bluuebunny/crossref_metadata_2025 huggingface dataset:
Low-frequency pseudo-Rayleigh and pseudo-Scholte waves at an interface of liquid/soft porous sediment with underlying hard porous sediment substrate
Authors: Qiu Haomiao , Xia Tangdai , Chen Weiyun , Yu Bingqi
Published: July 2019

The paper focuses on the propagation of low-frequency pseudo-Rayleigh and pseudo-Scholte waves at the liquid/soft porous sediment interface with an underlying hard porous sediment half-space. The overlying liquid is assumed to be ideal compressible medium and the porous sediments are modelled by Biot theory. Based on the boundary conditions, the closed-form dispersion equations of far-field interface waves are deduced using 2-D Helmholtz decomposition theorem and Fourier transform. The velocity and attenuation of pseudo-Rayleigh and pseudo-Scholte waves are determined by Newton iteration in a reasonable rooting interval. The analytical expressions of the displacement field and liquid pressure distribution caused by interface waves are also derived. Then, the dispersion equations for four degenerate systems are derived as special cases by assuming the thickness of the liquid layer or the sandwiched porous soft sediment layer to be zero or infinite. Lastly, numerical examples are used to verify the degeneracy of the system and to analyse the propagation characteristics of pseudo-Rayleigh and pseudo-Scholte waves. They show the dependences of the velocity and displacement field on dimensionless modulus and dimensionless wavelength. When the dimensionless wavelength is small or very large, the phase velocity and displacement field calculated by the present system is the same as the special cases, thus proving the validating of the new system.
Differences between heterogenous and homogenous slip in regional tsunami
hazards modelling
Authors: Melgar Diego , Williamson Amy L , Salazar-Monroy E Fernando
Published: July 2019

The homogenous slip finite fault model is commonly used in tsunami hazards for a variety of applications. These include early warning and short-term forecasts of tsunami amplitudes, scenario ruptures for risk assessments, and probabilistic tsunami hazard analysis (PTHA). Over the last decade, however, it has become feasible to calculate stochastic slip models which reflect the expected spatial statistics of slip observed in real events. In this paper we examine the impacts of the homogenous slip model when compared to stochastic slip distributions and ask whether, in light of these technical advancements, the homogenous slip assumption remains a reasonable one. We employ a simplified subduction zone geometry, free of complex path and site effects, and study simulated tsunamis from earthquakes in the magnitude 7 to magnitude 9 range. We find that homogenous slip models have lower tsunami potential energies and frequently underpredict the peak tsunami amplitudes and the resulting tsunami hazard, particularly at low probabilities of exceedance. This finding has important implications for all tsunami hazards applications. Calculating a suite of realistic stochastic slip distributions is now within reach of tsunami scientists, thus, we conclude that use of heterogeneous slip models for tsunami hazards applications is preferable
Interferometric time-lapse velocity analysis: application to a salt-water disposal well in British Columbia, Canada
Authors: Vaezi Yoones , Van der Baan Mirko
Published: July 2019

We investigate the possibility of passive monitoring of a salt-water disposal well in British Columbia, Canada, using continuously recorded ambient seismic noise. We find seismic velocity variations induced by a reduction of injection pressure in an effort to mitigate an elevated level of seismicity, most likely associated with the disposal of salt water. The relative velocity variations are derived from time-shifts measured between consecutive cross-correlation functions for each station pair in a surface array composed of five broad-band seismometers. The probable driving mechanisms responsible for the velocity changes are reduced pore pressures and/or lowered poroelastic stresses beyond the injection wellbore, respectively. Hydrologic data (e.g. snow and rainfall), noise energy trends and fluctuations in the incident direction of dominant noise sources do not correlate with the estimated relative velocity variations. Velocity variations are detected ahead of the zone of induced seismicity, thus indicating that seismic interferometry may aid in mitigation efforts to reduce the risk of induced seismicity by (1) providing verifiable and repeatable measurements of physical changes within the surrounding area and (2) providing hard constraints for modelling efforts to constrain how and where pore-pressure fronts change.
The effect of stress changes on time-dependent earthquake probabilities for the central Wasatch Fault Zone, Utah, USA.
Authors: Verdecchia A , Carena S , Pace B , DuRoss C B
Published: July 2019

Static and quasi-static Coulomb stress changes produced by large earthquakes can modify the probability of occurrence of subsequent events on neighboring faults. This approach is based on physical (Coulomb stress changes) and statistical (probability calculations) models, which are influenced by the quality and quantity of data available in the study region. Here, we focus on the Wasatch Fault Zone (WFZ), a well-studied active normal fault system having abundant geologic and paleoseismological data. Paleoseismological trench investigations of the WFZ indicate that at least 24 large, surface-faulting earthquakes have ruptured the fault's five central, 35–59-km long segments since ∼7 ka. Our goal is to determine if the stress changes due to the youngest paleoevents have significantly modified the present-day probability of occurrence of large earthquakes on each of the segments. For each segment, we modeled the cumulative (coseismic + postseismic) Coulomb stress changes (∆CFScum) due to earthquakes younger than the most recent event on the segment in question and applied the resulting values to the time-dependent probability calculations. Results from the Coulomb stress modeling suggest that the Brigham City, Salt Lake City, and Provo segments have accumulated ∆CFScum larger than 10 bars, whereas the Weber segment has experienced a stress decrease of 5 bars, in the scenario of recent rupture of the Great Salt Lake fault to the west. Probability calculations predict high probability of occurrence for the Brigham City and Salt Lake City segments, due to their long elapsed times (> 1–2 ka) when compared to the Weber, Provo, and Nephi segments (< 1 ka). The range of calculated coefficients of variation (CV) has a large influence on the final probabilities, mostly in the case of the Brigham City segment. Finally, when the Coulomb stress and the probability models are combined, our results indicate that the ∆CFScum resulting from earthquakes postdating the youngest events on each of the five segments substantially affects the probability calculations for three of the segments: Brigham City, Salt Lake City, and Provo. The probability of occurrence of a large earthquake in the next 50 years on these three segments may therefore be underestimated if a time-independent approach, or a time-dependent approach that does not consider ∆CFS, is adopted.
Direct fluorescent glycan labeling with recombinant sialyltransferases
Authors: Wu Zhengliang L , Person Anthony D , Burton Andrew J , Singh Ravinder , Burroughs Barbara , Fryxell Dan , Tatge Timothy J , Manning Timothy , Wu Guoping , Swift Karl A D , Kalabokis Vassili
Published: July 2019

Glycosylation is a common modification found on numerous proteins and lipids. However, direct detection of glycans on these intact biomolecules has been challenge. Here, utilizing enzymatic incorporation of fluorophore-conjugated sialic acids, dubbed as direct fluorescent glycan labeling, we report the labeling and detection of N- and O-glycans on glycoproteins. The method allows detection of specific glycans without the laborious gel blotting and chemiluminescence reactions used in Western blotting. The method can also be used with a variety of fluorescent dyes.
Gender and health literacy: men’s health beliefs and behaviour in Trinidad
Authors: Wills J , Sykes S , Hardy S , Kelly M , Moorley C , Ocho O
Published: July 2019

Gender variations in health literacy have implications for engagement in preventive behaviours and the uptake of health services, especially in areas such as the Caribbean where there are marked disparities in life expectancy and health service utilization. A self-reported questionnaire was used to examine men’s concepts of health, their help-seeking behaviours and their functional and interactive health literacy. Two hundred and forty-eight men across the life course participated at three sites in Trinidad. Data were analysed using descriptive statistics, with free-text responses analysed thematically. Men were concerned about, and accepted responsibility for their own health but social norms concerning sickness and masculinity were barriers to accessing health services. Almost one-third (31.5%) sought advice from a healthcare service when they were last sick because they were prompted to do so by their wife/partner or family. Levels of functional and interactive health literacy were not high among older men, who were reliant on healthcare professionals to communicate health messages. There was an age divide in e-health literacy. There is little published evidence on men’s health literacy, particularly from Caribbean countries such as Trinidad and Tobago. This study highlights the importance of the design and implementation of specific policies focusing on men’s health. A major challenge is to engage with men who do not access health services.
New imported inputs, wages and worker mobility
Authors: Colantone Italo , Matano Alessia , Naticchioni Paolo
Published: July 2019

We study how firms and industries adjust to increasing international trade in intermediate inputs. In particular, we provide a comprehensive assessment of the effects of new imported inputs on wage dynamics, on the skill-composition of the labor force, on worker mobility, and on assortative matching between firms and workers. We employ matched employer-employee data for Italy, over 1995–2007. We complement these data with information on the arrival of new imported inputs at the industry level. We find new imported inputs to have a positive effect on average wage growth at the firm level. This effect is driven by two factors: (1) an increase in the white-collar/blue-collar ratio; and (2) an increase in the average wage growth of blue-collar workers, while the wage growth of white collars is not significantly affected. The individual-level analysis reveals that the increase in the average wage of blue collars is driven by the displacement of the lowest paid workers, while continuously employed individuals are not affected. We estimate the unobserved skills of workers. We find evidence that new imported inputs lead to a positive selection of higher-skilled workers, and to an increase in the degree of positive assortative matching between firms and workers.
INTRODUCTION: Immune Relevant Animal Models: Opportunities and Challenges
Authors: Jungersen Gregers , Piedrahita Jorge
Published: July 2019

Valid interpretation of preclinical animal models in immunology-related clinical challenges is important to solve outstanding clinical needs. Given the overall complexity of the immune system and both species- and tissue-specific immune peculiarities, the selection and design of appropriate immune-relevant animal models is, however, not following a straightforward path. The topics in this issue of the ILAR Journal provide assessments of immune-relevant animal models used in oncology, hematopoietic-, CAR-T cell- and xenotransplantation, adjuvants and infectious diseases, and immune privileged inflammation that are providing key insights into unmet human clinical needs.
Ringel Duals of Brauer Algebras via Super Groups
Authors: Coulembier Kevin
Published: July 2019

We prove that the Brauer algebra, for all parameters for which it is quasi-hereditary, is Ringel dual to a category of representations of the orthosymplectic super group. As a consequence we obtain new and algebraic proofs for some results on the fundamental theorems of invariant theory for this super group over the complex numbers and also extend them to some cases in positive characteristic. Our methods also apply to the walled Brauer algebra in which case we obtain a duality with the general linear super group, with similar applications.
Efficacy and safety of tigecycline in treatment of pneumonia caused by MDR Acinetobacter baumannii: a systematic review and meta-analysis
Authors: Mei Hekun , Yang Tianli , Wang Jin , Wang Rui , Cai Yun
Published: July 2019

Background

Use of tigecycline in treating MDR Acinetobacter baumannii (MDRAB) remains controversial.

Objectives

To comprehensively assess the safety and efficacy of tigecycline in pneumonia caused by Acinetobacter baumannii.

Methods

PubMed, Embase, Web of Science and Cochrane library databases were searched up to 12 March 2019. Studies were included if they compared tigecycline-based regimens with other antibiotic regimens for treating AB pulmonary infections and we pooled the clinical outcomes, microbiological response, adverse events or mortality.

Results

One prospective study and nine retrospective studies were included in this meta-analysis. The results showed similar clinical cure rates (OR = 1.04, 95% CI = 0.60–1.81; P = 0.89) and mortality rates (OR = 1.11, 95% CI = 0.65–1.89; P = 0.71) comparing tigecycline groups with the control groups. However, a significantly lower microbiological eradication rate was found in the tigecycline groups (OR = 0.43, 95% CI = 0.27–0.66; P = 0.0001). Incidence of nephrotoxicity in tigecycline-based regimens was significantly lower than in colistin-based regimens (OR = 0.34, 95% CI = 0.16–0.74, I2 = 35%, P = 0.006). There were no randomized controlled trials (RCTs) included; incomplete safety data and regional bias caused by the majority of the studies originating in China are the main limitations of this meta-analysis.

Conclusions

Tigecycline can be used for treating MDRAB pulmonary infections owing to efficacy similar to that of other antibiotics. Moreover, tigecycline did not show a higher risk of mortality. Considering the lower microbiological eradication rate for tigecycline, which is likely to induce antimicrobial resistance, well-designed RCTs for high-dose tigecycline in treating pneumonia caused by AB are still needed.
Development of quality indicators for the management of Staphylococcus aureus bacteraemia
Authors: ten Oever Jaap , Jansen Joëll L , van der Vaart Thomas W , Schouten Jeroen A , Hulscher Marlies E J L , Verbon Annelies
Published: July 2019

Background

Staphylococcus aureus bacteraemia (SAB) is a serious and often fatal infectious disease. The quality of management of SAB is modifiable and can thus affect the outcome. Quality indicators (QIs) can be used to measure the quality of care of the various aspects of SAB management in hospitals, enabling professionals to identify targets for improvement and stimulating them to take action.

Objectives

To develop QIs for the management of hospitalized patients with SAB.

Methods

A RAND-modified Delphi procedure was used to develop a set of QIs for the management of SAB in hospitalized patients. First, available QIs for the management of SAB were extracted from the literature published since 1 January 2000 (MEDLINE and Embase databases). Thereafter, an international multidisciplinary expert panel appraised these QIs during two questionnaire rounds with an intervening face-to-face meeting.

Results

The literature search resulted in a list of 39 potential QIs. After appraisal by 30 medical specialists, 25 QIs describing recommended care at patient level were selected. These QIs defined appropriate follow-up blood cultures (n=2), echocardiography (n=6), source control (n=4), antibiotic therapy (n=7), antibiotic dose adjustment (n=2), intravenous-to-oral switch (n=2), infectious disease consultation (n=1) and medical discharge report (n=1).

Conclusions

A set of 25 QIs for the management of SAB for hospitalized patients was developed by using a RAND-modified Delphi procedure among international experts. These QIs can measure the quality of various aspects of SAB management. This information can be fed back to the relevant stakeholders in order to identify improvement targets and optimize care.
Comparison of the cohort selection performance of Australian Medicines Terminology to Anatomical Therapeutic Chemical mappings
Authors: Guo Guan N , Jonnagaddala Jitendra , Farshid Sanjay , Huser Vojtech , Reich Christian , Liaw Siaw-Teng
Published: July 2019

Objective

Electronic health records are increasingly utilized for observational and clinical research. Identification of cohorts using electronic health records is an important step in this process. Previous studies largely focused on the methods of cohort selection, but there is little evidence on the impact of underlying vocabularies and mappings between vocabularies used for cohort selection. We aim to compare the cohort selection performance using Australian Medicines Terminology to Anatomical Therapeutic Chemical (ATC) mappings from 2 different sources. These mappings were taken from the Observational Medical Outcomes Partnership Common Data Model (OMOP-CDM) and the Pharmaceutical Benefits Scheme (PBS) schedule.

Materials and Methods

We retrieved patients from the electronic Practice Based Research Network data repository using 3 ATC classification groups (A10, N02A, N06A). The retrieved patients were further verified manually and pooled to form a reference standard which was used to assess the accuracy of mappings using precision, recall, and F measure metrics.

Results

The OMOP-CDM mappings identified 2.6%, 15.2%, and 24.4% more drugs than the PBS mappings in the A10, N02A and N06A groups respectively. Despite this, the PBS mappings generally performed the same in cohort selection as OMOP-CDM mappings except for the N02A Opioids group, where a significantly greater number of patients were retrieved. Both mappings exhibited variable recall, but perfect precision, with all drugs found to be correctly identified.

Conclusion

We found that 1 of the 3 ATC groups had a significant difference and this affected cohort selection performance. Our findings highlighted that underlying terminology mappings can greatly impact cohort selection accuracy. Clinical researchers should carefully evaluate vocabulary mapping sources including methodologies used to develop those mappings.
To Flower and Fructify: Rational Religion and the Seeds of Islam in Nazir Ahmad’s (1830–1912) Late-career Religious Non-fiction
Authors: Lhost Elizabeth
Published: July 2019

Known primarily for his popular and moralizing novels, Nazir Ahmad’s (1830–1912) accomplishments as a scholar of Islam are often omitted from his biography. Yet in addition to working for the British Government of India, participating in Muslim social, political, and educational initiatives on the subcontinent, and demonstrating his linguistic and legal acumen by translating the law codes of British India into vernacular Urdu, Nazir Ahmad also translated religious texts and penned his own original compositions on themes of religion, society, and ethics. Reviewing the ideas presented in his comprehensive three-volume al-Ḥuqūq va-l-farāʾiż (1905–6) and his shorter catechism Ijtihād (1906), this article outlines Nazir Ahmad’s theory of worldly religion and introduces his concept of Islamic humanism in response to ulema-centric approaches to Islamic revival and reform in British India.
Determining Sexual Dimorphism of Living Aquatic Beetles, Stygoparnus comalensis (Coleoptera: Dryopidae) and Heterelmis comalensis (Coleoptera: Elmidae), Using Internal Abdominal Structures
Authors: Kosnicki Ely
Published: July 2019

The Comal Springs dryopid beetle, Stygoparnus comalensis Barr and Spangler, and the Comal Springs riffle beetle, Heterelmis comalensis Bosse, Tuff, and Brown, are protected by the United States Fish and Wildlife Service (USFWS), and the development of a captive self-propagating refuge is of importance to stakeholders within the Edwards Aquifer. Being able to reliably distinguish the sex of living subjects is desirable for establishing a successful refuge program. Ventrite, elytron, and pronotum measurements of S. comalensis were taken to determine if there were sexually dimorphic allometries. Various lighting techniques were also implemented to see if there were other characters that could potentially be used to distinguish females and males. Measurements were not found to satisfactorily separate sexes; however, lateral lighting was found to consistently illuminate internal abdominal structures of S. comalensis where sternite 8 was viewable in males and the fused gonocoxites were viewable in females. Lateral lighting was used to examine living specimens of H. comalensis, and it was found that sternite 8 could be viewed in both sexes where the anterior strut of females was much longer and discernible from the anterior strut of males. Commentary regarding the use of cameras and photography for observing living subjects is given.
Social Norms and Legal Design
Authors: Deffains Bruno , Fluet Claude
Published: July 2019

We consider legal obligations against a background of social norms, for example, societal norms, professional codes of conduct, or business standards. Violations of the law trigger reputational sanctions insofar as they signal nonadherence to underlying norms, raising the issue of the design of offenses. We show that the law generally ought to follow social norms or be stricter than them. When society is only concerned with the trade-off between deterrence and enforcement costs, legal standards defining offenses should align with underlying norms so long as the latter are not too deficient. When providing productive information to third parties is also a concern, legal standards should either align with underlying norms with fines that trade off deterrence against the provision of information; or legal standards should be more demanding and enforced with purely symbolic sanctions, for example, public reprimands. Our analysis has implications for general law enforcement and regulatory policies. (JEL: D8, K4, Z13)
Melanoma Incidence Among Non-Hispanic Whites in All 50 US States From 2001 Through 2015
Authors: Thrift Aaron P , Gudenkauf Franciska J
Published: July 2019

Background

The United States has large regional variation in primary prevention campaigns for skin cancer. We collected data from all 50 states to examine changes in melanoma incidence and performed age-period-cohort analyses to describe the simultaneous effects of age, period, and cohort on incidence rates.

Methods

Annual melanoma incidence rates for non-Hispanic whites from 2001 to 2015 were extracted from the US Cancer Statistics registry. Secular trends were examined overall and by sex and state. We used joinpoint regression to compute annual percent change and average annual percent change and corresponding 95% confidence intervals (CIs). We also analyzed incidence trends by 5-year age group and birth cohort using incidence rate ratios and age-period-cohort modeling.

Results

Melanoma incidence increased from 20.7 per 100 000 (95% CI = 20.5 to 20.9) in 2001 to 28.2 per 100 000 (95% CI = 28.0 to 28.5) in 2015, increasing by 3.90% (95% CI = 2.36% to 5.48%) annually between 2001 and 2005 and 1.68% (95% CI = 1.37% to 1.99%) annually from 2005 through 2015. The average annual percent change in melanoma incidence rates were similar for men (2.34%, 95% CI = 1.91 to 2.78) and women (2.25%, 95% CI = 1.60 to 2.91). Age-specific relative risk by birth cohort increased from circa 1921 to 1981 before decreasing. Compared with adults born circa 1956, those born circa 1991 had lower melanoma risk (incidence rate ratio  = 0.85; 95% CI = 0.77 to 0.94). Geographic variation was observed; some states still have melanoma rates trending upwards in all birth cohorts.

Conclusions

The continued increase in melanoma incidence among non-Hispanic whites, particularly in states where rates continue to rise among recent and current birth cohorts, underscores the need for increased public health campaigns aimed at reducing sun exposure.
Signatures of circumstellar interaction in the unusual transient AT 2018cow
Authors: Fox Ori D , Smith Nathan
Published: July 2019

AT 2018cow is a unique transient that stands out due to its relatively fast light curve, high peak bolometric luminosity, and blue colour. These properties distinguish it from typical radioactively powered core-collapse supernovae (SNe). Instead, the characteristics are more similar to a growing sample of Fast Blue Optical Transients (FBOTs). Mostly discovered at hundreds of Mpc, FBOT follow-up is usually limited to several photometry points and low signal-to-noise spectra. At only ∼60 Mpc, AT 2018cow offers an opportunity for detailed follow-up. Studies of this object published to date propose a number of interpretations for AT 2018cow, but none of these specifically consider the interacting Type Ibn SN subclass. We point out that while narrow lines do not dominate the spectrum of AT 2018cow, as narrow Balmer lines typically do in SNe IIn, the narrow lines in AT 2018cow may nevertheless include emission from pre-shock CSM. In particular, the He i lines in AT 2018cow are broader than H ii region lines in the same spectrum, and they closely resemble He i lines in some examples of SNe Ibn or transitional SNe Ibn/IIn objects. We compare AT 2018cow to interacting SNe Ibn and IIn and find a number of noteworthy similarities, including light-curve rise and fall times, peak magnitude, X-ray light curves, and spectroscopic properties. We therefore explore the hypothesis that CSM interaction in a relatively H-poor system might help explain some observed properties of AT 2018cow, and we go on to consider progenitor implications for AT 2018cow, FBOTs, and SNe Ibn.
Axion core–halo mass and the black hole–halo mass relation: constraints on a few parsec scales
Authors: Desjacques Vincent , Nusser Adi
Published: July 2019

If the dark matter is made of ultralight axions, stable solitonic cores form at the centres of virialized haloes. In some range for the mass m of the axion particle, these cores are sufficiently compact and can mimic supermassive black holes (SMBH) residing at galactic nuclei. We use the solitonic core–halo mass relation, validated in numerical simulations, to constrain a new range of allowed axion mass from measurements of the SMBH mass in (pseudo)bulge and bulgeless galaxies. These limits are based on observations of galactic nuclei on scales smaller than 10 pc. Our analysis suggests that $m\lesssim 10^{-18}\, {\rm eV}$ is ruled out by the data. We briefly discuss whether an attractive self-interaction among axions could alleviate this constraint.
X-ray study of spatial structures in Tycho’s supernova remnant using unsupervised deep learning
Authors: Iwasaki Hiroyoshi , Ichinohe Yuto , Uchiyama Yasunobu
Published: July 2019

Recent rapid development of deep learning algorithms, which can implicitly capture structures in high-dimensional data, opens a new chapter in astronomical data analysis. We report here a new implementation of deep learning techniques for X-ray analysis. We apply a variational autoencoder (VAE) using a deep neural network for spatio-spectral analysis of data obtained by Chandra X-ray Observatory from Tycho’s supernova remnant (SNR). We established an unsupervised learning method combining the VAE and a Gaussian mixture model (GMM), where the dimensions of the observed spectral data are reduced by the VAE, and clustering in feature space is performed by the GMM. We found that some characteristic spatial structures, such as the iron knot on the eastern rim, can be automatically recognized by this method, which uses only spectral properties. This result shows that unsupervised machine learning can be useful for extracting characteristic spatial structures from spectral information in observational data (without detailed spectral analysis), which would reduce human-intensive preprocessing costs for understanding fine structures in diffuse astronomical objects, e.g. SNRs or galaxy clusters. Such data-driven analysis can be used to select regions from which to extract spectra for detailed analysis and help us make the best use of the large amount of spectral data available currently and arriving in the coming decades.
Swift UVOT observations of the 2015 outburst of V404 Cygni
Authors: Oates S R , Motta S , Beardmore A P , Russell D M , Gandhi P , Kuin N P M , De Pasquale M , Altamirano D , Breeveld A A , Castro-Tirado A J , Knigge C , Page M J , Steeghs D
Published: July 2019

The black hole binary, V404 Cygni, went into outburst in 2015 June, after 26 years of X-ray quiescence. We observed the outburst with the Neil Gehrels Swift observatory. We present optical/UV observations taken with the Swift Ultra-violet Optical Telescope, and compare them with the X-ray observations obtained with the Swift X-ray Telescope. We find that dust extinction affecting the optical/UV does not correlate with absorption due to neutral hydrogen that affects the X-ray emission. We suggest there is a small inhomogeneous high-density absorber containing a negligible amount of dust, close to the black hole. Overall, temporal variations in the optical/UV appear to trace those in the X-rays. During some epochs we observe an optical time-lag of (15–35) s. For both the optical/UV and X-rays, the amplitude of the variations correlates with flux, but this correlation is less significant in the optical/UV. The variability in the light curves may be produced by a complex combination of processes. Some of the X-ray variability may be due to the presence of a local, inhomogeneous and dust-free absorber, while variability visible in both the X-ray and optical/UV may instead be driven by the accretion flow: the X-rays are produced in the inner accretion disc, some of which are reprocessed to the optical/UV; and/or the X-ray and optical/UV emission is produced within the jet.
Bondi–Hoyle–Lyttleton accretion in supergiant X-ray binaries: stability and disc formation
Authors: Xu Wenrui , Stone James M
Published: July 2019

We use 2D (axisymmetric) and 3D hydrodynamic simulations to study Bondi–Hoyle–Lyttleton accretion with and without transverse upstream gradients. We mainly focus on the regime of high (upstream) Mach number, weak upstream gradients, and small accretor size, which is relevant to neutron star accretion in wind-fed supergiant X-ray binaries (SgXBs). We present a systematic exploration of the flow in this regime. When there are no upstream gradients, the flow is always stable regardless of accretor size or Mach number. For finite upstream gradients, there are three main types of behaviour: stable flow (small upstream gradient), turbulent unstable flow without a disc (intermediate upstream gradient), and turbulent flow with a disc-like structure (relatively large upstream gradient). When the accretion flow is turbulent, the accretion rate decreases non-convergently as the accretor size decreases. The flow is more prone to instability and the disc is less likely to form than previously expected; the parameters of most observed SgXBs place them in the regime of a turbulent, disc-less accretion flow. Among the SgXBs with relatively well-determined parameters, we find OAO 1657−415 to be the only one that is likely to host a persistent disc (or disc-like structure); this finding is consistent with observations.
Constraining the initial planetary population in the gravitational instability model
Authors: Humphries J , Vazan A , Bonavita M , Helled R , Nayakshin S
Published: July 2019

Direct imaging (DI) surveys suggest that gas giants beyond 20 au are rare around FGK stars. However, it is not clear what this means for the formation frequency of gravitational instability (GI) protoplanets due to uncertainties in gap opening and migration efficiency. Here we combine state-of-the-art calculations of homogeneous planet contraction with a population synthesis code. We find DI constraints to be satisfied if protoplanet formation by GI occurs in tens of per cent of systems if protoplanets ‘supermigrate’ to small separations. In contrast, GI may occur in only a few per cent of systems if protoplanets remain stranded at wide orbits because their migration is ‘quenched’ by efficient gap opening. We then use the frequency of massive giants in radial velocity surveys inside 5 au to break this degeneracy – observations recently showed that this population does not correlate with the host star metallicity and is therefore suspected to have formed via GI followed by inward migration. We find that only the supermigration scenario can sufficiently explain this population while simultaneously satisfying the DI constraints and producing the right mass spectrum of planets inside 5 au. If massive gas giants inside 5 au formed via GI, then our models imply that migration must be efficient and that the formation of GI protoplanets occurs in at least tens of per cent of systems.
The luminosity function and formation rate of a complete sample of long gamma-ray bursts
Authors: Lan Guang-Xuan , Zeng Hou-Dun , Wei Jun-Jie , Wu Xue-Feng
Published: July 2019

We study the luminosity function and formation rate of long gamma-ray bursts (GRBs) by using a maximum likelihood method. This is the first time this method is applied to a well-defined sample of GRBs that is complete in redshift. The sample is composed of 99 bursts detected by the Swift satellite, 81 of them with measured redshift and luminosity for a completeness level of $82\, {\rm per\, cent}$. We confirm that a strong redshift evolution in luminosity (with an evolution index of $\delta =2.22^{+0.32}_{-0.31}$) or in density ($\delta =1.92^{+0.20}_{-0.21}$) is needed in order to reproduce the observations well. But since the predicted redshift and luminosity distributions in the two scenarios are very similar, it is difficult to distinguish between these two kinds of evolutions only on the basis of the current sample. Furthermore, we also consider an empirical density case in which the GRB rate density is directly described as a broken power-law function and the luminosity function is taken to be non-evolving. In this case, we find that the GRB formation rate rises like $(1+z)^{3.85^{+0.48}_{-0.45}}$ for $z\lesssim 2$ and is proportional to $(1+z)^{-1.07^{+0.98}_{-1.12}}$ for $z\gtrsim 2$. The local GRB rate is $1.49^{+0.63}_{-0.64}$ Gpc−3 yr−1. The GRB rate may be consistent with the cosmic star formation rate (SFR) at $z\lesssim 2$, but shows an enhancement compared to the SFR at $z\gtrsim 2$.
Bolometric correction factors for active galactic nuclei
Authors: Netzer Hagai
Published: July 2019

The bolometric luminosity of active galactic nuclei (AGNs) is difficult to determine, and various approximations have been used to calibrate it against different observed properties. Here, I combine theoretical calculations of optically thick, geometrically thin accretion discs, and observed X-ray properties of AGN, to provide new bolometric correction factors (kBOL) over a large range of black hole (BH) mass, accretion rate, and spin. This is particularly important in cases where the mass accretion rate cannot be determined from the observed spectral energy distribution, and in cases where luminosity-independent correction factors have been used. Simple power-law approximations of kBOL are provided for L(5100 Å), L(3000 Å), L(1400 Å), L(2–10 keV), and L(narrow Hβ). In all cases, the uncertainties are large mostly due to the unknown BH spin. Prior knowledge of the BH mass reduces the uncertainty considerably.
Pseudo-evolution of galaxies in Λ CDM cosmology
Authors: Balakrishna Subramani Vasanth , Kroupa Pavel , Shenavar Hossein , Muralidhara Vyoma
Published: July 2019

Our knowledge about galaxy evolution comes from transforming observed galaxy properties at different redshifts to comoving physical scales. This transformation depends on using a cosmological model. Here, the effects of unintentional mixing of two different cosmological models on the size evolution of galaxies is studied. As a gedanken experiment, a galaxy of fixed proper size and luminosity is moved across different redshifts. The apparent size of this galaxy is then interpreted with a cosmological model presumed by the observer, which is different compared to the cosmology exhibited by the Universe. In such a case, a spurious size evolution of the galaxy is observed. A galaxy behaving according to the Rh = ct and Neumann’s cosmology, when interpreted with the Λ cold dark matter (ΛCDM) cosmological model, shows an increase in size by a factor of 1.1 and 1.3 from $z$ = 7.5 to ≈ 0, respectively. The apparent size of a galaxy in a static Euclidean cosmology, when interpreted in the ΛCDM model, shows a factor of 23.8 increase in size between $z$ = 7.5 to ≈ 0. This is in close agreement with the observational data with a size increase of a factor of 6.8 between $z$ = 3.2 to ≈ 0. Furthermore, using the apparent size data, it is shown that the difference between the derived proper sizes in Rh = ct, Neumann’s and ΛCDM cosmological models are minimal.
An accurate low-redshift measurement of the cosmic neutral hydrogen density
Authors: Hu Wenkai , Hoppmann Laura , Staveley-Smith Lister , Geréb Katinka , Oosterloo Tom , Morganti Raffaella , Catinella Barbara , Cortese Luca , Lagos Claudia del P , Meyer Martin
Published: July 2019

Using a spectral stacking technique, we measure the neutral hydrogen (H i) properties of a sample of galaxies at z < 0.11 across 35 pointings of the Westerbork Synthesis Radio Telescope. The radio data contain 1895 galaxies with redshifts and positions known from the Sloan Digital Sky Survey. We carefully quantified the effects of sample bias, aperture used to extract spectra, sidelobes and weighting technique and use our data to provide a new estimate for the cosmic H i mass density. We find a cosmic H i mass density of $\Omega _{\rm H\,{\small I}} = (4.02 \pm 0.26)\times 10^{-4} h_{70}^{-1}$ at 〈z〉 = 0.066, consistent with measurements from blind H i surveys and other H i stacking experiments at low redshifts. The combination of the small interferometer beam size and the large survey volume makes our result highly robust against systematic effects due to confusion at small scales and cosmic variance at large scales. Splitting into three sub-samples with 〈z〉 = 0.038, 0.067, and 0.093 shows no significant evolution of the H i gas content at low redshift.
Energy of a quantum Coulomb liquid
Authors: Baiko D A
Published: July 2019

Using the Metropolis method to compute path integrals, the energy of a quantum strongly coupled Coulomb liquid (1 ≤ Γ ≤ 175), composed of distinguishable atomic nuclei and a uniform incompressible electron background, is calculated from first principles. The range of temperatures and densities considered represents fully ionized layers of white dwarfs and neutron stars. In particular, the results allow one to determine reliably the heat capacity of ions in dense fluid stellar matter, which is a crucial ingredient for modelling the thermal evolution of compact degenerate stars.
Effects of infall and outflow on massive star-forming regions
Authors: Li Qiang , Zhou Jianjun , Esimbek Jarken , He Yuxin , Baan Willem , Li Dalei , Wu Gang , Tang Xindi , Ji Weiguang , Komesh Toktarkhan , Sailanbek Serikbek
Published: July 2019

A total of 188 high-mass outflows have been identified from a sample of 694 clumps from the Millimetre Astronomy Legacy Team 90 GHz survey, representing a detection rate of approximately 27 per cent. The detection rate of outflows increases from the proto-stellar stage to the H ii stage, but decreases again at the photodissociation (PDR) stage suggesting that outflows are being switched off during the PDR stage. An intimate relationship is found between outflow action and the presence of masers, and water masers appear together with 6.7 GHz methanol masers. Comparing the infall detection rate of clumps with and without outflows, we find that outflow candidates have a lower infall detection rate. Finally, we find that outflow action has some influence on the local environment and the clump itself, and this influence decreases with increasing evolutionary time as the outflow action ceases.
Molecular envelope around the HII region RCW 120
Authors: Kirsanova M S , Pavlyuchenkov Ya N , Wiebe D S , Boley P A , Salii S V , Kalenskii S V , Sobolev A M , Anderson L D
Published: July 2019

The H ii region RCW 120 is a well-known object, which is often considered as a target to verify theoretical models of gas and dust dynamics in the interstellar medium. However, the exact geometry of RCW 120 is still a matter of debate. In this work, we analyse observational data on molecular emission in RCW 120 and show that 13CO(2–1) and C18O(2–1) lines are fitted by a 2D model representing a ring-like face-on structure. The changing of the C18O(3–2) line profile from double-peaked to single-peaked from the dense molecular Condensation 1 might be a signature of stalled expansion in this direction. In order to explain a self-absorption dip of the 13CO(2–1) and 13CO(3–2) lines, we suggest that RCW 120 is surrounded by a diffuse molecular cloud, and find confirmation of this cloud on a map of interstellar extinction. Optically thick 13CO(2–1) emission and the infrared 8 $\mu$m PAH band form a neutral envelope of the H ii region resembling a ring, while the envelope breaks into separate clumps on images made with optically thin C18O(2–1) line and far-infrared dust emission.
Population Gene Introgression and High Genome Plasticity for the Zoonotic Pathogen Streptococcus agalactiae
Authors: Richards Vincent P , Velsko Irina M , Alam Md Tauqeer , Zadoks Ruth N , Manning Shannon D , Pavinski Bitar Paulina D , Hassler Hayley B , Crestani Chiara , Springer Garrett H , Probert Brett M , Town Christopher D , Stanhope Michael J
Published: July 2019

The influence that bacterial adaptation (or niche partitioning) within species has on gene spillover and transmission among bacterial populations occupying different niches is not well understood. Streptococcus agalactiae is an important bacterial pathogen that has a taxonomically diverse host range making it an excellent model system to study these processes. Here, we analyze a global set of 901 genome sequences from nine diverse host species to advance our understanding of these processes. Bayesian clustering analysis delineated 12 major populations that closely aligned with niches. Comparative genomics revealed extensive gene gain/loss among populations and a large pan genome of 9,527 genes, which remained open and was strongly partitioned among niches. As a result, the biochemical characteristics of 11 populations were highly distinctive (significantly enriched). Positive selection was detected and biochemical characteristics of the dispensable genes under selection were enriched in ten populations. Despite the strong gene partitioning, phylogenomics detected gene spillover. In particular, tetracycline resistance (which likely evolved in the human-associated population) from humans to bovine, canines, seals, and fish, demonstrating how a gene selected in one host can ultimately be transmitted into another, and biased transmission from humans to bovines was confirmed with a Bayesian migration analysis. Our findings show high bacterial genome plasticity acting in balance with selection pressure from distinct functional requirements of niches that is associated with an extensive and highly partitioned dispensable genome, likely facilitating continued and expansive adaptation.
Utility of a Quantitative Approach Using Diffusion Tensor Imaging for Prognostication Regarding Motor and Functional Outcomes in Patients With Surgically Resected Deep Intracranial Cavernous Malformations
Authors: Abhinav Kumar , Nielsen Troels H , Singh Rhea , Weng Yingjie , Han Summer S , Iv Michael , Steinberg Gary K
Published: July 2019

BACKGROUND

Resection of deep intracranial cavernous malformations (CMs) is associated with a higher risk of neurological deterioration and uncertainty regarding clinical outcomes.

OBJECTIVE

To examine diffusion tractography imaging (DTI) data evaluating the corticospinal tract (CST) in relation to motor and functional outcomes in patients with surgically resected deep CMs.

METHODS

Perilesional CST was characterized as disrupted, displaced, or normal. Mean fractional anisotropy (FA) values were obtained for whole ipsilateral CST and in 3 regions: subcortical (proximal), perilesional, and distally. Mean FA values in anatomically equivalent regions in the contralateral CST were obtained. Clinical and radiological data were collected independently. Multivariable regression analysis was used for statistical analysis.

RESULTS

A total of 18 patients [brainstem (15) and thalamus/basal ganglia (3); median follow-up: 270 d] were identified over 2 yr. The CST was identified preoperatively as disrupted (6), displaced (8), and normal (4). Five of 6 patients with disruption had weakness. Higher preoperative mean FA values for distal ipsilateral CST segment were associated with better preoperative lower (P < .001), upper limb (P = .004), postoperative lower (P = .005), and upper limb (P < .001) motor examination. Preoperative mean FA values for distal ipsilateral CST segment (P = .001) and contralateral perilesional CST segment (P < .001) were negatively associated with postoperative modified Rankin scale scores.

CONCLUSION

Lower preoperative mean FA values for overall and defined CST segments corresponded to worse patient pre- and postoperative motor examination and/or functional status. FA value for the distal ipsilateral CST segment has prognostic potential with respect to clinical outcomes.
The Turn to Sabotage by The Congress Movement in South Africa*
Authors: Stevens Simon
Published: July 2019

Why did leaders of the Congress movement in South Africa abandon their exclusive reliance on non-violent means in the struggle against apartheid, form an armed unit (Umkhonto we Sizwe), and launch a campaign of spectacular sabotage bombings of symbols of apartheid in 1961? None of the earlier violent struggles from which Congress leaders drew inspiration, and none of the contemporaneous insurgencies against white minority rule elsewhere in southern Africa, involved a similar distinct, preliminary and extended phase of non-lethal symbolic sabotage. Following the 1960 Sharpeville massacre, Congress leaders feared the social and political consequences of increased popular enthusiasm for using violence. Nelson Mandela, Joe Slovo, and the other founders of Umkhonto we Sizwe did not launch their sabotage campaign because they believed it would prompt a change of heart among white South Africans, nor because they believed urban sabotage bombings were a necessary prelude to the launch of rural guerrilla warfare. Rather, the sabotage campaign was a spectacular placeholder, a stopgap intended to advertise the Congress movement's abandonment of exclusive non-violence and thus to discourage opponents of apartheid, both inside and outside South Africa, from supporting rival groups or initiating uncontrolled violent action themselves.