QPO evolution over sufficient baselines may indicate a neutron star, as the precession responds to spin-up which is not readily observable for black hole primaries.
Companion-launched jets and their effect on the dynamics of common envelope interaction simulations
Authors: Shiber Sagiv , Iaconi Roberto , De Marco Orsola , Soker Noam
Published: July 2019

We conduct three-dimensional hydrodynamic simulations of the common envelope binary interaction and show that if the companion were to launch jets while interacting with the giant primary star’s envelope, the jets would remove a substantial fraction of the envelope’s gas. We use the set-up and numerical code of an earlier common envelope study that did not include jets, with a 0.88-M⊙, 83-R⊙ red giant star and a 0.3-M⊙ companion. The assumption is that the companion star accretes mass via an accretion disc that is responsible for launching the jets which, in the simulations, are injected numerically. For the first time we conduct simulations that include jets as well as the gravitational energy released by the inspiralling core-companion system. We find that simulations with jets unbind approximately three times as much envelope mass than identical simulations that do not include jets, though the total fraction of unbound gas remains below 50 per cent for these particular simulations. The jets generate high-velocity outflows in the polar directions. The jets also increase the final core-companion orbital separation and lead to a kick velocity of the core-companion binary system. Our results show that, if able to form, jets could play a crucial role in ejecting the envelope and in shaping the outflow.
Mass loss from the exoplanet WASP-12b inferred from Spitzer phase curves
Authors: Bell Taylor J , Zhang Michael , Cubillos Patricio E , Dang Lisa , Fossati Luca , Todorov Kamen O , Cowan Nicolas B , Deming Drake , Zellem Robert T , Stevenson Kevin B , Crossfield Ian J M , Dobbs-Dixon Ian , Fortney Jonathan J , Knutson Heather A , Line Michael R
Published: July 2019

The exoplanet WASP-12b is the prototype for the emerging class of ultrahot, Jupiter-mass exoplanets. Past models have predicted – and near-ultraviolet observations have shown – that this planet is losing mass. We present an analysis of two sets of 3.6 and 4.5 $\mu \rm{m}$Spitzer phase curve observations of the system which show clear evidence of infrared radiation from gas stripped from the planet, and the gas appears to be flowing directly toward or away from the host star. This accretion signature is only seen at 4.5 $\mu \rm{m}$, not at 3.6 $\mu \rm{m}$, which is indicative either of CO emission at the longer wavelength or blackbody emission from cool, ≲600 K gas. It is unclear why WASP-12b is the only ultrahot Jupiter to exhibit this mass-loss signature, but perhaps WASP-12b’s orbit is decaying as some have claimed, while the orbits of other exoplanets may be more stable; alternatively, the high-energy irradiation from WASP-12A may be stronger than the other host stars. We also find evidence for phase offset variability at the level of 6.4σ (46.2°) at 3.6 $\mu \rm{m}$.
Impact of an off-centred dipole on neutron star binaries
Authors: Pétri J
Published: July 2019

Neutron stars are strongly magnetized rotating compact objects. Therefore, they also produce huge electric fields accelerating particles to ultrarelativistic energies. The simplest magnetic topology is a dipole traditionally located at the stellar centre. In this paper, we re-investigate the consequences of an off-centred rotating magnetic dipole, showing accurate magnetic field line geometries, the associated spin-down luminosity as well as the corresponding electromagnetic kick and torque imprinted to the neutron star. Results are obtained by time-dependent numerical simulations of Maxwell equations in vacuum using pseudo-spectral methods. We compare our results to known analytical expressions available to lowest order in the parameter ϵ = d/R, where d is the displacement of the dipole from the stellar centre and R the neutron star radius. We found good agreement between our numerical computations and our analytical approximations even for well off-centred dipoles having large displacements with a sizeable fraction of the radius, i.e. ϵ ≲ 1. An explanation for binary neutron star eccentricity distribution functions is given with an emphasize on highly eccentric systems as an alternative scenario to traditional binary formation.
Time-dependent evolution of the protoplanetary discs with magnetic winds
Authors: Shadmehri Mohsen , Ghoreyshi Sayyedeh Masoumeh
Published: July 2019

We study the evolution of the protoplanetary discs (PPDs) in the presence of magnetically driven winds with the stress relations motivated by the non-ideal MHD disc simulations. Contribution of the magnetic winds in the angular momentum removal and mass-loss is described using these relations which are quantified in terms of the plasma parameter. Evolution of the essential disc quantities including the surface density, accretion rate, and wind mass-loss rate are studied for a wide range of the model parameters. Two distinct phases of the disc evolution are found irrespective of the adopted input parameters. While at the early phase of the disc evolution, global disc quantities such as its total mass and magnetic flux undergo non-significant reductions, their rapid declines are found in the second phase of evolution. Duration of each phase, however, depends upon the model parameters including magnetic wind strength. Our model predicts that contributions of the magnetic winds in the disc evolution are significant during the second phase. We then calculated locus of points in the plane of the accretion rate and total disc mass corresponding to an ensemble of evolving PPDs. Our theoretical isochrone tracks exhibit reasonable fits to the observed PPDs in star-forming regions Lupus and σ-Orion.
21-cm power spectrum and ionization bias as a probe of long-mode modulated non-Gaussian sky
Authors: Khosravi Shahram , Ghazizadeh Amirabbas , Baghram Shant
Published: July 2019

The observed hemispherical power asymmetry in cosmic microwave background radiation can be explained by long-wavelength mode (long-mode) modulation. In this paper, we study the possibility of detecting this effect in the angular power spectrum of the 21-cm brightness temperature. For this task, we study the effect of the neutral hydrogen distribution on the angular power spectrum. This is done by formulating the bias parameter of the ionized fraction to the underlying matter distribution. We also discuss the possibility that the long-mode modulation is accompanied by a primordial non-Gaussianity of local type. In this case, we obtain the angular power spectrum with two effects of primordial non-Gaussianity and long-mode modulation. Finally, we show that the primordial non-Gaussianity enhances the long-mode modulated power of the 21-cm signal via the non-Gaussian scale-dependent bias up to four orders of magnitude. Accordingly, observations of the 21-cm signal with upcoming surveys, such as the Square Kilometer Array (SKA), will probably be capable of detecting hemispherical power asymmetry in the context of long-mode modulation.
Scaling relations for globular cluster systems in early-type galaxies
Authors: Caso Juan P , De Bórtoli Bruno J , Ennis Ana I , Bassino Lilia P
Published: July 2019

The formation and growth of globular cluster systems (GCSs) is closely related to the evolutionary processes experienced by their host galaxies. In particular, their radial distributions scale with several properties of the galaxies and their haloes. We performed a photometric study, by means of HST/ACS archival data of several intermediate luminosity galaxies located in low-density environments. It was supplemented with available photometric data of GCSs from the Virgo and Fornax clusters, resulting in a sample of almost 30 GCSs for which we fitted their radial profiles. The resulting overall properties agree with those from previous studies, as we found that the effective radius, extension, and concentration of the GCS radial profiles correlate with the stellar mass, effective radius, and number of globular clusters, presenting in some cases a bilinear relation. The extension also correlates with the central velocity dispersion for central galaxies, but not for satellites. From a statistical comparison with numerical simulations we obtained good agreement between the effective radius and extension of the GCS scale with the effective and virial radius of the haloes, respectively. Finally, we analysed these results in the literature context.
Metallicity of stars formed throughout the cosmic history based on the observational properties of star-forming galaxies
Authors: Chruslinska Martyna , Nelemans Gijs
Published: July 2019

Metallicity is one of the crucial factors that determine stellar evolution. To characterize the properties of stellar populations one needs to know the fraction of stars forming at different metallicities. Knowing how this fraction evolves over time is necessary e.g. to estimate the rates of occurrence of any stellar evolution related phenomena (e.g. double compact object mergers, gamma-ray bursts). Such theoretical estimates can be confronted with observational limits to validate the assumptions about the evolution of the progenitor system leading to a certain transient. However, to perform the comparison correctly one needs to know the uncertainties related to the assumed star formation history and chemical evolution of the Universe. We combine the empirical scaling relations and other observational properties of the star-forming galaxies to construct the distribution of the cosmic star formation rate density at different metallicities and redshifts. We address the question of uncertainty of this distribution due to currently unresolved questions, such as the absolute metallicity scale, the flattening in the star formation−mass relation or the low-mass end of the galaxy mass function. We find that the fraction of stellar mass formed at metallicities <10 per cent solar (>solar) since z = 3 varies by ∼18 per cent (∼26 per cent) between the extreme cases considered in our study. This uncertainty stems primarily from the differences in the mass–metallicity relations obtained with different methods. We confront our results with the local core-collapse supernovae observations. Our model is publicly available.
“Ghost Introgression” As a Cause of Deep Mitochondrial Divergence in a Bird Species Complex
Authors: Zhang Dezhi , Tang Linfang , Cheng Yalin , Hao Yan , Xiong Ying , Song Gang , Qu Yanhua , Rheindt Frank E , Alström Per , Jia Chenxi , Lei Fumin
Published: July 2019

In the absence of nuclear-genomic differentiation between two populations, deep mitochondrial divergence (DMD) is a form of mito-nuclear discordance. Such instances of DMD are rare and might variably be explained by unusual cases of female-linked selection, by male-biased dispersal, by “speciation reversal” or by mitochondrial capture through genetic introgression. Here, we analyze DMD in an Asian Phylloscopus leaf warbler (Aves: Phylloscopidae) complex. Bioacoustic, morphological, and genomic data demonstrate close similarity between the taxa affinis and occisinensis, even though DMD previously led to their classification as two distinct species. Using population genomic and comparative genomic methods on 45 whole genomes, including historical reconstructions of effective population size, genomic peaks of differentiation and genomic linkage, we infer that the form affinis is likely the product of a westward expansion in which it replaced a now-extinct congener that was the donor of its mtDNA and small portions of its nuclear genome. This study provides strong evidence of “ghost introgression” as the cause of DMD, and we suggest that “ghost introgression” may be a widely overlooked phenomenon in nature.
Transcriptional Enhancers in the FOXP2 Locus Underwent Accelerated Evolution in the Human Lineage
Authors: Caporale Alfredo Leandro , Gonda Catalina M , Franchini Lucía Florencia
Published: July 2019

Unique human features, such as complex language, are the result of molecular evolutionary changes that modified developmental programs of our brain. The human-specific evolution of the forkhead box P2 (FOXP2) gene-coding region has been linked to the emergence of speech and language in the human kind. However, little is known about how the expression of FOXP2 is regulated and whether its regulatory machinery evolved in a lineage-specific manner in humans. In order to identify FOXP2 regulatory regions containing human-specific changes, we used databases of human-accelerated noncoding sequences or HARs. We found that the topologically associating domain determined using developing human cerebral cortex containing the FOXP2 locus includes two clusters of 12 HARs, placing the locus occupied by FOXP2 among the top regions showing fast acceleration rates in noncoding regions in the human genome. Using in vivo enhancer assays in zebrafish, we found that at least five FOXP2-HARs behave as transcriptional enhancers throughout different developmental stages. In addition, we found that at least two FOXP2-HARs direct the expression of the reporter gene EGFP to foxP2-expressing regions and cells. Moreover, we uncovered two FOXP2-HARs showing reporter expression gain of function in the nervous system when compared with the chimpanzee ortholog sequences. Our results indicate that regulatory sequences in the FOXP2 locus underwent a human-specific evolutionary process suggesting that the transcriptional machinery controlling this gene could have also evolved differentially in the human lineage.
A new set of endogenous control genes for use in quantitative real-time PCR experiments show that formin Ldia2dex transcripts are enriched in the early embryo of the pond snail Lymnaea stagnalis (Panpulmonata)
Authors: Johnson Harriet F , Davison Angus
Published: July 2019

Although the pond snail Lymnaea stagnalis is an emerging model organism for molecular studies in a wide variety of fields, there are a limited number of verified endogenous control genes for use in quantitative real-time PCR. As part of a larger study on snail chirality, or left–right asymmetry, we assayed gene expression in pond snail embryos. We evaluated six candidate control genes, by comparing their expression in three tissues (ovotestis, foot and embryo) and used three software programmes (geNorm, Normfinder and Bestkeeper) to do so. The specific utility of these control genes was then tested by investigating the relative expression of six experimental transcripts, including formin Ldia2, a gene that has been associated with chiral variation in L. stagnalis. All six control genes were found to be suitable for use in the three tissues tested. Of the six experimental genes, it was found that all were relatively depleted in the early embryo compared with other tissues, except the formin Ldia2 gene. Instead, transcripts of the wild-type Ldia2dex were enriched in the embryo, whereas a nonfunctional frameshifted version, Ldia2sin, was severely depleted. These differences in Ldia2sin expression were less evident in the ovotestis and were not evident in the foot tissue, possibly because nonsense-mediated decay is obscured in actively transcribing tissues. Our work provides a set of control genes that may be useful to the wider community and illustrates how these genes may be used to assay differences in expression in a variety of tissues.
Weaving DNA strands: structural insight on ATP hydrolysis in RecA-induced homologous recombination
Authors: Boyer Benjamin , Danilowicz Claudia , Prentiss Mara , Prévost Chantal
Published: July 2019

Homologous recombination is a fundamental process in all living organisms that allows the faithful repair of DNA double strand breaks, through the exchange of DNA strands between homologous regions of the genome. Results of three decades of investigation and recent fruitful observations have unveiled key elements of the reaction mechanism, which proceeds along nucleofilaments of recombinase proteins of the RecA family. Yet, one essential aspect of homologous recombination has largely been overlooked when deciphering the mechanism: while ATP is hydrolyzed in large quantity during the process, how exactly hydrolysis influences the DNA strand exchange reaction at the structural level remains to be elucidated. In this study, we build on a previous geometrical approach that studied the RecA filament variability without bound DNA to examine the putative implication of ATP hydrolysis on the structure, position, and interactions of up to three DNA strands within the RecA nucleofilament. Simulation results on modeled intermediates in the ATP cycle bring important clues about how local distortions in the DNA strand geometries resulting from ATP hydrolysis can aid sequence recognition by promoting local melting of already formed DNA heteroduplex and transient reverse strand exchange in a weaving type of mechanism.
Simultaneous precise editing of multiple genes in human cells
Authors: Riesenberg Stephan , Chintalapati Manjusha , Macak Dominik , Kanis Philipp , Maricic Tomislav , Pääbo Svante
Published: July 2019

When double-strand breaks are introduced in a genome by CRISPR they are repaired either by non-homologous end joining (NHEJ), which often results in insertions or deletions (indels), or by homology-directed repair (HDR), which allows precise nucleotide substitutions to be introduced if a donor oligonucleotide is provided. Because NHEJ is more efficient than HDR, the frequency with which precise genome editing can be achieved is so low that simultaneous editing of more than one gene has hitherto not been possible. Here, we introduced a mutation in the human PRKDC gene that eliminates the kinase activity of the DNA-dependent protein kinase catalytic subunit (DNA-PKcs). This results in an increase in HDR irrespective of cell type and CRISPR enzyme used, sometimes allowing 87% of chromosomes in a population of cells to be precisely edited. It also allows for precise editing of up to four genes simultaneously (8 chromosomes) in the same cell. Transient inhibition of DNA-PKcs by the kinase inhibitor M3814 is similarly able to enhance precise genome editing.