bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Role of Adaptive Ray Tracing in Analyzing Black Hole Structure
Authors: Gelles Z. , Prather B. S. , Palumbo D. C. M. , Johnson M. D. , Wong G. N. , Georgiev B. 
Published: May 2021

Abstract
The recent advent of the Event Horizon Telescope (EHT) has made direct imaging of supermassive black holes a reality. Simulated images of black holes produced via general relativistic ray tracing and radiative transfer provide a key counterpart to these observational efforts. Black hole images have a wide range of physically interesting image structures, ranging from extremely fine scales in their lensed “photon rings” to the very large scales in their relativistic jets. The multiscale nature of the black hole system is therefore suitable for a multiscale approach to generate simulated images that capture all key elements of the system. Here, we present a prescription for adaptive ray tracing, which enables efficient computation of extremely high-resolution images of black holes. Using the polarized ray-tracing code ipole, we image a combination of semianalytic and general relativistic magnetohydrodynamic (GRMHD) models, and we show that images can be reproduced with a mean squared error of less than 0.1% even after tracing 12× fewer rays. We then use adaptive ray tracing to explore the properties of the photon ring. We illustrate the behavior of individual subrings in GRMHD simulations, and we explore their signatures in interferometric visibilities.
Haze Formation on Triton
Authors: Ohno Kazumasa , Zhang Xi , Tazaki Ryo , Okuzumi Satoshi 
Published: May 2021

Abstract
The largest moon of Neptune, Triton, possesses a cold and hazy atmosphere. Since the discovery of the near-surface haze layer during the Voyager fly in 1989, the haze formation mechanism has not been investigated in detail. Here we provide the first haze microphysical model on Triton. Our model solves the evolution of both size and porosity distributions of haze particles in a self-consistent manner. We simulated the formation of sphere and aggregate hazes with and without condensation of the C2H4 ice. The haze particles can grow into fractal aggregates with mass-equivalent sphere sizes of ∼0.1–1 μm and fractal dimensions of D
f = 1.8–2.2. The ice-free hazes cannot simultaneously explain both UV and visible observations of Voyager 2, while including the condensation of C2H4 ices provides two better solutions. For ice aggregates, the required total haze mass flux is ∼2 × 10−15 g cm−2 s−1. For the icy sphere scenario, the column-integrated C2H4 production rate is ∼8 × 10−15 g cm−2 s−1, and the ice-free mass flux is ∼6 × 10−17 g cm−2 s−1. The UV occultation observations at short wavelengths, <0.15 μm, may slightly favor the icy aggregates. Observations of the haze optical depth and the degree of forward scattering in UV and visible should be able to distinguish whether Triton’s hazes are icy spheres or ice aggregates in future Triton missions.
Dynamics of Laterally Propagating Flames in X-Ray Bursts. II. Realistic Burning and Rotation
Authors: Harpole A. , Ford N. M. , Eiden K. , Zingale M. , Willcox D. E. , Cavecchi Y. , Katz M. P. 
Published: May 2021

Abstract
We continue to investigate two-dimensional laterally propagating flames in type I X-ray bursts using fully compressible hydrodynamics simulations. In the current study we relax previous approximations where we artificially boosted the flames. We now use more physically realistic reaction rates, thermal conductivities, and rotation rates, exploring the effects of neutron star rotation rate and thermal structure on the flame. We find that at lower rotation rates the flame becomes harder to ignite, whereas at higher rotation rates the nuclear burning is enhanced by increased confinement from the Coriolis force and the flame propagates steadily. At higher crustal temperatures, the flame moves more quickly and accelerates as it propagates through the atmosphere. If the temperature is too high, instead of a flame propagating across the surface the entire atmosphere burns uniformly. Our findings could have implications for the relationship between observed burst rise times and neutron star rotation and accretion rates. All of the software used for these simulations is freely available.
La dernière demeure
Authors: Uribelarrea Gabriel 
Published: May 2021

Le vieillissement prématuré des personnes sans abri ainsi que la présence de plus en plus nombreuse de personnes âgées de 70 ans et plus dans les institutions de l’urgence sociale pose, pour les professionnels, la question de l’accompagnement à la fin de vie. À partir d’une enquête ethnographique dans une institution d’hébergement médicalisé pour sans-abri (les Lits halte soins santé [LHSS]), cet article analyse les épreuves rencontrées par les professionnels, les réponses qu’ils apportent et les solutions qu’ils expérimentent face aux situations de fin de vie. En parallèle, cet article essaie de penser en quoi ces réponses s’inscrivent dans un ordre écologique qui offre des « prises » à l’accompagnement et qui contribue à (re)définir les pratiques d’habiter des personnes accueillies. Selon les situations, l’institution apparaît comme un lieu de vie, avec ses inscriptions spatiales et sociales, où mourir. Dans d’autres cas, la mort surprend les personnes engagées dans des circulations entre la rue et l’assistance.
Les épreuves identitaires des femmes âgées à la rue
Authors: Maurin Marine 
Published: May 2021

Comment le recours à l’assistance constitue-t-il un circuit d’épreuves identitaires pour les femmes âgées qui vivent des situations de sans-abrisme ? Pour appréhender au plus près ces épreuves identitaires vécues, cet article propose de suivre l’histoire biographique d’une femme retraitée, Germaine, rencontrée lors d’une enquête ethnographique portant sur l’assistance aux femmes sans abri. À partir de son expérience critique et sensible, nous traiterons de la vieillesse selon deux acceptions interdépendantes. Dans un premier temps, la vieillesse sera abordée comme une épreuve identitaire qui dépend fortement du « passage à la retraite ». En effet, pour Germaine, l’obtention de ce statut social correspond à une revalorisation identitaire, c’est-à-dire à une reconnaissance d’une vie de travailleuse – expérience souvent oubliée et négligée lorsque l’on s’intéresse au sans-abrisme. Nous verrons que sa participation à la société salariale et sa reconnaissance au travers du statut de retraité ne signifient pas pour autant une transformation de ses conditions d’existence et de son rapport à l’assistance. Dans un second temps, la vieillesse sera appréhendée à partir des relations que Germaine entretient au sein du monde de l’assistance et de la rue. Nous verrons alors que le processus de vieillissement concerne également l’assignation identitaire à la figure de la « mamie », figure générationnelle et familiale a priori positive. Or, cette assignation implique par la même occasion, en situation, une désexualisation des relations des femmes âgées qui vivent des situations de sans-abrisme. Cet article cherche dès lors à montrer que l’expérience de la vieillesse des femmes à la rue constitue un processus relationnel complexe marqué par des formes de continuité et discontinuité identitaires articulant les rapports sociaux d’âge, de sexe et de sexualité.
A Multicenter Study of Student Engagement and Satisfaction in Online Programs
Authors: Hensley Angie , Hampton Debra , Wilson Jessica L. , Culp-Roche Amanda , Wiggins Amanda T. 
Published: May 2021

Background:
Students who are more satisfied and engaged in online courses have better learning experiences and outcomes.

Method:
Survey data were collected during a 4-month period in 2019. The research team created a survey to collect demographic information and assess student satisfaction. Student engagement was measured using the 19-item Online Student Engagement Scale.

Results:
Overall student engagement and satisfaction scores in online programs were moderately high. Generation Z participants and students from PhD programs were the most satisfied and engaged in their programs.

Conclusion:

Students who are more engaged in online coursework are more satisfied and thus are more likely to remain and successfully complete their respective programs.

[
J Nurs Educ
. 2021;60(5):259–264.]
Comparative Analysis of Antigen-Specific Anti–SARS-CoV-2 Antibody Isotypes in COVID-19 Patients
Authors: Fujigaki Hidetsugu , Inaba Masato , Osawa Michiko , Moriyama Saya , Takahashi Yoshimasa , Suzuki Tadaki , Yamase Kenya , Yoshida Yukihiro , Yagura Yo , Oyamada Takayoshi , Takemura Masao , Doi Yohei , Saito Kuniaki 
Published: May 2021

Abstract
Serological tests for detection of anti–severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Abs in blood are expected to identify individuals who have acquired immunity against SARS-CoV-2 and indication of seroprevalence of SARS-CoV-2 infection. Many serological tests have been developed to detect Abs against SARS-CoV-2. However, these tests have considerable variations in their specificity and sensitivity, and whether they can predict levels of neutralizing activity is yet to be determined. This study aimed to investigate the kinetics and neutralizing activity of various Ag-specific Ab isotypes against SARS-CoV-2 in serum of coronavirus disease 2019 (COVID-19) patients confirmed via PCR test. We developed IgG, IgM, and IgA measurement assays for each Ag, including receptor-binding domain (RBD) of spike (S) protein, S1 domain, full-length S protein, S trimer, and nucleocapsid (N) domain, based on ELISA. The assays of the S protein for all isotypes showed high specificity, whereas the assays for all isotypes against N protein showed lower specificity. The sensitivity of all Ag-specific Ab isotypes depended on the timing of the serum collection and all of them, except for IgM against N protein, reached more than 90% at 15–21 d postsymptom onset. The best correlation with virus-neutralizing activity was found for IgG against RBD, and levels of IgG against RBD in sera from four patients with severe COVID-19 increased concordantly with neutralizing activity. Our results provide valuable information regarding the selection of serological test for seroprevalence and vaccine evaluation studies.
Bedside Tracheostomy on COVID-19 Patients in the Intensive Care Unit
Authors: Swain Santosh Kumar , Acharya Satyabrata 
Published: May 2021

Introduction:
Currently, coronavirus disease 2019 (COVID-19) infection is a global challenge to the medical community, often resulting in acute respiratory distress syndrome and respiratory failure needing mechanical ventilation. Tracheostomy is needed for prolonged ventilation as the severity of respiratory failure often escalates, needing extended ventilation in an intensive care unit (ICU).

Objective:
The objective of study was to evaluate clinical details of performing tracheostomy including patient profile, surgical steps, complications and precautions by health-care workers in the ICU of a specially assigned hospital for COVID-19 patients.

Patients and Methods:
This is a retrospective study of 22 COVID-19 patients who underwent bedside surgical tracheostomy in the ICU. Patient profile such as age, gender, comorbidities, complication of tracheostomy, ventilator withdrawal after tracheostomy and nosocomial infections of health-care workers related to tracheostomy were analysed.

Results:
In the study period of 6 months, there were 12,850 COVID-19 patients admitted to our COVID-designated hospital, of whom 2452 patients needed ICU care. A total of 610 patients needed ventilatory support, with 22 patients aged between 42 and 75 years (mean age of 64 years) undergoing a tracheostomy (16 males and 6 females). The median duration from the day of the orotracheal intubation to the day of tracheostomy was 13 days.

Conclusion:
Surgical tracheostomy on COVID-19 patients is a high-risk aerosol-generating procedure for health-care workers. It should be performed with close communication between otorhinolaryngologists, anaesthesiologists and intensivists, along with adequate personal protective equipment for smooth management of the airway.
Is the Nature (Extent and Characteristics) of Schistosoma-Induced Chronic Inflammation Organ Dependents?
Authors: Bello Shamsu Sahalu , Atanda Akinfenwa Taoheed , Olatunde O. A. O. , Gana S. L. , Ibrahim-Saad A. B. 
Published: May 2021

Context:
Pathogenesis of schistosomiasis related bladder cancer has been attributed to induced chronic inflammation and its sequelae. There is paucity of studies on the inflammatory cell profile.

Aim:
This study, therefore, aims to characterise the degree and repertoire of this inflammatory response.

Settings and Design:
A retrospective study of all non-neoplastic cases of schistosomiasis histologically confirmed between January 2012 and December 2019 in a tertiary hospital.

Materials and Methods:
Data were retrieved from archives and slides made for the cases were evaluated for ova density, type and degree of inflammation and pattern of fibrosis.

Statistical Analysis:
The degree of inter observer variation (kappa value) was also calculated while statistical significance was set at P ≤ 0.5 at 95% confidence interval.

Results:
Eighty one cases were diagnosed in the study period. The mean age was 33.8 years and M:F ratio was 15:1. Bladder, ureter, gastrointestinal tract, testes and other less frequent sites accounted for 58.0%, 12.0%, 8.0%, 8.0% and 7.4% of cases, respectively. Eosinophilic infiltration and granulomatous reaction were predominantly minimal even in cases with significant oviposition. There was no significant difference between ova density and degree of overall inflammation (P = 0.9) or between ova density and degree of lymphocytic infiltration (P = 0.2). Similarly, even though fibrosis was more frequent in cases with high ova density, no significant difference was found in cases with low ova density.

Conclusion:
Even though carcinogenesis in bladder schistosomiasis has been attributed to chronic inflammation and fibrosis, this study, however, showed that there are no statistically significant differences between schistosoma ova density and degree of inflammation as well as fibrosis in both bladder and other organs.
Protective Effect of Alpha-Lipoic Acid against Liver Damage Induced by Cigarette Smoke
Authors: Gumral Nurhan , Aslankoc Rahime , Senol Nurgul , Cankara Fatma Nihan 
Published: May 2021

Background:
Long-term cigarette smoking damages the liver tissue. Alpha-lipoic acid (ALA) is used as a therapeutic agent in a number of conditions and is known to have ameliorative effects against oxidative stress in the liver.

Objective:
To investigate the ameliorative effects of ALA on cigarette smoke (CS)-induced oxidative liver damage by examining histopathological, immunohistopathological changes and biochemical parameters in an animal model.

Materials and Methods:
Twenty-eight female Sprague–Dawley rats were randomly divided into three groups. In the control group (n = 8), rats were exposed to fresh air twice a day and given 0.1 ml of saline by gavage once a day for 8 weeks. In the smoking group (n = 10), rats were exposed to CS for 1 h in the morning and afternoon and given 0.1 ml of saline by gavage once a day for 8 weeks. In the smoking + ALA group (n = 10), CS exposure was same as the smoking group in addition to 100 mg/kg of ALA per day for 8 weeks through gavage. Oxidative damage in the liver tissue was determined by evaluating malondialdehyde (MDA), catalase (CAT) and superoxide dismutase (SOD) levels. Aspartate aminotransferase (AST), alanine aminotransaminase (ALT), alkaline phosphatase (ALP), direct bilirubin and total bilirubin levels were measured in the blood. Histopathological and immunohistochemical examinations were performed.

Results:
MDA (P = 0.011), AST (P = 0.018) and total bilirubin levels (P < 0.001) were increased, while CAT activity (P = 0.009) and the efficiency of SOD (P = 0.010) were decreased in the smoking group compared with the control group. CAT activity was increased (P = 0.017) and AST (P = 0.018) and total bilirubin levels (P < 0.001) were decreased in ALA-treated group compared with the smoking group. We observed vascular dilatation and hemorrhagic areas in the smoking group. TNF-α expression was increased in the smoking group compared with the control group. However, TNF-α expression was high in some preparations in the ALA-treated group.

Conclusions:
ALA can enhance antioxidant activity, but studies with different doses of ALA are required to determine the extent of its hepatoprotective effect.
Standing and Walking Balance in Patients with Chronic Shoulder Pain
Authors: Alshami Ali M. , Alrammah Talal A. 
Published: May 2021

Background:
Patients with shoulder pain may have proprioceptive and balance deficits. However, studies on balance in patients with shoulder pain are scarce.

Objective:
This study aims to investigate if patients with chronic shoulder pain demonstrate deficits in standing and walking balance and to study the relationship between outcome measures of balance and age and body mass index (BMI).

Materials and Methods:
This case–control study was conducted at Dammam Medical Complex, Dammam, Saudi Arabia, between March and November 2018. The study recruited patients (n = 15) with chronic shoulder pain (>4 months) and healthy controls (n = 15) matched for age, gender and BMI. Standing balance was tested using a Challenge Disc test, the Romberg test and timed unipedal stance test (UPST). Walking balance was assessed using the timed up and go (TUG) test, stance phase duration and center of pressure (COP) deviation. Independent t-tests were used to investigate the differences between the two groups in demographic data and all the outcome measurements. Pearson correlation coefficients were used for correlation analysis.

Results:
No statistically significant differences were found between the two groups in any outcome of the standing balance (P ≥ 0.095) or walking balance (P ≥ 0.160). However, medium effect sizes were found for the UPST (η2: ≥0.06), Challenge Disc (η2: 0.06), TUG (Cohen's d: 0.54) and COP deviation (Cohen's d: 0.53). There was a moderate correlation between BMI and Challenge Disc (P = 0.025) and between age and Challenge Disc (P = 0.012) in both the groups.

Conclusion:
Patients with chronic shoulder pain had lower balance measurements compared with healthy people, although this difference was not statistically significant.
Natural History and Clinical Course of Symptomatic and Asymptomatic COVID-19 Patients in the Kingdom of Saudi Arabia
Authors: Almubark Rasha A. , Memish Ziad A. , Tamim Hani , Alenazi Thamer H. , Alabdulla Mohammed , Sanai Faisal M. , BinDhim Nasser F. , Alfaraj Sarah , Alqahtani Saleh A. 
Published: May 2021

Objectives:
To analyze symptomatic and asymptomatic COVID-19 patients in Saudi Arabia in terms of initial presentation, risk factors, laboratory findings, clinical outcomes and healthcare utilization.

Methods:
All laboratory-confirmed reverse transcription–polymerase chain reaction positive COVID-19 patients who had been tested at three governmental hospitals in Saudi Arabia (two in Riyadh and one in Makkah) between March 8 and May 18, 2020 were included. Demographics, COVID-19 variables, clinical characteristics and healthcare utilization variables were extracted and combined, and a descriptive analysis was conducted. Symptomatic and asymptomatic (on presentation) patients' data were compared.

Results:
Eighty percent of the patients were males (81.4% of symptomatic and 73.2% of asymptomatic patients, P = 0.02). Moreover, 47.6% and 38.4% of symptomatic and asymptomatic patients were aged 40–64 years, respectively. Fever, cough and breathing difficulties were frequent presenting symptoms. Overall, diabetes (16.4%), hypertension (11.7%), chronic respiratory disease (7.1%) were the most frequent comorbidities, with no differences between the two groups. Symptomatic patients had higher C-reactive protein levels (3.55 vs. 0.30 mg/L; P < 0.0001) and lower total lymphocytes (1.41 vs. 1.70; P = 0.02). ICU admission and mortality were 12.1% and 4.1% in symptomatic, compared to 6.0% and 2.9% in asymptomatic patients, respectively.

Conclusion:
In the studied COVID-19 cohort, symptomatic patients tended to be older, had higher C-reactive protein and more lymphopenia with worse outcome than asymptomatic patients. This granular analysis of COVID-19 cohorts enables identification of at-risk cohorts in future waves, optimizing development of patient pathways and public health interventions.
Density theorems for anisotropic point configurations
Authors: Kovač Vjekoslav 
Published: May 2021

AbstractSeveral results in the existing literature establish Euclidean density theorems of the following strong type. These results claim that every set of positive upper Banach density in the Euclidean space of an appropriate dimension contains isometric copies of all sufficiently large elements of a prescribed family of finite point configurations. So far, all results of this type discussed linear isotropic dilates of a fixed point configuration. In this paper, we initiate the study of analogous density theorems for families of point configurations generated by anisotropic dilations, i.e., families with power-type dependence on a single parameter interpreted as their size. More specifically, we prove nonisotropic power-type generalizations of a result by Bourgain on vertices of a simplex, a result by Lyall and Magyar on vertices of a rectangular box, and a result on distance trees, which is a particular case of the treatise of distance graphs by Lyall and Magyar. Another source of motivation for this paper is providing additional evidence for the versatility of the approach stemming from the work of Cook, Magyar, and Pramanik and its modification used recently by Durcik and the present author. Finally, yet another purpose of this paper is to single out anisotropic multilinear singular integral operators associated with the above combinatorial problems, as they are interesting on their own.
Overdiagnosis of Malaria Illness in an Endemic Setting: A Facility-Based Surveillance Study in Malawi
Authors: Peterson Ingrid , Kapito-Tembo Atupele , Bauleni Andrew , Nyirenda Osward , Pensulo Paul , Still William , Valim Clarissa , Cohee Lauren , Taylor Terrie , Mathanga Don P. , Laufer Miriam K. 
Published: May 2021

Abstract.In endemic settings where asymptomatic malaria infections are common, malaria infection can complicate fever diagnosis. Factors influencing fever misdiagnosis, including accuracy of malaria rapid diagnostic tests (mRDTs) and the malaria-attributable fraction of fevers (MAF), require further investigation. We conducted facility-based surveillance in Malawi, from January 2012 through December 2013 in settings of high perennial (Chikhwawa), high seasonal (Thoylo), and moderate seasonal (Ndirande) malaria transmission. Consecutive patients presenting to outpatient departments were screened; those with suspected malaria illness were tested by mRDT or routine thick-smear microscopy. Test positivity rates (TPRs), positive predictive value (PPVs) of mRDTs, and MAFs were calculated by site, age, and season. Of 41,471 patients, 10,052 (24.2%) tested positive for malaria. The TPR was significantly greater in Chikhwawa (29.9%; 95% CI, 28.6–30.0) compared with Thyolo (13.2%; 95% CI, 12.5–13.7) and Ndirande (13.1%; 95% CI, 12.2–14.4). The overall PPV was 77.8% (95% CI, 76.8–78.7); it was lowest among infants (69.9%; 95% CI, 65.5–74.2) and highest among school-age children (81.9%; 95% CI, 80.3–83.4). Malaria infection accounted for about 50% of fevers in children younger than 5 years old with microscopy-confirmed Plasmodium falciparum infection, and less than 20% of such fevers in school-age children. Outpatient settings in Malawi had a high burden of malaria illness, but also possible overdiagnosis of malaria illness. Interventions to reduce malaria transmission and rapid testing for other common febrile illness may improve diagnostic clarity among outpatients in malaria endemic settings.